ERIC Educational Resources Information Center
Pendrill, Ann-Marie
2005-01-01
Many modern rollercoasters feature loops. Although textbook loops are often circular, real rollercoaster loops are not. In this paper, we look into the mathematical description of various possible loop shapes, as well as their riding properties. We also discuss how a study of loop shapes can be used in physics education.
NASA Astrophysics Data System (ADS)
Blanco-Pillado, Jose J.; Olum, Ken D.; Shlaer, Benjamin
2015-09-01
We analyze the shapes of cosmic string loops found in large-scale simulations of an expanding-universe string network. The simulation does not include gravitational backreaction, but we model that process by smoothing the loop using Lorentzian convolution. We find that loops at formation consist of generally straight segments separated by kinks. We do not see cusps or any cusplike structure at the scale of the entire loop, although we do see very small regions of string that move with large Lorentz boosts. However, smoothing of the string almost always introduces two cusps on each loop. The smoothing process does not lead to any significant fragmentation of loops that were in non-self-intersecting trajectories before smoothing.
Optimum Building Shapes for Energy Conservation
ERIC Educational Resources Information Center
Berkoz, Esher Balkan
1977-01-01
An approach to optimum building shape design is summarized that is based on local climate and is especially important for heat control in lower cost construction with temperature-responsive thermal characteristics. The study was supported by Istanbul Technical University. For journal availability see HE 508 931. (Author/LBH)
Optimum design of hybrid phase locked loops
NASA Technical Reports Server (NTRS)
Lee, P.; Yan, T.
1981-01-01
The design procedure of phase locked loops is described in which the analog loop filter is replaced by a digital computer. Specific design curves are given for the step and ramp input changes in phase. It is shown that the designed digital filter depends explicitly on the product of the sampling time and the noise bandwidth of the phase locked loop. This technique of optimization can be applied to the design of digital analog loops for other applications.
Optimum shape of a blunt forebody in hypersonic flow
NASA Technical Reports Server (NTRS)
Maestrello, L.; Ting, L.
1989-01-01
The optimum shape of a blunt forebody attached to a symmetric wedge or cone is determined. The length of the forebody, its semi-thickness or base radius, the nose radius and the radius of the fillet joining the forebody to the wedge or cone are specified. The optimum shape is composed of simple curves. Thus experimental models can be built readily to investigate the utilization of aerodynamic heating for boundary layer control. The optimum shape based on the modified Newtonian theory can also serve as the preliminary shape for the numerical solution of the optimum shape using the governing equations for a compressible inviscid or viscous flow.
Optimum pulse shapes for stimulated Raman adiabatic passage
Vasilev, G. S.; Kuhn, A.; Vitanov, N. V.
2009-07-15
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.
Optimum Stack Position Within a Bottle-shaped Thermoacoustic Engine
NASA Astrophysics Data System (ADS)
Bassett, Elwin; Andersen, Bonnie
2009-10-01
Thermoacoustics involves turning heat energy into acoustic energy, or using sound to pump heat. A thermoacoustic engine with a transducer could be used, for example, to convert solar energy incident on a satellite into sound and then into electricity. This research focused on the optimization of stack placement within a bottle-shaped 1.4 kHz engine to achieve maximum acoustic pressure. The prime mover consisted of two connected cylinders: the bottle neck, 5 cm long and 1 cm in radius, and a cavity, 10 cm long and 2 cm in radius, with the stack located within the middle of the neck. Sound intensity is a function of both pressure and velocity; therefore, maximum intensity should be found in between their nodes. However, a phase shift is introduced for the velocity due to the thermoacoustic effect and the optimum position will not be exactly between the nodes. Therefore, 9 different stack positions within the neck were tested to determine the optimum location. The optimum was found to be 39% away from the closed end of the neck, which improved acoustic pressure by 50%. Further testing is planned, to verify the results and test different configurations.
Optimum Cavity Radius Within a Bottle-Shaped Thermoacoustic Engine
NASA Astrophysics Data System (ADS)
Bridge, Justin; Andersen, Bonnie
2009-10-01
Heat energy can be used to generate acoustic energy due to thermoacoustic interactions. These engines can be used to create sound waves without any moving parts, like pistons, and could be used in space to convert solar energy into electricity. This research focused on the optimization of the geometry of bottle-shaped resonators used for thermoacoustic prime movers. These resonators have the advantage of non-harmonic overtones compared with half-wave resonators. The resonators for this research were constructed of concentric cylinders consisting of a neck piece and a cavity. The dimensions were approximately 5 cm with an ID of 2 cm for the neck and 10 cm long with IDs varying from about 2 cm to 12 cm for the cavity, producing operating frequencies ranging from approximately 1.2 to 1.5 kHz, following a theoretical model. Twelve different cavity radii were tested. The optimal cavity radius of 2.06 cm had an onset time that was 27 s faster and an onset temperature difference that was lower by 12 C than the smallest cavity (a half-wave resonator). Future research will explore the quality factor and optimum stack to surface area ratio of the engines.
Beyond singular values and loop shapes
NASA Technical Reports Server (NTRS)
Stein, G.
1985-01-01
The status of singular value loop-shaping as a design paradigm for multivariable feedback systems is reviewed. It shows that this paradigm is an effective design tool whenever the problem specifications are spacially round. The tool can be arbitrarily conservative, however, when they are not. This happens because singular value conditions for robust performance are not tight (necessary and sufficient) and can severely overstate actual requirements. An alternate paradign is discussed which overcomes these limitations. The alternative includes a more general problem formulation, a new matrix function mu, and tight conditions for both robust stability and robust performance. The state of the art currently permits analysis of feedback systems within this new paradigm. Synthesis remains a subject of research.
Optimum Shape Design Using Automatic Differentiation in Reverse Mode
NASA Technical Reports Server (NTRS)
Hafez, M.; Mohammadi, B.; Pironneau, O.
1996-01-01
This paper shows how to use automatic differentiation in reverse mode as a powerful tool in optimization procedures. It is also shown that for aerodynamic applications the gradients have to be as accurate as possible. In particular, the effect of having the exact gradient of he first or second order spatial discretization schemes is presented. We show that the loss of precision in the gradient affects not only the convergence, but also the final shape. Both two and three dimensional configurations of transonic and supersonic flows have been investigated. These cases involve up to several thousand control parameters.
Preliminary studies on the optimum shape of dental bridges.
Proos, K; Steven, G; Swain, M; Ironside, J
2000-01-01
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
Drew, L.J.
1979-01-01
In this study the selection of the optimum type of drilling pattern to be used when exploring for elliptical shaped targets is examined. The rhombic pattern is optimal when the targets are known to have a preferred orientation. Situations can also be found where a rectangular pattern is as efficient as the rhombic pattern. A triangular or square drilling pattern should be used when the orientations of the targets are unknown. The way in which the optimum hole spacing varies as a function of (1) the cost of drilling, (2) the value of the targets, (3) the shape of the targets, (4) the target occurrence probabilities was determined for several examples. Bayes' rule was used to show how target occurrence probabilities can be revised within a multistage pattern drilling scheme. ?? 1979 Plenum Publishing Corporation.
NASA Astrophysics Data System (ADS)
Jeon, W. H.; Kim, N.; Lee, J. Y.
2014-12-01
This study aims to evaluate the influence of open loop ground source heat pump systems operation on hydrological conditions of aquifer. Test bed is located in Chuncheon, Korea. The step drawdown test was conducted in five stages for 300 minutes. The variation of groundwater levels by open loop ground source heat pump systems operation was estimated using Visual MODFLOW. Transmissivity ranged from 2.02×10-4 to 9.36×10-4, and storage coefficient ranged from 0.00067 to 0.021. The amount of optimum bleeding was calculated to be 240 m3/day. When bleeding will be 50, 90, 240 and 450 m3/day for 5 years, groundwater levels may decrease 1.84, 3.31, 8.89 and 17.0 m, respectively. If the amount of bleeding is 50 m3/day, the influence of bleeding will not reach the boundary regions of the Soyang River after 5 years. Regarding the open loop ground source heat pump system installed at the test bed, the amount of optimum bleeding in accordance with the stand are proposed by the government is 90 m3/day, which is 20% of the 450 m3/day circulation quantity of the system. However, if continuous bleeding of more than 90 m3/day occurs, then the radius of influence is expected to reach the boundary regions of the Soyang River after 5 years. These results indicate that amount of optimum bleeding differ in each open loop ground soured heat pump system. Therefore, the debate for the amount of optimum bleeding in open loop ground source heat pump systems is demanded. This work is supported by the Energy Efficiency and Resources of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant funded by the Korea government Ministry of Knowledge Economy (No.20123040110010).
Quantitative Evaluation of Closed-Loop-Shaped Cardiomyocyte Network by Using Ring-Shaped Electrode
NASA Astrophysics Data System (ADS)
Nomura, Fumimasa; Kaneko, Tomoyuki; Hamada, Tomoyo; Hattori, Akihiro; Yasuda, Kenji
2012-06-01
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 µm 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.
Feedback Control Systems Loop Shaping Design with Practical Considerations
NASA Technical Reports Server (NTRS)
Kopsakis, George
2007-01-01
This paper describes loop shaping control design in feedback control systems, primarily from a practical stand point that considers design specifications. Classical feedback control design theory, for linear systems where the plant transfer function is known, has been around for a long time. But it s still a challenge of how to translate the theory into practical and methodical design techniques that simultaneously satisfy a variety of performance requirements such as transient response, stability, and disturbance attenuation while taking into account the capabilities of the plant and its actuation system. This paper briefly addresses some relevant theory, first in layman s terms, so that it becomes easily understood and then it embarks into a practical and systematic design approach incorporating loop shaping design coupled with lead-lag control compensation design. The emphasis is in generating simple but rather powerful design techniques that will allow even designers with a layman s knowledge in controls to develop effective feedback control designs.
Optimum shape control of flexible beams by piezo-electric actuators
NASA Technical Reports Server (NTRS)
Baz, A.; Poh, S.
1987-01-01
The utilization of piezoelectric actuators in controlling the static deformation and shape of flexible beams is examined. An optimum design procedure is presented to enable the selection of the optimal location, thickness and excitation voltage of the piezoelectric actuators in a way that would minimize the deflection of the beam to which these actuators are bonded. Numerical examples are presented to illustrate the application of the developed optimization procedure in minimizing structural deformation of beams using ceramic and polymeric piezoelectric actuators bonded to the beams with a typical bonding agent. The obtained results emphasize the importance of the devised rational produce in designing beam-actuator systems with minimal elastic distortions.
{alpha}-Shaped DNA loops induced by MutS
Jia Yanxia; Bi Lijun; Li Feng; Chen Yuanyuan; Zhang Chenggang; Zhang Xianen
2008-08-08
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.
Practical Loop-Shaping Design of Feedback Control Systems
NASA Technical Reports Server (NTRS)
Kopasakis, George
2010-01-01
An improved methodology for designing feedback control systems has been developed based on systematically shaping the loop gain of the system to meet performance requirements such as stability margins, disturbance attenuation, and transient response, while taking into account the actuation system limitations such as actuation rates and range. Loop-shaping for controls design is not new, but past techniques do not directly address how to systematically design the controller to maximize its performance. As a result, classical feedback control systems are designed predominantly using ad hoc control design approaches such as proportional integral derivative (PID), normally satisfied when a workable solution is achieved, without a good understanding of how to maximize the effectiveness of the control design in terms of competing performance requirements, in relation to the limitations of the plant design. The conception of this improved methodology was motivated by challenges in designing control systems of the types needed for supersonic propulsion. But the methodology is generally applicable to any classical control-system design where the transfer function of the plant is known or can be evaluated. In the case of a supersonic aerospace vehicle, a major challenge is to design the system to attenuate anticipated external and internal disturbances, using such actuators as fuel injectors and valves, bypass doors, and ramps, all of which are subject to limitations in actuator response, rates, and ranges. Also, for supersonic vehicles, with long slim type of structures, coupling between the engine and the structural dynamics can produce undesirable effects that could adversely affect vehicle stability and ride quality. In order to design distributed controls that can suppress these potential adverse effects, within the full capabilities of the actuation system, it is important to employ a systematic control design methodology such as this that can maximize the effectiveness of the control design in a methodical and quantifiable way. The emphasis is in generating simple but rather powerful design techniques that will allow even designers with a layman s knowledge in controls to develop effective feedback control designs. Unlike conventional ad hoc methodologies of feedback control design, in this approach actuator rates are incorporated into the design right from the start: The relation between actuator speeds and the desired control bandwidth of the system is established explicitly. The technique developed is demonstrated via design examples in a step-by-step tutorial way. Given the actuation system rates and range limits together with design specifications in terms of stability margins, disturbance rejection, and transient response, the procedure involves designing the feedback loop gain to meet the requirements and maximizing the control system effectiveness, without exceeding the actuation system limits and saturating the controller. Then knowing the plant transfer function, the procedure involves designing the controller so that the controller transfer function together with the plant transfer function equate to the designed loop gain. The technique also shows what the limitations of the controller design are and how to trade competing design requirements such as stability margins and disturbance rejection. Finally, the technique is contrasted against other more familiar control design techniques, like PID control, to show its advantages.
Possible Cross-Section for a Coronal Loop of Given Shape?
NASA Astrophysics Data System (ADS)
Ruderman, M. S.
2015-02-01
We aim to answer the question about the cross-section of a planar coronal loop with a prescribed shape. We restrict the analysis to coronal loops embedded in a planar potential magnetic field. Then we carry out the analysis in the leading-order approximation with respect to the small parameter ? equal to the ratio of the characteristic size of the loop cross-section to the loop length. We show that, in this approximation, the loop cross-section can be prescribed arbitrarily at one of its footpoints. Then the loop cross-section at any other point is obtained by stretching or compressing the prescribed loop cross-section in the direction that is perpendicular to the loop axis and in the plane of the loop. The variation of the coefficient of stretching or compression along the loop can be chosen arbitrarily. In particular, it follows from this result that we can consider a planar loop of arbitrary shape and assume that its cross-section is circular everywhere and has a constant radius.
NASA Astrophysics Data System (ADS)
Luo, Quantian; Tong, Liyong
2007-10-01
This paper presents a segment based sequential least squares algorithm with optimum energy control for tracking the dynamic shapes of piezoelectric smart structures. In this algorithm, integration of the square difference between the desired and achieved dynamic shapes over a time period is employed as an error function. The total electrical energy consumption of all actuators is used as the other control target. Two control schemes are studied: (a) minimization of the square error over a time period with energy constraint and (b) minimization of control energy with specified square error constraint. The Lagrange multiplier technique is used to consider the constraint, in which the properties of the characteristic matrix and polynomials of the Lagrange multiplier are analysed. Based on the present analysis, a simple and efficient algorithm is proposed; the relationship between permissible energy constraint and achievable minimum square error is investigated. Numerical results are presented for tracking twisting shape variations of a smart plate. Optimum energy control for reducing conflicting effects of the applied actuation voltages is also discussed.
NASA Astrophysics Data System (ADS)
Ramakrishnan, C. V.; Singh, Nidur; Sehgal, D. K.
2007-05-01
In this paper an efficient GA based Three Phase Topology Optimization algorithm which is an improvement over the Two-Phase Method developed by the team at IIT Delhi is presented. The Solid Isotropic Material with Penalization approach is outlined and Sequential Linear Programming method with move limits is utilized for solving the compliance minimization and volume minimization problems with volume and displacement constraints respectively. The need for parametric studies with various penalty factors and initial starting constraints are emphasized. The availability of accurate constraint derivatives with minimal effort is a boon but as in any NLP problem with a large number of variables, the global nature of the optimum is somewhat suspect in SIMP based method. A detailed comparison of the performances of the two phase and three phase methods and the SIMP method is presented for problems of different size and general conclusions are drawn.
Tectonic stress feedback loop explains U-shaped glacial valleys
NASA Astrophysics Data System (ADS)
Schultz, Colin
2014-03-01
In the shadow of the Matterhorn, the broad form of the Matter Valley—like so many throughout the Alps—is interrupted by a deep U-shaped glacial trough. Carved into a landscape reflecting millennia of tectonic uplift and river erosion, growing evidence suggests the 100-meter-deep U-shaped groove was produced shortly after a shift toward major cycles of Alpine glaciation almost a million years ago. Subsequent glaciations may have therefore had little effect on the landscape.
The optimum shape for a rigid rotating shell enclosing an isotropic spherical planetary mass
NASA Technical Reports Server (NTRS)
Covington, Tatiana
1991-01-01
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.
Interpolating gain-scheduled H? loop shaping design for high speed ball screw feed drives.
Dong, Liang; Tang, WenCheng; Bao, DaFei
2015-03-01
This paper presents a method to design servo controllers for flexible ball screw drives with time-varying dynamics, which are mainly due to the time-varying table position and the workpiece mass. A gain-scheduled H? loop shaping controller is designed to achieve high tracking performance against the dynamic variations. H? loop shaping design procedure incorporates open loop shaping by a set of compensators to obtain performance/robust stability tradeoffs. The interpolating gain-scheduled controller is obtained by interpolating the state space model of the linear time-invariant (LTI) controllers estimated for fixed values of the scheduling parameters and a linear least squares problem can be solved. The proposed controller has been compared with P/PI with velocity and acceleration feedforward and adaptive backstepping sliding mode control experimentally. The experimental results indicate that the tracking performance has been improved and the robustness for time-varying dynamics has been achieved with the proposed scheme. PMID:25592980
Optimum Design of Forging Process Parameters and Preform Shape under Uncertainties
NASA Astrophysics Data System (ADS)
Repalle, Jalaja; Grandhi, Ramana V.
2004-06-01
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.
GA-based optimum design of a shape memory alloy device for seismic response mitigation
NASA Astrophysics Data System (ADS)
Ozbulut, O. E.; Roschke, P. N.; Y Lin, P.; Loh, C. H.
2010-06-01
Damping systems discussed in this work are optimized so that a three-story steel frame structure and its shape memory alloy (SMA) bracing system minimize response metrics due to a custom-tailored earthquake excitation. Multiple-objective numerical optimization that simultaneously minimizes displacements and accelerations of the structure is carried out with a genetic algorithm (GA) in order to optimize SMA bracing elements within the structure. After design of an optimal SMA damping system is complete, full-scale experimental shake table tests are conducted on a large-scale steel frame that is equipped with the optimal SMA devices. A fuzzy inference system is developed from data collected during the testing to simulate the dynamic material response of the SMA bracing subcomponents. Finally, nonlinear analyses of a three-story braced frame are carried out to evaluate the performance of comparable SMA and commonly used steel braces under dynamic loading conditions and to assess the effectiveness of GA-optimized SMA bracing design as compared to alternative designs of SMA braces. It is shown that peak displacement of a structure can be reduced without causing significant acceleration response amplification through a judicious selection of physical characteristics of the SMA devices. Also, SMA devices provide a recentering mechanism for the structure to return to its original position after a seismic event.
NASA Astrophysics Data System (ADS)
Ozen, Murat; Guler, Murat
2014-02-01
Aggregate gradation is one of the key design parameters affecting the workability and strength properties of concrete mixtures. Estimating aggregate gradation from hardened concrete samples can offer valuable insights into the quality of mixtures in terms of the degree of segregation and the amount of deviation from the specified gradation limits. In this study, a methodology is introduced to determine the particle size distribution of aggregates from 2D cross sectional images of concrete samples. The samples used in the study were fabricated from six mix designs by varying the aggregate gradation, aggregate source and maximum aggregate size with five replicates of each design combination. Each sample was cut into three pieces using a diamond saw and then scanned to obtain the cross sectional images using a desktop flatbed scanner. An algorithm is proposed to determine the optimum threshold for the image analysis of the cross sections. A procedure was also suggested to determine a suitable particle shape parameter to be used in the analysis of aggregate size distribution within each cross section. Results of analyses indicated that the optimum threshold hence the pixel distribution functions may be different even for the cross sections of an identical concrete sample. Besides, the maximum ferret diameter is the most suitable shape parameter to estimate the size distribution of aggregates when computed based on the diagonal sieve opening. The outcome of this study can be of practical value for the practitioners to evaluate concrete in terms of the degree of segregation and the bounds of mixture's gradation achieved during manufacturing.
NASA Astrophysics Data System (ADS)
Xu, F.-H.; Oey, L.-Y.; Miyazawa, Y.; Hamilton, P.
2013-09-01
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.
3D shape reconstruction of loop objects in X-ray protein crystallography.
Strutz, Tilo
2011-01-01
Knowledge of the shape of crystals can benefit data collection in X-ray crystallography. A preliminary step is the determination of the loop object, i.e., the shape of the loop holding the crystal. Based on the standard set-up of experimental X-ray stations for protein crystallography, the paper reviews a reconstruction method merely requiring 2D object contours and presents a dedicated novel algorithm. Properties of the object surface (e.g., texture) and depth information do not have to be considered. The complexity of the reconstruction task is significantly reduced by slicing the 3D object into parallel 2D cross-sections. The shape of each cross-section is determined using support lines forming polygons. The slicing technique allows the reconstruction of concave surfaces perpendicular to the direction of projection. In spite of the low computational complexity, the reconstruction method is resilient to noisy object projections caused by imperfections in the image-processing system extracting the contours. The algorithm developed here has been successfully applied to the reconstruction of shapes of loop objects in X-ray crystallography. PMID:20714026
Looped star polymers show conformational transition from spherical to flat toroidal shapes.
Reiss, Pascal; Fritsche, Miriam; Heermann, Dieter W
2011-11-01
Inspired by the topological organization of the circular Escherichia coli chromosome, which is compacted by separate domains, we study a polymer architecture consisting of a central ring to which either looped or linear side chains are grafted. A shape change from a spherical to a toroidal organization takes place as soon as the inner ring becomes large enough for the attached arms to fit within its circumference. Building up a torus, the system flattens, depending on the effective bending rigidity of the chain induced by entropic repulsion of the attached loops and, to a lesser extent, linear arms. Our results suggest that the natural formation of a toroidal structure with a decreased amount of writhe induced by a specific underlying topology could be one driving force, among others, that nature exploits to ensure proper packaging of the genetic material within a rod-shaped, bacterial envelope. PMID:22181447
Shaping of Looped Miniaturized Chalcogenide Fiber Sensing Heads for Mid-Infrared Sensing
Houizot, Patrick; Anne, Marie-Laure; Boussard-PlÃ©del, Catherine; LorÃ©al, Olivier; Tariel, Hugues; Lucas, Jacques; Bureau, Bruno
2014-01-01
Chalcogenide glass fibers are promising photonic tools to develop Fiber Evanescent Wave Spectroscopy (FEWS) optical sensors working in the mid-infrared region. Numerous pioneering works have already been carried out showing their efficiency, especially for bio-medical applications. Nevertheless, this technology remains confined to academic studies at the laboratory scale because chalcogenide glass fibers are difficult to shape to produce reliable, sensitive and compact sensors. In this paper, a new method for designing and fabricating a compact and robust sensing head with a selenide glass fiber is described. Compact looped sensing heads with diameter equal to 2 mm were thus shaped. This represents an outstanding achievement considering the brittleness of such uncoated fibers. FEWS experiments were implemented using alcoholic solutions as target samples showing that the sensitivity is higher than with the routinely used classical fiber. It is also shown that the best compromise in term of sensitivity is to fabricate a sensing head including two full loops. From a mechanical point of view, the breaking loads of the loop shaped head are also much higher than with classical fiber. Finally, this achievement paves the way for the use of mid-infrared technology during in situ and even in vivo medical operations. Indeed, is is now possible to slide a chalcogenide glass fiber in the operating channel of a standard 2.8 mm diameter catheter. PMID:25264953
FREQ: A computational package for multivariable system loop-shaping procedures
NASA Technical Reports Server (NTRS)
Giesy, Daniel P.; Armstrong, Ernest S.
1989-01-01
Many approaches in the field of linear, multivariable time-invariant systems analysis and controller synthesis employ loop-sharing procedures wherein design parameters are chosen to shape frequency-response singular value plots of selected transfer matrices. A software package, FREQ, is documented for computing within on unified framework many of the most used multivariable transfer matrices for both continuous and discrete systems. The matrices are evaluated at user-selected frequency-response values, and singular values against frequency. Example computations are presented to demonstrate the use of the FREQ code.
NASA Technical Reports Server (NTRS)
Fox, S. R.; Smetana, F. O.
1980-01-01
The contributions to the cruise drag of light aircraft arising from the shape of the engine cowl and the forward fuselage area and also that resulting from the cooling air mass flow through intake and exhaust sites on the nacelle were analyzed. The methods employed for the calculation of the potential flow about an arbitrary three dimensional body are described with modifications to include the effects of boundary layer displacement thickness, a nonuniform onset flow field (such as that due to a rotating propeller), and the presence of air intakes and exhausts. A simple, reliable, largely automated scheme to better define or change the shape of a body is also presented. A technique was developed which can yield physically acceptable skin friction and pressure drag coefficients for isolated light aircraft bodies. For test cases on a blunt nose Cessna 182 fuselage, the technique predicted drag reductions as much as 28.5% by body recontouring and proper placements and sizing of the cooling air intakes and exhausts.
NASA Technical Reports Server (NTRS)
Fox, S. R.; Smetana, F. O.
1980-01-01
The listings, user's instructions, sample inputs, and sample outputs of two computer programs which are especially useful in obtaining an approximate solution of the viscous flow over an arbitrary nonlifting three dimensional body are provided. The first program performs a potential flow solution by a well known panel method and readjusts this initial solution to account for the effects of the boundary layer displacement thickness, a nonuniform but unidirectional onset flow field, and the presence of air intakes and exhausts. The second program is effectually a geometry package which allows the user to change or refine the shape of a body to satisfy particular needs without a significant amount of human intervention. An effort to reduce the cruise drag of light aircraft through an analytical study of the contributions to the drag arising from the engine cowl shape and the foward fuselage area and also that resulting from the cooling air mass flowing through intake and exhaust sites on the nacelle is presented. The programs may be effectively used to determine the appropriate body modifications or flow port locations to reduce the cruise drag as well as to provide sufficient air flow for cooling the engine.
Inamura, T; Shimizu, R; Kim, H Y; Miyazaki, S; Hosoda, H
2016-04-01
The rolling rate (r) dependence of textures was investigated in the Ti-26Nb-3Al (mol%) alloy to reveal the conditions required to form the {001}<110> recrystallization texture, which is a desirable orientation for the Î²-titanium shape memory alloy. {001}<110> was the dominant cold-rolling texture when r=90% and it was transferred to the recrystallization texture without forming {112}<110>, which is detrimental for the isotropic mechanical properties of the rolled sheet. A further increase in r resulted in the formation of {112}<110> in both rolling and recrystallization textures. Therefore, r should be controlled to form only the {001}<110> rolling texture, because the {112}<110> texture can overwhelm the {001}<110> texture during recrystallization. PMID:26838877
Schoenly, J.E.; Seka. W.; Rechmann, P.
2010-02-25
A frequency-doubled Ti:sapphire laser is shown to selectively ablate dental calculus. The optimal transverse shape of the laser beam, including its variability under water-cooling, is determined for selective ablation of dental calculus. Intensity profiles under various water-cooling conditions were optically observed. The 400-nm laser was coupled into a multimode optical fiber using an f = 2.5-cm lens and light-shaping diffuser. Water-cooling was supplied coaxially around the fiber. Five human tooth samples (four with calculus and one pristine) were irradiated perpendicular to the tooth surface while the tooth was moved back and forth at 0.3 mm/second, varying between 20 and 180 iterations. The teeth were imaged before and after irradiation using light microscopy with a flashing blue light-emitting diode (LED). An environmental scanning electron microscope imaged each tooth after irradiation. High-order super-Gaussian intensity profiles are observed at the output of a fiber coiled around a 4-in. diameter drum. Super-Gaussian beams have a morehomogenous fluence distribution than Gaussian beams and have a higher energy efficiency for selective ablation. Coaxial water-cooling does not noticeably distort the intensity distribution within 1 mm from the optical fiber. In contrast, lasers focused to a Gaussian cross section (<=50-mm diameter) without fiber propagation and cooled by a water spray are heavily distorted and may lead to variable ablation. Calculus is preferentially ablated at high fluences (>= 2 J/cm^2); below this fluence, stalling occurs because of photo-bleaching of the calculus. Healthy dental hard tissue is not removed at fluences <=3 J/cm^2. Supplying laser light to a tooth using an optical fiber with coaxial water-cooling is determined to be the most appropriate method when selectively removing calculus with a frequency-doubled Ti:sapphire laser. Fluences over 2 J/cm^2 are required to remove calculus efficiently since photo-bleaching stalls calculus removal below that value.
Huang, Tianye; Fu, Songnian; Li, Jia; Chen, Lawrence R; Tang, Ming; Shum, Perry; Liu, Deming
2013-03-11
A reconfigurable impulse radio ultra-wideband (UWB) pulse generator for various UWB shapes (e.g., monocycle, doublet, and triplet pulses) based on a nonlinear optical loop mirror (NOLM) and differential detection is proposed and experimentally demonstrated. The proposed approach can be used with different modulation formats and may be suitable for implementation in future low-cost, high-speed, short-range UWB wireless access applications. PMID:23482210
Son, Byung-Chul; Kim, Deog-Ryeong
2015-01-01
A number of dynamic stabilization systems have been used to overcome the problems associated with spinal fusion with rigid fixation recently and the demand for an ideal dynamic stabilization system is greater for younger patients with multisegment disc degeneration. Nitinol, a shape memory alloy of nickel and titanium, is flexible at low temperatures and regains its original shape when heated, and the Nitinol shape memory loop (SML) implant has been used as a posterior tension band mostly in decompressive laminectomy cases because the Nitinol implant has various characteristics such as high elasticity and a tensile force, flexibility, and biological compatibility. The reported short-term outcomes of the application of SMLs as posterior column supporters in cervical and lumbar decompressive laminectomies seem to be positive, and complications are minimal except for the rare occurrence of pullout and fracture of the SML. However, there was no report of neurological complications related to neural compression in spite of the use of the loop of SML in the epidural space. The authors report a case of delayed development of radiating pain caused by subsidence of the SML resulting epidural compression. PMID:25674347
Kim, Deog-ryeong
2015-01-01
A number of dynamic stabilization systems have been used to overcome the problems associated with spinal fusion with rigid fixation recently and the demand for an ideal dynamic stabilization system is greater for younger patients with multisegment disc degeneration. Nitinol, a shape memory alloy of nickel and titanium, is flexible at low temperatures and regains its original shape when heated, and the Nitinol shape memory loop (SML) implant has been used as a posterior tension band mostly in decompressive laminectomy cases because the Nitinol implant has various characteristics such as high elasticity and a tensile force, flexibility, and biological compatibility. The reported short-term outcomes of the application of SMLs as posterior column supporters in cervical and lumbar decompressive laminectomies seem to be positive, and complications are minimal except for the rare occurrence of pullout and fracture of the SML. However, there was no report of neurological complications related to neural compression in spite of the use of the loop of SML in the epidural space. The authors report a case of delayed development of radiating pain caused by subsidence of the SML resulting epidural compression. PMID:25674347
Youm, Woosub; Jung, Jongkyu; Lee, Sungq; Park, Kyihwan
2008-01-01
The voice coil motor nanoscanner has the advantages of large working range, easy control, and low cost compared to the conventional lead zirconate titanate driven nanoscanner. However, it has a small damping problem which causes mechanical vibration. The mechanical vibration reduces the accuracy as well as servobandwidth, which deteoriates the atomic force microscopy (AFM) image of the samples. In order to solve the vibration problem, the loop shaping technique [for vertical (z)] and input prefilter [for lateral (xy)] are applied. Experimental results of the proposed techniques are presented for vertical (z) and lateral (xy) scanner. Finally, the AFM images are provided to investigate its effect. PMID:18248039
Bafghi, Ali Fatahi; Jebali, Ali; Daliri, Karim
2015-12-01
The main aim of this study was to evaluate the capability of silica nanowire conjugated with loop-shaped oligonucleotides (SNWCLSOs) to silence cysteine proteinase b (Cpb) gene in Leishmania (L) tropica. On the other hand, its toxicity on amastigotes and mouse peritoneal macrophages was evaluated by 5-diphenyl-tetrazolium bromide (MTT) assay. For control, two loop-shaped oligonucleotides (LSO) were considered. LSO1 and LSO2 were 5'-NH2-cccccaaaaaaaaaaaaaaaaaaaaaaaaaggggg-COOH-3' and LSO2: 5'-NH2-cccccttttttttttttttttttttttttttttttttttttttggggg-COOH-3', respectively. After 72h incubation at 37°C, AMSNW, LSO1, and LSO2 had no remarkable toxicity on L. tropica amastigote (2×10(5)/mL) and mouse peritoneal macrophages (2×10(5)/mL). In case of SNWCLSOs, they had high toxicity on L. tropica amastigote, but they had no effect on mouse peritoneal macrophages. At concentrations of 1, 10, and 25?g/mL, AMSNW, LSO1 and LSO2 had no effect on the gene expression. But, at concentration of 50 and 100?g/mL, decrease of gene expression was observed. In case of SNWCLSOs, they could dramatically decrease the gene expression. It could be concluded that since SNWCLSOs could silence Cpb gene with no remarkable toxicity, they are good choice for treat cutaneous leishmaniasis in future. As a new agent, it must be checked in vivo. PMID:26432619
NASA Technical Reports Server (NTRS)
Connolly, Joseph W.; Kopasakis, George
2010-01-01
This paper covers the propulsion system component modeling and controls development of an integrated mixed compression inlet and turbojet engine that will be used for an overall vehicle Aero-Propulso-Servo-Elastic (APSE) model. Using previously created nonlinear component-level propulsion system models, a linear integrated propulsion system model and loop shaping control design have been developed. The design includes both inlet normal shock position control and jet engine rotor speed control for a potential supersonic commercial transport. A preliminary investigation of the impacts of the aero-elastic effects on the incoming flow field to the propulsion system are discussed, however, the focus here is on developing a methodology for the propulsion controls design that prevents unstart in the inlet and minimizes the thrust oscillation experienced by the vehicle. Quantitative Feedback Theory (QFT) specifications and bounds, and aspects of classical loop shaping are used in the control design process. Model uncertainty is incorporated in the design to address possible error in the system identification mapping of the nonlinear component models into the integrated linear model.
Z-shaped duodenojejunal loop: sign of mesenteric fixation anomaly and congenital bands.
Ablow, R C; Hoffer, F A; Seashore, J H; Touloukian, R J
1983-09-01
Four children (ages 3-9 years) with intermittent abdominal pain and vomiting are reported. Upper gastrointestinal examinations revealed a sharply angulated to-and-fro course (Z configuration) of the distal duodenum and proximal jejunum, rather than the usual smooth duodenojejunal loop at the ligament of Treitz. At operation this configuration was associated with broad peritoneal bands extending across the involved small intestine without an accompanying volvulus at this level. The Z sign is diagnostic of incomplete rotation, even in the absence of duodenal obstruction and with a proximal jejunum that may appear to be properly placed. PMID:6603751
Influence of fourfold anisotropy form on hysteresis loop shape in ferromagnetic nanostructures
Ehrmann, Andrea; Blachowicz, Tomasz
2014-08-15
The dependence of the form of different mathematical depictions of fourfold magnetic anisotropies has been examined, using a simple macro-spin model. Strong differences in longitudinal and transverse hysteresis loops occur due to deviations from the usual phenomenological model, such as using absolute value functions. The proposed possible models can help understanding measurements on sophisticated magnetic nanosystems, like exchange bias layered structures employed in magnetic hard disk heads or magnetic nano-particles, and support the development of solutions with specific magnetization reversal behavior needed in novel magneto-electronic devices.
Tethered towing using open-loop input-shaping and discrete thrust levels
NASA Astrophysics Data System (ADS)
Jasper, Lee; Schaub, Hanspeter
2014-12-01
Asteroid retrieval, satellite servicing, and debris removal concepts often rely on a thrusting vehicle to redirect and steer a passive object. One effective way to tow the object is through a tether. This study employs a discretized tether model attached to six degree-of-freedom end bodies. To reduce the risk of a post-burn collision between the end bodies, discrete thrust input shaping profiles are considered including a Posicast input and a bang-off-bang thrust profile. These input shaping techniques attain desirable collision avoidance performance by inducing a tumbling or gravity gradient motion of the tethered formation. Their performance is compared to an earlier frequency notched thruster profile.
H? Loop Shaping Control for Plasma Vertical Position Instability on QUEST
NASA Astrophysics Data System (ADS)
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
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.
NASA Astrophysics Data System (ADS)
Mather, Amanda L.; Johnson, Richard L.
2014-10-01
Turbidity behavior in streams is a complex and dynamic function of both source material supply and event-driven transport. While the primary controls on turbidity behavior across time and space are still not fully understood, recent increases in the availability of high temporal resolution, colocated stream turbidity, and discharge data provide an opportunity for more detailed analysis. Here we examine methods to quantitatively characterize event responses by modeling the shape of turbidity-discharge hysteresis loops. A total of 1559 events from 20 gages in the Mid-Atlantic region of the U.S. were modeled using both previously reported models and new models combining elements of existing models. The results suggest that a more general power law-based model, utilizing both a discharge rate of change term and a "supply" term, allows characterization of a wide range of simple and complex events. Additionally, this study explores a decorrelation approach to address the strong correlation frequently observed between the power law model coefficient (a) and exponent (b), with the goal of exposing the underlying behavior of each parameter individually. An examination of seasonal parameter behavior suggests that this approach may facilitate greater physically based interpretation of the power law coefficient. The power law parameter decorrelation strategy and the loop models examined here provide a step toward the larger goal of understanding the physical controls on turbidity-discharge hysteretic behavior.
Closed-loop decoder adaptation shapes neural plasticity for skillful neuroprosthetic control.
Orsborn, Amy L; Moorman, Helene G; Overduin, Simon A; Shanechi, Maryam M; Dimitrov, Dragan F; Carmena, Jose M
2014-06-18
Neuroplasticity may play a critical role in developing robust, naturally controlled neuroprostheses. This learning, however, is sensitive to system changes such as the neural activity used for control. The ultimate utility of neuroplasticity in real-world neuroprostheses is thus unclear. Adaptive decoding methods hold promise for improving neuroprosthetic performance in nonstationary systems. Here, we explore the use of decoder adaptation to shape neuroplasticity in two scenarios relevant for real-world neuroprostheses: nonstationary recordings of neural activity and changes in control context. Nonhuman primates learned to control a cursor to perform a reaching task using semistationary neural activity in two contexts: with and without simultaneous arm movements. Decoder adaptation was used to improve initial performance and compensate for changes in neural recordings. We show that beneficial neuroplasticity can occur alongside decoder adaptation, yielding performance improvements, skill retention, and resistance to interference from native motor networks. These results highlight the utility of neuroplasticity for real-world neuroprostheses. PMID:24945777
Hiraga, F
2015-12-01
The beam-shaping assembly for boron neutron capture therapies with a compact accelerator-driven subcritical neutron multiplier was designed so that an epithermal neutron flux of 1.9×10(9) cm(-2) s(-1) at the treatment position was generated by 5 MeV protons in a beam current of 2 mA. Changes in the atomic density of (135)Xe in the nuclear fuel due to the operation of the beam-shaping assembly were estimated. The criticality safety of the beam-shaping assembly in terms of Xe poisoning is discussed. PMID:26235186
Michail, Konstantinos; Zolotas, Argyrios C; Goodall, Roger M
2014-01-01
This paper presents a systematic design framework for selecting the sensors in an optimised manner, simultaneously satisfying a set of given complex system control requirements, i.e. optimum and robust performance as well as fault tolerant control for high integrity systems. It is worth noting that optimum sensor selection in control system design is often a non-trivial task. Among all candidate sensor sets, the algorithm explores and separately optimises system performance with all the feasible sensor sets in order to identify fallback options under single or multiple sensor faults. The proposed approach combines modern robust control design, fault tolerant control, multiobjective optimisation and Monte Carlo techniques. Without loss of generality, it's efficacy is tested on an electromagnetic suspension system via appropriate realistic simulations. PMID:24041402
NASA Astrophysics Data System (ADS)
Vachirasricirikul, Sitthidet; Ngamroo, Issarachai; Kaitwanidvilai, Somyot
It is well known that the power system controller designed by H? control is complicated, high order and impractical. In power system applications, practical structures such as proportional integral derivative (PID) etc., are widely used, because of their simple structure, less number of tuning parameters and low-order. However, tuning of controller parameters to achieve a good performance and robustness is based on designer's experiences. To overcome this problem, this paper proposes a fixed structure robust H? loop shaping control to design Static Var Compensator (SVC) and Automatic Voltage Regulator (AVR) for robust stabilization of voltage fluctuation in an isolated wind-diesel hybrid power system. The structure of the robust controller of SVC and AVR is specified by a PID controller. In the system modeling, a normalized coprime factorization is applied to represent possible unstructured uncertainties in the power system such as variation of system parameters, generating and loading conditions etc. Based on the H? loop shaping, the performance and robust stability conditions are formulated as the optimization problem. The particle swarm optimization is applied to solve for PID control parameters of SVC and AVR simultaneously. Simulation studies confirm the control effect and robustness of the proposed control.
Optimum propeller wind turbines
NASA Astrophysics Data System (ADS)
Sanderson, R. J.; Archer, R. D.
1983-12-01
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.
Optimum propeller wind turbines
Sanderson, R.J.; Archer, R.D.
1983-11-01
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.
Interactions of Cations with RNA Loop-Loop Complexes
Singh, Abhishek; Sethaphong, Latsavongsakda; Yingling, YaroslavaÂ G.
2011-01-01
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. PMID:21806941
Optimum constrained image restoration filters
NASA Technical Reports Server (NTRS)
Riemer, T. E.; Mcgillem, C. D.
1974-01-01
The filter was developed in Hilbert space by minimizing the radius of gyration of the overall or composite system point-spread function subject to constraints on the radius of gyration of the restoration filter point-spread function, the total noise power in the restored image, and the shape of the composite system frequency spectrum. An iterative technique is introduced which alters the shape of the optimum composite system point-spread function, producing a suboptimal restoration filter which suppresses undesirable secondary oscillations. Finally this technique is applied to multispectral scanner data obtained from the Earth Resources Technology Satellite to provide resolution enhancement. An experimental approach to the problems involving estimation of the effective scanner aperture and matching the ERTS data to available restoration functions is presented.
Boyer, M. D.; Andre, R.; Gates, David A.; Gerhardt, S.; Goumiri, I. R.; Menard, Jon
2014-08-01
The high-performance operational goals of NSTX-U will require development of advanced feedback control algorithms, including control of ÃŸN and the safety factor profile. In this work, a novel approach to simultaneously controlling #12;ÃŸN and the value of the safety factor on the magnetic axis, q0, through manipulation of the plasma boundary shape and total beam power, is proposed. Simulations of the proposed scheme show promising results and motivate future experimental implementation and eventual integration into a more complex current profile control scheme planned to include actuation of individual beam powers, density, and loop voltage. As part of this work, a flexible framework for closed loop simulations within the high-fidelity code TRANSP was developed. The framework, used here to identify control-design-oriented models and to tune and test the proposed controller, exploits many of the predictive capabilities of TRANSP and provides a means for performing control calculations based on user-supplied data (controller matrices, target waveforms, etc.). The flexible framework should enable high-fidelity testing of a variety of control algorithms, thereby reducing the amount of expensive experimental time needed to implement new control algorithms on NSTX-U and other devices.
NASA Astrophysics Data System (ADS)
Boyer, M. D.; Andre, R.; Gates, D. A.; Gerhardt, S.; Goumiri, I. R.; Menard, J.
2015-05-01
The high-performance operational goals of NSTX-U will require development of advanced feedback control algorithms, including control of ?N and the safety factor profile. In this work, a novel approach to simultaneously controlling ?N and the value of the safety factor on the magnetic axis, q0, through manipulation of the plasma boundary shape and total beam power, is proposed. Simulations of the proposed scheme show promising results and motivate future experimental implementation and eventual integration into a more complex current profile control scheme planned to include actuation of individual beam powers, density, and loop voltage. As part of this work, a flexible framework for closed loop simulations within the high-fidelity code TRANSP was developed. The framework, used here to identify control-design-oriented models and to tune and test the proposed controller, exploits many of the predictive capabilities of TRANSP and provides a means for performing control calculations based on user-supplied data (controller matrices, target waveforms, etc). The flexible framework should enable high-fidelity testing of a variety of control algorithms, thereby reducing the amount of expensive experimental time needed to implement new control algorithms on NSTX-U and other devices.
Optimum constrained image restoration filters
NASA Technical Reports Server (NTRS)
Riemer, T. E.; Mcgillem, C. D.
1977-01-01
The research described centered on development of an optimum image restoration filter (IRF) minimizing the radius of gyration of the corrected or composite system point-spread function (P-SF) subject to contraints, and reducing 2-dimensional spatial smearing or blurring of an image. The constraints are imposed on the radius of gyration of the IRF P-SF, the total restored image noise power, and the shape of the composite system frequency spectrum. The image degradation corresponds to mapping many points from the original image into a single resolution element. The P-SF is obtained as solution to a set of simultaneous differential equations obeying nonlinear integral constraints. Truncation errors due to edge effects are controlled by constraining the radius of gyration of the IRF P-SF. An iterative technique suppresses sidelobes of the composite system P-SF.
Schuldberg, David
2015-10-01
Guastello (2015a) opened the call for articles for this issue with Goldberger (1991) and colleagues' findings of chaotic variability in healthy heart rate, noting, 'the principle of healthy variability has extended to other biomedical and psychological phenomena.' He suggests a dialectical underpinning for optimal variability involving 'a combination of the minimum entropy or free energy principle that pushes in a downward direction, and Ashby's Law of Requisite Variety that pushes in an upward direction.' Each of the papers in this issue addresses optimal variability across a variety of health-related areas. The present article surveys these seven papers in relation to five conceptual questions about optimal variability: (a) Is variability a positive or a negative, and how are positive things related to health? (b) How shall we define and measure variability? (c) What constitutes an optimum, and how do we locate one? (d) What is the relationship between optimum variability and health? Finally, it touches on (e) What are underlying principles and phenomena behind healthy variability, and can they inform our vocabulary for health? The paper concludes by discussing practical approaches to dealing with optimization. PMID:26375940
Regulative Loops, Step Loops and Task Loops
ERIC Educational Resources Information Center
VanLehn, Kurt
2016-01-01
This commentary suggests a generalization of the conception of the behavior of tutoring systems, which the target article characterized as having an outer loop that was executed once per task and an inner loop that was executed once per step of the task. A more general conception sees these two loops as instances of regulative loops, whichâ€¦
Achieving optimum pump performance
Henderson, E.D.
1996-05-01
Troublesome pump installations are an all to often occurrence. When a problem does happen, how can one determine if it is caused by the pump, valve, piping system, motor, or power supply? Most failures are related to the system the pump supplies. Because of the diversity of applications, it is helpful to have a problem-solving method that works everywhere. It is useful to understand pump curves and have a procedure to set and control pump output to match system requirements. Pump curves, pressure and temperature gauges, and simple formulas can be used to calculate the optimum performance point for a pump, as related to a system. There are three factors involved in a pump operating characteristic: flow, pressure, and arc of the pump curve. This paper discusses these operating characteristics and pump performance.
NASA Astrophysics Data System (ADS)
Cho, Hee Keun
The thesis describes advanced design techniques for composites associated with stress concentrations, buckling and dynamic behaviors. Due to a common presence of geometric discontinuities such as holes and notches and diverse operating environments, the research focuses on optimizing the design of perforated composites to reduce stress concentrations, increase buckling resistance and enhance their dynamic performance when operating in hygrothermal environments. Total Lagrangian nonlinear static, buckling and hygrothermal dynamic FEA formulation procedures for both 3D solid and laminated composite shell elements are newly established and their accuracies verified. Optimum design is achieved here primarily by synergizing finite element analysis (FEA) with a probabilistic evolutionary genetic algorithm (GA). This approach is well suited for enhancing the response of orthotropic and/or laminated composites which involve many design variables. Recognizing ability of the stiffness in the neighborhood of geometric discontinuities to influence composite performance, fiber directions within both individual finite elements and individual plies are optimized locally utilizing an integrated GA-FEA parallel numerical system. Results demonstrates the current approach is superior to more conventional design techniques such as modifying ply thickness or the stacking sequence of individual rectilinear plies.
Dutta, Mouparna; Kar, Debasish; Bansal, Ankita; Chakraborty, Sandeep; Ghosh, Anindya S
2015-04-01
Penicillin-binding protein 5 (PBP5), a dd-carboxypeptidase, maintains cell shape and intrinsic beta-lactam resistance in E. coli. A strain lacking PBP5 loses intrinsic beta-lactam resistance and simultaneous lack of two other PBPs results in aberrantly shaped cells. PBP5 expression in trans complements the shape and restores the lost beta-lactam resistance. PBP5 has an 'Î©-loop'-like region similar to that in class A beta-lactamases. It was previously predicted that Leu182 present in the 'Î©-like' loop of PBP5 corresponds to Glu166 in PER-1 beta-lactamase. Here, we studied the physiological and biochemical effects of the Leu182Glu mutation in PBP5. Upon overexpression in septuple PBP mutants, ~75â€Š% of cells were abnormally shaped and intrinsic beta-lactam resistance maintenance was partially lost. Biochemically, the purified soluble mutated PBP5 (smPBP5) retained low acylation ability for penicillin. The turnover number of smPBP5 for artificial and peptidoglycan mimetic substrates was ~10-fold less than that of the wild-type. Superimposition of the active-site residues of smPBP5 on PBP5 revealed that perturbation in the orientating key residues may explain the low turnover numbers. Therefore, we establish the involvement of Leu182 in maintaining the physiological and biochemical behaviour of E. coli PBP5. PMID:25667006
OPTIMUM PLASMA STATES FOR NEXT STEP TOKAMAKS
LIN-LIU,YR; STAMBAUGH,RD
2002-11-01
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.
Malanushenko, A.; Longcope, D. W.; McKenzie, D. E.
2009-12-20
Nonlinear force-free fields are the most general case of force-free fields, but the hardest to model as well. There are numerous methods of computing such fields by extrapolating vector magnetograms from the photosphere, but very few attempts have so far made quantitative use of coronal morphology. We present a method to make such quantitative use of X-ray and EUV images of coronal loops. Each individual loop is fit to a field line of a linear force-free field, allowing the estimation of the field line's twist, three-dimensional geometry, and the field strength along it. We assess the validity of such a reconstruction since the actual corona is probably not a linear force-free field, and that the superposition of linear force-free fields is generally not itself a force-free field. To do so, we perform a series of tests on nonlinear force-free fields, described in Low and Lou. For model loops we project field lines onto the photosphere. We compare several results of the method with the original field, in particular the three-dimensional loop shapes, local twist (coronal alpha), distribution of twist in the model photosphere, and strength of the magnetic field. We find that (1) for these trial fields, the method reconstructs twist with a mean absolute deviation of at most 15% of the range of photospheric twist, (2) heights of the loops are reconstructed with a mean absolute deviation of at most 5% of the range of trial heights, and (3) the magnitude of non-potential contribution to a photospheric field is reconstructed with a mean absolute deviation of at most 10% of the maximal value.
Optimum performance and potential flow field of hovering rotors
NASA Technical Reports Server (NTRS)
Wu, J. C.; Sigman, R. K.
1975-01-01
Rotor and propeller performance and induced potential flowfields were studied on the basis of a rotating actuator disk concept, with special emphasis on rotors hovering out of ground effect. A new theory for the optimum performance of rotors hovering OGE is developed and presented. An extended theory for the optimum performance of rotors and propellers in axial motion is also presented. Numerical results are presented for the optimum distributions of blade-bound circulation together with axial inflow and ultimate wake velocities for the hovering rotor over the range of thrust coefficient of interest in rotorcraft applications. Shapes of the stream tubes and of the velocities in the slipstream are obtained, using available methods, for optimum and off-optimum circulation distributions for rotors hovering in and out of ground effect. A number of explicit formulae useful in computing rotor and propeller induced flows are presented for stream functions and velocities due to distributions of circular vortices over axi-symmetric surfaces.
Optimum strong-motion array geometry for source inversion - II
Iida, M.
1990-01-01
Optimum strong-motion array geometry for source inversions is determined for each of three types of earthquake faults: strike-slip, dip-slip and offshore subduction thrust. It is found that the complete Green's function is capable of stabilizing the accuracy of an inversion solution obtained using theoretical seismograms, regardless of the differences in array configuration. The optimum strong-motion array for a strike-slip fault is characterized by stations well distributed in azimuth, while the optimum array for a dip-slip event has stations arranged in a grid-shaped form. -from Author
FISHER'S GEOMETRIC MODEL WITH A MOVING OPTIMUM
Matuszewski, Sebastian; Hermisson, Joachim; Kopp, Michael
2014-01-01
Fisher's geometric model has been widely used to study the effects of pleiotropy and organismic complexity on phenotypic adaptation. Here, we study a version of Fisher's model in which a population adapts to a gradually moving optimum. Key parameters are the rate of environmental change, the dimensionality of phenotype space, and the patterns of mutational and selectional correlations. We focus on the distribution of adaptive substitutions, that is, the multivariate distribution of the phenotypic effects of fixed beneficial mutations. Our main results are based on an “adaptive-walk approximation,” which is checked against individual-based simulations. We find that (1) the distribution of adaptive substitutions is strongly affected by the ecological dynamics and largely depends on a single composite parameter ?, which scales the rate of environmental change by the “adaptive potential” of the population; (2) the distribution of adaptive substitution reflects the shape of the fitness landscape if the environment changes slowly, whereas it mirrors the distribution of new mutations if the environment changes fast; (3) in contrast to classical models of adaptation assuming a constant optimum, with a moving optimum, more complex organisms evolve via larger adaptive steps. PMID:24898080
Optimum balancing of flexible rotor
NASA Astrophysics Data System (ADS)
Liu, Qizhou; Tao, Xiande
1992-10-01
A new criterion for optimum balancing of a flexible rotor is introduced, which is the minimum rotor strain energy criterion with constraints. This criterion meets the requirements for integral design of structure strength and performance of a gas turbine aeroengine. In this criterion, the balance correction masses (quantity and orientation) are the optimum design variable, the objective function of optimization is the total strain energy of the rotor and its supports. The response amplitudes at several cross sections along the rotor are taken as its constraints. The Powell's method and the net random-ray method are chosen as optimum methods. A program is written with FORTRAN 77 for the whole optimization procedure. The program has been testified by a numerical example in comparison with its experiments.
Electromagnetic inductive models for the loop-loop flaring interaction
NASA Astrophysics Data System (ADS)
Khodachenko, M.; Rucker, H.
2003-04-01
The solar corona is a highly structured medium. Coronal loops, which trace closed magnetic field lines, are the primary structural elements. These loops are the evolving non-stationary objects growing up and changing their shape. Complex dynamics of the loops together with action of possible under-photospheric dynamo mechanisms cause the majority of coronal magnetic loops to be very likely as the current-carrying ones. In that connection none of the loops can be considered as isolated from the surroundings. Moving relative each other current-carrying loops should interact via the magnetic field and currents. The simplest way to take account of this interaction consists in application of the equivalent electric circuit models of the loops. In these models each loop in the group is considered as an electric circuit with variable parameters (resistance, inductive coefficients) which depend on the geometry of the loop and its position with respect to neighbouring loops. Plasma parameters in the magnetic tube as well influence the electric characteristics of the equivalent circuit. It follows from observations that a large number of flares occurs in the regions where a new magnetic loop emerges and interacts with the existing loops. Such events are known as the "interacting flare loops". Here we present further development of the idea of the flaring loop-loop inductive interaction, which was first suggested by Melrose [1] and later applied by Aschwanden et al. [2] for interpretation of observations. In addition to [1] and [2], we note that relative motion of the loops before their reconnection creates significant inductive electromotive forces in their electric circuits which appear as a powerful source for changing the currents in the loops. Change of the currents disturbs the pre-existed thermal equilibrium of the loops and results in a change of the plasma temperature, which in its turn influences the resistivity of the circuit and the radiative energy losses. Each of the interacting flaring magnetic loops in our model is described by two equations: the equation for the equivalent electric circuit, which describes dynamics of the total longitudinal electric current in the loop, and the energy equation. By means of our model we describe the processes of fast, flare-like, plasma temperature increase in the inductively connected growing magnetic loops as well as run-away electrons acceleration in the loops by inductive electric fields. [0.8cm] References Melrose, D.B., 1997, ApJ, 486, 521. Aschwanden, M.J., Kosugi, T., Hanaoka, Y., Nishio, M., Melrose, D.B.,1999, ApJ, 526, 1026.
Performance characteristics of aerodynamically optimum turbines for wind energy generators
NASA Technical Reports Server (NTRS)
Rohrbach, C.; Worobel, R.
1975-01-01
This paper presents a brief discussion of the aerodynamic methodology for wind energy generator turbines, an approach to the design of aerodynamically optimum wind turbines covering a broad range of design parameters, some insight on the effect on performance of nonoptimum blade shapes which may represent lower fabrication costs, the annual wind turbine energy for a family of optimum wind turbines, and areas of needed research. On the basis of the investigation, it is concluded that optimum wind turbines show high performance over a wide range of design velocity ratios; that structural requirements impose constraints on blade geometry; that variable pitch wind turbines provide excellent power regulation and that annual energy output is insensitive to design rpm and solidity of optimum wind turbines.
Towards optimum demodulation of bandwidth-limited and low SNR square-wave subcarrier signals
NASA Technical Reports Server (NTRS)
Feria, Y.; Hurd, W.
1995-01-01
The optimum phase detector is presented for tracking square-wave subcarriers that have been bandwidth limited to a finite number of harmonics. The phase detector is optimum in the sense that the loop signal-to-noise ratio (SNR) is maximized and, hence, the rms phase tracking error is minimized. The optimum phase detector is easy to implement and achieves substantial improvement. Also presented are the optimum weights to combine the signals demodulated from each of the harmonics. The optimum weighting provides SNR improvement of 0.1 to 0.15 dB when the subcarrier loop SNR is low (15 dB) and the number of harmonics is high (8 to 16).
NASA Astrophysics Data System (ADS)
Belloli, Alberto; Ermanni, Paolo
2007-10-01
The vibration suppression efficiency of so-called shunted piezoelectric systems is decisively influenced by the number, shape, dimensions and position of the piezoelectric ceramic elements integrated into the structure. This paper presents a procedure based on evolutionary algorithms for optimum placement of piezoelectric ceramic modules on highly constrained lightweight structures. The optimization loop includes the CAD software CATIA V5, the FE package ANSYS and DynOPS, a proprietary software tool able to connect the Evolving Object library with any simulation software that can be started in batch mode. A user-defined piezoelectric shell element is integrated into ANSYS 9.0. The generalized electromechanical coupling coefficient is used as the optimization objective. Position, dimensions, orientation, embedding location in the composite lay-up and wiring of customized patches are determined for optimum vibration suppression under consideration of operational and manufacturing constraints, such as added mass, maximum strain and requirements on the control circuit. A rear wing of a racing car is investigated as the test object for complex, highly constrained geometries.
OPTIMUM FREQUENCY OF CALIBRATION MONITORING
The paper develops an algorithm by which to compute the optimal frequency of calibration monitoring to minimize the total cost of analyzing a set of samples and the required calibration standards. Optimum calibration monitoring is needed because of the high cost and calibration d...
Optimum designs for superpressure balloons
NASA Astrophysics Data System (ADS)
Smith, M. S.; Rainwater, E. L.
2004-01-01
The elastica shape is now well known to be the best basic shape for superpressure balloon design. This shape, also known as the pumpkin, or natural shape for balloons, has been well understood since the early 1900s when it was applied to the determination of the shape of descending parachutes. The elastica shape was also investigated in the 1950s when high strength films were used to produce superpressure cylinder balloons. The need for uniform stress distribution in shells of early superpressure balloons led to a long period of the development of spherical superpressure balloons. Not until the late 1970s was the elastica shape revisited for the purpose of the producing superpressure balloons. This paper will review various development efforts in the field of superpressure design and will elaborate on the current state-of-the-art with suggestions for future developments.
Determination of optimum plan forms for control surfaces
NASA Technical Reports Server (NTRS)
Jones, Robert T; Cohen, Doris
1942-01-01
Solutions found for a range of airfoil plan forms indicate that, regardless of the characteristics of the tail surface, the chord of the rudder or of the elevator should be very nearly constant over its span. The optimum ailerons are also of a characteristic shape, varying little with the plan form of the wing.
Optimum windmill-site matching
Salameh, Z.M.; Safari, I. )
1992-12-01
In this paper a methodology for the selection of the optimum windmill for a specific site is developed. The selection windmill for a specific site is developed. The selection is based on finding the capacity factors (CF) of the available windmills. This is done by using long term wind speed data recorded at different hours of the day for many years. This data is then used to generate mean wind speeds for a typical day in a month. Probability density functions for the mean wind speeds for the different hours of the day are generated with the manufacturer's specifications on windmills used to calculate the capacity factors for the windmills. The windmill with the highest average capacity factor for the specific site is the optimum one and to be recommended.
Optimum performance of hovering rotors
NASA Technical Reports Server (NTRS)
Wu, J. C.; Goorjian, P. M.
1972-01-01
A theory for the optimum performance of a rotor hovering out of ground effect is developed. The performance problem is formulated using general momentum theory for an infinitely bladed rotor, and the effect of a finite number of blades is estimated. The analysis takes advantage of the fact that a simple relation exists between the radial distributions of static pressure and angular velocity in the ultimate wake, far downstream of the rotor, since the radial velocity vanishes there. This relation permits the establishment of an optimum performance criterion in terms of the ultimate wake velocities by introducing a small local perturbation of the rotational velocity and requiring the resulting ratio of thrust and power changes to be independent of the radial location of the perturbation. This analysis fully accounts for the changes in static pressure distribution and axial velocity distribution throughout the wake as the result of the local perturbation of the rotational velocity component.
Chemical Looping Technology: Oxygen Carrier Characteristics.
Luo, Siwei; Zeng, Liang; Fan, Liang-Shih
2015-01-01
Chemical looping processes are characterized as promising carbonaceous fuel conversion technologies with the advantages of manageable CO2 capture and high energy conversion efficiency. Depending on the chemical looping reaction products generated, chemical looping technologies generally can be grouped into two types: chemical looping full oxidation (CLFO) and chemical looping partial oxidation (CLPO). In CLFO, carbonaceous fuels are fully oxidized to CO2 and H2O, as typically represented by chemical looping combustion with electricity as the primary product. In CLPO, however, carbonaceous fuels are partially oxidized, as typically represented by chemical looping gasification with syngas or hydrogen as the primary product. Both CLFO and CLPO share similar operational features; however, the optimum process configurations and the specific oxygen carriers used between them can vary significantly. Progress in both CLFO and CLPO is reviewed and analyzed with specific focus on oxygen carrier developments that characterize these technologies. PMID:25898071
Optical microfiber loop resonator
NASA Astrophysics Data System (ADS)
Sumetsky, M.; Dulashko, Y.; Fini, J. M.; Hale, A.
2005-04-01
We experimentally demonstrate an optical microfiber loop resonator. The resonator was formed in free space by creating a loop from the subwavelength-diameter waist of a short biconical optical fiber taper. The loop length was chosen so that the free spectrum range of the resonator was ˜100GHz at the optical communication wavelengths near 1.5?m. In order to change and optimize the spectral characteristics such as the effect of birefringence, the shape of resonances, and the free spectrum range, we manually varied the microfiber self-coupling by alignment of the input and output ends of the loop, which were attached to each other by Van der Waals and electrostatic forces. In particular, we tuned the microfiber loop resonator to exhibit resonances with a Q-factor exceeding 15 000 (finesse ?10) and, also, to the regime of critical coupling with the extinction ratio of transmission oscillations exceeding 34dB. This paper was in press when we achieved the values of 95 000 and 630 000 for the loaded and intrinsic Q-factor, respectively (see note added in proof). We believe that the demonstrated Q-factor can be significantly enhanced with the more uniform microfiber.
Swarms: Optimum aggregations of spacecraft
NASA Technical Reports Server (NTRS)
Mayer, H. L.
1980-01-01
Swarms are aggregations of spacecraft or elements of a space system which are cooperative in function, but physically isolated or only loosely connected. For some missions the swarm configuration may be optimum compared to a group of completely independent spacecraft or a complex rigidly integrated spacecraft or space platform. General features of swarms are induced by considering an ensemble of 26 swarms, examples ranging from Earth centered swarms for commercial application to swarms for exploring minor planets. A concept for a low altitude swarm as a substitute for a space platform is proposed and a preliminary design studied. The salient design feature is the web of tethers holding the 30 km swarm in a rigid two dimensional array in the orbital plane. A mathematical discussion and tutorial in tether technology and in some aspects of the distribution of services (mass, energy, and information to swarm elements) are included.
Warne, Larry Kevin; Lucero, Larry Martin; Langston, William L.; Salazar, Robert Austin; Coleman, Phillip Dale; Basilio, Lorena I.; Bacon, Larry Donald
2012-05-01
This report estimates inductively-coupled energy to a low-impedance load in a loop-to-loop arrangement. Both analytical models and full-wave numerical simulations are used and the resulting fields, coupled powers and energies are compared. The energies are simply estimated from the coupled powers through approximations to the energy theorem. The transmitter loop is taken to be either a circular geometry or a rectangular-loop (stripline-type) geometry that was used in an experimental setup. Simple magnetic field models are constructed and used to estimate the mutual inductance to the receiving loop, which is taken to be circular with one or several turns. Circuit elements are estimated and used to determine the coupled current and power (an equivalent antenna picture is also given). These results are compared to an electromagnetic simulation of the transmitter geometry. Simple approximate relations are also given to estimate coupled energy from the power. The effect of additional loads in the form of attached leads, forming transmission lines, are considered. The results are summarized in a set of susceptibility-type curves. Finally, we also consider drives to the cables themselves and the resulting common-to-differential mode currents in the load.
ERIC Educational Resources Information Center
Woodward, Tessa
2003-01-01
Discusses loop input, a specific type of experiential teacher training process that involves an alignment of the process and content of learning. This concept has gradually gained ground in English language teacher training since 1986 when the term was coined. (Author/VWL)
Dynamic Aperture-based Solar Loop Segmentation
NASA Technical Reports Server (NTRS)
Lee, Jon Kwan; Newman, Timothy S.; Gary, G. Allen
2006-01-01
A new method to automatically segment arc-like loop structures from intensity images of the Sun's corona is introduced. The method constructively segments credible loop structures by exploiting the Gaussian-like shape of loop cross-sectional intensity profiles. The experimental results show that the method reasonably segments most of the well-defined loops in coronal images. The method is only the second published automated solar loop segmentation method. Its advantage over the other published method is that it operates independently of supplemental time specific data.
The optimum hypersonic wind tunnel
NASA Technical Reports Server (NTRS)
Trimmer, L. L.; Cary, A., Jr.; Voisinet, R. L. P.
1986-01-01
The capabilities of existing hypersonic wind tunnels in the U.S. are assessed to form a basis for recommendations for a new, costly facility which would provide data for modeling the hypervelocity aerodynamics envisioned for the new generation of aerospace vehicles now undergoing early studies. Attention is given to the regimes, both entry and aerodynamic, which the new vehicles will encounter, and the shortcomings of data generated for the Orbiter before flight are discussed. The features of foreign-gas, impulse, aeroballistic range, arc-heated and combustion-heated facilities are examined, noting that in any hypersonic wind tunnel the flow must be preheated to prevent liquefaction upon expansion in the test channel. The limitations of the existing facilities and the identification of the regimes which must be studied lead to a description of the characteristics of an optimum hypersonic wind tunnel, including the operations and productivity, the instrumentation, the nozzle design and the flow quality. Three different design approaches are described, each costing at least $100 million to achieve workability.
Bryce Canyon's Navajo Loop Trail
Views along the Navajo Loop Trail in Bryce Canyon National Park. Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandston...
Optimum reentry trajectories of a lifting vehicle
NASA Technical Reports Server (NTRS)
Chern, J. S.; Vinh, N. X.
1980-01-01
Research results are presented of an investigation of the optimum maneuvers of advanced shuttle type spacecraft during reentry. The equations are formulated by means of modified Chapman variables resulting in a general set of equations for flight analysis which are exact for reentry and for flight in a vacuum. Four planar flight typical optimum manuevers are investigated. For three-dimensional flight the optimum trajectory for maximum cross range is discussed in detail. Techniques for calculating reentry footprints are presented.
Concepts for generating optimum vertical flight profiles
NASA Technical Reports Server (NTRS)
Sorensen, J. A.
1979-01-01
Algorithms for generating optimum vertical profiles are derived and examined. These algorithms form the basis for the design of onboard flight management concepts. The variations in the optimum vertical profiles (resulting from these concepts) due to variations in wind, takeoff weight, and range-to-destination are presented. Further considerations for mechanizing two different onboard methods of computing near-optimum flight profiles are then outlined. Finally, the results are summarized, and recommendations are made for further work. Technical details of optimum trajectory design, steering requirements for following these trajectories, and off-line computer programs for testing the concepts are included.
Aero-optimum hovering kinematics.
Nabawy, Mostafa R A; Crowther, William J
2015-08-01
Hovering flight for flapping wing vehicles requires rapid and relatively complex reciprocating movement of a wing relative to a stationary surrounding fluid. This note develops a compact analytical aero-kinematic model that can be used for optimization of flapping wing kinematics against aerodynamic criteria of effectiveness (maximum lift) and efficiency (minimum power for a given amount of lift). It can also be used to make predictions of required flapping frequency for a given geometry and basic aerodynamic parameters. The kinematic treatment is based on a consolidation of an existing formulation that allows explicit derivation of flapping velocity for complex motions whereas the aerodynamic model is based on existing quasi-steady analysis. The combined aero-kinematic model provides novel explicit analytical expressions for both lift and power of a hovering wing in a compact form that enables exploration of a rich kinematic design space. Good agreement is found between model predictions of flapping frequency and observed results for a number of insects and optimal hovering kinematics identified using the model are consistent with results from studies using higher order computational models. For efficient flight, the flapping angle should vary using a triangular profile in time leading to a constant velocity flapping motion, whereas for maximum effectiveness the shape of variation should be sinusoidal. For both cases the wing pitching motion should be rectangular such that pitch change at stroke reversal is as rapid as possible. PMID:26248884
Optimum design of radiating and convecting-radiating fins
Aziz, A.; Kraus, A.D.
1996-07-01
The design of fins of optimum dimensions of specified shapes has been pursued by numerous investigators, and a significant body of literature has accumulated over the past 70 years. Of this, the literature pertaining to purely convecting fins has been systematically organized in a review article by Aziz. At that time, it was felt that there was a need for a similar review covering the design of radiating and convecting-radiating fins with optimum dimensions. The present article has been prepared to fulfill this need. Like its predecessor, the article seeks to achieve three objectives. The first objective is to provide an overview of the literature and to identify future research needs. The second objective is to provide a convenient design reference for the practicing engineer. The third objective is to create an instructional resource on the topic. To meet the last two objectives, several design examples are interspersed throughout the article.
Griffith, Jack D.
2013-01-01
In the 1960s, I developed methods for directly visualizing DNA and DNA-protein complexes using an electron microscope. This made it possible to examine the shape of DNA and to visualize proteins as they fold and loop DNA. Early applications included the first visualization of true nucleosomes and linkers and the demonstration that repeating tracts of adenines can cause a curvature in DNA. The binding of DNA repair proteins, including p53 and BRCA2, has been visualized at three- and four-way junctions in DNA. The trombone model of DNA replication was directly verified, and the looping of DNA at telomeres was discovered. PMID:24005675
NASA Technical Reports Server (NTRS)
Brandt, J. C.; Maran, S. P.
1972-01-01
Four very large, shell-shaped features are known from the surveys of radio emission from the Galaxy. It is suggested that the giant loops represent a class of nebulae, induced by supernova radiation as opposed to supernova ejecta. The model considered provides a qualitative explanation for the spectral and polarization properties of the radio emission from giant loops. The radio emitting electrons are part of the general cosmic ray gas and need not arise specifically in the supernova that produced the fossil Stroemgren sphere.
ERIC Educational Resources Information Center
Jefimenko, Oleg
1974-01-01
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)
Optimum PWM waveform synthesis - a filtering approach
Divan, D.M.
1985-09-01
A fundamentally different approach is proposed for the synthesis of optimum pulsewidth modulated (PWM) waveforms for highpower inverter applications. Conventional optimum PWM waveform synthesis techniques which seek to control harmonic levels in the inverter output directly are seen to be equivalent to a filtering operation. Digital filter structures capable of processing PWM waveforms are examined and waveform synthesis strategies are proposed and verified experimentally. Finally, the design of a high-performance PWM waveform generator is detailed.
Observations of loops and prominences
NASA Technical Reports Server (NTRS)
Strong, Keith T.
1994-01-01
We review recent observations by the Yohkoh-SXT (Soft X-ray Telescope) in collaboration with other spacecraft and ground-based observatories of coronal loops and prominences. These new results point to problems that SoHO will be able to address. With a unique combination of rapid-cadence digital imaging (greater than or equal to 32 s full-disk and greater than or equal to 2 s partial-frame images), high spatial resolution (greater than or equal to 2.5 arcsec pixels), high sensitivity (EM less than or equal to 10(exp 42) cm(exp -3)), a low-scatter mirror, and large dynamic range, SXT can observe a vast range of targets on the Sun. Over the first 21 months of Yohkoh operations SXT has taken over one million images of the corona and so is building up an invaluable long-term database on the large-scale corona and loop geometry. The most striking thing about the SXT images is the range of loop sizes and shapes. The active regions are a bright tangle of magnetic field lines, surrounded by a network of large-scale quiet-Sun loops stretching over distances in excess of 105 km. The cross-section of most loops seems to be constant. Loops displaying significant Gamma's are the exception, not the rule, implying the presence of widespread currents in the corona. All magnetic structures show changes. Time scales range from seconds to months. The question of how these structures are formed, become filled with hot plasma, and are maintained is still open. While we see the propagation of brightenings along the length of active-region loops and in X-ray jets with velocities of several hundred km/s, much higher velocities are seen in the quiet Sun. In XBP flares, for example, velocities of over 1000 km/s are common. Active-region loops seem to be in constant motion, moving slowly outward, carrying plasma with them. During flares, loops often produce localized brightenings at the base and later at the apex of the loop. Quiescent filaments and prominences have been observed regularly. Their coronal manifestation seems to be an extended arcade of loops overlying the filament. Reliable alignment of the ground-based data with the X-ray images make it possible to make a detailed intercomparison of the hot and cold plasma structures over extended periods. Hence we are able to follow the long-term evolution of these structures and see how they become destabilized and erupt.
Study of optimum methods of optical communication
NASA Technical Reports Server (NTRS)
Harger, R. O.
1972-01-01
Optimum methods of optical communication accounting for the effects of the turbulent atmosphere and quantum mechanics, both by the semi-classical method and the full-fledged quantum theoretical model are described. A concerted effort to apply the techniques of communication theory to the novel problems of optical communication by a careful study of realistic models and their statistical descriptions, the finding of appropriate optimum structures and the calculation of their performance and, insofar as possible, comparing them to conventional and other suboptimal systems are discussed. In this unified way the bounds on performance and the structure of optimum communication systems for transmission of information, imaging, tracking, and estimation can be determined for optical channels.
Optimum viewing distance for target acquisition
NASA Astrophysics Data System (ADS)
Holst, Gerald C.
2015-05-01
Human visual system (HVS) "resolution" (a.k.a. visual acuity) varies with illumination level, target characteristics, and target contrast. For signage, computer displays, cell phones, and TVs a viewing distance and display size are selected. Then the number of display pixels is chosen such that each pixel subtends 1 min-1. Resolution of low contrast targets is quite different. It is best described by Barten's contrast sensitivity function. Target acquisition models predict maximum range when the display pixel subtends 3.3 min-1. The optimum viewing distance is nearly independent of magnification. Noise increases the optimum viewing distance.
Method for Determining Optimum Injector Inlet Geometry
NASA Technical Reports Server (NTRS)
Trinh, Huu P. (Inventor); Myers, W. Neill (Inventor)
2015-01-01
A method for determining the optimum inlet geometry of a liquid rocket engine swirl injector includes obtaining a throttleable level phase value, volume flow rate, chamber pressure, liquid propellant density, inlet injector pressure, desired target spray angle and desired target optimum delta pressure value between an inlet and a chamber for a plurality of engine stages. The method calculates the tangential inlet area for each throttleable stage. The method also uses correlation between the tangential inlet areas and delta pressure values to calculate the spring displacement and variable inlet geometry of a liquid rocket engine swirl injector.
Optimum Detection of Frequency-Hopped Signals
NASA Technical Reports Server (NTRS)
Cheng, Unjeng; Levitt, Barry; Polydoros, Andreas; Simon, Marvin K.
1992-01-01
This paper derives and analyzes optimum and near-optimum structures for detecting frequency-hopped (FH) signals with arbitrary modulation in additive white Gaussian noise. The principalmodulation formats considered are M-ary frequency-shift-keying (MFSK) with fast frequency hopping(FFH) wherein a single tone is transmitted per hop, and slow frequency hopping (SFH) with multipleMFSK tones (data symbols) per hop. The SFH detection category has not previously been addressedin the open literature and its analysis is generally more complex than FFH.
NASA Astrophysics Data System (ADS)
Sever, Amit; Vieira, Pedro; Wang, Tianheng
2011-11-01
We extend the Operator Product Expansion for Null Polygon Wilson loops to the Mason-Skinner-Caron-Huot super loop dual to non MHV gluon amplitudes. We explain how the known tree level amplitudes can be promoted into an infinite amount of data at any loop order in the OPE picture. As an application, we re-derive all one loop NMHV six gluon amplitudes by promoting their tree level expressions. We also present some new all loops predictions for these amplitudes.
Ganther, Jr., Kenneth R. (Olathe, KS); Snapp, Lowell D. (Independence, MO)
2002-09-10
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.
The preprocessed doacross loop
NASA Technical Reports Server (NTRS)
Saltz, Joel H.; Mirchandaney, Ravi
1990-01-01
Dependencies between loop iterations cannot always be characterized during program compilation. Doacross loops typically make use of a-priori knowledge of inter-iteration dependencies to carry out required synchronizations. A type of doacross loop is proposed that allows the scheduling of iterations of a loop among processors without advance knowledge of inter-iteration dependencies. The method proposed for loop iterations requires that parallelizable preprocessing and postprocessing steps be carried out during program execution.
Leaping of a flexible loop on water
NASA Astrophysics Data System (ADS)
Kim, Ho-Young; Yang, Eun Jin; Lee, Min-Hee; Shin, Bongsu
2008-11-01
Small aquatic arthropods, such as water striders and fishing spiders, are able to leap on water to a height several times their body length. We study a simple model using a floating flexible loop to provide fundamental understanding and mimicking principle of the leaping on water. Motion of a loop, initially bent into an ellipse from equilibrium circular shape using a thin thread, is visualized with a high speed camera upon cutting the thread with a laser. We find that the loop may merely oscillate while afloat, penetrate into the water, or soar into air depending on the hydrophobicity, the bending stiffness, the weight and the degree of initial deflection of the loop. We also construct a scaling law for the leaping height by balancing the initial elastic bending energy with the loop's translational and vibrational energy and a loss imparted to the water in the forms of interfacial, kinetic and viscous energy.
Common Core: Teaching Optimum Topic Exploration (TOTE)
ERIC Educational Resources Information Center
Karge, Belinda Dunnick; Moore, Roxane Kushner
2015-01-01
The Common Core has become a household term and yet many educators do not understand what it means. This article explains the historical perspectives of the Common Core and gives guidance to teachers in application of Teaching Optimum Topic Exploration (TOTE) necessary for full implementation of the Common Core State Standards. An effectiveâ€¦
Investigation of optimum wavelengths for oximetry
NASA Astrophysics Data System (ADS)
Huong, Audrey K. C.; Stockford, Ian M.; Crowe, John A.; Morgan, Stephen P.
2009-07-01
An evaluation of the optimum choice of wavelengths, when using the 'Modified Lambert-Beer law' to estimate blood oxygen saturation, that minimises the mean error across a range of oxygen saturation values is presented. The stability of this approach and its susceptibility to noise are also considered.
Rocket rendezvous at preassigned destinations with optimum entry trajectories
NASA Astrophysics Data System (ADS)
Nangia, A. K.
Optimum entry rendezvous trajectories of commuter rockets between initial noncoaxial coplanar elliptic orbits and destination orbits in an inverse square gravitational field have been determined. Results are presented for an optimum entry rendezvous between earth and Mars. For a given interception angle, the results show that the launch angle for optimum entry rendezvous is smaller than that for the optimum exit rendezvous.
Parametrization of optimum filter passbands for rotational Raman temperature measurements.
Hammann, Eva; Behrendt, Andreas
2015-11-30
We revisit the methodology of rotational Raman temperature measurements covering both lidar and non-range-resolved measurements, e.g., for aircraft control. The results of detailed optimization calculations are presented for the commonly used extraction of signals from the anti-Stokes branch. Different background conditions and realistic shapes of the filter transmission curves are taken into account. Practical uncertainties of the central passbands and widths are discussed. We found a simple parametrization for the optimum filter passband shifts depending on the atmospheric temperature range of interest and the background. The approximation errors of this parametrization are smaller than 2% for temperatures between 200 and 300 K and smaller than 4% between 180 and 200 K. PMID:26698709
NASA Astrophysics Data System (ADS)
Scott, Jason; Martens, P.
2006-06-01
We have created a database of all coronal loops for which we have been able to find measurements in the published open literature, from Skylab to TRACE. The loops and a set of their physical parameters are stored in the form of an IDL structure. The physical parameters considered are: the loop half length, the electron density of the loop, and the loop temperature. The studies that produced the physical parameters along with their observing instruments are recorded in the database as well. Correlations of pressure vs. temperature and heating rates vs. loop length are investigated. Instrumental selection effects are also considered. The loop parameters and correlations derived from the loop database are then compared to theoretical and numerical models for scaling laws and heating rates.This work is supported by NASA GSRP fellowship NNG05GK64H
Bipolar pulse shaping revisited
Fairstein, E.
1996-12-31
Compared with unipolar pulse shaping, bipolar shaping is insensitive to misadjusted or missing pole-zero cancellation, doesn`t require a baseline line restorer, and furnishes an amplitude-invariant time marker for coincidence measurements. These characteristics should be useful in amplifier arrays for integrated circuits (ASICs), despite the greater noise and resolving time. With ASIC technology in mind, unipolar and bipolar shaping methods are compared here. An item that emerged from the study is that two CR differentiators and two RC integrators are optimum from a cost-benefit viewpoint. The network can be adjusted to produce the transfer function (sin t - t) exp(-t), which has half the transmission loss and 8% shorter resolving time than the same configuration with all time constants alike.
Response of an all digital phase-locked loop
NASA Technical Reports Server (NTRS)
Garodnick, J.; Greco, J.; Schilling, D. L.
1974-01-01
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.
Lorentz self-forces on curved current loops
Garren, D.A.; Chen, J. )
1994-10-01
A derivation is presented for the Lorentz self-force arising from the interaction of a slender current loop of arbitrary shape with its own magnetic field. The self-force on any loop segment depends explicitly on the global shape of the remainder of the loop. Calculations of the self-force are presented for various model loops. For loops having small to moderate noncircularity, it is shown that the self-force on a segment with local major ([ital R]) and minor ([ital a]) radii is approximately that for an axisymmetric torus having uniform [ital R] and [ital a]. These properties of the self-force critically influence the equilibrium and dynamics of thin current loops in solar and astrophysical plasmas.
Optimum design calculations for detectors based on ZnSe(??,?) scintillators
NASA Astrophysics Data System (ADS)
Katrunov, K.; Ryzhikov, V.; Gavrilyuk, V.; Naydenov, S.; Lysetska, O.; Litichevskyi, V.
2013-06-01
Light collection in scintillators ZnSe(X), where X is an isovalent dopant, was studied using Monte Carlo calculations. Optimum design was determined for detectors of "scintillator—Si-photodiode" type, which can involve either one scintillation element or scintillation layers of large area made of small-crystalline grains. The calculations were carried out both for determination of the optimum scintillator shape and for design optimization of light guides, on the surface of which the layer of small-crystalline grains is formed.
Optimum design of voice coil motor with constant torque coefficients using evolution strategy
NASA Astrophysics Data System (ADS)
Koh, Chang Seop; Mohammed, Osama A.; Kim, Jun-o.; Hahn, Song-yop
1994-05-01
An effective optimum design method is presented. The method combines the three-dimensional boundary element method with the (1+1) evolution strategy. The reduced scalar potential formulation with the magnetic surface charge as the unknown variable is used under the assumption that the yokes are not saturated. It is found, through the numerical example, that the global optimum shape of the magnet can be easily found within a reasonable number of generations. More elaborate design can be achieved by increasing the number of design variables.
Phase-locked loops. [analog, hybrid, discrete and digital systems
NASA Technical Reports Server (NTRS)
Gupta, S. C.
1974-01-01
The basic analysis and design procedures are described for the realization of analog phase-locked loops (APLL), hybrid phase-locked loops (HPLL), discrete phase-locked loops, and digital phase-locked loops (DPLL). Basic configurations are diagrammed, and performance curves are given. A discrete communications model is derived and developed. The use of the APLL as an optimum angle demodulator and the Kalman-Bucy approach to APLL design are discussed. The literature in the area of phase-locked loops is reviewed, and an extensive bibliography is given. Although the design of APLLs is fairly well documented, work on discrete, hybrid, and digital PLLs is scattered, and more will have to be done in the future to pinpoint the formal design of DPLLs.
Chen Integrals, Generalized Loops and Loop Calculus
NASA Astrophysics Data System (ADS)
Tavares, J. N.
We use Chen iterated line integrals to construct a topological algebra {A}p of separating functions on the group of loops L?p. {A}p has a Hopf algebra structure which allows the construction of a group structure on its spectrum. We call this topological group the group of generalized loops widetilde {{L} {M}p } Then we develop a loop calculus, based on the end point and area derivative operators, providing a rigorous mathematical treatment of the early heuristic ideas of Gambini, Trias and also Mandelstam, Makeenko and Migdal. Finally, we define a natural action of the “pointed” diffeomorphism group Diffp(?) on widetilde {{L} {M}p }, and consider a variational derivative which allows the construction of homotopy invariants. This formalism is useful for constructing a mathematical theory of loop representation of gauge theories and quantum gravity.
Sandstone Formation on the Navajo Loop Trail
Views along the Navajo Loop Trail in Bryce Canyon National Park. Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandston...
Hoodoo on the Navajo Loop Trail
Views along the Navajo Loop Trail in Bryce Canyon National Park. Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandston...
Cedars on the Navajo Loop Trail
Views along the Navajo Loop Trail in Bryce Canyon National Park. Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandston...
Views along the Navajo Loop Trail in Bryce Canyon National Park. Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandston...
Optimum filters and pulsed signal storage devices
NASA Astrophysics Data System (ADS)
Lezin, Y. S.
1982-05-01
The design, and operating mechanism of optimum signal detection filters and analog and digital storage devices for repeated pulsed signals operating against a background of Gaussian noise are described. The practical realizations of these devices is discussed in detail. The methods considered are reduced to engineering formulas. The results of calculations made using these formulas are presented in graphs and tables which facilitate comparisons of different systems and selection of their individual parameters. The data provided enable this monograph to be used as a reference manual for the design of noise proof radio apparatus.
Optimum displacement estimates using mean field annealing
NASA Astrophysics Data System (ADS)
Abdelqader, Ikhlas M.; Rajala, Sarah A.; Bilbro, Griff L.; Snyder, Wesley E.
1993-06-01
In this paper a new algorithm to estimate dense displacement fields from a sequence of images is developed. The algorithm is based on modeling the displacement fields as Markov Random fields. The Markov Random fields-Gibbs equivalence is then used to convert the problem into one of finding an appropriate energy function that describes the motion and any constraints imposed on it. Mean field annealing, a technique which finds global minima in nonconvex optimization problems, is used to minimize the energy function, and solve for the optimum displacement fields. The algorithm results in accurate estimates even for scenes with noise or discontinuities.
Pseudo-elastic hysteresis in shape memory alloys
NASA Astrophysics Data System (ADS)
MÃ¼ller, I.
2012-05-01
Observations of pseudo-elastic hysteresis loops in the shape memory alloy CuAlNi are presented. Particular emphasis is laid on the interior of the overall loop and the phenomena of internal yield and recovery and internal loops are discussed. A thermodynamic argument is presented which may afford an interpretation of the observed phenomena in terms of interfacial energies.
PID controller auto-tuning based on process step response and damping optimum criterion.
Pavkovi?, Danijel; Polak, Siniša; Zorc, Davor
2014-01-01
This paper presents a novel method of PID controller tuning suitable for higher-order aperiodic processes and aimed at step response-based auto-tuning applications. The PID controller tuning is based on the identification of so-called n-th order lag (PTn) process model and application of damping optimum criterion, thus facilitating straightforward algebraic rules for the adjustment of both the closed-loop response speed and damping. The PTn model identification is based on the process step response, wherein the PTn model parameters are evaluated in a novel manner from the process step response equivalent dead-time and lag time constant. The effectiveness of the proposed PTn model parameter estimation procedure and the related damping optimum-based PID controller auto-tuning have been verified by means of extensive computer simulations. PMID:24035643
Optimum design of geodesically stiffened composite plates
NASA Technical Reports Server (NTRS)
Guerdal, Zafer; Phillips, John L.
1988-01-01
With the goal of tailorability in mind, the in-plane stiffness characteristics of a particular grid stiffened plate configuration under axial and shear loads have been studied. The contribution of the skin to the stiffener network and the resultant skin/rib interaction is analyzed. For the given plate geometry and loads, it is shown that an optimum configuration does exist. To achieve optimally designed practical plate configurations, buckling constraints need to be included in the design. Due to the complex geometry and loading of the plates, a simplified local buckling analysis of isolated stiffeners and triangular skin elements between the stiffeners is considered. Development of a stiffener buckling analysis represent stiffeners as shear deformable plate elements is presented.
Optimum runway orientation relative to crosswinds
NASA Technical Reports Server (NTRS)
Falls, L. W.; Brown, S. C.
1972-01-01
Specific magnitudes of crosswinds may exist that could be constraints to the success of an aircraft mission such as the landing of the proposed space shuttle. A method is required to determine the orientation or azimuth of the proposed runway which will minimize the probability of certain critical crosswinds. Two procedures for obtaining the optimum runway orientation relative to minimizing a specified crosswind speed are described and illustrated with examples. The empirical procedure requires only hand calculations on an ordinary wind rose. The theoretical method utilizes wind statistics computed after the bivariate normal elliptical distribution is applied to a data sample of component winds. This method requires only the assumption that the wind components are bivariate normally distributed. This assumption seems to be reasonable. Studies are currently in progress for testing wind components for bivariate normality for various stations. The close agreement between the theoretical and empirical results for the example chosen substantiates the bivariate normal assumption.
Kinetic optimum of volmer-weber growth.
Kaganer, Vladimir M; Jenichen, Bernd; Shayduk, Roman; Braun, Wolfgang; Riechert, Henning
2009-01-01
We find that the molecular beam epitaxy of Fe3Si on GaAs(001) observed by real-time x-ray diffraction begins by the abrupt formation of 3 monolayer (ML) high islands and approaches two-dimensional layer-by-layer growth at a thickness of 7 ML. A surface energy increase is confirmed by ab initio calculations and allows us to identify the growth as a strain-free Volmer-Weber transient. Kinetic Monte Carlo simulations incorporating this energy increase correctly reproduce the characteristic x-ray intensity oscillations found in the experiment. Simulations indicate an optimum growth rate for Volmer-Weber growth in between two limits, the appearance of trenches at slow growth and surface roughening at fast growth. PMID:19257216
Starting, stopping, and resetting biological oscillators: in search of optimum perturbations.
Forger, Daniel B; Paydarfar, David
2004-10-21
Biological oscillators are commonly subjected to a single brief stimulus to perturb the ongoing rhythm. After stimulation, the oscillator can recover although its phase may be advanced or delayed relative to the original cycle. A single transient perturbation can also stop the ongoing rhythm. Arthur Winfree systematically classified these responses to brief perturbations, as determined by the strength of the stimulus, and the phase within the cycle at which the stimulus was given. A natural question arises from Winfree's work. Are certain stimulus shapes better than others at achieving a desired effect? The present study explores this question using: (1) analysis of phase space geometry, (2) calculus of variations, and (3) analysis of responses to noisy perturbations. Methods 1 and 2 can yield exact solutions, but have limited applicability in biology because they require a detailed mathematical description of the oscillator. Method 3 is applicable to any oscillator without mathematical prerequisites. We validate this method by finding optimum stimuli that start and stop repetitive firing in a neural pacemaker model, and the optimum light stimulus for resetting the circadian rhythm in a model of the human circadian clock. We propose that the elucidation of optimum stimulus shapes may be useful for studying many periodic phenomena in biology and medicine. Optimum stimuli can be used to induce a desired behavior without producing undesirable side effects. PMID:15363673
Optimum conditions for microbial carbonate precipitation.
Okwadha, George D O; Li, Jin
2010-11-01
The type of bacteria, bacterial cell concentration, initial urea concentration, reaction temperature, the initial Ca(2+) concentration, ionic strength, and the pH of the media are some factors that control the activity of the urease enzyme, and may have a significant impact on microbial carbonate precipitation (MCP). Factorial experiments were designed based on these factors to determine the optimum conditions that take into consideration economic advantage while at the same time giving quality results. Sporosarcina pasteurii strain ATCC 11859 was used at constant temperature (25Â°C) and ionic strength with varying amounts of urea, Ca(2+), and bacterial cell concentration. The results indicate that the rate of ureolysis (k(urea)) increases with bacterial cell concentration, and the bacterial cell concentration had a greater influence on k(urea) than initial urea concentration. At 25 mM Ca(2+) concentration, increasing bacterial cell concentration from 10(6) to 10(8)cells mLâ»Â¹ increased the CaCO(3) precipitated and CO(2) sequestrated by over 30%. However, when the Ca(2+) concentration was increased 10-fold to 250 mM Ca(2+), the amount of CaCO(3) precipitated and CO(2) sequestrated increased by over 100% irrespective of initial urea concentration. Consequently, the optimum conditions for MCP under our experimental conditions were 666 mM urea and 250 mM Ca(2+) at 2.3Ã—10â¸ cells mLâ»Â¹ bacterial cell concentration. However, a greater CaCO(3) deposition is achievable with higher concentrations of urea, Ca(2+), and bacterial cells so long as the respective quantities are within their economic advantage. X-ray Diffraction, Scanning Electron Microscopy and Energy Dispersive X-ray analyzes confirmed that the precipitate formed was CaCO(3) and composed of predominantly calcite crystals with little vaterite crystals. PMID:20947128
Optimum multistage genomic selection in dairy cattle.
Börner, V; Teuscher, F; Reinsch, N
2012-04-01
The availability of different single nucleotide polymorphism (SNP) chips and the development of imputation algorithms allow for multistage dairy cattle breeding schemes applying various genomic selection strategies. These SNP genotypes yield genomically estimated breeding values (GEBV) with different accuracies at different costs. Thus, the optimum allocation of investments to different selection paths and strategies to maximize the genetic gain per year (?G(a)) and its sensitivity to changes in cost and accuracies of GEBV is of great interest. This is even more relevant under the constraints of limited financial resources. With deterministic methods, optimum multistage breeding plans maximizing ?G(a) were identified in which selection could take place on GEBV derived from high-density (GEBV(HD)) and low-density (GEBV(LD)) SNP genotypes. To account for the uncertainty of cost and accuracies of GEBV, these parameters were varied in a semi-continuous manner. Overall breeding costs were limited to the crucial expenses of a traditional breeding program with 50 progeny-tested young bulls per year. Results clearly show that, in an optimal selection strategy, selection on GEBV(LD) is predominantly used for the identification of future bull dams but the main part of ?G(a) is still generated from selection of sires. The low selection intensity in the path dam to sire induced a higher sensitivity of ?G(a) to changes in cost and accuracies of GEBV(LD) compared with the same changes of GEBV(HD). On the contrary, the genetic gain generated from selection of males was only affected by changes in accuracies of GEBV(HD) but almost unaffected by any changes in cost. Thus, changes in cost and accuracies of GEBV(LD) put the most pressure on the breeding scheme structure to maintain a high ?G(a). Furthermore, genomic selection of bull dams produced by far the majority of breeding cost but the lowest genetic gain. PMID:22459855
Simulations of gyrosynchrotron microwave emission from an oscillating magnetic loop
NASA Astrophysics Data System (ADS)
Kuznetsov, Alexey; Reznikova, Veronika; Van Doorsselaere, Tom; Antolin, Patrick
Radio observations of solar flares often reveal various periodic or quasi-periodic oscillations. Most likely, these oscillations are caused by MHD oscillations of flaring loops which modulate the radio emission via variations of the magnetic field and electron concentration. We perform numerical simulations of gyrosynchrotron radiation from a toroidal-shaped magnetic loop containing sausage-mode MHD oscillations. Different parameters of the loop and MHD oscillations and different loop orientations are considered. The simulation results are compared with the observations of the Nobeyama Radioheliograph.
NASA Technical Reports Server (NTRS)
Ott, Eric A.
2005-01-01
Scoping of shape changing airfoil concepts including both aerodynamic analysis and materials-related technology assessment effort was performed. Three general categories of potential components were considered-fan blades, booster and compressor blades, and stator airfoils. Based on perceived contributions to improving engine efficiency, the fan blade was chosen as the primary application for a more detailed assessment. A high-level aerodynamic assessment using a GE90-90B Block 4 engine cycle and fan blade geometry indicates that blade camber changes of approximately +/-4deg would be sufficient to result in fan efficiency improvements nearing 1 percent. Constraints related to flight safety and failed mode operation suggest that use of the baseline blade shape with actuation to the optimum cruise condition during a portion of the cycle would be likely required. Application of these conditions to the QAT fan blade and engine cycle was estimated to result in an overall fan efficiency gain of 0.4 percent.
Equilibrium Models of Coronal Loops That Involve Curvature and Buoyancy
NASA Astrophysics Data System (ADS)
Hindman, Bradley W.; Jain, Rekha
2013-12-01
We construct magnetostatic models of coronal loops in which the thermodynamics of the loop is fully consistent with the shape and geometry of the loop. This is achieved by treating the loop as a thin, compact, magnetic fibril that is a small departure from a force-free state. The density along the loop is related to the loop's curvature by requiring that the Lorentz force arising from this deviation is balanced by buoyancy. This equilibrium, coupled with hydrostatic balance and the ideal gas law, then connects the temperature of the loop with the curvature of the loop without resorting to a detailed treatment of heating and cooling. We present two example solutions: one with a spatially invariant magnetic Bond number (the dimensionless ratio of buoyancy to Lorentz forces) and the other with a constant radius of the curvature of the loop's axis. We find that the density and temperature profiles are quite sensitive to curvature variations along the loop, even for loops with similar aspect ratios.
Equilibrium models of coronal loops that involve curvature and buoyancy
Hindman, Bradley W.; Jain, Rekha
2013-12-01
We construct magnetostatic models of coronal loops in which the thermodynamics of the loop is fully consistent with the shape and geometry of the loop. This is achieved by treating the loop as a thin, compact, magnetic fibril that is a small departure from a force-free state. The density along the loop is related to the loop's curvature by requiring that the Lorentz force arising from this deviation is balanced by buoyancy. This equilibrium, coupled with hydrostatic balance and the ideal gas law, then connects the temperature of the loop with the curvature of the loop without resorting to a detailed treatment of heating and cooling. We present two example solutions: one with a spatially invariant magnetic Bond number (the dimensionless ratio of buoyancy to Lorentz forces) and the other with a constant radius of the curvature of the loop's axis. We find that the density and temperature profiles are quite sensitive to curvature variations along the loop, even for loops with similar aspect ratios.
An integrated optimum design approach for high speed prop rotors
NASA Technical Reports Server (NTRS)
Chattopadhyay, Aditi; Mccarthy, Thomas R.
1995-01-01
The objective is to develop an optimization procedure for high-speed and civil tilt-rotors by coupling all of the necessary disciplines within a closed-loop optimization procedure. Both simplified and comprehensive analysis codes are used for the aerodynamic analyses. The structural properties are calculated using in-house developed algorithms for both isotropic and composite box beam sections. There are four major objectives of this study. (1) Aerodynamic optimization: The effects of blade aerodynamic characteristics on cruise and hover performance of prop-rotor aircraft are investigated using the classical blade element momentum approach with corrections for the high lift capability of rotors/propellers. (2) Coupled aerodynamic/structures optimization: A multilevel hybrid optimization technique is developed for the design of prop-rotor aircraft. The design problem is decomposed into a level for improved aerodynamics with continuous design variables and a level with discrete variables to investigate composite tailoring. The aerodynamic analysis is based on that developed in objective 1 and the structural analysis is performed using an in-house code which models a composite box beam. The results are compared to both a reference rotor and the optimum rotor found in the purely aerodynamic formulation. (3) Multipoint optimization: The multilevel optimization procedure of objective 2 is extended to a multipoint design problem. Hover, cruise, and take-off are the three flight conditions simultaneously maximized. (4) Coupled rotor/wing optimization: Using the comprehensive rotary wing code CAMRAD, an optimization procedure is developed for the coupled rotor/wing performance in high speed tilt-rotor aircraft. The developed procedure contains design variables which define the rotor and wing planforms.
Optimum arousal level preservation system using biosignals.
Takahashi, Issey; Ohashi, Hayato; Yokoyama, Kiyoko
2011-12-01
The purpose of this study is to develop a driver's optimum arousal level preservation system while driving. The important point of developing this system is how we keep a driver's adequate conditions on driving. Most of the systems, which have been already put to practical use, are using audible sound or warning messages on a display to urge driver to take a rest. However, arousal levels are strongly related to the balance of autonomic modulations; therefore we need the stimulation that preserves a driver's adequate condition physiologically. Some preceding studies reported that the stimulation using the biological rhythms especially heart beating rhythms are influential to human body. We gave a consideration to this fact and made a course of using driver's heartbeat rhythm for the feedback stimulation to realize the demand. In this paper, we examined the stimulation from two points of views. The one is to investigate the possibilities of controlling a driver's heartbeat rhythms by making synchronization between the driver's heartbeat and a vibratory stimulation. The other one is to find out the stimulation that induces RSA (Respiratory Sinus Arrhythmia) in order to adjust the parasympathetic modulations. The result of the experiment indicated that the 1 [s] constant beat stimulation has an effect of inducing RSA, and the stimulation using a rhythm of heartbeat has a possibility of controlling driver's heart rate variability, and its' efficiency might be possible to be improved by adjusting the rhythm of the stimulation to the driver's heartbeat rhythms. PMID:25665216
Improve filtration for optimum equipment reliability
Cervera, S.M.
1996-01-01
The introduction 20 years ago of the American Petroleum Institute Standard API-614 as a purchase specification for lubrication, shaft sealing and control oil systems, had a considerable impact and did much to improve system reliability at that time. Today, however, these recommendations regarding filter rating and flushing cleanliness are outdated. Much research in the tribology field correlates clearance size particulate contamination with accelerated component wear, fatigue and performance degradation. Some of these studies demonstrate that by decreasing the population of clearance size particulate in lubrication oils, component life increases exponentially. Knowing the dynamic clearances of a piece of machinery makes it possible, using the ISO 4406 Cleanliness Code, to determine what cleanliness level will minimize contamination-related component wear/fatigue and thus help optimize machinery performance and reliability. Data obtained by the author through random sampling of rotating equipment lube and seal oil systems indicate that the API-614 standard, as it pertains to filtration and flushing, is insufficient to ensure that particulate contamination is maintained to within the levels necessary to achieve optimum equipment reliability and safety, without increasing operating cost. Adopting and practicing the guidelines presented should result in the following benefits: (1) the frequency of bearing, oil pump, mechanical seal, fluid coupling, gearbox and hydraulic control valve failures would be minimized; (2) the mean time between planned maintenance (MTBPM) would be increased. The result will be a substantial increase in safety and cost savings to the operator.
Optimum deposition conditions of ultrasmooth silver nanolayers
2014-01-01
Reduction of surface plasmon-polariton losses due to their scattering on metal surface roughness still remains a challenge in the fabrication of plasmonic devices for nanooptics. To achieve smooth silver films, we study the dependence of surface roughness on the evaporation temperature in a physical vapor deposition process. At the deposition temperature range 90 to 500 K, the mismatch of thermal expansion coefficients of Ag, Ge wetting layer, and sapphire substrate does not deteriorate the metal surface. To avoid ice crystal formation on substrates, the working temperature of the whole physical vapor deposition process should exceed that of the sublimation at the evaporation pressure range. At optimum room temperature, the root-mean-square (RMS) surface roughness was successfully reduced to 0.2 nm for a 10-nm Ag layer on sapphire substrate with a 1-nm germanium wetting interlayer. Silver layers of 10- and 30-nm thickness were examined using an atomic force microscope (AFM), X-ray reflectometry (XRR), and two-dimensional X-ray diffraction (XRD2). PACS 63.22.Np Layered systems; 68. Surfaces and interfaces; thin films and nanosystems (structure and nonelectronic properties); 81.07.-b Nanoscale materials and structures: fabrication and characterization PMID:24685115
Optimum flight paths of turbojet aircraft
NASA Technical Reports Server (NTRS)
Miele, Angelo
1955-01-01
The climb of turbojet aircraft is analyzed and discussed including the accelerations. Three particular flight performances are examined: minimum time of climb, climb with minimum fuel consumption, and steepest climb. The theoretical results obtained from a previous study are put in a form that is suitable for application on the following simplifying assumptions: the Mach number is considered an independent variable instead of the velocity; the variations of the airplane mass due to fuel consumption are disregarded; the airplane polar is assumed to be parabolic; the path curvatures and the squares of the path angles are disregarded in the projection of the equation of motion on the normal to the path; lastly, an ideal turbojet with performance independent of the velocity is involved. The optimum Mach number for each flight condition is obtained from the solution of a sixth order equation in which the coefficients are functions of two fundamental parameters: the ratio of minimum drag in level flight to the thrust and the Mach number which represents the flight at constant altitude and maximum lift-drag ratio.
Dehumidification -- Closed loop systems
Wyatt, C.H.; Crowe, A.R.
1995-12-01
Dehumidification is the removal of water from the air. Dehumidification equipment treats the ambient air before the air 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.
Dehumidification -- Closed loop systems
Wyatt, C.H.; Crowe, A.R.
1996-05-01
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.
Demonstration of Automatically-Generated Adjoint Code for Use in Aerodynamic Shape Optimization
NASA Technical Reports Server (NTRS)
Green, Lawrence; Carle, Alan; Fagan, Mike
1999-01-01
Gradient-based optimization requires accurate derivatives of the objective function and constraints. These gradients may have previously been obtained by manual differentiation of analysis codes, symbolic manipulators, finite-difference approximations, or existing automatic differentiation (AD) tools such as ADIFOR (Automatic Differentiation in FORTRAN). Each of these methods has certain deficiencies, particularly when applied to complex, coupled analyses with many design variables. Recently, a new AD tool called ADJIFOR (Automatic Adjoint Generation in FORTRAN), based upon ADIFOR, was developed and demonstrated. Whereas ADIFOR implements forward-mode (direct) differentiation throughout an analysis program to obtain exact derivatives via the chain rule of calculus, ADJIFOR implements the reverse-mode counterpart of the chain rule to obtain exact adjoint form derivatives from FORTRAN code. Automatically-generated adjoint versions of the widely-used CFL3D computational fluid dynamics (CFD) code and an algebraic wing grid generation code were obtained with just a few hours processing time using the ADJIFOR tool. The codes were verified for accuracy and were shown to compute the exact gradient of the wing lift-to-drag ratio, with respect to any number of shape parameters, in about the time required for 7 to 20 function evaluations. The codes have now been executed on various computers with typical memory and disk space for problems with up to 129 x 65 x 33 grid points, and for hundreds to thousands of independent variables. These adjoint codes are now used in a gradient-based aerodynamic shape optimization problem for a swept, tapered wing. For each design iteration, the optimization package constructs an approximate, linear optimization problem, based upon the current objective function, constraints, and gradient values. The optimizer subroutines are called within a design loop employing the approximate linear problem until an optimum shape is found, the design loop limit is reached, or no further design improvement is possible due to active design variable bounds and/or constraints. The resulting shape parameters are then used by the grid generation code to define a new wing surface and computational grid. The lift-to-drag ratio and its gradient are computed for the new design by the automatically-generated adjoint codes. Several optimization iterations may be required to find an optimum wing shape. Results from two sample cases will be discussed. The reader should note that this work primarily represents a demonstration of use of automatically- generated adjoint code within an aerodynamic shape optimization. As such, little significance is placed upon the actual optimization results, relative to the method for obtaining the results.
Natively unstructured loops differ from other loops.
Schlessinger, Avner; Liu, Jinfeng; Rost, Burkhard
2007-07-01
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. PMID:17658943
Introduction to Loop Heat Pipes
NASA Technical Reports Server (NTRS)
Ku, Jentung
2015-01-01
This is the presentation file for the short course Introduction to Loop Heat Pipes, to be conducted at the 2015 Thermal Fluids and Analysis Workshop, August 3-7, 2015, Silver Spring, Maryland. This course will discuss operating principles and performance characteristics of a loop heat pipe. Topics include: 1) pressure profiles in the loop; 2) loop operating temperature; 3) operating temperature control; 4) loop startup; 4) loop shutdown; 5) loop transient behaviors; 6) sizing of loop components and determination of fluid inventory; 7) analytical modeling; 8) examples of flight applications; and 9) recent LHP developments.
Implementation of optimum solar electricity generating system
NASA Astrophysics Data System (ADS)
Singh, Balbir Singh Mahinder; Sivapalan, Subarna; Najib, Nurul Syafiqah Mohd; Menon, Pradeep; Karim, Samsul Ariffin A.
2014-10-01
Under the 10th Malaysian Plan, the government is expecting the renewable energy to contribute approximately 5.5% to the total electricity generation by the year 2015, which amounts to 98MW. One of the initiatives to ensure that the target is achievable was to establish the Sustainable Energy Development Authority of Malaysia. SEDA is given the authority to administer and manage the implementation of the feed-in tariff (FiT) mechanism which is mandated under the Renewable Energy Act 2011. The move to establish SEDA is commendable and the FiT seems to be attractive but there is a need to create awareness on the implementation of the solar electricity generating system (SEGS). In Malaysia, harnessing technologies related to solar energy resources have great potential for implementation. However, the main issue that plagues the implementation of SEGS is the intermittent nature of this source of energy. The availability of sunlight is during the day time, and there is a need for electrical energy storage system, so that there is electricity available during the night time as well. The meteorological condition such as clouds, haze and pollution affects the SEGS as well. The PV based SEGS is seems to be promising electricity generating system that can contribute towards achieving the 5.5% target and will be able to minimize the negative effects of utilizing fossil fuels for electricity generation on the environment. Malaysia is committed to Kyoto Protocol, which emphasizes on fighting global warming by achieving stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system. In this paper, the technical aspects of the implementation of optimum SEGS is discussed, especially pertaining to the positioning of the PV panels.
Implementation of optimum solar electricity generating system
Singh, Balbir Singh Mahinder Karim, Samsul Ariffin A.; Sivapalan, Subarna; Najib, Nurul Syafiqah Mohd; Menon, Pradeep
2014-10-24
Under the 10{sup th} Malaysian Plan, the government is expecting the renewable energy to contribute approximately 5.5% to the total electricity generation by the year 2015, which amounts to 98MW. One of the initiatives to ensure that the target is achievable was to establish the Sustainable Energy Development Authority of Malaysia. SEDA is given the authority to administer and manage the implementation of the feed-in tariff (FiT) mechanism which is mandated under the Renewable Energy Act 2011. The move to establish SEDA is commendable and the FiT seems to be attractive but there is a need to create awareness on the implementation of the solar electricity generating system (SEGS). In Malaysia, harnessing technologies related to solar energy resources have great potential for implementation. However, the main issue that plagues the implementation of SEGS is the intermittent nature of this source of energy. The availability of sunlight is during the day time, and there is a need for electrical energy storage system, so that there is electricity available during the night time as well. The meteorological condition such as clouds, haze and pollution affects the SEGS as well. The PV based SEGS is seems to be promising electricity generating system that can contribute towards achieving the 5.5% target and will be able to minimize the negative effects of utilizing fossil fuels for electricity generation on the environment. Malaysia is committed to Kyoto Protocol, which emphasizes on fighting global warming by achieving stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system. In this paper, the technical aspects of the implementation of optimum SEGS is discussed, especially pertaining to the positioning of the PV panels.
Optimum wavelengths for two color ranging
NASA Technical Reports Server (NTRS)
Degnan, John J.
1993-01-01
The range uncertainties associated with the refractive atmosphere can be mitigated by the technique of two color, or dual wavelength, ranging. The precision of the differential time of flight (DTOF) measurement depends on the atmospheric dispersion between the two wavelengths, the received pulsewidths and photoelectron counts, and on the amount of temporal averaging. In general, the transmitted wavelengths are not independently chosen but instead are generated via nonlinear optics techniques (harmonic crystals, Raman scattering, etc.) which also determine their relative pulsewidths. The mean received photoelectrons at each wavelength are calculated via the familiar radar link equation which contains several wavelength dependent parameters. By collecting the various wavelength dependent terms, one can define a wavelength figure of merit for a two color laser ranging system. In this paper, we apply the wavelength figure of merit to the case of an extremely clear atmosphere and draw several conclusions regarding the relative merits of fundamental-second harmonic, fundamental-third harmonic, second-third harmonic, and Raman two color systems. We find that, in spite of the larger dispersion between wavelengths, fundamental-third harmonic systems have the lowest figure of merit due to a combination of poor detector performance at the fundamental and poor atmospheric transmission at the third harmonic. The fundamental-second harmonic systems (approximately 700 nm and 350 nm) have the highest figure of merit, but second-third harmonic systems, using fundamental transmitters near 1000 nm, are a close second. Raman-shifted transmitters appear to offer no advantage over harmonic systems because of the relatively small wavelength separation that can be achieved in light gases such as hydrogen and the lack of good ultrashort pulse transmitters with an optimum fundamental wavelength near 400 nm.
NASA Technical Reports Server (NTRS)
Emslie, A. Gordon
1989-01-01
The somewhat questionable concept of an isolated flare loop and the various physical mechanisms believed to be responsible, to some degree, for energy transport within the loop structure is reviewed. Observational evidence suggests a predominant role for high-energy electrons as an energy transport mechanism, and the consequences of such a scenario is explored in some detail, focusing on radiation signatures in the soft X-ray, hard X-ray, and EUV wavebands, as observed by recent satellite observatories. It is found that the predictions of flare loop models are in fact in excellent agreement with these observations, reinforcing both the notion of the loop as a fundamental component of solar flares and the belief that electron acceleration is an integral part of the flare energy release process.
NASA Astrophysics Data System (ADS)
Bojowald, Martin
2013-02-01
Inhomogeneous space-times in loop quantum cosmology have come under better control with recent advances in effective methods. Even highly inhomogeneous situations, for which multiverse scenarios provide extreme examples, can now be considered at least qualitatively.
Optimum rotationally symmetric shells for flywheel rotors
Blake, Henry W.
2000-01-01
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.
Optimum rotationally symmetric shells for flywheel rotors
Blake, H.W.
2000-04-04
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.
Elevated CO2 and warming effects on CH4 uptake in a semiarid grassland below optimum soil moisture
Technology Transfer Automated Retrieval System (TEKTRAN)
Semiarid rangelands are a significant global sink for methane (CH4), but this sink strength may be altered by climate change. The uptake of CH4 is sensitive to soil moisture showing a hump-shaped relationship with a distinct optimum soil moisture level. Both CO2 and temperature affect soil moistur...
Grignani, Gianluca; Karczmarek, Joanna L.; Semenoff, Gordon W.
2010-07-15
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.
NASA Technical Reports Server (NTRS)
Klimchuk, James A.; Karpen, Judy T.; Patsourakos, Spiros
2008-01-01
One of the great mysteries of coronal physics that has come to light in the last few years is the discovery that warn (- 1 INK) coronal loops are much denser than expected for quasi-static equilibrium. Both the excess densities and relatively long lifetimes of the loops can be explained with bundles of unresolved strands that are heated impulsively to very high temperatures. Since neighboring strands are at different stages of cooling, the composite loop bundle is multi-thermal, with the distribution of temperatures depending on the details of the "nanoflare storm." Emission hotter than 2 MK is predicted, but it is not clear that such emission is always observed. We consider 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 plasma heating; (2) loops are bundles of strands that undergo thermal nonequilibrium that results when steady heating is sufficiently concentrated near the footpoints. We present numerical hydro simulations of both of these possibilities and explore the observational consequences, including the production of hard X-ray emission and absorption by cool material in the corona.
Global optimum protein threading with gapped alignment and empirical pair score functions.
Lathrop, R H; Smith, T F
1996-02-01
We describe a branch-and-bound search algorithm for finding the exact global optimum gapped sequence-structure alignment ("threading") between a protein sequence and a protein core or structural model, using an arbitrary amino acid pair score function (e.g. contact potentials, knowledge-based potentials, potentials of mean force, etc.). The search method imposes minimal conditions on how structural environments are defined or the form of the score function, and allows arbitrary sequence-specific functions for scoring loops and active site residues. Consequently the search method can be used with many different score functions and threading methodologies; this paper illustrates five from the literature. On a desktop workstation running LISP, we have found the global optimum protein sequence-structure alignment in NP-hard search spaces as large as 9.6 x 10(31), at rates ranging as high as 6.8 x 10(28) equivalent threadings per second (most of which are pruned before they ever are examined explicitly). Continuing the procedure past the global optimum enumerates successive candidate threadings in monotonically increasing score order. We give efficient algorithms for search space size, uniform random sampling, segment placement probabilities, mean, standard deviation and partition function. The method should prove useful for structure prediction, as well as for critical evaluation of new pair score functions. PMID:8568903
Transverse Oscillations of Two Coronal Loops
NASA Astrophysics Data System (ADS)
Luna, M.; Terradas, J.; Oliver, R.; Ballester, J. L.
2008-03-01
We study transverse fast magnetohydrodynamic waves in a system of two coronal loops modeled as smoothed, dense plasma cylinders in a uniform magnetic field. The collective oscillatory properties of the system due to the interaction between the individual loops are investigated from two points of view. First, the frequency and spatial structure of the normal modes are studied. The system supports four trapped normal modes in which the loops move rigidly in the transverse direction. The direction of the motions is either parallel or perpendicular to the plane containing the axes of the loops. Two of these modes correspond to oscillations of the loops in phase, while in the other two they move in antiphase. Thus, these solutions are the generalization of the kink mode of a single cylinder to the double cylinder case. Second, we analyze the time-dependent problem of the excitation of the pair of tubes. We find that depending on the shape and location of the initial disturbance, different normal modes can be excited. The frequencies of normal modes are accurately recovered from the numerical simulations. In some cases, because of the simultaneous excitation of several eigenmodes, the system shows beating.
Optimum aerodynamic design via boundary control
NASA Technical Reports Server (NTRS)
Jameson, Antony
1994-01-01
These lectures describe the implementation of optimization techniques based on control theory for airfoil and wing design. In previous studies it was shown that control theory could be used to devise an effective optimization procedure for two-dimensional profiles in which the shape is determined by a conformal transformation from a unit circle, and the control is the mapping function. Recently the method has been implemented in an alternative formulation which does not depend on conformal mapping, so that it can more easily be extended to treat general configurations. The method has also been extended to treat the Euler equations, and results are presented for both two and three dimensional cases, including the optimization of a swept wing.
Classical Physics and Quantum Loops
Barry R. Holstein; John F. Donoghue
2004-05-01
The standard picture of the loop expansion associates a factor of h-bar with each loop, suggesting that the tree diagrams are to be associated with classical physics, while loop effects are quantum mechanical in nature. We discuss examples wherein classical effects arise from loop contributions and display the relationship between the classical terms and the long range effects of massless particles.
COMMERCIAL FEASIBILITY OF AN OPTIMUM RESIDENTIAL OIL BURNER HEAD
The report gives results of a study of the feasibility of commercializing optimum oil burner head technology developed earlier for EPA. The study included: selecting the best commercial method for fabricating optimum heads; determining that prototype simulated-production heads co...
50 CFR 600.310 - National Standard 1-Optimum Yield.
Code of Federal Regulations, 2014 CFR
2014-10-01
... 50 Wildlife and Fisheries 12 2014-10-01 2014-10-01 false National Standard 1-Optimum Yield. 600.310 Section 600.310 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT, NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION, DEPARTMENT OF COMMERCE MAGNUSON-STEVENS ACT PROVISIONS National Standards Â§ 600.310 National Standard 1â€”Optimum Yield....
50 CFR 600.310 - National Standard 1-Optimum Yield.
Code of Federal Regulations, 2012 CFR
2012-10-01
... 50 Wildlife and Fisheries 12 2012-10-01 2012-10-01 false National Standard 1-Optimum Yield. 600.310 Section 600.310 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT, NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION, DEPARTMENT OF COMMERCE MAGNUSON-STEVENS ACT PROVISIONS National Standards Â§ 600.310 National Standard 1â€”Optimum Yield....
50 CFR 600.310 - National Standard 1-Optimum Yield.
Code of Federal Regulations, 2013 CFR
2013-10-01
... 50 Wildlife and Fisheries 12 2013-10-01 2013-10-01 false National Standard 1-Optimum Yield. 600.310 Section 600.310 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT, NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION, DEPARTMENT OF COMMERCE MAGNUSON-STEVENS ACT PROVISIONS National Standards Â§ 600.310 National Standard 1â€”Optimum Yield....
Piezoactuator design considering the optimum placement of FGM piezoelectric material
NASA Astrophysics Data System (ADS)
Carbonari, Ronny C.; Nishiwaki, Shinji; Paulino, Glaucio H.; Nelli Silva, Emílio C.
2007-04-01
Functionally Graded Materials (FGMs) possess continuous variation of material properties and are characterized by spatially varying microstructures. Recently, the FGM concept has been explored in piezoelectric materials to improve properties and to increase the lifetime of piezoelectric actuators. Elastic, piezoelectric, and dielectric properties are graded along the thickness of a piezoceramic FGM. Thus, the gradation of piezoceramic properties can influence the performance of piezoactuators, and an optimum gradation can be sought through optimization techniques. However, the design of these FGM piezoceramics are usually limited to simple shapes. An interesting approach to be investigated is the design of FGM piezoelectric mechanisms which essentially can be defined as a FGM structure with complex topology made of piezoelectric and non-piezoelectric material that must generate output displacement and force at a certain specified point of the domain and direction. This can be achieved by using topology optimization method. Thus, in this work, a topology optimization formulation that allows the simultaneous distribution of void and FGM piezoelectric material (made of piezoelectric and non-piezoelectric material) in the design domain, to achieve certain specified actuation movements, will be presented. The method is implemented based on the SIMP material model where fictitious densities are interpolated in each finite element, providing a continuum material distribution in the domain. The optimization algorithm employed is based on sequential linear programming (SLP) and the finite element method is based on the graded finite element concept where the properties change smoothly inside the element. This approach provides a continuum approximation of material distribution, which is appropriate to model FGMs. Some FGM piezoelectric mechanisms were designed to demonstrate the usefulness of the proposed method. Examples are limited to two-dimensional models, due to FGM manufacturing constraints and the fact that most of the applications for such FGM piezoelectric mechanisms are planar devices. An one-dimensional constraint of the material gradation is imposed to provide more realistic designs.
NASA Astrophysics Data System (ADS)
Brown, T. W.
2008-06-01
We consider the one-loop two-point function for multi-trace operators in the U(2) sector of Script N = 4 supersymmetric Yang-Mills at finite N. We derive an expression for it in terms of U(N) and Sn+1 group theory data, where n is the length of the operators. The Clebsch-Gordan operators constructed in [1], which are diagonal at tree level, only mix at one loop if you can reach the same (n+1)-box Young diagram by adding a single box to each of the n-box Young diagrams of their U(N) representations (which organise their multi-trace structure). Similar results are expected for higher loops and for other sectors of the global symmetry group.
The Energy Landscape of Hyperstable LacI-DNA Loops
NASA Astrophysics Data System (ADS)
Kahn, Jason
2009-03-01
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.
A method for optimum heating and cooling boiler components of a complex shape
NASA Astrophysics Data System (ADS)
Duda, Piotr; RzÄ…sa, Dariusz
2015-06-01
A numerical method for determining a transient fluid temperature is presented. The method is formulated to minimizethe total time of heating and cooling operation based on the assumption that maximum tensile and compressivetotal stresses in a solid can not exceed the allowable value during the entire process. The method can be used for any construction element of a simple or complicated geometry. In this method, material properties of solids can be assumed as constant or temperature dependent. The method will be implemented for the heating operationof an outlet header. This construction element is mounted in supercritical power plants. The outlet header is installed in the 460 MW power unit and it is designed for the working pressure of p w = 26.5 MPa and the steam working temperature of T w = 554Â°C. The results obtained from the proposed method will be compared with the calculations according to TRD 301 - German boiler code
NASA Astrophysics Data System (ADS)
Chiou, Dah-Wei
2015-12-01
This paper presents an "in-a-nutshell" yet self-contained introductory review on loop quantum gravity (LQG) — a background-independent, nonperturbative approach to a consistent quantum theory of gravity. Instead of rigorous and systematic derivations, it aims to provide a general picture of LQG, placing emphasis on the fundamental ideas and their significance. The canonical formulation of LQG, as the central topic of the paper, is presented in a logically orderly fashion with moderate details, while the spin foam theory, black hole thermodynamics, and loop quantum cosmology are covered briefly. Current directions and open issues are also summarized.
Automatic one-loop calculations with Sherpa+OpenLoops
NASA Astrophysics Data System (ADS)
Cascioli, F.; Höche, S.; Krauss, F.; Maierhöfer, P.; Pozzorini, S.; Siegert, F.
2014-06-01
We report on the OpenLoops generator for one-loop matrix elements and its application to four-lepton production in association with up to one jet. The open loops algorithm uses a numerical recursion to construct the numerator of one-loop Feynman diagrams as functions of the loop momentum. In combination with tensor integrals this results in a highly efficient and numerically stable matrix element generator. In order to obtain a fully automated setup for the simulation of next-to-leading order scattering processes we interfaced OpenLoops to the Sherpa Monte Carlo event generator.
Closed-loop operation with alternative dewatering technology
Halliday, W.S.; Bray, R.P.; Youens, J.W.
1993-03-01
The introduction of dewatering devices for closed-loop drilling-fluid circulating systems and reserve pits is derived from technology that has been used in the industrial- and sanitary-waste treatment industries for years. This paper describes an overview of the need for closed-loop systems and provides the optimum design layout, including the fit of a dewatering device, for a drilling location. The introduction of a nonconventional dewatering device, called a screw press/thickener, is reviewed. A case history describing use of this technology in a southern Louisiana inland-marsh-area well is analyzed for the technical and economic viability of operating in a closed-loop mode. Results from this effort include a viable alternative to hauling off waste fluids from drilling sites and the realization that use of this technology can be justified economically.
Livermore Compiler Analysis Loop Suite
2013-03-01
LCALS is designed to evaluate compiler optimizations and performance of a variety of loop kernels and loop traversal software constructs. Some of the loop kernels are pulled directly from "Livermore Loops Coded in C", developed at LLNL (see item 11 below for details of earlier code versions). The older suites were used to evaluate floating-point performances of hardware platforms prior to porting larger application codes. The LCALS suite is geared toward assissing C++ compiler optimizations and platform performance related to SIMD vectorization, OpenMP threading, and advanced C++ language features. LCALS contains 20 of 24 loop kernels from the older Livermore Loop suites, plus various others representative of loops found in current production appkication codes at LLNL. The latter loops emphasize more diverse loop constructs and data access patterns than the others, such as multi-dimensional difference stencils. The loops are included in a configurable framework, which allows control of compilation, loop sampling for execution timing, which loops are run and their lengths. It generates timing statistics for analysis and comparing variants of individual loops. Also, it is easy to add loops to the suite as desired.
Livermore Compiler Analysis Loop Suite
Energy Science and Technology Software Center (ESTSC)
2013-03-01
LCALS is designed to evaluate compiler optimizations and performance of a variety of loop kernels and loop traversal software constructs. Some of the loop kernels are pulled directly from "Livermore Loops Coded in C", developed at LLNL (see item 11 below for details of earlier code versions). The older suites were used to evaluate floating-point performances of hardware platforms prior to porting larger application codes. The LCALS suite is geared toward assissing C++ compiler optimizationsmoreÂ Â» and platform performance related to SIMD vectorization, OpenMP threading, and advanced C++ language features. LCALS contains 20 of 24 loop kernels from the older Livermore Loop suites, plus various others representative of loops found in current production appkication codes at LLNL. The latter loops emphasize more diverse loop constructs and data access patterns than the others, such as multi-dimensional difference stencils. The loops are included in a configurable framework, which allows control of compilation, loop sampling for execution timing, which loops are run and their lengths. It generates timing statistics for analysis and comparing variants of individual loops. Also, it is easy to add loops to the suite as desired.Â«Â less
ERIC Educational Resources Information Center
California Integrated Waste Management Board, Sacramento.
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)…
NETL - Chemical Looping Reactor
2013-07-24
NETL's Chemical Looping Reactor unit is a high-temperature integrated CLC process with extensive instrumentation to improve computational simulations. A non-reacting test unit is also used to study solids flow at ambient temperature. The CLR unit circulates approximately 1,000 pounds per hour at temperatures around 1,800 degrees Fahrenheit.
ERIC Educational Resources Information Center
Naylor, Michael
2006-01-01
In the mid-1800s, Englishman John Venn invented a type of diagram to help visualize logical relationships. A Venn diagram is simply a rectangular box with circular loops in it that overlap to show how objects are related. This article describes activities with Venn diagrams that can be a fun way to sharpen students' logic skills and develop numberâ€¦
NETL - Chemical Looping Reactor
None
2014-06-26
NETL's Chemical Looping Reactor unit is a high-temperature integrated CLC process with extensive instrumentation to improve computational simulations. A non-reacting test unit is also used to study solids flow at ambient temperature. The CLR unit circulates approximately 1,000 pounds per hour at temperatures around 1,800 degrees Fahrenheit.
ERIC Educational Resources Information Center
Banta, Trudy W.; Blaich, Charles
2011-01-01
Accreditors, speakers at assessment conferences, and campus leaders all decry the fact that too few faculty are closing the loop--that is, studying assessment findings to see what improvements might be suggested and taking the appropriate steps to make them. This is difficult enough with locally developed measures; adding the need to interpret…
Holographic calculations of Euclidean Wilson loop correlator in Euclidean anti-de Sitter space
NASA Astrophysics Data System (ADS)
Ziama, Sannah
2015-04-01
The correlation functions of two or more Euclidean Wilson loops of various shapes in Euclidean anti-de Sitter space are computed by considering the minimal area surfaces connecting the loops. The surfaces are parametrized by Riemann theta functions associated with genus three hyperelliptic Riemann surfaces. In the case of two loops, the distance L by which they are separated can be adjusted by continuously varying a specific branch point of the auxiliary Riemann surface. When L is much larger than the characteristic size of the loops, then the loops are approximately regarded as local operators and their correlator as the correlator of two local operators. Similarly, when a loop is very small compared to the size of another loop, the small loop is considered as a local operator corresponding to a light supergravity mode.
Energy Release in Driven Twisted Coronal Loops
NASA Astrophysics Data System (ADS)
Bareford, M. R.; Gordovskyy, M.; Browning, P. K.; Hood, A. W.
2016-01-01
We investigate magnetic reconnection in twisted magnetic fluxtubes, representing coronal loops. The main goal is to establish the influence of the field geometry and various thermodynamic effects on the stability of twisted fluxtubes and on the size and distribution of heated regions. In particular, we aim to investigate to what extent the earlier idealised models, based on the initially cylindrically symmetric fluxtubes, are different from more realistic models, including the large-scale curvature, atmospheric stratification, thermal conduction and other effects. In addition, we compare the roles of Ohmic heating and shock heating in energy conversion during magnetic reconnection in twisted loops. The models with straight fluxtubes show similar distribution of heated plasma during the reconnection: it initially forms a helical shape, which subsequently becomes very fragmented. The heating in these models is rather uniformly distributed along fluxtubes. At the same time, the hot plasma regions in curved loops are asymmetric and concentrated close to the loop tops. Large-scale curvature has a destabilising influence: less twist is needed for instability. Footpoint convergence normally delays the instability slightly, although in some cases, converging fluxtubes can be less stable. Finally, introducing a stratified atmosphere gives rise to decaying wave propagation, which has a destabilising effect.
Energy Release in Driven Twisted Coronal Loops
NASA Astrophysics Data System (ADS)
Bareford, M. R.; Gordovskyy, M.; Browning, P. K.; Hood, A. W.
2015-12-01
We investigate magnetic reconnection in twisted magnetic fluxtubes, representing coronal loops. The main goal is to establish the influence of the field geometry and various thermodynamic effects on the stability of twisted fluxtubes and on the size and distribution of heated regions. In particular, we aim to investigate to what extent the earlier idealised models, based on the initially cylindrically symmetric fluxtubes, are different from more realistic models, including the large-scale curvature, atmospheric stratification, thermal conduction and other effects. In addition, we compare the roles of Ohmic heating and shock heating in energy conversion during magnetic reconnection in twisted loops. The models with straight fluxtubes show similar distribution of heated plasma during the reconnection: it initially forms a helical shape, which subsequently becomes very fragmented. The heating in these models is rather uniformly distributed along fluxtubes. At the same time, the hot plasma regions in curved loops are asymmetric and concentrated close to the loop tops. Large-scale curvature has a destabilising influence: less twist is needed for instability. Footpoint convergence normally delays the instability slightly, although in some cases, converging fluxtubes can be less stable. Finally, introducing a stratified atmosphere gives rise to decaying wave propagation, which has a destabilising effect.
FINE STRUCTURES AND OVERLYING LOOPS OF CONFINED SOLAR FLARES
Yang, Shuhong; Zhang, Jun; Xiang, Yongyuan
2014-10-01
Using the HÎ± observations from the New Vacuum Solar Telescope at the Fuxian Solar Observatory, we focus on the fine structures of three confined flares and the issue why all the three flares are confined instead of eruptive. All the three confined flares take place successively at the same location and have similar morphologies, so can be termed homologous confined flares. In the simultaneous images obtained by the Solar Dynamics Observatory, many large-scale coronal loops above the confined flares are clearly observed in multi-wavelengths. At the pre-flare stage, two dipoles emerge near the negative sunspot, and the dipolar patches are connected by small loops appearing as arch-shaped HÎ± fibrils. There exists a reconnection between the small loops, and thus the HÎ± fibrils change their configuration. The reconnection also occurs between a set of emerging HÎ± fibrils and a set of pre-existing large loops, which are rooted in the negative sunspot, a nearby positive patch, and some remote positive faculae, forming a typical three-legged structure. During the flare processes, the overlying loops, some of which are tracked by activated dark materials, do not break out. These direct observations may illustrate the physical mechanism of confined flares, i.e., magnetic reconnection between the emerging loops and the pre-existing loops triggers flares and the overlying loops prevent the flares from being eruptive.
COLD TEST LOOP INTEGRATED TEST LOOP RESULTS
Abraham, TJ
2003-10-22
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.
A GIS-based shape index for land parcels
NASA Astrophysics Data System (ADS)
Demetriou, Demetris; Stillwell, John; See, Linda
2013-08-01
Shape analysis is of interest in many fields of spatial science and planning including land management in rural areas. In particular, evaluating the shape of existing land parcels is critical when implementing rural development schemes such as land consolidation. However, existing land parcel shape indices have major deficiencies: completely different shapes of parcels may have the same index value or similar parcel shapes may have different index scores. Thus, there is a clear requirement for a more accurate and reliable measurement method. This paper therefore presents a new parcel shape index (PSI) which integrates a geographical information system (GIS) with a multi-attribute decision-making (MADM) method. It involves the amalgamated outcome of six geometric measures represented by value functions involving a mathematical representation of judgements by experts that compare each geometric measure with that of an optimum parcel shape defined for land consolidation projects. The optimum shape has a PSI value of 1 while the worst shape has a value close to 0. The shape measures used in the model include length of sides, acute angles, reflex angles, boundary points, compactness and regularity. The paper uses data for two case study areas in Cyprus to demonstrate the superiority of the new PSI over three existing shape indices employed in other studies. The methodology utilized here can be implemented in other disciplines dealing with the assessment of objects that can be compared to an optimum.
Optimum testing of multiple hypotheses in quantum detection theory
NASA Technical Reports Server (NTRS)
Yuen, H. P.; Kennedy, R. S.; Lax, M.
1975-01-01
The problem of specifying the optimum quantum detector in multiple hypotheses testing is considered for application to optical communications. The quantum digital detection problem is formulated as a linear programming problem on an infinite-dimensional space. A necessary and sufficient condition is derived by the application of a general duality theorem specifying the optimum detector in terms of a set of linear operator equations and inequalities. Existence of the optimum quantum detector is also established. The optimality of commuting detection operators is discussed in some examples. The structure and performance of the optimal receiver are derived for the quantum detection of narrow-band coherent orthogonal and simplex signals. It is shown that modal photon counting is asymptotically optimum in the limit of a large signaling alphabet and that the capacity goes to infinity in the absence of a bandwidth limitation.
On the optimum polarizations of incoherently reflected waves
NASA Technical Reports Server (NTRS)
Van Zyl, Jakob J.; Elachi, Charles; Papas, Charles H.
1987-01-01
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.
Optimum conditions for composites fiber coating by chemical vapor infiltration
Griffiths, S.K.; Nilson, R.H.
1997-04-01
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.
LoopIng: a template-based tool for predicting the structure of protein loops
Messih, Mario Abdel; Lepore, Rosalba; Tramontano, Anna
2015-01-01
Motivation: Predicting the structure of protein loops is very challenging, mainly because they are not necessarily subject to strong evolutionary pressure. This implies that, unlike the rest of the protein, standard homology modeling techniques are not very effective in modeling their structure. However, loops are often involved in protein function, hence inferring their structure is important for predicting protein structure as well as function. Results: We describe a method, LoopIng, based on the Random Forest automated learning technique, which, given a target loop, selects a structural template for it from a database of loop candidates. Compared to the most recently available methods, LoopIng is able to achieve similar accuracy for short loops (4–10 residues) and significant enhancements for long loops (11–20 residues). The quality of the predictions is robust to errors that unavoidably affect the stem regions when these are modeled. The method returns a confidence score for the predicted template loops and has the advantage of being very fast (on average: 1?min/loop). Availability and implementation: www.biocomputing.it/looping Contact: anna.tramontano@uniroma1.it Supplementary information: Supplementary data are available at Bioinformatics online. PMID:26249814
Loop Heat Pipes and Capillary Pumped Loops: An Applications Perspective
NASA Technical Reports Server (NTRS)
Butler, Dan; Ku, Jentung; Swanson, Theodore; Obenschain, Arthur F. (Technical Monitor)
2001-01-01
Capillary pumped loops (CPLS) and loop heat pipes (LHPS) are versatile two-phase heat transfer devices which have recently gained increasing acceptance in space applications. Both systems work based on the same principles and have very similar designs. Nevertheless, some differences exist in the construction of the evaporator and the hydro-accumulator, and these differences lead to very distinct operating characteristics for each loop. This paper presents comparisons of the two loops from an applications perspective, and addresses their impact on spacecraft design, integration, and test. Some technical challenges and issues for both loops are also addressed.
FRET studies of a landscape of Lac repressor-mediated DNA loops
Haeusler, Aaron R.; Goodson, Kathy A.; Lillian, Todd D.; Wang, Xiaoyu; Goyal, Sachin; Perkins, Noel C.; Kahn, Jason D.
2012-01-01
DNA looping mediated by the Lac repressor is an archetypal test case for modeling protein and DNA flexibility. Understanding looping is fundamental to quantitative descriptions of gene expression. Systematic analysis of LacI•DNA looping was carried out using a landscape of DNA constructs with lac operators bracketing an A-tract bend, produced by varying helical phasings between operators and the bend. Fluorophores positioned on either side of both operators allowed direct Förster resonance energy transfer (FRET) detection of parallel (P1) and antiparallel (A1, A2) DNA looping topologies anchored by V-shaped LacI. Combining fluorophore position variant landscapes allows calculation of the P1, A1 and A2 populations from FRET efficiencies and also reveals extended low-FRET loops proposed to form via LacI opening. The addition of isopropyl-?-d-thio-galactoside (IPTG) destabilizes but does not eliminate the loops, and IPTG does not redistribute loops among high-FRET topologies. In some cases, subsequent addition of excess LacI does not reduce FRET further, suggesting that IPTG stabilizes extended or other low-FRET loops. The data align well with rod mechanics models for the energetics of DNA looping topologies. At the peaks of the predicted energy landscape for V-shaped loops, the proposed extended loops are more stable and are observed instead, showing that future models must consider protein flexibility. PMID:22307389
NASA Astrophysics Data System (ADS)
Opolski, Antoni
2014-12-01
Professor Antoni Opolski was actively interested in astronomy after his retirement in 1983. He especially liked to study the works of the famous astronomer Copernicus getting inspiration for his own work. Opolski started his work on planetary loops in 2011 continuing it to the end of 2012 . During this period calculations, drawings, tables, and basic descriptions of all the planets of the Solar System were created with the use of a piece of paper and a pencil only. In 2011 Antoni Opolski asked us to help him in editing the manuscript and preparing it for publication. We have been honored having the opportunity to work on articles on planetary loops with Antoni Opolski in his house for several months. In the middle of 2012 the detailed material on Jupiter was ready. However, professor Opolski improved the article by smoothing the text and preparing new, better drawings. Finally the article ''Loops of Jupiter'', written by the 99- year old astronomer, was published in the year of his 100th birthday.
Verification of Loop Diagnostics
NASA Technical Reports Server (NTRS)
Winebarger, A.; Lionello, R.; Mok, Y.; Linker, J.; Mikic, Z.
2014-01-01
Many different techniques have been used to characterize the plasma in the solar corona: density-sensitive spectral line ratios are used to infer the density, the evolution of coronal structures in different passbands is used to infer the temperature evolution, and the simultaneous intensities measured in multiple passbands are used to determine the emission measure. All these analysis techniques assume that the intensity of the structures can be isolated through background subtraction. In this paper, we use simulated observations from a 3D hydrodynamic simulation of a coronal active region to verify these diagnostics. The density and temperature from the simulation are used to generate images in several passbands and spectral lines. We identify loop structures in the simulated images and calculate the loop background. We then determine the density, temperature and emission measure distribution as a function of time from the observations and compare with the true temperature and density of the loop. We find that the overall characteristics of the temperature, density, and emission measure are recovered by the analysis methods, but the details of the true temperature and density are not. For instance, the emission measure curves calculated from the simulated observations are much broader than the true emission measure distribution, though the average temperature evolution is similar. These differences are due, in part, to inadequate background subtraction, but also indicate a limitation of the analysis methods.
Chemical Looping Combustion Kinetics
Edward Eyring; Gabor Konya
2009-03-31
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).
NASA Astrophysics Data System (ADS)
Vernier, Eric; Lykke Jacobsen, Jesper; Saleur, Hubert
2016-02-01
We study a model of dilute oriented loops on the square lattice, where each loop is compatible with a fixed, alternating orientation of the lattice edges. This implies that loop strands are not allowed to go straight at vertices, and results in an enhancement of the usual {{O}}(n) symmetry to {{U}}(n). The corresponding transfer matrix acts on a number of representations (standard modules) that grows exponentially with the system size. We derive their dimension and those of the centralizer by both combinatorial and algebraic techniques. A mapping onto a field theory permits us to identify the conformal field theory governing the critical range, nâ‰¤slant 1. We establish the phase diagram and the critical exponents of low-energy excitations. For generic n, there is a critical line in the universality class of the dilute {{O}}(2n) model, terminating in an {{SU}}(n+1) point. The case n = 1 maps onto the critical line of the six-vertex model, along which exponents vary continuously.
Cosmic string loop microlensing
NASA Astrophysics Data System (ADS)
Bloomfield, Jolyon K.; Chernoff, David F.
2014-06-01
Cosmic superstring loops within the galaxy microlens background point sources lying close to the observer-string line of sight. For suitable alignments, multiple paths coexist and the (achromatic) flux enhancement is a factor of two. We explore this unique type of lensing by numerically solving for geodesics that extend from source to observer as they pass near an oscillating string. We characterize the duration of the flux doubling and the scale of the image splitting. We probe and confirm the existence of a variety of fundamental effects predicted from previous analyses of the static infinite straight string: the deficit angle, the Kaiser-Stebbins effect, and the scale of the impact parameter required to produce microlensing. Our quantitative results for dynamical loops vary by O(1) factors with respect to estimates based on infinite straight strings for a given impact parameter. A number of new features are identified in the computed microlensing solutions. Our results suggest that optical microlensing can offer a new and potentially powerful methodology for searches for superstring loop relics of the inflationary era.
A comparison of methods for DPLL loop filter design
NASA Technical Reports Server (NTRS)
Aguirre, S.; Hurd, W. J.; Kumar, R.; Statman, J.
1986-01-01
Four design methodologies for loop filters for a class of digital phase-locked loops (DPLLs) are presented. The first design maps an optimum analog filter into the digital domain; the second approach designs a filter that minimizes in discrete time weighted combination of the variance of the phase error due to noise and the sum square of the deterministic phase error component; the third method uses Kalman filter estimation theory to design a filter composed of a least squares fading memory estimator and a predictor. The last design relies on classical theory, including rules for the design of compensators. Linear analysis is used throughout the article to compare different designs, and includes stability, steady state performance and transient behavior of the loops. Design methodology is not critical when the loop update rate can be made high relative to loop bandwidth, as the performance approaches that of continuous time. For low update rates, however, the miminization method is significantly superior to the other methods.
NASA Technical Reports Server (NTRS)
Simon, M. K.; Alem, W. K.
1978-01-01
Unbalanced quadriphase-shift-keying (QPSK) is an attractive means for transmitting two digital data streams which in general have different average powers, data rates, and data formats. Previous analyses of the tracking performance of Costas loop demodulators of unbalanced QPSK have accounted only for the filtering effect produced by the loop's two arm filters on the equivalent additive noise perturbing the loop. When the bandwidth of these filters is selected on the basis of the order of the data rate, as is typical of optimum Costas loop design, the filtering degradations of the data modulations themselves and the cross-modulation noise produced by their multiplication in the loop often cannot be neglected. The purpose of this paper is to incorporate these additional filtering effects into the analysis. Many of the results obtained herein are in the form of closed-form expressions which can easily be evaluated numerically for design and performance prediction purposes.
Emerging Flux and the Heating of Coronal Loops
NASA Astrophysics Data System (ADS)
Schmieder, B.; Rust, D. M.; Georgoulis, M. K.; DÃ©moulin, P.; Bernasconi, P. N.
2004-01-01
We use data collected by a multiwavelength campaign of observations to describe how the fragmented, asymmetric emergence of magnetic flux in NOAA active region 8844 triggers the dynamics in the active-region atmosphere. Observations of various instruments on board Yohkoh, SOHO, and TRACE complement high-resolution observations of the balloon-borne Flare Genesis Experiment obtained on 2000 January 25. We find that coronal loops appeared and evolved rapidly ~6+/-2 hr after the first detection of emerging magnetic flux. In the low chromosphere, flux emergence resulted in intense Ellerman bomb activity. Besides the chromosphere, we find that Ellerman bombs may also heat the transition region, which showed ``moss'' ~100% brighter in areas with Ellerman bombs as compared to areas without Ellerman bombs. In the corona, we find a spatiotemporal anticorrelation between the soft X-ray (SXT) and the extreme ultraviolet (TRACE) loops. First, SXT loops preceded the appearance of the TRACE loops by 30-40 minutes. Second, the TRACE and SXT loops had different shapes and different footpoints. Third, the SXT loops were longer and higher than the TRACE loops. We conclude that the TRACE and the SXT loops were formed independently. TRACE loops were mainly heated at their footpoints, while SXT loops brightened in response to coronal magnetic reconnection. In summary, we observed a variety of coupled activity, from the photosphere to the active-region corona. Links between different aspects of this activity lead to a unified picture of the evolution and the energy release in the active region.
On Modeling Morphogenesis of the Looping Heart Following Mechanical Perturbations
Ramasubramanian, Ashok; Nerurkar, Nandan L.; Achtien, Kate H.; Filas, Benjamin A.; Voronov, Dmitry A.; Taber, Larry A.
2008-01-01
Looping is a crucial early phase during heart development, as the initially straight heart tube (HT) deforms into a curved tube to lay out the basic plan of the mature heart. This paper focuses on the first phase of looping, called c-looping, when the HT bends ventrally and twists dextrally (rightward) to create a c-shaped tube. Previous research has shown that bending is an intrinsic process, while dextral torsion is likely caused by external forces acting on the heart. However, the specific mechanisms that drive and regulate looping are not yet completely understood. Here, we present new experimental data and finite element models to help define these mechanisms for the torsional component of c-looping. First, with regions of growth and contraction specified according to experiments on chick embryos, a three-dimensional model exhibits morphogenetic deformation consistent with observations for normal looping. Next, the model is tested further using experiments in which looping is perturbed by removing structures that exert forces on the heart â€” a membrane (splanchnopleure, SPL) that presses against the ventral surface of the heart and the left and right primitive atria. In all cases, the model predicts the correct qualitative behavior. Finally, a two-dimensional model of the HT cross section is used to study a feedback mechanism for stress-based regulation of looping. The model is tested using experiments in which the SPL is removed before, during, and after c-looping. In each simulation, the model predicts the correct response. Hence, these models provide new insight into the mechanical mechanisms that drive and regulate cardiac looping. PMID:19045547
Two Bridges Formation on the Navajo Loop Trail
Views along the Navajo Loop Trail in Bryce Canyon National Park. Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandston...
A Culture-Behavior-Brain Loop Model of Human Development.
Han, Shihui; Ma, Yina
2015-11-01
Increasing evidence suggests that cultural influences on brain activity are associated with multiple cognitive and affective processes. These findings prompt an integrative framework to account for dynamic interactions between culture, behavior, and the brain. We put forward a culture-behavior-brain (CBB) loop model of human development that proposes that culture shapes the brain by contextualizing behavior, and the brain fits and modifies culture via behavioral influences. Genes provide a fundamental basis for, and interact with, the CBB loop at both individual and population levels. The CBB loop model advances our understanding of the dynamic relationships between culture, behavior, and the brain, which are crucial for human phylogeny and ontogeny. Future brain changes due to cultural influences are discussed based on the CBB loop model. PMID:26440111
A Moral Experience Feedback Loop: Modeling a System of Moral Self-Cultivation in Everyday Life
ERIC Educational Resources Information Center
Sherblom, Stephen A.
2015-01-01
This "systems thinking" model illustrates a common feedback loop by which people engage the moral world and continually reshape their moral sensibility. The model highlights seven processes that collectively form this feedback loop: beginning with (1) one's current moral sensibility which shapes processes of (2) perception, (3)â€¦
A Moral Experience Feedback Loop: Modeling a System of Moral Self-Cultivation in Everyday Life
ERIC Educational Resources Information Center
Sherblom, Stephen A.
2015-01-01
This "systems thinking" model illustrates a common feedback loop by which people engage the moral world and continually reshape their moral sensibility. The model highlights seven processes that collectively form this feedback loop: beginning with (1) one's current moral sensibility which shapes processes of (2) perception, (3)…
de Oliveira, Leandro C.; da Silva, Viviam M.; Colussi, Francieli; Cabral, Aline D.; de Oliveira Neto, Mario; Squina, Fabio M.; Garcia, Wanius
2015-01-01
Endo-Î²-1, 4-mannanase from Thermotoga petrophila (TpMan) is a modular hyperthermostable enzyme involved in the degradation of mannan-containing polysaccharides. The degradation of these polysaccharides represents a key step for several industrial applications. Here, as part of a continuing investigation of TpMan, the region corresponding to the GH5 domain (TpManGH5) was characterized as a function of pH and temperature. The results indicated that the enzymatic activity of the TpManGH5 is pH-dependent, with its optimum activity occurring at pH 6. At pH 8, the studies demonstrated that TpManGH5 is a molecule with a nearly spherical tightly packed core displaying negligible flexibility in solution, and with size and shape very similar to crystal structure. However, TpManGH5 experiences an increase in radius of gyration in acidic conditions suggesting expansion of the molecule. Furthermore, at acidic pH values, TpManGH5 showed a less globular shape, probably due to a loop region slightly more expanded and flexible in solution (residues Y88 to A105). In addition, molecular dynamics simulations indicated that conformational changes caused by pH variation did not change the core of the TpManGH5, which means that only the above mentioned loop region presents high degree of fluctuations. The results also suggested that conformational changes of the loop region may facilitate polysaccharide and enzyme interaction. Finally, at pH 6 the results indicated that TpManGH5 is slightly more flexible at 65Â°C when compared to the same enzyme at 20Â°C. The biophysical characterization presented here is well correlated with the enzymatic activity and provide new insight into the structural basis for the temperature and pH-dependent activity of the TpManGH5. Also, the data suggest a loop region that provides a starting point for a rational design of biotechnological desired features. PMID:25723179
de Oliveira, Leandro C; da Silva, Viviam M; Colussi, Francieli; Cabral, Aline D; de Oliveira Neto, Mario; Squina, Fabio M; Garcia, Wanius
2015-01-01
Endo-?-1, 4-mannanase from Thermotoga petrophila (TpMan) is a modular hyperthermostable enzyme involved in the degradation of mannan-containing polysaccharides. The degradation of these polysaccharides represents a key step for several industrial applications. Here, as part of a continuing investigation of TpMan, the region corresponding to the GH5 domain (TpManGH5) was characterized as a function of pH and temperature. The results indicated that the enzymatic activity of the TpManGH5 is pH-dependent, with its optimum activity occurring at pH 6. At pH 8, the studies demonstrated that TpManGH5 is a molecule with a nearly spherical tightly packed core displaying negligible flexibility in solution, and with size and shape very similar to crystal structure. However, TpManGH5 experiences an increase in radius of gyration in acidic conditions suggesting expansion of the molecule. Furthermore, at acidic pH values, TpManGH5 showed a less globular shape, probably due to a loop region slightly more expanded and flexible in solution (residues Y88 to A105). In addition, molecular dynamics simulations indicated that conformational changes caused by pH variation did not change the core of the TpManGH5, which means that only the above mentioned loop region presents high degree of fluctuations. The results also suggested that conformational changes of the loop region may facilitate polysaccharide and enzyme interaction. Finally, at pH 6 the results indicated that TpManGH5 is slightly more flexible at 65°C when compared to the same enzyme at 20°C. The biophysical characterization presented here is well correlated with the enzymatic activity and provide new insight into the structural basis for the temperature and pH-dependent activity of the TpManGH5. Also, the data suggest a loop region that provides a starting point for a rational design of biotechnological desired features. PMID:25723179
The Role of Entropic Effects on DNA Loop Formation
NASA Astrophysics Data System (ADS)
Wilson, David; Tkachenko, Alexei; Lillian, Todd; Perkins, Noel; Meiners, Jens Christian
2009-03-01
The formation of protein mediated DNA loops often regulates gene expression. Typically, a protein is simultaneously bound to two DNA operator sites. An example is the lactose repressor which binds to the Lac operon of E. coli. We characterize the mechanics of this system by calculating the free energy cost of loop formation. We construct a Hamiltonian that describes the change in DNA bending energy due to linear perturbations about the looped and open states, starting from a non-linear mechanical rod model that determines the shape and bending energy of the inter-operator DNA loop while capturing the intrinsic curvature and sequence-dependent elasticity of the DNA. The crystal structure of the LacI protein provides the boundary conditions for the DNA. We then calculate normal modes of the open and closed loops to account for the thermal fluctuations. The ratio of determinants of the two Hamiltonians yields the partition function, and the enthalphic and entropic cost of looping. This calculation goes beyond standard elastic energy models because it fully accounts for the substantial entropic differences between the two states. It also includes effects of sequence dependent curvature and stiffness and allows anisotropic variations in persistence length. From the free energy we then calculate the J-factor and ratio of loop lifetimes.
Efficiently computing exact geodesic loops within finite steps.
Xin, Shi-Qing; He, Ying; Fu, Chi-Wing
2012-06-01
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
Coupled dual loop absorption heat pump
Sarkisian, Paul H.; Reimann, Robert C.; Biermann, Wendell J.
1985-01-01
A coupled dual loop absorption system which utilizes two separate complete loops. Each individual loop operates at three temperatures and two pressures. This low temperature loop absorber and condenser are thermally coupled to the high temperature loop evaporator, and the high temperature loop condenser and absorber are thermally coupled to the low temperature generator.
Optical parametric loop mirror
NASA Astrophysics Data System (ADS)
Mori, K.; Morioka, T.; Saruwatari, M.
1995-06-01
A novel configuration for four-wave mixing (FWM) is proposed that offers the remarkable feature of inherently separating the FWM wave from the input pump and signal waves and suppressing their background amplified stimulated emission without optical filtering. In the proposed configuration, an optical parametric loop mirror, two counterpropagating FWM waves generated in a Sagnac interferometer interfere with a relative phase difference that is introduced deliberately. FWM frequency-conversion experiments in a polarization-maintaining fiber achieved more than 35 dB of input-wave suppression against the FWM wave.
Dassau, E; Atlas, E; Phillip, M
2011-02-01
Closed-loop algorithms can be found in every aspect of everyday modern life. Automation and control are used constantly to provide safety and to improve quality of life. Closed-loop systems and algorithms can be found in home appliances, automobiles, aviation and more. Can one imagine nowadays driving a car without ABS, cruise control or even anti-sliding control? Similar principles of automation and control can be used in the management of diabetes mellitus (DM). The idea of an algorithmic/technological way to control glycaemia is not new and has been researched for more than four decades. However, recent improvements in both glucose-sensing technology and insulin delivery together with advanced control and systems engineering made this dream of an artificial pancreas possible. The artificial pancreas may be the next big step in the treatment of DM since the use of insulin analogues. An artificial pancreas can be described as internal or external devices that use continuous glucose measurements to automatically manage exogenous insulin delivery with or without other hormones in an attempt to restore glucose regulation in individuals with DM using a control algorithm. This device as described can be internal or external; can use different types of control algorithms with bi-hormonal or uni-hormonal design; and can utilise different ways to administer them. The different designs and implementations have transitioned recently from in silico simulations to clinical evaluation stage with practical applications in mind. This may mark the beginning of a new era in diabetes management with the introduction of semi-closed-loop systems that can prevent or minimise nocturnal hypoglycaemia, to hybrid systems that will manage blood glucose (BG) levels with minimal user intervention to finally fully automated systems that will take the user out of the loop. More and more clinical trials will be needed for the artificial pancreas to become a reality but initial encouraging results are proof that we are on the right track. We attempted to select recent publications that will present these current achievements in the quest for the artificial pancreas and that will inspire others to continue to progress this field of research. PMID:21323809
Oscillation of Newly Formed Loops after Magnetic Reconnection in the Solar Chromosphere
NASA Astrophysics Data System (ADS)
Yang, Shuhong; Xiang, Yongyuan
2016-03-01
With the high spatial and temporal resolution HÎ± images from the New Vacuum Solar Telescope, we focus on two groups of loops with an X-shaped configuration in the dynamic chromosphere. We find that the anti-directed loops approach each other and reconnect continually. The connectivity of the loops is changed and new loops are formed and stack together. The stacked loops are sharply bent, implying that they are greatly impacted by the magnetic tension force. When another reconnection process takes place, one new loop is formed and stacks with the previously formed ones. Meanwhile, the stacked loops retract suddenly and move toward the balance position, performing an overshoot movement, which led to an oscillation with an average period of about 45 s. The oscillation of newly formed loops after magnetic reconnection in the chromosphere is observed for the first time. We suggest that the stability of the stacked loops is destroyed due to the attachment of the last new loop and then suddenly retract under the effect of magnetic tension. Because of the retraction, another lower loop is pushed outward and performs an oscillation with a period of about 25 s. The different oscillation periods may be due to their difference in three parameters, i.e., loop length, plasma density, and magnetic field strength.
Determining the Optimum Number of Increments in Composite Sampling
Hathaway, John E.; Schaalje, G Bruce; Gilbert, Richard O.; Pulsipher, Brent A.; Matzke, Brett D.
2008-09-30
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.
Digital Parallel Processor Array for Optimum Path Planning
NASA Technical Reports Server (NTRS)
Kremeny, Sabrina E. (Inventor); Fossum, Eric R. (Inventor); Nixon, Robert H. (Inventor)
1996-01-01
The invention computes the optimum path across a terrain or topology represented by an array of parallel processor cells interconnected between neighboring cells by links extending along different directions to the neighboring cells. Such an array is preferably implemented as a high-speed integrated circuit. The computation of the optimum path is accomplished by, in each cell, receiving stimulus signals from neighboring cells along corresponding directions, determining and storing the identity of a direction along which the first stimulus signal is received, broadcasting a subsequent stimulus signal to the neighboring cells after a predetermined delay time, whereby stimulus signals propagate throughout the array from a starting one of the cells. After propagation of the stimulus signal throughout the array, a master processor traces back from a selected destination cell to the starting cell along an optimum path of the cells in accordance with the identity of the directions stored in each of the cells.
Optimum quantum dot size for highly efficient fluorescence bioimaging
NASA Astrophysics Data System (ADS)
Martínez Maestro, Laura; Jacinto, Carlos; Rocha, Uéslen; Carmen Iglesias-de la Cruz, M.; Sanz-Rodriguez, Francisco; Juarranz, Angeles; García Solé, José; Jaque, Daniel
2012-01-01
Semiconductor quantum dots of few nanometers have demonstrated a great potential for bioimaging. The size determines the emitted color, but it is also expected to play an important role in the image brightness. In this work, the size dependence of the fluorescence quantum yield of the highly thermal sensitive CdTe quantum dots has been systematically investigated by thermal lens spectroscopy. It has been found that an optimum quantum yield is reached for 3.8-nm quantum dots. The presence of this optimum size has been corroborated in both one-photon excited fluorescence experiments and two-photon fluorescence microscopy of dot-incubated cancer cells. Combination of quantum yield and fluorescence decay time measurements supports that the existence of this optimum size emerges from the interplay between the frequency-dependent radiative emission rate and the size-dependent coupling strength between bulk excitons and surface trapping states.
Two loop divergences studied with one loop constrained differential renormalization
Seijas, Cesar . E-mail: cesar@fpaxp1.usc.es
2007-08-15
In the context of differential renormalization, using constrained differential renormalization rules at one-loop, we show how to obtain concrete results in two-loop calculations without making use of Ward identities. In order to do that, we obtain a list of integrals with overlapping divergences compatible with CDR that can be applied to various two-loop background field calculations. As an example, we obtain the two-loop coefficient of the beta function of QED, SuperQED and Yang-Mills theory.
The research on the optimum working conditions of photoconductive antenna
NASA Astrophysics Data System (ADS)
Shi, Wei; Dai, Yang; Zhang, Like; Yang, Lei; Yan, Zhijin; Chen, Suguo; Hou, Lei
2015-11-01
The photoconductive antenna (PCA) is one of the most common devices to generate terahertz (THz) wave, whose radiation efficiency is largely determined by the working conditions. In order to improve the power of THz wave, the influence of pump laser and bias voltage on the intensity of the THz wave radiated by PCA was studied through experiment and the optimum working conditions of PCA was obtained through the theoretical analysis, these are the maximum safe voltage and saturated laser energy. Only under the optimum conditions can the signal-to-noise ratio(SNR)of THz wave radiated by PCA be the highest and the PCA would not breakdown.
Optimum profiles for asymmetrical longitudinal fins in annular ducts
Fabbri, G.
2000-04-01
In the present work the geometry of annular ducts with asymmetrical longitudinal fins is optimized in order to enhance the heat transfer under laminar coolant flow conditions. The heat transferred is also maximized for a given amount of material or hydraulic resistance. Polynomial profiles are assigned to the two lateral fin surfaces. Velocity and temperature distributions on the annular duct cross section are determined with the help of a finite-element model. A global heat transfer coefficient and an equivalent Nusselt number are then calculated. Lastly, optimum asymmetrical fins obtained by means of a genetic algorithm are shown for different situations and their performance is compared with those of optimum symmetrical fins.
Optimum control forces for multibody systems with intermittent motion
NASA Technical Reports Server (NTRS)
Ider, Sitki Kemal; Amirouche, F. M. L.
1989-01-01
The objective is to address the continuity of motion when a dynamical system is suddenly subjected to constraint conditions. Motion discontinuity due to the initial constraint violation is avoided by prior control forces that adjust the motion and yield velocity and acceleration consistent at the point of application of the constraint. The optimum control forces are determined for a specified control interval. The method proposed provides an optimum adjustment of the system's motion and assures that the stresses developed at the system components are kept within acceptable limits. The procedures developed will be illustrated making use of inequality constraints applied to obstacle avoidance problems in robotics.
Optimum high temperature strength of two-dimensional nanocomposites
Monclús, M. A.; Molina-Aldareguía, J. M.; Polcar, T.; Llorca, J.
2013-11-01
High-temperature nanoindentation was used to reveal nano-layer size effects on the hardness of two-dimensional metallic nanocomposites. We report the existence of a critical layer thickness at which strength achieves optimal thermal stability. Transmission electron microscopy and theoretical bicrystal calculations show that this optimum arises due to a transition from thermally activated glide within the layers to dislocation transmission across the layers. We demonstrate experimentally that the atomic-scale properties of the interfaces profoundly affect this critical transition. The strong implications are that interfaces can be tuned to achieve an optimum in high temperature strength in layered nanocomposite structures.
Accelerating the loop expansion
Ingermanson, R.
1986-07-29
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.
Ekpyrotic loop quantum cosmology
Wilson-Ewing, Edward
2013-08-01
We consider the ekpyrotic paradigm in the context of loop quantum cosmology. In loop quantum cosmology the classical big-bang singularity is resolved due to quantum gravity effects, and so the contracting ekpyrotic branch of the universe and its later expanding phase are connected by a smooth bounce. Thus, it is possible to explicitly determine the evolution of scalar perturbations, from the contracting ekpyrotic phase through the bounce and to the post-bounce expanding epoch. The possibilities of having either one or two scalar fields have been suggested for the ekpyrotic universe, and both cases will be considered here. In the case of a single scalar field, the constant mode of the curvature perturbations after the bounce is found to have a blue spectrum. On the other hand, for the two scalar field ekpyrotic model where scale-invariant entropy perturbations source additional terms in the curvature perturbations, the power spectrum in the post-bounce expanding cosmology is shown to be nearly scale-invariant and so agrees with observations.
Transequatorial Loops: General Statistics
NASA Astrophysics Data System (ADS)
Pevtsov, A. A.
2003-05-01
Transequatorial loops (TLs), -- coronal structures connecting magnetic fields in opposite hemispheres -- were first found in Skylab data, and later studied in more detail using Yohkoh SXT images. TLs are most clearly found in a few MK data (including EIT284Å). They may connect quiet Sun and/or active region areas in opposite hemispheres. In some cases, TLs may develop shortly after emergence of active region magnetic field, but sometimes they may be present before the active region emerges. Helicity of connected areas appears to play more important role that the separation between the regions. In most cases interconnected regions have the same sign of helicity. Often, TLs may connect two regions of same helicity that are far apart (> 70o) and be absent between much closer regions (< 20o) whose helicity is opposite to each other. There is an indication that TLs may repeatedly appear at certain longitudes, similar to complexes of activity. In this talk, I will review the observational properties of transequatorial loops and the corresponding magnetic fields.
Optimizing coherent anti-Stokes Raman scattering by genetic algorithm controlled pulse shaping
NASA Astrophysics Data System (ADS)
Yang, Wenlong; Sokolov, Alexei
2010-10-01
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.
The double loop mattress suture
Biddlestone, John; Samuel, Madan; Creagh, Terry; Ahmad, Tariq
2014-01-01
An interrupted stitch type with favorable tissue characteristics will reduce local wound complications. We describe a novel high-strength, low-tension repair for the interrupted closure of skin, cartilage, and muscle, the double loop mattress stitch, and compare it experimentally with other interrupted closure methods. The performance of the double loop mattress technique in porcine cartilage and skeletal muscle is compared with the simple, mattress, and loop mattress interrupted sutures in both a novel porcine loading chamber and mechanical model. Wound apposition is assessed by electron microscopy. The performance of the double loop mattress in vivo was confirmed using a series of 805 pediatric laparotomies/laparoscopies. The double loop mattress suture is 3.5 times stronger than the loop mattress in muscle and 1.6 times stronger in cartilage (p ? 0.001). Additionally, the double loop mattress reduces tissue tension by 66% compared with just 53% for the loop mattress (p ? 0.001). Wound gapping is equal, and wound eversion appears significantly improved (p ? 0.001) compared with the loop mattress in vitro. In vivo, the double loop mattress performs as well as the loop mattress and significantly better than the mattress stitch in assessments of wound eversion and dehiscence. There were no episodes of stitch extrusion in our series of patients. The mechanical advantage of its intrinsic pulley arrangement gives the double loop mattress its favorable properties. Wound dehiscence is reduced because this stitch type is stronger and exerts less tension on the tissue than the mattress stitch. We advocate the use of this novel stitch wherever a high-strength, low-tension repair is required. These properties will enhance wound repair, and its application will be useful to surgeons of all disciplines. PMID:24698436
Unstable anisotropic loop quantum cosmology
Nelson, William; Sakellariadou, Mairi
2009-09-15
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.
Optimum Onager: The Classical Mechanics of a Classical Siege Engine
ERIC Educational Resources Information Center
Denny, Mark
2009-01-01
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 thisâ€¦
DETERMINING OPTIMUM HARVEST TIME FOR GUAYULE LATEX AND BIOMASS
Technology Transfer Automated Retrieval System (TEKTRAN)
Guayule (Parthenium argentatum Gray) is a perennial shrub native to the Chihuahuan Desert of Northern Mexico and the Big Bend area of southwest Texas. One of the most valuable products from guayule is its hypoallergenic latex. However, little research has been done on the optimum harvest time for la...
Site survey for optimum location of Optical Communication Experimental Facility
NASA Technical Reports Server (NTRS)
1968-01-01
Site survey was made to determine the optimum location for an Optical Communication Experimental Facility /OCEF/ and to recommend several sites, graded according to preference. A site was desired which could perform two-way laser communication with a spacecraft and laser tracking with a minimum of interruption by weather effects.
An Application of Calculus: Optimum Parabolic Path Problem
ERIC Educational Resources Information Center
Atasever, Merve; Pakdemirli, Mehmet; Yurtsever, Hasan Ali
2009-01-01
A practical and technological application of calculus problem is posed to motivate freshman students or junior high school students. A variable coefficient of friction is used in modelling air friction. The case in which the coefficient of friction is a decreasing function of altitude is considered. The optimum parabolic path for a flying object…
Selection of Wavelengths for Optimum Precision in Simultaneous Spectrophotometric Determinations.
ERIC Educational Resources Information Center
DiTusa, Michael R.; Schilt, Alfred A.
1985-01-01
Although many textbooks include a description of simultaneous determinations employing absorption spectrophotometry and treat the mathematics necessary for analytical quantitations, treatment of analytical wavelength selection has been mostly qualitative. Therefore, a general method for selecting wavelengths for optimum precision in simultaneousâ€¦
Optimum Onager: The Classical Mechanics of a Classical Siege Engine
ERIC Educational Resources Information Center
Denny, Mark
2009-01-01
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…
METHODOLOGY FOR DESIGNING AN OPTIMUM AIR QUALITY MONITORING NETWORK
A two-step objective method is presented for determining the optimum number and disposition of ambient air quality stations in a monitoring network. The method uses a data base consisting of a comprehensive set of simulated or measured air quality patterns representative of the r...
Optimum Design of Aerospace Structural Components Using Neural Networks
NASA Technical Reports Server (NTRS)
Berke, L.; Patnaik, S. N.; Murthy, P. L. N.
1993-01-01
The application of artificial neural networks to capture structural design expertise is demonstrated. The principal advantage of a trained neural network is that it requires a trivial computational effort to produce an acceptable new design. For the class of problems addressed, the development of a conventional expert system would be extremely difficult. In the present effort, a structural optimization code with multiple nonlinear programming algorithms and an artificial neural network code NETS were used. A set of optimum designs for a ring and two aircraft wings for static and dynamic constraints were generated using the optimization codes. The optimum design data were processed to obtain input and output pairs, which were used to develop a trained artificial neural network using the code NETS. Optimum designs for new design conditions were predicted using the trained network. Neural net prediction of optimum designs was found to be satisfactory for the majority of the output design parameters. However, results from the present study indicate that caution must be exercised to ensure that all design variables are within selected error bounds.
Automatic planning concept - An analysis of optimum scheduling
NASA Technical Reports Server (NTRS)
Rebelein, P. R.; Truenbels, P.
1968-01-01
Study considers resource costs, mission constraints, and experiment results as linear functions, insofar as possible, in an effort to develop optimum scheduling by the use of linear programming. It involves a mathematical approach in which a number of constraints are considered operative.
Optimum mix of conservation and solar energy in buildings
Balcomb, J.D.
1980-01-01
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.
An Application of Calculus: Optimum Parabolic Path Problem
ERIC Educational Resources Information Center
Atasever, Merve; Pakdemirli, Mehmet; Yurtsever, Hasan Ali
2009-01-01
A practical and technological application of calculus problem is posed to motivate freshman students or junior high school students. A variable coefficient of friction is used in modelling air friction. The case in which the coefficient of friction is a decreasing function of altitude is considered. The optimum parabolic path for a flying objectâ€¦
Selection of Wavelengths for Optimum Precision in Simultaneous Spectrophotometric Determinations.
ERIC Educational Resources Information Center
DiTusa, Michael R.; Schilt, Alfred A.
1985-01-01
Although many textbooks include a description of simultaneous determinations employing absorption spectrophotometry and treat the mathematics necessary for analytical quantitations, treatment of analytical wavelength selection has been mostly qualitative. Therefore, a general method for selecting wavelengths for optimum precision in simultaneous…
Loop-the-Loop: Bringing Theory into Practice
ERIC Educational Resources Information Center
Suwonjandee, N.; Asavapibhop, B.
2012-01-01
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,…
Loop-the-Loop: Bringing Theory into Practice
ERIC Educational Resources Information Center
Suwonjandee, N.; Asavapibhop, B.
2012-01-01
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,â€¦
Pei, L.; Klebaner, A.; Theilacker, J.; Soyars, W.; Martinez, A.; Bossert, R.; DeGraff, B.; Darve, C.; /Fermilab
2011-06-01
The Horizontal Test Stand (HTS) SRF Cavity and Cryomodule 1 (CM1) of eight 9-cell, 1.3GHz SRF cavities are operating at Fermilab. For the cryogenic control system, how to hold liquid level constant in the cryostat by regulation of its Joule-Thompson JT-valve is very important after cryostat cool down to 2.0 K. The 72-cell cryostat liquid level response generally takes a long time delay after regulating its JT-valve; therefore, typical PID control loop should result in some cryostat parameter oscillations. This paper presents a type of PID parameter self-optimal and Time-Delay control method used to reduce cryogenic system parameters oscillation.
Chesi, Stefano; CEMS, RIKEN, Wako, Saitama 351-0198 ; Jaffe, Arthur; Department of Physics, University of Basel, Basel; Institute for Theoretical Physics, ETH ZÃ¼rich, ZÃ¼rich ; Loss, Daniel; Department of Physics, University of Basel, Basel ; Pedrocchi, Fabio L.
2013-11-15
We investigate the role that vortex loops play in characterizing eigenstates of interacting Majoranas. We give some general results and then focus on ladder Hamiltonian examples as a test of further ideas. Two methods yield exact results: (i) A mapping of certain spin Hamiltonians to quartic interactions of Majoranas shows that the spectra of these two examples coincide. (ii) In cases with reflection-symmetric Hamiltonians, we use reflection positivity for Majoranas to characterize vortices in the ground states. Two additional methods suggest wider applicability of these results: (iii) Numerical evidence suggests similar behavior for certain systems without reflection symmetry. (iv) A perturbative analysis also suggests similar behavior without the assumption of reflection symmetry.
On the Role of Intrinsic and Extrinsic Forces in Early Cardiac S-looping
Ramasubramanian, Ashok; Chu-LaGraff, Quynh B.; Buma, Takashi; Chico, Kevin T.; Carnes, Meagan E.; Burnett, Kyra R.; Bradner, Sarah A.; Gordon, Shaun S.
2014-01-01
Background Looping is a crucial phase during heart development when the initially straight heart tube is transformed into a shape that more closely resembles the mature heart. Although the genetic and biochemical pathways of cardiac looping are well-studied, the biophysical mechanisms that actually effect the looping process remain poorly understood. Using a combined experimental (chick embryo) and computational (finite element modeling) approach, we study the forces driving early s-looping when the primitive ventricle moves to its definitive position inferior to the common atrium. Results New results from our study indicate that the primitive heart has no intrinsic ability to form an s-loop and that extrinsic forces are necessary to effect early s-looping. They support previous studies that established an important role for cervical flexure in causing early cardiac s-looping. Our results also show that forces applied by the splanchnopleure cannot be ignored during early s-looping and shed light on the role of cardiac jelly. Using available experimental data and computer modeling, we successfully developed and tested a hypothesis for the force mechanisms driving s-loop formation. Conclusions Forces external to the primitive heart tube are necessary in the later stages of cardiac looping. Experimental and model results support our proposed hypothesis for forces driving early s-looping. PMID:23553909
Closed-form solution for loop transfer recovery via reduced-order observers
NASA Technical Reports Server (NTRS)
Bacon, Barton J.
1989-01-01
A well-known property of the reduced-order observer is exploited to obtain the controller solution of the loop transfer recovery problem. In that problem, the controller is sought that generates some desired loop shape at the plant's input or output channels. Past approaches to this problem have typically yielded controllers generating loop shapes that only converge pointwise to the desired loop shape. In the proposed approach, however, the solution (at the input) is obtained directly when the plant's first Markov parameter is full rank. In the more general case when the plant's first Markov parameter is not full rank, the solution is obtained in an analogous manner by appending a special set of input and output signals to the original set. A dual form of the reduced-order observer is shown to yield the LTR solution at the output channel.
The Projectile Inside the Loop
ERIC Educational Resources Information Center
Varieschi, Gabriele U.
2006-01-01
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.
Sodium loop framework structural analysis
Nguyen, P.M.
1995-06-06
This document provides the structural analysis of the Sodium Loop framework in a drop condition. The drop is similar to the US Department of Transportation non-bulk, performance-oriented packaging (Packaging Group I) drop test. The drop height evaluated for the Sodium Loop framework is 5.9 ft.
Loop Heat Pipe Startup Behaviors
NASA Technical Reports Server (NTRS)
Ku, Jentung
2014-01-01
A loop heat pipe must start successfully before it can commence its service. The start-up transient represents one of the most complex phenomena in the loop heat pipe operation. This paper discusses various aspects of loop heat pipe start-up behaviors. Topics include the four start-up scenarios, the initial fluid distribution between the evaporator and reservoir that determines the start-up scenario, factors that affect the fluid distribution between the evaporator and reservoir, difficulties encountered during the low power start-up, and methods to enhance the start-up success. Also addressed are the thermodynamic constraint between the evaporator and reservoir in the loop heat pipe operation, the superheat requirement for nucleate boiling, pressure spike and pressure surge during the start-up transient, and repeated cycles of loop start-up andshutdown under certain conditions.
Shang, Jer-Yu (Fairfax, VA); Mei, Joseph S. (Morgantown, WV); Slagle, Frank D. (Kingwood, WV); Notestein, John E. (Morgantown, WV)
1984-01-01
The present invention is directed to a combustion apparatus in the configuration of a oblong annulus defining a closed loop. Particulate coal together with a sulfur sorbent such as sulfur or dolomite is introduced into the closed loop, ignited, and propelled at a high rate of speed around the loop. Flue gas is withdrawn from a location in the closed loop in close proximity to an area in the loop where centrifugal force imposed upon the larger particulate material maintains these particulates at a location spaced from the flue gas outlet. Only flue gas and smaller particulates resulting from the combustion and innerparticle grinding are discharged from the combustor. This structural arrangement provides increased combustion efficiency due to the essentially complete combustion of the coal particulates as well as increased sulfur absorption due to the innerparticle grinding of the sorbent which provides greater particle surface area.
Superordinate Shape Classification Using Natural Shape Statistics
ERIC Educational Resources Information Center
Wilder, John; Feldman, Jacob; Singh, Manish
2011-01-01
This paper investigates the classification of shapes into broad natural categories such as "animal" or "leaf". We asked whether such coarse classifications can be achieved by a simple statistical classification of the shape skeleton. We surveyed databases of natural shapes, extracting shape skeletons and tabulating their parameters within eachâ€¦
Superordinate Shape Classification Using Natural Shape Statistics
ERIC Educational Resources Information Center
Wilder, John; Feldman, Jacob; Singh, Manish
2011-01-01
This paper investigates the classification of shapes into broad natural categories such as "animal" or "leaf". We asked whether such coarse classifications can be achieved by a simple statistical classification of the shape skeleton. We surveyed databases of natural shapes, extracting shape skeletons and tabulating their parameters within each…
Emittance measurements for optimum operation of the J-PARC RF-driven H- ion source
NASA Astrophysics Data System (ADS)
Ueno, A.; Ohkoshi, K.; Ikegami, K.; Takagi, A.; Yamazaki, S.; Oguri, H.
2015-04-01
In order to satisfy the Japan Proton Accelerator Research Complex (J-PARC) second stage requirements of an H- ion beam of 60mA within normalized emittances of 1.5?mm•mrad both horizontally and vertically, a flat top beam duty factor of 1.25% (500?s×25Hz) and a life-time of longer than 1month, the J-PARC cesiated RF-driven H- ion source was developed by using an internal-antenna developed at the Spallation Neutron Source (SNS). The transverse emittances of the source were measured with various conditions to find out the optimum operation conditions minimizing the horizontal and vertical rms normalized emittances. The transverse emittances were most effectively reduced by operating the source with the plasma electrode temperature lower than 70°C. The optimum value of the cesium (Cs) density around the beam hole of the plasma electrode seems to be proportional to the plasma electrode temperature. The fine control of the Cs density is indispensable, since the emittances seem to increase proportionally to the excessiveness of the Cs density. Furthermore, the source should be operated with the Cs density beyond a threshold value, since the plasma meniscus shape and the ellipse parameters of the transverse emittances seem to be changed step-function-likely on the threshold Cs value.
Superordinate shape classification using natural shape statistics
Wilder, John; Feldman, Jacob; Singh, Manish
2011-01-01
This paper investigates the classification of shapes into broad natural categories such as animal or leaf. We asked whether such coarse classifications can be achieved by a simple statistical classification of the shape skeleton. We surveyed databases of natural shapes, extracting shape skeletons and tabulating their parameters within each class, seeking shape statistics that effectively discriminated the classes. We conducted two experiments in which human subjects were asked to classify novel shapes into the same natural classes. We compared subjects’ classifications to those of a naive Bayesian classifier based on the natural shape statistics, and found good agreement. We conclude that human superordinate shape classifications can be well understood as involving a simple statistical classification of the shape skeleton that has been “tuned” to the natural statistics of shape. PMID:21440250
The principle of space coherent laser communication based on Costas phase-locked loop
NASA Astrophysics Data System (ADS)
Zheng, Yang; Zheng, Jianping; Tong, Shoufeng; Jiang, Huilin; He, Wenjun
2013-08-01
The space coherent laser communication is a very potential mean for high-speed laser communication in the future, because the excellent receiver sensitivities can be achieved by coherent detection techniques. The best coherent receiver sensitivity amounts to -59.4dBm at a data rate of 10Gbit/s and a bit error rate of 10-9, which is obtained with phase-shift keying modulation in combination with homodyne detection. In this paper, we investigated optical homodyne detection based on Costas phase-locked loop in the space coherent laser communication system. We obtain optimum loop bandwidth of Costas phase-locked loop and the maximum permissible laser line width based on Costas phase locked loop.
A methodology for selecting optimum organizations for space communities
NASA Technical Reports Server (NTRS)
Ragusa, J. M.
1978-01-01
This paper suggests that a methodology exists for selecting optimum organizations for future space communities of various sizes and purposes. Results of an exploratory study to identify an optimum hypothetical organizational structure for a large earth-orbiting multidisciplinary research and applications (R&A) Space Base manned by a mixed crew of technologists are presented. Since such a facility does not presently exist, in situ empirical testing was not possible. Study activity was, therefore, concerned with the identification of a desired organizational structural model rather than the empirical testing of it. The principal finding of this research was that a four-level project type 'total matrix' model will optimize the effectiveness of Space Base technologists. An overall conclusion which can be reached from the research is that application of this methodology, or portions of it, may provide planning insights for the formal organizations which will be needed during the Space Industrialization Age.
Design of helicopter rotor blades for optimum dynamic characteristics
NASA Technical Reports Server (NTRS)
Peters, D. A.; Ko, T.; Korn, A. E.; Rossow, M. P.
1983-01-01
The possibilities and limitations of tailoring blade mass and stiffness distributions to give an optimum blade design in terms of weight, inertia, and dynamic characteristics are discussed. The extent that changes in mass of stiffness distribution can be used to place rotor frequencies at desired locations is determined. Theoretical limits to the amount of frequency shift are established. Realistic constraints on blade properties based on weight, mass, moment of inertia, size, strength, and stability are formulated. The extent that the hub loads can be minimized by proper choice of E1 distribution, and the minimum hub loads which can be approximated by a design for a given set of natural frequencies are determined. Aerodynamic couplings that might affect the optimum blade design, and the relative effectiveness of mass and stiffness distribution on the optimization procedure are investigated.
Optimum Structure of Whipple Shield against Hypervelocity Impact
NASA Astrophysics Data System (ADS)
Lee, Minhyung
2013-06-01
It has been known that the spacecraft protection issues against space debris or meteoroid impact damage are of great importance. Whipple shield structures (double spaced plates) have been investigated and empirical ballistic limit curve (BLCs) are developed. In this paper, we like to investigate an optimum Whipple Shield structure of fixed areal density and space. To do this, a new in-house SPH code has been used. Last 20 years SPH (Smoothed Particle Hydrodynamics) numerical scheme has been widely applied to the hypervelocity impact problems because of the limited velocity range and cost of test. We first examined the extent of debris spreading which seems to be a key factor to the back plate impact. The debris cloud expansion angle shows a maximum value. Then, a series of hypervelocity impact simulations were conducted to predict the critical impacting sphere diameter. It has been found that there is an optimum thickness ratio of front bumper to real wall.
Design of helicopter rotor blades for optimum dynamic characteristics
NASA Technical Reports Server (NTRS)
Peters, D. A.; Ko, T.; Korn, A. E.; Rossow, M. P.
1982-01-01
The possibilities and the limitations of tailoring blade mass and stiffness distributions to give an optimum blade design in terms of weight, inertia, and dynamic characteristics are investigated. Changes in mass or stiffness distribution used to place rotor frequencies at desired locations are determined. Theoretical limits to the amount of frequency shift are established. Realistic constraints on blade properties based on weight, mass moment of inertia size, strength, and stability are formulated. The extent hub loads can be minimized by proper choice of EL distribution is determined. Configurations that are simple enough to yield clear, fundamental insights into the structural mechanisms but which are sufficiently complex to result in a realistic result for an optimum rotor blade are emphasized.
Multilevel polarization shift keying: Optimum receiver structure and performance evaluation
Benedetto, S.; Poggiolini, P.T.
1994-02-01
Multilevel digital coherent optical modulation schemes based on the state of polarization of a fully polarized lightwave are proposed and analyzed. Based on the complete statistical characterization of the Stokes parameters, extracted though appropriate signal processing in the presence of shot and additive gaussian noise, the optimum maximum likelihood receiver operating symbol by symbol is derived. The exact performance in terms of the average symbol error probability is found. Optimum constellations for the case of equipower 4, 8, 16 and 32 signals are found on the basis of the minimization of the error probability for a given average power. Their performance turns out to be promising as compared to other standard modulation techniques. The spectral analysis of polarization modulated signals is presented. A new receiver structure, which solves the problem of the excess penalties incurred in the presence of channel dichroism, is proposed and analyzed. 22 refs.
Implementation of an optimum profile guidance system on STOLAND
NASA Technical Reports Server (NTRS)
Flanagan, P. F.
1978-01-01
The implementation on the STOLAND airborne digital computer of an optimum profile guidance system for the augmentor wing jet STOL research aircraft is described. Major tasks were to implement the guidance and control logic to airborne computer software and to integrate the module with the existing STOLAND navigation, display, and autopilot routines. The optimum profile guidance system comprises an algorithm for synthesizing mimimum fuel trajectories for a wide range of starting positions in the terminal area and a control law for flying the aircraft automatically along the trajectory. The avionics software developed is described along with a FORTRAN program that was constructed to reflect the modular nature and algorthms implemented in the avionics software.
Optimum detection of an optical image on a photoelectric surface.
NASA Technical Reports Server (NTRS)
Helstrom, C. W.; Wang, L.
1973-01-01
The image-detecting performance of an optimum counting detector is compared with that of a threshold detector and that of a detector basing its decisions on the total number of photoelectrons from a finite area of the image. The illuminance of the image is assumed to have a Gaussian spatial distribution. The optimum detector works with the pristine datum (and not with the photoelectric response) which is the spatiotemporal electromagnetic field at the aperture of the observing optical instrument. It is shown that little is to be gained by using details of the illuminance distribution beyond the crude knowledge of its breadth as embodied in a simple counter of emitted photoelectrons. All three detectors exhibit accordingly about the same reliability.
Parallel operation of NH3 screw compressors - the optimum way
NASA Astrophysics Data System (ADS)
Pijnenburg, B.; Ritmann, J.
2015-08-01
The use of more smaller industrial NH3 screw compressors operating in parallel seems to offer the optimum way when it comes to fulfilling maximum part load efficiency, increased redundancy and other highly requested features in the industrial refrigeration industry today. Parallel operation in an optimum way can be selected to secure continuous operation and can in most applications be configured to ensure lower overall operating economy. New compressors are developed to meet requirements for flexibility in operation and are controlled in an intelligent way. The intelligent control system keeps focus on all external demands, but yet striving to offer always the lowest possible absorbed power, including in future scenarios with connection to smart grid.
The Population of Small Comets: Optimum Techniques for Detection
NASA Technical Reports Server (NTRS)
Brandt, John C.
1997-01-01
The goals of this project were: (1) to present evidence to the scientific community for the importance of the small comet population and (2) to develop techniques for optimum detection in order to characterize the population. Our work on techniques has been to develop algorithms for searching images for SCs based on the distinctive properties of comets; (1) motion with respect to background stars; (2) extended source with most light coming from the coma rather than the nucleus; and characteristic spectral signature.
The Population of Small Comets: Optimum Techniques for Detection
NASA Technical Reports Server (NTRS)
Schleicher, D.; AHearn, M.; Stewart, I. A. F.; Randall, C.; Brandt, J.
1999-01-01
The goals of this project were: (1) to present evidence to the scientific community for the importance of the small comet population and (2) to develop techniques for optimum detection in order to characterize the population. The work has been carried out by D. Schleicher (Lowell Observatory), M. A'Hearn and Y. Fernandez (University of Maryland), I.A.F. Stewart, C. Randall, and J. Brandt (University of Colorado).
Optimum Input Selection For Data Driven Modeling. Mirage or Reality?
NASA Astrophysics Data System (ADS)
Elshorbagy, Amin; Izadifar, Zohreh
2010-05-01
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 data driven modeling. In this study, the research question of "is it possible to select the optimum inputs of data driven models a priori?" is addressed. This question, in various forms, received considerable attention in data driven modeling literature, and ANN literature in particular. The case study of estimating the hourly actual evapotranspiration (AET) using multiple meteorological variables (air temperature, net radiation, ground temperature, relative humidity, and wind speed) was used. The correlation between the various inputs and the output, and the input contribution to the output predictability were investigated using simple correlation matrix, step-wise regression, mutual and partial mutual information, Gamma test, and wavelet analysis in an attempt to identify the optimum inputs a priori. Neural networks, genetic programming, and multiple linear regression techniques were also used to develop the AET models with trial and error to select the best inputs. The performances of the models were assessed based on their accuracy, identifiability, uncertainty, and parsimony. It was found that, even though input selection methods might provide partial help and information regarding the most relevant inputs, it is impossible or impractical to fully identify the optimum inputs without trial and error with the modeling techniques themselves. The complexity of the interrelationships among the hydrological inputs makes it impossible to identify the relative merits of the individual inputs versus the compound effects of endless possible combinations of inputs. Even though the partial possibility of input selection a priori cannot be denied, the mirage cannot be refuted.
Achieving optimum performance in a high pressure sodium lighting system
Kao, C.; Kane, R.
1982-07-01
In spite of the many advantages of a high pressure sodium (HPS) lighting system, some problems do exist and compromises must be made. The lighting designer should be thoroughly familiar with the characteristics of all the integral components which make it up, such as lamps, ballasts, starters, luminaires, and poles. The most pertinent characteristics of these components are discussed. By proper selection of various components, they can function well together to achieve an optimum system performance.
Analysis of spent beam refocusing to achieve optimum collector efficiency
NASA Technical Reports Server (NTRS)
Stankiewicz, N.
1977-01-01
A reasonable criterion for evaluating the effectiveness of spent beam refocusing is the reduction of spent beam turbulence. The rms deviation of particle angles where the angles are calculated from the ratio of radial velocity to axial velocity is one measure of beam turbulence. It is demonstrated that the angular deviation can be reduced by almost half in some magnetic field configurations. Experimental evidence indicates that beam processing of this type is most likely to yield an optimum collector efficiency.
Development of agri-pellet production cost and optimum size.
Sultana, Arifa; Kumar, Amit; Harfield, Don
2010-07-01
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
Four letters in the genetic alphabet: a frozen evolutionary optimum?
SzathmÃ¡ry, E
1991-08-22
Piccirilli et al. (Nature, Lond. 343, 33-37 (1990)) have shown experimentally that the replicatable introduction of new base pairs into the genetic alphabet is chemically feasible. The fact that our current genetic alphabet uses only two base pairs can be explained provided that this basic feature of organisms became fixed in an RNA world utilizing ribozymes rather than protein enzymes. The fitness of such ribo-organisms is determined by two factors: replication fidelity and overall catalytic efficiency (basic metabolic or growth rate). Replication fidelity is shown to decrease roughly exponentially, and catalytic efficiency is shown to increase with diminishing returns, with the number of letters for a fixed genome length; hence their product, i.e. fitness, gives rise to a set of values with an optimum. Under a wide range of parameter values the optimum rests at two base pairs. The chemical identity of the particular choice in our genetic alphabet can also be rationalized. This optimum is considered frozen, as currently the dominant catalysts are proteins rather than RNAs. PMID:1719561
Optimum Damping in a Non-Linear Base Isolation System
NASA Astrophysics Data System (ADS)
Jangid, R. S.
1996-02-01
Optimum isolation damping for minimum acceleration of a base-isolated structure subjected to earthquake ground excitation is investigated. The stochastic model of the El-Centro1940 earthquake, which preserves the non-stationary evolution of amplitude and frequency content of ground motion, is used as an earthquake excitation. The base isolated structure consists of a linear flexible shear type multi-storey building supported on a base isolation system. The resilient-friction base isolator (R-FBI) is considered as an isolation system. The non-stationary stochastic response of the system is obtained by the time dependent equivalent linearization technique as the force-deformation of the R-FBI system is non-linear. The optimum damping of the R-FBI system is obtained under important parametric variations; i.e., the coefficient of friction of the R-FBI system, the period and damping of the superstructure; the effective period of base isolation. The criterion selected for optimality is the minimization of the top floor root mean square (r.m.s.) acceleration. It is shown that the above parameters have significant effects on optimum isolation damping.
Optimum threshold selection method of centroid computation for Gaussian spot
NASA Astrophysics Data System (ADS)
Li, Xuxu; Li, Xinyang; Wang, Caixia
2015-10-01
Centroid computation of Gaussian spot is often conducted to get the exact position of a target or to measure wave-front slopes in the fields of target tracking and wave-front sensing. Center of Gravity (CoG) is the most traditional method of centroid computation, known as its low algorithmic complexity. However both electronic noise from the detector and photonic noise from the environment reduces its accuracy. In order to improve the accuracy, thresholding is unavoidable before centroid computation, and optimum threshold need to be selected. In this paper, the model of Gaussian spot is established to analyze the performance of optimum threshold under different Signal-to-Noise Ratio (SNR) conditions. Besides, two optimum threshold selection methods are introduced: TmCoG (using m % of the maximum intensity of spot as threshold), and TkCoG ( using?n +?? n as the threshold), ?n and ?n are the mean value and deviation of back noise. Firstly, their impact on the detection error under various SNR conditions is simulated respectively to find the way to decide the value of k or m. Then, a comparison between them is made. According to the simulation result, TmCoG is superior over TkCoG for the accuracy of selected threshold, and detection error is also lower.
Automated optimum design of wing structures. Deterministic and probabilistic approaches
NASA Technical Reports Server (NTRS)
Rao, S. S.
1982-01-01
The automated optimum design of airplane wing structures subjected to multiple behavior constraints is described. The structural mass of the wing is considered the objective function. The maximum stress, wing tip deflection, root angle of attack, and flutter velocity during the pull up maneuver (static load), the natural frequencies of the wing structure, and the stresses induced in the wing structure due to landing and gust loads are suitably constrained. Both deterministic and probabilistic approaches are used for finding the stresses induced in the airplane wing structure due to landing and gust loads. A wing design is represented by a uniform beam with a cross section in the form of a hollow symmetric double wedge. The airfoil thickness and chord length are the design variables, and a graphical procedure is used to find the optimum solutions. A supersonic wing design is represented by finite elements. The thicknesses of the skin and the web and the cross sectional areas of the flanges are the design variables, and nonlinear programming techniques are used to find the optimum solution.
Optimum design of structures subject to general periodic loads
NASA Technical Reports Server (NTRS)
Reiss, Robert; Qian, B.
1989-01-01
A simplified version of Icerman's problem regarding the design of structures subject to a single harmonic load is discussed. The nature of the restrictive conditions that must be placed on the design space in order to ensure an analytic optimum are discussed in detail. Icerman's problem is then extended to include multiple forcing functions with different driving frequencies. And the conditions that now must be placed upon the design space to ensure an analytic optimum are again discussed. An important finding is that all solutions to the optimality condition (analytic stationary design) are local optima, but the global optimum may well be non-analytic. The more general problem of distributing the fixed mass of a linear elastic structure subject to general periodic loads in order to minimize some measure of the steady state deflection is also considered. This response is explicitly expressed in terms of Green's functional and the abstract operators defining the structure. The optimality criterion is derived by differentiating the response with respect to the design parameters. The theory is applicable to finite element as well as distributed parameter models.
The optimum decision rules for the oddity task.
Versfeld, N J; Dai, H; Green, D M
1996-01-01
This paper presents the optimum decision rule for an m-interval oddity task in which m-1 intervals contain the same signal and one is different or odd. The optimum decision rule depends on the degree of correlation among observations. The present approach unifies the different strategies that occur with "roved" or "fixed" experiments (Macmillan & Creelman, 1991, p. 147). It is shown that the commonly used decision rule for an m-interval oddity task corresponds to the special case of highly correlated observations. However, as is also true for the same-different paradigm, there exists a different optimum decision rule when the observations are independent. The relation between the probability of a correct response and d' is derived for the three-interval oddity task. Tables are presented of this relation for the three-, four-, and five-interval oddity task. Finally, an experimental method is proposed that allows one to determine the decision rule used by the observer in an oddity experiment. PMID:8668510
Assessing catchment connectivity using hysteretic loops
NASA Astrophysics Data System (ADS)
Keesstra, Saskia; Masselink, Rens; Goni, Mikel; Campo, Miguel Angel; Gimenez, Rafael; Casali, Javier; Seeger, Manuel
2015-04-01
Sediment connectivity is a concept which can explain the origin, pathways and sinks of sediments within landscapes. This information is valuable for land managers to be able to take appropriate action at the correct place. Hysteresis between sediment and water discharge can give important information about the sources , pathways and conditions of sediment that arrives at the outlet of a catchment. "Hysteresis" happens when the sediment concentration associated with a certain flow rate is different depending on the direction in which the analysis is performed -towards the increase or towards the diminution of the flow. This phenomenon to some extent reflects the way in which the runoff generation processes are conjugated with those of the production and transport of sediments, hence the usefulness of hysteresis as a diagnostic hydrological parameter. However, the complexity of the phenomena and factors which determine hysteresis make its interpretation uncertain or, at the very least, problematic. Many types of hysteretic loops have been described as well as the cause for the shape of the loop, mainly describing the origin of the sediments. In this study, several measures to objectively classify hysteretic loops in an automated way were developed. These were consecutively used to classify several hundreds of loops from several agricultural catchments in Northern Spain. The data set for this study comes from four experimental watersheds in Navarre (Spain), owned and maintained by the Government of Navarre. These experimental watersheds have been monitored and studied since 1996 (La Tejería and Latxaga) and 2001 (Oskotz "principal", Op, and Oskotz "woodland", Ow). La Tejería and Latxaga watersheds, located in the Central Western part of Navarre, are roughly similar to each other regarding size (approximately 200 ha), geology (marls and sandstones), soils (fine texture topsoil), climate (humid sub Mediterranean) and land use (80-90% cultivated with winter grain crops). On the other hand, Op (ca.1,700 ha) is covered with forest and pasture (cattle-breeding); while Ow (ca. 500 ha), a sub-watershed of the Op, is almost completely covered with forest. The predominant climate in Op/Ow is sub-Atlantic. Furthermore, antecedent conditions and event characteristics were analysed. The loops were compared quantitatively and qualitatively between catchments for similar events and within the catchments for events with different characteristics.
McCormack, B.; Kaita, R.; Kugel, H.; Hatcher, R.
2000-01-06
The Rogowski Loop is one of the most basic diagnostics for tokamak operations. On the National Spherical Torus Experiment (NSTX), the plasma current Rogowski Loop had the constraints of the very limited space available on the center stack, 5,000 volt isolation, flexibility requirements as it remained a part of the Center Stack assembly after the first phase of operation, and a +120 C temperature requirement. For the second phase of operation, four Halo Current Rogowski Loops under the Center Stack tiles will be installed having +600 C and limited space requirements. Also as part of the second operational phase, up to ten Rogowski Loops will installed to measure eddy currents in the Passive Plate support structures with +350 C, restricted space, and flexibility requirements. This presentation will provide the details of the material selection, fabrication techniques, testing, and installation results of the Rogowski Loops that were fabricated for the high temperature operational and bakeout requirements, high voltage isolation requirements, and the space and flexibility requirements imposed upon the Rogowski Loops. In the future operational phases of NSTX, additional Rogowski Loops could be anticipated that will measure toroidal plasma currents in the vacuum vessel and in the Passive Plate assemblies.
Physical Meaning of the Optimum Measurement Process in Quantum Detection Theory
NASA Technical Reports Server (NTRS)
Osaki, Masao; Kozuka, Haruhisa; Hirota, Osamu
1996-01-01
The optimum measurement processes are represented as the optimum detection operators in the quantum detection theory. The error probability by the optimum detection operators goes beyond the standard quantum limit automatically. However the optimum detection operators are given by pure mathematical descriptions. In order to realize a communication system overcoming the standard quantum limit, we try to give the physical meaning of the optimum detection operators.
Sica, Domenic A; Carter, Barry; Cushman, William; Hamm, Lee
2011-09-01
KEY POINTS AND PRACTICAL RECOMMENDATIONS: • ?Although chlorthalidone and hydrochlorothiazide are structurally similar, they are very different pharmacokinetically, with chlorthalidone having both an extremely long half-life (approximately 40 to 60 hours) and a large volume of distribution, with gradual elimination from the plasma compartment by tubular secretion. • ?Furosemide usage, the most widely used diuretic in the loop diuretic class, can be complicated by extremely erratic absorption, with a bioavailability range of 12% to 112%. • ?Chlorthalidone, at a dose of 25 mg, is comparatively more potent than 50 mg of hydrochlorothiazide, particularly as related to overnight blood pressure reduction. • ?In ALLHAT, there was no difference among chlorthalidone, amlodipine, lisinopril, and doxazosin for the primary outcome or mortality. • ?Secondary outcomes were similar except for a 38% higher rate of heart failure with amlodipine; a 10% higher rate of combined cardiovascular disease, a 15% higher rate of stroke, and a 19% higher rate of heart failure with lisinopril; and a 20% higher rate of cardiovascular disease, a 20% higher rate of stroke (40% higher rate in blacks), and an 80% higher rate of heart failure with doxazosin, compared with chlorthalidone. • ?The ACCOMPLISH study may affect future practice guidelines as a result of its findings favoring the amlodipine/benazepril combination; however, the generalizability to patient populations with a lesser cardiovascular risk profile remains in question and the dose of hydrochlorothiazide was only 12.5 mg to 25 mg daily, which was a dose lower than that used in placebo-controlled trials using hydrochlorothiazide. • ?Certain low-renin patient groups (eg, blacks, the elderly, and diabetics) as well as those who manifest the metabolic syndrome are commonly more responsive to thiazide-type diuretic therapy. • ?Diuretics can be successfully combined with ?-blockers, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, centrally acting agents, and even calcium channel blockers. • ?Although thiazide-type diuretics are among the best-tolerated antihypertensive agents in terms of symptomatic adverse effects, diuretic-related adverse side effects include those with established mechanisms (eg, such as electrolyte changes and/or metabolic abnormalities) and other side effects, which are less well understood mechanistically (eg, impotence), although the latter is not universally accepted as a diuretic-related side effect. • ?Thiazide-induced hypokalemia is associated with increased blood glucose, and treatment of thiazide-induced hypokalemia may reverse glucose intolerance and possibly prevent diabetes. • ?Thiazide-induced hyperuricemia occurs as a result of volume contraction and competition with uric acid for renal tubular secretion, but does not necessarily contraindicate using a thiazide, especially if a uric acid-lowering drug such as allopurinol is being used. • ?Adverse interactions include the blunting of thiazide effects by nonsteroidal anti-inflammatory drugs and the potential to increase fatigue, lethargy, and increase in glucose when combined with ?-blockers. • ?Thiazide-type diuretics are useful first-line agents in the treatment of hypertension because they have been proven to reduce cardiovascular mortality and morbidity in systolic and diastolic forms of hypertension and do so at low cost. • ?Loop diuretics should not be used as first-line therapy in hypertension since there are no outcome data with them. They should be reserved for conditions of clinically significant fluid overload (eg, heart failure and significant fluid retention with vasodilator drugs, such as minoxidil) or with advanced renal failure and can be combined with thiazide-type diuretics. PMID:21896142
Kalibjian, R.; Chong, Y.P.; Prono, D.S.; Cavagnolo, H.R.
1984-06-01
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.
NASA Astrophysics Data System (ADS)
Blanco-Pillado, Jose J.; Olum, Ken D.; Shlaer, Benjamin
2014-01-01
Using recent simulation results, we provide the mass and speed spectrum of cosmic string loops. This is the quantity of primary interest for many phenomenological signatures of cosmic strings, and it can be accurately predicted using recently acquired detailed knowledge of the loop production function. We emphasize that gravitational smoothing of long strings plays a negligible role in determining the total number of existing loops. We derive a bound on the string tension imposed by recent constraints on the stochastic gravitational wave background from pulsar timing arrays, finding GÎ¼ â‰¤2.8Ã—10-9. We also provide a derivation of the Boltzmann equation for cosmic string loops in the language of differential forms.
Integrated optical phase locked loop.
Lentine, Anthony L.; Kim, Jungwon; Trotter, Douglas Chandler; DeRose, Christopher T.; Kartner, Franz X.; Byun, Hyunil; Nejadmalayeri, Amir H.; Watts, Michael R.; Zortman, William A.
2010-12-01
A silicon photonics based integrated optical phase locked loop is utilized to synchronize a 10.2 GHz voltage controlled oscillator with a 509 MHz mode locked laser, achieving 32 fs integrated jitter over 300 kHz bandwidth.
Automatic blocking of nested loops
NASA Technical Reports Server (NTRS)
Schreiber, Robert; Dongarra, Jack J.
1990-01-01
Blocked algorithms have much better properties of data locality and therefore can be much more efficient than ordinary algorithms when a memory hierarchy is involved. On the other hand, they are very difficult to write and to tune for particular machines. The reorganization is considered of nested loops through the use of known program transformations in order to create blocked algorithms automatically. The program transformations used are strip mining, loop interchange, and a variant of loop skewing in which invertible linear transformations (with integer coordinates) of the loop indices are allowed. Some problems are solved concerning the optimal application of these transformations. It is shown, in a very general setting, how to choose a nearly optimal set of transformed indices. It is then shown, in one particular but rather frequently occurring situation, how to choose an optimal set of block sizes.
Loop Electrosurgical Excision Procedure (LEEP)
... that acts like a scalpel (surgical knife). An electric current is passed through the loop, which cuts away ... A procedure in which an instrument works with electric current to destroy tissue. Local Anesthesia: The use of ...
Closed loop spray cooling apparatus
NASA Technical Reports Server (NTRS)
Alger, D. L.; Schwab, W. B.; Furman, E. R. (Inventor)
1979-01-01
A closed loop apparatus for jet spraying coolant against the back of a radiation target is described. The coolant is circulated through a closed loop with a bubble of inert gas being maintained around the spray. Mesh material is disposed between the bubble and the surface of the liquid coolant which is below the bubble at a predetermined level. In a second arrangement no inert gas is used, the bubble consists of vapor produced when the coolant is sprayed against the target.
Principles and history of closed-loop controlled ventilation.
Brunner, J X
2001-09-01
Respiratory management of intubated patients is a complex problem, even if airway management, sedation, and infection control are excluded and only the limited problem of "how to set a ventilator" is considered. Four dimensions shape the overall strategy for setting a ventilator: time, physiologic task, primary lung disease, and general therapeutic approach. Initiation (start-up), maintenance, and weaning are the principal dimensions in time. This article discusses the closed-loop control method. PMID:11517027
The Coronal Loop Inventory Project
NASA Astrophysics Data System (ADS)
Schmelz, J. T.; Pathak, S.; Christian, G. M.; Dhaliwal, R. S. S.; Paul, K. S.
2015-11-01
Most coronal physicists now seem to agree that loops are composed of tangled magnetic strands and have both isothermal and multithermal cross-field temperature distributions. As yet, however, there is no information on the relative importance of each of these categories, and we do not know how common one is with respect to the other. In this paper, we investigate these temperature properties for all loop segments visible in the 171-Ã… image of AR 11294, which was observed by the Atmospheric Imaging Assembly (AIA) on 2011 September 15. Our analysis revealed 19 loop segments, but only 2 of these were clearly isothermal. Six additional segments were effectively isothermal, that is, the plasma emission to which AIA is sensitive could not be distinguished from isothermal emission, within measurement uncertainties. One loop had both isothermal transition region and multithermal coronal solutions. Another five loop segments require multithermal plasma to reproduce the AIA observations. The five remaining loop segments could not be separated reliably from the background in the crucial non-171-Ã… AIA images required for temperature analysis. We hope that the direction of coronal heating models and the efforts modelers spend on various heating scenarios will be influenced by these results.
Adaptive shaping of femtosecond polarization profiles
NASA Astrophysics Data System (ADS)
Brixner, T.; Damrauer, N. H.; Krampert, G.; Niklaus, P.; Gerber, G.
2003-05-01
We report the experimental implementation of femtosecond polarization pulse shaping within an adaptive learning loop. This technique makes it possible to optimally and automatically generate light fields in which intensity, momentary frequency, and light polarization (i.e., ellipticity and orientation) change as a function of time within a single femtosecond laser pulse. By use of second-harmonic generation as a feedback signal in an evolutionary algorithm, specific phase- and polarization-modulated laser pulses are generated. Material dispersion and time-dependent modulations of the polarization state can be compensated. These experiments demonstrate the feasibility of adaptive quantum control experiments with polarization-shaped femtosecond laser pulses.
Shaping the meristem by mechanical forces.
Laufs, Patrick; Peaucelle, Alexis; HÃ¶fte, Herman
2009-01-01
A recent report shows that cells in the Arabidopsis apical meristem orientate their cortical microtubules along mechanical stress patterns generated during tissue morphogenesis. This in turn is expected to influence the mechanical properties of the cell via the modification of the cortical microtubule network and the cell wall. This feedback loop controlling the shape of the meristem may act in parallel with auxin signalling, which determines the site of organ primordium formation. PMID:20948640
An optimum solar wind coupling function for the AL index
NASA Astrophysics Data System (ADS)
McPherron, Robert L.; Hsu, Tung-Shin; Chu, Xiangning
2015-04-01
We define a coupling function as a product of solar wind factors that partially linearizes the relation between it and a magnetic index. We consider functions that are a product of factors of solar wind speed V, density N, transverse magnetic field B?, and interplanetary magnetic field (IMF) clock angle ?c each raised to a different power. The index is the auroral lower (AL index) which monitors the strength of the westward electrojet. Solar wind data 1995-2014 provide hour averages of the factors needed to calculate optimum exponents. Nonlinear inversion determines both the exponents and linear prediction filters of short data segments. The averages of all exponents are taken as optimum exponents and for V, N, B?, and sin(?c/2) are [1.92, 0.10, 0.79, 3.67] with errors in the second decimal. Hourly values from 1966 to 2014 are used next to calculate the optimum function (opn) and the functions VBs (eys), epsilon (eps), and universal coupling function (ucf). A yearlong window is advanced by 27 days calculating linear prediction filters for the four functions. The functions eps, eys, ucf, and opn, respectively, predict 43.7, 61.2, 65.6, and 68.3% of AL variance. The opn function is 2.74% better than ucf with a confidence interval 2.60-2.86%. Coupling strength defined as the sum of filter weights (nT/mV/m) is virtually identical for all functions and varies systematically with the solar cycle being strongest (188 nT/mV/m) at solar minimum and weakest (104) at solar maximum. Saturation of the polar cap potential approaching solar maximum may explain the variation.
Optimum Thread Rolling Process That Improves SCC Resistance
A.R. Kephart
2001-10-29
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).
Coronal loops above an active region: Observation versus model
NASA Astrophysics Data System (ADS)
Bourdin, Philippe-A.; Bingert, Sven; Peter, Hardi
2014-12-01
We conducted a high-resolution numerical simulation of the solar corona above a stable active region. The aim is to test the field line braiding mechanism for a sufficient coronal energy input. We also check the applicability of scaling laws for coronal loop properties like the temperature and density. Our 3D MHD model is driven from below by Hinode observations of the photosphere, in particular a high-cadence time series of line-of-sight magnetograms and horizontal velocities derived from the magnetograms. This driving applies stress to the magnetic field and thereby delivers magnetic energy into the corona, where currents are induced that heat the coronal plasma by Ohmic dissipation. We compute synthetic coronal emission that we directly compare to coronal observations of the same active region taken by Hinode. In the model, coronal loops form at the same places as they are found in coronal observations. Even the shapes of the synthetic loops in 3D space match those found from a stereoscopic reconstruction based on STEREO spacecraft data. Some loops turn out to be slightly over-dense in the model, as expected from observations. This shows that the spatial and temporal distribution of the Ohmic heating produces the structure and dynamics of a coronal loops system close to what is found in observations.
Design optimum frac jobs using virtual intelligence techniques
NASA Astrophysics Data System (ADS)
Mohaghegh, Shahab; Popa, Andrei; Ameri, Sam
2000-10-01
Designing optimal frac jobs is a complex and time-consuming process. It usually involves the use of a two- or three-dimensional computer model. For the computer models to perform as intended, a wealth of input data is required. The input data includes wellbore configuration and reservoir characteristics such as porosity, permeability, stress and thickness profiles of the pay layers as well as the overburden layers. Among other essential information required for the design process is fracturing fluid type and volume, proppant type and volume, injection rate, proppant concentration and frac job schedule. Some of the parameters such as fluid and proppant types have discrete possible choices. Other parameters such as fluid and proppant volume, on the other hand, assume values from within a range of minimum and maximum values. A potential frac design for a particular pay zone is a combination of all of these parameters. Finding the optimum combination is not a trivial process. It usually requires an experienced engineer and a considerable amount of time to tune the parameters in order to achieve desirable outcome. This paper introduces a new methodology that integrates two virtual intelligence techniques, namely, artificial neural networks and genetic algorithms to automate and simplify the optimum frac job design process. This methodology requires little input from the engineer beyond the reservoir characterizations and wellbore configuration. The software tool that has been developed based on this methodology uses the reservoir characteristics and an optimization criteria indicated by the engineer, for example a certain propped frac length, and provides the detail of the optimum frac design that will result in the specified criteria. An ensemble of neural networks is trained to mimic the two- or three-dimensional frac simulator. Once successfully trained, these networks are capable of providing instantaneous results in response to any set of input parameters. These networks will be used as the fitness function for a genetic algorithm routine that will search for the best combination of the design parameters for the frac job. The genetic algorithm will search through the entire solution space and identify the optimal combination of parameters to be used in the design process. Considering the complexity of this task this methodology converges relatively fast, providing the engineer with several near-optimum scenarios for the frac job design. These scenarios, which can be achieved in just a minute or two, can be valuable initial points for the engineer to start his/her design job and save him/her hours of runs on the simulator.
Optimum paths for systems subject to internal noise
NASA Astrophysics Data System (ADS)
Einchcomb, S. J. B.; McKane, A. J.
1995-02-01
We formulate the stochastic dynamics of a particle subject to internal non-white (coloured) noise in terms of path-integrals. In the simplest case, where the noise is exponentially correlated, the weak-noise limit is characterised by optimum paths which are given by third-order differential equations. In contrast to system subjects to white noise or external coloured noise, the overdamped limit for these systems is singular. We analyse the origin of this behaviour. The whole formalism is generalised to more general noise processes and the essential features are shown to be similar to the exponentially correlated case.
Modeling and optimum time performance for concurrent processing
NASA Technical Reports Server (NTRS)
Mielke, Roland R.; Stoughton, John W.; Som, Sukhamoy
1988-01-01
The development of a new graph theoretic model for describing the relation between a decomposed algorithm and its execution in a data flow environment is presented. Called ATAMM, the model consists of a set of Petri net marked graphs useful for representing decision-free algorithms having large-grained, computationally complex primitive operations. Performance time measures which determine computing speed and throughput capacity are defined, and the ATAMM model is used to develop lower bounds for these times. A concurrent processing operating strategy for achieving optimum time performance is presented and illustrated by example.
Optimum Onager: The Classical Mechanics of a Classical Siege Engine
NASA Astrophysics Data System (ADS)
Denny, Mark
2009-12-01
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.
Optimum angles for determining the optical constants from reflectivity measurements
NASA Astrophysics Data System (ADS)
Logofatu, P. C.; Apostol, D.; Damian, V.; Tumbar, R.
1996-01-01
Avery's and Simon's reflection methods for determining the optical constants n and k were analysed in order to determine the corresponding angles of incidence of greatest sensitivity. For estimating the method sensitivity we used the point sensitivity defined as the Jacobian 0957-0233/7/1/007/img1. The existence of the ambiguities for a method was linked with the Jacobian sign change. We found that Simon's method is practically unambiguous and its sensitivity has a weak dependence on the choice of angles. Also, we found that Avery's method may be ambiguous for certain angles but not for its optimum angles.
Optimum path selection in automated radio relay link design
NASA Astrophysics Data System (ADS)
Danilovich, O. S.; Kichigin, V. N.
1985-01-01
This study investigates the selection of the locations of radio relay stations so that the stability of the radio relay link satisfies the corresponding CCIR recommendations, so that the effective station construction and operation costs are minimized. A mathematical model for selecting the optimum radio relay link route is described. The construction of a hypothetical radio relay link 1400 km long with an average repeater section link of 50 km is analyzed as an example. The algorithm is shown to be especially effective for rough terrain where it is often impossible to place the stations close to roads.
Optimum cruise lift coefficient in initial design of jet aircraft
Martinez-Val, R.; Perez, E. )
1992-08-01
An attempt is made to develop a more realistic model of the optimum cruise of a jet aircraft by considering the effect of the Mach number on the specific fuel consumption. It is assumed that the specific fuel consumption is influenced by the Mach number in accordance with a potential law, which, along with the constant altitude constraint, allows a simple analytical treatment of the range equation and related expressions. The final results are written in closed form. An application of the results to performance prediction is illustrated. 12 refs.
Optimum value of original events on the PEPT technique
Sadremomtaz, Alireza; Taherparvar, Payvand
2011-12-26
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.
Effects of mean flow on duct mode optimum suppression rates
NASA Technical Reports Server (NTRS)
Kraft, R. E.; Wells, W. R.
1976-01-01
The nature of the solution to the convected acoustic wave equation and associated boundary conditions for rectangular ducts containing uniform mean flow is examined in terms of the complex mapping between the wall admittance and characteristic mode eigenvalues. It is shown that the Cremer optimum suppression criteria must be modified to account for the effects of flow below certain critical values of the nondimensional frequency parameter of duct height divided by sound wavelength. The implications of these results on the design of low frequency suppressors are considered.
Determination of optimum electrolyte composition for molten carbonate fuel cells
Yuh, C.Y.; Pigeaud, A.
1988-03-01
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.
Determination of optimum electrolyte composition for molten carbonate fuel cells
Yuh, C.Y.; Pigeaud, A.
1988-06-01
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.
Matching technique yields optimum LNA performance. [Low Noise Amplifiers
NASA Technical Reports Server (NTRS)
Sifri, J. D.
1986-01-01
The present article is concerned with a case in which an optimum noise figure and unconditional stability have been designed into a 2.385-GHz low-noise preamplifier via an unusual method for matching the input with a suspended line. The results obtained with several conventional line-matching techniques were not satisfactory. Attention is given to the minimization of thermal noise, the design procedure, requirements for a high-impedance line, a sampling of four matching networks, the noise figure of the single-line matching network as a function of frequency, and the approaches used to achieve unconditional stability.
Shape anisotropy in zero-magnetostrictive rapidly solidified amorphous nanowires
NASA Astrophysics Data System (ADS)
RotÄƒrescu, C.; Atitoaie, A.; Stoleriu, L.; Ã“vÃ¡ri, T.-A.; Lupu, N.; Chiriac, H.
2016-04-01
The magnetic behavior of zero-magnetostrictive rapidly solidified amorphous nanowires has been investigated in order to understand their magnetic bistability. The study has been performed both experimentally - based on inductive hysteresis loop measurements - and theoretically, by means of micromagnetic simulations. Experimental hysteresis loops have shown that the amorphous nanowires display an axial magnetic bistability, characterized by a single-step magnetization reversal when the applied field reaches a critical value called switching field. The simulated loops allowed us to understand the effect of shape anisotropy on coercivity. The results are key for understanding and controlling the magnetization processes in these novel nanowires, with important application possibilities in new miniaturized sensing devices.
Shape optimization of corrugated airfoils
NASA Astrophysics Data System (ADS)
Jain, Sambhav; Bhatt, Varun Dhananjay; Mittal, Sanjay
2015-12-01
The effect of corrugations on the aerodynamic performance of a Mueller C4 airfoil, placed at a 5Â° angle of attack and Re=10{,}000, is investigated. A stabilized finite element method is employed to solve the incompressible flow equations in two dimensions. A novel parameterization scheme is proposed that enables representation of corrugations on the surface of the airfoil, and their spontaneous appearance in the shape optimization loop, if indeed they improve aerodynamic performance. Computations are carried out for different location and number of corrugations, while holding their height fixed. The first corrugation causes an increase in lift and drag. Each of the later corrugations leads to a reduction in drag. Shape optimization of the Mueller C4 airfoil is carried out using various objective functions and optimization strategies, based on controlling airfoil thickness and camber. One of the optimal shapes leads to 50 % increase in lift coefficient and 23 % increase in aerodynamic efficiency compared to the Mueller C4 airfoil.
2015-05-20
A new plastic developed by ORNL and Washington State University transforms from its original shape through a series of temporary shapes and returns to its initial form. The shape-shifting process is controlled through changes in temperature
Investigation of Various Essential Factors for Optimum Infrared Thermography
OKADA, Keiji; TAKEMURA, Kei; SATO, Shigeru
2013-01-01
ABSTRACT We investigated various essential factors for optimum infrared thermography for cattle clinics. The effect of various factors on the detection of surface temperature was investigated in an experimental room with a fixed ambient temperature using a square positioned on a wall. Various factors of animal objects were examined using cattle to determine the relationships among presence of hair, body surface temperature, surface temperature of the eyeball, the highest temperature of the eye circle, rectum temperature and ambient temperature. Also, the surface temperature of the flank at different time points after eating was examined. The best conditions of thermography for cattle clinics were determined and were as follows: (1) The distance between a thermal camera and an object should be fixed, and the camera should be set within a 45-degree angle with respect to the objects using the optimum focal length. (2) Factors that affect the camera temperature, such as extreme cold or heat, direct sunshine, high humidity and wind, should be avoided. (3) For the comparison of thermographs, imaging should be performed under identical conditions. If this is not achievable, hairless parts should be used. PMID:23759714
Optimum take-off angle in the long jump.
Linthorne, Nicholas P; Guzman, Maurice S; Bridgett, Lisa A
2005-07-01
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
Carbon sequestration, optimum forest rotation and their environmental impact
Kula, Erhun; Gunalay, Yavuz
2012-11-15
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.
Optimum Discharge Burnup and Cycle Length for PWRs
Secker, Jeffrey R.; Johansen, Baard J.; Stucker, David L.; Ozer, Odelli; Ivanov, Kostadin; Yilmaz, Serkan; Young, E.H
2005-08-15
This paper discusses the results of a pressurized water reactor fuel management study determining the optimum discharge burnup and cycle length. A comprehensive study was performed considering 12-, 18-, and 24-month fuel cycles over a wide range of discharge burnups. A neutronic study was performed followed by an economic evaluation. The first phase of the study limited the fuel enrichments used in the study to <5 wt% {sup 235}U consistent with constraints today. The second phase extended the range of discharge burnups for 18-month cycles by using fuel enriched in excess of 5 wt%. The neutronic study used state-of-the-art reactor physics methods to accurately determine enrichment requirements. Energy requirements were consistent with today's high capacity factors (>98%) and short (15-day) refueling outages. The economic evaluation method considers various component costs including uranium, conversion, enrichment, fabrication and spent-fuel storage costs as well as the effect of discounting of the revenue stream. The resulting fuel cycle costs as a function of cycle length and discharge burnup are presented and discussed. Fuel costs decline with increasing discharge burnup for all cycle lengths up to the maximum discharge burnup considered. The choice of optimum cycle length depends on assumptions for outage costs.
Use of geostatistics in planning optimum drilling program
Ghose S. )
1989-08-01
Application of geostatistics in the natural resources industry is well established. In a typical process of estimation, the statistically dependent geological data are used to predict the characteristics of a deposit. The estimator used is the best linear unbiased estimator (or BLUE), and a numerical factor of confidence is also provided. The natural inhomogeneity and anisotropy of a deposit are also quantified with preciseness. Drilling is the most reliable way of obtaining data for mining and related industries. However, it is often difficult to decide what is the optimum number of drill holes necessary for evaluation. In this paper, sequential measures of percent variation at 95% confidence level of a geological variable have been used to decipher economically optimum drilling density. A coal reserve model has been used to illustrate the method and findings. Fictitious drilling data were added (within the domain of population characteristics) in stages, to obtain a point of stability, beyond which the gain was significant (diminishing marginal benefit). The final relations are established by graphically projecting and comparing two variables - cost and precision. By mapping the percent variation at each stage, the localized areas of discrepancies can be identified. These are the locations where additional drilling is needed. The system can be controlled if performed at progressive stages and the preciseness toward stability is monitored.
Optimum receiver array design for magnetic induction tomography.
Gürsoy, Doga; Scharfetter, Hermann
2009-05-01
Magnetic induction tomography (MIT) is an imaging modality that aims at mapping the distribution of the electrical conductivity inside the body. Eddy currents are induced in the body by magnetic induction and the resulting fields are measured by an array of receiver coils. In MIT, the location of the receivers affects the quality of the image reconstruction. In this paper, a fast deterministic algorithm was applied to obtain optimum receiver array designs for a given specific excitation. The design strategy is based on the iterative exclusion of receiver locations, which yield poor conductivity information, from the space spanning all possible locations until a feasible design is reached. The applicability of "regionally focused" MIT designs that increase the image resolution at a particular region was demonstrated. Currently used design geometries and the corresponding reconstructed images were compared to the images obtained by optimized designs. The eigenvalue analysis of the Hessian matrix showed that the algorithm tends to maintain identical conductivity information content sensed by the receivers. Although the method does not guarantee finding the optimum design globally, the results demonstrate the practical usability of this algorithm in MIT experimental designs. PMID:19203883
Determination of optimum oven cooking procedures for lean beef products.
Rodas-González, Argenis; Larsen, Ivy L; Uttaro, Bethany; Juárez, Manuel; Parslow, Joyce; Aalhus, Jennifer L
2015-11-01
In order to determine optimum oven cooking procedures for lean beef, the effects of searing at 232 or 260°C for 0, 10, 20 or 30 min, and roasting at 160 or 135°C on semimembranosus (SM) and longissimus lumborum (LL) muscles were evaluated. In addition, the optimum determined cooking method (oven-seared for 10 min at 232°C and roasted at 135°C) was applied to SM roasts varying in weight from 0.5 to 2.5 kg. Mainly, SM muscles seared for 0 or 10 min at 232°C followed by roast at 135°C had lower cooking loss, higher external browning color, more uniform internal color, and were more tender and flavorful (P < 0.05). Roast weights ?1 kg had lesser cooking loss, more uniform internal color and tender compared to 0.5 kg (P < 0.05). Consequently, roasting at low temperature without searing is the recommended oven cooking procedure; with best response from muscle roast weight ?1 kg. PMID:26788289
Optimum flywheel sizing for parallel and series hybrid vehicles
Aceves, S.M.; Smith, J.R.
1996-12-20
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.
Developments of optimum flip-chip bonding process
NASA Astrophysics Data System (ADS)
Jang, Dong H.; Kang, Sa Y.; Lee, Y. M.; Oh, S. Y.
1997-08-01
Flip-chip soldering is the critical technology for solving the current issues of electronic packaging industries that require the high I/O's. In order to increase the manufacturing ability of flip-chip technology, however, yield and reliability tissues should overcome. In this study, optimum flip-chip bonding process has been developed by using the test chips that had the electroplated solder bumps. Test chips are composed of three different types that are i) peripheral array pad chip, ii) peripheral array pad chip, and iii) area array pad chip. Each test chip has the daisy chain to consider the effect of reliability test. The electrical resistance was measured before and after reliability test. Based on these measurement, failure mode resulted from the moisture absorption was studied using scanning acoustic microscope. To achieve an optimum reflow profile of solder bump, correct temperature profile was set up with respect to the resin base flux. Different bonding forces were tested. Four underfill encapsulants were evaluated for minimum voids that caused the severe defects after reliability test. Also, the gap heights were measured with respect to applied bonding force after underfill was performed. Results from the moisture absorption and thermal cycling were discussed for flip-chip bonding on BT-resin substrates. The test vehicles using flip-chip technology have passed moisture preconditioning and temperature cycling tests.
Optimum pinch grips in the handling of dies.
Heffernan, C; Freivalds, A
2000-08-01
Handling roller-press dies has caused numerous work-related musculoskeletal disorders in the leather industry. The dies are quite large (0.61 x 0.30 m), heavy (3.5 kg) and are difficult to handle because of the large pinch span requirements (up to 16 cm). The purpose of this study was to determine the optimum pinch span and optimum crossbar angulation to minimize die handling forces. Five-finger pulp-pinch forces were measured on five males and five females with a force-sensitive-resistor instrumented glove while handling a simulated adjustable die. Maximum pinch forces occurred at pinch spans between 1.27 and 3.81 cm, with average female strengths being 57% of average male pinch strengths. Minimum pinch forces to hold the die occurred at a 45 degrees angulation and increased linearly as the angle approached 90 degrees or the normal vertical orientation. The simplest solution to redesigning the dies is to: (1) decrease the distance between the braces to less than 4 cm and (2) slant the braces at 45 degrees. PMID:10975667
Optimum management of pediatric patients with fever and neutropenia.
Gaur, Aditya H; Flynn, Patricia M; Shenep, Jerry L
2004-09-01
Fever with neutropenia is a common clinical problem in patients receiving cancer treatment. Prevention and optimum management of infectious complications is critical to the overall success of cancer therapy. This article provides an overview of the current status of this evolving subject. While the basic principles of rapid institution of broad spectrum antibiotics, early intervention with empiric antifungal therapy and continuation of antimicrobials during period of risk are unlikely to change, there is increasing interest in titrating this aggressive approach based on the projected risk of the development of a serious invasive infection. Oral antibiotic therapy and outpatient management are currently being studied in pediatric oncology patients, but even when successful these alternatives to the traditional "in hospital, parenteral antibiotic therapy" approach are unlikely to be applicable in all patient populations and clinical settings. While there is no replacement for clinical acumen and careful monitoring, judicious use of diagnostic resources such as blood cultures and imaging studies is a key component of optimum care. Selection of empiric antibiotics based on ongoing monitoring of antimicrobial susceptibility patterns is emphasized. PMID:15448391
High permittivity material selection for design of optimum Hk VDMOS
NASA Astrophysics Data System (ADS)
Naugarhiya, Alok; Kondekar, Pravin N.
2015-07-01
In this paper, we have proposed a novel approach for the selection of high permittivity (Hk) material for the optimum design of Hk vertical double diffused MOS (VDMOS). The optimum design parameters under consideration are geometry, doping concentration and breakdown voltage (BV). We have investigated reliability and sensitivity of the Hk VDMOS using BV and figure-of-merit (FOM) analysis, respectively. Further, we have compared results of Hk VDMOS with superjunction (SJ) VDMOS and conventional VDMOS. The observation clarifies that the higher doping concentration can be used in the drift region of Hk n-pillar when comparing with a SJ VDMOS and conventional VDMOS without affecting the BV. Due to this, the area-specific ON-resistance (Ron A) of the Hk VDMOS is less as compared to the SJ VDMOS and conventional VDMOS with the same BV. Using FOM, we can select the Hk material for maximum doping concentration and maximum BV with lowest Ron A for specific design application of Hk VDMOS.
Kalman Orbit Optimized Loop Tracking
NASA Technical Reports Server (NTRS)
Young, Lawrence E.; Meehan, Thomas K.
2011-01-01
Under certain conditions of low signal power and/or high noise, there is insufficient signal to noise ratio (SNR) to close tracking loops with individual signals on orbiting Global Navigation Satellite System (GNSS) receivers. In addition, the processing power available from flight computers is not great enough to implement a conventional ultra-tight coupling tracking loop. This work provides a method to track GNSS signals at very low SNR without the penalty of requiring very high processor throughput to calculate the loop parameters. The Kalman Orbit-Optimized Loop (KOOL) tracking approach constitutes a filter with a dynamic model and using the aggregate of information from all tracked GNSS signals to close the tracking loop for each signal. For applications where there is not a good dynamic model, such as very low orbits where atmospheric drag models may not be adequate to achieve the required accuracy, aiding from an IMU (inertial measurement unit) or other sensor will be added. The KOOL approach is based on research JPL has done to allow signal recovery from weak and scintillating signals observed during the use of GPS signals for limb sounding of the Earth s atmosphere. That approach uses the onboard PVT (position, velocity, time) solution to generate predictions for the range, range rate, and acceleration of the low-SNR signal. The low- SNR signal data are captured by a directed open loop. KOOL builds on the previous open loop tracking by including feedback and observable generation from the weak-signal channels so that the MSR receiver will continue to track and provide PVT, range, and Doppler data, even when all channels have low SNR.
Affective loop experiences: designing for interactional embodiment
Höök, Kristina
2009-01-01
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
Filter for third order phase locked loops
NASA Technical Reports Server (NTRS)
Crow, R. B.; Tausworthe, R. C. (Inventor)
1973-01-01
Filters for third-order phase-locked loops are used in receivers to acquire and track carrier signals, particularly signals subject to high doppler-rate changes in frequency. A loop filter with an open-loop transfer function and set of loop constants, setting the damping factor equal to unity are provided.
Study of the Open Loop and Closed Loop Oscillator Techniques
Imel, George R.; Baker, Benjamin; Riley, Tony; Langbehn, Adam; Aryal, Harishchandra; Benzerga, M. Lamine
2015-04-11
This report presents the progress and completion of a five-year study undertaken at Idaho State University of the measurement of very small worth reactivity samples comparing open and closed loop oscillator techniques.The study conclusively demonstrated the equivalency of the two techniques with regard to uncertainties in reactivity values, i.e., limited by reactor noise. As those results are thoroughly documented in recent publications, in this report we will concentrate on the support work that was necessary. For example, we describe in some detail the construction and calibration of a pilot rod for the closed loop system. We discuss the campaign to measure the required reactor parameters necessary for inverse-kinetics. Finally, we briefly discuss the transfer of the open loop technique to other reactor systems.
Hyperstaticity and loops in frictional granular packings
NASA Astrophysics Data System (ADS)
Tordesillas, Antoinette; Lam, Edward; Metzger, Philip T.
2009-06-01
The hyperstatic nature of granular packings of perfectly rigid disks is analyzed algebraically and through numerical simulation. The elementary loops of grains emerge as a fundamental element in addressing hyperstaticity. Loops consisting of an odd number of grains behave differently than those with an even number. For odd loops, the latent stresses are exterior and are characterized by the sum of frictional forces around each loop. For even loops, the latent stresses are interior and are characterized by the alternating sum of frictional forces around each loop. The statistics of these two types of loop sums are found to be Gibbsian with a "temperature" that is linear with the friction coefficient ? when ?<1.
Hutchinson incisors; Abnormal tooth shape; Peg teeth; Mulberry teeth; Conical teeth ... The appearance of normal teeth varies, especially the molars. ... conditions. Specific diseases can affect tooth shape, tooth ...
MAGNETIC RECONNECTION BETWEEN SMALL-SCALE LOOPS OBSERVED WITH THE NEW VACUUM SOLAR TELESCOPE
Yang, Shuhong; Zhang, Jun; Xiang, Yongyuan
2015-01-01
Using the high tempo-spatial resolution HÎ± images observed with the New Vacuum Solar Telescope, we report solid observational evidence of magnetic reconnection between two sets of small-scale, anti-parallel loops with an X-shaped topology. The reconnection process contains two steps: a slow step with a duration of more than several tens of minutes, and a rapid step lasting for only about three minutes. During the slow reconnection, two sets of anti-parallel loops gradually reconnect, and new loops are formed and stacked together. During the rapid reconnection, the anti-parallel loops approach each other quickly, and then rapid reconnection takes place, resulting in the disappearance of the former loops. In the meantime, new loops are formed and separate. The region between the approaching loops is brightened, and the thickness and length of this region are determined to be about 420Â km and 1.4 Mm, respectively. During the rapid reconnection process, obvious brightenings at the reconnection site and apparent material ejections outward along reconnected loops are observed. These observed signatures are consistent with predictions by reconnection models. We suggest that the successive slow reconnection changes the conditions around the reconnection site and triggers instabilities, thus leading to the rapid approach of the anti-parallel loops and resulting in the rapid reconnection.
Creating the feedback loop: closed-loop neurostimulation.
Hebb, Adam O; Zhang, Jun Jason; Mahoor, Mohammad H; Tsiokos, Christos; Matlack, Charles; Chizeck, Howard Jay; Pouratian, Nader
2014-01-01
Current DBS therapy delivers a train of electrical pulses at set stimulation parameters. This open-loop design is effective for movement disorders, but therapy may be further optimized by a closed loop design. The technology to record biosignals has outpaced our understanding of their relationship to the clinical state of the whole person. Neuronal oscillations may represent or facilitate the cooperative functioning of brain ensembles, and may provide critical information to customize neuromodulation therapy. This review addresses advances to date, not of the technology per se, but of the strategies to apply neuronal signals to trigger or modulate stimulation systems. PMID:24262909
Loop cosmology: Regularization vs. quantization
NASA Astrophysics Data System (ADS)
Haro, J.; Elizalde, E.
2010-03-01
It is argued that it is the regularization of the classical Hamiltonian —the first step in loop cosmology in order to build a well-defined quantum theory— that is already able to avoid the Big Bang and Big Rip singularities, rather than the usually invoked quantum corrections coming from the quantization of the Hamiltonian. To prove such statement, the classical regularized Hamiltonian corresponding to loop gravity is obtained, and it is shown that it coincides, up to terms of order planck, with the so-called effective Hamiltonian which is calculated from the quantum regularized Hamiltonian using semi-classical techniques. From that comparison it is concluded that both types of singularities are avoided at the "classical level" already, i.e., using loop cosmology, in the sense that only the quantum nature of the geometry is invoked (the loop cut-off) in order to construct the regularized Hamiltonian and to fix the parameter on which it depends. Such finding constitutes a key manifestation of the intrinsic power of loop gravity, as compared with other alternatives.
Bandwidth controller for phase-locked-loop
NASA Technical Reports Server (NTRS)
Brockman, Milton H. (Inventor)
1992-01-01
A phase locked loop utilizing digital techniques to control the closed loop bandwidth of the RF carrier phase locked loop in a receiver provides high sensitivity and a wide dynamic range for signal reception. After analog to digital conversion, a digital phase locked loop bandwidth controller provides phase error detection with automatic RF carrier closed loop tracking bandwidth control to accommodate several modes of transmission.
Picophytoplankton physiology and the microbial loop
NASA Astrophysics Data System (ADS)
Stawiarski, Beate
2013-04-01
Physiological observations are needed for a better understanding of the complexity of marine ecosystem processes. This information is important for a better model formulation and parameterisation to identify the consequences of, and feedbacks to, global change and to make future projections. Picophytoplankton form the smallest component of the phytoplankton community (˜ 3?m) and show a substantial contribution to phytoplankton biomass in oligotrophic oceans. Here they also have an important function as primary producers in the microbial loop. They include cyanobacteria, represented by Prochlorococcus and Synechococcus, and picoeukaryotes. The aim of this project is to achieve a better representation of picophytoplankton in the global biogeochemical model PlankTOM 10. PlankTOM 10 simplifies the complex ecosystem into 10 conceptual groups also known as plankton functional types (PFTs). These groups of organisms are defined by physiological and biochemical parameters (6 of phytoplankton, 3 of zooplankton and 1 of bacteria). Furthermore, the question will be addressed, whether picophytoplankton are typical K-strategists with low minimum nutrient and high maximum chlorophyll quota relative to carbon, or by having superior nutrient uptake kinetics and light harvesting (high ?Chl). Laboratory experiments showed that the smaller picoprokaryotes respond faster to increasing light intensities than their picoeukaryotic counterpart. Preliminary data show that the initial slope of the photosynthesis vs. irradiance curve (?Chl) of picoprokaryotes is about 1.5 times higher than of picoeukaryotes. This is consistent with their common distribution at the deep chlorophyll maximum. The maximum chlorophyll quota are not significantly different. Temperature experiments confirmed that the maximum growth rates of picophytoplankton at the optimum temperature (0.47 ± 0.17 d-1 for prokaryotes and 1.05 ± 0.47 d-1 for eukaryotes) are significantly lower than of diatoms (1.57 ± 0.73 d-1, Chollet et al. in prep.) and not significantly different from coccolithophores (0.68 ± 0.10 d-1, Buitenhuis et al. 2008), consistent with the characterisation of picophytoplanton as K-strategists. Their optimum temperatures were found to be 22.7 ± 2.0 ° C for prokaryotes and 23.6 ± 3.1 ° C for eukaryotes. Nutrient limitation experiments will be conducted to characterize the nutrient uptake and elemental composition of picophytoplankton. Finally the results of all experiments will then be used to improve the representation of picophytoplankton in PlankTOM10, evaluated against a recently compiled global database of picophytoplankton biomass.
Design, fabrication and delivery of an improved single Elastic Loop Mobility System (ELMS)
NASA Technical Reports Server (NTRS)
Trautwein, W.
1972-01-01
Several significant design improvements have been incorporated into the second-generation full-scale ELMS unit. A major improved design accomplishment was the increase of the load carrying capacity of elastic loops without severe weight or stress penalties. Redesign of the loop form and size, plus selection of a more advanced titanium alloy, resulted in performance characteristics representing a marked improvement over the first-generation unit. Another important design improvement was the shaping of the loop's footprint into a favorable form for uniform pressure distribution. Other improvements are associated with a more efficient drive torque transmission from the internal drive drums to the elastic loop which are expected to reduce the internal losses of the drive system. The new ELMS unit will be capable of being integrated, on a modularized basis, with a multi-loop articulated ELMS test vehicle as the next logical step in the development of the mobility concept.
Optimum conditions for high-quality 3D reconstruction in confocal scanning microscopy
NASA Astrophysics Data System (ADS)
Kim, Taehoon; Kim, Taejoong; Lee, SeungWoo; Gweon, Dae-Gab; Seo, Jungwoo
2006-02-01
Confocal Scanning Microscopy (CSM) is very useful to reconstruct 3D image of Bio-cells and the objects that have specification shape in higher axial and lateral resolution and widely used as measurement instrument. A 3D reconstruction is used to visualize confocal images and consists of following processes. The First process is to get 3D data by collecting a series of images at regular focus intervals (Optical Sectioning). The Second process is to fit a curve to a series of 3D data points each pixel. The Third process is to search height information that has maximum value from curve-fitting. However, because of various systematic errors (NOISE) occurred when collecting the information of images through Optical Sectioning and large peak deviation occurred from curve-fitting error, high quality 3D reconstruction is not expected. Also, it takes much time to 3d Reconstruction by using many 3D data in order to acquire high quality and much cost to improve signal-to-noise (SNR) using a higher power laser. So, we are going to define SNR, peak deviation and the order of curve-fitting as important factors and simulate the relation between the factors in order to find a optimum condition for high quality 3D reconstruction in Confoal Scanning Microscopy. If we use optimum condition obtained by this simulation, using a suitable SNR and the suitable number of data and the suitable n-th order curve-fitting, small peak deviation is expected and then, 3D reconstruction of little better quality is expected. Also, it is expected to save.
NASA Technical Reports Server (NTRS)
Demaret, J. C.
1975-01-01
The parameters of non-uniform and uniform quantizers up to ten bits of quantization, optimum for a Gaussian input probability and for the magnitude-error distortion criterion are computed. Optimum quantizers must be understood as quantizers with minimum distortion. The numerical method used for the optimization converges relatively rapidly. The comparison between optimum non-uniform quantizers and optimum uniform quantizers is made.
Criteria for saturated magnetization loop
NASA Astrophysics Data System (ADS)
Harres, A.; Mikhov, M.; Skumryev, V.; Andrade, A. M. H. de; Schmidt, J. E.; Geshev, J.
2016-03-01
Proper estimation of magnetization curve parameters is vital in studying magnetic systems. In the present article, criteria for discrimination non-saturated (minor) from saturated (major) hysteresis loops are proposed. These employ the analysis of (i) derivatives of both ascending and descending branches of the loop, (ii) remanent magnetization curves, and (iii) thermomagnetic curves. Computational simulations are used in order to demonstrate their validity. Examples illustrating the applicability of these criteria to well-known real systems, namely Fe3O4 and Ni fine particles, are provided. We demonstrate that the anisotropy-field value estimated from a visual examination of an only apparently major hysteresis loop could be more than two times lower than the real one.
NASA Astrophysics Data System (ADS)
Wang, T. J.
The corona is visible in the optical band only during a total solar eclipse or with a coronagraph. Coronal loops are believed to be plasma-filled closed magnetic flux anchored in the photosphere. Based on the temperature regime, they are generally classified into cool, warm, and hot loops. The magnetized coronal structures support propagation of various types of magnetohydrodynamics (MHD) waves. This chapter reviews the recent progress made in studies based on observations of four types of wave phenomena mainly occurring in coronal loops of active regions, including: flare-excited slow-mode waves; impulsively excited kink-mode waves; propagating slow magnetoacoustic waves; and ubiquitous propagating kink (AlfvÃ©nic) waves. This review not only comprehensively discusses these waves and coronal seismology but also topics that are newly emerging or hotly debated in order to provide the reader with useful guidance on further studies.
NASA Technical Reports Server (NTRS)
Thomas, Jr., Jess B. (Inventor)
1991-01-01
An improved digital phase lock loop incorporates several distinctive features that attain better performance at high loop gain and better phase accuracy. These features include: phase feedback to a number-controlled oscillator in addition to phase rate; analytical tracking of phase (both integer and fractional cycles); an amplitude-insensitive phase extractor; a more accurate method for extracting measured phase; a method for changing loop gain during a track without loss of lock; and a method for avoiding loss of sampled data during computation delay, while maintaining excellent tracking performance. The advantages of using phase and phase-rate feedback are demonstrated by comparing performance with that of rate-only feedback. Extraction of phase by the method of modeling provides accurate phase measurements even when the number-controlled oscillator phase is discontinuously updated.
The contraction of flare loops
NASA Astrophysics Data System (ADS)
Ji, Haisheng; Wang, Haimin
In recent years, several authors have reported a contracting motion for solar flare loops in many flares. That is, during the early impulsive phase of solar flares, hard X-ray (HXR) looptop sources or radio/extreme-ultraviolet (EUV) flaring loops have a descending or shrinking motion and, at the same time, H? ribbons or HXR footpoints (FPs) are converging. Only after the impulsive phase does there begin to appear an upward motion for the looptop sources and flaring loops and a corresponding outward motion (the usual separation motion) for the flare ribbons or FPs. In this talk, we will give a brief review to all events in literature. We will try demonstrate that this new solar flare phenomenon implies magnetic reconnection in a highly sheared magnetic field.
Optimum compositions for thermal insulation of burners and regenerators
Zasypkin, V.I.; Popov, O.N.
1988-07-01
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.
Optimum periodicity of repeated contractile actions applied in mass transport
NASA Astrophysics Data System (ADS)
Ahn, Sungsook; Lee, Sang Joon
2015-01-01
Dynamically repeated periodic patterns are abundant in natural and artificial systems, such as tides, heart beats, stock prices, and the like. The characteristic repeatability and periodicity are expected to be optimized in effective system-specific functions. In this study, such optimum periodicity is experimentally evaluated in terms of effective mass transport using one-valve and multi-valve systems working in contractile fluid flows. A set of nanoscale gating functions is utilized, operating in nanocomposite networks through which permeates selectively pass under characteristic contractile actions. Optimized contractile periodicity exists for effective energy impartment to flow in a one-valve system. In the sequential contractile actions for a multi-valve system, synchronization with the fluid flow is critical for effective mass transport. This study provides fundamental understanding on the various repeated periodic patterns and dynamic repeatability occurring in nature and mechanical systems, which are useful for broad applications.
A Decision Support System for Optimum Use of Fertilizers
Hoskinson, Reed Louis; Hess, John Richard; Fink, Raymond Keith
1999-07-01
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 systemsâ€™ 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.
A Decision Support System for Optimum Use of Fertilizers
R. L. Hoskinson; J. R. Hess; R. K. Fink
1999-07-01
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.
Optimum survival strategies against zombie infestations - a population dynamics approach
NASA Astrophysics Data System (ADS)
Mota, Bruno
2014-03-01
We model a zombie infestation by three coupled ODEs that jointly describe the time evolution of three populations: regular humans, zombies, and survivors (humans that have survived at least one zombie encounter). This can be generalized to take into account more levels of expertise and/or skill degradation. We compute the fixed points, and stability thereof, that correspond to one of three possible outcomes: human extinction, zombie extermination or, if one allows for a human non-zero birth-rate, co-habitation. We obtain analytically the optimum strategy for humans in terms of the model's parameters (essentially, whether to flee and hide, or fight). Zombies notwithstanding, this can also be seen as a toy model for infections of immune system cells, such as CD4+ T cells in AIDS, and macrophages in tuberculosis, whereby cells are both the target of infection, and mediate the acquired immunity response against the same infection. I thank FAPERJ for financial support.
Optimum Integrated Heterodyne Photoreceiver for Coherent Lidar Applications
NASA Technical Reports Server (NTRS)
Amzajerdian, Farzin; Pierrottet, Diego; Singh, Upendra; Kavaya, Michael
2005-01-01
Many coherent lidar applications, particularly airborne and space-based applications, impose stringent power and size constraints while requiring high levels of sensitivity. For this reason, optimization of the lidar heterodyne photoreceiver is one of the critical steps in ensuring full utilization of limited resources to achieve the required sensitivity. The analysis of 2-micron heterodyne receivers shows that substantial improvement of the order of 3 dB can be obtained by proper optimization of the receiver key control parameters and elimination of its parasitic capacitances by integrating the detector, its bias circuit, and the preamplifier on a single substrate. This paper describes analytical steps for defining optimum heterodyne receiver design parameters and development of experimental devices operating at 2-micron wavelength.
Optimum design of 2D micro-angle sensor
NASA Astrophysics Data System (ADS)
Liu, Qinggang; Zhao, Heng; Lou, Xiaona; Jiang, Ningchuan; Hu, Xiaotang
2008-12-01
To improve dynamic measurement performance and resolution, an optimum design on two-dimensional (2D) micro-angle sensor based on optical internal-reflection method via critical-angle refractive index measurement is presented in the paper. The noise signals were filtered effectively by modulating laser-driven and demodulating in signal proceeding. The system's accuracy and response speed are improved further by using 16-bit high-precision AD converter and MSP430 CPU which present with a high-speed performance during signals processes such as fitting angle-voltage curve through specific arithmetic, full range and zero point calibration, filter, scaling transformation etc. The experiment results indicated that, dynamic signal measurement range can be up to +/-600arcsec, the measurement resolution can be better than 0.1arcsec, and the repeatability could be better than +/-0.5arcsec.
Simpler Alternative to an Optimum FQPSK-B Viterbi Receiver
NASA Technical Reports Server (NTRS)
Lee, Dennis; Simon, Marvin; Yan, Tsun-Yee
2003-01-01
A reduced-complexity alternative to an optimum FQPSK-B Viterbi receiver has been invented. As described, the reduction in complexity is achieved at the cost of only a small reduction in power performance [performance expressed in terms of a bit-energy-to-noise-energy ratio (Eb/N0) for a given bit-error rate (BER)]. The term "FQPSK-B" denotes a baseband-filtered version of Feher quadrature-phase-shift keying, which is a patented, bandwidth-efficient phase-modulation scheme named after its inventor. Heretofore, commercial FQPSK-B receivers have performed symbol-by-symbol detection, in each case using a detection filter (either the proprietary FQPSK-B filter for better BER performance, or a simple integrate-and-dump filter with degraded performance) and a sample-and-hold circuit.
Methodology for designing an optimum air quality monitoring network
Liu, M.; Avrin, J.
1981-02-01
A two-step objective method is presented for determining th optimum number and disposition of ambient air quality stations in a monitoring network. The method uses a data base consisting of a comprehensive set of simulated or measured air quality patterns representative of the region of interest. In the first step, the most desirable monitoring locations are identified and ranked. The minimum number of required locations is determined in the second step through eliminating redundancies among the locations identified in the first step with regard to spatial coverage over the region of interest. As a demonstration, the method is applied to the Las Vegas Valley of Nevada for the pollutant species carbon monoxide.
Methodology for designing an optimum air quality monitoring network
Liu, M.; Avrin, J.
1981-02-01
A two-step objective method is presented for determining the optimum number and disposition of ambient air quality stations in a monitoring network. The method uses a data base consisting of a comprehensive set of simulated or measured air quality patterns representative of the region of interest. In the first step, the most desirable monitoring locations are identified and ranked. The minimum number of required locations is determined in the second step through eliminating redundancies among the locations identified in the first step with regard to spatial coverage over the region of interest. As a demonstration, the method is applied to the Las Vegas Valley of Nevada for the pollutant species carbon monoxide.
Optimum fiber spacing in a hollow fiber bioreactor.
Chresand, T J; Gillies, R J; Dale, B E
1988-10-01
A high surface area hollow fiber reactor was developed for mammalian cell culture. The reactor employs an interfiber gel matrix of agar or collagen for cell support. A model was developed to predict cell density as a function of fiber spacing. Optimum spacings are calculated for two sizes of Celgard hollow fibers. Ehrlich Ascites Tumor (EAT) cells were grown to an estimated density of 1.1 x 10(8) viable cells/mL in the extracapillary space-corresponding to an overall reactor density of 7 x 10(7) cells/mL. On the basis of available kinetic and diffusivity data, the model predicts that lactate accumulation may limit cell growth in the early stage of medium utilization, while oxygen delivery becomes limiting at later stages. PMID:18587816
Optimum periodicity of repeated contractile actions applied in mass transport
Ahn, Sungsook; Lee, Sang Joon
2015-01-01
Dynamically repeated periodic patterns are abundant in natural and artificial systems, such as tides, heart beats, stock prices, and the like. The characteristic repeatability and periodicity are expected to be optimized in effective system-specific functions. In this study, such optimum periodicity is experimentally evaluated in terms of effective mass transport using one-valve and multi-valve systems working in contractile fluid flows. A set of nanoscale gating functions is utilized, operating in nanocomposite networks through which permeates selectively pass under characteristic contractile actions. Optimized contractile periodicity exists for effective energy impartment to flow in a one-valve system. In the sequential contractile actions for a multi-valve system, synchronization with the fluid flow is critical for effective mass transport. This study provides fundamental understanding on the various repeated periodic patterns and dynamic repeatability occurring in nature and mechanical systems, which are useful for broad applications. PMID:25622949
Simulation of an Optimum Multilevel Dynamic Round Robin Scheduling Algorithm
NASA Astrophysics Data System (ADS)
Goel, Neetu; B. Garg, R.
2013-08-01
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.
Variational methods in simultaneous optimum interpolation and initialization
NASA Technical Reports Server (NTRS)
Wahba, G.
1982-01-01
The duality between optimum interpolation and variational objective analysis, is reviewed. This duality is used to set up a variational approach to objective analysis which uses prior information concerning the atmospheric spectral energy distribution, in the variational problem. In the wind analysis example, the wind field is partitioned into divergent and nondivergent parts, and a control parameter governing the relative energy in the two parts is estimated from the observational data being analyzed by generalized cross validation, along with a bandwidth parameter. A variational approach to combining objective analysis and initialization in a single step is proposed. In a simple example of this approach, data, forecast, and prior information concerning atmospheric energy distribution is combined into a single variational problem. This problem has (at least) one bandwidth parameter, one partitioning parameter governing the relative energy in fast slow modes, and one parameter governing the relative weight to be given to observational and forecast data.
Optimum Actuator Selection with a Genetic Algorithm for Aircraft Control
NASA Technical Reports Server (NTRS)
Rogers, James L.
2004-01-01
The placement of actuators on a wing determines the control effectiveness of the airplane. One approach to placement maximizes the moments about the pitch, roll, and yaw axes, while minimizing the coupling. For example, the desired actuators produce a pure roll moment without at the same time causing much pitch or yaw. For a typical wing, there is a large set of candidate locations for placing actuators, resulting in a substantially larger number of combinations to examine in order to find an optimum placement satisfying the mission requirements and mission constraints. A genetic algorithm has been developed for finding the best placement for four actuators to produce an uncoupled pitch moment. The genetic algorithm has been extended to find the minimum number of actuators required to provide uncoupled pitch, roll, and yaw control. A simplified, untapered, unswept wing is the model for each application.
Optimum detection of tones transmitted by a spacecraft
NASA Technical Reports Server (NTRS)
Simon, M. K.; Shihabi, M. M.; Moon, T.
1995-01-01
The performance of a scheme proposed for automated routine monitoring of deep-space missions is presented. The scheme uses four different tones (sinusoids) transmitted from the spacecraft (S/C) to a ground station with the positive identification of each of them used to indicate different states of the S/C. Performance is measured in terms of detection probability versus false alarm probability with detection signal-to-noise ratio as a parameter. The cases where the phase of the received tone is unknown and where both the phase and frequency of the received tone are unknown are treated separately. The decision rules proposed for detecting the tones are formulated from average-likelihood ratio and maximum-likelihood ratio tests, the former resulting in optimum receiver structures.
Optimum detection of an optical image on a photoelectric surface
NASA Technical Reports Server (NTRS)
Helstrom, C. W.; Wang, L.
1972-01-01
The detection of an optical image in the presence of uniform background light is based on a likelihood ratio formed of the numbers of photoelectrons emitted from small elements of a photoelectric surface onto which the image is focused. When diffraction is negligible and the surface has unit quantum efficiency, this detector is equipollent with the optimum detector of the image forming light. Its performance is compared with that of the threshold detector and that of a detector basing its decisions on the total number of photoelectrons from a finite area of the image. The illuminance of the image is postulated to have a Gaussian spatial distribution. All three detectors exhibit nearly the same reliability.
Optimum periodicity of repeated contractile actions applied in mass transport.
Ahn, Sungsook; Lee, Sang Joon
2015-01-01
Dynamically repeated periodic patterns are abundant in natural and artificial systems, such as tides, heart beats, stock prices, and the like. The characteristic repeatability and periodicity are expected to be optimized in effective system-specific functions. In this study, such optimum periodicity is experimentally evaluated in terms of effective mass transport using one-valve and multi-valve systems working in contractile fluid flows. A set of nanoscale gating functions is utilized, operating in nanocomposite networks through which permeates selectively pass under characteristic contractile actions. Optimized contractile periodicity exists for effective energy impartment to flow in a one-valve system. In the sequential contractile actions for a multi-valve system, synchronization with the fluid flow is critical for effective mass transport. This study provides fundamental understanding on the various repeated periodic patterns and dynamic repeatability occurring in nature and mechanical systems, which are useful for broad applications. PMID:25622949
Screening actuator locations for static shape control
NASA Technical Reports Server (NTRS)
Haftka, Raphael T.
1990-01-01
Correction of shape distortion due to zero-mean normally distributed errors in structural sizes which are random variables is examined. A bound on the maximum improvement in the expected value of the root-mean-square shape error is obtained. The shape correction associated with the optimal actuators is also characterized. An actuator effectiveness index is developed and shown to be helpful in screening actuator locations in the structure. The results are specialized to a simple form for truss structures composed of nominally identical members. The bound and effectiveness index are tested on a 55-m radiometer antenna truss structure. It is found that previously obtained results for optimum actuators had a performance close to the bound obtained here. Furthermore, the actuators associated with the optimum design are shown to have high effectiveness indices. Since only a small fraction of truss elements tend to have high effectiveness indices, the proposed screening procedure can greatly reduce the number of truss members that need to be considered as actuator sites.
The optimum choice of gate width for neutron coincidence counting
NASA Astrophysics Data System (ADS)
Croft, S.; Henzlova, D.; Favalli, A.; Hauck, D. K.; Santi, P. A.
2014-11-01
In the measurement field of international nuclear safeguards, passive neutron coincidence counting is used to quantify the spontaneous fission rate of certain special nuclear materials. The shift register autocorrelation analysis method is the most commonly used approach. However, the Feynman-Y technique, which is more commonly applied in reactor noise analysis, provides an alternative means to extract the correlation information from a pulse train. In this work we consider how to select the optimum gate width for each of these two time-correlation analysis techniques. The optimum is considered to be that which gives the lowest fractional precision on the net doublets rate. Our theoretical approach is approximate but is instructional in terms of revealing the key functional dependence. We show that in both cases the same performance figure of merit applies so that common design criteria apply to the neutron detector head. Our prediction is that near optimal results, suitable for most practical applications, can be obtained from both techniques using a common gate width setting. The estimated precision is also comparable in the two cases. The theoretical expressions are tested experimentally using 252Cf spontaneous fission sources measured in two thermal well counters representative of the type in common use by international inspectorates. Fast accidental sampling was the favored method of acquiring the Feynman-Y data. Our experimental study confirmed the basic functional dependences predicted although experimental results when available are preferred. With an appropriate gate setting Feynman-Y analysis provides an alternative to shift register analysis for safeguards applications which is opening up new avenues of data collection and data reduction to explore.
Energy levels and far-infrared spectra of oval-shaped nanorings
GutiÃ©rrez, W.; GarcÃa, L. F.; Mikhailov, I. D.
2014-05-15
The evolution of the Aharonov-Bohm oscillation of low-lying states and far infrared spectrum associated to variation of the path curvature for electron motion along nanorings with centerlines in a form of a set of Cassini ovals, whose shape is changed continuously from a single elongated loop to two separated loops is theoretically investigated.
Two-channel Costas loop tracking performance for UQPSK signals with arbitrary data formats
NASA Technical Reports Server (NTRS)
Simon, M. K.
1981-01-01
Previous results on the tracking performance of two-channel Costas-type carrier synchronization loops are generalized and corrected, in order that they may be applied to several mixed-format cases. In particular, the mean-square phase jitter performance of these loops with active arm filters, synchronous or asynchronous symbol clocks, and arbitrary data formats on the two channels is examined. It is demonstrated that for each case, selection of the channel gain ratio, as motivated by the MAP estimation theory, does not guarantee optimum loop tracking performance: in some instances, a conventional single-channel Costas loop would outperform the two-channel version with the MAP choice of gain ratio. It is suggested that the gain ratio be chosen to directly minimize the mean-square phase tracking jitter which is equivalent to minimizing the loop's 'squaring loss'. This can, in some cases, improve the performance measure, although in all cases, the two-channel loop will still outperform the single-channel version.
Effects of plasma mass flow on Alfven wave phase mixing in coronal loops
NASA Technical Reports Server (NTRS)
Peredo, M.; Tataronis, J. A.
1990-01-01
Ground-based and space observations suggest that flow phenomena are intrinsic to the solar corona loops. The present analysis addresses flow effects on Alfven wave behavior in coronal loops. The effect of flow on the shear Alfven wave continuum and the associated damping process resulting from phase-mixing is investigated. Flow Doppler-shifts the Alfven wave continuum, thus displacing the range of frequencies for optimum heating. The present study explores Alfven resonance effects on surface waves propagating along coronal loops that are under the influence of flow. Coupling to the Alfven resonance leads to damping of the surface waves. The damping rate in the presence of sub-Alfvenic flows is computed. Flow increases the damping rate of certain modes, thus enhancing the heating effectiveness of those modes. Therefore, these calculations suggest that flow is potentially an important ingredient for an accurate evaluation of heating the solar corona by dissipation of Alfven waves via phase-mixing.
Wilson, Thomas S.; Bearinger, Jane P.
2015-06-09
New shape memory polymer compositions, methods for synthesizing new shape memory polymers, and apparatus comprising an actuator and a shape memory polymer wherein the shape memory polymer comprises at least a portion of the actuator. A shape memory polymer comprising a polymer composition which physically forms a network structure wherein the polymer composition has shape-memory behavior and can be formed into a permanent primary shape, re-formed into a stable secondary shape, and controllably actuated to recover the permanent primary shape. Polymers have optimal aliphatic network structures due to minimization of dangling chains by using monomers that are symmetrical and that have matching amine and hydroxyl groups providing polymers and polymer foams with clarity, tight (narrow temperature range) single transitions, and high shape recovery and recovery force that are especially useful for implanting in the human body.
Beam shaping for holographic techniques
NASA Astrophysics Data System (ADS)
Laskin, Alexander; Laskin, Vadim; Ostrun, Aleksei
2014-09-01
Uniform intensity of laser radiation is very important in holographic and interferometry technologies, therefore transformation of typical Gaussian distribution of a TEM00 laser to flat-top (top hat) is an actual technical task, it is solved by applying beam shaping optics. Holography and interferometry have specific requirements to a uniform laser beam, most important of them are flatness of phase front and extended depth of field. There are different refractive and diffractive beam shaping approaches used in laser industrial and scientific applications, but only few of them are capable to fulfil the optimum conditions for beam quality demanding holography and interferometry. We suggest applying refractive field mapping beam shapers piShaper, which operational principle presumes almost lossless transformation of Gaussian to flat-top beam with flatness of output wavefront, conserving of beam consistency, providing collimated low divergent output beam, high transmittance, extended depth of field, negligible wave aberration, and achromatic design provides capability to work with several lasers with different wavelengths simultaneously. This approach is used in SLM-based technologies of Computer Generated Holography, Dot-Matrix mastering of security holograms, holographic data storage, holographic projection, lithography, interferometric recording of Volume Bragg Gratings. High optical quality of resulting flat-top beam allows applying additional optical components to vary beam size and shape, thus adapting an optical system to requirements of a particular application. This paper will describe design basics of refractive beam shapers and optical layouts of their applying in holographic systems. Examples of real implementations and experimental results will be presented as well.
OUTER LOOP LANDFILL CASE STUDY
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...
Closed-Loop Neuromorphic Benchmarks.
Stewart, Terrence C; DeWolf, Travis; Kleinhans, Ashley; Eliasmith, Chris
2015-01-01
Evaluating the effectiveness and performance of neuromorphic hardware is difficult. It is even more difficult when the task of interest is a closed-loop task; that is, a task where the output from the neuromorphic hardware affects some environment, which then in turn affects the hardware's future input. However, closed-loop situations are one of the primary potential uses of neuromorphic hardware. To address this, we present a methodology for generating closed-loop benchmarks that makes use of a hybrid of real physical embodiment and a type of "minimal" simulation. Minimal simulation has been shown to lead to robust real-world performance, while still maintaining the practical advantages of simulation, such as making it easy for the same benchmark to be used by many researchers. This method is flexible enough to allow researchers to explicitly modify the benchmarks to identify specific task domains where particular hardware excels. To demonstrate the method, we present a set of novel benchmarks that focus on motor control for an arbitrary system with unknown external forces. Using these benchmarks, we show that an error-driven learning rule can consistently improve motor control performance across a randomly generated family of closed-loop simulations, even when there are up to 15 interacting joints to be controlled. PMID:26696820
Closed-Loop Neuromorphic Benchmarks
Stewart, Terrence C.; DeWolf, Travis; Kleinhans, Ashley; Eliasmith, Chris
2015-01-01
Evaluating the effectiveness and performance of neuromorphic hardware is difficult. It is even more difficult when the task of interest is a closed-loop task; that is, a task where the output from the neuromorphic hardware affects some environment, which then in turn affects the hardware's future input. However, closed-loop situations are one of the primary potential uses of neuromorphic hardware. To address this, we present a methodology for generating closed-loop benchmarks that makes use of a hybrid of real physical embodiment and a type of â€œminimalâ€ simulation. Minimal simulation has been shown to lead to robust real-world performance, while still maintaining the practical advantages of simulation, such as making it easy for the same benchmark to be used by many researchers. This method is flexible enough to allow researchers to explicitly modify the benchmarks to identify specific task domains where particular hardware excels. To demonstrate the method, we present a set of novel benchmarks that focus on motor control for an arbitrary system with unknown external forces. Using these benchmarks, we show that an error-driven learning rule can consistently improve motor control performance across a randomly generated family of closed-loop simulations, even when there are up to 15 interacting joints to be controlled. PMID:26696820
Closed loop refrigerant recovery system
Ager, F.L.
1992-07-21
This patent describes a closed loop refrigerant recover system for removing non-condensable gases from an air conditioning system. It comprises a primary purge condenser; a purge compressor; a secondary purge condenser; a relief valve connected to the secondary purge condenser.
Maximizing loop squareness by minimizing gradients in the microstructure
Branagan, D.J.; Kramer, M.J.; Tang, Y.L.; McCallum, R.W.
1999-04-01
Enhanced energy product and higher operating fields can be achieved by improving the squareness of the demagnetization loop. In isotropic materials, increasing loop squareness can be achieved by minimizing microstructural gradients and maximizing homogeneity. Achieving homogeneity by melt spinning can be difficult due to localized changes in cooling conditions from extrinsic factors such as gas entrapment between the melt and the chill surface and intrinsic effects resulting from the stochastic nature of nucleation on a surface. These localized variations are reduced by altering the solidification kinetics of the alloy, thus reducing its sensitivity to localized changes in cooling conditions. This was achieved through development of a nine-element modified Nd{endash}Fe{endash}B alloy which solidified with a uniform glass structure at much lower cooling rates. After crystallization, enhanced microstructural homogeneity was verified by electron microscopy and described by parameters based on the loop shape. The nine-element alloy had squarer loops and uniformly high hard magnetic properties ({gt}12 MGthinspOe) for cooling rates over 10 m/s. {copyright} {ital 1999 American Institute of Physics.}
Wilson loops and minimal area surfaces in hyperbolic space
NASA Astrophysics Data System (ADS)
Kruczenski, Martin
2014-11-01
The AdS/CFT correspondence relates Wilson loops in SYM theory to minimal area surfaces in AdS space. If the loop is a plane curve the minimal surface lives in hyperbolic space ?3 (or equivalently Euclidean AdS 3 space). We argue that finding the area of such extremal surface can be easily done if we solve the following problem: given two real periodic functions V 0,1( s), V 0,1( s +2 ?) = V 0,1( s) a third periodic function V 2( s) is to be found such that all solutions to the equation are anti-periodic in s ? [0 , 2 ?] for any value of ?. This problem is equivalent to the statement that the monodromy matrix is trivial. It can be restated as that of finding a one complex parameter family of curves X( ?, s) where X( ? = 1 , s) is the given shape of the Wilson loop and such that the Schwarzian derivative { X( ?, s) , s} is meromorphic in ? with only two simple poles. We present a formula for the area in terms of the functions V 0,1,2 and discuss solutions to these equivalent problems in terms of theta functions. Finally, we also consider the near circular Wilson loop clarifying its integrability properties and rederiving its area using the methods described in this paper.
Automated Coronal Loop Identification Using Digital Image Processing Techniques
NASA Technical Reports Server (NTRS)
Lee, Jong K.; Gary, G. Allen; Newman, Timothy S.
2003-01-01
The results of a master thesis project on a study of computer algorithms for automatic identification of optical-thin, 3-dimensional solar coronal loop centers from extreme ultraviolet and X-ray 2-dimensional images will be presented. These center splines are proxies of associated magnetic field lines. The project is pattern recognition problems in which there are no unique shapes or edges and in which photon and detector noise heavily influence the images. The study explores extraction techniques using: (1) linear feature recognition of local patterns (related to the inertia-tensor concept), (2) parametric space via the Hough transform, and (3) topological adaptive contours (snakes) that constrains curvature and continuity as possible candidates for digital loop detection schemes. We have developed synthesized images for the coronal loops to test the various loop identification algorithms. Since the topology of these solar features is dominated by the magnetic field structure, a first-order magnetic field approximation using multiple dipoles provides a priori information in the identification process. Results from both synthesized and solar images will be presented.
Optimized conical shaped charge design using the SCAP (Shaped Charge Analysis Program) code
Vigil, M.G.
1988-09-01
The Shaped Charge Analysis Program (SCAP) is used to analytically model and optimize the design of Conical Shaped Charges (CSC). A variety of existing CSCs are initially modeled with the SCAP code and the predicted jet tip velocities, jet penetrations, and optimum standoffs are compared to previously published experimental results. The CSCs vary in size from 0.69 inch (1.75 cm) to 9.125 inch (23.18 cm) conical liner inside diameter. Two liner materials (copper and steel) and several explosives (Octol, Comp B, PBX-9501) are included in the CSCs modeled. The target material was mild steel. A parametric study was conducted using the SCAP code to obtain the optimum design for a 3.86 inch (9.8 cm) CSC. The variables optimized in this study included the CSC apex angle, conical liner thickness, explosive height, optimum standoff, tamper/confinement thickness, and explosive width. The non-dimensionalized jet penetration to diameter ratio versus the above parameters are graphically presented. 12 refs., 10 figs., 7 tabs.
Optimum conditions for prebiotic evolution in extraterrestrial environments
NASA Astrophysics Data System (ADS)
Abbas, Ousama H.
The overall goal of the dissertation was to devise synthetic pathways leading to the production of peptides and amino acids from smaller organic precursors. To this end, eight different zeolites were tested in order to determine their catalytic potential in the conversion of amino acids to peptides. The zeolites tested were either synthetic or naturally occurring. Acidic solutions of amino acids were prepared with or without zeolites and their reactivity was monitored over a four-week time interval. The kinetics and feasibility of peptide synthesis from selected amino acid combinations was investigated via the paper chromatography technique. Nine different amino acids were tested. The nature and extent of product were measured at constant time intervals. It was found that two ZSM-5 synthetic zeolites as well as the Fisher Scientific zeolite mix without alumina salts may have a catalytic potential in the conversion of amino acids to peptides. The conversion was verified by matching the paper chromatogram of the experimental product with that of a known peptide. The experimental results demonstrate that the optimum solvent system for paper chromatographic analysis of the zeolite-catalyzed self-assembly of the amino acids L-aspartic acid, L- asparagine, L-histidine, and L-serine is a 50:50 mixture of 1-butanol and acetone by volume. For the amino acids L-alanine, L-glycine, and L-valine, the optimum solvent was found to be a 30:70 mixture of ammonia and propanol by volume. A mathematical model describing the distance traveled (spot position) versus reaction time was constructed for the zeolite-catalyzed conversion of L- leucine and L-tyrosine and was found to approximately follow the function f(t) = 25 ln t. Two case studies for prebiotic synthesis leading to the production of amino acids or peptides in extraterrestrial environments were discussed: one involving Saturn's moon Titan, and the other involving Jupiter's moon Europa. In the Titan study, it was determined that organic synthesis, based on simple precursors, may lead in the Titan environment to the production of biologically important molecules such as amino acids. In the Europa study, three synthetic schemes using hydrogen peroxide, sulfuric acid, and hydrocyanic acid, and leading to the production of larger biologically important molecules such as amino acids were presented. (Abstract shortened by UMI.)
Shape tuning of adaptive structures for MEMS actuator applications
NASA Astrophysics Data System (ADS)
Ma, Zhichun; Lee, Yung-Cheng
2005-05-01
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.
Geometry of mediating protein affects the probability of loop formation in DNA.
Agrawal, Neeraj J; Radhakrishnan, Ravi; Purohit, Prashant K
2008-04-15
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
Loop quantum gravity without the Hamiltonian constraint
NASA Astrophysics Data System (ADS)
Bodendorfer, N.; Stottmeister, A.; Thurn, A.
2013-04-01
We show that under certain technical assumptions, including the existence of a constant mean curvature (CMC) slice and strict positivity of the scalar field, general relativity conformally coupled to a scalar field can be quantized on a partially reduced phase space, meaning reduced only with respect to the Hamiltonian constraint and a proper gauge fixing. More precisely, we introduce, in close analogy to shape dynamics, the generator of a local conformal transformation acting on both, the metric and the scalar field, which coincides with the CMC gauge condition. A new metric, which is invariant under this transformation, is constructed and used to define connection variables which can be quantized by standard loop quantum gravity methods. Since this connection is invariant under the local conformal transformation, the generator of which is shown to be a good gauge fixing for the Hamiltonian constraint, the Dirac bracket associated with implementing these constraints coincides with the Poisson bracket for the connection. Thus, the well developed kinematical quantization techniques for loop quantum gravity are available, while the Hamiltonian constraint has been solved (more precisely, gauge fixed) classically. The physical interpretation of this system is that of general relativity on a fixed spatial CMC slice, the associated ‘time’ of which is given by the CMC. While it is hard to address dynamical problems in this framework (due to the complicated ‘time’ function), it seems, due to good accessibility properties of the CMC gauge, to be well suited for problems such as the computation of black hole entropy, where actual physical states can be counted and the dynamics is only of indirect importance. The corresponding calculation yields the surprising result that the usual prescription of fixing the Barbero-Immirzi parameter ? to a constant value in order to obtain the well-known formula S = a(?)A/(4G) does not work for the black holes under consideration, while a recently proposed prescription involving an analytic continuation of ? to the case of a self-dual space-time connection yields the correct result. Also, the interpretation of the geometric operators gets an interesting twist, which exemplifies the deep relationship between observables and the choice of a time function and has consequences for loop quantum cosmology.
Loop quantum cosmology from quantum reduced loop gravity
NASA Astrophysics Data System (ADS)
Alesci, Emanuele; Cianfrani, Francesco
2015-08-01
We show how loop quantum cosmology can be derived as an effective semiclassical description of loop quantum gravity. Using the tools of QRLG, a gauge fixed version of LQG, we take the coherent states of the fundamental microscopic theory suitable to describe a Bianchi I Universe and we find a mapping between the expectation value of the Hamiltonian and the dynamics of LQC. Our results are in agreement with a lattice refinement framework for LQC, thus the so-called “old” and “improved-dynamics” regularization schemes can be reproduced. These amount to different choices of relations between local variables and the smeared ones entering the definition of the coherent states. The leading order of the fundamental theory corresponds to LQC, but we also find different inverse volume corrections, that depend on a purely quantum observable, namely the number of nodes of the states.
Low temperature enantiotropic nematic phases from V-shaped, shape-persistent molecules
Seltmann, Jens
2009-01-01
Summary A series of V-shaped, shape-persistent thiadiazole nematogens, based on an oligo(phenylene ethynylene) scaffold with ester groups connected via alkyloxy spacers, was efficiently prepared by a two-step procedure. Phase engineering results in an optimum of the mesophase range and low melting temperature when the nematogens are desymmetrised with a butoxy and a heptyloxy spacer. The mesophases are enantiotropic and over the whole temperature range nematic. For the optimised mesogen structure, optical investigations by conoscopy monitored a uniaxial nematic phase upon cooling from the isotropic phase to room temperature (?T = 150 °C). X-ray studies on magnetic-field-aligned samples of this mesogen family revealed a general pattern, indicating the alignment of two molecular axes along individual directors in the magnetic field. These observations may be rationalised with larger assemblies of V-shaped molecules isotropically distributed around the direction of the magnetic field. PMID:20300458
Optimum viscous flow in pressure-swirl atomizers
NASA Astrophysics Data System (ADS)
Amini, Ghobad; Pereira, Aaron; Yun, Sangsig; Li, Xianguo
2013-11-01
Due to their simple configuration and reliable operation, pressure-swirl atomizers are widely used in applications such as combustion, painting, humidification, and sprinkling. The liquid is swirled by entering into the atomizer tangentially and its surface area is increased as discharges in a large spray angle. Understanding the effects of nozzle geometry and inlet flow condition on the discharge coefficient and spray angle is very important in nozzle design. To this end, the flow field inside a pressure-swirl atomizer has been studied theoretically. The main body of the liquid is taken to be moving in circles round the axis. Within the boundary layer, containing transverse and longitudinal velocity components, the retarded liquid is slowed down by viscosity and driven towards the exit orifice by pressure gradient. The swirling motion of liquid creates a low pressure zone near the nozzle axis and leads to the formation of a helical air-core. Through studying the growth of the boundary layer from nozzle entry to the orifice exit, the portions of the outflow exits the orifice from boundary layer current and also from the main body of the swirling liquid are specified. For a given range of pressure drop values, the optimum nozzle geometry and liquid flowrate are predicted. Additionally, the reason of increasing the flow by increasing liquid viscosity or decreasing orifice diameter is explained. A series of experiments and numerical modeling have also been carried out to support the theoretical results.
Optimum frequency for subsurface-imaging synthetic-aperture radar
Brock, B.C.; Patitz, W.E.
1993-05-01
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.
Optimum Heart Rate to Minimize Pulsatile External Cardiac Power
NASA Astrophysics Data System (ADS)
Pahlevan, Niema; Gharib, Morteza
2011-11-01
The workload on the left ventricle is composed of steady and pulsatile components. Clinical investigations have confirmed that an abnormal pulsatile load plays an important role in the pathogenesis of left ventricular hypertrophy (LVH) and progression of LVH to congestive heart failure (CHF). The pulsatile load is the result of the complex dynamics of wave propagation and reflection in the compliant arterial vasculature. We hypothesize that aortic waves can be optimized to reduce the left ventricular (LV) pulsatile load. We used an in-vitro experimental approach to investigate our hypothesis. A unique hydraulic model was used for in-vitro experiments. This model has physical and dynamical properties similar to the heart-aorta system. Different compliant models of the artificial aorta were used to test the hypothesis under various aortic rigidities. Our results indicate that: i) there is an optimum heart rate that minimizes LV pulsatile power (this is in agreement with our previous computational study); ii) introducing an extra reflection site at the specific location along the aorta creates constructive wave conditions that reduce the LV pulsatile power.
Optimum radiation source for radiation therapy of skin cancer.
Safigholi, Habib; Song, William Y; Meigooni, Ali S
2015-01-01
Several different applicators have been designed for treatment of skin cancers, such as scalp, hand, and legs using Ir-192 HDR brachytherapy sources (IR-HDRS), miniature electronic brachytherapy sources (eBT), and external electron beam radiation therapy (EEBRT). Although, all of these methodologies may deliver the desired radiation dose to the skin, but the dose to the underlying bone may become the limiting factor for selection of the optimum treatment technique. In this project, dose to the underlying bone has been evaluated as a function of the radiation type, thickness of the bone, and thickness of the soft tissue on top of bone, assuming the same radiation dose delivery to the skin. These evaluations are performed using Monte Carlo (MC) simulation technique with MCNP5 code. The results of these investigations indicate that, for delivery of the same skin dose with a 50keV eBT, 4 MeV or 6 MeV EEBRT techniques, the average doses received by the underlying bones are 5.31, 2, or 1.75 times the dose received from IR-HDRS technique, respectively. These investigations indicate that, for the treatment of skin cancer condition with bone immediately beneath skin, the eBT technique may not be the most suitable technique, as it may lead to excessive bone dose relative to IR-HDRS and 6 MeV or 4 MeV electron beams. PMID:26699302
Determination of optimum data points for scaling factor determination
Fernandez, Michael Dennis T.; Sang Chui Lee; Kun Jai Lee
2007-07-01
Scaling factors are calculated based on a database from radiochemical analyses of representative waste samples. Several data points are needed to derive a reliable scaling factor. The more the number of data points, the better is the correlation, but more costly because of number of needed radiochemical analyses. Therefore, optimization of data points should be considered to minimize the cost without compromising reliability and prediction of the scaling factor. Scaling factors for Ni-63, Sr-90, and C-14 were calculated using Co-60 and Cs-137 as Key nuclides based on the published data in EPRI-4037. Correlation coefficient, percent error and relative standard deviation were plotted against the number of data points used in the estimation of scaling factor. The optimum number of data points was obtained to where there was no significant improvement in the statistical uncertainties by using additional samples. Even though non-segregated (all data points) has greater effect in calculating scaling factor because of its more data points, this study showed that even segregated data points can also give good DTM characterization. (authors)
Optimum design of a gearbox for low vibration
NASA Technical Reports Server (NTRS)
Inoue, Katsumi; Townsend, Dennis P.; Coy, John J.
1992-01-01
A computer program was developed for designing a low vibration gearbox. The code is based on a finite element shell analysis, a modal analysis, and a structural optimization method. In the finite element analysis, a triangular shell element with 18 degrees-of-freedom is used. In the optimization method, the overall vibration energy of the gearbox is used as the objective function and is minimized at the exciting frequency by varying the finite element thickness. Modal analysis is used to derive the sensitivity of the vibration energy with respect to the design variable. The sensitivity is representative of both eigenvalues and eigenvectors. The optimum value is computed by the gradient projection method and a unidimensional search procedure under the constraint condition of constant weight. The computer code is applied to a design problem derived from an experimental gearbox in use at the NASA Lewis Research Center. The top plate and two side plates of the gearbox are redesigned and the contribution of each surface to the total vibration is determined. Results show that optimization of the top plate alone is effective in reducing total gearbox vibration.
Optimum design of a gearbox for low vibration
NASA Astrophysics Data System (ADS)
Inoue, Katsumi; Townsend, Dennis P.; Coy, John J.
1992-04-01
A computer program was developed for designing a low vibration gearbox. The code is based on a finite element shell analysis, a modal analysis, and a structural optimization method. In the finite element analysis, a triangular shell element with 18 degrees-of-freedom is used. In the optimization method, the overall vibration energy of the gearbox is used as the objective function and is minimized at the exciting frequency by varying the finite element thickness. Modal analysis is used to derive the sensitivity of the vibration energy with respect to the design variable. The sensitivity is representative of both eigenvalues and eigenvectors. The optimum value is computed by the gradient projection method and a unidimensional search procedure under the constraint condition of constant weight. The computer code is applied to a design problem derived from an experimental gearbox in use at the NASA Lewis Research Center. The top plate and two side plates of the gearbox are redesigned and the contribution of each surface to the total vibration is determined. Results show that optimization of the top plate alone is effective in reducing total gearbox vibration.
OPTIMUM INTEGRAL DESIGN FOR MAXIMIZING THE FIELD IN SHORT MAGNETS.
GUPTA,R.
2004-10-03
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.
Optimum design of radial flow impellers for variable load operation
Tuccillo, R.; Senatore, A.
1994-12-31
The authors present, in this paper, an improved methodology for optimum design of radial flow impellers. The base methodology was recently proposed by the authors and consisted of a mathematical optimization technique matched to a flow model based upon an inviscid ``quasi 3-D`` method linked to a prediction of the boundary layer growth along both blade and end-wall surfaces. The enhanced strategy proposed in the present paper utilizes a genetic optimization algorithm and a number of refinement steps. This allows an effective exploration of a wide range of the independent variables. The latter define the impeller geometry defined under several aspects related to blade curvature and twisting, inlet and discharge angles, axial and radial displacements. The objective of maximum in total-to-total efficiency for a given level of pressure ratio is pursued within constraints on load levels, inlet and discharge Mach numbers, peripheral velocity. In this paper, the authors also deal with the search of an impeller configuration for satisfactory performance in an assigned field of operation. Off-design could, in fact, emphasize some problems related to choking or flow separation which are satisfactory solved at the design point. The control exerted by the optimizing procedure on the flow model, also in terms of boundary layer development, is helpful for finding more impeller characteristics for a better fitting of the operating field.
Improved global sea surface temperature analyses using optimum interpolation
Reynolds, R.W.; Smith, T.M. )
1994-06-01
The new NOAA operational global sea surface temperature (SST) analysis is described. The analyses use 7 days of in situ (ship and buoy) and satellite SST. These analyses are produced weekly and daily using optimum interpolation (OI) on a 1[degrees] grid. The OI technique requires the specification of data and analysis error statistics. These statistics are derived and show that the SST rms data errors from ships are almost twice as large as the data errors from buoys or satellites. In addition, the average e-folding spatial error scales have been found to be 850 km in the zonal direction and 615 km in the meridional direction. The analysis also includes a preliminary step that corrects any satellite biases relative to the in situ data using Poisson's equation. The importance of this correction is demonstrated using recent data following the 1991 eruptions of Mt. Pinatubo. The OI analysis has been computed using the in situ and bias-corrected satellite data for the period 1985 to present. 20 refs., 19 figs., 3 tabs.
Optimum Conditions for Artificial Fruiting Body Formation of Cordyceps cardinalis
Kim, Soo-Young; Shrestha, Bhushan; Sung, Gi-Ho; Han, Sang-Kuk
2010-01-01
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 25â„ƒ, 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. PMID:23956641
Sea-land-line extraction using weighted optimum neighborhood algorithm
NASA Astrophysics Data System (ADS)
Lan, Jinhui; Jia, Zengli; Wu, Chunhong; Yang, Jun
2013-12-01
In the field of automatic target recognition, research on automatic target recognition in water becomes increasingly important due to its value in maritime security and defense. Sea-land-line extraction under complicated sea-land-sky background plays an important role in water surface target recognition. The weighted optimum neighborhood algorithm is proposed by the feature of complicated sea-land-sky background images. Firstly pretreatment operations and Hough transform are taken in the image to find the potential sea-land-lines. There are several false sea-land-lines and a true sealand- line in these sea-land-lines. In the next step, the weighted values of the fitted sea-land lines' neighborhood are calculated and the fitted line, which has the biggest weighted value, is the correct sea-land-line. The experimental results show that the algorithm can detect the sea-land-line under complicated sea-land-sky background correctly and effectively, and has advantages such as strong robustness, more accurate and high practical value.
Subscriber loop economics: defining fiber's competitive edge
NASA Astrophysics Data System (ADS)
Tumolillo, Allan M.
1993-02-01
Loop economics (capital, operating cost, revenues, and present worth) is not well known for any loop technology, hampering deployment of new loop technologies. Local Exchange Carriers (LECs) must establish a base economic case for copper since the LECs have generally required fiber to be deployed when 'cost competitive with copper for POTS.' However, LEC management information systems do not capture copper costs in a format useful to loop planners. Results of one detailed analysis of loop economics are presented, showing loop density as key cost driver. Work in progress suggests how fiber in the loop (FITL) can be compared to copper's POTS cost, revenue and value structures. Using different revenue streams due to fiber's service enhancements, present worth analysis will demonstrate the range of loop densities that fiber may have an advantage in today.
Noise Performance Of A Digital Tanlock Loop
NASA Technical Reports Server (NTRS)
Hurd, W. J.; Pomalaza-Raez, C. A.
1988-01-01
Slight improvement over sinusoidal phase-lock loop achieved. Report discusses theoretical studies and numerical simulations of performance of digital tangent phase-lock loop (DTL), in presence of noise.
Decentralized Control of Sound Radiation Using Iterative Loop Recovery
NASA Technical Reports Server (NTRS)
Schiller, Noah H.; Cabell, Randolph H.; Fuller, Chris R.
2009-01-01
A decentralized model-based control strategy is designed to reduce low-frequency sound radiation from periodically stiffened panels. While decentralized control systems tend to be scalable, performance can be limited due to modeling error introduced by the unmodeled interaction between neighboring control units. Since bounds on modeling error are not known in advance, it is difficult to ensure the decentralized control system will be robust without making the controller overly conservative. Therefore an iterative approach is suggested, which utilizes frequency-shaped loop recovery. The approach accounts for modeling error introduced by neighboring control loops, requires no communication between subsystems, and is relatively simple. The control strategy is evaluated numerically using a model of a stiffened aluminum panel that is representative of the sidewall of an aircraft. Simulations demonstrate that the iterative approach can achieve significant reductions in radiated sound power from the stiffened panel without destabilizing neighboring control units.
Fragmentation of cosmic-string loops
NASA Technical Reports Server (NTRS)
York, Thomas
1989-01-01
The fragmentation of cosmic string loops is discussed, and the results of a simulation of this process are presented. The simulation can evolve any of a large class of loops essentially exactly, including allowing fragments that collide to join together. Such reconnection enhances the production of small fragments, but not drastically. With or without reconnections, the fragmentation process produces a collection of nonself-intersecting loops whose typical length is on the order of the persistence length of the initial loop.
Loop Diuretics in Clinical Practice
Oh, Se Won
2015-01-01
Diuretics are commonly used to control edema across various clinical fields. Diuretics inhibit sodium reabsorption in specific renal tubules, resulting in increased urinary sodium and water excretion. Loop diuretics are the most potent diuretics. In this article, we review five important aspects of loop diuretics, in particular furosemide, which must be considered when prescribing this medicine: (1) oral versus intravenous treatment, (2) dosage, (3) continuous versus bolus infusion, (4) application in chronic kidney disease patients, and (5) side effects. The bioavailability of furosemide differs between oral and intravenous therapy. Additionally, the threshold and ceiling doses of furosemide differ according to the particular clinical condition of the patient, for example in patients with severe edema or chronic kidney disease. To maximize the efficiency of furosemide, a clear understanding of how the mode of delivery will impact bioavailability and the required dosage is necessary. PMID:26240596
Lock detection in Costas loops
NASA Technical Reports Server (NTRS)
Mileant, A.; Hinedi, S.
1992-01-01
Previous analyses of lock detector algorithms for Costas loops have ignored the effects of the inherent correlation between samples of the phase error process. In this paper, both analysis and simulations are used to quantify the effects of phase correlation on lock detection for the 'square law' and 'absolute value' type detectors. Results are obtained which depict the lock detection probability as a function of loop signal-to-noise ratio for a given false alarm rate. It is shown that the square law detector experiences less degradation due to phase jitter than the absolute value detector and that the degradation in detector signal-to-noise ratio is more pronounced for squarewave than for sinewave signals.
Looping: Adding Time, Strengthening Relationships. ERIC Digest.
ERIC Educational Resources Information Center
Burke, Daniel L.
"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 positiveâ€¦
2014-01-01
Background Owing to the harmfulness and seriousness of Schistosomiasis japonica in China, the control and prevention of S. japonica transmission are imperative. As the unique intermediate host of this disease, Oncomelania hupensis plays an important role in the transmission. It has been reported that the snail population in Qiangliang Lake district, Dongting Lake Region has been naturally declining and is slowly becoming extinct. Considering the changes of environmental factors that may cause this phenomenon, we try to explore the relationship between circumstance elements and snails, and then search for the possible optimum scopes of environmental factors for snails. Methods Moisture content of soil, pH, temperature of soil and elevation were collected by corresponding apparatus in the study sites. The LISA statistic and GWR model were used to analyze the association between factors and mean snail density, and the values in high-high clustered areas and low-low clustered areas were extracted to find out the possible optimum ranges of these elements for snails. Results A total of 8,589 snail specimens were collected from 397 sampling sites in the study field. Besides the mean snail density, three environmental factors including water content, pH and temperature had high spatial autocorrelation. The spatial clustering suggested that the possible optimum scopes of moisture content, pH, temperature of the soil and elevation were 58.70 to 68.93%, 6.80 to 7.80, 22.73 to 24.23°C and 23.50 to 25.97 m, respectively. Moreover, the GWR model showed that the possible optimum ranges of these four factors were 36.58 to 61.08%, 6.541 to 6.89, 24.30 to 25.70°C and 23.50 to 29.44 m, respectively. Conclusion The results indicated the association between snails and environmental factors was not linear but U-shaped. Considering the results of two analysis methods, the possible optimum scopes of moisture content, pH, temperature of the soil and elevation were 58.70% to 68.93%, 6.6 to 7.0, 22.73°C to 24.23°C, and 23.5 m to 26.0 m, respectively. The findings in this research will help in making an effective strategy to control snails and provide a method to analyze other factors. PMID:24886456
Open loop digital frequency multiplier
NASA Technical Reports Server (NTRS)
Moore, R. C. (inventor)
1977-01-01
An open loop digital frequency multiplier is described which has a multiplied output synchronized to low frequency clock pulse. The system includes a multistage digital counter which provides a pulse output as a function of an integer divisor. The integer divisor and the timing or counting cycle of the counter are interrelated to the frequency of a clock input. The counting cycle is controlled by a one shot multivibrator which, in turn, is driven by a reference frequency input.
Fiber laser with loop reflector
NASA Astrophysics Data System (ADS)
Florczyk, P.; Anders, K.; Gdula, P.; Jusza, A.; Piramidowicz, R.
2010-09-01
In this paper we present our recent works on design and development of a compact erbium doped fiber laser with fiber loop reflector dedicated to application in student's laboratory. The scope covers the detailed analysis of spectroscopic properties of erbium doped glass samples, theoretical modeling of fundamental lasing properties, design and preparation of laser components and, finally, preparation and characterization of developed fiber laser setup.
ERIC Educational Resources Information Center
Albertazzi, Liliana; Da Pos, Osvaldo; Canal, Luisa; Micciolo, Rocco; Malfatti, Michela; Vescovi, Massimo
2013-01-01
This article presents an experimental study on the naturally biased association between shape and color. For each basic geometric shape studied, participants were asked to indicate the color perceived as most closely related to it, choosing from the Natural Color System Hue Circle. Results show that the choices of color for each shape were not…
ERIC Educational Resources Information Center
Albertazzi, Liliana; Da Pos, Osvaldo; Canal, Luisa; Micciolo, Rocco; Malfatti, Michela; Vescovi, Massimo
2013-01-01
This article presents an experimental study on the naturally biased association between shape and color. For each basic geometric shape studied, participants were asked to indicate the color perceived as most closely related to it, choosing from the Natural Color System Hue Circle. Results show that the choices of color for each shape were notâ€¦
Weyl and Dirac loop superconductors
NASA Astrophysics Data System (ADS)
Nandkishore, Rahul
2016-01-01
We study three-dimensional systems where the parent metallic state contains a loop of Weyl points. We introduce the minimal k .p Hamiltonian, and discuss its symmetries. Guided by this symmetry analysis, we classify the superconducting instabilities that may arise. For a doped Weyl loop material, we argue that—independent of microscopic details—the leading superconducting instability should be to a fully gapped chiral superconductor in three dimensions—an unusual state made possible only by the nontrivial topology of the Fermi surface. This state, which we dub the "meron superconductor," is neither fully topological nor fully trivial. Meanwhile, at perfect compensation additional states are possible (including some that are fully topological), but the leading instability depends on microscopic details. We discuss the influence of disorder on pairing. In the presence of a spin degeneracy ("Dirac loops") still more complex superconducting states can arise, including a "skyrmion" superconductor with topological properties similar to superfluid He III-B, which additionally breaks lattice rotation symmetry and exhibits nematic order.
Polyhedra in loop quantum gravity
Bianchi, Eugenio; Speziale, Simone; Dona, Pietro
2011-02-15
Intertwiners are the building blocks of spin-network states. The space of intertwiners is the quantization of a classical symplectic manifold introduced by Kapovich and Millson. Here we show that a theorem by Minkowski allows us to interpret generic configurations in this space as bounded convex polyhedra in R{sup 3}: A polyhedron is uniquely described by the areas and normals to its faces. We provide a reconstruction of the geometry of the polyhedron: We give formulas for the edge lengths, the volume, and the adjacency of its faces. At the quantum level, this correspondence allows us to identify an intertwiner with the state of a quantum polyhedron, thus generalizing the notion of the quantum tetrahedron familiar in the loop quantum gravity literature. Moreover, coherent intertwiners result to be peaked on the classical geometry of polyhedra. We discuss the relevance of this result for loop quantum gravity. In particular, coherent spin-network states with nodes of arbitrary valence represent a collection of semiclassical polyhedra. Furthermore, we introduce an operator that measures the volume of a quantum polyhedron and examine its relation with the standard volume operator of loop quantum gravity. We also comment on the semiclassical limit of spin foams with nonsimplicial graphs.
Optimum Anthropometric Criteria for Ideal Body Composition Related Fitness
Kilani, Hashem; Abu-Eisheh, Asem
2010-01-01
Objectives The three aims of this study were to establish equations for ideal body composition related fitness to be used by adults willing to gain optimum body composition related fitness; to predict the possible symmetrical major muscle circumference, and to compute the ideal body fat percentage (BFP) with ideal body weight (IBW) based on the body mass index (BMI). Methods Twenty-four athletes were intentionally selected, with heights of 166–190 cm and aged 20–42 years, according to a judging committee that used modified International Fitness Federation criteria for the Mr. Fitness competition “super body category”. Common anthropometric and body composition measurements were taken for the following independent variables: body height, upper limb length, lower limb length, thigh length, arm length, shoulder width, forearm length, shank length, and wrist girth; and for the following dependent variables: circumferences of shoulder, thigh, waist, hip, chest, biceps, forearm, shank, and neck. Skin fold thickness was measured at three sites by a Harpenden caliper to calculate BFP. Results The findings indicate that there was a predictive correlation between major independent variables and body circumferences. The mean range used to find out the ideal BFP percentage which was 5.6–6.7 %. The BMI equation used to find the IBW was H2 × 23.77 ± 2 SE. Stepwise multiple regressions were also used to derive predictive equations. The most predictive independent variables were wrist girth and height. Conclusion It is suggested that the above equations, the ideal BFP percentage and the IBW be used as criteria in training sessions to achieve ideal body composition related fitness. PMID:21509084
Optimum dose of radiotherapy for chemodectomas of the middle ear
Kim, J.A.; Elkon, D.; Lim, M.L.; Constable, W.C.
1980-07-01
Forty patients with chemodectomas of the middle ear were seen at the University of Virginia Hospital from 1932 to 1978. Surgery, post-operative radiotherapy or radiotherapy alone were the treatment modalities employed depending on the extent of the disease. These have been reviewed with regard to the clinical presentation and results of treatment with long term follow-up of 1 to 30 years. An attempt was made to determine the optimum dose of radiotherapy based on our data and reported cases in the literature. The majority of patients complaining of tinnitus, otalgia and pulsation obtained significant if not complete relief of symptoms. Cranial nerve defects, however, ofter persisted after therapy. Tumor was considered to be controlled if there was no increase in its size or progression of symptoms. Tumor control was obtained in eight of 10 early patients but only in two of seven more patients with advanced disease with total resection. Control rate with post-operative radiotherapy after subtotal resection was 85%. Radiotherapy alone was used for inoperable or recurrent tumors and control was obtained in 88% of them. In addition to our data, the radiation dose used in over 200 patients reported in the literature was analyzed. There was only a 2% recurrence rate in patients who received 4000 rad/4 weeks or higher. Twenty-two percent of patients treated with less than 4000 rad developed recurrence. The tendency is to use a lower dose of postoperative treatment and a higher dose for gross inoperable tumors. 4000 rad/4 weeks seems to be adequate for control of postoperative residual disease and no more than 5000 rad/5 weeks are required even for advanced inoperable cases. By keeping the dose below 5000 rad/5 weeks, the incidence of complications such as brain necrosis is greatly decreased.
Optimum interpolation analysis of Aquarius sea surface salinity
NASA Astrophysics Data System (ADS)
Melnichenko, Oleg; Hacker, Peter; Maximenko, Nikolai; Lagerloef, Gary; Potemra, James
2016-01-01
A new high-resolution sea surface salinity (SSS) analysis has been produced using Aquarius satellite observations from September 2011 to June 2015. The motivation for the new product is twofold: to produce Level-4 SSS analysis that is consistent with existing in situ observations such as from Argo profile data, and to reduce the large-scale satellite biases that have existed in all versions of the standard Level-3 Aquarius products. The new product is a weekly SSS analysis on a nearly global 0.5Â° grid. The analysis method is optimum interpolation (OI) that takes into account analyzed errors of the observations, specific to the Aquarius instrument. The method also includes a large-scale correction for satellite biases, filtering of along-track SSS data prior to OI, and the use of realistic correlation scales of SSS anomalies. All these features of the analysis are shown to result in more accurate SSS maps. In particular, the method reduces the effects of relative biases between the Aquarius beams and eliminates most of the large-scale, space-varying, and time-varying satellite biases relative to in situ data, including spurious annual signals. Statistical comparison between the weekly OI SSS maps and concurrent buoy data demonstrates that the global root-mean-square error of the analysis is smaller than 0.2 pss for nearly all weeks over the Ëœ4 year period of comparison. The utility of the OI SSS analysis is also exemplified by the derived patterns of regional SSS variability.
Optimum conditions for aerobic thermophilic pretreatment of municipal sludge
Cheunbarn, T.; Pagilla, K.R.
1998-07-01
Lab scale experiments were conducted to determine optimum sludge residence time (SRT) and temperature of aerobic thermophilic pretreatment (ATP) of mixed (thickened waste activated and primary) sludge to achieve maximum pathogen destruction and best process performance. 4L lab scale ATP reactors were operated at SRT of 0.6, 1.0, and 1.5 days, and at temperature of 55, 58, 62 and 65 C. ATP at temperature {ge} 62 C and SRT {ge} 0.6 days reduced the feed sludge fecal coliform density by at least 4-logs from 10{sup 7} MPN/g total solids to < 10{sup 4} MPN/g total solids. Salmonella in the feed sludge was reduced to < 1 MPN/g total solids from 2 to 18 MPN/4 g total solids by ATP at temperature {ge} 55 C and SRT {ge} 0.6 days. ATP was able to increase sludge volatile acids concentration by 100--200% over the feed sludge volatile acid concentration, and reduce the supernatant COD from 20,000--22,000 mg/L in the feed to 13,000--17,000 mg/L in ATP reactor sludge. Volatile solids destruction by ATP was increased from 25% to 40% when SRT was increased from 0.6 days to 1.5 days, and only 5% increase in volatile solids destruction was seen at each SRT of 0.6, 1.0, and 1.5 days when ATP temperature was increased from 55 to 65 C.
Optimized input shaping for a single flexible robot link
Wilson, D.G.; Stokes, D.; Starr, G.; Robinett, R.D.
1996-03-01
This paper will discuss the design of an input shaped open-loop control for a single flexible robot link. The authors develop the equations of motion, including the first flexible mode shape and the actuator dynamics. Additional content includes the hardware system identification iterative runs used to update the model. Optimized input shaped commands for the flexible robot link to produce a rest-to-rest, residual vibration-free, 90 degree maneuver are developed. Correlation between both experimental and analytical results of the 90{degree} slew, using two different identification models, are reviewed.
Z-Sum approach to loop integrals
NASA Astrophysics Data System (ADS)
Rottmann, Paulo A.
We study the applicability of the Z-Sum approach to multi-loop calculations with massive particles in perturbative quantum field theory. We systematically analyze the case of one-loop scalar integrals, which represent the building blocks of any higher-loop calculation. We focus in particular on triangle one-loop integrals and identify strengths and limitations of the Z-Sum approach, extending our results to the case of one-loop box integrals when appropriate. We conclude with the calculation of a specific physical example: the calculation of heavy flavor corrections to the renormalized scattering amplitude for deep inelastic scattering.
General shape optimization capability
NASA Technical Reports Server (NTRS)
Chargin, Mladen K.; Raasch, Ingo; Bruns, Rudolf; Deuermeyer, Dawson
1991-01-01
A method is described for calculating shape sensitivities, within MSC/NASTRAN, in a simple manner without resort to external programs. The method uses natural design variables to define the shape changes in a given structure. Once the shape sensitivities are obtained, the shape optimization process is carried out in a manner similar to property optimization processes. The capability of this method is illustrated by two examples: the shape optimization of a cantilever beam with holes, loaded by a point load at the free end (with the shape of the holes and the thickness of the beam selected as the design variables), and the shape optimization of a connecting rod subjected to several different loading and boundary conditions.
NASA Astrophysics Data System (ADS)
Sheiko, Sergei; Zhou, Jing; White, Sarah; Ashby, Valerie
2012-02-01
An ``Achilles' heel'' of shape memory materials is that shape transformations triggered by an external stimulus are usually irreversible. Here we present a new concept of reversible transitions between two well-defined shapes by controlling hierarchic crystallization of a dual-network elastomer. The reversibility was demonstrated for different types of shape transformations including rod bending, winding of a helical coil, and widening an aperture. The distinct feature of the reversible shape alterations is that both counter-shapes are infinitely stable at a temperature of exploitation. Shape reversibility is highly desirable property in many practical applications such as non-surgical removal of a previously inserted catheter and handfree wrapping up of an earlier unraveled solar sail on a space shuttle.
ERIC Educational Resources Information Center
Alterovitz, Gil
2004-01-01
This research analyzed both engineering and nontechnical issues involved in the use of Induction Loop Amplification (ILA) devices in auditoriums or large gathering places for hard-of-hearing individuals. A variety of parameters need to be taken into account to determine an optimal shape/configuration for the ILA device. In many cases, an optimal…
Palynological Investigation of the Holocene Thermal Optimum in New Zealand
NASA Astrophysics Data System (ADS)
Newnham, R. M.; McGlone, M. S.; Wilmshurst, J. M.
2005-12-01
It has long been assumed in New Zealand (NZ) that the Holocene Thermal Optimum (HTO) occurred at the beginning of the Holocene. Nearly 40 years ago, Hendy and Wilson pioneered the use of 18O/16O composition of calcite in NZ speleothems to reconstruct past climate and in so doing showed an HTO occurring earlier in NZ than in comparable Northern Hemisphere records (Hendy & Wilson,1968). More recent work on NZ speleothems (Williams et al., 2005) corroborates the concept of an early HTO dated between ca 11.7 and 10.6 ka, but there is no definitive description of the event as a NZ-wide phenomenon, no intensive dating of it, nor temperature quantification. Moreover, there is no firm conclusion as to whether it is registered consistently between different proxies and across NZ regions. Until recently, attempts to quantify past climate change from NZ pollen data have been hindered by failure to demonstrate robust relationships between modern pollen assemblages and climate due, it is thought, to strong anthropogenic modification of natural vegetation patterns and steep climatic gradients (Norton et al., 1986). However, as deforestation commenced only ca 700 years ago, and is unambiguously detected in pollen records from throughout NZ, an almost unique opportunity exists to develop pollen-climate transfer functions using pre-human pollen-vegetation sources. McGlone and Wilmshurst have assembled an extensive (138-site) `modern' pollen database, based on ca 700 yr BP pre-deforestation pollen assemblages from peat and lake cores. This now provides a basis for more secure pollen-climate reconstruction than hitherto has been possible. Statistical modelling of the environmental determinants of patterns in the pre-deforestation pollen database indicates the strongest relationship (r2 > 0.8) is with Mean Annual Temperature (MAT) and suggests that this parameter can be reliably reconstructed, with error estimates, from Late Quaternary NZ pollen profiles. We use this database to quantify MAT for a selected range of pollen profiles spanning the last glacial-Holocene interval from across the NZ region. We use the resulting MAT profiles to test the "early HTO hypothesis" (that is, a warming at the beginning of, or even just prior to, the Holocene). As well, we examine the amplitude and spatial uniformity of the HTO and its possible cause. References Hendy CH, Wilson AT. 1968. Nature 219, 48-51. Norton DA, McGlone MS, Wigley TML. 1986. NZJBot 24,331-342. Williams PW et al 2005. EPSL 230, 301-317.
On optimum orthodontic force theory as applied to canine retraction.
Nikolai, R J
1975-09-01
The study reported here was undertaken in an attempt to contribute, from a theoretical standpoint, to the knowledge and understanding of optimum force theory, particularly as it may be relevant to canine retraction. The following statements are derived from my analysis of the applicable published literature and the results of the present investigation: 1. This study lends support to the beliefs, from the findings of previous investigations, 20, 22 that the center of rotation for simple tipping is three tenths to four tenths of the distance from the root apex to the alveolar crest and that the center of resistance is at approximately midroot for the single-rooted tooth. 2. For a given distal driving force, increasing the countertipping couple from zero causes the center of rotation to "move" from a point near the apical end of the middle third of the root to the root apex and then to infinity. That is, the couple to be developed by the appliance to produce crown movement is smaller than required for bodily movement. Also, increasing the rotational stiffness of a canine-retraction appliance will result in greater inherent potential for canine root control and a greater probability of achieving bodily movement. 3. In a specific orthodontic case, an average periodontal stress value (active force divided by root area) can be used as a basis of comparison of suggested active force magnitudes among several single-rooted teeth having different root surface areas, provided all teeth are to experience the same form of displacement (for example, bodily movement). Similarly, differences in average stress magnitudes developed in the periodontium, rather than differences in root surface areas, are actually the basis for the differential force theory. 4. Clinical studies have suggested that the size of active force for bodily movement or root movement of a given tooth be two to three times that employed in simple tipping of the same tooth. Induced stress levels in the periodontium, especially at the root apex and alveolar crest locations, can be related to suggested magnitudes of aplied crown force components. PMID:1057850
Optimum synthetic-aperture imaging of extended astronomical objects.
van der Avoort, Casper; Pereira, Silvania F; Braat, Joseph J M; den Herder, Jan-Willem
2007-04-01
In optical aperture-synthesis imaging of stellar objects, different beam combination strategies are used and proposed. Coaxial Michelson interferometers are very common and a homothetic multiaxial interferometer is recently realized in the Large Binocular Telescope. Laboratory experiments have demonstrated the working principles of two new approaches: densified pupil imaging and wide field-of-view (FOV) coaxial imaging using a staircase-shaped mirror. We develop a common mathematical formulation for direct comparison of the resolution and noise sensitivity of these four telescope configurations for combining beams from multiple apertures for interferometric synthetic aperture, wide-FOV imaging. Singular value decomposition techniques are used to compare the techniques and observe their distinct signal-to-noise ratio behaviors. We conclude that for a certain chosen stellar object, clear differences in performance of the imagers are identifiable. PMID:17361290
A study on the optimum fast neutron flux for boron neutron capture therapy of deep-seated tumors.
Rasouli, Fatemeh S; Masoudi, S Farhad
2015-02-01
High-energy neutrons, named fast neutrons which have a number of undesirable biological effects on tissue, are a challenging problem in beam designing for Boron Neutron Capture Therapy, BNCT. In spite of this fact, there is not a widely accepted criterion to guide the beam designer to determine the appropriate contribution of fast neutrons in the spectrum. Although a number of researchers have proposed a target value for the ratio of fast neutron flux to epithermal neutron flux, it can be shown that this criterion may not provide the optimum treatment condition. This simulation study deals with the determination of the optimum contribution of fast neutron flux in the beam for BNCT of deep-seated tumors. Since the dose due to these high-energy neutrons damages shallow tissues, delivered dose to skin is considered as a measure for determining the acceptability of the designed beam. To serve this purpose, various beam shaping assemblies that result in different contribution of fast neutron flux are designed. The performances of the neutron beams corresponding to such configurations are assessed in a simulated head phantom. It is shown that the previously used criterion, which suggests a limit value for the contribution of fast neutrons in beam, does not necessarily provide the optimum condition. Accordingly, it is important to specify other complementary limits considering the energy of fast neutrons. By analyzing various neutron spectra, two limits on fast neutron flux are proposed and their validity is investigated. The results show that considering these limits together with the widely accepted IAEA criteria makes it possible to have a more realistic assessment of sufficiency of the designed beam. Satisfying these criteria not only leads to reduction of delivered dose to skin, but also increases the advantage depth in tissue and delivered dose to tumor during the treatment time. The Monte Carlo Code, MCNP-X, is used to perform these simulations. PMID:25479433
Changes in lung tumor shape during respiration
NASA Astrophysics Data System (ADS)
Kyriakou, E.; McKenzie, D. R.
2012-02-01
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.
Novel design methods for magnetic flux loops in the National Compact Stellarator Experiment
Pomphrey, N.; Lazarus, E.; Zarnstorff, M.; Boozer, A.; Brooks, A.
2007-05-15
Magnetic pickup loops on the vacuum vessel (VV) can provide an abundance of equilibrium information for stellarators. A substantial effort has gone into designing flux loops for the National Compact Stellarator Experiment (NCSX) [Zarnstorff et al., Plasma Phys. Controlled Fusion 43, A237 (2001)], a three-field period quasi-axisymmetric stellarator under construction at the Princeton Plasma Physics Laboratory. The design philosophy, to measure all of the magnetic field distributions normal to the VV that can be measured, has necessitated the development of singular value decomposition algorithms for identifying efficient loop locations. Fields are expected to be predominantly stellarator symmetric (SS)--the symmetry of the machine design--with toroidal mode numbers per torus (n) equal to a multiple of 3 and possessing reflection symmetry in a period. However, plasma instabilities and coil imperfections will generate non-SS fields that must also be diagnosed. The measured symmetric fields will yield important information on the plasma current and pressure profile as well as on the plasma shape. All fields that obey the design symmetries could be measured by placing flux loops in a single half-period of the VV, but accurate resolution of nonsymmetric modes, quantified by the condition number of a matrix, requires repositioning loops to equivalent locations on the full torus. A subarray of loops located along the inside wall of the vertically elongated cross section was designed to detect n=3, m=5 or 6 resonant field perturbations that can cause important islands. Additional subarrays included are continuous in the toroidal and poloidal directions. Loops are also placed at symmetry points of the VV to obtain maximal sensitivity to asymmetric perturbations. Combining results from various calculations which have made extensive use of a database of 2500 free-boundary VMEC equilibria, has led to the choice of 225 flux loops for NCSX, of which 151 have distinct shapes.
Hadron loops and hybrid mixing
Close, F. E.; Thomas, C. E.
2009-04-15
We investigate how coupling of valence qq to meson pairs can modify the properties of conventional qq and hybrid mesons. In a symmetry limit the mixing between hybrids and conventional qq with the same J{sup PC} is shown to vanish. Flavor mixing between heavy and light qq due to meson loops is shown to be dual to the results of gluon mediated pQCD and qualitatively different from mixing involving light flavors alone. The validity of the OZI rule for conventional qq and hybrid mesons is discussed.
Singularities in loop quantum cosmology.
Cailleteau, Thomas; Cardoso, Antonio; Vandersloot, Kevin; Wands, David
2008-12-19
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
Loop Virasoro Lie conformal algebra
Wu, Henan Chen, Qiufan; Yue, Xiaoqing
2014-01-15
The Lie conformal algebra of loop Virasoro algebra, denoted by CW, is introduced in this paper. Explicitly, CW is a Lie conformal algebra with C[âˆ‚]-basis (L{sub i} | iâˆˆZ) and Î»-brackets [L{sub i}â€‰{sub Î»}â€‰L{sub j}] = (âˆ’âˆ‚âˆ’2Î»)L{sub i+j}. Then conformal derivations of CW are determined. Finally, rank one conformal modules and Z-graded free intermediate series modules over CW are classified.
Sagnac interferometric multipass loop amplifier.
Roither, S; Verhoef, A J; Mücke, O D; Reider, G A; Pugžlys, A; Baltuška, A
2012-10-22
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
Emittance measurements for optimum operation of the J-PARC RF-driven H{sup âˆ’} ion source
Ueno, A. Ohkoshi, K.; Ikegami, K.; Takagi, A.; Yamazaki, S.; Oguri, H.
2015-04-08
In order to satisfy the Japan Proton Accelerator Research Complex (J-PARC) second stage requirements of an H{sup âˆ’} ion beam of 60mA within normalized emittances of 1.5Ï€mmâ€¢mrad both horizontally and vertically, a flat top beam duty factor of 1.25% (500Î¼sÃ—25Hz) and a life-time of longer than 1month, the J-PARC cesiated RF-driven H{sup âˆ’} ion source was developed by using an internal-antenna developed at the Spallation Neutron Source (SNS). The transverse emittances of the source were measured with various conditions to find out the optimum operation conditions minimizing the horizontal and vertical rms normalized emittances. The transverse emittances were most effectively reduced by operating the source with the plasma electrode temperature lower than 70Â°C. The optimum value of the cesium (Cs) density around the beam hole of the plasma electrode seems to be proportional to the plasma electrode temperature. The fine control of the Cs density is indispensable, since the emittances seem to increase proportionally to the excessiveness of the Cs density. Furthermore, the source should be operated with the Cs density beyond a threshold value, since the plasma meniscus shape and the ellipse parameters of the transverse emittances seem to be changed step-function-likely on the threshold Cs value.
NASA Astrophysics Data System (ADS)
Kallus, Yoav
2014-03-01
The question of which convex shapes leave the most empty space in their densest packing is the subject of Reinhardt's conjecture in two dimensions and Ulam's conjecture in three dimensions. Such conjectures about pessimal packing shapes have proven notoriously difficult to make progress on. I show that the regular heptagon is a local pessimum among all convex shapes, and that the 3D ball is a local pessimum among origin-symmetric shapes. Any shape sufficiently close in the space of shapes to these local pessima can be packed at a greater efficiency than they. In two dimensions and in dimensions above three, the ball is not a local pessimum, so the situation in 3D is unusual and intriguing. I will discuss what conditions conspire to make the 3D ball a local pessimum and whether we can prove that it is also a global pessimum.
Shape Optimization of Rubber Bushing Using Differential Evolution Algorithm
2014-01-01
The objective of this study is to design rubber bushing at desired level of stiffness characteristics in order to achieve the ride quality of the vehicle. A differential evolution algorithm based approach is developed to optimize the rubber bushing through integrating a finite element code running in batch mode to compute the objective function values for each generation. Two case studies were given to illustrate the application of proposed approach. Optimum shape parameters of 2D bushing model were determined by shape optimization using differential evolution algorithm. PMID:25276848
Shape optimization of rubber bushing using differential evolution algorithm.
Kaya, Necmettin
2014-01-01
The objective of this study is to design rubber bushing at desired level of stiffness characteristics in order to achieve the ride quality of the vehicle. A differential evolution algorithm based approach is developed to optimize the rubber bushing through integrating a finite element code running in batch mode to compute the objective function values for each generation. Two case studies were given to illustrate the application of proposed approach. Optimum shape parameters of 2D bushing model were determined by shape optimization using differential evolution algorithm. PMID:25276848
Magnetogenesis from cosmic string loops
Battefeld, Diana; Battefeld, Thorsten; Wesley, Daniel H; Wyman, Mark E-mail: tbattefe@princeton.edu E-mail: mwyman@perimeterinstitute.ca
2008-02-15
Large scale coherent magnetic fields are observed in galaxies and clusters, but their ultimate origin remains a mystery. We reconsider the prospects for primordial magnetogenesis by a cosmic string network. We show that the magnetic flux produced by long strings has been overestimated in the past, and give improved estimates. We also compute the fields created by the loop population, and find that it gives the dominant contribution to the total magnetic field strength on present-day galactic scales. We present numerical results obtained by evolving semi-analytic models of string networks (including both one-scale and velocity-dependent one-scale models) in a {Lambda}CDM cosmology, including the forces and torques on loops from Hubble redshifting, dynamical friction, and gravitational wave emission. Our predictions include the magnetic field strength as a function of the correlation length, as well as the volume covered by magnetic fields. We conclude that string networks could account for magnetic fields on galactic scales, but only if coupled with an efficient dynamo amplification mechanism.
NASA Astrophysics Data System (ADS)
Durak, Nurcan; Nasraoui, Olfa; Schmelz, Joan
2010-07-01
Arch-shaped coronal loops that are isolated from the background are typically acquired manually from massive online image databases to be used in solar coronal research. The manual search for special coronal loops is not only subject to human mistakes but is also time consuming and tedious. In this study, we propose a completely automated image-retrieval system that identifies coronal-loop regions located outside of the solar disk from 17.1 nm EIT images. To achieve this aim, we first apply image-preprocessing techniques to bring out loop structures from their background and to reduce the effect of undesired patterns. Then we extract principal contours from the solar image regions. The geometrical attributes of the extracted principal contours reveal the existence of loops in a given region. Our completely automated decision-making procedure gives promising results in separating the regions with loops from the regions without loops. Based on our loop-detection procedure, we have developed an automated image-retrieval tool that is capable of retrieving images containing loops from a collection of solar images.
Rotation Angle for the Optimum Tracking of One-Axis Trackers
Marion, W. F.; Dobos, A. P.
2013-07-01
An equation for the rotation angle for optimum tracking of one-axis trackers is derived along with equations giving the relationships between the rotation angle and the surface tilt and azimuth angles. These equations are useful for improved modeling of the solar radiation available to a collector with tracking constraints and for determining the appropriate motor revolutions for optimum tracking.
Luthra, Amit
2015-01-01
The lips and the eyes enhance facial beauty, and they have been highlighted since time immemorial. Rejuvenating the lips with fillers, frequently hyaluronic acid (HA), is a common procedure but requires expertise. The objective of this text is to describe the procedure in detail and cover the practical aspects of injecting lips with fillers. An analysis of treating lips with needles and cannulae has been made with special emphasis on achieving optimum results. PMID:26644736
Construction and performance of fully numerical optimum atomic basis sets
NASA Astrophysics Data System (ADS)
Lange, Björn; Freysoldt, Christoph; Neugebauer, Jörg
2011-08-01
We propose a method for constructing small atomic basis sets that optimally mimic the Kohn-Sham wave functions of an underlying plane-wave calculation. The key quantity of the optimization procedure is the spillage: the relative amount of the occupied Hilbert-space norm lost in the projection onto the atomic basis. To ensure full flexibility in the radial shape, we represent the basis functions by radial momentum-space spline functions. With our approach we reach spillages in the order of 10-4 when using minimal basis sets. Band structure calculations on top of a self-consistent linear-combination-of-atomic-orbitals (LCAO) run reproduce the occupied part of the band structure within a few tens meV. However, minimal basis sets are not flexible enough for obtaining material properties such as the lattice constant and the bulk modulus but require basis sets with f orbitals. Basis sets generated for Si, GaN, Al, and NaCl reach a spillage of ˜10-5 and reproduce lattice constants and bulk moduli within 0.03% and 5%, respectively.
Wilson loop from a Dyson equation
Pak, M.; Reinhardt, H.
2009-12-15
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.
Pidgeon, C.; McNeely, S.; Schmidt, T.; Johnson, J.E.
1987-01-13
Liposome structure and solute entrapment in multilayered vesicles (MLVs) prepared by reverse-phase evaporation (REV) were studied. MLV-REV vesicles prepared from ether/water emulsions have high entrapment. Entrapment depends on drug, drug concentration, lipid, lipid concentration, and the container used to prepare the vesicles. By use of 300 /sup +/L of aqueous phase and 100 mg of phosphatidylcholine (PC), vesicles prepared in a test tube 25 mm x 175 mm have higher entrapment than vesicles prepared in a 100-mL round-bottom or pear-shaped flask. By use of a test tube, 100 mg of PC, and 300 ..mu..L of aqueous phase containing sucrose (1-50 mg/mL), >90% sucrose entrapment was obtained. Increasing lipid content to 150 mg of PC decreased entrapment to approx.80%. Neutral PC MLV-REV vesicles have optimum entrapment. Mixing negatively charged lipids or cholesterol (CH) with PC to make MLV-REV vesicles results in decreased entrapment compared to using only PC. Preparing vesicles with the solid lipid dipalmitoylphosphatidylcholine (DPPC) or DPPC/CH mixtures results in 30-40% entrapment when diethyl ether is used to make the MLV-REV emulsion. The high entrapment found for MLV vesicles prepared from water/organic solvent emulsions depends on maintaining a core during the process of liposome formation. A method to calculate the fraction of water residing in the liposomes' core is presented and used to compare multilayered vesicles prepared by different processes. X-ray diffraction data demonstrate that a heterogeneous distribution of lipid may exist in multilayered vesicles prepared by the REV process.
Optimum design of bridges with superelastic-friction base isolators against near-field earthquakes
NASA Astrophysics Data System (ADS)
Ozbulut, Osman E.; Hurlebaus, Stefan
2010-04-01
The seismic response of a multi-span continuous bridge isolated with novel superelastic-friction base isolator (S-FBI) is investigated under near-field earthquakes. The isolation system consists of a flat steel-Teflon sliding bearing and a superelastic NiTi shape memory alloy (SMA) device. Sliding bearings limit the maximum seismic forces transmitted to the superstructure to a certain value that is a function of friction coefficient of sliding interface. Superelastic SMA device provides restoring capability to the isolation system together with additional damping characteristics. The key design parameters of an S-FBI system are the natural period of the isolated, yielding displacement of SMA device, and the friction coefficient of the sliding bearings. The goal of this study is to obtain optimal values for each design parameter by performing sensitivity analyses of the isolated bridge. First, a three-span continuous bridge is modeled as a two-degrees-of-freedom with S-FBI system. A neuro-fuzzy model is used to capture rate-dependent nonlinear behavior of SMA device. A time-dependent method which employs wavelets to adjust accelerograms to match a target response spectrum with minimum changes on the other characteristics of ground motions is used to generate ground motions used in the simulations. Then, a set of nonlinear time history analyses of the isolated bridge is performed. The variation of the peak response quantities of the isolated bridge is shown as a function of design parameters. Also, the influence of temperature variations on the effectiveness of S-FBI system is evaluated. The results show that the optimum design of the isolated bridge with S-FBI system can be achieved by a judicious specification of design parameters.
Intercomparison of numerical models of flaring coronal loops
NASA Technical Reports Server (NTRS)
Kopp, R. A.; Fisher, G. H.; Macneice, P.; Mcwhirter, R. W. P.; Peres, G.
1986-01-01
The proposed Benchmark Problem consists of an infinitesimal magnetic flux tube containing a low-beta plasma. The field strength is assumed to be so large that the plasma can move only along the flux tube, whose shape remains invariant with time (i.e., the fluid motion is essentially one-dimensional). The flux tube cross section is taken to be constant over its entire length. In planar view the flux tube has a semi-circular shape, symmetric about its midpoint s = s sub max and intersecting the chromosphere-corona interface (CCI) perpendicularly at each foot point. The arc length from the loop apex to the CCI is 10,000 km. The flux tube extends an additional 2000 km below the CCI to include the chromosphere, which initially has a uniform temperature of 8000 K. The temperature at the top of the loop was fixed initially at 2 X 1 million K. The plasma is assumed to be a perfect gas (gamma = 5/3), consisting of pure hydrogen which is considered to be fully ionized at all temperatures. For simplicity, moreover, the electron and ion temperatures are taken to be everywhere equal at all times (corresponding to an artificially enhanced electron-ion collisional coupling). While there was more-or-less unanimous agreement as to certain global properties of the system behavior (peak temperature reached, thermal-wave time scales, etc.), no two groups could claim satisfactory accord when a more detailed comparison of solutions was attempted.
Wedding ring shaped excitation coil
MacLennan, Donald A.; Tsai, Peter
2001-01-01
A high frequency inductively coupled electrodeless lamp includes an excitation coil with an effective electrical length which is less than one half wavelength of a driving frequency applied thereto, preferably much less. The driving frequency may be greater than 100 MHz and is preferably as high as 915 MHz. Preferably, the excitation coil is configured as a non-helical, semi-cylindrical conductive surface having less than one turn, in the general shape of a wedding ring. At high frequencies, the current in the coil forms two loops which are spaced apart and parallel to each other. Configured appropriately, the coil approximates a Helmholtz configuration. The lamp preferably utilizes an bulb encased in a reflective ceramic cup with a pre-formed aperture defined therethrough. The ceramic cup may include structural features to aid in alignment and/or a flanged face to aid in thermal management. The lamp head is preferably an integrated lamp head comprising a metal matrix composite surrounding an insulating ceramic with the excitation integrally formed on the ceramic. A novel solid-state oscillator preferably provides RF power to the lamp. The oscillator is a single active element device capable of providing over 70 watts of power at over 70% efficiency.
Management of afferent loop obstruction: Reoperation or endoscopic and percutaneous interventions?
Blouhos, Konstantinos; Boulas, Konstantinos Andreas; Tsalis, Konstantinos; Hatzigeorgiadis, Anestis
2015-09-27
Afferent loop obstruction is a purely mechanical complication that infrequently occurs following construction of a gastrojejunostomy. The operations most commonly associated with this complication are gastrectomy with Billroth II or Roux-en-Y reconstruction, and pancreaticoduodenectomy with conventional loop or Roux-en-Y reconstruction. Etiology of afferent loop obstruction includes: (1) entrapment, compression and kinking by postoperative adhesions; (2) internal herniation, volvulus and intussusception; (3) stenosis due to ulceration at the gastrojejunostomy site and radiation enteritis of the afferent loop; (4) cancer recurrence; and (5) enteroliths, bezoars and foreign bodies. Acute afferent loop obstruction is associated with complete obstruction of the afferent loop and represents a surgical emergency, whereas chronic afferent loop obstruction is associated with partial obstruction. Abdominal multiple detector computed tomography is the diagnostic study of choice. CT appearance of the obstructed afferent loop consists of a C-shaped, fluid-filled tubular mass located in the midline between the abdominal aorta and the superior mesenteric artery with valvulae conniventes projecting into the lumen. The cornerstone of treatment is surgery. Surgery includes: (1) adhesiolysis and reconstruction for benign causes; and (2) by-pass or excision and reconstruction for malignant causes. However, endoscopic enteral stenting, transhepatic percutaneous enteral stenting and direct percutaneous tube enterostomy have the principal role in management of malignant and radiation-induced obstruction. Nevertheless, considerable limitations exist as a former Roux-en-Y reconstruction limits endoscopic access to the afferent loop and percutaneous approaches for enteral stenting and tube enterostomy have only been reported in the literature as isolated cases. PMID:26425267
Management of afferent loop obstruction: Reoperation or endoscopic and percutaneous interventions?
Blouhos, Konstantinos; Boulas, Konstantinos Andreas; Tsalis, Konstantinos; Hatzigeorgiadis, Anestis
2015-01-01
Afferent loop obstruction is a purely mechanical complication that infrequently occurs following construction of a gastrojejunostomy. The operations most commonly associated with this complication are gastrectomy with Billroth II or Roux-en-Y reconstruction, and pancreaticoduodenectomy with conventional loop or Roux-en-Y reconstruction. Etiology of afferent loop obstruction includes: (1) entrapment, compression and kinking by postoperative adhesions; (2) internal herniation, volvulus and intussusception; (3) stenosis due to ulceration at the gastrojejunostomy site and radiation enteritis of the afferent loop; (4) cancer recurrence; and (5) enteroliths, bezoars and foreign bodies. Acute afferent loop obstruction is associated with complete obstruction of the afferent loop and represents a surgical emergency, whereas chronic afferent loop obstruction is associated with partial obstruction. Abdominal multiple detector computed tomography is the diagnostic study of choice. CT appearance of the obstructed afferent loop consists of a C-shaped, fluid-filled tubular mass located in the midline between the abdominal aorta and the superior mesenteric artery with valvulae conniventes projecting into the lumen. The cornerstone of treatment is surgery. Surgery includes: (1) adhesiolysis and reconstruction for benign causes; and (2) by-pass or excision and reconstruction for malignant causes. However, endoscopic enteral stenting, transhepatic percutaneous enteral stenting and direct percutaneous tube enterostomy have the principal role in management of malignant and radiation-induced obstruction. Nevertheless, considerable limitations exist as a former Roux-en-Y reconstruction limits endoscopic access to the afferent loop and percutaneous approaches for enteral stenting and tube enterostomy have only been reported in the literature as isolated cases. PMID:26425267
Magnetic monopole in the loop representation
Leal, Lorenzo; Lopez, Alexander
2006-01-15
We quantize, within the Loop Representation formalism, the electromagnetic field in the presence of a static magnetic pole. It is found that the loop-dependent physical wave functionals of the quantum Maxwell theory become multivalued, through a topological phase factor depending on the solid angle subtended at the monopole by a surface bounded by the loop. It is discussed how this fact generalizes what occurs in ordinary quantum mechanics in multiply connected spaces.
Integration rules for loop scattering equations
NASA Astrophysics Data System (ADS)
Baadsgaard, Christian; Bjerrum-Bohr, N. E. J.; Bourjaily, Jacob L.; Damgaard, Poul H.; Feng, Bo
2015-11-01
We formulate new integration rules for one-loop scattering equations analogous to those at tree-level, and test them in a number of non-trivial cases for amplitudes in scalar ? 3-theory. This formalism greatly facilitates the evaluation of amplitudes in the CHY representation at one-loop order, without the need to explicitly sum over the solutions to the loop-level scattering equations.
Biopolymer hairpin loops sustained by polarons
NASA Astrophysics Data System (ADS)
Chakrabarti, B.; Piette, B. M. A. G.; Zakrzewski, W. J.
2012-08-01
We show that polarons can sustain looplike configurations in flexible biopolymers and that the size of the loops depend on both the flexural rigidity of the polymer and the electron-phonon coupling constant. In particular we show that for single stranded DNA (ssDNA) and polyacetylene such loops can have as few as seven monomers. We also show that these configurations are very stable under thermal fluctuations and so could facilitate the formation of hairpin loops of ssDNA.
Catheterization of Intestinal Loops in Ruminants Does Not Adversely Affect Loop Function
Inglis, G Douglas; Kastelic, John P; Uwiera, Richard R E
2010-01-01
Catheterized intestinal loops may be a valuable model to elucidate key components of the host response to various treatments within the small intestine of ruminants. We examined whether catheterizing ileal loops in sheep affected the overall health of animals and intestinal function, whether a bacterial treatment could be introduced into the loops through the catheters, and whether broad-spectrum antibiotics could sterilize the loops. Escherichia coli cells transformed to express the GFP gene were introduced readily into the loops through the catheters, and GFP E. coli cells were localized within the injected loops. Catheterized loops, interspaces, and intact ileum exhibited no abnormalities in tissue appearance or electrical resistance. Expression of the IFNÎ³, IL1Î±, IL4, IL6, IL12p40, IL18, TGFÎ²1, and TNFÎ± cytokine genes did not differ significantly among the intact ileum, catheterized loops, and interspaces, nor did the expression of the gene for inducible nitric oxide synthase. Broad-spectrum antibiotics administered during surgery did not sterilize the loops or interspaces and did not substantively change the composition of the microbiota. However, antibiotics reduced the overall number of bacterial cells within the loop and the relative abundance of community constituents. We concluded that catheterization of intestinal loops did not adversely affect health or loop function in sheep. Furthermore, allowing animals to recover fully from surgery and to clear pharmaceuticals will remove any confounding effects due to these factors, making catheterized intestinal loops a feasible model for studying host responses in ruminants. PMID:21262134
Suzuki, K.
1983-10-04
A shape memory alloy is disclosed consisting essentially of, by weight ratio, 2 to 15% aluminium, 0.01 to 3% beryllium and the balance being substantially copper, with impurities being inevitably present in the process of preparation, and a shape memory alloy further including 0.05 to 15% zinc, both including composition ranges which allows cold work.
Multi-instrument observations of coronal loops
NASA Astrophysics Data System (ADS)
Scott, Jason Terrence
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.
Loop statistics in polymers in crowded environment.
Haydukivska, K; Blavatska, V
2016-02-28
We analyze the probability to find a single loop in a long flexible polymer chain in disordered environment in d dimensions. The structural defects are considered to be correlated on large distances r according to a power law âˆ¼r(-a). Working within the frames of continuous chain model and applying the direct polymer renormalization scheme, we obtain the values of critical exponents governing the scaling of probabilities to find the loops of various positions along the chain as function of loops' length. Our results quantitatively reveal that the presence of structural defects in environment decreases the probability of loop formation in polymer macromolecules. PMID:26931720
Analysis Of Lock Detection In Costas Loops
NASA Technical Reports Server (NTRS)
Mileant, Alexander; Hinedi, Sami M.
1991-01-01
Report presents analysis of detection of phase lock in Costas loops, used in coherent binary-phase-shift-keying communication systems to track both subcarrier and suppressed carrier signals. Detection of phase lock important part of operation and monitoring of operation of Costas or other tracking loop, provides insight into behavior of loop in real time. Focuses on effects of phase jitter and correlation between samples of phase error in all-digital Costas loop, in which lock detection implemented via algorithm. Applicable to both sinusoidal and square-law carrier signals, incorporates new mathematical models of square-law and absolute-value detectors.
Binary phase locked loops for Omega receivers
NASA Technical Reports Server (NTRS)
Chamberlin, K.
1974-01-01
An all-digital phase lock loop (PLL) is considered because of a number of problems inherent in an employment of analog PLL. The digital PLL design presented solves these problems. A single loop measures all eight Omega time slots. Memory-aiding leads to the name of this design, the memory-aided phase lock loop (MAPLL). Basic operating principles are discussed and the superiority of MAPLL over the conventional digital phase lock loop with regard to the operational efficiency for Omega applications is demonstrated.
Skeldon, Mark D. (Penfield, NY); Letzring, Samuel A. (Jemez Springs, NM)
1999-03-23
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, M.D.; Letzring, S.A.
1999-03-23
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.
Shaped composite liquid marbles.
Bormashenko, Edward; Balter, Revital; Aharoni, Hadas; Aurbach, Doron
2014-03-01
Shaped "cubic" non-stick droplets are reported. Shaped composite droplets were manufactured via a two-stage process. In the first stage, cubic foamed-polystyrene particles were hydrophilized with cold radiofrequency plasma. Then particles were wetted with water. In the second stage, they were coated with solid, colloidal particles such as lycopodium, Teflon or carbon black. Thus, "liquid marble"-like non-stick shaped droplets were obtained. The shaped "cubic" droplets remained stable when supported by a NaCl water solution. Shaped Janus droplets coated on one side with dielectric Teflon and with semiconductor carbon black on the other side, were prepared. Janus marbles were actuated with an electric field. PMID:24407678
Transverse, propagating velocity perturbations in solar coronal loops
NASA Astrophysics Data System (ADS)
De Moortel, I.; Pascoe, D. J.; Wright, A. N.; Hood, A. W.
2016-01-01
As waves and oscillations carry both energy and information, they have enormous potential as a plasma heating mechanism and, through seismology, to provide estimates of local plasma properties which are hard to obtain from direct measurements. Being sufficiently near to allow high-resolution observations, the atmosphere of the Sun forms a natural plasma laboratory. Recent observations have revealed that an abundance of waves and oscillations is present in the solar atmosphere, leading to a renewed interest in wave heating mechanisms. This short review paper gives an overview of recently observed transverse, propagating velocity perturbations in coronal loops. These ubiquitous perturbations are observed to undergo strong damping as they propagate. Using 3D numerical simulations of footpoint-driven transverse waves propagating in a coronal plasma with a cylindrical density structure, in combination with analytical modelling, it is demonstrated that the observed velocity perturbations can be understood in terms of coupling of different wave modes in the inhomogeneous boundaries of the loops. Mode coupling in the inhomogeneous boundary layers of the loops leads to the coupling of the transversal (kink) mode to the azimuthal (AlfvÃ©n) mode, observed as the decay of the transverse kink oscillations. Both the numerical and analytical results show the spatial profile of the damped wave has a Gaussian shape to begin with, before switching to exponential decay at large heights. In addition, recent analysis of CoMP (Coronal Multi-channel Polarimeter) Doppler shift observations of large, off-limb, trans-equatorial loops shows that Fourier power at the apex appears to be higher in the high-frequency part of the spectrum than expected from theoretical models. This excess high-frequency FFT power could be tentative evidence for the onset of a cascade of the low-to-mid frequency waves into (AlfvÃ©nic) turbulence.
An automatic frequency control loop using overlapping DFTs (Discrete Fourier Transforms)
NASA Technical Reports Server (NTRS)
Aguirre, S.
1988-01-01
An automatic frequency control (AFC) loop is introduced and analyzed in detail. The new scheme is a generalization of the well known Cross Product AFC loop that uses running overlapping discrete Fourier transforms (DFTs) to create a discriminator curve. Linear analysis is included and supported with computer simulations. The algorithm is tested in a low carrier to noise ratio (CNR) dynamic environment, and the probability of loss of lock is estimated via computer simulations. The algorithm discussed is a suboptimum tracking scheme with a larger frequency error variance compared to an optimum strategy, but offers simplicity of implementation and a very low operating threshold CNR. This technique can be applied during the carrier acquisition and re-acquisition process in the Advanced Receiver.
Loop-mediated isothermal amplification (LAMP) method for detection of genetically modified maize T25
Xu, Junyi; Zheng, Qiuyue; Yu, Ling; Liu, Ran; Zhao, Xin; Wang, Gang; Wang, Qinghua; Cao, Jijuan
2013-01-01
The loop-mediated isothermal amplification (LAMP) assay indicates a potential and valuable means for genetically modified organism (GMO) detection especially for its rapidity, simplicity, and low cost. We developed and evaluated the specificity and sensitivity of the LAMP method for rapid detection of the genetically modified (GM) maize T25. A set of six specific primers was successfully designed to recognize six distinct sequences on the target gene, including a pair of inner primers, a pair of outer primers, and a pair of loop primers. The optimum reaction temperature and time were verified to be 65Â°C and 45 min, respectively. The detection limit of this LAMP assay was 5 g kgâˆ’1 GMO component. Comparative experiments showed that the LAMP assay was a simple, rapid, accurate, and specific method for detecting the GM maize T25. PMID:24804053
NASA Technical Reports Server (NTRS)
Palkovic, R. A.
1974-01-01
A FORTRAN 4 computer program provides convenient simulation of an all-digital phase-lock loop (DPLL). The DPLL forms the heart of the Omega navigation receiver prototype. Through the DPLL, the phase of the 10.2 KHz Omega signal is estimated when the true signal phase is contaminated with noise. This investigation has provided a convenient means of evaluating loop performance in a variety of noise environments, and has proved to be a useful tool for evaluating design changes. The goals of the simulation are to: (1) analyze the circuit on a bit-by-bit level in order to evaluate the overall design; (2) see easily the effects of proposed design changes prior to actual breadboarding; and (3) determine the optimum integration time for the DPLL in an environment typical of general aviation conditions.
NASA Technical Reports Server (NTRS)
Wieserman, W. R.; Schwarze, G. E.; Niedra, J. M.
1990-01-01
Limited experimental data exists for the specific core loss and dynamic B-H loops for soft magnetic materials for the combined conditions of high frequency and high temperature. This experimental study investigates the specific core loss and dynamic B-H loop characteristics of Supermalloy and Metglas 2605SC over the frequency range of 1 to 50 kHz and temperature range of 23 to 300 C under sinusoidal voltage excitation. The experimental setup used to conduct the investigation is described. The effects of the maximum magnetic flux density, frequency, and temperature on the specific core loss and on the size and shape of the B-H loops are examined.
Wieserman, W.R.; Schwarze, G.E.; Niedra, J.M.
1994-09-01
Limited experimental data exists for the specific core loss and dynamic B-H loops for soft magnetic materials for the combined conditions of high frequency and high temperature. This experimental study investigates the specific core loss and dynamic B-H loop characteristics of Supermalloy and Metglass 2605SC over the frequency range of 1-50 kHz and temperature range of 23-300 C under sinusoidal voltage excitation. The experimental setup used to conduct the investigation is described. The effects of the maximum magnetic flux density, frequency, and temperature on the specific core loss and on the size and shape of the B-H loops are examined.
NASA Astrophysics Data System (ADS)
Ogawa, J.; Fukui, S.; Oka, T.; Yamaguchi, M.; Sato, T.; Yamaya, K.; Hamada, T.; Tanaka, H.
2007-10-01
In this study, we investigated AC transport current measurement using a pick-up loop. In a single HTS tape the correction factors for different pick-up loop shapes correspond with the experimental and numerical results. In an assembled conductor, we experimentally investigated the difference in the correction factors for the serial and parallel connected transport current in each HTS tape. In parallel mode, the correction factor has a constant value against the total transport current, while in serial mode the correction factor varies. These results can be explained by the relation between the transport current distribution in each HTS tape and the position of the pick-up loops.
Loops in exceptional field theory
NASA Astrophysics Data System (ADS)
Bossard, Guillaume; Kleinschmidt, Axel
2016-01-01
We study certain four-graviton amplitudes in exceptional field theory in dimensions D â‰¥ 4 up to two loops. As the formulation is manifestly invariant under the U-duality group {E}_{11-D}({Z}) , our resulting expressions can be expressed in terms of automorphic forms. In the low energy expansion, we find terms in the M-theory effective action of type R 4, âˆ‡4 R 4 and âˆ‡6 R 4 with automorphic coefficient functions in agreement with independent derivations from string theory. This provides in particular an explicit integral formula for the exact string theory âˆ‡6 R 4 threshold function. We exhibit moreover that the usual supergravity logarithmic divergences cancel out in the full exceptional field theory amplitude, within an appropriately defined dimensional regularisation scheme. We also comment on terms of higher derivative order and the role of the section constraint for possible counterterms.
[Morbidity of lateral loop ileostomy].
François, Y; Griot, J B; Molter, A; Gilly, F N; Carry, P Y; Sayag, A; Vignal, J
1996-01-01
The aim of this retrospective study was to assess the morbidity of twisted loop ileostomy (TLI). Between 1985 and 1994, 83 TLI were performed in 79 patients. Before TLI closure, 13 patients (16%) presented complications, requiring surgery in 5 cases. Small bowel obstruction (7 cases: 8%) and high stoma output (4 cases: 5%) were the commonest complications. After stoma closure (performed in 76 cases), 8 patients (10.5%) presented complications, requiring surgery in 3 cases. The most commonest complication was enteric fistula (4 cases: 5.3%) requiring reoperation in 2 cases. This procedure adds a separate set of postoperative complications, which tend to be minor in nature without any permanent sequelae and which can be minimized by a meticulous surgical technique. This technique remains a safe and effective procedure for fecal diversion. PMID:8758522
Delay locked loop integrated circuit.
Brocato, Robert Wesley
2007-10-01
This report gives a description of the development of a Delay Locked Loop (DLL) integrated circuit (IC). The DLL was developed and tested as a stand-alone IC test chip to be integrated into a larger application specific integrated circuit (ASIC), the Quadrature Digital Waveform Synthesizer (QDWS). The purpose of the DLL is to provide a digitally programmable delay to enable synchronization between an internal system clock and external peripherals with unknown clock skew. The DLL was designed and fabricated in the IBM 8RF process, a 0.13 {micro}m CMOS process. It was designed to operate with a 300MHz clock and has been tested up to 500MHz.
Closed loop steam cooled airfoil
Widrig, Scott M.; Rudolph, Ronald J.; Wagner, Gregg P.
2006-04-18
An airfoil, a method of manufacturing an airfoil, and a system for cooling an airfoil is provided. The cooling system can be used with an airfoil located in the first stages of a combustion turbine within a combined cycle power generation plant and involves flowing closed loop steam through a pin array set within an airfoil. The airfoil can comprise a cavity having a cooling chamber bounded by an interior wall and an exterior wall so that steam can enter the cavity, pass through the pin array, and then return to the cavity to thereby cool the airfoil. The method of manufacturing an airfoil can include a type of lost wax investment casting process in which a pin array is cast into an airfoil to form a cooling chamber.
UWB communication receiver feedback loop
Spiridon, Alex; Benzel, Dave; Dowla, Farid U.; Nekoogar, Faranak; Rosenbury, Erwin T.
2007-12-04
A novel technique and structure that maximizes the extraction of information from reference pulses for UWB-TR receivers is introduced. The scheme efficiently processes an incoming signal to suppress different types of UWB as well as non-UWB interference prior to signal detection. Such a method and system adds a feedback loop mechanism to enhance the signal-to-noise ratio of reference pulses in a conventional TR receiver. Moreover, sampling the second order statistical function such as, for example, the autocorrelation function (ACF) of the received signal and matching it to the ACF samples of the original pulses for each transmitted bit provides a more robust UWB communications method and system in the presence of channel distortions.
Priest, David G; Kumar, Sandip; Yan, Yan; Dunlap, David D; Dodd, Ian B; Shearwin, Keith E
2014-10-21
Eukaryotic gene regulation involves complex patterns of long-range DNA-looping interactions between enhancers and promoters, but how these specific interactions are achieved is poorly understood. Models that posit other DNA loops--that aid or inhibit enhancer-promoter contact--are difficult to test or quantitate rigorously in eukaryotic cells. Here, we use the well-characterized DNA-looping proteins Lac repressor and phage ? CI to measure interactions between pairs of long DNA loops in E. coli cells in the three possible topological arrangements. We find that side-by-side loops do not affect each other. Nested loops assist each other's formation consistent with their distance-shortening effect. In contrast, alternating loops, where one looping element is placed within the other DNA loop, inhibit each other's formation, thus providing clear support for the loop domain model for insulation. Modeling shows that combining loop assistance and loop interference can provide strong specificity in long-range interactions. PMID:25288735
Detailed analysis of the predictions of loop quantum cosmology for the primordial power spectra
NASA Astrophysics Data System (ADS)
Agullo, Ivan; Morris, Noah A.
2015-12-01
We provide an exhaustive numerical exploration of the predictions of loop quantum cosmology with a postbounce phase of inflation for the primordial power spectrum of scalar and tensor perturbations. We extend previous analysis by characterizing the phenomenologically relevant parameter space and by constraining it using observations. Furthermore, we characterize the shape of loop quantum cosmology corrections to observable quantities across this parameter space. Our analysis provides a framework to contrast more accurately the theory with forthcoming polarization data, and it also paves the road for the computation of other observables beyond the power spectra, such as non-Gaussianity.
Medial Patellofemoral Ligament Reconstruction Using a Femoral Loop Button Fixation Technique
Godin, Jonathan A.; Karas, Vasili; Visgauss, Julia D.; Garrett, William E.
2015-01-01
Medial patellofemoral ligament (MPFL) reconstruction is a common procedure used to treat both acute and chronic patellar instability. Although many variations of MPFL reconstruction have been described, there is no consensus regarding the optimal surgical technique. We describe a technique for MPFL reconstruction with a looped gracilis tendon autograft using suture anchors to secure the graft to the patella and a suspensory loop button system for fixation to the femur. This technique replicates the native shape of the MPFL while minimizing the risk of patellar fracture and allowing for gradual tensioning of the graft. PMID:26900561
Optimum Projection Angle for Attaining Maximum Distance in a Soccer Punt Kick
Linthorne, Nicholas P.; Patel, Dipesh S.
2011-01-01
To produce the greatest horizontal distance in a punt kick the ball must be projected at an appropriate angle. Here, we investigated the optimum projection angle that maximises the distance attained in a punt kick by a soccer goalkeeper. Two male players performed many maximum-effort kicks using projection angles of between 10° and 90°. The kicks were recorded by a video camera at 100 Hz and a 2 D biomechanical analysis was conducted to obtain measures of the projection velocity, projection angle, projection height, ball spin rate, and foot velocity at impact. The player’s optimum projection angle was calculated by substituting mathematical equations for the relationships between the projection variables into the equations for the aerodynamic flight of a soccer ball. The calculated optimum projection angles were in agreement with the player’s preferred projection angles (40° and 44°). In projectile sports even a small dependence of projection velocity on projection angle is sufficient to produce a substantial shift in the optimum projection angle away from 45°. In the punt kicks studied here, the optimum projection angle was close to 45° because the projection velocity of the ball remained almost constant across all projection angles. This result is in contrast to throwing and jumping for maximum distance, where the projection velocity the athlete is able to achieve decreases substantially with increasing projection angle and so the optimum projection angle is well below 45°. Key points The optimum projection angle that maximizes the distance of a punt kick by a soccer goalkeeper is about 45°. The optimum projection angle is close to 45° because the projection velocity of the ball is almost the same at all projection angles. This result is in contrast to throwing and jumping for maximum distance, where the optimum projection angle is well below 45° because the projection velocity the athlete is able to achieve decreases substantially with increasing projection angle. PMID:24149315
Development of Non-Optimum Factors for Launch Vehicle Propellant Tank Bulkhead Weight Estimation
NASA Technical Reports Server (NTRS)
Wu, K. Chauncey; Wallace, Matthew L.; Cerro, Jeffrey A.
2012-01-01
Non-optimum factors are used during aerospace conceptual and preliminary design to account for the increased weights of as-built structures due to future manufacturing and design details. Use of higher-fidelity non-optimum factors in these early stages of vehicle design can result in more accurate predictions of a concept s actual weights and performance. To help achieve this objective, non-optimum factors are calculated for the aluminum-alloy gores that compose the ogive and ellipsoidal bulkheads of the Space Shuttle Super-Lightweight Tank propellant tanks. Minimum values for actual gore skin thicknesses and weld land dimensions are extracted from selected production drawings, and are used to predict reference gore weights. These actual skin thicknesses are also compared to skin thicknesses predicted using classical structural mechanics and tank proof-test pressures. Both coarse and refined weights models are developed for the gores. The coarse model is based on the proof pressure-sized skin thicknesses, and the refined model uses the actual gore skin thicknesses and design detail dimensions. To determine the gore non-optimum factors, these reference weights are then compared to flight hardware weights reported in a mass properties database. When manufacturing tolerance weight estimates are taken into account, the gore non-optimum factors computed using the coarse weights model range from 1.28 to 2.76, with an average non-optimum factor of 1.90. Application of the refined weights model yields non-optimum factors between 1.00 and 1.50, with an average non-optimum factor of 1.14. To demonstrate their use, these calculated non-optimum factors are used to predict heavier, more realistic gore weights for a proposed heavy-lift launch vehicle s propellant tank bulkheads. These results indicate that relatively simple models can be developed to better estimate the actual weights of large structures for future launch vehicles.
Role of an Absolutely Conserved Tryptophan Pair in the Extracellular Domain of Cys-Loop Receptors.
Braun, Nina; Lynagh, Timothy; Yu, Rilei; Biggin, Philip C; Pless, Stephan A
2016-03-16
Cys-loop receptors mediate fast synaptic transmission in the nervous system, and their dysfunction is associated with a number of diseases. While some sequence variability is essential to ensure specific recognition of a chemically diverse set of ligands, other parts of the underlying amino acid sequences show a high degree of conservation, possibly to preserve the overall structural fold across the protein family. In this study, we focus on the only two absolutely conserved residues across the Cys-loop receptor family, two Trp side chains in the WXD motif of Loop D and in the WXPD motif of Loop A. Using a combination of conventional mutagenesis, unnatural amino acid incorporation, immunohistochemistry and MD simulations, we demonstrate the crucial contributions of these two Trp residues to receptor expression and function in two prototypical Cys-loop receptors, the anion-selective GlyR Î±1 and the cation-selective nAChR Î±7. Specifically, our results rule out possible electrostatic contributions of these Trp side chains and instead suggest that the overall size and shape of this aromatic pair is required in stabilizing the Cys-loop receptor extracellular domain. PMID:26764897
Research on the Dynamic Hysteresis Loop Model of the Residence Times Difference (RTD)-Fluxgate
Wang, Yanzhang; Wu, Shujun; Zhou, Zhijian; Cheng, Defu; Pang, Na; Wan, Yunxia
2013-01-01
Based on the core hysteresis features, the RTD-fluxgate core, while working, is repeatedly saturated with excitation field. When the fluxgate simulates, the accurate characteristic model of the core may provide a precise simulation result. As the shape of the ideal hysteresis loop model is fixed, it cannot accurately reflect the actual dynamic changing rules of the hysteresis loop. In order to improve the fluxgate simulation accuracy, a dynamic hysteresis loop model containing the parameters which have actual physical meanings is proposed based on the changing rule of the permeability parameter when the fluxgate is working. Compared with the ideal hysteresis loop model, this model has considered the dynamic features of the hysteresis loop, which makes the simulation results closer to the actual output. In addition, other hysteresis loops of different magnetic materials can be explained utilizing the described model for an example of amorphous magnetic material in this manuscript. The model has been validated by the output response comparison between experiment results and fitting results using the model. PMID:24002230
NASA Astrophysics Data System (ADS)
Soler, Roberto; Goossens, Marcel; Terradas, Jaume; Oliver, Ramón
2014-02-01
The seismology of coronal loops using observations of damped transverse oscillations in combination with results from theoretical models is a tool to indirectly infer physical parameters in the solar atmospheric plasma. Existing seismology schemes based on approximations of the period and damping time of kink oscillations are often used beyond their theoretical range of applicability. These approximations assume that the variation of density across the loop is confined to a nonuniform layer much thinner than the radius of the loop, but the results of the inversion problem often do not satisfy this preliminary hypothesis. Here, we determine the accuracy of the analytic approximations of the period and damping time, and the impact on seismology estimates when largely nonuniform loops are considered. We find that the accuracy of the approximations when used beyond their range of applicability is strongly affected by the form of the density profile across the loop, that is observationally unknown and so must be arbitrarily imposed as part of the theoretical model. The error associated with the analytic approximations can be larger than 50% even for relatively thin nonuniform layers. This error directly affects the accuracy of approximate seismology estimates compared to actual numerical inversions. In addition, assuming different density profiles can produce noncoincident intervals of the seismic variables in inversions of the same event. The ignorance about the true shape of density variation across the loop is an important source of error that may dispute the reliability of parameters seismically inferred assuming an ad hoc density profile.
Soler, Roberto; Terradas, Jaume; Oliver, RamÃ³n; Goossens, Marcel
2014-02-01
The seismology of coronal loops using observations of damped transverse oscillations in combination with results from theoretical models is a tool to indirectly infer physical parameters in the solar atmospheric plasma. Existing seismology schemes based on approximations of the period and damping time of kink oscillations are often used beyond their theoretical range of applicability. These approximations assume that the variation of density across the loop is confined to a nonuniform layer much thinner than the radius of the loop, but the results of the inversion problem often do not satisfy this preliminary hypothesis. Here, we determine the accuracy of the analytic approximations of the period and damping time, and the impact on seismology estimates when largely nonuniform loops are considered. We find that the accuracy of the approximations when used beyond their range of applicability is strongly affected by the form of the density profile across the loop, that is observationally unknown and so must be arbitrarily imposed as part of the theoretical model. The error associated with the analytic approximations can be larger than 50% even for relatively thin nonuniform layers. This error directly affects the accuracy of approximate seismology estimates compared to actual numerical inversions. In addition, assuming different density profiles can produce noncoincident intervals of the seismic variables in inversions of the same event. The ignorance about the true shape of density variation across the loop is an important source of error that may dispute the reliability of parameters seismically inferred assuming an ad hoc density profile.
Shape memory piezoelectric actuator
NASA Astrophysics Data System (ADS)
Morita, Takeshi; Kadota, Yoichi; Hosaka, Hiroshi
2007-02-01
The shape memory piezoelectric actuator can be operated using a pulsed voltage, so that small energy consumption and small voltage operation can be realized. To realize shape memory operation, the imprint electrical field was induced by treatment with a high electrical field of 3.5kV/mm in a 150°C environment. The actuator had two stable positions that were dependent on the piezoelectric polarization and could be maintained without the use of an external electrical field. This shape memory effect indicated that the imprint electrical field contributes to other functional properties, such as a permittivity, optical refractive index, and mechanical compliance.
NASA Astrophysics Data System (ADS)
Stanciu, Dorin; Stanciu, Camelia; Paraschiv, Ioana
2016-01-01
The paper presents a mathematical modeling of the optimum tilt for solar collectors for intercepting maximum solar irradiance (power density), at different geographical locations, periods of time and different base-ground types. The solar irradiance received by the collector is estimated based on isotropic sky analysis models, namely Hottel & Woertz model and Liu & Jordan model. The optimum value for the tilt is considered for maximum hourly and respectively daily noon incident solar irradiance. This paper emphasizes the mathematical link between the optima computed under the two considered models assumptions. Also the ground reflectance factor influence on the optimum tilt difference between considered models is presented related to latitude.
The searching method of quasi-optimum group SYNC codes on the subset of PN sequences
NASA Astrophysics Data System (ADS)
Cao, Jie; Xie, Qiu-Cheng
This paper gives a searching method of quasi-optimum group sync codes on a small subset of PN sequences - cut-tail searching method and prefix-suffix searching method. Quasi-optimum group sync codes have been searched out for their lengths N = 32-63 by this method and they have been compared with corresponding optimum group sync codes for their lengths N = 32-54. The total searching time is only several seconds. This method may solve problems of error sync probability, code length, and searching time. Hence it is a good and practical searching method for long code.
SP-100 liquid metal test loop design
NASA Astrophysics Data System (ADS)
Fallas, T. Ted; Kruger, Gordon B.; Wiltshire, Frank R.; Jensen, Grant C.; Clay, Harold; Upton, Hugh A.; Gamble, Robert E.; Kjaer-Olsen, Christian; Lee, Keith
1992-01-01
The SP-100 Power System Qualification (PSO) program validates the technology readiness of the SP-100 Generic Flight System (GFS). As part of the PSQ, the GFS reactor, heat transport and power generation systems are being validated, by test, in high temperature liquid metal test loops. The liquid metal test loop program consists of two test loops. The first, a natural circulation material test loop (MTL), has been successfully operating for the last year at GE's test facility in San Jose. The second, a forced circulation Component Test Loop (CTL) is in the preliminary design phase. Fabrication of the CTL and modifications to the Test Facility will be completed in FY94 with component testing scheduled to begin in FY95. The CTL is a Nb-1Zr test loop with an Electromagnetic (EM) pump providing forced circulation for the liquid lithium coolant. The CTL test program is comprised of a series of individual component tests. Test components containing thermoelectric cells will have their cold side ducts piped to an existing heat rejection loop external to the CTL vacuum vessel. The test assembly and test components are being designed by GE. The detail design of several loop components is being performed by Westinghouse Atomic Energy Systems (WAES). The CTL will be assembled and the test performed at GE's facilties in San Jose, California.
Conformal anomaly of super Wilson loop
NASA Astrophysics Data System (ADS)
Belitsky, A. V.
2012-09-01
Classically supersymmetric Wilson loop on a null polygonal contour possesses all symmetries required to match it onto non-MHV amplitudes in maximally supersymmetric Yang-Mills theory. However, to define it quantum mechanically, one is forced to regularize it since perturbative loop diagrams are not well defined due to presence of ultraviolet divergences stemming from integration in the vicinity of the cusps. A regularization that is adopted by practitioners by allowing one to use spinor helicity formalism, on the one hand, and systematically go to higher orders of perturbation theory is based on a version of dimensional regularization, known as Four-Dimensional Helicity scheme. Recently it was demonstrated that its use for the super Wilson loop at one loop breaks both conformal symmetry and PoincarÃ© supersymmetry. Presently, we exhibit the origin for these effects and demonstrate how one can undo this breaking. The phenomenon is alike the one emerging in renormalization group mixing of conformal operators in conformal theories when one uses dimensional regularization. The rotation matrix to the diagonal basis is found by means of computing the anomaly in the Ward identity for the conformal boost. Presently, we apply this ideology to the super Wilson loop. We compute the one-loop conformal anomaly for the super Wilson loop and find that the anomaly depends on its Grassmann coordinates. By subtracting this anomalous contribution from the super Wilson loop we restore its interpretation as a dual description for reduced non-MHV amplitudes which are expressed in terms of superconformal invariants.
The Cygnus Loop: An Older Supernova Remnant.
ERIC Educational Resources Information Center
Straka, William
1987-01-01
Describes the Cygnus Loop, one of brightest and most easily studied of the older "remnant nebulae" of supernova outbursts. Discusses some of the historical events surrounding the discovery and measurement of the Cygnus Loop and makes some projections on its future. (TW)
External Tank CIL Closed Loop Verification System
NASA Technical Reports Server (NTRS)
Hartley, Eugene A., Jr.
2005-01-01
Lockheed Martin was requested to develop a closed loop CIL system following the Challenger accident. The system that was developed has proven to be very robust with minimal problems since implementation, having zero escapes in the last 7 years (27 External Tanks). We are currently investigating expansion of the CIL Closed Loop system to include "MI" CILs.
On Novice Loop Boundaries and Range Conceptions
ERIC Educational Resources Information Center
Ginat, David
2004-01-01
The paper presents a study of novice difficulties with range conceptions in loop design. CS2 students were asked to solve four related enumeration tasks, which required various loop boundary specifications. The student solutions varied considerably in conciseness and efficiency. The solution diversity reveals significant differences in range…
Three loop balanced bridge feedback pointing control
NASA Technical Reports Server (NTRS)
Lurie, Boris J.
1988-01-01
The balanced bridge feedback (BBF) technique developed in communication engineering is applied to the multiloop pointing control problem. Using colocated sensors, BBF decouples the motor loop from the mechanical plant and increases the feedback bandwidth in the motor and plant loops.
Droplet flows through periodic loop networks
NASA Astrophysics Data System (ADS)
Jeanneret, Raphael; Schindler, Michael; Bartolo, Denis
2010-11-01
Numerous microfluidic experiments have revealed non-trivial traffic dynamics when droplets flow through a channel including a single loop. A complex encoding of the time intervals between the droplets is achieved by the binary choices they make as they enter the loop. Very surprisingly, another set of experiments has demonstrated that the addition of a second loop does not increase the complexity of the droplet pattern. Conversely, the second loop decodes the temporal signal encrypted by the first loop [1]. In this talk we show that no first principle argument based on symmetry or conservation laws can account for this unexpected decoding process. Then, to better understand how a loop maps time intervals between droplets, we consider a simplified model which has proven to describe accurately microfluidic droplet flows. Combining numerical simulations and analytical calculations for the dynamic of three droplets travelling through N loops: (i) We show that three different traffic regimes exist, yet none of them yields exact decoding. (ii) We uncover that for a wide class of loop geometry, the coding process is analogous to a Hamiltonian mapping: regular orbits are destabilized in island chains and separatrix. (iii) Eventually, we propose a simple explanation to solve the apparent paradox with the coding/decoding dynamics observed in experiments. [1] M.J. Fuerstman, P. Garstecki, and G.M. Whitesides, Science, 315:828, 2007.
Aerodynamic Shape Optimization Using Hybridized Differential Evolution
NASA Technical Reports Server (NTRS)
Madavan, Nateri K.
2003-01-01
An aerodynamic shape optimization method that uses an evolutionary algorithm known at Differential Evolution (DE) in conjunction with various hybridization strategies is described. DE is a simple and robust evolutionary strategy that has been proven effective in determining the global optimum for several difficult optimization problems. Various hybridization strategies for DE are explored, including the use of neural networks as well as traditional local search methods. A Navier-Stokes solver is used to evaluate the various intermediate designs and provide inputs to the hybrid DE optimizer. The method is implemented on distributed parallel computers so that new designs can be obtained within reasonable turnaround times. Results are presented for the inverse design of a turbine airfoil from a modern jet engine. (The final paper will include at least one other aerodynamic design application). The capability of the method to search large design spaces and obtain the optimal airfoils in an automatic fashion is demonstrated.
Improved peak shape fitting in alpha spectra.
Pommé, S; Caro Marroyo, B
2015-02-01
Peak overlap is a recurrent issue in alpha-particle spectrometry, not only in routine analyses but also in the high-resolution spectra from which reference values for alpha emission probabilities are derived. In this work, improved peak shape formulae are presented for the deconvolution of alpha-particle spectra. They have been implemented as fit functions in a spreadsheet application and optimum fit parameters were searched with built-in optimisation routines. Deconvolution results are shown for a few challenging spectra with high statistical precision. The algorithm outperforms the best available routines for high-resolution spectrometry, which may facilitate a more reliable determination of alpha emission probabilities in the future. It is also applicable to alpha spectra with inferior energy resolution. PMID:25497323
A Method of Tuning Resonant Loops
Baity, F. W.; Goulding, R. H.; Pinsker, R. I.
2007-09-28
A convenient method of tuning resonant loops has been developed for use on the Long-Pulse Fast Wave Current Drive antennas on DIII-D. These 4-element antennas are fed from a single RF source, with a 90 deg. hybrid junction feeding two resonant loops. Each resonant loop connects a pair of non-adjacent current straps, and a decoupler allows independent impedance matching of each output leg of the hybrid junction. The tuning method involves only measurement of the reflection coefficient of each resonant loop and the transmission from one loop to the other. It will be shown that this method of tuning equalizes the currents in all four current straps and 90 deg. phasing between adjacent elements.
NASA Astrophysics Data System (ADS)
Zhou, Jing; Li, Qiaoxi; Turner, Sara; Brosnan, Sarah; Tippets, Cary; Carrillo, Jan-Michael; Nykypnachuk, Dmytro; Gang, Oleg; Dobrynin, Andrey; Lopez, Rene; Ashby, Valerie; Sheiko, Sergei
2014-03-01
Reversible shape memory has been achieved on various shapes, e.g. hairpin, origami, coil, robotic gripper and flow rate control device, allowing for multiple switching between encoded shapes without applying any external force. Also, the reversible photonic structure molded in dielectric elastomers has been designed. Maximum reversibility can be achieved by tuning the crosslinking density and the degree of crystallinity of semi-crystalline elastomers. Different crystallization protocols including isothermal and cooling crystallization have been applied to develop a universal picture integrating different shape memory (SM) behaviors: conventional one-way SM, two-way reversible SM, and one-way reversible SM. Acknowledge financial support from the NSF DMR-1122483, DMR- 1004576, and DMR-1206957.
Companding through shaped superconductors
NASA Astrophysics Data System (ADS)
Badri Narayana, T.; Satyam, M.
1998-01-01
Companding has been performed through the use of a shaped superconductor and a design procedure for arriving at the required profile of the superconductor to obtain the required law of companding as described.
Electrostatically shaped membranes
NASA Technical Reports Server (NTRS)
Silverberg, Larry M. (Inventor)
1994-01-01
Disclosed is a method and apparatus for electrostatically shaping a membrane suitable for use in antennas or the like, comprising an electrically conductive thin membrane where the periphery of said membrane is free to move in at least one direction, a first charge on the electrically conductive thin membrane to electrostatically stiffen the membrane, a second charge which shapes the electrostatically stiffened thin membrane and a restraint for limiting the movement of at least one point of the thin membrane relative to the second charge. Also disclosed is a method and apparatus for adaptively controlling the shape of the thin membrane by sensing the shape of the membrane and selectively controlling the first and second charge to achieve a desired performance characteristic of the membrane.
Thermal spray shape deposition
NASA Astrophysics Data System (ADS)
Weiss, L. E.; Prinz, F. B.; Adams, D. A.; Siewiorek, D. P.
1992-09-01
This paper describes a new spray-forming process based on thermal spray shape deposition. Shape deposition processes build 3D shapes by incremental material buildup of thin, planar cross-sectional layers. These processes do not require preformed mandrels and can directly build 3D structures of arbitrary geometric complexity. The basis for the thermal spray approach is to spray each layer using a disposable mask that has the shape of the current cross section. Masks can be produced from paper rolls, for example, with a CO2 laser. In addition to applications for rapid prototyping, this approach makes possible the fabrication of composite structures and integrated electronic/mechanical assemblies that are not feasible with conventional manufacturing technologies.
A communication scheme for the distrubted execution of loop nests with while loops
Griebl, M.; Lengauer, C.
1995-10-01
The mathematical model for the parallelization, or {open_quotes}space-time mapping,{close_quotes} of loop nests is the polyhedron model. The presence of while loops in the nest complicates matters for two reasons: (1) the parallelized loop nest does not correspond to a polyhedron but instead to a subset that resembles a (multi-dimensional) comb and (2) it is not clear when the entire loop nest has terminated. We describe a communication scheme which can deal with both problems and which can be added to the parallel target loop nest by a compiler.
Study of one-dimensional electron hopping and its effects on ESR line shape
Tang, Jau; Dikshit, S.N.; Norris, J.R. |
1997-08-01
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.
NASA Technical Reports Server (NTRS)
Chen, George T.
1987-01-01
An automatic control scheme for spacecraft proximity operations is presented. The controller is capable of holding the vehicle at a prescribed location relative to a target, or maneuvering it to a different relative position using straight line-of-sight translations. The autopilot uses a feedforward loop to initiate and terminate maneuvers, and for operations at nonequilibrium set-points. A multivariate feedback loop facilitates precise position and velocity control in the presence of sensor noise. The feedback loop is formulated using the Linear Quadratic Gaussian (LQG) with Loop Transfer Recovery (LTR) design procedure. Linear models of spacecraft dynamics, adapted from Clohessey-Wiltshire Equations, are augmented and loop shaping techniques are applied to design a target feedback loop. The loop transfer recovery procedure is used to recover the frequency domain properties of the target feedback loop. The resulting compensator is integrated into an autopilot which is tested in a high fidelity Space Shuttle Simulator. The autopilot performance is evaluated for a variety of proximity operations tasks envisioned for future Shuttle flights.
Cygnus Loop Supernova Blast Wave
NASA Technical Reports Server (NTRS)
1993-01-01
This is an image of a small portion of the Cygnus Loop supernova remnant, which marks the edge of a bubble-like, expanding blast wave from a colossal stellar explosion, occurring about 15,000 years ago. The HST image shows the structure behind the shock waves, allowing astronomers for the first time to directly compare the actual structure of the shock with theoretical model calculations. Besides supernova remnants, these shock models are important in understanding a wide range of astrophysical phenomena, from winds in newly-formed stars to cataclysmic stellar outbursts. The supernova blast is slamming into tenuous clouds of insterstellar gas. This collision heats and compresses the gas, causing it to glow. The shock thus acts as a searchlight revealing the structure of the interstellar medium. The detailed HST image shows the blast wave overrunning dense clumps of gas, which despite HST's high resolution, cannot be resolved. This means that the clumps of gas must be small enough to fit inside our solar system, making them relatively small structures by interstellar standards. A bluish ribbon of light stretching left to right across the picture might be a knot of gas ejected by the supernova; this interstellar 'bullet' traveling over three million miles per hour (5 million kilometres) is just catching up with the shock front, which has slowed down by ploughing into interstellar material. The Cygnus Loop appears as a faint ring of glowing gases about three degrees across (six times the diameter of the full Moon), located in the northern constellation, Cygnus the Swan. The supernova remnant is within the plane of our Milky Way galaxy and is 2,600 light-years away. The photo is a combination of separate images taken in three colors, oxygen atoms (blue) emit light at temperatures of 30,000 to 60,000 degrees Celsius (50,000 to 100,000 degrees Farenheit). Hydrogen atoms (green) arise throughout the region of shocked gas. Sulfur atoms (red) form when the gas cools to around 10,000 degrees Celsius (18,000 degrees Farenheit).
Universality of fragment shapes
NASA Astrophysics Data System (ADS)
Domokos, Gábor; Kun, Ferenc; Sipos, András Árpád; Szabó, Tímea
2015-03-01
The shape of fragments generated by the breakup of solids is central to a wide variety of problems ranging from the geomorphic evolution of boulders to the accumulation of space debris orbiting Earth. Although the statistics of the mass of fragments has been found to show a universal scaling behavior, the comprehensive characterization of fragment shapes still remained a fundamental challenge. We performed a thorough experimental study of the problem fragmenting various types of materials by slowly proceeding weathering and by rapid breakup due to explosion and hammering. We demonstrate that the shape of fragments obeys an astonishing universality having the same generic evolution with the fragment size irrespective of materials details and loading conditions. There exists a cutoff size below which fragments have an isotropic shape, however, as the size increases an exponential convergence is obtained to a unique elongated form. We show that a discrete stochastic model of fragmentation reproduces both the size and shape of fragments tuning only a single parameter which strengthens the general validity of the scaling laws. The dependence of the probability of the crack plan orientation on the linear extension of fragments proved to be essential for the shape selection mechanism.
Universality of fragment shapes.
Domokos, Gábor; Kun, Ferenc; Sipos, András Árpád; Szabó, Tímea
2015-01-01
The shape of fragments generated by the breakup of solids is central to a wide variety of problems ranging from the geomorphic evolution of boulders to the accumulation of space debris orbiting Earth. Although the statistics of the mass of fragments has been found to show a universal scaling behavior, the comprehensive characterization of fragment shapes still remained a fundamental challenge. We performed a thorough experimental study of the problem fragmenting various types of materials by slowly proceeding weathering and by rapid breakup due to explosion and hammering. We demonstrate that the shape of fragments obeys an astonishing universality having the same generic evolution with the fragment size irrespective of materials details and loading conditions. There exists a cutoff size below which fragments have an isotropic shape, however, as the size increases an exponential convergence is obtained to a unique elongated form. We show that a discrete stochastic model of fragmentation reproduces both the size and shape of fragments tuning only a single parameter which strengthens the general validity of the scaling laws. The dependence of the probability of the crack plan orientation on the linear extension of fragments proved to be essential for the shape selection mechanism. PMID:25772300
On Characterizing Particle Shape
NASA Technical Reports Server (NTRS)
Ennis, Bryan J.; Rickman, Douglas; Rollins, A. Brent; Ennis, Brandon
2014-01-01
It is well known that particle shape affects flow characteristics of granular materials, as well as a variety of other solids processing issues such as compaction, rheology, filtration and other two-phase flow problems. The impact of shape crosses many diverse and commercially important applications, including pharmaceuticals, civil engineering, metallurgy, health, and food processing. Two applications studied here include the dry solids flow of lunar simulants (e.g. JSC-1, NU-LHT-2M, OB-1), and the flow properties of wet concrete, including final compressive strength. A multi-dimensional generalized, engineering method to quantitatively characterize particle shapes has been developed, applicable to both single particle orientation and multi-particle assemblies. The two-dimension, three dimension inversion problem is also treated, and the application of these methods to DEM model particles will be discussed. In the case of lunar simulants, flow properties of six lunar simulants have been measured, and the impact of particle shape on flowability - as characterized by the shape method developed here -- is discussed, especially in the context of three simulants of similar size range. In the context of concrete processing, concrete construction is a major contributor to greenhouse gas production, of which the major contributor is cement binding loading. Any optimization in concrete rheology and packing that can reduce cement loading and improve strength loading can also reduce currently required construction safety factors. The characterization approach here is also demonstrated for the impact of rock aggregate shape on concrete slump rheology and dry compressive strength.
Universality of fragment shapes
Domokos, GÃ¡bor; Kun, Ferenc; Sipos, AndrÃ¡s ÃrpÃ¡d; SzabÃ³, TÃmea
2015-01-01
The shape of fragments generated by the breakup of solids is central to a wide variety of problems ranging from the geomorphic evolution of boulders to the accumulation of space debris orbiting Earth. Although the statistics of the mass of fragments has been found to show a universal scaling behavior, the comprehensive characterization of fragment shapes still remained a fundamental challenge. We performed a thorough experimental study of the problem fragmenting various types of materials by slowly proceeding weathering and by rapid breakup due to explosion and hammering. We demonstrate that the shape of fragments obeys an astonishing universality having the same generic evolution with the fragment size irrespective of materials details and loading conditions. There exists a cutoff size below which fragments have an isotropic shape, however, as the size increases an exponential convergence is obtained to a unique elongated form. We show that a discrete stochastic model of fragmentation reproduces both the size and shape of fragments tuning only a single parameter which strengthens the general validity of the scaling laws. The dependence of the probability of the crack plan orientation on the linear extension of fragments proved to be essential for the shape selection mechanism. PMID:25772300
Simulations of Gyrosynchrotron Microwave Emission from an Oscillating 3D Magnetic Loop
NASA Astrophysics Data System (ADS)
Kuznetsov, A. A.; Van Doorsselaere, T.; Reznikova, V. E.
2015-04-01
Radio observations of solar flares often reveal various periodic or quasi-periodic oscillations. Most likely, these oscillations are caused by magnetohydrodynamic (MHD) oscillations of flaring loops which modulate the emission. Interpreting the observations requires comparing them with simulations. We simulated the gyrosynchrotron radio emission from a semicircular (toroidal-shaped) magnetic loop containing sausage-mode MHD oscillations. The aim was to detect the observable signatures specific to the considered MHD mode and to study their dependence on the various source parameters. The MHD waves were simulated using a linear three-dimensional model of a magnetized plasma cylinder; both standing and propagating waves were considered. The curved loop was formed by replicating the MHD solutions along the plasma cylinder and bending the cylinder; this model allowed us to study the effect of varying the viewing angle along the loop. The radio emission was simulated using a three-dimensional model, and its spatial and temporal variations were analyzed. We considered several loop orientations and different parameters of the magnetic field, plasma, and energetic electrons in the loop. In the model with low plasma density, the intensity oscillations at all frequencies are synchronous (with the exception of a narrow spectral region below the spectral peak). In the model with high plasma density, the emission at low frequencies (where the Razin effect is important) oscillates in anti-phase with the emissions at higher frequencies. The oscillations at high and low frequencies are more pronounced in different parts of the loop (depending on the loop orientation). The layers where the line-of-sight component of the magnetic field changes sign can produce additional peculiarities in the oscillation patterns.
Priest, David G.; Kumar, Sandip; Yan, Yan; Dunlap, David D.; Dodd, Ian B.; Shearwin, Keith E.
2014-01-01
Eukaryotic gene regulation involves complex patterns of long-range DNA-looping interactions between enhancers and promoters, but how these specific interactions are achieved is poorly understood. Models that posit other DNA loopsâ€”that aid or inhibit enhancerâ€“promoter contactâ€”are difficult to test or quantitate rigorously in eukaryotic cells. Here, we use the well-characterized DNA-looping proteins Lac repressor and phage Î» CI to measure interactions between pairs of long DNA loops in E. coli cells in the three possible topological arrangements. We find that side-by-side loops do not affect each other. Nested loops assist each otherâ€™s formation consistent with their distance-shortening effect. In contrast, alternating loops, where one looping element is placed within the other DNA loop, inhibit each otherâ€™s formation, thus providing clear support for the loop domain model for insulation. Modeling shows that combining loop assistance and loop interference can provide strong specificity in long-range interactions. PMID:25288735
Looping probabilities of elastic chains: a path integral approach.
Cotta-Ramusino, Ludovica; Maddocks, John H
2010-11-01
We consider an elastic chain at thermodynamic equilibrium with a heat bath, and derive an approximation to the probability density function, or pdf, governing the relative location and orientation of the two ends of the chain. Our motivation is to exploit continuum mechanics models for the computation of DNA looping probabilities, but here we focus on explaining the novel analytical aspects in the derivation of our approximation formula. Accordingly, and for simplicity, the current presentation is limited to the illustrative case of planar configurations. A path integral formalism is adopted, and, in the standard way, the first approximation to the looping pdf is obtained from a minimal energy configuration satisfying prescribed end conditions. Then we compute an additional factor in the pdf which encompasses the contributions of quadratic fluctuations about the minimum energy configuration along with a simultaneous evaluation of the partition function. The original aspects of our analysis are twofold. First, the quadratic Lagrangian describing the fluctuations has cross-terms that are linear in first derivatives. This, seemingly small, deviation from the structure of standard path integral examples complicates the necessary analysis significantly. Nevertheless, after a nonlinear change of variable of Riccati type, we show that the correction factor to the pdf can still be evaluated in terms of the solution to an initial value problem for the linear system of Jacobi ordinary differential equations associated with the second variation. The second novel aspect of our analysis is that we show that the Hamiltonian form of these linear Jacobi equations still provides the appropriate correction term in the inextensible, unshearable limit that is commonly adopted in polymer physics models of, e.g. DNA. Prior analyses of the inextensible case have had to introduce nonlinear and nonlocal integral constraints to express conditions on the relative displacement of the end points. Our approximation formula for the looping pdf is of quite general applicability as, in contrast to most prior approaches, no assumption is made of either uniformity of the elastic chain, nor of a straight intrinsic shape. If the chain is uniform the Jacobi system evaluated at certain minimum energy configurations has constant coefficients. In such cases our approximate pdf can be evaluated in an entirely explicit, closed form. We illustrate our analysis with a planar example of this type and compute an approximate probability of cyclization, i.e., of forming a closed loop, from a uniform elastic chain whose intrinsic shape is an open circular arc. PMID:21230517
The effect of air-passage length on the optimum fin spacing for maximum cooling
NASA Technical Reports Server (NTRS)
Brevoort, Maurice J
1938-01-01
The effect on cooling of baffle length with optimum cylinder finning is discussed. Results from tests of several streamlined cylinders are given. It is shown that by employing several baffles the cooling can be increased several times.
Optimum projection angle for attaining maximum distance in a rugby place kick.
Linthorne, Nicholas P; Stokes, Thomas G
2014-01-01
This study investigated the effect of projection angle on the distance attained in a rugby place kick. A male rugby player performed 49 maximum-effort kicks using projection angles of between 20 and 50°. The kicks were recorded by a video camera at 50 Hz and a 2 D biomechanical analysis was conducted to obtain measures of the projection velocity and projection angle of the ball. The player's optimum projection angle was calculated by substituting a mathematical expression for the relationship between projection velocity and projection angle into the equations for the aerodynamic flight of a rugby ball. We found that the player's calculated optimum projection angle (30.6°, 95% confidence limits ± 1.9°) was in close agreement with his preferred projection angle (mean value 30.8°, 95% confidence limits ± 2.1°). The player's calculated optimum projection angle was also similar to projection angles previously reported for skilled rugby players. The optimum projection angle in a rugby place kick is considerably less than 45° because the projection velocity that a player can produce decreases substantially as projection angle is increased. Aerodynamic forces and the requirement to clear the crossbar have little effect on the optimum projection angle. Key PointsThe optimum projection angle in a rugby place kick is about 30°.The optimum projection angle is considerably less than 45° because the projection velocity that a player can produce decreases substantially as projection angle is increased.Aerodynamic forces and the requirement to clear the crossbar have little effect on the optimum projection angle. PMID:24570626
Optimum Projection Angle for Attaining Maximum Distance in a Rugby Place Kick
Linthorne, Nicholas P.; Stokes, Thomas G.
2014-01-01
This study investigated the effect of projection angle on the distance attained in a rugby place kick. A male rugby player performed 49 maximum-effort kicks using projection angles of between 20 and 50Â°. The kicks were recorded by a video camera at 50 Hz and a 2 D biomechanical analysis was conducted to obtain measures of the projection velocity and projection angle of the ball. The playerâ€™s optimum projection angle was calculated by substituting a mathematical expression for the relationship between projection velocity and projection angle into the equations for the aerodynamic flight of a rugby ball. We found that the playerâ€™s calculated optimum projection angle (30.6Â°, 95% confidence limits Â± 1.9Â°) was in close agreement with his preferred projection angle (mean value 30.8Â°, 95% confidence limits Â± 2.1Â°). The playerâ€™s calculated optimum projection angle was also similar to projection angles previously reported for skilled rugby players. The optimum projection angle in a rugby place kick is considerably less than 45Â° because the projection velocity that a player can produce decreases substantially as projection angle is increased. Aerodynamic forces and the requirement to clear the crossbar have little effect on the optimum projection angle. Key Points The optimum projection angle in a rugby place kick is about 30Â°. The optimum projection angle is considerably less than 45Â° because the projection velocity that a player can produce decreases substantially as projection angle is increased. Aerodynamic forces and the requirement to clear the crossbar have little effect on the optimum projection angle. PMID:24570626
Improved vertical directional coupler for optimum edge coupling to an embedded photodetector
NASA Astrophysics Data System (ADS)
Noutsios, P. C.; Yip, G. L.
1995-11-01
An improved vertical coupling structure, consisting of a graded-index planar buried waveguide in glass and a dielectric overlayer, is designed and realized to provide an optimum edge coupling to a modeled GaAs photodetector. Calculations of the attenuation coefficient and coupling efficiency show an optimum absorption behavior. Normal-mode measurements and beam-propagation calculations of the coupling length and power transfer ratio are compared.
Method for determining optimum concentration of hydration inhibitor for clays in drilling fluids
Wilcox, R. D.
1985-01-29
A method is provided for selecting the optimum concentration of inhibitors such as soluble salts to effect maximum clay swelling and dispersion inhibition in an aqueous fluid of water-swellable, argillaceous materials including clays as exemplified by bentonite and argillaceous sediments, such as shales, encountered in drilling operations. In this method filtration measurements are first taken to develop a filtration parameter from which the optimum inhibitor concentration is readily determined.
Towards Loop Quantum Supergravity (LQSG)
NASA Astrophysics Data System (ADS)
Bodendorfer, N.; Thiemann, T.; Thurn, A.
2012-05-01
Should nature be supersymmetric, then it will be described by Quantum Supergravity at least in some energy regimes. The currently most advanced description of Quantum Supergravity and beyond is Superstring Theory/M-Theory in 10/11 dimensions. String Theory is a top-to-bottom approach to Quantum Supergravity in that it postulates a new object, the string, from which classical Supergravity emerges as a low energy limit. On the other hand, one may try more traditional bottom-to-top routes and apply the techniques of Quantum Field Theory. Loop Quantum Gravity (LQG) is a manifestly background independent and non-perturbative approach to the quantisation of classical General Relativity, however, so far mostly without supersymmetry. The main obstacle to the extension of the techniques of LQG to the quantisation of higher dimensional Supergravity is that LQG rests on a specific connection formulation of General Relativity which exists only in D+1=4 dimensions. In this Letter we introduce a new connection formulation of General Relativity which exists in all space-time dimensions. We show that all LQG techniques developed in D+1=4 can be transferred to the new variables in all dimensions and describe how they can be generalised to the new types of fields that appear in Supergravity theories as compared to standard matter, specifically Rarita-Schwinger and p-form gauge fields.
Determination of thermodynamic parameters for HIV DIS type loop–loop kissing complexes
Weixlbaumer, Albert; Werner, Andreas; Flamm, Christoph; Westhof, Eric; Schroeder, Renée
2004-01-01
The HIV-1 type dimerization initiation signal (DIS) loop was used as a starting point for the analysis of the stability of Watson–Crick (WC) base pairs in a tertiary structure context. We used ultraviolet melting to determine thermodynamic parameters for loop–loop tertiary interactions and compared them with regular secondary structure RNA helices of the same sequences. In 1 M Na+ the loop–loop interaction of a HIV-1 DIS type pairing is 4 kcal/mol more stable than its sequence in an equivalent regular and isolated RNA helix. This difference is constant and sequence independent, suggesting that the rules governing the stability of WC base pairs in the secondary structure context are also valid for WC base pairs in the tertiary structure context. Moreover, the effect of ion concentration on the stability of loop–loop tertiary interactions differs considerably from that of regular RNA helices. The stabilization by Na+ and Mg2+ is significantly greater if the base pairing occurs within the context of a loop–loop interaction. The dependence of the structural stability on salt concentration was defined via the slope of a Tm/log [ion] plot. The short base-paired helices are stabilized by 8°C/log [Mg2+] or 11°C/log [Na+], whereas base-paired helices forming tertiary loop–loop interactions are stabilized by 16°C/log [Mg2+] and 26°C/log [Na+]. The different dependence on ionic strength that is observed might reflect the contribution of specific divalent ion binding to the preformation of the hairpin loops poised for the tertiary kissing loop–loop contacts. PMID:15459283
Hardware-Based Non-Optimum Factors for Launch Vehicle Structural Design
NASA Technical Reports Server (NTRS)
Wu, K. Chauncey; Cerro, Jeffrey A.
2010-01-01
During aerospace vehicle conceptual and preliminary design, empirical non-optimum factors are typically applied to predicted structural component weights to account for undefined manufacturing and design details. Non-optimum factors are developed here for 32 aluminum-lithium 2195 orthogrid panels comprising the liquid hydrogen tank barrel of the Space Shuttle External Tank using measured panel weights and manufacturing drawings. Minimum values for skin thickness, axial and circumferential blade stiffener thickness and spacing, and overall panel thickness are used to estimate individual panel weights. Panel non-optimum factors computed using a coarse weights model range from 1.21 to 1.77, and a refined weights model (including weld lands and skin and stiffener transition details) yields non-optimum factors of between 1.02 and 1.54. Acreage panels have an average 1.24 non-optimum factor using the coarse model, and 1.03 with the refined version. The observed consistency of these acreage non-optimum factors suggests that relatively simple models can be used to accurately predict large structural component weights for future launch vehicles.