Science.gov

Sample records for fabricating convoluted shaped

  1. A Novel Method of Fabricating Convoluted Shaped Electrode Arrays for Neural and Retinal Prostheses

    PubMed Central

    Bhandari, R.; Negi, S.; Rieth, L.; Normann, R. A.; Solzbacher, F.

    2008-01-01

    A novel fabrication technique has been developed for creating high density (6.25 electrodes/mm2), out of plane, high aspect ratio silicon-based convoluted microelectrode arrays for neural and retinal prostheses. The convoluted shape of the surface defined by the tips of the electrodes could compliment the curved surfaces of peripheral nerves and the cortex, and in the case of retina, its spherical geometry. The geometry of these electrode arrays has the potential to facilitate implantation in the nerve fascicles and to physically stabilize it against displacement after insertion. This report presents a unique combination of variable depth dicing and wet isotropic etching for the fabrication of a variety of convoluted neural array geometries. Also, a method of deinsulating the electrode tips using photoresist as a mask and the limitations of this technique on uniformity are discussed. PMID:19122774

  2. Adapting line integral convolution for fabricating artistic virtual environment

    NASA Astrophysics Data System (ADS)

    Lee, Jiunn-Shyan; Wang, Chung-Ming

    2003-04-01

    Vector field occurs not only extensively in scientific applications but also in treasured art such as sculptures and paintings. Artist depicts our natural environment stressing valued directional feature besides color and shape information. Line integral convolution (LIC), developed for imaging vector field in scientific visualization, has potential of producing directional image. In this paper we present several techniques of exploring LIC techniques to generate impressionistic images forming artistic virtual environment. We take advantage of directional information given by a photograph, and incorporate many investigations to the work including non-photorealistic shading technique and statistical detail control. In particular, the non-photorealistic shading technique blends cool and warm colors into the photograph to imitate artists painting convention. Besides, we adopt statistical technique controlling integral length according to image variance to preserve details. Furthermore, we also propose method for generating a series of mip-maps, which revealing constant strokes under multi-resolution viewing and achieving frame coherence in an interactive walkthrough system. The experimental results show merits of emulating satisfyingly and computing efficiently, as a consequence, relying on the proposed technique successfully fabricates a wide category of non-photorealistic rendering (NPR) application such as interactive virtual environment with artistic perception.

  3. Patterned fabric defect detection via convolutional matching pursuit dual-dictionary

    NASA Astrophysics Data System (ADS)

    Jing, Junfeng; Fan, Xiaoting; Li, Pengfei

    2016-05-01

    Automatic patterned fabric defect detection is a promising technique for textile manufacturing due to its low cost and high efficiency. The applicability of most existing algorithms, however, is limited by their intensive computation. To overcome or alleviate the problem, this paper presents a convolutional matching pursuit (CMP) dual-dictionary algorithm for patterned fabric defect detection. A preprocessing with mean sampling is performed to eliminate the influence of background texture of fabric defects. Subsequently, a set of defect-free image blocks are selected as a sample set by sliding window. Dual-dictionary and sparse coefficiencies of the defect-free sample set are obtained via CMP and the K-singular value decomposition (K-SVD) based on a Gabor filter. Then we employ the defect-free and defective fabric image's projections onto the dual-dictionary as features for defect detection. Finally, the test results are determined by comparing the distance between the features to be measured. Experimental results reveal that the proposed algorithm is effective for patterned fabric defect detection and an acceptable average detection rate reaches by 94.2%.

  4. Illustrating Surface Shape in Volume Data via Principal Direction-Driven 3D Line Integral Convolution

    NASA Technical Reports Server (NTRS)

    Interrante, Victoria

    1997-01-01

    The three-dimensional shape and relative depth of a smoothly curving layered transparent surface may be communicated particularly effectively when the surface is artistically enhanced with sparsely distributed opaque detail. This paper describes how the set of principal directions and principal curvatures specified by local geometric operators can be understood to define a natural 'flow' over the surface of an object, and can be used to guide the placement of the lines of a stroke texture that seeks to represent 3D shape information in a perceptually intuitive way. The driving application for this work is the visualization of layered isovalue surfaces in volume data, where the particular identity of an individual surface is not generally known a priori and observers will typically wish to view a variety of different level surfaces from the same distribution, superimposed over underlying opaque structures. By advecting an evenly distributed set of tiny opaque particles, and the empty space between them, via 3D line integral convolution through the vector field defined by the principal directions and principal curvatures of the level surfaces passing through each gridpoint of a 3D volume, it is possible to generate a single scan-converted solid stroke texture that may intuitively represent the essential shape information of any level surface in the volume. To generate longer strokes over more highly curved areas, where the directional information is both most stable and most relevant, and to simultaneously downplay the visual impact of directional information in the flatter regions, one may dynamically redefine the length of the filter kernel according to the magnitude of the maximum principal curvature of the level surface at the point around which it is applied.

  5. Shape Engineered Nanoparticle Fabrication for Biomedical Applications

    NASA Astrophysics Data System (ADS)

    Nasrullah, Azeem

    Semiconductor fabrication research has developed technologies that allow for the deposition and patterning of thin films, and can be applied to many different industries, including the field of medicine. One such application is the fabrication of nanoparticles. There is a wide variety of nanoparticle-based medical diagnostics and therapies, including drug delivery and cancer imaging. Most of the nanoparticles being studied are chemically synthesized and spherical in shape, and studies have shown that other shapes can be more useful in certain applications, especially those that involve in vivo analysis and treatment. Fabrication of particles using a tool set developed from the semiconductor industry can allow for a detailed study of size and shape dependence on nanoparticle uptake in the bloodstream. Particle fabrication is achieved using thin film deposition, ion beam proximity lithography, wet etching, and lift-off, all similar to techniques commonly found in the semiconductor industry. The particles are formed using patterns developed with proximity lithography, and this represents the largest effort in this work. An ion beam, generated by a saddle-field ion source, is used to irradiate a polymeric resist with a thin membrane stencil mask placed in close proximity to the resist coated substrate in order to define the pattern. A saddle-field ion source was constructed and characterized for proximity lithography, with a beam diameter of 4.8 mm for a +/-5% tolerance in current density, a source size range of 0.3--0.9 mm, an average brightness value of 15 nAcm2˙sr , and average exposure times of ≈30 s. Stencil masks were fabricated from silicon nitride membranes in order to generate the pattern for the nanoparticles, and the particles were fabricated using a bi-layer resist and a sacrificial copper layer for release into solution.

  6. Variations in size, shape and asymmetries of the third frontal convolution in hominids: paleoneurological implications for hominin evolution and the origin of language.

    PubMed

    Balzeau, Antoine; Gilissen, Emmanuel; Holloway, Ralph L; Prima, Sylvain; Grimaud-Hervé, Dominique

    2014-11-01

    The study of brain structural asymmetries as anatomical substrates of functional asymmetries in extant humans, great apes, and fossil hominins is of major importance in understanding the structural basis of modern human cognition. We propose methods to quantify the variation in size, shape and bilateral asymmetries of the third frontal convolution (or posterior inferior frontal gyrus) among recent modern humans, bonobos and chimpanzees, and fossil hominins using actual and virtual endocasts. These methodological improvements are necessary to extend previous qualitative studies of these features. We demonstrate both an absolute and relative bilateral increase in the size of the third frontal convolution in width and length between Pan species, as well as in hominins. We also observed a global bilateral increase in the size of the third frontal convolution across all species during hominin evolution, but also non-allometric intra-group variations independent of brain size within the fossil samples. Finally, our results show that the commonly accepted leftward asymmetry of Broca's cap is biased by qualitative observation of individual specimens. The trend during hominin evolution seems to be a reduction in size on the left compared with the right side, and also a clearer definition of the area. The third frontal convolution considered as a whole projects more laterally and antero-posteriorly in the right hemisphere. As a result, the left 'Broca's cap' looks more globular and better defined. Our results also suggest that the pattern of brain asymmetries is similar between Pan paniscus and hominins, leaving the gradient of the degree of asymmetry as the only relevant structural parameter. As the anatomical substrate related to brain asymmetry has been present since the appearance of the hominin lineage, it is not possible to prove a direct relationship between the extent of variations in the size, shape, and asymmetries of the third frontal convolution and the origin of

  7. Fabrication of trough-shaped solar collectors

    DOEpatents

    Schertz, William W.

    1978-01-01

    There is provided a radiant energy concentration and collection device formed of a one-piece thin-walled plastic substrate including a plurality of nonimaging troughs with certain metallized surfaces of the substrate serving as reflective side walls for each trough. The one-piece plastic substrate is provided with a seating surface at the bottom of each trough which conforms to the shape of an energy receiver to be seated therein.

  8. Optofluidic fabrication for 3D-shaped particles.

    PubMed

    Paulsen, Kevin S; Di Carlo, Dino; Chung, Aram J

    2015-01-01

    Complex three-dimensional (3D)-shaped particles could play unique roles in biotechnology, structural mechanics and self-assembly. Current methods of fabricating 3D-shaped particles such as 3D printing, injection moulding or photolithography are limited because of low-resolution, low-throughput or complicated/expensive procedures. Here, we present a novel method called optofluidic fabrication for the generation of complex 3D-shaped polymer particles based on two coupled processes: inertial flow shaping and ultraviolet (UV) light polymerization. Pillars within fluidic platforms are used to deterministically deform photosensitive precursor fluid streams. The channels are then illuminated with patterned UV light to polymerize the photosensitive fluid, creating particles with multi-scale 3D geometries. The fundamental advantages of optofluidic fabrication include high-resolution, multi-scalability, dynamic tunability, simple operation and great potential for bulk fabrication with full automation. Through different combinations of pillar configurations, flow rates and UV light patterns, an infinite set of 3D-shaped particles is available, and a variety are demonstrated. PMID:25904062

  9. Optofluidic fabrication for 3D-shaped particles

    NASA Astrophysics Data System (ADS)

    Paulsen, Kevin S.; di Carlo, Dino; Chung, Aram J.

    2015-04-01

    Complex three-dimensional (3D)-shaped particles could play unique roles in biotechnology, structural mechanics and self-assembly. Current methods of fabricating 3D-shaped particles such as 3D printing, injection moulding or photolithography are limited because of low-resolution, low-throughput or complicated/expensive procedures. Here, we present a novel method called optofluidic fabrication for the generation of complex 3D-shaped polymer particles based on two coupled processes: inertial flow shaping and ultraviolet (UV) light polymerization. Pillars within fluidic platforms are used to deterministically deform photosensitive precursor fluid streams. The channels are then illuminated with patterned UV light to polymerize the photosensitive fluid, creating particles with multi-scale 3D geometries. The fundamental advantages of optofluidic fabrication include high-resolution, multi-scalability, dynamic tunability, simple operation and great potential for bulk fabrication with full automation. Through different combinations of pillar configurations, flow rates and UV light patterns, an infinite set of 3D-shaped particles is available, and a variety are demonstrated.

  10. Net shape fabrication of Alpha Silicon Carbide turbine components

    NASA Technical Reports Server (NTRS)

    Storm, R. S.

    1982-01-01

    Development of Alpha Silicon Carbide components by net shape fabrication techniques has continued in conjunction with several turbine engine programs. Progress in injection molding of simple parts has been extended to much larger components. Turbine rotors fabricated by a one piece molding have been successfully spin tested above design speeds. Static components weighing up to 4.5 kg and 33 cc in diameter have also been produced using this technique. Use of sintering fixtures significantly improves dimensional control. A new Si-SiC composite material has also been developed with average strengths up to 1000 MPa (150 ksi) at 1200 C.

  11. Laser engineered net shaping for direct fabrication of metal components

    SciTech Connect

    Dimos, D.; Schlienger, M.E.

    1997-09-01

    Sandia National Laboratories is developing a new technology to fabricate three-dimensional metallic components directly from CAD solid models. This process, called Laser Engineered Net Shaping (LENS{trademark}), exhibits enormous potential to revolutionize the way in which metal parts, such as complex prototypes, tooling, and small lot production parts, are produced. To perform the process, metal powder is injected into a molten pool created by a focused, high powered laser beam. Simultaneously, the substrate on which the deposition is occurring is scanned under the beam/powder interaction zone to fabricate the desired cross-sectional geometry. Consecutive layers are sequentially deposited, thereby producing a three-dimensional metal component.

  12. Fabrication of Custom-Shaped Grafts for Cartilage Regeneration

    PubMed Central

    Koo, Seungbum; Hargreaves, Brian A.; Gold, Garry E.; Dragoo, Jason L.

    2011-01-01

    Transplantation of engineered cartilage grafts is a promising method to treat diseased articular cartilage. The interfacial areas between the graft and the native tissues play an important role in the successful integration of the graft to adjacent native tissues. The purposes of the study were to create a custom shaped graft through 3D tissue shape reconstruction and rapid-prototype molding methods using MRI data, and to test the accuracy of the custom shaped graft against the original anatomical defect. An iatrogenic defect on the distal femur was identified with a 1.5 Tesla MRI and its shape was reconstructed into a three-dimensional (3D) computer model by processing the 3D MRI data. First, the accuracy of the MRI-derived 3D model was tested against a laser-scan based 3D model of the defect. A custom-shaped polyurethane graft was fabricated from the laser-scan based 3D model by creating custom molds through computer aided design and rapid-prototyping methods. The polyurethane tissue was laser-scanned again to calculate the accuracy of this process compared to the original defect. The volumes of the defect models from MRI and laser-scan were 537 mm3 and 405 mm3, respectively, implying that the MRI model was 33% larger than the laser-scan model. The average (±SD) distance deviation of the exterior surface of the MRI model from the laser-scan model was 0.4±0.4 mm. The custom-shaped tissue created from the molds was qualitatively very similar to the original shape of the defect. The volume of the custom-shaped cartilage tissue was 463 mm3 which was 15% larger than the laser-scan model. The average (±SD) distance deviation between the two models was 0.04±0.19 mm. Custom-shaped engineered grafts can be fabricated from standard sequence 3-D MRI data with the use of CAD and rapid-prototyping technology, which may help solve the interfacial problem between native cartilage and graft, if the grafts are custom made for the specific defect. The major source of error in

  13. Fabrication of a helical coil shape memory alloy actuator

    SciTech Connect

    O`Donnell, R.E.

    1992-02-01

    A fabrication process was developed to form, heat treat, and join NiTi shape memory alloy helical coils for use as mechanical actuators. Tooling and procedures were developed to wind both extension and compression-type coils on a manual lathe. Heat treating fixtures and techniques were used to set the ``memory`` of the NiTi alloy to the desired configuration. A swaging process was devised to fasten shape memory alloy extension coils to end fittings for use in actuator testing and for potential attachment to mechanical devices. The strength of this mechanical joint was evaluated.

  14. Fabrication of a helical coil shape memory alloy actuator

    SciTech Connect

    O'Donnell, R.E.

    1992-02-01

    A fabrication process was developed to form, heat treat, and join NiTi shape memory alloy helical coils for use as mechanical actuators. Tooling and procedures were developed to wind both extension and compression-type coils on a manual lathe. Heat treating fixtures and techniques were used to set the memory'' of the NiTi alloy to the desired configuration. A swaging process was devised to fasten shape memory alloy extension coils to end fittings for use in actuator testing and for potential attachment to mechanical devices. The strength of this mechanical joint was evaluated.

  15. EDITORIAL: Designer fabrication: nanotemplates get in shape Designer fabrication: nanotemplates get in shape

    NASA Astrophysics Data System (ADS)

    Demming, Anna

    2013-02-01

    People working in device design rarely see something that works without thinking how it could be made to work better. The work on anodic aluminum oxide materials in this issue provides a case in point [1]. Over the past century researchers have observed, manipulated and exploited the porous structures that result when anodizing aluminum in for example oxalic, sulfuric, and phosphoric acid solutions [1, 2]. The self-organized pore arrays have demonstrated the potential to facilitate high through-put, low-cost fabrication of nanocomposites as well as other nanostructures. The straight self-aligned nanochannels in porous anodic aluminum oxide (AAO) have long been accepted as an inherent property of these films and for many applications they are an attractive attribute. However, researchers in Taiwan have considered a novel manifestation of AAO materials which may enhance their natural attributes by generating arrays that bend [3]. Their work is an example of how even well studied systems continue to harbour surprises and scope for creative innovation. As the authors point out, 'This novel fan-out platform facilitates probing and handling many signals from different areas on a sample's surface and is therefore promising for applications in detection and manipulation at the nanoscale level'. It has long been recognized that the inter-pore distance, pore diameter and pore depth in AAO can be controlled by changing the anodization conditions. These accommodating features have motivated researchers to seek a better understanding of how to optimize fabrication conditions. A collaboration of researchers in Sweden, Chile and Uruguay studied the structural and optical properties of silver nanowires electrodeposited in commercially available nanoporous alumina templates, with a nominal pore diameter of 20 nm [4]. Their results revealed a decrease in the uniformity of pore filling with increasing deposition overpotential and suggested that overpotentials were preferred for the

  16. EDITORIAL: Designer fabrication: nanotemplates get in shape Designer fabrication: nanotemplates get in shape

    NASA Astrophysics Data System (ADS)

    Demming, Anna

    2013-02-01

    People working in device design rarely see something that works without thinking how it could be made to work better. The work on anodic aluminum oxide materials in this issue provides a case in point [1]. Over the past century researchers have observed, manipulated and exploited the porous structures that result when anodizing aluminum in for example oxalic, sulfuric, and phosphoric acid solutions [1, 2]. The self-organized pore arrays have demonstrated the potential to facilitate high through-put, low-cost fabrication of nanocomposites as well as other nanostructures. The straight self-aligned nanochannels in porous anodic aluminum oxide (AAO) have long been accepted as an inherent property of these films and for many applications they are an attractive attribute. However, researchers in Taiwan have considered a novel manifestation of AAO materials which may enhance their natural attributes by generating arrays that bend [3]. Their work is an example of how even well studied systems continue to harbour surprises and scope for creative innovation. As the authors point out, 'This novel fan-out platform facilitates probing and handling many signals from different areas on a sample's surface and is therefore promising for applications in detection and manipulation at the nanoscale level'. It has long been recognized that the inter-pore distance, pore diameter and pore depth in AAO can be controlled by changing the anodization conditions. These accommodating features have motivated researchers to seek a better understanding of how to optimize fabrication conditions. A collaboration of researchers in Sweden, Chile and Uruguay studied the structural and optical properties of silver nanowires electrodeposited in commercially available nanoporous alumina templates, with a nominal pore diameter of 20 nm [4]. Their results revealed a decrease in the uniformity of pore filling with increasing deposition overpotential and suggested that overpotentials were preferred for the

  17. Thermocapillary Technique for Shaping and Fabricating Optical Ribbon Waveguides

    NASA Astrophysics Data System (ADS)

    Fiedler, Kevin; Troian, Sandra

    The demand for ever increasing bandwidth and higher speed communication has ushered the next generation optoelectronic integrated circuits which directly incorporate polymer optical waveguide devices. Polymer melts are very versatile materials which have been successfully cast into planar single- and multimode waveguides using techniques such as embossing, photolithography and direct laser writing. In this talk, we describe a novel thermocapillary patterning method for fabricating waveguides in which the free surface of an ultrathin molten polymer film is exposed to a spatially inhomogeneous temperature field via thermal conduction from a nearby cooled mask pattern held in close proximity. The ensuring surface temperature distribution is purposely designed to pool liquid selectively into ribbon shapes suitable for optical waveguiding, but with rounded and not rectangular cross sectional areas due to capillary forces. The solidified waveguide patterns which result from this non-contact one step procedure exhibit ultrasmooth interfaces suitable for demanding optoelectronic applications. To complement these studies, we have also conducted finite element simulations for quantifying the influence of non-rectangular cross-sectional shapes on mode propagation and losses. Kf gratefully acknowledges support from a NASA Space Technology Research Fellowship.

  18. Distal Convoluted Tubule

    PubMed Central

    Ellison, David H.

    2014-01-01

    The distal convoluted tubule is the nephron segment that lies immediately downstream of the macula densa. Although short in length, the distal convoluted tubule plays a critical role in sodium, potassium, and divalent cation homeostasis. Recent genetic and physiologic studies have greatly expanded our understanding of how the distal convoluted tubule regulates these processes at the molecular level. This article provides an update on the distal convoluted tubule, highlighting concepts and pathophysiology relevant to clinical practice. PMID:24855283

  19. Fabrication of ceramic components using mold shape deposition manufacturing

    NASA Astrophysics Data System (ADS)

    Cooper, Alexander G.

    Mold Shape Deposition Manufacturing (Mold SDM) is a new process for the fabrication of geometrically complex, structural ceramic components. This thesis describes the development of the Mold SDM process, including process steps, materials selection, planning strategies and automation. Initial characterization results are presented and these are used to compare the process to competing manufacturing processes. A range of current and potential applications for ceramic, as well as metal and polymer parts are discussed. The benefits and limitations of ceramic materials for structural applications are discussed to motivate the need for a manufacturing process capable of rapidly producing high quality, geometrically complex, structural ceramic components. The Mold SDM process was developed to address this need. Mold SDM is based on Shape Deposition Manufacturing (SDM) and uses SDM techniques to build fugitive wax molds which can then be used to build ceramic parts by gelcasting. SDM is an additive-subtractive layered manufacturing process which allows it to build geometrically complex parts. The subtraction step differentiates Mold SDM from other layered manufacturing processes and allows accurate, high quality surfaces to be produced. The performance of the process was increased by identifying the key material properties and then selecting improved materials combinations. Candidate materials were evaluated in terms of machinability, shrinkage, heat resistance and chemical compatibility. A number of preferred materials combinations were developed and used to produce ceramic, metal and polymer parts. A number of new process planning strategies and build techniques were developed. The manufacturability analysis determines whether a part is manufacturable and the orientation selection guidelines help in the selection of optimum build directions. New decomposition techniques take advantage of process capabilities to improve part quality and build rate. Initial process

  20. Fabrication of Adhesive Lenses Using Free Surface Shaping

    NASA Astrophysics Data System (ADS)

    Hoheisel, D.; Kelb, C.; Wall, M.; Roth, B.; Rissing, L.

    2013-09-01

    Two approaches for fabricating polymer lenses are presented in this paper. Both are based on filling circular holes with UV curing adhesives. Initially, the viscous adhesive material creates a liquid and spherical free surface due to its own surface tension. This shape is then preserved by curing with UV-hardening light. For the first approach, the holes are generated in a 4 inch Si-wafer by deep reactive ion etching (DRIE) and for the second, a polydimethylsiloxane (PDMS) mould is manufactured. Three types of UV-curing adhesives are investigated (NOA 61, NOA 88 and NEA 121 by Norland Products). Preliminary to the determination of the lens curvature, a contact angle goniometer is used for taking side view images of the lenses. The radius of curvature is then extracted via image processing with the software MATLAB®. Furthermore, the surface roughness of the PDMS mould and the generated lenses is measured with a white light interferometer to characterize the casting process. The resolution power of the generated lenses is evaluated by measurement of their point spread functions (psf) and modulation transfer functions (mtf), respectively.

  1. Fabrication of silicon-based shape memory alloy micro-actuators

    NASA Technical Reports Server (NTRS)

    Johnson, A. David; Busch, John D.; Ray, Curtis A.; Sloan, Charles L.

    1992-01-01

    Thin film shape memory alloy has been integrated with silicon in a new actuation mechanism for microelectromechanical systems. This paper compares nickel-titanium film with other actuators, describes recent results of chemical milling processes developed to fabricate shape memory alloy microactuators in silicon, and describes simple actuation mechanisms which have been fabricated and tested.

  2. Method for fabricating uranium alloy articles without shape memory effects

    DOEpatents

    Banker, John G.

    1985-01-01

    Uranium-rich niobium and niobium-zirconium alloys possess a characteristic known as shape memory effect wherein shaped articles of these alloys recover their original shape when heated. The present invention circumvents this memory behavior by forming the alloys into the desired configuration at elevated temperatures with "cold" matched dies and maintaining the shaped articles between the dies until the articles cool to ambient temperature.

  3. Method for fabricating uranium alloy articles without shape memory effects

    DOEpatents

    Banker, J.G.

    1980-05-21

    Uranium-rich niobium and niobium-zirconium alloys possess a characteristic known as shape memory effect wherein shaped articles of these alloys recover their original shape when heated. The present invention circumvents this memory behavior by forming the alloys into the desired configuration at elevated temperatures with cold matched dies and maintaining the shaped articles between the dies until the articles cool to ambient temperature.

  4. Adjustable reed for weaving net-shaped tailored fabrics

    NASA Technical Reports Server (NTRS)

    Farley, Gary L. (Inventor)

    1995-01-01

    An apparatus and method for forming woven fabrics through the use of an adjustable reed. The adjustable reed has multiple groups of reed wires that guide the warp yarns. The groups of reed wires move on reed rails parallel to the warp direction. In addition, rail expanders permit the space between the reed wires to be modified and telescoping rods attached to the rail sliders can be turned to permit the reed wires to be skewed to alter the fill yarn angle. These adjustments to the reed permit simultaneous variation of fill yarn angles and fabric widths and allow these variations to be made during fabrication, without the need to halt production.

  5. Fabrication of porous NiTi shape memory alloy structures using laser engineered net shaping.

    PubMed

    Krishna, B Vamsi; Bose, Susmita; Bandyopadhyay, Amit

    2009-05-01

    Porous NiTi alloy samples were fabricated with 12-36% porosity from equiatomic NiTi alloy powder using laser engineered net shaping (LENS). The effects of processing parameters on density and properties of laser-processed NiTi alloy samples were investigated. It was found that the density increased rapidly with increasing the specific energy input up to 50 J/mm(3). Further increase in the energy input had small effect on density. High cooling rates associated with LENS processing resulted in higher amount of cubic B2 phase, and increased the reverse transformation temperatures of porous NiTi samples due to thermally induced stresses and defects. Transformation temperatures were found to be independent of pore volume, though higher pore volume in the samples decreased the maximum recoverable strain from 6% to 4%. Porous NiTi alloy samples with 12-36% porosity exhibited low Young's modulus between 2 and 18 GPa as well as high compressive strength and recoverable strain. Because of high open pore volume between 36% and 62% of total volume fraction porosity, these porous NiTi alloy samples can potentially accelerate the healing process and improve biological fixation when implanted in vivo. Thus porous NiTi is a promising biomaterial for hard tissue replacements. PMID:18937263

  6. Net-Shape Tailored Fabrics For Complex Composite Structures

    NASA Technical Reports Server (NTRS)

    Farley, Gary L.

    1995-01-01

    Proposed novel looms used to make fabric preforms for complex structural elements, both stiffening elements and skin, from continuous fiber-reinforced composite material. Components of looms include custom reed and differential fabric takeup system. Structural parts made best explained by reference to curved "I" cross-section frame. Technology not limited to these fiber orientations or geometry; fiber angles, frame radius of curvature, frame height, and flange width changed along length of structure. Weaving technology equally applicable to structural skins, such as wing of fuselage skins.

  7. Method for fabrication of cylindrical microlenses of selected shape

    DOEpatents

    Snyder, J.J.; Baer, T.M.

    1992-01-14

    The present invention provides a diffraction limited, high numerical aperture (fast) cylindrical microlens. The method for making the microlens is adaptable to produce a cylindrical lens that has almost any shape on its optical surfaces. The cylindrical lens may have a shape, such as elliptical or hyperbolic, designed to transform some particular given input light distribution into some desired output light distribution. In the method, the desired shape is first formed in a glass preform. Then, the preform is heated to the minimum drawing temperature and a fiber is drawn from it. The cross-sectional shape of the fiber bears a direct relation to the shape of the preform from which it was drawn. During the drawing process, the surfaces become optically smooth due to fire polishing. The present invention has many applications, such as integrated optics, optical detectors and laser diodes. The lens, when connected to a laser diode bar, can provide a high intensity source of laser radiation for pumping a high average power solid state laser. In integrated optics, a lens can be used to couple light into and out of apertures such as waveguides. The lens can also be used to collect light, and focus it on a detector. 11 figs.

  8. Method for fabrication of cylindrical microlenses of selected shape

    DOEpatents

    Snyder, James J.; Baer, Thomas M.

    1992-01-01

    The present invention provides a diffraction limited, high numerical aperture (fast) cylindrical microlens. The method for making the microlens is adaptable to produce a cylindrical lens that has almost any shape on its optical surfaces. The cylindrical lens may have a shape, such as elliptical or hyperbolic, designed to transform some particular given input light distribution into some desired output light distribution. In the method, the desired shape is first formed in a glass preform. Then, the preform is heated to the minimum drawing temperature and a fiber is drawn from it. The cross-sectional shape of the fiber bears a direct relation to the shape of the preform from which it was drawn. During the drawing process, the surfaces become optically smooth due to fire polishing. The present invention has many applications, such as integrated optics, optical detectors and laser diodes. The lens, when connected to a laser diode bar, can provide a high intensity source of laser radiation for pumping a high average power solid state laser. In integrated optics, a lens can be used to couple light into and out of apertures such as waveguides. The lens can also be used to collect light, and focus it on a detector.

  9. Progress in net shape fabrication of alpha sic turbine components

    NASA Technical Reports Server (NTRS)

    Sweeting, T. B.; Frechette, F. J.; Macbeth, J. W.

    1984-01-01

    An update of the status of ceramic component development of the AGT Programs is presented. Activity on AGTO Program focussed on the following: successful transition from the prototype to engine configuration rotor, investigation of alternate rotor molding techniques, and completion of scroll assemblies. Progress on the Garrett AGT Program was highlighted by the introduction of plastic molding and extrusion to parts which were previously fabricated by slip casting and isopressing respectively.

  10. Manipulating cell shape by placing cells into micro-fabricated chambers.

    PubMed

    Chang, Fred; Atilgan, Erdinc; Burgess, David; Minc, Nicolas

    2014-01-01

    Cell shape is an important cellular parameter that influences the spatial organization and function of cells. However, it has often been challenging to study the effects of cell shape because of difficulties in experimentally controlling cell shape in a defined way. We describe here a method of physically manipulating sea urchin cells into specified shapes by inserting them into micro-fabricated chambers of different shapes. This method allows for generation of large systematic and quantitative data sets and may be adaptable for different cell types and contexts. PMID:24633802

  11. Fabrication of bamboo-shaped GaN nanorods

    NASA Astrophysics Data System (ADS)

    Li, H.; Li, J. Y.; He, M.; Chen, X. L.; Zhang, Z.

    Bamboo-shaped GaN nanorods were formed through a simple sublimation method. They were characterized by means of X-ray powder diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and selected-area electron diffraction (SAED). The TEM image showed that the nanorods were bamboo-like. XRD, HRTEM and SAED patterns indicated that the nanorods were single-crystal wurtzite GaN.

  12. Fabrication of Pillar Shaped Electrode Arrays for Artificial Retinal Implants

    PubMed Central

    Kim, Eui Tae; Seo, Jong-Mo; Woo, Se Joon; Zhou, Jing Ai; Chung, Hum; Kim, Sung June

    2008-01-01

    Polyimide has been widely applied to neural prosthetic devices, such as the retinal implants, due to its well-known biocompatibility and ability to be micropatterned. However, planar films of polyimide that are typically employed show a limited ability in reducing the distance between electrodes and targeting cell layers, which limits site resolution for effective multi-channel stimulation. In this paper, we report a newly designed device with a pillar structure that more effectively interfaces with the target. Electrode arrays were successfully fabricated and safely implanted inside the rabbit eye in suprachoroidal space. Optical Coherence Tomography (OCT) showed well-preserved pillar structures of the electrode without damage. Bipolar stimulation was applied through paired sites (6:1) and the neural responses were successfully recorded from several regions in the visual cortex. Electrically evoked cortical potential by the pillar electrode array stimulation were compared to visual evoked potential under full-field light stimulation.

  13. Near net shape processing for solar thermal propulsion hardware using directed light fabrication

    SciTech Connect

    Milewski, J.O.; Fonseca, J.C.; Lewis, G.K.

    1998-12-01

    Directed light fabrication (DLF) is a direct metal deposition process that fuses gas delivered powder, in the focal zone of a high powered laser beam to form fully fused near net shaped components. The near net shape processing of rhenium, tungsten, iridium and other high temperature materials may offer significant cost savings compared with conventional processing. This paper describes a 3D parametric solid model, integrated with a manufacturing model, and creating a control field which runs on the DLF machine directly depositing a fully dense, solid metal, near net shaped, nozzle component. Examples of DLF deposited rhenium, iridium and tantalum, from previous work, show a continuously solidified microstructure in rod and tube shapes. Entrapped porosity indicates the required direction for continued process development. These combined results demonstrate the potential for a new method to fabricate complex near net shaped components using materials of interest to the space and aerospace industries.

  14. New gelling systems to fabricate complex-shaped transparent ceramics

    NASA Astrophysics Data System (ADS)

    Yang, Yan; Wu, Yiquan

    2013-06-01

    The aim of this work was to prepare transparent ceramics with large size and complex-shapes by a new water-soluble gelling agent poly(isobutylene-alt-maleic anhydride). Alumina was used as an example of the application of the new gelling system. A stable suspension with 38vol% was prepared by ball milling. Trapped bubbles were removed before casting to obtain homogenous green bodies. The microstructure and particle distribution of alumina raw material were tested. The thermal behavior of the alumina green body was investigated, which exhibited low weight loss when compared with other gelling processes. The influence of solid loading and gelling agent addition were studied on the basis of rheological behavior of the suspension. The microstructures of alumina powders, green bodies before and after de-bindering process, were compared to understand the gelling condition between alumina particles and gelling agent.

  15. Method of forming variable cross-sectional shaped three-dimensional fabrics

    NASA Technical Reports Server (NTRS)

    Mohamed, Mansour H. (Inventor); Zhang, Zhong-Huai (Inventor)

    1992-01-01

    Method of weaving a variable cross-sectional shaped three-dimensional fabric which utilizes different weft yarn insertion from at least one side of the warp layers for selectively inserting weft yarns into different portions of the fabric cross-sectional profile defined by the warp yarn layers during the weaving process. If inserted from both sides of the warp yarn layers, the weft yarns may be inserted simultaneously or alternately from each side of the warp yarn layers. The vertical yarn is then inserted into the fabric by reciprocation of a plurality of harnesses which separate the vertical yarn into a plurality of vertical yarn systems as required by the shape of the three-dimensional fabric being formed.

  16. Scalable, Shape-specific, Top-down Fabrication Methods for the Synthesis of Engineered Colloidal Particles

    PubMed Central

    Merkel, Timothy J.; Herlihy, Kevin P.; Nunes, Janine; Orgel, Ryan M.; Rolland, Jason P.; DeSimone, Joseph M.

    2010-01-01

    The search for a method to fabricate non-spherical colloidal particles from a variety of materials is of growing interest. As the commercialization of nanotechnology continues to expand, the ability to translate particle fabrication methods from a laboratory to an industrial scale is of increasing significance. In this article, we examine several of the most readily scalable top-down methods for the fabrication of such shape specific particles and compare their capabilities with respect to particle composition, size, shape and complexity as well as the scalability of the method. We offer an extensive examination of Particle Replication In Non-wetting Templates (PRINT®) with regards to the versatility and scalability of this technique. We also detail the specific methods used in PRINT particle fabrication, including harvesting, purification and surface modification techniques, with examination of both past and current methods. PMID:20000620

  17. Asymmetric quantum convolutional codes

    NASA Astrophysics Data System (ADS)

    La Guardia, Giuliano G.

    2016-01-01

    In this paper, we construct the first families of asymmetric quantum convolutional codes (AQCCs). These new AQCCs are constructed by means of the CSS-type construction applied to suitable families of classical convolutional codes, which are also constructed here. The new codes have non-catastrophic generator matrices, and they have great asymmetry. Since our constructions are performed algebraically, i.e. we develop general algebraic methods and properties to perform the constructions, it is possible to derive several families of such codes and not only codes with specific parameters. Additionally, several different types of such codes are obtained.

  18. Shape-controllable, bottom-up fabrication of microlens using oblique angle deposition.

    PubMed

    Choi, Hee Ju; Kang, Eun Kyu; Ju, Gun Wu; Song, Young Min; Lee, Yong Tak

    2016-07-15

    This Letter reports a novel method for the simple fabrication of microlens arrays with a controlled shape and diameter on glass substrates. Multilayer stacks of silicon dioxide deposited by oblique angle deposition with hole mask patterns enable microlens formation. Precise control of mask height and distance, as well as oblique angle steps between deposited layers, supports the controllability of microlens geometry. The fabricated microlens arrays with designed geometry exhibit uniform optical properties. PMID:27420527

  19. Understanding the microstructure and properties of components fabricated by laser engineered net shaping (LENS)

    SciTech Connect

    GRIFFITH,MICHELLE L.; ENSZ,MARK T.; PUSKAR,JOSEPH D.; ROBINO,CHARLES V.; BROOKS,JOHN A.; PHILLIBER,JOEL A.; SMUGERESKY,JOHN E.; HOFMEISTER,W.H.

    2000-05-18

    Laser Engineered Net Shaping (LENS) is a novel manufacturing process for fabricating metal parts directly from Computer Aided Design (CAD) solid models. The process is similar to rapid prototyping technologies in its approach to fabricate a solid component by layer additive methods. However, the LENS technology is unique in that fully dense metal components with material properties that are similar to that of wrought materials can be fabricated. The LENS process has the potential to dramatically reduce the time and cost required realizing functional metal parts. In addition, the process can fabricate complex internal features not possible using existing manufacturing processes. The real promise of the technology is the potential to manipulate the material fabrication and properties through precision deposition of the material, which includes thermal behavior control, layered or graded deposition of multi-materials, and process parameter selection. This paper describes the authors' research to understand solidification aspects, thermal behavior, and material properties for laser metal deposition technologies.

  20. Fabrication and Characterization of Carbon Nanofiber Reinforced Shape Memory Epoxy (CNFR-SME) Composites

    NASA Astrophysics Data System (ADS)

    Wang, Jiuyang

    Shape memory polymers have a wide range of applications due to their ability to mechanically change shapes upon external stimulus, while their achievable composite counterparts prove even more versatile. An overview of literature on shape memory materials, fillers and composites was provided to pave a foundation for the materials used in the current study and their inherent benefits. This study details carbon nanofiber and composite fabrication and contrasts their material properties. In the first section, the morphology and surface chemistry of electrospun-poly(acrylonitrile)-based carbon nanofiber webs were tailored through various fabrication methods and impregnated with a shape memory epoxy. The morphologies, chemical compositions, thermal stabilities and electrical resistivities of the carbon nanofibers and composites were then characterized. In the second section, an overview of thermal, mechanical and shape memory characterization techniques for shape memory polymers and their composites was provided. Thermal and mechanical properties in addition to the kinetic and dynamic shape memory performances of neat epoxy and carbon nanofiber/epoxy composites were characterized. The various carbon nanofiber web modifications proved to have notable influence on their respective composite performances. The results from these two sections lead to an enhanced understanding of these carbon nanofiber reinforced shape memory epoxy composites and provided insight for future studies to tune these composites at will.

  1. Fabrication and Testing of a Leading-Edge-Shaped Heat Pipe

    NASA Technical Reports Server (NTRS)

    Glass, David E.; Merrigan, Michael A.; Sena, J. Tom; Reid, Robert S.

    1998-01-01

    The development of a refractory-composite/heat-pipe-cooled leading edge has evolved from the design stage to the fabrication and testing of a full size, leading-edge-shaped heat pipe. The heat pipe had a 'D-shaped' cross section and was fabricated from arc cast Mo-4lRe. An artery was included in the wick. Several issues were resolved with the fabrication of the sharp leading edge radius heat pipe. The heat pipe was tested in a vacuum chamber at Los Alamos National Laboratory using induction heating and was started up from the frozen state several times. However, design temperatures and heat fluxes were not obtained due to premature failure of the heat pipe resulting from electrical discharge between the induction heating apparatus and the heat pipe. Though a testing anomaly caused premature failure of the heat pipe, successful startup and operation of the heat pipe was demonstrated.

  2. Scalable shape-controlled fabrication of curved microstructures using a femtosecond laser wet-etching process.

    PubMed

    Bian, Hao; Yang, Qing; Chen, Feng; Liu, Hewei; Du, Guangqing; Deng, Zefang; Si, Jinhai; Yun, Feng; Hou, Xun

    2013-07-01

    Materials with curvilinear surface microstructures are highly desirable for micro-optical and biomedical devices. However, realization of such devices efficiently remains technically challenging. This paper demonstrates a facile and flexible method to fabricate curvilinear microstructures with controllable shapes and dimensions. The method composes of femtosecond laser exposures and chemical etching process with the hydrofluoric acid solutions. By fixed-point and step-in laser irradiations followed by the chemical treatments, concave microstructures with different profiles such as spherical, conical, bell-like and parabola were fabricated on silica glasses. The convex structures were replicated on polymers by the casting replication process. In this work, we used this technique to fabricate high-quality microlens arrays and high-aspect-ratio microwells which can be used in 3D cell culture. This approach offers several advantages such as high-efficient, scalable shape-controllable and easy manipulations. PMID:23623098

  3. Rapid fabrication of cylindrical microlens array by shaped femtosecond laser direct writing

    NASA Astrophysics Data System (ADS)

    Luo, Zhi; Wang, Cong; Yin, Kai; Dong, Xinran; Chu, Dongkai; Duan, Ji'an

    2016-07-01

    In this study, a remarkable spatial shaping approach is proposed to transform Gaussian femtosecond laser into quasi-Bessel optical field with compressed central lobe and amplified side lobes of the spatial intensity profile. Based on this technique, inward bulge trench (IBT) structures are fabricated with high efficiency on the surface of PMMA by a single illumination step, whose cross-sectional profile is opposite to the results fabricated by Gaussian beam. And plano-convex cylindrical microlens array, which is consistent in size and shape throughout a large sample area, is formed through simply piecing together the IBT structures during fabricating process. Furthermore, numerical simulations of optical field in radial direction and on-axial direction are exploited to rationalize the dependence of the patterned microstructures on the spatial intensity distribution of femtosecond laser.

  4. Free form fabrication of metallic components using laser engineered net shaping (LENS{trademark})

    SciTech Connect

    Griffith, M.L.; Keicher, D.M.; Atwood, C.L.

    1996-09-01

    Solid free form fabrication is one of the fastest growing automated manufacturing technologies that has significantly impacted the length of time between initial concept and actual part fabrication. Starting with CAD renditions of new components, several techniques such as stereolithography and selective laser sintering are being used to fabricate highly accurate complex three-dimensional concept models using polymeric materials. Coupled with investment casting techniques, sacrificial polymeric objects are used to minimize costs and time to fabricate tooling used to make complex metal castings. This paper will describe recent developments in a new technology, known as LENS{sup {trademark}} (Laser Engineered Net Shaping), to fabricate metal components directly from CAD solid models and thus further reduce the lead times for metal part fabrication. In a manner analogous to stereolithography or selective sintering, the LENS{sup {trademark}} process builds metal parts line by line and layer by layer. Metal particles are injected into a laser beam, where they are melted and deposited onto a substrate as a miniature weld pool. The trace of the laser beam on the substrate is driven by the definition of CAD models until the desired net-shaped densified metal component is produced.

  5. Laser Spray Fabrication for Net-Shape Rapid Product Realization LDRD

    SciTech Connect

    Atwood, C.L.; Ensz, M.T.; Greene, D.L.; Griffith, M.L.; Harwell, L.D.; Jeantette, F.P.; Keicher, D.M.; Oliver, M.S.; Reckaway, D.E.; Romero, J.A.; Schlienger, M.E.; Smugeresky, J.D.

    1999-04-01

    The primary purpose of this LDRD project was to characterize the laser deposition process and determine the feasibility of fabricating complex near-net shapes directly from a CAD solid model. Process characterization provided direction in developing a system to fabricate complex shapes directly from a CAD solid model. Our goal for this LDRD was to develop a system that is robust and provides a significant advancement to existing technologies (e.g., polymeric-based rapid prototyping, laser welding). Development of the process will allow design engineers to produce functional models of their designs directly from CAD files. The turnaround time for complex geometrical shaped parts will be hours instead of days and days instead of months. With reduced turnaround time, more time can be spent on the product-design phase to ensure that the best component design is achieved. Maturation of this technology will revolutionize the way the world produces structural components.

  6. Fabrication method for cores of structural sandwich materials including star shaped core cells

    DOEpatents

    Christensen, Richard M.

    1997-01-01

    A method for fabricating structural sandwich materials having a core pattern which utilizes star and non-star shaped cells. The sheets of material are bonded together or a single folded sheet is used, and bonded or welded at specific locations, into a flat configuration, and are then mechanically pulled or expanded normal to the plane of the sheets which expand to form the cells. This method can be utilized to fabricate other geometric cell arrangements than the star/non-star shaped cells. Four sheets of material (either a pair of bonded sheets or a single folded sheet) are bonded so as to define an area therebetween, which forms the star shaped cell when expanded.

  7. Fabrication method for cores of structural sandwich materials including star shaped core cells

    DOEpatents

    Christensen, R.M.

    1997-07-15

    A method for fabricating structural sandwich materials having a core pattern which utilizes star and non-star shaped cells is disclosed. The sheets of material are bonded together or a single folded sheet is used, and bonded or welded at specific locations, into a flat configuration, and are then mechanically pulled or expanded normal to the plane of the sheets which expand to form the cells. This method can be utilized to fabricate other geometric cell arrangements than the star/non-star shaped cells. Four sheets of material (either a pair of bonded sheets or a single folded sheet) are bonded so as to define an area therebetween, which forms the star shaped cell when expanded. 3 figs.

  8. Femtosecond laser microchannels fabrication based on electrons dynamics control using temporally or spatially shaped pulses

    NASA Astrophysics Data System (ADS)

    Yan, Xueliang; Hu, Jie; Li, Xiaowei; Xia, Bo; Liu, Pengjun; Lu, Yongfeng; Jiang, Lan

    2014-11-01

    With ultrashort pulse durations and ultrahigh power densities, femtosecond laser presents unique advantages of high precision and high quality fabrication of microchannels in transparent materials. In our study, by shaping femtosecond laser pulse energy distribution in temporal or spatial domains, localized transient electrons dynamics and the subsequent processes, such as phase changes, can be controlled, leading to the dramatic increases in the capability of femtosecond laser microchannels fabrication. The temporally shaped femtosecond laser pulse trains can significantly enhance the material removal rate in both water-assisted femtosecond laser drilling and femtosecond laser irradiation followed by chemical etching. Besides, high-aspect-ratio and small-diameter microchannels are drilled by spatially shaped femtosecond laser pulses.

  9. Powder-Coated Towpreg: Avenues to Near Net Shape Fabrication of High Performance Composites

    NASA Technical Reports Server (NTRS)

    Johnston, N. J.; Cano, R. J.; Marchello, J. M.; Sandusky, D. A.

    1995-01-01

    Near net shape parts were fabricated from powder-coated preforms. Key issues including powder loss during weaving and tow/tow friction during braiding were addressed, respectively, by fusing the powder to the fiber prior to weaving and applying a water-based gel to the towpreg prior to braiding. A 4:1 debulking of a complex 3-D woven powder-coated preform was achieved in a single step utilizing expansion rubber molding. Also, a process was developed for using powder-coated towpreg to fabricate consolidated ribbon having good dimensional integrity and low voids. Such ribbon will be required for in situ fabrication of structural components via heated head advanced tow placement. To implement process control and ensure high quality ribbon, the ribbonizer heat transfer and pulling force were modeled from fundamental principles. Most of the new ribbons were fabricated from dry polyarylene ether and polymide powders.

  10. Understanding deep convolutional networks.

    PubMed

    Mallat, Stéphane

    2016-04-13

    Deep convolutional networks provide state-of-the-art classifications and regressions results over many high-dimensional problems. We review their architecture, which scatters data with a cascade of linear filter weights and nonlinearities. A mathematical framework is introduced to analyse their properties. Computations of invariants involve multiscale contractions with wavelets, the linearization of hierarchical symmetries and sparse separations. Applications are discussed. PMID:26953183

  11. Laser engineered net shaping (LENS) for the fabrication of metallic components

    SciTech Connect

    Griffith, M.L.; Keicher, D.L.; Romero, J.A.; Atwood, C.L.; Harwell, L.D.; Greene, D.L.; Smugeresky, J.E.

    1996-06-01

    Solid free form fabrication is a fast growing automated manufacturing technology that has reduced the time between initial concept and fabrication. Starting with CAD renditions of new components, techniques such as stereolithography and selective laser sintering are being used to fabricate highly accurate complex 3-D objects using polymers. Together with investment casting, sacrificial polymeric objects are used to minimize cost and time to fabricate tooling used to make complex metal casting. This paper describes recent developments in LENS{trademark} (Laser Engineered Net Shaping) to fabricate the metal components {ital directly} from CAD solid models and thus further reduce the lead time. Like stereolithography or selective sintering, LENS builds metal parts line by line and layer by layer. Metal particles are injected into a laser beam where they are melted and deposited onto a substrate as a miniature weld pool. The trace of the laser beam on the substrate is driven by the definition of CAD models until the desired net-shaped densified metal component is produced.

  12. Laser Engineered Net Shaping (LENS(TM)): A Tool for Direct Fabrication of Metal Parts

    SciTech Connect

    Atwood, C.; Ensz, M.; Greene, D.; Griffith, M.; Harwell, L.; Reckaway, D.; Romero, T.; Schlienger, E.; Smugeresky, J.

    1998-11-05

    For many years, Sandia National Laboratories has been involved in the development and application of rapid prototyping and dmect fabrication technologies to build prototype parts and patterns for investment casting. Sandia is currently developing a process called Laser Engineered Net Shaping (LENS~) to fabricate filly dense metal parts dwectly from computer-aided design (CAD) solid models. The process is similar to traditional laser-initiated rapid prototyping technologies such as stereolithography and selective laser sintering in that layer additive techniques are used to fabricate physical parts directly from CAD data. By using the coordinated delivery of metal particles into a focused laser beam apart is generated. The laser beam creates a molten pool of metal on a substrate into which powder is injected. Concurrently, the substrate on which the deposition is occurring is moved under the beam/powder interaction zone to fabricate the desired cross-sectiwal geometry. Consecutive layers are additively deposited, thereby producing a three-dmensional part. This process exhibits enormous potential to revolutionize the way in which metal parts, such as complex prototypes, tooling, and small-lot production parts, are produced. The result is a comple~ filly dense, near-net-shape part. Parts have been fabricated from 316 stainless steel, nickel-based alloys, H13 tool steel, and titanium. This talk will provide a general overview of the LENS~ process, discuss potential applications, and display as-processed examples of parts.

  13. Fabrication and Characteristics of Free Standing Shaped Pupil Masks for TPF-Coronagraph

    NASA Technical Reports Server (NTRS)

    Balasubramanian, Kunjithapatham; Echternach, Pierre M.; Dickie, Matthew R.; Muller, Richard E.; White, Victor E.; Hoppe, Daniel J.; Shaklan, Stuart B.; Belikov, Ruslan; Kasdin, N. Jeremy; Vanderbei, Robert J.; Ceperley, Daniel; Neureuther, Andrew R.

    2006-01-01

    Direct imaging and characterization of exo-solar terrestrial planets require coronagraphic instruments capable of suppressing star light to 10-10. Pupil shaping masks have been proposed and designed1 at Princeton University to accomplish such a goal. Based on Princeton designs, free standing (without a substrate) silicon masks have been fabricated with lithographic and deep etching techniques. In this paper, we discuss the fabrication of such masks and present their physical and optical characteristics in relevance to their performance over the visible to near IR bandwidth.

  14. Controllable fabrication of PS/Ag core-shell-shaped nanostructures

    PubMed Central

    2012-01-01

    In this paper, based on the previous steps, a facile in situ reduction method was developed to controllably prepare polystyrene/Ag (PS/Ag) core-shell-shaped nanostructures. The crucial procedure includes surface treatment of polystyrene core particles by cationic polyelectrolyte polyethyleneimine, in situ formation of Ag nanoparticles, and immobilization of the Ag nanoparticles onto the surface of the polystyrene colloids via functional group NH from the polyethyleneimine. The experimental parameters, such as the reaction temperature, the reaction time, and the silver precursors were optimized for improvement of dispersion and Ag coat coverage of the core-shell-shaped nanostructures. Ultimately, the optimum parameters were obtained through a series of experiments, and well-dispersed, uniformly coated PS/Ag core-shell-shaped nanostructures were successfully fabricated. The formation mechanism of the PS/Ag core-shell-shaped nanostructures was also explained. PMID:23092195

  15. Tunable Diffractive Optical Elements Based on Shape-Memory Polymers Fabricated via Hot Embossing.

    PubMed

    Schauer, Senta; Meier, Tobias; Reinhard, Maximilian; Röhrig, Michael; Schneider, Marc; Heilig, Markus; Kolew, Alexander; Worgull, Matthias; Hölscher, Hendrik

    2016-04-13

    We introduce actively tunable diffractive optical elements fabricated from shape-memory polymers (SMPs). By utilizing the shape-memory effect of the polymer, at least one crucial attribute of the diffractive optical element (DOE) is tunable and adjustable subsequent to the completed fabrication process. A thermoplastic, transparent, thermoresponsive polyurethane SMP was structured with diverse diffractive microstructures via hot embossing. The tunability was enabled by programming a second, temporary shape into the diffractive optical element by mechanical deformation, either by stretching or a second embossing cycle at low temperatures. Upon exposure to the stimulus heat, the structures change continuously and controllable in a predefined way. We establish the novel concept of shape-memory diffractive optical elements by illustrating their capabilities, with regard to tunability, by displaying the morphing diffractive pattern of a height tunable and a period tunable structure, respectively. A sample where an arbitrary structure is transformed to a second, disparate one is illustrated as well. To prove the applicability of our tunable shape-memory diffractive optical elements, we verified their long-term stability and demonstrated the precise adjustability with a detailed analysis of the recovery dynamics, in terms of temperature dependence and spatially resolved, time-dependent recovery. PMID:26998646

  16. Fabrication of cone-shaped boron doped diamond and gold nanoelectrodes for AFM-SECM

    NASA Astrophysics Data System (ADS)

    Avdic, A.; Lugstein, A.; Wu, M.; Gollas, B.; Pobelov, I.; Wandlowski, T.; Leonhardt, K.; Denuault, G.; Bertagnolli, E.

    2011-04-01

    We demonstrate a reliable microfabrication process for a combined atomic force microscopy (AFM) and scanning electrochemical microscopy (SECM) measurement tool. Integrated cone-shaped sensors with boron doped diamond (BDD) or gold (Au) electrodes were fabricated from commercially available AFM probes. The sensor formation process is based on mature semiconductor processing techniques, including focused ion beam (FIB) machining, and highly selective reactive ion etching (RIE). The fabrication approach preserves the geometry of the original AFM tips resulting in well reproducible nanoscaled sensors. The feasibility and functionality of the fully featured tips are demonstrated by cyclic voltammetry, showing good agreement between the measured and calculated currents of the cone-shaped AFM-SECM electrodes.

  17. Laundering durable antibacterial cotton fabrics grafted with pomegranate-shaped polymer wrapped in silver nanoparticle aggregations

    NASA Astrophysics Data System (ADS)

    Liu, Hanzhou; Lv, Ming; Deng, Bo; Li, Jingye; Yu, Ming; Huang, Qing; Fan, Chunhai

    2014-08-01

    To improve the laundering durability of the silver functionalized antibacterial cotton fabrics, a radiation-induced coincident reduction and graft polymerization is reported herein where a pomegranate-shaped silver nanoparticle aggregations up to 500 nm can be formed due to the coordination forces between amino group and silver and the wrapping procedure originated from the coincident growth of the silver nanoparticles and polymer graft chains. This pomegranate-shaped silver NPAs functionalized cotton fabric exhibits outstanding antibacterial activities and also excellent laundering durability, where it can inactivate higher than 90% of both E. coli and S. aureus even after 50 accelerated laundering cycles, which is equivalent to 250 commercial or domestic laundering cycles.

  18. Fabrication of cone-shaped boron doped diamond and gold nanoelectrodes for AFM-SECM.

    PubMed

    Avdic, A; Lugstein, A; Wu, M; Gollas, B; Pobelov, I; Wandlowski, T; Leonhardt, K; Denuault, G; Bertagnolli, E

    2011-04-01

    We demonstrate a reliable microfabrication process for a combined atomic force microscopy (AFM) and scanning electrochemical microscopy (SECM) measurement tool. Integrated cone-shaped sensors with boron doped diamond (BDD) or gold (Au) electrodes were fabricated from commercially available AFM probes. The sensor formation process is based on mature semiconductor processing techniques, including focused ion beam (FIB) machining, and highly selective reactive ion etching (RIE). The fabrication approach preserves the geometry of the original AFM tips resulting in well reproducible nanoscaled sensors. The feasibility and functionality of the fully featured tips are demonstrated by cyclic voltammetry, showing good agreement between the measured and calculated currents of the cone-shaped AFM-SECM electrodes. PMID:21368355

  19. Progress in net shape fabrication of alpha SiC turbine components

    NASA Technical Reports Server (NTRS)

    Storm, R. S.; Naum, R. G.

    1983-01-01

    The development status of component technology in an automotive gas turbine Ceramic Applications in Turbine Engines program is discussed, with attention to such materials and processes having a low cost, net shape fabrication potential as sintered alpha-SiC that has been fashioned by means of injection molding, slip casting, and isostatic pressing. The gas turbine elements produced include a gasifier turbine rotor, a turbine wheel, a connecting duct, a combustor baffle, and a transition duct.

  20. Development of a method for fabricating metallic matrix composite shapes by a continuous mechanical process

    NASA Technical Reports Server (NTRS)

    Divecha, A. P.

    1974-01-01

    Attempts made to develop processes capable of producing metal composites in structural shapes and sizes suitable for space applications are described. The processes must be continuous and promise to lower fabrication costs. Special attention was given to the aluminum boride (Al/b) composite system. Results show that despite adequate temperature control, the consolidation characteristics did not improve as expected. Inadequate binder removal was identified as the cause responsible. An Al/c (aluminum-graphite) composite was also examined.

  1. Vision-based in-line fabric defect detection using yarn-specific shape features

    NASA Astrophysics Data System (ADS)

    Schneider, Dorian; Aach, Til

    2012-01-01

    We develop a methodology for automatic in-line flaw detection in industrial woven fabrics. Where state of the art detection algorithms apply texture analysis methods to operate on low-resolved ({200 ppi) image data, we describe here a process flow to segment single yarns in high-resolved ({1000 ppi) textile images. Four yarn shape features are extracted, allowing a precise detection and measurement of defects. The degree of precision reached allows a classification of detected defects according to their nature, providing an innovation in the field of automatic fabric flaw detection. The design has been carried out to meet real time requirements and face adverse conditions caused by loom vibrations and dirt. The entire process flow is discussed followed by an evaluation using a database with real-life industrial fabric images. This work pertains to the construction of an on-loom defect detection system to be used in manufacturing practice.

  2. Fine-tuned grayscale optofluidic maskless lithography for three-dimensional freeform shape microstructure fabrication.

    PubMed

    Song, Suk-Heung; Kim, Kibeom; Choi, Sung-Eun; Han, Sangkwon; Lee, Ho-Suk; Kwon, Sunghoon; Park, Wook

    2014-09-01

    This article presents free-floating three-dimensional (3D) microstructure fabrication in a microfluidic channel using direct fine-tuned grayscale image lithography. The image is designed as a freeform shape and is composed of gray shades as light-absorbing features. Gray shade levels are modulated through multiple reflections of light in a digital micromirror device (DMD) to produce different height formations. Whereas conventional photolithography has several limitations in producing grayscale colors on photomask features, our method focuses on a maskless, single-shot process for fabrication of freeform 3D micro-scale shapes. The fine-tuned gray image is designed using an 8-bit grayscale color; thus, each pixel is capable of displaying 256 gray shades. The pattern of the UV light reflecting on the DMD is transferred to a photocurable resin flowing through a microfluidic channel. Here, we demonstrate diverse free-floating 3D microstructure fabrication using fine-tuned grayscale image lithography. Additionally, we produce polymeric microstructures with locally embedded gray encoding patterns, such as grayscale-encoded microtags. This functional microstructure can be applied to a biophysical detection system combined with 3D microstructures. This method would be suitable for fabricating 3D microstructures that have a specific morphology to be used for particular biological or medical applications. PMID:25166099

  3. Simple and Reliable Fabrication of Bioinspired Mushroom-Shaped Micropillars with Precisely Controlled Tip Geometries.

    PubMed

    Yi, Hoon; Kang, Minsu; Kwak, Moon Kyu; Jeong, Hoon Eui

    2016-08-31

    We present a simple yet scalable method with detailed process protocols for fabricating dry adhesives with mushroom-shaped micropillars of controlled tip geometries. The method involves using photo-lithography with a bilayer stack combining SU-8 and lift-off resist, and subsequent replica molding process. This approach utilizes widely used and commercially available materials and can thus be used to generate mushroom-shaped micropillars with precisely controlled tip diameters and thicknesses in a simple, reproducible, and cost-effective manner. The fabricated mushroom-shaped micropillar arrays exhibited highly different tendencies in adhesion strength and repeatability depending on tip geometries, such as tip diameter and thickness, thereby demonstrating the importance of precise tunability of tip geometry of micropillars. The fabricated dry adhesives with optimized tip geometries not only exhibited strong pull-off strength of up to ∼34.8 N cm(-2) on the Si surface but also showed high durability. By contrast, dry adhesives with nonoptimized tips displayed low pull-off strength of ∼3.6 N cm(-2) and poor durability. PMID:27548917

  4. 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.

  5. Programmable and self-demolding microstructured molds fabricated from shape-memory polymers

    NASA Astrophysics Data System (ADS)

    Meier, Tobias; Bur, Julia; Reinhard, Maximilian; Schneider, Marc; Kolew, Alexander; Worgull, Matthias; Hölscher, Hendrik

    2015-06-01

    We introduce shape memory polymers as materials to augment molds with programmable switching between different micro and nanostructures as functional features of the mold and self-demolding properties. These polymer molds can be used for hot embossing (or nanoimprinting) and casting. Furthermore, they enable the replication of nano- and microstructures on curved surfaces as well as embedded structures like on the inside walls of a microfluidic channel. The shape memory polymer molds can be replicated from master molds fabricated by conventional techniques. We tested their durability for microfabrication processes and demonstrated the advantages of shape memory molds for hot embossing and casting by replicating microstructures with high aspect ratios and optical grade surface quality.

  6. Microfluidic Fabrication of Polymeric and Biohybrid Fibers with Predesigned Size and Shape

    PubMed Central

    Boyd, Darryl A.; Adams, Andre A.; Daniele, Michael A.; Ligler, Frances S.

    2014-01-01

    A “sheath” fluid passing through a microfluidic channel at low Reynolds number can be directed around another “core” stream and used to dictate the shape as well as the diameter of a core stream. Grooves in the top and bottom of a microfluidic channel were designed to direct the sheath fluid and shape the core fluid. By matching the viscosity and hydrophilicity of the sheath and core fluids, the interfacial effects are minimized and complex fluid shapes can be formed. Controlling the relative flow rates of the sheath and core fluids determines the cross-sectional area of the core fluid. Fibers have been produced with sizes ranging from 300 nm to ~1 mm, and fiber cross-sections can be round, flat, square, or complex as in the case with double anchor fibers. Polymerization of the core fluid downstream from the shaping region solidifies the fibers. Photoinitiated click chemistries are well suited for rapid polymerization of the core fluid by irradiation with ultraviolet light. Fibers with a wide variety of shapes have been produced from a list of polymers including liquid crystals, poly(methylmethacrylate), thiol-ene and thiol-yne resins, polyethylene glycol, and hydrogel derivatives. Minimal shear during the shaping process and mild polymerization conditions also makes the fabrication process well suited for encapsulation of cells and other biological components. PMID:24430733

  7. Microfluidic fabrication of polymeric and biohybrid fibers with predesigned size and shape.

    PubMed

    Boyd, Darryl A; Adams, Andre A; Daniele, Michael A; Ligler, Frances S

    2014-01-01

    A "sheath" fluid passing through a microfluidic channel at low Reynolds number can be directed around another "core" stream and used to dictate the shape as well as the diameter of a core stream. Grooves in the top and bottom of a microfluidic channel were designed to direct the sheath fluid and shape the core fluid. By matching the viscosity and hydrophilicity of the sheath and core fluids, the interfacial effects are minimized and complex fluid shapes can be formed. Controlling the relative flow rates of the sheath and core fluids determines the cross-sectional area of the core fluid. Fibers have been produced with sizes ranging from 300 nm to ~1 mm, and fiber cross-sections can be round, flat, square, or complex as in the case with double anchor fibers. Polymerization of the core fluid downstream from the shaping region solidifies the fibers. Photoinitiated click chemistries are well suited for rapid polymerization of the core fluid by irradiation with ultraviolet light. Fibers with a wide variety of shapes have been produced from a list of polymers including liquid crystals, poly(methylmethacrylate), thiol-ene and thiol-yne resins, polyethylene glycol, and hydrogel derivatives. Minimal shear during the shaping process and mild polymerization conditions also makes the fabrication process well suited for encapsulation of cells and other biological components. PMID:24430733

  8. Microstereolithography-Based Fabrication of Anatomically Shaped Beta-Tricalcium Phosphate Scaffolds for Bone Tissue Engineering

    PubMed Central

    Du, Dajiang; Asaoka, Teruo; Shinohara, Makoto; Kageyama, Tomonori; Ushida, Takashi; Furukawa, Katsuko Sakai

    2015-01-01

    Porous ceramic scaffolds with shapes matching the bone defects may result in more efficient grafting and healing than the ones with simple geometries. Using computer-assisted microstereolithography (MSTL), we have developed a novel gelcasting indirect MSTL technology and successfully fabricated two scaffolds according to CT images of rabbit femur. Negative resin molds with outer 3D dimensions conforming to the femur and an internal structure consisting of stacked meshes with uniform interconnecting struts, 0.5 mm in diameter, were fabricated by MSTL. The second mold type was designed for cortical bone formation. A ceramic slurry of beta-tricalcium phosphate (β-TCP) with room temperature vulcanization (RTV) silicone as binder was cast into the molds. After the RTV silicone was completely cured, the composite was sintered at 1500°C for 5 h. Both gross anatomical shape and the interpenetrating internal network were preserved after sintering. Even cortical structure could be introduced into the customized scaffolds, which resulted in enhanced strength. Biocompatibility was confirmed by vital staining of rabbit bone marrow mesenchymal stromal cells cultured on the customized scaffolds for 5 days. This fabrication method could be useful for constructing bone substitutes specifically designed according to local anatomical defects. PMID:26504839

  9. Microstereolithography-Based Fabrication of Anatomically Shaped Beta-Tricalcium Phosphate Scaffolds for Bone Tissue Engineering.

    PubMed

    Du, Dajiang; Asaoka, Teruo; Shinohara, Makoto; Kageyama, Tomonori; Ushida, Takashi; Furukawa, Katsuko Sakai

    2015-01-01

    Porous ceramic scaffolds with shapes matching the bone defects may result in more efficient grafting and healing than the ones with simple geometries. Using computer-assisted microstereolithography (MSTL), we have developed a novel gelcasting indirect MSTL technology and successfully fabricated two scaffolds according to CT images of rabbit femur. Negative resin molds with outer 3D dimensions conforming to the femur and an internal structure consisting of stacked meshes with uniform interconnecting struts, 0.5 mm in diameter, were fabricated by MSTL. The second mold type was designed for cortical bone formation. A ceramic slurry of beta-tricalcium phosphate (β-TCP) with room temperature vulcanization (RTV) silicone as binder was cast into the molds. After the RTV silicone was completely cured, the composite was sintered at 1500°C for 5 h. Both gross anatomical shape and the interpenetrating internal network were preserved after sintering. Even cortical structure could be introduced into the customized scaffolds, which resulted in enhanced strength. Biocompatibility was confirmed by vital staining of rabbit bone marrow mesenchymal stromal cells cultured on the customized scaffolds for 5 days. This fabrication method could be useful for constructing bone substitutes specifically designed according to local anatomical defects. PMID:26504839

  10. Microfluidic fabrication of complex-shaped microfibers by liquid template-aided multiphase microflow.

    PubMed

    Choi, Chang-Hyung; Yi, Hyunmin; Hwang, Sora; Weitz, David A; Lee, Chang-Soo

    2011-04-21

    This study presents a simple microfluidic approach to the rapid fabrication of complex-shaped microfibers (e.g., single hollow, double hollow, and microbelt), with highly uniform structures, based on a combination of the spontaneous formation of polymeric jet streams and in situ photopolymerization. Two laminar flows of a photocurable fluid and a liquid template (nonpolymerizing fluid) spontaneously form jet streams in equilibrium states in microfluidic channels because of the minimization of the interfacial energy between the two fluids. The formation of the jet streams strongly depends on the spreading coefficients and the evolution time along the downstream of the microfluidic system. Thus, the simple control of the spreading coefficients can guide microfibers into various shapes. The sizes of the core and shell of the hollow fibers can also be readily manipulated by the flow rates of the polymerizing fluid and the liquid template phase. Asymmetric hollow fibers can also be produced in different evolutionary states in the microfluidic system. The microfluidic approach shown here represents a significant step toward the easy fabrication of microfibers with readily controllable structures and geometries. We anticipate that this novel fabrication approach and the prediction method based on spreading coefficients presented in this work can be applied to produce a wide variety of functional microfibrous materials. PMID:21390381

  11. Net shape fabrication of calcium phosphate scaffolds with multiple material domains.

    PubMed

    Xie, Yangmin; Rustom, Laurence E; McDermott, Anna M; Boerckel, Joel D; Johnson, Amy J Wagoner; Alleyne, Andrew G; Hoelzle, David J

    2016-03-01

    Calcium phosphate (CaP) materials have been proven to be efficacious as bone scaffold materials, but are difficult to fabricate into complex architectures because of the high processing temperatures required. In contrast, polymeric materials are easily formed into scaffolds with near-net-shape forms of patient-specific defects and with domains of different materials; however, they have reduced load-bearing capacity compared to CaPs. To preserve the merits of CaP scaffolds and enable advanced scaffold manufacturing, this manuscript describes an additive manufacturing process that is coupled with a mold support for overhanging features; we demonstrate that this process enables the fabrication of CaP scaffolds that have both complex, near-net-shape contours and distinct domains with different microstructures. First, we use a set of canonical structures to study the manufacture of complex contours and distinct regions of different material domains within a mold. We then apply these capabilities to the fabrication of a scaffold that is designed for a 5 cm orbital socket defect. This scaffold has complex external contours, interconnected porosity on the order of 300 μm throughout, and two distinct domains of different material microstructures. PMID:26744897

  12. Convolutional coding techniques for data protection

    NASA Technical Reports Server (NTRS)

    Massey, J. L.

    1975-01-01

    Results of research on the use of convolutional codes in data communications are presented. Convolutional coding fundamentals are discussed along with modulation and coding interaction. Concatenated coding systems and data compression with convolutional codes are described.

  13. Fabrication

    NASA Technical Reports Server (NTRS)

    Angel, Roger; Helms, Richard; Bilbro, Jim; Brown, Norman; Eng, Sverre; Hinman, Steve; Hull-Allen, Greg; Jacobs, Stephen; Keim, Robert; Ulmer, Melville

    1992-01-01

    What aspects of optical fabrication technology need to be developed so as to facilitate existing planned missions, or enable new ones? Throughout the submillimeter to UV wavelengths, the common goal is to push technology to the limits to make the largest possible apertures that are diffraction limited. At any one wavelength, the accuracy of the surface must be better than lambda/30 (rms error). The wavelength range is huge, covering four orders of magnitude from 1 mm to 100 nm. At the longer wavelengths, diffraction limited surfaces can be shaped with relatively crude techniques. The challenge in their fabrication is to make as large as possible a reflector, given the weight and volume constraints of the launch vehicle. The limited cargo diameter of the shuttle has led in the past to emphasis on deployable or erectable concepts such as the Large Deployable Reflector (LDR), which was studied by NASA for a submillimeter astrophysics mission. Replication techniques that can be used to produce light, low-cost reflecting panels are of great interest for this class of mission. At shorter wavelengths, in the optical and ultraviolet, optical fabrication will tax to the limit the most refined polishing methods. Methods of mechanical and thermal stabilization of the substrate will be severely stressed. In the thermal infrared, the need for large aperture is tempered by the even stronger need to control the telescope's thermal emission by cooled or cryogenic operation. Thus, the SIRTF mirror at 1 meter is not large and does not require unusually high accuracy, but the fabrication process must produce a mirror that is the right shape at a temperature of 4 K. Future large cooled mirrors will present more severe problems, especially if they must also be accurate enough to work at optical wavelengths. At the very shortest wavelengths accessible to reflecting optics, in the x-ray domain, the very low count fluxes of high energy photons place a premium on the collecting area. It is

  14. Determinate-state convolutional codes

    NASA Technical Reports Server (NTRS)

    Collins, O.; Hizlan, M.

    1991-01-01

    A determinate state convolutional code is formed from a conventional convolutional code by pruning away some of the possible state transitions in the decoding trellis. The type of staged power transfer used in determinate state convolutional codes proves to be an extremely efficient way of enhancing the performance of a concatenated coding system. The decoder complexity is analyzed along with free distances of these new codes and extensive simulation results is provided of their performance at the low signal to noise ratios where a real communication system would operate. Concise, practical examples are provided.

  15. Free form fabrication using the laser engineered net shaping (LENS{trademark}) process

    SciTech Connect

    Keicher, D.M.; Romero, J.A.; Atwood, C.L.; Griffith, M.L.; Jeantette, F.P.; Harwell, L.D.; Greene, D.L.; Smugeresky, J.E.

    1996-12-31

    Sandia National Laboratories is developing a technology called Laser Engineered Net Shaping{trademark} (LENS{trademark}). This process allows complex 3-dimensional solid metallic objects to be directly fabricated for a CAD solid model. Experiments performed demonstrate that complex alloys such as Inconel{trademark} 625 and ANSI stainless steel alloy 316 can be used in the LENS{trademark} process to produce solid metallic-shapes. In fact, the fabricated structures exhibit grain growth across the deposition layer boundaries. Mechanical testing data of deposited 316 stainless steel material indicates that the deposited material strength and elongation are greater than that reported for annealed 316 stainless steel. Electron microprobe analysis of the deposited Inconel{trademark} 625 material shows no compositional degradation of the 625 alloy and that 100% dense structures can be obtained using this technique. High speed imaging used to acquire process data during experimentation shows that the powder particle size range can significantly affect the stability, and subsequently, the performance of the powder deposition process. Finally, dimensional studies suggest that dimensional accuracy to {+-} 0.002 inches (in the horizontal direction) can be maintained.

  16. Fabrication and characterization of cuprous oxide solar cell with net-shaped counter electrode

    NASA Astrophysics Data System (ADS)

    Basuki, Stefanus; Uranus, Henri P.; Pangaribuan, Julinda

    2015-01-01

    In this work, simple solar cells using cuprous oxide were fabricated and characterized. The solar cells in this experiment used cuprous oxide plate as detecting electrode and copper wires which were woven into a net-shape with a gap size of 2 x 2 cm as a counter electrode. Twenty samples of solar cells were fabricated with oxide layer which were thermally grown in temperature up to 550 oC. Samples with variations in oxidation time (15 minutes, 30 minutes, 40 minutes, and 45 minutes) and distance between electrodes (2 cm, 3 cm, and 4 cm) with an electrolyte solution of NaCl with molarity of 2.188 mol/l were produced. The samples were characterized by measuring their V-I curve. For this purpose, a simple, own-made solar simulator were fabricated and characterized. Using curve fitting technique, parameters such as FF (Fill Factor), efficiency, open circuit voltage, short circuit current, internal resistance, and performance degradation as a function of time of the cells were extracted. The result shows optimum efficiency of 4.573. 10-4%, while optimum oxidation time is 40 minutes and optimum distance between electrodes is 3 cm.

  17. Fabrication and In Vitro Deployment of a Laser-Activated Shape Memory Polymer Vascular Stent

    SciTech Connect

    Baer, G M; Small IV, W; Wilson, T S; Benett, W J; Matthews, D L; Hartman, J; Maitland, D J

    2007-04-25

    Vascular stents are small tubular scaffolds used in the treatment of arterial stenosis (narrowing of the vessel). Most vascular stents are metallic and are deployed either by balloon expansion or by self-expansion. A shape memory polymer (SMP) stent may enhance flexibility, compliance, and drug elution compared to its current metallic counterparts. The purpose of this study was to describe the fabrication of a laser-activated SMP stent and demonstrate photothermal expansion of the stent in an in vitro artery model. A novel SMP stent was fabricated from thermoplastic polyurethane. A solid SMP tube formed by dip coating a stainless steel pin was laser-etched to create the mesh pattern of the finished stent. The stent was crimped over a fiber-optic cylindrical light diffuser coupled to an infrared diode laser. Photothermal actuation of the stent was performed in a water-filled mock artery. At a physiological flow rate, the stent did not fully expand at the maximum laser power (8.6 W) due to convective cooling. However, under zero flow, simulating the technique of endovascular flow occlusion, complete laser actuation was achieved in the mock artery at a laser power of {approx}8 W. We have shown the design and fabrication of an SMP stent and a means of light delivery for photothermal actuation. Though further studies are required to optimize the device and assess thermal tissue damage, photothermal actuation of the SMP stent was demonstrated.

  18. Fabrication and in vitro deployment of a laser-activated shape memory polymer vascular stent

    PubMed Central

    Baer, Géraldine M; Small, Ward; Wilson, Thomas S; Benett, William J; Matthews, Dennis L; Hartman, Jonathan; Maitland, Duncan J

    2007-01-01

    Background Vascular stents are small tubular scaffolds used in the treatment of arterial stenosis (narrowing of the vessel). Most vascular stents are metallic and are deployed either by balloon expansion or by self-expansion. A shape memory polymer (SMP) stent may enhance flexibility, compliance, and drug elution compared to its current metallic counterparts. The purpose of this study was to describe the fabrication of a laser-activated SMP stent and demonstrate photothermal expansion of the stent in an in vitro artery model. Methods A novel SMP stent was fabricated from thermoplastic polyurethane. A solid SMP tube formed by dip coating a stainless steel pin was laser-etched to create the mesh pattern of the finished stent. The stent was crimped over a fiber-optic cylindrical light diffuser coupled to an infrared diode laser. Photothermal actuation of the stent was performed in a water-filled mock artery. Results At a physiological flow rate, the stent did not fully expand at the maximum laser power (8.6 W) due to convective cooling. However, under zero flow, simulating the technique of endovascular flow occlusion, complete laser actuation was achieved in the mock artery at a laser power of ~8 W. Conclusion We have shown the design and fabrication of an SMP stent and a means of light delivery for photothermal actuation. Though further studies are required to optimize the device and assess thermal tissue damage, photothermal actuation of the SMP stent was demonstrated. PMID:18042294

  19. Fabrication and characterization of graphitic carbon nanostructures with controllable size, shape, and position.

    PubMed

    Du, Rongbing; Ssenyange, Solomon; Aktary, Mirwais; McDermott, Mark T

    2009-05-01

    The incorporation of carbon materials in micro- and nanoscale devices is being widely investigated due to the promise of enhanced functionality. Challenges in the positioning and addressability of carbon nanotubes provide the motivation for the development of new processes to produce nanoscale carbon materials. Here, the fabrication of conducting, nanometer-sized carbon structures using a combination of electron beam lithography (EBL) and carbonisation is reported. EBL is used to directly write predefined nanometer-sized patterns in a thin layer of negative resist in controllable locations. Careful heat treatment results in carbon nanostructures with the size, shape, and location originally defined by EBL. The pyrolysis process results in significant shrinkage of the structures in the vertical direction and minimal loss in the horizontal direction. Characterization of the carbonized material indicates a structure consisting of both amorphous and graphitized carbon with low levels of oxygen. The resistivity of the material is similar to other disordered carbon materials and the resistivity is maintained from the bulk to the nanoscale. This is demonstrated by fabricating a nanoscale structure with predictable resistance. The ability to fabricate these conductive structures with known dimensions and in predefined locations can be exploited for a number of applications. Their use as nanoband electrodes is also demonstrated. PMID:19235195

  20. A fabrication method of unique Nafion® shapes by painting for ionic polymer–metal composites

    NASA Astrophysics Data System (ADS)

    Trabia, Sarah; Hwang, Taeseon; Kim, Kwang J.

    2016-08-01

    Ionic polymer–metal composites (IPMC) are useful actuators because of their ability to be fabricated in different shapes and move in various ways. However, producing unique or intricate shapes can be difficult based upon the current fabrication techniques. Presented here is a fabrication method of producing the Nafion® membrane or thin film through a painting method. Using an airbrush, a Nafion water dispersion is sprayed onto an acrylonitrile butadiene styrene surface with a stencil of the desired shape. To verify that this method of fabrication produces a Nafion membrane similar to that which is commercially available, a sample that was made using the painting method and Nafion 117 purchased from DuPont™ were tested for various characteristics and compared. The results show promising similarities. The painted Nafion sample was chemically plated with platinum and compared with a traditional IPMC for its displacement and blocking force capabilities. The painted IPMC sample showed comparable results.

  1. Facile moldless fabrication of disk-shaped and reed blood cell-like microparticles using photopolymerization of tripropylene glycol diacrylate

    NASA Astrophysics Data System (ADS)

    Choi, Jongchul; Won, June; Song, Simon

    2014-12-01

    A facile method for the moldless fabrication of 2- or 3-dimensional microparticles is proposed by using a photopolymerization technique. Using only a monomer solution of tripropylene glycol diacrylate, a film mask and standard UV lithography equipment, we were able to fabricate microparticles of various shapes, such as disks, dimpled disks similar in shape to red blood cells, and slender gourd shapes, unlike previous moldless fabrication techniques requiring expensive and/or sophisticated equipment. The simple method could produce more than one million particles in a single batch, indicating that it can be applied to the mass production of polymer microparticles. Analyses of scanning electron micrographs and optical micrographs of the microparticles indicated that their size distribution was highly monodisperse. Detailed fabrication processes and statistics on the microparticle sizes are given in this paper.

  2. Entanglement-assisted quantum convolutional coding

    SciTech Connect

    Wilde, Mark M.; Brun, Todd A.

    2010-04-15

    We show how to protect a stream of quantum information from decoherence induced by a noisy quantum communication channel. We exploit preshared entanglement and a convolutional coding structure to develop a theory of entanglement-assisted quantum convolutional coding. Our construction produces a Calderbank-Shor-Steane (CSS) entanglement-assisted quantum convolutional code from two arbitrary classical binary convolutional codes. The rate and error-correcting properties of the classical convolutional codes directly determine the corresponding properties of the resulting entanglement-assisted quantum convolutional code. We explain how to encode our CSS entanglement-assisted quantum convolutional codes starting from a stream of information qubits, ancilla qubits, and shared entangled bits.

  3. Lipid Nanotube Tailored Fabrication of Uniquely Shaped Polydopamine Nanofibers as Photothermal Converters.

    PubMed

    Ding, Wuxiao; Chechetka, Svetlana A; Masuda, Mitsutoshi; Shimizu, Toshimi; Aoyagi, Masaru; Minamikawa, Hiroyuki; Miyako, Eijiro

    2016-03-18

    Helically coiled and linear polydopamine (PDA) nanofibers were selectively fabricated with two different types of lipid nanotubes (LNTs) that acted as templates. The obtained coiled PDA-LNT hybrid showed morphological advantages such as higher light absorbance and photothermal conversion effect compared to a linear counterpart. Laser irradiation of the coiled PDA-LNT hybrid induced a morphological change and subsequent release of the encapsulated guest molecule. In cellular experiments, the coiled PDA-LNT efficiently eliminated HeLa cells because of its strong affinity with the tumor cells. This work illustrates the first approach to construct characteristic morphologies of PDA nanofibers using LNTs as simple templates, and the coiled PDA-LNT hybrid exhibits attractive photothermal features derived from its unique coiled shape. PMID:26849459

  4. WFIRST-AFTA coronagraph shaped pupil masks: design, fabrication, and characterization

    NASA Astrophysics Data System (ADS)

    Balasubramanian, Kunjithapatham; White, Victor; Yee, Karl; Echternach, Pierre; Muller, Richard; Dickie, Matthew; Cady, Eric; Prada, Camilo Mejia; Ryan, Daniel; Poberezhskiy, Ilya; Kern, Brian; Zhou, Hanying; Krist, John; Nemati, Bijan; Eldorado Riggs, A. J.; Zimmerman, Neil T.; Kasdin, N. Jeremy

    2016-01-01

    NASA WFIRST-AFTA mission study includes a coronagraph instrument to find and characterize exoplanets. Various types of masks could be employed to suppress the host starlight to about 10-9 level contrast over a broad spectrum to enable the coronagraph mission objectives. Such masks for high-contrast internal coronagraphic imaging require various fabrication technologies to meet a wide range of specifications, including precise shapes, micron scale island features, ultralow reflectivity regions, uniformity, wave front quality, and achromaticity. We present the approaches employed at JPL to produce pupil plane and image plane coronagraph masks by combining electron beam, deep reactive ion etching, and black silicon technologies with illustrative examples of each, highlighting milestone accomplishments from the High Contrast Imaging Testbed at JPL and from the High Contrast Imaging Lab at Princeton University.

  5. Fabrication and Characterization of Cylindrical Light Diffusers Comprised of Shape Memory Polymer

    SciTech Connect

    Small IV, W; Buckley, P R; Wilson, T S; Loge, J M; Maitland, K D; Maitland, D J

    2007-01-29

    We have developed a technique for constructing light diffusing devices comprised of a flexible shape memory polymer (SMP) cylindrical diffuser attached to the tip of an optical fiber. Devices were fabricated by casting an SMP rod over the cleaved tip of an optical fiber and media blasting the SMP rod to create a light diffusing surface. The axial and polar emission profiles and circumferential (azimuthal) uniformity were characterized for various blasting pressures, nozzle-to-sample distances, and nozzle translation speeds. The diffusers were generally strongly forward-directed and consistently withstood over 8 W of incident infrared laser light without suffering damage when immersed in water. These devices are suitable for various endoluminal and interstitial biomedical applications.

  6. Fabrication of shape controlled Fe{sub 3}O{sub 4} nanostructure

    SciTech Connect

    Zheng, Y.Y.; Wang, X.B.; Shang, L.; Li, C.R.; Cui, C.; Dong, W.J.; Tang, W.H.; Chen, B.Y.

    2010-04-15

    Shape-controlled Fe{sub 3}O{sub 4} nanostructure has been successfully prepared using polyethylene glycol as template in a water system at room temperature. Different morphologies of Fe{sub 3}O{sub 4} nanostructures, including spherical, cubic, rod-like, and dendritic nanostructure, were obtained by carefully controlling the concentration of the Fe{sup 3+}, Fe{sup 2+}, and the molecular weight of the polyethylene glycol. Transmission Electron Microscope images, X-ray powder diffraction patterns and magnetic properties were used to characterize the final product. This easy procedure for Fe{sub 3}O{sub 4} nanostructure fabrication offers the possibility of a generalized approach to the production of single and complex nanocrystalline oxide with tunable morphology.

  7. Fabrication of porous titanium scaffold with controlled porous structure and net-shape using magnesium as spacer.

    PubMed

    Kim, Sung Won; Jung, Hyun-Do; Kang, Min-Ho; Kim, Hyoun-Ee; Koh, Young-Hag; Estrin, Yuri

    2013-07-01

    This paper reports a new approach to fabricating biocompatible porous titanium with controlled pore structure and net-shape. The method is based on using sacrificial Mg particles as space holders to produce compacts that are mechanically stable and machinable. Using magnesium granules and Ti powder, Ti/Mg compacts with transverse rupture strength (~85 MPa) sufficient for machining were fabricated by warm compaction, and a complex-shape Ti scaffold was eventually produced by removal of Mg granules from the net-shape compact. The pores with the average size of 132-262 μm were well distributed and interconnected. Due to anisotropy and alignment of the pores the compressive strength varied with the direction of compression. In the case of pores aligned with the direction of compression, the compressive strength values (59-280 MPa) high enough for applications in load bearing implants were achieved. To verify the possibility of controlled net-shape, conventional machining process was performed on Ti/Mg compact. Compact with screw shape and porous Ti scaffold with hemispherical cup shape were fabricated by the results. Finally, it was demonstrated by cell tests using MC3T3-E1 cell line that the porous Ti scaffolds fabricated by this technique are biocompatible. PMID:23623100

  8. Fabrication and Characterization of Nitinol-Copper Shape Memory Alloy Bimorph Actuators

    NASA Astrophysics Data System (ADS)

    Wongweerayoot, E.; Srituravanich, W.; Pimpin, A.

    2015-02-01

    This study aims to examine the effect of annealing conditions on nitinol (NiTi) characteristics and applies this knowledge to fabricate a NiTi-copper shape memory alloy bimorph actuator. The effect of the annealing conditions was investigated at various temperatures, i.e., 500, 600, and 650 °C, for 30 min. With the characterizations using x-ray diffraction, energy dispersive spectroscopy, and differential scanning calorimetry techniques, the results showed that annealing temperatures at 600 and 650 °C were able to appropriately form the crystalline structure of NiTi. However, at these high annealing temperatures, the oxide on a surface was unavoidable. In the fabrication of actuator, the annealing at 650 °C for 30 min was chosen, and it was performed at two pre-stressing conditions, i.e., straight and curved molds. From static and dynamic response experiments, the results suggested that the annealing temperature significantly affected the deflection of the actuator. On the other hand, the effect of pre-stressing conditions was relatively small. Furthermore, the micro gripper consisting of two NiTi-copper bimorph actuators successfully demonstrated for the viability of small object manipulation as the gripper was able to grasp and hold a small plastic ball with its weight of around 0.5 mg.

  9. Facile 3D Metal Electrode Fabrication for Energy Applications via Inkjet Printing and Shape Memory Polymer

    NASA Astrophysics Data System (ADS)

    Roberts, R. C.; Wu, J.; Hau, N. Y.; Chang, Y. H.; Feng, S. P.; Li, D. C.

    2014-11-01

    This paper reports on a simple 3D metal electrode fabrication technique via inkjet printing onto a thermally contracting shape memory polymer (SMP) substrate. Inkjet printing allows for the direct patterning of structures from metal nanoparticle bearing liquid inks. After deposition, these inks require thermal curing steps to render a stable conductive film. By printing onto a SMP substrate, the metal nanoparticle ink can be cured and substrate shrunk simultaneously to create 3D metal microstructures, forming a large surface area topology well suited for energy applications. Polystyrene SMP shrinkage was characterized in a laboratory oven from 150-240°C, resulting in a size reduction of 1.97-2.58. Silver nanoparticle ink was patterned into electrodes, shrunk, and the topology characterized using scanning electron microscopy. Zinc-Silver Oxide microbatteries were fabricated to demonstrate the 3D electrodes compared to planar references. Characterization was performed using 10M potassium hydroxide electrolyte solution doped with zinc oxide (57g/L). After a 300s oxidation at 3Vdc, the 3D electrode battery demonstrated a 125% increased capacity over the reference cell. Reference cells degraded with longer oxidations, but the 3D electrodes were fully oxidized for 4 hours, and exhibited a capacity of 5.5mA-hr/cm2 with stable metal performance.

  10. Die and telescoping punch form convolutions in thin diaphragm

    NASA Technical Reports Server (NTRS)

    1965-01-01

    Die and punch set forms convolutions in thin dished metal diaphragm without stretching the metal too thin at sharp curvatures. The die corresponds to the metal shape to be formed, and the punch consists of elements that progressively slide against one another under the restraint of a compressed-air cushion to mate with the die.

  11. Near-Net Shape Fabrication Using Low-Cost Titanium Alloy Powders

    SciTech Connect

    Dr. David M. Bowden; Dr. William H. Peter

    2012-03-31

    The use of titanium in commercial aircraft production has risen steadily over the last half century. The aerospace industry currently accounts for 58% of the domestic titanium market. The Kroll process, which has been used for over 50 years to produce titanium metal from its mineral form, consumes large quantities of energy. And, methods used to convert the titanium sponge output of the Kroll process into useful mill products also require significant energy resources. These traditional approaches result in product forms that are very expensive, have long lead times of up to a year or more, and require costly operations to fabricate finished parts. Given the increasing role of titanium in commercial aircraft, new titanium technologies are needed to create a more sustainable manufacturing strategy that consumes less energy, requires less material, and significantly reduces material and fabrication costs. A number of emerging processes are under development which could lead to a breakthrough in extraction technology. Several of these processes produce titanium alloy powder as a product. The availability of low-cost titanium powders may in turn enable a more efficient approach to the manufacture of titanium components using powder metallurgical processing. The objective of this project was to define energy-efficient strategies for manufacturing large-scale titanium structures using these low-cost powders as the starting material. Strategies include approaches to powder consolidation to achieve fully dense mill products, and joining technologies such as friction and laser welding to combine those mill products into near net shape (NNS) preforms for machining. The near net shape approach reduces material and machining requirements providing for improved affordability of titanium structures. Energy and cost modeling was used to define those approaches that offer the largest energy savings together with the economic benefits needed to drive implementation. Technical

  12. Glass-on-Glass Fabrication of Bottle-Shaped Tunable Microlasers and their Applications

    NASA Astrophysics Data System (ADS)

    Ward, Jonathan M.; Yang, Yong; Nic Chormaic, Síle

    2016-04-01

    We describe a novel method for making microbottle-shaped lasers by using a CO2 laser to melt Er:Yb glass onto silica microcapillaries or fibres. This is realised by the fact that the two glasses have different melting points. The CO2 laser power is controlled to flow the doped glass around the silica cylinder. In the case of a capillary, the resulting geometry is a hollow, microbottle-shaped resonator. This is a simple method for fabricating a number of glass whispering gallery mode (WGM) lasers with a wide range of sizes on a single, micron-scale structure. The Er:Yb doped glass outer layer is pumped at 980 nm via a tapered optical fibre and WGM lasing is recorded around 1535 nm. This structure facilitates a new way to thermo-optically tune the microlaser modes by passing gas through the capillary. The cooling effect of the gas flow shifts the WGMs towards shorter wavelengths and thermal tuning of the lasing modes over 70 GHz is achieved. Results are fitted using the theory of hot wire anemometry, allowing the flow rate to be calibrated with a flow sensitivity as high as 72 GHz/sccm. Strain tuning of the microlaser modes by up to 60 GHz is also demonstrated.

  13. Glass-on-Glass Fabrication of Bottle-Shaped Tunable Microlasers and their Applications.

    PubMed

    Ward, Jonathan M; Yang, Yong; Nic Chormaic, Síle

    2016-01-01

    We describe a novel method for making microbottle-shaped lasers by using a CO2 laser to melt Er:Yb glass onto silica microcapillaries or fibres. This is realised by the fact that the two glasses have different melting points. The CO2 laser power is controlled to flow the doped glass around the silica cylinder. In the case of a capillary, the resulting geometry is a hollow, microbottle-shaped resonator. This is a simple method for fabricating a number of glass whispering gallery mode (WGM) lasers with a wide range of sizes on a single, micron-scale structure. The Er:Yb doped glass outer layer is pumped at 980 nm via a tapered optical fibre and WGM lasing is recorded around 1535 nm. This structure facilitates a new way to thermo-optically tune the microlaser modes by passing gas through the capillary. The cooling effect of the gas flow shifts the WGMs towards shorter wavelengths and thermal tuning of the lasing modes over 70 GHz is achieved. Results are fitted using the theory of hot wire anemometry, allowing the flow rate to be calibrated with a flow sensitivity as high as 72 GHz/sccm. Strain tuning of the microlaser modes by up to 60 GHz is also demonstrated. PMID:27121151

  14. An innovative method and experiment for fabricating bulgy shape nanochannel using AFM

    NASA Astrophysics Data System (ADS)

    Lin, Zone-Ching; Jheng, Hao-Yuan; Ding, Hao-Yang

    2015-08-01

    The paper proposes using atomic force microscopy (AFM) and the concept of specific down force energy (SDFE) to establish an innovative offset cycle cutting method for fabricating a bulgy shape nanochannel on a single-crystal silicon substrate. In the offset cycle cutting method, cutting is performed at a constant down force in all cutting passes. After the first cutting pass, the AFM probe is offset rightward for the second pass and subsequently offset leftward to the middle (i.e., between the positions of the first two cutting passes) for the third cutting pass. Applying a step-by-step method to modify the offset distance and approach the defined SDFE value, this study determined the depth of the middle cutting pass and smaller values of upward bulginess and downward indentation at the bottom of the nanochannel. The nanochannel width can be increased by increasing the number of offset cycle cutting passes. In addition, by applying the proposed method, this study involved a simulation and experiment concerning the cutting path plan of bulgy shape nanochannels. Furthermore, using a small down force along the burr path is proposed for reducing burr height. The results of the simulation and experiment were compared to verify the feasibility of the method.

  15. Fabrication and lithium storage performance of sugar apple-shaped SiOx@C nanocomposite spheres

    NASA Astrophysics Data System (ADS)

    Li, Mingqi; Zeng, Ying; Ren, Yurong; Zeng, Chunmei; Gu, Jingwei; Feng, Xiaofang; He, Hongyan

    2015-08-01

    Nonstoichiometric SiOx is a kind of very attractive anode material for high-energy lithium-ion batteries because of a high specific capacity and facile synthesis. However, the poor electrical conductivity and unstable electrode structure of SiOx severely limit its electrochemical performance as anode in lithium-ion batteries. In this work, highly durable sugar apple-shaped SiOx@C nanocomposite spheres are fabricated to achieve significantly improved electrochemical performance. The composite is synthesized by homogenous one-pot synthesis, using ethyltriethoxysilanes (EtSi(OEt)3) and resorcinol/formaldehyde (RF) as starting materials. The morphology, composition and structure of the composite are investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), elemental analysis (EA) and X-ray photoelectron spectroscopy (XPS). At a current density of 50 mA g-1, the sugar apple-shaped SiOx@C spheres exhibit a stable discharge capacity of about 630 mAh g-1 calculated on the total mass of both SiOx and C. At a current density of 100 mA g-1, a stable discharge capacity of about 550 mAh g-1 is obtained and the capacity has been kept up to 400 cycles. The excellent cycling performance is attributed to the homogeneous dispersion of SiOx in disordered carbon at the nanometer scale and the unique structure of the composite.

  16. Glass-on-Glass Fabrication of Bottle-Shaped Tunable Microlasers and their Applications

    PubMed Central

    Ward, Jonathan M.; Yang, Yong; Nic Chormaic, Síle

    2016-01-01

    We describe a novel method for making microbottle-shaped lasers by using a CO2 laser to melt Er:Yb glass onto silica microcapillaries or fibres. This is realised by the fact that the two glasses have different melting points. The CO2 laser power is controlled to flow the doped glass around the silica cylinder. In the case of a capillary, the resulting geometry is a hollow, microbottle-shaped resonator. This is a simple method for fabricating a number of glass whispering gallery mode (WGM) lasers with a wide range of sizes on a single, micron-scale structure. The Er:Yb doped glass outer layer is pumped at 980 nm via a tapered optical fibre and WGM lasing is recorded around 1535 nm. This structure facilitates a new way to thermo-optically tune the microlaser modes by passing gas through the capillary. The cooling effect of the gas flow shifts the WGMs towards shorter wavelengths and thermal tuning of the lasing modes over 70 GHz is achieved. Results are fitted using the theory of hot wire anemometry, allowing the flow rate to be calibrated with a flow sensitivity as high as 72 GHz/sccm. Strain tuning of the microlaser modes by up to 60 GHz is also demonstrated. PMID:27121151

  17. Some easily analyzable convolutional codes

    NASA Technical Reports Server (NTRS)

    Mceliece, R.; Dolinar, S.; Pollara, F.; Vantilborg, H.

    1989-01-01

    Convolutional codes have played and will play a key role in the downlink telemetry systems on many NASA deep-space probes, including Voyager, Magellan, and Galileo. One of the chief difficulties associated with the use of convolutional codes, however, is the notorious difficulty of analyzing them. Given a convolutional code as specified, say, by its generator polynomials, it is no easy matter to say how well that code will perform on a given noisy channel. The usual first step in such an analysis is to computer the code's free distance; this can be done with an algorithm whose complexity is exponential in the code's constraint length. The second step is often to calculate the transfer function in one, two, or three variables, or at least a few terms in its power series expansion. This step is quite hard, and for many codes of relatively short constraint lengths, it can be intractable. However, a large class of convolutional codes were discovered for which the free distance can be computed by inspection, and for which there is a closed-form expression for the three-variable transfer function. Although for large constraint lengths, these codes have relatively low rates, they are nevertheless interesting and potentially useful. Furthermore, the ideas developed here to analyze these specialized codes may well extend to a much larger class.

  18. 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.

  19. Fabrication of AlGaN/GaN Ω-shaped nanowire fin-shaped FETs by a top-down approach

    NASA Astrophysics Data System (ADS)

    Im, Ki-Sik; Sindhuri, Vodapally; Jo, Young-Woo; Son, Dong-Hyeok; Lee, Jae-Hoon; Cristoloveanu, Sorin; Lee, Jung-Hee

    2015-06-01

    An AlGaN/GaN-based Ω-shaped nanowire fin-shaped FET (FinFET) with a fin width of 50 nm was fabricated using tetramethylammonium hydroxide (TMAH)-based lateral wet etching. An atomic layer deposited (ALD) HfO2 side-wall layer served as the etching mask. ALD Al2O3 and TiN layers were used as the gate dielectric and gate metal, respectively. The Ω-shaped gate structure fully depletes the active fin body and almost completely separates the depleted fin from the underlying thick GaN buffer layer, resulting in superior device performance. The top-down processing proposed in this work provides a viable pathway towards gate-all-around devices for III-nitride semiconductors.

  20. Convolutional virtual electric field for image segmentation using active contours.

    PubMed

    Wang, Yuanquan; Zhu, Ce; Zhang, Jiawan; Jian, Yuden

    2014-01-01

    Gradient vector flow (GVF) is an effective external force for active contours; however, it suffers from heavy computation load. The virtual electric field (VEF) model, which can be implemented in real time using fast Fourier transform (FFT), has been proposed later as a remedy for the GVF model. In this work, we present an extension of the VEF model, which is referred to as CONvolutional Virtual Electric Field, CONVEF for short. This proposed CONVEF model takes the VEF model as a convolution operation and employs a modified distance in the convolution kernel. The CONVEF model is also closely related to the vector field convolution (VFC) model. Compared with the GVF, VEF and VFC models, the CONVEF model possesses not only some desirable properties of these models, such as enlarged capture range, u-shape concavity convergence, subject contour convergence and initialization insensitivity, but also some other interesting properties such as G-shape concavity convergence, neighboring objects separation, and noise suppression and simultaneously weak edge preserving. Meanwhile, the CONVEF model can also be implemented in real-time by using FFT. Experimental results illustrate these advantages of the CONVEF model on both synthetic and natural images. PMID:25360586

  1. Fabrication of MEMS ZnO dome-shaped-diaphragm transducers for high-frequency ultrasonic imaging

    NASA Astrophysics Data System (ADS)

    Feng, Guo-Hua; Sharp, Charles C.; Zhou, Q. F.; Pang, Wei; Sok Kim, Eun; Shung, K. K.

    2005-03-01

    This paper presents the microfabrication technique for a dome-shaped-diaphragm transducer (DSDT) for 200 MHz cellular microstructure imaging. The DSDT uses piezoelectric ZnO film to generate acoustic waves, and is fabricated on a silicon substrate. The fabricated DSDTs have been tested with a pulse-echo method using a quartz target, and shown to produce an echo signal at 210 MHz with 20% bandwidth. The DSDT fabrication uses spherical balls to precisely shape wax molds, onto which parylene is deposited as a support layer for the DSDT. The wax molds are removed by toluene to release the parylene dome diaphragms. Piezoelectric ZnO film is sputter deposited on the parylene dome diaphragm. E-Solder silver epoxy is placed and cured on the back surface to function both as an acoustic backing and as structural support. Quarter wavelength thick parylene is deposited on the front side of the wafer for acoustic matching. The fabrication technique for the DSDTs is meant for low-cost mass production of the devices for high-frequency biomedical imaging. Moreover, the technique allows the precise control of the radius and curvature of the dome-shaped diaphragm through adjusting the size of the front-to-backside thru holes using different radii of the spherical balls.

  2. Cost-efficient and flexible fabrication of rectangular-shaped microlens arrays with controllable aspect ratio and spherical morphology

    NASA Astrophysics Data System (ADS)

    Hu, Yang; Yang, Qing; Chen, Feng; Bian, Hao; Deng, Zefang; Du, Guangqing; Si, Jinhai; Yun, Feng; Hou, Xun

    2014-02-01

    This paper presents a cost-efficient and flexible approach to the development of controllable-shape concave and convex microlens arrays by using femtosecond laser wet etch and replication techniques. Periodic concave rectangular-shaped microlens arrays with different length-width ratios were achieved by firstly introducing periodic microcraters on silica glass using an 800 nm femtosecond laser, and subsequently enlarging the craters into microlens with smooth curved surfaces in hydrofluoric (HF) acid solution. The concave microlens can serve as molds of replication to obtain convex microlenses on polymers. Over 10,000 rectangular-shaped concave and convex microlens with controllable aspect ratio, high fill factor and spherical morphology can be fabricated in 5 h. A simulation result and a projection experiment result verify the optical performance of these rectangular-shaped spherical microlens arrays (MLAs).

  3. Fabrication of petal-shaped masks for suppression of the on-axis Poisson spot in telescope systems.

    PubMed

    Shiri, Ron; Stein, Ryan; Murphy, Kaitlin; Hagopian, Kimberly; Salari, Shirin; Sankar, Shannon; Hagopian, John; Showalter, Matthew; Stevenson, Thomas; Quijada, Manuel; Threat, Felix; Friedlander, Jay; Dillon, Thomas; Livas, Jeffrey

    2016-04-01

    The presence of a bright (Poisson) spot in the geometrical shadow of circular/spherical shapes has been known for the past two centuries. A broad class of telescopes that involve simultaneous transmit and receive require suppression of the reflected light from the secondary mirror on the detector. For instance, the on-axis design of optical telescope for the evolved Laser Interferometric Space Antenna (eLISA), a re-scoped version of the baseline LISA mission concept, requires suppression of reflected laser light from the secondary mirror on the detector. In the past few years, the hypergaussian functions with petal-shaped realization have been shown to significantly suppress intensity along the optical axis. This work reports on fabrication of a series of petal-shaped masks using a variety of techniques such as 3D printing, photolithography, and wire Electro Discharge Machining. These masks are designed and fabricated to operate in the range of Fresnel numbers between 4 and 120. This paper discusses the challenges, successes, and failures of each fabrication technique and the optical performance of typical masks with suggestions for potential follow up work. PMID:27131659

  4. Fabrication of petal-shaped masks for suppression of the on-axis Poisson spot in telescope systems

    NASA Astrophysics Data System (ADS)

    Shiri, Ron; Stein, Ryan; Murphy, Kaitlin; Hagopian, Kimberly; Salari, Shirin; Sankar, Shannon; Hagopian, John; Showalter, Matthew; Stevenson, Thomas; Quijada, Manuel; Threat, Felix; Friedlander, Jay; Dillon, Thomas; Livas, Jeffrey

    2016-04-01

    The presence of a bright (Poisson) spot in the geometrical shadow of circular/spherical shapes has been known for the past two centuries. A broad class of telescopes that involve simultaneous transmit and receive require suppression of the reflected light from the secondary mirror on the detector. For instance, the on-axis design of optical telescope for the evolved Laser Interferometric Space Antenna (eLISA), a re-scoped version of the baseline LISA mission concept, requires suppression of reflected laser light from the secondary mirror on the detector. In the past few years, the hypergaussian functions with petal-shaped realization have been shown to significantly suppress intensity along the optical axis. This work reports on fabrication of a series of petal-shaped masks using a variety of techniques such as 3D printing, photolithography, and wire Electro Discharge Machining. These masks are designed and fabricated to operate in the range of Fresnel numbers between 4 and 120. This paper discusses the challenges, successes, and failures of each fabrication technique and the optical performance of typical masks with suggestions for potential follow up work.

  5. Approximating large convolutions in digital images.

    PubMed

    Mount, D M; Kanungo, T; Netanyahu, N S; Piatko, C; Silverman, R; Wu, A Y

    2001-01-01

    Computing discrete two-dimensional (2-D) convolutions is an important problem in image processing. In mathematical morphology, an important variant is that of computing binary convolutions, where the kernel of the convolution is a 0-1 valued function. This operation can be quite costly, especially when large kernels are involved. We present an algorithm for computing convolutions of this form, where the kernel of the binary convolution is derived from a convex polygon. Because the kernel is a geometric object, we allow the algorithm some flexibility in how it elects to digitize the convex kernel at each placement, as long as the digitization satisfies certain reasonable requirements. We say that such a convolution is valid. Given this flexibility we show that it is possible to compute binary convolutions more efficiently than would normally be possible for large kernels. Our main result is an algorithm which, given an m x n image and a k-sided convex polygonal kernel K, computes a valid convolution in O(kmn) time. Unlike standard algorithms for computing correlations and convolutions, the running time is independent of the area or perimeter of K, and our techniques do not rely on computing fast Fourier transforms. Our algorithm is based on a novel use of Bresenham's (1965) line-drawing algorithm and prefix-sums to update the convolution incrementally as the kernel is moved from one position to another across the image. PMID:18255522

  6. Fabrication of a membrane filter with controlled pore shape and its application to cell separation and strong single cell trapping

    NASA Astrophysics Data System (ADS)

    Choi, Dong-Hoon; Yoon, Gun-Wook; Park, Jeong Won; Ihm, Chunhwa; Lee, Dae-Sik; Yoon, Jun-Bo

    2015-10-01

    A porous membrane filter is one of the key components for sample preparation in lab-on-a-chip applications. However, most of the membranes reported to date have only been used for size-based separation since it is difficult to provide functionality to the membrane or improve the performance of the membrane. In this work, as a method to functionalize the membrane filter, controlling the shape of the membrane pores is suggested, and a convenient and mass-producible fabrication method is provided. With the proposed method, membrane filters with round, conical and funnel shape pores were successfully fabricated, and we demonstrated that the sidewall slope of the conical shape pores could be precisely controlled. To verify that the membrane filter can be functionalized by controlled pore shape, we investigated filtration and trapping performance of the membrane filter with conical shape pores. In a filtration test of 1000 cancer cells (MCF-7, a breast cancer cell line) spiked in phosphate buffered saline (PBS) solution, 77% of the total cancer cells were retained on the membrane, and each cell from among 99.3% of the retained cells was automatically isolated in a single conical pore during the filtration process. Thanks to its engineered pore shape, trapping ability of the membrane with conical pores is dramatically improved. Microparticles trapped in the conical pores maintain their locations without any losses even at a more than 30 times faster external flow rate com-pared with those mounted on conventional cylindrical pores. Also, 78% of the cells trapped in the conical pores withstand an external flow of over 300 μl min-1 whereas only 18% of the cells trapped in the cylindrical pores remain on the membrane after 120 μl min-1 of an external flow is applied.

  7. The Convolution Method in Neutrino Physics Searches

    SciTech Connect

    Tsakstara, V.; Kosmas, T. S.; Chasioti, V. C.; Divari, P. C.; Sinatkas, J.

    2007-12-26

    We concentrate on the convolution method used in nuclear and astro-nuclear physics studies and, in particular, in the investigation of the nuclear response of various neutrino detection targets to the energy-spectra of specific neutrino sources. Since the reaction cross sections of the neutrinos with nuclear detectors employed in experiments are extremely small, very fine and fast convolution techniques are required. Furthermore, sophisticated de-convolution methods are also needed whenever a comparison between calculated unfolded cross sections and existing convoluted results is necessary.

  8. Effect of Fabrication-Dependent Shape and Composition of Solid-State Nanopores on Single Nanoparticle Detection

    PubMed Central

    Liu, Shuo; Yuzvinsky, Thomas D.; Schmidt, Holger

    2013-01-01

    Solid-state nanopores can be fabricated in a variety of ways and form the basis for label-free sensing of single nanoparticles: as individual nanoparticles traverse the nanopore, they alter the ionic current across it in a characteristic way. Typically, nanopores are described by the diameter of their limiting aperture, and less attention has been paid to other, fabrication-dependent parameters. Here, we report a comprehensive analysis of the properties and sensing performance of three types of nanopore with identical 50nm aperture, but fabricated using three different techniques: direct ion beam milling, ion beam sculpting, and electron beam sculpting. The nanopores differ substantially in physical shape and chemical composition as identified by ion-beam assisted cross sectioning and energy dispersive x-ray spectroscopy. Concomitant differences in electrical sensing of single 30nm beads, such as variations in blockade depth, duration, and electric field dependence, are observed and modeled using hydrodynamic simulations. The excellent agreement between experiment and physical modeling shows that the physical properties (shape) and not the chemical surface composition determine the sensing performance of a solid-state nanopore in the absence of deliberate surface modification. Consequently, nanoparticle sensing performance can be accurately predicted once the full three dimensional structure of the nanopore is known. PMID:23697604

  9. Fabrication and Characterization of a Micromachined Swirl-Shaped Ionic Polymer Metal Composite Actuator with Electrodes Exhibiting Asymmetric Resistance

    PubMed Central

    Feng, Guo-Hua; Liu, Kim-Min

    2014-01-01

    This paper presents a swirl-shaped microfeatured ionic polymer-metal composite (IPMC) actuator. A novel micromachining process was developed to fabricate an array of IPMC actuators on a glass substrate and to ensure that no shortcircuits occur between the electrodes of the actuator. We demonstrated a microfluidic scheme in which surface tension was used to construct swirl-shaped planar IPMC devices of microfeature size and investigated the flow velocity of Nafion solutions, which formed the backbone polymer of the actuator, within the microchannel. The unique fabrication process yielded top and bottom electrodes that exhibited asymmetric surface resistance. A tool for measuring surface resistance was developed and used to characterize the resistances of the electrodes for the fabricated IPMC device. The actuator, which featured asymmetric electrode resistance, caused a nonzero-bias current when the device was driven using a zero-bias square wave, and we propose a circuit model to describe this phenomenon. Moreover, we discovered and characterized a bending and rotating motion when the IPMC actuator was driven using a square wave. We observed a strain rate of 14.6% and a displacement of 700 μm in the direction perpendicular to the electrode surfaces during 4.5-V actuation. PMID:24824370

  10. Convolution-deconvolution in DIGES

    SciTech Connect

    Philippacopoulos, A.J.; Simos, N.

    1995-05-01

    Convolution and deconvolution operations is by all means a very important aspect of SSI analysis since it influences the input to the seismic analysis. This paper documents some of the convolution/deconvolution procedures which have been implemented into the DIGES code. The 1-D propagation of shear and dilatational waves in typical layered configurations involving a stack of layers overlying a rock is treated by DIGES in a similar fashion to that of available codes, e.g. CARES, SHAKE. For certain configurations, however, there is no need to perform such analyses since the corresponding solutions can be obtained in analytic form. Typical cases involve deposits which can be modeled by a uniform halfspace or simple layered halfspaces. For such cases DIGES uses closed-form solutions. These solutions are given for one as well as two dimensional deconvolution. The type of waves considered include P, SV and SH waves. The non-vertical incidence is given special attention since deconvolution can be defined differently depending on the problem of interest. For all wave cases considered, corresponding transfer functions are presented in closed-form. Transient solutions are obtained in the frequency domain. Finally, a variety of forms are considered for representing the free field motion both in terms of deterministic as well as probabilistic representations. These include (a) acceleration time histories, (b) response spectra (c) Fourier spectra and (d) cross-spectral densities.

  11. The trellis complexity of convolutional codes

    NASA Technical Reports Server (NTRS)

    Mceliece, R. J.; Lin, W.

    1995-01-01

    It has long been known that convolutional codes have a natural, regular trellis structure that facilitates the implementation of Viterbi's algorithm. It has gradually become apparent that linear block codes also have a natural, though not in general a regular, 'minimal' trellis structure, which allows them to be decoded with a Viterbi-like algorithm. In both cases, the complexity of the Viterbi decoding algorithm can be accurately estimated by the number of trellis edges per encoded bit. It would, therefore, appear that we are in a good position to make a fair comparison of the Viterbi decoding complexity of block and convolutional codes. Unfortunately, however, this comparison is somewhat muddled by the fact that some convolutional codes, the punctured convolutional codes, are known to have trellis representations that are significantly less complex than the conventional trellis. In other words, the conventional trellis representation for a convolutional code may not be the minimal trellis representation. Thus, ironically, at present we seem to know more about the minimal trellis representation for block than for convolutional codes. In this article, we provide a remedy, by developing a theory of minimal trellises for convolutional codes. (A similar theory has recently been given by Sidorenko and Zyablov). This allows us to make a direct performance-complexity comparison for block and convolutional codes. A by-product of our work is an algorithm for choosing, from among all generator matrices for a given convolutional code, what we call a trellis-minimal generator matrix, from which the minimal trellis for the code can be directly constructed. Another by-product is that, in the new theory, punctured convolutional codes no longer appear as a special class, but simply as high-rate convolutional codes whose trellis complexity is unexpectedly small.

  12. 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

  13. On the growth and form of cortical convolutions

    NASA Astrophysics Data System (ADS)

    Tallinen, Tuomas; Chung, Jun Young; Rousseau, François; Girard, Nadine; Lefèvre, Julien; Mahadevan, L.

    2016-06-01

    The rapid growth of the human cortex during development is accompanied by the folding of the brain into a highly convoluted structure. Recent studies have focused on the genetic and cellular regulation of cortical growth, but understanding the formation of the gyral and sulcal convolutions also requires consideration of the geometry and physical shaping of the growing brain. To study this, we use magnetic resonance images to build a 3D-printed layered gel mimic of the developing smooth fetal brain; when immersed in a solvent, the outer layer swells relative to the core, mimicking cortical growth. This relative growth puts the outer layer into mechanical compression and leads to sulci and gyri similar to those in fetal brains. Starting with the same initial geometry, we also build numerical simulations of the brain modelled as a soft tissue with a growing cortex, and show that this also produces the characteristic patterns of convolutions over a realistic developmental course. All together, our results show that although many molecular determinants control the tangential expansion of the cortex, the size, shape, placement and orientation of the folds arise through iterations and variations of an elementary mechanical instability modulated by early fetal brain geometry.

  14. Fabrication and static characterization of carbon-fiber-reinforced polymers with embedded NiTi shape memory wire actuators

    NASA Astrophysics Data System (ADS)

    de Araújo, C. J.; Rodrigues, L. F. A.; Coutinho Neto, J. F.; Reis, R. P. B.

    2008-12-01

    In this work, unidirectional carbon-fiber-reinforced polymers (CFRP) with embedded NiTi shape memory alloy (SMA) wire actuators were manufactured using a universal testing machine equipped with a thermally controlled chamber. Beam specimens containing cold-worked, annealed and trained NiTi SMA wires distributed along their neutral plane were fabricated. Several tests in a three-point bending mode at different constant temperatures were performed. To verify thermal buckling effects, electrical activation of the specimens was realized in a cantilevered beam mode and the influence of the SMA wire actuators on the tip deflection of the composite is demonstrated.

  15. Runge-Kutta based generalized convolution quadrature

    NASA Astrophysics Data System (ADS)

    Lopez-Fernandez, Maria; Sauter, Stefan

    2016-06-01

    We present the Runge-Kutta generalized convolution quadrature (gCQ) with variable time steps for the numerical solution of convolution equations for time and space-time problems. We present the main properties of the method and a convergence result.

  16. Symbol synchronization in convolutionally coded systems

    NASA Technical Reports Server (NTRS)

    Baumert, L. D.; Mceliece, R. J.; Van Tilborg, H. C. A.

    1979-01-01

    Alternate symbol inversion is sometimes applied to the output of convolutional encoders to guarantee sufficient richness of symbol transition for the receiver symbol synchronizer. A bound is given for the length of the transition-free symbol stream in such systems, and those convolutional codes are characterized in which arbitrarily long transition free runs occur.

  17. Rolling-Convolute Joint For Pressurized Glove

    NASA Technical Reports Server (NTRS)

    Kosmo, Joseph J.; Bassick, John W.

    1994-01-01

    Rolling-convolute metacarpal/finger joint enhances mobility and flexibility of pressurized glove. Intended for use in space suit to increase dexterity and decrease wearer's fatigue. Also useful in diving suits and other pressurized protective garments. Two ring elements plus bladder constitute rolling-convolute joint balancing torques caused by internal pressurization of glove. Provides comfortable grasp of various pieces of equipment.

  18. The general theory of convolutional codes

    NASA Technical Reports Server (NTRS)

    Mceliece, R. J.; Stanley, R. P.

    1993-01-01

    This article presents a self-contained introduction to the algebraic theory of convolutional codes. This introduction is partly a tutorial, but at the same time contains a number of new results which will prove useful for designers of advanced telecommunication systems. Among the new concepts introduced here are the Hilbert series for a convolutional code and the class of compact codes.

  19. Fabrication and characterization of shape memory polymers at small-scales

    NASA Astrophysics Data System (ADS)

    Wornyo, Edem

    The objective of this research is to thoroughly investigate the shape memory effect in polymers, characterize, and optimize these polymers for applications in information storage systems. Previous research effort in this field concentrated on shape memory metals for biomedical applications such as stents. Minimal work has been done on shape memory polymers; and the available work on shape memory polymers has not characterized the behaviors of this category of polymers fully. Copolymer shape memory materials based on diethylene glycol dimethacrylate (DEGDMA) crosslinker, and tert butyl acrylate (tBA) monomer are designed. The design encompasses a careful control of the backbone chemistry of the materials. Characterization methods such as dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC); and novel nanoscale techniques such as atomic force microscopy (AFM), and nanoindentation are applied to this system of materials. Designed experiments are conducted on the materials to optimize spin coating conditions for thin films. Furthermore, the recovery, a key for the use of these polymeric materials for information storage, is examined in detail with respect to temperature. In sum, the overarching objectives of the proposed research are to: (i) Design shape memory polymers based on polyethylene glycol dimethacrylate (PEGDMA) and diethylene glycol dimethacrylate (DEGDMA) crosslinkers, 2-hydroxyethyl methacrylate (HEMA) and tert-butyl acrylate monomer (tBA). (ii) Utilize dynamic mechanical analysis (DMA) to comprehend the thermomechanical properties of shape memory polymers based on DEGDMA and tBA. (iii) Utilize nanoindentation and atomic force microscopy (AFM) to understand the nanoscale behavior of these SMPs, and explore the strain storage and recovery of the polymers from a deformed state. (iv) Study spin coating conditions on thin film quality with designed experiments. (iv) Apply neural networks and genetic algorithms to optimize these systems.

  20. Direct Fabrication of Free-Standing MOF Superstructures with Desired Shapes by Micro-Confined Interfacial Synthesis.

    PubMed

    Kim, Jin-Oh; Min, Kyoung-Ik; Noh, Hyunwoo; Kim, Dong-Hwi; Park, Soo-Young; Kim, Dong-Pyo

    2016-06-13

    Recently, metal-organic frameworks (MOFs) with multifunctional pore chemistry have been intensively investigated for positioning the desired morphology at specific locations onto substrates for manufacturing devices. Herein, we develop a micro-confined interfacial synthesis (MIS) approach for fabrication of a variety of free-standing MOF superstructures with desired shapes. This approach for engineering MOFs provides three key features: 1) in situ synthesis of various free-standing MOF superstructures with controlled compositions, shape, and thickness using a mold membrane; 2) adding magnetic functionality into MOF superstructures by loading with Fe3 O4 nanoparticles; 3) transferring the synthesized MOF superstructural array on to flat or curved surface of various substrates. The MIS route with versatile potential opens the door for a number of new perspectives in various applications. PMID:27140805

  1. Search for optimal distance spectrum convolutional codes

    NASA Technical Reports Server (NTRS)

    Connor, Matthew C.; Perez, Lance C.; Costello, Daniel J., Jr.

    1993-01-01

    In order to communicate reliably and to reduce the required transmitter power, NASA uses coded communication systems on most of their deep space satellites and probes (e.g. Pioneer, Voyager, Galileo, and the TDRSS network). These communication systems use binary convolutional codes. Better codes make the system more reliable and require less transmitter power. However, there are no good construction techniques for convolutional codes. Thus, to find good convolutional codes requires an exhaustive search over the ensemble of all possible codes. In this paper, an efficient convolutional code search algorithm was implemented on an IBM RS6000 Model 580. The combination of algorithm efficiency and computational power enabled us to find, for the first time, the optimal rate 1/2, memory 14, convolutional code.

  2. Achieving unequal error protection with convolutional codes

    NASA Technical Reports Server (NTRS)

    Mills, D. G.; Costello, D. J., Jr.; Palazzo, R., Jr.

    1994-01-01

    This paper examines the unequal error protection capabilities of convolutional codes. Both time-invariant and periodically time-varying convolutional encoders are examined. The effective free distance vector is defined and is shown to be useful in determining the unequal error protection (UEP) capabilities of convolutional codes. A modified transfer function is used to determine an upper bound on the bit error probabilities for individual input bit positions in a convolutional encoder. The bound is heavily dependent on the individual effective free distance of the input bit position. A bound relating two individual effective free distances is presented. The bound is a useful tool in determining the maximum possible disparity in individual effective free distances of encoders of specified rate and memory distribution. The unequal error protection capabilities of convolutional encoders of several rates and memory distributions are determined and discussed.

  3. Prototype fabrication and preliminary in vitro testing of a shape memory endovascular thrombectomy device.

    PubMed

    Small, Ward; Wilson, Thomas S; Buckley, Patrick R; Benett, William J; Loge, Jeffrey M; Hartman, Jonathan; Maitland, Duncan J

    2007-09-01

    An electromechanical microactuator comprised of shape memory polymer (SMP) and shape memory nickel-titanium alloy (nitinol) was developed and used in an endovascular thrombectomy device prototype. The microactuator maintains a straight rod shape until an applied current induces electro-resistive (Joule) heating, causing the microactuator to transform into a corkscrew shape. The straight-to-corkscrew transformation geometry was chosen to permit endovascular delivery through (straight form) and retrieval of (corkscrew form) a stroke-causing thrombus (blood clot) in the brain. Thermal imaging of the microactuator during actuation in air indicated that the steady-state temperature rise caused by Joule heating varied quadratically with applied current and that actuation occurred near the glass transition temperature of the SMP (86 degrees C). To demonstrate clinical application, the device was used to retrieve a blood clot in a water-filled silicone neurovascular model. Numerical modeling of the heat transfer to the surrounding blood and associated thermal effects on the adjacent artery potentially encountered during clinical use suggested that any thermal damage would likely be confined to localized areas where the microactuator was touching the artery wall. This shape memory mechanical thrombectomy device is a promising tool for treating ischemic stroke without the need for infusion of clot-dissolving drugs. PMID:17867358

  4. Adaptive decoding of convolutional codes

    NASA Astrophysics Data System (ADS)

    Hueske, K.; Geldmacher, J.; Götze, J.

    2007-06-01

    Convolutional codes, which are frequently used as error correction codes in digital transmission systems, are generally decoded using the Viterbi Decoder. On the one hand the Viterbi Decoder is an optimum maximum likelihood decoder, i.e. the most probable transmitted code sequence is obtained. On the other hand the mathematical complexity of the algorithm only depends on the used code, not on the number of transmission errors. To reduce the complexity of the decoding process for good transmission conditions, an alternative syndrome based decoder is presented. The reduction of complexity is realized by two different approaches, the syndrome zero sequence deactivation and the path metric equalization. The two approaches enable an easy adaptation of the decoding complexity for different transmission conditions, which results in a trade-off between decoding complexity and error correction performance.

  5. Hydrothermal fabrication of octahedral-shaped Fe3O4 nanoparticles and their magnetorheological response

    NASA Astrophysics Data System (ADS)

    Jung, H. S.; Choi, H. J.

    2015-05-01

    Octahedral-shaped Fe3O4 nanoparticles were synthesized in the presence of 1,3-diaminopropane using a hydrothermal method and assessed as a potential magnetorheological (MR) material. Their morphology, crystal structure, and magnetic properties were examined by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and vibrating sample magnetometry, respectively. The MR characteristics of the octahedral-shaped, Fe3O4 nanoparticle-based MR particles when dispersed in silicone oil with a 10 vol. % particle concentration were examined using a rotational rheometer under an external magnetic field. The resulting MR fluids exhibited a Bingham-like behavior with a distinctive yield stress from their flow curves.

  6. Single-step direct laser fabrication of complex shaped microoptical components

    NASA Astrophysics Data System (ADS)

    Žukauskas, Albertas; Tikuišis, Kristupas K.; Ščiuka, Mindaugas; Melninkaitis, Andrius; Gadonas, Roaldas; Reinhardt, Carsten; Malinauskas, Mangirdas

    2012-06-01

    We report on the fabrication of the minimized conventional microoptical components out of the hybrid organic- inorganic SZ2080 and SG4060 photoresins using laser direct writing technique. An ascending laser focus multiscan approach is introduced as a method for the structuring of 2D nanolines. The diameters and heights of the nanolines are comparable to the ones written with the electron beam lithography. Using our proposed laser direct writing approach one can write 3D microstructures with the 2D nanofeatures in a single step procedure. As demonstration of this technology, microlenses with 1D, 2D and circular transmission gratings were fabricated. Additionally, for the rst time, ISO certied laser-induced damage testing was applied to determine the optical breakdown threshold of the SZ2080 photoresin used for the laser direct writing.

  7. Microfluidic fabrication of shape-tunable alginate microgels: effect of size and impact velocity.

    PubMed

    Hu, Yuandu; Azadi, Glareh; Ardekani, Arezoo M

    2015-04-20

    We report on a capillary-based microfluidic platform for the fabrication of non-spherical sodium alginate microgels. The sodium alginate droplets were crosslinked off-chip in a mixture of barium acetate and glycerol solution. Novel morphologies such as tear drop, lamp-like, mushroom-like, double-dimpled and bowl-like microgels were fabricated by controlling the size, impact velocity (at the crosslinking solution/oil interface), and concentration of sodium alginate solution. We monitored the microscale deformation process in situ at the interface and proposeed a deformation mechanism resulting in unique morphologies. Additionally, we constructed microgel superstructures by assembling the non-spherical alginate microgels to spherical poly(N-isopropylacrylamide) (pNIPAAm) microgels via electrostatic interaction. PMID:25662685

  8. Near-net-shape fabrication of continuous Ag-Clad Bi-Based superconductors

    SciTech Connect

    Lanagan, M. T. et al.

    1998-04-01

    We have developed a near-net-shape process for Ag-clad Bi-2212 superconductors as an alternative to the powder-in-tube process. This new process offers the advantages of nearly continuous processing, minimization of processing steps, reasonable ability to control the Bi-2212/Ag ratio, and early development of favorable texture of the Bi-2212 grains. Superconducting properties are discussed.

  9. A Finger-Shaped Tactile Sensor for Fabric Surfaces Evaluation by 2-Dimensional Active Sliding Touch

    PubMed Central

    Hu, Haihua; Han, Yezhen; Song, Aiguo; Chen, Shanguang; Wang, Chunhui; Wang, Zheng

    2014-01-01

    Sliding tactile perception is a basic function for human beings to determine the mechanical properties of object surfaces and recognize materials. Imitating this process, this paper proposes a novel finger-shaped tactile sensor based on a thin piezoelectric polyvinylidene fluoride (PVDF) film for surface texture measurement. A parallelogram mechanism is designed to ensure that the sensor applies a constant contact force perpendicular to the object surface, and a 2-dimensional movable mechanical structure is utilized to generate the relative motion at a certain speed between the sensor and the object surface. By controlling the 2-dimensional motion of the finger-shaped sensor along the object surface, small height/depth variation of surface texture changes the output charge of PVDF film then surface texture can be measured. In this paper, the finger-shaped tactile sensor is used to evaluate and classify five different kinds of linen. Fast Fourier Transformation (FFT) is utilized to get original attribute data of surface in the frequency domain, and principal component analysis (PCA) is used to compress the attribute data and extract feature information. Finally, low dimensional features are classified by Support Vector Machine (SVM). The experimental results show that this finger-shaped tactile sensor is effective and high accurate for discriminating the five textures. PMID:24618775

  10. A finger-shaped tactile sensor for fabric surfaces evaluation by 2-dimensional active sliding touch.

    PubMed

    Hu, Haihua; Han, Yezhen; Song, Aiguo; Chen, Shanguang; Wang, Chunhui; Wang, Zheng

    2014-01-01

    Sliding tactile perception is a basic function for human beings to determine the mechanical properties of object surfaces and recognize materials. Imitating this process, this paper proposes a novel finger-shaped tactile sensor based on a thin piezoelectric polyvinylidene fluoride (PVDF) film for surface texture measurement. A parallelogram mechanism is designed to ensure that the sensor applies a constant contact force perpendicular to the object surface, and a 2-dimensional movable mechanical structure is utilized to generate the relative motion at a certain speed between the sensor and the object surface. By controlling the 2-dimensional motion of the finger-shaped sensor along the object surface, small height/depth variation of surface texture changes the output charge of PVDF film then surface texture can be measured. In this paper, the finger-shaped tactile sensor is used to evaluate and classify five different kinds of linen. Fast Fourier Transformation (FFT) is utilized to get original attribute data of surface in the frequency domain, and principal component analysis (PCA) is used to compress the attribute data and extract feature information. Finally, low dimensional features are classified by Support Vector Machine (SVM). The experimental results show that this finger-shaped tactile sensor is effective and high accurate for discriminating the five textures. PMID:24618775

  11. Properties of Porous TiNbZr Shape Memory Alloy Fabricated by Mechanical Alloying and Hot Isostatic Pressing

    NASA Astrophysics Data System (ADS)

    Ma, L. W.; Chung, C. Y.; Tong, Y. X.; Zheng, Y. F.

    2011-07-01

    In the past decades, systematic researches have been focused on studying Ti-Nb-based SMAs by adding ternary elements, such as Mo, Sn, Zr, etc. However, only arc melting or induction melting methods, with subsequent hot or cold rolling, were used to fabricate these Ni-free SMAs. There is no work related to powder metallurgy and porous structures. This study focuses on the fabrication and characterization of porous Ti-22Nb-6Zr (at.%) shape memory alloys produced using elemental powders by means of mechanical alloying and hot isostatic pressing. It is found that the porous Ti-22Nb-6Zr alloys prepared by the HIP process exhibit a homogenous pore distribution with spherical pores, while the pores have irregular shape in the specimen prepared by conventional sintering. X-ray diffraction analysis showed that the solid solution-treated Ti-22Nb-6Zr alloy consists of both β phase and α″ martensite phase. Morphologies of martensite were observed. Finally, the porous Ti-22Nb-6Zr SMAs produced by both MA and HIP exhibit good mechanical properties, such as superior superelasticity, with maximum recoverable strain of ~3% and high compressive strength.

  12. A study of shape-dependent partial volume correction in pet imaging using ellipsoidal phantoms fabricated via rapid prototyping

    NASA Astrophysics Data System (ADS)

    Mille, Matthew M.

    Positron emission tomography (PET) with 2-[18F]fluoro-2-deoxy-D-glucose (FDG) is being increasingly recognized as an important tool for quantitative assessment of tumor response because of its ability to capture functional information about the tumor's metabolism. However, despite many advances in PET technology, measurements of tumor radiopharmaceutical uptake in PET are still challenged by issues of accuracy and consistency, thereby compromising the use of PET as a surrogate endpoint in clinical trials. One limiting component of the overall uncertainty in PET is the relatively poor spatial resolution of the images which directly affects the accuracy of the tumor radioactivity measurements. These spatial resolution effects, colloquially known as the partial volume effect (PVE), are a function of the characteristics of the scanner as well as the tumor being imaged. Previous efforts have shown that the PVE depends strongly on the tumor volume and the background-to-tumor activity concentration ratio. The PVE is also suspected to be a function of tumor shape, although to date no systematic study of this effect has been performed. This dissertation seeks to help fill the gap in the current knowledge about the shape-dependence of the PVE by attempting to quantify, through both theoretical calculation and experimental measurement, the magnitude of the shape effect for ellipsoidal tumors. An experimental investigation of the tumor shape effect necessarily requires tumor phantoms of multiple shapes. Hence, a prerequisite for this research was the design and fabrication of hollow tumor phantoms which could be filled uniformly with radioactivity and imaged on a PET scanner. The phantom fabrication was achieved with the aid of stereolithography and included prolate ellipsoids of various axis ratios. The primary experimental method involved filling the tumor phantoms with solutions of 18F whose activity concentrations were known and traceable to primary radioactivity standards

  13. Design, simulation, fabrication, packaging, and characterization of a MEMS-based mirror array for femtosecond pulse-shaping in phase and amplitude.

    PubMed

    Weber, Stefan M; Bonacina, Luigi; Noell, Wilfried; Kiselev, Denis; Extermann, Jérôme; Jutzi, Fabio; Lani, Sébastien; Nenadl, Ondrej; Wolf, Jean-Pierre; de Rooij, Nico F

    2011-07-01

    We present an in-detail description of the design, simulation, fabrication, and packaging of a linear micromirror array specifically designed for temporal pulse shaping of ultrashort laser pulses. The innovative features of this device include a novel comb-drive actuator allowing both piston and tilt motion for phase- and amplitude-shaping, and an X-shaped laterally reinforced spring preventing lateral snap-in while providing high flexibility for both degrees of freedom. PMID:21806226

  14. Design, simulation, fabrication, packaging, and characterization of a MEMS-based mirror array for femtosecond pulse-shaping in phase and amplitude

    NASA Astrophysics Data System (ADS)

    Weber, Stefan M.; Bonacina, Luigi; Noell, Wilfried; Kiselev, Denis; Extermann, Jérôme; Jutzi, Fabio; Lani, Sébastien; Nenadl, Ondrej; Wolf, Jean-Pierre; de Rooij, Nico F.

    2011-07-01

    We present an in-detail description of the design, simulation, fabrication, and packaging of a linear micromirror array specifically designed for temporal pulse shaping of ultrashort laser pulses. The innovative features of this device include a novel comb-drive actuator allowing both piston and tilt motion for phase- and amplitude-shaping, and an X-shaped laterally reinforced spring preventing lateral snap-in while providing high flexibility for both degrees of freedom.

  15. Nanograined Net-Shaped Fabrication of Rhenium Components by EB-PVD

    NASA Astrophysics Data System (ADS)

    Singh, Jogender; Wolfe, Douglas E.

    2004-02-01

    Cost-effective net-shaped forming components have brought considerable interest into DoD, NASA and DoE. Electron beam physical vapor deposition (EB-PVD) offers flexibility in forming net-shaped components with tailored microstructure and chemistry. High purity rhenium (Re) components including rhenium-coated graphite balls, Re- plates and tubes have been successfully manufactured by EB-PVD. EB-PVD Re components exhibited sub-micron and nano-sized grains with high hardness and strength as compared to CVD. It is estimated that the cost of Re components manufactured by EB-PVD would be less than the current CVD and powder-HIP Technologies.

  16. Nanograined Net-Shaped Fabrication of Rhenium Components by EB-PVD

    SciTech Connect

    Singh, Jogender; Wolfe, Douglas E.

    2004-02-04

    Cost-effective net-shaped forming components have brought considerable interest into DoD, NASA and DoE. Electron beam physical vapor deposition (EB-PVD) offers flexibility in forming net-shaped components with tailored microstructure and chemistry. High purity rhenium (Re) components including rhenium-coated graphite balls, Re- plates and tubes have been successfully manufactured by EB-PVD. EB-PVD Re components exhibited sub-micron and nano-sized grains with high hardness and strength as compared to CVD. It is estimated that the cost of Re components manufactured by EB-PVD would be less than the current CVD and powder-HIP Technologies.

  17. Fabrication of a Bioactive, PCL-based "Self-fitting" Shape Memory Polymer Scaffold.

    PubMed

    Nail, Lindsay N; Zhang, Dawei; Reinhard, Jessica L; Grunlan, Melissa A

    2015-01-01

    Tissue engineering has been explored as an alternative strategy for the treatment of critical-sized cranio-maxillofacial (CMF) bone defects. Essential to the success of this approach is a scaffold that is able to conformally fit within an irregular defect while also having the requisite biodegradability, pore interconnectivity and bioactivity. By nature of their shape recovery and fixity properties, shape memory polymer (SMP) scaffolds could achieve defect "self-fitting." In this way, following exposure to warm saline (~60 ºC), the SMP scaffold would become malleable, permitting it to be hand-pressed into an irregular defect. Subsequent cooling (~37 ºC) would return the scaffold to its relatively rigid state within the defect. To meet these requirements, this protocol describes the preparation of SMP scaffolds prepared via the photochemical cure of biodegradable polycaprolactone diacrylate (PCL-DA) using a solvent-casting particulate-leaching (SCPL) method. A fused salt template is utilized to achieve pore interconnectivity. To realize bioactivity, a polydopamine coating is applied to the surface of the scaffold pore walls. Characterization of self-fitting and shape memory behaviors, pore interconnectivity and in vitro bioactivity are also described. PMID:26556112

  18. 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.

  19. 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.

  20. Magnetic fabric of saucer-shaped sills in the Karoo Large Igneous Province

    NASA Astrophysics Data System (ADS)

    Polteau, S.; Ferre, E. C.; Planke, S.; Neumann, E.; Chevallier, L.

    2007-12-01

    Magmatic sill intrusions commonly exhibit a saucer geometry in undeformed sedimentary basins and volcanic rifted margins. Current emplacement models are based on the analysis of the intrusion geometry and their spatial relationships with potential feeders, not on the knowledge of the magma flow geometry. The Karoo Basin of South Africa hosts hundreds of saucer-shaped sills. Amongst these, the Golden Valley Sill is well-exposed and displays the connections with adjacent and nested saucers. A combination of detailed fieldwork observations and the anisotropy of magnetic susceptibility measurements were used to identify strain markers that can be interpreted in terms of magma flow directions. A total of 113 localities (6 specimens/site), mostly including opposite sill margins, have been sampled for anisotropy of magnetic susceptibility (AMS) analyses. The magnetic properties were defined by measuring hysteresis cycles and K-T curves on 34 and 19 specimens, respectively. The majority of the localities display well-defined magnetic foliations that consistently dip outward from the centre of the Golden Valley Sill. This orientation of the magnetic foliation most likely represents inflation/deflation cycles of the intruding sill that interacts with non-static enclosing walls. In addition, four magma channels were identified and display an imbrication of the magnetic foliation that indicates an outward magma flow direction. In conclusion, the observed magma flow geometries derived from macroscopic flow indicators and the AMS data correlate well and are used to constrain an emplacement model for the Golden Valley Sill Complex. Finally, the emplacement model of sill complexes repeats the cycle -injection of magma - formation of a saucer-shaped sill - pressure build up - fracturation and pressure drop - channeling of magma - injection of (new batch of) magma - formation of a new saucer-shaped sill- until the magma supply stops.

  1. Top-Down Particle Fabrication: Control of Size and Shape for Diagnostic Imaging and Drug Delivery

    PubMed Central

    Canelas, Dorian A.; Herlihy, Kevin P.; DeSimone, Joseph M.

    2009-01-01

    This review discusses rational design of particles for use as therapeutic vectors and diagnostic imaging agent carriers. The emerging importance of both particle size and shape is considered, and the adaptation and modification of soft lithography methods to produce nanoparticles is highlighted. To this end, studies utilizing particles made via a process called Particle Replication In Non-wetting Templates (PRINT™) are discussed. In addition, insights gained into therapeutic cargo and imaging agent delivery from related types of polymer-based carriers are considered. PMID:20049805

  2. Fabrication of anatomically-shaped cartilage constructs using decellularized cartilage-derived matrix scaffolds.

    PubMed

    Rowland, Christopher R; Colucci, Lina A; Guilak, Farshid

    2016-06-01

    The native extracellular matrix of cartilage contains entrapped growth factors as well as tissue-specific epitopes for cell-matrix interactions, which make it a potentially attractive biomaterial for cartilage tissue engineering. A limitation to this approach is that the native cartilage extracellular matrix possesses a pore size of only a few nanometers, which inhibits cellular infiltration. Efforts to increase the pore size of cartilage-derived matrix (CDM) scaffolds dramatically attenuate their mechanical properties, which makes them susceptible to cell-mediated contraction. In previous studies, we have demonstrated that collagen crosslinking techniques are capable of preventing cell-mediated contraction in CDM disks. In the current study, we investigated the effects of CDM concentration and pore architecture on the ability of CDM scaffolds to resist cell-mediated contraction. Increasing CDM concentration significantly increased scaffold mechanical properties, which played an important role in preventing contraction, and only the highest CDM concentration (11% w/w) was able to retain the original scaffold dimensions. However, the increase in CDM concentration led to a concomitant decrease in porosity and pore size. Generating a temperature gradient during the freezing process resulted in unidirectional freezing, which aligned the formation of ice crystals during the freezing process and in turn produced aligned pores in CDM scaffolds. These aligned pores increased the pore size of CDM scaffolds at all CDM concentrations, and greatly facilitated infiltration by mesenchymal stem cells (MSCs). These methods were used to fabricate of anatomically-relevant CDM hemispheres. CDM hemispheres with aligned pores supported uniform MSC infiltration and matrix deposition. Furthermore, these CDM hemispheres retained their original architecture and did not contract, warp, curl, or splay throughout the entire 28-day culture period. These findings demonstrate that given the

  3. Bernoulli convolutions and 1D dynamics

    NASA Astrophysics Data System (ADS)

    Kempton, Tom; Persson, Tomas

    2015-10-01

    We describe a family {φλ} of dynamical systems on the unit interval which preserve Bernoulli convolutions. We show that if there are parameter ranges for which these systems are piecewise convex, then the corresponding Bernoulli convolution will be absolutely continuous with bounded density. We study the systems {φλ} and give some numerical evidence to suggest values of λ for which {φλ} may be piecewise convex.

  4. Net Shaped Component Fabrication of Refractory Metal Alloys using Vacuum Plasma Spraying

    NASA Technical Reports Server (NTRS)

    Sen, S.; ODell, S.; Gorti, S.; Litchford, R.

    2006-01-01

    The vacuum plasma spraying (VPS) technique was employed to produce dense and net shaped components of a new tungsten-rhenium (W-Re) refractory metal alloy. The fine grain size obtained using this technique enhanced the mechanical properties of the alloy at elevated temperatures. The alloy development also included incorporation of thermodynamically stable dispersion phases to pin down grain boundaries at elevated temperatures and thereby circumventing the inherent problem of recrystallization of refractory alloys at elevated temperatures. Requirements for such alloys as related to high temperature space propulsion components will be discussed. Grain size distribution as a function of cooling rate and dispersion phase loading will be presented. Mechanical testing and grain growth results as a function of temperature will also be discussed.

  5. Coset Codes Viewed as Terminated Convolutional Codes

    NASA Technical Reports Server (NTRS)

    Fossorier, Marc P. C.; Lin, Shu

    1996-01-01

    In this paper, coset codes are considered as terminated convolutional codes. Based on this approach, three new general results are presented. First, it is shown that the iterative squaring construction can equivalently be defined from a convolutional code whose trellis terminates. This convolutional code determines a simple encoder for the coset code considered, and the state and branch labelings of the associated trellis diagram become straightforward. Also, from the generator matrix of the code in its convolutional code form, much information about the trade-off between the state connectivity and complexity at each section, and the parallel structure of the trellis, is directly available. Based on this generator matrix, it is shown that the parallel branches in the trellis diagram of the convolutional code represent the same coset code C(sub 1), of smaller dimension and shorter length. Utilizing this fact, a two-stage optimum trellis decoding method is devised. The first stage decodes C(sub 1), while the second stage decodes the associated convolutional code, using the branch metrics delivered by stage 1. Finally, a bidirectional decoding of each received block starting at both ends is presented. If about the same number of computations is required, this approach remains very attractive from a practical point of view as it roughly doubles the decoding speed. This fact is particularly interesting whenever the second half of the trellis is the mirror image of the first half, since the same decoder can be implemented for both parts.

  6. YVO 4:Eu 3+ arrays with flower-like and rod-like shape fabricated by a hydrothermal method

    NASA Astrophysics Data System (ADS)

    Bao, Amurisana; Lai, Hua; Yang, Yuming; Xu, Weiwei; Tao, Chunyan; Zhang, Hua; Yang, Hua

    2008-09-01

    Large-scale well-aligned rod-like and flower-like YVO 4:Eu 3+ crystals were prepared on glass substrates by a hydrothermal method in a controllable way with additive ethylenediamine tetraacetic acid disodium salt [Na 2H 2L·2H 2O]. No extra surfactants or templates were used. In the synthesis process, well-aligned YVO 4:Eu 3+ microrods were fabricated on YVO 4:Eu 3+-seed-coated substrates. The YVO 4:Eu 3+ seed precursor was prepared by a sol-gel reaction. And well-defined flower-like YVO 4:Eu 3+ microstructures were fabricated on bare substrates. The products were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and photoluminescence (PL). TEM and SEM studies reveal that the flower-like superstructure is composed of dozens of radially oriented rhombus-shaped microrods and the crystalline microrods with rectangle cross-sections and well-defined crystallographic faces are grown directly onto the substrates. This convenient method may be applicable to prepare other orthovanadate phosphors with 3D morphologies.

  7. Design and Fabrication of a Biodegradable, Covalently Crosslinked Shape-Memory Alginate Scaffold for Cell and Growth Factor Delivery

    PubMed Central

    Wang, Lin; Shansky, Janet; Borselli, Cristina; Mooney, David

    2012-01-01

    The successful use of transplanted cells and/or growth factors for tissue repair is limited by a significant cell loss and/or rapid growth factor diffusion soon after implantation. Highly porous alginate scaffolds formed with covalent crosslinking have been used to improve cell survival and growth factor release kinetics, but require open-wound surgical procedures for insertion and have not previously been designed to readily degrade in vivo. In this study, a biodegradable, partially crosslinked alginate scaffold with shape-memory properties was fabricated for minimally invasive surgical applications. A mixture of high and low molecular weight partially oxidized alginate modified with RGD peptides was covalently crosslinked using carbodiimide chemistry. The scaffold was compressible 11-fold and returned to its original shape when rehydrated. Scaffold degradation properties in vitro indicated ∼85% mass loss by 28 days. The greater than 90% porous scaffolds released the recombinant growth factor insulin-like growth factor-1 over several days in vitro and allowed skeletal muscle cell survival, proliferation, and migration from the scaffold over a 28-day period. The compressible scaffold thus has the potential to be delivered by a minimally invasive technique, and when rehydrated in vivo with cells and/or growth factors, could serve as a temporary delivery vehicle for tissue repair. PMID:22646518

  8. Design and fabrication of a bat-inspired flapping-flight platform using shape memory alloy muscles and joints

    NASA Astrophysics Data System (ADS)

    Furst, Stephen J.; Bunget, George; Seelecke, Stefan

    2013-01-01

    This work focuses on the development of a concept for a micro-air vehicle (MAV) based on a bio-inspired flapping motion that is generated from integrated smart materials. Since many smart materials have their own biomimetic characteristics and the potential to be highly efficient, lightweight, and streamlined, they are ideal candidates for use in structural or actuator components in MAVs. In this work, shape memory alloy (SMA) actuator wires are used as analogs for biological muscles, and super-elastic SMAs are implemented as flexible joints capable of large bending angles. While biological organisms have an intrinsic sensing array composed of nerves, the SMA wires also provide self-sensing by virtue of a phase-dependent resistance change. Study of the biology and flight characteristics of natural fliers concluded that the bat provides an ideal platform for SMA muscle wires because of its comparatively low wingbeat frequency and superb maneuverability. A first-generation prototype is built to further the understanding of fabricating Nature’s designs. The engineering design is then improved further in a second-generation prototype that combines 3D printing and new techniques for embedding SMA wires and shaping SMA joints for improved robustness, reproducibility, and lifetime. These prototypes are on display at the North Carolina Museum of Natural Science’s Nature Research Center, which has the goal of bridging the gaps between biology and engineering.

  9. Do a bit more with convolution.

    PubMed

    Olsthoorn, Theo N

    2008-01-01

    Convolution is a form of superposition that efficiently deals with input varying arbitrarily in time or space. It works whenever superposition is applicable, that is, for linear systems. Even though convolution is well-known since the 19th century, this valuable method is still missing in most textbooks on ground water hydrology. This limits widespread application in this field. Perhaps most papers are too complex mathematically as they tend to focus on the derivation of analytical expressions rather than solving practical problems. However, convolution is straightforward with standard mathematical software or even a spreadsheet, as is demonstrated in the paper. The necessary system responses are not limited to analytic solutions; they may also be obtained by running an already existing ground water model for a single stress period until equilibrium is reached. With these responses, high-resolution time series of head or discharge may then be computed by convolution for arbitrary points and arbitrarily varying input, without further use of the model. There are probably thousands of applications in the field of ground water hydrology that may benefit from convolution. Therefore, its inclusion in ground water textbooks and courses is strongly needed. PMID:18181860

  10. Cost-Benefit Analysis for the Advanced Near Net Shape Technology (ANNST) Method for Fabricating Stiffened Cylinders

    NASA Technical Reports Server (NTRS)

    Stoner, Mary Cecilia; Hehir, Austin R.; Ivanco, Marie L.; Domack, Marcia S.

    2016-01-01

    This cost-benefit analysis assesses the benefits of the Advanced Near Net Shape Technology (ANNST) manufacturing process for fabricating integrally stiffened cylinders. These preliminary, rough order-of-magnitude results report a 46 to 58 percent reduction in production costs and a 7-percent reduction in weight over the conventional metallic manufacturing technique used in this study for comparison. Production cost savings of 35 to 58 percent were reported over the composite manufacturing technique used in this study for comparison; however, the ANNST concept was heavier. In this study, the predicted return on investment of equipment required for the ANNST method was ten cryogenic tank barrels when compared with conventional metallic manufacturing. The ANNST method was compared with the conventional multi-piece metallic construction and composite processes for fabricating integrally stiffened cylinders. A case study compared these three alternatives for manufacturing a cylinder of specified geometry, with particular focus placed on production costs and process complexity, with cost analyses performed by the analogy and parametric methods. Furthermore, a scalability study was conducted for three tank diameters to assess the highest potential payoff of the ANNST process for manufacture of large-diameter cryogenic tanks. The analytical hierarchy process (AHP) was subsequently used with a group of selected subject matter experts to assess the value of the various benefits achieved by the ANNST method for potential stakeholders. The AHP study results revealed that decreased final cylinder mass and quality assurance were the most valued benefits of cylinder manufacturing methods, therefore emphasizing the relevance of the benefits achieved with the ANNST process for future projects.

  11. Variation in mouthguard thickness according to heating conditions during fabrication Part 2: sheet shape and effect of thermal shrinkage.

    PubMed

    Takahashi, Mutsumi; Koide, Kaoru

    2016-06-01

    The aim of this study was to investigate the influence of the thermal shrinkage to thickness of the mouthguard with the heating method by the setting position of a sheet and the working model using an ethylene vinyl acetate sheet prepared by extrusion. Mouthguards were fabricated with EVA sheets (4.0 mm thick) using a vacuum-forming machine. Two forming conditions were compared: the square sheet was pinched by the clamping frame attached to the forming machine (S); and the round sheet was pinched at the top and bottom and stabilized by the circle tray (R). The sheet was aligned to make the sheet's extrusion direction vertical (V) or parallel (P) to the midline of the working model. The following two heating conditions were compared: (i) the sheet was molded when it sagged 15 mm below the level of the sheet frame measured at the top of the post in condition S (S-0), or that sagged 10 mm in condition R (R-0) in the usual position; (ii) the sheet frame was lowered by 50 mm from the ordinary height (S-50, R-50). Postmolding thickness was determined using a measuring device. Measurement points were the incisal and molar portion. Differences in the change of thickness of mouthguards molded under different heating conditions and extrusion directions for each sheet shape were analyzed by two-way analysis of variance (anova). The results of this study showed that by lowering the height of the sheet frame, the difference of the sheet temperature of each part was reduced. Among all sheets, condition V produced under S-50 and R-50 had the largest thickness independently of shape sheet. Furthermore, thickness reduction is effectively suppressed by aligning the direction of the extruded sheet to be vertical to the midline of the model. PMID:26337263

  12. Fabrication of cyclodextrins-procainamide supramolecular self-assembly: shape-shifting of nanosheet into microtubular structure.

    PubMed

    Siva, S; Kothai Nayaki, S; Rajendiran, N

    2015-05-20

    Encapsulation behavior of α- and β-cyclodextrins (α-CD, β-CD) with procainamide hydrochloride (PCA) has been investigated by absorption, fluorescence, time-resolved fluorescence, proton nuclear magnetic resonance spectroscopy, scanning electron microscope, Fourier transform-infrared spectroscopy, differential scanning calorimetry, and powder X-ray diffraction techniques. Spectral results revealed that PCA forms 1:2 drug-CD2 inclusion complexes with CDs. Novel supramolecular self-assemblies have been fabricated by inclusion complexation of PCA with α-CD/β-CD and characterized by transmission electron microscope and micro-Raman imaging. The obtained results from transmission electron microscope indicated that PCA/α-CD complex could form nano-sized particles. However, when the macrocyclic ring with six glucose units was switched into seven glucose units, the resultant PCA/β-CD complex could be self-assembled to micro-sized tubular structures. Shape-shifting of 2D nanosheet into 1D microtube by simple rolling mechanism was analyzed. Thermodynamic parameters of inclusion process were determined by Parameter Method 3 calculations. PMID:25817651

  13. Spring Characteristics of Circular Arc Shaped 3D Micro-cantilevers Fabricated Using III-V Semiconductor Strain-driven Bending Process

    NASA Astrophysics Data System (ADS)

    Sasaki, T. K.; Iwase, H.; Wang, J.; Akabori, M.; Yamada, S.

    2011-12-01

    We have investigated the characteristics of the circular arc shaped 3D micro-cantilever. The cantilever was fabricated using strain driven self-bending process based on the epitaxial growth. The arc shape can be used as the spring element in the various micro electro- mechanical- system (MEMS) applications. In this work, we focused on the force-deflection relationships, which would give the spring constant of the arc spring. In the case of the arc spring, spring constant depends on the dimensional parameters such as width, thickness and curvature radius. From the dependence of curvature radius on width, there seems no stress relaxation in width direction (transverse to deformation direction). Moreover, the measured spring constants of the fabricated cantilevers were also larger than the estimated ones from the curvature radius. The discrepancy indicates a possibility of stiffness enhancement of the circular arc shaped cantilevers.

  14. Sequential Syndrome Decoding of Convolutional Codes

    NASA Technical Reports Server (NTRS)

    Reed, I. S.; Truong, T. K.

    1984-01-01

    The algebraic structure of convolutional codes are reviewed and sequential syndrome decoding is applied to those codes. These concepts are then used to realize by example actual sequential decoding, using the stack algorithm. The Fano metric for use in sequential decoding is modified so that it can be utilized to sequentially find the minimum weight error sequence.

  15. Number-Theoretic Functions via Convolution Rings.

    ERIC Educational Resources Information Center

    Berberian, S. K.

    1992-01-01

    Demonstrates the number theory property that the number of divisors of an integer n times the number of positive integers k, less than or equal to and relatively prime to n, equals the sum of the divisors of n using theory developed about multiplicative functions, the units of a convolution ring, and the Mobius Function. (MDH)

  16. Precise two-dimensional D-bar reconstructions of human chest and phantom tank via sinc-convolution algorithm

    PubMed Central

    2012-01-01

    Background Electrical Impedance Tomography (EIT) is used as a fast clinical imaging technique for monitoring the health of the human organs such as lungs, heart, brain and breast. Each practical EIT reconstruction algorithm should be efficient enough in terms of convergence rate, and accuracy. The main objective of this study is to investigate the feasibility of precise empirical conductivity imaging using a sinc-convolution algorithm in D-bar framework. Methods At the first step, synthetic and experimental data were used to compute an intermediate object named scattering transform. Next, this object was used in a two-dimensional integral equation which was precisely and rapidly solved via sinc-convolution algorithm to find the square root of the conductivity for each pixel of image. For the purpose of comparison, multigrid and NOSER algorithms were implemented under a similar setting. Quality of reconstructions of synthetic models was tested against GREIT approved quality measures. To validate the simulation results, reconstructions of a phantom chest and a human lung were used. Results Evaluation of synthetic reconstructions shows that the quality of sinc-convolution reconstructions is considerably better than that of each of its competitors in terms of amplitude response, position error, ringing, resolution and shape-deformation. In addition, the results confirm near-exponential and linear convergence rates for sinc-convolution and multigrid, respectively. Moreover, the least degree of relative errors and the most degree of truth were found in sinc-convolution reconstructions from experimental phantom data. Reconstructions of clinical lung data show that the related physiological effect is well recovered by sinc-convolution algorithm. Conclusions Parametric evaluation demonstrates the efficiency of sinc-convolution to reconstruct accurate conductivity images from experimental data. Excellent results in phantom and clinical reconstructions using sinc-convolution

  17. About closedness by convolution of the Tsallis maximizers

    NASA Astrophysics Data System (ADS)

    Vignat, C.; Hero, A. O., III; Costa, J. A.

    2004-09-01

    In this paper, we study the stability under convolution of the maximizing distributions of the Tsallis entropy under energy constraint (called hereafter Tsallis distributions). These distributions are shown to obey three important properties: a stochastic representation property, an orthogonal invariance property and a duality property. As a consequence of these properties, the behavior of Tsallis distributions under convolution is characterized. At last, a special random convolution, called Kingman convolution, is shown to ensure the stability of Tsallis distributions.

  18. Multiple deep convolutional neural networks averaging for face alignment

    NASA Astrophysics Data System (ADS)

    Zhang, Shaohua; Yang, Hua; Yin, Zhouping

    2015-05-01

    Face alignment is critical for face recognition, and the deep learning-based method shows promise for solving such issues, given that competitive results are achieved on benchmarks with additional benefits, such as dispensing with handcrafted features and initial shape. However, most existing deep learning-based approaches are complicated and quite time-consuming during training. We propose a compact face alignment method for fast training without decreasing its accuracy. Rectified linear unit is employed, which allows all networks approximately five times faster convergence than a tanh neuron. An eight learnable layer deep convolutional neural network (DCNN) based on local response normalization and a padding convolutional layer (PCL) is designed to provide reliable initial values during prediction. A model combination scheme is presented to further reduce errors, while showing that only two network architectures and hyperparameter selection procedures are required in our approach. A three-level cascaded system is ultimately built based on the DCNNs and model combination mode. Extensive experiments validate the effectiveness of our method and demonstrate comparable accuracy with state-of-the-art methods on BioID, labeled face parts in the wild, and Helen datasets.

  19. Fabrication of a three-layer SU-8 mould with inverted T-shaped cavities based on a sacrificial photoresist layer technique.

    PubMed

    Liu, Junshan; Zhang, Dong; Sha, Baoyong; Yin, Penghe; Xu, Zheng; Liu, Chong; Wang, Liding; Xu, Feng; Wang, Lin

    2014-10-01

    A novel method for fabricating a three-layer SU-8 mould with inverted T-shaped cavities is presented. The first two SU-8 layers were spin coated and exposed separately, and simultaneously developed to fabricate the bottom and the horizontal part of the inverted T-shaped cavity. Then, a positive photoresist was filled into the cavity, and a wet lapping process was performed to remove the excess photoresist and make a temporary substrate. The third SU-8 layer was spin coated on the temporary substrate to make the vertical part of the inverted T-shaped cavity. The sacrificial photoresist layer can prevent the first two SU-8 layers from being secondly exposed, and make a temporary substrate for the third SU-8 layer at the same time. Moreover, the photoresist can be easily removed with the development of the third SU-8 layer. A polydimethylsiloxane (PDMS) microchip with arrays of T-shaped cantilevers for studying the mechanics of cells was fabricated by using the SU-8 mould. PMID:24850230

  20. Design and fabrication of 3D-printed anatomically shaped lumbar cage for intervertebral disc (IVD) degeneration treatment.

    PubMed

    Serra, T; Capelli, C; Toumpaniari, R; Orriss, I R; Leong, J J H; Dalgarno, K; Kalaskar, D M

    2016-01-01

    Spinal fusion is the gold standard surgical procedure for degenerative spinal conditions when conservative therapies have been unsuccessful in rehabilitation of patients. Novel strategies are required to improve biocompatibility and osseointegration of traditionally used materials for lumbar cages. Furthermore, new design and technologies are needed to bridge the gap due to the shortage of optimal implant sizes to fill the intervertebral disc defect. Within this context, additive manufacturing technology presents an excellent opportunity to fabricate ergonomic shape medical implants. The goal of this study is to design and manufacture a 3D-printed lumbar cage for lumbar interbody fusion. Optimisations of the proposed implant design and its printing parameters were achieved via in silico analysis. The final construct was characterised via scanning electron microscopy, contact angle, x-ray micro computed tomography (μCT), atomic force microscopy, and compressive test. Preliminary in vitro cell culture tests such as morphological assessment and metabolic activities were performed to access biocompatibility of 3D-printed constructs. Results of in silico analysis provided a useful platform to test preliminary cage design and to find an optimal value of filling density for 3D printing process. Surface characterisation confirmed a uniform coating of nHAp with nanoscale topography. Mechanical evaluation showed mechanical properties of final cage design similar to that of trabecular bone. Preliminary cell culture results showed promising results in terms of cell growth and activity confirming biocompatibility of constructs. Thus for the first time, design optimisation based on computational and experimental analysis combined with the 3D-printing technique for intervertebral fusion cage has been reported in a single study. 3D-printing is a promising technique for medical applications and this study paves the way for future development of customised implants in spinal

  1. Fabrication of transparent, tough, and conductive shape-memory polyurethane films by incorporating a small amount of high-quality graphene.

    PubMed

    Jung, Yong Chae; Kim, Jin Hee; Hayashi, Takuya; Kim, Yoong Ahm; Endo, Morinobu; Terrones, Mauricio; Dresselhaus, Mildred S

    2012-04-23

    We report a mechanically strong, electrically and thermally conductive, and optically transparent shape-memory polyurethane composite which was fabricated by introducing a small amount (0.1 wt%) of high-quality graphene as a filler. Geometrically large (≈4.6 μm(2)), but highly crystallized few-layer graphenes, verified by Raman spectroscopy and transmission electron microscopy, were prepared by the sonication of expandable graphite in an organic solvent. Oxygen- containing functional groups at the edge plane of graphene were crucial for an effective stress transfer from the graphene to polyurethane. Homogeneously dispersed few-layered graphene enabled polyurethane to have a high shape recovery force of 1.8 MPa cm(-3). Graphene, which is intrinsically stretchable up to 10%, will enable high-performance composites to be fabricated at relatively low cost and we thus envisage that such composites may replace carbon nanotubes for various applications in the near future. PMID:22328293

  2. Dip TIPS as a Facile and Versatile Method for Fabrication of Polymer Foams with Controlled Shape, Size and Pore Architecture for Bioengineering Applications

    PubMed Central

    Kasoju, Naresh; Kubies, Dana; Kumorek, Marta M.; Kříž, Jan; Fábryová, Eva; Machová, Lud'ka; Kovářová, Jana; Rypáček, František

    2014-01-01

    The porous polymer foams act as a template for neotissuegenesis in tissue engineering, and, as a reservoir for cell transplants such as pancreatic islets while simultaneously providing a functional interface with the host body. The fabrication of foams with the controlled shape, size and pore structure is of prime importance in various bioengineering applications. To this end, here we demonstrate a thermally induced phase separation (TIPS) based facile process for the fabrication of polymer foams with a controlled architecture. The setup comprises of a metallic template bar (T), a metallic conducting block (C) and a non-metallic reservoir tube (R), connected in sequence T-C-R. The process hereinafter termed as Dip TIPS, involves the dipping of the T-bar into a polymer solution, followed by filling of the R-tube with a freezing mixture to induce the phase separation of a polymer solution in the immediate vicinity of T-bar; Subsequent free-drying or freeze-extraction steps produced the polymer foams. An easy exchange of the T-bar of a spherical or rectangular shape allowed the fabrication of tubular, open- capsular and flat-sheet shaped foams. A mere change in the quenching time produced the foams with a thickness ranging from hundreds of microns to several millimeters. And, the pore size was conveniently controlled by varying either the polymer concentration or the quenching temperature. Subsequent in vivo studies in brown Norway rats for 4-weeks demonstrated the guided cell infiltration and homogenous cell distribution through the polymer matrix, without any fibrous capsule and necrotic core. In conclusion, the results show the “Dip TIPS” as a facile and adaptable process for the fabrication of anisotropic channeled porous polymer foams of various shapes and sizes for potential applications in tissue engineering, cell transplantation and other related fields. PMID:25275373

  3. Fabrication and characterization of a foamed polylactic acid (PLA)/ thermoplastic polyurethane (TPU) shape memory polymer (SMP) blend for biomedical and clinical applications

    NASA Astrophysics Data System (ADS)

    Song, Janice J.; Srivastava, Ijya; Kowalski, Jennifer; Naguib, Hani E.

    2014-03-01

    Shape memory polymers (SMP) are a class of stimuli-responsive materials that are able to respond to external stimulus such as heat by altering their shape. Bio-compatible SMPs have a number of advantages over static materials and are being studied extensively for biomedical and clinical applications (such as tissue stents and scaffolds). A previous study has demonstrated that the bio-compatible polymer blend of polylactic acid (PLA)/ thermoplastic polyurethane (TPU) (50/50 and 70/30) exhibit good shape memory properties. In this study, the mechanical and thermo-mechanical (shape memory) properties of TPU/PLA SMP blends were characterized; the compositions studied were 80/20, 65/35, and 50/50 TPU/PLA. In addition, porous TPU/PLA SMP blends were fabricated with a gas-foaming technique; and the morphology of the porous structure of these SMPs foams were characterized with scanning electron microscopy (SEM). The TPU/PLA bio-compatible SMP blend was fabricated with melt-blending and compression molding. The glass transition temperature (Tg) of the SMP blends was determined with a differential scanning calorimeter (DSC). The mechanical properties studied were the stress-strain behavior, tensile strength, and elastic modulus; and the thermomechanical (or shape memory) properties studied were the shape fixity rate (Rf), shape recovery rate (Rr), response time, and the effect of recovery temperature on Rr. The porous 80/20 PLA/TPU SMP blend was found to have the highest tensile strength, toughness and percentage extension, as well as the lowest density and uniform pore structure in the micron and submicron scale. The porous 80/20 TPU/PLA SMP blend may be further developed for specific biomedical and clinical applications where a combination of tensile strength, toughness, and low density are required.

  4. Deep Learning with Hierarchical Convolutional Factor Analysis

    PubMed Central

    Chen, Bo; Polatkan, Gungor; Sapiro, Guillermo; Blei, David; Dunson, David; Carin, Lawrence

    2013-01-01

    Unsupervised multi-layered (“deep”) models are considered for general data, with a particular focus on imagery. The model is represented using a hierarchical convolutional factor-analysis construction, with sparse factor loadings and scores. The computation of layer-dependent model parameters is implemented within a Bayesian setting, employing a Gibbs sampler and variational Bayesian (VB) analysis, that explicitly exploit the convolutional nature of the expansion. In order to address large-scale and streaming data, an online version of VB is also developed. The number of basis functions or dictionary elements at each layer is inferred from the data, based on a beta-Bernoulli implementation of the Indian buffet process. Example results are presented for several image-processing applications, with comparisons to related models in the literature. PMID:23787342

  5. A convolutional neural network neutrino event classifier

    DOE PAGESBeta

    Aurisano, A.; Radovic, A.; Rocco, D.; Himmel, A.; Messier, M. D.; Niner, E.; Pawloski, G.; Psihas, F.; Sousa, A.; Vahle, P.

    2016-09-01

    Here, convolutional neural networks (CNNs) have been widely applied in the computer vision community to solve complex problems in image recognition and analysis. We describe an application of the CNN technology to the problem of identifying particle interactions in sampling calorimeters used commonly in high energy physics and high energy neutrino physics in particular. Following a discussion of the core concepts of CNNs and recent innovations in CNN architectures related to the field of deep learning, we outline a specific application to the NOvA neutrino detector. This algorithm, CVN (Convolutional Visual Network) identifies neutrino interactions based on their topology withoutmore » the need for detailed reconstruction and outperforms algorithms currently in use by the NOvA collaboration.« less

  6. Quantum convolutional codes derived from constacyclic codes

    NASA Astrophysics Data System (ADS)

    Yan, Tingsu; Huang, Xinmei; Tang, Yuansheng

    2014-12-01

    In this paper, three families of quantum convolutional codes are constructed. The first one and the second one can be regarded as a generalization of Theorems 3, 4, 7 and 8 [J. Chen, J. Li, F. Yang and Y. Huang, Int. J. Theor. Phys., doi:10.1007/s10773-014-2214-6 (2014)], in the sense that we drop the constraint q ≡ 1 (mod 4). Furthermore, the second one and the third one attain the quantum generalized Singleton bound.

  7. Satellite image classification using convolutional learning

    NASA Astrophysics Data System (ADS)

    Nguyen, Thao; Han, Jiho; Park, Dong-Chul

    2013-10-01

    A satellite image classification method using Convolutional Neural Network (CNN) architecture is proposed in this paper. As a special case of deep learning, CNN classifies classes of images without any feature extraction step while other existing classification methods utilize rather complex feature extraction processes. Experiments on a set of satellite image data and the preliminary results show that the proposed classification method can be a promising alternative over existing feature extraction-based schemes in terms of classification accuracy and classification speed.

  8. Spatio-spectral concentration of convolutions

    NASA Astrophysics Data System (ADS)

    Hanasoge, Shravan M.

    2016-05-01

    Differential equations may possess coefficients that vary on a spectrum of scales. Because coefficients are typically multiplicative in real space, they turn into convolution operators in spectral space, mixing all wavenumbers. However, in many applications, only the largest scales of the solution are of interest and so the question turns to whether it is possible to build effective coarse-scale models of the coefficients in such a manner that the large scales of the solution are left intact. Here we apply the method of numerical homogenisation to deterministic linear equations to generate sub-grid-scale models of coefficients at desired frequency cutoffs. We use the Fourier basis to project, filter and compute correctors for the coefficients. The method is tested in 1D and 2D scenarios and found to reproduce the coarse scales of the solution to varying degrees of accuracy depending on the cutoff. We relate this method to mode-elimination Renormalisation Group (RG) and discuss the connection between accuracy and the cutoff wavenumber. The tradeoff is governed by a form of the uncertainty principle for convolutions, which states that as the convolution operator is squeezed in the spectral domain, it broadens in real space. As a consequence, basis sparsity is a high virtue and the choice of the basis can be critical.

  9. Convolutional Neural Network Based dem Super Resolution

    NASA Astrophysics Data System (ADS)

    Chen, Zixuan; Wang, Xuewen; Xu, Zekai; Hou, Wenguang

    2016-06-01

    DEM super resolution is proposed in our previous publication to improve the resolution for a DEM on basis of some learning examples. Meanwhile, the nonlocal algorithm is introduced to deal with it and lots of experiments show that the strategy is feasible. In our publication, the learning examples are defined as the partial original DEM and their related high measurements due to this way can avoid the incompatibility between the data to be processed and the learning examples. To further extent the applications of this new strategy, the learning examples should be diverse and easy to obtain. Yet, it may cause the problem of incompatibility and unrobustness. To overcome it, we intend to investigate a convolutional neural network based method. The input of the convolutional neural network is a low resolution DEM and the output is expected to be its high resolution one. A three layers model will be adopted. The first layer is used to detect some features from the input, the second integrates the detected features to some compressed ones and the final step transforms the compressed features as a new DEM. According to this designed structure, some learning DEMs will be taken to train it. Specifically, the designed network will be optimized by minimizing the error of the output and its expected high resolution DEM. In practical applications, a testing DEM will be input to the convolutional neural network and a super resolution will be obtained. Many experiments show that the CNN based method can obtain better reconstructions than many classic interpolation methods.

  10. Blind Identification of Convolutional Encoder Parameters

    PubMed Central

    Su, Shaojing; Zhou, Jing; Huang, Zhiping; Liu, Chunwu; Zhang, Yimeng

    2014-01-01

    This paper gives a solution to the blind parameter identification of a convolutional encoder. The problem can be addressed in the context of the noncooperative communications or adaptive coding and modulations (ACM) for cognitive radio networks. We consider an intelligent communication receiver which can blindly recognize the coding parameters of the received data stream. The only knowledge is that the stream is encoded using binary convolutional codes, while the coding parameters are unknown. Some previous literatures have significant contributions for the recognition of convolutional encoder parameters in hard-decision situations. However, soft-decision systems are applied more and more as the improvement of signal processing techniques. In this paper we propose a method to utilize the soft information to improve the recognition performances in soft-decision communication systems. Besides, we propose a new recognition method based on correlation attack to meet low signal-to-noise ratio situations. Finally we give the simulation results to show the efficiency of the proposed methods. PMID:24982997

  11. Recent Advances in Near-Net-Shape Fabrication of Al-Li Alloy 2195 for Launch Vehicles

    NASA Technical Reports Server (NTRS)

    Wagner, John; Domack, Marcia; Hoffman, Eric

    2007-01-01

    Recent applications in launch vehicles use 2195 processed to Super Lightweight Tank specifications. Potential benefits exist by tailoring heat treatment and other processing parameters to the application. Assess the potential benefits and advocate application of Al-Li near-net-shape technologies for other launch vehicle structural components. Work with manufacturing and material producers to optimize Al-Li ingot shape and size for enhanced near-net-shape processing. Examine time dependent properties of 2195 critical for reusable applications.

  12. Differences in the thickness of mouthguards fabricated from ethylene vinyl acetate copolymer sheets with differently arranged v-shaped grooves: part 2 - effect of shape on the working model.

    PubMed

    Takahashi, Mutsumi; Koide, Kaoru; Mizuhashi, Fumi

    2014-12-01

    The aim of this study was to evaluate the change in thickness of a working model mouthguard sheet due to different shape. Mouthguards were fabricated with ethylene vinyl acetate (EVA) sheets (4.0 mm thick) using a vacuum-forming machine. Two shapes of the sheet were compared: normal sheet or v-shaped groove 10-40 mm from the anterior end. Additionally, two shapes of the working model were compared; the basal plane was vertical to the tooth axis of the maxillary central incisor (condition A), and the occlusal plane was parallel to the basal plane (condition B). Sheets were heated until they sagged 15 mm below the clamp. Postmolding thickness was determined for the incisal portion (incisal edge and labial surface) and molar portion (cusp and buccal surface). Differences in the change in thickness due to the shape of the sheets and model were analyzed using two-way anova followed by a Bonferroni's multiple comparison tests. The thickness of the mouthguard sheet with v-shaped grooves was more than that of the normal sheet at all measuring points under condition A and condition B (P < 0.01). The thickness of condition B was less than that of condition A, there the incisal portion in the normal sheet and the incisal edge in the sheet with v-shaped grooves (P < 0.01). The present results suggested that thickness after molding was secured by the use of the sheet with v-shaped grooves. In particular, the model with the undercut on the labial surface may be clinically useful. PMID:25039583

  13. Fabrication of ordered arrays of micro- and nanoscale features with control over their shape and size via templated solid-state dewetting

    PubMed Central

    Ye, Jongpil

    2015-01-01

    Templated solid-state dewetting of single-crystal films has been shown to be used to produce regular patterns of various shapes. However, the materials for which this patterning method is applicable, and the size range of the patterns produced are still limited. Here, it is shown that ordered arrays of micro- and nanoscale features can be produced with control over their shape and size via solid-state dewetting of patches patterned from single-crystal palladium and nickel films of different thicknesses and orientations. The shape and size characteristics of the patterns are found to be widely controllable with varying the shape, width, thickness, and orientation of the initial patches. The morphological evolution of the patches is also dependent on the film material, with different dewetting behaviors observed in palladium and nickel films. The mechanisms underlying the pattern formation are explained in terms of the influence on Rayleigh-like instability of the patch geometry and the surface energy anisotropy of the film material. This mechanistic understanding of pattern formation can be used to design patches for the precise fabrication of micro- and nanoscale structures with the desired shapes and feature sizes. PMID:25951816

  14. The analysis of convolutional codes via the extended Smith algorithm

    NASA Technical Reports Server (NTRS)

    Mceliece, R. J.; Onyszchuk, I.

    1993-01-01

    Convolutional codes have been the central part of most error-control systems in deep-space communication for many years. Almost all such applications, however, have used the restricted class of (n,1), also known as 'rate 1/n,' convolutional codes. The more general class of (n,k) convolutional codes contains many potentially useful codes, but their algebraic theory is difficult and has proved to be a stumbling block in the evolution of convolutional coding systems. In this article, the situation is improved by describing a set of practical algorithms for computing certain basic things about a convolutional code (among them the degree, the Forney indices, a minimal generator matrix, and a parity-check matrix), which are usually needed before a system using the code can be built. The approach is based on the classic Forney theory for convolutional codes, together with the extended Smith algorithm for polynomial matrices, which is introduced in this article.

  15. QCDNUM: Fast QCD evolution and convolution

    NASA Astrophysics Data System (ADS)

    Botje, M.

    2011-02-01

    The QCDNUM program numerically solves the evolution equations for parton densities and fragmentation functions in perturbative QCD. Un-polarised parton densities can be evolved up to next-to-next-to-leading order in powers of the strong coupling constant, while polarised densities or fragmentation functions can be evolved up to next-to-leading order. Other types of evolution can be accessed by feeding alternative sets of evolution kernels into the program. A versatile convolution engine provides tools to compute parton luminosities, cross-sections in hadron-hadron scattering, and deep inelastic structure functions in the zero-mass scheme or in generalised mass schemes. Input to these calculations are either the QCDNUM evolved densities, or those read in from an external parton density repository. Included in the software distribution are packages to calculate zero-mass structure functions in un-polarised deep inelastic scattering, and heavy flavour contributions to these structure functions in the fixed flavour number scheme. Program summaryProgram title: QCDNUM version: 17.00 Catalogue identifier: AEHV_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEHV_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: GNU Public Licence No. of lines in distributed program, including test data, etc.: 45 736 No. of bytes in distributed program, including test data, etc.: 911 569 Distribution format: tar.gz Programming language: Fortran-77 Computer: All Operating system: All RAM: Typically 3 Mbytes Classification: 11.5 Nature of problem: Evolution of the strong coupling constant and parton densities, up to next-to-next-to-leading order in perturbative QCD. Computation of observable quantities by Mellin convolution of the evolved densities with partonic cross-sections. Solution method: Parametrisation of the parton densities as linear or quadratic splines on a discrete grid, and evolution of the spline

  16. Convolutional coding combined with continuous phase modulation

    NASA Technical Reports Server (NTRS)

    Pizzi, S. V.; Wilson, S. G.

    1985-01-01

    Background theory and specific coding designs for combined coding/modulation schemes utilizing convolutional codes and continuous-phase modulation (CPM) are presented. In this paper the case of r = 1/2 coding onto a 4-ary CPM is emphasized, with short-constraint length codes presented for continuous-phase FSK, double-raised-cosine, and triple-raised-cosine modulation. Coding buys several decibels of coding gain over the Gaussian channel, with an attendant increase of bandwidth. Performance comparisons in the power-bandwidth tradeoff with other approaches are made.

  17. Convolution neural networks for ship type recognition

    NASA Astrophysics Data System (ADS)

    Rainey, Katie; Reeder, John D.; Corelli, Alexander G.

    2016-05-01

    Algorithms to automatically recognize ship type from satellite imagery are desired for numerous maritime applications. This task is difficult, and example imagery accurately labeled with ship type is hard to obtain. Convolutional neural networks (CNNs) have shown promise in image recognition settings, but many of these applications rely on the availability of thousands of example images for training. This work attempts to under- stand for which types of ship recognition tasks CNNs might be well suited. We report the results of baseline experiments applying a CNN to several ship type classification tasks, and discuss many of the considerations that must be made in approaching this problem.

  18. Geometric multi-resolution analysis and data-driven convolutions

    NASA Astrophysics Data System (ADS)

    Strawn, Nate

    2015-09-01

    We introduce a procedure for learning discrete convolutional operators for generic datasets which recovers the standard block convolutional operators when applied to sets of natural images. They key observation is that the standard block convolutional operators on images are intuitive because humans naturally understand the grid structure of the self-evident functions over images spaces (pixels). This procedure first constructs a Geometric Multi-Resolution Analysis (GMRA) on the set of variables giving rise to a dataset, and then leverages the details of this data structure to identify subsets of variables upon which convolutional operators are supported, as well as a space of functions that can be shared coherently amongst these supports.

  19. Convolutional fountain distribution over fading wireless channels

    NASA Astrophysics Data System (ADS)

    Usman, Mohammed

    2012-08-01

    Mobile broadband has opened the possibility of a rich variety of services to end users. Broadcast/multicast of multimedia data is one such service which can be used to deliver multimedia to multiple users economically. However, the radio channel poses serious challenges due to its time-varying properties, resulting in each user experiencing different channel characteristics, independent of other users. Conventional methods of achieving reliability in communication, such as automatic repeat request and forward error correction do not scale well in a broadcast/multicast scenario over radio channels. Fountain codes, being rateless and information additive, overcome these problems. Although the design of fountain codes makes it possible to generate an infinite sequence of encoded symbols, the erroneous nature of radio channels mandates the need for protecting the fountain-encoded symbols, so that the transmission is feasible. In this article, the performance of fountain codes in combination with convolutional codes, when used over radio channels, is presented. An investigation of various parameters, such as goodput, delay and buffer size requirements, pertaining to the performance of fountain codes in a multimedia broadcast/multicast environment is presented. Finally, a strategy for the use of 'convolutional fountain' over radio channels is also presented.

  20. Convolution Inequalities for the Boltzmann Collision Operator

    NASA Astrophysics Data System (ADS)

    Alonso, Ricardo J.; Carneiro, Emanuel; Gamba, Irene M.

    2010-09-01

    We study integrability properties of a general version of the Boltzmann collision operator for hard and soft potentials in n-dimensions. A reformulation of the collisional integrals allows us to write the weak form of the collision operator as a weighted convolution, where the weight is given by an operator invariant under rotations. Using a symmetrization technique in L p we prove a Young’s inequality for hard potentials, which is sharp for Maxwell molecules in the L 2 case. Further, we find a new Hardy-Littlewood-Sobolev type of inequality for Boltzmann collision integrals with soft potentials. The same method extends to radially symmetric, non-increasing potentials that lie in some {Ls_{weak}} or L s . The method we use resembles a Brascamp, Lieb and Luttinger approach for multilinear weighted convolution inequalities and follows a weak formulation setting. Consequently, it is closely connected to the classical analysis of Young and Hardy-Littlewood-Sobolev inequalities. In all cases, the inequality constants are explicitly given by formulas depending on integrability conditions of the angular cross section (in the spirit of Grad cut-off). As an additional application of the technique we also obtain estimates with exponential weights for hard potentials in both conservative and dissipative interactions.

  1. Convolution formulations for non-negative intensity.

    PubMed

    Williams, Earl G

    2013-08-01

    Previously unknown spatial convolution formulas for a variant of the active normal intensity in planar coordinates have been derived that use measured pressure or normal velocity near-field holograms to construct a positive-only (outward) intensity distribution in the plane, quantifying the areas of the vibrating structure that produce radiation to the far-field. This is an extension of the outgoing-only (unipolar) intensity technique recently developed for arbitrary geometries by Steffen Marburg. The method is applied independently to pressure and velocity data measured in a plane close to the surface of a point-driven, unbaffled rectangular plate in the laboratory. It is demonstrated that the sound producing regions of the structure are clearly revealed using the derived formulas and that the spatial resolution is limited to a half-wavelength. A second set of formulas called the hybrid-intensity formulas are also derived which yield a bipolar intensity using a different spatial convolution operator, again using either the measured pressure or velocity. It is demonstrated from the experiment results that the velocity formula yields the classical active intensity and the pressure formula an interesting hybrid intensity that may be useful for source localization. Computations are fast and carried out in real space without Fourier transforms into wavenumber space. PMID:23927105

  2. Quasi-In vivo Heart Electrocardiogram Measurement of ST Period Using Convolution of Cell Network Extracellular Field Potential Propagation in Lined-Up Cardiomyocyte Cell-Network Circuit

    NASA Astrophysics Data System (ADS)

    Kaneko, Tomoyuki; Nomura, Fumimasa; Yasuda, Kenji

    2011-07-01

    A model for the quasi-in vivo heart electrocardiogram (ECG) measurement of the ST period has been developed. As the part of ECG data at the ST period is the convolution of the extracellular field potentials (FPs) of cardiomyocytes in a ventricle, we have fabricated a lined-up cardiomyocyte cell-network on a lined-up microelectrode array and a circular microelectrode in an agarose microchamber, and measured the convoluted FPs. When the ventricular tachyarrhythmias of beating occurred in the cardiomyocyte network, the convoluted FP profile showed similar arrhythmia ECG-like profiles, indicating the convoluted FPs of the in vitro cell network include both the depolarization data and the propagation manner of beating in the heart.

  3. Cell differentiation on disk- and string-shaped hydrogels fabricated from Ca(2+) -responsive self-assembling peptides.

    PubMed

    Fukunaga, Kazuto; Tsutsumi, Hiroshi; Mihara, Hisakazu

    2016-11-01

    We recently developed a self-assembling peptide, E1Y9, that self-assembles into nanofibers and forms a hydrogel in the presence of Ca(2+) . E1Y9 derivatives conjugated with functional peptide sequences derived from extracellular matrices (ECMs) reportedly self-assemble into peptide nanofibers that enhance cell adhesion and differentiation. In this study, E1Y9/E1Y9-IKVAV-mixed hydrogels were constructed to serve as artificial ECMs that promote cell differentiation. E1Y9 and E1Y9-IKVAV co-assembled into networked nanofibers, and hydrogels with disk and string shapes were formed in response to Ca(2+) treatment. The neuronal differentiation of PC12 cells was facilitated on hydrogels of both shapes that contained the IKVAV motifs. Moreover, long neurites extended along the long axis of the string-shaped gel, suggesting that the structure of hydrogels of this shape can affect cellular orientation. Thus, E1Y9 hydrogels can potentially be used as artificial ECMs with desirable bioactivities and shapes that could be useful in tissue engineering applications. © 2015 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 106: 476-483, 2016. PMID:26501895

  4. A dual-directional light-control film with a high-sag and high-asymmetrical-shape microlens array fabricated by a UV imprinting process

    NASA Astrophysics Data System (ADS)

    Lin, Ta-Wei; Chen, Chi-Feng; Yang, Jauh-Jung; Liao, Yunn-Shiuan

    2008-09-01

    A dual-directional light-control film with a high-sag and high-asymmetric-shape long gapless hexagonal microlens array fabricated by an ultra-violent (UV) imprinting process is presented. Such a lens array is designed by ray-tracing simulation and fabricated by a micro-replication process including gray-scale lithography, electroplating process and UV curing. The shape of the designed lens array is similar to that of a near half-cylindrical lens array with a periodical ripple. The measurement results of a prototype show that the incident lights using a collimated LED with the FWHM of dispersion angle, 12°, are diversified differently in short and long axes. The numerical and experimental results show that the FWHMs of the view angle for angular brightness in long and short axis directions through the long hexagonal lens are about 34.3° and 18.1° and 31° and 13°, respectively. Compared with the simulation result, the errors in long and short axes are about 5% and 16%, respectively. Obviously, the asymmetric gapless microlens array can realize the aim of the controlled asymmetric angular brightness. Such a light-control film can be used as a power saving screen compared with convention diffusing film for the application of a rear projection display.

  5. SU-E-T-08: A Convolution Model for Head Scatter Fluence in the Intensity Modulated Field

    SciTech Connect

    Chen, M; Mo, X; Chen, Y; Parnell, D; Key, S; Olivera, G; Galmarini, W; Lu, W

    2014-06-01

    Purpose: To efficiently calculate the head scatter fluence for an arbitrary intensity-modulated field with any source distribution using the source occlusion model. Method: The source occlusion model with focal and extra focal radiation (Jaffray et al, 1993) can be used to account for LINAC head scatter. In the model, the fluence map of any field shape at any point can be calculated via integration of the source distribution within the visible range, as confined by each segment, using the detector eye's view. A 2D integration would be required for each segment and each fluence plane point, which is time-consuming, as an intensity-modulated field contains typically tens to hundreds of segments. In this work, we prove that the superposition of the segmental integrations is equivalent to a simple convolution regardless of what the source distribution is. In fact, for each point, the detector eye's view of the field shape can be represented as a function with the origin defined at the point's pinhole reflection through the center of the collimator plane. We were thus able to reduce hundreds of source plane integration to one convolution. We calculated the fluence map for various 3D and IMRT beams and various extra-focal source distributions using both the segmental integration approach and the convolution approach and compared the computation time and fluence map results of both approaches. Results: The fluence maps calculated using the convolution approach were the same as those calculated using the segmental approach, except for rounding errors (<0.1%). While it took considerably longer time to calculate all segmental integrations, the fluence map calculation using the convolution approach took only ∼1/3 of the time for typical IMRT fields with ∼100 segments. Conclusions: The convolution approach for head scatter fluence calculation is fast and accurate and can be used to enhance the online process.

  6. Image statistics decoding for convolutional codes

    NASA Technical Reports Server (NTRS)

    Pitt, G. H., III; Swanson, L.; Yuen, J. H.

    1987-01-01

    It is a fact that adjacent pixels in a Voyager image are very similar in grey level. This fact can be used in conjunction with the Maximum-Likelihood Convolutional Decoder (MCD) to decrease the error rate when decoding a picture from Voyager. Implementing this idea would require no changes in the Voyager spacecraft and could be used as a backup to the current system without too much expenditure, so the feasibility of it and the possible gains for Voyager were investigated. Simulations have shown that the gain could be as much as 2 dB at certain error rates, and experiments with real data inspired new ideas on ways to get the most information possible out of the received symbol stream.

  7. Some partial-unit-memory convolutional codes

    NASA Technical Reports Server (NTRS)

    Abdel-Ghaffar, K.; Mceliece, R. J.; Solomon, G.

    1991-01-01

    The results of a study on a class of error correcting codes called partial unit memory (PUM) codes are presented. This class of codes, though not entirely new, has until now remained relatively unexplored. The possibility of using the well developed theory of block codes to construct a large family of promising PUM codes is shown. The performance of several specific PUM codes are compared with that of the Voyager standard (2, 1, 6) convolutional code. It was found that these codes can outperform the Voyager code with little or no increase in decoder complexity. This suggests that there may very well be PUM codes that can be used for deep space telemetry that offer both increased performance and decreased implementational complexity over current coding systems.

  8. Bacterial colony counting by Convolutional Neural Networks.

    PubMed

    Ferrari, Alessandro; Lombardi, Stefano; Signoroni, Alberto

    2015-08-01

    Counting bacterial colonies on microbiological culture plates is a time-consuming, error-prone, nevertheless fundamental task in microbiology. Computer vision based approaches can increase the efficiency and the reliability of the process, but accurate counting is challenging, due to the high degree of variability of agglomerated colonies. In this paper, we propose a solution which adopts Convolutional Neural Networks (CNN) for counting the number of colonies contained in confluent agglomerates, that scored an overall accuracy of the 92.8% on a large challenging dataset. The proposed CNN-based technique for estimating the cardinality of colony aggregates outperforms traditional image processing approaches, becoming a promising approach to many related applications. PMID:26738016

  9. Effect of the surface texturing shapes fabricated using dry etching on the extraction efficiency of vertical light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Lee, H. C.; Park, J. B.; Bae, J. W.; Thuy, Pham Thi Thu; Yoo, M. C.; Yeom, G. Y.

    2008-08-01

    On the surfaces of GaN-based light-emitting diodes (LEDs) having an n-side-up vertical electrode structure formed by the laser lift-off, various shapes of photoresist-patterned surface textures were formed by inductively coupled plasma etching and their effect on the light emission efficiencies was investigated. By the formation of various shapes of surface textures, the light output efficiency was increased from 37% to 45% compared to that without surface textures. The increase of light output efficiency was related to the increase of sidewall scattering, the decrease of reflected loss, and the decrease of cavity wall effect that occurs for the vertical LEDs by the increase of sidewall surface area.

  10. Hydrothermal fabrication of octahedral-shaped Fe{sub 3}O{sub 4} nanoparticles and their magnetorheological response

    SciTech Connect

    Jung, H. S.; Choi, H. J.

    2015-05-07

    Octahedral-shaped Fe{sub 3}O{sub 4} nanoparticles were synthesized in the presence of 1,3-diaminopropane using a hydrothermal method and assessed as a potential magnetorheological (MR) material. Their morphology, crystal structure, and magnetic properties were examined by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and vibrating sample magnetometry, respectively. The MR characteristics of the octahedral-shaped, Fe{sub 3}O{sub 4} nanoparticle-based MR particles when dispersed in silicone oil with a 10 vol. % particle concentration were examined using a rotational rheometer under an external magnetic field. The resulting MR fluids exhibited a Bingham-like behavior with a distinctive yield stress from their flow curves.

  11. Examination of anticipated chemical shift and shape distortion effect on materials commonly used in prosthetic socket fabrication when measured using MRI: a validation study.

    PubMed

    Safari, Mohammad Reza; Rowe, Philip; Buis, Arjan

    2013-01-01

    The quality of lower-limb prosthetic socket fit is influenced by shape and volume consistency during the residual limb shape-capturing process (i.e., casting). Casting can be quantified with magnetic resonance imaging (MRI) technology. However, chemical shift artifact and image distortion may influence the accuracy of MRI when common socket/casting materials are used. We used a purpose-designed rig to examine seven different materials commonly used in socket fabrication during exposure to MRI. The rig incorporated glass marker tubes filled with water doped with 1 g/L copper sulfate (CS) and 9 plastic sample vials (film containers) to hold the specific material specimens. The specimens were scanned 9 times in different configurations. The absolute mean difference of the glass marker tube length was 1.39 mm (2.98%) (minimum = 0.13 mm [0.30%], maximum = 5.47 mm [14.03%], standard deviation = 0.89 mm). The absolute shift for all materials was <1.7 mm. This was less than the measurement tolerance of +/-2.18 mm based on voxel (three-dimensional pixel) dimensions. The results show that MRI is an accurate and repeatable method for dimensional measurement when using matter containing water. Additionally, silicone and plaster of paris plus 1 g/L CS do not show a significant shape distortion nor do they interfere with the MRI image of the residual limb. PMID:23516081

  12. Fabrication of MEMS-based Micro-fluxgate Sensor with Runway-shaped Co-based Amorphous Alloy Core

    NASA Astrophysics Data System (ADS)

    Wu, Shaobin; Chen, Shi; Ouyang, Jun; Zuo, Chao; Yu, Lei; Yang, Xiaofei

    2011-01-01

    High-precision magnetic micro-sensor is an interdisciplinary subject of magnetic field measurement techniques and micro-electromechanical systems (MEMS) technology. A micro-fluxgate magnetic sensor based MEMS technology was designed and fabricated in this paper. This device is a micro-magnetic sensor with a symmetric construction, closed magnetic circuits and differential form. A 25μm thick Fluxgate core of runway model, made by Co-based amorphous alloy, was etched by laser and pasted on the substrate accurately. Excitation coil and sensing coil of 3D solenoid structure were prepared by RF magnetron sputtering and UV-lithography. The minimum line width of the coil is 50 μm. The experimental result shows that micro-fluxgate devices with the size of 5.7mm×7.1mm×60μm had a stable structure.

  13. Multi-modal vertebrae recognition using Transformed Deep Convolution Network.

    PubMed

    Cai, Yunliang; Landis, Mark; Laidley, David T; Kornecki, Anat; Lum, Andrea; Li, Shuo

    2016-07-01

    Automatic vertebra recognition, including the identification of vertebra locations and naming in multiple image modalities, are highly demanded in spinal clinical diagnoses where large amount of imaging data from various of modalities are frequently and interchangeably used. However, the recognition is challenging due to the variations of MR/CT appearances or shape/pose of the vertebrae. In this paper, we propose a method for multi-modal vertebra recognition using a novel deep learning architecture called Transformed Deep Convolution Network (TDCN). This new architecture can unsupervisely fuse image features from different modalities and automatically rectify the pose of vertebra. The fusion of MR and CT image features improves the discriminativity of feature representation and enhances the invariance of the vertebra pattern, which allows us to automatically process images from different contrast, resolution, protocols, even with different sizes and orientations. The feature fusion and pose rectification are naturally incorporated in a multi-layer deep learning network. Experiment results show that our method outperforms existing detection methods and provides a fully automatic location+naming+pose recognition for routine clinical practice. PMID:27104497

  14. Solution-Based Fabrication of Narrow-Disperse ABC Three-Segment and Θ-Shaped Nanoparticles.

    PubMed

    Zhang, Zhen; Zhou, Changming; Dong, Haiyan; Chen, Daoyong

    2016-05-17

    Nanoparticles sized tens of nm with not only a highly complex but also a highly regular nanostructure, although ubiquitous in nature, are very difficult to prepare artificially. Herein, we report efficient solution-based preparation of narrow-disperse ABC three-segment hierarchical nanoparticles (HNPs) with a size of tens of nm through a three-level hierarchical self-assembly of A-b-B-b-C triblock copolymers in solution. An ABC HNP is composed of three nanoparticles, A, B, and C that are linearly connected; in the ABC HNP, the B nanoparticle is sandwiched between the A and C nanoparticles. The method for the preparation is highly efficient, because all of the A-b-B-b-C chains in the solution are converted into the ABC HNPs. Furthermore, the ABC HNPs self-assembled into Θ-shaped HNPs tens nm in size. Both the ABC and Θ-shaped HNPs, are highly complex but highly regular, and are novel HNPs, and they should be very promising for addressing various theoretical and practical problems. PMID:27071692

  15. Convolution modeling of two-domain, nonlinear water-level responses in karst aquifers (Invited)

    NASA Astrophysics Data System (ADS)

    Long, A. J.

    2009-12-01

    Convolution modeling is a useful method for simulating the hydraulic response of water levels to sinking streamflow or precipitation infiltration at the macro scale. This approach is particularly useful in karst aquifers, where the complex geometry of the conduit and pore network is not well characterized but can be represented approximately by a parametric impulse-response function (IRF) with very few parameters. For many applications, one-dimensional convolution models can be equally effective as complex two- or three-dimensional models for analyzing water-level responses to recharge. Moreover, convolution models are well suited for identifying and characterizing the distinct domains of quick flow and slow flow (e.g., conduit flow and diffuse flow). Two superposed lognormal functions were used in the IRF to approximate the impulses of the two flow domains. Nonlinear response characteristics of the flow domains were assessed by observing temporal changes in the IRFs. Precipitation infiltration was simulated by filtering the daily rainfall record with a backward-in-time exponential function that weights each day’s rainfall with the rainfall of previous days and thus accounts for the effects of soil moisture on aquifer infiltration. The model was applied to the Edwards aquifer in Texas and the Madison aquifer in South Dakota. Simulations of both aquifers showed similar characteristics, including a separation on the order of years between the quick-flow and slow-flow IRF peaks and temporal changes in the IRF shapes when water levels increased and empty pore spaces became saturated.

  16. Flexible Fabrication of Shape-Controlled Collagen Building Blocks for Self-Assembly of 3D Microtissues.

    PubMed

    Zhang, Xu; Meng, Zhaoxu; Ma, Jingyun; Shi, Yang; Xu, Hui; Lykkemark, Simon; Qin, Jianhua

    2015-08-12

    Creating artificial tissue-like structures that possess the functionality, specificity, and architecture of native tissues remains a big challenge. A new and straightforward strategy for generating shape-controlled collagen building blocks with a well-defined architecture is presented, which can be used for self-assembly of complex 3D microtissues. Collagen blocks with tunable geometries are controllably produced and released via a membrane-templated microdevice. The formation of functional microtissues by embedding tissue-specific cells into collagen blocks with expression of specific proteins is described. The spontaneous self-assembly of cell-laden collagen blocks into organized tissue constructs with predetermined configurations is demonstrated, which are largely driven by the synergistic effects of cell-cell and cell-matrix interactions. This new strategy would open up new avenues for the study of tissue/organ morphogenesis, and tissue engineering applications. PMID:25920010

  17. Accelerated unsteady flow line integral convolution.

    PubMed

    Liu, Zhanping; Moorhead, Robert J

    2005-01-01

    Unsteady flow line integral convolution (UFLIC) is a texture synthesis technique for visualizing unsteady flows with high temporal-spatial coherence. Unfortunately, UFLIC requires considerable time to generate each frame due to the huge amount of pathline integration that is computed for particle value scattering. This paper presents Accelerated UFLIC (AUFLIC) for near interactive (1 frame/second) visualization with 160,000 particles per frame. AUFLIC reuses pathlines in the value scattering process to reduce computationally expensive pathline integration. A flow-driven seeding strategy is employed to distribute seeds such that only a few of them need pathline integration while most seeds are placed along the pathlines advected at earlier times by other seeds upstream and, therefore, the known pathlines can be reused for fast value scattering. To maintain a dense scattering coverage to convey high temporal-spatial coherence while keeping the expense of pathline integration low, a dynamic seeding controller is designed to decide whether to advect, copy, or reuse a pathline. At a negligible memory cost, AUFLIC is 9 times faster than UFLIC with comparable image quality. PMID:15747635

  18. Blind source separation of convolutive mixtures

    NASA Astrophysics Data System (ADS)

    Makino, Shoji

    2006-04-01

    This paper introduces the blind source separation (BSS) of convolutive mixtures of acoustic signals, especially speech. A statistical and computational technique, called independent component analysis (ICA), is examined. By achieving nonlinear decorrelation, nonstationary decorrelation, or time-delayed decorrelation, we can find source signals only from observed mixed signals. Particular attention is paid to the physical interpretation of BSS from the acoustical signal processing point of view. Frequency-domain BSS is shown to be equivalent to two sets of frequency domain adaptive microphone arrays, i.e., adaptive beamformers (ABFs). Although BSS can reduce reverberant sounds to some extent in the same way as ABF, it mainly removes the sounds from the jammer direction. This is why BSS has difficulties with long reverberation in the real world. If sources are not "independent," the dependence results in bias noise when obtaining the correct separation filter coefficients. Therefore, the performance of BSS is limited by that of ABF. Although BSS is upper bounded by ABF, BSS has a strong advantage over ABF. BSS can be regarded as an intelligent version of ABF in the sense that it can adapt without any information on the array manifold or the target direction, and sources can be simultaneously active in BSS.

  19. Metaheuristic Algorithms for Convolution Neural Network.

    PubMed

    Rere, L M Rasdi; Fanany, Mohamad Ivan; Arymurthy, Aniati Murni

    2016-01-01

    A typical modern optimization technique is usually either heuristic or metaheuristic. This technique has managed to solve some optimization problems in the research area of science, engineering, and industry. However, implementation strategy of metaheuristic for accuracy improvement on convolution neural networks (CNN), a famous deep learning method, is still rarely investigated. Deep learning relates to a type of machine learning technique, where its aim is to move closer to the goal of artificial intelligence of creating a machine that could successfully perform any intellectual tasks that can be carried out by a human. In this paper, we propose the implementation strategy of three popular metaheuristic approaches, that is, simulated annealing, differential evolution, and harmony search, to optimize CNN. The performances of these metaheuristic methods in optimizing CNN on classifying MNIST and CIFAR dataset were evaluated and compared. Furthermore, the proposed methods are also compared with the original CNN. Although the proposed methods show an increase in the computation time, their accuracy has also been improved (up to 7.14 percent). PMID:27375738

  20. Metaheuristic Algorithms for Convolution Neural Network

    PubMed Central

    Fanany, Mohamad Ivan; Arymurthy, Aniati Murni

    2016-01-01

    A typical modern optimization technique is usually either heuristic or metaheuristic. This technique has managed to solve some optimization problems in the research area of science, engineering, and industry. However, implementation strategy of metaheuristic for accuracy improvement on convolution neural networks (CNN), a famous deep learning method, is still rarely investigated. Deep learning relates to a type of machine learning technique, where its aim is to move closer to the goal of artificial intelligence of creating a machine that could successfully perform any intellectual tasks that can be carried out by a human. In this paper, we propose the implementation strategy of three popular metaheuristic approaches, that is, simulated annealing, differential evolution, and harmony search, to optimize CNN. The performances of these metaheuristic methods in optimizing CNN on classifying MNIST and CIFAR dataset were evaluated and compared. Furthermore, the proposed methods are also compared with the original CNN. Although the proposed methods show an increase in the computation time, their accuracy has also been improved (up to 7.14 percent). PMID:27375738

  1. Fabrication of cone-shaped CNF/SiC-coated Si-nanocone composite structures and their excellent field emission performance

    NASA Astrophysics Data System (ADS)

    Teng, I.-Ju; Hsu, Hui-Lin; Jian, Sheng-Rui; Kuo, Cheng-Tzu; Juang, Jenh-Yih

    2012-11-01

    Novel cone-shaped carbon nanofiber (CNF)/silicon carbide (SiC)-coated Si-nanocone (Si-NC) composite structures with excellent field emission (FE) performance have been fabricated by a simple microwave plasma chemical vapour deposition process. Transmission electron microscopy analyses reveal that the newly developed cone-shaped composite structures are composed of bamboo-like herringbone CNFs grown vertically on the tips of conical SiC layers with a flat-top Si cone embedded underneath. For this CNF/SiC-coated Si-NC composite array, a ultra-low threshold field of 0.32 V μm-1 (at 10 mA cm-2), a large emission current density of 668 mA cm-2 at 1.05 V μm-1, and a field enhancement factor as high as ~48 349 are obtained. In addition, the FE lifetime test performed at a large emission current density of 200 mA cm-2 under an applied field of 1 V μm-1 shows no discernible decay during a period of over 260 minutes. We deduce that this superior FE performance can be attributed to the specific bamboo-like herringbone CNFs with numerous open graphitic edges and a faceted top end, and the conical base SiC/Si structures with sufficient adhesion to the substrate surface. Such a novel structure with promising emission characteristics makes it a potential material for electron field emitters.

  2. Fabrication of cone-shaped CNF/SiC-coated Si-nanocone composite structures and their excellent field emission performance.

    PubMed

    Teng, I-Ju; Hsu, Hui-Lin; Jian, Sheng-Rui; Kuo, Cheng-Tzu; Juang, Jenh-Yih

    2012-12-01

    Novel cone-shaped carbon nanofiber (CNF)/silicon carbide (SiC)-coated Si-nanocone (Si-NC) composite structures with excellent field emission (FE) performance have been fabricated by a simple microwave plasma chemical vapour deposition process. Transmission electron microscopy analyses reveal that the newly developed cone-shaped composite structures are composed of bamboo-like herringbone CNFs grown vertically on the tips of conical SiC layers with a flat-top Si cone embedded underneath. For this CNF/SiC-coated Si-NC composite array, a ultra-low threshold field of 0.32 V μm(-1) (at 10 mA cm(-2)), a large emission current density of 668 mA cm(-2) at 1.05 V μm(-1), and a field enhancement factor as high as ~48,349 are obtained. In addition, the FE lifetime test performed at a large emission current density of 200 mA cm(-2) under an applied field of 1 V μm(-1) shows no discernible decay during a period of over 260 minutes. We deduce that this superior FE performance can be attributed to the specific bamboo-like herringbone CNFs with numerous open graphitic edges and a faceted top end, and the conical base SiC/Si structures with sufficient adhesion to the substrate surface. Such a novel structure with promising emission characteristics makes it a potential material for electron field emitters. PMID:23108379

  3. Noise-enhanced convolutional neural networks.

    PubMed

    Audhkhasi, Kartik; Osoba, Osonde; Kosko, Bart

    2016-06-01

    Injecting carefully chosen noise can speed convergence in the backpropagation training of a convolutional neural network (CNN). The Noisy CNN algorithm speeds training on average because the backpropagation algorithm is a special case of the generalized expectation-maximization (EM) algorithm and because such carefully chosen noise always speeds up the EM algorithm on average. The CNN framework gives a practical way to learn and recognize images because backpropagation scales with training data. It has only linear time complexity in the number of training samples. The Noisy CNN algorithm finds a special separating hyperplane in the network's noise space. The hyperplane arises from the likelihood-based positivity condition that noise-boosts the EM algorithm. The hyperplane cuts through a uniform-noise hypercube or Gaussian ball in the noise space depending on the type of noise used. Noise chosen from above the hyperplane speeds training on average. Noise chosen from below slows it on average. The algorithm can inject noise anywhere in the multilayered network. Adding noise to the output neurons reduced the average per-iteration training-set cross entropy by 39% on a standard MNIST image test set of handwritten digits. It also reduced the average per-iteration training-set classification error by 47%. Adding noise to the hidden layers can also reduce these performance measures. The noise benefit is most pronounced for smaller data sets because the largest EM hill-climbing gains tend to occur in the first few iterations. This noise effect can assist random sampling from large data sets because it allows a smaller random sample to give the same or better performance than a noiseless sample gives. PMID:26700535

  4. A Geometric Construction of Cyclic Cocycles on Twisted Convolution Algebras

    NASA Astrophysics Data System (ADS)

    Angel, Eitan

    2010-09-01

    In this thesis we give a construction of cyclic cocycles on convolution algebras twisted by gerbes over discrete translation groupoids. In his seminal book, Connes constructs a map from the equivariant cohomology of a manifold carrying the action of a discrete group into the periodic cyclic cohomology of the associated convolution algebra. Furthermore, for proper étale groupoids, J.-L. Tu and P. Xu provide a map between the periodic cyclic cohomology of a gerbe twisted convolution algebra and twisted cohomology groups. Our focus will be the convolution algebra with a product defined by a gerbe over a discrete translation groupoid. When the action is not proper, we cannot construct an invariant connection on the gerbe; therefore to study this algebra, we instead develop simplicial notions related to ideas of J. Dupont to construct a simplicial form representing the Dixmier-Douady class of the gerbe. Then by using a JLO formula we define a morphism from a simplicial complex twisted by this simplicial Dixmier-Douady form to the mixed bicomplex of certain matrix algebras. Finally, we define a morphism from this complex to the mixed bicomplex computing the periodic cyclic cohomology of the twisted convolution algebras.

  5. Two dimensional convolute integers for machine vision and image recognition

    NASA Technical Reports Server (NTRS)

    Edwards, Thomas R.

    1988-01-01

    Machine vision and image recognition require sophisticated image processing prior to the application of Artificial Intelligence. Two Dimensional Convolute Integer Technology is an innovative mathematical approach for addressing machine vision and image recognition. This new technology generates a family of digital operators for addressing optical images and related two dimensional data sets. The operators are regression generated, integer valued, zero phase shifting, convoluting, frequency sensitive, two dimensional low pass, high pass and band pass filters that are mathematically equivalent to surface fitted partial derivatives. These operators are applied non-recursively either as classical convolutions (replacement point values), interstitial point generators (bandwidth broadening or resolution enhancement), or as missing value calculators (compensation for dead array element values). These operators show frequency sensitive feature selection scale invariant properties. Such tasks as boundary/edge enhancement and noise or small size pixel disturbance removal can readily be accomplished. For feature selection tight band pass operators are essential. Results from test cases are given.

  6. Error-trellis syndrome decoding techniques for convolutional codes

    NASA Technical Reports Server (NTRS)

    Reed, I. S.; Truong, T. K.

    1985-01-01

    An error-trellis syndrome decoding technique for convolutional codes is developed. This algorithm is then applied to the entire class of systematic convolutional codes and to the high-rate, Wyner-Ash convolutional codes. A special example of the one-error-correcting Wyner-Ash code, a rate 3/4 code, is treated. The error-trellis syndrome decoding method applied to this example shows in detail how much more efficient syndrome decordig is than Viterbi decoding if applied to the same problem. For standard Viterbi decoding, 64 states are required, whereas in the example only 7 states are needed. Also, within the 7 states required for decoding, many fewer transitions are needed between the states.

  7. Error-trellis Syndrome Decoding Techniques for Convolutional Codes

    NASA Technical Reports Server (NTRS)

    Reed, I. S.; Truong, T. K.

    1984-01-01

    An error-trellis syndrome decoding technique for convolutional codes is developed. This algorithm is then applied to the entire class of systematic convolutional codes and to the high-rate, Wyner-Ash convolutional codes. A special example of the one-error-correcting Wyner-Ash code, a rate 3/4 code, is treated. The error-trellis syndrome decoding method applied to this example shows in detail how much more efficient syndrome decoding is than Viterbi decoding if applied to the same problem. For standard Viterbi decoding, 64 states are required, whereas in the example only 7 states are needed. Also, within the 7 states required for decoding, many fewer transitions are needed between the states.

  8. Robustly optimal rate one-half binary convolutional codes

    NASA Technical Reports Server (NTRS)

    Johannesson, R.

    1975-01-01

    Three optimality criteria for convolutional codes are considered in this correspondence: namely, free distance, minimum distance, and distance profile. Here we report the results of computer searches for rate one-half binary convolutional codes that are 'robustly optimal' in the sense of being optimal for one criterion and optimal or near-optimal for the other two criteria. Comparisons with previously known codes are made. The results of a computer simulation are reported to show the importance of the distance profile to computational performance with sequential decoding.

  9. Knowledge Based 3d Building Model Recognition Using Convolutional Neural Networks from LIDAR and Aerial Imageries

    NASA Astrophysics Data System (ADS)

    Alidoost, F.; Arefi, H.

    2016-06-01

    In recent years, with the development of the high resolution data acquisition technologies, many different approaches and algorithms have been presented to extract the accurate and timely updated 3D models of buildings as a key element of city structures for numerous applications in urban mapping. In this paper, a novel and model-based approach is proposed for automatic recognition of buildings' roof models such as flat, gable, hip, and pyramid hip roof models based on deep structures for hierarchical learning of features that are extracted from both LiDAR and aerial ortho-photos. The main steps of this approach include building segmentation, feature extraction and learning, and finally building roof labeling in a supervised pre-trained Convolutional Neural Network (CNN) framework to have an automatic recognition system for various types of buildings over an urban area. In this framework, the height information provides invariant geometric features for convolutional neural network to localize the boundary of each individual roofs. CNN is a kind of feed-forward neural network with the multilayer perceptron concept which consists of a number of convolutional and subsampling layers in an adaptable structure and it is widely used in pattern recognition and object detection application. Since the training dataset is a small library of labeled models for different shapes of roofs, the computation time of learning can be decreased significantly using the pre-trained models. The experimental results highlight the effectiveness of the deep learning approach to detect and extract the pattern of buildings' roofs automatically considering the complementary nature of height and RGB information.

  10. Space reactor shielding fabrication

    NASA Technical Reports Server (NTRS)

    Welch, F. H.

    1972-01-01

    The fabrication of space reactor neutron shielding by a melting and casting process utilizing lithium hydride is described. The first neutron shield fabricated is a large pancake shape 86 inches in diameter, containing about 1700 pounds of lithium hydride. This shield, fabricated by the unique melting and casting process, is the largest lithium hydride shield ever built.

  11. Maximum-likelihood estimation of circle parameters via convolution.

    PubMed

    Zelniker, Emanuel E; Clarkson, I Vaughan L

    2006-04-01

    The accurate fitting of a circle to noisy measurements of circumferential points is a much studied problem in the literature. In this paper, we present an interpretation of the maximum-likelihood estimator (MLE) and the Delogne-Kåsa estimator (DKE) for circle-center and radius estimation in terms of convolution on an image which is ideal in a certain sense. We use our convolution-based MLE approach to find good estimates for the parameters of a circle in digital images. In digital images, it is then possible to treat these estimates as preliminary estimates into various other numerical techniques which further refine them to achieve subpixel accuracy. We also investigate the relationship between the convolution of an ideal image with a "phase-coded kernel" (PCK) and the MLE. This is related to the "phase-coded annulus" which was introduced by Atherton and Kerbyson who proposed it as one of a number of new convolution kernels for estimating circle center and radius. We show that the PCK is an approximate MLE (AMLE). We compare our AMLE method to the MLE and the DKE as well as the Cramér-Rao Lower Bound in ideal images and in both real and synthetic digital images. PMID:16579374

  12. Voltage measurements at the vacuum post-hole convolute of the Z pulsed-power accelerator

    SciTech Connect

    Waisman, E. M.; McBride, R. D.; Cuneo, M. E.; Wenger, D. F.; Fowler, W. E.; Johnson, W. A.; Basilio, L. I.; Coats, R. S.; Jennings, C. A.; Sinars, D. B.; Vesey, R. A.; Jones, B.; Ampleford, D. J.; Lemke, R. W.; Martin, M. R.; Schrafel, P. C.; Lewis, S. A.; Moore, J. K.; Savage, M. E.; Stygar, W. A.

    2014-12-08

    Presented are voltage measurements taken near the load region on the Z pulsed-power accelerator using an inductive voltage monitor (IVM). Specifically, the IVM was connected to, and thus monitored the voltage at, the bottom level of the accelerator’s vacuum double post-hole convolute. Additional voltage and current measurements were taken at the accelerator’s vacuum-insulator stack (at a radius of 1.6 m) by using standard D-dot and B-dot probes, respectively. During postprocessing, the measurements taken at the stack were translated to the location of the IVM measurements by using a lossless propagation model of the Z accelerator’s magnetically insulated transmission lines (MITLs) and a lumped inductor model of the vacuum post-hole convolute. Across a wide variety of experiments conducted on the Z accelerator, the voltage histories obtained from the IVM and the lossless propagation technique agree well in overall shape and magnitude. However, large-amplitude, high-frequency oscillations are more pronounced in the IVM records. It is unclear whether these larger oscillations represent true voltage oscillations at the convolute or if they are due to noise pickup and/or transit-time effects and other resonant modes in the IVM. Results using a transit-time-correction technique and Fourier analysis support the latter. Regardless of which interpretation is correct, both true voltage oscillations and the excitement of resonant modes could be the result of transient electrical breakdowns in the post-hole convolute, though more information is required to determine definitively if such breakdowns occurred. Despite the larger oscillations in the IVM records, the general agreement found between the lossless propagation results and the results of the IVM shows that large voltages are transmitted efficiently through the MITLs on Z. These results are complementary to previous studies [R. D. McBride et al., Phys. Rev. ST Accel. Beams 13, 120401 (2010)] that

  13. Voltage measurements at the vacuum post-hole convolute of the Z pulsed-power accelerator

    NASA Astrophysics Data System (ADS)

    Waisman, E. M.; McBride, R. D.; Cuneo, M. E.; Wenger, D. F.; Fowler, W. E.; Johnson, W. A.; Basilio, L. I.; Coats, R. S.; Jennings, C. A.; Sinars, D. B.; Vesey, R. A.; Jones, B.; Ampleford, D. J.; Lemke, R. W.; Martin, M. R.; Schrafel, P. C.; Lewis, S. A.; Moore, J. K.; Savage, M. E.; Stygar, W. A.

    2014-12-01

    Presented are voltage measurements taken near the load region on the Z pulsed-power accelerator using an inductive voltage monitor (IVM). Specifically, the IVM was connected to, and thus monitored the voltage at, the bottom level of the accelerator's vacuum double post-hole convolute. Additional voltage and current measurements were taken at the accelerator's vacuum-insulator stack (at a radius of 1.6 m) by using standard D -dot and B -dot probes, respectively. During postprocessing, the measurements taken at the stack were translated to the location of the IVM measurements by using a lossless propagation model of the Z accelerator's magnetically insulated transmission lines (MITLs) and a lumped inductor model of the vacuum post-hole convolute. Across a wide variety of experiments conducted on the Z accelerator, the voltage histories obtained from the IVM and the lossless propagation technique agree well in overall shape and magnitude. However, large-amplitude, high-frequency oscillations are more pronounced in the IVM records. It is unclear whether these larger oscillations represent true voltage oscillations at the convolute or if they are due to noise pickup and/or transit-time effects and other resonant modes in the IVM. Results using a transit-time-correction technique and Fourier analysis support the latter. Regardless of which interpretation is correct, both true voltage oscillations and the excitement of resonant modes could be the result of transient electrical breakdowns in the post-hole convolute, though more information is required to determine definitively if such breakdowns occurred. Despite the larger oscillations in the IVM records, the general agreement found between the lossless propagation results and the results of the IVM shows that large voltages are transmitted efficiently through the MITLs on Z . These results are complementary to previous studies [R. D. McBride et al., Phys. Rev. ST Accel. Beams 13, 120401 (2010)] that showed efficient

  14. Voltage measurements at the vacuum post-hole convolute of the Z pulsed-power accelerator

    DOE PAGESBeta

    Waisman, E. M.; McBride, R. D.; Cuneo, M. E.; Wenger, D. F.; Fowler, W. E.; Johnson, W. A.; Basilio, L. I.; Coats, R. S.; Jennings, C. A.; Sinars, D. B.; et al

    2014-12-08

    Presented are voltage measurements taken near the load region on the Z pulsed-power accelerator using an inductive voltage monitor (IVM). Specifically, the IVM was connected to, and thus monitored the voltage at, the bottom level of the accelerator’s vacuum double post-hole convolute. Additional voltage and current measurements were taken at the accelerator’s vacuum-insulator stack (at a radius of 1.6 m) by using standard D-dot and B-dot probes, respectively. During postprocessing, the measurements taken at the stack were translated to the location of the IVM measurements by using a lossless propagation model of the Z accelerator’s magnetically insulated transmission lines (MITLs)more » and a lumped inductor model of the vacuum post-hole convolute. Across a wide variety of experiments conducted on the Z accelerator, the voltage histories obtained from the IVM and the lossless propagation technique agree well in overall shape and magnitude. However, large-amplitude, high-frequency oscillations are more pronounced in the IVM records. It is unclear whether these larger oscillations represent true voltage oscillations at the convolute or if they are due to noise pickup and/or transit-time effects and other resonant modes in the IVM. Results using a transit-time-correction technique and Fourier analysis support the latter. Regardless of which interpretation is correct, both true voltage oscillations and the excitement of resonant modes could be the result of transient electrical breakdowns in the post-hole convolute, though more information is required to determine definitively if such breakdowns occurred. Despite the larger oscillations in the IVM records, the general agreement found between the lossless propagation results and the results of the IVM shows that large voltages are transmitted efficiently through the MITLs on Z. These results are complementary to previous studies [R. D. McBride et al., Phys. Rev. ST Accel. Beams 13, 120401 (2010)] that showed

  15. ARKCoS: artifact-suppressed accelerated radial kernel convolution on the sphere

    NASA Astrophysics Data System (ADS)

    Elsner, F.; Wandelt, B. D.

    2011-08-01

    We describe a hybrid Fourier/direct space convolution algorithm for compact radial (azimuthally symmetric) kernels on the sphere. For high resolution maps covering a large fraction of the sky, our implementation takes advantage of the inexpensive massive parallelism afforded by consumer graphics processing units (GPUs). Its applications include modeling of instrumental beam shapes in terms of compact kernels, computation of fine-scale wavelet transformations, and optimal filtering for the detection of point sources. Our algorithm works for any pixelization where pixels are grouped into isolatitude rings. Even for kernels that are not bandwidth-limited, ringing features are completely absent on an ECP grid. We demonstrate that they can be highly suppressed on the popular HEALPix pixelization, for which we develop a freely available implementation of the algorithm. As an example application, we show that running on a high-end consumer graphics card our method speeds up beam convolution for simulations of a characteristic Planck high frequency instrument channel by two orders of magnitude compared to the commonly used HEALPix implementation on one CPU core, while typically maintaining a fractional RMS accuracy of about 1 part in 105.

  16. Projection of fMRI data onto the cortical surface using anatomically-informed convolution kernels.

    PubMed

    Operto, G; Bulot, R; Anton, J-L; Coulon, O

    2008-01-01

    As surface-based data analysis offer an attractive approach for intersubject matching and comparison, the projection of voxel-based 3D volumes onto the cortical surface is an essential problem. We present here a method that aims at producing representations of functional brain data on the cortical surface from functional MRI volumes. Such representations are for instance required for subsequent cortical-based functional analysis. We propose a projection technique based on the definition, around each node of the gray/white matter interface mesh, of convolution kernels whose shape and distribution rely on the geometry of the local anatomy. For one anatomy, a set of convolution kernels is computed that can be used to project any functional data registered with this anatomy. Therefore resulting in anatomically-informed projections of data onto the cortical surface, this kernel-based approach offers better sensitivity, specificity than other classical methods and robustness to misregistration errors. Influences of mesh and volumes spatial resolutions were also estimated for various projection techniques, using simulated functional maps. PMID:17931891

  17. Evaluation of convolutional neural networks for visual recognition.

    PubMed

    Nebauer, C

    1998-01-01

    Convolutional neural networks provide an efficient method to constrain the complexity of feedforward neural networks by weight sharing and restriction to local connections. This network topology has been applied in particular to image classification when sophisticated preprocessing is to be avoided and raw images are to be classified directly. In this paper two variations of convolutional networks--neocognitron and a modification of neocognitron--are compared with classifiers based on fully connected feedforward layers (i.e., multilayer perceptron, nearest neighbor classifier, auto-encoding network) with respect to their visual recognition performance. Beside the original neocognitron a modification of the neocognitron is proposed which combines neurons from perceptron with the localized network structure of neocognitron. Instead of training convolutional networks by time-consuming error backpropagation, in this work a modular procedure is applied whereby layers are trained sequentially from the input to the output layer in order to recognize features of increasing complexity. For a quantitative experimental comparison with standard classifiers two very different recognition tasks have been chosen: handwritten digit recognition and face recognition. In the first example on handwritten digit recognition the generalization of convolutional networks is compared to fully connected networks. In several experiments the influence of variations of position, size, and orientation of digits is determined and the relation between training sample size and validation error is observed. In the second example recognition of human faces is investigated under constrained and variable conditions with respect to face orientation and illumination and the limitations of convolutional networks are discussed. PMID:18252491

  18. FAST PIXEL SPACE CONVOLUTION FOR COSMIC MICROWAVE BACKGROUND SURVEYS WITH ASYMMETRIC BEAMS AND COMPLEX SCAN STRATEGIES: FEBeCoP

    SciTech Connect

    Mitra, S.; Rocha, G.; Gorski, K. M.; Lawrence, C. R.; Huffenberger, K. M.; Eriksen, H. K.; Ashdown, M. A. J. E-mail: graca@caltech.edu E-mail: Charles.R.Lawrence@jpl.nasa.gov E-mail: h.k.k.eriksen@astro.uio.no

    2011-03-15

    Precise measurement of the angular power spectrum of the cosmic microwave background (CMB) temperature and polarization anisotropy can tightly constrain many cosmological models and parameters. However, accurate measurements can only be realized in practice provided all major systematic effects have been taken into account. Beam asymmetry, coupled with the scan strategy, is a major source of systematic error in scanning CMB experiments such as Planck, the focus of our current interest. We envision Monte Carlo methods to rigorously study and account for the systematic effect of beams in CMB analysis. Toward that goal, we have developed a fast pixel space convolution method that can simulate sky maps observed by a scanning instrument, taking into account real beam shapes and scan strategy. The essence is to pre-compute the 'effective beams' using a computer code, 'Fast Effective Beam Convolution in Pixel space' (FEBeCoP), that we have developed for the Planck mission. The code computes effective beams given the focal plane beam characteristics of the Planck instrument and the full history of actual satellite pointing, and performs very fast convolution of sky signals using the effective beams. In this paper, we describe the algorithm and the computational scheme that has been implemented. We also outline a few applications of the effective beams in the precision analysis of Planck data, for characterizing the CMB anisotropy and for detecting and measuring properties of point sources.

  19. Segmenting delaminations in carbon fiber reinforced polymer composite CT using convolutional neural networks

    NASA Astrophysics Data System (ADS)

    Sammons, Daniel; Winfree, William P.; Burke, Eric; Ji, Shuiwang

    2016-02-01

    Nondestructive evaluation (NDE) utilizes a variety of techniques to inspect various materials for defects without causing changes to the material. X-ray computed tomography (CT) produces large volumes of three dimensional image data. Using the task of identifying delaminations in carbon fiber reinforced polymer (CFRP) composite CT, this work shows that it is possible to automate the analysis of these large volumes of CT data using a machine learning model known as a convolutional neural network (CNN). Further, tests on simulated data sets show that with a robust set of experimental data, it may be possible to go beyond just identification and instead accurately characterize the size and shape of the delaminations with CNNs.

  20. UFLIC: A Line Integral Convolution Algorithm for Visualizing Unsteady Flows

    NASA Technical Reports Server (NTRS)

    Shen, Han-Wei; Kao, David L.; Chancellor, Marisa K. (Technical Monitor)

    1997-01-01

    This paper presents an algorithm, UFLIC (Unsteady Flow LIC), to visualize vector data in unsteady flow fields. Using the Line Integral Convolution (LIC) as the underlying method, a new convolution algorithm is proposed that can effectively trace the flow's global features over time. The new algorithm consists of a time-accurate value depositing scheme and a successive feed-forward method. The value depositing scheme accurately models the flow advection, and the successive feed-forward method maintains the coherence between animation frames. Our new algorithm can produce time-accurate, highly coherent flow animations to highlight global features in unsteady flow fields. CFD scientists, for the first time, are able to visualize unsteady surface flows using our algorithm.

  1. Deep learning for steganalysis via convolutional neural networks

    NASA Astrophysics Data System (ADS)

    Qian, Yinlong; Dong, Jing; Wang, Wei; Tan, Tieniu

    2015-03-01

    Current work on steganalysis for digital images is focused on the construction of complex handcrafted features. This paper proposes a new paradigm for steganalysis to learn features automatically via deep learning models. We novelly propose a customized Convolutional Neural Network for steganalysis. The proposed model can capture the complex dependencies that are useful for steganalysis. Compared with existing schemes, this model can automatically learn feature representations with several convolutional layers. The feature extraction and classification steps are unified under a single architecture, which means the guidance of classification can be used during the feature extraction step. We demonstrate the effectiveness of the proposed model on three state-of-theart spatial domain steganographic algorithms - HUGO, WOW, and S-UNIWARD. Compared to the Spatial Rich Model (SRM), our model achieves comparable performance on BOSSbase and the realistic and large ImageNet database.

  2. Two-dimensional convolute integers for analytical instrumentation

    NASA Technical Reports Server (NTRS)

    Edwards, T. R.

    1982-01-01

    As new analytical instruments and techniques emerge with increased dimensionality, a corresponding need is seen for data processing logic which can appropriately address the data. Two-dimensional measurements reveal enhanced unknown mixture analysis capability as a result of the greater spectral information content over two one-dimensional methods taken separately. It is noted that two-dimensional convolute integers are merely an extension of the work by Savitzky and Golay (1964). It is shown that these low-pass, high-pass and band-pass digital filters are truly two-dimensional and that they can be applied in a manner identical with their one-dimensional counterpart, that is, a weighted nearest-neighbor, moving average with zero phase shifting, convoluted integer (universal number) weighting coefficients.

  3. a Convolutional Network for Semantic Facade Segmentation and Interpretation

    NASA Astrophysics Data System (ADS)

    Schmitz, Matthias; Mayer, Helmut

    2016-06-01

    In this paper we present an approach for semantic interpretation of facade images based on a Convolutional Network. Our network processes the input images in a fully convolutional way and generates pixel-wise predictions. We show that there is no need for large datasets to train the network when transfer learning is employed, i. e., a part of an already existing network is used and fine-tuned, and when the available data is augmented by using deformed patches of the images for training. The network is trained end-to-end with patches of the images and each patch is augmented independently. To undo the downsampling for the classification, we add deconvolutional layers to the network. Outputs of different layers of the network are combined to achieve more precise pixel-wise predictions. We demonstrate the potential of our network based on results for the eTRIMS (Korč and Förstner, 2009) dataset reduced to facades.

  4. Study on Expansion of Convolutional Compactors over Galois Field

    NASA Astrophysics Data System (ADS)

    Arai, Masayuki; Fukumoto, Satoshi; Iwasaki, Kazuhiko

    Convolutional compactors offer a promising technique of compacting test responses. In this study we expand the architecture of convolutional compactor onto a Galois field in order to improve compaction ratio as well as reduce X-masking probability, namely, the probability that an error is masked by unknown values. While each scan chain is independently connected by EOR gates in the conventional arrangement, the proposed scheme treats q signals as an element over GF(2q), and the connections are configured on the same field. We show the arrangement of the proposed compactors and the equivalent expression over GF(2). We then evaluate the effectiveness of the proposed expansion in terms of X-masking probability by simulations with uniform distribution of X-values, as well as reduction of hardware overheads. Furthermore, we evaluate a multi-weight arrangement of the proposed compactors for non-uniform X distributions.

  5. Image Super-Resolution Using Deep Convolutional Networks.

    PubMed

    Dong, Chao; Loy, Chen Change; He, Kaiming; Tang, Xiaoou

    2016-02-01

    We propose a deep learning method for single image super-resolution (SR). Our method directly learns an end-to-end mapping between the low/high-resolution images. The mapping is represented as a deep convolutional neural network (CNN) that takes the low-resolution image as the input and outputs the high-resolution one. We further show that traditional sparse-coding-based SR methods can also be viewed as a deep convolutional network. But unlike traditional methods that handle each component separately, our method jointly optimizes all layers. Our deep CNN has a lightweight structure, yet demonstrates state-of-the-art restoration quality, and achieves fast speed for practical on-line usage. We explore different network structures and parameter settings to achieve trade-offs between performance and speed. Moreover, we extend our network to cope with three color channels simultaneously, and show better overall reconstruction quality. PMID:26761735

  6. Face Detection Using GPU-Based Convolutional Neural Networks

    NASA Astrophysics Data System (ADS)

    Nasse, Fabian; Thurau, Christian; Fink, Gernot A.

    In this paper, we consider the problem of face detection under pose variations. Unlike other contributions, a focus of this work resides within efficient implementation utilizing the computational powers of modern graphics cards. The proposed system consists of a parallelized implementation of convolutional neural networks (CNNs) with a special emphasize on also parallelizing the detection process. Experimental validation in a smart conference room with 4 active ceiling-mounted cameras shows a dramatic speed-gain under real-life conditions.

  7. New syndrome decoder for (n, 1) convolutional codes

    NASA Technical Reports Server (NTRS)

    Reed, I. S.; Truong, T. K.

    1983-01-01

    The letter presents a new syndrome decoding algorithm for the (n, 1) convolutional codes (CC) that is different and simpler than the previous syndrome decoding algorithm of Schalkwijk and Vinck. The new technique uses the general solution of the polynomial linear Diophantine equation for the error polynomial vector E(D). A recursive, Viterbi-like, algorithm is developed to find the minimum weight error vector E(D). An example is given for the binary nonsystematic (2, 1) CC.

  8. Fine-grained representation learning in convolutional autoencoders

    NASA Astrophysics Data System (ADS)

    Luo, Chang; Wang, Jie

    2016-03-01

    Convolutional autoencoders (CAEs) have been widely used as unsupervised feature extractors for high-resolution images. As a key component in CAEs, pooling is a biologically inspired operation to achieve scale and shift invariances, and the pooled representation directly affects the CAEs' performance. Fine-grained pooling, which uses small and dense pooling regions, encodes fine-grained visual cues and enhances local characteristics. However, it tends to be sensitive to spatial rearrangements. In most previous works, pooled features were obtained by empirically modulating parameters in CAEs. We see the CAE as a whole and propose a fine-grained representation learning law to extract better fine-grained features. This representation learning law suggests two directions for improvement. First, we probabilistically evaluate the discrimination-invariance tradeoff with fine-grained granularity in the pooled feature maps, and suggest the proper filter scale in the convolutional layer and appropriate whitening parameters in preprocessing step. Second, pooling approaches are combined with the sparsity degree in pooling regions, and we propose the preferable pooling approach. Experimental results on two independent benchmark datasets demonstrate that our representation learning law could guide CAEs to extract better fine-grained features and performs better in multiclass classification task. This paper also provides guidance for selecting appropriate parameters to obtain better fine-grained representation in other convolutional neural networks.

  9. Automatic localization of vertebrae based on convolutional neural networks

    NASA Astrophysics Data System (ADS)

    Shen, Wei; Yang, Feng; Mu, Wei; Yang, Caiyun; Yang, Xin; Tian, Jie

    2015-03-01

    Localization of the vertebrae is of importance in many medical applications. For example, the vertebrae can serve as the landmarks in image registration. They can also provide a reference coordinate system to facilitate the localization of other organs in the chest. In this paper, we propose a new vertebrae localization method using convolutional neural networks (CNN). The main advantage of the proposed method is the removal of hand-crafted features. We construct two training sets to train two CNNs that share the same architecture. One is used to distinguish the vertebrae from other tissues in the chest, and the other is aimed at detecting the centers of the vertebrae. The architecture contains two convolutional layers, both of which are followed by a max-pooling layer. Then the output feature vector from the maxpooling layer is fed into a multilayer perceptron (MLP) classifier which has one hidden layer. Experiments were performed on ten chest CT images. We used leave-one-out strategy to train and test the proposed method. Quantitative comparison between the predict centers and ground truth shows that our convolutional neural networks can achieve promising localization accuracy without hand-crafted features.

  10. A Discriminative Representation of Convolutional Features for Indoor Scene Recognition

    NASA Astrophysics Data System (ADS)

    Khan, Salman H.; Hayat, Munawar; Bennamoun, Mohammed; Togneri, Roberto; Sohel, Ferdous A.

    2016-07-01

    Indoor scene recognition is a multi-faceted and challenging problem due to the diverse intra-class variations and the confusing inter-class similarities. This paper presents a novel approach which exploits rich mid-level convolutional features to categorize indoor scenes. Traditionally used convolutional features preserve the global spatial structure, which is a desirable property for general object recognition. However, we argue that this structuredness is not much helpful when we have large variations in scene layouts, e.g., in indoor scenes. We propose to transform the structured convolutional activations to another highly discriminative feature space. The representation in the transformed space not only incorporates the discriminative aspects of the target dataset, but it also encodes the features in terms of the general object categories that are present in indoor scenes. To this end, we introduce a new large-scale dataset of 1300 object categories which are commonly present in indoor scenes. Our proposed approach achieves a significant performance boost over previous state of the art approaches on five major scene classification datasets.

  11. Fabricating superhydrophilic wool fabrics.

    PubMed

    Chen, Dong; Tan, Longfei; Liu, Huiyu; Hu, Junyan; Li, Yi; Tang, Fangqiong

    2010-04-01

    A simple method for fabricating environmentally stable superhydrophilic wool fabrics is reported here. An ultrathin silica layer coated on the wool altered both the surface roughness and the surface energy of the fiber and endowed the wool fabrics with excellent water absorption. The process of coating silica sols was dependent on an acid solution of low pH, which influenced the electrostatic interactions between nanoparticles and wool fibers. The morphology and composition of silica-sol-coated wool fabrics were characterized by a combination of SEM, TEM, EDX, FTIR, and XPS measurements. The possible mechanism and size effect of silica nanoparticles on the hydrophilic property of wool fabric were discussed. The washing fastness of the superhydrophilic wool fabrics in perchlorethylene and water was also evaluated. This study shows that wool fabrics modified by optical transparence, chemical stability, and nontoxic silica sols are promising in constructing smart textiles. PMID:19908843

  12. Testing airplane fabrics

    NASA Technical Reports Server (NTRS)

    Proll, A

    1924-01-01

    The following considerations determine the strength of airplane fabrics: 1. maximum air forces acting on the surfaces (including local stresses); 2. tensions produced in the fabrics, in the directions of both warp and filling; 3. factor of safety required. The question of the permissible depression of the fabric as affecting the aerodynamic requirements in regard to the maintenance of shape of the section, the tenacity and extensibility of the layer of dope, its strength and its permeability to water is almost as important.

  13. Learning Contextual Dependence With Convolutional Hierarchical Recurrent Neural Networks

    NASA Astrophysics Data System (ADS)

    Zuo, Zhen; Shuai, Bing; Wang, Gang; Liu, Xiao; Wang, Xingxing; Wang, Bing; Chen, Yushi

    2016-07-01

    Existing deep convolutional neural networks (CNNs) have shown their great success on image classification. CNNs mainly consist of convolutional and pooling layers, both of which are performed on local image areas without considering the dependencies among different image regions. However, such dependencies are very important for generating explicit image representation. In contrast, recurrent neural networks (RNNs) are well known for their ability of encoding contextual information among sequential data, and they only require a limited number of network parameters. General RNNs can hardly be directly applied on non-sequential data. Thus, we proposed the hierarchical RNNs (HRNNs). In HRNNs, each RNN layer focuses on modeling spatial dependencies among image regions from the same scale but different locations. While the cross RNN scale connections target on modeling scale dependencies among regions from the same location but different scales. Specifically, we propose two recurrent neural network models: 1) hierarchical simple recurrent network (HSRN), which is fast and has low computational cost; and 2) hierarchical long-short term memory recurrent network (HLSTM), which performs better than HSRN with the price of more computational cost. In this manuscript, we integrate CNNs with HRNNs, and develop end-to-end convolutional hierarchical recurrent neural networks (C-HRNNs). C-HRNNs not only make use of the representation power of CNNs, but also efficiently encodes spatial and scale dependencies among different image regions. On four of the most challenging object/scene image classification benchmarks, our C-HRNNs achieve state-of-the-art results on Places 205, SUN 397, MIT indoor, and competitive results on ILSVRC 2012.

  14. Faster GPU-based convolutional gridding via thread coarsening

    NASA Astrophysics Data System (ADS)

    Merry, B.

    2016-07-01

    Convolutional gridding is a processor-intensive step in interferometric imaging. While it is possible to use graphics processing units (GPUs) to accelerate this operation, existing methods use only a fraction of the available flops. We apply thread coarsening to improve the efficiency of an existing algorithm, and observe performance gains of up to 3.2 × for single-polarization gridding and 1.9 × for quad-polarization gridding on a GeForce GTX 980, and smaller but still significant gains on a Radeon R9 290X.

  15. Convolution seal for transition duct in turbine system

    SciTech Connect

    Flanagan, James Scott; LeBegue, Jeffrey Scott; McMahan, Kevin Weston; Dillard, Daniel Jackson; Pentecost, Ronnie Ray

    2015-03-10

    A turbine system is disclosed. In one embodiment, the turbine system includes a transition duct. The transition duct includes an inlet, an outlet, and a passage extending between the inlet and the outlet and defining a longitudinal axis, a radial axis, and a tangential axis. The outlet of the transition duct is offset from the inlet along the longitudinal axis and the tangential axis. The transition duct further includes an interface member for interfacing with a turbine section. The turbine system further includes a convolution seal contacting the interface member to provide a seal between the interface member and the turbine section.

  16. Convolution seal for transition duct in turbine system

    SciTech Connect

    Flanagan, James Scott; LeBegue, Jeffrey Scott; McMahan, Kevin Weston; Dillard, Daniel Jackson; Pentecost, Ronnie Ray

    2015-05-26

    A turbine system is disclosed. In one embodiment, the turbine system includes a transition duct. The transition duct includes an inlet, an outlet, and a passage extending between the inlet and the outlet and defining a longitudinal axis, a radial axis, and a tangential axis. The outlet of the transition duct is offset from the inlet along the longitudinal axis and the tangential axis. The transition duct further includes an interface feature for interfacing with an adjacent transition duct. The turbine system further includes a convolution seal contacting the interface feature to provide a seal between the interface feature and the adjacent transition duct.

  17. Convolutional neural networks for mammography mass lesion classification.

    PubMed

    Arevalo, John; Gonzalez, Fabio A; Ramos-Pollan, Raul; Oliveira, Jose L; Guevara Lopez, Miguel Angel

    2015-08-01

    Feature extraction is a fundamental step when mammography image analysis is addressed using learning based approaches. Traditionally, problem dependent handcrafted features are used to represent the content of images. An alternative approach successfully applied in other domains is the use of neural networks to automatically discover good features. This work presents an evaluation of convolutional neural networks to learn features for mammography mass lesions before feeding them to a classification stage. Experimental results showed that this approach is a suitable strategy outperforming the state-of-the-art representation from 79.9% to 86% in terms of area under the ROC curve. PMID:26736382

  18. Continuous speech recognition based on convolutional neural network

    NASA Astrophysics Data System (ADS)

    Zhang, Qing-qing; Liu, Yong; Pan, Jie-lin; Yan, Yong-hong

    2015-07-01

    Convolutional Neural Networks (CNNs), which showed success in achieving translation invariance for many image processing tasks, are investigated for continuous speech recognitions in the paper. Compared to Deep Neural Networks (DNNs), which have been proven to be successful in many speech recognition tasks nowadays, CNNs can reduce the NN model sizes significantly, and at the same time achieve even better recognition accuracies. Experiments on standard speech corpus TIMIT showed that CNNs outperformed DNNs in the term of the accuracy when CNNs had even smaller model size.

  19. A digital model for streamflow routing by convolution methods

    USGS Publications Warehouse

    Doyle, W.H., Jr.; Shearman, H.O.; Stiltner, G.J.; Krug, W.O.

    1984-01-01

    U.S. Geological Survey computer model, CONROUT, for routing streamflow by unit-response convolution flow-routing techniques from an upstream channel location to a downstream channel location has been developed and documented. Calibration and verification of the flow-routing model and subsequent use of the model for simulation is also documented. Three hypothetical examples and two field applications are presented to illustrate basic flow-routing concepts. Most of the discussion is limited to daily flow routing since, to date, all completed and current studies of this nature involve daily flow routing. However, the model is programmed to accept hourly flow-routing data. (USGS)

  20. New Syndrome Decoding Techniques for the (n, K) Convolutional Codes

    NASA Technical Reports Server (NTRS)

    Reed, I. S.; Truong, T. K.

    1983-01-01

    This paper presents a new syndrome decoding algorithm for the (n,k) convolutional codes (CC) which differs completely from an earlier syndrome decoding algorithm of Schalkwijk and Vinck. The new algorithm is based on the general solution of the syndrome equation, a linear Diophantine equation for the error polynomial vector E(D). The set of Diophantine solutions is a coset of the CC. In this error coset a recursive, Viterbi-like algorithm is developed to find the minimum weight error vector (circumflex)E(D). An example, illustrating the new decoding algorithm, is given for the binary nonsystemmatic (3,1)CC.

  1. New syndrome decoding techniques for the (n, k) convolutional codes

    NASA Technical Reports Server (NTRS)

    Reed, I. S.; Truong, T. K.

    1984-01-01

    This paper presents a new syndrome decoding algorithm for the (n, k) convolutional codes (CC) which differs completely from an earlier syndrome decoding algorithm of Schalkwijk and Vinck. The new algorithm is based on the general solution of the syndrome equation, a linear Diophantine equation for the error polynomial vector E(D). The set of Diophantine solutions is a coset of the CC. In this error coset a recursive, Viterbi-like algorithm is developed to find the minimum weight error vector (circumflex)E(D). An example, illustrating the new decoding algorithm, is given for the binary nonsystemmatic (3, 1)CC. Previously announced in STAR as N83-34964

  2. Simplified Syndrome Decoding of (n, 1) Convolutional Codes

    NASA Technical Reports Server (NTRS)

    Reed, I. S.; Truong, T. K.

    1983-01-01

    A new syndrome decoding algorithm for the (n, 1) convolutional codes (CC) that is different and simpler than the previous syndrome decoding algorithm of Schalkwijk and Vinck is presented. The new algorithm uses the general solution of the polynomial linear Diophantine equation for the error polynomial vector E(D). This set of Diophantine solutions is a coset of the CC space. A recursive or Viterbi-like algorithm is developed to find the minimum weight error vector cirumflex E(D) in this error coset. An example illustrating the new decoding algorithm is given for the binary nonsymmetric (2,1)CC.

  3. Is turbulent mixing a self-convolution process?

    PubMed

    Venaille, Antoine; Sommeria, Joel

    2008-06-13

    Experimental results for the evolution of the probability distribution function (PDF) of a scalar mixed by a turbulent flow in a channel are presented. The sequence of PDF from an initial skewed distribution to a sharp Gaussian is found to be nonuniversal. The route toward homogeneization depends on the ratio between the cross sections of the dye injector and the channel. In connection with this observation, advantages, shortcomings, and applicability of models for the PDF evolution based on a self-convolution mechanism are discussed. PMID:18643510

  4. A Fortran 90 code for magnetohydrodynamics. Part 1, Banded convolution

    SciTech Connect

    Walker, D.W.

    1992-03-01

    This report describes progress in developing a Fortran 90 version of the KITE code for studying plasma instabilities in Tokamaks. In particular, the evaluation of convolution terms appearing in the numerical solution is discussed, and timing results are presented for runs performed on an 8k processor Connection Machine (CM-2). Estimates of the performance on a full-size 64k CM-2 are given, and range between 100 and 200 Mflops. The advantages of having a Fortran 90 version of the KITE code are stressed, and the future use of such a code on the newly announced CM5 and Paragon computers, from Thinking Machines Corporation and Intel, is considered.

  5. Visualizing Vector Fields Using Line Integral Convolution and Dye Advection

    NASA Technical Reports Server (NTRS)

    Shen, Han-Wei; Johnson, Christopher R.; Ma, Kwan-Liu

    1996-01-01

    We present local and global techniques to visualize three-dimensional vector field data. Using the Line Integral Convolution (LIC) method to image the global vector field, our new algorithm allows the user to introduce colored 'dye' into the vector field to highlight local flow features. A fast algorithm is proposed that quickly recomputes the dyed LIC images. In addition, we introduce volume rendering methods that can map the LIC texture on any contour surface and/or translucent region defined by additional scalar quantities, and can follow the advection of colored dye throughout the volume.

  6. Simple, Inexpensive, and Rapid Approach to Fabricate Cross-Shaped Memristors Using an Inorganic-Nanowire-Digital-Alignment Technique and a One-Step Reduction Process.

    PubMed

    Xu, Wentao; Lee, Yeongjun; Min, Sung-Yong; Park, Cheolmin; Lee, Tae-Woo

    2016-01-20

    A rapid, scalable, and designable approach to produce a cross-shaped memristor array is demonstrated using an inorganic-nanowire digital-alignment technique and a one-step reduction process. Two-dimensional arrays of perpendicularly aligned, individually conductive Cu-nanowires with a nanometer-scale Cux O layer sandwiched at each cross point are produced. PMID:26585580

  7. Convolution and non convolution Perfectly Matched Layer techniques optimized at grazing incidence for high-order wave propagation modelling

    NASA Astrophysics Data System (ADS)

    Martin, Roland; Komatitsch, Dimitri; Bruthiaux, Emilien; Gedney, Stephen D.

    2010-05-01

    We present and discuss here two different unsplit formulations of the frequency shift PML based on convolution or non convolution integrations of auxiliary memory variables. Indeed, the Perfectly Matched Layer absorbing boundary condition has proven to be very efficient from a numerical point of view for the elastic wave equation to absorb both body waves with non-grazing incidence and surface waves. However, at grazing incidence the classical discrete Perfectly Matched Layer method suffers from large spurious reflections that make it less efficient for instance in the case of very thin mesh slices, in the case of sources located very close to the edge of the mesh, and/or in the case of receivers located at very large offset. In [1] we improve the Perfectly Matched Layer at grazing incidence for the seismic wave equation based on an unsplit convolution technique. This improved PML has a cost that is similar in terms of memory storage to that of the classical PML. We illustrate the efficiency of this improved Convolutional Perfectly Matched Layer based on numerical benchmarks using a staggered finite-difference method on a very thin mesh slice for an isotropic material and show that results are significantly improved compared with the classical Perfectly Matched Layer technique. We also show that, as the classical model, the technique is intrinsically unstable in the case of some anisotropic materials. In this case, retaining an idea of [2], this has been stabilized by adding correction terms adequately along any coordinate axis [3]. More specifically this has been applied to the spectral-element method based on a hybrid first/second order time integration scheme in which the Newmark time marching scheme allows us to match perfectly at the base of the absorbing layer a velocity-stress formulation in the PML and a second order displacement formulation in the inner computational domain.Our CPML unsplit formulation has the advantage to reduce the memory storage of CPML

  8. Discriminative Unsupervised Feature Learning with Exemplar Convolutional Neural Networks.

    PubMed

    Dosovitskiy, Alexey; Fischer, Philipp; Springenberg, Jost Tobias; Riedmiller, Martin; Brox, Thomas

    2016-09-01

    Deep convolutional networks have proven to be very successful in learning task specific features that allow for unprecedented performance on various computer vision tasks. Training of such networks follows mostly the supervised learning paradigm, where sufficiently many input-output pairs are required for training. Acquisition of large training sets is one of the key challenges, when approaching a new task. In this paper, we aim for generic feature learning and present an approach for training a convolutional network using only unlabeled data. To this end, we train the network to discriminate between a set of surrogate classes. Each surrogate class is formed by applying a variety of transformations to a randomly sampled 'seed' image patch. In contrast to supervised network training, the resulting feature representation is not class specific. It rather provides robustness to the transformations that have been applied during training. This generic feature representation allows for classification results that outperform the state of the art for unsupervised learning on several popular datasets (STL-10, CIFAR-10, Caltech-101, Caltech-256). While features learned with our approach cannot compete with class specific features from supervised training on a classification task, we show that they are advantageous on geometric matching problems, where they also outperform the SIFT descriptor. PMID:26540673

  9. Convolutional neural network architectures for predicting DNA–protein binding

    PubMed Central

    Zeng, Haoyang; Edwards, Matthew D.; Liu, Ge; Gifford, David K.

    2016-01-01

    Motivation: Convolutional neural networks (CNN) have outperformed conventional methods in modeling the sequence specificity of DNA–protein binding. Yet inappropriate CNN architectures can yield poorer performance than simpler models. Thus an in-depth understanding of how to match CNN architecture to a given task is needed to fully harness the power of CNNs for computational biology applications. Results: We present a systematic exploration of CNN architectures for predicting DNA sequence binding using a large compendium of transcription factor datasets. We identify the best-performing architectures by varying CNN width, depth and pooling designs. We find that adding convolutional kernels to a network is important for motif-based tasks. We show the benefits of CNNs in learning rich higher-order sequence features, such as secondary motifs and local sequence context, by comparing network performance on multiple modeling tasks ranging in difficulty. We also demonstrate how careful construction of sequence benchmark datasets, using approaches that control potentially confounding effects like positional or motif strength bias, is critical in making fair comparisons between competing methods. We explore how to establish the sufficiency of training data for these learning tasks, and we have created a flexible cloud-based framework that permits the rapid exploration of alternative neural network architectures for problems in computational biology. Availability and Implementation: All the models analyzed are available at http://cnn.csail.mit.edu. Contact: gifford@mit.edu Supplementary information: Supplementary data are available at Bioinformatics online. PMID:27307608

  10. Classification of Histology Sections via Multispectral Convolutional Sparse Coding*

    PubMed Central

    Zhou, Yin; Barner, Kenneth; Spellman, Paul

    2014-01-01

    Image-based classification of histology sections plays an important role in predicting clinical outcomes. However this task is very challenging due to the presence of large technical variations (e.g., fixation, staining) and biological heterogeneities (e.g., cell type, cell state). In the field of biomedical imaging, for the purposes of visualization and/or quantification, different stains are typically used for different targets of interest (e.g., cellular/subcellular events), which generates multi-spectrum data (images) through various types of microscopes and, as a result, provides the possibility of learning biological-component-specific features by exploiting multispectral information. We propose a multispectral feature learning model that automatically learns a set of convolution filter banks from separate spectra to efficiently discover the intrinsic tissue morphometric signatures, based on convolutional sparse coding (CSC). The learned feature representations are then aggregated through the spatial pyramid matching framework (SPM) and finally classified using a linear SVM. The proposed system has been evaluated using two large-scale tumor cohorts, collected from The Cancer Genome Atlas (TCGA). Experimental results show that the proposed model 1) outperforms systems utilizing sparse coding for unsupervised feature learning (e.g., PSD-SPM [5]); 2) is competitive with systems built upon features with biological prior knowledge (e.g., SMLSPM [4]). PMID:25554749