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Sample records for adaptive beam shaping

  1. Beam shaping for laser-based adaptive optics in astronomy.

    PubMed

    Béchet, Clémentine; Guesalaga, Andrés; Neichel, Benoit; Fesquet, Vincent; González-Núñez, Héctor; Zúñiga, Sebastián; Escarate, Pedro; Guzman, Dani

    2014-06-01

    The availability and performance of laser-based adaptive optics (AO) systems are strongly dependent on the power and quality of the laser beam before being projected to the sky. Frequent and time-consuming alignment procedures are usually required in the laser systems with free-space optics to optimize the beam. Despite these procedures, significant distortions of the laser beam have been observed during the first two years of operation of the Gemini South multi-conjugate adaptive optics system (GeMS). A beam shaping concept with two deformable mirrors is investigated in order to provide automated optimization of the laser quality for astronomical AO. This study aims at demonstrating the correction of quasi-static aberrations of the laser, in both amplitude and phase, testing a prototype of this two-deformable mirror concept on GeMS. The paper presents the results of the preparatory study before the experimental phase. An algorithm to control amplitude and phase correction, based on phase retrieval techniques, is presented with a novel unwrapping method. Its performance is assessed via numerical simulations, using aberrations measured at GeMS as reference. The results predict effective amplitude and phase correction of the laser distortions with about 120 actuators per mirror and a separation of 1.4 m between the mirrors. The spot size is estimated to be reduced by up to 15% thanks to the correction. In terms of AO noise level, this has the same benefit as increasing the photon flux by 40%. PMID:24921496

  2. Adaptive electron beam shaping using a photoemission gun and spatial light modulator

    NASA Astrophysics Data System (ADS)

    Maxson, Jared; Lee, Hyeri; Bartnik, Adam C.; Kiefer, Jacob; Bazarov, Ivan

    2015-02-01

    The need for precisely defined beam shapes in photoelectron sources has been well established. In this paper, we use a spatial light modulator and simple shaping algorithm to create arbitrary, detailed transverse laser shapes with high fidelity. We transmit this shaped laser to the photocathode of a high voltage dc gun. Using beam currents where space charge is negligible, and using an imaging solenoid and fluorescent viewscreen, we show that the resultant beam shape preserves these detailed features with similar fidelity. Next, instead of transmitting a shaped laser profile, we use an active feedback on the unshaped electron beam image to create equally accurate and detailed shapes. We demonstrate that this electron beam feedback has the added advantage of correcting for electron optical aberrations, yielding shapes without skew. The method may serve to provide precisely defined electron beams for low current target experiments, space-charge dominated beam commissioning, as well as for online adaptive correction of photocathode quantum efficiency degradation.

  3. Adaptive optimisation of a generalised phase contrast beam shaping system

    NASA Astrophysics Data System (ADS)

    Kenny, F.; Choi, F. S.; Glückstad, J.; Booth, M. J.

    2015-05-01

    The generalised phase contrast (GPC) method provides versatile and efficient light shaping for a range of applications. We have implemented a generalised phase contrast system that used two passes on a single spatial light modulator (SLM). Both the pupil phase distribution and the phase contrast filter were generated by the SLM. This provided extra flexibility and control over the parameters of the system including the phase step magnitude, shape, radius and position of the filter. A feedback method for the on-line optimisation of these properties was also developed. Using feedback from images of the generated light field, it was possible to dynamically adjust the phase filter parameters to provide optimum contrast.

  4. Adaptive optimisation of a generalised phase contrast beam shaping system

    PubMed Central

    Kenny, F.; Choi, F.S.; Glückstad, J.; Booth, M.J.

    2015-01-01

    The generalised phase contrast (GPC) method provides versatile and efficient light shaping for a range of applications. We have implemented a generalised phase contrast system that used two passes on a single spatial light modulator (SLM). Both the pupil phase distribution and the phase contrast filter were generated by the SLM. This provided extra flexibility and control over the parameters of the system including the phase step magnitude, shape, radius and position of the filter. A feedback method for the on-line optimisation of these properties was also developed. Using feedback from images of the generated light field, it was possible to dynamically adjust the phase filter parameters to provide optimum contrast. PMID:26089573

  5. Adaptive optical beam shaping for compensating projection-induced focus deformation

    NASA Astrophysics Data System (ADS)

    Pütsch, Oliver; Stollenwerk, Jochen; Loosen, Peter

    2016-02-01

    Scanner-based applications are already widely used for the processing of surfaces, as they allow for highly dynamic deflection of the laser beam. Particularly, the processing of three-dimensional surfaces with laser radiation initiates the development of highly innovative manufacturing techniques. Unfortunately, the focused laser beam suffers from deformation caused by the involved projection mechanisms. The degree of deformation is field variant and depends on both the surface geometry and the working position of the laser beam. Depending on the process sensitivity, the deformation affects the process quality, which motivates a method of compensation. Current approaches are based on a local adaption of the laser power to maintain constant intensity within the interaction zone. For advanced manufacturing, this approach is insufficient, as the residual deformation of the initial circular laser spot is not taken into account. In this paper, an alternative approach is discussed. Additional beam-shaping devices are integrated between the laser source and the scanner, and allow for an in situ compensation to ensure a field-invariant circular focus spot within the interaction zone. Beyond the optical design, the approach is challenging with respect to the control theory's point of view, as both the beam deflection and the compensation have to be synchronized.

  6. Laser beam shaping techniques

    SciTech Connect

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

    2000-03-16

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

  7. 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.

  8. Beam shaping unit for micromachining

    NASA Astrophysics Data System (ADS)

    Laskin, Alexander; Å iaulys, Nerijus; Å lekys, Gintas; Laskin, Vadim

    2013-09-01

    Uniform irradiance distribution of laser spot is highly advisable in various micromachining techniques like scribing, PCB and Through-Silicon Via (TSV) drilling, repair techniques in display making technologies. Scanning over whole working field with using popular 2- and 3-axis galvo mirror scanners is another important part of microprocessing systems. Therefore, combining of beam shaping optics, converting Gaussian to flattop (uniform) laser beam profile, with scanning optical heads is an insistent technical task. To provide flattop irradiance profile it is suggested to apply field mapping refractive beam shaping optics πShaper being characterized by some important features: low output divergence, high transmittance, extended depth of field, capability to work with TEM00 and multimode lasers, as result providing a freedom in building various optical systems. De-magnifying of flattop laser beam can be realized with using imaging technique; the imaging optical system to be composed from F-theta lens of scanning head and additional collimating system to be used right after a πShaper. One of the problems in this approach is implementation of compact design of the collimating part. As a solution it is suggested to apply a specially designed Beam Shaping Unit (BSU) to be installed between a laser and a scanning head and providing: conversion from Gaussian to flattop laser beam irradiance profile, compact collimator design, and functions of laser beam adjustment and adaptation to a laser and a scanning head used in particular equipment. There will be considered design features of refractive beam shapers πShaper and BSU, examples of optical layouts to generate flattop laser spots, which sizes span from several tens of microns to millimetres. Examples of real implementations and results of material processing will be presented as well.

  9. Shaping propagation invariant laser beams

    NASA Astrophysics Data System (ADS)

    Soskind, Michael; Soskind, Rose; Soskind, Yakov

    2015-11-01

    Propagation-invariant structured laser beams possess several unique properties and play an important role in various photonics applications. The majority of propagation invariant beams are produced in the form of laser modes emanating from stable laser cavities. Therefore, their spatial structure is limited by the intracavity mode formation. We show that several types of anamorphic optical systems (AOSs) can be effectively employed to shape laser beams into a variety of propagation invariant structured fields with different shapes and phase distributions. We present a propagation matrix approach for designing AOSs and defining mode-matching conditions required for preserving propagation invariance of the output shaped fields. The propagation matrix approach was selected, as it provides a more straightforward approach in designing AOSs for shaping propagation-invariant laser beams than the alternative technique based on the Gouy phase evolution, especially in the case of multielement AOSs. Several practical configurations of optical systems that are suitable for shaping input laser beams into a diverse variety of structured propagation invariant laser beams are also presented. The laser beam shaping approach was applied by modeling propagation characteristics of several input laser beam types, including Hermite-Gaussian, Laguerre-Gaussian, and Ince-Gaussian structured field distributions. The influence of the Ince-Gaussian beam semifocal separation parameter and the azimuthal orientation between the input laser beams and the AOSs onto the resulting shape of the propagation invariant laser beams is presented as well.

  10. Concept for image-guided vitreo-retinal fs-laser surgery: adaptive optics and optical coherence tomography for laser beam shaping and positioning

    NASA Astrophysics Data System (ADS)

    Matthias, Ben; Brockmann, Dorothee; Hansen, Anja; Horke, Konstanze; Knoop, Gesche; Gewohn, Timo; Zabic, Miroslav; Krüger, Alexander; Ripken, Tammo

    2015-03-01

    Fs-lasers are well established in ophthalmic surgery as high precision tools for corneal flap cutting during laser in situ keratomileusis (LASIK) and increasingly utilized for cutting the crystalline lens, e.g. in assisting cataract surgery. For addressing eye structures beyond the cornea, an intraoperative depth resolved imaging is crucial to the safety and success of the surgical procedure due to interindividual anatomical disparities. Extending the field of application even deeper to the posterior eye segment, individual eye aberrations cannot be neglected anymore and surgery with fs-laser is impaired by focus degradation. Our demonstrated concept for image-guided vitreo-retinal fs-laser surgery combines adaptive optics (AO) for spatial beam shaping and optical coherence tomography (OCT) for focus positioning guidance. The laboratory setup comprises an adaptive optics assisted 800 nm fs-laser system and is extended by a Fourier domain optical coherence tomography system. Phantom structures are targeted, which mimic tractional epiretinal membranes in front of excised porcine retina within an eye model. AO and OCT are set up to share the same scanning and focusing optics. A Hartmann-Shack sensor is employed for aberration measurement and a deformable mirror for aberration correction. By means of adaptive optics the threshold energy for laser induced optical breakdown is lowered and cutting precision is increased. 3D OCT imaging of typical ocular tissue structures is achieved with sufficient resolution and the images can be used for orientation of the fs-laser beam. We present targeted dissection of the phantom structures and its evaluation regarding retinal damage.

  11. Morphable Beam Device and Beam Shape Generation Algorithm

    NASA Astrophysics Data System (ADS)

    Matunaga, Saburo; Iljic, Thomas; Tanaka, Yohei; Miura, Yoshiyuki

    To conduct remote inspection missions, an experimental device using a flexible beam without any articulated joints was developed and it is called Morphable Beam Device (MBD). A beam is deployed, enabling a wide range of shapes and lengths in a microgravity environment for various space applications, such as an inspection device, a crew support device and a variable geometry beam member of space structures. In this paper, a beam shape modeling made by the MBD considering retro-bending and beam shape generation algorithms are described, and feasibility of the proposed methods are demonstrated.

  12. Global beam shaping with nonuniformly polarized beams: a proposal.

    PubMed

    Ramírez-Sánchez, V; Piquero, G

    2006-12-10

    A procedure for global beam shaping by modifying some global spatial parameters characteristic of the beam is proposed. This method is based on the generation of a nonuniformly polarized beam using a Mach-Zehnder system with two suitably shaped intensity transmittances and orthogonal linear polarizers. The changes in beam quality and kurtosis parameters after a linear polarizer placed at the output of the system are investigated. PMID:17119590

  13. Global beam shaping with nonuniformly polarized beams: a proposal

    NASA Astrophysics Data System (ADS)

    Ramírez-Sánchez, V.; Piquero, G.

    2006-12-01

    A procedure for global beam shaping by modifying some global spatial parameters characteristic of the beam is proposed. This method is based on the generation of a nonuniformly polarized beam using a Mach-Zehnder system with two suitably shaped intensity transmittances and orthogonal linear polarizers. The changes in beam quality and kurtosis parameters after a linear polarizer placed at the output of the system are investigated.

  14. Active beam shaping in multiple laser guide stars

    NASA Astrophysics Data System (ADS)

    Jones, Katharine J.

    2012-10-01

    Adaptive beam shaping is a critical part of multiple Laser Guide Stars (LGS) for Multiple Conjugate Adaptive Optics (MCAO) for ground-based astronomical telescopes. There are two kinds of Laser Guide Stars: Na Laser Guide Stars (at 589 nm and 92 km altitude) and Rayleigh Laser Guide Stars (at 532 nm and 20 km altitude). Multiple Conjugate Adaptive Optics (MCAO) corrects for each "layer" of atmosphere independently. Multiple Laser Guide Stars are being developed to achieve a measure of tilt and increase the isoplanatic patch. Multiple Laser Guide Stars are being combined with Multiple Conjugate Optics in the Large Binocular Telescope (LBT): more than one Laser Guide Star (4-5) and two different wavelengths: 589 nm and 532 nm. Other observatories have multiple Laser Guide Stars but only one wavelength: 589 nm or 532 nm. Because Laser Guide Stars are launched into the atmosphere, adaptive beam shaping will be carried out before the laser is launched and will be different depending on which laser is being used, presumably to effect the tightest beam which can be achieved at the power level which is required to provide the requisite return to gound-based wavefront sensors. A complete range of devices are used. Beam attenuation and divergnece will take place. Multiple Laser Guide Stars of major observatories (SOR, LBT, MMT, ESO VLT and Gemini South) will be evaluated for effective adaptive beam shaping and impact on performance

  15. Square shaped flat-top beam in refractive beam shapers

    NASA Astrophysics Data System (ADS)

    Laskin, Alexander; Laskin, Vadim; Ostrun, Aleksei

    2015-08-01

    Lossless transformation of round Gaussian to square shaped flat-top collimated beam is important in building highpower solid state laser systems to improve optical pumping or amplification. There are industrial micromachining applications like scribing, display repair, which performance is improved when a square shaped spot with uniform intensity is created. Proved beam shaping solutions to these techniques are refractive field mapping beam shapers having some important features: flatness of output phase front, small output divergence, high transmittance, extended depth of field, operation with TEM00 and multimode lasers. Usual approach to design refractive beam shapers implies that input and output beams have round cross-section, therefore the only way to create a square shaped output beam is using a square mask, which leads to essential losses. When an input laser beam is linearly polarized it is suggested to generate square shaped flat-top output by applying beam shaper lenses from birefringent materials or by using additional birefringent components. Due to birefringence there is introduced phase retardation in beam parts and is realized a square shaped interference pattern at the beam shaper output. Realization of this approach requires small phase retardation, therefore weak birefringence effect is enough and birefringent optical components, operating in convergent or divergent beams, can be made from refractive materials, which crystal optical axis is parallel to optical axis of entire beam shaper optical system. There will be considered design features of beam shapers creating square shaped flat-top beams. Examples of real implementations and experimental results will be presented as well.

  16. Electron beam machining using rotating and shaped beam power distribution

    DOEpatents

    Elmer, John W.; O'Brien, Dennis W.

    1996-01-01

    An apparatus and method for electron beam (EB) machining (drilling, cutting and welding) that uses conventional EB guns, power supplies, and welding machine technology without the need for fast bias pulsing technology. The invention involves a magnetic lensing (EB optics) system and electronic controls to: 1) concurrently bend, focus, shape, scan, and rotate the beam to protect the EB gun and to create a desired effective power-density distribution, and 2) rotate or scan this shaped beam in a controlled way. The shaped beam power-density distribution can be measured using a tomographic imaging system. For example, the EB apparatus of this invention has the ability to drill holes in metal having a diameter up to 1000 .mu.m (1 mm or larger), compared to the 250 .mu.m diameter of laser drilling.

  17. Electron beam machining using rotating and shaped beam power distribution

    DOEpatents

    Elmer, J.W.; O`Brien, D.W.

    1996-07-09

    An apparatus and method are disclosed for electron beam (EB) machining (drilling, cutting and welding) that uses conventional EB guns, power supplies, and welding machine technology without the need for fast bias pulsing technology. The invention involves a magnetic lensing (EB optics) system and electronic controls to: (1) concurrently bend, focus, shape, scan, and rotate the beam to protect the EB gun and to create a desired effective power-density distribution, and (2) rotate or scan this shaped beam in a controlled way. The shaped beam power-density distribution can be measured using a tomographic imaging system. For example, the EB apparatus of this invention has the ability to drill holes in metal having a diameter up to 1,000 {micro}m (1 mm or larger), compared to the 250 {micro}m diameter of laser drilling. 5 figs.

  18. Flexible beam control using an adaptive truss

    NASA Technical Reports Server (NTRS)

    Warrington, Thomas J.; Horner, C. Garnett

    1990-01-01

    To demonstrate the feasibility of adaptive trusses for vibration suppression, a 12-ft-long beam is attached to a single cell of an adaptive truss which has three active battens. With the base of the adaptive truss attached to the laboratory frame, the measured strain of the vibrating beam shows the adaptive truss to be very effective in suppressing vibration when subjected to initial conditions. Control is accomplished by a PC/XT computer that implements an LQR-designed control law.

  19. Diffractive beam shaping for enhanced laser polymer welding

    NASA Astrophysics Data System (ADS)

    Rauschenberger, J.; Vogler, D.; Raab, C.; Gubler, U.

    2015-03-01

    Laser welding of polymers increasingly finds application in a large number of industries such as medical technology, automotive, consumer electronics, textiles or packaging. More and more, it replaces other welding technologies for polymers, e. g. hot-plate, vibration or ultrasonic welding. At the same rate, demands on the quality of the weld, the flexibility of the production system and on processing speed have increased. Traditionally, diode lasers were employed for plastic welding with flat-top beam profiles. With the advent of fiber lasers with excellent beam quality, the possibility to modify and optimize the beam profile by beam-shaping elements has opened. Diffractive optical elements (DOE) can play a crucial role in optimizing the laser intensity profile towards the optimal M-shape beam for enhanced weld seam quality. We present results on significantly improved weld seam width constancy and enlarged process windows compared to Gaussian or flat-top beam profiles. Configurations in which the laser beam diameter and shape can be adapted and optimized without changing or aligning the laser, fiber-optic cable or optical head are shown.

  20. Shape optimization including finite element grid adaptation

    NASA Technical Reports Server (NTRS)

    Kikuchi, N.; Taylor, J. E.

    1984-01-01

    The prediction of optimal shape design for structures depends on having a sufficient level of precision in the computation of structural response. These requirements become critical in situations where the region to be designed includes stress concentrations or unilateral contact surfaces, for example. In the approach to shape optimization discussed here, a means to obtain grid adaptation is incorporated into the finite element procedures. This facility makes it possible to maintain a level of quality in the computational estimate of response that is surely adequate for the shape design problem.

  1. Beam shaping in high-power laser systems with using refractive beam shapers

    NASA Astrophysics Data System (ADS)

    Laskin, Alexander; Laskin, Vadim

    2012-06-01

    Beam Shaping of the spatial (transverse) profile of laser beams is highly desirable by building optical systems of high-power lasers as well in various applications with these lasers. Pumping of the crystals of Ti:Sapphire lasers by the laser radiation with uniform (flattop) intensity profile improves performance of these ultrashort pulse high-power lasers in terms of achievable efficiency, peak-power and stability, output beam profile. Specifications of the solid-state lasers built according to MOPA configuration can be also improved when radiation of the master oscillator is homogenized and then is amplified by the power amplifier. Features of building these high power lasers require that a beam shaping solution should be capable to work with single mode and multimode beams, provide flattop and super-Gauss intensity distributions, the consistency and divergence of a beam after the intensity re-distribution should be conserved and low absorption provided. These specific conditions are perfectly fulfilled by the refractive field mapping beam shapers due to their unique features: almost lossless intensity profile transformation, low output divergence, high transmittance and flatness of output beam profile, extended depth of field, adaptability to real intensity profiles of TEM00 and multimode laser sources. Combining of the refractive field mapping beam shapers with other optical components, like beam-expanders, relay imaging lenses, anamorphic optics makes it possible to generate the laser spots of necessary shape, size and intensity distribution. There are plenty of applications of high-power lasers where beam shaping bring benefits: irradiating photocathode of Free Electron Lasers (FEL), material ablation, micromachining, annealing in display making techniques, cladding, heat treating and others. This paper will describe some design basics of refractive beam shapers of the field mapping type, with emphasis on the features important for building and applications

  2. Beam shaping for cosmetic hair removal

    NASA Astrophysics Data System (ADS)

    Lizotte, Todd E.; Tuttle, Tracie

    2007-09-01

    Beam shaping has the potential to provide comfort to people who require or seek laser based cosmetic skin procedures. Of immediate interest is the procedure of aesthetic hair removal. Hair removal is performed using a variety of wavelengths from 480 to 1200 nm by means of filtered Xenon flash lamps (pulsed light) or 810 nm diode lasers. These wavelengths are considered the most efficient means available for hair removal applications, but current systems use simple reflector designs and plane filter windows to direct the light to the surface being exposed. Laser hair removal is achieved when these wavelengths at sufficient energy levels are applied to the epidermis. The laser energy is absorbed by the melanin (pigment) in the hair and hair follicle which in turn is transformed into heat. This heat creates the coagulation process, which causes the removal of the hair and prevents growth of new hair [1]. This paper outlines a technique of beam shaping that can be applied to a non-contact based hair removal system. Several features of the beam shaping technique including beam uniformity and heat dispersion across its operational treatment area will be analyzed. A beam shaper design and its fundamental testing will be discussed in detail.

  3. Laser beam shaping for biomedical microscopy techniques

    NASA Astrophysics Data System (ADS)

    Laskin, Alexander; Kaiser, Peter; Laskin, Vadim; Ostrun, Aleksei

    2016-04-01

    Uniform illumination of a working field is very important in optical systems of confocal microscopy and various implementations of fluorescence microscopy like TIR, SSIM, STORM, PALM to enhance performance of these laser-based research techniques. Widely used TEM00 laser sources are characterized by essentially non-uniform Gaussian intensity profile which leads usually to non-uniform intensity distribution in a microscope working field or in a field of microlenses array of a confocal microscope optical system, this non-uniform illumination results in instability of measuring procedure and reducing precision of quantitative measurements. Therefore transformation of typical Gaussian distribution of a TEM00 laser to flat-top (top hat) profile is an actual technical task, it is solved by applying beam shaping optics. Due to high demands to optical image quality the mentioned techniques have specific requirements to a uniform laser beam: flatness of phase front and extended depth of field, - from this point of view the microscopy techniques are similar to holography and interferometry. 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 required in discussed microscopy techniques. We suggest applying refractive field mapping beam shapers πShaper, 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. The main function of a beam shaper is transformation of laser intensity profile, further beam transformation to provide optimum for a particular technique spot size and shape has to

  4. Doppler-shifted neutral beam line shape and beam transmission

    SciTech Connect

    Kamperschroer, J.H.; Grisham, L.R.; Kokatnur, N.; Lagin, L.J.; Newman, R.A.; O`Connor, T.E.; Stevenson, T.N.; von Halle, A.

    1994-04-01

    Analysis of Doppler-shifted Balmer-{alpha} line emission from the TFTR neutral beam injection systems has revealed that the line shape is well approximated by the sum of two Gaussians, or, alternatively, by a Lorentzian. For the sum of two Gaussians, the broad portion of the distribution contains 40% of the beam power and has a divergence five times that of the narrow part. Assuming a narrow 1/e- divergence of 1.3{degrees} (based on fits to the beam shape on the calorimeter), the broad part has a divergence of 6.9{degrees}. The entire line shape is also well approximated by a Lorentzian with a half-maximum divergence of 0.9{degrees}. Up to now, fusion neutral beam modelers have assumed a single Gaussian velocity distribution, at the extraction plane, in each direction perpendicular to beam propagation. This predicts a beam transmission efficiency from the ion source to the calorimeter of 97%. Waterflow calorimetry data, however, yield a transmission efficiency of {approximately}75%, a value in rough agreement with predictions of the Gaussian or Lorentzian models presented here. The broad wing of the two Gaussian distribution also accurately predicts the loss in the neutralizer. An average angle of incidence for beam loss at the exit of the neutralizer is 2.2{degrees}, rather than the 4.95{degrees} subtended by the center of the ion source. This average angle of incidence, which is used in computing power densities on collimators, is shown to be a function of beam divergence.

  5. Incoherent beam shaping with freeform mirror

    NASA Astrophysics Data System (ADS)

    Michaelis, Dirk; Kudaev, Sergey; Steinkopf, Ralf; Gebhardt, Andreas; Schreiber, Peter; Bräuer, Andreas

    2008-08-01

    Beam shaping of incoherent light sources (LEDs, halogen lamps) for arbitrary target light distribution is obtained by a single free-shape mirror. Special design algorithm ensures continuous profile without abrupt changes and shadowing regions. The mirror is manufactured by single point diamond turning combined with Fast-Tool-Servo (FTS) for simultaneous figuring of base surface and fine structure (for redistributing the light energy). Lateral and axial resolution of the fine structure is determined by FTS and considered during the design and data transfer. Directly turned surfaces can be used as replication tools for polymer or glass moulding and embossing.

  6. Intracavity beam shaping using an SLM

    NASA Astrophysics Data System (ADS)

    Burger, L.; Litvin, I.; Ngcobo, S.; Forbes, A.

    2015-08-01

    Intracavity laser beam shaping has been achieved by adding intensity or phase filters to a Fabry-Perot resonator. Changing the output beam from one mode to another is a tedious process, requiring the replacing of custom optical elements, and careful realignment. The digital laser [1] is an innovation which allows the laser beam produced by a laser to be dynamically controlled by a computer. Essentially, one of the resonator mirrors is replaced by a spatial light modulator (SLM), which is a computer controlled, pixellated, liquid-crystal device. While the concept is the device is simple, the implementation revealed subtle properties of spatial light modulators and the liquid crystals contained in them. These properties had to be well understood before their undesirable characteristics could be overcome, allowing the laser to function as conceived in the design.

  7. Wafer dicing utilizing unique beam shapes

    NASA Astrophysics Data System (ADS)

    Lizotte, Todd; Ohar, Orest

    2007-09-01

    Laser dicing of wafers is of keen interest to the semiconductor and LED industry. Devices such as ASICs, Ultra-thin Wafer Scale Packages and LEDS are unique in that they typically are formed from various materials in a multilayered structure. Many of these layers include active device materials, passivation coatings, conductors and dielectric films all deposited on top of a bulk wafer substrate and all potentially having differing ablation thresholds. These composite multi-layered structures require high finesse laser processes to ensure yields, cut quality and low process cost. Such processes have become very complex over the years as new devices have become miniaturized, requiring smaller kerf sizes. Of critical concern is the need to minimize substrate micro-cracking or lift off of upper layers along the dicing streets which directly corresponds to bulk device strength and device operational integrity over its projected lifetime. Laser processes involving the sequential use of single or multiple diode pumped solid state (DPSS) lasers, such as UV DPSS (355nn, 266nm, 532 nm), VIS DPSS (~532 nm) and IR DPSS (1064nm, 1070nm) as well as (UV, VIS, NIR, FIR and Eye Safe Wavelengths) DPFL (Diode Pumped Fiber Lasers) lasers to penetrate various and differing material layers and substrates including Silicon Carbide (SiC), Silicon, GaAs and Sapphire. Development of beam shaping optics with the purpose of permitting two or more differing energy densities within a single focused or imaged beam spot would provide opportunities for pre-processing or pre-scribing of thinner cover layers, while following through with a higher energy density segment to cut through the bulk base substrates. This paper will describe the development of beam shaping optical elements with unique beam shapes that could benefit dicing and patterning of delicate thin film coatings. Various designs will be described, with processing examples using LED wafer materials.

  8. Beam shaping for laser initiated optical primers

    NASA Astrophysics Data System (ADS)

    Lizotte, Todd E.

    2008-08-01

    Remington was one of the first firearm manufacturing companies to file a patent for laser initiated firearms, in 1969. Nearly 40 years later, the development of laser initiated firearms has not become a mainstream technology in the civilian market. Requiring a battery is definitely a short coming, so it is easy to see how such a concept would be problematic. Having a firearm operate reliably and the delivery of laser energy in an efficient manner to ignite the shock-sensitive explosive primer mixtures is a tall task indeed. There has been considerable research on optical element based methods of transferring or compressing laser energy to ignite primer charges, including windows, laser chip primers and various lens shaped windows to focus the laser energy. The focusing of laser light needs to achieve igniting temperatures upwards of >400°C. Many of the patent filings covering this type of technology discuss simple approaches where a single point of light might be sufficient to perform this task. Alternatively a multi-point method might provide better performance, especially for mission critical applications, such as precision military firearms. This paper covers initial design and performance test of the laser beam shaping optics to create simultaneous multiple point ignition locations and a circumferential intense ring for igniting primer charge compounds. A simple initial test of the ring beam shaping technique was evaluated on a standard large caliber primer to determine its effectiveness on igniting the primer material. Several tests were conducted to gauge the feasibility of laser beam shaping, including optic fabrication and mounting on a cartridge, optic durability and functional ignition performance. Initial data will be presented, including testing of optically elements and empirical primer ignition / burn analysis.

  9. Annular beam shaping and optical trepanning

    NASA Astrophysics Data System (ADS)

    Zeng, Danyong

    Percussion drilling and trepanning are two laser drilling methods. Percussion drilling is accomplished by focusing the laser beam to approximately the required diameter of the hole, exposing the material to one or a series of laser pulses at the same spot to melt and vaporize the material. Drilling by trepanning involves cutting a hole by rotating a laser beam with an optical element or an x-y galvo-scanner. Optical trepanning is a new laser drilling method using an annular beam. The annular beams allow numerous irradiance profiles to supply laser energy to the workpiece and thus provide more flexibility in affecting the hole quality than a traditional circular laser beam. Heating depth is important for drilling application. Since there are no good ways to measure the temperature inside substrate during the drilling process, an analytical model for optical trepanning has been developed by considering an axisymmetric, transient heat conduction equation, and the evolutions of the melting temperature isotherm, which is referred to as the melt boundary in this study, are calculated to investigate the influences of the laser pulse shapes and intensity profiles on the hole geometry. This mathematical model provides a means of understanding the thermal effect of laser irradiation with different annular beam shapes. To take account of conduction in the solid, vaporization and convection due to the melt flow caused by an assist gas, an analytical two-dimensional model is developed for optical trepanning. The influences of pulse duration, laser pulse length, pulse repetition rate, intensity profiles and beam radius are investigated to examine their effects on the recast layer thickness, hole depth and taper. The ray tracing technique of geometrical optics is employed to design the necessary optics to transform a Gaussian laser beam into an annular beam of different intensity profiles. Such profiles include half Gaussian with maximum intensities at the inner and outer

  10. Finite Element Analysis of Adaptive-Stiffening and Shape-Control SMA Hybrid Composites

    NASA Technical Reports Server (NTRS)

    Gao, Xiujie; Burton, Deborah; Turner, Travis L.; Brinson, Catherine

    2005-01-01

    Shape memory alloy hybrid composites with adaptive-stiffening or morphing functions are simulated using finite element analysis. The composite structure is a laminated fiber-polymer composite beam with embedded SMA ribbons at various positions with respect to the neutral axis of the beam. Adaptive stiffening or morphing is activated via selective resistance heating of the SMA ribbons or uniform thermal loads on the beam. The thermomechanical behavior of these composites was simulated in ABAQUS using user-defined SMA elements. The examples demonstrate the usefulness of the methods for the design and simulation of SMA hybrid composites. Keywords: shape memory alloys, Nitinol, ABAQUS, finite element analysis, post-buckling control, shape control, deflection control, adaptive stiffening, morphing, constitutive modeling, user element

  11. Adaptive optimisation of illumination beam profiles in fluorescence microscopy

    NASA Astrophysics Data System (ADS)

    Mitchell, T. J.; Saunter, C. D.; O'Nions, W.; Girkin, J. M.; Love, G. D.

    2015-03-01

    Wide-field fluorescence microscope techniques such as single/selective plane illumination microscope (SPIM) are typically configured to image large regions of a sample at once. Here the illumination beam provides uniform excitation of several biological features across the region, `sliced' to a thickness of between 5-10 microns. In this paper we propose a simple alteration to the optical configuration of a SPIM by switching the light-sheet- forming cylindrical lens with a spatial light modulator. This has the potential to adaptively reconfigure the light sheet geometry to improve the optical sectioning of specific biological features, rather than the thicker sectioning of several features at once across a larger observation field-of-view. We present a prototype version of such a system, referred to as an Adaptive-SPIM (A-SPIM) system. We then suggest that the direct recording of illumination beam shapes within the working microscope system can better facilitate the analysis and subsequent re-configuration of the illumination beam to a specific geometry, and summarise the design and operation of a device that we have developed specifically for this purpose. We finally present reconstructed quantitative three dimensional flux maps of illumination beams from three microscope configurations taken using this miniature high-dynamic range beam profiling device, comparing the beam geometry of a regular SPIM system with our prototype A-SPIM system, and suggesting future improvements.

  12. Active Beam Shaping System and Method Using Sequential Deformable Mirrors

    NASA Technical Reports Server (NTRS)

    Norman, Colin A. (Inventor); Pueyo, Laurent A. (Inventor)

    2015-01-01

    An active optical beam shaping system includes a first deformable mirror arranged to at least partially intercept an entrance beam of light and to provide a first reflected beam of light, a second deformable mirror arranged to at least partially intercept the first reflected beam of light from the first deformable mirror and to provide a second reflected beam of light, and a signal processing and control system configured to communicate with the first and second deformable mirrors. The first deformable mirror, the second deformable mirror and the signal processing and control system together provide a large amplitude light modulation range to provide an actively shaped optical beam.

  13. Multiple-beam pulse shaping and preamplification

    SciTech Connect

    Wilcox, R.B.; VanWonterghem, B.W.; Burkhart, S.C.; Davin, J.M.

    1994-11-09

    Glass fusion laser systems typically use a master oscillator-power amplifier (MOPA) architecture, where control of the optical pulse temporal and spatial parameters is accomplished mainly in the master oscillator and low power optics. The pulses from this low power ``front end`` are amplified in the power amplifier, which modifies the pulse shape temporally and spatially. Nonlinear frequency conversion crystals following the amplifier further change the pulse before it reaches the target. To effectively control the optical pulse on target for different types of experiments, and compensate for nonlinearity in the preceding optics, the front end system must be versatile enough to easily control many pulse parameters over a large range. The front end pulse generation system described in this article represents a new approach to this problem. The proposed National Ignition Facility (NIF) has 192 beamlines, each of which requires an input pulse of up to 12 Joules in around 4 ns equivalent square pulse length. Considerations of laser architecture for supplying each of these beamlines from a central oscillator system were crucial in the design of the front end. Previous lasers have used bulk optics to split a single oscillator signal and report beams to multiple amplifier chains. A key idea in the current design is to replace bulk optic transport with fibers, eliminating large opto-mechanical subsystems. Another important concept is convenient pulse forming using low voltage integrated optic modulators. The integrated optic and fiber optic concepts resulted in the current pulse generation designs for NEF. An important advantage is that each of the beamlines can have an independently controlled temporal pulse shape, which provides for precise balance of instantaneous power on target.

  14. Observation of shape-preserving accelerating underwater acoustic beams

    NASA Astrophysics Data System (ADS)

    Bar-Ziv, Uri; Postan, Aharon; Segev, Mordechai

    2015-09-01

    We present the experimental generation and observation of an underwater acoustic accelerating beam. The beam was generated by phase modulating a single projector using a tailored acoustic phase mask. The beam is propagating for a range in excess of 800 wavelengths, which are about six Rayleigh lengths, while preserving its shape and transversely accelerating. Such beams have promising applications in the fields of sonar, hydrography, and medical ultrasound and can provide new means to study nonlinear interaction of acoustic beams.

  15. Experimental demonstration of static shape control. [using flexible beam facility for large space structure development

    NASA Technical Reports Server (NTRS)

    Eldred, D.; Schaechter, D.

    1981-01-01

    Results of a microprocessor-controlled implementation of static shape control using a specially constructed flexible beam facility are presented. The discussion covers the development of shape control algorithms, adaptation of the algorithms for use with finite element models, construction of a flexible beam, characterization and calibration of the facility, development of a finite element model for the beam, and the development of computer hardware and software. It is shown that feedback control yields better results than open-loop control, and that the use of more than two sensors in the control loop has little effect on the system performance.

  16. Optical fiber antenna generating spiral beam shapes

    SciTech Connect

    Sarkar Pal, S.; Mondal, S. K. Kumar, R.; Akula, A.; Ghosh, R.; Bhatnagar, R.; Kumbhakar, D.

    2014-01-20

    A simple method is proposed here to generate vortex beam and spiral intensity patterns from a Gaussian source. It uses a special type of optical fiber antenna of aperture ∼80 nm having naturally grown surface curvature along its length. The antenna converts linearly polarized Gaussian beam into a beam with spiral intensity patterns. The experimentally obtained spiral patterns with single and double spiral arms manifest the orbital angular momentum, l = ±1, 2, carried by the output beam. Such beam can be very useful for optical tweezer, metal machining, and similar applications.

  17. The effect of object shape and laser beam shape on lidar system resolution

    NASA Astrophysics Data System (ADS)

    Cheng, Hongchang; Wang, Jingyi; Ke, Jun

    2016-06-01

    In a LIDAR system, a pulsed laser beam is propagated to a scene, and then reflected back by objects. Ideally if the beam diameter and the pulse width are close to zero, then the reflected beam in time domain is similar to a delta function, which can accurately locate an object's position. However, in a practical system, the beam has finite size. Therefore, even if the pulse width is small, an object shape will make the reflected beam stretched along the time axis, then affect system resolution. In this paper, we assume the beam with Gaussian shape. The beam can be formulated as a delta function convolved with a shape function, such as a rectangular function, in time domain. Then the reflected beam can be defined as a system response function convolved with the shape function. We use symmetric objects to analyze the reflected beam. Corn, sphere, and cylinder objects are used to find a LIDAR system's response function. The case for large beam size is discussed. We assume the beam shape is similar to a plane wave. With this assumption, we get the simplified LIDAR system response functions for the three kinds of objects. Then we use tiny spheres to emulate an arbitrary object, and study its effect to the returned beam.

  18. Optical simulation of laser beam phase-shaping focusing optimization in biological tissues

    NASA Astrophysics Data System (ADS)

    Gomes, Ricardo; Vieira, Pedro; Coelho, João. M. P.

    2013-11-01

    In this paper we report the development of an optical simulator that can be used in the development of methodologies for compensate/decrease the light scattering effect of most biological tissues through phase-shaping methods. In fact, scattering has long been a major limitation for the medical applications of lasers where in-depth tissues concerns due to the turbid nature of most biological media in the human body. In developing the simulator, two different approaches were followed: one using multiple identical beams directed to the same target area and the other using a phase-shaped beam. In the multiple identical beams approach (used mainly to illustrate the limiting effect of scattering on the beam's propagation) there was no improvement in the beam focus at 1 mm compared to a single beam layout but, in phase-shaped beam approach, a 8x improvement on the radius of the beam at the same depth was achieved. The models were created using the optical design software Zemax and numerical algorithms created in Matlab programming language to shape the beam wavefront. A dedicated toolbox allowed communication between both programs. The use of the two software's proves to be a simple and powerful solution combining the best of the two and allowing a significant potential for adapting the simulations to new systems and thus allow to assess their response and define critical engineering parameters prior to laboratorial implementation.

  19. Shaping micron-sized cold neutron beams

    NASA Astrophysics Data System (ADS)

    Ott, Frédéric; Kozhevnikov, Sergey; Thiaville, André; Torrejón, Jacob; Vázquez, Manuel

    2015-07-01

    In the field of neutron scattering, the need for micro-sized (1-50 μm) thermal or cold neutron beams has recently appeared, typically in the field of neutron imaging to probe samples with a high spatial resolution. We discuss various possibilities of producing such micro-sized neutron beams. The advantages and drawbacks of the different techniques are discussed. We show that reflective optics offers the most flexible way of producing tiny neutron beams together with an enhanced signal to background ratio. The use of such micro beams is illustrated by the study of micrometric diameter magnetic wires.

  20. A Beam Shape Oscillation Monitor for HERA

    NASA Astrophysics Data System (ADS)

    Afanasyev, O. V.; Baluev, A. B.; Gubrienko, K. I.; Merker, E. A.; Wittenburg, K.; Krouptchenkow, I.

    2006-11-01

    The perfect matching of the injecting beam phase space with the accelerator lattice is a very important problem. Its successful solution allows excluding possible mismatch emittance blow-up and worsening of the beam characteristics, that is necessary to get the highest possible luminosity in hadron accelerators. The mismatch can be controlled by measuring sizes oscillation on the first revolutions of the injected beam at a certain orbit point. Designed for this purpose the construction, acquisition electronics, software controlling of the operation and data processing of such a monitor are described. A first test result with beam is presented.

  1. Isotropic beam bouquets for shaped beam linear accelerator radiosurgery

    NASA Astrophysics Data System (ADS)

    Wagner, Thomas H.; Meeks, Sanford L.; Bova, Frank J.; Friedman, William A.; Buatti, John M.; Bouchet, Lionel G.

    2001-10-01

    In stereotactic radiosurgery and radiotherapy treatment planning, the steepest dose gradient is obtained by using beam arrangements with maximal beam separation. We propose a treatment plan optimization method that optimizes beam directions from the starting point of a set of isotropically convergent beams, as suggested by Webb. The optimization process then individually steers each beam to the best position, based on beam's-eye-view (BEV) critical structure overlaps with the target projection and the target's projected cross sectional area at each beam position. This final optimized beam arrangement maintains a large angular separation between adjacent beams while conformally avoiding critical structures. As shown by a radiosurgery plan, this optimization method improves the critical structure sparing properties of an unoptimized isotropic beam bouquet, while maintaining the same degree of dose conformity and dose gradient. This method provides a simple means of designing static beam radiosurgery plans with conformality indices that are within established guidelines for radiosurgery planning, and with dose gradients that approach those achieved in conventional radiosurgery planning.

  2. Complete shaping of optical vector beams.

    PubMed

    Chen, Zhaozhong; Zeng, Tingting; Qian, Binjie; Ding, Jianping

    2015-07-13

    We propose and experimentally demonstrate the complete and simultaneous modulation of the amplitude, phase and arbitrary state of polarization of optical beams. Based on a 4-f system including a spatial light modulator (SLM), two orthogonally polarized beams serving as the base vector components are produced by a computer generated hologram. The complex amplitude of orthogonal components is realized by a macro-pixel encoding technique purposely designed for phase-only SLMs. Vector beams can be created from the coaxial superposition of the two base beams. This enables us to design optical fields with arbitrarily structured amplitude, phase and polarization by using only one SLM, and thus provides an easy-to-implement route for exploring the novel effects and expanding the functionality of vector beams with space-variant parameters. PMID:26191832

  3. Adaptive Vlasov Simulations of Intense Beams

    SciTech Connect

    Sonnendruecker, Eric; Gutnic, Michael; Haefele, Matthieu; Lemaire, Jean-Louis

    2005-06-08

    Most simulations of intense particle beams are performed nowadays using Particle In Cell (PIC) techniques. Direct grid based Vlasov methods have also been used but mostly for 1D simulations as they become very costly in higher dimensions when using uniform phase space grids. We have recently introduced adaptive mesh refinement techniques that allow us to automatically concentrate the grid points at places where the distribution function is varying most. In this paper we shall introduce this technique and show how it can be used to improve the efficiency of grid based Vlasov solvers.

  4. Spatial shaping of intense femtosecond beams for the generation of high-energy attosecond pulses

    NASA Astrophysics Data System (ADS)

    Constant, E.; Dubrouil, A.; Hort, O.; Petit, S.; Descamps, D.; Mével, E.

    2012-04-01

    We generate high-order harmonics with a spatially shaped TW laser beam. We present and analyse in detail a new approach for shaping an intense laser field to a flat-top intensity profile near focus. We show that this approach is well adapted for high harmonic generation with high-energy fundamental pulses and highlight the possibilities for generating high-energy attosecond pulses.

  5. C-shaped electron beams: design, experimental production and application

    NASA Astrophysics Data System (ADS)

    Mousley, M.; Thirunavukkarasu, G.; Babiker, M.; Yuan, J.

    2015-08-01

    The development of metamaterials operating at visible light wavelengths requires metamaterials to be produced with nanoscale structure over large areas. Improvements in the efficiency of electron beam lithography (EBL) could play an important role in accelerating this development. In this paper we show the production of a shaped probe for use in EBL. A phase structured electron wave containing vortices can be focused to produce a C-shaped cross section. Local spatial frequency analysis shows that both the gap and overall size of the C-shape can be easily controlled. We present the generation of such a C-shaped electron beam using a holographic binary amplitude diffraction mask. Thin AlF3 film is exposed to the C-shaped diffraction order and demonstrates the facile production of both a metallic C-shaped structure as well as the etching of a C-shaped hole.

  6. An Adaptable Metric Shapes Perceptual Space.

    PubMed

    Hisakata, Rumi; Nishida, Shin'ya; Johnston, Alan

    2016-07-25

    How do we derive a sense of the separation of points in the world within a space-variant visual system? Visual directions are thought to be coded directly by a process referred to as local sign, in which a neuron acts as a labeled line for the perceived direction associated with its activation [1, 2]. The separations of visual directions, however, are not given, nor are they directly related to the separations of signals on the receptive surface or in the brain, which are modified by retinal and cortical magnification, respectively [3]. To represent the separation of directions veridically, the corresponding neural signals need to be scaled in some way. We considered this scaling process may be influenced by adaptation. Here, we describe a novel adaptation paradigm, which can alter both apparent spatial separation and size. We measured the perceived separation of two dots and the size of geometric figures after adaptation to random dot patterns. We show that adapting to high-density texture not only increases the apparent sparseness (average element separation) of a lower-density pattern, as expected [4], but paradoxically, it reduces the apparent separation of dot pairs and induces apparent shrinkage of geometric form. This demonstrates for the first time a contrary linkage between perceived density and perceived extent. Separation and size appear to be expressed relative to a variable spatial metric whose properties, while not directly observable, are revealed by reductions in both apparent size and texture density. PMID:27426520

  7. Beam Shaping for CARS Measurements in Turbulent Environments

    NASA Technical Reports Server (NTRS)

    Magnotti, Gaetano; Cutler, Andrew D.; Danehy, Paul M.

    2010-01-01

    This paper describes a new technique to mitigate the effect of beam steering on CARS measurements in turbulent, variable density environments. The new approach combines Planar BOXCARS phase-matching with elliptical shaping of one of the beams to generate a signal insensitive to beam steering, while keeping the same spatial resolution. Numerical and experimental results are provided to demonstrate the effectiveness of this approach. One set of experiments investigated the effect of beam shaping in the presence of a controlled and well quantified displacement of the beams at the focal plane. Another set of experiments, more qualitative, proved the effectiveness of the technique in the presence of severe beam steering due to turbulence.

  8. Shaping Bessel beams with a generalized differential operator approach

    NASA Astrophysics Data System (ADS)

    Lopez-Mago, Dorilian; Gutiérrez-Vega, Julio C.

    2016-09-01

    We apply a differential creation operator to an integer order Bessel beam in order to generate novel nondiffracting structures. The resulting phase structure and orbital angular momentum are discussed in detail. We find the parameters that preserve the orbital angular momentum of the seed beam and show how to produce and control shape preserving vortex arrays. In analogy to the Poincaré sphere, our approach is used to develop an operator sphere connecting higher-order Bessel beams.

  9. Simple Array Beam-Shaping Using Phase-Only Adjustments.

    SciTech Connect

    Doerry, Armin W.

    2015-07-01

    Conventional beam-shaping for array antennas is accomplished via an amplitude-taper on the elemental radiators. It is well known that proper manipulation of the elemental phases can also shape the antenna far-field pattern. A fairly simple transformation from a desired amplitude-taper to a phase-taper can yield nearly equivalent results.

  10. Shape threat detection via adaptive computed tomography

    NASA Astrophysics Data System (ADS)

    Masoudi, Ahmad; Thamvichai, Ratchaneekorn; Neifeld, Mark A.

    2016-05-01

    X-ray Computed Tomography (CT) is used widely for screening purposes. Conventional x-ray threat detection systems employ image reconstruction and segmentation algorithms prior to making threat/no-threat decisions. We find that in many cases these pre-processing steps can degrade detection performance. Therefore in this work we will investigate methods that operate directly on the CT measurements. We analyze a fixed-gantry system containing 25 x-ray sources and 2200 photon counting detectors. We present a new method for improving threat detection performance. This new method is a so-called greedy adaptive algorithm which at each time step uses information from previous measurements to design the next measurement. We utilize sequential hypothesis testing (SHT) in order to derive both the optimal "next measurement" and the stopping criterion to insure a target probability of error Pe. We find that selecting the next x-ray source according to such a greedy adaptive algorithm, we can reduce Pe by a factor of 42.4× relative to the conventional measurement sequence employing all 25 sources in sequence.

  11. Optical beam shaping and diffraction free waves: A variational approach

    NASA Astrophysics Data System (ADS)

    Gemmer, John A.; Venkataramani, Shankar C.; Durfee, Charles G.; Moloney, Jerome V.

    2014-08-01

    We investigate the problem of shaping radially symmetric annular beams into desired intensity patterns along the optical axis. Within the Fresnel approximation, we show that this problem can be expressed in a variational form equivalent to the one arising in phase retrieval. Using the uncertainty principle we prove various rigorous lower bounds on the functional; these lower bounds estimate the L2 error for the beam shaping problem in terms of the design parameters. We also use the method of stationary phase to construct a natural ansatz for a minimizer in the short wavelength limit. We illustrate the implications of our results by applying the method of stationary phase coupled with the Gerchberg-Saxton algorithm to beam shaping problems arising in the remote delivery of beams and pulses.

  12. Shape and Individual Variability of the Blur Adaptation Curve

    PubMed Central

    Vera-Diaz, Fuensanta A.; Woods, Russell L.; Peli, Eli

    2010-01-01

    We are interested in clinical implications of adaptation to blurred and sharpened images. Therefore, we investigated repeatability, individual variability and characteristics of the adaptation curves in normally-sighted individuals (n=39). The point of subjective neutrality (PSN – the slope of the spatial spectrum of the image that appears normal) following adaptation was measured for each adaptation level and was used to derive individual adaptation curves for each subject. Adaptation curves were fitted with a modified Tukey biweight function as the curves were found to be tumbled-S shaped and asymmetrical for blur and sharp in some subjects. The adaptation curve was found to be an individual characteristic as inter-subject variability exceeds test-retest variability. The existence of individual variability may have implications for the prescription and clinical success of optical devices as well as image enhancement rehabilitation options. PMID:20417657

  13. Data exploder for variable shaped beam exposure

    NASA Astrophysics Data System (ADS)

    Nogatch, John; Kirsch, Hartmut; Shi, Jun

    2007-05-01

    As the industry moves to 45nm and beyond, rapidly increasing file sizes are an obstacle to achieving fast turnaround time for mask manufacturing. Conventional Mask Data Preparation (MDP) requires the production of large files, in a format specific to each make and model of E-beam tool. An alternative approach extracts the data from a data file already present in the MDP flow, and provides it directly to the E-beam tool. This extraction is called a "Data Exploder", because the output data volume can be larger than the input data. Exploding the data in real-time saves the time required to write and then read large disk files. The Data Exploder is compatible with multithread and multiprocess parallel reading. The practical application and limitations of the Data Exploder are described, including throughput performance, requirements for disk storage, network interconnect, and CPU configurations.

  14. How Neutrophils Shape Adaptive Immune Responses

    PubMed Central

    Leliefeld, Pieter H. C.; Koenderman, Leo; Pillay, Janesh

    2015-01-01

    Neutrophils are classically considered as cells pivotal for the first line of defense against invading pathogens. In recent years, evidence has accumulated that they are also important in the orchestration of adaptive immunity. Neutrophils rapidly migrate in high numbers to sites of inflammation (e.g., infection, tissue damage, and cancer) and are subsequently able to migrate to draining lymph nodes (LNs). Both at the site of inflammation as well as in the LNs, neutrophils can engage with lymphocytes and antigen-presenting cells. This crosstalk occurs either directly via cell–cell contact or via mediators, such as proteases, cytokines, and radical oxygen species. In this review, we will discuss the current knowledge regarding locations and mechanisms of interaction between neutrophils and lymphocytes in the context of homeostasis and various pathological conditions. In addition, we will highlight the complexity of the microenvironment that is involved in the generation of suppressive or stimulatory neutrophil phenotypes. PMID:26441976

  15. Beam profile shaping for laser radars that use detector arrays.

    PubMed

    Veldkamp, W B; Kastner, C J

    1982-01-15

    The beam shaper we developed shapes the transmit beam of a CO(2) laser radar that uses a linear detector array. It consists of a diffraction grating and an anamorphic prism beam compressor and produces a stretched profile that efficiently and uniformly illuminates the far-field footprint of the detector array. The diffraction grating phase modulates the near field or the laser beam to generate a far-field flattop intensity profile, whereas the compressor produces the necessary profile eccentricity. We have achieved conversion efficiencies in the 70-90% range. PMID:20372453

  16. Fiber optical beam shaping using polymeric structures

    NASA Astrophysics Data System (ADS)

    Rodrigues Ribeiro, R. S.; Queirós, R. B.; Guerreiro, A.; Ecoffet, C.; Soppera, O.; Jorge, P. A. S.

    2014-05-01

    A method to control the output intensity profile of optical fibers is presented. Using guided wave photopolymerization in multimode structures the fabrication with modal assisted shaping of polymeric micro lenses is demonstrated. Results showing that a given linear polarized mode can be selectively excited controlling the intensity distribution at the fiber tip are presented. This pattern is then reproduced in the polymeric micro structure fabricated at the fiber tip thus modulating its output intensity distribution. Such structures can therefore be used to obtain at the fiber tip predetermined intensity patterns for attaining optical trapping or patterned illumination.

  17. Coherent backscattering cone shape depends on the beam size.

    PubMed

    Bi, Renzhe; Dong, Jing; Lee, Kijoon

    2012-09-10

    Coherent backscattering (CBS) is a beautiful physical phenomenon that takes place in a highly scattering medium, which has potential application in noninvasive optical property measurement. The current model that explains the CBS cone shape, however, assumes the incoming beam diameter is infinitely large compared to the transport length. In this paper, we evaluate the effect of a finite scalar light illumination area on the CBS cone, both theoretically and experimentally. The quantitative relationship between laser beam size and the CBS cone shape is established by using two different finite beam models (uniform top hat and Gaussian distribution). A series of experimental data with varying beam diameters is obtained for comparison with the theory. Our study shows the CBS cone shape begins to show distortion when beam size becomes submillimeter, and this effect should not be ignored in general. In biological tissue where a normal large beam CBS cone is too narrow for detection, this small beam CBS may be more advantageous for more accurate and higher resolution tissue characterization. PMID:22968267

  18. Dynamically deformable reflective membrane for laser beam shaping and smoothing

    NASA Astrophysics Data System (ADS)

    Masson, J.; Bitterli, R.; Bich, A.; Noell, W.; Voelkel, R.; Weible, K.; de Rooij, N.

    2012-03-01

    We show a laser beam shaping device made of a deformable continuous reflective membrane fabricated over a scanning stage. The combination of two actuator schemes enables shaping and smoothing of a laser beam with a unique compact device. It is designed to shape an input laser beam into a flat top or Gaussian intensity profile, to support high optical load and to potentially reduce speckle contrast. One single electrode is needed to deform the whole membrane into multiple sub-reflecting concave elements. The scanning stage is used simultaneously to smooth out the remaining interference patterns. The fabrication process is based on SOI wafer and parylene refilling to enable the fabrication of a 100 % fill factor 5 by 5 mm2 deformable membrane. Applications for such device are laser machining and laser display.

  19. Scattered electron beams shaped by a multileaf collimator

    NASA Astrophysics Data System (ADS)

    Moran, Jean Marie

    Recent developments in conformal radiation therapy have focused primarily on applying computer-controlled equipment and techniques to photon beams. Despite favorable characteristics of the dose fall-off with depth for electron beams, their application to conformal therapy has been limited. Factors such as geometrically limiting applicator systems, lack of automatic field shaping, and dose calculation model limitations must be addressed before routine clinical use of electron beams for conformal radiotherapy becomes common. This work evaluates dose characteristics and modeling of dose distributions and output factors for a system specifically designed for computer-controlled collimation of dual-foil scattered and scanned electron beams. Dose characteristics determined from measured depth dose curves and profiles were evaluated for multileaf- collimated and applicator-collimated beams produced by the dual-foil scattered gantry of a two-gantry racetrack microtron system. The resulting dose distributions and characteristics were used to evaluate and modify the existing 3-D electron pencil beam algorithm in UMPlan, the University of Michigan treatment planning system, to predict relative dose distributions for MLC-shaped fields. Output factors (dose of a field relative to that of a reference field) were measured, analyzed, and modeled for MLC-collimated rectangular and shaped fields. For output factor calculations, two models were evaluated: a pencil beam-derived model and an empirical edge model originally developed for photon dose calculations. The current work shows that the dosimetric characteristics of MLC and applicator-collimated beams of the racetrack microtron are similar once the collimation geometry is accounted for. The dosimetric characteristics are also consistent with those for other dual-foil scattered machines with applicator systems and earlier generation scanned beams collimated with trimmer bars. By accounting for collimation geometry, electron

  20. Freeform beam shaping for high-power multimode lasers

    NASA Astrophysics Data System (ADS)

    Laskin, Alexander; Laskin, Vadim

    2014-03-01

    Widening of using high power multimode lasers in industrial laser material processing is accompanied by special requirements to irradiance profiles in such technologies like metal or plastics welding, cladding, hardening, brazing, annealing, laser pumping and amplification in MOPA lasers. Typical irradiance distribution of high power multimode lasers: free space solid state, fiber-coupled solid state and diodes lasers, fiber lasers, is similar to Gaussian. Laser technologies can be essentially improved when irradiance distribution on a workpiece is uniform (flattop) or inverse-Gauss; when building high-power pulsed lasers it is possible to enhance efficiency of pumping and amplification by applying super-Gauss irradiance distribution with controlled convexity. Therefore, "freeform" beam shaping of multimode laser beams is an important task. A proved solution is refractive field mapping beam shaper like Shaper capable to control resulting irradiance profile - with the same unit it is possible to get various beam profiles and choose optimum one for a particular application. Operational principle of these devices implies transformation of laser irradiance distribution by conserving beam consistency, high transmittance, providing collimated low divergent output beam. Using additional optics makes it possible to create resulting laser spots of necessary size and round, elliptical or linear shape. Operation out of focal plane and, hence, in field of lower wavefront curvature, allows extending depth of field. The refractive beam shapers are implemented as telescopes and collimating systems, which can be connected directly to fiber-coupled lasers or fiber lasers, thus combining functions of beam collimation and irradiance transformation.

  1. Adaptive beam shaper based on a single liquid crystal cell

    NASA Astrophysics Data System (ADS)

    Zenou, Michael; Reznikov, Mitya; Manevich, Michael; Varshal, Joseph; Reznikov, Yuriy; Kotler, Zvi

    2013-03-01

    We describe a method allowing rapid transformation of a Gaussian input laser beam into a variety of beam profiles such as top-hat and ring-shaped. A liquid crystal cell with a simple binary phase structure was designed and prepared using microlithographic processes. The new design provides an electrically tunable, variable mode, beam shaping device with millisecond response time (ton˜5 ms and toff˜35 ms).

  2. Laser Beam Steering/shaping for Free Space Optical Communication

    NASA Technical Reports Server (NTRS)

    Wang, Xinghua; Wang, Bin; Bos, Philip J.; Anderson, James E.; Pouch, John; Miranda, Felix; McManamon, Paul F.

    2004-01-01

    The 2-D Optical Phased Array (OPA) antenna based on a Liquid Crystal On Silicon (LCoS) device can be considered for use in free space optical communication as an active beam controlling device. Several examples of the functionality of the device include: beam steering in the horizontal and elevation direction; high resolution wavefront compensation in a large telescope; and beam shaping with the computer generated kinoform. Various issues related to the diffraction efficiency, steering range, steering accuracy as well as the magnitude of wavefront compensation are discussed.

  3. Crack detection in beams in noisy conditions using scale fractal dimension analysis of mode shapes

    NASA Astrophysics Data System (ADS)

    Bai, R. B.; Ostachowicz, W.; Cao, M. S.; Su, Z.

    2014-06-01

    Fractal dimension analysis of mode shapes has been actively studied in the area of structural damage detection. The most prominent features of fractal dimension analysis are high sensitivity to damage and instant determination of damage location. However, an intrinsic deficiency is its susceptibility to measurement noise, likely obscuring the features of damage. To address this deficiency, this study develops a novel damage detection method, scale fractal dimension (SFD) analysis of mode shapes, based on combining the complementary merits of a stationary wavelet transform (SWT) and Katz’s fractal dimension in damage characterization. With this method, the SWT is used to decompose a mode shape into a set of scale mode shapes at scale levels, with damage information and noise separated into distinct scale mode shapes because of their dissimilar scale characteristics; the Katz’s fractal dimension individually runs on every scale mode shape in the noise-adaptive condition provided by the SWT to canvass damage. Proof of concept for the SFD analysis is performed on cracked beams simulated by the spectral finite element method; the reliability of the method is assessed using Monte Carlo simulation to mimic the operational variability in realistic damage diagnosis. The proposed method is further experimentally validated on a cracked aluminum beam with mode shapes acquired by a scanning laser vibrometer. The results show that the SFD analysis of mode shapes provides a new strategy for damage identification in noisy conditions.

  4. A method for generating double-ring-shaped vector beams

    NASA Astrophysics Data System (ADS)

    Huan, Chen; Xiao-Hui, Ling; Zhi-Hong, Chen; Qian-Guang, Li; Hao, Lv; Hua-Qing, Yu; Xu-Nong, Yi

    2016-07-01

    We propose a method for generating double-ring-shaped vector beams. A step phase introduced by a spatial light modulator (SLM) first makes the incident laser beam have a nodal cycle. This phase is dynamic in nature because it depends on the optical length. Then a Pancharatnam–Berry phase (PBP) optical element is used to manipulate the local polarization of the optical field by modulating the geometric phase. The experimental results show that this scheme can effectively create double-ring-shaped vector beams. It provides much greater flexibility to manipulate the phase and polarization by simultaneously modulating the dynamic and the geometric phases. Project supported by the National Natural Science Foundation of China (Grant No. 11547017), the Hubei Engineering University Research Foundation, China (Grant No. z2014001), and the Natural Science Foundation of Hubei Province, China (Grant No. 2014CFB578).

  5. Beam based alignment of C-shaped quadrupole magnets

    SciTech Connect

    Portmann, G.; Robin, D.

    1998-06-01

    Many storage rings have implemented a method of finding the positional offset between the electrical center of the beam position monitors (BPM) and the magnetic center of the adjacent quadrupole magnets. The algorithm for accomplishing this is usually based on modulating the current in the quadrupole magnet and finding the beam position that minimizes the orbit perturbation. When the quadrupole magnet is C-shaped, as it is for many light sources, the modulation method can produce an erroneous measurement of the magnetic center in the horizontal plane. When the current in a C-shaped quadrupole is changed, there is an additional dipole component in the vertical field. Due to nonlinearities in the hysteresis cycle of the C-magnet geometry, the beam-based alignment technique at the Advanced Light Source (ALS) deviated horizontally by .5 mm from the actual magnetic center. By modifying the technique, the offsets were measured to an accuracy of better than 50 {micro}m.

  6. Meta-q-plate for complex beam shaping

    PubMed Central

    Ji, Wei; Lee, Chun-Hong; Chen, Peng; Hu, Wei; Ming, Yang; Zhang, Lijian; Lin, Tsung-Hsien; Chigrinov, Vladimir; Lu, Yan-Qing

    2016-01-01

    Optical beam shaping plays a key role in optics and photonics. In this work, meta-q-plate featured by arbitrarily space-variant optical axes is proposed and demonstrated via liquid crystal photoalignment based on a polarization-sensitive alignment agent and a dynamic micro-lithography system. Meta-q-plates with multiple-, azimuthally/radially variant topological charges and initial azimuthal angles are fabricated. Accordingly, complex beams with elliptical, asymmetrical, multi-ringed and hurricane transverse profiles are generated, making the manipulation of optical vortex up to an unprecedented flexibility. The evolution, handedness and Michelson interferogram of the hurricane one are theoretically analysed and experimentally verified. The design facilitates the manipulation of polarization and spatial degrees of freedom of light in a point-to-point manner. The realization of meta-q-plate drastically enhances the capability of beam shaping and may pave a bright way towards optical manipulations, OAM based informatics, quantum optics and other fields. PMID:27149897

  7. Meta-q-plate for complex beam shaping.

    PubMed

    Ji, Wei; Lee, Chun-Hong; Chen, Peng; Hu, Wei; Ming, Yang; Zhang, Lijian; Lin, Tsung-Hsien; Chigrinov, Vladimir; Lu, Yan-Qing

    2016-01-01

    Optical beam shaping plays a key role in optics and photonics. In this work, meta-q-plate featured by arbitrarily space-variant optical axes is proposed and demonstrated via liquid crystal photoalignment based on a polarization-sensitive alignment agent and a dynamic micro-lithography system. Meta-q-plates with multiple-, azimuthally/radially variant topological charges and initial azimuthal angles are fabricated. Accordingly, complex beams with elliptical, asymmetrical, multi-ringed and hurricane transverse profiles are generated, making the manipulation of optical vortex up to an unprecedented flexibility. The evolution, handedness and Michelson interferogram of the hurricane one are theoretically analysed and experimentally verified. The design facilitates the manipulation of polarization and spatial degrees of freedom of light in a point-to-point manner. The realization of meta-q-plate drastically enhances the capability of beam shaping and may pave a bright way towards optical manipulations, OAM based informatics, quantum optics and other fields. PMID:27149897

  8. Meta-q-plate for complex beam shaping

    NASA Astrophysics Data System (ADS)

    Ji, Wei; Lee, Chun-Hong; Chen, Peng; Hu, Wei; Ming, Yang; Zhang, Lijian; Lin, Tsung-Hsien; Chigrinov, Vladimir; Lu, Yan-Qing

    2016-05-01

    Optical beam shaping plays a key role in optics and photonics. In this work, meta-q-plate featured by arbitrarily space-variant optical axes is proposed and demonstrated via liquid crystal photoalignment based on a polarization-sensitive alignment agent and a dynamic micro-lithography system. Meta-q-plates with multiple-, azimuthally/radially variant topological charges and initial azimuthal angles are fabricated. Accordingly, complex beams with elliptical, asymmetrical, multi-ringed and hurricane transverse profiles are generated, making the manipulation of optical vortex up to an unprecedented flexibility. The evolution, handedness and Michelson interferogram of the hurricane one are theoretically analysed and experimentally verified. The design facilitates the manipulation of polarization and spatial degrees of freedom of light in a point-to-point manner. The realization of meta-q-plate drastically enhances the capability of beam shaping and may pave a bright way towards optical manipulations, OAM based informatics, quantum optics and other fields.

  9. Adaptive optics for laser power beaming

    NASA Technical Reports Server (NTRS)

    Leland, Robert P.

    1992-01-01

    It has been proposed to use a high energy pulsed laser to beam power into space for satellites or a lunar base. The effects of atmospheric transmission are critical to such a system. Thermal blooming in the atmosphere can cause the beam to spread rapidly. Atmospheric turbulence can cause beam bending or beam spreading, resulting in the loss of transmitted energy that fails to hit the target receiver.

  10. Diamond turning considerations in the manufacture of beam shaping optics

    NASA Astrophysics Data System (ADS)

    Davis, Gregg E.; Herrit, Gary L.; Hedges, Alan R.

    2011-10-01

    Advances in diamond turning technology have offered optical designers new degrees of freedom in beam shaping optics. While designers have these new manufacturing methods at their disposal, they may not be aware of special process limitations and cost drivers. The purpose of this paper is to present some of these critical manufacturing issues. We will discuss briefly special beam shaping optic types and applications. Then in more detail we will discuss the four key diamond turning techniques and the types of optics they can produce. These four key manufacturing techniques are: standard 2 axis diamond turning, slow tool servo, fast tool servo, micromilling. During the discussion we will present surface shapes, process limitations, as well as cost drivers for each technique. In summary will we present this data in a matrix that will aid the designer in selecting manufacturing techniques and optic types.

  11. Interference and Shaping in Sensorimotor Adaptations with Rewards

    PubMed Central

    Darshan, Ran; Leblois, Arthur; Hansel, David

    2014-01-01

    When a perturbation is applied in a sensorimotor transformation task, subjects can adapt and maintain performance by either relying on sensory feedback, or, in the absence of such feedback, on information provided by rewards. For example, in a classical rotation task where movement endpoints must be rotated to reach a fixed target, human subjects can successfully adapt their reaching movements solely on the basis of binary rewards, although this proves much more difficult than with visual feedback. Here, we investigate such a reward-driven sensorimotor adaptation process in a minimal computational model of the task. The key assumption of the model is that synaptic plasticity is gated by the reward. We study how the learning dynamics depend on the target size, the movement variability, the rotation angle and the number of targets. We show that when the movement is perturbed for multiple targets, the adaptation process for the different targets can interfere destructively or constructively depending on the similarities between the sensory stimuli (the targets) and the overlap in their neuronal representations. Destructive interferences can result in a drastic slowdown of the adaptation. As a result of interference, the time to adapt varies non-linearly with the number of targets. Our analysis shows that these interferences are weaker if the reward varies smoothly with the subject's performance instead of being binary. We demonstrate how shaping the reward or shaping the task can accelerate the adaptation dramatically by reducing the destructive interferences. We argue that experimentally investigating the dynamics of reward-driven sensorimotor adaptation for more than one sensory stimulus can shed light on the underlying learning rules. PMID:24415925

  12. Adaptive shaping of cortical response selectivity in the vibrissa pathway

    PubMed Central

    Zheng, He J. V.; Wang, Qi

    2015-01-01

    One embodiment of context-dependent sensory processing is bottom-up adaptation, where persistent stimuli decrease neuronal firing rate over hundreds of milliseconds. Adaptation is not, however, simply the fatigue of the sensory pathway, but shapes the information flow and selectivity to stimulus features. Adaptation enhances spatial discriminability (distinguishing stimulus location) while degrading detectability (reporting presence of the stimulus), for both the ideal observer of the cortex and awake, behaving animals. However, how the dynamics of the adaptation shape the cortical response and this detection and discrimination tradeoff is unknown, as is to what degree this phenomenon occurs on a continuum as opposed to a switching of processing modes. Using voltage-sensitive dye imaging in anesthetized rats to capture the temporal and spatial characteristics of the cortical response to tactile inputs, we showed that the suppression of the cortical response, in both magnitude and spatial spread, is continuously modulated by the increasing amount of energy in the adapting stimulus, which is nonuniquely determined by its frequency and velocity. Single-trial ideal observer analysis demonstrated a tradeoff between detectability and spatial discriminability up to a moderate amount of adaptation, which corresponds to the frequency range in natural whisking. This was accompanied by a decrease in both detectability and discriminability with high-energy adaptation, which indicates a more complex coupling between detection and discrimination than a simple switching of modes. Taken together, the results suggest that adaptation operates on a continuum and modulates the tradeoff between detectability and discriminability that has implications for information processing in ethological contexts. PMID:25787959

  13. Multifunctional micro-optical elements for laser beam homogenizing and beam shaping

    NASA Astrophysics Data System (ADS)

    Bich, A.; Rieck, J.; Dumouchel, C.; Roth, S.; Weible, K. J.; Eisner, M.; Voelkel, R.; Zimmermann, M.; Rank, M.; Schmidt, M.; Bitterli, R.; Ramanan, N.; Ruffieux, P.; Scharf, T.; Noell, W.; Herzig, H.-P.; De Rooij, Nico

    2008-02-01

    Refractive, diffractive and reflective micro-optical elements for laser beam shaping and homogenizing have been manufactured and tested. The presented multifunctional optical elements are used for shaping arbitrary laser beam profiles into a variety of geometries like, a homogeneous spot array or line pattern, a laser light sheet or flat-top intensity profiles. The resulting profiles are strongly influenced by the beam properties of the laser and by diffraction and interference effects at the micro-optical elements. We present general design rules for beam shaping and homogenizing. We demonstrate the application of such multifunctional micro-optical elements for a variety of applications from micro-laser machining to laser diagnostic systems.

  14. Filamentation of Beam-Shaped Femtosecond Laser Pulses

    SciTech Connect

    Polynkin, Pavel; Kolesik, Miroslav; Moloney, Jerome

    2010-10-08

    When ultra-intense and ultra-short optical pulses propagate in transparent dielectrics, the dynamic balance between multiple linear and nonlinear effects results in the generation of laser filaments. These peculiar objects have numerous interesting properties and can be potentially used in a variety of applications from remote sensing to the optical pulse compression down to few optical cycles to guiding lightning discharges away from sensitive sites. Materializing this practical potential is not straightforward owing to the complexity of the physical picture of filamentation. In this paper, we discuss recent experiments on using beam shaping as a means of control over the filament formation and dynamics. Two particular beam shapes that we have investigated so far are Bessel and Airy beams. The diffraction-free propagation of femtosecond Bessel beams allows for the creation of extended plasma channels in air. These extended filaments can be used for the generation of energetic optical pulses with the duration in the few-cycle range. In the case of filamentation of femtosecond Airy beams, the self-bending property of these beams allows for the creation of curved filaments. This is a new regime of the intense laser-pulse propagation in which the linear self-bending property of the beam competes against the nonlinear self-channeling. The bent filaments generated by ultra-intense Airy beams emit forward-propagating broadband radiation. Analysis of the spatial and spectral distribution of this emission provides for a valuable tool for analyzing the evolution of the ultra-intense optical pulse along the optical path.

  15. Electron-beam-assisted superplastic shaping of nanoscale amorphous silica

    PubMed Central

    Zheng, Kun; Wang, Chengcai; Cheng, Yong-Qiang; Yue, Yonghai; Han, Xiaodong; Zhang, Ze; Shan, Zhiwei; Mao, Scott X; Ye, Miaomiao; Yin, Yadong; Ma, Evan

    2010-01-01

    Glasses are usually shaped through the viscous flow of a liquid before its solidification, as practiced in glass blowing. At or near room temperature (RT), oxide glasses are known to be brittle and fracture upon any mechanical deformation for shape change. Here, we show that with moderate exposure to a low-intensity (<1.8×10−2 A cm−2) electron beam (e-beam), dramatic shape changes can be achieved for nanoscale amorphous silica, at low temperatures and strain rates >10−4 per second. We show not only large homogeneous plastic strains in compression for nanoparticles but also superplastic elongations >200% in tension for nanowires (NWs). We also report the first quantitative comparison of the load-displacement responses without and with the e-beam, revealing dramatic difference in the flow stress (up to four times). This e-beam-assisted superplastic deformability near RT is useful for processing amorphous silica and other conventionally-brittle materials for their applications in nanotechnology. PMID:20975693

  16. Gaussian beam profile shaping apparatus, method therefore and evaluation thereof

    DOEpatents

    Dickey, F.M.; Holswade, S.C.; Romero, L.A.

    1999-01-26

    A method and apparatus maps a Gaussian beam into a beam with a uniform irradiance profile by exploiting the Fourier transform properties of lenses. A phase element imparts a design phase onto an input beam and the output optical field from a lens is then the Fourier transform of the input beam and the phase function from the phase element. The phase element is selected in accordance with a dimensionless parameter which is dependent upon the radius of the incoming beam, the desired spot shape, the focal length of the lens and the wavelength of the input beam. This dimensionless parameter can also be used to evaluate the quality of a system. In order to control the radius of the incoming beam, optics such as a telescope can be employed. The size of the target spot and the focal length can be altered by exchanging the transform lens, but the dimensionless parameter will remain the same. The quality of the system, and hence the value of the dimensionless parameter, can be altered by exchanging the phase element. The dimensionless parameter provides design guidance, system evaluation, and indication as to how to improve a given system. 27 figs.

  17. Gaussian beam profile shaping apparatus, method therefor and evaluation thereof

    DOEpatents

    Dickey, Fred M.; Holswade, Scott C.; Romero, Louis A.

    1999-01-01

    A method and apparatus maps a Gaussian beam into a beam with a uniform irradiance profile by exploiting the Fourier transform properties of lenses. A phase element imparts a design phase onto an input beam and the output optical field from a lens is then the Fourier transform of the input beam and the phase function from the phase element. The phase element is selected in accordance with a dimensionless parameter which is dependent upon the radius of the incoming beam, the desired spot shape, the focal length of the lens and the wavelength of the input beam. This dimensionless parameter can also be used to evaluate the quality of a system. In order to control the radius of the incoming beam, optics such as a telescope can be employed. The size of the target spot and the focal length can be altered by exchanging the transform lens, but the dimensionless parameter will remain the same. The quality of the system, and hence the value of the dimensionless parameter, can be altered by exchanging the phase element. The dimensionless parameter provides design guidance, system evaluation, and indication as to how to improve a given system.

  18. Optical Manipulation with Plasmonic Beam Shaping Antenna Structures

    DOE PAGESBeta

    Jun, Young Chul; Brener, Igal

    2012-01-01

    Near-field optical trapping of objects using plasmonic antenna structures has recently attracted great attention. However, metal nanostructures also provide a compact platform for general wavefront engineering of intermediate and far-field beams. Here, we analyze optical forces generated by plasmonic beam shaping antenna structures and show that they can be used for general optical manipulation such as guiding of a dielectric particle along a linear or curved trajectory. This removes the need for bulky diffractive optical components and facilitates the integration of optical force manipulation into a highly functional, compact system.

  19. Shape Adaptive, Robust Iris Feature Extraction from Noisy Iris Images

    PubMed Central

    Ghodrati, Hamed; Dehghani, Mohammad Javad; Danyali, Habibolah

    2013-01-01

    In the current iris recognition systems, noise removing step is only used to detect noisy parts of the iris region and features extracted from there will be excluded in matching step. Whereas depending on the filter structure used in feature extraction, the noisy parts may influence relevant features. To the best of our knowledge, the effect of noise factors on feature extraction has not been considered in the previous works. This paper investigates the effect of shape adaptive wavelet transform and shape adaptive Gabor-wavelet for feature extraction on the iris recognition performance. In addition, an effective noise-removing approach is proposed in this paper. The contribution is to detect eyelashes and reflections by calculating appropriate thresholds by a procedure called statistical decision making. The eyelids are segmented by parabolic Hough transform in normalized iris image to decrease computational burden through omitting rotation term. The iris is localized by an accurate and fast algorithm based on coarse-to-fine strategy. The principle of mask code generation is to assign the noisy bits in an iris code in order to exclude them in matching step is presented in details. An experimental result shows that by using the shape adaptive Gabor-wavelet technique there is an improvement on the accuracy of recognition rate. PMID:24696801

  20. Shape adaptive, robust iris feature extraction from noisy iris images.

    PubMed

    Ghodrati, Hamed; Dehghani, Mohammad Javad; Danyali, Habibolah

    2013-10-01

    In the current iris recognition systems, noise removing step is only used to detect noisy parts of the iris region and features extracted from there will be excluded in matching step. Whereas depending on the filter structure used in feature extraction, the noisy parts may influence relevant features. To the best of our knowledge, the effect of noise factors on feature extraction has not been considered in the previous works. This paper investigates the effect of shape adaptive wavelet transform and shape adaptive Gabor-wavelet for feature extraction on the iris recognition performance. In addition, an effective noise-removing approach is proposed in this paper. The contribution is to detect eyelashes and reflections by calculating appropriate thresholds by a procedure called statistical decision making. The eyelids are segmented by parabolic Hough transform in normalized iris image to decrease computational burden through omitting rotation term. The iris is localized by an accurate and fast algorithm based on coarse-to-fine strategy. The principle of mask code generation is to assign the noisy bits in an iris code in order to exclude them in matching step is presented in details. An experimental result shows that by using the shape adaptive Gabor-wavelet technique there is an improvement on the accuracy of recognition rate. PMID:24696801

  1. An adaptive control system for wing TE shape control

    NASA Astrophysics Data System (ADS)

    Dimino, I.; Concilio, A.; Schueller, M.; Gratias, A.

    2013-03-01

    A key technology to enable morphing aircraft for enhanced aerodynamic performance is the design of an adaptive control system able to emulate target structural shapes. This paper presents an approach to control the shape of a morphing wing by employing internal, integrated actuators acting on the trailing edge. The adaptive-wing concept employs active ribs, driven by servo actuators, controlled in turn by a dedicated algorithm aimed at shaping the wing cross section, according to a pre-defined geometry. The morphing control platform is presented and a suitable control algorithm is implemented in a dedicated routine for real-time simulations. The work is organized as follows. A finite element model of the uncontrolled, non-actuated structure is used to obtain the plant model for actuator torque and displacement control. After having characterized and simulated pure rotary actuator behavior over the structure, selected target wing shapes corresponding to rigid trailing edge rotations are achieved through both open-loop and closed-loop control logics.

  2. Phylogeny and adaptation shape the teeth of insular mice.

    PubMed

    Ledevin, Ronan; Chevret, Pascale; Ganem, Guila; Britton-Davidian, Janice; Hardouin, Emilie A; Chapuis, Jean-Louis; Pisanu, Benoit; da Luz Mathias, Maria; Schlager, Stefan; Auffray, Jean-Christophe; Renaud, Sabrina

    2016-02-10

    By accompanying human travels since prehistorical times, the house mouse dispersed widely throughout the world, and colonized many islands. The origin of the travellers determined the phylogenetic source of the insular mice, which encountered diverse ecological and environmental conditions on the various islands. Insular mice are thus an exceptional model to disentangle the relative role of phylogeny, ecology and climate in evolution. Molar shape is known to vary according to phylogeny and to respond to adaptation. Using for the first time a three-dimensional geometric morphometric approach, compared with a classical two-dimensional quantification, the relative effects of size variation, phylogeny, climate and ecology were investigated on molar shape diversity across a variety of islands. Phylogeny emerged as the factor of prime importance in shaping the molar. Changes in competition level, mostly driven by the presence or absence of the wood mouse on the different islands, appeared as the second most important effect. Climate and size differences accounted for slight shape variation. This evidences a balanced role of random differentiation related to history of colonization, and of adaptation possibly related to resource exploitation. PMID:26842576

  3. Finite Element Analysis of Adaptive-Stiffening and Shape-Control SMA Hybrid Composites

    NASA Technical Reports Server (NTRS)

    Gao, Xiu-Jie; Turner, Travis L.; Burton, Deborah; Brinson, L. Catherine

    2005-01-01

    The usage of shape memory materials has extended rapidly to many fields, including medical devices, actuators, composites, structures and MEMS devices. For these various applications, shape memory alloys (SMAs) are available in various forms: bulk, wire, ribbon, thin film, and porous. In this work, the focus is on SMA hybrid composites with adaptive-stiffening or morphing functions. These composites are created by using SMA ribbons or wires embedded in a polymeric based composite panel/beam. Adaptive stiffening or morphing is activated via selective resistance heating or uniform thermal loads. To simulate the thermomechanical behavior of these composites, a SMA model was implemented using ABAQUS user element interface and finite element simulations of the systems were studied. Several examples are presented which show that the implemented model can be a very useful design and simulation tool for SMA hybrid composites.

  4. Ultra-precise holographic beam shaping for microscopic quantum control.

    PubMed

    Zupancic, Philip; Preiss, Philipp M; Ma, Ruichao; Lukin, Alexander; Eric Tai, M; Rispoli, Matthew; Islam, Rajibul; Greiner, Markus

    2016-06-27

    High-resolution addressing of individual ultracold atoms, trapped ions or solid state emitters allows for exquisite control in quantum optics experiments. This becomes possible through large aperture magnifying optics that project microscopic light patterns with diffraction limited performance. We use programmable amplitude holograms generated on a digital micromirror device to create arbitrary microscopic beam shapes with full phase and amplitude control. The system self-corrects for aberrations of up to several λ and reduces them to λ/50, leading to light patterns with a precision on the 10-4 level. We demonstrate aberration-compensated beam shaping in an optical lattice experiment and perform single-site addressing in a quantum gas microscope for 87Rb. PMID:27410551

  5. Ultra-precise holographic beam shaping for microscopic quantum control

    NASA Astrophysics Data System (ADS)

    Zupancic, Philip; Preiss, Philipp M.; Ma, Ruichao; Lukin, Alexander; Eric Tai, M.; Rispoli, Matthew; Islam, Rajibul; Greiner, Markus

    2016-06-01

    High-resolution addressing of individual ultracold atoms, trapped ions or solid state emitters allows for exquisite control in quantum optics experiments. This becomes possible through large aperture magnifying optics that project microscopic light patterns with diffraction limited performance. We use programmable amplitude holograms generated on a digital micromirror device to create arbitrary microscopic beam shapes with full phase and amplitude control. The system self-corrects for aberrations of up to several $\\lambda$ and reduces them to $\\lambda/50$, leading to light patterns with a precision on the $10^{-4}$ level. We demonstrate aberration-compensated beam shaping in an optical lattice experiment and perform single-site addressing in a quantum gas microscope for $^{87}$Rb.

  6. Controlled-Shape, Ultrasonic-Angle-Beam Standard Reflector

    NASA Technical Reports Server (NTRS)

    Berry, J., Robertf.

    1986-01-01

    New ultrasonic angle-beam standard reflector uses impression of letter "l" steel-die stamp. NDE techniques and standard reflector apply to use of pulse-echo-type ultrasonic equipment for inspection of wrought metals including forgings and forging stock; rolled billet, bar or plate; and extruded bar, tube, and shapes. "l" reference standard reflector affords advantages of easy insertion in inspected item using common hand-tools and greatly reduced implementation time through elimination of machining operations.

  7. Flexible beam shaping system using fly's eye condenser.

    PubMed

    Lindlein, Norbert; Bich, Andreas; Eisner, Martin; Harder, Irina; Lano, Maik; Voelkel, Reinhard; Weible, Ken; Zimmermann, Maik

    2010-04-20

    Normally, fly's eye condensers are used to homogenize light. However, in the case of fully coherent light, a fly's eye condenser, in connection with some simple optical elements, such as a diffractive axicon, a grating, and a telescope, can be used as a quite flexible beam shaping system, forming arrays of rings, parts of rings, or other structures with varying diameters. We present the principle, some simulation results, and some first experimental results. PMID:20411020

  8. Design of a shape adaptive airfoil actuated by a Shape Memory Alloy strip for airplane tail

    NASA Astrophysics Data System (ADS)

    Shirzadeh, R.; Raissi Charmacani, K.; Tabesh, M.

    2011-04-01

    Of the factors that mainly affect the efficiency of the wing during a special flow regime, the shape of its airfoil cross section is the most significant. Airfoils are generally designed for a specific flight condition and, therefore, are not fully optimized in all flight conditions. It is very desirable to have an airfoil with the ability to change its shape based on the current regime. Shape memory alloy (SMA) actuators activate in response to changes in the temperature and can recover their original configuration after being deformed. This study presents the development of a method to control the shape of an airfoil using SMA actuators. To predict the thermomechanical behaviors of an SMA thin strip, 3D incremental formulation of the SMA constitutive model is implemented in FEA software package ABAQUS. The interactions between the airfoil structure and SMA thin strip actuator are investigated. Also, the aerodynamic performance of a standard airfoil with a plain flap is compared with an adaptive airfoil.

  9. Aplanatic beam shaping for diffraction limited beam circularization of tapered laser diodes

    NASA Astrophysics Data System (ADS)

    Heinrich, Arne; Hagen, Clemens; Harlander, Maximilian; Nussbaumer, Bernhard

    2014-03-01

    Many laser applications require a circular, astigmatism-free, diffraction limited, high power beam. A tapered laser diode can generate up to 6 W output power in a diffraction limited beam. However the beam is elliptical and highly astigmatic rendering the design of beam shaping challenging. We present a diffraction limited beam shaping design, especially suitable to circularize and collimate highly astigmatic beams. The setup consists of a simple plano-convex cylindrical lens in the aplanatic condition and an asphere. The first lens matches the divergence of the fast- to the slow axis at the point where the beam is circular while the following asphere collimates the beam. The aplanatic condition is fulfilled by choosing a glass with a specific refractive index depending on the ratio between fast- and slow axis divergence. This cylindrical lens introduces neither spherical error nor primary coma, which makes it insensitive to misalignment. The setup has been tested with a high power laser diode at 980 nm with a 6 mm long taper (angle 6°) and a facet width of 425 μm. The optics have a transmission of about 90% and the resulting beam has a M2 < 1.5. As a proof of principle 3.2 W were coupled into a 15 μm (NA 0.06) LMA fiber with 55% efficiency corresponding to a brightness B = 140 MW/(cm2 sr). Furthermore the presented beam shaping can easily be extended to bars or multiple emitters to reach power levels that are to date only achievable with complex wavelength combination techniques.

  10. Wave propagation in beams with periodic arrays of airfoil-shaped resonating units

    NASA Astrophysics Data System (ADS)

    Casadei, Filippo; Bertoldi, Katia

    2014-12-01

    This paper presents an analytical and numerical study on the dispersion properties of an Euler-Bernoulli beam immersed in a steady fluid flow with periodic arrays of airfoil-shaped vibration absorbers attached to it. The resonance characteristics of the airfoils generate strong attenuation of flexural waves in the beam occurring at frequencies defined by the properties of the airfoils and the speed of the incident fluid. Analytical and numerical tools are developed to investigate the effects of the incident flow on the dispersion properties and the bandgaps of the system. Both steady and unsteady aerodynamic models are used to model the lift force and the pitching moment acting on the resonators and their effect on the dispersion relations of the system is evaluated. Finally, an effective medium description of the beam is developed to capture its behavior at long-wavelengths. In this regime, the system can be effectively considered as an acoustic metamaterial with adaptive dispersion properties.

  11. 21 CFR 892.5710 - Radiation therapy beam-shaping block.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Radiation therapy beam-shaping block. 892.5710... (CONTINUED) MEDICAL DEVICES RADIOLOGY DEVICES Therapeutic Devices § 892.5710 Radiation therapy beam-shaping block. (a) Identification. A radiation therapy beam-shaping block is a device made of a...

  12. 21 CFR 892.5710 - Radiation therapy beam-shaping block.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Radiation therapy beam-shaping block. 892.5710... (CONTINUED) MEDICAL DEVICES RADIOLOGY DEVICES Therapeutic Devices § 892.5710 Radiation therapy beam-shaping block. (a) Identification. A radiation therapy beam-shaping block is a device made of a...

  13. 21 CFR 892.5710 - Radiation therapy beam-shaping block.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Radiation therapy beam-shaping block. 892.5710... (CONTINUED) MEDICAL DEVICES RADIOLOGY DEVICES Therapeutic Devices § 892.5710 Radiation therapy beam-shaping block. (a) Identification. A radiation therapy beam-shaping block is a device made of a...

  14. 21 CFR 892.5710 - Radiation therapy beam-shaping block.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Radiation therapy beam-shaping block. 892.5710... (CONTINUED) MEDICAL DEVICES RADIOLOGY DEVICES Therapeutic Devices § 892.5710 Radiation therapy beam-shaping block. (a) Identification. A radiation therapy beam-shaping block is a device made of a...

  15. Low Temperature Shape Memory Alloys for Adaptive, Autonomous Systems Project

    NASA Technical Reports Server (NTRS)

    Falker, John; Zeitlin, Nancy; Williams, Martha; Benafan, Othmane; Fesmire, James

    2015-01-01

    The objective of this joint activity between Kennedy Space Center (KSC) and Glenn Research Center (GRC) is to develop and evaluate the applicability of 2-way SMAs in proof-of-concept, low-temperature adaptive autonomous systems. As part of this low technology readiness (TRL) activity, we will develop and train low-temperature novel, 2-way shape memory alloys (SMAs) with actuation temperatures ranging from 0 C to 150 C. These experimental alloys will also be preliminary tested to evaluate their performance parameters and transformation (actuation) temperatures in low- temperature or cryogenic adaptive proof-of-concept systems. The challenge will be in the development, design, and training of the alloys for 2-way actuation at those temperatures.

  16. Shape memory alloy actuated adaptive exhaust nozzle for jet engine

    NASA Technical Reports Server (NTRS)

    Song, Gangbing (Inventor); Ma, Ning (Inventor)

    2009-01-01

    The proposed adaptive exhaust nozzle features an innovative use of the shape memory alloy (SMA) actuators for actively control of the opening area of the exhaust nozzle for jet engines. The SMA actuators remotely control the opening area of the exhaust nozzle through a set of mechanism. An important advantage of using SMA actuators is the reduction of weight of the actuator system for variable area exhaust nozzle. Another advantage is that the SMA actuator can be activated using the heat from the exhaust and eliminate the need of other energy source. A prototype has been designed and fabricated. The functionality of the proposed SMA actuated adaptive exhaust nozzle is verified in the open-loop tests.

  17. Coral thermal tolerance shaped by local adaptation of photosymbionts

    NASA Astrophysics Data System (ADS)

    Howells, E. J.; Beltran, V. H.; Larsen, N. W.; Bay, L. K.; Willis, B. L.; van Oppen, M. J. H.

    2012-02-01

    Coral thermal tolerance is strongly influenced by the identity of obligate photosymbionts, which encompass numerous types belonging to the dinoflagellate genus Symbiodinium. Physiological advantages achieved by partnering with functionally diverse symbionts have been assumed to be available only to corals that can form associations with multiple Symbiodinium types. Functional variation among populations of the same type of Symbiodinium has been overlooked, despite local adaptation being feasible because of large population sizes, genetic isolation and short asexual generation times. Here we demonstrate divergent thermal tolerance in a generalist Symbiodinium type from two different thermal environments. Symbiodinium from the warmer reef maintained greater photo-chemical performance and survivorship when exposed to an elevated temperature of 32°C, both in symbiosis and in culture. Juvenile corals associated with Symbiodinium from the warmer reef grew rapidly when exposed to 32°C, yet underwent bleaching and tissue death when associated with Symbiodinium from the cooler reef. These results demonstrate that Symbiodinium types can adapt to local differences in thermal climate and that this adaptation shapes the fitness of coral hosts. If Symbiodinium populations are able to further adapt to increases in temperature at the pace at which ocean climates warm, they may assist corals to increase their thermal tolerance and persist into the future.

  18. Seed Pubescence and Shape Modulate Adaptive Responses to Fire Cues.

    PubMed

    Gómez-González, Susana; Ojeda, Fernando; Torres-Morales, Patricio; Palma, Jazmín E

    2016-01-01

    Post-fire recruitment by seeds is regarded as an adaptive response in fire-prone ecosystems. Nevertheless, little is known about which heritable seed traits are functional to the main signals of fire (heat and smoke), thus having the potential to evolve. Here, we explored whether three seed traits (pubescence, dormancy and shape) and fire regime modulate seed response to fire cues(heat and smoke). As a model study system, we used Helenium aromaticum (Asteraceae), a native annual forb from the Chilean matorral, where fires are anthropogenic. We related seed trait values with fitness responses (germination and survival) after exposure to heat-shock and smoke experimental treatments on seeds from 10 H. aromaticum wild populations. We performed a phenotypic selection experiment to examine the relationship of seed traits with post-treatment fitness within a population (adaptive hypothesis). We then explored whether fire frequency in natural habitats was associated with trait expression across populations, and with germination and survival responses to experimental fire-cues. We found that populations subjected to higher fire frequency had, in average, more rounded and pubescent seeds than populations from rarely burned areas. Populations with more rounded and pubescent seeds were more resistant to 80°C heat-shock and smoke treatments.There was correlated selection on seed traits: pubescent-rounded or glabrouscent-elongated seeds had the highest probability of germinating after heat-shock treatments. Seed pubescence and shape in H. aromaticum are heritable traits that modulate adaptive responses to fire. Our results provide new insights into the process of plant adaptation to fire and highlight the relevance of human-made fires as a strong evolutionary agent in the Anthropocene. PMID:27438267

  19. Seed Pubescence and Shape Modulate Adaptive Responses to Fire Cues

    PubMed Central

    Gómez-González, Susana; Ojeda, Fernando; Torres-Morales, Patricio; Palma, Jazmín E.

    2016-01-01

    Post-fire recruitment by seeds is regarded as an adaptive response in fire-prone ecosystems. Nevertheless, little is known about which heritable seed traits are functional to the main signals of fire (heat and smoke), thus having the potential to evolve. Here, we explored whether three seed traits (pubescence, dormancy and shape) and fire regime modulate seed response to fire cues(heat and smoke). As a model study system, we used Helenium aromaticum (Asteraceae), a native annual forb from the Chilean matorral, where fires are anthropogenic. We related seed trait values with fitness responses (germination and survival) after exposure to heat-shock and smoke experimental treatments on seeds from 10 H. aromaticum wild populations. We performed a phenotypic selection experiment to examine the relationship of seed traits with post-treatment fitness within a population (adaptive hypothesis). We then explored whether fire frequency in natural habitats was associated with trait expression across populations, and with germination and survival responses to experimental fire-cues. We found that populations subjected to higher fire frequency had, in average, more rounded and pubescent seeds than populations from rarely burned areas. Populations with more rounded and pubescent seeds were more resistant to 80°C heat-shock and smoke treatments.There was correlated selection on seed traits: pubescent-rounded or glabrouscent-elongated seeds had the highest probability of germinating after heat-shock treatments. Seed pubescence and shape in H. aromaticum are heritable traits that modulate adaptive responses to fire. Our results provide new insights into the process of plant adaptation to fire and highlight the relevance of human-made fires as a strong evolutionary agent in the Anthropocene. PMID:27438267

  20. Beam-shape distortion caused by transverse wake fields

    SciTech Connect

    Chao, A.W.; Kheifets, S.

    1983-02-01

    As a particle bunch in a storage ring passes through a region with a transverse impedance, it generates a transverse wake electromagnetic field that is proportional to the transverse displacement of the bunch in the region. The field acts back on the bunch, causing various effects (such as instabilities) in the motion of the bunch. We study one such effect in which a transverse impedance causes the beam to be distorted in its shape. Observed at a fixed location in the storage ring, this distortion does not change from turn to turn; rather, the distortion is static in time. To describe the distortion, the bunch is considered to be divided longitudinally into many slices and the centers of change of the slices are connected into a curve. In the absence of transverse impedance, this curve is a straight line parallel to the direction of motion of the bunch. Perturbed by the transverse wake field, the curve becomes distorted. What we find in this paper is the shape of such a curve. The results obtained are applied to the PEP storage ring. The impedance is assumed to come solely from the rf cavities. We find that the beam shape is sufficiently distorted and hence that loss of luminosity due to this effect becomes a possibility.

  1. Beaconless adaptive-optics technique for HEL beam control

    NASA Astrophysics Data System (ADS)

    Khizhnyak, Anatoliy; Markov, Vladimir

    2016-05-01

    Effective performance of forthcoming laser systems capable of power delivery on a distant target requires an adaptive optics system to correct atmospheric perturbations on the laser beam. The turbulence-induced effects are responsible for beam wobbling, wandering, and intensity scintillation, resulting in degradation of the beam quality and power density on the target. Adaptive optics methods are used to compensate for these negative effects. In its turn, operation of the AOS system requires a reference wave that can be generated by the beacon on the target. This report discusses a beaconless approach for wavefront correction with its performance based on the detection of the target-scattered light. Postprocessing of the beacon-generated light field enables retrieval and detailed characterization of the turbulence-perturbed wavefront -data that is essential to control the adaptive optics module of a high-power laser system.

  2. Laser beacon adaptive optics for power beaming applications

    SciTech Connect

    Fugate, R.Q.

    1994-12-31

    This paper discusses the laser beam control system requirements for power beaming applications. Power beaming applications include electric and thermal engine propulsion for orbit transfer, station changing, and recharging batteries. Beam control includes satellite acquisition, high accuracy tracking, higher order atmospheric compensation using adaptive optics, and precision point-ahead. Beam control may also include local laser beam clean-up with a low order adaptive optics system. This paper also presents results of tracking and higher-order correction experiments on astronomical objects. The results were obtained with a laser beacon adaptive optics system at Phillips Laboratory`s Starfire Optical Range near Albuquerque, NM. At a wavelength of 0.85 {mu}m, the author has achieved Strehl ratios of {approximately}0.50 using laser beacons and {approximately}0.65 using natural stars for exposures longer than one minute on objects of {approximately}8{sup th} magnitude. The resulting point spread function has a full width half maximum (FWHM) of 0.13 arcsec.

  3. Application of genetic algorithm on optimization of laser beam shaping.

    PubMed

    Tsai, Cheng-Mu; Fang, Yi-Chin; Lin, Chia-Te

    2015-06-15

    This study proposes a newly developed optimization method for an aspherical lens system employed in a refractive laser beam shaping system, which performs transformations on laser spots such that they are transformed into flat-tops of any size. In this paper, a genetic algorithm (GA) with multipoint search is proposed as the optimization method, together with macro language in optical simulation software, in order to search for ideal and optimized parameters. In comparison to a traditional two-dimensional (2D) computational method, using the one-dimensional (1D) computation for laser beam shaping can search for the optimal solution approximately twice as fast (after experiments). The optimal results show that when the laser spot shrinks from 3 mm to 1.07 mm, 88% uniformity is achieved, and when the laser spot increases from 3 mm to 5.273 mm, 90% uniformity is achieved. The distances between the lenses for both systems described above are even smaller than the thickness for the first lens, enabling us to conclude that our design objectives of extra light and slimness in the system are achieved. PMID:26193566

  4. Finishing of additively manufactured titanium alloy by shape adaptive grinding (SAG)

    NASA Astrophysics Data System (ADS)

    Beaucamp, Anthony T.; Namba, Yoshiharu; Charlton, Phillip; Jain, Samyak; Graziano, Arthur A.

    2015-06-01

    In recent years, rapid prototyping of titanium alloy components for medical and aeronautics application has become viable thanks to advances in technologies such as electron beam melting (EBM) and selective laser sintering (SLS). However, for many applications the high surface roughness generated by additive manufacturing techniques demands a post-finishing operation to improve the surface quality prior to usage. In this paper, the novel shape adaptive grinding process has been applied to finishing titanium alloy (Ti6Al4V) additively manufactured by EBM and SLS. It is shown that the micro-structured surface layer resulting from the melting process can be removed, and the surface can then be smoothed down to less than 10 nm Ra (starting from 4-5 μm Ra) using only three different diamond grit sizes. This paper also demonstrates application of the technology to freeform shapes, and documents the dimensional accuracy of finished artifacts.

  5. A Programmable Beam Shaping System for Tailoring the Profile of High Fluence Laser Beams

    SciTech Connect

    Heebner, J; Borden, M; Miller, P; Stolz, C; Suratwala, T; Wegner, P; Hermann, M; Henesian, M; Haynam, C; Hunter, S; Christensen, K; Wong, N; Seppala, L; Brunton, G; Tse, E; Awwal, A; Franks, M; Marley, E; Williams, K; Scanlan, M; Budge, T; Monticelli, M; Walmer, D; Dixit, S; Widmayer, C; Wolfe, J; Bude, J; McCarty, K; DiNicola, J

    2010-11-10

    Customized spatial light modulators have been designed and fabricated for use as precision beam shaping devices in fusion class laser systems. By inserting this device in a low-fluence relay plane upstream of the amplifier chain, 'blocker' obscurations can be programmed into the beam profile to shadow small isolated flaws on downstream optical components that might otherwise limit the system operating energy. In this two stage system, 1920 x 1080 bitmap images are first imprinted on incoherent, 470 nm address beams via pixilated liquid crystal on silicon (LCoS) modulators. To realize defined masking functions with smooth apodized shapes and no pixelization artifacts, address beam images are projected onto custom fabricated optically-addressable light valves. Each valve consists of a large, single pixel liquid cell in series with a photoconductive Bismuth silicon Oxide (BSO) crystal. The BSO crystal enables bright and dark regions of the address image to locally control the voltage supplied to the liquid crystal layer which in turn modulates the amplitude of the coherent beams at 1053 nm. Valves as large as 24 mm x 36 mm have been fabricated with low wavefront distortion (<0.5 waves) and antireflection coatings for high transmission (>90%) and etalon suppression to avoid spectral and temporal ripple. This device in combination with a flaw inspection system and optic registration strategy represents a new approach for extending the operational lifetime of high fluence laser optics.

  6. Shaping the beam profile of an elliptical Gaussian beam by an elliptical phase aperture

    NASA Astrophysics Data System (ADS)

    Wen, Wei; Wu, Gaofeng; Song, Kehui; Dong, Yiming

    2013-03-01

    Based on the generalized Collins integral formula, an analytical paraxial propagation formula for an elliptical Gaussian beam (EGB) passing through an astigmatic ABCD optical system with an elliptical phase aperture is derived by use of a tensor method. As an application example, we study the propagation properties of an EGB passing through an elliptical aperture in free space. It is found that the elliptical phase aperture can be used for shaping the beam profile of an EGB, which is useful in many applications, such as free space optical communication and material thermal processing. The elliptical phase aperture induced changes of the propagation factors of an EGB are also analyzed.

  7. Adaptive Shape Functions and Internal Mesh Adaptation for Modelling Progressive Failure in Adhesively Bonded Joints

    NASA Technical Reports Server (NTRS)

    Stapleton, Scott; Gries, Thomas; Waas, Anthony M.; Pineda, Evan J.

    2014-01-01

    Enhanced finite elements are elements with an embedded analytical solution that can capture detailed local fields, enabling more efficient, mesh independent finite element analysis. The shape functions are determined based on the analytical model rather than prescribed. This method was applied to adhesively bonded joints to model joint behavior with one element through the thickness. This study demonstrates two methods of maintaining the fidelity of such elements during adhesive non-linearity and cracking without increasing the mesh needed for an accurate solution. The first method uses adaptive shape functions, where the shape functions are recalculated at each load step based on the softening of the adhesive. The second method is internal mesh adaption, where cracking of the adhesive within an element is captured by further discretizing the element internally to represent the partially cracked geometry. By keeping mesh adaptations within an element, a finer mesh can be used during the analysis without affecting the global finite element model mesh. Examples are shown which highlight when each method is most effective in reducing the number of elements needed to capture adhesive nonlinearity and cracking. These methods are validated against analogous finite element models utilizing cohesive zone elements.

  8. Adaptive shape coding for perceptual decisions in the human brain

    PubMed Central

    Kourtzi, Zoe; Welchman, Andrew E.

    2015-01-01

    In its search for neural codes, the field of visual neuroscience has uncovered neural representations that reflect the structure of stimuli of variable complexity from simple features to object categories. However, accumulating evidence suggests an adaptive neural code that is dynamically shaped by experience to support flexible and efficient perceptual decisions. Here, we review work showing that experience plays a critical role in molding midlevel visual representations for perceptual decisions. Combining behavioral and brain imaging measurements, we demonstrate that learning optimizes feature binding for object recognition in cluttered scenes, and tunes the neural representations of informative image parts to support efficient categorical judgements. Our findings indicate that similar learning mechanisms may mediate long-term optimization through development, tune the visual system to fundamental principles of feature binding, and optimize feature templates for perceptual decisions. PMID:26024511

  9. Binary hologram generation based on shape adaptive sampling

    NASA Astrophysics Data System (ADS)

    Tsang, P. W. M.; Pan, Y.; Poon, T.-C.

    2014-05-01

    Past research has revealed that by down-sampling the projected intensity profile of a source object scene with a regular sampling lattice, a binary Fresnel hologram can be generated swiftly to preserve favorable quality on its reconstructed image. However, this method also results in a prominent textural pattern which is conflicting to the geometrical profile of the object scene, leading to an unnatural visual perception. In this paper, we shall overcome this problem with a down-sampling process that is adaptive to the geometry of the object. Experimental results demonstrate that by applying our proposed method to generate a binary hologram, the reconstructed image is rendered with a texture which abides with the shape of the three-dimensional object(s).

  10. Measurement and Prediction of the Thermomechanical Response of Shape Memory Alloy Hybrid Composite Beams

    NASA Technical Reports Server (NTRS)

    Davis, Brian; Turner, Travis L.; Seelecke, Stefan

    2008-01-01

    An experimental and numerical investigation into the static and dynamic responses of shape memory alloy hybrid composite (SMAHC) beams is performed to provide quantitative validation of a recently commercialized numerical analysis/design tool for SMAHC structures. The SMAHC beam specimens consist of a composite matrix with embedded pre-strained SMA actuators, which act against the mechanical boundaries of the structure when thermally activated to adaptively stiffen the structure. Numerical results are produced from the numerical model as implemented into the commercial finite element code ABAQUS. A rigorous experimental investigation is undertaken to acquire high fidelity measurements including infrared thermography and projection moire interferometry for full-field temperature and displacement measurements, respectively. High fidelity numerical results are also obtained from the numerical model and include measured parameters, such as geometric imperfection and thermal load. Excellent agreement is achieved between the predicted and measured results of the static and dynamic thermomechanical response, thereby providing quantitative validation of the numerical tool.

  11. Adaptive cascaded beam-based feedback at the SLC

    SciTech Connect

    Himel, T.; Allison, S.; Grossberg, P.; Hendrickson, L.; Sass, R.; Shoaee, H.

    1993-05-01

    The SLAC Linear Collider now has a total of twenty-four beam-steering feedback loops used to keep the electron and positron beams on their desired trajectories. Seven of these loops measure and control the same beam as it proceeds down the linac through the arcs to the final focus. Ideally each loop should correct only for disturbances that occur between it and the immediate upstream loop. In fact, in the original system each loop corrected for all upstream disturbances. This resulted in undesirable over-correction and ringing. We added MIMO (Multiple Input Multiple Output) adaptive noise cancellers to separate the signal we wish to correct from disturbances further up-stream. This adaptive control improved performance in the 1992 run.

  12. Experimental evaluation of shape memory alloy actuation technique in adaptive antenna design concepts

    NASA Technical Reports Server (NTRS)

    Kefauver, W. Neill; Carpenter, Bernie F.

    1994-01-01

    Creation of an antenna system that could autonomously adapt contours of reflecting surfaces to compensate for structural loads induced by a variable environment would maximize performance of space-based communication systems. Design of such a system requires the comprehensive development and integration of advanced actuator, sensor, and control technologies. As an initial step in this process, a test has been performed to assess the use of a shape memory alloy as a potential actuation technique. For this test, an existing, offset, cassegrain antenna system was retrofit with a subreflector equipped with shape memory alloy actuators for surface contour control. The impacts that the actuators had on both the subreflector contour and the antenna system patterns were measured. The results of this study indicate the potential for using shape memory alloy actuation techniques to adaptively control antenna performance; both variations in gain and beam steering capabilities were demonstrated. Future development effort is required to evolve this potential into a useful technology for satellite applications.

  13. Effects of laser beam propagation and saturation on the spatial shape of sodium laser guide stars.

    PubMed

    Marc, Fabien; Guillet de Chatellus, Hugues; Pique, Jean-Paul

    2009-03-30

    The possibility to produce diffraction-limited images by large telescopes through Adaptive Optics is closely linked to the precision of measurement of the position of the guide star on the wavefront sensor. In the case of laser guide stars, many parameters can lead to a strong distortion on the shape of the LGS spot. Here we study the influence of both the saturation of the sodium layer excited by different types of lasers, the spatial quality of the laser mode at the ground and the influence of the atmospheric turbulence on the upward propagation of the laser beam. Both shape and intensity of the LGS spot are found to depend strongly on these three effects with important consequences on the precision on the wavefront analysis. PMID:19333251

  14. Point Scanning Microscope with Adaptive Illumination Beam Intensity

    NASA Astrophysics Data System (ADS)

    Das, Abhijit; Boruah, B. R.

    2011-10-01

    In this paper we describe a point scanning optical microscope where the illumination beam can be programmably controlled in real time using a liquid crystal spatial light modulator (LCSLM). With an appropriate pattern displayed on the LCSLM, the device can be made to act as a binary diffraction hologram. In the proposed microscope the illumination beam is in fact the +1 order beam diffracted from the binary hologram. By displaying a sequence of binary holograms it is possible to make a beam scanning, similar to a conventional scanning microscope. Here we use a computer generated holography technique to compute the binary holograms which facilitate complete control of the amplitude and phase profile of the illumination beam. In a number of microscopy applications using reflected light, the reflectivity of the sample plane may differ from region to region. Therefore if a single illumination beam intensity is used for the whole sample plane, then the regions with less reflectivity will be imaged with poor signal to noise ratio. In our proposed microscope the sample plane is first imaged to determine the regions of weak reflectivity. Holograms are then computed to make the illumination beam adapt to the reflectivity variations in the given sample plane. The image obtained with the modified set of holograms have superior signal to noise ratio all over, relative to a conventional point scanning microscope with a fixed intensity illumination beam. In this paper we present some preliminary results using the proposed setup.

  15. Extension of Ko Straight-Beam Displacement Theory to Deformed Shape Predictions of Slender Curved Structures

    NASA Technical Reports Server (NTRS)

    Ko, William L.; Fleischer, Van Tran

    2011-01-01

    The Ko displacement theory originally developed for shape predictions of straight beams is extended to shape predictions of curved beams. The surface strains needed for shape predictions were analytically generated from finite-element nodal stress outputs. With the aid of finite-element displacement outputs, mathematical functional forms for curvature-effect correction terms are established and incorporated into straight-beam deflection equations for shape predictions of both cantilever and two-point supported curved beams. The newly established deflection equations for cantilever curved beams could provide quite accurate shape predictions for different cantilever curved beams, including the quarter-circle cantilever beam. Furthermore, the newly formulated deflection equations for two-point supported curved beams could provide accurate shape predictions for a range of two-point supported curved beams, including the full-circular ring. Accuracy of the newly developed curved-beam deflection equations is validated through shape prediction analysis of curved beams embedded in the windward shallow spherical shell of a generic crew exploration vehicle. A single-point collocation method for optimization of shape predictions is discussed in detail

  16. Programmable Beam Spatial Shaping System for the National Ignition Facility

    SciTech Connect

    Heebner, J; Borden, M; Miller, P; Hunter, S; Christensen, K; Scanlan, M; Haynam, C; Wegner, P; Hermann, M; Brunton, G; Tse, E; Awwal, A; Wong, N; Seppala, L; Franks, M; Marley, E; Wong, N; Seppala, L; Franks, M; Marley, E; Williams, K; Budge, T; Henesian, M; Stolz, C; Suratwala, T; Monticelli, M; Walmer, D; Dixit, S; Widmayer, C; Wolfe, J; Bude, J; McCarty, K; DiNicola, J M

    2011-01-21

    A system of customized spatial light modulators has been installed onto the front end of the laser system at the National Ignition Facility (NIF). The devices are capable of shaping the beam profile at a low-fluence relay plane upstream of the amplifier chain. Their primary function is to introduce 'blocker' obscurations at programmed locations within the beam profile. These obscurations are positioned to shadow small, isolated flaws on downstream optical components that might otherwise limit the system operating energy. The modulators were designed to enable a drop-in retrofit of each of the 48 existing Pre Amplifier Modules (PAMs) without compromising their original performance specifications. This was accomplished by use of transmissive Optically Addressable Light Valves (OALV) based on a Bismuth Silicon Oxide photoconductive layer in series with a twisted nematic liquid crystal (LC) layer. These Programmable Spatial Shaper packages in combination with a flaw inspection system and optic registration strategy have provided a robust approach for extending the operational lifetime of high fluence laser optics on NIF.

  17. Studies of pear-shaped nuclei using accelerated radioactive beams.

    PubMed

    Gaffney, L P; Butler, P A; Scheck, M; Hayes, A B; Wenander, F; Albers, M; Bastin, B; Bauer, C; Blazhev, A; Bönig, S; Bree, N; Cederkäll, J; Chupp, T; Cline, D; Cocolios, T E; Davinson, T; De Witte, H; Diriken, J; Grahn, T; Herzan, A; Huyse, M; Jenkins, D G; Joss, D T; Kesteloot, N; Konki, J; Kowalczyk, M; Kröll, Th; Kwan, E; Lutter, R; Moschner, K; Napiorkowski, P; Pakarinen, J; Pfeiffer, M; Radeck, D; Reiter, P; Reynders, K; Rigby, S V; Robledo, L M; Rudigier, M; Sambi, S; Seidlitz, M; Siebeck, B; Stora, T; Thoele, P; Van Duppen, P; Vermeulen, M J; von Schmid, M; Voulot, D; Warr, N; Wimmer, K; Wrzosek-Lipska, K; Wu, C Y; Zielinska, M

    2013-05-01

    There is strong circumstantial evidence that certain heavy, unstable atomic nuclei are 'octupole deformed', that is, distorted into a pear shape. This contrasts with the more prevalent rugby-ball shape of nuclei with reflection-symmetric, quadrupole deformations. The elusive octupole deformed nuclei are of importance for nuclear structure theory, and also in searches for physics beyond the standard model; any measurable electric-dipole moment (a signature of the latter) is expected to be amplified in such nuclei. Here we determine electric octupole transition strengths (a direct measure of octupole correlations) for short-lived isotopes of radon and radium. Coulomb excitation experiments were performed using accelerated beams of heavy, radioactive ions. Our data on (220)Rn and (224)Ra show clear evidence for stronger octupole deformation in the latter. The results enable discrimination between differing theoretical approaches to octupole correlations, and help to constrain suitable candidates for experimental studies of atomic electric-dipole moments that might reveal extensions to the standard model. PMID:23657348

  18. Structured beam shaping for precision laser dicing of multilayered substrates

    NASA Astrophysics Data System (ADS)

    Lizotte, Todd; Ohar, Orest

    2007-02-01

    Laser dicing of wafer based devices; such as light emitting diodes (LEDs) is multifaceted since these devices are formed from various materials in a layered structure. Many of these layers include active device materials, passivation coatings, conductors and dielectric films all deposited on top of a bulk wafer substrate and all potentially having different ablation thresholds. These composite multi-layered structures require high finesse laser processes to ensure yields, high quality and low cost. Such processes have become very complex over the years as new devices become miniaturized, requiring smaller micro-machined features, greater precision and reduction of thermal stress to minimize substrate micro-cracking and maintain device integrity over its projected lifetime. Newer laser processes often involve the sequential use of single or multiple diode pumped solid state (DPSS) lasers, such as UV DPSS (355nn, 266nm), VIS DPSS (~532 nm) and IR DPSS (1064nm, 1070nm) as well as DPFL (Diode Pumped Fiber Lasers) lasers to penetrate various and differing material layers and substrates including SiC, Silicon and Sapphire. Development of beam shaping optics with the purpose of permitting two or more differing energy densities within a single focused or imaged beam spot would provide opportunities for pre-processing or pre-scribing of thinner cover layers, while following through with a higher energy density portion to cut through base substrates. This technique is also possible using multiple wavelengths simultaneously for micro-machining or dicing. Using multiple wavelengths offers advantages where high photon energies from such wavelengths as 266 nm can cause adverse effects to doped materials such as silicon or to active device layers such as GaN or other III-V materials deposited on the substrate surface. This paper will describe the development of variable intensity beam shaping optical elements targeting micromachining, dicing and patterning of delicate thin film

  19. Proteasome function shapes innate and adaptive immune responses.

    PubMed

    Kammerl, Ilona E; Meiners, Silke

    2016-08-01

    The proteasome system degrades more than 80% of intracellular proteins into small peptides. Accordingly, the proteasome is involved in many essential cellular functions, such as protein quality control, transcription, immune responses, cell signaling, and apoptosis. Moreover, degradation products are loaded onto major histocompatibility class I molecules to communicate the intracellular protein composition to the immune system. The standard 20S proteasome core complex contains three distinct catalytic active sites that are exchanged upon stimulation with inflammatory cytokines to form the so-called immunoproteasome. Immunoproteasomes are constitutively expressed in immune cells and have different proteolytic activities compared with standard proteasomes. They are rapidly induced in parenchymal cells upon intracellular pathogen infection and are crucial for priming effective CD8(+) T-cell-mediated immune responses against infected cells. Beyond shaping these adaptive immune reactions, immunoproteasomes also regulate the function of immune cells by degradation of inflammatory and immune mediators. Accordingly, they emerge as novel regulators of innate immune responses. The recently unraveled impairment of immunoproteasome function by environmental challenges and by genetic variations of immunoproteasome genes might represent a currently underestimated risk factor for the development and progression of lung diseases. In particular, immunoproteasome dysfunction will dampen resolution of infections, thereby promoting exacerbations, may foster autoimmunity in chronic lung diseases, and possibly contributes to immune evasion of tumor cells. Novel pharmacological tools, such as site-specific inhibitors of the immunoproteasome, as well as activity-based probes, however, hold promises as innovative therapeutic drugs for respiratory diseases and biomarker profiling, respectively. PMID:27343191

  20. Simultaneous beam sampling and aperture shape optimization for SPORT

    SciTech Connect

    Zarepisheh, Masoud; Li, Ruijiang; Xing, Lei; Ye, Yinyu

    2015-02-15

    Purpose: Station parameter optimized radiation therapy (SPORT) was recently proposed to fully utilize the technical capability of emerging digital linear accelerators, in which the station parameters of a delivery system, such as aperture shape and weight, couch position/angle, gantry/collimator angle, can be optimized simultaneously. SPORT promises to deliver remarkable radiation dose distributions in an efficient manner, yet there exists no optimization algorithm for its implementation. The purpose of this work is to develop an algorithm to simultaneously optimize the beam sampling and aperture shapes. Methods: The authors build a mathematical model with the fundamental station point parameters as the decision variables. To solve the resulting large-scale optimization problem, the authors devise an effective algorithm by integrating three advanced optimization techniques: column generation, subgradient method, and pattern search. Column generation adds the most beneficial stations sequentially until the plan quality improvement saturates and provides a good starting point for the subsequent optimization. It also adds the new stations during the algorithm if beneficial. For each update resulted from column generation, the subgradient method improves the selected stations locally by reshaping the apertures and updating the beam angles toward a descent subgradient direction. The algorithm continues to improve the selected stations locally and globally by a pattern search algorithm to explore the part of search space not reachable by the subgradient method. By combining these three techniques together, all plausible combinations of station parameters are searched efficiently to yield the optimal solution. Results: A SPORT optimization framework with seamlessly integration of three complementary algorithms, column generation, subgradient method, and pattern search, was established. The proposed technique was applied to two previously treated clinical cases: a head and

  1. Exploring the unlimited possibilities of modular aspheric Gauss to top-hat beam shaping

    NASA Astrophysics Data System (ADS)

    Möhl, Anna; Fuchs, Ulrike

    2016-06-01

    Beam shaping is a field of research with growing importance. Therefore, a new refractive beam shaping system is presented. The knowledge gained from analyzing patent systems was used to derive our own improved design. It is compared to a patent system, and some selected results are presented in this work. Furthermore, possibilities to scale the entrance and exit beam diameters with the help of SPA™ Beam Expander Kit and SPA™ AspheriColl (both from asphericon GmbH, Jena, Germany) are shown, so that a modular top-hat generation is achievable. Additionally, the large spectral range in which the beam shaping system is applicable is demonstrated, and it is demonstrated how the beam shaping system can be used to improve the performance of other optical elements that require a top-hat beam profile.

  2. Ultrafast rotating dipole or propeller-shaped patterns: subwavelength shaping of a beam of light on a femtosecond time scale.

    PubMed

    Khonina, Svetlana N; Golub, Ilya

    2016-04-01

    We report on a remarkable property of azimuthally (radially) polarized light beams containing a vortex or an orbital angular momentum: upon tight focusing of a first-order vortex beam, the subwavelength spot has a shape of an electric (magnetic) dipole rotating at an optical frequency. For beams with a vortex of order m, the generated pattern is propeller-shaped and rotates at a 1/m fraction of the optical frequency. The applications include petahertz control of electrical or optical conductance between two electrodes or waveguides of two-terminal junctions. PMID:27192298

  3. Adaptive Shape Kernel-Based Mean Shift Tracker in Robot Vision System

    PubMed Central

    2016-01-01

    This paper proposes an adaptive shape kernel-based mean shift tracker using a single static camera for the robot vision system. The question that we address in this paper is how to construct such a kernel shape that is adaptive to the object shape. We perform nonlinear manifold learning technique to obtain the low-dimensional shape space which is trained by training data with the same view as the tracking video. The proposed kernel searches the shape in the low-dimensional shape space obtained by nonlinear manifold learning technique and constructs the adaptive kernel shape in the high-dimensional shape space. It can improve mean shift tracker performance to track object position and object contour and avoid the background clutter. In the experimental part, we take the walking human as example to validate that our method is accurate and robust to track human position and describe human contour. PMID:27379165

  4. Measurement and Prediction of the Thermomechanical Response of Shape Memory Alloy Hybrid Composite Beams

    NASA Technical Reports Server (NTRS)

    Davis, Brian; Turner, Travis L.; Seelecke, Stefan

    2005-01-01

    Previous work at NASA Langley Research Center (LaRC) involved fabrication and testing of composite beams with embedded, pre-strained shape memory alloy (SMA) ribbons within the beam structures. That study also provided comparison of experimental results with numerical predictions from a research code making use of a new thermoelastic model for shape memory alloy hybrid composite (SMAHC) structures. The previous work showed qualitative validation of the numerical model. However, deficiencies in the experimental-numerical correlation were noted and hypotheses for the discrepancies were given for further investigation. The goal of this work is to refine the experimental measurement and numerical modeling approaches in order to better understand the discrepancies, improve the correlation between prediction and measurement, and provide rigorous quantitative validation of the numerical analysis/design tool. The experimental investigation is refined by a more thorough test procedure and incorporation of higher fidelity measurements such as infrared thermography and projection moire interferometry. The numerical results are produced by a recently commercialized version of the constitutive model as implemented in ABAQUS and are refined by incorporation of additional measured parameters such as geometric imperfection. Thermal buckling, post-buckling, and random responses to thermal and inertial (base acceleration) loads are studied. The results demonstrate the effectiveness of SMAHC structures in controlling static and dynamic responses by adaptive stiffening. Excellent agreement is achieved between the predicted and measured results of the static and dynamic thermomechanical response, thereby providing quantitative validation of the numerical tool.

  5. An interpretation and guide to single-pass beam shaping methods using SLMs and DMDs

    NASA Astrophysics Data System (ADS)

    Stilgoe, Alexander B.; Kashchuk, Anatolii V.; Preece, Daryl; Rubinsztein-Dunlop, Halina

    2016-06-01

    Exquisite manipulations of light can be performed with devices such as spatial light modulators (SLMs) and digital micromirror devices (DMDs). These devices can be used to simulate transverse paraxial beam wavefunction eigenstates such as the Hermite–Laguerre–Gaussian mode families. We investigate several beam shaping methods in terms of the wavefunctions of scattered light. Our analysis of the efficiency, behaviour and limitations of beam shaping methods is applied to both theory and experiment. The deviation from the ideal output from a valid beam shaping method is shown to be due to experimental factors which are not necessarily being accounted for. Incident beam mode shape, aberration, and the amplitude/phase transfer functions of the DMD and SLM impact the distribution of scattered light and hence the effectiveness and efficiency of a beam shaping method. Correcting for these particular details of the optical system accounts for all differences in efficiency and mode fidelity between experiment and theory. We explicitly show the impact of experimental parameter variations so that these problems may be diagnosed and corrected in an experimental beam shaping apparatus. We show that several beam shaping methods can be used for the production of beam modes in a single pass and the choice is based on the particular experimental conditions.

  6. Correction of linear-array lidar intensity data using an optimal beam shaping approach

    NASA Astrophysics Data System (ADS)

    Xu, Fan; Wang, Yuanqing; Yang, Xingyu; Zhang, Bingqing; Li, Fenfang

    2016-08-01

    The linear-array lidar has been recently developed and applied for its superiority of vertically non-scanning, large field of view, high sensitivity and high precision. The beam shaper is the key component for the linear-array detection. However, the traditional beam shaping approaches can hardly satisfy our requirement for obtaining unbiased and complete backscattered intensity data. The required beam distribution should roughly be oblate U-shaped rather than Gaussian or uniform. Thus, an optimal beam shaping approach is proposed in this paper. By employing a pair of conical lenses and a cylindrical lens behind the beam expander, the expanded Gaussian laser was shaped to a line-shaped beam whose intensity distribution is more consistent with the required distribution. To provide a better fit to the requirement, off-axis method is adopted. The design of the optimal beam shaping module is mathematically explained and the experimental verification of the module performance is also presented in this paper. The experimental results indicate that the optimal beam shaping approach can effectively correct the intensity image and provide ~30% gain of detection area over traditional approach, thus improving the imaging quality of linear-array lidar.

  7. 32 nm imprint masks using variable shape beam pattern generators

    NASA Astrophysics Data System (ADS)

    Selinidis, Kosta; Thompson, Ecron; Schmid, Gerard; Stacey, Nick; Perez, Joseph; Maltabes, John; Resnick, Douglas J.; Yeo, Jeongho; Kim, Hoyeon; Eynon, Ben

    2008-05-01

    Imprint lithography has been included on the ITRS Lithography Roadmap at the 32, 22 and 16 nm nodes. Step and Flash Imprint Lithography (S-FIL ®) is a unique method that has been designed from the beginning to enable precise overlay for creating multilevel devices. A photocurable low viscosity monomer is dispensed dropwise to meet the pattern density requirements of the device, thus enabling imprint patterning with a uniform residual layer across a field and across entire wafers. Further, S-FIL provides sub-100 nm feature resolution without the significant expense of multi-element, high quality projection optics or advanced illumination sources. However, since the technology is 1X, it is critical to address the infrastructure associated with the fabrication of templates. For sub-32 nm device manufacturing, one of the major technical challenges remains the fabrication of full-field 1x templates with commercially viable write times. Recent progress in the writing of sub-40 nm patterns using commercial variable shape e-beam tools and non-chemically amplified resists has demonstrated a very promising route to realizing these objectives, and in doing so, has considerably strengthened imprint lithography as a competitive manufacturing technology for the sub 32nm node. Here we report the first imprinting results from sub-40 nm full-field patterns, using Samsung's current flash memory production device design. The fabrication of the template is discussed and the resulting critical dimension control and uniformity are discussed, along with image placement results. The imprinting results are described in terms of CD uniformity, etch results, and overlay.

  8. A line scanned light-sheet microscope with phase shaped self-reconstructing beams.

    PubMed

    Fahrbach, Florian O; Rohrbach, Alexander

    2010-11-01

    We recently demonstrated that Microscopy with Self-Reconstructing Beams (MISERB) increases both image quality and penetration depth of illumination beams in strongly scattering media. Based on the concept of line scanned light-sheet microscopy, we present an add-on module to a standard inverted microscope using a scanned beam that is shaped in phase and amplitude by a spatial light modulator. We explain technical details of the setup as well as of the holograms for the creation, positioning and scaling of static light-sheets, Gaussian beams and Bessel beams. The comparison of images from identical sample areas illuminated by different beams allows a precise assessment of the interconnection between beam shape and image quality. The superior propagation ability of Bessel beams through inhomogeneous media is demonstrated by measurements on various scattering media. PMID:21164769

  9. How adaptation shapes spike rate oscillations in recurrent neuronal networks

    PubMed Central

    Augustin, Moritz; Ladenbauer, Josef; Obermayer, Klaus

    2012-01-01

    Neural mass signals from in-vivo recordings often show oscillations with frequencies ranging from <1 to 100 Hz. Fast rhythmic activity in the beta and gamma range can be generated by network-based mechanisms such as recurrent synaptic excitation-inhibition loops. Slower oscillations might instead depend on neuronal adaptation currents whose timescales range from tens of milliseconds to seconds. Here we investigate how the dynamics of such adaptation currents contribute to spike rate oscillations and resonance properties in recurrent networks of excitatory and inhibitory neurons. Based on a network of sparsely coupled spiking model neurons with two types of adaptation current and conductance-based synapses with heterogeneous strengths and delays we use a mean-field approach to analyze oscillatory network activity. For constant external input, we find that spike-triggered adaptation currents provide a mechanism to generate slow oscillations over a wide range of adaptation timescales as long as recurrent synaptic excitation is sufficiently strong. Faster rhythms occur when recurrent inhibition is slower than excitation and oscillation frequency increases with the strength of inhibition. Adaptation facilitates such network-based oscillations for fast synaptic inhibition and leads to decreased frequencies. For oscillatory external input, adaptation currents amplify a narrow band of frequencies and cause phase advances for low frequencies in addition to phase delays at higher frequencies. Our results therefore identify the different key roles of neuronal adaptation dynamics for rhythmogenesis and selective signal propagation in recurrent networks. PMID:23450654

  10. Shaped beam scattering by an aggregate of particles using generalized Lorenz-Mie theory

    NASA Astrophysics Data System (ADS)

    Briard, Paul; Wang, Jia jie; Han, Yi Ping

    2016-04-01

    In this paper, the light scattering by an aggregate of particles illuminated by an arbitrary shaped beam is analyzed within the framework of generalized Lorenz-Mie theory (GLMT). The theoretical derivations of aggregated particles illuminated by an arbitrary shaped beam are revisited, with special attention paid to the computation of beam shape coefficients of a shaped beam for aggregated particles. The theoretical treatments as well as a home-made code are then verified by making comparisons between our numerical results and those calculated using a public available T-Matrix code MSTM. Good agreements are achieved which partially indicate the correctness of both codes. Additionally, more numerical results are presented to study the scattered fields of aggregated particles illuminated by a focused Gaussian beam. Several large enhancements in the scattered intensity distributions are found which are believed to be due to the Bragg's scattering by a linear chain of spheres.

  11. Hopfield network with constraint parameter adaptation for overlapped shape recognition.

    PubMed

    Suganthan, P N; Teoh, E K; Mital, D P

    1999-01-01

    In this paper, we propose an energy formulation for homomorphic graph matching by the Hopfield network and a Lyapunov indirect method-based learning approach to adaptively learn the constraint parameter in the energy function. The adaptation scheme eliminates the need to specify the constraint parameter empirically and generates valid and better quality mappings than the analog Hopfield network with a fixed constraint parameter. The proposed Hopfield network with constraint parameter adaptation is applied to match silhouette images of keys and results are presented. PMID:18252543

  12. Study of adaptive correlation filter synthesis guided by the peak and shape of the correlation output

    NASA Astrophysics Data System (ADS)

    Campos Trujillo, Oliver G.; Díaz Blancas, Gerardo

    2014-09-01

    In recent years, many proposals that consider an adaptive perspective had been developed to solve some drawbacks, such as geometric distortions, background noise and target discrimination. The metrics are based only in the correlation peak output for the filter synthesis. In this paper, the correlation shape is studied to implement adaptive correlation filters guided by the peak and shape of the correlation output. Furthermore, the shape of correlation output is studied to improve the search in the filters bank. In addition, parallel algorithms are developed for accelerated the search in the filters bank. Some results are shown, such as time of synthesis, filter performance and comparisons with other adaptive correlation filter proposals.

  13. High voltage pulse shaping of e-beam diode using perveance variation

    NASA Astrophysics Data System (ADS)

    Mitra, S.; Sharma, V.; Senthil, K.; Roy, A.; Kumar, D. D. P.; Menon, Rakhee; Singh, S. K.; Sharma, Archana; Nagesh, K. V.; Chakravarthy, D. P.

    2011-08-01

    This paper presents a new high voltage pulse shaping methodology for pulsed power applications. The aim is to generate high voltage square pulse across anode cathode gap of e-beam diodes. The non-linear time varying perveance characteristics of e-beam diodes are used for shaping of output voltage pulse across it, generated directly from Marx generator. Analytically, it has been shown in the paper that under certain conditions, if achieved, Marx generator feeding an e-beam diode can produce a square-like pulse at the output, without any extra pulse shaping arrangements. Experimental results to support the analysis are also presented in the paper.

  14. High voltage pulse shaping of e-beam diode using perveance variation.

    PubMed

    Mitra, S; Sharma, V; Senthil, K; Roy, A; Kumar, D D P; Menon, Rakhee; Singh, S K; Sharma, Archana; Nagesh, K V; Chakravarthy, D P

    2011-08-01

    This paper presents a new high voltage pulse shaping methodology for pulsed power applications. The aim is to generate high voltage square pulse across anode cathode gap of e-beam diodes. The non-linear time varying perveance characteristics of e-beam diodes are used for shaping of output voltage pulse across it, generated directly from Marx generator. Analytically, it has been shown in the paper that under certain conditions, if achieved, Marx generator feeding an e-beam diode can produce a square-like pulse at the output, without any extra pulse shaping arrangements. Experimental results to support the analysis are also presented in the paper. PMID:21895264

  15. Effects of laser beam shapes on depths of penetration in dermatology

    NASA Astrophysics Data System (ADS)

    Saghafi, S.; Withford, M.; Farhadi, M.; Ghaderi, R.; Granmayeh, A.; Ghoranneviss, Z.; Moravej, F.

    2006-04-01

    For many medical laser applications, a particular beam shape is required. The output beam of a laser can be approximated by a Gaussian, higher-order Gaussian, annular or a flat-top (uniform) distribution. Here, we investigate, analytically and experimentally, the effects of laser beam shapes on the depths of penetration in treatments of any types of vascular malformation. In order to do this, the physical and optical parameters of the skin must be known and measured correctly. Using the Monte-Carlo method for seven layers of skin, a software predicting the beam propagation and intensity distribution inside of tissue has been developed in our centre. In this paper, a 15 watts copper vapour laser producing (511nm and 578 nm) for treatments of patients having PWS (Port Wine Stains) of different sizes is employed. The output beam of this laser was Gaussian. We have designed a beam homogenizer converting a Gaussian beam into flat-top distribution. Therefore, the effects of the laser irradiance beam shape (before and after beam shaping) on the depth of penetration have been investigated before people's treatments. Initially, two laser beams having Gaussian output distribution of the same power are considered. The diameter of one beam is 5mm and the other one is 10 mm. The intensity distribution of these beam inside of similar tissues are predicted and it is concluded that for deep but small size PWS the Gaussian beam having smaller beam diameter is more suitable than the larger spot size. Then, the beam intensity distribution inside of the same tissue (similar parameters) for two flat-top beams of the same power but different diameters (one is 5mm and the other is 10 mm) is calculated. It can be seen that the flat top beam of bigger spot-size has smaller penetration depth but it illuminates a larger area uniformly (suitable for large but not deep area). The depth of penetration of flat-top beam with smaller spot size is deeper but it illuminates a smaller area uniformly

  16. Effect of the focal shaping generated from different double-mode cylindrical vector beams.

    PubMed

    Cui, Wenjing; Song, Feng; Ju, Dandan; Chen, Gui-Yang; Song, Feifei

    2015-08-01

    We investigate three-dimensional focus shaping generated from double-mode cylindrical vector beams with the Gaussian and Bessel-Gaussian pupil apodization functions by choosing the suitable polarization states of beams. Further, we compare them with that generated from the Laguerre-Gaussian pupil apodization function in the same situation. We find that the focus shaping generated from the Gaussian beam has the smallest zero intensity spot size. However, the situation of the Bessel-Gaussian beam not only possesses stability, which makes it suitable when applied in optical trapping, but also shows the best uniformity, which indicates its excellent performance in super-resolution fluorescence microscopy. PMID:26367303

  17. High-speed femtosecond laser beam shaping based on binary holography using a digital micromirror device.

    PubMed

    Cheng, Jiyi; Gu, Chenglin; Zhang, Dapeng; Chen, Shih-Chi

    2015-11-01

    In this Letter, we present a digital micromirror device (DMD)-based ultrafast beam shaper, i.e., DUBS. To our knowledge, the DUBS is the first binary laser beam shaper that can generate high-resolution (1140×912 pixels) arbitrary beam modes for femtosecond lasers at a rate of 4.2 kHz; the resolution and pattern rate are limited by the DMD. In the DUBS, the spectrum of the input pulsed laser is first angularly dispersed by a transmission grating and subsequently imaged to a DMD with beam modulation patterns; the transmission grating and a high-reflectivity mirror together compensate the angular dispersion introduced by the DMD. The mode of the output beam is monitored by a CCD camera. In the experiments, the DUBS is programmed to generate four different beam modes, including an Airy beam, Bessel beam, Laguerre-Gaussian (LG) beam, and a custom-designed "peace-dove" beam via the principle of binary holography. To verify the high shaping rate, the Airy beam and LG beam are generated alternately at 4.2 kHz, i.e., the maximum pattern rate of our DMD. The overall efficiency of the DUBS is measured to be 4.7%. With the high-speed and high-resolution beam-shaping capability, the DUBS may find important applications in nonlinear microscopy, optical manipulation, and microscale/nanoscale laser machining, etc. PMID:26512472

  18. Improve beam quality of laser proton acceleration with funnel-shaped-hole target

    NASA Astrophysics Data System (ADS)

    Yang, Peng; Fan, Da Peng; Li, Yu Xiao

    2016-03-01

    Improve beam quality of laser proton acceleration using a funnel-shaped-hole target is demonstrated through particle simulations. When an intense short pulse laser illuminates a thin foil target with a hole at the rear surface, the proton beam divergence is suppressed compared with that obtained in a traditional flat target. In this paper, a funnel-shaped-hole target is proposed to improve the proton beam quality. Using two-dimensional particle-in-cell (PIC) simulations, three different shapes of target (funnel-shaped-hole target, cylinder-shaped-hole target and flat target) are simulated and compared. The funnel-shaped hole in the rear surface of the target helps to focus the electron cloud significantly and improve the maximum proton energy and suppress the proton beam divergence. Different thicknesses of the new target are also simulated, and the effects of thickness on the divergence angle and proton spectra are investigated. The optimal size of the new target is obtained and the quality of the proton beam is improved significantly. The funnel-shaped-hole target serves as a new method to improve the proton beam quality in laser-plasma interactions.

  19. Design a freeform microlens array module for any arbitrary-shape collimated beam shaping and color mixing

    NASA Astrophysics Data System (ADS)

    Chen, Enguo; Wu, Rengmao; Guo, Tailiang

    2014-06-01

    Collimated beam shaping with freeform surface usually employs a predefined mapping to tailor one or multiple freeform surfaces. Limitation on those designs is that the source, the freeform optics and the target are in fixed one-to-one correspondence with each other. To overcome this drawback, this paper presents a kind of freeform microlens array module integrated with an ultra-thin freeform microlens array and a condenser lens to reshape any arbitrary-shape collimated beam into a prescribed uniform rectangular illumination and achieve color mixing. The design theory is explicitly given, and some key issues are addressed. Several different application examples are given, and the target is obtained with high uniformity and energy efficiency. This freeform microlens array module, which shows better flexibility and practicality than the regular designs, can be used not only to reshape any arbitrary-shape collimated beam (or a collimated beam integrated with several sub-collimated beams), but also most importantly to achieve color mixing. With excellent optical performance and ultra-compact volume, this optical module together with the design theory can be further introduced into other applications and will have a huge market potential in the near future.

  20. Ultrafast laser spatial beam shaping based on Zernike polynomials for surface processing.

    PubMed

    Houzet, J; Faure, N; Larochette, M; Brulez, A-C; Benayoun, S; Mauclair, C

    2016-03-21

    In femtosecond laser machining, spatial beam shaping can be achieved with wavefront modulators. The wavefront modulator displays a pre-calculated phase mask that modulates the laser wavefront to generate a target intensity distribution in the processing plane. Due to the non-perfect optical response of wavefront modulators, the experimental distribution may significantly differ from the target, especially for continuous shapes. We propose an alternative phase mask calculation method that can be adapted to the phase modulator optical performance. From an adjustable number of Zernike polynomials according to this performance, a least square fitting algorithm numerically determines their coefficients to obtain the desired wavefront modulation. We illustrate the technique with an optically addressed liquid-crystal light valve to produce continuous intensity distributions matching a desired ablation profile, without the need of a wavefront sensor. The projection of the experimental laser distribution shows a 5% RMS error compared to the calculated one. Ablation of steel is achieved following user-defined micro-dimples and micro-grooves targets on mold surfaces. The profiles of the microgrooves and the injected polycarbonate closely match the target (RMS below 4%). PMID:27136844

  1. Transverse beam shape measurements of intense proton beams using optical transition radiation

    SciTech Connect

    Scarpine, Victor E.; /Fermilab

    2012-03-01

    A number of particle physics experiments are being proposed as part of the Department of Energy HEP Intensity Frontier. Many of these experiments will utilize megawatt level proton beams onto targets to form secondary beams of muons, kaons and neutrinos. These experiments require transverse size measurements of the incident proton beam onto target for each beam spill. Because of the high power levels, most beam intercepting profiling techniques will not work at full beam intensity. The possibility of utilizing optical transition radiation (OTR) for high intensity proton beam profiling is discussed. In addition, previous measurements of OTR beam profiles from the NuMI beamline are presented.

  2. The use of intensity-modulated radiation therapy photon beams for improving the dose uniformity of electron beams shaped with MLC

    SciTech Connect

    Mosalaei, Homeira; Karnas, Scott; Shah, Sheel; Van Doodewaard, Sharon; Foster, Tim; Chen, Jeff

    2012-04-01

    Electrons are ideal for treating shallow tumors and sparing adjacent normal tissue. Conventionally, electron beams are collimated by cut-outs that are time-consuming to make and difficult to adapt to tumor shape throughout the course of treatment. We propose that electron cut-outs can be replaced using photon multileaf collimator (MLC). Two major problems of this approach are that the scattering of electrons causes penumbra widening because of a large air gap, and available commercial treatment planning systems (TPSs) do not support MLC-collimated electron beams. In this study, these difficulties were overcome by (1) modeling electron beams collimated by photon MLC for a commercial TPS, and (2) developing a technique to reduce electron beam penumbra by adding low-energy intensity-modulated radiation therapy (IMRT) photons (4 MV). We used blocks to simulate MLC shielding in the TPS. Inverse planning was used to optimize boost photon beams. This technique was applied to a parotid and a central nervous system (CNS) clinical case. Combined photon and electron plans were compared with conventional plans and verified using ion chamber, film, and a 2D diode array. Our studies showed that the beam penumbra for mixed beams with 90 cm source to surface distance (SSD) is comparable with electron applicators and cut-outs at 100 cm SSD. Our mixed-beam technique yielded more uniform dose to the planning target volume and lower doses to various organs at risk for both parotid and CNS clinical cases. The plans were verified with measurements, with more than 95% points passing the gamma criteria of 5% in dose difference and 5 mm for distance to agreement. In conclusion, the study has demonstrated the feasibility and potential advantage of using photon MLC to collimate electron beams with boost photon IMRT fields.

  3. The use of intensity-modulated radiation therapy photon beams for improving the dose uniformity of electron beams shaped with MLC.

    PubMed

    Mosalaei, Homeira; Karnas, Scott; Shah, Sheel; Van Doodewaard, Sharon; Foster, Tim; Chen, Jeff

    2012-01-01

    Electrons are ideal for treating shallow tumors and sparing adjacent normal tissue. Conventionally, electron beams are collimated by cut-outs that are time-consuming to make and difficult to adapt to tumor shape throughout the course of treatment. We propose that electron cut-outs can be replaced using photon multileaf collimator (MLC). Two major problems of this approach are that the scattering of electrons causes penumbra widening because of a large air gap, and available commercial treatment planning systems (TPSs) do not support MLC-collimated electron beams. In this study, these difficulties were overcome by (1) modeling electron beams collimated by photon MLC for a commercial TPS, and (2) developing a technique to reduce electron beam penumbra by adding low-energy intensity-modulated radiation therapy (IMRT) photons (4 MV). We used blocks to simulate MLC shielding in the TPS. Inverse planning was used to optimize boost photon beams. This technique was applied to a parotid and a central nervous system (CNS) clinical case. Combined photon and electron plans were compared with conventional plans and verified using ion chamber, film, and a 2D diode array. Our studies showed that the beam penumbra for mixed beams with 90 cm source to surface distance (SSD) is comparable with electron applicators and cut-outs at 100 cm SSD. Our mixed-beam technique yielded more uniform dose to the planning target volume and lower doses to various organs at risk for both parotid and CNS clinical cases. The plans were verified with measurements, with more than 95% points passing the gamma criteria of 5% in dose difference and 5 mm for distance to agreement. In conclusion, the study has demonstrated the feasibility and potential advantage of using photon MLC to collimate electron beams with boost photon IMRT fields. PMID:21925867

  4. Controlling high harmonics generation by spatial shaping of high-energy femtosecond beam.

    PubMed

    Dubrouil, A; Mairesse, Y; Fabre, B; Descamps, D; Petit, S; Mével, E; Constant, E

    2011-07-01

    We demonstrate controlled high-order harmonic generation in gas using high-energy femtosecond pulses (50 fs-50 mJ on target) by performing spatial shaping of the terrawatt fundamental laser beam. We have developed a two optical paths mirror that can withstand high power and shape the pump beam into a quasi-flat-top profile (super Gaussian) near focus. We observe clear signatures of the spatial shaping on the harmonic beam in terms of profile, divergence, level of signal, and spectrum. The harmonic generation in neon with a quasi-flat-top beam results in a broadband extreme UV beam with extremely low divergence (~340 μrad). PMID:21725453

  5. Skull shapes of the Lissodelphininae: radiation, adaptation and asymmetry.

    PubMed

    Galatius, Anders; Goodall, R Natalie P

    2016-06-01

    Within Delphinidae, the sub-family Lissodelphininae consists of 8 Southern Ocean species and 2 North Pacific species. Lissodelphininae is a result of recent phylogenetic revisions based on molecular methods. Thus, morphological radiation within the taxon has not been investigated previously. The sub-family consists of ecologically diverse groups such as (1) the Cephalorhynchus genus of 4 small species inhabiting coastal and shelf waters, (2) the robust species in the Lagenorhynchus genus with the coastal La. australis, the offshore La. cruciger, the pelagic species La. obscurus and La. obliquidens, and (3) the morphologically aberrant genus Lissodelphis. Here, the shapes of 164 skulls from adults of all 10 species were compared using 3-dimensional geometric morphometrics. The Lissodelphininae skulls were supplemented by samples of Lagenorhynchus albirostris and Delphinus delphis to obtain a context for the variation found within the subfamily. Principal components analysis was used to map the most important components of shape variation on phylogeny. The first component of shape variation described an elongation of the rostrum, lateral and dorsoventral compression of the neurocranium and smaller temporal fossa. The two Lissodelphis species were on the high extreme of this spectrum, while Lagenorhynchus australis, La. cruciger and Cephalorhynchus heavisidii were at the low extreme. Along the second component, La. cruciger was isolated from the other species by its expanded neurocranium and concave facial profile. Shape variation supports the gross phylogenetic relationships proposed by recent molecular studies. However, despite the great diversity of ecology and external morphology within the subfamily, shape variation of the feeding apparatus was modest, indicating a similar mode of feeding across the subfamily. All 10 species were similar in their pattern of skull asymmetry, but interestingly, two species using narrowband high frequency clicks (La. cruciger and C

  6. 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.

  7. Multistable wireless micro-actuator based on antagonistic pre-shaped double beams

    NASA Astrophysics Data System (ADS)

    Liu, X.; Lamarque, F.; Doré, E.; Pouille, P.

    2015-07-01

    This paper presents a monolithic multistable micro-actuator based on antagonistic pre-shaped double beams. The designed micro-actuator is formed by two rows of bistable micro-actuators providing four stable positions. The bistable mechanism for each row is a pair of antagonistic pre-shaped beams. This bistable mechanism has an easier pre-load operation compared to the pre-compressed bistable beams method. Furthermore, it solves the asymmetrical force output problem of parallel pre-shaped bistable double beams. At the same time, the geometrical limit is lower than parallel pre-shaped bistable double beams, which ensures a smaller stroke of the micro-actuator with the same dimensions. The designed micro-actuator is fabricated using laser cutting machine on medium density fiberboard (MDF). The bistability and merits of antagonistic pre-shaped double beams are experimentally validated. Finally, a contactless actuation test is performed using 660 nm wavelength laser heating shape memory alloy (SMA) active elements.

  8. Ecomorphological disparity in an adaptive radiation: opercular bone shape and stable isotopes in Antarctic icefishes

    PubMed Central

    Wilson, Laura A B; Colombo, Marco; Hanel, Reinhold; Salzburger, Walter; Sánchez-Villagra, Marcelo R

    2013-01-01

    To assess how ecological and morphological disparity is interrelated in the adaptive radiation of Antarctic notothenioid fish we used patterns of opercle bone evolution as a model to quantify shape disparity, phylogenetic patterns of shape evolution, and ecological correlates in the form of stable isotope values. Using a sample of 25 species including representatives from four major notothenioid clades, we show that opercle shape disparity is higher in the modern fauna than would be expected under the neutral evolution Brownian motion model. Phylogenetic comparative methods indicate that opercle shape data best fit a model of directional selection (Ornstein–Uhlenbeck) and are least supported by the “early burst” model of adaptive radiation. The main evolutionary axis of opercle shape change reflects movement from a broad and more symmetrically tapered opercle to one that narrows along the distal margin, but with only slight shape change on the proximal margin. We find a trend in opercle shape change along the benthic–pelagic axis, underlining the importance of this axis for diversification in the notothenioid radiation. A major impetus for the study of adaptive radiations is to uncover generalized patterns among different groups, and the evolutionary patterns in opercle shape among notothenioids are similar to those found among other adaptive radiations (three-spined sticklebacks) promoting the utility of this approach for assessing ecomorphological interactions on a broad scale. PMID:24102002

  9. Shape anomaly detection under strong measurement noise: An analytical approach to adaptive thresholding

    NASA Astrophysics Data System (ADS)

    Krasichkov, Alexander S.; Grigoriev, Eugene B.; Bogachev, Mikhail I.; Nifontov, Eugene M.

    2015-10-01

    We suggest an analytical approach to the adaptive thresholding in a shape anomaly detection problem. We find an analytical expression for the distribution of the cosine similarity score between a reference shape and an observational shape hindered by strong measurement noise that depends solely on the noise level and is independent of the particular shape analyzed. The analytical treatment is also confirmed by computer simulations and shows nearly perfect agreement. Using this analytical solution, we suggest an improved shape anomaly detection approach based on adaptive thresholding. We validate the noise robustness of our approach using typical shapes of normal and pathological electrocardiogram cycles hindered by additive white noise. We show explicitly that under high noise levels our approach considerably outperforms the conventional tactic that does not take into account variations in the noise level.

  10. Modeling the spatial shape of nondiffracting beams: Experimental generation of Frozen Waves via holographic method

    NASA Astrophysics Data System (ADS)

    Vieira, Tárcio A.; Zamboni-Rached, Michel; Gesualdi, Marcos R. R.

    2014-03-01

    In this paper we experimentally implement the spatial shape modeling of nondiffracting optical beams via computer generated holograms reconstructed optically by spatial light modulators. The results reported here are an experimental confirmation of the so-called Frozen Wave method, developed a few years ago. Optical beams of this type have potential applications in optical tweezers, medicine, atom guiding, remote sensing, etc.

  11. Neighboring genes shaping a single adaptive mimetic trait.

    PubMed

    Pardo-Diaz, Carolina; Jiggins, Chris D

    2014-01-01

    The colorful wing patterns of Heliconius butterflies represent an excellent system in which to study the genetic and developmental control of adaptation and convergence. Using qRT-PCR and in situ hybridization on developing wings of the co-mimic species Heliconius melpomene and Heliconius erato, we have profiled the expression of three candidate genes located in the genomic locus controlling red color pattern variation. We found convergent domains of gene expression in H. melpomene and H. erato associated with red wing elements in the two genes optix and kinesin. During early pupal development of both species, the expression of optix perfectly associated with all red pattern elements whereas that of kinesin was specifically correlated with the presence of the red forewing band. These results provide evidence for the use of these two tightly linked patterning genes, acting together to create convergent wing phenotypes in Heliconius and constituting a hotspot of adaptation. PMID:24393463

  12. Design concept for diffractive elements shaping partially coherent laser beams.

    PubMed

    Schäfer, D

    2001-11-01

    A new two-step design algorithm for the calculation of a diffractive phase element (DPE) for use with partially coherent laser beams is presented. The optical reconstruction of the DPE is modeled by the convolution of a coherent diffraction pattern and the far-field intensity distribution of a partially coherent laser beam. Numerical deconvolution is applied to derive a suitable amplitude pattern as signal input to a standard iterative Fourier transform algorithm (IFTA). Theory and numerical results are presented. Compared with a single-step IFTA design, this new approach yields nearly equal diffraction efficiencies and a relative improvement of 15% in signal reconstruction error. PMID:11688882

  13. Altered Visual Adaptation to Body Shape in Eating Disorders: Implications for Body Image Distortion.

    PubMed

    Mohr, Harald M; Rickmeyer, Constanze; Hummel, Dennis; Ernst, Mareike; Grabhorn, Ralph

    2016-07-01

    Previous research has shown that after adapting to a thin body, healthy participants (HP) perceive pictures of their own bodies as being fatter and vice versa. This aftereffect might contribute to the development of perceptual body image disturbances in eating disorders (ED).In the present study, HP and ED completed a behavioral experiment to rate manipulated pictures of their own bodies after adaptation to thin or fat body pictures. After adapting to a thin body, HP judged a thinner than actual body picture to be the most realistic and vice versa, resembling a typical aftereffect. ED only showed such an adaptation effect when they adapted to fat body pictures.The reported results indicate a relationship between body image distortion in ED and visual body image adaptation. It can be suspected that due to a pre-existing, long-lasting adaptation to thin body shapes in ED, an additional visual adaption to thin body shapes cannot be induced. Hence this pre-existing adaptation to thin body shapes could induce perceptual body image distortions in ED. PMID:26921409

  14. Ultrafast laser beam shaping for material processing at imaging plane by geometric masks using a spatial light modulator

    NASA Astrophysics Data System (ADS)

    Kuang, Zheng; Li, Jiangning; Edwardson, Stuart; Perrie, Walter; Liu, Dun; Dearden, Geoff

    2015-07-01

    We have demonstrated an original ultrafast laser beam shaping technique for material processing using a spatial light modulator (SLM). Complicated and time-consuming diffraction far-field phase hologram calculations based on Fourier transformations are avoided, while simple and direct geometric masks are used to shape the incident beam at diffraction near-field. Various beam intensity shapes, such as square, triangle, ring and star, are obtained and then reconstructed at the imaging plane of an f-theta lens. The size of the shaped beam is approximately 20 μm, which is comparable to the beam waist at the focal plane. A polished stainless steel sample is machined by the shaped beam at the imaging plane. The shape of the ablation footprint well matches the beam shape.

  15. Effect of axial load on mode shapes and frequencies of beams

    NASA Technical Reports Server (NTRS)

    Shaker, F. J.

    1975-01-01

    An investigation of the effect of axial load on the natural frequencies and mode shapes of uniform beams and of a cantilevered beam with a concentrated mass at the tip is presented. Characteristic equations which yield the frequencies and mode shape functions for the various cases are given. The solutions to these equations are presented by a series of graphs so that frequency as a function of axial load can readily be determined. The effect of axial load on the mode shapes are also depicted by another series of graphs.

  16. Woven type smart soft composite beam with in-plane shape retention

    NASA Astrophysics Data System (ADS)

    Wu, Renzhe; Han, Min-Woo; Lee, Gil-Yong; Ahn, Sung-Hoon

    2013-12-01

    Shape memory alloy (SMA) wire embedded composites (SMAECs) are widely used as morphing structures in small-size and high-output systems. However, conventional SMAECs cannot keep deformed shapes without additional energy. In this paper, a new kind of smart structure named the woven type smart soft composite (SSC) beam is introduced, which is not only capable of morphing, but also maintaining its deformed shape without additional energy. The woven type SSC beam consists of two parts: woven wires and matrix. The selected woven wires are nitinol (Ni-Ti) SMA wires and glass fibers, while the matrix part is polydimethylsiloxane (PDMS). In order to evaluate the performance of the woven type SSC beam in areas such as in-plane deformation, blocking force and repeatability, a beam-shape specimen is prepared of size 100 mm (length) × 8 mm (width) ×3 mm (thickness). The fabricated SSC beam achieved 21 mm deformation and 16 mm shape retention. Blocking force was measured using a dynamometer, and was about 60 mN. In the repeatability test, it recovered almost the same position when its cooling time was 90 s more. Consequently, the woven type SSC beam can be applied to bio-mimicking, soft morphing actuators, consuming less energy than traditional SMAECs.

  17. Shaping single walled nanotubes with an electron beam

    SciTech Connect

    Zobelli, A.; Gloter, A.; Colliex, C.; Ewels, C. P.

    2008-01-15

    We show that electron irradiation in a dedicated scanning transmission microscope can be used as a nano-electron-lithography technique allowing the controlled reshaping of single walled carbon and boron nitride nanotubes. The required irradiation conditions have been optimized on the basis of total knock-on cross sections calculated within density functional based methods. It is then possible to induce morphological modifications, such as a local change of the tube chirality, by sequentially removing several tens of atoms with a nanometrical spatial resolution. We show that electron beam heating effects are limited. Thus, electron beam induced vacancy migration and nucleation might be excluded. These irradiation techniques could open new opportunities for nanoengineering a large variety of nanostructured materials.

  18. Hybrid laser-beam-shaping system for rotatable dual beams with long depth of focus

    NASA Astrophysics Data System (ADS)

    Chou, Fu-Lung; Chen, Cheng-Huan; Lin, Yu-Chung; Lin, Mao-Chi

    2016-08-01

    A laser processing system consisting of two diffractive elements and one refractive element is proposed enabling a Gaussian laser beam to be transformed into two beams with a depth of focus of up to 150 µm and focal spot smaller than 5 µm. For specific laser processing, the two beams are rotatable when the beam-splitting diffractive element is rotated. The overall system is versatile for laser cutting and drilling.

  19. Beam-shape effects in nonlinear Compton and Thomson scattering

    SciTech Connect

    Heinzl, T.; Seipt, D.; Kaempfer, B.

    2010-02-15

    We discuss intensity effects in collisions between beams of optical photons from a high-power laser and relativistic electrons. Our main focus is on the modifications of the emission spectra due to realistic finite-beam geometries. By carefully analyzing the classical limit we precisely quantify the distinction between strong-field QED Compton scattering and classical Thomson scattering. A purely classical, but fully covariant, calculation of the bremsstrahlung emitted by an electron in a plane-wave laser field yields radiation into harmonics, as expected. This result is generalized to pulses of finite duration and explains the appearance of line broadening and harmonic substructure as an interference phenomenon. The ensuing numerical treatment confirms that strong focusing of the laser leads to a broad continuum while higher harmonics become visible only at moderate focusing, and hence lower intensity. We present a scaling law for the backscattered photon spectral density which facilitates averaging over electron beam phase space. Finally, we propose a set of realistic parameters such that the observation of intensity-induced spectral red shift, higher harmonics, and their substructure becomes feasible.

  20. Numerical optimization approaches of single-pulse conduction laser welding by beam shape tailoring

    NASA Astrophysics Data System (ADS)

    Sundqvist, J.; Kaplan, A. F. H.; Shachaf, L.; Brodsky, A.; Kong, C.; Blackburn, J.; Assuncao, E.; Quintino, L.

    2016-04-01

    While circular laser beams are usually applied in laser welding, for certain applications tailoring of the laser beam shape, e.g. by diffractive optical elements, can optimize the process. A case where overlap conduction mode welding should be used to produce a C-shaped joint was studied. For the dimensions studied in this paper, the weld joint deviated significantly from the C-shape of the single-pulse laser beam. Because of the complex heat flow interactions, the process requires optimization. Three approaches for extracting quantitative indicators for understanding the essential heat flow contributions process and for optimizing the C-shape of the weld and of the laser beam were studied and compared. While integral energy properties through a control volume and temperature gradients at key locations only partially describe the heat flow behaviour, the geometrical properties of the melt pool isotherm proved to be the most reliable method for optimization. While pronouncing the C-ends was not sufficient, an additional enlargement of the laser beam produced the desired C-shaped weld joint. The approach is analysed and the potential for generalization is discussed.

  1. New vistas in refractive laser beam shaping with an analytic design approach

    NASA Astrophysics Data System (ADS)

    Duerr, Fabian; Thienpont, Hugo

    2014-05-01

    Many commercial, medical and scientific applications of the laser have been developed since its invention. Some of these applications require a specific beam irradiance distribution to ensure optimal performance. Often, it is possible to apply geometrical methods to design laser beam shapers. This common design approach is based on the ray mapping between the input plane and the output beam. Geometric ray mapping designs with two plano-aspheric lenses have been thoroughly studied in the past. Even though analytic expressions for various ray mapping functions do exist, the surface profiles of the lenses are still calculated numerically. In this work, we present an alternative novel design approach that allows direct calculation of the rotational symmetric lens profiles described by analytic functions. Starting from the example of a basic beam expander, a set of functional differential equations is derived from Fermat's principle. This formalism allows calculating the exact lens profiles described by Taylor series coefficients up to very high orders. To demonstrate the versatility of this new approach, two further cases are solved: a Gaussian to at-top irradiance beam shaping system, and a beam shaping system that generates a more complex dark-hollow Gaussian (donut-like) irradiance profile with zero intensity in the on-axis region. The presented ray tracing results confirm the high accuracy of all calculated solutions and indicate the potential of this design approach for refractive beam shaping applications.

  2. Electrowetting-Controlled Dual Liquid Prism for Adaptive Beam Steering

    NASA Astrophysics Data System (ADS)

    Cheng, Jiangtao

    2015-03-01

    The use of concentrating photovoltaic (CPV) technology has been the most promising method of harvesting solar radiation. These CPV systems often require motor-driven tracking devices to steer the sun's beams onto solar cells. The cost of maintaining these tracking systems is the primary inhibitor for widespread application. We aim to overcome the need for mechanical trackers through the use of an electrowetting-driven solar tracking (EWST) system. The electrowetting-driven solar tracking system consists of an array of novel electrowetting-controlled dual liquid prisms, which are filled with immiscible fluids that have large differences in refractive indices. The naturally formed meniscus between the fluids can function as a dynamic optical prism. Via the full-range modulation of the liquid prisms, incident sunlight can be adaptively tracked, steered, and focused onto CPV cells through a fixed optical condenser. Furthermore, unlike the conventional and cumbersome motor-driven tracking systems used today, the liquid prism system would be suitable for rooftop applications. The results of this project reveal that the EWST system has the potential to generate ~ 70% more green energy at 50% of the conventional capital cost.

  3. Optical apparatus using liquid crystals for shaping the spatial intensity of optical beams having designated wavelengths

    DOEpatents

    Jacobs, Stephen D.; Cerqua, Kathleen A.

    1987-01-01

    The spatial intensity profile of an optical beam of designated wavelengths, such as a laser beam, is shaped (the beam is apodized) by means of cholesteric liquid crystals of opposite chirality disposed successively along the path of the beam. The crystals have curved surfaces, which may be defined by a lens which defines the thickness of the liquid crystal fluid gap in a liquid crystal cell, so as to vary the selective reflection of the designated wavelength across the aperture of the beam. In this way, a soft aperture is provided. By using tandem cell pairs having liquid crystals of opposite chirality, but of different pitch, and with lenses of different curvature, beams of different wavelengths which are projected colinearly along the path may be individually tailored in spatial intensity profile.

  4. Optical apparatus using liquid crystals for shaping the spatial intensity of optical beams having designated wavelengths

    DOEpatents

    Jacobs, S.D.; Cerqua, K.A.

    1987-07-14

    The spatial intensity profile of an optical beam of designated wavelengths, such as a laser beam, is shaped (the beam is apodized) by means of cholesteric liquid crystals of opposite chirality disposed successively along the path of the beam. The crystals have curved surfaces, which may be defined by a lens which defines the thickness of the liquid crystal fluid gap in a liquid crystal cell, so as to vary the selective reflection of the designated wavelength across the aperture of the beam. In this way, a soft aperture is provided. By using tandem cell pairs having liquid crystals of opposite chirality, but of different pitch, and with lenses of different curvature, beams of different wavelengths which are projected colinearly along the path may be individually tailored in spatial intensity profile. 11 figs.

  5. Dynamic plasmonic beam shaping by vector beams with arbitrary locally linear polarization states

    SciTech Connect

    Man, Zhongsheng; Zhang, Yuquan; Zhang, Chonglei; Du, Luping; Min, Changjun E-mail: xcyuan@szu.edu.cn; Yuan, X.-C. E-mail: xcyuan@szu.edu.cn; Zhu, Siwei; Paul Urbach, H.

    2014-07-07

    Vector beams, which have space-variant state of polarization (SOP) comparing with scalar beams with spatially homogeneous SOP, are used to manipulate surface plasmon polarizations (SPPs). We find that the excitation, orientation, and distribution of the focused SPPs excited in a high numerical aperture microscopic configuration highly depend on the space-variant polarization of the incident vector beam. When it comes to vector beam with axial symmetry, multi-foci of SPPs with the same size and uniform intensity can be obtained, and the number of foci is depending on the polarization order n. Those properties can be of great value in biological sensor and plasmonic tweezers applications.

  6. Neural adaptation to non-symbolic number and visual shape: an electrophysiological study.

    PubMed

    Soltész, Fruzsina; Szűcs, Dénes

    2014-12-01

    Several studies assumed that the analysis of numerical information happens in a fast and automatic manner in the human brain. Utilizing the high temporal resolution of electroencephalography (EEG) in a passive oddball adaptation paradigm, we compared event-related brain potentials (ERPs) evoked by unattended shape changes and unattended numerosity changes. We controlled visual stimulus properties in a stringent manner. Unattended changes in shape elicited significant, gradual adaptation effects in the range of early visual components, indicating the fast and automatic processing of shapes. Changes in numerosity did not elicit significant changes in these early ERP components. The lack of early number-specific effects was qualified by a significant interaction between Shape and Number conditions. Number change elicited gradual ERP effects only on late ERP components. We conclude that numerosity is a higher-level property assembled from naturally correlating perceptual cues and hence, it is identified later in the cognitive processing stream. PMID:25258032

  7. Shaped beam scattering from a single lymphocyte cell by generalized Lorenz-Mie theory

    NASA Astrophysics Data System (ADS)

    Wang, Jia Jie; Han, Lu; Han, Yi Ping; Gouesbet, Gerard; Wu, Xuecheng; Wu, Yingchun

    2014-01-01

    With the aim of improving the measurement capabilities of laser-based diagnostic instruments for cells, an eccentric stratified dielectric sphere model illuminated by an arbitrary shaped beam is applied to the modeling of light scattering by a single nucleated cell within the framework of the generalized Lorenz-Mie theory (GLMT). A particular attention is paid to the study of scattering properties of a lymphocyte cell from an arbitrary incident Gaussian beam. Numerical results concerning the influence of shaped beam parameters (beam waist radius, incident angle, location of beam center) as well as of cellular parameters (ratio of nucleus size to cell size, location of the nucleus within the cell) on the scattering properties are presented and discussed, with comparisons to the scattering behaviors from a concentric stratified sphere model. The results reveal that the forward scattering intensities are mainly determined by the cell size regardless of the nucleus/cell ratio, while sideward scattering signals are sensitive to the change of cell internal structure. As the beam waist radius varies, the scattering patterns in the present cases are similar to each other, although the absolute intensities are different. Additionally, location of the nucleus within the cell, incident angle of the beam as well as location of the beam waist center play significant effects on the light scattering intensity distributions.

  8. Load carrying capacity of RCC beams by replacing steel reinforcement bars with shape memory alloy bars

    NASA Astrophysics Data System (ADS)

    Bajoria, Kamal M.; Kaduskar, Shreya S.

    2016-04-01

    In this paper the structural behavior of reinforced concrete (RC) beams with smart rebars under two point loading system has been numerically studied, using Finite Element Method. The material used in this study is Super-elastic Shape Memory Alloys (SE SMAs) which contains nickel and titanium. In this study, different quantities of steel and SMA rebars have been used for reinforcement and the behavior of these models under two point bending loading system is studied. A comparison of load carrying capacity for the model between steel reinforced concrete beam and the beam reinforced with S.M.A and steel are performed. The results show that RC beams reinforced with combination of shape memory alloy and steel show better performance.

  9. Precision shape modification of nanodevices with a low-energy electron beam

    DOEpatents

    Zettl, Alex; Yuzvinsky, Thomas David; Fennimore, Adam

    2010-03-09

    Methods of shape modifying a nanodevice by contacting it with a low-energy focused electron beam are disclosed here. In one embodiment, a nanodevice may be permanently reformed to a different geometry through an application of a deforming force and a low-energy focused electron beam. With the addition of an assist gas, material may be removed from the nanodevice through application of the low-energy focused electron beam. The independent methods of shape modification and material removal may be used either individually or simultaneously. Precision cuts with accuracies as high as 10 nm may be achieved through the use of precision low-energy Scanning Electron Microscope scan beams. These methods may be used in an automated system to produce nanodevices of very precise dimensions. These methods may be used to produce nanodevices of carbon-based, silicon-based, or other compositions by varying the assist gas.

  10. Electro-bending characterization of adaptive 3D fiber reinforced plastics based on shape memory alloys

    NASA Astrophysics Data System (ADS)

    Ashir, Moniruddoza; Hahn, Lars; Kluge, Axel; Nocke, Andreas; Cherif, Chokri

    2016-03-01

    The industrial importance of fiber reinforced plastics (FRPs) is growing steadily in recent years, which are mostly used in different niche products, has been growing steadily in recent years. The integration of sensors and actuators in FRP is potentially valuable for creating innovative applications and therefore the market acceptance of adaptive FRP is increasing. In particular, in the field of highly stressed FRP, structural integrated systems for continuous component parts monitoring play an important role. This presented work focuses on the electro-mechanical characterization of adaptive three-dimensional (3D)FRP with integrated textile-based actuators. Here, the friction spun hybrid yarn, consisting of shape memory alloy (SMA) in wire form as core, serves as an actuator. Because of the shape memory effect, the SMA-hybrid yarn returns to its original shape upon heating that also causes the deformation of adaptive 3D FRP. In order to investigate the influences of the deformation behavior of the adaptive 3D FRP, investigations in this research are varied according to the structural parameters such as radius of curvature of the adaptive 3D FRP, fabric types and number of layers of the fabric in the composite. Results show that reproducible deformations can be realized with adaptive 3D FRP and that structural parameters have a significant impact on the deformation capability.

  11. Laser beam shape converter using spatially variable waveplate made by nanogratings inscription in fused silica

    NASA Astrophysics Data System (ADS)

    Gertus, T.; Michailovas, A.; Michailovas, K.; PetrauskienÄ--, V.

    2015-03-01

    In this work we present a beam shaping technique based on a spatially variable phase retardation plate inscribed inside bulk of fused silica glass by femtosecond laser pulses. Formation of self-assembled periodic nanostructures was exploited to fabricate the converter. During the fabrication process we control induced nanogratings orientation and retardance. Combination of a spatially variable waveplate and a polarizer acts as a spatially variable transmission filter. With a converter fabricated to transform an initially Gaussian beam to a flat-top beam we preserve more than 50% of initial laser power. Theoretically, the efficiency of the proposed converter could be up to 70%. The proposed converter with no absorbing elements possesses resistance to optical damage similar to that of fused silica. Additionally, the already-fabricated converter allows for on-the-fly adjustment of the beam shape from flat-top to a shape with a dip in the middle. The shaped beam was tested in a high power picosecond pulse amplifier.

  12. Ring beam shaping optics fabricated with ultra-precision cutting for YAG laser processing

    NASA Astrophysics Data System (ADS)

    Kuwano, Ryoichi; Koga, Toshihiko; Tokunaga, Tsuyoshi; Wakayama, Toshitaka; Otani, Yukitoshi; Fujii, Nobuyuki

    2012-03-01

    In this study, a method for generating ring intensity distribution at a refraction-type lens with an aspheric element was proposed, and the beam shaping optical element was finished using only ultra-precision cutting. The shape of the optical element and its irradiance pattern were determined from numerical calculation based on its geometrical and physical optics. An ultra-precision lathe was employed to fabricate beam shaping optical elements, and acrylic resin was used as the material. The transmittance of an optical element (a rotationally symmetrical body) with an aspheric surface fabricated using a single-crystal diamond tool was over 98%, and its surface roughness was 9.6 nm Ra. The method enabled the formation of a circular melting zone on a piece of stainless steel with a thickness of 300 μm through pulse YAG laser ( λ 1:06 μm) processing such that the average radius was 610 μm and the width was 100-200 μm. Circular processing using a ring beam shaping optical element can be realized by single-pulse beam irradiation without beam scanning.

  13. Effect of angular spread on the intensity distribution of arbitrarily shaped electron beams

    SciTech Connect

    Mohan, R.; Chui, C.S.; Fontenla, D.; Han, K.; Ballon, D.

    1988-03-01

    Knowledge of the relative intensity distribution at the patient's surface is essential for pencil beam calculations of three-dimensional dose distributions for arbitrarily shaped electron beams. To calculate the relative intensity distribution, the spatial spread resulting from angular spread is convolved with a two-dimensional step function whose shape corresponds to the applicator aperture. Two different approaches to obtain angular spread or the equivalent spatial spread are investigated. In the first method, the pencil beam angular spread is assumed to be Gaussian in shape. The angular spread constants (sigma theta) are then obtained from the slopes of measured intensity profiles. In the second method, the angular spread, in the form of an array of numerical values, is obtained by the deconvolution of measured intensity profiles. After obtaining the angular spread, the calculation for convolution is done in a number of parallel planes normal to the central axis at various distances from the electron collimator. Intensity at any arbitrary point in space is computed by interpolating between intensity distributions in adjacent planes on either side of the point. The effects of variations in angular spread as a function of field size for two treatment machines, one with a scanned electron beam and the other with a scattering foil, have been studied. The consequences of assuming angular spread to be of Gaussian shape are also examined. The electron intensity calculation techniques described in this paper apply primarily to methods of dose calculations that employ pencil beams generated using Monte Carlo simulations.

  14. Far field diffraction of an optical vortex beam by a fork-shaped grating

    NASA Astrophysics Data System (ADS)

    Stoyanov, Lyubomir; Topuzoski, Suzana; Stefanov, Ivan; Janicijevic, Ljiljana; Dreischuh, Alexander

    2015-09-01

    In this work we report experimental data confirming the analytically predicted transformation of the topological charge (TC) of an input optical vortex (OV) beam, generated by means of fork-shaped binary computer-generated hologram (CGH), after a second fork-shaped binary CGH. The final TC of the vortex is confirmed to be equal to the TC of the incident beam plus the diffraction order (with its sign) times the TC encoded in the binary grating. The radii of the transformed OVs in the far field also are found to agree fairly well with these predicted by the analytical theory.

  15. Piezoelectric energy harvesting from an L-shaped beam-mass structure

    NASA Astrophysics Data System (ADS)

    Erturk, Alper; Renno, Jamil M.; Inman, Daniel J.

    2008-03-01

    Cantilevered piezoelectric harvesters have been extensively considered in the energy harvesting literature. Mostly, a traditional cantilevered beam with one or more piezoceramic layers is located on a vibrating host structure. Motion of the host structure results in vibrations of the harvester beam and that yields an alternating voltage output. As an alternative to classical cantilevered beams, this paper presents a novel harvesting device; a flexible L-shaped beam-mass structure that can be tuned to have a two-to-one internal resonance to a primary resonance ω II ≅ 2ω I which is not possible for classical cantilevers). The L-shaped structure has been well investigated in the literature of nonlinear dynamics since the two-to-one internal resonance, along with the consideration of quadratic nonlinearities, may yield modal energy exchange (for excitation frequency ω≅ ω Ior the so-called saturation phenomenon (for ω≅ω II). As a part of our ongoing research on piezoelectric energy harvesting, we are investigating the possibility of improving the electrical outputs in energy harvesting by employing these features of the L-shaped structure. This paper aims to introduce the idea, describes the important features of the L-shaped harvester configuration and develops a linear distributed parameter model for predicting the electromechanically coupled response. In addition, this work proposes a direct application of the L-shaped piezoelectric energy harvester configuration for use as landing gears in unmanned air vehicle applications.

  16. Micro drilling using deformable mirror for beam shaping of ultra-short laser pulses

    NASA Astrophysics Data System (ADS)

    Smarra, Marco; Strube, Anja; Dickmann, Klaus

    2016-03-01

    Using ultra-short laser pulses for micro structuring or drilling applications reduces the thermal influence to the surrounding material. The best achievable beam profile equals a Gaussian beam. Drilling with this beam profile results in cylindrical holes. To vary the shape of the holes, the beam can either be scanned or - for single pulse and percussion drilling - manipulated by masks or lenses. A high flexible method for beam shaping can be realized by using a deformable mirror. This mirror contains a piezo-electric ceramic, which can be deformed by an electric potential. By separating the ceramic into independent controllable segments, the shape of the surface can be varied individually. Due to the closed surface of the mirror, there is no loss of intensity due to diffraction. The mirror deformation is controlled by Zernike polynomials and results e.g. in a lens behavior. In this study a deformable mirror was used to generate e.g. slits in thin steel foils by percussion drilling using ultra-short laser pulses. The influence of the cylindrical deformation to the laser beam and the resulting geometry of the generated holes was studied. It was demonstrated that due to the high update rate up to 150 Hz the mirror surface can be varied in each scan cycle, which results in a high flexible drilling process.

  17. Generic method for automatic bladder segmentation on cone beam CT using a patient-specific bladder shape model

    SciTech Connect

    Schoot, A. J. A. J. van de Schooneveldt, G.; Wognum, S.; Stalpers, L. J. A.; Rasch, C. R. N.; Bel, A.; Hoogeman, M. S.; Chai, X.

    2014-03-15

    Purpose: The aim of this study is to develop and validate a generic method for automatic bladder segmentation on cone beam computed tomography (CBCT), independent of gender and treatment position (prone or supine), using only pretreatment imaging data. Methods: Data of 20 patients, treated for tumors in the pelvic region with the entire bladder visible on CT and CBCT, were divided into four equally sized groups based on gender and treatment position. The full and empty bladder contour, that can be acquired with pretreatment CT imaging, were used to generate a patient-specific bladder shape model. This model was used to guide the segmentation process on CBCT. To obtain the bladder segmentation, the reference bladder contour was deformed iteratively by maximizing the cross-correlation between directional grey value gradients over the reference and CBCT bladder edge. To overcome incorrect segmentations caused by CBCT image artifacts, automatic adaptations were implemented. Moreover, locally incorrect segmentations could be adapted manually. After each adapted segmentation, the bladder shape model was expanded and new shape patterns were calculated for following segmentations. All available CBCTs were used to validate the segmentation algorithm. The bladder segmentations were validated by comparison with the manual delineations and the segmentation performance was quantified using the Dice similarity coefficient (DSC), surface distance error (SDE) and SD of contour-to-contour distances. Also, bladder volumes obtained by manual delineations and segmentations were compared using a Bland-Altman error analysis. Results: The mean DSC, mean SDE, and mean SD of contour-to-contour distances between segmentations and manual delineations were 0.87, 0.27 cm and 0.22 cm (female, prone), 0.85, 0.28 cm and 0.22 cm (female, supine), 0.89, 0.21 cm and 0.17 cm (male, supine) and 0.88, 0.23 cm and 0.17 cm (male, prone), respectively. Manual local adaptations improved the segmentation

  18. Adaptive Square-Shaped Trajectory-Based Service Location Protocol in Wireless Sensor Networks

    PubMed Central

    Lim, Hwa-Jung; Lee, Joa-Hyoung; Lee, Heon-Guil

    2010-01-01

    In this paper we propose an adaptive square-shaped trajectory (ASST)-based service location method to ensure load scalability in wireless sensor networks. This first establishes a square-shaped trajectory over the nodes that surround a target point computed by the hash function and any user can access it, using the hash. Both the width and the size of the trajectory are dynamically adjustable, depending on the number of queries made to the service information on the trajectory. The number of sensor nodes on the trajectory varies in proportion to the changing trajectory shape, allowing high loads to be distributed around the hot spot area. PMID:22399889

  19. Beam shaping assembly optimization for (7)Li(p,n)(7)Be accelerator based BNCT.

    PubMed

    Minsky, D M; Kreiner, A J

    2014-06-01

    Within the framework of accelerator-based BNCT, a project to develop a folded Tandem-ElectroStatic-Quadrupole accelerator is under way at the Atomic Energy Commission of Argentina. The proposed accelerator is conceived to deliver a proton beam of 30mA at about 2.5MeV. In this work we explore a Beam Shaping Assembly (BSA) design based on the (7)Li(p,n)(7)Be neutron production reaction to obtain neutron beams to treat deep seated tumors. PMID:24345525

  20. Proton beam shaped by "particle lens" formed by laser-driven hot electrons

    NASA Astrophysics Data System (ADS)

    Zhai, S. H.; Shen, B. F.; Wang, W. P.; Zhang, H.; He, S. K.; Lu, F.; Zhang, F. Q.; Deng, Z. G.; Dong, K. G.; Wang, S. Y.; Zhou, K. N.; Xie, N.; Wang, X. D.; Zhang, L. G.; Huang, S.; Liu, H. J.; Zhao, Z. Q.; Gu, Y. Q.; Zhang, B. H.; Xu, Z. Z.

    2016-05-01

    Two-dimensional tailoring of a proton beam is realized by a "particle lens" in our experiment. A large quantity of electrons, generated by an intense femtosecond laser irradiating a polymer target, produces an electric field strong enough to change the trajectory and distribution of energetic protons flying through the electron area. The experiment shows that a strip pattern of the proton beam appears when hot electrons initially converge inside the plastic plate. Then the shape of the proton beam changes to a "fountain-like" pattern when these hot electrons diffuse after propagating a distance.

  1. A Shape Memory Polymer Dialysis Needle Adapter for the Reduction of Hemodynamic Stress within Arteriovenous Grafts

    SciTech Connect

    Ortega, J M; Small, W; Wilson, T S; Benett, W; Loge, J; Maitland, D J

    2006-08-16

    A deployable, shape memory polymer adapter is investigated for reducing the hemodynamic stress caused by a dialysis needle flow within an arteriovenous graft. Computational fluid dynamics simulations of dialysis sessions with and without the adapter demonstrate that the adapter provides a significant decrease in the wall shear stress. In vitro flow visualization measurements are made within a graft model following delivery and actuation of a prototype shape memory polymer adapter. Vascular access complications resulting from arteriovenous (AV) graft failures account for over $1 billion per year in the health care costs of dialysis patients in the U.S.[1] The primary mode of failure of arteriovenous fistulas (AVF's) and polytetrafluoroethylene (PTFE) grafts is the development of intimal hyperplasia (IH) and the subsequent formation of stenotic lesions, resulting in a graft flow decline. The hemodynamic stresses arising within AVF's and PTFE grafts play an important role in the pathogenesis of IH. Studies have shown that vascular damage can occur in regions where there is flow separation, oscillation, or extreme values of wall shear stress (WSS).[2] Nevaril et al.[3] show that exposure of red blood cells to WSS's on the order of 1500 dynes/cm2 can result in hemolysis. Hemodynamic stress from dialysis needle flow has recently been investigated for the role it plays in graft failure. Using laser Doppler velocimetry measurements, Unnikrishnan et al.[4] show that turbulence intensities are 5-6 times greater in the AV flow when the needle flow is present and that increased levels of turbulence exist for approximately 7-8cm downstream of the needle. Since the AVF or PTFE graft is exposed to these high levels of hemodynamic stress several hours each week during dialysis sessions, it is quite possible that needle flow is an important contributor to vascular access occlusion.[4] We present a method for reducing the hemodynamic stress in an AV graft by tailoring the fluid

  2. Dynamic MEMS-based linear (1D) diffusers for laser beam homogenizing and beam shaping

    NASA Astrophysics Data System (ADS)

    Masson, J.; Bich, A.; Noell, W.; Voelkel, R.; Weible, K. J.; De Rooij, N. F.

    2009-08-01

    We present a dynamic laser beam shaper based on MEMS technology. We show a prototype of a dynamic diffuser made of single crystal silicon. A linearly deformable silicon micromembrane is used to diffuse a laser beam in one dimension. Resonance frequencies of the membrane can range from 1 kHz to 100 kHz. Diffusing angle can be tuned by adjusting the driving voltage. We measured a diffusing angle of 0.16° for an actuation voltage of 20 V.

  3. Active vibration control of a flexible cantilever beam using shape memory alloy actuators

    NASA Astrophysics Data System (ADS)

    Suzuki, Y.; Kagawa, Y.

    2010-08-01

    This paper demonstrates the feasibility of using shape memory alloys (SMAs) as actuators to control the vibration of a flexible cantilever beam. In a tendon mechanism, SMAs are controlled in a push-pull fashion based on H-infinity theory and taking into account the uncertainty in the actuator performance. Using this mechanism, the four vibrational modes (three bending and one torsional) of the cantilever beam can be simultaneously damped. To control bending and torsional vibrational modes of a flexible beam, we install SMAs obliquely in a beam-SMA structure, then measure and theoretically model the properties of an actuator consisting of an SMA and a spring. Using the properties of the actuator, we introduce the state equations based on the dynamic model of the proposed beam-SMA structure and design the active control system according to H-infinity theory. Finally, we experimentally verify the functioning of the system.

  4. Shaping of light beams by 3D direct laser writing on facets of nonlinear crystals.

    PubMed

    Lightman, Shlomi; Gvishi, Raz; Hurvitz, Gilad; Arie, Ady

    2015-10-01

    We demonstrate experimentally spatial-mode conversions of light beams generated in a quadratic nonlinear process by micron-scale structures placed on the facets of nonlinear crystals. These structures were printed on the crystal facets using a three-dimensional (3D) direct laser writing system. The functional structures were designed to modify the phase of the beam at specific wavelengths, thereby enabling conversion of a fundamental Gaussian laser beam into different high-order Hermite-Gaussian modes, Laguerre-Gaussian modes, and zeroth-order Bessel beams of the second harmonic. This facet functionalization opens exciting new opportunities for robust and compact beam shaping in a nonlinear interaction without compromising the conversion efficiency. PMID:26421556

  5. Conservatism and Adaptability during Squirrel Radiation: What Is Mandible Shape Telling Us?

    PubMed Central

    Casanovas-Vilar, Isaac; van Dam, Jan

    2013-01-01

    Both functional adaptation and phylogeny shape the morphology of taxa within clades. Herein we explore these two factors in an integrated way by analyzing shape and size variation in the mandible of extant squirrels using landmark-based geometric morphometrics in combination with a comparative phylogenetic analysis. Dietary specialization and locomotion were found to be reliable predictors of mandible shape, with the prediction by locomotion probably reflecting the underlying diet. In addition a weak but significant allometric effect could be demonstrated. Our results found a strong phylogenetic signal in the family as a whole as well as in the main clades, which is in agreement with the general notion of squirrels being a conservative group. This fact does not preclude functional explanations for mandible shape, but rather indicates that ancient adaptations kept a prominent role, with most genera having diverged little from their ancestral clade morphologies. Nevertheless, certain groups have evolved conspicuous adaptations that allow them to specialize on unique dietary resources. Such adaptations mostly occurred in the Callosciurinae and probably reflect their radiation into the numerous ecological niches of the tropical and subtropical forests of Southeastern Asia. Our dietary reconstruction for the oldest known fossil squirrels (Eocene, 36 million years ago) show a specialization on nuts and seeds, implying that the development from protrogomorphous to sciuromorphous skulls was not necessarily related to a change in diet. PMID:23593456

  6. Method for reconstruction of shape of specular surfaces using scanning beam deflectometry

    NASA Astrophysics Data System (ADS)

    Miks, Antonin; Novak, Jiri; Novak, Pavel

    2013-07-01

    A new method is presented for reconstruction of the shape of specular surfaces using scanning beam deflectometry. A description and an analysis of a deflectometric technique for 3D measurements of specular surfaces is provided and it is derived that a surface reconstruction problem leads to a theoretical description by a nonlinear partial differential equation. The surface shape can be calculated by solution of the derived equation. A method was proposed, which makes possible to find effectively the solution of the deflectometric differential equation for the shape reconstruction. The presented method is noncontact and no reference surface is needed as in interferometry.

  7. Minimal-effort planning of active alignment processes for beam-shaping optics

    NASA Astrophysics Data System (ADS)

    Haag, Sebastian; Schranner, Matthias; Müller, Tobias; Zontar, Daniel; Schlette, Christian; Losch, Daniel; Brecher, Christian; Roßmann, Jürgen

    2015-03-01

    In science and industry, the alignment of beam-shaping optics is usually a manual procedure. Many industrial applications utilizing beam-shaping optical systems require more scalable production solutions and therefore effort has been invested in research regarding the automation of optics assembly. In previous works, the authors and other researchers have proven the feasibility of automated alignment of beam-shaping optics such as collimation lenses or homogenization optics. Nevertheless, the planning efforts as well as additional knowledge from the fields of automation and control required for such alignment processes are immense. This paper presents a novel approach of planning active alignment processes of beam-shaping optics with the focus of minimizing the planning efforts for active alignment. The approach utilizes optical simulation and the genetic programming paradigm from computer science for automatically extracting features from a simulated data basis with a high correlation coefficient regarding the individual degrees of freedom of alignment. The strategy is capable of finding active alignment strategies that can be executed by an automated assembly system. The paper presents a tool making the algorithm available to end-users and it discusses the results of planning the active alignment of the well-known assembly of a fast-axis collimator. The paper concludes with an outlook on the transferability to other use cases such as application specific intensity distributions which will benefit from reduced planning efforts.

  8. 21 CFR 892.5710 - Radiation therapy beam-shaping block.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Radiation therapy beam-shaping block. 892.5710 Section 892.5710 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES RADIOLOGY DEVICES Therapeutic Devices § 892.5710 Radiation therapy...

  9. Optimal shape control of a beam using piezoelectric actuators with low control voltage

    NASA Astrophysics Data System (ADS)

    Yu, Y.; Zhang, X. N.; Xie, S. L.

    2009-09-01

    This paper deals with the shape control of a cantilever beam structure by using laminated piezoelectric actuators (LPAs) with a low control voltage. The shape control equation of the cantilever beam partially covered with LPAs is derived based on the constitutive relations of the elastic material and piezoelectric material and shear deformation beam theory (Timoshenko theory). The actuating forces produced by the LPAs are formulated as well. It reveals how the actuating forces depend on the number of piezoelectric layers, the thickness of piezoelectric layers and the position of the actuators. The driving voltages of the LPAs are then determined by a genetic optimization algorithm. The shape control of the cantilever beam from applying the optimal voltage to the LPAs is simulated. The simulation results show that an LPA of large layer number is able to diminish effectively the pre-deflection of the beam under a low control voltage. The voltage applied to the LPA of five layers was almost five times smaller than that of one layer. In addition, increasing the number of LPA layers can significantly improve the control performance as the acting forces of the LPA are a quadratic function of the LPA layer number. The L2 norm of the displacement array of all nodes is diminished about 30% after optimization. Also with the same low control voltage, the LPA can obtain a better control performance than the conventional single layer piezoelectric actuator.

  10. Design of a gradient-index beam shaping system via a genetic algorithm optimization method

    NASA Astrophysics Data System (ADS)

    Evans, Neal C.; Shealy, David L.

    2000-10-01

    Geometrical optics - the laws of reflection and refraction, ray tracing, conservation of energy within a bundle of rays, and the condition of constant optical path length - provides a foundation for design of laser beam shaping systems. This paper explores the use of machine learning techniques, concentrating on genetic algorithms, to design laser beam shaping systems using geometrical optics. Specifically, a three-element GRIN laser beam shaping system has been designed to expand and transform a Gaussian input beam profile into one with a uniform irradiance profile. Solution to this problem involves the constrained optimization of a merit function involving a mix of discrete and continuous parameters. The merit function involves terms that measure the deviation of the output beam diameter, divergence, and irradiance from target values. The continuous parameters include the distances between the lens elements, the thickness, and radii of the lens elements. The discrete parameters include the GRIN glass types from a manufacturer's database, the gradient direction of the GRIN elements (positive or negative), and the actual number of lens elements in the system (one to four).

  11. Beam shaping system based on a prism array for improving the throughput of a dispersive spectrometer.

    PubMed

    Shi, Zhendong; Fang, Liang; Fan, Bin; Zhou, Chongxi

    2015-04-01

    A beam shaping system (BSS) for improving the throughput of a dispersive spectrometer is presented by employing two anamorphic lenses and a prism array to segment the beam. The BSS was designed based on the inverse method of beam shaping for laser diode bars and the means of an optical slicer. In an experiment, a BSS was set up so that the incident light of a neon lamp with a circular spot from an input fiber was transformed into an elliptical spot coupled into a slit of a spectrometer without a change of divergence. Spectral measurement results demonstrate that the throughput of the dispersive spectrometer was doubled without loss of spectral resolution. The BSS can be combined with the existing dispersive spectrometer to improve the luminous flux and signal-to-noise ratio. PMID:25967181

  12. Surface-active element effects on the shape of GTA, laser, and electron-beam welds

    SciTech Connect

    Heiple, C.R.; Roper, J.R.; Stagner, R.T.; Aden, R.J.

    1983-03-01

    Laser and electron-beam welds were passed across selenium-doped zones in 21-6-9 stainless steel. The depth/width (d/w) ratio of a defocused laser weld with a weld pool shape similar to a GTA weld increased by over 200% in a zone where 66 ppm selenium had been added. Smaller increases were observed in selenium-doped zones for a moderately defocused electron beam weld with a higher d/w ratio in undoped base metal. When laser or electron beam weld penetration was by a keyhole mechanism, no change in d/w ratio occurred in selenium-doped zones. The results confirm the surface-tension-driven fluid-flow model for the effect of minor elements on GTA weld pool shape. Other experimental evidence bearing on the effect of minor elements on GTA weld penetration is summarized.

  13. Measurements of Variable-Shaped Electron Beams with Solid-State Detector and Scattering Aperture

    NASA Astrophysics Data System (ADS)

    Sakakibara, Makoto; Ohta, Hiroya; Kanosue, Tadashi; Sohda, Yasunari; Ban, Naoma

    2007-09-01

    A highly accurate method for measuring beam properties in a variable-shaped electron beam (VSB) system has been developed. This method is based on a knife-edge method with a solid-state detector (SSD) and scattering apertures. In VSB system, it is necessary to measure both beam profile and beam position for a long time. To meet this requirement, many aperture marks on a silicon membrane were prepared in a measurement unit. Using this unit, the accuracy and stability of beam-size and beam position measurements were evaluated in VBS system (HL-7000D, Hitachi-HITEC). As a result, the repeatability error for beam size was obtained to be smaller than 2 nm (3σ) and the repeatability error for beam position was obtained to be 0.82 nm (3σ). Moreover, a multitude of repeat experiments showed that this measurement unit can be used for more than ten years. Consequently, it was confirmed that this measurement method is useful for the high accuracy of a VSB system.

  14. New family of light beams and mirror shapes for future LIGO interferometers

    NASA Astrophysics Data System (ADS)

    Bondarescu, Mihai; Thorne, Kip S.

    2006-10-01

    Advanced LIGO’s present baseline design uses arm cavities with Gaussian light beams supported by spherical mirrors. Because Gaussian beams have large intensity gradients in regions of high intensity, they average somewhat poorly over fluctuating bumps and valleys on the mirror surfaces (thermal noise). Flat-topped light beams (mesa beams) are being considered as an alternative because they average over thermal noise more effectively. However, the proposed mesa beams are supported by nearly-flat mirrors, which experience a very serious tilt instability. In this paper we propose an alternative configuration in which mesa-shaped beams are supported by nearly-concentric spheres, which experience only a weak tilt instability. The tilt instability is analyzed for these mirrors in a companion paper by Savov and Vyatchanin. We also propose a one-parameter family of light beams and mirrors in which, as the parameter α varies continuously from 0 to π, the beams and supporting mirrors get deformed continuously from the nearly-flat-mirrored mesa configuration (FM) at α=0, to the nearly-concentric-mirrored mesa configuration (CM) at α=π. The FM and CM configurations at the endpoints are close to optically unstable, and as α moves away from 0 or π, the optical stability improves.

  15. Generalization of the extended optical theorem for scalar arbitrary-shape acoustical beams in spherical coordinates.

    PubMed

    Mitri, F G; Silva, G T

    2014-11-01

    The extended optical theorem is generalized for scalar acoustical beams of arbitrary character with any angle of incidence interacting with an object of arbitrary geometric shape and size, and placed randomly in the beam's path with any scattering angle. Analytical expressions for the extinction, absorption, and scattering cross sections are derived, and the connections with the axial (i.e., along the direction of wave propagation) torque and radiation force calculations are discussed. As examples to illustrate the analysis for a viscoelastic object, the extinction, absorption, and scattering cross sections are provided for an infinite plane progressive wave, infinite nondiffracting Bessel beams, a zero-order spherical quasi-Gaussian beam, and a Bessel-Gauss vortex beam emanating from a finite circular aperture, which reduces to a finite high-order Bessel beam, a finite zero-order Bessel beam, and a finite piston radiator vibrating uniformly with appropriate selection of beam parameters. The similarity with the asymptotic quantum inelastic cross sections is also mentioned. PMID:25493897

  16. New family of light beams and mirror shapes for future LIGO interferometers

    SciTech Connect

    Bondarescu, Mihai; Thorne, Kip S.

    2006-10-15

    Advanced LIGO's present baseline design uses arm cavities with Gaussian light beams supported by spherical mirrors. Because Gaussian beams have large intensity gradients in regions of high intensity, they average somewhat poorly over fluctuating bumps and valleys on the mirror surfaces (thermal noise). Flat-topped light beams (mesa beams) are being considered as an alternative because they average over thermal noise more effectively. However, the proposed mesa beams are supported by nearly-flat mirrors, which experience a very serious tilt instability. In this paper we propose an alternative configuration in which mesa-shaped beams are supported by nearly-concentric spheres, which experience only a weak tilt instability. The tilt instability is analyzed for these mirrors in a companion paper by Savov and Vyatchanin. We also propose a one-parameter family of light beams and mirrors in which, as the parameter {alpha} varies continuously from 0 to {pi}, the beams and supporting mirrors get deformed continuously from the nearly-flat-mirrored mesa configuration (FM) at {alpha}=0, to the nearly-concentric-mirrored mesa configuration (CM) at {alpha}={pi}. The FM and CM configurations at the endpoints are close to optically unstable, and as {alpha} moves away from 0 or {pi}, the optical stability improves.

  17. Experimental investigation on the beam quality improvement of the fiber laser by adaptive optics

    NASA Astrophysics Data System (ADS)

    Bian, Q.; Huang, L.; Wang, X. J.; Ma, X. K.; Yan, P.; Gong, M. L.

    2015-12-01

    This paper describes an adaptive optical system that is introduced to improve the beam quality of a fiber laser. Since a distorted wavefront would degrade the beam quality of a laser beam, a deformable mirror is employed to compensate for the wavefront aberration using closed-loop control in this system. The beam quality factor is measured and the far-field focus spot is detected as well. The experiment results show that the beam quality factor can be improved from 5-7 to 3-4 and the focus spot can be improved as well. The feasibility of the system is proved.

  18. High-damage-threshold static laser beam shaping using optically patterned liquid-crystal devices.

    PubMed

    Dorrer, C; Wei, S K-H; Leung, P; Vargas, M; Wegman, K; Boulé, J; Zhao, Z; Marshall, K L; Chen, S H

    2011-10-15

    Beam shaping of coherent laser beams is demonstrated using liquid crystal (LC) cells with optically patterned pixels. The twist angle of a nematic LC is locally set to either 0 or 90° by an alignment layer prepared via exposure to polarized UV light. The two distinct pixel types induce either no polarization rotation or a 90° polarization rotation, respectively, on a linearly polarized optical field. An LC device placed between polarizers functions as a binary transmission beam shaper with a highly improved damage threshold compared to metal beam shapers. Using a coumarin-based photoalignment layer, various devices have been fabricated and tested, with a measured single-shot nanosecond damage threshold higher than 30 J/cm2. PMID:22002377

  19. Adaptation to shape switching by component selection in a constitutional dynamic system.

    PubMed

    Ulrich, Sébastien; Lehn, Jean-Marie

    2009-04-22

    Molecules having different accessible shape states, which can be addressed in an effector-controlled manner, may be termed morphological switches. A dynamic covalent system can undergo adaptation to each state of a two-state morphological switch by generation of an optimal constitution through component selection. We have studied such a component selection in the dynamic covalent constituents generated by metal cation-induced shape switching of a core component between two states of W and U shape, characterized by both different geometries and different coordination features. The system performs shape-dependent self-sorting of metal ions and components. The origin of the selectivity was investigated through competition experiments, in solution and by analysis of solid state structures, which reveal the role of the molecular shape in the formation of a particular self-assembled architecture. The coordination features of each state as well as phase change also play an important role, in addition to the shape plasticity, in steering the covalent dynamic system toward the formation of a given entity by the selection of the most appropriate components. Different examples are described which show that the morphological switching of one component of a given self-assembled entity can lead to the exchange of the complementary one, which is no longer the best partner, for a new partner, able to form a more stable new assembly. Thus, the constitutional evolution of these dynamic systems is steered by the shape of a given state via both its geometry and its coordination features toward metal ions, leading to incorporation/decorporation of the most appropriate components. The controlled interconversion of the shape states of the morphological switches, induced by addition/removal of metal ions, results in a constitutional adaptation behavior through inversion of the selection preferences. PMID:19206535

  20. An inverse finite element method for beam shape sensing: theoretical framework and experimental validation

    NASA Astrophysics Data System (ADS)

    Gherlone, Marco; Cerracchio, Priscilla; Mattone, Massimiliano; Di Sciuva, Marco; Tessler, Alexander

    2014-04-01

    Shape sensing, i.e., reconstruction of the displacement field of a structure from surface-measured strains, has relevant implications for the monitoring, control and actuation of smart structures. The inverse finite element method (iFEM) is a shape-sensing methodology shown to be fast, accurate and robust. This paper aims to demonstrate that the recently presented iFEM for beam and frame structures is reliable when experimentally measured strains are used as input data. The theoretical framework of the methodology is first reviewed. Timoshenko beam theory is adopted, including stretching, bending, transverse shear and torsion deformation modes. The variational statement and its discretization with C0-continuous inverse elements are briefly recalled. The three-dimensional displacement field of the beam structure is reconstructed under the condition that least-squares compatibility is guaranteed between the measured strains and those interpolated within the inverse elements. The experimental setup is then described. A thin-walled cantilevered beam is subjected to different static and dynamic loads. Measured surface strains are used as input data for shape sensing at first with a single inverse element. For the same test cases, convergence is also investigated using an increasing number of inverse elements. The iFEM-recovered deflections and twist rotations are then compared with those measured experimentally. The accuracy, convergence and robustness of the iFEM with respect to unavoidable measurement errors, due to strain sensor locations, measurement systems and geometry imperfections, are demonstrated for both static and dynamic loadings.

  1. System for generating shaped optical pulses and measuring optical pulses using spectral beam deflection (SBD)

    DOEpatents

    Skupsky, S.; Kessler, T.J.; Letzring, S.A.

    1993-11-16

    A temporally shaped or modified optical output pulse is generated from a bandwidth-encoded optical input pulse in a system in which the input pulse is in the form of a beam which is spectrally spread into components contained within the bandwidth, followed by deflection of the spectrally spread beam (SBD) thereby spatially mapping the components in correspondence with the temporal input pulse profile in the focal plane of a lens, and by spatially selective attenuation of selected components in that focal plane. The shaped or modified optical output pulse is then reconstructed from the attenuated spectral components. The pulse-shaping system is particularly useful for generating optical pulses of selected temporal shape over a wide range of pulse duration, such pulses finding application in the fields of optical communication, optical recording and data storage, atomic and molecular spectroscopy and laser fusion. An optical streak camera is also provided which uses SBD to display the beam intensity in the focal plane as a function of time during the input pulse. 10 figures.

  2. System for generating shaped optical pulses and measuring optical pulses using spectral beam deflection (SBD)

    DOEpatents

    Skupsky, Stanley; Kessler, Terrance J.; Letzring, Samuel A.

    1993-01-01

    A temporally shaped or modified optical output pulse is generated from a bandwidth-encoded optical input pulse in a system in which the input pulse is in the form of a beam which is spectrally spread into components contained within the bandwidth, followed by deflection of the spectrally spread beam (SBD) thereby spatially mapping the components in correspondence with the temporal input pulse profile in the focal plane of a lens, and by spatially selective attenuation of selected components in that focal plane. The shaped or modified optical output pulse is then reconstructed from the attenuated spectral components. The pulse-shaping system is particularly useful for generating optical pulses of selected temporal shape over a wide range of pulse duration, such pulses finding application in the fields of optical communication, optical recording and data storage, atomic and molecular spectroscopy and laser fusion. An optical streak camera is also provided which uses SBD to display the beam intensity in the focal plane as a function of time during the input pulse.

  3. Quasi-static shape estimation and control of adaptive truss structures

    NASA Technical Reports Server (NTRS)

    Kuwao, Fumihiro; Chen, Gun-Shing; Wada, Ben K.

    1991-01-01

    Methods for estimating the deformation of adaptive truss structures are proposed which employ internal displacement sensors to measure changes in the length of selected truss members. Based on the measured data from the instrumented truss member, the total truss deformation pattern can be estimated through direct interpolation. To verify the validity of the methods presented here, numerical simulations are carried out for simple plane trusses, a beam truss, and a tetrahedral truss.

  4. Laser forming of a bowl shaped surface with a stationary laser beam

    NASA Astrophysics Data System (ADS)

    Chakraborty, Shitanshu Shekhar; More, Harshit; Nath, Ashish Kumar

    2016-02-01

    Despite a lot of research done in the field of laser forming, generation of a symmetric bowl shaped surface by this process is still a challenge mainly because only a portion of the sheet is momentarily deformed in this process, unlike conventional sheet metal forming like deep drawing where the entire blank undergoes forming simultaneously reducing asymmetry to a minimum. The motion of laser beam also makes the process asymmetric. To counter these limitations this work proposes a new approach for laser forming of a bowl shaped surface by irradiating the centre of a flat circular blank with a stationary laser beam. With high power lasers, power density sufficient for laser forming, can be availed at reasonably large spot sizes. This advantage is exploited in this technique. Effects of duration of laser irradiation and beam spot diameter on the amount of bending and asymmetry in the formed surface were investigated. Laser power was kept constant while varying irradiation time. While varying laser spot diameter laser power was chosen so as to keep the surface temperature nearly constant at just below melting. Experimental conditions promoted almost uniform heating through sheet thickness. The amount of bending increased with irradiation time and spot diameter. It was interesting to observe that blanks bent towards the laser beam for smaller laser beam diameters and the reverse happened for larger spot diameters (~10 times of the sheet thickness). Effect of spot diameter variation has been explained with the help of coupled thermal-structural finite element simulations.

  5. Estimating the vibration level of an L-shaped beam using power flow techniques

    NASA Technical Reports Server (NTRS)

    Cuschieri, J. M.; Mccollum, M.; Rassineux, J. L.; Gilbert, T.

    1986-01-01

    The response of one component of an L-shaped beam, with point force excitation on the other component, is estimated using the power flow method. The transmitted power from the source component to the receiver component is expressed in terms of the transfer and input mobilities at the excitation point and the joint. The response is estimated both in narrow frequency bands, using the exact geometry of the beams, and as a frequency averaged response using infinite beam models. The results using this power flow technique are compared to the results obtained using finite element analysis (FEA) of the L-shaped beam for the low frequency response and to results obtained using statistical energy analysis (SEA) for the high frequencies. The agreement between the FEA results and the power flow method results at low frequencies is very good. SEA results are in terms of frequency averaged levels and these are in perfect agreement with the results obtained using the infinite beam models in the power flow method. The narrow frequency band results from the power flow method also converge to the SEA results at high frequencies. The advantage of the power flow method is that detail of the response can be retained while reducing computation time, which will allow the narrow frequency band analysis of the response to be extended to higher frequencies.

  6. Beam-shaping optics for a slit-scan flow cytometer.

    PubMed

    Noguchi, Y; Kashima, S; Aikata, T

    1993-10-01

    Two sets of beam-shaping optical systems for slit-scan flow cytometry were made for 360 nm and 488 nm wavelength argon-ion lasers. A thin, ribbonlike laser beam was formed by compressing the zero-order component of Fraunhofer diffraction patterns caused by a slit vertically long and horizontally narrow by means of an objective with a numerical aperture of 0.5. The objectives were designed to include a jet stream that performed as a cylindrical lens. The characteristic values of the optical systems and lens alignments of the systems are described in this work. The beam size at focus was 0.95 micron in thinness and 85.0 microns in width on design values. The actual beam thinness for the UV laser was estimated to be 1.3 microns, based on shapes of pulses generated when fluorescence microspheres of diameter 1.0 microns passed across the beam. The usefulness of the optical systems was also proved by its ability to measure HeLa chromosomes. PMID:8243211

  7. Simultaneous power and beam-shape optimization of an OPSL resonator

    NASA Astrophysics Data System (ADS)

    Haag, Sebastian; Sauer, Sebastian; Garlich, Torsten; Seelert, Wolf; Brecher, Christian; Müller, Tobias; Zontar, Daniel

    2015-03-01

    In the assembly of optical resonators of optically pumped semiconductor lasers (OPSL), the highly reflective resonator mirror is the most crucial component. In previous cooperation, Coherent and Fraunhofer IPT have developed a robust active alignment strategy to optimize the output power of the OPSL resonator using search strategies for finding the laser threshold as well as hill-climbing algorithms for maximizing the output power. Beam-shape as well as the laser mode have major influence on the quality and the duration of subsequent beam-shaping and fiber-coupling steps. Therefore, the alignment algorithm optimizing the output power has been extended recently by simultaneous image processing for ensuring a Gaussian beam as the result of alignment. The paper describes the enhanced approach of automated alignment by additionally scanning along the optical resonator and subsequently evaluating and optimizing the roundness of the beam as well as minimizing the beam radius through twisting and tilting of the mirror. A quality metric combining these measures is defined substituting an M² measurement. The paper also describes the approach for automated assembly including the measuring setup, micromanipulation and dispensing devices.

  8. Research on relation between bending stress and characteristic frequency of H-shaped beam by free vibration deflection

    SciTech Connect

    Yoshida, Tsutomu; Watanabe, Takeshi

    2014-05-27

    In order to investigate a relation between a bending stress and a characteristic frequency of a beam, 4-point loading which had constant moment region was conducted to a beam with H shape configuration experimentally and numerically. H-shaped beam has many characteristic deformation modes. Axial tensile stress in the beam made its characteristic frequency higher, and compressive stress lower. In the experiment, some characteristic frequencies got higher by a bending stress, and the others stayed in a small frequency fluctuation. The distinction is anticipated as a capability to measure a bending stress of a beam by its characteristic frequencies.

  9. Arbitrary shaping of on-axis amplitude of femtosecond Bessel beams with a single phase-only spatial light modulator.

    PubMed

    Ouadghiri-Idrissi, Ismail; Giust, Remo; Froehly, Luc; Jacquot, Maxime; Furfaro, Luca; Dudley, John M; Courvoisier, Francois

    2016-05-30

    Arbitrary shaping of the on-axis intensity of Bessel beams requires spatial modulation of both amplitude and phase. We develop a non-iterative direct space beam shaping method to generate Bessel beams with high energy throughput from direct space with a single phase-only spatial light modulator. For this purpose, we generalize the approach of Bolduc et al. to non-uniform input beams. We point out the physical limitations imposed on the on-axis intensity profile for unidirectional beams. Analytical, numerical and experimental results are provided. PMID:27410077

  10. Shaping of spherical light intensity based on the interference of tightly focused beams with different polarizations

    NASA Astrophysics Data System (ADS)

    Khonina, Svetlana N.; Ustinov, Andrey V.; Volotovsky, Sergey G.

    2014-08-01

    We consider the shaping of spherical intensity distributions based on the interference of counter-propagating tightly focused vortex beams with different polarizations. The formation of 3D distributions is performed using a simple method of optimization of the width and position of the single annular aperture. The optimum parameters for the narrow aperture are calculated analytically. In addition the wide aperture parameters are numerically adjusted. It is shown that depending on the polarization, the additional vortex phase and/or phase shift in the beams allow to form either solid light balls or light spheres of subwavelength radius. They consist of the various electric field components.

  11. Application of nondiffracting Bessel beams for shaping of surface metal microstructures

    NASA Astrophysics Data System (ADS)

    Drampyan, Rafael; Leonov, Nikita; Vartanyan, Tigran

    2016-08-01

    A novel method of laser-controlled shaping of metal microstructures based on the processes of metal atoms adsorption on the surface of crystalline substrate and simultaneous control of photostimulated desorption of atoms by spatially modulated nondiffracting laser beam illumination is presented. The experiments were performed for sodium atoms deposition to the sapphire substrate, which was illuminated by Bessel beam at 532 nm wavelength and 2 W/cm2 intensity. Experiments showed that the optical pattern was well reproduced in the sodium deposits thus creating the annularly microstructured metal film with few tens nanometre thickness.

  12. Ion beam sputter deposition of TiNi shape memory alloy thin films

    NASA Astrophysics Data System (ADS)

    Davies, Sam T.; Tsuchiya, Kazuyoshi

    1999-08-01

    The development of functional or smart materials for integration into microsystem is of increasing interest. An example is the shape memory effect exhibited by certain metal alloys which, in principle, can be exploited in the fabrication of micro-scale manipulators or actuators, thereby providing on-chip micromechanical functionality. We have investigated an ion beam sputter deposition process for the growth of TiNi shape memory alloy thin films and demonstrated the required control to produce equiatomic composition, uniform coverage and atomic layer-by-layer growth rates on engineering surfaces. The process uses argon ions at intermediate energy produced by a Kaufman-type ion source to sputter non-alloyed targets of high purity titanium and nickel. Precise measurements of deposition rates allows compositional control during thin film growth. As the sputtering targets and substrates are remote from the discharge plasma, deposition occurs under good vacuum of approximately 10-6 mtorr thus promoting high quality films. Furthermore, the ion beam energetics allow deposition at relatively low substrate temperatures of < 150 degrees C with as-deposited films exhibiting shape memory properties without post-process high temperature annealing. Thermal imagin is used to monitor changes which are characteristic of the shape memory effect and is indicative of changes in specific heat capacity and thermal conductivity as the TiNi shape memory alloy undergoes martensitic to austenitic phase transformations.

  13. Overview of Alternative Bunching and Current-shaping Techniques for Low-Energy Electron Beams

    SciTech Connect

    Piot, Philippe

    2015-12-01

    Techniques to bunch or shape an electron beam at low energies (E <15 MeV) have important implications toward the realization of table-top radiation sources [1] or to the design of compact multi-user free-electron lasers[2]. This paper provides an overview of alternative methods recently developed including techniques such as wakefield-based bunching, space-charge-driven microbunching via wave-breaking [3], ab-initio shaping of the electron-emission process [4], and phase space exchangers. Practical applications of some of these methods to foreseen free-electron-laser configurations are also briefly discussed [5].

  14. Thermomechanical Characterization and Modeling of Superelastic Shape Memory Alloy Beams and Frames

    NASA Astrophysics Data System (ADS)

    Watkins, Ryan

    Of existing applications, the majority of shape memory alloy (SMA) devices consist of beam (orthodontic wire, eye glasses frames, catheter guide wires) and framed structures (cardiovascular stents, vena cava filters). Although uniaxial tension data is often sufficient to model basic beam behavior (which has been the main focus of the research community), the tension-compression asymmetry and complex phase transformation behavior of SMAs suggests more information is necessary to properly model higher complexity states of loading. In this work, SMA beams are experimentally characterized under general loading conditions (including tension, compression, pure bending, and buckling); furthermore, a model is developed with respect to general beam deformation based on the relevant phenomena observed in the experimental characterization. Stress induced phase transformation within superelastic SMA beams is shown to depend on not only the loading mode, but also kinematic constraints imposed by beam geometry (such as beam cross-section and length). In the cases of tension and pure bending, the structural behavior is unstable and corresponds to phase transformation localization and propagation. This unstable behavior is the result of a local level up--down--up stress/strain response in tension, which is measured here using a novel composite-based experimental technique. In addition to unstable phase transformation, intriguing post-buckling straightening is observed in short SMA columns during monotonic loading (termed unbuckling here). Based on this phenomenological understanding of SMA beam behavior, a trilinear based material law is developed in the context of a Shanley column model and is found to capture many of the relevant features of column buckling, including the experimentally observed unbuckling behavior. Due to the success of this model, it is generalized within the context of beam theory and, in conjunction with Bloch wave stability analysis, is used to model and

  15. Phase-only shaping algorithm for Gaussian-apodized Bessel beams.

    PubMed

    Durfee, Charles G; Gemmer, John; Moloney, Jerome V

    2013-07-01

    Gaussian-apodized Bessel beams can be used to create a Bessel-like axial line focus at a distance from the focusing lens. For many applications it is desirable to create an axial intensity profile that is uniform along the Bessel zone. In this article, we show that this can be accomplished through phase-only shaping of the wavefront in the far field where the beam has an annular ring structure with a Gaussian cross section. We use a one-dimensional transform to map the radial input field to the axial Bessel field and then optimized the axial intensity with a Gerchberg-Saxton algorithm. By separating out the quadratic portion of the shaping phase the algorithm converges more rapidly. PMID:23842364

  16. Correction of vortex laser beam in a closed-loop adaptive system with bimorph mirror.

    PubMed

    Starikov, F A; Kochemasov, G G; Koltygin, M O; Kulikov, S M; Manachinsky, A N; Maslov, N V; Sukharev, S A; Aksenov, V P; Izmailov, I V; Kanev, F Yu; Atuchin, V V; Soldatenkov, I S

    2009-08-01

    The phase correction of a vortex laser beam is undertaken in the closed-loop adaptive system including a Hartmann-Shack wavefront sensor with singular reconstruction technique and a bimorph piezoceramic mirror. After correction the vortex doughnutlike beam is focused into a beam with bright axial spot that considerably increases the Strehl ratio and optical system resolution. Since the phase break cannot be exactly reproduced on the flexible mirror surface, off-axis vortices appear in the far field at the beam periphery. PMID:19649065

  17. Evaluation of intensity based beam-shaping method with Rib-phantom HIFU sonications

    NASA Astrophysics Data System (ADS)

    Tillander, Matti; Köhler, Max; Koskela, Julius; Ylihautala, Mika

    2012-11-01

    The relation between rib bone heating during HIFU therapy and incident intensity on the bone surface was examined using an experimental setup and simulations with ray-tracer. The relation was found to be linear yet the data had large variance. The result was successfully applied to an intensity-based beam-shaping algorithm, which was fast enough for online therapy planning, and used to protect the ribs from overheating during intercostal sonications to a HIFU phantom containing two porcine rib bones.

  18. Beam shaping concepts for kW-class CW and QCW diode lasers

    NASA Astrophysics Data System (ADS)

    Unger, Andreas; Fassbender, Willhelm; Müntz, Holger; Köhler, Bernd; Biesenbach, Jens

    2016-03-01

    In modern diode lasers beam shaping of the highly asymmetric laser beam, which exits the front facet of the semiconductor laser material, is a crucial step towards cost efficient high brightness laser modules which in turn can be further combined towards kW-class diode lasers and can be efficiently fiber coupled. In order to scale up the power of a single laser module in an economic way, high fill factor laser bars are employed. The increased power density from such a laser bar requires improved cooling technologies. On the other hand the increased fill factor of the bar makes advanced beam shaping necessary to be able to achieve small focal spot sizes and couple the laser module efficiently into optical fibers. Finally, to be able to mass produce the laser modules, it is desirable to design the module in a way that allows automated packaging and optics alignment. In this talk, the beam shaping concepts developed at DILAS for high fill factor bars are presented. Starting from optical simulation and choice of optical elements the laser modules incorporating these bars are presented. The concepts developed enable very compact laser modules of up to 2kW of power at a single wavelength with beam qualities of less than 40mm x mrad. Optionally these modules can be wavelength stabilized via external feedback. The packaging technology developed enables the automated alignment of the optics and cooling is DI-water free. Based on the same concepts very compact free space and fiber coupled QCW packages are presented as well.

  19. Shape-modification of patterned nanoparticles by an ion beam treatment

    NASA Astrophysics Data System (ADS)

    Heo, Kyong Chan; Gwag, Jin Seog

    2015-02-01

    This paper evaluated a practical approach to the fabrication of arrays of non-spherical nanoparticles by colloidal etching without a mask involving exposure to a low energy ion beam. A spherical nanoparticle array was transferred using a soft nanolithography technique, which is a simple and effective pattern transfer method for nanostructures on the surface of thin adhesive polymers on a planar substrate, after placing the spherical nanoparticles on a patterned PDMS [poly(dimethysiloxane)] stamp produced from a patterned Si wafer. The resulting non-spherical nanoparticle array was driven from a spherical nanoparticle array shape-modified by ion beam irradiation. A well-arrayed layer of cone-like-shapes were produced using a head-on ion beam for different exposure times. Also, a variety of mushroom-like-shapes depending on the exposure angle were produced on a substrate with a well-arranged spherical nanoparticle array. This technique has potential applications in nanophotonics, field emission displays (FEDs) and microfluid.

  20. Variable shaped beam writing throughput at the 45nm node and beyond

    NASA Astrophysics Data System (ADS)

    Sowers, A.; Shumway, M.; Kamna, M.; Wilcox, N.; Vernon, M.; Cole, D.; Chandramouli, M.

    2006-10-01

    Aggressive 193nm optical lithography solutions have in turn led to increasingly complex model-based OPC methodologies. This complexity married with the inevitable march of Moore's Law has produced a figure count explosion at the mask writer level. Variable shaped beam equipment manufacturers have tried to mollify the impact of this figure count explosion on the write time by the introduction of new technologies such as increased beam current density, faster DAC amplifiers and more efficient stage algorithms. Despite these efforts, mask manufacturers continue to explore ways of increasing writer throughput and available capacity. This study models the impact of further improvements in beam current density and settling times. Furthermore, this model will be used to prescribe the necessary improvement rates needed to keep pace with the shot count trends extending beyond the 45nm node.

  1. Investigation into the effect of beam shape on melt pool characteristics using analytical modelling

    NASA Astrophysics Data System (ADS)

    Ahmed, N.; Voisey, K. T.; McCartney, D. G.

    2010-05-01

    An established analytical model is used to simulate an extended laser beam. Multiple Gaussian sources are superimposed to form a rectangular beam and results are compared with a single circular Gaussian source model as well as experimental results from a high power diode laser with a rectangular beam. Melt depth and melt pool profile and progression have been predicted by modeling, which are compared with experimental results from melting of Inconel 625. The model produced is shown to give a reasonable prediction of melt pool shape and can be usefully employed to help optimise overlap required for laser surface processing applications. The value of absorptivity used in the model can be used as a fitting parameter to optimise the match between experimental and predicted results.

  2. Spatial beam shaping for high-power frequency tripling lasers based on a liquid crystal spatial light modulator

    NASA Astrophysics Data System (ADS)

    Li, Sensen; Wang, Yulei; Lu, Zhiwei; Ding, Lei; Cui, Can; Chen, Yi; Pengyuan, Du; Ba, Dexin; Zheng, Zhenxing; Yuan, Hang; Shi, Lei; Bai, Zhenxu; Liu, Zhaohong; Zhu, Chengyu; Dong, Yongkang; Zhou, Luoxian

    2016-05-01

    We propose and demonstrate a spatial beam shaping method to achieve high-quality near-field for a high-power frequency tripling laser system by using a liquid crystal spatial light modulator (SLM). Considering the nonlinear relationship between the output 3ω intensity and the input 1ω intensity of the frequency conversion system and the transmittance nonuniformity of the whole laser system, we introduce an efficient spatial beam shaping method that improves the output near-field beam quality of frequency tripling laser dramatically. Results show that the near-field peak-to-mean value of the frequency tripling laser improves from 1.83:1 to 1.42:1 after spatial beam shaping within four shots. This method provides effective guidance for spatial beam shaping of high-power frequency tripling laser systems.

  3. Adaptive robust control of longitudinal and transverse electron beam profiles

    NASA Astrophysics Data System (ADS)

    Rezaeizadeh, Amin; Schilcher, Thomas; Smith, Roy S.

    2016-05-01

    Feedback control of the longitudinal and transverse electron beam profiles are considered to be critical for beam control in accelerators. In the feedback scheme, the longitudinal or transverse beam profile is measured and compared to a desired profile to give an error estimate. The error is then used to act on the appropriate actuators to correct the profile. The role of the transverse feedback is to steer the beam in a particular trajectory, known as the "orbit." The common approach for orbit correction is based on approximately inverting the response matrix, and in the best case, involves regulating or filtering the singular values. In the current contribution, a more systematic and structured way of handling orbit correction is introduced giving robustness against uncertainties in the response matrix. Moreover, the input bounds are treated to avoid violating the limits of the corrector currents. The concept of the robust orbit correction has been successfully tested at the SwissFEL injector test facility. In the SwissFEL machine, a photo-injector laser system extracts electrons from a cathode and a similar robust control method is developed for the longitudinal feedback control of the current profile of the electron bunch. The method manipulates the angles of the crystals in the laser system to produce a desired charge distribution over the electron bunch length. This approach paves the way towards automation of laser pulse stacking.

  4. Nonlinear analysis of cantilever shape memory alloy beams of variable cross section

    NASA Astrophysics Data System (ADS)

    Ashiqur Rahman, Muhammad; Arefin Kowser, Muhammad

    2007-04-01

    Cantilever beams, made of shape memory alloy (SMA), undergo much larger deflection in comparison to those made of other materials. Again, cantilever beams with reducing cross section along the span show much larger deflections compared to those of constant cross section beams. Analysis was conducted for such a cantilever beam with reducing cross-sectional area made of SMA, taking into account its highly nonlinear stress-strain curves. A computer code in C has been developed using the Runge-Kutta technique for the purpose of simulation. For rigorous analysis, the true stress-strain curves in tension as well as in compression have been used for the study. Moment-curvature and reduced modulus-curvature relations are obtained from the nonlinear stress-strain relations for different sections of the beam and used in the simulation. It is seen that load-deflection curves are initially linear but nonlinear and convex upward at a high load. Furthermore, the compressive stress in the beam is significantly higher than the tensile stress because of asymmetry. Interestingly, for the different cases considered, it is found that part of the SMA beam material may remain in the parent austenite phase, mixed phase or in the stress-induced martensitic phase. Importantly, it is found that more material can be removed from an SMA beam of uniform strength, originally designed without considering geometric nonlinearity and the effect of end-shortening. Comparison of the numerical results with the available theory shows very good agreement, verifying the soundness of the entire numerical simulation scheme.

  5. Time course of shape and category selectivity revealed by EEG rapid adaptation.

    PubMed

    Scholl, Clara A; Jiang, Xiong; Martin, Jacob G; Riesenhuber, Maximilian

    2014-02-01

    A hallmark of human cognition is the ability to rapidly assign meaning to sensory stimuli. It has been suggested that this fast visual object categorization ability is accomplished by a feedforward processing hierarchy consisting of shape-selective neurons in occipito-temporal cortex that feed into task circuits in frontal cortex computing conceptual category membership. We performed an EEG rapid adaptation study to test this hypothesis. Participants were trained to categorize novel stimuli generated with a morphing system that precisely controlled both stimulus shape and category membership. We subsequently performed EEG recordings while participants performed a category matching task on pairs of successively presented stimuli. We used space-time cluster analysis to identify channels and latencies exhibiting selective neural responses. Neural signals before 200 msec on posterior channels demonstrated a release from adaptation for shape changes, irrespective of category membership, compatible with a shape- but not explicitly category-selective neural representation. A subsequent cluster with anterior topography appeared after 200 msec and exhibited release from adaptation consistent with explicit categorization. These signals were subsequently modulated by perceptual uncertainty starting around 300 msec. The degree of category selectivity of the anterior signals was strongly predictive of behavioral performance. We also observed a posterior category-selective signal after 300 msec exhibiting significant functional connectivity with the initial anterior category-selective signal. In summary, our study supports the proposition that perceptual categorization is accomplished by the brain within a quarter second through a largely feedforward process culminating in frontal areas, followed by later category-selective signals in posterior regions. PMID:24001003

  6. Experimental evaluation of a shape memory alloy wire actuator with a modulated adaptive controller for position control

    NASA Astrophysics Data System (ADS)

    Senthilkumar, P.; Dayananda, G. N.; Umapathy, M.; Shankar, V.

    2012-01-01

    This paper presents an experimental investigation of position control of a shape memory alloy (SMA) wire actuator with adaptive and modulated adaptive controllers. The transfer function model of the SMA wire actuator is determined from the experimental open loop response. Adaptive controllers, namely LMS-GSPI, RLS-GSPI and Kalman-GSPI, and modulated adaptive controllers using pulse width modulation (PWM) are designed. The performances of these controllers are experimentally investigated for the position control of an SMA wire actuator with and without thermal disturbance. Experimental results demonstrate that the modulated adaptive controllers outperform adaptive controllers.

  7. Adapting High Brightness Relativistic Electron Beams for Ultrafast Science

    NASA Astrophysics Data System (ADS)

    Scoby, Cheyne Matthew

    This thesis explores the use of ultrashort bunches generated by a radiofrequency electron photoinjector driven by a femtosecond laser. Rf photoinjector technology has been developed to generate ultra high brightness beams for advanced accelerators and to drive advanced light source applications. The extremely good quality of the beams generated by this source has played a key role in the development of 4th generation light sources such as the Linac Coherent Light Source, thus opening the way to studies of materials science and biological systems with high temporal and spatial resolution. At the Pegasus Photoinjector Lab, we have developed the application of a BNL/SLAC/UCLA 1.6-cell rf photoinjector as a tool for ultrafast science in its own right. It is the aim of this work to explore the generation of ultrashort electron bunches, give descriptions of the novel ultrafast diagnostics developed to be able to characterize the electron bunch and synchronize it with a pump laser, and share some of the scientific results that were obtained with this technology at the UCLA Pegasus laboratory. This dissertation explains the requirements of the drive laser source and describes the principles of rf photoinjector design and operation necessary to produce electron bunches with an rms longitudinal length < 100 femtoseconds containing 107 - 108 electrons per bunch. In this condition, when the laser intensity is sufficiently high, multiphoton photoemission is demonstrated to be more efficient in terms of charge yield than single photon photoemission. When a short laser pulse hits the cathode the resulting beam dynamics are dominated by a strong space charge driven longitudinal expansion which leads to the creation of a nearly ideal uniformly filled ellipsoidal distribution. These beam distributions are characterized by linear space charge forces and hence by high peak brightness and small transverse emittances. This regime of operation of the RF photoinjector is also termed the

  8. Generation of doughnut spot for high-power laser technologies using refractive beam shaping

    NASA Astrophysics Data System (ADS)

    Laskin, Alexander; Laskin, Vadim; Ostrun, Aleksei

    2015-03-01

    Doughnut and inverse-Gauss intensity distributions of laser spot are required in laser technologies like welding, cladding where high power fiber coupled diode or solid-state lasers as well as fiber lasers are used. In comparison to Gaussian and flat-top distributions the doughnut and inverse-Gauss profiles provide more uniform temperature distribution on a work piece - this improves the technology, increase stability of processes and efficiency of using the laser energy, reduce the heat affected zone (HAZ). This type of beam shaping has become frequently asked by users of multimode lasers, especially multimode fiber coupled diode lasers. Refractive field mapping beam shapers are applied as one of solutions for the task to manipulate intensity distribution of multimode lasers. The operation principle of these devices presumes almost lossless transformation of laser beam irradiance from Gaussian to flat-top, doughnut or inverse-Gauss through controlled wavefront manipulation inside a beam shaper using lenses with smooth optical surfaces. This paper will describe some design basics of refractive beam shapers of the field mapping type and optical layouts of their applying with high-power multimode lasers. Examples of real implementations and experimental results will be presented as well.

  9. High-resolution adaptive nulling performance for a lightweight agile EHF multiple beam antenna

    NASA Astrophysics Data System (ADS)

    Fenn, A. J.; Johnson, J. R.; Rispin, L. W.; Cummings, W. C.; Potts, B. M.

    The design and experimental performance of a lightweight high-resolution adaptive nulling extremely high-frequency multiple beam antenna (MBA) are addressed. A 127-beam MBA and a four-channel RF nulling network operating over the 43.5-to-45.5-GHz band were used to adaptively null a jammer in anechoic chamber measurements. Lightweight waveguide transmission lines together with ferrite switches were used to select beam ports from the 127-beam MBA. The MBA was designed to provide simultaneous coverage for three communications system users while providing pattern discrimination or nulling of jammers located within 0.1 deg of the user. Cancellation greater than 30 dB when operating in a wideband mode was experimentally demonstrated.

  10. Stability of adaptive control of a light beam in the presence of nonstationary thermal blooming in a moving medium

    SciTech Connect

    Egorov, K.D.

    1988-06-01

    The adaptive control problem for a nonlinearly propagating light beam in a moving atmosphere presupposes continuous optimization of the beam parameters while the characteristics of the medium are varying. If the time scales of such variations are comparable to the characteristic times for the establishment of a thermal lens along the ray path, the beam can be controlled under highly nonstationary propagation conditions. We investigate the mechanism of stability loss during adaptive focusing of a light beam subject to wind refraction. In the aberrationless approximation, we examine the dynamics of beam parameters controlled by adaptive systems capable of operating at different speeds.

  11. Interferometric adaptive optics for high-power laser beam correction in fast ignition experiments

    SciTech Connect

    Homoelle, D C; Baker, K L; Patel, P K; Utterback, E; Rushford, M C; Siders, C W; Barty, C J

    2009-10-22

    We present the design for a high-speed adaptive optics system that will be used to achieve the necessary laser pointing and beam-quality performance for initial fast-ignition coupling experiments. This design makes use of a 32 x 32 pixellated MEMS device as the adaptive optic and a two-channel interferometer as the wave-front sensor. We present results from a system testbed that demonstrates improvement of the Strehl ratio from 0.09 to 0.61 and stabilization of beam pointing from {approx}75{micro}rad to <2{micro}rad.

  12. Adaptive control of lasers and their interactions with matter using femtosecond pulse shaping

    NASA Astrophysics Data System (ADS)

    Efimov, Anatoly

    Coherent control of chemical reactions, atomic and molecular systems, lattice dynamics, and electronic motion rely on femtosecond laser sources capable of producing programmable arbitrarily shaped waveforms. To enter the time scale of natural dynamic processes in many systems, femtosecond pulse shaping techniques must be extended to the ultrashort pulse domain (<50 fs). Concurrently, reliable high-fidelity amplification of shaped waveforms is required in many applications. We demonstrate ultrabroad bandwidth pulse shaping of 13 fs pulses with Fourier-domain phase-only filtering using a liquid crystal array. We further demonstrate the amplification of shaped pulses in a multipass chirped pulse amplifier (CPA) system to produce millijoule-level optical waveforms with 30 fs resolution. Recently, a new approach to coherent control of physical systems was introduced, which, instead of relying on formidable theoretical calculations of complex system dynamics, makes use of an appropriate experimental feedback from the system itself to control its evolution. We apply this adaptive feedback approach for enhancement of ionization rates in a femtosecond plasma with the goal of minimization of phase distortions in the amplifier system. With the help of a learning algorithm and survival principles of nature, we teach our laser to control its own phase by using spectral blueshifting in a rapidly created plasma as a feedback to the algorithm. Control of lattice vibrations has long been sought as a means of studying phonon-related processes in solids. In addition, generation and control of large-amplitude optical phonon modes may open a path to femtosecond time- resolved studies of structural phase transitions and production of ultrashort shaped X-ray pulses. We perform pump-probe phase-resolved measurements and control of optical A1g mode in sapphire through shaped-pulse impulsive stimulated Raman scattering (ISRS). We chose this material as a candidate for possible nonlinear

  13. Optimal piezoelectric beam shape for single and broadband vibration energy harvesting: Modeling, simulation and experimental results

    NASA Astrophysics Data System (ADS)

    Muthalif, Asan G. A.; Nordin, N. H. Diyana

    2015-03-01

    Harvesting energy from the surroundings has become a new trend in saving our environment. Among the established ones are solar panels, wind turbines and hydroelectric generators which have successfully grown in meeting the world's energy demand. However, for low powered electronic devices; especially when being placed in a remote area, micro scale energy harvesting is preferable. One of the popular methods is via vibration energy scavenging which converts mechanical energy (from vibration) to electrical energy by the effect of coupling between mechanical variables and electric or magnetic fields. As the voltage generated greatly depends on the geometry and size of the piezoelectric material, there is a need to define an optimum shape and configuration of the piezoelectric energy scavenger. In this research, mathematical derivations for unimorph piezoelectric energy harvester are presented. Simulation is done using MATLAB and COMSOL Multiphysics software to study the effect of varying the length and shape of the beam to the generated voltage. Experimental results comparing triangular and rectangular shaped piezoelectric beam are also presented.

  14. Capacity achieving nonbinary LDPC coded non-uniform shaping modulation for adaptive optical communications.

    PubMed

    Lin, Changyu; Zou, Ding; Liu, Tao; Djordjevic, Ivan B

    2016-08-01

    A mutual information inspired nonbinary coded modulation design with non-uniform shaping is proposed. Instead of traditional power of two signal constellation sizes, we design 5-QAM, 7-QAM and 9-QAM constellations, which can be used in adaptive optical networks. The non-uniform shaping and LDPC code rate are jointly considered in the design, which results in a better performance scheme for the same SNR values. The matched nonbinary (NB) LDPC code is used for this scheme, which further improves the coding gain and the overall performance. We analyze both coding performance and system SNR performance. We show that the proposed NB LDPC-coded 9-QAM has more than 2dB gain in symbol SNR compared to traditional LDPC-coded star-8-QAM. On the other hand, the proposed NB LDPC-coded 5-QAM and 7-QAM have even better performance than LDPC-coded QPSK. PMID:27505775

  15. Reciprocity breaking during nonlinear propagation of adapted beams through random media.

    PubMed

    Palastro, J P; Peñano, J; Nelson, W; DiComo, G; Helle, M; Johnson, L A; Hafizi, B

    2016-08-22

    Adaptive optics (AO) systems rely on the principle of reciprocity, or symmetry with respect to the interchange of point sources and receivers. These systems use the light received from a low power emitter on or near a target to compensate phase aberrations acquired by a laser beam during linear propagation through random media. If, however, the laser beam propagates nonlinearly, reciprocity is broken, potentially undermining AO correction. Here we examine the consequences of this breakdown, providing the first analysis of AO applied to high peak power laser beams. While discussed for general random and nonlinear media, we consider specific examples of Kerr-nonlinear, turbulent atmosphere. PMID:27557166

  16. Focusing, wavelength tuning, beam steering and beam shaping of circular grating surface emitting distributed Bragg reflector lasers

    NASA Astrophysics Data System (ADS)

    Penner, Robert Scott

    Over the past decade, circular grating surface emitting DBR lasers (CGSELs) have progressed from theory to reality. These devices possess several properties that make them attractive options for such applications as optical interconnects and laser arrays. These advantages include low divergence angles, circular beam profiles, and high power output. In this dissertation, the addition of new functionality to these lasers including wavelength tunability, focusing, beam steering and beam shaping is investigated. The theory governing device operation is presented. Pertinent discussions include the coupled mode equations, grating coupling, focusing and changes to the effective index of refraction resulting from current injection through a transparent electrode on the grating. The development and refinement of the device fabrication process is detailed. Key milestones in the grating writing process included achieving first order gratings (Λ = 0.15 μm), creating chirped period gratings for focusing and optimizing the linewidth and uniformity of the grating for high power devices. Of equal importance in obtaining high efficiency devices was the reactive ion etch process. Two different etch recipes were developed: one for mesa-definition and a shallower grating-defining etch. Significant evaluation of the electrical and optical properties of the transparent electrode, Indium Tin Oxide, was performed. Incorporating ITO into the fabrication process required optimization of deposition, patterning, etching and annealing. Device performance, efficiency and functionality improved with each generation. Consequentially, over 225 mW of output power for a injection current of 600 mA, or a slope efficiency of 0.43 mW/mA, was produced by the final generation of high power CGSELs. Focusing was demonstrated by the creation of individual devices with different focal lengths. Coarse mode selection was obtained by removing radial segments of the circular grating thereby eliminating both

  17. Y-shaped jets driven by an ultrasonic beam reflecting on a wall.

    PubMed

    Moudjed, Brahim; Botton, Valéry; Henry, Daniel; Millet, Séverine; Ben Hadid, Hamda

    2016-05-01

    This paper presents an original experimental and numerical investigation of acoustic streaming driven by an acoustic beam reflecting on a wall. The water experiment features a 2 MHz acoustic beam totally reflecting on one of the tank glass walls. The velocity field in the plane containing the incident and reflected beam axes is investigated using Particle Image Velocimetry (PIV). It exhibits an original y-shaped structure: the impinging jet driven by the incident beam is continued by a wall jet, and a second jet is driven by the reflected beam, making an angle with the impinging jet. The flow is also numerically modeled as that of an incompressible fluid undergoing a volumetric acoustic force. This is a classical approach, but the complexity of the acoustic field in the reflection zone, however, makes it difficult to derive an exact force field in this area. Several approximations are thus tested; we show that the observed velocity field only weakly depends on the approximation used in this small region. The numerical model results are in good agreement with the experimental results. The spreading of the jets around their impingement points and the creeping of the wall jets along the walls are observed to allow the interaction of the flow with a large wall surface, which can even extend to the corners of the tank; this could be an interesting feature for applications requiring efficient heat and mass transfer at the wall. More fundamentally, the velocity field is shown to have both similarities and differences with the velocity field in a classical centered acoustic streaming jet. In particular its magnitude exhibits a fairly good agreement with a formerly derived scaling law based on the balance of the acoustic forcing with the inertia due to the flow acceleration along the beam axis. PMID:26907890

  18. Fresnel and Fraunhofer diffraction of a Gaussian laser beam by fork-shaped gratings.

    PubMed

    Janicijevic, Ljiljana; Topuzoski, Suzana

    2008-11-01

    Expressions describing the vortex beams that are generated by the process of Fresnel diffraction of a Gaussian beam incident out of waist on fork-shaped gratings of arbitrary integer charge p, and vortex spots in the case of Fraunhofer diffraction by these gratings, are deduced. The common general transmission function of the gratings is defined and specialized for the cases of amplitude holograms, binary amplitude gratings, and their phase versions. Optical vortex beams, or carriers of phase singularity with charges mp and -mp, are the higher negative and positive diffraction-order beams. The radial part of their wave amplitudes is described by the product of the mpth-order Gauss-doughnut function and a Kummer function, or by the first-order Gauss-doughnut function and the difference of two modified Bessel functions whose orders do not match the singularity charge value. The wave amplitude and the intensity distributions are discussed for the near and far fields in the focal plane of a convergent lens, as well as the specialization of the results when the grating charge p=0; i.e., the grating turns from forked into rectilinear. The analytical expressions for the vortex radii are also discussed. PMID:18978843

  19. Simulation of sheet-shaped lithium beam probe performance for two-dimensional edge plasma measurement

    SciTech Connect

    Tsuchiya, H.; Morisaki, T.; Komori, A.; Motojima, O.

    2006-10-15

    A sheet-shaped thermal lithium beam probe has been developed for two-dimensional density measurements in the edge region of the torus plasma. A numerical simulation was carried out to confirm the validity of the diagnostics for fast and transient phenomena such as edge localized modes or blobs, etc., where the velocity of blobs is faster than that of the probe beam. It was found in the simulation that the density of the blob itself is reconstructed to be low and unexpected ghosts appear in the reconstructed density profile near the blob, if the conventional reconstruction method is employed. These results invite our attention to the numerical errors in the density reconstruction process. On the other hand, the errors can be corrected by using the simulation results.

  20. Optimal Neutron Source & Beam Shaping Assembly for Boron Neutron Capture Therapy

    SciTech Connect

    J. Vujic; E. Greenspan; W.E. Kastenber; Y. Karni; D. Regev; J.M. Verbeke, K.N. Leung; D. Chivers; S. Guess; L. Kim; W. Waldron; Y. Zhu

    2003-04-30

    There were three objectives to this project: (1) The development of the 2-D Swan code for the optimization of the nuclear design of facilities for medical applications of radiation, radiation shields, blankets of accelerator-driven systems, fusion facilities, etc. (2) Identification of the maximum beam quality that can be obtained for Boron Neutron Capture Therapy (BNCT) from different reactor-, and accelerator-based neutron sources. The optimal beam-shaping assembly (BSA) design for each neutron source was also to e obtained. (3) Feasibility assessment of a new neutron source for NCT and other medical and industrial applications. This source consists of a state-of-the-art proton or deuteron accelerator driving and inherently safe, proliferation resistant, small subcritical fission assembly.

  1. Optical trap for both transparent and absorbing particles in air using a single shaped laser beam.

    PubMed

    Redding, Brandon; Pan, Yong-Le

    2015-06-15

    Optical trapping of airborne particles is emerging as an essential tool in applications ranging from online characterization of living cells and aerosols to particle transport and delivery. However, existing optical trapping techniques using a single laser beam can trap only transparent particles (via the radiative pressure force) or absorbing particles (via the photophoretic force), but not particles of either type-limiting the utility of trapping-enabled aerosol characterization techniques. Here, we present the first optical trapping technique capable of trapping both transparent and absorbing particles with arbitrary morphology using a single shaped laser beam. Such a general-purpose optical trapping mechanism could enable new applications such as trapping-enabled aerosol characterization with high specificity. PMID:26076265

  2. Gaussian-to-top-hat beam shaping: an overview of parameters, methods, and applications

    NASA Astrophysics Data System (ADS)

    Homburg, O.; Mitra, T.

    2012-02-01

    Direct laser patterning of various materials is today widely used in several micro-system production lines like inkjet printing, solar cell technology, flat-panel display production, LEDs, OLEDs, semiconductors and medicine. Typically single-mode solid state lasers and their higher harmonics (e. g. 266, 355, 532 and 1064 nm) are used especially for machining of holes and grooves. The striking advantages of flat top intensity distributions compared to Gaussian beam profiles with respect to the efficiency and quality of these processes were already demonstrated. Here we will give an overview of parameters, methods and applications of Gaussian-to-top-hat beam shaping. The top hat field size can start from about 30 μm with no upper size limitation in the far field of the optics. Beam shaping for various wavelengths were realized with field geometries of squares, rectangles and circles. With LIMO's compact Gaussian-to-top-hat converter an inhomogeneity better than 5% contrast was reached. Special focus is put on the integration of Gaussian-to-top-hat beam shapers in fast scanning systems employing Galvo mirrors and a specially developed f-Theta lens to avoid destruction of the top hat profile within the scan field. Results with a 50x50μm2 top hat size (inhomogeneity down to <10%) in a scan area of 156x156mm² are presented. The minimal distortions of the top hat observed within the scan area make LIMO's compact Gaussian-to-top-hat converter excellently suited for industrial scanning applications, e.g. for the processing of solar panels.

  3. Beam orientation optimization for intensity modulated radiation therapy using adaptive l2,1-minimization

    NASA Astrophysics Data System (ADS)

    Jia, Xun; Men, Chunhua; Lou, Yifei; Jiang, Steve B.

    2011-10-01

    Beam orientation optimization (BOO) is a key component in the process of intensity modulated radiation therapy treatment planning. It determines to what degree one can achieve a good treatment plan in the subsequent plan optimization process. In this paper, we have developed a BOO algorithm via adaptive l2, 1-minimization. Specifically, we introduce a sparsity objective function term into our model which contains weighting factors for each beam angle adaptively adjusted during the optimization process. Such an objective function favors a small number of beam angles. By optimizing a total objective function consisting of a dosimetric term and the sparsity term, we are able to identify unimportant beam angles and gradually remove them without largely sacrificing the dosimetric objective. In one typical prostate case, the convergence property of our algorithm, as well as how beam angles are selected during the optimization process, is demonstrated. Fluence map optimization (FMO) is then performed based on the optimized beam angles. The resulting plan quality is presented and is found to be better than that of equiangular beam orientations. We have further systematically validated our algorithm in the contexts of 5-9 coplanar beams for five prostate cases and one head and neck case. For each case, the final FMO objective function value is used to compare the optimized beam orientations with the equiangular ones. It is found that, in the majority of cases tested, our BOO algorithm leads to beam configurations which attain lower FMO objective function values than those of corresponding equiangular cases, indicating the effectiveness of our BOO algorithm. Superior plan qualities are also demonstrated by comparing DVH curves between BOO plans and equiangular plans.

  4. Large Deflection of Ideal Pseudo-Elastic Shape Memory Alloy Cantilever Beam

    NASA Astrophysics Data System (ADS)

    Cui, Shitang; Hu, Liming; Yan, Jun

    This paper deals with the large deflections of pseudo-elastic shape memory alloy cantilever beams subjected to a concentrated load at the free end. Because of the large deflections, geometry nonlinearity arises and this analysis employs the nonlinear bending theory. The exact expression of curvature is used in the moment-curvature relationship. As a vertical force at the tip of cantilever, curvature and bending moment distribution expressions are deduced. The curvature changed distinctly when the surface material undergoes phase transformation. The length of phase transformation region was affected greatly with the force at the free end.

  5. Electron Beam Crosslinked Polyurethane Shape Memory Polymers with Tunable Mechanical Properties

    PubMed Central

    Hearon, Keith; Nash, Landon D.; Volk, Brent L.; Ware, Taylor; Lewicki, James P.; Voit, Walter E.; Wilson, Thomas S.

    2014-01-01

    Novel electron beam crosslinked polyurethane shape memory polymers with advanced processing capabilities and tunable thermomechanical properties have been synthesized and characterized. We demonstrate the ability to manipulate crosslink density in order to finely tune rubbery modulus, strain capacity, ultimate tensile strength, recovery stress, and glass transition temperature. This objective is accomplished for the first time in a low-molecular-weight polymer system through the precise engineering of thermoplastic resin precursors suitable for mass thermoplastic processing. Neurovascular stent prototypes were fabricated by dip-coating and laser machining to demonstrate processability. PMID:25411531

  6. Investigation of the Thermomechanical Response of Shape Memory Alloy Hybrid Composite Beams

    NASA Technical Reports Server (NTRS)

    Davis, Brian A.

    2005-01-01

    Previous work at NASA Langley Research Center (LaRC) involved fabrication and testing of composite beams with embedded, pre-strained shape memory alloy (SMA) ribbons. That study also provided comparison of experimental results with numerical predictions from a research code making use of a new thermoelastic model for shape memory alloy hybrid composite (SMAHC) structures. The previous work showed qualitative validation of the numerical model. However, deficiencies in the experimental-numerical correlation were noted and hypotheses for the discrepancies were given for further investigation. The goal of this work is to refine the experimental measurement and numerical modeling approaches in order to better understand the discrepancies, improve the correlation between prediction and measurement, and provide rigorous quantitative validation of the numerical model. Thermal buckling, post-buckling, and random responses to thermal and inertial (base acceleration) loads are studied. Excellent agreement is achieved between the predicted and measured results, thereby quantitatively validating the numerical tool.

  7. Quantification of shape variation of prostate and seminal vesicles during external beam radiotherapy

    SciTech Connect

    Deurloo, Kirsten; Rasch, Coen . E-mail: portal@nki.nl

    2005-01-01

    Purpose: The prostate is known to translate and rotate under influence of rectal filling changes and many studies have addressed the magnitude of these motions. However, prostate shape variations also have been reported. For image-guided radiotherapy, it is essential to know the relative magnitude of translations, rotations, and shape variation so that the most appropriate correction strategy can be chosen. However, no quantitative analysis of shape variation has been performed. It is, therefore, the purpose of this article to develop a method to determine shape variation of complex organs and apply it to determine shape variation during external beam radiotherapy of a GTV (gross tumor volume) consisting of prostate and seminal vesicles. Methods and materials: For this study, the data of 19 patients with prostate cancer were used. Each patient received a planning computed tomography (CT) scan and 8-12 (11 on average) repeat CT scans that were made during the course of conformal radiotherapy. One observer delineated the GTV in all scans, and volume variations were measured. After matching the GTVs for each patient for translation and rotation, a coverage probability matrix was constructed and the 50% isosurface was taken to determine the average GTV surface. Perpendicular distances between the average GTV and the individual GTVs were calculated for each point of the average GTV, and their variation was expressed in terms of local standard deviation (SD). The local SDs of the shape variation of all 19 patients were mapped onto a reference case by matching and morphing of the individual average GTVs. Repeated delineation of the GTV was done for 6 patients to determine intraobserver variation. Finally, the measured shape variation was corrected for intraobserver variation to estimate the 'real' shape variation. Results: No significant variations in GTV volume were observed. The measured shape variation (including delineation variation) was largest at the tip of the

  8. Local stereo matching with adaptive shape support window based cost aggregation.

    PubMed

    Xu, Yafan; Zhao, Yan; Ji, Mengqi

    2014-10-10

    Cost aggregation is the most important step in a local stereo algorithm. In this work, a novel local stereo-matching algorithm with a cost-aggregation method based on adaptive shape support window (ASSW) is proposed. First, we compute the initial cost volume, which uses both absolute intensity difference and gradient similarity to measure dissimilarity. Second, we apply an ASSW-based cost-aggregation method to get the aggregated cost within the support window. There are two main parts: at first we construct a local support skeleton anchoring each pixel with four varying arm lengths decided on color similarity; as a result, the support window integral of multiple horizontal segments spanned by pixels in the neighboring vertical is established. Then we utilize extended implementation of guided filter to aggregate cost volume within the ASSW, which has better edge-preserving smoothing property than bilateral filter independent of the filtering kernel size. In this way, the number of bad pixels located in the incorrect depth regions can be effectively reduced through finding optimal support windows with an arbitrary shape and size adaptively. Finally, the initial disparity value of each pixel is selected using winner takes all optimization and post processing symmetrically, considering both the reference and the target image, is adopted. The experimental results demonstrate that the proposed algorithm achieves outstanding matching performance compared with other existing local algorithms on the Middlebury stereo benchmark, especially in depth discontinuities and piecewise smooth regions. PMID:25322396

  9. An adaptive noise cancelling system used for beam control at the Stanford Linear Accelerator Center

    SciTech Connect

    Himel, T.; Allison, S.; Grossberg, P.; Hendrickson, L.; Sass, R.; Shoaee, H.

    1993-06-01

    The SLAC Linear Collider now has a total of twenty-four beam-steering feedback loops used to keep the electron and positron beams on their desired trajectories. Seven of these loops measure and control the same beam as it proceeds down the linac through the arcs to the final focus. Ideally by each loop should correct only for disturbances that occur between it and the immediate upstream loop. In fact, in the original system each loop corrected for all upstream disturbances. This resulted in undesirable over-correction and ringing. We added MIMO (Multiple Input Multiple Output) adaptive noise cancellers to separate the signal we wish to correct from disturbances further upstream. This adaptive control improved performance in the 1992 run.

  10. Supine proton beam craniospinal radiotherapy using a novel tabletop adapter.

    PubMed

    Buchsbaum, Jeffrey C; Besemer, Abby; Simmons, Joseph; Hoene, Ted; Simoneaux, Victor; Sandefur, Amy; Wolanski, Mark; Li, Zhao; Cheng, Chee-Wei

    2013-01-01

    To develop a device that allows supine craniospinal proton and photon therapy to the vast majority of proton and photon facilities currently experiencing limitations as a result of couch design issues. Plywood and carbon fiber were used for the development of a prototype unit. Once this was found to be satisfactory after all design issues were addressed, computer-assisted design (CAD) was used and carbon fiber tables were built to our specifications at a local manufacturer of military and racing car carbon fiber parts. Clinic-driven design was done using real-time team discussion for a prototype design. A local machinist was able to construct a prototype unit for us in <2 weeks after the start of our project. Once the prototype had been used successfully for several months and all development issues were addressed, a custom carbon fiber design was developed in coordination with a carbon fiber manufacturer in partnership. CAD methods were used to design the units to allow oblique fields from head to thigh on patients up to 200 cm in height. Two custom-designed carbon fiber craniospinal tabletop designs now exist: one long and one short. Four are in successful use in our facility. Their weight tolerance is greater than that of our robot table joint (164 kg). The long unit allows for working with taller patients and can be converted into a short unit as needed. An affordable, practical means of doing supine craniospinal therapy with protons or photons can be used in most locations via the use of these devices. This is important because proton therapy provides a much lower integral dose than all other therapy methods for these patients and the supine position is easier for patients to tolerate and for anesthesia delivery. These units have been successfully used for adult and pediatric supine craniospinal therapy, proton therapy using oblique beams to the low pelvis, treatment of various spine tumors, and breast-sparing Hodgkin's therapy. PMID:22951538

  11. Supine proton beam craniospinal radiotherapy using a novel tabletop adapter

    SciTech Connect

    Buchsbaum, Jeffrey C.; Besemer, Abby; Simmons, Joseph; Hoene, Ted; Simoneaux, Victor; Sandefur, Amy; Wolanski, Mark; Li, Zhao; Cheng, Chee-Wei

    2013-04-01

    To develop a device that allows supine craniospinal proton and photon therapy to the vast majority of proton and photon facilities currently experiencing limitations as a result of couch design issues. Plywood and carbon fiber were used for the development of a prototype unit. Once this was found to be satisfactory after all design issues were addressed, computer-assisted design (CAD) was used and carbon fiber tables were built to our specifications at a local manufacturer of military and racing car carbon fiber parts. Clinic-driven design was done using real-time team discussion for a prototype design. A local machinist was able to construct a prototype unit for us in <2 weeks after the start of our project. Once the prototype had been used successfully for several months and all development issues were addressed, a custom carbon fiber design was developed in coordination with a carbon fiber manufacturer in partnership. CAD methods were used to design the units to allow oblique fields from head to thigh on patients up to 200 cm in height. Two custom-designed carbon fiber craniospinal tabletop designs now exist: one long and one short. Four are in successful use in our facility. Their weight tolerance is greater than that of our robot table joint (164 kg). The long unit allows for working with taller patients and can be converted into a short unit as needed. An affordable, practical means of doing supine craniospinal therapy with protons or photons can be used in most locations via the use of these devices. This is important because proton therapy provides a much lower integral dose than all other therapy methods for these patients and the supine position is easier for patients to tolerate and for anesthesia delivery. These units have been successfully used for adult and pediatric supine craniospinal therapy, proton therapy using oblique beams to the low pelvis, treatment of various spine tumors, and breast-sparing Hodgkin's therapy.

  12. Adaptive digital fringe projection technique for high dynamic range three-dimensional shape measurement.

    PubMed

    Lin, Hui; Gao, Jian; Mei, Qing; He, Yunbo; Liu, Junxiu; Wang, Xingjin

    2016-04-01

    It is a challenge for any optical method to measure objects with a large range of reflectivity variation across the surface. Image saturation results in incorrect intensities in captured fringe pattern images, leading to phase and measurement errors. This paper presents a new adaptive digital fringe projection technique which avoids image saturation and has a high signal to noise ratio (SNR) in the three-dimensional (3-D) shape measurement of objects that has a large range of reflectivity variation across the surface. Compared to previous high dynamic range 3-D scan methods using many exposures and fringe pattern projections, which consumes a lot of time, the proposed technique uses only two preliminary steps of fringe pattern projection and image capture to generate the adapted fringe patterns, by adaptively adjusting the pixel-wise intensity of the projected fringe patterns based on the saturated pixels in the captured images of the surface being measured. For the bright regions due to high surface reflectivity and high illumination by the ambient light and surfaces interreflections, the projected intensity is reduced just to be low enough to avoid image saturation. Simultaneously, the maximum intensity of 255 is used for those dark regions with low surface reflectivity to maintain high SNR. Our experiments demonstrate that the proposed technique can achieve higher 3-D measurement accuracy across a surface with a large range of reflectivity variation. PMID:27137056

  13. Three-dimensional piezoelectric vibration energy harvester using spiral-shaped beam with triple operating frequencies.

    PubMed

    Zhao, Nian; Yang, Jin; Yu, Qiangmo; Zhao, Jiangxin; Liu, Jun; Wen, Yumei; Li, Ping

    2016-01-01

    This work has demonstrated a novel piezoelectric energy harvester without a complex structure and appended component that is capable of scavenging vibration energy from arbitrary directions with multiple resonant frequencies. In this harvester, a spiral-shaped elastic thin beam instead of a traditional thin cantilever beam was adopted to absorb external vibration with arbitrary direction in three-dimensional (3D) spaces owing to its ability to bend flexibly and stretch along arbitrary direction. Furthermore, multiple modes in the elastic thin beam contribute to a possibility to widen the working bandwidth with multiple resonant frequencies. The experimental results show that the harvester was capable of scavenging the vibration energy in 3D arbitrary directions; they also exhibited triple power peaks at about 16 Hz, 21 Hz, and 28 Hz with the powers of 330 μW, 313 μW, and 6 μW, respectively. In addition, human walking and water wave energies were successfully converted into electricity, proving that our harvester was practical to scavenge the time-variant or multi-directional vibration energies in our daily life. PMID:26827346

  14. Three-dimensional piezoelectric vibration energy harvester using spiral-shaped beam with triple operating frequencies

    NASA Astrophysics Data System (ADS)

    Zhao, Nian; Yang, Jin; Yu, Qiangmo; Zhao, Jiangxin; Liu, Jun; Wen, Yumei; Li, Ping

    2016-01-01

    This work has demonstrated a novel piezoelectric energy harvester without a complex structure and appended component that is capable of scavenging vibration energy from arbitrary directions with multiple resonant frequencies. In this harvester, a spiral-shaped elastic thin beam instead of a traditional thin cantilever beam was adopted to absorb external vibration with arbitrary direction in three-dimensional (3D) spaces owing to its ability to bend flexibly and stretch along arbitrary direction. Furthermore, multiple modes in the elastic thin beam contribute to a possibility to widen the working bandwidth with multiple resonant frequencies. The experimental results show that the harvester was capable of scavenging the vibration energy in 3D arbitrary directions; they also exhibited triple power peaks at about 16 Hz, 21 Hz, and 28 Hz with the powers of 330 μW, 313 μW, and 6 μW, respectively. In addition, human walking and water wave energies were successfully converted into electricity, proving that our harvester was practical to scavenge the time-variant or multi-directional vibration energies in our daily life.

  15. Adaptable beam profiles from a dual-cavity Nd:YAG laser.

    PubMed

    Kim, D J; Mackenzie, J I; Kim, J W

    2016-04-15

    We report a technique to tailor a laser beam profile from a donut to quasi-top-hat intensity distribution, directly from the laser, simply achieved by simultaneous excitation and control of the relative contributions of the fundamental (TEM00) and first-order Laguerre-Gaussian (LG01) transverse modes. Exploiting a dual-cavity configuration with a single Nd:YAG gain element, adaptable continuous-wave laser beam profiles from the primary cavity could be obtained by varying the diffraction loss of an acousto-optic modulator in the secondary cavity. We investigate the resultant beam profiles as a function of pump power and the AOM diffraction loss, and discuss the prospects for tunable laser beams profiles. PMID:27082333

  16. A DSP-Based Beam Current Monitoring System for Machine Protection Using Adaptive Filtering

    SciTech Connect

    J. Musson; H. Dong; R. Flood; C. Hovater; J. Hereford

    2001-06-01

    The CEBAF accelerator at Jefferson Lab is currently using an analog beam current monitoring (BCM) system for its machine protection system (MPS), which has a loss accuracy of 2 micro-amps. Recent burn-through simulations predict catastrophic beam line component failures below 1 micro-amp of loss, resulting in a blind spot for the MPS. Revised MPS requirements target an ultimate beam loss accuracy of 250 nA. A new beam current monitoring system has been developed which utilizes modern digital receiver technology and digital signal processing concepts. The receiver employs a direct-digital down converter integrated circuit, mated with a Jefferson Lab digital signal processor VME card. Adaptive filtering is used to take advantage of current-dependent burn-through rates. Benefits of such a system include elimination of DC offsets, generic algorithm development, extensive filter options, and interfaces to UNIX-based control systems.

  17. Adaptive slab laser beam quality improvement using a weighted least-squares reconstruction algorithm.

    PubMed

    Chen, Shanqiu; Dong, LiZhi; Chen, XiaoJun; Tan, Yi; Liu, Wenjin; Wang, Shuai; Yang, Ping; Xu, Bing; Ye, YuTang

    2016-04-10

    Adaptive optics is an important technology for improving beam quality in solid-state slab lasers. However, there are uncorrectable aberrations in partial areas of the beam. In the criterion of the conventional least-squares reconstruction method, it makes the zones with small aberrations nonsensitive and hinders this zone from being further corrected. In this paper, a weighted least-squares reconstruction method is proposed to improve the relative sensitivity of zones with small aberrations and to further improve beam quality. Relatively small weights are applied to the zones with large residual aberrations. Comparisons of results show that peak intensity in the far field improved from 1242 analog digital units (ADU) to 2248 ADU, and beam quality β improved from 2.5 to 2.0. This indicates the weighted least-squares method has better performance than the least-squares reconstruction method when there are large zonal uncorrectable aberrations in the slab laser system. PMID:27139877

  18. Adaptive step-size algorithm for Fourier beam-propagation method with absorbing boundary layer of auto-determined width

    DOE PAGESBeta

    Learn, R.; Feigenbaum, E.

    2016-05-27

    Two algorithms that enhance the utility of the absorbing boundary layer are presented, mainly in the framework of the Fourier beam-propagation method. One is an automated boundary layer width selector that chooses a near-optimal boundary size based on the initial beam shape. Furthermore, the second algorithm adjusts the propagation step sizes based on the beam shape at the beginning of each step in order to reduce aliasing artifacts.

  19. Inverted Gabor holography principle for tailoring arbitrary shaped three-dimensional beams

    PubMed Central

    Latychevskaia, Tatiana; Fink, Hans-Werner

    2016-01-01

    It is well known that by modifying the wavefront in a certain manner, the light intensity can be turned into a certain shape. However, all known light modulation techniques allow for limited light modifications only: focusing within a restricted region in space, shaping into a certain class of parametric curves along the optical axis or bending described by a quadratic-dependent deflection as in the case of Airy beams. We show a general case of classical light wavefront shaping that allows for intensity and phase redistribution into an arbitrary profile including pre-determined switching-off of the intensity. To create an arbitrary three-dimensional path of intensity, we represent the path as a sequence of closely packed individual point-like absorbers and simulate the in-line hologram of the created object set; when such a hologram is contrast inverted, thus giving rise to a diffractor, it creates the pre-determined three-dimensional path of intensity behind the diffractor under illumination. The crucial parameter for a smooth optical path is the sampling of the predetermined curves, which is given by the lateral and axial resolution of the optical system. We provide both, simulated and experimental results to demonstrate the power of this novel method. PMID:27199254

  20. Inverted Gabor holography principle for tailoring arbitrary shaped three-dimensional beams.

    PubMed

    Latychevskaia, Tatiana; Fink, Hans-Werner

    2016-01-01

    It is well known that by modifying the wavefront in a certain manner, the light intensity can be turned into a certain shape. However, all known light modulation techniques allow for limited light modifications only: focusing within a restricted region in space, shaping into a certain class of parametric curves along the optical axis or bending described by a quadratic-dependent deflection as in the case of Airy beams. We show a general case of classical light wavefront shaping that allows for intensity and phase redistribution into an arbitrary profile including pre-determined switching-off of the intensity. To create an arbitrary three-dimensional path of intensity, we represent the path as a sequence of closely packed individual point-like absorbers and simulate the in-line hologram of the created object set; when such a hologram is contrast inverted, thus giving rise to a diffractor, it creates the pre-determined three-dimensional path of intensity behind the diffractor under illumination. The crucial parameter for a smooth optical path is the sampling of the predetermined curves, which is given by the lateral and axial resolution of the optical system. We provide both, simulated and experimental results to demonstrate the power of this novel method. PMID:27199254

  1. Inverted Gabor holography principle for tailoring arbitrary shaped three-dimensional beams

    NASA Astrophysics Data System (ADS)

    Latychevskaia, Tatiana; Fink, Hans-Werner

    2016-05-01

    It is well known that by modifying the wavefront in a certain manner, the light intensity can be turned into a certain shape. However, all known light modulation techniques allow for limited light modifications only: focusing within a restricted region in space, shaping into a certain class of parametric curves along the optical axis or bending described by a quadratic-dependent deflection as in the case of Airy beams. We show a general case of classical light wavefront shaping that allows for intensity and phase redistribution into an arbitrary profile including pre-determined switching-off of the intensity. To create an arbitrary three-dimensional path of intensity, we represent the path as a sequence of closely packed individual point-like absorbers and simulate the in-line hologram of the created object set; when such a hologram is contrast inverted, thus giving rise to a diffractor, it creates the pre-determined three-dimensional path of intensity behind the diffractor under illumination. The crucial parameter for a smooth optical path is the sampling of the predetermined curves, which is given by the lateral and axial resolution of the optical system. We provide both, simulated and experimental results to demonstrate the power of this novel method.

  2. Adaptive correction of the focused beam in conditions with strong fluctuations of intensity

    NASA Astrophysics Data System (ADS)

    Lukin, Vladimir P.; Fortes, Boris V.

    2000-07-01

    The adaptive correction was frequently treated as straightening of wavefront, if deal with receiving of the deformed wave. For adaptive focusing of beams the correction was considered as predistortion of wavefront. However with infringement of a condition smoothness of wavefront, the situation varies. It is known, that dislocations of wavefront conterminous to points where instant meaning of intensity equal to zero, arise with distances approximately equal diffraction length. With presence of such points the wavefront of a reference wave cannot be determined as a smooth one-coherent surface, therefore efficiency of adaptive systems with flexible mirrors begins to be reduced. At the same time, the numerical experiment with model of a compound phase corrector has shown, that its efficiency practically does not change with transition in area of strong fluctuations of intensity. We have found out, that the efficiency of adaptive system with a compound corrector does not vary with transition from area weak fluctuations of intensity in area strong fluctuations.

  3. MR-guided adaptive focusing of therapeutic ultrasound beams in the human head

    PubMed Central

    Marsac, Laurent; Chauvet, Dorian; Larrat, Benoît; Pernot, Mathieu; Robert, B.; Fink, Mathias; Boch, Anne-Laure; Aubry, Jean-François; Tanter, Mickaël

    2012-01-01

    Purpose This study aims to demonstrate, using human cadavers the feasibility of energy-based adaptive focusing of ultrasonic waves using Magnetic Resonance Acoustic Radiation Force Imaging (MR-ARFI) in the framework of non-invasive transcranial High Intensity Focused Ultrasound (HIFU) therapy. Methods Energy-based adaptive focusing techniques were recently proposed in order to achieve aberration correction. We evaluate this method on a clinical brain HIFU system composed of 512 ultrasonic elements positioned inside a full body 1.5 T clinical Magnetic Resonance (MR) imaging system. Cadaver heads were mounted onto a clinical Leksell stereotactic frame. The ultrasonic wave intensity at the chosen location was indirectly estimated by the MR system measuring the local tissue displacement induced by the acoustic radiation force of the ultrasound (US) beams. For aberration correction, a set of spatially encoded ultrasonic waves was transmitted from the ultrasonic array and the resulting local displacements were estimated with the MR-ARFI sequence for each emitted beam. A non-iterative inversion process was then performed in order to estimate the spatial phase aberrations induced by the cadaver skull. The procedure was first evaluated and optimized in a calf brain using a numerical aberrator mimicking human skull aberrations. The full method was then demonstrated using a fresh human cadaver head. Results The corrected beam resulting from the direct inversion process was found to focus at the targeted location with an acoustic intensity 2.2 times higher than the conventional non corrected beam. In addition, this corrected beam was found to give an acoustic intensity 1.5 times higher than the focusing pattern obtained with an aberration correction using transcranial acoustic simulation based on X-ray computed tomography (CT) scans. Conclusion The proposed technique achieved near optimal focusing in an intact human head for the first time. These findings confirm the strong

  4. A method for robust segmentation of arbitrarily shaped radiopaque structures in cone-beam CT projections

    SciTech Connect

    Poulsen, Per Rugaard; Fledelius, Walther; Keall, Paul J.; Weiss, Elisabeth; Lu Jun; Brackbill, Emily; Hugo, Geoffrey D.

    2011-04-15

    Purpose: Implanted markers are commonly used in radiotherapy for x-ray based target localization. The projected marker position in a series of cone-beam CT (CBCT) projections can be used to estimate the three dimensional (3D) target trajectory during the CBCT acquisition. This has important applications in tumor motion management such as motion inclusive, gating, and tumor tracking strategies. However, for irregularly shaped markers, reliable segmentation is challenged by large variations in the marker shape with projection angle. The purpose of this study was to develop a semiautomated method for robust and reliable segmentation of arbitrarily shaped radiopaque markers in CBCT projections. Methods: The segmentation method involved the following three steps: (1) Threshold based segmentation of the marker in three to six selected projections with large angular separation, good marker contrast, and uniform background; (2) construction of a 3D marker model by coalignment and backprojection of the threshold-based segmentations; and (3) construction of marker templates at all imaging angles by projection of the 3D model and use of these templates for template-based segmentation. The versatility of the segmentation method was demonstrated by segmentation of the following structures in the projections from two clinical CBCT scans: (1) Three linear fiducial markers (Visicoil) implanted in or near a lung tumor and (2) an artificial cardiac valve in a lung cancer patient. Results: Automatic marker segmentation was obtained in more than 99.9% of the cases. The segmentation failed in a few cases where the marker was either close to a structure of similar appearance or hidden behind a dense structure (data cable). Conclusions: A robust template-based method for segmentation of arbitrarily shaped radiopaque markers in CBCT projections was developed.

  5. Vibrational behavior of adaptive aircraft wing structures modelled as composite thin-walled beams

    NASA Technical Reports Server (NTRS)

    Song, O.; Librescu, L.; Rogers, C. A.

    1992-01-01

    The vibrational behavior of cantilevered aircraft wings modeled as thin-walled beams and incorporating piezoelectric effects is studied. Based on the converse piezoelectric effect, the system of piezoelectric actuators conveniently located on the wing yield the control of its associated vertical and lateral bending eigenfrequencies. The possibility revealed by this study enabling one to increase adaptively the eigenfrequencies of thin-walled cantilevered beams could play a significant role in the control of the dynamic response and flutter of wing and rotor blade structures.

  6. Reciprocity breaking during nonlinear propagation of adapted beams through random media

    NASA Astrophysics Data System (ADS)

    Palastro, J. P.; Peñano, J.; Nelson, W.; DiComo, G.; Helle, M.; Johnson, L. A.; Hafizi, B.

    2016-08-01

    Adaptive optics (AO) systems rely on the principle of reciprocity, or symmetry with respect to the interchange of point sources and receivers. These systems use the light received from a low power emitter on or near a target to compensate profile aberrations acquired by a laser beam during linear propagation through random media. If, however, the laser beam propagates nonlinearly, reciprocity is broken, potentially undermining AO correction. Here we examine the consequences of this breakdown. While discussed for general random and nonlinear media, we consider specific examples of Kerr-nonlinear, turbulent atmosphere.

  7. Controlled Aeroelastic Response and Airfoil Shaping Using Adaptive Materials and Integrated Systems

    NASA Technical Reports Server (NTRS)

    Pinkerton, Jennifer L.; McGowan, Anna-Maria R.; Moses, Robert W.; Scott, Robert C.; Heeg, Jennifer

    1996-01-01

    This paper presents an overview of several activities of the Aeroelasticity Branch at the NASA Langley Research Center in the area of applying adaptive materials and integrated systems for controlling both aircraft aeroelastic response and airfoil shape. The experimental results of four programs are discussed: the Piezoelectric Aeroelastic Response Tailoring Investigation (PARTI); the Adaptive Neural Control of Aeroelastic Response (ANCAR) program; the Actively Controlled Response of Buffet Affected Tails (ACROBAT) program; and the Airfoil THUNDER Testing to Ascertain Characteristics (ATTACH) project. The PARTI program demonstrated active flutter control and significant rcductions in aeroelastic response at dynamic pressures below flutter using piezoelectric actuators. The ANCAR program seeks to demonstrate the effectiveness of using neural networks to schedule flutter suppression control laws. Th,e ACROBAT program studied the effectiveness of a number of candidate actuators, including a rudder and piezoelectric actuators, to alleviate vertical tail buffeting. In the ATTACH project, the feasibility of using Thin-Layer Composite-Uimorph Piezoelectric Driver and Sensor (THUNDER) wafers to control airfoil aerodynamic characteristics was investigated. Plans for future applications are also discussed.

  8. Controlled aeroelastic response and airfoil shaping using adaptive materials and integrated systems

    NASA Astrophysics Data System (ADS)

    Pinkerton, Jennifer L.; McGowan, Anna-Maria R.; Moses, Robert W.; Scott, Robert C.; Heeg, Jennifer

    1996-05-01

    This paper presents an overview of several activities of the Aeroelasticity Branch at the NASA Langley Research Center in the area of applying adaptive materials and integrated systems for controlling both aircraft aeroelastic response and airfoil shape. The experimental results of four programs are discussed: the Piezoelectric Aeroelastic Response Tailoring Investigation (PARTI); the adaptive neural control of aeroelastic response (ANCAR) program; the actively controlled response of buffet affected tails (ACROBAT) program; and the Airfoil THUNDER Testing to ascertain charcteristics (ATTACH) project. The PARTI program demonstrated active flutter control and significant reductions in aeroelastic response at dynamic pressures below flutter using piezoelectric actuators. The ANCAR program seeks to demonstrate the effectiveness of using neural networks to schedule flutter suppression control laws. The ACROBAT program studied the effectiveness of a number of candidate actuators, including a rudder and piezoelectric actuators, to alleviate vertical tail buffeting. In the ATTACH project, the feasibility of using thin-layer composite-unimorph piezoelectric driver and sensor (THUNDER) wafers to control airfoil aerodynamic characteristics was investigated. Plans for future applications are also discussed.

  9. Adaptive niche radii and niche shapes approaches for niching with the CMA-ES.

    PubMed

    Shir, Ofer M; Emmerich, Michael; Bäck, Thomas

    2010-01-01

    While the motivation and usefulness of niching methods is beyond doubt, the relaxation of assumptions and limitations concerning the hypothetical search landscape is much needed if niching is to be valid in a broader range of applications. Upon the introduction of radii-based niching methods with derandomized evolution strategies (ES), the purpose of this study is to address the so-called niche radius problem. A new concept of an adaptive individual niche radius is applied to niching with the covariance matrix adaptation evolution strategy (CMA-ES). Two approaches are considered. The first approach couples the radius to the step size mechanism, while the second approach employs the Mahalanobis distance metric with the covariance matrix mechanism for the distance calculation, for obtaining niches with more complex geometrical shapes. The proposed approaches are described in detail, and then tested on high-dimensional artificial landscapes at several levels of difficulty. They are shown to be robust and to achieve satisfying results. PMID:20064027

  10. Orientation and shape-control of an orbiting flexible beam under the influence of solar radiation pressure

    NASA Technical Reports Server (NTRS)

    Krishna, R.; Bainum, P. M.

    1984-01-01

    In this paper, the uncontrolled and controlled dynamics of a thin flexible beam in orbit and in the presence of solar radiation disturbance are analyzed. A beam nominally oriented along (i) the local horizontal and carrying a gimballed rigid dumbbell for gravity stabilization, and (ii) a beam nominally oriented along the local vertical are considered. The uncontrolled dynamics of the beam in the presence of the solar radiation pressure disturbance shows the excitation of the rigid pitch mode. The control laws previously designed for the case where the environmental effects were neglected, are found to be inadequate to control the shape and orientation of very flexible beams that are exposed to solar radiation disturbances. The control laws and the gain parameters are reevaluated for both cases of nominal beam orientations; this results, in general, in increased robustness of the closed-loop system. Methods of obtaining a robust control system in the presence of environmental perturbations are discussed.

  11. Treatment of absolute painful glaucoma with dynamic arcs using novalis shaped beam radiosurgery

    SciTech Connect

    Gonzalez-Olhovich, Irene . E-mail: irenegonol@hotmail.com; Celis, Miguel Angel; Larraga-Gutierrez, Jose; Lopez-Ayala, Temuchino; Suarez-Campos, Jose; Garcia-Garduno, Amanda; Herrera-Gomez, Leopoldo; Hernandez-Bojorquez, Mariana B.Sc.

    2006-11-15

    Purpose: We assessed the effect of shaped beam conformal stereotactic radiosurgery (SRS) in 1 patient with chronic painful glaucoma in one eye refractory to medical treatment. Methods and Materials: Left eye ciliary body was targeted at 18 Gy (90% isodose curve) with a dedicated linear accelerator (Novalis, BrainLAB, Germany) SRS. Interval follow-up was performed weekly for the first month, and every 2 months until 1 year was completed with clinical examinations and intraocular pressure (IOP) measurements. Results: Ocular pain resolved at 6 weeks after SRS treatment. IOP decreased and normalized at 1 year. Conclusions: We present a case in which SRS appears to be an effective treatment of chronic refractory painful glaucoma. Further Phase I studies are needed to know the best parameters for radiation dose, tolerance of organs at risk, and pathophysiologic effects.

  12. Generation of isolated attosecond pulses by spatial shaping of a femtosecond laser beam

    NASA Astrophysics Data System (ADS)

    Strelkov, V. V.; Mével, E.; Constant, E.

    2008-08-01

    We present a new method for generating isolated attosecond pulses via high-order harmonic generation in gases. It relies on using collective effects to achieve transient phase-matching which provides both a high efficiency and a strong temporal confinement under specific conditions. By controlling the spatial shape of the fundamental beam and the geometry of the laser gas interaction, this transient phase matching leads to the generation of isolated broadband attosecond pulses with long driving pulses (10 20 fs) even without controlling their carrier envelope phase. Such laser pulses are becoming available at high energy levels and our approach offers a route to increase the energy of isolated attosecond pulses by orders of magnitude as compared to existing sources.

  13. Tight focusing of a double-ring-shaped, azimuthally polarized beam through a dielectric interface.

    PubMed

    Shu, Jianhua; Chen, Ziyang; Pu, Jixiong; Liu, Yongxin

    2014-06-01

    We investigate the tight focusing properties of a double-ring-shaped, azimuthally polarized vector beam (DRS-APVB) by use of vectorial Debye theory. It is shown that a dark channel with an ultralong depth of focus (~106λ) and subwavelength focal holes (~0.5λ) can be generated by focusing a DRS-APVB through a dielectric interface with an annular high-numerical aperture (NA) objective lens. The influence of the NA of the objective, the relative refractive indices of two dielectric media, and the probe depth of the system on the focusing properties of the dark channel has been studied in detail. Such a non-diffracting dark channel could find potential applications in atom optical experiments, such as with atomic lenses, atom traps, and atom switches. PMID:24977354

  14. Solving tolerancing and 3D beam shaping problems by multifunctional wave optical design

    NASA Astrophysics Data System (ADS)

    Buehling, Sven; Wyrowski, Frank

    2000-10-01

    A strategy for designing optical systems that are optimized for multiple optical functions on the basis of wave optics is presented. Each optical function is composed of an input field, a set of fixed system parameters, and a merit function. A design algorithm is proposed which is applicable for optical systems consisting of an transmission operator followed by an arbitrary linear operator. The goal is to find the transmission operator which is optimal for all optical functions simultaneously. In later design steps, the found transmission operator can be transformed to real optical elements, for instance by using the thin element approximation. It is shown that the algorithm is efficiently applicable by investigating two sample applications for multifunctional wave optical design: the design of tolerant systems and 3D beam shaping.

  15. Directionality effects in the transfer of X-rays from a magnetized atmosphere: Beam pulse shape

    NASA Technical Reports Server (NTRS)

    Meszaros, P.; Bonazzola, S.

    1981-01-01

    A formalism is presented for radiation transfer in two normal polarization modes in finite and semiinfinite plane parallel uniform atmospheres with a magnetic field perpendicular to the surface and arbitrary propagation angles. This method is based on the coupled integral equations of transfer, including emission, absorption, and scattering. Calculations are performed for atmosphere parameters typical of X-ray pulsars. The directionality of the escaping radiation is investigated for several cases, varying the input distributions. Theoretical pencil beam profiles and X-ray pulse shapes are obtained assuming the radiation is emitted from the polar caps of spinning neutron stars. Implications for realistic models of accreting magnetized X-ray sources are briefly discussed.

  16. Laser beam propagation through turbulence and adaptive optics for beam delivery improvement

    NASA Astrophysics Data System (ADS)

    Nicolas, Stephane

    2015-10-01

    We report results from numerical simulations of laser beam propagation through atmospheric turbulence. In particular, we study the statistical variations of the fractional beam energy hitting inside an optical aperture placed at several kilometer distance. The simulations are performed for different turbulence conditions and engagement ranges, with and without the use of turbulence mitigation. Turbulence mitigation is simulated with phase conjugation. The energy fluctuations are deduced from time sequence realizations. It is shown that turbulence mitigation leads to an increase of the mean energy inside the aperture and decrease of the fluctuations even in strong turbulence conditions and long distance engagement. As an example, the results are applied to a high energy laser countermeasure system, where we determine the probability that a single laser pulse, or one of the pulses in a sequence, will provide a lethal energy inside the target aperture. Again, turbulence mitigation contributes to increase the performance of the system at long-distance and for strong turbulence conditions in terms of kill probability. We also discuss a specific case where turbulence contributes to increase the pulse energy within the target aperture. The present analysis can be used to evaluate the performance of a variety of systems, such as directed countermeasures, laser communication, and laser weapons.

  17. A new method for beam-damage-diagnosis using adaptive fuzzy neural structure and wavelet analysis

    NASA Astrophysics Data System (ADS)

    Nguyen, Sy Dzung; Ngo, Kieu Nhi; Tran, Quang Thinh; Choi, Seung-Bok

    2013-08-01

    In this work, we present a new beam-damage-locating (BDL) method based on an algorithm which is a combination of an adaptive fuzzy neural structure (AFNS) and an average quantity solution to wavelet transform coefficient (AQWTC) of beam vibration signal. The AFNS is used for remembering undamaged-beam dynamic properties, while the AQWTC is used for signal analysis. Firstly, the beam is divided into elements and excited to be vibrated. Vibrating signal at each element, which is displacement in this work, is measured, filtered and transformed into wavelet signal with a used-scale-sheet to calculate the corresponding difference of AQWTC between two cases: undamaged status and the status at the checked time. Database about this difference is then used for finding out the elements having strange features in wavelet quantitative analysis, which directly represents the beam-damage signs. The effectiveness of the proposed approach which combines fuzzy neural structure and wavelet transform methods is demonstrated by experiment on measured data sets in a vibrated beam-type steel frame structure. `

  18. Correction of resist heating effect on variable shaped beam mask writer

    NASA Astrophysics Data System (ADS)

    Nakayamada, Noriaki; Suganuma, Mizuna; Nomura, Haruyuki; Kato, Yasuo; Kamikubo, Takashi; Ogasawara, Munehiro; Zable, Harold; Masuda, Yukihiro; Fujimura, Aki

    2016-04-01

    The specifications for critical dimension (CD) accuracy and line edge roughness are getting tighter to promote every photomask manufacturer to choose electron beam resists of lower sensitivity. When the resist is exposed by too many electrons, it is excessively heated up to have higher sensitivity at a higher temperature, which results in degraded CD uniformity. This effect is called "resist heating effect" and is now the most critical error source in CD control on a variable shaped beam (VSB) mask writer. We have developed an on-tool, real-time correction system for the resist heating effect. The system is composed of correction software based on a simple thermal diffusion model and computational hardware equipped with more than 100 graphical processing unit chips. We have demonstrated that the designed correction accuracy was obtained and the runtime of correction was sufficiently shorter than the writing time. The system is ready to be deployed for our VSB mask writers to retain the writing time as short as possible for lower sensitivity resists by removing the need for increased pass count.

  19. Shaping symmetric Airy beam through binary amplitude modulation for ultralong needle focus

    SciTech Connect

    Fang, Zhao-Xiang; Gong, Lei; Ren, Yu-Xuan; Vaveliuk, Pablo; Chen, Yue; Lu, Rong-De

    2015-11-28

    Needle-like electromagnetic field has various advantages for the applications in high-resolution imaging, Raman spectroscopy, as well as long-distance optical transportation. The realization of such field often requires high numerical aperture (NA) objective lens and the transmission masks. We demonstrate an ultralong needle-like focus in the optical range produced with an ordinary lens. This is achieved by focusing a symmetric Airy beam (SAB) generated via binary spectral modulation with a digital micromirror device. Such amplitude modulation technique is able to shape traditional Airy beams, SABs, as well as the dynamic transition modes between the one-dimensional and two-dimensional (2D) symmetric Airy modes. The created 2D SAB was characterized through measurement of the propagating fields with one of the four main lobes blocked by an opaque mask. The 2D SAB was verified to exhibit self-healing property against propagation with the obstructed major lobe reconstructed after a certain distance. We further produced an elongated focal line by concentrating the SAB via lenses with different NAs and achieved an ultralong longitudinal needle focus. The produced long needle focus will be applied in optical, chemical, and biological sciences.

  20. Hippocampal Dose With Radiosurgery for Multiple Intracranial Targets: The Rationale for Proactive Beam Shaping.

    PubMed

    Chang, Jennifer S; Ma, Lijun; Barani, Igor J; McDermott, Michael W; Sneed, Penny K; Larson, David A

    2016-08-01

    Stereotactic radiosurgery provides conformal treatment of intracranial lesions, but when multiple lesions are treated, cumulative dose to structures such as the hippocampi may be increased. We analyzed hippocampal dose for patients treated with radiosurgery for multiple brain metastases. We then investigated a means to minimize hippocampal dose. We randomly selected 8 patients treated with single-session, frame-based radiosurgery for 6 to 12 intracranial metastases. Standard planning was employed to deliver 16 to 20 Gy to each lesion without hippocampal avoidance. Each case was replanned using the software's dynamic shaping function to minimize direct beam hippocampal irradiation, while maintaining conformality and target coverage. With standard planning, the maximum hippocampal dose varied from 0.8 to 9.0 Gy but was >3 Gy only when a lesion was <10 mm from the hippocampus. There was no clear correlation between hippocampal dose and the number or the total volume of lesions. Replanning with direct beam avoidance decreased the mean hippocampal dose by an average of 35% but increased treatment time by a mean of 20%. Sparing was most pronounced when the closest lesion was in close proximity to the hippocampus. This is the first study reporting hippocampal dose for multilesion intracranial radiosurgery. It illustrates that when multiple intracranial targets are treated with radiosurgery, substantial hippocampal dose can result. Active beam shielding and optimization can lower hippocampal dose, especially with lesions <10 mm from the hippocampus. These results raise the prospect that the risk of neurocognitive side effects may be further decreased with a hippocampal-sparing approach. PMID:26113558

  1. Adaptive beam tracking and steering via electrowetting-controlled liquid prism

    NASA Astrophysics Data System (ADS)

    Cheng, Jiangtao; Chen, Chung-Lung

    2011-11-01

    We report an electrowetting-controlled optofluidic system for adaptive beam tracking and agile steering. With two immiscible fluids in a transparent cell, we can actively control the contact angle along the fluid-fluid-solid tri-junction line and hence the orientation of the fluid-fluid interface via electrowetting. The naturally formed meniscus between the two liquids can function as an optical prism. We have fabricated a liquid prism module with an aperture size of 10 mm × 10mm. With 1 wt. % KCl and 1 wt. % Sodium Dodecyl Sulfate added into deionized water, the orientation of the water-silicone oil interface has been modulated between -26° and 26° that can deflect and steer beam within the incidence angle of 0°-15°. The wide-range beam tracking and steering enables the liquid prism work as an electrowetting solar cell.

  2. Adaptive beam tracking and steering via electrowetting-controlled liquid prism

    SciTech Connect

    Cheng, JT; Chen, CL

    2011-11-07

    We report an electrowetting-controlled optofluidic system for adaptive beam tracking and agile steering. With two immiscible fluids in a transparent cell, we can actively control the contact angle along the fluid-fluid-solid tri-junction line and hence the orientation of the fluid-fluid interface via electrowetting. The naturally formed meniscus between the two liquids can function as an optical prism. We have fabricated a liquid prism module with an aperture size of 10 mm -10mm. With 1 wt.% KCl and 1 wt.% Sodium Dodecyl Sulfate added into deionized water, the orientation of the water-silicone oil interface has been modulated between -26 degrees and 26 degrees that can deflect and steer beam within the incidence angle of 0 degrees-15 degrees. The wide-range beam tracking and steering enables the liquid prism work as an electrowetting solar cell. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3660578

  3. Decentralized adaptive sliding mode control for beam synchronization of tethered InSAR system

    NASA Astrophysics Data System (ADS)

    Zhang, Jinxiu; Zhang, Zhigang; Wu, Baolin

    2016-10-01

    Beam synchronization problem of tethered interferometric synthetic aperture radar (InSAR) is addressed in this paper. Two antennas of the system are carried by separate satellites connected through a tether to obtain a preferable baseline. A Total Zero Doppler Steering (TZDS) is implemented to mother-satellite to cancel the residual Doppler. Subsequently attitude reference trajectories for the two satellites are generated to achieve the beam synchronization and TZDS. Thereafter, a decentralized adaptive sliding mode control law is proposed to track these reference trajectories in the presence of model uncertainties and external disturbances. Finally, the stability of closed-loop system is proved by the corollary of Barbalat's Lemma. Simulation results show the proposed control law is effective to achieve beam synchronization of the system.

  4. Highly energy-efficient agricultural lighting by B+R LEDs with beam shaping using micro-lens diffuser

    NASA Astrophysics Data System (ADS)

    Lee, Xuan-Hao; Chang, Yu-Yu; Sun, Ching-Cherng

    2013-03-01

    This paper presents a high-performance LED agricultural luminaire that uses a beam-shaping diffuser to achieve high optical efficiency and energy saving. The agricultural luminaire performs an optical efficiency as high as 84.2%. The beam shaping effect also obtains irradiance uniformity of 1/2.56 and excellent spatial color uniformity. The enhancement ratio of optical utilization factor in the proposed agricultural luminaire is 360% in comparison with traditional lighting. Under the designed case, the total utilization factor, including optical utilization factor and spectral utilization factor, of the B+R LED lamp can save 86.1% of power consumption in comparison with compact fluorescent bulbs.

  5. Shape memory alloy adaptive control of gas turbine engine compressor blade tip clearance

    NASA Astrophysics Data System (ADS)

    Schetky, Lawrence M.; Steinetz, Bruce M.

    1998-06-01

    The ambient air ingested through the inlet of a gas turbine is first compressed by an axial compressor followed by further compression in a centrifugal compressor and then fed into the combustion chamber where ignition and expansion take place to produce the engine thrust. The axial compressor typically has five or more stages which consist of revolving blades and stators and the overall performance of the turbine is strongly affected by the compressor efficiency. When the turbine is turned on, to accommodate the rapid initial increase in the compressor blade length due to centrifugal force, the cold turbine has a built in clearance between the turbine blade tip and the casing. As the turbine reached its operating temperature there is a further increase in the blade length due to thermal expansion and, at the same time, the diameter of the casing increases. The net result is that when these various components have reached their equilibrium temperatures, the initial cold build clearance is reduced, but there remains a residual clearance. The magnitude of this clearance has a direct effect on the compressor efficiency and can be stated as: Δη/Δ CLR equals 0.5 where η is efficiency and CLR is the tip clearance. The concept of adaptive tip clearance control is based on the ability of a shape memory alloy ring to shrink to a predetermined diameter when heated to the temperature of a particular stage, and thus reducing the tip clearance. The ring is fabricated from a CuAlNi shape memory alloy and is mounted in the casing so as to be coaxial with the rotating blades of the particular stage. When cold, the ring dimensions are such as to provide the required cold build clearance, but when at operating temperature the reduced diameter creates a very small tip clearance. The clearance provided by this concept is much smaller than the clearance normally obtained for a turbine of the size being studied.

  6. Truss beam having convex-curved rods, shear web panels, and self-aligning adapters

    NASA Technical Reports Server (NTRS)

    Fernandez, Ian M. (Inventor)

    2013-01-01

    A truss beam comprised of a plurality of joined convex-curved rods with self-aligning adapters (SAA) adhesively attached at each end of the truss beam is disclosed. Shear web panels are attached to adjacent pairs of rods, providing buckling resistance for the truss beam. The rods are disposed adjacent to each other, centered around a common longitudinal axis, and oriented so that adjacent rod ends converge to at least one virtual convergence point on the common longitudinal axis, with the rods' curvature designed to increase prevent buckling for the truss beam. Each SAA has longitudinal bores that provide self-aligning of the rods in the SAA, the self-aligning feature enabling creation of strong adhesive bonds between each SAA and the rods. In certain embodiments of the present invention, pultruded unidirectional carbon fiber rods are coupled with carbon fiber shear web panels and metal SAA(s), resulting in a lightweight, low-cost but strong truss beam that is highly resistant to buckling.

  7. EB-X1: an accurate x-ray mask writer using a variable-shaped beam

    NASA Astrophysics Data System (ADS)

    Shimazu, Nobuo; Watanabe, Takashi; Morosawa, Tetsuo; Morita, Hirofumi; Kuriyama, Youichi; Kunioka, Tatsuya

    1994-11-01

    The EB-X1 is an accurate X-ray mask writer with high-throughput that was developed by modifying one of our EB60 variable-shaped E-beam systems. For high resolution, we developed an electron optical system whose 50-nm beam edge sharpness, a 15 A/cm2 beam current density, and 1.0-micrometers X 0.5-micrometers maximum beam size with an acceleration voltage under 30 keV were determined by proximity-effect Monte Carlo simulation. We adopt a three-pronged approach for accurate pattern placement. First, we improve the beam positioning resolution from 20 nm to 5 nm. Because we suppress mechanical vibration, we can attain a 11-nm standard mark detection accuracy, resulting in a 20-nm compensation accuracy in the beam deflection distortion and a 25-nm field stitching accuracy. Second, our new column with its short beam-path and demagnification image of variable-shaped beam optics can attain a beam position stability within 30 nm over two hours. Finally, the use of an electrostatic chuck to firmly hold the mask-substrate with little holding- deformation and large heat transmission reduces mask-substrate deformation to 23 nm during pattern writing. Experiments confirm the EB-X1 can write a 0.2-micrometers minimum-feature sized pattern, has a pattern placement accuracy of 50 nm (3 (sigma) ) and a high throughput approximately ten times higher than that of a conventional point-beam exposure system. Using optimized correction coefficients for a specific layer, an average pattern placement accuracy of 33 nm (3 (sigma) ) can be achieved. The EB-X1 is now being used in the X-ray mask fabrication process line at NTT LSI Laboratories.

  8. Shape, size and multiplicity of main-belt asteroids. I. Keck Adaptive Optics survey

    NASA Astrophysics Data System (ADS)

    Marchis, F.; Kaasalainen, M.; Hom, E. F. Y.; Berthier, J.; Enriquez, J.; Hestroffer, D.; Le Mignant, D.; de Pater, I.

    2006-11-01

    This paper presents results from a high spatial resolution survey of 33 main-belt asteroids with diameters >40 km using the Keck II Adaptive Optics (AO) facility. Five of these (45 Eugenia, 87 Sylvia, 107 Camilla, 121 Hermione, 130 Elektra) were confirmed to have satellite. Assuming the same albedo as the primary, these moonlets are relatively small (˜5% of the primary size) suggesting that they are fragments captured after a disruptive collision of a parent body or captured ejecta due to an impact. For each asteroid, we have estimated the minimum size of a moonlet that can positively detected within the Hill sphere of the system by estimating and modeling a 2- σ detection profile: in average on the data set, a moonlet located at 2/100×R ( 1/4×R) with a diameter larger than 6 km (4 km) would have been unambiguously seen. The apparent size and shape of each asteroid was estimated after deconvolution using a new algorithm called AIDA. The mean diameter for the majority of asteroids is in good agreement with IRAS radiometric measurements, though for asteroids with a D<200 km, it is underestimated on average by 6-8%. Most asteroids had a size ratio that was very close to those determined by lightcurve measurements. One observation of 104 Klymene suggests it has a bifurcated shape. The bi-lobed shape of 121 Hermione described in Marchis et al. [Marchis, F., Hestroffer, D., Descamps, P., Berthier, J., Laver, C., de Pater, I., 2005c. Icarus 178, 450-464] was confirmed after deconvolution. The ratio of contact binaries in our survey, which is limited to asteroids larger than 40 km, is surprisingly high (˜6%), suggesting that a non-single configuration is common in the main-belt. Several asteroids have been analyzed with lightcurve inversions. We compared lightcurve inversion models for plane-of-sky predictions with the observed images (9 Metis, 52 Europa, 87 Sylvia, 130 Elektra, 192 Nausikaa, and 423 Diotima, 511 Davida). The AO images allowed us to determine a unique

  9. Shape, size and multiplicity of main-belt asteroids I. Keck Adaptive Optics survey

    PubMed Central

    Marchis, F.; Kaasalainen, M.; Hom, E.F.Y.; Berthier, J.; Enriquez, J.; Hestroffer, D.; Le Mignant, D.; de Pater, I.

    2008-01-01

    This paper presents results from a high spatial resolution survey of 33 main-belt asteroids with diameters >40 km using the Keck II Adaptive Optics (AO) facility. Five of these (45 Eugenia, 87 Sylvia, 107 Camilla, 121 Hermione, 130 Elektra) were confirmed to have satellite. Assuming the same albedo as the primary, these moonlets are relatively small (∼5% of the primary size) suggesting that they are fragments captured after a disruptive collision of a parent body or captured ejecta due to an impact. For each asteroid, we have estimated the minimum size of a moonlet that can positively detected within the Hill sphere of the system by estimating and modeling a 2-σ detection profile: in average on the data set, a moonlet located at 2/100 × RHill (1/4 × RHill) with a diameter larger than 6 km (4 km) would have been unambiguously seen. The apparent size and shape of each asteroid was estimated after deconvolution using a new algorithm called AIDA. The mean diameter for the majority of asteroids is in good agreement with IRAS radiometric measurements, though for asteroids with a D < 200 km, it is underestimated on average by 6–8%. Most asteroids had a size ratio that was very close to those determined by lightcurve measurements. One observation of 104 Klymene suggests it has a bifurcated shape. The bi-lobed shape of 121 Hermione described in Marchis et al. [Marchis, F., Hestroffer, D., Descamps, P., Berthier, J., Laver, C., de Pater, I., 2005c. Icarus 178, 450–464] was confirmed after deconvolution. The ratio of contact binaries in our survey, which is limited to asteroids larger than 40 km, is surprisingly high (∼6%), suggesting that a non-single configuration is common in the main-belt. Several asteroids have been analyzed with lightcurve inversions. We compared lightcurve inversion models for plane-of-sky predictions with the observed images (9 Metis, 52 Europa, 87 Sylvia, 130 Elektra, 192 Nausikaa, and 423 Diotima, 511 Davida). The AO images allowed us to

  10. Adapted fan-beam volume reconstruction for stationary digital breast tomosynthesis

    NASA Astrophysics Data System (ADS)

    Wu, Gongting; Inscoe, Christine; Calliste, Jabari; Lee, Yueh Z.; Zhou, Otto; Lu, Jianping

    2015-03-01

    Digital breast tomosynthesis (DBT) provides 3D images which remove tissue overlapping and enables better cancer detection. Stationary DBT (s-DBT) uses a fixed X-ray source array to eliminate image blur associated with the x-ray tube motion and provides better image quality as well as faster scanning speed. For limited angle tomography, it is known that iterative reconstructions generally produces better images with fewer artifacts. However classical iterative tomosynthesis reconstruction methods are considerably slower than the filtered back-projection (FBP) reconstruction. The linear x-ray source array used in s-DBT enables a computationally more efficient volume reconstruction using adapted fan beam slice sampling, which transforms the 3-D cone beam reconstruction to a series of 2-D fan beam slice reconstructions. In this paper, we report the first results of the adapted fan-beam volume reconstruction (AFVR) for the s-DBT system currently undergoing clinical trial at UNC, using a simultaneous algebraic reconstruction technique (SART). An analytic breast phantom is used to quantitatively analyze the performance of the AFVR. Image quality of a CIRS biopsy phantom reconstructed using the AFVR method are compared to that using FBP algorithm with a commercial package. Our results show a significant reduction in memory usage and an order of magnitude speed increase in reconstructing speed using AFVR compared to that of classical 3-D cone beam reconstruction. We also observed that images reconstructed by AFVR with SART had a better sharpness and contrast compared to that using FBP. Preliminary results on patient images demonstrates the improved detectability of the s-DBT system over the mammography. By utilizing parallel computing with graphics processing unit (GPU), it is expected that the AFVR method will enable iterative reconstruction technique to be practical for clinical applications.

  11. In-beam PET imaging for on-line adaptive proton therapy: an initial phantom study

    NASA Astrophysics Data System (ADS)

    Shao, Yiping; Sun, Xishan; Lou, Kai; Zhu, Xiaorong R.; Mirkovic, Dragon; Poenisch, Falk; Grosshans, David

    2014-07-01

    We developed and investigated a positron emission tomography (PET) system for use with on-line (both in-beam and intra-fraction) image-guided adaptive proton therapy applications. The PET has dual rotating depth-of-interaction measurable detector panels by using solid-state photomultiplier (SSPM) arrays and LYSO scintillators. It has a 44 mm diameter trans-axial and 30 mm axial field-of-view (FOV). A 38 mm diameter polymethyl methacrylate phantom was placed inside the FOV. Both PET and phantom axes were aligned with a collimated 179.2 MeV beam. Each beam delivered ˜50 spills (0.5 s spill and 1.5 s inter-spill time, 3.8 Gy at Bragg peak). Data from each beam were acquired with detectors at a given angle. Nine datasets for nine beams with detectors at nine different angles over 180° were acquired for full-tomographic imaging. Each dataset included data both during and 5 min after irradiations. The positron activity-range was measured from the PET image reconstructed from all nine datasets and compared to the results from simulated images. A 22Na disc-source was also imaged after each beam to monitor the PET system's performance. PET performed well except for slight shifts of energy photo-peak positions (<1%) after each beam, due mainly to the neutron exposure of SSPM that increased the dark-count noise. This minor effect was corrected offline with a shifting 350-650 keV energy window for each dataset. The results show a fast converging of activity-ranges measured by the prototype PET with high sensitivity and uniform resolution. Sub-mm activity-ranges were achieved with minimal 6 s acquisition time and three spill irradiations. These results indicate the feasibility of PET for intra-fraction beam-range verification. Further studies are needed to develop and apply a novel clinical PET system for on-line image-guided adaptive proton therapy.

  12. Modeling of astigmatic-elliptical beam shaping during fs-laser waveguide writing including beam truncation and diffraction effects

    NASA Astrophysics Data System (ADS)

    Ruiz De la Cruz, A.; Ferrer, A.; del Hoyo, J.; Siegel, J.; Solis, J.

    2011-08-01

    In this work, we report a model for accurately calculating the focal volumes corresponding to astigmatic elliptical beams used in fs-laser waveguide writing. The model is based on the use of the ABCD matrix formalism for the propagation of a Gaussian beam. The code includes the effects of propagation on the astigmatic elliptical beam, and the effects of beam truncation and diffraction at the entrance pupil of the focusing objective due to beam clipping when overfilling the pupil. The results predict that for a given astigmatism value and propagation distance it is possible to efficiently suppress the astigmatic focus closer to the surface. This explains previous experimental results where single structure waveguides with controllable aspect-ratio were fabricated using astigmatic-elliptical beams. Furthermore, we investigate the respective roles of astigmatism and beam propagation, as well as the strong impact of truncation and diffraction effects caused by clipping the beam at the pupil of the focusing optics. Finally, based on the results from our model, we present some practical considerations in terms of beam propagation and phase wrapping constraints.

  13. Population diversity and adaptive evolution in keratinization genes: impact of environment in shaping skin phenotypes.

    PubMed

    Gautam, Pramod; Chaurasia, Amit; Bhattacharya, Aniket; Grover, Ritika; Mukerji, Mitali; Natarajan, Vivek T

    2015-03-01

    Several studies have demonstrated the role of climatic factors in shaping skin phenotypes, particularly pigmentation. Keratinization is another well-designed feature of human skin, which is involved in modulating transepidermal water loss (TEWL). Although this physiological process is closely linked to climate, presently it is not clear whether genetic diversity is observed in keratinization and whether this process also responds to the environmental pressure. To address this, we adopted a multipronged approach, which involved analysis of 1) copy number variations in diverse Indian and HapMap populations from varied geographical regions; 2) genetic association with geoclimatic parameters in 61 populations of dbCLINE database in a set of 549 genes from four processes namely keratinization, pigmentation, epidermal differentiation, and housekeeping functions; 3) sequence divergence in 4,316 orthologous promoters and corresponding exonic regions of human and chimpanzee with macaque as outgroup, and 4) protein sequence divergence (Ka/Ks) across nine vertebrate classes, which differ in their extent of TEWL. Our analyses demonstrate that keratinization and epidermal differentiation genes are under accelerated evolution in the human lineage, relative to pigmentation and housekeeping genes. We show that this entire pathway may have been driven by environmental selection pressure through concordant functional polymorphisms across several genes involved in skin keratinization. Remarkably, this underappreciated function of skin may be a crucial determinant of adaptation to diverse environmental pressures across world populations. PMID:25534032

  14. Object-adapted trapping and shape-tracking to probe a bacterial protein chain motor

    NASA Astrophysics Data System (ADS)

    Roth, Julian; Koch, Matthias; Rohrbach, Alexander

    2015-03-01

    The helical bacterium Spiroplasma is a motile plant and anthropod pathogen which swims by propagating pairs of kinks along its cell body. As a well suited model system for bacterial locomotion, understanding the cell's molecular motor is of vital interest also regarding the combat of bacterial diseases. The extensive deformations related to these kinks are caused by a contractile cytoskeletal protein ribbon representing a linear motor in contrast to common rotary motors as, e.g., flagella. We present new insights into the working of this motor through experiments with object-adapted optical traps and shape-tracking techniques. We use the given laser irradiation from the optical trap to hinder bacterial energy (ATP) production through the production of O2 radicals. The results are compared with experiments performed under the influence of an O2-Scavenger and ATP inhibitors, respectively. Our results show clear dependences of the kinking properties on the ATP concentration inside the bacterium. The experiments are supported by a theoretical model which we developed to describe the switching of the ribbon's protein subunits.

  15. Propagation, beam geometry, and detection distortions of peak shapes in two-dimensional Fourier transform spectra.

    PubMed

    Yetzbacher, Michael K; Belabas, Nadia; Kitney, Katherine A; Jonas, David M

    2007-01-28

    Using a solution of Maxwell's equations in the three-dimensional frequency domain, femtosecond two-dimensional Fourier transform (2DFT) spectra that include distortions due to phase matching, absorption, dispersion, and noncollinear excitation and detection of the signal are calculated for Bloch, Kubo, and Brownian oscillator relaxation models. For sample solutions longer than a wavelength, the resonant propagation distortions are larger than resonant local field distortions by a factor of approximately L/lambda, where L is the sample thickness and lambda is the optical wavelength. For the square boxcars geometry, the phase-matching distortion is usually least important, and depends on the dimensionless parameter, L sin(2)(beta)Deltaomega/(nc), where beta is the half angle between beams, n is the refractive index, c is the speed of light, and Deltaomega is the width of the spectrum. Directional filtering distortions depend on the dimensionless parameter, [(Deltaomega)w(0) sin(beta)/c](2), where w(0) is the beam waist at the focus. Qualitatively, the directional filter discriminates against off diagonal amplitude. Resonant absorption and dispersion can distort 2D spectra by 10% (20%) at a peak optical density of 0.1 (0.2). Complicated distortions of the 2DFT peak shape due to absorption and dispersion can be corrected to within 10% (15%) by simple operations that require knowledge only of the linear optical properties of the sample and the distorted two-dimensional spectrum measured at a peak optical density of up to 0.5 (1). PMID:17286491

  16. Propagation, beam geometry, and detection distortions of peak shapes in two-dimensional Fourier transform spectra

    NASA Astrophysics Data System (ADS)

    Yetzbacher, Michael K.; Belabas, Nadia; Kitney, Katherine A.; Jonas, David M.

    2007-01-01

    Using a solution of Maxwell's equations in the three-dimensional frequency domain, femtosecond two-dimensional Fourier transform (2DFT) spectra that include distortions due to phase matching, absorption, dispersion, and noncollinear excitation and detection of the signal are calculated for Bloch, Kubo, and Brownian oscillator relaxation models. For sample solutions longer than a wavelength, the resonant propagation distortions are larger than resonant local field distortions by a factor of ˜L/λ, where L is the sample thickness and λ is the optical wavelength. For the square boxcars geometry, the phase-matching distortion is usually least important, and depends on the dimensionless parameter, Lsin2(β )Δω/(nc), where β is the half angle between beams, n is the refractive index, c is the speed of light, and Δω is the width of the spectrum. Directional filtering distortions depend on the dimensionless parameter, [(Δω )w0sin(β)/c]2, where w0 is the beam waist at the focus. Qualitatively, the directional filter discriminates against off diagonal amplitude. Resonant absorption and dispersion can distort 2D spectra by 10% (20%) at a peak optical density of 0.1 (0.2). Complicated distortions of the 2DFT peak shape due to absorption and dispersion can be corrected to within 10% (15%) by simple operations that require knowledge only of the linear optical properties of the sample and the distorted two-dimensional spectrum measured at a peak optical density of up to 0.5 (1).

  17. Preliminary results of a prototype C-shaped PET designed for an in-beam PET system

    NASA Astrophysics Data System (ADS)

    Kim, Hyun-Il; Chung, Yong Hyun; Lee, Kisung; Kim, Kyeong Min; Kim, Yongkwon; Joung, Jinhun

    2016-06-01

    Positron emission tomography (PET) can be utilized in particle beam therapy to verify the dose distribution of the target volume as well as the accuracy of the treatment. We present an in-beam PET scanner that can be integrated into a particle beam therapy system. The proposed PET scanner consisted of 14 detector modules arranged in a C-shape to avoid blockage of the particle beam line by the detector modules. Each detector module was composed of a 9×9 array of 4.0 mm×4.0 mm×20.0 mm LYSO crystals optically coupled to four 29-mm-diameter PMTs using the photomultiplier-quadrant-sharing (PQS) technique. In this study, a Geant4 Application for Tomographic Emission (GATE) simulation study was conducted to design a C-shaped PET scanner and then experimental evaluation of the proposed design was performed. The spatial resolution and sensitivity were measured according to NEMA NU2-2007 standards and were 6.1 mm and 5.61 cps/kBq, respectively, which is in good agreement with our simulation, with an error rate of 12.0%. Taken together, our results demonstrate the feasibility of the proposed C-shaped in-beam PET system, which we expect will be useful for measuring dose distribution in particle therapy.

  18. Passive damping and exact annihilation of vibrations of beams using shaped piezoelectric layers and tuned inductive networks

    NASA Astrophysics Data System (ADS)

    Schoeftner, J.; Irschik, H.

    2009-12-01

    The present paper is devoted to the development of an extended Bernoulli-Euler beam theory for passive piezoelectric composite structures which takes into account the presence of electric networks. The theory considers electromechanical coupling between the beam deformation and the electric circuit due to the piezoelectric effect that relates mechanical properties like displacement, strain and stress to electrical properties like electric field, voltage and current. Thereby, kinematic relations within the Bernoulli-Euler theory, a one-dimensional form of the constitutive relations for piezoelastic structures and a linear electric network, are presumed. Eventually, an adjusted one-dimensional formulation of a beam theory is obtained. It is shown that this formulation can be used for both power harvesting and passive shunt damping applications. Within the presented theory it is possible to analyse the influence of geometrical dimensions, piezoelectric constants and impedances of electric networks on the displacement field and on the energy flow between the mechanical and electrical parts. The second part of the paper is devoted to the concept of shape control and its application to passive damping and exact annihilation of vibrations of beams using shaped piezoelectric layers and tuned inductive networks. As a main result of the present paper, it is shown that, under certain conditions, concerning the shape of the piezoelastic material and the impedances of the electric circuits, exact annihilation of vibrations for a cantilever beam is possible.

  19. Sub-second pencil beam dose calculation on GPU for adaptive proton therapy

    NASA Astrophysics Data System (ADS)

    da Silva, Joakim; Ansorge, Richard; Jena, Rajesh

    2015-06-01

    Although proton therapy delivered using scanned pencil beams has the potential to produce better dose conformity than conventional radiotherapy, the created dose distributions are more sensitive to anatomical changes and patient motion. Therefore, the introduction of adaptive treatment techniques where the dose can be monitored as it is being delivered is highly desirable. We present a GPU-based dose calculation engine relying on the widely used pencil beam algorithm, developed for on-line dose calculation. The calculation engine was implemented from scratch, with each step of the algorithm parallelized and adapted to run efficiently on the GPU architecture. To ensure fast calculation, it employs several application-specific modifications and simplifications, and a fast scatter-based implementation of the computationally expensive kernel superposition step. The calculation time for a skull base treatment plan using two beam directions was 0.22 s on an Nvidia Tesla K40 GPU, whereas a test case of a cubic target in water from the literature took 0.14 s to calculate. The accuracy of the patient dose distributions was assessed by calculating the γ-index with respect to a gold standard Monte Carlo simulation. The passing rates were 99.2% and 96.7%, respectively, for the 3%/3 mm and 2%/2 mm criteria, matching those produced by a clinical treatment planning system.

  20. Beam width and transmitter power adaptive to tracking system performance for free-space optical communication.

    PubMed

    Arnon, S; Rotman, S; Kopeika, N S

    1997-08-20

    The basic free-space optical communication system includes at least two satellites. To communicate between them, the transmitter satellite must track the beacon of the receiver satellite and point the information optical beam in its direction. Optical tracking and pointing systems for free space suffer during tracking from high-amplitude vibration because of background radiation from interstellar objects such as the Sun, Moon, Earth, and stars in the tracking field of view or the mechanical impact from satellite internal and external sources. The vibrations of beam pointing increase the bit error rate and jam communication between the two satellites. One way to overcome this problem is to increase the satellite receiver beacon power. However, this solution requires increased power consumption and weight, both of which are disadvantageous in satellite development. Considering these facts, we derive a mathematical model of a communication system that adapts optimally the transmitter beam width and the transmitted power to the tracking system performance. Based on this model, we investigate the performance of a communication system with discrete element optical phased array transmitter telescope gain. An example for a practical communication system between a Low Earth Orbit Satellite and a Geostationary Earth Orbit Satellite is presented. From the results of this research it can be seen that a four-element adaptive transmitter telescope is sufficient to compensate for vibration amplitude doubling. The benefits of the proposed model are less required transmitter power and improved communication system performance. PMID:18259455

  1. Sub-second pencil beam dose calculation on GPU for adaptive proton therapy.

    PubMed

    da Silva, Joakim; Ansorge, Richard; Jena, Rajesh

    2015-06-21

    Although proton therapy delivered using scanned pencil beams has the potential to produce better dose conformity than conventional radiotherapy, the created dose distributions are more sensitive to anatomical changes and patient motion. Therefore, the introduction of adaptive treatment techniques where the dose can be monitored as it is being delivered is highly desirable. We present a GPU-based dose calculation engine relying on the widely used pencil beam algorithm, developed for on-line dose calculation. The calculation engine was implemented from scratch, with each step of the algorithm parallelized and adapted to run efficiently on the GPU architecture. To ensure fast calculation, it employs several application-specific modifications and simplifications, and a fast scatter-based implementation of the computationally expensive kernel superposition step. The calculation time for a skull base treatment plan using two beam directions was 0.22 s on an Nvidia Tesla K40 GPU, whereas a test case of a cubic target in water from the literature took 0.14 s to calculate. The accuracy of the patient dose distributions was assessed by calculating the γ-index with respect to a gold standard Monte Carlo simulation. The passing rates were 99.2% and 96.7%, respectively, for the 3%/3 mm and 2%/2 mm criteria, matching those produced by a clinical treatment planning system. PMID:26040956

  2. Development and analysis of elastically tailored composite star shaped beam sections

    NASA Astrophysics Data System (ADS)

    Kim, Inn B.

    Elastically tailored composite materials provide an extra degree of freedom to meet design requirements efficiently and economically. In particular, extension-twist coupled laminates have potential for use in rotary wing aircraft where an increase in centrifugal load can result in a sectional change in pitch angle of the rotor blades. Consequently, the propulsive efficiency could be improved by utilizing this concept in tilt rotor aircraft application. To this end, a family of new open cross-sectional configuration is developed and analyzed to tailor the torsional and bending rigidities compared to those of flat strips without a loss in the level of extension-twist coupling. In addition, the developed configurations are modified by incorporating closed-cell cores with variable diameters and wall thickness to further tailor the torsional stiffness more effectively. A closed form analytical model for the configuration without a core is obtained based on an extension of the analytical model of flat strips and compared with the finite element analysis. Several star shaped composite beams are manufactured using a custom designed mold. The manufactured beams are tested and used as an experimental verification of analytical model predictions as well as finite element results. It is found that analytical predictions, finite element analysis and experimental results are in good agreement. Similarly, a set of modified star configurations that incorporate closed-cell cores is analyzed. The configurations are prismatic and of variable diameter and wall thickness leading to tailorable torsional stiffness and large extension-twist coupling with constant axial stiffness. A parametric study is performed using a linear as well as a geometrically nonlinear finite element codes. Several composite modified star beam configurations are manufactured and tested to provide an experimental verification of the finite element predictions. The comparison of test results and finite element

  3. Analytical and finite-element study of optimal strain distribution in various beam shapes for energy harvesting applications

    NASA Astrophysics Data System (ADS)

    Ooi, B. L.; Gilbert, J. M.; Aziz, A. Rashid A.

    2016-05-01

    Owing to the increasing demand for harvesting energy from environmental vibration for use in self-powered electronic applications, cantilever-based vibration energy harvesting has attracted considerable interest from various parties and has become one of the most common approaches to converting redundant mechanical energy into electrical energy. As the output voltage produced from a piezoelectric material depends largely on the geometric shape and the size of the beam, there is a need to model and compare the performance of cantilever beams of differing geometries. This paper presents the study of strain distribution in various shapes of cantilever beams, including a convex and concave edge profile elliptical beam that have not yet been discussed in any prior literature. Both analytical and finite-element models are derived and the resultant strain distributions in the beam are computed based on a MATLAB solver and ANSYS finite-element analysis tools. An optimum geometry for a vibration-based energy harvesting system is verified. Finally, experimental results comparing the power density for triangular and rectangular piezoelectric beams are also presented to validate the findings of the study, and the claim, as suggested in the literature, is verified.

  4. Analytical and finite-element study of optimal strain distribution in various beam shapes for energy harvesting applications

    NASA Astrophysics Data System (ADS)

    Ooi, B. L.; Gilbert, J. M.; Aziz, A. Rashid A.

    2016-08-01

    Owing to the increasing demand for harvesting energy from environmental vibration for use in self-powered electronic applications, cantilever-based vibration energy harvesting has attracted considerable interest from various parties and has become one of the most common approaches to converting redundant mechanical energy into electrical energy. As the output voltage produced from a piezoelectric material depends largely on the geometric shape and the size of the beam, there is a need to model and compare the performance of cantilever beams of differing geometries. This paper presents the study of strain distribution in various shapes of cantilever beams, including a convex and concave edge profile elliptical beam that have not yet been discussed in any prior literature. Both analytical and finite-element models are derived and the resultant strain distributions in the beam are computed based on a MATLAB solver and ANSYS finite-element analysis tools. An optimum geometry for a vibration-based energy harvesting system is verified. Finally, experimental results comparing the power density for triangular and rectangular piezoelectric beams are also presented to validate the findings of the study, and the claim, as suggested in the literature, is verified.

  5. Simulation of electrostatic turbulence in the plasma sheet boundary layer with electron currents and bean-shaped ion beams

    NASA Technical Reports Server (NTRS)

    Nishikawa, K.-I.; Frank, L. A.; Huang, C. Y.

    1988-01-01

    Plasma data from ISEE-1 show the presence of electron currents as well as energetic ion beams in the plasma sheet boundary layer. Broadband electrostatic noise and low-frequency electromagnetic bursts are detected in the plasma sheet boundary layer, especially in the presence of strong ion flows, currents, and steep spacial gradients in the fluxes of few-keV electrons and ions. Particle simulations have been performed to investigate electrostatic turbulence driven by a cold electron beam and/or ion beams with a bean-shaped velocity distribution. The simulation results show that the counterstreaming ion beams as well as the counterstreaming of the cold electron beam and the ion beam excite ion acoustic waves with a given Doppler-shifted real frequency. However, the effect of the bean-shaped ion velocity distributions reduces the growth rates of ion acoustic instability. The simulation results also show that the slowing down of the ion bean is larger at the larger perpendicular velocity. The wave spectra of the electric fields at some points of the simulations show turbulence generated by growing waves.

  6. Fabrication and evaluation results of a micro elliptical collimator lens for a beam shape form of laser diode

    NASA Astrophysics Data System (ADS)

    Okada, K.; Oohira, F.; Hosogi, M.; Hashiguchi, G.; Mihara, Y.; Ogawa, K.

    2005-12-01

    This paper describes a new fabrication process of a micro elliptical collimator lens to form a beam shape for LD(Laser Diode), and the evaluation results of the optical characteristic for this lens. Beam shape of LD is an ellipse because divergent light angle is different between horizontal and vertical direction, which increases a coupling loss with an optical fiber. In this presentation, we propose the lens to form the divergent light of an elliptical beam shape to the collimated light of a circular beam shape. This lens makes it possible to reduce the coupling loss with the optical fiber. For this purpose, we designed one lens, which has different curvature radiuses between incident and output surfaces. In the incident surface, the divergent light is formed to the convergent light, and in the output surface, the convergent light is formed to the collimated light. We simulated the optical characteristic of this lens, and designed for various parameters. In order to fabricate this lens, we propose a new process using a chemically absorbed monomolecular layer, which has an excellent hydrophobic property. This layer is patterned and deposited by a photolithographic technique. Next, we drop a UV(Ultra Violet) cure material on the hydrophilic area, as the result, we can fabricate a micro elliptical lens shape. The curvature radius of this lens can be controlled by the amount of a dropped UV cure material and an elliptical pattern size in horizontal and vertical direction. The formed lens shapes are transferred by the electro-plating and then the micro dies are fabricated. And they are used for molding the plastic lens.

  7. The adaptation of megavoltage cone beam CT for use in standard radiotherapy treatment planning

    NASA Astrophysics Data System (ADS)

    Thomas, T. Hannah Mary; Devakumar, D.; Purnima, S.; Ravindran, B. Paul

    2009-04-01

    Potential areas where megavoltage computed tomography (MVCT) could be used are second- and third-phase treatment planning in 3D conformal radiotherapy and IMRT, adaptive radiation therapy, single fraction palliative treatment and for the treatment of patients with metal prostheses. A feasibility study was done on using MV cone beam CT (CBCT) images generated by proprietary 3D reconstruction software based on the FDK algorithm for megavoltage treatment planning. The reconstructed images were converted to a DICOM file set. The pixel values of megavoltage cone beam computed tomography (MV CBCT) were rescaled to those of kV CT for use with a treatment planning system. A calibration phantom was designed and developed for verification of geometric accuracy and CT number calibration. The distance measured between two marker points on the CBCT image and the physical dimension on the phantom were in good agreement. Point dose verification for a 10 cm × 10 cm beam at a gantry angle of 0° and SAD of 100 cm were performed for a 6 MV beam for both kV and MV CBCT images. The point doses were found to vary between ±6.1% of the dose calculated from the kV CT image. The isodose curves for 6 MV for both kV CT and MV CBCT images were within 2% and 3 mm distance-to-agreement. A plan with three beams was performed on MV CBCT, simulating a treatment plan for cancer of the pituitary. The distribution obtained was compared with those corresponding to that obtained using the kV CT. This study has shown that treatment planning with MV cone beam CT images is feasible.

  8. The adaptation of megavoltage cone beam CT for use in standard radiotherapy treatment planning.

    PubMed

    Thomas, T Hannah Mary; Devakumar, D; Purnima, S; Ravindran, B Paul

    2009-04-01

    Potential areas where megavoltage computed tomography (MVCT) could be used are second- and third-phase treatment planning in 3D conformal radiotherapy and IMRT, adaptive radiation therapy, single fraction palliative treatment and for the treatment of patients with metal prostheses. A feasibility study was done on using MV cone beam CT (CBCT) images generated by proprietary 3D reconstruction software based on the FDK algorithm for megavoltage treatment planning. The reconstructed images were converted to a DICOM file set. The pixel values of megavoltage cone beam computed tomography (MV CBCT) were rescaled to those of kV CT for use with a treatment planning system. A calibration phantom was designed and developed for verification of geometric accuracy and CT number calibration. The distance measured between two marker points on the CBCT image and the physical dimension on the phantom were in good agreement. Point dose verification for a 10 cm x 10 cm beam at a gantry angle of 0 degrees and SAD of 100 cm were performed for a 6 MV beam for both kV and MV CBCT images. The point doses were found to vary between +/-6.1% of the dose calculated from the kV CT image. The isodose curves for 6 MV for both kV CT and MV CBCT images were within 2% and 3 mm distance-to-agreement. A plan with three beams was performed on MV CBCT, simulating a treatment plan for cancer of the pituitary. The distribution obtained was compared with those corresponding to that obtained using the kV CT. This study has shown that treatment planning with MV cone beam CT images is feasible. PMID:19287087

  9. Measuring contact angle and meniscus shape with a reflected laser beam

    NASA Astrophysics Data System (ADS)

    Eibach, T. F.; Fell, D.; Nguyen, H.; Butt, H. J.; Auernhammer, G. K.

    2014-01-01

    Side-view imaging of the contact angle between an extended planar solid surface and a liquid is problematic. Even when aligning the view perfectly parallel to the contact line, focusing one point of the contact line is not possible. We describe a new measurement technique for determining contact angles with the reflection of a widened laser sheet on a moving contact line. We verified this new technique measuring the contact angle on a cylinder, rotating partially immersed in a liquid. A laser sheet is inclined under an angle φ to the unperturbed liquid surface and is reflected off the meniscus. Collected on a screen, the reflection image contains information to determine the contact angle. When dividing the laser sheet into an array of laser rays by placing a mesh into the beam path, the shape of the meniscus can be reconstructed from the reflection image. We verified the method by measuring the receding contact angle versus speed for aqueous cetyltrimethyl ammonium bromide solutions on a smooth hydrophobized as well as on a rough polystyrene surface.

  10. Microstructural and micromechanical characterization of IN718 theta shaped specimens built with electron beam melting

    DOE PAGESBeta

    Cakmak, Ercan; Kirka, Michael M.; Watkins, Thomas R.; Cooper, Ryan C.; An, Ke; Choo, Hahn; Wu, Wei; Dehoff, Ryan R.; Babu, Sudarsanam S.

    2016-02-23

    Theta-shaped specimens were additively manufactured out of Inconel 718 powders using an electron beam melting technique, as a model complex load bearing structure. We employed two different build strategies; producing two sets of specimens. Microstructural and micro-mechanical characterizations were performed using electron back-scatter, synchrotron x-ray and in-situ neutron diffraction techniques. In particular, the cross-members of the specimens were the focus of the synchrotron x-ray and in-situ neutron diffraction measurements. The build strategies employed resulted in the formation of distinct microstructures and crystallographic textures, signifying the importance of build-parameter manipulation for microstructural optimization. Large strain anisotropy of the different lattice planesmore » was observed during in-situ loading. Texture was concluded to have a distinct effect upon both the axial and transverse strain responses of the cross-members. In particular, the (200), (220) and (420) transverse lattice strains all showed unexpected overlapping trends in both builds. This was related to the strong {200} textures along the build/loading direction, providing agreement between the experimental and calculated results.« less

  11. Measuring contact angle and meniscus shape with a reflected laser beam

    SciTech Connect

    Eibach, T. F.; Nguyen, H.; Butt, H. J.; Auernhammer, G. K.; Fell, D.

    2014-01-15

    Side-view imaging of the contact angle between an extended planar solid surface and a liquid is problematic. Even when aligning the view perfectly parallel to the contact line, focusing one point of the contact line is not possible. We describe a new measurement technique for determining contact angles with the reflection of a widened laser sheet on a moving contact line. We verified this new technique measuring the contact angle on a cylinder, rotating partially immersed in a liquid. A laser sheet is inclined under an angle φ to the unperturbed liquid surface and is reflected off the meniscus. Collected on a screen, the reflection image contains information to determine the contact angle. When dividing the laser sheet into an array of laser rays by placing a mesh into the beam path, the shape of the meniscus can be reconstructed from the reflection image. We verified the method by measuring the receding contact angle versus speed for aqueous cetyltrimethyl ammonium bromide solutions on a smooth hydrophobized as well as on a rough polystyrene surface.

  12. A disturbance observer-based adaptive control approach for flexure beam nano manipulators.

    PubMed

    Zhang, Yangming; Yan, Peng; Zhang, Zhen

    2016-01-01

    This paper presents a systematic modeling and control methodology for a two-dimensional flexure beam-based servo stage supporting micro/nano manipulations. Compared with conventional mechatronic systems, such systems have major control challenges including cross-axis coupling, dynamical uncertainties, as well as input saturations, which may have adverse effects on system performance unless effectively eliminated. A novel disturbance observer-based adaptive backstepping-like control approach is developed for high precision servo manipulation purposes, which effectively accommodates model uncertainties and coupling dynamics. An auxiliary system is also introduced, on top of the proposed control scheme, to compensate the input saturations. The proposed control architecture is deployed on a customized-designed nano manipulating system featured with a flexure beam structure and voice coil actuators (VCA). Real time experiments on various manipulating tasks, such as trajectory/contour tracking, demonstrate precision errors of less than 1%. PMID:26546099

  13. Hard real-time beam scheduler enables adaptive images in multi-probe systems

    NASA Astrophysics Data System (ADS)

    Tobias, Richard J.

    2014-03-01

    Real-time embedded-system concepts were adapted to allow an imaging system to responsively control the firing of multiple probes. Large-volume, operator-independent (LVOI) imaging would increase the diagnostic utility of ultrasound. An obstacle to this innovation is the inability of current systems to drive multiple transducers dynamically. Commercial systems schedule scanning with static lists of beams to be fired and processed; here we allow an imager to adapt to changing beam schedule demands, as an intelligent response to incoming image data. An example of scheduling changes is demonstrated with a flexible duplex mode two-transducer application mimicking LVOI imaging. Embedded-system concepts allow an imager to responsively control the firing of multiple probes. Operating systems use powerful dynamic scheduling algorithms, such as fixed priority preemptive scheduling. Even real-time operating systems lack the timing constraints required for ultrasound. Particularly for Doppler modes, events must be scheduled with sub-nanosecond precision, and acquired data is useless without this requirement. A successful scheduler needs unique characteristics. To get close to what would be needed in LVOI imaging, we show two transducers scanning different parts of a subjects leg. When one transducer notices flow in a region where their scans overlap, the system reschedules the other transducer to start flow mode and alter its beams to get a view of the observed vessel and produce a flow measurement. The second transducer does this in a focused region only. This demonstrates key attributes of a successful LVOI system, such as robustness against obstructions and adaptive self-correction.

  14. 0.25-μm lithography using a 50-kV shaped electron-beam vector scan system

    NASA Astrophysics Data System (ADS)

    Gesley, Mark A.; Mulera, Terry; Nurmi, C.; Radley, J.; Sagle, Allan L.; Standiford, Keith P.; Tan, Zoilo C. H.; Thomas, John R.; Veneklasen, Lee

    1995-05-01

    Performance data from a prototype 50 kV shaped electron-beam (e-beam) pattern generator is presented. This technology development is targeted towards 180-130 nm device design rules. It will be able to handle 1X NIST X-ray membranes, glass reduction reticles, and 4- to 8-inch wafers. The prototype system uses a planar stage adapted from the IBM EL-4 design. The electron optics is an 50 kV extension of the AEBLE%+TM) design. Lines and spaces of 0.12 micrometers with < 40 nm corner radius are resolved in 0.4 micrometers thick resist at 50 kV. This evolutionary platform will evolve further to include a new 100 kV column with telecentric deflection and a 21-bit (0.5 mm) major field for improved placement accuracy. A unique immersion shaper, faster data path electronics, and 15-bit (32 micrometers ) minor field deflection electronics will substantially increase the flash rate. To match its much finer address structure, the pattern generator figure word size will increase from 80 to 96 bits. The data path electronics uses field programmable gate array (FPGA) logic allowing writing strategy optimization via software reconfiguration. An advanced stage position control (ASPC) includes three-axis, (lambda) /1024 interferometry and a high bandwidth dynamic corrections processor (DCP). Along with its normal role of coordinate transformation and dynamic correction of deflection distortion, astigmatism, and defocus; the DCP improves accuracy by modifying deflection conditions and focus according to measured substrate height variations. It also enables yaw calibration and correction for Write-on-the FlyTM motion. The electronics incorporates JTAG components for built-in self- test (BIST), as well as syndrome checking to ensure data integrity. The design includes diagnostic capabilities from offsite as well as from the operator console. A combination of third-party software and an internal job preparation software system is used to fracture patterns. It handles tone reversal

  15. Experimental and Simulated Characterization of a Beam Shaping Assembly for Accelerator- Based Boron Neutron Capture Therapy (AB-BNCT)

    NASA Astrophysics Data System (ADS)

    Burlon, Alejandro A.; Girola, Santiago; Valda, Alejandro A.; Minsky, Daniel M.; Kreiner, Andrés J.

    2010-08-01

    In the frame of the construction of a Tandem Electrostatic Quadrupole Accelerator facility devoted to the Accelerator-Based Boron Neutron Capture Therapy, a Beam Shaping Assembly has been characterized by means of Monte-Carlo simulations and measurements. The neutrons were generated via the 7Li(p, n)7Be reaction by irradiating a thick LiF target with a 2.3 MeV proton beam delivered by the TANDAR accelerator at CNEA. The emerging neutron flux was measured by means of activation foils while the beam quality and directionality was evaluated by means of Monte Carlo simulations. The parameters show compliance with those suggested by IAEA. Finally, an improvement adding a beam collimator has been evaluated.

  16. Experimental and Simulated Characterization of a Beam Shaping Assembly for Accelerator- Based Boron Neutron Capture Therapy (AB-BNCT)

    SciTech Connect

    Burlon, Alejandro A.; Valda, Alejandro A.; Girola, Santiago; Minsky, Daniel M.; Kreiner, Andres J.

    2010-08-04

    In the frame of the construction of a Tandem Electrostatic Quadrupole Accelerator facility devoted to the Accelerator-Based Boron Neutron Capture Therapy, a Beam Shaping Assembly has been characterized by means of Monte-Carlo simulations and measurements. The neutrons were generated via the {sup 7}Li(p, n){sup 7}Be reaction by irradiating a thick LiF target with a 2.3 MeV proton beam delivered by the TANDAR accelerator at CNEA. The emerging neutron flux was measured by means of activation foils while the beam quality and directionality was evaluated by means of Monte Carlo simulations. The parameters show compliance with those suggested by IAEA. Finally, an improvement adding a beam collimator has been evaluated.

  17. Adaptive planning using megavoltage fan-beam CT for radiation therapy with testicular shielding

    SciTech Connect

    Yadav, Poonam; Kozak, Kevin; Tolakanahalli, Ranjini; Ramasubramanian, V.; Paliwal, Bhudatt R.; Welsh, James S.; Rong, Yi

    2012-07-01

    This study highlights the use of adaptive planning to accommodate testicular shielding in helical tomotherapy for malignancies of the proximal thigh. Two cases of young men with large soft tissue sarcomas of the proximal thigh are presented. After multidisciplinary evaluation, preoperative radiation therapy was recommended. Both patients were referred for sperm banking and lead shields were used to minimize testicular dose during radiation therapy. To minimize imaging artifacts, kilovoltage CT (kVCT) treatment planning was conducted without shielding. Generous hypothetical contours were generated on each 'planning scan' to estimate the location of the lead shield and generate a directionally blocked helical tomotherapy plan. To ensure the accuracy of each plan, megavoltage fan-beam CT (MVCT) scans were obtained at the first treatment and adaptive planning was performed to account for lead shield placement. Two important regions of interest in these cases were femurs and femoral heads. During adaptive planning for the first patient, it was observed that the virtual lead shield contour on kVCT planning images was significantly larger than the actual lead shield used for treatment. However, for the second patient, it was noted that the size of the virtual lead shield contoured on the kVCT image was significantly smaller than the actual shield size. Thus, new adaptive plans based on MVCT images were generated and used for treatment. The planning target volume was underdosed up to 2% and had higher maximum doses without adaptive planning. In conclusion, the treatment of the upper thigh, particularly in young men, presents several clinical challenges, including preservation of gonadal function. In such circumstances, adaptive planning using MVCT can ensure accurate dose delivery even in the presence of high-density testicular shields.

  18. Optimum design and criticality safety of a beam-shaping assembly with an accelerator-driven subcritical neutron multiplier for boron neutron capture therapies.

    PubMed

    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

  19. SU-E-T-295: Simultaneous Beam Sampling and Aperture Shape Optimization for Station Parameter Optimized Radiation Therapy (SPORT)

    SciTech Connect

    Zarepisheh, M; Li, R; Xing, L; Ye, Y; Boyd, S

    2014-06-01

    Purpose: Station Parameter Optimized Radiation Therapy (SPORT) was recently proposed to fully utilize the technical capability of emerging digital LINACs, in which the station parameters of a delivery system, (such as aperture shape and weight, couch position/angle, gantry/collimator angle) are optimized altogether. SPORT promises to deliver unprecedented radiation dose distributions efficiently, yet there does not exist any optimization algorithm to implement it. The purpose of this work is to propose an optimization algorithm to simultaneously optimize the beam sampling and aperture shapes. Methods: We build a mathematical model whose variables are beam angles (including non-coplanar and/or even nonisocentric beams) and aperture shapes. To solve the resulting large scale optimization problem, we devise an exact, convergent and fast optimization algorithm by integrating three advanced optimization techniques named column generation, gradient method, and pattern search. Column generation is used to find a good set of aperture shapes as an initial solution by adding apertures sequentially. Then we apply the gradient method to iteratively improve the current solution by reshaping the aperture shapes and updating the beam angles toward the gradient. Algorithm continues by pattern search method to explore the part of the search space that cannot be reached by the gradient method. Results: The proposed technique is applied to a series of patient cases and significantly improves the plan quality. In a head-and-neck case, for example, the left parotid gland mean-dose, brainstem max-dose, spinal cord max-dose, and mandible mean-dose are reduced by 10%, 7%, 24% and 12% respectively, compared to the conventional VMAT plan while maintaining the same PTV coverage. Conclusion: Combined use of column generation, gradient search and pattern search algorithms provide an effective way to optimize simultaneously the large collection of station parameters and significantly improves

  20. The potential for optical beam shaping of UV laser sources for mass scale quarantine disinfection applications

    NASA Astrophysics Data System (ADS)

    Lizotte, Todd

    2010-08-01

    disinfection systems using high intensity UV laser sources instead of UV bulb techniques by using laser beam shaping optics in conjunction with traditional optical laser beam delivery techniques.

  1. Polyhedral shape model for terrain correction of gravity and gravity gradient data based on an adaptive mesh

    NASA Astrophysics Data System (ADS)

    Guo, Zhikui; Chen, Chao; Tao, Chunhui

    2016-04-01

    Since 2007, there are four China Da yang cruises (CDCs), which have been carried out to investigate polymetallic sulfides in the southwest Indian ridge (SWIR) and have acquired both gravity data and bathymetry data on the corresponding survey lines(Tao et al., 2014). Sandwell et al. (2014) published a new global marine gravity model including the free air gravity data and its first order vertical gradient (Vzz). Gravity data and its gradient can be used to extract unknown density structure information(e.g. crust thickness) under surface of the earth, but they contain all the mass effect under the observation point. Therefore, how to get accurate gravity and its gradient effect of the existing density structure (e.g. terrain) has been a key issue. Using the bathymetry data or ETOPO1 (http://www.ngdc.noaa.gov/mgg/global/global.html) model at a full resolution to calculate the terrain effect could spend too much computation time. We expect to develop an effective method that takes less time but can still yield the desired accuracy. In this study, a constant-density polyhedral model is used to calculate the gravity field and its vertical gradient, which is based on the work of Tsoulis (2012). According to gravity field attenuation with distance and variance of bathymetry, we present an adaptive mesh refinement and coarsening strategies to merge both global topography data and multi-beam bathymetry data. The local coarsening or size of mesh depends on user-defined accuracy and terrain variation (Davis et al., 2011). To depict terrain better, triangular surface element and rectangular surface element are used in fine and coarse mesh respectively. This strategy can also be applied to spherical coordinate in large region and global scale. Finally, we applied this method to calculate Bouguer gravity anomaly (BGA), mantle Bouguer anomaly(MBA) and their vertical gradient in SWIR. Further, we compared the result with previous results in the literature. Both synthetic model

  2. High-efficiency high-power diode laser beam shaping and focusing with constant optical-path length equalization

    NASA Astrophysics Data System (ADS)

    Bonora, Stefano; Villoresi, Paolo

    2006-04-01

    In this work we report on a novel optical design for beam shaping and focalization of high-power diode laser bars. The goals of our study are: the increase the optical throughput of the beam shaping device with respect to standard solutions and either to enhance the irradiance on a target or to inject the laser beam into a smaller fibre than with respect to beam shaping system based on plane surfaces. The high power diode laser bars pose serious difficulties in their optical handling due to their strong difference between the two transverse axes, which induce a strong astigmatic and asymmetric output radiation. As is well known, the beam quality is very different in the two axes called slow axis and fast axis, and in particular the slow axis is composed by the superposition of several multimodal sources. The beam quality in this axis is very low (its etendue may exceed 2000 mm mrad). On the other hand, the fast axis has a very high beam quality, near diffraction limited, although with very high divergence (30°-50°). The common solution for the application of the laser radiation is a fast axis aspheric micro lens in front of the emitters, in order to achieve its collimation. Typical values of the fast axis collimated beam are 0.7mm and less than 6mrad. However, the so obtained collimated beam is poorly focusable with a standard lens, and a few methods were proposed to overcome the problem. The more relevant solutions include: the stepped mirror technique, the plane parallel mirrors pair, micro prisms array and confocal micro lens array. Each of these techniques is based on the equalization of the beam parameter product by the subdivision of the beam in the slow axis and its reshaping. For all these techniques the efficiency spans from 50% to 70%. The best focalization results allow the coupling in a fibre of 400μm diameter, with NA-0.22. The aim of this work is the design and the realization of a new device, that is considered as target the following aspects: 1

  3. Adaptive beamlet-based finite-size pencil beam dose calculation for independent verification of IMRT and VMAT

    SciTech Connect

    Park, Justin C.; Li, Jonathan G.; Arhjoul, Lahcen; Yan, Guanghua; Lu, Bo; Fan, Qiyong; Liu, Chihray

    2015-04-15

    Purpose: The use of sophisticated dose calculation procedure in modern radiation therapy treatment planning is inevitable in order to account for complex treatment fields created by multileaf collimators (MLCs). As a consequence, independent volumetric dose verification is time consuming, which affects the efficiency of clinical workflow. In this study, the authors present an efficient adaptive beamlet-based finite-size pencil beam (AB-FSPB) dose calculation algorithm that minimizes the computational procedure while preserving the accuracy. Methods: The computational time of finite-size pencil beam (FSPB) algorithm is proportional to the number of infinitesimal and identical beamlets that constitute an arbitrary field shape. In AB-FSPB, dose distribution from each beamlet is mathematically modeled such that the sizes of beamlets to represent an arbitrary field shape no longer need to be infinitesimal nor identical. As a result, it is possible to represent an arbitrary field shape with combinations of different sized and minimal number of beamlets. In addition, the authors included the model parameters to consider MLC for its rounded edge and transmission. Results: Root mean square error (RMSE) between treatment planning system and conventional FSPB on a 10 × 10 cm{sup 2} square field using 10 × 10, 2.5 × 2.5, and 0.5 × 0.5 cm{sup 2} beamlet sizes were 4.90%, 3.19%, and 2.87%, respectively, compared with RMSE of 1.10%, 1.11%, and 1.14% for AB-FSPB. This finding holds true for a larger square field size of 25 × 25 cm{sup 2}, where RMSE for 25 × 25, 2.5 × 2.5, and 0.5 × 0.5 cm{sup 2} beamlet sizes were 5.41%, 4.76%, and 3.54% in FSPB, respectively, compared with RMSE of 0.86%, 0.83%, and 0.88% for AB-FSPB. It was found that AB-FSPB could successfully account for the MLC transmissions without major discrepancy. The algorithm was also graphical processing unit (GPU) compatible to maximize its computational speed. For an intensity modulated radiation therapy (

  4. Adaptive optics system for fast automatic control of laser beam jitters in air

    NASA Astrophysics Data System (ADS)

    Grasso, Salvatore; Acernese, Fausto; Romano, Rocco; Barone, Fabrizio

    2010-04-01

    Adaptive Optics (AO) Systems can operate fast automatic control of laser beam jitters for several applications of basic research as well as for the improvement of industrial and medical devices. We here present our theoretical and experimental research showing the opportunity of suppressing laser beam geometrical fluctuations of higher order Hermite Gauss modes in interferometric Gravitational Waves (GW) antennas. This in turn allows to significantly reduce the noise that originates from the coupling of the laser source oscillations with the interferometer asymmetries and introduces the concrete possibility of overcoming the sensitivity limit of the GW antennas actually set at 10-23 1 Hz value. We have carried out the feasibility study of a novel AO System which performs effective laser jitters suppression in the 200 Hz bandwidth. It extracts the wavefront error signals in terms of Hermite Gauss (HG) coefficients and performs the wavefront correction using the Zernike polynomials. An experimental Prototype of the AO System has been implemented and tested in our laboratory at the University of Salerno and the results we have achieved fully confirm effectiveness and robustness of the control upon first and second order laser beam geometrical fluctuations, in good accordance with GW antennas requirements. Above all, we have measured 60 dB reduction of astigmatism and defocus modes at low frequency below 1 Hz and 20 dB reduction in the 200 Hz bandwidth.

  5. Factors shaping the adaptive landscape for arboviruses: implications for the emergence of disease

    PubMed Central

    Coffey, Lark L; Forrester, Naomi; Tsetsarkin, Konstantin; Vasilakis, Nikos; Weaver, Scott C

    2013-01-01

    Many examples of the emergence or re-emergence of infectious diseases involve the adaptation of zoonotic viruses to new amplification hosts or to humans themselves. These include several instances of simple mutational adaptations, often to hosts closely related to the natural reservoirs. However, based on theoretical grounds, arthropod-borne viruses, or arboviruses, may face several challenges for adaptation to new hosts. Here, we review recent findings regarding adaptive evolution of arboviruses and its impact on disease emergence. We focus on the zoonotic alphaviruses Venezuelan equine encephalitis and chikungunya viruses, which have undergone adaptive evolution that mediated recent outbreaks of disease, as well as the flaviviruses dengue and West Nile viruses, which have emerged via less dramatic adaptive mechanisms. PMID:23374123

  6. Two-photon excitation in scattering media by spatiotemporally shaped beams and their application in optogenetic stimulation

    PubMed Central

    Bègue, Aurélien; Papagiakoumou, Eirini; Leshem, Ben; Conti, Rossella; Enke, Leona; Oron, Dan; Emiliani, Valentina

    2013-01-01

    The use of wavefront shaping to generate extended optical excitation patterns which are confined to a predetermined volume has become commonplace on various microscopy applications. For multiphoton excitation, three-dimensional confinement can be achieved by combining the technique of temporal focusing of ultra-short pulses with different approaches for lateral light shaping, including computer generated holography or generalized phase contrast. Here we present a theoretical and experimental study on the effect of scattering on the propagation of holographic beams with and without temporal focusing. Results from fixed and acute cortical slices show that temporally focused spatial patterns are extremely robust against the effects of scattering and this permits their three-dimensionally confined excitation for depths more than 500 µm. Finally we prove the efficiency of using temporally focused holographic beams in two-photon stimulation of neurons expressing the red-shifted optogenetic channel C1V1. PMID:24409387

  7. FK506 binding protein 51 integrates pathways of adaptation: FKBP51 shapes the reactivity to environmental change.

    PubMed

    Rein, Theo

    2016-09-01

    This review portraits FK506 binding protein (FKBP) 51 as "reactivity protein" and collates recent publications to develop the concept of FKBP51 as contributor to different levels of adaptation. Adaptation is a fundamental process that enables unicellular and multicellular organisms to adjust their molecular circuits and structural conditions in reaction to environmental changes threatening their homeostasis. FKBP51 is known as chaperone and co-chaperone of heat shock protein (HSP) 90, thus involved in processes ensuring correct protein folding in response to proteotoxic stress. In mammals, FKBP51 both shapes the stress response and is calibrated by the stress levels through an ultrashort molecular feedback loop. More recently, it has been linked to several intracellular pathways related to the reactivity to drug exposure and stress. Through its role in autophagy and DNA methylation in particular it influences adaptive pathways, possibly also in a transgenerational fashion. Also see the video abstract here. PMID:27374865

  8. Modular optical design for flexible beam shaping of a top-hat profile

    NASA Astrophysics Data System (ADS)

    Möhl, A.; Wickenhagen, S.; Fuchs, U.

    2015-09-01

    For practical application of refractive laser beam shapers it is of major interest to know the desired manufacturing specifications to fabricate the particular elements so that an appropriate quality of the top-hat beam profile can be achieved. In the scope of this paper two different systems consisting of aspheric lenses are described, which efficiently transform a collimated Gaussian beam to a collimated top-hat beam. Both systems are of the Galilean telescope type. The design principles are discussed and the as-built performance is analyzed and compared quantitatively with the theoretical design. For this different criteria to evaluate the quality of the top-hat beam profile are defined. Additionally, the effects of deviations from the actual optical design conditions such as wavelength, input beam profile and working distance are considered for the as-built system. Consequently, valuable statements on the manufacturing requirements of the aspheric lenses can be made.

  9. Inquiry in Interaction: How Local Adaptations of Curricula Shape Classroom Communities

    ERIC Educational Resources Information Center

    Enyedy, Noel; Goldberg, Jennifer

    2004-01-01

    In this study, we seek a better understanding of how individuals and their daily interactions shape and reshape social structures that constitute a classroom community. Moreover, we provide insight into how discourse and classroom interactions shape the nature of a learning community, as well as which aspects of the classroom culture may be…

  10. Multiple beam interference lithography: A tool for rapid fabrication of plasmonic arrays of arbitrary shaped nanomotifs.

    PubMed

    Vala, M; Homola, J

    2016-07-11

    A novel method enabling rapid fabrication of 2D periodic arrays of plasmonic nanoparticles across large areas is presented. This method is based on the interference of multiple coherent beams originating from diffraction of large-diameter collimated beam on a transmission phase mask. Mutual orientation of the interfering beams is determined by parameters of the used phase mask. Herein, parameters of the phase mask (periods and modulation depth) are selected to yield an interference pattern with high contrast and narrow well-separated maxima. Finally, multiple beam interference lithography (MBIL)-based fabrication of periodic plasmonic arrays with selected nanomotifs including discs, disc dimers, rods and bowtie antennas is demonstrated. PMID:27410838

  11. SU-E-J-135: Feasibility of Using Quantitative Cone Beam CT for Proton Adaptive Planning

    SciTech Connect

    Jingqian, W; Wang, Q; Zhang, X; Wen, Z; Zhu, X; Frank, S; Li, H; Tsui, T; Zhu, L; Wei, J

    2015-06-15

    Purpose: To investigate the feasibility of using scatter corrected cone beam CT (CBCT) for proton adaptive planning. Methods: Phantom study was used to evaluate the CT number difference between the planning CT (pCT), quantitative CBCT (qCBCT) with scatter correction and calibrated Hounsfield units using adaptive scatter kernel superposition (ASKS) technique, and raw CBCT (rCBCT). After confirming the CT number accuracy, prostate patients, each with a pCT and several sets of weekly CBCT, were investigated for this study. Spot scanning proton treatment plans were independently generated on pCT, qCBCT and rCBCT. The treatment plans were then recalculated on all images. Dose-volume-histogram (DVH) parameters and gamma analysis were used to compare between dose distributions. Results: Phantom study suggested that Hounsfield unit accuracy for different materials are within 20 HU for qCBCT and over 250 HU for rCBCT. For prostate patients, proton dose could be calculated accurately on qCBCT but not on rCBCT. When the original plan was recalculated on qCBCT, tumor coverage was maintained when anatomy was consistent with pCT. However, large dose variance was observed when patient anatomy change. Adaptive plan using qCBCT was able to recover tumor coverage and reduce dose to normal tissue. Conclusion: It is feasible to use qu antitative CBCT (qCBCT) with scatter correction and calibrated Hounsfield units for proton dose calculation and adaptive planning in proton therapy. Partly supported by Varian Medical Systems.

  12. Adaptive frequency comb illumination for interferometry in the case of nested two-beam cavities

    SciTech Connect

    Harder, Irina; Leuchs, Gerd; Mantel, Klaus; Schwider, Johannes

    2011-09-01

    The homogeneity test of glass plates in a Fizeau interferometer is hampered by the superposition of multiple interference signals coming from the surfaces of the glass plate as well as the empty Fizeau cavity. To evaluate interferograms resulting from such nested cavities, various approaches such as the use of broadband light sources have been applied. In this paper, we propose an adaptive frequency comb interferometer to accomplish the cavity selection. An adjustable Fabry-Perot resonator is used to generate a variable frequency comb that can be matched to the length of the desired cavity. Owing to its flexibility, the number of measurements needed for the homogeneity test can be reduced to four. Furthermore, compared to approaches using a two-beam interferometer as a filter for the broadband light source, the visibility of the fringe system is considerably higher if a Fabry-Perot filter is applied.

  13. Evolution of opercle shape in cichlid fishes from Lake Tanganyika - adaptive trait interactions in extant and extinct species flocks

    PubMed Central

    Wilson, Laura A. B.; Colombo, Marco; Sánchez-Villagra, Marcelo R.; Salzburger, Walter

    2015-01-01

    Phenotype-environment correlations and the evolution of trait interactions in adaptive radiations have been widely studied to gain insight into the dynamics underpinning rapid species diversification. In this study we explore the phenotype-environment correlation and evolution of operculum shape in cichlid fishes using an outline-based geometric morphometric approach combined with stable isotope indicators of macrohabitat and trophic niche. We then apply our method to a sample of extinct saurichthyid fishes, a highly diverse and near globally distributed group of actinopterygians occurring throughout the Triassic, to assess the utility of extant data to inform our understanding of ecomorphological evolution in extinct species flocks. A series of comparative methods were used to analyze shape data for 54 extant species of cichlids (N = 416), and 6 extinct species of saurichthyids (N = 44). Results provide evidence for a relationship between operculum shape and feeding ecology, a concentration in shape evolution towards present along with evidence for convergence in form, and significant correlation between the major axes of shape change and measures of gut length and body elongation. The operculum is one of few features that can be compared in extant and extinct groups, enabling reconstruction of phenotype-environment interactions and modes of evolutionary diversification in deep time. PMID:26584885

  14. Evolution of opercle shape in cichlid fishes from Lake Tanganyika - adaptive trait interactions in extant and extinct species flocks.

    PubMed

    Wilson, Laura A B; Colombo, Marco; Sánchez-Villagra, Marcelo R; Salzburger, Walter

    2015-01-01

    Phenotype-environment correlations and the evolution of trait interactions in adaptive radiations have been widely studied to gain insight into the dynamics underpinning rapid species diversification. In this study we explore the phenotype-environment correlation and evolution of operculum shape in cichlid fishes using an outline-based geometric morphometric approach combined with stable isotope indicators of macrohabitat and trophic niche. We then apply our method to a sample of extinct saurichthyid fishes, a highly diverse and near globally distributed group of actinopterygians occurring throughout the Triassic, to assess the utility of extant data to inform our understanding of ecomorphological evolution in extinct species flocks. A series of comparative methods were used to analyze shape data for 54 extant species of cichlids (N = 416), and 6 extinct species of saurichthyids (N = 44). Results provide evidence for a relationship between operculum shape and feeding ecology, a concentration in shape evolution towards present along with evidence for convergence in form, and significant correlation between the major axes of shape change and measures of gut length and body elongation. The operculum is one of few features that can be compared in extant and extinct groups, enabling reconstruction of phenotype-environment interactions and modes of evolutionary diversification in deep time. PMID:26584885

  15. Tailoring the laser pulse shape to improve the quality of the self-injected electron beam in laser wakefield acceleration

    SciTech Connect

    Upadhyay, Ajay K.; Samant, Sushil A.; Krishnagopal, S.

    2013-01-15

    In laser wakefield acceleration, tailoring the shape of the laser pulse is one way of influencing the laser-plasma interaction and, therefore, of improving the quality of the self-injected electron beam in the bubble regime. Using three-dimensional particle-in-cell simulations, the evolution dynamics of the laser pulse and the quality of the self-injected beam, for a Gaussian pulse, a positive skew pulse (i.e., one with sharp rise and slow fall), and a negative skew pulse (i.e., one with a slow rise and sharp fall) are studied. It is observed that with a negative skew laser pulse there is a substantial improvement in the emittance (by around a factor of two), and a modest improvement in the energy-spread, compared to Gaussian as well as positive skew pulses. However, the injected charge is less in the negative skew pulse compared to the other two. It is also found that there is an optimal propagation distance that gives the best beam quality; beyond this distance, though the energy increases, the beam quality deteriorates, but this deterioration is least for the negative skew pulse. Thus, the negative skew pulse gives an improvement in terms of beam quality (emittance and energy spread) over what one can get with a Gaussian or positive skew pulse. In part, this is because of the lesser injected charge, and the strong suppression of continuous injection for the negative skew pulse.

  16. TU-C-17A-07: FusionARC Treatment with Adaptive Beam Selection Method

    SciTech Connect

    Kim, H; Li, R; Xing, L; Lee, R

    2014-06-15

    Purpose: Recently, a new treatment scheme, FusionARC, has been introduced to compensate for the pitfalls in single-arc VMAT planning. It basically allows for the static field treatment in selected locations, while the remaining is treated by single-rotational arc delivery. The important issue is how to choose the directions for static field treatment. This study presents an adaptive beam selection method to formulate fusionARC treatment scheme. Methods: The optimal plan for single-rotational arc treatment is obtained from two-step approach based on the reweighted total-variation (TV) minimization. To choose the directions for static field treatment with extra segments, a value of our proposed cost function at each field is computed on the new fluence-map, which adds an extra segment to the designated field location only. The cost function is defined as a summation of equivalent uniform dose (EUD) of all structures with the fluence-map, while assuming that the lower cost function value implies the enhancement of plan quality. Finally, the extra segments for static field treatment would be added to the selected directions with low cost function values. A prostate patient data was applied and evaluated with three different plans: conventional VMAT, fusionARC, and static IMRT. Results: The 7 field locations, corresponding to the lowest cost function values, are chosen to insert extra segment for step-and-shoot dose delivery. Our proposed fusionARC plan with the selected angles improves the dose sparing to the critical organs, relative to static IMRT and conventional VMAT plans. The dose conformity to the target is significantly enhanced at the small expense of treatment time, compared with VMAT plan. Its estimated treatment time, however, is still much faster than IMRT. Conclusion: The fusionARC treatment with adaptive beam selection method could improve the plan quality with insignificant damage in the treatment time, relative to the conventional VMAT.

  17. Evaluation of mounting bolt loads for Space Shuttle Get Away Special (GAS) adapter beam

    NASA Technical Reports Server (NTRS)

    Talapatra, D. C.

    1983-01-01

    During the prototype vibration tests of the GAS adapter beam, significant impacting of the beam at its support points was observed. The cause of the impacting was traced to gaps under the mounting bolt heads. Because of the nonlinear nature of the response, it was difficult to evaluate the effects which Shuttle launch dynamics might have on the mounting bolt loads. A series of tests were conducted on an electrodynamic exciter in which the transient acceleration time histories, which had been measured during the Space Transportation System-1 (STS-1; Space Shuttle mission 1) launch, were simulated. The actual flight data had to be filtered and compensated so that it could be reproduced on the shaker without exceeding displacement and velocity limitations. Mounting bolt loads were measured directly by strain gages applied to the bolts. Various gap thicknesses and bolt torques were investigated. Although increased gap thickness resulted in greater accelerations due to impacting, the bolt loads were not significantly affected. This is attributed to the fact that impacting excited mostly higher frequency modes which do not have significant modal mass.

  18. Design optimization of a smooth headlamp reflector to SAE/DOT beam-shape requirements

    NASA Astrophysics Data System (ADS)

    Shatz, Narkis E.; Bortz, John C.; Dassanayake, Mahendra S.

    1999-10-01

    The optical design of Ford Motor Company's 1992 Mercury Grand Marquis headlamp utilized a Sylvania 9007 filament source, a paraboloidal reflector and an array of cylindrical lenses (flutes). It has been of interest to Ford to determine the practicality of closely reproducing the on- road beam pattern performance of this headlamp, with an alternate optical arrangement whereby the control of the beam would be achieved solely by means of the geometry of the surface of the reflector, subject to a requirement of smooth-surface continuity; replacing the outer lens with a clear plastic cover having no beam-forming function. To this end the far-field intensity distribution produced by the 9007 bulb was measured at the low-beam setting. These measurements were then used to develop a light-source model for use in ray tracing simulations of candidate reflector geometries. An objective function was developed to compare candidate beam patterns with the desired beam pattern. Functional forms for the 3D reflector geometry were developed with free parameters to be subsequently optimized. A solution was sought meeting the detailed US SAE/DOT constraints for minimum and maximum permissible levels of illumination in the different portions of the beam pattern. Simulated road scenes were generated by Ford Motor Company to compare the illumination properties of the new design with those of the original Grand Marquis headlamp.

  19. Segmented adaptive optic mirrors for laser power beaming and other space applications

    SciTech Connect

    Bennett, H.E.

    1996-12-31

    In order to effectively beam laser power into space to power satellites or to remove space debris in mid or high earth orbit very large mirrors (perhaps 12 m in diameter or more) and an adaptive optic system to penetrate the atmosphere are required. Mirrors with adaptive optic segment sizes less than the equivalent Fried coefficient for atmospheric turbulence (typically 3 - 5 cm at zenith in the visible region of the spectrum) are optimum for atmospheric penetration. These new mirrors may have hundreds of thousands of segments. The behavior of such mirrors under high powered laser irradiation is not clear, although for a large mirror both average and peak irradiation levels will be very low. Attention must be paid to penetration of laser energy into the gaps between segments and to the cumulative effect of edge diffraction. These problems do not appear to be severe and this new class of optics appears to offer new possibilities for use in space. It may change the way in which one looks at telescopes for space applications.

  20. Three-dimensional anisotropic adaptive filtering of projection data for noise reduction in cone beam CT

    PubMed Central

    Maier, Andreas; Wigström, Lars; Hofmann, Hannes G.; Hornegger, Joachim; Zhu, Lei; Strobel, Norbert; Fahrig, Rebecca

    2011-01-01

    .9-fold speed-up of the processing (from 1336 to 150 s). Conclusions: Adaptive anisotropic filtering has the potential to substantially improve image quality and∕or reduce the radiation dose required for obtaining 3D image data using cone beam CT. PMID:22047354

  1. Three-dimensional anisotropic adaptive filtering of projection data for noise reduction in cone beam CT

    SciTech Connect

    Maier, Andreas; Wigstroem, Lars; Hofmann, Hannes G.; Hornegger, Joachim; Zhu Lei; Strobel, Norbert; Fahrig, Rebecca

    2011-11-15

    speed-up of the processing (from 1336 to 150 s). Conclusions: Adaptive anisotropic filtering has the potential to substantially improve image quality and/or reduce the radiation dose required for obtaining 3D image data using cone beam CT.

  2. Molecular Specificity, Convergence and Constraint Shape Adaptive Evolution in Nutrient-Poor Environments

    PubMed Central

    Hong, Jungeui; Gresham, David

    2014-01-01

    One of the central goals of evolutionary biology is to explain and predict the molecular basis of adaptive evolution. We studied the evolution of genetic networks in Saccharomyces cerevisiae (budding yeast) populations propagated for more than 200 generations in different nitrogen-limiting conditions. We find that rapid adaptive evolution in nitrogen-poor environments is dominated by the de novo generation and selection of copy number variants (CNVs), a large fraction of which contain genes encoding specific nitrogen transporters including PUT4, DUR3 and DAL4. The large fitness increases associated with these alleles limits the genetic heterogeneity of adapting populations even in environments with multiple nitrogen sources. Complete identification of acquired point mutations, in individual lineages and entire populations, identified heterogeneity at the level of genetic loci but common themes at the level of functional modules, including genes controlling phosphatidylinositol-3-phosphate metabolism and vacuole biogenesis. Adaptive strategies shared with other nutrient-limited environments point to selection of genetic variation in the TORC1 and Ras/PKA signaling pathways as a general mechanism underlying improved growth in nutrient-limited environments. Within a single population we observed the repeated independent selection of a multi-locus genotype, comprised of the functionally related genes GAT1, MEP2 and LST4. By studying the fitness of individual alleles, and their combination, as well as the evolutionary history of the evolving population, we find that the order in which these mutations are acquired is constrained by epistasis. The identification of repeatedly selected variation at functionally related loci that interact epistatically suggests that gene network polymorphisms (GNPs) may be a frequent outcome of adaptive evolution. Our results provide insight into the mechanistic basis by which cells adapt to nutrient-limited environments and suggest that

  3. Large deflection angle, high-power adaptive fiber optics collimator with preserved near-diffraction-limited beam quality.

    PubMed

    Zhi, Dong; Ma, Yanxing; Chen, Zilun; Wang, Xiaolin; Zhou, Pu; Si, Lei

    2016-05-15

    We report on the development of a monolithic adaptive fiber optics collimator, with a large deflection angle and preserved near-diffraction-limited beam quality, that has been tested at a maximal output power at the 300 W level. Additionally, a new measurement method of beam quality (M2 factor) is developed. Experimental results show that the deflection angle of the collimated beam is in the range of 0-0.27 mrad in the X direction and 0-0.19 mrad in the Y direction. The effective working frequency of the device is about 710 Hz. By employing the new measurement method of the M2 factor, we calculate that the beam quality is Mx2=1.35 and My2=1.24, which is in agreement with the result from the beam propagation analyzer and is preserved well with the increasing output power. PMID:27176966

  4. Cone Beam Computed Tomography-Derived Adaptive Radiotherapy for Radical Treatment of Esophageal Cancer

    SciTech Connect

    Hawkins, Maria A.; Brooks, Corrinne; Hansen, Vibeke N.; Aitken, Alexandra; Tait, Diana M.

    2010-06-01

    Purpose: To investigate the potential for reduction in normal tissue irradiation by creating a patient specific planning target volume (PTV) using cone beam computed tomography (CBCT) imaging acquired in the first week of radiotherapy for patients receiving radical radiotherapy. Methods and materials: Patients receiving radical RT for carcinoma of the esophagus were investigated. The PTV is defined as CTV(tumor, nodes) plus esophagus outlined 3 to 5 cm cranio-caudally and a 1.5-cm circumferential margin is added (clinical plan). Prefraction CBCT are acquired on Days 1 to 4, then weekly. No correction for setup error made. The images are imported into the planning system. The tumor and esophagus for the length of the PTV are contoured on each CBCT and 5 mm margin is added. A composite volume (PTV1) is created using Week 1 composite CBCT volumes. The same process is repeated using CBCT Week 2 to 6 (PTV2). A new plan is created using PTV1 (adaptive plan). The coverage of the 95% isodose of PTV1 is evaluated on PTV2. Dose-volume histograms (DVH) for lungs, heart, and cord for two plans are compared. Results: A total of 139 CBCT for 14 cases were analyzed. For the adaptive plan the coverage of the 95% prescription isodose for PTV1 = 95.6% +- 4% and the PTV2 = 96.8% +- 4.1% (t test, 0.19). Lungs V20 (15.6 Gy vs. 10.2 Gy) and heart mean dose (26.9 Gy vs. 20.7 Gy) were significantly smaller for the adaptive plan. Conclusions: A reduced planning volume can be constructed within the first week of treatment using CBCT. A single plan modification can be performed within the second week of treatment with considerable reduction in organ at risk dose.

  5. Light adaptation alters inner retinal inhibition to shape OFF retinal pathway signaling.

    PubMed

    Mazade, Reece E; Eggers, Erika D

    2016-06-01

    The retina adjusts its signaling gain over a wide range of light levels. A functional result of this is increased visual acuity at brighter luminance levels (light adaptation) due to shifts in the excitatory center-inhibitory surround receptive field parameters of ganglion cells that increases their sensitivity to smaller light stimuli. Recent work supports the idea that changes in ganglion cell spatial sensitivity with background luminance are due in part to inner retinal mechanisms, possibly including modulation of inhibition onto bipolar cells. To determine how the receptive fields of OFF cone bipolar cells may contribute to changes in ganglion cell resolution, the spatial extent and magnitude of inhibitory and excitatory inputs were measured from OFF bipolar cells under dark- and light-adapted conditions. There was no change in the OFF bipolar cell excitatory input with light adaptation; however, the spatial distributions of inhibitory inputs, including both glycinergic and GABAergic sources, became significantly narrower, smaller, and more transient. The magnitude and size of the OFF bipolar cell center-surround receptive fields as well as light-adapted changes in resting membrane potential were incorporated into a spatial model of OFF bipolar cell output to the downstream ganglion cells, which predicted an increase in signal output strength with light adaptation. We show a prominent role for inner retinal spatial signals in modulating the modeled strength of bipolar cell output to potentially play a role in ganglion cell visual sensitivity and acuity. PMID:26912599

  6. Active vibration control of Flexible Joint Manipulator using Input Shaping and Adaptive Parameter Auto Disturbance Rejection Controller

    NASA Astrophysics Data System (ADS)

    Li, W. P.; Luo, B.; Huang, H.

    2016-02-01

    This paper presents a vibration control strategy for a two-link Flexible Joint Manipulator (FJM) with a Hexapod Active Manipulator (HAM). A dynamic model of the multi-body, rigid-flexible system composed of an FJM, a HAM and a spacecraft was built. A hybrid controller was proposed by combining the Input Shaping (IS) technique with an Adaptive-Parameter Auto Disturbance Rejection Controller (APADRC). The controller was used to suppress the vibration caused by external disturbances and input motions. Parameters of the APADRC were adaptively adjusted to ensure the characteristic of the closed loop system to be a given reference system, even if the configuration of the manipulator significantly changes during motion. Because precise parameters of the flexible manipulator are not required in the IS system, the operation of the controller was sufficiently robust to accommodate uncertainties in system parameters. Simulations results verified the effectiveness of the HAM scheme and controller in the vibration suppression of FJM during operation.

  7. A Computational Approach to Model Vascular Adaptation During Chronic Hemodialysis: Shape Optimization as a Substitute for Growth Modeling

    NASA Astrophysics Data System (ADS)

    Mahmoudzadeh Akherat, S. M. Javid; Boghosian, Michael; Cassel, Kevin; Hammes, Mary

    2015-11-01

    End-stage-renal disease patients depend on successful long-term hemodialysis via vascular access, commonly facilitated via a Brachiocephalic Fistula (BCF). The primary cause of BCF failure is Cephalic Arch Stenosis (CAS). It is believed that low Wall Shear Stress (WSS) regions, which occur because of the high flow rates through the natural bend in the cephalic vein, create hemodynamic circumstances that trigger the onset and development of Intimal Hyperplasia (IH) and subsequent CAS. IH is hypothesized to be a natural effort to reshape the vessel, aiming to bring the WSS values back to a physiologically acceptable range. We seek to explore the correlation between regions of low WSS and subsequent IH and CAS in patient-specific geometries. By utilizing a shape optimization framework, a method is proposed to predict cardiovascular adaptation that could potentially be an alternative to vascular growth and remodeling. Based on an objective functional that seeks to alter the vessel shape in such a way as to readjust the WSS to be within the normal physiological range, CFD and shape optimization are then coupled to investigate whether the optimal shape evolution is correlated with actual patient-specific geometries thereafter. Supported by the National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health (R01 DK90769).

  8. Surface-enhanced Raman spectroscopy-active substrates: adapting the shape of plasmonic nanoparticles for different biological applications.

    PubMed

    Vitol, Elina A; Friedman, Gary; Gogotsi, Yury

    2014-04-01

    We discuss the relationship between the shape of plasmonic nanoparticles and the biological surface-enhanced Raman spectroscopy (SERS) applications which they can enable. As a step forward in developing SERS-active substrates adapted to a particular application, we demonstrate that a modification of the widely used protocol for the sodium citrate mediated reduction of chloroauric acid, which is typically employed only for obtaining spherical gold nanoparticles, can yield flat polygonal nanoparticles at room temperature and a decreased amount of the reducing agent. The significant advantage of the described approach is that it allows for synthesis of nanoparticles with different geometries using a well-established synthesis protocol without the need for any additional chemicals or special synthesis apparatus. By contrasting spherical and anisotropically shaped nanoparticles, we demonstrate that multifaceted nanoparticles with sharp edges are better suitable for SERS analysis of low concentration analytes requiring strong SERS enhancement. On the other hand, gold nanoparticles with isotropic shapes, while giving a smaller enhancement, can provide a more reproducible SERS signal. This is important for analytical applications of complex biological systems where large SERS enhancement may not always be required, whereas data reproducibility and minimal false positive rate are imperative. Using a SERS-active substrate comprising isotropically shaped gold nanoparticles, we demonstrate the differences between Gram-negative (E. coli) and Gram-positive (S. aureus) bacteria, attributable to the outer membrane and peptidoglycan layer, with the level of detail which has not been previously reported with optical spectroscopic techniques. PMID:24734732

  9. Wide variety of flower-color and -shape mutants regenerated from leaf cultures irradiated with ion beams

    NASA Astrophysics Data System (ADS)

    Okamura, M.; Yasuno, N.; Ohtsuka, M.; Tanaka, A.; Shikazono, N.; Hase, Y.

    2003-05-01

    The efficiency of ion-beam irradiation combined with tissue culture in obtaining floral mutants was investigated and compared with those of gamma rays and X-rays in carnation. Leaf segments of carnation plants in vitro were irradiated with the 220 MeV carbon ions, and cultured till the shoot regenerated. The carbon ion had the highest effect in reducing the regeneration frequency, and the RBE value with respect to gamma-rays was four. The higher mutation frequency and the wider mutation spectrum were obtained in plants irradiated with the carbon ions than low LET radiations. Three new carnation varieties developed by ion-beam irradiation were applied for the registration of the Japanese Ministry of Agriculture, Forestry and Fisheries. The results indicate that ion beam irradiation could induce wide variety of flower-color and -shape mutants, and that the combined method of ion-beam irradiation with tissue culture is useful to obtain the commercial varieties in a short time.

  10. Susceptibility to a metal under global warming is shaped by thermal adaptation along a latitudinal gradient.

    PubMed

    Dinh Van, Khuong; Janssens, Lizanne; Debecker, Sara; De Jonge, Maarten; Lambret, Philippe; Nilsson-Örtman, Viktor; Bervoets, Lieven; Stoks, Robby

    2013-09-01

    Global warming and contamination represent two major threats to biodiversity that have the potential to interact synergistically. There is the potential for gradual local thermal adaptation and dispersal to higher latitudes to mitigate the susceptibility of organisms to contaminants and global warming at high latitudes. Here, we applied a space-for-time substitution approach to study the thermal dependence of the susceptibility of Ischnura elegans damselfly larvae to zinc in a common garden warming experiment (20 and 24 °C) with replicated populations from three latitudes spanning >1500 km in Europe. We observed a striking latitude-specific effect of temperature on the zinc-induced mortality pattern; local thermal adaptation along the latitudinal gradient made Swedish, but not French, damselfly larvae more susceptible to zinc at 24 °C. Latitude- and temperature-specific differences in zinc susceptibility may be related to the amount of energy available to defend against and repair damage since Swedish larvae showed a much stronger zinc-induced reduction of food intake at 24 °C. The pattern of local thermal adaptation indicates that the predicted temperature increase of 4 °C by 2100 will strongly magnify the impact of a contaminant such as zinc at higher latitudes unless there is thermal evolution and/or migration of lower latitude genotypes. Our results underscore the critical importance of studying the susceptibility to contaminants under realistic warming scenarios taking into account local thermal adaptation across natural temperature gradients. PMID:23640735

  11. Fluidic origami: a plant-inspired adaptive structure with shape morphing and stiffness tuning

    NASA Astrophysics Data System (ADS)

    Li, Suyi; Wang, K. W.

    2015-10-01

    Inspired by the physics behind the rapid plant movements and the rich topologies in origami folding, this research creates a unique class of multi-functional adaptive structure through exploring the innovation of fluidic origami. The idea is to connect multiple Miura folded sheets along their crease lines into a space-filling structure, and fill the tubular cells in-between with working fluids. The pressure and fluid flow in these cells can be strategically controlled much like in plants for nastic movements. The relationship between the internal fluid volume and the overall structure deformation is primarily determined by the kinematics of folding. This relationship can be exploited so that fluidic origami can achieve actuation/morphing by actively changing the internal fluid volume, and stiffness tuning by constraining the fluid volume. In order to characterize the working principles and performance potentials of these two adaptive functions, this research develops an equivalent truss frame model on a fluidic origami unit cell to analyze its fundamental elastic characteristics. Eigen-stiffness analysis based on this model reveals the primary modes of deformation and their relationships with initial folding configurations. Performances of the adaptive functions are correlated to the crease pattern design. In parallel to analytical studies, the feasibility of the morphing and stiffness tuning is also examined experimentally via a 3D printed multi-material prototype demonstrator. The research reported in this paper could lead to the synthesis of adaptive fluidic origami cellular metastructures or metamaterial systems for various engineering applications.

  12. Shaping the Cities of Tomorrow: Integrating Local Urban Adaptation within an Environmental Framework

    NASA Astrophysics Data System (ADS)

    Georgescu, M.

    2014-12-01

    Contemporary methods focused on increasing urban sustainability are largely based on the reduction of greenhouse gas emissions. While these efforts are essential steps forward, continued characterization of urban sustainability solely within a biogeochemical framework, with neglect of the biophysical impact of the built environment, omits regional hydroclimatic forcing of the same order of magnitude as greenhouse gas emissions. Using a suite of continuous, multi-year and multi-member continental scale numerical simulations with the WRF model for the U.S., we examine hydroclimatic impacts for a variety of U.S. urban expansion scenarios (for the year 2100) and urban adaptation futures (cool roofs, green roofs, and a hypothetical hybrid approach integrating biophysical properties of both cool and green roofs), and compare those to experiments utilizing a contemporary urban extent. Widespread adoption of adaptation strategies exhibits regionally and seasonally dependent hydroclimatic impacts. For some regions and seasons, urban-induced warming in excess of 3°C can be completely offset by all adaptation approaches examined. For other regions, widespread adoption of some adaptation approaches leads to significant rainfall decline. Sustainable urban expansion therefore requires an integrated assessment that also incorporates biophysically induced urban impacts, and demands tradeoff assessment of various strategies aimed to ameliorate deleterious consequences of growth (e.g., urban heat island reduction).

  13. Vector fuzzy control iterative algorithm for the design of sub-wavelength diffractive optical elements for beam shaping

    NASA Astrophysics Data System (ADS)

    Lin, Yong; Hu, Jiasheng; Wu, Kenan

    2009-08-01

    The vector fuzzy control iterative algorithm (VFCIA) is proposed for the design of phase-only sub-wavelength diffractive optical elements (SWDOEs) for beam shaping. The vector diffraction model put forward by Mansuripur is applied to relate the field distributions between the SWDOE plane and the output plane. Fuzzy control theory is used to decide the constraint method for each iterative process of the algorithm. We have designed a SWDOE that transforms a circular flat-top beam to a square irradiance pattern. Computer design results show that the SWDOE designed by the VFCIA can produce better results than the vector iterative algorithm (VIA). And the finite difference time-domain method (FDTD), a rigorous electromagnetic analysis technique, is used to analyze the designed SWDOE for further confirming the validity of the proposed method.

  14. High-pressure generation using double stage micro-paired diamond anvils shaped by focused ion beam

    SciTech Connect

    Sakai, Takeshi Ohfuji, Hiroaki; Yagi, Takehiko; Irifune, Tetsuo; Ohishi, Yasuo; Hirao, Naohisa; Suzuki, Yuya; Kuroda, Yasushi; Asakawa, Takayuki; Kanemura, Takashi

    2015-03-15

    Micron-sized diamond anvils with a 3 μm culet were successfully processed using a focused ion beam (FIB) system and the generation of high pressures was confirmed using the double stage diamond anvil cell technique. The difficulty of aligning two second-stage micro-anvils was solved via the paired micro-anvil method. Micro-manufacturing using a FIB system enables us to control anvil shape, process any materials, including nano-polycrystalline diamond and single crystal diamond, and assemble the sample exactly in a very small space between the second-stage anvils. This method is highly reproducible. High pressures over 300 GPa were achieved, and the pressure distribution around the micro-anvil culet was evaluated by using a well-focused synchrotron micro-X-ray beam.

  15. High-pressure generation using double stage micro-paired diamond anvils shaped by focused ion beam

    NASA Astrophysics Data System (ADS)

    Sakai, Takeshi; Yagi, Takehiko; Ohfuji, Hiroaki; Irifune, Tetsuo; Ohishi, Yasuo; Hirao, Naohisa; Suzuki, Yuya; Kuroda, Yasushi; Asakawa, Takayuki; Kanemura, Takashi

    2015-03-01

    Micron-sized diamond anvils with a 3 μm culet were successfully processed using a focused ion beam (FIB) system and the generation of high pressures was confirmed using the double stage diamond anvil cell technique. The difficulty of aligning two second-stage micro-anvils was solved via the paired micro-anvil method. Micro-manufacturing using a FIB system enables us to control anvil shape, process any materials, including nano-polycrystalline diamond and single crystal diamond, and assemble the sample exactly in a very small space between the second-stage anvils. This method is highly reproducible. High pressures over 300 GPa were achieved, and the pressure distribution around the micro-anvil culet was evaluated by using a well-focused synchrotron micro-X-ray beam.

  16. Adaptive Aft Signature Shaping of a Low-Boom Supersonic Aircraft Using Off-Body Pressures

    NASA Technical Reports Server (NTRS)

    Ordaz, Irian; Li, Wu

    2012-01-01

    The design and optimization of a low-boom supersonic aircraft using the state-of-the- art o -body aerodynamics and sonic boom analysis has long been a challenging problem. The focus of this paper is to demonstrate an e ective geometry parameterization scheme and a numerical optimization approach for the aft shaping of a low-boom supersonic aircraft using o -body pressure calculations. A gradient-based numerical optimization algorithm that models the objective and constraints as response surface equations is used to drive the aft ground signature toward a ramp shape. The design objective is the minimization of the variation between the ground signature and the target signature subject to several geometric and signature constraints. The target signature is computed by using a least-squares regression of the aft portion of the ground signature. The parameterization and the deformation of the geometry is performed with a NASA in- house shaping tool. The optimization algorithm uses the shaping tool to drive the geometric deformation of a horizontal tail with a parameterization scheme that consists of seven camber design variables and an additional design variable that describes the spanwise location of the midspan section. The demonstration cases show that numerical optimization using the state-of-the-art o -body aerodynamic calculations is not only feasible and repeatable but also allows the exploration of complex design spaces for which a knowledge-based design method becomes less effective.

  17. Parental antagonism and parent–offspring co-adaptation interact to shape family life

    PubMed Central

    Meunier, Joël; Kölliker, Mathias

    2012-01-01

    The family is an arena for conflicts between offspring, mothers and fathers that need resolving to promote the evolution of parental care and the maintenance of family life. Co-adaptation is known to contribute to the resolution of parent–offspring conflict over parental care by selecting for combinations of offspring demand and parental supply that match to maximize the fitness of family members. However, multiple paternity and differences in the level of care provided by mothers and fathers can generate antagonistic selection on offspring demand (mediated, for example, by genomic imprinting) and possibly hamper co-adaptation. While parent–offspring co-adaptation and parental antagonism are commonly considered two major processes in the evolution of family life, their co-occurrence and the evolutionary consequences of their joint action are poorly understood. Here, we demonstrate the simultaneous and entangled effects of these two processes on outcomes of family interactions, using a series of breeding experiments in the European earwig, Forficula auricularia, an insect species with uniparental female care. As predicted from parental antagonism, we show that paternally inherited effects expressed in offspring influence both maternal care and maternal investment in future reproduction. However, and as expected from the entangled effects of parental antagonism and co-adaptation, these effects critically depended on postnatal interactions with caring females and maternally inherited effects expressed in offspring. Our results demonstrate that parent–offspring co-adaptation and parental antagonism are entangled key drivers in the evolution of family life that cannot be fully understood in isolation. PMID:22810433

  18. In-beam spectroscopic studies of shape coexistence and collectivity in the neutron-deficient Z ≈ 82 nuclei

    NASA Astrophysics Data System (ADS)

    Julin, R.; Grahn, T.; Pakarinen, J.; Rahkila, P.

    2016-02-01

    In the present paper we focus on studies of shape coexistence in even-mass nuclei in the neutron-deficient Pb region. They are based on experiments carried out using tagging techniques in the Accelerator Laboratory of the University of Jyväskylä, Finland. Excited states in many of these nuclei can only be accessed via fusion-evaporation reactions employing high-intensity stable-ion beams. The key features in these experiments are high selectivity, clean spectra and instrumentation that enables high count rates. We review three spectroscopic highlights in this region.

  19. INDIRECT INTELLIGENT SLIDING MODE CONTROL OF A SHAPE MEMORY ALLOY ACTUATED FLEXIBLE BEAM USING HYSTERETIC RECURRENT NEURAL NETWORKS

    PubMed Central

    Hannen, Jennifer C.; Crews, John H.; Buckner, Gregory D.

    2012-01-01

    This paper introduces an indirect intelligent sliding mode controller (IISMC) for shape memory alloy (SMA) actuators, specifically a flexible beam deflected by a single offset SMA tendon. The controller manipulates applied voltage, which alters SMA tendon temperature to track reference bending angles. A hysteretic recurrent neural network (HRNN) captures the nonlinear, hysteretic relationship between SMA temperature and bending angle. The variable structure control strategy provides robustness to model uncertainties and parameter variations, while effectively compensating for system nonlinearities, achieving superior tracking compared to an optimized PI controller. PMID:22962538

  20. GaN nanowires with pentagon shape cross-section by ammonia-source molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Lin, Yong; Leung, Benjamin; Li, Qiming; Figiel, Jeffrey. J.; Wang, George T.

    2015-10-01

    Ammonia-based molecular beam epitaxy (NH3-MBE) was used to grow catalyst-assisted GaN nanowires on (1 1 bar 02) r-plane sapphire substrates. Dislocation free [ 11 2 bar 0 ] oriented nanowires are formed with pentagon shape cross-section, instead of the usual triangular shape facet configuration. Specifically, the cross-section is the result of the additional two nonpolar { 10 1 bar 0 } side facets, which appear due to a decrease in relative growth rate of the { 10 1 bar 0 } facets to the { 10 1 bar 1 } and { 10 1 bar 1 } facets under the growth regime in NH3-MBE. Compared to GaN nanowires grown by Ni-catalyzed metal-organic chemical vapor deposition, the NH3-MBE grown GaN nanowires show more than an order of magnitude increase in band-edge to yellow luminescence intensity ratio, as measured by cathodoluminescence, indicating improved microstructural and optical properties.

  1. Reducing Near-Field RF Levels and Noise Temperature on a 34-m Beam-Waveguide Antenna by Strut Shaping

    NASA Astrophysics Data System (ADS)

    Khayatian, B.; Hoppe, D. J.; Britcliffe, M. J.; Gama, E.

    2013-02-01

    Strut shaping of NASA's Deep Space Network (DSN) 34-m beam-waveguide (BWG) antenna has been implemented to reduce near-field RF exposure while improving the antenna noise temperature. Strut shaping was achieved by introducing an RF shield that does not compromise the structural integrity of the existing structure. Reduction in the RF near-field exposure will compensate for the planned transmit power increase of the antenna from 20 kW to 80 kW while satisfying safety requirements for RF exposure. Antenna noise temperature was also improved by as much as 1.5 K for the low elevation angles and 0.5 K in other areas. Both reductions of RF near-field exposure and antenna noise temperature were verified through measurements and agree very well with calculated results.

  2. Strut Shaping of 34m Beam Waveguide Antenna for Reductions in Near-Field RF and Noise Temperature

    NASA Technical Reports Server (NTRS)

    Khayatian, Behrouz; Hoppe, Daniel J.; Britcliffe, Michael J.; Gama, Eric

    2012-01-01

    Strut shaping of NASA's Deep Space Network (DSN) 34m Beam Waveguide (BWG) antenna has been implemented to reduce near-field RF exposure while improving the antenna noise temperature. Strut shaping was achieved by introducing an RF shield that does not compromise the structural integrity of the existing antenna. Reduction in the RF near-field level will compensate for the planned transmit power increase of the antenna from 20 kW to 80 kW while satisfying safety requirements for RF exposure. Measured antenna noise temperature was also improved by as much as 1.5 K for the low elevation angles and 0.5 K in other areas.

  3. Strut Shaping of 34m Beam Waveguide Antenna for Reductions in Near-Field RF and Noise Temeperature

    NASA Technical Reports Server (NTRS)

    Khayatian, Behrouz; Hoppe, Daniel J.; Britcliffe, Michael J.; Gama, Eric

    2012-01-01

    Struts shaping of the NASA's Deep Space Network (DSN) 34m Beam Waveguide (BWG) antenna has been implemented to reduce near-field RF exposure while improving the antenna noise temperature. Strut shaping was achieved by introducing an RF shield that does not compromise the structural integrity of the existing structure. Reduction in the RF near-field exposure will compensate for the planned transmit power increase of the antenna from 20 kW to 80 kW while satisfying safety requirements for RF exposure. Antenna noise temperature was also improved by as much as 1.5 K for the low elevation angles and 0.5 K in other areas. Both reductions of RF near-field exposure and antenna noise temperature were verified through measurements and agree very well with calculated results.

  4. Emittance control of a beam by shaping the transverse charge distribution, using a tomography diagnostic

    SciTech Connect

    Yakimenko, V.; Babzien, M.; Ben-Zvi, I.; Malone, R.; Wang, X.J.

    1998-06-01

    A high-brightness beam is very important for many applications. A diagnostic that measures the multi-dimensional phase-space density-distribution of the electron bunch is a must for obtaining such beams. Measurement of a slice emittance has been achieved. Tomographic reconstruction of phase space was suggested and implemented using a single quadrupole scan. In the present work the authors give special attention to the accuracy of the phase space reconstruction and present an analysis using a transport line with nine focusing magnets and techniques to control the optical functions and phases. This diagnostic, coupled with control of the radial charge distribution of presents an opportunity to improve the beam brightness. Combining the slice emittance and tomography diagnostics lead to an unprecedented visualization of phase space distributions in 5 dimensional phase-space and an opportunity to perform high-order emittance corrections.

  5. EMITTANCE CONTROL OF A BEAM BY SHAPING THE TRANSVERSE CHARGE DISTRIBUTION, USING A TOMOGRAPHY DIAGNOSTIC.

    SciTech Connect

    YAKIMENKO,V.

    1998-06-26

    A high-brightness beam is very important for many applications. A diagnostic that measures the multi-dimensional phase-space density-distribution of the electron bunch is a must for obtaining such beams. Measurement of a slice emittance has been achieved [1]. Tomographic reconstruction of phase space was suggested [2] and implemented [3,4] using a single quadrupole scan. In the present work we give special attention to the accuracy of the phase space reconstruction and present an analysis using a transport line with nine focusing magnets and techniques to control the optical functions and phases. This diagnostic, coupled with control of the radial charge distribution of presents an opportunity to improve the beam brightness. Combining the slice emittance and tomography diagnostics lead to an unprecedented visualization of phase space distributions in 5 dimensional phase-space and an opportunity to perform high-order emittance corrections.

  6. Node-Wise Topological Shape Optimum Design for Structural Reinforced Modeling of Michell-Type Concrete Deep Beams

    NASA Astrophysics Data System (ADS)

    Lee, Dongkyu; Park, Sungsoo; Shin, Soomi

    This study presents an associated structural design to continuous material topology optimization and a particular case of shape optimization using node-wise densities as design parameters. The generation of optimal shapes and topologies represented in this study is based on a three-dimensional density function bilinearly interpolated by element shape functions and nodal densities. The material interface between void and solid regions is described by a specific 0.5 cut-off level of continuous and smooth iso-lines of the nodal density function on a fixed mesh. This approach allows us to perform a simultaneous node-wise topology and shape optimization, which can be easily implemented by existing gradient-based optimization codes. Contrary to those of conventional material topology optimization methods, these optimal solutions are similar to ideal optimal solutions from analytical optimization techniques. Numerical examples for structural reinforced modeling of Michell-type concrete deep beams are used to demonstrate the efficiency and superiority of the resolutions of the present method.

  7. Selective Bottlenecks Shape Evolutionary Pathways Taken during Mammalian Adaptation of a 1918-like Avian Influenza Virus.

    PubMed

    Moncla, Louise H; Zhong, Gongxun; Nelson, Chase W; Dinis, Jorge M; Mutschler, James; Hughes, Austin L; Watanabe, Tokiko; Kawaoka, Yoshihiro; Friedrich, Thomas C

    2016-02-10

    Avian influenza virus reassortants resembling the 1918 human pandemic virus can become transmissible among mammals by acquiring mutations in hemagglutinin (HA) and polymerase. Using the ferret model, we trace the evolutionary pathway by which an avian-like virus evolves the capacity for mammalian replication and airborne transmission. During initial infection, within-host HA diversity increased drastically. Then, airborne transmission fixed two polymerase mutations that do not confer a detectable replication advantage. In later transmissions, selection fixed advantageous HA1 variants. Transmission initially involved a "loose" bottleneck, which became strongly selective after additional HA mutations emerged. The stringency and evolutionary forces governing between-host bottlenecks may therefore change throughout host adaptation. Mutations occurred in multiple combinations in transmitted viruses, suggesting that mammalian transmissibility can evolve through multiple genetic pathways despite phenotypic constraints. Our data provide a glimpse into avian influenza virus adaptation in mammals, with broad implications for surveillance on potentially zoonotic viruses. PMID:26867176

  8. Bulimic symptomatology: the role of adaptive perfectionism, shape and weight concern, and self-esteem.

    PubMed

    Watson, Hunna J; Steele, Anna L; Bergin, Jacqueline L; Fursland, Anthea; Wade, Tracey D

    2011-09-01

    An interactive model implicating high perfectionism, high weight and shape concern, and low self-esteem in the onset and maintenance of bulimic symptoms (Bardone, Vohs, Abramson, Heatherton, & Joiner, 2000; Vohs, Bardone, Joiner, Abramson, & Heatherton, 1999) has received mixed support. This study aimed to replicate the cross-sectional model in a clinical sample of women with eating disorders, and to investigate whether the model could predict changes in binge eating and purging at the end of treatment. Eating disorder outpatients (n=353) completed measures of perfectionism, weight/shape concern, self-esteem, and bulimic symptoms at pre-treatment and discharge. Contrary to the hypotheses, the three-way interaction did not predict binge eating or purging cross-sectionally or prospectively as a moderator of psychotherapy outcome. It was concluded that the robustness of the interactive model seems questionable and may be impacted by an inadequate conceptualization of the perfectionism construct. PMID:21704980

  9. Mutation of a Cuticular Protein, BmorCPR2, Alters Larval Body Shape and Adaptability in Silkworm, Bombyx mori

    PubMed Central

    Qiao, Liang; Xiong, Gao; Wang, Ri-xin; He, Song-zhen; Chen, Jie; Tong, Xiao-ling; Hu, Hai; Li, Chun-lin; Gai, Ting-ting; Xin, Ya-qun; Liu, Xiao-fan; Chen, Bin; Xiang, Zhong-huai; Lu, Cheng; Dai, Fang-yin

    2014-01-01

    Cuticular proteins (CPs) are crucial components of the insect cuticle. Although numerous genes encoding cuticular proteins have been identified in known insect genomes to date, their functions in maintaining insect body shape and adaptability remain largely unknown. In the current study, positional cloning led to the identification of a gene encoding an RR1-type cuticular protein, BmorCPR2, highly expressed in larval chitin-rich tissues and at the mulberry leaf-eating stages, which is responsible for the silkworm stony mutant. In the Dazao-stony strain, the BmorCPR2 allele is a deletion mutation with significantly lower expression, compared to the wild-type Dazao strain. Dysfunctional BmorCPR2 in the stony mutant lost chitin binding ability, leading to reduced chitin content in larval cuticle, limitation of cuticle extension, abatement of cuticle tensile properties, and aberrant ratio between internodes and intersegmental folds. These variations induce a significant decrease in cuticle capacity to hold the growing internal organs in the larval development process, resulting in whole-body stiffness, tightness, and hardness, bulging intersegmental folds, and serious defects in larval adaptability. To our knowledge, this is the first study to report the corresponding phenotype of stony in insects caused by mutation of RR1-type cuticular protein. Our findings collectively shed light on the specific role of cuticular proteins in maintaining normal larval body shape and will aid in the development of pest control strategies for the management of Lepidoptera. PMID:24514903

  10. Mutation of a cuticular protein, BmorCPR2, alters larval body shape and adaptability in silkworm, Bombyx mori.

    PubMed

    Qiao, Liang; Xiong, Gao; Wang, Ri-xin; He, Song-zhen; Chen, Jie; Tong, Xiao-ling; Hu, Hai; Li, Chun-lin; Gai, Ting-ting; Xin, Ya-qun; Liu, Xiao-fan; Chen, Bin; Xiang, Zhong-huai; Lu, Cheng; Dai, Fang-yin

    2014-04-01

    Cuticular proteins (CPs) are crucial components of the insect cuticle. Although numerous genes encoding cuticular proteins have been identified in known insect genomes to date, their functions in maintaining insect body shape and adaptability remain largely unknown. In the current study, positional cloning led to the identification of a gene encoding an RR1-type cuticular protein, BmorCPR2, highly expressed in larval chitin-rich tissues and at the mulberry leaf-eating stages, which is responsible for the silkworm stony mutant. In the Dazao-stony strain, the BmorCPR2 allele is a deletion mutation with significantly lower expression, compared to the wild-type Dazao strain. Dysfunctional BmorCPR2 in the stony mutant lost chitin binding ability, leading to reduced chitin content in larval cuticle, limitation of cuticle extension, abatement of cuticle tensile properties, and aberrant ratio between internodes and intersegmental folds. These variations induce a significant decrease in cuticle capacity to hold the growing internal organs in the larval development process, resulting in whole-body stiffness, tightness, and hardness, bulging intersegmental folds, and serious defects in larval adaptability. To our knowledge, this is the first study to report the corresponding phenotype of stony in insects caused by mutation of RR1-type cuticular protein. Our findings collectively shed light on the specific role of cuticular proteins in maintaining normal larval body shape and will aid in the development of pest control strategies for the management of Lepidoptera. PMID:24514903

  11. Cold adaptation shapes the robustness of metabolic networks in Drosophila melanogaster

    PubMed Central

    Williams, CM; Watanabe, M; Guarracino, MR; Ferraro, MB; Edison, AS; Morgan, TJ; Boroujerdi, AFB; Hahn, DA

    2015-01-01

    When ectotherms are exposed to low temperatures, they enter a cold-induced coma (chill coma) that prevents resource acquisition, mating, oviposition, and escape from predation. There is substantial variation in time taken to recover from chill coma both within and among species, and this variation is correlated with habitat temperatures such that insects from cold environments recover more quickly. This suggests an adaptive response, but the mechanisms underlying variation in recovery times are unknown, making it difficult to decisively test adaptive hypotheses. We use replicated lines of Drosophila melanogaster selected in the laboratory for fast (hardy) or slow (susceptible) chill-coma recovery times to investigate modifications to metabolic profiles associated with cold adaptation. We measured metabolite concentrations of flies before, during, and after cold exposure using NMR spectroscopy to test the hypotheses that hardy flies maintain metabolic homeostasis better during cold exposure and recovery, and that their metabolic networks are more robust to cold-induced perturbations. The metabolites of cold-hardy flies were less cold responsive and their metabolic networks during cold exposure were more robust, supporting our hypotheses. Metabolites involved in membrane lipid synthesis, tryptophan metabolism, oxidative stress, energy balance, and proline metabolism were altered by selection on cold tolerance. We discuss the potential significance of these alterations. PMID:25308124

  12. Adaptive-Predictive Organ Localization Using Cone-Beam Computed Tomography for Improved Accuracy in External Beam Radiotherapy for Bladder Cancer

    SciTech Connect

    Lalondrelle, Susan; Huddart, Robert; Warren-Oseni, Karole; Hansen, Vibeke Nordmark; McNair, Helen; Thomas, Karen; Dearnaley, David; Horwich, Alan; Khoo, Vincent

    2011-03-01

    Purpose: To examine patterns of bladder wall motion during high-dose hypofractionated bladder radiotherapy and to validate a novel adaptive planning method, A-POLO, to prevent subsequent geographic miss. Methods and Materials: Patterns of individual bladder filling were obtained with repeat computed tomography planning scans at 0, 15, and 30 minutes after voiding. A series of patient-specific plans corresponding to these time-displacement points was created. Pretreatment cone-beam computed tomography was performed before each fraction and assessed retrospectively for adaptive intervention. In fractions that would have required intervention, the most appropriate plan was chosen from the patient's 'library,' and the resulting target coverage was reassessed with repeat cone-beam computed tomography. Results: A large variation in patterns of bladder filling and interfraction displacement was seen. During radiotherapy, predominant translations occurred cranially (maximum 2.5 cm) and anteriorly (maximum 1.75 cm). No apparent explanation was found for this variation using pretreatment patient factors. A need for adaptive planning was demonstrated by 51% of fractions, and 73% of fractions would have been delivered correctly using A-POLO. The adaptive strategy improved target coverage and was able to account for intrafraction motion also. Conclusions: Bladder volume variation will result in geographic miss in a high proportion of delivered bladder radiotherapy treatments. The A-POLO strategy can be used to correct for this and can be implemented from the first fraction of radiotherapy; thus, it is particularly suited to hypofractionated bladder radiotherapy regimens.

  13. Low-speckle holographic beam shaping of high-coherence EUV sources

    SciTech Connect

    Anderson, Christopher N.; Miyakawa, Ryan H.; Naulleau, Patrick

    2010-08-01

    This paper describes a method to arbitrarily shape and homogenize high-coherence extreme ultraviolet sources using time-varying holographic optical elements and a scanning subsystem to mitigate speckle. In systems with integration times longer than 100 ms, a speckle contrast below 1% can be achieved.

  14. Deformable image registration of CT and truncated cone-beam CT for adaptive radiation therapy

    NASA Astrophysics Data System (ADS)

    Zhen, Xin; Yan, Hao; Zhou, Linghong; Jia, Xun; Jiang, Steve B.

    2013-11-01

    Truncation of a cone-beam computed tomography (CBCT) image, mainly caused by the limited field of view (FOV) of CBCT imaging, poses challenges to the problem of deformable image registration (DIR) between computed tomography (CT) and CBCT images in adaptive radiation therapy (ART). The missing information outside the CBCT FOV usually causes incorrect deformations when a conventional DIR algorithm is utilized, which may introduce significant errors in subsequent operations such as dose calculation. In this paper, based on the observation that the missing information in the CBCT image domain does exist in the projection image domain, we propose to solve this problem by developing a hybrid deformation/reconstruction algorithm. As opposed to deforming the CT image to match the truncated CBCT image, the CT image is deformed such that its projections match all the corresponding projection images for the CBCT image. An iterative forward-backward projection algorithm is developed. Six head-and-neck cancer patient cases are used to evaluate our algorithm, five with simulated truncation and one with real truncation. It is found that our method can accurately register the CT image to the truncated CBCT image and is robust against image truncation when the portion of the truncated image is less than 40% of the total image. Part of this work was presented at the 54th AAPM Annual Meeting (Charlotte, NC, USA, 29 July-2 August 2012).

  15. Intelligent correction of laser beam propagation through turbulent media using adaptive optics

    NASA Astrophysics Data System (ADS)

    Ko, Jonathan; Wu, Chensheng; Davis, Christopher C.

    2014-10-01

    Adaptive optics methods have long been used by researchers in the astronomy field to retrieve correct images of celestial bodies. The approach is to use a deformable mirror combined with Shack-Hartmann sensors to correct the slightly distorted image when it propagates through the earth's atmospheric boundary layer, which can be viewed as adding relatively weak distortion in the last stage of propagation. However, the same strategy can't be easily applied to correct images propagating along a horizontal deep turbulence path. In fact, when turbulence levels becomes very strong (Cn 2>10-13 m-2/3), limited improvements have been made in correcting the heavily distorted images. We propose a method that reconstructs the light field that reaches the camera, which then provides information for controlling a deformable mirror. An intelligent algorithm is applied that provides significant improvement in correcting images. In our work, the light field reconstruction has been achieved with a newly designed modified plenoptic camera. As a result, by actively intervening with the coherent illumination beam, or by giving it various specific pre-distortions, a better (less turbulence affected) image can be obtained. This strategy can also be expanded to much more general applications such as correcting laser propagation through random media and can also help to improve designs in free space optical communication systems.

  16. Multiscale registration of planning CT and daily cone beam CT images for adaptive radiation therapy

    SciTech Connect

    Paquin, Dana; Levy, Doron; Xing Lei

    2009-01-15

    Adaptive radiation therapy (ART) is the incorporation of daily images in the radiotherapy treatment process so that the treatment plan can be evaluated and modified to maximize the amount of radiation dose to the tumor while minimizing the amount of radiation delivered to healthy tissue. Registration of planning images with daily images is thus an important component of ART. In this article, the authors report their research on multiscale registration of planning computed tomography (CT) images with daily cone beam CT (CBCT) images. The multiscale algorithm is based on the hierarchical multiscale image decomposition of E. Tadmor, S. Nezzar, and L. Vese [Multiscale Model. Simul. 2(4), pp. 554-579 (2004)]. Registration is achieved by decomposing the images to be registered into a series of scales using the (BV, L{sup 2}) decomposition and initially registering the coarsest scales of the image using a landmark-based registration algorithm. The resulting transformation is then used as a starting point to deformably register the next coarse scales with one another. This procedure is iterated at each stage using the transformation computed by the previous scale registration as the starting point for the current registration. The authors present the results of studies of rectum, head-neck, and prostate CT-CBCT registration, and validate their registration method quantitatively using synthetic results in which the exact transformations our known, and qualitatively using clinical deformations in which the exact results are not known.

  17. Method for shaping and aiming narrow beams. [sonar mapping and target identification

    NASA Technical Reports Server (NTRS)

    Heyser, R. C. (Inventor)

    1981-01-01

    A sonar method and apparatus is discribed which utilizes a linear frequency chirp in a transmitter/receiver having a correlator to synthesize a narrow beamwidth pattern from otherwise broadbeam transducers when there is relative velocity between the transmitter/receiver and the target. The chirp is so produced in a generator in bandwidth, B, and time, T, as to produce a time bandwidth product, TB, that is increased for a narrower angle. A replica of the chirp produced in a generator is time delayed and Doppler shifted for use as a reference in the receiver for correlation of received chirps from targets. This reference is Doppler shifted to select targets preferentially, thereby to not only synthesize a narrow beam but also aim the beam in azimuth and elevation.

  18. A QUEST FOR SYSTEM FRIENDLINESS WITH THE SNS ION BEAM BUNCH SHAPE MONITOR

    SciTech Connect

    Dickson, Richard W; Aleksandrov, Alexander V

    2012-01-01

    A new system for measuring the SNS ion beam longitudinal profile was recently upgraded to operational status. The hardware for this device was developed and delivered by Institute of Nuclear Research to the SNS as a part of its initial construction. The supplied LabVIEW user interface software was intended for proof-of-operation and initial setup of the instrument. While satisfactory for this, it was tedious to use in a practical context and lacked any form of interface to the SNS EPICS based control system. This paper will describe the software features added to make this instrument both easily tunable to the prevalent beam conditions by system engineers and easily usable by accelerator physicists only interested in its output data.

  19. Influence of beam shape on in-vitro cellular transformations in human skin fibroblasts

    NASA Astrophysics Data System (ADS)

    Mthunzi, Patience; Forbes, Andrew; Hawkins, Denise; Abrahamse, Heidi; Karsten, Aletta E.

    2005-08-01

    A variety of strategies have been utilised for prevention and treatment of chronic wounds such as leg ulcers, diabetic foot ulcers and pressure sores1. Low Level Laser Therapy (LLLT) has been reported to be an invaluable tool in the enhancement of wound healing through stimulating cell proliferation, accelerating collagen synthesis and increasing ATP synthesis in mitochondria to name but a few2. This study focused on an in-vitro analysis of the cellular responses induced by treatment with three different laser beam profiles namely, the Gaussian (G), Super Gaussian (SG) and Truncated Gaussian (TG), on normal wounded irradiated (WI) and wounded non-irradiated (WNI) human skin fibroblast cells (WS1), to test their influence in wound healing at 632.8 nm using a helium neon (HeNe) laser. For each beam profile, measurements were made using average energy densities over the sample ranging from 0.2 to 1 J, with single exposures on normal wounded cells. The cells were subjected to different post irradiation incubation periods, ranging from 0 to 24 hours to evaluate the duration (time) dependent effects resulting from laser irradiation. The promoted cellular alterations were measured by increase in cell viability, cell proliferation and cytotoxicity. The results obtained showed that treatment with the G compared to the SG and TG beams resulted in a marked increase in cell viability and proliferation. The data also showed that when cells undergo laser irradiation some cellular processes are driven by the peak energy density rather than the energy of the laser beam. We show that there exist threshold values for damage, and suggest optimal operating regimes for laser based wound healing.

  20. Comparing flat top and Gaussian focal beam shapes when micromachining steel

    NASA Astrophysics Data System (ADS)

    Lizotte, Todd E.; Ohar, Orest

    2011-10-01

    Laser micromachining, drilling and marking is extensively used within the aerospace, automotive and firearms industries. The unique properties of lasers make them ideal tools for micromachining a wide diversity of materials, including steel alloys [1]. We describe the results of micromachining of low carbon steel and stainless steel alloys, using a high powered diode pumped solid state (DPSS) laser operating at a wavelength of 355nm. The laser was configured with beam conditioning optics to produce either a flat top beam or a Gaussian output which was then sent through a galvanometer scanner and telecentric lens beam delivery system. This paper outlines the interrelationship of process variables when micromachining fine features in steel and stainless steel alloys. Process variables measured included the optimum laser focus plane, energy density, galvanometer scan rate, and pulse overlap and focal spot diameter. Optimum process performance was evaluated based on a dimensional comparison of the micromachined features from each test coupon, including uniformity and surface roughness of the micromachined surface and the minimization of surface irregularities (stalagmite type slag / debris / corn row patterns) and taper angle of the micromachined feature side walls.

  1. Eco-physiological adaptation shapes the response of calcifying algae to nutrient limitation

    NASA Astrophysics Data System (ADS)

    Šupraha, Luka; Gerecht, Andrea C.; Probert, Ian; Henderiks, Jorijntje

    2015-11-01

    The steady increase in global ocean temperature will most likely lead to nutrient limitation in the photic zone. This will impact the physiology of marine algae, including the globally important calcifying coccolithophores. Understanding their adaptive patterns is essential for modelling carbon production in a low-nutrient ocean. We investigated the physiology of Helicosphaera carteri, a representative of the abundant but under-investigated flagellated functional group of coccolithophores. Two strains isolated from contrasting nutrient regimes (South Atlantic and Mediterranean Sea) were grown in phosphorus-replete and phosphorus-limited batch cultures. While growing exponentially in a phosphorus-replete medium, the Mediterranean strain exhibited on average 24% lower growth rate, 36% larger coccosphere volume and 21% lower particulate inorganic carbon (PIC) production than the Atlantic strain. Under phosphorus limitation, the same strain was capable of reaching a 2.6 times higher cell density than the Atlantic strain due to lower phosphorus requirements. These results suggest that local physiological adaptation can define the performance of this species under nutrient limitation.

  2. Thermal adaptation and phosphorus shape thermal performance in an assemblage of rainforest ants.

    PubMed

    Kaspari, Michael; Clay, Natalie A; Lucas, Jane; Revzen, Shai; Kay, Adam; Yanoviak, Stephen P

    2016-04-01

    We studied the Thermal Performance Curves (TPCs) of 87 species of rainforest ants and found support for both the Thermal Adaptation and Phosphorus-Tolerance hypotheses. TPCs relate a fitness proxy (here, worker speed) to environmental temperature. Thermal Adaptation posits that thermal generalists (ants with flatter, broader TPCs) are favored in the hotter, more variable tropical canopy compared to the cooler, less variable litter below. As predicted, species nesting in the forest canopy 1) had running speeds less sensitive to temperature; 2) ran over a greater range of temperatures; and 3) ran at lower maximum speeds. Tradeoffs between tolerance and maximum performance are often invoked for constraining the evolution of thermal generalists. There was no evidence that ant species traded off thermal tolerance for maximum speed, however. Phosphorus-Tolerance is a second mechanism for generating ectotherms able to tolerate thermal extremes. It posits that ants active at high temperatures invest in P-rich machinery to buffer their metabolism against thermal extremes. Phosphorus content in ant tissue varied three-fold, and as predicted, temperature sensitivity was lower and thermal range was higher in P-rich species. Combined, we show how the vertical distribution of hot and variable vs. cooler and stable microclimates in a single forest contribute to a diversity of TPCs and suggest that a widely varying P stoichiometry among these ants may drive some of these differences. PMID:27220219

  3. Eco-physiological adaptation shapes the response of calcifying algae to nutrient limitation

    PubMed Central

    Šupraha, Luka; Gerecht, Andrea C.; Probert, Ian; Henderiks, Jorijntje

    2015-01-01

    The steady increase in global ocean temperature will most likely lead to nutrient limitation in the photic zone. This will impact the physiology of marine algae, including the globally important calcifying coccolithophores. Understanding their adaptive patterns is essential for modelling carbon production in a low-nutrient ocean. We investigated the physiology of Helicosphaera carteri, a representative of the abundant but under-investigated flagellated functional group of coccolithophores. Two strains isolated from contrasting nutrient regimes (South Atlantic and Mediterranean Sea) were grown in phosphorus-replete and phosphorus-limited batch cultures. While growing exponentially in a phosphorus-replete medium, the Mediterranean strain exhibited on average 24% lower growth rate, 36% larger coccosphere volume and 21% lower particulate inorganic carbon (PIC) production than the Atlantic strain. Under phosphorus limitation, the same strain was capable of reaching a 2.6 times higher cell density than the Atlantic strain due to lower phosphorus requirements. These results suggest that local physiological adaptation can define the performance of this species under nutrient limitation. PMID:26560531

  4. A spiral-shaped harvester with an improved harvesting element and an adaptive storage circuit.

    PubMed

    Hu, Hongping; Xue, Huan; Hu, Yuantai

    2007-06-01

    A piezoelectric energy harvester consists of a spiral-shaped piezoelectric bimorph to transfer mechanical energy into electric energy, an electrochemical battery to store the scavenged electric energy, and a rectifier together with a step-down dc-dc converter to connect the two components as an integrated system. A spiral-shaped harvesting structure is studied in this paper because it is very useful in the microminiaturization of advanced sensing technology. The aim of employing a step-down dc-dc converter in the storage circuit is to match the optimal output voltage of the piezoelectric bimorph with the battery voltage for efficient charging. In order to raise the output power density of a harvesting element, moreover, we apply a synchronized switch harvesting on inductor (SSHI) in parallel with the piezoelectric bimorph to artificially extend the closed-circuit interval of the rectifier. Numerical results show that the introduction of a dc-dc converter in the storage circuit or a SSHI in the harvesting structure can raise the charging efficiency several times higher than a harvester without a dc-dc converter or an SSHI. PMID:17571816

  5. An adaptive explanation for the horse-like shape of seahorses.

    PubMed

    Van Wassenbergh, Sam; Roos, Gert; Ferry, Lara

    2011-01-25

    The body shape of seahorses resembles the head and neck of horses because of their curved trunk, their ventrally bent head and their long snout. Seahorses evolved from ancestral, pipefish-like species, which have a straight body. Here, we use a biomechanical analysis and show that the seahorse's peculiar head, neck and trunk posture allows for the capture of small shrimps at larger distances from the eyes compared with pipefish. The results from the mathematical modelling were confirmed by kinematic data of prey-capturing syngnathids: compared with straight-bodied pipefish, all seahorse species studied consistently show an additional forward-reaching component in the path travelled by the mouth during their strikes at prey. This increased strike distance enlarges the volume of water they can probe for food, which is especially useful for tail-attached, sit-and-wait predators like seahorses. The biomechanics of prey capture thus provides a putative selective advantage that may explain the bending of the trunk into a horse-like shape. PMID:21266964

  6. Inquiry in interaction: How local adaptations of curricula shape classroom communities

    NASA Astrophysics Data System (ADS)

    Enyedy, Noel; Goldberg, Jennifer

    2004-11-01

    In this study, we seek a better understanding of how individuals and their daily interactions shape and reshape social structures that constitute a classroom community. Moreover, we provide insight into how discourse and classroom interactions shape the nature of a learning community, as well as which aspects of the classroom culture may be consequential for learning. The participants in this study include two teachers who are implementing a new environmental science program, Global Learning through Observation to Benefit the Environment (GLOBE), and interacting with 54 children in an urban middle school. Both qualitative and quantitative data are analyzed and presented. To gain a better understanding of the inquiry teaching within classroom communities, we compare and contrast the discourse and interactions of the two teachers during three parallel environmental science lessons. The focus of our analysis includes (1) how the community identifies the object or goal of its activity; and (2) how the rights, rules, and roles for members are established and inhabited in interaction. Quantitative analyses of student pre- and posttests suggest greater learning for students in one classroom over the other, providing support for the influence of the classroom community and interactional choices of the teacher on student learning. Implications of the findings from this study are discussed in the context of curricular design, professional development, and educational reform. ? 2004 Wiley Periodicals, Inc. J Res Sci Teach 41: 905-935, 2004.

  7. Effect of Beam Smoothing and Pulse Shape on the Implosion of DD-Filled CH Shell Targets on OMEGA

    NASA Astrophysics Data System (ADS)

    Delettrez, J. A.; Glebov, V. Yu.; Marshall, F. J.; Stoeckl, C.; Yaakobi, B.; Meyerhofer, D. D.

    1999-11-01

    Over the past two years several implosion experiments were carried out on the 60-beam OMEGA laser in which DD-filled CH shells (some with a CHTi layer imbedded) were irradiated with various laser pulse shapes and smoothing conditions. Target CH shell thicknesses varied from 20 μm to 27 μm with DD-fill variations from 3 to 20 atm, sometimes mixed with ^3He. Two pulse shapes---a 1-ns square pulse and a 2.5-ns pulse with a 10%, 1-ns foot, with and without SSD---provide several levels of laser imprint. Diagnostics include measured neutron yields, fuel ion temperatures, fuel ρR, and shell ρR. Simulations for these experimental conditions were carried out with the 2-D hydrocode ORCHID. The results are compared with the experimental results. The degradation of target performance due to laser nonuniformity is analyzed by comparing the 2-D results with those of 1-D simulations. The effects of pulse shape, target thickness, convergence ratio, and smoothing are presented. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC03-92SF19460, the University of Rochester, and the New York State Energy Research and Development Authority.

  8. Molecular beam epitaxial growth and characterization of single crystal ferromagnetic shape memory nickel-manganese-gallium films

    NASA Astrophysics Data System (ADS)

    Dong, Jianwei

    In this thesis, single-crystal ferromagnetic shape memory Ni2MnGa thin films have been grown by molecular beam epitaxy (MBE) on GaAs substrates. The properties of the as-grown and free-standing Ni2MnGa films have been thoroughly investigated. It is demonstrated for the first time that the free-standing Ni2MnGa films can be deformed macroscopically by an external magnetic field, which strongly supports the idea of developing Ni2MnGa-based ferromagnetic micro-electro-mechanical-system (MEMS) actuators to realize both large strain and fast response. The MBE growth of Ni2MnGa thin films was carried out using GaAs (001) substrates. The effects of NiGa and ScErAs interlayers, alternate layer epitaxy, and growth temperatures on the structural and magnetic properties of the epitaxial Ni2MnGa films have been studied to optimize the growth. Three MBE-stabilized tetragonal phases as well as two martensite structures have been confirmed. The films are ferromagnetic at room temperature and have Curie temperatures ˜340 K. Free-standing patterned Ni2MnGa films were processed using bulk micro-machining techniques in both bridge and cantilever forms with dimensions ranging from 100 to 400 mum. Tent-like configurations have been observed in released bridges at room temperature (RT) in a film with a composition of ˜Ni50Mn30Ga20. Magnetic measurements confirmed that the film was in the martensitic phase at RT with enhanced magnetic anisotropy. In a free-standing cantilever, repeatable martensitic phase transformation and a unique two-way shape memory effect have been observed by polarized light microscopy. Magnetic field induced strain in a free-standing stoichiometric Ni 2MnGa film was studied at low temperatures. When a magnetic field was applied perpendicularly to the film surface at 135--150 K, dramatic shape change has been observed in free-standing bridges. The shape change saturated at ˜1.2 Tesla. Heating the film up to ˜200 K reverted the sample to the austenite phase and

  9. Mandible shape and dwarfism in squirrels (Mammalia, Rodentia): interaction of allometry and adaptation

    NASA Astrophysics Data System (ADS)

    Hautier, Lionel; Fabre, Pierre-Henri; Michaux, Jacques

    2009-06-01

    Squirrels include several independent lineages of dwarf forms distributed into two ecological groups: the dwarf tree and flying squirrels. The mandible of dwarf tree squirrels share a highly reduced coronoid process and a condylar process drawn backwards. Dwarf flying squirrels on the other hand, have an elongated coronoid process and a well-differentiated condylar process. To interpret such a difference, Elliptic Fourier Transform was used to evaluate how mandible shape varies with dwarfism in sciurids. The results obtained show that this clear-cut difference cannot be explained by a simple allometric relationship in relation with size decrease. We concluded that the retention of anteriorly positioned eye sockets, in relation with distance estimation, allowed the conservation of a well-differentiated coronoid process in all flying species, despite the trend towards its reduction observed among sciurids as their size decreases.

  10. Mandible shape and dwarfism in squirrels (Mammalia, Rodentia): interaction of allometry and adaptation.

    PubMed

    Hautier, Lionel; Fabre, Pierre-Henri; Michaux, Jacques

    2009-06-01

    Squirrels include several independent lineages of dwarf forms distributed into two ecological groups: the dwarf tree and flying squirrels. The mandible of dwarf tree squirrels share a highly reduced coronoid process and a condylar process drawn backwards. Dwarf flying squirrels on the other hand, have an elongated coronoid process and a well-differentiated condylar process. To interpret such a difference, Elliptic Fourier Transform was used to evaluate how mandible shape varies with dwarfism in sciurids. The results obtained show that this clear-cut difference cannot be explained by a simple allometric relationship in relation with size decrease. We concluded that the retention of anteriorly positioned eye sockets, in relation with distance estimation, allowed the conservation of a well-differentiated coronoid process in all flying species, despite the trend towards its reduction observed among sciurids as their size decreases. PMID:19288073

  11. Laser welding of polymers: phenomenological model for a quick and reliable process quality estimation considering beam shape influences

    NASA Astrophysics Data System (ADS)

    Timpe, Nathalie F.; Stuch, Julia; Scholl, Marcus; Russek, Ulrich A.

    2016-03-01

    This contribution presents a phenomenological, analytical model for laser welding of polymers which is suited for a quick process quality estimation for the practitioner. Besides material properties of the polymer and processing parameters like welding pressure, feed rate and laser power the model is based on a simple few parameter description of the size and shape of the laser power density distribution (PDD) in the processing zone. The model allows an estimation of the weld seam tensile strength. It is based on energy balance considerations within a thin sheet with the thickness of the optical penetration depth on the surface of the absorbing welding partner. The joining process itself is modelled by a phenomenological approach. The model reproduces the experimentally known process windows for the main process parameters correctly. Using the parameters describing the shape of the laser PDD the critical dependence of the process windows on the PDD shape will be predicted and compared with experiments. The adaption of the model to other laser manufacturing processes where the PDD influence can be modelled comparably will be discussed.

  12. Robust breathing signal extraction from cone beam CT projections based on adaptive and global optimization techniques.

    PubMed

    Chao, Ming; Wei, Jie; Li, Tianfang; Yuan, Yading; Rosenzweig, Kenneth E; Lo, Yeh-Chi

    2016-04-21

    We present a study of extracting respiratory signals from cone beam computed tomography (CBCT) projections within the framework of the Amsterdam Shroud (AS) technique. Acquired prior to the radiotherapy treatment, CBCT projections were preprocessed for contrast enhancement by converting the original intensity images to attenuation images with which the AS image was created. An adaptive robust z-normalization filtering was applied to further augment the weak oscillating structures locally. From the enhanced AS image, the respiratory signal was extracted using a two-step optimization approach to effectively reveal the large-scale regularity of the breathing signals. CBCT projection images from five patients acquired with the Varian Onboard Imager on the Clinac iX System Linear Accelerator (Varian Medical Systems, Palo Alto, CA) were employed to assess the proposed technique. Stable breathing signals can be reliably extracted using the proposed algorithm. Reference waveforms obtained using an air bellows belt (Philips Medical Systems, Cleveland, OH) were exported and compared to those with the AS based signals. The average errors for the enrolled patients between the estimated breath per minute (bpm) and the reference waveform bpm can be as low as -0.07 with the standard deviation 1.58. The new algorithm outperformed the original AS technique for all patients by 8.5% to 30%. The impact of gantry rotation on the breathing signal was assessed with data acquired with a Quasar phantom (Modus Medical Devices Inc., London, Canada) and found to be minimal on the signal frequency. The new technique developed in this work will provide a practical solution to rendering markerless breathing signal using the CBCT projections for thoracic and abdominal patients. PMID:27008349

  13. Adaptive Radiotherapy for Prostate Cancer Using Kilovoltage Cone-Beam Computed Tomography: First Clinical Results

    SciTech Connect

    Nijkamp, Jasper; Pos, Floris J. Nuver, Tonnis T.; Jong, Rianne de; Remeijer, Peter; Sonke, Jan-Jakob; Lebesque, Joos V.

    2008-01-01

    Purpose: To evaluate the first clinical results of an off-line adaptive radiotherapy (ART) protocol for prostate cancer using kilovoltage cone-beam computed tomography (CBCT) in combination with a diet and mild laxatives. Methods and Materials: Twenty-three patients began treatment with a planning target volume (PTV) margin of 10 mm. The CBCT scans acquired during the first six fractions were used to generate an average prostate clinical target volume (AV-CTV), and average rectum (AV-Rect). Using these structures, a new treatment plan was generated with a 7-mm PTV margin. Weekly CBCT scans were used to monitor the CTV coverage. A diet and mild laxatives were introduced to improve image quality and reduce prostate motion. Results: Twenty patients were treated with conform ART protocol. For these patients, 91% of the CBCT scans could be used to calculate the AV-CTV and AV-Rect. In 96% of the follow-up CBCT scans, the CTV was located within the average PTV. In the remaining 4%, the prostate extended the PTV by a maximum of 1 mm. Systematic and random errors for organ motion were reduced by a factor of two compared with historical data without diet and laxatives. An average PTV reduction of 29% was achieved. The volume of the AV-Rect that received >65 Gy was reduced by 19%. The mean dose to the anal wall was reduced on average by 4.8 Gy. Conclusions: We safely reduced the high-dose region by 29%. The reduction in irradiated volume led to a significant reduction in the dose to the rectum. The diet and laxatives improved the image quality and tended to reduce prostate motion.

  14. Robust breathing signal extraction from cone beam CT projections based on adaptive and global optimization techniques

    NASA Astrophysics Data System (ADS)

    Chao, Ming; Wei, Jie; Li, Tianfang; Yuan, Yading; Rosenzweig, Kenneth E.; Lo, Yeh-Chi

    2016-04-01

    We present a study of extracting respiratory signals from cone beam computed tomography (CBCT) projections within the framework of the Amsterdam Shroud (AS) technique. Acquired prior to the radiotherapy treatment, CBCT projections were preprocessed for contrast enhancement by converting the original intensity images to attenuation images with which the AS image was created. An adaptive robust z-normalization filtering was applied to further augment the weak oscillating structures locally. From the enhanced AS image, the respiratory signal was extracted using a two-step optimization approach to effectively reveal the large-scale regularity of the breathing signals. CBCT projection images from five patients acquired with the Varian Onboard Imager on the Clinac iX System Linear Accelerator (Varian Medical Systems, Palo Alto, CA) were employed to assess the proposed technique. Stable breathing signals can be reliably extracted using the proposed algorithm. Reference waveforms obtained using an air bellows belt (Philips Medical Systems, Cleveland, OH) were exported and compared to those with the AS based signals. The average errors for the enrolled patients between the estimated breath per minute (bpm) and the reference waveform bpm can be as low as  -0.07 with the standard deviation 1.58. The new algorithm outperformed the original AS technique for all patients by 8.5% to 30%. The impact of gantry rotation on the breathing signal was assessed with data acquired with a Quasar phantom (Modus Medical Devices Inc., London, Canada) and found to be minimal on the signal frequency. The new technique developed in this work will provide a practical solution to rendering markerless breathing signal using the CBCT projections for thoracic and abdominal patients.

  15. Dose calculation accuracy using cone-beam CT (CBCT) for pelvic adaptive radiotherapy

    NASA Astrophysics Data System (ADS)

    Guan, Huaiqun; Dong, Hang

    2009-10-01

    This study is to evaluate the dose calculation accuracy using Varian's cone-beam CT (CBCT) for pelvic adaptive radiotherapy. We first calibrated the Hounsfield Unit (HU) to electron density (ED) for CBCT using a mini CT QC phantom embedded into an IMRT QA phantom. We then used a Catphan 500 with an annulus around it to check the calibration. The combined CT QC and IMRT phantom provided correct HU calibration, but not Catphan with an annulus. For the latter, not only was the Teflon an incorrect substitute for bone, but the inserts were also too small to provide correct HUs for air and bone. For the former, three different scan ranges (6 cm, 12 cm and 20.8 cm) were used to investigate the HU dependence on the amount of scatter. To evaluate the dose calculation accuracy, CBCT and plan-CT for a pelvic phantom were acquired and registered. The single field plan, 3D conformal and IMRT plans were created on both CT sets. Without inhomogeneity correction, the two CT generated nearly the same plan. With inhomogeneity correction, the dosimetric difference between the two CT was mainly from the HU calibration difference. The dosimetric difference for 6 MV was found to be the largest for the single lateral field plan (maximum 6.7%), less for the 3D conformal plan (maximum 3.3%) and the least for the IMRT plan (maximum 2.5%). Differences for 18 MV were generally 1-2% less. For a single lateral field, calibration with 20.8 cm achieved the minimum dosimetric difference. For 3D and IMRT plans, calibration with a 12 cm range resulted in better accuracy. Because Catphan is the standard QA phantom for the on-board imager (OBI) device, we specifically recommend not using it for the HU calibration of CBCT.

  16. Code OK2—A simulation code of ion-beam illumination on an arbitrary shape and structure target

    NASA Astrophysics Data System (ADS)

    Ogoyski, A. I.; Kawata, S.; Someya, T.

    2004-08-01

    For computer simulations on heavy ion beam (HIB) irradiation on a spherical fuel pellet in heavy ion fusion (HIF) the code OK1 was developed and presented in [Comput. Phys. Commun. 157 (2004) 160-172]. The new code OK2 is a modified upgraded computer program for more common purposes in research fields of medical treatment, material processing as well as HIF. OK2 provides computational capabilities of a three-dimensional ion beam energy deposition on a target with an arbitrary shape and structure. Program summaryTitle of program: OK2 Catalogue identifier: ADTZ Other versions of this program [1] : Title of the program: OK1 Catalogue identifier: ADST Program summary URL:http://cpc.cs.qub.as.uk/summaries/ADTZ Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Computer: PC (Pentium 4, ˜1 GHz or more recommended) Operating system: Windows or UNIX Program language used: C++ Memory required to execute with typical data: 2048 MB No. of bits in a word: 32 No. of processors used: 1CPU Has the code been vectorized or parallelized: No No. of bytes in distributed program, including test data: 17 334 No of lines in distributed program, including test date: 1487 Distribution format: tar gzip file Nature of physical problem: In research areas of HIF (Heavy Ion Beam Inertial Fusion) energy [1-4] and medical material sciences [5], ion energy deposition profiles need to be evaluated and calculated precisely. Due to a favorable energy deposition behavior of ions in matter [1-4] it is expected that ion beams would be one of preferable candidates in various fields including HIF and material processing. Especially in HIF for a successful fuel ignition and a sufficient fusion energy release, a stringent requirement is imposed on the HIB irradiation non-uniformity, which should be less than a few percent [4,6,7]. In order to meet this requirement we need to evaluate the uniformity of a realistic HIB irradiation and energy deposition pattern. The HIB

  17. Optimized mirror shape tuning using beam weightings based on distance, angle of incidence, reflectivity, and power.

    PubMed

    Goldberg, Kenneth A; Yashchuk, Valeriy V

    2016-05-01

    For glancing-incidence optical systems, such as short-wavelength optics used for nano-focusing, incorporating physical factors in the calculations used for shape optimization can improve performance. Wavefront metrology, including the measurement of a mirror's shape or slope, is routinely used as input for mirror figure optimization on mirrors that can be bent, actuated, positioned, or aligned. Modeling shows that when the incident power distribution, distance from focus, angle of incidence, and the spatially varying reflectivity are included in the optimization, higher Strehl ratios can be achieved. Following the works of Maréchal and Mahajan, optimization of the Strehl ratio (for peak intensity with a coherently illuminated system) occurs when the expectation value of the phase error's variance is minimized. We describe an optimization procedure based on regression analysis that incorporates these physical parameters. This approach is suitable for coherently illuminated systems of nearly diffraction-limited quality. Mathematically, this work is an enhancement of the methods commonly applied for ex situ alignment based on uniform weighting of all points on the surface (or a sub-region of the surface). It follows a similar approach to the optimization of apodized and non-uniformly illuminated optical systems. Significantly, it reaches a different conclusion than a more recent approach based on minimization of focal plane ray errors. PMID:27250372

  18. Airfoil-shaped extension-twist-coupled composite star-beams for rotor blade tip applications

    NASA Astrophysics Data System (ADS)

    Mahadev, Sthanu

    Rotorcraft blade tips provide the most effective region for aerodynamic control. Rotor blade airloads are proportional to dynamic pressure and as a consequence are typically the highest in the distal blade tip region. Therefore, blade control using aerodynamic forces and moments is most effectively accomplished over the distal region of the blade. Composite materials represent the preferred material option for modern rotor blade design, especially in the field of rotorcraft and wind energy, due to superior strength-to-weight ratio, fatigue resistance and their ability to be easily tailored to incorporate different coupling (bend-twist, extension-twist, etc.) among elastic modes of deformation within the structure. An additional form of tailoring can produce compliant mechanisms: structures that are capable of producing a deformation such that the resulting displacement field is similar to the kinematics of an actual mechanism. In prior research, a family of tailored composite structures referred to as "star-beams" and "modified star-beams" have been proposed and investigated as viable candidates for tension-torsion bar applications, including the case of extension-twist coupling, for which "star-beams" preserve the high level of coupling achievable in composite strips. The present work seeks to develop and investigate the extension of prior work to the case of an extension-twist coupled torsionally compliant integral blade tip configuration. The implementation of this structural concept ensures a smooth outer blade-lifting surface and that the smoothness is preserved throughout the desired deformation range while allowing out of plane cross-sectional warping via relative longitudinal sliding along the blade joints. This work focuses on passive control of pitch applications via extension-twist coupling as a result of changes in axial force, typically obtained as a result of change in centrifugal load with rotor speed for a constant thickness, symmetric NACA 0012

  19. Effects of a realistic adaptive optics system on the atmospheric propagation of a high energy laser beam

    NASA Astrophysics Data System (ADS)

    Digumarthi, Ramji V.; Mehta, Naresh C.; Blankinship, Ross M.

    1990-05-01

    An adaptive optics (AO) correction system is generally required to compensate for beam degradations caused by interactions between a high energy laser (HEL) beam and the atmosphere. The GRAND propagation code includes a model of a realistic AO system representing many features of a state-of-the-art beam control system. This AO system includes models of a wavefront sensor, a tilt mirror, a focus (secondary) mirror, and a woofer-tweeter deformable mirror arrangement. This paper reports the results of a study to assess the impact of the realistic AO system on the correctability of HEL-atmosphere interactions. The GRAND code results compare the performance of the low-pass filter model and the realistic AO system model in the presence of turbulence and moderate-to-severe thermal blooming. In addition, the effects of low frequency Kolmogorov turbulence were studied in terms of its impact on the AO system requirements.

  20. Coherent terahertz radiation generated from a square-shaped free-electron beam passing through multiple stacked layers with sub-wavelength holes

    NASA Astrophysics Data System (ADS)

    Zhou, Yucong; Zhang, Yaxin; Jiang, Guili; Wu, Zhenhua

    2015-09-01

    This paper presents terahertz (THz) coherent radiation from the interaction between a square-shaped electron beam and guiding wave mode in a multiple stacked layers with sub-wavelength holes structure. The simulated results show that such a guiding wave mode enhances the field intensity in the electron beam channel so that the interaction is more efficient than the electron beam-surface wave interaction in traditional grating and bi-grating structures. This electron-beam-driven THz source provides a way with much simpler fabrication processes and a larger square size electron beam rather than sheet beam. Furthermore, such a source can be integrated to construct a 2D source-array structure, which demonstrates a good opportunity to generate high power THz radiation.

  1. Semianalytic theory of self-similar optical propagation and mode locking using a shape-adaptive model pulse

    SciTech Connect

    Jirauschek, Christian; Ilday, F. Oemer

    2011-06-15

    A semianalytic theory for the pulse dynamics in similariton amplifiers and lasers is presented, based on a model pulse with adaptive shape. By changing a single parameter, this test function can be continuously tweaked between a pure Gaussian and a pure parabolic profile and can even represent sech-like pulses, the shape of a soliton. This approach allows us to describe the pulse evolution in the self-similar and other regimes of optical propagation. Employing the method of moments, the evolution equations for the characteristic pulse parameters are derived from the governing nonlinear Schroedinger or Ginzburg-Landau equation. Due to its greatly reduced complexity, this description allows for extensive parameter optimization, and can aid intuitive understanding of the dynamics. As an application of this approach, we model a soliton-similariton laser and validate the results against numerical simulations. This constitutes a semianalytic model of the soliton-similariton laser. Due to the versatility of the model pulse, it can also prove useful in other application areas.

  2. An Update on 34-m Beam-Waveguide Antenna Strut Shaping; Results for Four Strut Shields

    NASA Astrophysics Data System (ADS)

    Hoppe, D. J.; Khayatian, B.; Franco, M.; Britcliffe, M. J.; Gama, E.

    2015-05-01

    In a previous article, theoretical and experimental results were presented for the performance of a pair of strut shields designed to reduce the ground scatter from 34-m beam-waveguide antenna struts at low elevation angle. While the motivation for adding these shields was reduction of the ground scatter during 7.2-GHz uplink operation at 80 kW, a beneficial reduction in antenna noise temperature was also realized at low elevation angles, as expected. In addition, a somewhat unexpected but beneficial reduction in antenna noise temperature near zenith was also observed. This led to the addition of a second set of shields on the two remaining struts and experimental measurement of the zenith ground scatter, as well as a second set of noise temperature data. These four-shield results are described in this article.

  3. Fast spatial beam shaping by acousto-optic diffraction for 3D non-linear microscopy.

    PubMed

    Akemann, Walther; Léger, Jean-François; Ventalon, Cathie; Mathieu, Benjamin; Dieudonné, Stéphane; Bourdieu, Laurent

    2015-11-01

    Acousto-optic deflection (AOD) devices offer unprecedented fast control of the entire spatial structure of light beams, most notably their phase. AOD light modulation of ultra-short laser pulses, however, is not straightforward to implement because of intrinsic chromatic dispersion and non-stationarity of acousto-optic diffraction. While schemes exist to compensate chromatic dispersion, non-stationarity remains an obstacle. In this work we demonstrate an efficient AOD light modulator for stable phase modulation using time-locked generation of frequency-modulated acoustic waves at the full repetition rate of a high power laser pulse amplifier of 80 kHz. We establish the non-local relationship between the optical phase and the generating acoustic frequency function and verify the system for temporal stability, phase accuracy and generation of non-linear two-dimensional phase functions. PMID:26561090

  4. Feasibility of sealed D-T neutron generator as neutron source for liver BNCT and its beam shaping assembly.

    PubMed

    Liu, Zheng; Li, Gang; Liu, Linmao

    2014-04-01

    This paper involves the feasibility of boron neutron capture therapy (BNCT) for liver tumor with four sealed neutron generators as neutron source. Two generators are placed on each side of the liver. The high energy of these emitted neutrons should be reduced by designing a beam shaping assembly (BSA) to make them useable for BNCT. However, the neutron flux decreases as neutrons pass through different materials of BSA. Therefore, it is essential to find ways to increase the neutron flux. In this paper, the feasibility of using low enrichment uranium as a neutron multiplier is investigated to increase the number of neutrons emitted from D-T neutron generators. The neutron spectrum related to our system has a proper epithermal flux, and the fast and thermal neutron fluxes comply with the IAEA recommended values. PMID:24448270

  5. Characterization, adaptive traffic shaping, and multiplexing of real-time MPEG II video

    NASA Astrophysics Data System (ADS)

    Agrawal, Sanjay; Barry, Charles F.; Binnai, Vinay; Kazovsky, Leonid G.

    1997-01-01

    We obtain network traffic model for real-time MPEG-II encoded digital video by analyzing video stream samples from real-time encoders from NUKO Information Systems. MPEG-II sample streams include a resolution intensive movie, City of Joy, an action intensive movie, Aliens, a luminance intensive (black and white) movie, Road To Utopia, and a chrominance intensive (color) movie, Dick Tracy. From our analysis we obtain a heuristic model for the encoded video traffic which uses a 15-stage Markov process to model the I,B,P frame sequences within a group of pictures (GOP). A jointly-correlated Gaussian process is used to model the individual frame sizes. Scene change arrivals are modeled according to a gamma process. Simulations show that our MPEG-II traffic model generates, I,B,P frame sequences and frame sizes that closely match the sample MPEG-II stream traffic characteristics as they relate to latency and buffer occupancy in network queues. To achieve high multiplexing efficiency we propose a traffic shaping scheme which sets preferred 1-frame generation times among a group of encoders so as to minimize the overall variation in total offered traffic while still allowing the individual encoders to react to scene changes. Simulations show that our scheme results in multiplexing gains of up to 10% enabling us to multiplex twenty 6 Mbps MPEG-II video streams instead of 18 streams over an ATM/SONET OC3 link without latency or cell loss penalty. This scheme is due for a patent.

  6. Adaptation.

    PubMed

    Broom, Donald M

    2006-01-01

    The term adaptation is used in biology in three different ways. It may refer to changes which occur at the cell and organ level, or at the individual level, or at the level of gene action and evolutionary processes. Adaptation by cells, especially nerve cells helps in: communication within the body, the distinguishing of stimuli, the avoidance of overload and the conservation of energy. The time course and complexity of these mechanisms varies. Adaptive characters of organisms, including adaptive behaviours, increase fitness so this adaptation is evolutionary. The major part of this paper concerns adaptation by individuals and its relationships to welfare. In complex animals, feed forward control is widely used. Individuals predict problems and adapt by acting before the environmental effect is substantial. Much of adaptation involves brain control and animals have a set of needs, located in the brain and acting largely via motivational mechanisms, to regulate life. Needs may be for resources but are also for actions and stimuli which are part of the mechanism which has evolved to obtain the resources. Hence pigs do not just need food but need to be able to carry out actions like rooting in earth or manipulating materials which are part of foraging behaviour. The welfare of an individual is its state as regards its attempts to cope with its environment. This state includes various adaptive mechanisms including feelings and those which cope with disease. The part of welfare which is concerned with coping with pathology is health. Disease, which implies some significant effect of pathology, always results in poor welfare. Welfare varies over a range from very good, when adaptation is effective and there are feelings of pleasure or contentment, to very poor. A key point concerning the concept of individual adaptation in relation to welfare is that welfare may be good or poor while adaptation is occurring. Some adaptation is very easy and energetically cheap and

  7. Spontaneous decoration of Au nanoparticles on micro-patterned reduced graphene oxide shaped by focused laser beam

    SciTech Connect

    Wan, Y. C.; Tok, E. S.; Teoh, H. F.; Sow, C. H.

    2015-02-07

    We report a facile, two-step method for the micro-landscaping of Au nanoparticles(NPs) on reduced graphene oxide (rGO) film en route to micro-patterned Au(NPs)-rGO hybrid functional materials. This method employs a focused laser beam to first locally convert GO to rGO before immersing the micro-patterned GO-rGO film into HAuCl{sub 4} solution. The rGO micro-pattern, shaped by the focused laser beam, serves as nucleation sites for the reduction of Au ions. The reduction mechanism that governs the decoration of Au NPs on rGO films is akin to electroless deposition process. In this instance, surface charges that are formed during laser reduction of GO to rGO provide active nucleation sites for Au{sup 3+} ions to form Au NPs when HAuCl{sub 4} solution is introduced. The number density, the size, and size distribution of the Au NPs can thus be directly tuned and preferentially anchored onto the rGO micro-pattern by varying the incident laser power, the scanning speed of the laser, or the concentration of HAuCl{sub 4}. The resulting hybrid materials can be used as a substrate for Surface Enhanced Raman Spectroscopy (SERS). Using Rhodamine 6G as the test subject, we found an improvement of SERS enhancement over bare rGO of up to four times, depending on the size of the Au NPs.

  8. Compact D-D Neutron Source-Driven Subcritical Multiplier and Beam-Shaping Assembly for Boron Neutron Capture Therapy

    SciTech Connect

    Francesco Ganda; Jasmina Vujic; Ehud Greenspan; Ka-Ngo Leung

    2010-12-01

    This work assesses the feasibility of using a small, safe, and inexpensive keff 0.98 subcritical fission assembly [subcritical neutron multiplier (SCM)] to amplify the treatment neutron beam intensity attainable from a compact deuterium-deuterium (D-D) fusion neutron source delivering [approximately]1012 n/s. The objective is to reduce the treatment time for deep-seated brain tumors to [approximately]1 h. The paper describes the optimal SCM design and two optimal beam-shaping assemblies (BSAs) - one designed to maximize the dose rate and the other designed to maximize the total dose that can be delivered to a deep-seated tumor. The neutron beam intensity amplification achieved with the optimized SCM and BSA results in an increase in the treatment dose rate by a factor of 18: from 0.56 Gy/h without the SCM to 10.1 Gy/h. The entire SCM is encased in an aluminum structure. The total amount of 20% enriched uranium required for the SCM is 8.5 kg, and the cost (not including fabrication) is estimated to be less than $60,000. The SCM power level is estimated at 400 W when driven by a 1012 n/s D-D neutron source. This translates into consumption of only [approximately]0.6% of the initially loaded 235U atoms during 50 years of continuous operation and implies that the SCM could operate continuously for the entire lifetime of the facility without refueling. Cooling the SCM does not pose a challenge; it may be accomplished by natural circulation as the maximum heat flux is only 0.034 W/cm2.

  9. GaN nanowires with pentagon shape cross-section by ammonia-source molecular beam epitaxy

    DOE PAGESBeta

    Lin, Yong; Leung, Benjamin; Li, Qiming; Figiel, Jeffrey J.; Wang, George T.

    2015-07-14

    In this study, ammonia-based molecular beam epitaxy (NH3-MBE) was used to grow catalyst-assisted GaN nanowires on (11¯02) r-plane sapphire substrates. Dislocation free [112¯0] oriented nanowires are formed with pentagon shape cross-section, instead of the usual triangular shape facet configuration. Specifically, the cross-section is the result of the additional two nonpolar {101¯0} side facets, which appear due to a decrease in relative growth rate of the {101¯0} facets to the {101¯1} and {101¯1} facets under the growth regime in NH3-MBE. Compared to GaN nanowires grown by Ni-catalyzed metal–organic chemical vapor deposition, the NH3-MBE grown GaN nanowires show more than an ordermore » of magnitude increase in band-edge to yellow luminescence intensity ratio, as measured by cathodoluminescence, indicating improved microstructural and optical properties.« less

  10. GaN nanowires with pentagon shape cross-section by ammonia-source molecular beam epitaxy

    SciTech Connect

    Lin, Yong; Leung, Benjamin; Li, Qiming; Figiel, Jeffrey J.; Wang, George T.

    2015-07-14

    In this study, ammonia-based molecular beam epitaxy (NH3-MBE) was used to grow catalyst-assisted GaN nanowires on (11¯02) r-plane sapphire substrates. Dislocation free [112¯0] oriented nanowires are formed with pentagon shape cross-section, instead of the usual triangular shape facet configuration. Specifically, the cross-section is the result of the additional two nonpolar {101¯0} side facets, which appear due to a decrease in relative growth rate of the {101¯0} facets to the {101¯1} and {101¯1} facets under the growth regime in NH3-MBE. Compared to GaN nanowires grown by Ni-catalyzed metal–organic chemical vapor deposition, the NH3-MBE grown GaN nanowires show more than an order of magnitude increase in band-edge to yellow luminescence intensity ratio, as measured by cathodoluminescence, indicating improved microstructural and optical properties.

  11. A Mode-Shape-Based Fault Detection Methodology for Cantilever Beams

    NASA Technical Reports Server (NTRS)

    Tejada, Arturo

    2009-01-01

    An important goal of NASA's Internal Vehicle Health Management program (IVHM) is to develop and verify methods and technologies for fault detection in critical airframe structures. A particularly promising new technology under development at NASA Langley Research Center is distributed Bragg fiber optic strain sensors. These sensors can be embedded in, for instance, aircraft wings to continuously monitor surface strain during flight. Strain information can then be used in conjunction with well-known vibrational techniques to detect faults due to changes in the wing's physical parameters or to the presence of incipient cracks. To verify the benefits of this technology, the Formal Methods Group at NASA LaRC has proposed the use of formal verification tools such as PVS. The verification process, however, requires knowledge of the physics and mathematics of the vibrational techniques and a clear understanding of the particular fault detection methodology. This report presents a succinct review of the physical principles behind the modeling of vibrating structures such as cantilever beams (the natural model of a wing). It also reviews two different classes of fault detection techniques and proposes a particular detection method for cracks in wings, which is amenable to formal verification. A prototype implementation of these methods using Matlab scripts is also described and is related to the fundamental theoretical concepts.

  12. Electron Beam Freeform Fabrication (EBF3) for Cost Effective Near-Net Shape Manufacturing

    NASA Technical Reports Server (NTRS)

    Taminger, Karen M.; Hafley, Robert A.

    2006-01-01

    Manufacturing of structural metal parts directly from computer aided design (CAD) data has been investigated by numerous researchers over the past decade. Researchers at NASA Langley Research Center are developing a new solid freeform fabrication process, electron beam freeform fabrication (EBF3), as a rapid metal deposition process that works efficiently with a variety of weldable alloys. EBF3 deposits of 2219 aluminium and Ti-6Al-4V have exhibited a range of grain morphologies depending upon the deposition parameters. These materials have exhibited excellent tensile properties comparable to typical handbook data for wrought plate product after post-processing heat treatments. The EBF3 process is capable of bulk metal deposition at deposition rates in excess of 2500 cubic centimeters per hour (150 in3/hr) or finer detail at lower deposition rates, depending upon the desired application. This process offers the potential for rapidly adding structural details to simpler cast or forged structures rather than the conventional approach of machining large volumes of chips to produce a monolithic metallic structure. Selective addition of metal onto simpler blanks of material can have a significant effect on lead time reduction and lower material and machining costs.

  13. Electron Beam Freeform Fabrication for Cost Effective Near-Net Shape Manufacturing

    NASA Technical Reports Server (NTRS)

    Taminger, Karen M.; Hafley, Robert A.

    2006-01-01

    Manufacturing of structural metal parts directly from computer aided design (CAD) data has been investigated by numerous researchers over the past decade. Researchers at NASA Langley Research Center are developing a new solid freeform fabrication process, electron beam freeform fabrication (EBF3), as a rapid metal deposition process that works efficiently with a variety of weldable alloys. EBF3 deposits of 2219 aluminium and Ti-6Al-4V have exhibited a range of grain morphologies depending upon the deposition parameters. These materials have exhibited excellent tensile properties comparable to typical handbook data for wrought plate product after post-processing heat treatments. The EBF3 process is capable of bulk metal deposition at deposition rates in excess of 2500 cm3/hr (150 in3/hr) or finer detail at lower deposition rates, depending upon the desired application. This process offers the potential for rapidly adding structural details to simpler cast or forged structures rather than the conventional approach of machining large volumes of chips to produce a monolithic metallic structure. Selective addition of metal onto simpler blanks of material can have a significant effect on lead time reduction and lower material and machining costs.

  14. Beam shaping assembly of a D-T neutron source for BNCT and its dosimetry simulation in deeply-seated tumor

    NASA Astrophysics Data System (ADS)

    Faghihi, F.; Khalili, S.

    2013-08-01

    This article involves two aims for BNCT. First case includes a beam shaping assembly estimation for a D-T neutron source to find epi-thermal neutrons which are the goal in the BNCT. Second issue is the percent depth dose calculation in the adult Snyder head phantom. Monte-Carlo simulations and verification of a suggested beam shaping assembly (including internal neutron multiplier, moderator, filter, external neutron multiplier, collimator, and reflector dimensions) for thermalizing a D-T neutron source as well as increasing neutron flux are carried out and our results are given herein. Finally, we have simulated its corresponding doses for treatment planning of a deeply-seated tumor.

  15. Investigation Into the Optimum Beam Shape and Fluence for Selective Ablation of Dental Calculus at lambda = 400 nm

    SciTech Connect

    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

  16. Controllable shape-matched propagation of two signal beams in a double-Λ atomic ensemble

    NASA Astrophysics Data System (ADS)

    Li, Zhuan; Deng, Li-Ping; Xu, Li-Sen; Wang, Kaige

    2006-10-01

    We study a four-level double-Λ atomic ensemble interacting with two time-dependent signal fields and two stationary control fields. Though, in each Λ channel, a pair of signal and control fields couple resonantly with the two lower levels of atoms, the occurrences of electromagnetically induced transparency (EIT) is affected by the coherence of the four fields. In the discussion of atomic susceptibilities, we show that the quantum coherence between the two lower levels can be either formed or released according to the phase matching of the four fields. We analyze the propagation equation of the two signal fields, and find two characteristic solutions: the stationary transmission wave and the transient decay wave. The former corresponds to a correlated EIT effect in which two signal pulses are shape-matched. The latter is an opposite effect to the correlated EIT in which two pulses quench simultaneously, thus named as the correlated two-signal absorption (CTSA). We propose the CTSA condition in correspondence with the EIT condition. The numerical simulation shows that the double-Λ configuration is capable of manipulating synchronous optical signals and thus provides multiplicity and versatility in quantum information process.

  17. Accurate axial localization by conical diffraction beam shaping generating a dark-helix PSF

    NASA Astrophysics Data System (ADS)

    Fallet, Clement; Lassalle, Astrid; Dubois-Delumeau, Maxime; Sirat, Gabriel Y.

    2016-02-01

    We present here a new PSF-shaping technique using biaxial crystals to generate a highly z-dependent distribution in single molecule localization microscopy (SMLM). This distribution features two zeros of intensity that rotate together with defocus. This PSF features similarities to the double-helix introduced by Moerner and Piestun and thus has been dubbed dark-helix since we track zeros of intensity. Preliminary numerical studies based on Cramer-Rao Lower Bound (CRLB) show that this PSF has the potential to obtain up to 20nm localization precision. This PSF can be easily generated by a very simple, monolithic add-on added in front of the detection camera. Additionally, the PSF remains of the approximate size of the Airy PSF, the x-y localization precision is not substantially affected and no trade-off is required. The xy compacity of the PSF also enables theoretically a higher density of emitters than the double-helix which spreads on a larger scale. Limiting factors for SMLM such as loss of photons, complexity and robustness will be discussed and considerations about the practical implementation of such techniques will be given.

  18. a New Dynamic Finite Element (dfe) Formulation for Lateral Free Vibrations of EULER-BERNOULLI Spinning Beams Using Trigonometric Shape Functions

    NASA Astrophysics Data System (ADS)

    Hashemi, S. M.; Richard, M. J.; Dhatt, G.

    1999-03-01

    This paper presents a new Dynamic Finite Element (DFE) formulation for the vibrational analysis of spinning beams. A non-dimensional formulation is adopted, and the frequency dependent trigonometric shape functions are used to find a simple frequency dependent element stiffness matrix which has both mass and stiffness properties. An appropriate bisection method, based on a Sturm sequence root counting technique, is used and the flexural natural frequencies of cantilevered beams, for a variety of configurations, are studied. The results are compared to those found by the Dynamic Stiffness Matrix and the classical Finite Elements Method, using “Hermite” beam elements. Much better convergency rates are found using the proposed DFE method.

  19. SU-E-J-78: Adaptive Planning Workflow in a Pencil Beam Scanning Proton Therapy Center

    SciTech Connect

    Blakey, M; Price, S; Robison, B; Niek, S; Moe, S; Renegar, J; Mark, A; Spenser, W

    2015-06-15

    Purpose: The susceptibility of proton therapy to changes in patient setup and anatomy necessitates an adaptive planning process. With the right planning tools and clinical workflow, an adaptive plan can be created in a timely manner without adding significant workload to the treatment planning staff. Methods: In our center, a weekly QA CT is performed on most patients to assess setup, anatomy change, and tumor response. The QA CT is fused to the treatment planning CT, the contours are transferred via deformable registration, and the plan dose is recalculated on the QA CT. A physicist assesses the dose distribution, and an adaptive plan is requested based on tumor coverage or OAR dose changes. After the physician confirms or alters the deformed contours, a dosimetrist develops an adaptive plan using our TPS adaptation module. The plan is assessed for robustness and is then reviewed by the physician. Patient QA is performed within three days following the first adapted treatment. Results: Of the patients who received QA CTs, 19% required at least one adaptive plan (18.5% H&N, 18.5% brain, 11.1% breast, 14.8% chestwall, 14.8% lung, 18.5% pelvis and 3.8% abdomen). Of these patients, 14% went on a break, while the remainder was treated with the previous plan during the re-planning process. Adaptive plans were performed based on tumor shrinkage, anatomy change or positioning uncertainties for 37.9%, 44.8%, and 17.3% of the patients, respectively. On average, 3 full days are required between the QA CT and the first adapted plan treatment. Conclusion: Adaptive planning is a crucial component of proton therapy and should be applied to any site when the QA CT shows significant deviation from the plan. With an efficient workflow, an adaptive plan can be applied without delaying patient treatment or burdening the dosimetry and medical physics team.

  20. A highly shape-adaptive, stretchable design based on conductive liquid for energy harvesting and self-powered biomechanical monitoring

    PubMed Central

    Yi, Fang; Wang, Xiaofeng; Niu, Simiao; Li, Shengming; Yin, Yajiang; Dai, Keren; Zhang, Guangjie; Lin, Long; Wen, Zhen; Guo, Hengyu; Wang, Jie; Yeh, Min-Hsin; Zi, Yunlong; Liao, Qingliang; You, Zheng; Zhang, Yue; Wang, Zhong Lin

    2016-01-01

    The rapid growth of deformable and stretchable electronics calls for a deformable and stretchable power source. We report a scalable approach for energy harvesters and self-powered sensors that can be highly deformable and stretchable. With conductive liquid contained in a polymer cover, a shape-adaptive triboelectric nanogenerator (saTENG) unit can effectively harvest energy in various working modes. The saTENG can maintain its performance under a strain of as large as 300%. The saTENG is so flexible that it can be conformed to any three-dimensional and curvilinear surface. We demonstrate applications of the saTENG as a wearable power source and self-powered sensor to monitor biomechanical motion. A bracelet-like saTENG worn on the wrist can light up more than 80 light-emitting diodes. Owing to the highly scalable manufacturing process, the saTENG can be easily applied for large-area energy harvesting. In addition, the saTENG can be extended to extract energy from mechanical motion using flowing water as the electrode. This approach provides a new prospect for deformable and stretchable power sources, as well as self-powered sensors, and has potential applications in various areas such as robotics, biomechanics, physiology, kinesiology, and entertainment. PMID:27386560

  1. A highly shape-adaptive, stretchable design based on conductive liquid for energy harvesting and self-powered biomechanical monitoring.

    PubMed

    Yi, Fang; Wang, Xiaofeng; Niu, Simiao; Li, Shengming; Yin, Yajiang; Dai, Keren; Zhang, Guangjie; Lin, Long; Wen, Zhen; Guo, Hengyu; Wang, Jie; Yeh, Min-Hsin; Zi, Yunlong; Liao, Qingliang; You, Zheng; Zhang, Yue; Wang, Zhong Lin

    2016-06-01

    The rapid growth of deformable and stretchable electronics calls for a deformable and stretchable power source. We report a scalable approach for energy harvesters and self-powered sensors that can be highly deformable and stretchable. With conductive liquid contained in a polymer cover, a shape-adaptive triboelectric nanogenerator (saTENG) unit can effectively harvest energy in various working modes. The saTENG can maintain its performance under a strain of as large as 300%. The saTENG is so flexible that it can be conformed to any three-dimensional and curvilinear surface. We demonstrate applications of the saTENG as a wearable power source and self-powered sensor to monitor biomechanical motion. A bracelet-like saTENG worn on the wrist can light up more than 80 light-emitting diodes. Owing to the highly scalable manufacturing process, the saTENG can be easily applied for large-area energy harvesting. In addition, the saTENG can be extended to extract energy from mechanical motion using flowing water as the electrode. This approach provides a new prospect for deformable and stretchable power sources, as well as self-powered sensors, and has potential applications in various areas such as robotics, biomechanics, physiology, kinesiology, and entertainment. PMID:27386560

  2. Adapt

    NASA Astrophysics Data System (ADS)

    Bargatze, L. F.

    2015-12-01

    Active Data Archive Product Tracking (ADAPT) is a collection of software routines that permits one to generate XML metadata files to describe and register data products in support of the NASA Heliophysics Virtual Observatory VxO effort. ADAPT is also a philosophy. The ADAPT concept is to use any and all available metadata associated with scientific data to produce XML metadata descriptions in a consistent, uniform, and organized fashion to provide blanket access to the full complement of data stored on a targeted data server. In this poster, we present an application of ADAPT to describe all of the data products that are stored by using the Common Data File (CDF) format served out by the CDAWEB and SPDF data servers hosted at the NASA Goddard Space Flight Center. These data servers are the primary repositories for NASA Heliophysics data. For this purpose, the ADAPT routines have been used to generate data resource descriptions by using an XML schema named Space Physics Archive, Search, and Extract (SPASE). SPASE is the designated standard for documenting Heliophysics data products, as adopted by the Heliophysics Data and Model Consortium. The set of SPASE XML resource descriptions produced by ADAPT includes high-level descriptions of numerical data products, display data products, or catalogs and also includes low-level "Granule" descriptions. A SPASE Granule is effectively a universal access metadata resource; a Granule associates an individual data file (e.g. a CDF file) with a "parent" high-level data resource description, assigns a resource identifier to the file, and lists the corresponding assess URL(s). The CDAWEB and SPDF file systems were queried to provide the input required by the ADAPT software to create an initial set of SPASE metadata resource descriptions. Then, the CDAWEB and SPDF data repositories were queried subsequently on a nightly basis and the CDF file lists were checked for any changes such as the occurrence of new, modified, or deleted

  3. Phase Adaptation and Correction by Adaptive Optics

    NASA Astrophysics Data System (ADS)

    Tiziani, Hans J.

    2010-04-01

    Adaptive optical elements and systems for imaging or laser beam propagation are used for some time in particular in astronomy, where the image quality is degraded by atmospheric turbulence. In astronomical telescopes a deformable mirror is frequently used to compensate wavefront-errors due to deformations of the large mirror, vibrations as well as turbulence and hence to increase the image quality. In the last few years interesting elements like Spatial Light Modulators, SLM's, such as photorefractive crystals, liquid crystals and micro mirrors and membrane mirrors were introduced. The development of liquid crystals and micro mirrors was driven by data projectors as consumer products. They contain typically a matrix of individually addressable pixels of liquid crystals and flip mirrors respectively or more recently piston mirrors for special applications. Pixel sizes are in the order of a few microns and therefore also appropriate as active diffractive elements in digital holography or miniature masks. Although liquid crystals are mainly optimized for intensity modulation; they can be used for phase modulation. Adaptive optics is a technology for beam shaping and wavefront adaptation. The application of spatial light modulators for wavefront adaptation and correction and defect analysis as well as sensing will be discussed. Dynamic digital holograms are generated with liquid crystal devices (LCD) and used for wavefront correction as well as for beam shaping and phase manipulation, for instance. Furthermore, adaptive optics is very useful to extend the measuring range of wavefront sensors and for the wavefront adaptation in order to measure and compare the shape of high precision aspherical surfaces.

  4. Ablation depth control with 40 nm resolution on ITO thin films using a square, flat top beam shaped femtosecond NIR laser

    NASA Astrophysics Data System (ADS)

    Kim, Hoon-Young; Yoon, Ji-Wook; Choi, Won-Suk; Kim, Kwang-Ryul; Cho, Sung-Hak

    2016-09-01

    We reported on the ablation depth control with a resolution of 40 nm on indium tin oxide (ITO) thin film using a square beam shaped femtosecond (190 fs) laser (λp=1030 nm). A slit is used to make the square, flat top beam shaped from the Gaussian spatial profile of the femtosecond laser. An ablation depth of 40 nm was obtained using the single pulse irradiation at a peak intensity of 2.8 TW/cm2. The morphologies of the ablated area were characterized using an optical microscope, atomic force microscope (AFM), and energy dispersive X-ray spectroscopy (EDS). Ablations with square and rectangular types with various sizes were demonstrated on ITO thin film using slits with varying x-y axes. The stereo structure of the ablation with the depth resolution of approximately 40 nm was also fabricated successfully using the irradiation of single pulses with different shaped sizes of femtosecond laser.

  5. Improvement of uniformity of the negative ion beams by tent-shaped magnetic field in the JT-60 negative ion source

    SciTech Connect

    Yoshida, Masafumi Hanada, Masaya; Kojima, Atsushi; Kashiwagi, Mieko; Akino, Noboru; Endo, Yasuei; Komata, Masao; Mogaki, Kazuhiko; Nemoto, Shuji; Ohzeki, Masahiro; Seki, Norikazu; Sasaki, Shunichi; Shimizu, Tatsuo; Terunuma, Yuto; Grisham, Larry R.

    2014-02-15

    Non-uniformity of the negative ion beams in the JT-60 negative ion source with the world-largest ion extraction area was improved by modifying the magnetic filter in the source from the plasma grid (PG) filter to a tent-shaped filter. The magnetic design via electron trajectory calculation showed that the tent-shaped filter was expected to suppress the localization of the primary electrons emitted from the filaments and created uniform plasma with positive ions and atoms of the parent particles for the negative ions. By modifying the magnetic filter to the tent-shaped filter, the uniformity defined as the deviation from the averaged beam intensity was reduced from 14% of the PG filter to ∼10% without a reduction of the negative ion production.

  6. Cylindrical Illumination Confocal Spectroscopy: Rectifying the Limitations of Confocal Single Molecule Spectroscopy through One-Dimensional Beam Shaping

    PubMed Central

    Liu, Kelvin J.; Wang, Tza-Huei

    2008-01-01

    Cylindrical illumination confocal spectroscopy (CICS) is a new implementation of single molecule detection that can be generically incorporated into any microfluidic system and allows highly quantitative and accurate analysis of single fluorescent molecules. Through theoretical modeling of confocal optics and Monte Carlo simulations, one-dimensional beam shaping is used to create a highly uniform sheet-like observation volume that enables the detection of digital fluorescence bursts while retaining single fluorophore sensitivity. First, we theoretically show that when used to detect single molecules in a microchannel, CICS can be optimized to obtain near 100% mass detection efficiency, <10% relative SD in burst heights, and a high signal/noise ratio. As a result, CICS is far less sensitive to thresholding artifacts than traditional single molecule detection and significantly more accurate at determining both burst rate and burst parameters. CICS is then experimentally implemented, optically characterized, and integrated into separate two microfluidic devices for the analysis of fluorescently stained plasmid DNA and single Cy5 labeled oligonucleotides. CICS rectifies the limitations of traditional confocal spectroscopy-based single molecule detection without the significant operational complications of competing technologies. PMID:18515376

  7. Input shaping for vibration-damped slewing of a flexible beam using a heavy-lift hydraulic robot

    SciTech Connect

    Parker, G.G.; Eisler, R.; Phelan, J.; Robinett, R.D.

    1994-08-01

    An input shaping scheme originally used to slew flexible beams via a tabletop D.C. motor is modified for use with an industrial-type, hydraulic-drive robot. This trajectory generation method was originally developed to produce symmetric, rest-to-rest maneuvers of flexible rotating rods where the angular velocity vector and gravitational vector were collinear. In that configuration, out-of-plane oscillations were excited due to centripetal acceleration of the rod. The bang-coast-bang acceleration profile resulted in no oscillations in either plane at the end of the symmetric slew maneuver. In this paper, a smoothed version of the bang-coast-bang acceleration is used for symmetric maneuvers where the angular velocity vector is orthogonal to the gravitational vector. Furthermore, the hydraulic robot servo dynamics are considered explicitly in determining the input joint angle trajectory. An instrumented mass is attached to the tip of a flexible aluminum rod. The first natural frequency of this system is about 1.0Hz. Joint angle responses obtained with encoder sensors are used to identify the servo actuator dynamics.

  8. An evaluation on the design of beam shaping assembly based on the D-T reaction for BNCT

    NASA Astrophysics Data System (ADS)

    Asnal, M.; Liamsuwan, T.; Onjun, T.

    2015-05-01

    Boron Neutron Capture Therapy (BNCT) can be achieved by using a compact neutron generator such as a compact D-T neutron source, in which neutron energy must be in the epithermal energy range with sufficient flux. For these requirements, a Beam Shaping Assembly (BSA) is needed. In this paper, three BSA designs based on the D-T reaction for BNCT are discussed. It is found that the BSA configuration designed by Rasouli et al. satisfies all of the International Atomic Energy Agency (IAEA) criteria. It consists of 14 cm uranium as multiplier, 23 cm TiF3 and 36 cm Fluental as moderator, 4 cm Fe as fast neutron filter, 1 mm Li as thermal neutron filter, 2.6 cm Bi as gamma ray filter, and Pb as collimator and reflector. It is also found that use of specific filters is important for removing the fast and thermal neutrons and gamma contamination. Moreover, an appropriate neutron source plays a key role in providing a proper epithermal flux.

  9. Adjustable mounting device for high-volume production of beam-shaping systems for high-power diode lasers

    NASA Astrophysics Data System (ADS)

    Haag, Sebastian; Bernhardt, Henning; Rübenach, Olaf; Haverkamp, Tobias; Müller, Tobias; Zontar, Daniel; Brecher, Christian

    2015-02-01

    In many applications for high-power diode lasers, the production of beam-shaping and homogenizing optical systems experience rising volumes and dynamical market demands. The automation of assembly processes on flexible and reconfigurable machines can contribute to a more responsive and scalable production. The paper presents a flexible mounting device designed for the challenging assembly of side-tab based optical systems. It provides design elements for precisely referencing and fixating two optical elements in a well-defined geometric relation. Side tabs are presented to the machine allowing the application of glue and a rotating mechanism allows the attachment to the optical elements. The device can be adjusted to fit different form factors and it can be used in high-volume assembly machines. The paper shows the utilization of the device for a collimation module consisting of a fast-axis and a slow-axis collimation lens. Results regarding the repeatability and process capability of bonding side tab assemblies as well as estimates from 3D simulation for overall performance indicators achieved such as cycle time and throughput will be discussed.

  10. Adaptation of ion beam technology to microfabrication of solid state devices and transducers

    NASA Technical Reports Server (NTRS)

    Topich, J. A.

    1978-01-01

    A number of areas were investigated to determine the potential uses of ion beam techniques in the construction of solid state devices and transducers and the packaging of implantable electronics for biomedical applications. The five areas investigated during the past year were: (1) diode-like devices fabricated on textured silicon; (2) a photolithographic technique for patterning ion beam sputtered PVC (polyvinyl chloride); (3) use of sputtered Teflon as a protective coating for implantable pressure sensors; (4) the sputtering of Macor to seal implantable hybrid circuits; and (5) the use of sputtered Teflon to immobilize enzymes.

  11. Adaptation of ion beam technology to microfabrication of solid state devices and transducers

    NASA Technical Reports Server (NTRS)

    Topich, J. A.

    1977-01-01

    It was found that ion beam texturing of silicon surfaces can be used to increase the effective surface area of MOS capacitors. There is, however, a problem with low dielectric breakdown. Preliminary work was begun on the fabrication of ion implanted resistors on textured surfaces and the potential improvement of wire bond strength by bonding to a textured surface. In the area of ion beam sputtering, the techniques for sputtering PVC were developed. A PVC target containing valinomycin was used to sputter an ion selective membrane on a field effect transistor to form a potassium ion sensor.

  12. Proton-beam driven fast ignition of inertially confined fuels: Reduction of the ignition energy by the use of two proton beams with radially shaped profiles

    SciTech Connect

    Temporal, M.; Honrubia, J. J.; Atzeni, S.

    2008-05-15

    Fast ignition of a spherical compressed deuterium-tritium assembly induced by the energy deposition of laser-accelerated proton beams is considered. An efficient way to reduce the ignition energy consists of using a two proton beams scheme [M. Temporal, Phys Plasmas 13, 122704 (2006)]. For a uniformly compressed fuel at 500 g/cm{sup 3} irradiated by proton beams with Maxwellian energy distribution with a temperature of 4 MeV, the ignition energy is 10 kJ using only one proton beam and reduces to a total of 8 kJ with the two-beam scheme. Further reduction of the ignition energy is found by using a first beam with annular radial profile and a second beam with the uniform radial profile. It is found that the first beam causes some additional fuel compression and confinement that decrease the total beam energy required for the ignition to 6 kJ, which is 40% smaller than in the case of a single beam with uniform radial profile.

  13. Investigations on ring-shaped pumping distributions for the generation of beams with radial polarization in an Yb:YAG thin-disk laser.

    PubMed

    Dietrich, Tom; Rumpel, Martin; Graf, Thomas; Ahmed, Marwan Abdou

    2015-10-01

    We present experimental investigations on the generation of radially polarized laser beams excited by a ring-shaped pump intensity distribution in combination with polarizing grating waveguide mirrors in an Yb:YAG thin-disk laser resonator. Hollow optical fiber components were implemented in the pump beam path to transform the commonly used flattop pumping distribution into a ring-shaped distribution. The investigation was focused on finding the optimum mode overlap between the ring-shaped pump spot and the excited first order Laguerre-Gaussian (LG(01)) doughnut mode. The power, efficiency and polarization state of the emitted laser beam as well as the thermal behavior of the disk was compared to that obtained with a standard flattop pumping distribution. A maximum output power of 107 W with a high optical efficiency of 41.2% was achieved by implementing a 300 mm long specially manufactured hollow fiber into the pump beam path. Additionally it was found that at a pump power of 280 W the maximum temperature increase is about 21% below the one observed with standard homogeneous pumping. PMID:26480177

  14. Thermal deformation of cryogenically cooled silicon crystals under intense X-ray beams: measurement and finite-element predictions of the surface shape.

    PubMed

    Zhang, Lin; Sánchez Del Río, Manuel; Monaco, Giulio; Detlefs, Carsten; Roth, Thomas; Chumakov, Aleksandr I; Glatzel, Pieter

    2013-07-01

    X-ray crystal monochromators exposed to white-beam X-rays in third-generation synchrotron light sources are subject to thermal deformations that must be minimized using an adequate cooling system. A new approach was used to measure the crystal shape profile and slope of several cryogenically cooled (liquid nitrogen) silicon monochromators as a function of beam power in situ and under heat load. The method utilizes multiple angular scans across the Bragg peak (rocking curve) at various vertical positions of a narrow-gap slit downstream from the monochromator. When increasing the beam power, the surface of the liquid-nitrogen-cooled silicon crystal deforms from a concave shape at low heat load to a convex shape at high heat load, passing through an approximately flat shape at intermediate heat load. Finite-element analysis is used to calculate the crystal thermal deformations. The simulated crystal profiles and slopes are in excellent agreement with experiments. The parameters used in simulations, such as material properties, absorbed power distribution on the crystal and cooling boundary conditions, are described in detail as they are fundamental for obtaining accurate results. PMID:23765298

  15. Thermal deformation of cryogenically cooled silicon crystals under intense X-ray beams: measurement and finite-element predictions of the surface shape

    PubMed Central

    Zhang, Lin; Sánchez del Río, Manuel; Monaco, Giulio; Detlefs, Carsten; Roth, Thomas; Chumakov, Aleksandr I.; Glatzel, Pieter

    2013-01-01

    X-ray crystal monochromators exposed to white-beam X-rays in third-generation synchrotron light sources are subject to thermal deformations that must be minimized using an adequate cooling system. A new approach was used to measure the crystal shape profile and slope of several cryogenically cooled (liquid nitrogen) silicon monochromators as a function of beam power in situ and under heat load. The method utilizes multiple angular scans across the Bragg peak (rocking curve) at various vertical positions of a narrow-gap slit downstream from the monochromator. When increasing the beam power, the surface of the liquid-nitrogen-cooled silicon crystal deforms from a concave shape at low heat load to a convex shape at high heat load, passing through an approximately flat shape at intermediate heat load. Finite-element analysis is used to calculate the crystal thermal deformations. The simulated crystal profiles and slopes are in excellent agreement with experiments. The parameters used in simulations, such as material properties, absorbed power distribution on the crystal and cooling boundary conditions, are described in detail as they are fundamental for obtaining accurate results. PMID:23765298

  16. Shaping ability of Reciproc and TF Adaptive systems in severely curved canals of rapid microCT-based prototyping molar replicas

    PubMed Central

    ORDINOLA-ZAPATA, Ronald; BRAMANTE, Clovis Monteiro; DUARTE, Marco Antonio Húngaro; CAVENAGO, Bruno Cavalini; JARAMILLO, David; VERSIANI, Marco Aurélio

    2014-01-01

    Objective: To evaluate the shaping ability of Reciproc and Twisted-File Adaptive systems in rapid prototyping replicas. Material and Methods: Two mandibular molars showing S-shaped and 62-degree curvatures in the mesial root were scanned by using a microcomputed tomography (μCT) system. The data were exported in the stereolitograhic format and 20 samples of each molar were printed at 16 µm resolution. The mesial canals of 10 replicas of each specimen were prepared with each system. Transportation was measured by overlapping radiographs taken before and after preparation and resin thickness after instrumentation was measured by μCT. Results: Both systems maintained the original shape of the apical third in both anatomies (P>0.05). Overall, considering the resin thickness in the 62-degree replicas, no statistical difference was found between the systems (P>0.05). In the S-shaped curvature replica, Reciproc significantly decreased the thickness of the resin walls in comparison with TF Adaptive. Conclusions: The evaluated systems were able to maintain the original shape at the apical third of severely curved mesial canals of molar replicas. PMID:24918662

  17. Experimental Profiling of a Non-truncated Focused Gaussian Beam and Fine-tuning of the Quadratic Phase in the Fresnel Gaussian Shape Invariant

    SciTech Connect

    S., Juan Manuel Franco; Cywiak, Moises; Cywiak, David; Mourad, Idir

    2015-06-24

    A homodyne profiler is used for recording the intensity distribution of focused non-truncated Gaussian beams. The spatial distributions are obtained at planes in the vicinity of the back-focal plane of a focusing lens placed at different distances from a He–Ne laser beam with a Gaussian intensity profile. Comparisons of the experimental data with those obtained from the analytical equations for an ideal focusing lens allow us to propose formulae to fine-tune the quadratic term in the Fresnel Gaussian shape invariant at each interface of the propagated field. Furthermore, we give analytical expressions to calculate adequately the propagation of the field through an optical system.

  18. Adaptation of a polyphagous herbivore to a novel host plant extensively shapes the transcriptome of herbivore and host.

    PubMed

    Wybouw, Nicky; Zhurov, Vladimir; Martel, Catherine; Bruinsma, Kristie A; Hendrickx, Frederik; Grbić, Vojislava; Van Leeuwen, Thomas

    2015-09-01

    Generalist arthropod herbivores rapidly adapt to a broad range of host plants. However, the extent of transcriptional reprogramming in the herbivore and its hosts associated with adaptation remains poorly understood. Using the spider mite Tetranychus urticae and tomato as models with available genomic resources, we investigated the reciprocal genomewide transcriptional changes in both spider mite and tomato as a consequence of mite's adaptation to tomato. We transferred a genetically diverse mite population from bean to tomato where triplicated populations were allowed to propagate for 30 generations. Evolving populations greatly increased their reproductive performance on tomato relative to their progenitors when reared under identical conditions, indicative of genetic adaptation. Analysis of transcriptional changes associated with mite adaptation to tomato revealed two main components. First, adaptation resulted in a set of mite genes that were constitutively downregulated, independently of the host. These genes were mostly of an unknown function. Second, adapted mites mounted an altered transcriptional response that had greater amplitude of changes when re-exposed to tomato, relative to nonadapted mites. This gene set was enriched in genes encoding detoxifying enzymes and xenobiotic transporters. Besides the direct effects on mite gene expression, adaptation also indirectly affected the tomato transcriptional responses, which were attenuated upon feeding of adapted mites, relative to the induced responses by nonadapted mite feeding. Thus, constitutive downregulation and increased transcriptional plasticity of genes in a herbivore may play a central role in adaptation to host plants, leading to both a higher detoxification potential and reduced production of plant defence compounds. PMID:26211543

  19. Mechanically adaptive and shape-memory behaviour of chitosan-modified cellulose whisker/elastomer composites in different pH environments.

    PubMed

    Wu, Tongfei; Su, Yuli; Chen, Biqiong

    2014-09-15

    Biomimetic polymer composites with water-active mechanically adaptive and shape-memory behaviour in different pH environments are synthesised by using chitosan-modified cellulose whiskers (CS-CWs) as the stimulus-responsive phase and thermoplastic polyurethane (TPU) as the resilient matrix. The effect of surface modification on the mechanically adaptive behaviour of CS-CW/TPU composites is investigated by using three representative solutions with various pH values. The results show that surface modification significantly enhances the modulus contrast under wet and dry conditions with the acidic solution as the stimulus, while maintaining the high modulus contrast with the basic solution as the stimulus. CS-CW/TPU composites also exhibit excellent shape-memory effects in all three solutions that are comparable to those pristine CW/TPU composites. Furthermore, activation of force generation in the stretched CS-CW/TPU composites by water absorption/desorption was observed. PMID:24976483

  20. Uniform longitudinal beam profiles in the Fermilab Recycler using adaptive rf correction

    SciTech Connect

    Hu, Martin; Broemmelsiek, Daniel Robert; Chase, Brian; Crisp, James L.; Eddy, Nathan; Joireman, Paul W.; Ng, King Yuen; /Fermilab

    2007-06-01

    The Fermilab Recycler Ring is a permanent magnet based 8 GeV anti-proton storage ring. A wideband RF system, driven with ARB's (ARBitrary waveform generators), allows the system to produce programmable barrier waveforms. Beam current profile distortion was observed, its origin verified both experimentally and theoretically, and an FPGA-based correction system was designed, tested and implemented to level the bunch profile.

  1. Beam Halo Measurements at UMER and the JLAB FEL Using an Adaptive Masking Method

    SciTech Connect

    Zhang, H D; Fiorito, R B; Kishek, R A; O' Shea, P G; Shkvarunets, A G; Benson, S V; Douglas, D; Wilson, F G

    2011-03-01

    Beam halo is a chal­leng­ing issue for in­tense beams since it can cause beam loss, emit­tance growth, nu­cle­ar ac­ti­va­tion and sec­ondary elec­tron emis­sion. Be­cause of the po­ten­tial­ly low num­ber of par­ti­cles in the halo com­pared with beam core, tra­di­tion­al imag­ing meth­ods may not have suf­fi­cient con­trast to de­tect faint halos. We have de­vel­oped a high dy­nam­ic range, adap­tive mask­ing method to mea­sure halo using a dig­i­tal mi­cro-mir­ror array de­vice and demon­strat­ed its ef­fec­tive­ness ex­per­i­men­tal­ly on the Uni­ver­si­ty of Mary­land Elec­tron Ring (UMER). We also re­port on sim­i­lar ex­per­i­ments cur­rent­ly in progress at the Jef­fer­son Lab Free Elec­tron Laser (FEL) using this method.

  2. Differential Polarization Nonlinear Optical Microscopy with Adaptive Optics Controlled Multiplexed Beams

    PubMed Central

    Samim, Masood; Sandkuijl, Daaf; Tretyakov, Ian; Cisek, Richard; Barzda, Virginijus

    2013-01-01

    Differential polarization nonlinear optical microscopy has the potential to become an indispensable tool for structural investigations of ordered biological assemblies and microcrystalline aggregates. Their microscopic organization can be probed through fast and sensitive measurements of nonlinear optical signal anisotropy, which can be achieved with microscopic spatial resolution by using time-multiplexed pulsed laser beams with perpendicular polarization orientations and photon-counting detection electronics for signal demultiplexing. In addition, deformable membrane mirrors can be used to correct for optical aberrations in the microscope and simultaneously optimize beam overlap using a genetic algorithm. The beam overlap can be achieved with better accuracy than diffraction limited point-spread function, which allows to perform polarization-resolved measurements on the pixel-by-pixel basis. We describe a newly developed differential polarization microscope and present applications of the differential microscopy technique for structural studies of collagen and cellulose. Both, second harmonic generation, and fluorescence-detected nonlinear absorption anisotropy are used in these investigations. It is shown that the orientation and structural properties of the fibers in biological tissue can be deduced and that the orientation of fluorescent molecules (Congo Red), which label the fibers, can be determined. Differential polarization microscopy sidesteps common issues such as photobleaching and sample movement. Due to tens of megahertz alternating polarization of excitation pulses fast data acquisition can be conveniently applied to measure changes in the nonlinear signal anisotropy in dynamically changing in vivo structures. PMID:24022688

  3. Design, development, and performance of an adapter for simulation of ocular melanoma patients in supine position for proton beam therapy

    NASA Astrophysics Data System (ADS)

    Daftari, I.; Phillips, T. L.

    2003-06-01

    A patient assembly adapter system for ocular melanoma patient simulation was developed and its performance evaluated. The aim for the construction of the apparatus was to simulate the patients in supine position using a commercial x-ray simulator. The apparatus consists of a base plate, head immobilization holder, patient assembly system that includes fixation light and collimator system. The reproducibility of the repeated fixation was initially tested with a head phantom. Simulation and verification films were studied for seven consecutive patients treated with proton beam therapy. Patient's simulation was performed in a supine position using a dental fixation bite block and a thermoplastic head mask immobilization device with a patient adapter system. Two orthogonal x rays were used to obtain the x, y, and z coordinates of sutured tantalum rings for treatment planning with the EYEPLAN software. The verification films were obtained in treatment position with the fixation light along the central axis of the eye. The results indicate good agreement within 0.5 mm deviations. The results of this investigation showed that the same planning accuracy could be achieved by performing simulation using the adapter described above with a patient in the supine position as that obtained by performing simulation with the patient in the seated, treatment position. The adapter can also be attached to the head of the chair for simulating in the seated position using a fixed x-ray unit. This has three advantages: (1) this will save radiation therapists time; (2) it eliminates the need for arranging access to the treatment room, thus avoiding potential conflicts in treatment room usage; and (3) it allows the use of a commercial simulator.

  4. An adaptation of modal analysis to the computation of steady bending loads on a rotating beam

    NASA Astrophysics Data System (ADS)

    Corrigan, J.; Sadler, G.; Yuce, Mithat

    Modal summation or modal displacement methods are not capable of computing the steady bending moments on a rotating beam. Even if it were possible to use an infinite number of blade modes, it would not be possible to obtain a correct solution. There is a way to circumvent this problem by properly combining a force integration formulation with a modal summation approach. At Bell Helicopter Textron, Inc., modifications have been made in the blade loads methodology which allow for the computation of steady loads. The methodology was recently enhanced further to accommodate all types of rotor hubs.

  5. The novel adaptive rotating beam test unmasks sensorimotor impairments in a transgenic mouse model of Parkinson's disease.

    PubMed

    Gerstenberger, Julia; Bauer, Anne; Helmschrodt, Christin; Richter, Angelika; Richter, Franziska

    2016-05-01

    Development of disease modifying therapeutics for Parkinson's disease (PD), the second most common neurodegenerative disorder, relies on availability of animal models which recapitulate the disease hallmarks. Only few transgenic mouse models, which mimic overexpression of alpha-synuclein, show dopamine loss, behavioral impairments and protein aggregation. Mice overexpressing human wildtype alpha-synuclein under the Thy-1 promotor (Thy1-aSyn) replicate these features. However, female mice do not exhibit a phenotype. This was attributed to a potentially lower transgene expression located on the X chromosome. Here we support that female mice overexpress human wildtype alpha-synuclein only about 1.5 fold in the substantia nigra, compared to about 3 fold in male mice. Since female Thy1-aSyn mice were shown previously to exhibit differences in corticostriatal communication and synaptic plasticity similar to their male counterparts we hypothesized that female mice use compensatory mechanisms and strategies to not show overt motor deficits despite an underlying endophenotype. In order to unmask these deficits we translated recent findings in PD patients that sensory abnormalities can enhance motor dysfunction into a novel behavioral test, the adaptive rotating beam test. We found that under changing sensory input female Thy1-aSyn mice showed an overt phenotype. Our data supports that the integration of sensorimotor information is likely a major contributor to symptoms of movement disorders and that even low levels of overexpression of human wildtype alpha-synuclein has the potential to disrupt processing of these information. The here described adaptive rotating beam test represents a sensitive behavioral test to detect moderate sensorimotor alterations in mouse models. PMID:26880341

  6. Conceptual design of a high precision dual directional beam position monitoring system for beam crosstalk cancellation and improved output pulse shapes

    SciTech Connect

    Thieberger P.; Dawson, C.; Fischer, W.; Gassner, D.; Hulsart, R.; Mernick, K.; Michnoff, R.; Minty, M.

    2012-04-15

    The Relativistic Heavy Ions Collider (RHIC) would benefit from improved beam position measurements near the interaction points that see both beams, especially as the tolerances become tighter when reducing the beam sizes to obtain increased luminosity. Two limitations of the present beam position monitors (BPMs) would be mitigated if the proposed approach is successful. The small but unavoidable cross-talk between signals from bunches traveling in opposite directions when using conventional BPMs will be reduced by adopting directional BPMs. Further improvements will be achieved by cancelling residual cross-talk using pairs of such BPMs. Appropriately delayed addition and integration of the signals will also provide pulses with relatively flat maxima that will be easier to digitize by relaxing the presently very stringent timing requirements.

  7. Analysis of shape and spatial interaction of synaptic vesicles using data from focused ion beam scanning electron microscopy (FIB-SEM)

    PubMed Central

    Khanmohammadi, Mahdieh; Waagepetersen, Rasmus P.; Sporring, Jon

    2015-01-01

    The spatial interactions of synaptic vesicles in synapses were assessed after a detailed characterization of size, shape, and orientation of the synaptic vesicles. We hypothesized that shape and orientation of the synaptic vesicles are influenced by their movement toward the active zone causing deviations from spherical shape and systematic trends in their orientation. We studied three-dimensional representations of synapses obtained by manual annotation of focused ion beam scanning electron microscopy (FIB-SEM) images of male mouse brain. The configurations of synaptic vesicles were regarded as marked point patterns, where the points are the centers of the vesicles, and the mark of a vesicle is given by its size, shape, and orientation characteristics. Statistics for marked point processes were employed to study spatial interactions between vesicles. We found that the synaptic vesicles in excitatory synapses appeared to be of oblate ellipsoid shape and in inhibitory synapses appeared to be of cigar ellipsoid shape, and followed a systematic pattern regarding their orientation toward the active zone. Moreover, there was strong evidence of spatial alignment in the orientations of pairs of synaptic vesicles, and of repulsion between them only in excitatory synapses, beyond that caused by their physical extent. PMID:26388743

  8. A new adaptive light beam focusing principle for scanning light stimulation systems

    SciTech Connect

    Bitzer, L. A.; Meseth, M.; Benson, N.; Schmechel, R.

    2013-02-15

    In this article a novel principle to achieve optimal focusing conditions or rather the smallest possible beam diameter for scanning light stimulation systems is presented. It is based on the following methodology: First, a reference point on a camera sensor is introduced where optimal focusing conditions are adjusted and the distance between the light focusing optic and the reference point is determined using a laser displacement sensor. In a second step, this displacement sensor is used to map the topography of the sample under investigation. Finally, the actual measurement is conducted, using optimal focusing conditions in each measurement point at the sample surface, that are determined by the height difference between camera sensor and the sample topography. This principle is independent of the measurement values, the optical or electrical properties of the sample, the used light source, or the selected wavelength. Furthermore, the samples can be tilted, rough, bent, or of different surface materials. In the following the principle is implemented using an optical beam induced current system, but basically it can be applied to any other scanning light stimulation system. Measurements to demonstrate its operation are shown, using a polycrystalline silicon solar cell.

  9. Process Optimization through Adaptation of Shielding Gas Selection and Feeding during Laser Beam Welding

    NASA Astrophysics Data System (ADS)

    Patschger, Andreas; Sahib, Christoffer; Bergmann, Jean Pierre; Bastick, André

    For this paper the influence of the shielding gas itself as well as the feeding method on austenitic welding joints was examined with thin sheets frequently used in the household appliance industry. The composition of the shielding gas mixture with active and/or inert gases was varied in the examination, and the effect on the weld seam could be made clear. By comparing different shielding gas feeding concepts, the process was optimized with regard to seam formation. Moreover, the influence of oxygen on the seam shape was examined in the deep welding regime on a specific example.

  10. SU-E-T-107: Development of a GPU-Based Dose Delivery System for Adaptive Pencil Beam Scanning

    SciTech Connect

    Giordanengo, S; Russo, G; Marchetto, F; Attili, A; Monaco, V; Varasteh, M; Pella, A

    2014-06-01

    Purpose: A description of a GPU-based dose delivery system (G-DDS) to integrate a fast forward planning implementing in real-time the prescribed sequence of pencil beams. The system, which is under development, is designed to evaluate the dose distribution deviations due to range variations and interplay effects affecting mobile tumors treatments. Methods: The Dose Delivery System (DDS) in use at the Italian Centro Nazionale di Adroterapia Oncologica (CNAO), is the starting point for the presented system. A fast and partial forward planning (FP) tool has been developed to evaluate in few seconds the delivered dose distributions using the DDS data (on-line measurements of spot properties, i.e. number of particles and positions). The computation is performed during the intervals between synchrotron spills and, made available at the end of each spill. In the interval between two spills, the G-DDS will evaluate the delivered dose distributions taking into account the real-time target positions measured by a tracking system. The sequence of prescribed pencil beams for the following spill will be adapted taking into account the variations with respect to the original plan due to the target motion. In order to speed up the computation required to modify pencil beams distribution (up to 400 times has been reached), the Graphics Processing Units (GPUs) and advanced Field Programmable Gate Arrays (FPGAs) are used. Results: An existing offline forward planning is going to be optimized for the CUDA architecture: the gain in time will be presented. The preliminary performances of the developed GPU-based FP algorithms will be shown. Conclusion: A prototype of a GPU-based dose delivery system is under development and will be presented. The system workflow will be illustrated together with the approach adopted to integrate the three main systems, i.e. CNAO dose delivery system, fast forward planning, and tumor tracking system.

  11. An adaptive optics approach for laser beam correction in turbulence utilizing a modified plenoptic camera

    NASA Astrophysics Data System (ADS)

    Ko, Jonathan; Wu, Chensheng; Davis, Christopher C.

    2015-09-01

    Adaptive optics has been widely used in the field of astronomy to correct for atmospheric turbulence while viewing images of celestial bodies. The slightly distorted incoming wavefronts are typically sensed with a Shack-Hartmann sensor and then corrected with a deformable mirror. Although this approach has proven to be effective for astronomical purposes, a new approach must be developed when correcting for the deep turbulence experienced in ground to ground based optical systems. We propose the use of a modified plenoptic camera as a wavefront sensor capable of accurately representing an incoming wavefront that has been significantly distorted by strong turbulence conditions (C2n <10-13 m- 2/3). An intelligent correction algorithm can then be developed to reconstruct the perturbed wavefront and use this information to drive a deformable mirror capable of correcting the major distortions. After the large distortions have been corrected, a secondary mode utilizing more traditional adaptive optics algorithms can take over to fine tune the wavefront correction. This two-stage algorithm can find use in free space optical communication systems, in directed energy applications, as well as for image correction purposes.

  12. The performance of an optical cone-beam CT scanner adapted for radiochromic film dosimetry.

    PubMed

    Babic, Steven; Jordan, Kevin

    2012-11-01

    The primary purpose of this study was to evaluate commercial optical cone-beam computed tomography (CBCT) scanners as devices for reading EBT2 radiochromic film. A secondary objective was to implement a spatial correction for stray light present within optical CBCT systems. Square (12.7 × 12.7 cm²) EBT2 films were positioned vertically in the middle of a small water-filled tank, co-linear with the central beam axis of a 12 MeV electron beam. A total dose of 4.0 Gy was delivered at depth of 3.0 cm. Films were imaged prior to irradiation and 24 hours post-irradiation. Two different models of scanners, Vista15™ and Vista10™, were used to read out the irradiated films. In the Vista15™ scanner, residual light scatter was corrected for using: 1) a single vertical slot array and 2) a slot pair array that produced a vertical fan beam of light. Vista10™ was modified to have a smaller acceptance angle of scattered light and further corrections for residual scatter were made using a multiple slot array. With these different geometries, composite 'open field' and 'shadow field' images were generated and processed to create 'glare-free' pre and post-irradiation film images respectively, from which the net optical density (OD) was calculated. Results were compared against the open light field measurement in which no correction for stray light was made. Using the above scanners, EBT2 films were additionally read out to obtain 12 MeV electron and 6 MV photon percentage depth doses. By correcting for stray light it was found that the central-axis change in the net OD increased particularly in the 12 MeV electron build-up region and at the depth of maximum dose (d(max) = 3.0 cm) where light transmission is lowest. In the open light field measurement acquired with the Vista15™ scanner the net OD was 0.87 +/-0.02. Using single vertical slot array geometry to correct for stray light, the net OD was 0.94 +/-0.02, while with the slot pair array the net OD was 0.99 +/-0

  13. Adaptive array antenna for satellite cellular and direct broadcast communications

    NASA Technical Reports Server (NTRS)

    Horton, Charles R.; Abend, Kenneth

    1993-01-01

    Adaptive phased-array antennas provide cost-effective implementation of large, light weight apertures with high directivity and precise beamshape control. Adaptive self-calibration allows for relaxation of all mechanical tolerances across the aperture and electrical component tolerances, providing high performance with a low-cost, lightweight array, even in the presence of large physical distortions. Beam-shape is programmable and adaptable to changes in technical and operational requirements. Adaptive digital beam-forming eliminates uplink contention by allowing a single electronically steerable antenna to service a large number of receivers with beams which adaptively focus on one source while eliminating interference from others. A large, adaptively calibrated and fully programmable aperture can also provide precise beam shape control for power-efficient direct broadcast from space. Advanced adaptive digital beamforming technologies are described for: (1) electronic compensation of aperture distortion, (2) multiple receiver adaptive space-time processing, and (3) downlink beam-shape control. Cost considerations for space-based array applications are also discussed.

  14. Theoretical explanation of the polarization-converting system achieved by beam shaping and combination technique and its performance under high power conditions

    NASA Astrophysics Data System (ADS)

    Wang, Peng; Li, Xiao; Shang, YaPing; Xu, XiaoJun

    2015-10-01

    The fiber laser has very obvious advantages and broad applications in remote welding, 3D cutting and national defense compared with the traditional solid laser. But influenced by heat effect of gain medium, nonlinear effect, stress birefringence effect and other negative factors, it's very difficult to get high power linearly polarized laser just using a single laser. For these limitations a polarization-converting system is designed using beam shaping and combination technique which is able to transform naturally polarized laser to linearly polarized laser at real time to resolve difficulties of generating high-power linearly polarized laser from fiber lasers in this paper. The principle of the Gaussian beam changing into the hollow beam passing through two axicons and the combination of the Gaussian beam and the hollow beam is discussed. In the experimental verification the energy conversion efficiency reached 93.1% with a remarkable enhancement of the extinction ratio from 3% to 98% benefited from the high conversion efficiency of axicons and the system worked fine under high power conditions. The system also kept excellent far field divergence. The experiment phenomenon also agreed with the simulation quite well. The experiment proves that this polarization-converting system will not affect laser structure which controls easily and needs no feedback and controlling system with stable and reliable properties at the same time. It can absolutely be applied to the polarization-conversion of high power laser.

  15. Static shape determination and control for large space structures. I - The flexible beam. II - A large space antenna

    NASA Technical Reports Server (NTRS)

    Weeks, C. J.

    1984-01-01

    A method for determining and controlling the shape of large, continuous space structures by means of discrete or pointwise observations and control devices is presented. The general linear boundary value problem satisfied by a one-dimensional shape function is defined, and the existence of solutions is studied. The static shape control problems for one-dimensional systems with and without rigid body modes and the static shape estimation problem are presented and solved. Eigenfunction expansions are presented which provide approximations to the algorithm terms when the associated Green's function is not known. An integral operator approach is applied to the multidimensional static problem, and the results are illustrated with a finite element model of the disk of a large space antenna which assumes no rigid body modes. It is shown that the shape control algorithm must be modified for systems with rigid body modes.

  16. Reversible adaptation to photoinduced shape switching by oligomer-macrocycle interconversion with component selection in a three-state constitutional dynamic system.

    PubMed

    Vantomme, Ghislaine; Lehn, Jean-Marie

    2014-12-01

    Light irradiation of the molecular photoswitch 1-E causes isomerization into the 1-Z configuration stabilized by an internal hydrogen bond. 1-E bears aldehyde groups allowing for dynamic covalent reaction with linear diamines. On photoinduced E/Z shape switching of 1 in presence of diamines, the system undergoes interconversion between two states, a non-cyclic oligomeric one and a macrocyclic one, corresponding respectively to the E and Z configurations of 1. With a mixture of linear α,ω-diamines, 1-E yields non-selective dynamic oligomers by random incorporation of diamine components. Photoswitching to the 1-Z form leads to constitutional adaptation with preferential formation of the macrocycle incorporating the best suited diamine, H2 N(CH2 )7 NH2 . In presence of metal cations, the E form switches from its unbound W shape to its coordinated U shape and yields the macrocycle resulting from the selective incorporation of the diamine H2 NCH2 CH2 OCH2 CH2 NH2 that contains an additional O coordination site. Taken together, the results obtained describe constitutional adaptation in a triple state system: an oligomeric one and two different macrocyclic ones generated in response to two orthogonal agents, a physical stimulus, light, or a chemical effector, metal cations. These three states present, towards the incorporation of diamine components, respectively no selection, photoselection and metalloselection. PMID:25297846

  17. Adaptive Beam Smoothing with Plasma-Pinholes for Laser-Entrance-Hole Transmission Studies

    NASA Astrophysics Data System (ADS)

    Geissel, Matthias; Ruggles, Lawrence E.; Smith, Ian C.; Shores, Jonathn E.; Speas, C. Shane; Porter, John L.

    2014-10-01

    The concept of Magnetized Liner Inertial Fusion (MagLIF) requires the deposition of laser energy into a fuel-filled cylinder that is exposed to a magnetic field. To improve process, it is essential to optimize transmission through the foil covered laser entrance hole (LEH), which involves minimizing laser-plasma-instabilities (LPI). Laser beam smoothing is the most common approach to minimize LPI. It typically involves a Random-Phase-Plate (RPP) and smoothing by spectral dispersion (SSD). This approach can still cause LPI issues due to intensity ``hot-spots'' on a ps-time scale, and it inconveniently fixes the usable spot size. Changing laser spot sizes requires multiple dedicated RPPs. To study ideal spot sizes on a MagLIF LEH, the RPP/SSD approach gets cost prohibitive. As alternative, we use sacrificial thin foils (500 nm or less) at the laser focus, which instantly turn into a plasma-pinhole, acting as spatial filter. The smoothed laser spot size grows linearly with distance from best focus. We present experimental data for smoothing performance and resulting LEH transmission. Sandia is a multiprogram laboratory managed and operated by Sandia Corp., a wholly owned subsidiary of Lockheed Martin Corp., for the U.S. DOE's Nat'l Nucl. Sec. Admin. under Contract DE-AC04-94AL85000.

  18. Analysis of C-shaped root canal configuration in maxillary molars in a Korean population using cone-beam computed tomography

    PubMed Central

    Jo, Hyoung-Hoon; Min, Jeong-Bum

    2016-01-01

    Objectives The purpose of this study was to investigate the incidence of root fusion and C-shaped root canals in maxillary molars, and to classify the types of C-shaped canal by analyzing cone-beam computed tomography (CBCT) in a Korean population. Materials and Methods Digitized CBCT images from 911 subjects were obtained in Chosun University Dental Hospital between February 2010 and July 2012 for orthodontic treatment. Among them, a total of selected 3,553 data of maxillary molars were analyzed retrospectively. Tomography sections in the axial, coronal, and sagittal planes were displayed by PiViewstar and Rapidia MPR software (Infinitt Co.). The incidence and types of root fusion and C-shaped root canals were evaluated and the incidence between the first and the second molar was compared using Chi-square test. Results Root fusion was present in 3.2% of the first molars and 19.5% of the second molars, and fusion of mesiobuccal and palatal root was dominant. C-shaped root canals were present in 0.8% of the first molars and 2.7% of the second molars. The frequency of root fusion and C-shaped canal was significantly higher in the second molar than the first molar (p < 0.001). Conclusions In a Korean population, maxillary molars showed total 11.3% of root fusion and 1.8% of C-shaped root canals. Furthermore, root fusion and C-shaped root canals were seen more frequently in the maxillary second molars. PMID:26877991

  19. Rotor-bearing system integrated with shape memory alloy springs for ensuring adaptable dynamics and damping enhancement-Theory and experiment

    NASA Astrophysics Data System (ADS)

    Enemark, Søren; Santos, Ilmar F.

    2016-05-01

    Helical pseudoelastic shape memory alloy (SMA) springs are integrated into a dynamic system consisting of a rigid rotor supported by passive magnetic bearings. The aim is to determine the utility of SMAs for vibration attenuation via their mechanical hysteresis, and for adaptation of the dynamic behaviour via their temperature dependent stiffness properties. The SMA performance, in terms of vibration attenuation and adaptability, is compared to a benchmark configuration of the system having steel springs instead of SMA springs. A theoretical multidisciplinary approach is used to quantify the weakly nonlinear coupled dynamics of the rotor-bearing system. The nonlinear forces from the thermo-mechanical shape memory alloy springs and from the passive magnetic bearings are coupled to the rotor and bearing housing dynamics. The equations of motion describing rotor tilt and bearing housing lateral motion are solved in the time domain. The SMA behaviour is also described by the complex modulus to form approximative equations of motion, which are solved in the frequency domain using continuation techniques. Transient responses, ramp-ups and steady-state frequency responses of the system are investigated experimentally and numerically. By using the proper SMA temperature, vibration reductions up to around 50 percent can be achieved using SMAs instead of steel. Regarding system adaptability, both the critical speeds, the mode shapes and the modes' sensitivity to disturbances (e.g. imbalance) highly depend on the SMA temperature. Examples show that vibration reduction at constant rotational speeds up to around 75 percent can be achieved by changing the SMA temperature, primarily because of stiffness change, whereas hysteresis only limits large vibrations. The model is able to capture and explain the experimental dynamic behaviour.

  20. Incorporation of fiber optic beam shaping into a laparoscopic probe for laser stimulation of the cavernous nerves

    NASA Astrophysics Data System (ADS)

    Tozburun, Serhat; Lagoda, Gwen A.; Mayeh, Mona; Burnett, Arthur L.; Farahi, Faramarz; Fried, Nathaniel M.

    2010-02-01

    The cavernous nerves (CN) course along the prostate surface and are responsible for erectile function. Improved identification and preservation of the CN's is critical to maintaining sexual potency after prostate cancer surgery. Noncontact optical nerve stimulation (ONS) of the CN's was recently demonstrated in a rat model, in vivo, as a potential alternative to electrical nerve stimulation (ENS) for identification of the CN's during prostate surgery. However, the therapeutic window for ONS is narrow, so optimal design of the fiber optic delivery system is critical for safe, reproducible stimulation. This study describes modeling, assembly, and testing of an ONS probe for delivering a small, collimated, flat-top laser beam for uniform CN stimulation. A direct comparison of the magnitude and response time of the intracavernosal pressure (ICP) for both Gaussian and flat-top spatial beam profiles was performed. Thulium fiber laser radiation (λ=1870 nm) was delivered through a 200-μm fiber, with distal fiber tip chemically etched to convert a Gaussian to flat-top beam profile. The laser beam was collimated to a 1-mm-diameter spot using an aspheric lens. Computer simulations of light propagation were used to optimize the probe design. The 10-Fr (3.4-mm-OD) laparoscopic probe provided a constant radiant exposure at the nerve surface. The probe was tested in four rats, in vivo. ONS of the CN's was performed with a 1-mm-diameter spot, 5- ms pulse duration, and pulse rate of 20 Hz for a duration of 15-30 s. The flat-top laser beam profile consistently produced a faster and higher ICP response at a lower radiant exposure than the Gaussian beam profile due, in part, to easier alignment of the more uniform beam with nerve. With further development, ONS may be used as a diagnostic tool for identification of the CN's during laparoscopic and robotic nerve-sparing prostate cancer surgery.

  1. Does conflict help or hurt cognitive control? Initial evidence for an inverted U-shape relationship between perceived task difficulty and conflict adaptation

    PubMed Central

    van Steenbergen, Henk; Band, Guido P. H.; Hommel, Bernhard

    2015-01-01

    Sequential modulation of congruency effects in conflict tasks indicates that cognitive control quickly adapts to changing task demands. We investigated in four experiments how this behavioral congruency-sequence effect relates to different levels of perceived task difficulty in a flanker and a Stroop task. In addition, online measures of pupil diameter were used as a physiological index of effort mobilization. Consistent with motivational accounts predicting that increased levels of perceived task difficulty will increase effort mobilization only up to a certain limit, reliable dynamic conflict-driven adjustment in cognitive control was only observed when task difficulty was relatively low. Instead, tasks tentatively associated with high levels of difficulty showed no or reversed conflict adaptation. Although the effects could not be linked consistently to effects in self-reported task difficulty in all experiments, regression analyses showed associations between perceived task difficulty and conflict adaptation in some of the experiments, which provides some initial evidence for an inverted U-shape relationship between perceived difficulty and adaptations in cognitive control. Furthermore, high levels of task difficulty were associated with a conflict-driven reduction in pupil dilation, suggesting that pupil dilation can be used as a physiological marker of mental overload. Our findings underscore the importance of developing models that are grounded in motivational accounts of cognitive control. PMID:26217287

  2. Adaptive Radiation Therapy for Postprostatectomy Patients Using Real-Time Electromagnetic Target Motion Tracking During External Beam Radiation Therapy

    SciTech Connect

    Zhu, Mingyao; Bharat, Shyam; Michalski, Jeff M.; Gay, Hiram A.; Hou, Wei-Hsien; Parikh, Parag J.

    2013-03-15

    Purpose: Using real-time electromagnetic (EM) transponder tracking data recorded by the Calypso 4D Localization System, we report inter- and intrafractional target motion of the prostate bed, describe a strategy to evaluate treatment adequacy in postprostatectomy patients receiving intensity modulated radiation therapy (IMRT), and propose an adaptive workflow. Methods and Materials: Tracking data recorded by Calypso EM transponders was analyzed for postprostatectomy patients that underwent step-and-shoot IMRT. Rigid target motion parameters during beam delivery were calculated from recorded transponder positions in 16 patients with rigid transponder geometry. The delivered doses to the clinical target volume (CTV) were estimated from the planned dose matrix and the target motion for the first 3, 5, 10, and all fractions. Treatment adequacy was determined by comparing the delivered minimum dose (D{sub min}) with the planned D{sub min} to the CTV. Treatments were considered adequate if the delivered CTV D{sub min} is at least 95% of the planned CTV D{sub min}. Results: Translational target motion was minimal for all 16 patients (mean: 0.02 cm; range: −0.12 cm to 0.07 cm). Rotational motion was patient-specific, and maximum pitch, yaw, and roll were 12.2, 4.1, and 10.5°, respectively. We observed inadequate treatments in 5 patients. In these treatments, we observed greater target rotations along with large distances between the CTV centroid and transponder centroid. The treatment adequacy from the initial 10 fractions successfully predicted the overall adequacy in 4 of 5 inadequate treatments and 10 of 11 adequate treatments. Conclusion: Target rotational motion could cause underdosage to partial volume of the postprostatectomy targets. Our adaptive treatment strategy is applicable to post-prostatectomy patients receiving IMRT to evaluate and improve radiation therapy delivery.

  3. Design and optimization of a beam shaping assembly for BNCT based on D-T neutron generator and dose evaluation using a simulated head phantom.

    PubMed

    Rasouli, Fatemeh S; Masoudi, S Farhad

    2012-12-01

    A feasibility study was conducted to design a beam shaping assembly for BNCT based on D-T neutron generator. The optimization of this configuration has been realized in different steps. This proposed system consists of metallic uranium as neutron multiplier, TiF(3) and Al(2)O(3) as moderators, Pb as reflector, Ni as shield and Li-Poly as collimator to guide neutrons toward the patient position. The in-air parameters recommended by IAEA were assessed for this proposed configuration without using any filters which enables us to have a high epithermal neutron flux at the beam port. Also a simulated Snyder head phantom was used to evaluate dose profiles due to the irradiation of designed beam. The dose evaluation results and depth-dose curves show that the neutron beam designed in this work is effective for deep-seated brain tumor treatments even with D-T neutron generator with a neutron yield of 2.4×10(12) n/s. The Monte Carlo Code MCNP-4C is used in order to perform these calculations. PMID:23041781

  4. A Structural Approach to Establishing a Platform Chemistry for the Tunable, Bulk Electron Beam Cross-Linking of Shape Memory Polymer Systems

    PubMed Central

    Hearon, Keith; Besset, Celine J.; Lonnecker, Alexander T.; Ware, Taylor; Voit, Walter E.; Wilson, Thomas S.; Wooley, Karen L.; Maitland, Duncan J.

    2014-01-01

    The synthetic design and thermomechanical characterization of shape memory polymers (SMPs) built from a new polyurethane chemistry that enables facile, bulk and tunable cross-linking of low-molecular weight thermoplastics by electron beam irradiation is reported in this study. SMPs exhibit stimuli-induced geometry changes and are being proposed for applications in numerous fields. We have previously reported a polyurethane SMP system that exhibits the complex processing capabilities of thermoplastic polymers and the mechanical robustness and tunability of thermomechanical properties that are often characteristic of thermoset materials. These previously reported polyurethanes suffer practically because the thermoplastic molecular weights needed to achieve target cross-link densities severely limit high-throughput thermoplastic processing and because thermally unstable radiation-sensitizing additives must be used to achieve high enough cross-link densities to enable desired tunable shape memory behavior. In this study, we demonstrate the ability to manipulate cross-link density in low-molecular weight aliphatic thermoplastic polyurethane SMPs (Mw as low as ~1.5 kDa) without radiation-sensitizing additives by incorporating specific structural motifs into the thermoplastic polymer side chains that we hypothesized would significantly enhance susceptibility to e-beam cross-linking. A custom diol monomer was first synthesized and then implemented in the synthesis of neat thermoplastic polyurethane SMPs that were irradiated at doses ranging from 1 to 500 kGy. Dynamic mechanical analysis (DMA) demonstrated rubbery moduli to be tailorable between 0.1 and 55 MPa, and both DMA and sol/gel analysis results provided fundamental insight into our hypothesized mechanism of electron beam cross-linking, which enables controllable bulk cross-linking to be achieved in highly processable, low-molecular weight thermoplastic shape memory polymers without sensitizing additives. PMID

  5. Experimental thermo-stress analysis for a bending shape control of composite beams embedded with SMA wires

    NASA Astrophysics Data System (ADS)

    Zhou, Gang; Lloyd, Peter

    2009-07-01

    An experimental study has been conducted to design and fabricate smart composite beams embedded with prestrained nitinol wire actuators. The fabrication process developed allowed both quasi-isotropic E-glass/epoxy and carbon/epoxy hosts to be eccentrically embedded with 10 parallel prestrained wires with a purpose-made alignment device and cured successfully in an autoclave. Smart composite beams of three different lengths were made for each type of host. Both single-cycle and multi-cycle thermomechanical bending actuations of these beams in the cantilever set-up were characterised experimentally by applying various levels of electric current to the nitinol wires. The performance characteristics showed that the present fabrication process was repeatable and reliable. While the end deflections of up to 41 mm were easily achieved from smart E-glass/epoxy beams, the limited end deflections were observed from the smart carbon/epoxy beams due primarily to our inability to insulate the nitinol wires. Moreover, it seemed necessary to overheat the prestrained wires to much higher temperatures beyond the complete reverse transformation in order to generate recovery stress.

  6. Functional adaptations in the craniofacial morphology of Malagasy primates: shape variations associated with gummivory in the family Cheirogaleidae.

    PubMed

    Viguier, Bénédicte

    2004-12-01

    The infraorder Lemuriformes is characterized by a high level of homoplasy that clouds the evolutionary signal. The analysis of the morphological disparity of the Malagasy primates' crania and mandibles demonstrates the high determinism of functional specializations and developmental constraints, regardless of the phylogeny. In the present work, the weight of functional constraints linked to diet--a putative source of homoplasy--is analyzed first at the level of the infraorder Lemuriformes as a whole, and secondly at the level of a single family, the Cheirogaleidae, chosen because it contains taxa with two different diets (omnivory and gummivory). Malagasy primates are characterized by a great variety of dietary habits: some of them are omnivores, folivores, frugivores, gummivores, insectivores or even specialized hard-object feeders. All cheirogaleids feed on tree exudates, but while gum consumption is occasional or limited for Microcebus, Cheirogaleus and Mirza, gums are the dominant food source for Phaner and Allocebus. Craniofacial shape variations are analyzed using geometric morphometrics: methods based on landmark identification (Procrustes superimpositions) are chosen for cranium shape analysis, and methods based on outline decomposition (elliptical Fourier functions) for study of mandible shape. The morphospaces obtained at the level of the infraorder appear to be highly constrained by dietary habits, especially in the case of the mandibles. At the finer level of the family Cheirogaleidae, the analyses permit (1) separation of craniomandibular shape variation associated with the two dietary categories and (2) among the omnivorous category, to distinguish variation associated with the percentage of gum consumption. PMID:15646283

  7. Simple beam profile monitor

    SciTech Connect

    Gelbart, W.; Johnson, R. R.; Abeysekera, B.

    2012-12-19

    An inexpensive beam profile monitor is based on the well proven rotating wire method. The monitor can display beam position and shape in real time for particle beams of most energies and beam currents up to 200{mu}A. Beam shape, position cross-section and other parameters are displayed on a computer screen.

  8. Preparation of ion-track membranes of poly( p-phenylene terephthalamide): Control of pore shape by irradiation with different ion beams

    NASA Astrophysics Data System (ADS)

    Suzuki, Yasuyuki; Yamaki, Tetsuya; Koshikawa, Hiroshi; Asano, Masaharu; Voss, Kay-Obbe; Neumann, Reinhard; Yoshida, Masaru

    2007-07-01

    The preparation of ion-track membranes of thermally stable poly( p-phenylene terephthalamide) (PPTA) was performed by ion beam irradiation followed by chemical etching with a sodium hypochlorite solution. Cylindrical pores were observed in the membrane irradiated with 197Au and 238U ions at an energy of 11.1 MeV/n. In contrast, funnel shape pores appeared in the membrane irradiated with 84Kr, 102Ru and 129Xe ion at energies of 6.2, 3.6 and 3.5 MeV/n, respectively. The 197Au and 238U ion irradiation was found to exhibit more than four times larger sensitivity to the track etching under the same etching conditions. Consequently, the pore shape can be controlled by the masses and energies of the irradiated ions, in close relation to the etching sensitivity of the track.

  9. The combination of digital surface scanners and cone beam computed tomography technology for guided implant surgery using 3Shape implant studio software: a case history report.

    PubMed

    Lanis, Alejandro; Álvarez Del Canto, Orlando

    2015-01-01

    The incorporation of virtual engineering into dentistry and the digitization of information are providing new perspectives and innovative alternatives for dental treatment modalities. The use of digital surface scanners with surgical planning software allows for the combination of the radiographic, prosthetic, surgical, and laboratory fields under a common virtual scenario, permitting complete digital treatment planning. In this article, the authors present a clinical case in which a guided implant surgery was performed based on a complete digital surgical plan combining the information from a cone beam computed tomography scan and the virtual simulation obtained from the 3Shape TRIOS intraoral surface scanner. The information was imported to and combined in the 3Shape Implant Studio software for guided implant surgery planning. A surgical guide was obtained by a 3D printer, and the surgical procedure was done using the Biohorizons Guided Surgery Kit and its protocol. PMID:25822304

  10. Improving thoracic four-dimensional cone-beam CT reconstruction with anatomical-adaptive image regularization (AAIR)

    PubMed Central

    Shieh, Chun-Chien; Kipritidis, John; O’Brien, Ricky T; Cooper, Benjamin J; Kuncic, Zdenka; Keall, Paul J

    2015-01-01

    Total-variation (TV) minimization reconstructions can significantly reduce noise and streaks in thoracic four-dimensional cone-beam computed tomography (4D CBCT) images compared to the Feldkamp-Davis-Kress (FDK) algorithm currently used in practice. TV minimization reconstructions are, however, prone to over-smoothing anatomical details and are also computationally inefficient. The aim of this study is to demonstrate a proof of concept that these disadvantages can be overcome by incorporating the general knowledge of the thoracic anatomy via anatomy segmentation into the reconstruction. The proposed method, referred as the anatomical-adaptive image regularization (AAIR) method, utilizes the adaptive-steepest-descent projection-onto-convex-sets (ASD-POCS) framework, but introduces an additional anatomy segmentation step in every iteration. The anatomy segmentation information is implemented in the reconstruction using a heuristic approach to adaptively suppress over-smoothing at anatomical structures of interest. The performance of AAIR depends on parameters describing the weighting of the anatomy segmentation prior and segmentation threshold values. A sensitivity study revealed that the reconstruction outcome is not sensitive to these parameters as long as they are chosen within a suitable range. AAIR was validated using a digital phantom and a patient scan, and was compared to FDK, ASD-POCS, and the prior image constrained compressed sensing (PICCS) method. For the phantom case, AAIR reconstruction was quantitatively shown to be the most accurate as indicated by the mean absolute difference and the structural similarity index. For the patient case, AAIR resulted in the highest signal-to-noise ratio (i.e. the lowest level of noise and streaking) and the highest contrast-to-noise ratios for the tumor and the bony anatomy (i.e. the best visibility of anatomical details). Overall, AAIR was much less prone to over-smoothing anatomical details compared to ASD-POCS, and

  11. Improving thoracic four-dimensional cone-beam CT reconstruction with anatomical-adaptive image regularization (AAIR)

    NASA Astrophysics Data System (ADS)

    Shieh, Chun-Chien; Kipritidis, John; O'Brien, Ricky T.; Cooper, Benjamin J.; Kuncic, Zdenka; Keall, Paul J.

    2015-01-01

    Total-variation (TV) minimization reconstructions can significantly reduce noise and streaks in thoracic four-dimensional cone-beam computed tomography (4D CBCT) images compared to the Feldkamp-Davis-Kress (FDK) algorithm currently used in practice. TV minimization reconstructions are, however, prone to over-smoothing anatomical details and are also computationally inefficient. The aim of this study is to demonstrate a proof of concept that these disadvantages can be overcome by incorporating the general knowledge of the thoracic anatomy via anatomy segmentation into the reconstruction. The proposed method, referred as the anatomical-adaptive image regularization (AAIR) method, utilizes the adaptive-steepest-descent projection-onto-convex-sets (ASD-POCS) framework, but introduces an additional anatomy segmentation step in every iteration. The anatomy segmentation information is implemented in the reconstruction using a heuristic approach to adaptively suppress over-smoothing at anatomical structures of interest. The performance of AAIR depends on parameters describing the weighting of the anatomy segmentation prior and segmentation threshold values. A sensitivity study revealed that the reconstruction outcome is not sensitive to these parameters as long as they are chosen within a suitable range. AAIR was validated using a digital phantom and a patient scan and was compared to FDK, ASD-POCS and the prior image constrained compressed sensing (PICCS) method. For the phantom case, AAIR reconstruction was quantitatively shown to be the most accurate as indicated by the mean absolute difference and the structural similarity index. For the patient case, AAIR resulted in the highest signal-to-noise ratio (i.e. the lowest level of noise and streaking) and the highest contrast-to-noise ratios for the tumor and the bony anatomy (i.e. the best visibility of anatomical details). Overall, AAIR was much less prone to over-smoothing anatomical details compared to ASD-POCS and did

  12. Study on reinforced concrete beams strengthened using shape memory alloy wires in combination with carbon-fiber-reinforced polymer plates

    NASA Astrophysics Data System (ADS)

    Li, Hui; Liu, Zhi-qiang; Ou, Jin-ping

    2007-12-01

    It has been proven that carbon-fiber-reinforced polymer (CFRP) sheets or plates are capable of improving the strength of reinforced concrete (RC) structures. However, residual deformation of RC structures in service reduces the effect of CFRP strengthening. SMA can be applied to potentially decrease residual deformation and even close concrete cracks because of its recovery forces imposed on the concrete when heated. Therefore, a method of a RC structure strengthened by CFRP plates in combination with SMA wires is proposed in this paper. The strengthening effect of this method is investigated through experiments and numerical study based on the nonlinear finite element software ABAQUS in simple RC beams. Parametric analysis and assessment of damage by defining a damage index are carried out. The results indicate that recovery forces of SMA wires can decrease deflections and even close cracks in the concrete. The recovery rate of deflection of the beam increases with increasing the ratio of SMA wires. The specimen strengthened with CFRP plates has a relatively large stiffness and smaller damage index value when the residual deformation of the beam is first reduced by activation of the SMA wires. The effectiveness of this strengthening method for RC beams is verified by experimental and numerical results.

  13. Complex interplay between neutral and adaptive evolution shaped differential genomic background and disease susceptibility along the Italian peninsula

    PubMed Central

    Sazzini, Marco; Gnecchi Ruscone, Guido Alberto; Giuliani, Cristina; Sarno, Stefania; Quagliariello, Andrea; De Fanti, Sara; Boattini, Alessio; Gentilini, Davide; Fiorito, Giovanni; Catanoso, Mariagrazia; Boiardi, Luigi; Croci, Stefania; Macchioni, Pierluigi; Mantovani, Vilma; Di Blasio, Anna Maria; Matullo, Giuseppe; Salvarani, Carlo; Franceschi, Claudio; Pettener, Davide; Garagnani, Paolo; Luiselli, Donata

    2016-01-01

    The Italian peninsula has long represented a natural hub for human migrations across the Mediterranean area, being involved in several prehistoric and historical population movements. Coupled with a patchy environmental landscape entailing different ecological/cultural selective pressures, this might have produced peculiar patterns of population structure and local adaptations responsible for heterogeneous genomic background of present-day Italians. To disentangle this complex scenario, genome-wide data from 780 Italian individuals were generated and set into the context of European/Mediterranean genomic diversity by comparison with genotypes from 50 populations. To maximize possibility of pinpointing functional genomic regions that have played adaptive roles during Italian natural history, our survey included also ~250,000 exomic markers and ~20,000 coding/regulatory variants with well-established clinical relevance. This enabled fine-grained dissection of Italian population structure through the identification of clusters of genetically homogeneous provinces and of genomic regions underlying their local adaptations. Description of such patterns disclosed crucial implications for understanding differential susceptibility to some inflammatory/autoimmune disorders, coronary artery disease and type 2 diabetes of diverse Italian subpopulations, suggesting the evolutionary causes that made some of them particularly exposed to the metabolic and immune challenges imposed by dietary and lifestyle shifts that involved western societies in the last centuries. PMID:27582244

  14. Complex interplay between neutral and adaptive evolution shaped differential genomic background and disease susceptibility along the Italian peninsula.

    PubMed

    Sazzini, Marco; Gnecchi Ruscone, Guido Alberto; Giuliani, Cristina; Sarno, Stefania; Quagliariello, Andrea; De Fanti, Sara; Boattini, Alessio; Gentilini, Davide; Fiorito, Giovanni; Catanoso, Mariagrazia; Boiardi, Luigi; Croci, Stefania; Macchioni, Pierluigi; Mantovani, Vilma; Di Blasio, Anna Maria; Matullo, Giuseppe; Salvarani, Carlo; Franceschi, Claudio; Pettener, Davide; Garagnani, Paolo; Luiselli, Donata

    2016-01-01

    The Italian peninsula has long represented a natural hub for human migrations across the Mediterranean area, being involved in several prehistoric and historical population movements. Coupled with a patchy environmental landscape entailing different ecological/cultural selective pressures, this might have produced peculiar patterns of population structure and local adaptations responsible for heterogeneous genomic background of present-day Italians. To disentangle this complex scenario, genome-wide data from 780 Italian individuals were generated and set into the context of European/Mediterranean genomic diversity by comparison with genotypes from 50 populations. To maximize possibility of pinpointing functional genomic regions that have played adaptive roles during Italian natural history, our survey included also ~250,000 exomic markers and ~20,000 coding/regulatory variants with well-established clinical relevance. This enabled fine-grained dissection of Italian population structure through the identification of clusters of genetically homogeneous provinces and of genomic regions underlying their local adaptations. Description of such patterns disclosed crucial implications for understanding differential susceptibility to some inflammatory/autoimmune disorders, coronary artery disease and type 2 diabetes of diverse Italian subpopulations, suggesting the evolutionary causes that made some of them particularly exposed to the metabolic and immune challenges imposed by dietary and lifestyle shifts that involved western societies in the last centuries. PMID:27582244

  15. Inversions and adaptation to the plant toxin ouabain shape DNA sequence variation within and between chromosomal inversions of Drosophila subobscura.

    PubMed Central

    Pegueroles, Cinta; Ferrés-Coy, Albert; Martí-Solano, Maria; Aquadro, Charles F; Pascual, Marta; Mestres, Francesc

    2016-01-01

    Adaptation is defined as an evolutionary process allowing organisms to succeed in certain habitats or conditions. Chromosomal inversions have the potential to be key in the adaptation processes, since they can contribute to the maintenance of favoured combinations of adaptive alleles through reduced recombination between individuals carrying different inversions. We have analysed six genes (Pif1A, Abi, Sqd, Yrt, Atpα and Fmr1), located inside and outside three inversions of the O chromosome in European populations of Drosophila subobscura. Genetic differentiation was significant between inversions despite extensive recombination inside inverted regions, irrespective of gene distance to the inversion breakpoints. Surprisingly, the highest level of genetic differentiation between arrangements was found for the Atpα gene, which is located outside the O1 and O7 inversions. Two derived unrelated arrangements (O3+4+1 and O3+4+7) are nearly fixed for several amino acid substitutions at the Atpα gene that have been described to confer resistance in other species to the cardenolide ouabain, a plant toxin capable of blocking ATPases. Similarities in the Atpα variants, conferring ouabain resistance in both arrangements, may be the result of convergent substitution and be favoured in response to selective pressures presumably related to the presence of plants containing ouabain in the geographic locations where both inversions are present. PMID:27029337

  16. Production data from a Leica ZBA31H+ shaped e-beam mask writer located at the Photronics facility, Manchester, England

    NASA Astrophysics Data System (ADS)

    Johnson, Stephen; Loughran, Dominic; Osborne, Peter; Sixt, Pierre; Doering, Hans-Joachim

    1999-06-01

    The ZBA31H+) is a variable shaped spot, vector scan e- beam lithography system operating at 20 keV. The specified performance is designed to produce reticles to 250 nanometer design rules, and beyond. In November 98 the acceptance results of a newly installed Leica ZBA31H+), at Photonic Manchester, were presented in a paper at the VDE/VDI 15th European Conference on Mask Technology. This paper is a continuation of that work and presents data from a capability study carried out, on 4000 angstrom EBR9 HS31 resist. Analysis of: mean to target, uniformity, X/Y bias, isolated vs. dense linewidths, linearity, and registration performance of the tool is presented, and the effects of re- iterative develop on process capability compared. Theoretically, a shaped beam system has advantages over raster scan in terms of write time and edge definition capabilities. In this paper, comparative write times against an Etec Mebes 4500 system are included. The ZBA31H+) has to write very small polygons in order to image non-axial or non-45 degree features. The resulting effect on image quality and write time is investigated. In order to improve the fidelity of small OPC structures, Leica have investigated alternative writing strategies, and their results to data are presented here.

  17. Structural behavior of SMA composite beams

    SciTech Connect

    Hebda, D.A.; White, S.R.

    1995-12-31

    Shape memory alloy (SMA) composites are one class of adaptive materials in which SMA wires are embedded in a polymer matrix composite material. By selectively activating the SMA, wires, the beam shape can be controlled or {open_quotes}adapted{close_quotes} to different loading conditions. For instance, an adaptive beam could be used as a torque box for an aircraft wing where coupled bending-twisting behavior may be desirable. SMA composite beams were manufactured using a procedure developed previously and mechanically tested under static loading conditions. Nitinol (SMA) wires composed of 55% nickel and 45% titanium were trained for two-way shape memory (TWSM) and tested to determine the transformation temperatures. Once trained, the wires undergo a reversible phase transformation from martensite to austenite as the temperature is increased. This transformation leads to shape recovery and associated recovery strains. These recovery strains are used to apply forces which deflect the SMA beams during static actuation. Their structural behavior is correlated using simple beam theory. Thermal effects during processing are shown to have a major influence on structural behavior.

  18. Robust, easily shaped, and epoxy-free carbon-fiber-aluminum cathodes for generating high-current electron beams

    NASA Astrophysics Data System (ADS)

    Liu, Lie; Li, Limin; Wen, Jianchun; Wan, Hong

    2009-02-01

    This paper presents the construction of carbon-fiber-aluminum (CFA) cathode by squeezing casting and its applications for generating high-current electron beams to drive high-power microwave sources. The fabrication process avoided using epoxy, a volatile deteriorating the vacuum system. These cathodes had a higher hardness than conventional aluminum, facilitating machining. After surface treatment, carbon fibers became the dominator determining emission property. A multineedle CFA cathode was utilized in a triode virtual cathode oscillator (vircator), powered by a ˜450 kV, ˜400 ns pulse. It was found that 300-400 MW, ˜250 ns microwave was radiated at a dominant frequency of 2.6 GHz. Further, this cathode can endure high-current-density emission without detectable degradation in performance as the pulse shot proceeded, showing the robust nature of carbon fibers as explosive emitters. Overall, this new class of cold cathodes offers a potential prospect of developing high-current electron beam sources.

  19. A feasibility study of the use of bounded beams resembling the shape of evanescent and inhomogeneous waves.

    PubMed

    Declercq, Nico F; Leroy, Oswald

    2011-08-01

    Plane waves are solutions of the visco-elastic wave equation. Their wave vector can be real for homogeneous plane waves or complex for inhomogeneous and evanescent plane waves. Although interesting from a theoretical point of view, complex wave vectors normally only emerge naturally when propagation or scattering is studied of sound under the appearance of damping effects. Because of the particular behavior of inhomogeneous and evanescent waves and their estimated efficiency for surface wave generation, bounded beams, experimentally mimicking their infinite counterparts similar to (wide) Gaussian beams imitating infinite harmonic plane waves, are of special interest in this report. The study describes the behavior of bounded inhomogeneous and bounded evanescent waves in terms of amplitude and phase distribution as well as energy flow direction. The outcome is of importance to the applicability of bounded inhomogeneous ultrasonic waves for nondestructive testing. PMID:21453948

  20. The Influence of Inspection Angle, Wave Type and Beam Shape on Signal-to-Noise Ratios in Ultrasonic Pitch-Catch Inspections

    NASA Astrophysics Data System (ADS)

    Margetan, F. J.; Li, Anxiang; Thompson, R. B.

    2007-03-01

    Grain noise, which arises from the scattering of sound waves by microstructure, can limit the detection of small internal defects in metal components. Signal-to-noise (S/N) ratios for ultrasonic pitch/catch inspections are primarily determined by three factors: the scattering ability of the defect; the inherent noisiness of the microstructure (per unit volume); and finite-beam effects. An approximate single-scattering model has been formulated which contains terms representing each of these factors. In this paper the model is applied to a representative pitch/catch inspection problem, namely, the detection of a circular crack in a nickel cylinder. The object is to estimate S/N ratios for various choices of the inspection angle and sonic wave types, and to demonstrate how S/N is determined by the interplay of the defect, microstructure, and finite-beam factors. We also explore how S/N is influenced by the sizes, shapes, and orientations of the transmitter and receiver sound beams.

  1. Gravitational effects on weld pool shape and microstructural evolution during gas tungsten arc and laser beam welding on 304 stainless steel, nickel, and aluminum-4 wt.% copper alloy

    NASA Astrophysics Data System (ADS)

    Kang, Namhyun

    The objective of the present work was to investigate effects of gravitational (acceleration) level and orientation on Ni 200 alloy (99.5% Ni purity), 304 stainless steel, and Al-4 wt.% Cu alloy during gas tungsten arc welding (GTAW) and laser beam welding (LBW). Main characterization was focused on the weld pool shape, microstructure, and solute distribution as a function of gravitational level and orientation. The welds were divided into two classes, i.e., 'stable' and 'unstable' welds, in view of the variation of weld pool shape as a function of gravitational level and orientation. In general, higher arc current and translational GTAW produced more significant effects of gravitational orientation on the weld pool shape than the case of lower arc current and spot welding. Cross-sectional area (CSA) was a secondary factor in determining the stability of weld pool shape. For the 'stable' weld of 304 stainless steel GTAW, the II-U weld showed less convexity in the pool bottom and more depression of the free surface, therefore producing deeper penetration (10--20%) than the case of II-D weld. The II-D weld of 304 stainless steel showed 31% deeper penetration, 28% narrower width, and more hemispherical shape of the weld pool than the case of II-U weld. For GTAW on 304 stainless steel, gravitational level variation from low gravity (LG ≈ 1.2 go) to high gravity (HG ≈ 1.8 go) caused 10% increase in width and 10% decrease in depth while maintaining the overall weld pool volume. Furthermore, LBW on 304 stainless steels showed mostly constant shape of weld pool as a function of gravitational orientation. GTAW on Ni showed similar trends of weld pool shape compared with GTAW on 304 stainless steel, i.e., the weld pool became unstable by showing more penetration in the II-D weld for slower arc translational velocity (V a) and larger weld pool size. However, the Ni weld pool shape had greater stability of the weld pool shape with respect to the gravitational orientation

  2. Sports teams as complex adaptive systems: manipulating player numbers shapes behaviours during football small-sided games.

    PubMed

    Silva, Pedro; Vilar, Luís; Davids, Keith; Araújo, Duarte; Garganta, Júlio

    2016-01-01

    Small-sided and conditioned games (SSCGs) in sport have been modelled as complex adaptive systems. Research has shown that the relative space per player (RSP) formulated in SSCGs can impact on emergent tactical behaviours. In this study we adopted a systems orientation to analyse how different RSP values, obtained through manipulations of player numbers, influenced four measures of interpersonal coordination observed during performance in SSCGs. For this purpose we calculated positional data (GPS 15 Hz) from ten U-15 football players performing in three SSCGs varying in player numbers (3v3, 4v4 and 5v5). Key measures of SSCG system behaviours included values of (1) players' dispersion, (2) teams' separateness, (3) coupling strength and time delays between participants' emerging movements, respectively. Results showed that values of participants' dispersion increased, but the teams' separateness remained identical across treatments. Coupling strength and time delay also showed consistent values across SSCGs. These results exemplified how complex adaptive systems, like football teams, can harness inherent degeneracy to maintain similar team spatial-temporal relations with opponents through changes in inter-individual coordination modes (i.e., players' dispersion). The results imply that different team behaviours might emerge at different ratios of field dimension/player numbers. Therefore, sport pedagogists should carefully evaluate the effects of changing RSP in SSCGs as a way of promoting increased or decreased pressure on players. PMID:27026887

  3. Transverse writing of three-dimensional tubular optical waveguides in glass with a slit-shaped femtosecond laser beam.

    PubMed

    Liao, Yang; Qi, Jia; Wang, Peng; Chu, Wei; Wang, Zhaohui; Qiao, Lingling; Cheng, Ya

    2016-01-01

    We report on fabrication of tubular optical waveguides buried in ZBLAN glass based on transverse femtosecond laser direct writing. Irradiation in ZBLAN with focused femtosecond laser pulses leads to decrease of refractive index in the modified region. Tubular optical waveguides of variable mode areas are fabricated by forming the four sides of the cladding with slit-shaped femtosecond laser pulses, ensuring single mode waveguiding with a mode field dimension as small as ~4 μm. PMID:27346285

  4. Transverse writing of three-dimensional tubular optical waveguides in glass with a slit-shaped femtosecond laser beam

    NASA Astrophysics Data System (ADS)

    Liao, Yang; Qi, Jia; Wang, Peng; Chu, Wei; Wang, Zhaohui; Qiao, Lingling; Cheng, Ya

    2016-06-01

    We report on fabrication of tubular optical waveguides buried in ZBLAN glass based on transverse femtosecond laser direct writing. Irradiation in ZBLAN with focused femtosecond laser pulses leads to decrease of refractive index in the modified region. Tubular optical waveguides of variable mode areas are fabricated by forming the four sides of the cladding with slit-shaped femtosecond laser pulses, ensuring single mode waveguiding with a mode field dimension as small as ~4 μm.

  5. Transverse writing of three-dimensional tubular optical waveguides in glass with a slit-shaped femtosecond laser beam

    PubMed Central

    Liao, Yang; Qi, Jia; Wang, Peng; Chu, Wei; Wang, Zhaohui; Qiao, Lingling; Cheng, Ya

    2016-01-01

    We report on fabrication of tubular optical waveguides buried in ZBLAN glass based on transverse femtosecond laser direct writing. Irradiation in ZBLAN with focused femtosecond laser pulses leads to decrease of refractive index in the modified region. Tubular optical waveguides of variable mode areas are fabricated by forming the four sides of the cladding with slit-shaped femtosecond laser pulses, ensuring single mode waveguiding with a mode field dimension as small as ~4 μm. PMID:27346285

  6. Shape transitions and island nucleation for Si/Ge molecular beam epitaxy on stripe-patterned Si (001) substrate

    SciTech Connect

    Sanduijav, B.; Chen, G.; Springholz, G.; Matei, D.

    2009-09-15

    Si and Ge growth on the stripe patterned Si (001) substrates is studied using scanning tunneling microscopy. During Si buffer growth, the stripe morphology rapidly evolves from multifaceted ''U'' to ''V''-shaped forms. This involves successive transitions between different low energy (11n) side facets, where n continuously decreases from n=3 to 20. Ge growth on such stripes induces the formation of a pronounced side wall ripple structure when the Ge thickness exceeds three monolayers. This ripple structure consists of alternating (105) microfacets oriented perpendicularly to the stripes. Depending of the side wall geometry, Ge nanoislands subsequently nucleate either on the side walls or at the bottom of grooves. The latter only occurs for ''V''-shaped stripes, where the side wall ripples extend all the way from the top to the bottom of the grooves, allowing efficient downward mass transport. For multifaceted ''U'' stripes, the side wall ripples are interrupted by steeper side wall segments such that mounds and subsequently, pyramids and domes grow on the side walls instead of at the bottom of the grooves. The island shapes strongly depend on their position on the pattern topography, which also affects the critical coverage for island nucleation as well as for the transition from pyramids to domes. The mechanisms for nucleation at different positions are clarified by detailed analysis and the role of kinetic as well as energetic factors identified.

  7. SU-D-207-04: GPU-Based 4D Cone-Beam CT Reconstruction Using Adaptive Meshing Method

    SciTech Connect

    Zhong, Z; Gu, X; Iyengar, P; Mao, W; Wang, J; Guo, X

    2015-06-15

    Purpose: Due to the limited number of projections at each phase, the image quality of a four-dimensional cone-beam CT (4D-CBCT) is often degraded, which decreases the accuracy of subsequent motion modeling. One of the promising methods is the simultaneous motion estimation and image reconstruction (SMEIR) approach. The objective of this work is to enhance the computational speed of the SMEIR algorithm using adaptive feature-based tetrahedral meshing and GPU-based parallelization. Methods: The first step is to generate the tetrahedral mesh based on the features of a reference phase 4D-CBCT, so that the deformation can be well captured and accurately diffused from the mesh vertices to voxels of the image volume. After the mesh generation, the updated motion model and other phases of 4D-CBCT can be obtained by matching the 4D-CBCT projection images at each phase with the corresponding forward projections of the deformed reference phase of 4D-CBCT. The entire process of this 4D-CBCT reconstruction method is implemented on GPU, resulting in significantly increasing the computational efficiency due to its tremendous parallel computing ability. Results: A 4D XCAT digital phantom was used to test the proposed mesh-based image reconstruction algorithm. The image Result shows both bone structures and inside of the lung are well-preserved and the tumor position can be well captured. Compared to the previous voxel-based CPU implementation of SMEIR, the proposed method is about 157 times faster for reconstructing a 10 -phase 4D-CBCT with dimension 256×256×150. Conclusion: The GPU-based parallel 4D CBCT reconstruction method uses the feature-based mesh for estimating motion model and demonstrates equivalent image Result with previous voxel-based SMEIR approach, with significantly improved computational speed.

  8. Robust, easily shaped, and epoxy-free carbon-fiber-aluminum cathodes for generating high-current electron beams.

    PubMed

    Liu, Lie; Li, Limin; Wen, Jianchun; Wan, Hong

    2009-02-01

    This paper presents the construction of carbon-fiber-aluminum (CFA) cathode by squeezing casting and its applications for generating high-current electron beams to drive high-power microwave sources. The fabrication process avoided using epoxy, a volatile deteriorating the vacuum system. These cathodes had a higher hardness than conventional aluminum, facilitating machining. After surface treatment, carbon fibers became the dominator determining emission property. A multineedle CFA cathode was utilized in a triode virtual cathode oscillator (vircator), powered by a approximately 450 kV, approximately 400 ns pulse. It was found that 300-400 MW, approximately 250 ns microwave was radiated at a dominant frequency of 2.6 GHz. Further, this cathode can endure high-current-density emission without detectable degradation in performance as the pulse shot proceeded, showing the robust nature of carbon fibers as explosive emitters. Overall, this new class of cold cathodes offers a potential prospect of developing high-current electron beam sources. PMID:19256641

  9. Laser-Driven Coherent Betatron Oscillation in a Laser-Wakefield Cavity: Formation of Sinusoid Beam Shapes and Coherent Trajectories

    SciTech Connect

    Nemeth, Karoly; Li Yuelin; Shang Hairong; Harkay, Katherine C.; Shen Baifei; Crowell, Robert; Cary, John R.

    2009-01-22

    High amplitude coherent electron-trajectories have been seen in 3D particle-in-cell simulations of the colliding pulse injection scheme of laser-wakefield accelerators in the bubble regime, and explained as a consequence of laser-driven coherent betatron oscillation in our recent paper [K. Nemeth et al., Phys. Rev. Lett. 100, 095002 (2008)]. In the present paper we provide more details on the shape of the trajectories, their relationship to the phase velocity of the laser and indicate the dependence of the phenomenon on the accuracy of the numerical representation and choice of laser/plasma parameters.

  10. Pulse shaping effects on weld porosity in laser beam spot welds : contrast of long- & short- pulse welds.

    SciTech Connect

    Ellison, Chad M.; Perricone, Matthew J.; Faraone, Kevin M.; Norris, Jerome T.

    2007-10-01

    Weld porosity is being investigated for long-pulse spot welds produced by high power continuous output lasers. Short-pulse spot welds (made with a pulsed laser system) are also being studied but to a much small extent. Given that weld area of a spot weld is commensurate with weld strength, the loss of weld area due to an undefined or unexpected pore results in undefined or unexpected loss in strength. For this reason, a better understanding of spot weld porosity is sought. Long-pulse spot welds are defined and limited by the slow shutter speed of most high output power continuous lasers. Continuous lasers typically ramp up to a simmer power before reaching the high power needed to produce the desired weld. A post-pulse ramp down time is usually present as well. The result is a pulse length tenths of a second long as oppose to the typical millisecond regime of the short-pulse pulsed laser. This study will employ a Lumonics JK802 Nd:YAG laser with Super Modulation pulse shaping capability and a Lasag SLS C16 40 W pulsed Nd:YAG laser. Pulse shaping will include square wave modulation of various peak powers for long-pulse welds and square (or top hat) and constant ramp down pulses for short-pulse welds. Characterization of weld porosity will be performed for both pulse welding methods.

  11. Spectral shape of a signal in light-induced diffusive pulling (pushing) of particles into a light beam

    NASA Astrophysics Data System (ADS)

    Parkhomenko, A. I.; Shalagin, A. M.

    2015-02-01

    We study theoretically how the dependences of transport collision frequencies νi, collision broadening γ and collision shift Δ of the levels on the velocity v of resonant particles influence lightinduced diffusive pulling (pushing) (LDP) effects in the framework of a generalised model of strong collisions in the case of velocitydependent collision rates (so-called kangaroo model). It is found that allowance for the dependences νi(v), γ(v) and Δ(v) does not change the spectral shape of an LDP signal. In particular, in the case of low-intensity radiation, the spectral dependence of the LDP signal coincides with the absorption line shape. It is shown that the magnitude of the LDP effect is proportional to the difference between the diffusion coefficients of particles in the excited and ground states. It is found that the spectral anomalies previously predicted in the LDP effect [Gel'mukhanov F.Kh. JETP Lett., 55, 214 (1992)] for an idealised model of the Lorentz gas (the limiting case of heavy buffer particles), which arise due to the dependences νi(v), γ(v) and Δ(v), are typical only for this gas. At a realistic ratio of the masses of absorbing and buffer particles, spectral anomalies do not occur in the LDP effect.

  12. Relativistic electron beam generator

    DOEpatents

    Mooney, L.J.; Hyatt, H.M.

    1975-11-11

    A relativistic electron beam generator for laser media excitation is described. The device employs a diode type relativistic electron beam source having a cathode shape which provides a rectangular output beam with uniform current density.

  13. RECENT PROGRESS IN EMITTANCE CONTROL OF THE PHOTOELECTRON BEAM USING TRANSVERSE LASER SHAPE MODULATION AND TOMOGRAPHY TECHNIQUE.

    SciTech Connect

    BABZIEN,M.; BEN-ZVI,I.; MALONE,R.; WANG,X.J.; YAKIMENKO,V.

    1999-03-29

    A low emittance beam is very important for many applications, such as short-wavelength Free-Electron Lasers. A diagnostic that provides detailed information on the density distribution of the electron bunch in multi-dimensional phase-space is an essential tool for obtaining small emittance at a reasonable charge. Accurate phase space reconstruction and an analysis using a transport line with nine focusing magnets and techniques to control the optical functions and phases was demonstrated in previous publication. Relatively long time of measurements (approximately 30 minutes) was improved by installing Hall probes into each quadrupole magnet. This eliminated necessity to degauss all quadrupoles between each measurement points. Additional phase control of RF system and driving laser should also improve confidence in 5 dimensional phase space reconstruction.

  14. Enhancement of Light Output Power and Modification of Beam Profile in InGaN/GaN Light Emitting Diodes with Micro Polygon Column Shaped Transparent

    NASA Astrophysics Data System (ADS)

    Lee, Mi So; Kim, Hyung Gu; Hye Kang, Ji; Ryu, Jae Hyoung; Kim, Hyun Kyu; Kim, Hee Yun; Uthirakumar, Periyayya; Hong, Chang-Hee

    2010-11-01

    We report on the fabrication of GaN-based light-emitting diodes (LEDs) with micro-polygon columns (MPC) obtained by selective area growth (SAG) using the technique of metal organic chemical vapor deposition (MOCVD). The SAG makes it possible to control the density, size and position of the micro polygon columns. The facet structure consists of a polygon column covered with {1101} facets. Columns with rough occur on the (0001) surface. The light output power of the MPC-LED was 53% higher than conventional LED. In addition, the light extraction efficiency of InGaN/GaN LEDs is significantly improved owing to the photon path length is shorter. It is possible to modify the beam profile via shaped transparent layer. Thus, this structure can provide photons with multiple chances of escaping from the LEDs surfaces.

  15. An innovative approach to achieve re-centering and ductility of cement mortar beams through randomly distributed pseudo-elastic shape memory alloy fibers

    NASA Astrophysics Data System (ADS)

    Shajil, N.; Srinivasan, S. M.; Santhanam, M.

    2012-04-01

    Fibers can play a major role in post cracking behavior of concrete members, because of their ability to bridge cracks and distribute the stress across the crack. Addition of steel fibers in mortar and concrete can improve toughness of the structural member and impart significant energy dissipation through slow pull out. However, steel fibers undergo plastic deformation at low strain levels, and cannot regain their shape upon unloading. This is a major disadvantage in strong cyclic loading conditions, such as those caused by earthquakes, where self-centering ability of the fibers is a desired characteristic in addition to ductility of the reinforced cement concrete. Fibers made from an alternative material such as shape memory alloy (SMA) could offer a scope for re-centering, thus improving performance especially after a severe loading has occurred. In this study, the load-deformation characteristics of SMA fiber reinforced cement mortar beams under cyclic loading conditions were investigated to assess the re-centering performance. This study involved experiments on prismatic members, and related analysis for the assessment and prediction of re-centering. The performances of NiTi fiber reinforced mortars are compared with mortars with same volume fraction of steel fibers. Since re-entrant corners and beam columns joints are prone to failure during a strong ground motion, a study was conducted to determine the behavior of these reinforced with NiTi fiber. Comparison is made with the results of steel fiber reinforced cases. NiTi fibers showed significantly improved re-centering and energy dissipation characteristics compared to the steel fibers.

  16. Shaping of adaptive immune responses to soluble proteins by TLR agonists: a role for IFN-alpha/beta.

    PubMed

    Durand, Vanessa; Wong, Simon Yc; Tough, David F; Le Bon, Agnes

    2004-12-01

    Toll-like receptors (TLR) are believed to play a major role in the recognition of invading organisms, although their ability to shape immune responses is not completely understood. Our aim was to investigate in vivo the effect of different TLR stimuli on the generation of antibody responses and the induction of CD8+ T-cell cross-priming after immunization with soluble protein antigens. While all TLR agonists tested elicited the production of immunomodulatory cytokines, marked differences were observed in their ability to stimulate antigen-specific immune responses. Zymosan, poly(I:C) and CpG DNA, which signal through TLR2/6, 3 and 9, respectively, were found to strongly induce the production of IgG2a antibodies, whereas R-848 (TLR7) and LPS (TLR4) did so much more weakly. In contrast, LPS, poly(I:C) and CpG DNA, but not zymosan, induced functional CD8+ T-cell responses against OVA; peptidoglycan (TLR2/?) and R-848 were also ineffective in stimulating cross-priming. Experiments using IFN-alpha/beta R-deficient mice showed that the induction of cross-priming by LPS and poly(I:C) was abrogated in the absence of IFN-alpha/beta signalling, and induction by CpG DNA was greatly reduced. Overall, our results identify LPS as another TLR agonist that is able to generate functional cross-priming against a soluble protein antigen. In addition, our results demonstrate that the ability of TLR stimuli to initiate CD8+ T-cell responses against soluble protein antigens is largely dependent on the IFN-alpha/beta signalling pathway. PMID:15550117

  17. TH-E-BRE-11: Adaptive-Beamlet Based Finite Size Pencil Beam (AB-FSPB) Dose Calculation Algorithm for Independent Verification of IMRT and VMAT

    SciTech Connect

    Park, C; Arhjoul, L; Yan, G; Lu, B; Li, J; Liu, C

    2014-06-15

    Purpose: In current IMRT and VMAT settings, the use of sophisticated dose calculation procedure is inevitable in order to account complex treatment field created by MLCs. As a consequence, independent volumetric dose verification procedure is time consuming which affect the efficiency of clinical workflow. In this study, the authors present an efficient Pencil Beam based dose calculation algorithm that minimizes the computational procedure while preserving the accuracy. Methods: The computational time of Finite Size Pencil Beam (FSPB) algorithm is proportional to the number of infinitesimal identical beamlets that constitute the arbitrary field shape. In AB-FSPB, the dose distribution from each beamlet is mathematically modelled such that the sizes of beamlets to represent arbitrary field shape are no longer needed to be infinitesimal nor identical. In consequence, it is possible to represent arbitrary field shape with combinations of different sized and minimal number of beamlets. Results: On comparing FSPB with AB-FSPB, the complexity of the algorithm has been reduced significantly. For 25 by 25 cm2 squared shaped field, 1 beamlet of 25 by 25 cm2 was sufficient to calculate dose in AB-FSPB, whereas in conventional FSPB, minimum 2500 beamlets of 0.5 by 0.5 cm2 size were needed to calculate dose that was comparable to the Result computed from Treatment Planning System (TPS). The algorithm was also found to be GPU compatible to maximize its computational speed. On calculating 3D dose of IMRT (∼30 control points) and VMAT plan (∼90 control points) with grid size 2.0 mm (200 by 200 by 200), the dose could be computed within 3∼5 and 10∼15 seconds. Conclusion: Authors have developed an efficient Pencil Beam type dose calculation algorithm called AB-FSPB. The fast computation nature along with GPU compatibility has shown performance better than conventional FSPB. This completely enables the implantation of AB-FSPB in the clinical environment for independent

  18. Reconstructing Cone-beam CT with Spatially Varying Qualities for Adaptive Radiotherapy, a Proof-of-Principle Study1

    PubMed Central

    Lu, Wenting; Yan, Hao; Gu, Xuejun; Tian, Zhen; Luo, Ouyang; Yang, Liu; Zhou, Linghong; Cervino, Laura; Wang, Jing; Jiang, Steve; Jia, Xun

    2014-01-01

    With the aim of maximally reducing imaging dose while meeting requirements for adaptive radiation therapy (ART), we propose in this paper a new cone beam CT (CBCT) acquisition and reconstruction method that delivers images with a low noise level inside a region of interest (ROI) and a relatively high noise level outside the ROI. The acquired projection images include two groups: densely sampled projections at a low exposure with a large field of view (FOV) and sparsely sampled projections at a high exposure with a small FOV corresponding to the ROI. A new algorithm combining the conventional filtered back-projection algorithm and the tight-frame iterative reconstruction algorithm is also designed to reconstruct the CBCT based on these projection data. We have validated our method on a simulated head-and-neck (HN) patient case, a semi-real experiment conducted on a HN cancer patient under a full-fan scan mode, as well as a Catphan phantom under a half-fan scan mode. Relative root-mean-square errors (RRMSE) of less than 3% for the entire image and ~1% within the ROI compared to the ground truth have been observed. These numbers demonstrate the ability of our proposed method to reconstruct high-quality images inside the ROI. As for the part outside ROI, although the images are relatively noisy, it can still provide sufficient information for radiation dose calculations in ART. Dose distributions calculated on our CBCT image and on a standard CBCT image are in agreement, with a mean relative difference of 0.082% inside the ROI and 0.038% outside the ROI. Compared with the standard clinical CBCT scheme, an imaging dose reduction of approximately 3–6 times inside the ROI was achieved, as well as an 8 times outside the ROI. Regarding computational efficiency, it takes 1–3 min to reconstruct a CBCT image depending on the number of projections used. These results indicate that the proposed method has the potential for application in ART. PMID:25255957

  19. Reconstructing cone-beam CT with spatially varying qualities for adaptive radiotherapy: a proof-of-principle study

    NASA Astrophysics Data System (ADS)

    Lu, Wenting; Yan, Hao; Gu, Xuejun; Tian, Zhen; Ouyang, Luo; Yang, Liu; Zhou, Linghong; Cervino, Laura; Wang, Jing; Jiang, Steve; Jia, Xun

    2014-10-01

    With the aim of maximally reducing imaging dose while meeting requirements for adaptive radiation therapy (ART), we propose in this paper a new cone beam CT (CBCT) acquisition and reconstruction method that delivers images with a low noise level inside a region of interest (ROI) and a relatively high noise level outside the ROI. The acquired projection images include two groups: densely sampled projections at a low exposure with a large field of view (FOV) and sparsely sampled projections at a high exposure with a small FOV corresponding to the ROI. A new algorithm combining the conventional filtered back-projection algorithm and the tight-frame iterative reconstruction algorithm is also designed to reconstruct the CBCT based on these projection data. We have validated our method on a simulated head-and-neck (HN) patient case, a semi-real experiment conducted on a HN cancer patient under a full-fan scan mode, as well as a Catphan phantom under a half-fan scan mode. Relative root-mean-square errors (RRMSEs) of less than 3% for the entire image and ~1% within the ROI compared to the ground truth have been observed. These numbers demonstrate the ability of our proposed method to reconstruct high-quality images inside the ROI. As for the part outside ROI, although the images are relatively noisy, it can still provide sufficient information for radiation dose calculations in ART. Dose distributions calculated on our CBCT image and on a standard CBCT image are in agreement, with a mean relative difference of 0.082% inside the ROI and 0.038% outside the ROI. Compared with the standard clinical CBCT scheme, an imaging dose reduction of approximately 3-6 times inside the ROI was achieved, as well as an 8 times outside the ROI. Regarding computational efficiency, it takes 1-3 min to reconstruct a CBCT image depending on the number of projections used. These results indicate that the proposed method has the potential for application in ART.

  20. Central safety factor and βN control on NSTX-U via beam power and plasma boundary shape modification, using TRANSP for closed loop simulations

    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 βN and the safety factor profile. In this work, a novel approach to simultaneously controlling βN 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.