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Sample records for effective near-net shape

  1. Near-net-shape titanium alloy extrusions

    SciTech Connect

    Boyer, R.R.; Barta, E.R.; Henderson, J.W.

    1989-03-01

    The Ti-10V-2Fe-3Al has been used in an experimental program involving the development of Ti-alloy extrusion processes capable of achieving surfaces that do not require 100-percent machining. Attention was given to the effects of extrusion temperature and heat treatment on the mechanical properties of the near-net-shape extrusions; in general, the properties of direct-aged materials are found to be sensitive to extrusion temperatures, with tensile strength increasing with extrusion temperature. The double open-hole fatigue strength of extrusion specimens was ascertained. Direct-aged specimens tested at 276 MPa are projected to fail at 100,000 cycles. 7 refs.

  2. 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.

  3. 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.

  4. Production of aluminum-lithium near net shape extruded cylinders

    NASA Technical Reports Server (NTRS)

    Hartley, Paula J.

    1995-01-01

    In the late 1980's, under funding from the Advanced Launch System Program, numerous near net shape technologies were investigated as a means for producing high quality, low cost Aluminum-Lithium (Al-Li) hardware. Once such option was to extrude near net shape barrel panels instead of producing panels by machining thick plate into a final tee-stiffened configuration (which produced up to 90% scrap). This method offers a reduction in the volume of scrap and consequently reduces the buy-to-fly cost. Investigation into this technology continued under Shuttle-C funding where four Al alloys 2219, 2195, 2096, and RX 818 were extruded. Presented herein are the results of that program. Each alloy was successfully extruded at Wyman Gordon, opened and flattened at Ticorm, and solution heat treated and stretched at Reynolds Metals Company. The first two processes were quite successful while the stretching process did offer some challenges. Due to the configuration of the panels and the stretch press set-up, it was difficult to induce a consistent percentage of cold work throughout the length and width of each panel. The effects of this variation will be assessed in the test program to be conducted at a future date.

  5. Electrohydraulic Forming of Near Net Shape Automotive Panels

    SciTech Connect

    2009-01-01

    This factsheet describes a research project whose goal is to develop the electrohydraulic forming (EHF) process as a near net shape automotive panel manufacturing technology that simultaneously reduces the energy embedded in vehicles and the energy consumed while producing automotive structures.

  6. Near Net Shape Manufacturing of New Titanium Powders for Industry

    SciTech Connect

    2009-05-01

    This factsheet describes a research project whose goal is to develop a manufacturing technology to process new titanium powders into fully consolidated near net shape components for industrial applications. This will be achieved using various technologies, including press and sinter, pneumatic isostatic forging (PIF), hot isostatic pressing (HIP), and adiabatic compaction.

  7. Near-Net Shape Powder Metallurgy Rhenium Thruster

    NASA Technical Reports Server (NTRS)

    Leonhardt, Todd; Hamister, Mark; Carlen, Jan C.; Biaglow, James; Reed, Brian

    2001-01-01

    This paper describes the development of a method to produce a near-net shape (NNS) powder metallurgy (PM) rhenium combustion chamber of the size 445 N (100 lbf) used in a high performance liquid apogee engine. These engines are used in low earth Orbit and geostationary orbit for satellite positioning systems. The developments in near-net shape powder metallurgy rhenium combustion chambers reported in this paper will reduce manufacturing cost of the rhenium chambers by 25 percent, and reduce the manufacturing time by 30 to 40 percent. The quantity of rhenium metal powder used to produce a rhenium chamber is reduced by approximately 70 percent and the subsequent reduction in machining schedule and costs is nearly 50 percent.

  8. Near Net Shape production of metal components using LENS

    SciTech Connect

    Schlienger, E.; Dimos, D.; Griffith, M.; Michael, J.; Oliver, M.; Romero, T.; Smugeresky, J.

    1998-03-01

    Rapid Prototyping and Near Net Shape manufacturing technologies are the subject of considerable attention and development efforts. At Sandia National Laboratories, one such effort is LENS (Laser Engineered Net Shaping). The LENS process utilizes a stream of powder and a focused Nd YAG laser to build near net shape fully dense metal parts. In this process, a 3-D solid model is sliced, then an X-Y table is rastered under the beam to build each slice. The laser 1 powder head is incremented upward with each slice and the deposition process is controlled via shuttering of the laser. At present, this process is capable of producing fully dense metal parts of iron, nickel and titanium alloys including tool steels and aluminides. Tungsten components have also been produced. A unique aspect of this process is the ability to produce components wherein the composition varies at differing locations in the part. Such compositional variations may be accomplished in either a stepped or graded fashion. In this paper, the details of the process will be described. The deposition mechanism will be characterized and microstructures and their associated properties will be discussed. Examples of parts which have been produced will be shown and issues regarding dimensional control and surface finish will be addressed.

  9. Electrohydraulic Forming of Near-Net Shape Automotive Panels

    SciTech Connect

    Golovaschenko, Sergey F.

    2013-09-26

    The objective of this project was to develop the electrohydraulic forming (EHF) process as a near-net shape automotive panel manufacturing technology that simultaneously reduces the energy embedded in vehicles and the energy consumed while producing automotive structures. Pulsed pressure is created via a shockwave generated by the discharge of high voltage capacitors through a pair of electrodes in a liquid-filled chamber. The shockwave in the liquid initiated by the expansion of the plasma channel formed between two electrodes propagates towards the blank and causes the blank to be deformed into a one-sided die cavity. The numerical model of the EHF process was validated experimentally and was successfully applied to the design of the electrode system and to a multi-electrode EHF chamber for full scale validation of the process. The numerical model was able to predict stresses in the dies during pulsed forming and was validated by the experimental study of the die insert failure mode for corner filling operations. The electrohydraulic forming process and its major subsystems, including durable electrodes, an EHF chamber, a water/air management system, a pulse generator and integrated process controls, were validated to be capable to operate in a fully automated, computer controlled mode for forming of a portion of a full-scale sheet metal component in laboratory conditions. Additionally, the novel processes of electrohydraulic trimming and electrohydraulic calibration were demonstrated at a reduced-scale component level. Furthermore, a hybrid process combining conventional stamping with EHF was demonstrated as a laboratory process for a full-scale automotive panel formed out of AHSS material. The economic feasibility of the developed EHF processes was defined by developing a cost model of the EHF process in comparison to the conventional stamping process.

  10. 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.

  11. The potential of squeeze casting for the production of near net shape uranium parts

    SciTech Connect

    Robertson, E.

    1993-11-01

    This report was written to provide a detailed summary of a literature survey on the near net shape squeeze casting process. Squeeze casting was evaluated as a possible method for achieving the goals of the LANL program titled Near Net Shape Casting of Uranium for Reduced Environmental, Safety, and Health Impact. In this report the squeeze casting process is reviewed and an assessment of its ability to achieve the near net shape and waste minimization goals of the LANL program is made. It is concluded that although squeeze casting is capable of producing near net shaped parts and reducing the amount of subsequent machining (thereby decreasing wastes), to use the process with uranium would require the design of a unique piece of equipment capable of performing the melting, pouring and squeezing operations in close proximity and in a vacuum.

  12. Near-Net-Shape Processing of Sintered Fibrous Ceramics Achieved

    NASA Technical Reports Server (NTRS)

    Angel, Paul W.

    2000-01-01

    A variety of sintered fibrous ceramic (SFC) materials have been developed over the last 50 years as thermal barrier materials for reentry applications. SFC materials typically exhibit very low thermal conductivities combined with low densities and good thermal stability up to 2500 F. These materials have flown successfully on the space shuttle orbiters since the 1960's. More recently, the McDonnell Douglas Corporation successfully used SFC tiles as a heat shield on the underside of its DC X test vehicle. For both of these applications, tiles are machined from blocks of a specific type of SFC called an alumina-enhanced thermal barrier (AETB). The sizes of these blocks have been limited by the manufacturing process. In addition, as much as 80 to 90 percent of the material can be lost during the machining of tiles with significant amounts of curvature. To address these problems, the NASA Glenn Research Center at Lewis Field entered a cooperative contract with the Boeing Company to develop a vacuum-assisted forming process that can produce large (approximately 4 square feet), severely contoured panels of AETB while saving costs in comparison to the conventional cast-and-machine billet process. For shuttle use, AETB is slurry cast, drained, and fired to form square billets conforming to the shape of the filtration box. The billets are then cut into tiles of the appropriate size for thermally protecting the space shuttle. Processing techniques have limited the maximum size of AETB billets to 21.5 square inches by 6.5-in. thick, but the space shuttles use discrete heat shield tiles no more than 8 to 12 square inches. However, in other applications, large, complex shapes are needed, and the tiling approach is undesirable. For such applications, vacuum-assisted forming can produce large parts with complex shapes while reducing machining waste and eliminating cemented joints between bonded billets. Because it allows contoured shapes to be formed, material utilization is

  13. The potential of centrifugal casting for the production of near net shape uranium parts

    SciTech Connect

    Robertson, E.

    1993-09-01

    This report was written to provide a detailed summary of a literature survey on the near net shape casting process of centrifugal casting. Centrifugal casting is one potential casting method which could satisfy the requirements of the LANL program titled Near Net Shape Casting of Uranium for Reduced Environmental, Safety and Health Impact. In this report, centrifugal casting techniques are reviewed and an assessment of the ability to achieve the near net shape and waste minimization goals of the LANL program by using these techniques is made. Based upon the literature reviewed, it is concluded that if properly modified for operation within a vacuum, vertical or horizontal centrifugation could be used to safely cast uranium for the production of hollow, cylindrical parts. However, for the production of components of geometries other than hollow tubes, vertical centrifugation could be combined with other casting methods such as semi-permanent mold or investment casting.

  14. 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.

  15. Near net shape forming processes for chemically prepared zinc oxide varistors.

    SciTech Connect

    Lockwood, Steven John; Voigt, James A.; Tuttle, Bruce Andrew; Bell, Nelson Simmons

    2005-01-01

    Chemically prepared zinc oxide powders are fabricated for the production of high aspect ratio varistor components. Colloidal processing in water was performed to reduce agglomerates to primary particles, form a high solids loading slurry, and prevent dopant migration. The milled and dispersed powder exhibited a viscoelastic to elastic behavioral transition at a volume loading of 43-46%. The origin of this transition was studied using acoustic spectroscopy, zeta potential measurements and oscillatory rheology. The phenomenon occurs due to a volume fraction solids dependent reduction in the zeta potential of the solid phase. It is postulated to result from divalent ion binding within the polyelectrolyte dispersant chain, and was mitigated using a polyethylene glycol plasticizing additive. Chemically prepared zinc oxide powders were processed for the production of high aspect ratio varistor components. Near net shape casting methods including slip casting and agarose gelcasting were evaluated for effectiveness in achieving a uniform green microstructure achieving density values near the theoretical maximum during sintering. The structure of the green parts was examined by mercury porisimetry. Agarose gelcasting produced green parts with low solids loading values and did not achieve high fired density. Isopressing the agarose cast parts after drying raised the fired density to greater than 95%, but the parts exhibited catastrophic shorting during electrical testing. Slip casting produced high green density parts, which exhibited high fired density values. The electrical characteristics of slip cast parts are comparable with dry pressed powder compacts. Alternative methods for near net shape forming of ceramic dispersions were investigated for use with the chemically prepared ZnO material. Recommendations for further investigation to achieve a viable production process are presented.

  16. Mechanical Properties of Cold Gas Dynamic-Sprayed Near-Net-Shaped Fin Arrays

    NASA Astrophysics Data System (ADS)

    Cormier, Yannick; Dupuis, Philippe; Jodoin, Bertrand; Corbeil, Antoine

    2015-02-01

    This work focuses on the study of the adhesion and thermal performance of near-net-shaped pyramidal fin arrays manufactured by cold spray on aluminum alloy substrate coated with various bond coats: a cold-sprayed bond coat as well as nitrogen- and air-propelled arc-sprayed bond coats. Furthermore, the effects of the fin density, fin height, and substrate surface roughness on the adhesion strength of the fins deposited on Al6061 substrates were characterized. It was found that the fin density, the fin height, and the substrate roughness have little impact on the adhesion strength of this system. The adhesion strength was found to be inversely proportional to the surface hardness when investigating these parameters for the different thermal-spray bond coatings, with all the fin systems having a much greater strength than the theoretical application stresses. Finally, it was found that the increase in the fin's base layer's roughness increases the overall heat transfer, with the bond coat material having a negligible effect on the thermal resistance for this type of heat-exchanger configuration.

  17. 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.

  18. Near-net-shape manufacturing: Spray-formed metal matrix composites and tooling

    NASA Technical Reports Server (NTRS)

    Mchugh, Kevin M.

    1994-01-01

    Spray forming is a materials processing technology in which a bulk liquid metal is converted to a spray of fine droplets and deposited onto a substrate or pattern to form a near-net-shape solid. The technology offers unique opportunities for simplifying materials processing without sacrificing, and oftentimes substantially improving, product quality. Spray forming can be performed with a wide range of metals and nonmetals, and offers property improvements resulting from rapid solidification (e.g. refined microstructures, extended solid solubilities and reduced segregation). Economic benefits result from process simplification and the elimination of unit operations. The Idaho National Engineering Laboratory is developing a unique spray-forming method, the Controlled Aspiration Process (CAP), to produce near-net-shape solids and coatings of metals, polymers, and composite materials. Results from two spray-accompanying technical and economic benefits. These programs involved spray forming aluminum strip reinforced with SiC particulate, and the production of tooling, such as injection molds and dies, using low-melting-point metals.

  19. The near-net-shape manufacturing of affordable titanium components for the M777 lightweight howitzer

    NASA Astrophysics Data System (ADS)

    Klug, Kevin L.; Ucok, Ibrahim; Gungor, Mehmet N.; Guclu, Mustafa; Kramer, Lawrence S.; Tack, Wm. Troy; Nastac, Laurentiu; Martin, Nicholas R.; Dong, Hao; Pickens, Joseph R.

    2004-11-01

    The U.S. Marines’ and U.S. Army’s next-generation, titanium-intensive M777 howitzer offers reduced weight, increased mobility, and improved survivability over its aging, M198 steel-based predecessor. The National Center for Excellence in Metalworking Technology (NCEMT), operated by Concurrent Technologies Corporation, is helping to meet M777 program goals for cost, performance, and production schedule by developing near-net-shape manufacturing routes for traditionally machined and welded components. Under two projects sponsored by the Navy Manufacturing Technology Program, the NCEMT has developed investment cast spade and saddle components as well as flowformed tubes and forged bell housings. This paper summarizes the results of the two ongoing projects.

  20. 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.

  1. 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

  2. Characterization of Al-Cu-Li Alloy 2090 Near Net Shape Extrusion

    NASA Technical Reports Server (NTRS)

    Birt, M. J.; Domack, M. S.; Hafley, R. A.; Pollock, W. D.

    1998-01-01

    Aluminum-lithium (Al-Li) alloys near net shape extrusions are being evaluated for potential application in launch vehicle structures. The objective of this study was to determine tensile and fracture properties, corrosion resistance, and weldability of integrally stiffened panels of Al-Cu-Li alloy 2090 in the T8 temper. The microstructure was pre-dominantly unrecrystallized. Texture analyses revealed the presence of fiber components in the stiffeners and a combination of fiber and rolling components in the skin. Variations in grain morphology and texture through the extruded cross section were correlated with the tensile, fracture, and corrosion behavior. Tensile strengths at room and cryogenic temperatures of the 2090 extrusions were similar to other 2090 product forms and were higher than 2219-T87, the primary structural material in the Space Shuttle external tank; however, ductilities were lower. The fracture resistance of the 2090 extrusion was lower than 2219-T87 plate at room temperature. At cryogenic temperatures, tensile ductility and fracture behavior of the 2090 extrusion were similar to other 2090 product forms but were lower than 2219-T87 plate. The exfoliation and stress corrosion resistance of the 2090 extrusion compared favorably with the characteristics of other 2090 product forms. The weldability and weldment properties of the extrusions were similar to 2090 and 2219 plates.

  3. Properties of near-net shape metallic components made by the directed light fabrication process

    SciTech Connect

    Lewis, G.K.; Milewski, J.O.; Thoma, D.B.; Nemec, R.B.

    1997-10-01

    Directed Light Fabrication (DLF) is a process invented at Los Alamos National Laboratory that can be used to fuse any metal powder directly to a fully dense, near-net shape component with full structural integrity. A solid model design of a desired component is first developed on a computer work station. A motion path, produced from the solid model definition, is translated to actual machine commands through a post-processor, specific to the deposition equipment. The DLF process uses a multi-axis positioning system to move the laser focal zone over the part cross section defined by the part boundaries and desired layer thickness. Metal powders, delivered in an argon stream, enter the focal zone where they melt and continuously form a molten pool of material that moves with the laser focal spot. Position and movement of the spot is controlled through the post-processor. Successive cross-sectional layers are added by advancing the spot one layer thickness beyond the previous layer until the entire part is deposited. The system has 4 powder feeders attached for co-deposition of multiple materials to create alloys at the focal zone or form dissimilar metal joint combinations by changing powder composition from one material to another. Parts produced by the DLF process vary in complexity from simple bulk solid forms to detailed components fabricated from difficult to process metals and alloys. Parts have been deposited at rates up to 33 cm{sup 3}/hr with 12 cm{sup 3}/hr more typical. Feasibility of processing any metal ranging in melting point from aluminium to tungsten has been demonstrated. Mechanical properties for bulk DLF deposits of three alloy powders were measured for this study. Ti-6Al-4V and 316 stainless steel powders were fabricated into rectangular bar, and Inconel 690 powder was fabricated into a solid cylinder.

  4. Near-Net-Shape Production of Hollow Titanium Alloy Components via Electrochemical Reduction of Metal Oxide Precursors in Molten Salts

    NASA Astrophysics Data System (ADS)

    Hu, Di; Xiao, Wei; Chen, George Z.

    2013-04-01

    Metal oxide precursors (ca. 90 wt pct Ti, 6 wt pct Al, and 4 wt pct V) were prepared with a hollow structure in various shapes such as a sphere, miniature golf club head, and cup using a one-step solid slip-casting process. The precursors were then electro-deoxidized in molten calcium chloride [3.2 V, 1173 K (900 °C)] against a graphite anode. After 24 hours of electrolysis, the near-net-shape Ti-6Al-4V product maintained its original shape with controlled shrinkage. Oxygen contents in the Ti-6Al-4V components were typically below 2000 ppm. The maximum compressive stress and modulus of electrolytic products obtained in this work were approximately 243 MPa and 14 GPa, respectively, matching with the requirement for medical implants. Further research directions are discussed for mechanical improvement of the products via densification during or after electrolysis. This simple, fast, and energy-efficient near-net-shape manufacturing method could allow titanium alloy components with desired geometries to be prepared directly from a mixture of metal oxides, promising an innovative technology for the low-cost production of titanium alloy components.

  5. Superplastic deformation in carbonate apatite ceramics under constant compressive loading for near-net-shape production of bioresorbable bone substitutes.

    PubMed

    Adachi, Masanori; Wakamatsu, Nobukazu; Doi, Yutaka

    2008-01-01

    To produce carbonate apatite (CAP) ceramics with the desired complex shapes using superplastic deformation, deformation behavior of CAP ceramics under constant loading as well as physical properties after deformation were evaluated. Sintered CAP ceramics were plastically deformed in an electric furnace attached to a universal hydraulic testing machine under a constant load. CAP ceramics subjected to an initial compressive pressure of 10 MPa showed an appreciable amount of plastic deformation at temperatures ranging from 720 to 800 degrees C. Plastic deformation increased with increasing temperature from about 10% to 70% after two hours of loading. X-ray diffraction analysis and SEM observation further revealed that some CAP crystals were elongated and aligned with the c-axis normal to the loading direction during superplastic deformation. It was thus concluded that a marked plastic deformation of about 70% at 800 degrees C would be sufficient for near-net-shape production of bioresorbable CAP bone substitutes with complex shapes.

  6. Catalogue of X-Ray Texture Data for Al-Cu-Li Alloy 1460, 2090, 2096 and 2195 Near-Net-Shape Extrusions, Sheet and Plate

    NASA Technical Reports Server (NTRS)

    Hales, Stephen J.; Hafley, Robert A.; Alexa, Joel A.

    1998-01-01

    The effect of crystallographic texture on the mechanical properties of near-net-shape extrusions is of major interest ff these products are to find application in launch vehicle or aircraft structures. The objective of this research was to produce a catalogue containing quantitative texture information for extruded product, sheet and plate. The material characterized was extracted from wide, integrally stiffened panels fabricated from the Al-Cu-Li alloys 1460, 2090, 2096 and 2195. The textural characteristics of sheet and plate products of the same alloys were determined for comparison purposes. The approach involved using X-ray diffraction to generate pole figures in combination with orientation distribution function analysis. The data were compiled as a function of location in the extruded cross-sections and the variation in the major deformation- and recrystallization-related texture components was identified.

  7. 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.

  8. A novel one-pot process for near-net-shape fabrication of open-porous resorbable hydroxyapatite/protein composites and in vivo assessment.

    PubMed

    Mueller, Berit; Koch, Dietmar; Lutz, Rainer; Schlegel, Karl A; Treccani, Laura; Rezwan, Kurosch

    2014-09-01

    We present a mild one-pot freeze gelation process for fabricating near-net, complex-shaped hydroxyapatite scaffolds and to directly incorporate active proteins during scaffold processing. In particular, the direct protein incorporation enables a simultaneous adjustment and control of scaffold microstructure, porosity, resorbability and enhancement of initial mechanical and handling stability. Two proteins, serum albumin and lysozyme, are selected and their effect on scaffold stability and microstructure investigated by biaxial strength tests, electron microscopy, and mercury intrusion porosimetry. The resulting hydroxyapatite/protein composites feature adjustable porosities from 50% to 70% and a mechanical strength ranging from 2 to 6 MPa comparable to that of human spongiosa without any sintering step. Scaffold degradation behaviour and protein release are assessed by in vitro studies. A preliminary in vivo assessment of scaffold biocompatibility and resorption behaviour in adult domestic pigs is discussed. After implantation, composites were resorbed up to 50% after only 4 weeks and up to 65% after 8 weeks. In addition, 14% new bone formation after 4 weeks and 37% after 8 weeks were detected. All these investigations demonstrate the outstanding suitability of the one-pot-process to create, in a customisable and reliable way, biocompatible scaffolds with sufficient mechanical strength for handling and surgical insertion, and for potential use as biodegradable bone substitutes and versatile platform for local drug delivery.

  9. A novel one-pot process for near-net-shape fabrication of open-porous resorbable hydroxyapatite/protein composites and in vivo assessment.

    PubMed

    Mueller, Berit; Koch, Dietmar; Lutz, Rainer; Schlegel, Karl A; Treccani, Laura; Rezwan, Kurosch

    2014-09-01

    We present a mild one-pot freeze gelation process for fabricating near-net, complex-shaped hydroxyapatite scaffolds and to directly incorporate active proteins during scaffold processing. In particular, the direct protein incorporation enables a simultaneous adjustment and control of scaffold microstructure, porosity, resorbability and enhancement of initial mechanical and handling stability. Two proteins, serum albumin and lysozyme, are selected and their effect on scaffold stability and microstructure investigated by biaxial strength tests, electron microscopy, and mercury intrusion porosimetry. The resulting hydroxyapatite/protein composites feature adjustable porosities from 50% to 70% and a mechanical strength ranging from 2 to 6 MPa comparable to that of human spongiosa without any sintering step. Scaffold degradation behaviour and protein release are assessed by in vitro studies. A preliminary in vivo assessment of scaffold biocompatibility and resorption behaviour in adult domestic pigs is discussed. After implantation, composites were resorbed up to 50% after only 4 weeks and up to 65% after 8 weeks. In addition, 14% new bone formation after 4 weeks and 37% after 8 weeks were detected. All these investigations demonstrate the outstanding suitability of the one-pot-process to create, in a customisable and reliable way, biocompatible scaffolds with sufficient mechanical strength for handling and surgical insertion, and for potential use as biodegradable bone substitutes and versatile platform for local drug delivery. PMID:25063103

  10. Development of a near-net-shape casting technology for the U-6Nb alloy. Part 1: Materials characterization, experiment design, and model construction

    SciTech Connect

    Taylor, M.J.; Keeney, J.A.; Wendel, M.W.; Demint, A.L.

    1997-01-01

    The Oak Ridge Y-12 Plant (Y-12) is conducting highly coupled experimental and numerical studies to develop the technology needed to produce near-net-shape (NNS)-cast uranium-6 wt% niobium (U-6Nb) components which have a controlled carbon content. Current activities are focused on defining mechanical and metallurgical properties of cast material; experimental studies to define NNS casting, carbide particle flotation, and immersion-quench physics; and developing the numerical models needed to support the optimized design of NNS components. This paper summarizes the material characterization, experiment design, and model development activities.

  11. Producing Zirconium Diboride Components with Complex, Near-Net Shape Geometries by Aqueous Room-Temperature Injection Molding

    NASA Technical Reports Server (NTRS)

    Wiesner, Valerie L.; Youngblood, Jeffrey; Trice, Rodney

    2014-01-01

    Room-temperature injection molding is proposed as a novel, low-cost and more energy efficient manufacturing process capable of forming complex-shaped zirconium diboride (ZrB2) parts. This innovative processing method utilized aqueous suspensions with high powder loading and a minimal amount (5 vol.) of water-soluble polyvinylpyrrolidone (PVP), which was used as a viscosity modifier. Rheological characterization was performed to evaluate the room-temperature flow properties of ZrB2-PVP suspensions. ZrB2 specimens were fabricated with high green body strength and were machinable prior to binder removal despite their low polymer content. After binder burnout and pressureless sintering, the bulk density and microstructure of specimens were characterized using Archimedes technique and scanning electron microscopy. X-Ray Diffraction was used to determine the phase compositions present in sintered specimens. Ultimate strength of sintered specimens will be determined using ASTM C1323-10 compressive C-ring test.

  12. Final report to the strategic environmental research and development program on near-net shape casting of uranium-6% niobium alloys

    SciTech Connect

    Gourdin, W.H.

    1996-01-01

    Fabrication methods traditionally used in the fabrication of depleted uranium parts within the Department of Energy (DOE) are extremely wasteful, with only 3% of the starting material actually appearing as finished product. The current effort, funded by the Strategic Environmental Research and Development Program (SERDP) at Los Alamos National Laboratory (LANL), Sandia National Laboratories, Albuquerque (SNLA), and Lawrence Livermore National Laboratory (LLNL), was conceived as a means to drastically reduce this inefficiency and the accompanying waste by demonstrating the technology to cast simple parts close to their final shape in molds made from a variety of materials. As a part of this coordinated study, LLNL was given, and has achieved, two primary objectives: (1) to demonstrate the feasibility of using refractory metal for reusable molds in the production of castings of uranium-6 wt% niobium alloy (U-6Nb); and (2) to demonstrate the utility of detailed simulations of thermal and fluid flow characteristics in the understanding and improvement of the near-net shape casting process. In both cases, our efforts were focused on a flat plate castings, which serve as simple prototypical parts. This report summarizes the results of LLNL work in each area.

  13. Near-Net Forging Technology Demonstration Program

    NASA Technical Reports Server (NTRS)

    Hall, I. Keith

    1996-01-01

    Significant advantages in specific mechanical properties, when compared to conventional aluminum (Al) alloys, make aluminum-lithium (Al-Li) alloys attractive candidate materials for use in cryogenic propellant tanks and dry bay structures. However, the cost of Al-Li alloys is typically five times that of 2219 aluminum. If conventional fabrication processes are employed to fabricate launch vehicle structure, the material costs will restrict their utilization. In order to fully exploit the potential cost and performance benefits of Al-Li alloys, it is necessary that near-net manufacturing methods be developed to off-set or reduce raw material costs. Near-net forging is an advanced manufacturing method that uses elevated temperature metal movement (forging) to fabricate a single piece, near-net shape, structure. This process is termed 'near-net' because only a minimal amount of post-forge machining is required. The near-net forging process was developed to reduce the material scrap rate (buy-to-fly ratio) and fabrication costs associated with conventional manufacturing methods. The goal for the near-net forging process, when mature, is to achieve an overall cost reduction of approximately 50 percent compared with conventional manufacturing options for producing structures fabricated from Al-Li alloys. This NASA Marshall Space Flight Center (MSFC) sponsored program has been a part of a unique government / industry partnership, coordinated to develop and demonstrate near-net forging technology. The objective of this program was to demonstrate scale-up of the near-net forging process. This objective was successfully achieved by fabricating four integrally stiffened, 170- inch diameter by 20-inch tall, Al-Li alloy 2195, Y-ring adapters. Initially, two 2195 Al-Li ingots were converted and back extruded to produce four cylindrical blockers. Conventional ring rolling of the blockers was performed to produce ring preforms, which were then contour ring rolled to produce

  14. Some Metallurgical Issues Concerning Austenite Conditioning in Nb-Ti and Nb-Mo Microalloyed Steels Processed by Near-Net-Shape Casting and Direct Rolling Technologies

    NASA Astrophysics Data System (ADS)

    López, Beatriz; Rodriguez-Ibabe, Jose M.

    2016-08-01

    As thin slab direct rolling technologies are moving to the production of higher quality steel grades, chemical compositions based on Nb-Ti and Nb-Mo become a good option. However, with the use of multiple microalloying additions, the as-cast austenite conditioning becomes more complex. This paper analyzes some of the microstructural features that should be taken into account during the as-cast austenite conditioning in Nb-Ti and Nb-Mo microalloyed steel grades. In the case of Nb-Ti grades, it has been observed that the process parameters during solidification and post-solidification steps affect the austenite evolution during hot rolling. This is due to the differences in the size and volume fraction of TiN particles that can be formed. Fine TiN precipitates have been shown to be able to delay recrystallization kinetics. Moreover, the solute drag effect of Ti cannot be ignored in the case of hyperstoichiometric Ti/N ratios. It is observed that Nb-Ti grades tend to have lower non-recrystallization temperatures compared to Nb grades, which means that pancaking of the austenite is more difficult for these steels. The opposite is observed for the Nb-Mo grades, although in both cases the behavior is affected by the nominal content of Nb.

  15. Near Net Manufacturing Using Thin Gage Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Takeshita, Jennifer; Potter, David; Holquin, Michael

    2006-01-01

    Friction Stir Welding (FSW) and near net spin forming of FSW aluminumn blanks were investigated for large-scale pressure vessel applications. With a specific focus on very thin gage 2xxx and 7xxx aluminum alloys, the program concentrated on the following: the criteria used for material selection, a potential manufacturing flow, and the effectiveness and associated risks of near net spin forming. Discussion will include the mechanical properties of the friction stir welds and the parent material from before and after the spin forming process. This effort was performed under a NASA Space Exploration initiative focused on increasing the affordability, reliability and performance of pressure vessels larger than 10 ft. diameter.

  16. Near net shape processing of continuous lengths of superconducting wire

    DOEpatents

    Danyluk, Steven; McNallan, Michael; Troendly, Robert; Poeppel, Roger; Goretta, Kenneth; Lanagan, Michael

    1997-01-01

    A system and method for mechanically forming a ceramic superconductor product. A system for making the ceramic superconductor includes a metallic channel portion having a cross section for receiving a ceramic superconductor powder, a roll to mechanically reduce the channel cross section and included superconductor powder and a cap portion welded to the channel portion using a localized high energy source. The assembled bar is then mechanically reduced to form a tape or wire end product.

  17. Near net shape processing of continuous lengths of superconducting wire

    DOEpatents

    Danyluk, S.; McNallan, M.; Troendly, R.; Poeppel, R.; Goretta, K.; Lanagan, M.

    1997-08-26

    A system and method for mechanically forming a ceramic superconductor product are disclosed. A system for making the ceramic superconductor includes a metallic channel portion having a cross section for receiving a ceramic superconductor powder, a roll to mechanically reduce the channel cross section and included superconductor powder and a cap portion welded to the channel portion using a localized high energy source. The assembled bar is then mechanically reduced to form a tape or wire end product. 9 figs.

  18. Heavy metals processing near-net-forming summary progress report

    SciTech Connect

    Watson, L.D.; Thompson, J.E.

    1994-09-01

    This study utilized a converging-diverging nozzle to spray-form an alloy having a weight percent composition of 49.6% iron, 49.6% tungsten, and 0.8% carbon into samples for analysis. The alloy was a surrogate that displayed metallurgical characteristics similar to the alloys used in the heavy metals processing industry. US DOE facilities are evaluating advanced technologies which can simplify component fabrication, reduce handling steps, and minimize final machining. The goal of producing net-shaped components can be approached from several directions. In spray forming, molten metal is converted by a nozzle into a plume of fine droplets which quickly cool in flight and solidify against a substrate. The near-final dimension product that is formed receives additional benefits from rapid solidification. This single-step processing approach would aid the heavy metals industry by streamlining fabrication, improving production yields, and minimizing the generation of processing wastes. This Program effort provided a large selection of as-sprayed specimens. These samples were sprayed with gas-to-metal mass ratios ranging from 0.8:1 to 4:1. Samples targeted for analysis were produced from different spray conditions. Metallography on some samples revealed areas that were fully dense and homogeneous at 5,000X. These areas averaged grain sizes of 1 micron diameter. Other samples when viewed at 2,000X were highly segregated in the 10 micron diameter range. Deposit efficiencies of greater than 90% were demonstrated using the untailored spray system. Discharge gases were analyzed and two categories of particles were identified. One category of particle had a chemical composition characteristic of the alloy being sprayed and the second type of particle had a chemical composition characteristic of the ceramics used in the spray system component fabrication. Particles ranged in size from 0.07 to 3 microns in diameter. 8 refs., 67 figs., 20 tabs.

  19. Reaction-Forming Method for Producing Near Net-Shape Refractory Metal Carbides

    SciTech Connect

    Palmisiano, Marc N.; Jakubenas, Kevin J.; Baranwal, Rita

    2004-07-20

    A method for reaction forming refractory metal carbides. The method involves the fabrication of a glassy carbon preform by casting an organic, resin-based liquid mixture into a mold and subsequently heat treating it in two steps, which cures and pyrolizes the resin resulting in a porous carbon preform. By varying the amounts of the constituents in the organic, resin-based liquid mixture, control over the density of the carbon preform is obtained. Control of the density and microstructure of the carbon preform allows for determination of the microstructure and properties of the refractory metal carbide material produced. The glassy carbon preform is placed on a bed of refractory metal or refractory metal--silicon alloy. The pieces are heated above the melting point of the metal or alloy. The molten metal wicks inside the porous carbon preform and reacts, forming the refractory metal carbide or refractory metal carbide plus a minor secondary phase.

  20. Chemically Induced Solidification: A New Way to Produce Thin Solid-Near-Net Shapes

    NASA Astrophysics Data System (ADS)

    Slater, Carl; Spooner, Stephen; Davis, Claire; Sridhar, Seetharaman

    2016-09-01

    In situ observation of the solidification of high-carbon steel (4 wt pct C) through decarburization has been carried out as a feasibility study into reducing high-power usage and high CO2 production involved in steel making. Decarburization has been carried out under both air and pure N2 atmospheres at temperatures of 1573 K and 1673 K (1300 °C and 1400 °C). A solidified shell of around 500 μm was formed with carbon concentrations reduced down to 1 pct in as short as 18 seconds.

  1. Towards robust and effective shape modeling: sparse shape composition.

    PubMed

    Zhang, Shaoting; Zhan, Yiqiang; Dewan, Maneesh; Huang, Junzhou; Metaxas, Dimitris N; Zhou, Xiang Sean

    2012-01-01

    Organ shape plays an important role in various clinical practices, e.g., diagnosis, surgical planning and treatment evaluation. It is usually derived from low level appearance cues in medical images. However, due to diseases and imaging artifacts, low level appearance cues might be weak or misleading. In this situation, shape priors become critical to infer and refine the shape derived by image appearances. Effective modeling of shape priors is challenging because: (1) shape variation is complex and cannot always be modeled by a parametric probability distribution; (2) a shape instance derived from image appearance cues (input shape) may have gross errors; and (3) local details of the input shape are difficult to preserve if they are not statistically significant in the training data. In this paper we propose a novel Sparse Shape Composition model (SSC) to deal with these three challenges in a unified framework. In our method, a sparse set of shapes in the shape repository is selected and composed together to infer/refine an input shape. The a priori information is thus implicitly incorporated on-the-fly. Our model leverages two sparsity observations of the input shape instance: (1) the input shape can be approximately represented by a sparse linear combination of shapes in the shape repository; (2) parts of the input shape may contain gross errors but such errors are sparse. Our model is formulated as a sparse learning problem. Using L1 norm relaxation, it can be solved by an efficient expectation-maximization (EM) type of framework. Our method is extensively validated on two medical applications, 2D lung localization in X-ray images and 3D liver segmentation in low-dose CT scans. Compared to state-of-the-art methods, our model exhibits better performance in both studies. PMID:21963296

  2. Shape effects on asteroid spectra

    NASA Astrophysics Data System (ADS)

    Davalos, J.; Carvano, J.

    2014-07-01

    The objective of this work is to probe how the shape of a body like an asteroid could be modifying its observed spectra and the derived mineralogical interfaces based on spectral modeling. To model this effect, we construct an oblate ellipsoid with triangular facets, where each facet contributes to the overall reflectance. The synthetic spectra is generated by the isotropic multiple-scattering approximation (IMSA) reflectance model of Hapke (1993). First, we obtained optical constants by inverting the spectra of meteorites, obtained from the RELAB spectral database. These optical constants were found inverting the reflectance bidirectional equation of Hapke; this is made in two steps: (i) The first inversion is to find the single-scattering albedo π (ii) in the model of Hapke, this albedo is found under the regime of the geometric optics, where the particle size is much larger than the wavelength of the incident radiation. Here we assumed a constant value for the real part of the optical constant n=1.5. With these optical constants, we can construct synthetic spectra for any particle size. The phase function used is the double Henyey-Greenstein phase function and an accurate expression for the H-functions. We started with the ellipsoidal shape a=1.0, b=c=0.5 for two particle size 50 and 250 μ m, in this part, we found good differences in the BAR parameter between the two geometric models, this was done for 100 Eucrite meteorites spectra. In this first study, we found that the BAR parameter between the two models is bigger when the particle size increases. In the second part, we started with different ellipsoidal shapes and produced synthetic spectra for material with eucrite and diogenite composition with a phase angle of 20 degrees, incidence and emission angles of 10 degrees, and particle size at 250 μ m. All spectra was generated for four parameters of phase angle b=[0.2,0.4,0.6,0.8] taking the empirical relation between the phase constants of Hapke (2012

  3. Triple shape memory effect of star-shaped polyurethane.

    PubMed

    Yang, Xifeng; Wang, Lin; Wang, Wenxi; Chen, Hongmei; Yang, Guang; Zhou, Shaobing

    2014-05-14

    In this study, we synthesized one type of star-shaped polyurethane (SPU) with star-shaped poly(ε-caprolactone) (SPCL) containing different arm numbers as soft segment and 4,4'-diphenyl methane diisocyanate (MDI) as well as chain extender 1,4-butylene glycol (BDO) as hard segment. Proton nuclear magnetic resonance (1H-NMR) confirmed the chemical structure of the material. Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) results indicated that both the melting temperature (Tm) and transition temperature (Ttrans) of SPU decreased with the hard segment composition increase. X-ray diffraction (XRD) results demonstrated that the increase of the crystallinity of SPU following the raised arm numbers endowed a high shape fixity of six-arm star-shaped polyurethane (6S-PU) and a wide melting temperature range, which resulted in an excellent triple-shape memory effect of 6S-PU. The in vitro cytotoxicity assay evaluated with osteoblasts through Alamar blue assay demonstrates that this copolymer possessed good cytocompatibility. This material can be potentially used as a new smart material in the field of biomaterials.

  4. Energy performance of net-zero and near net-zero energy homes in New England

    NASA Astrophysics Data System (ADS)

    Thomas, Walter D.

    Net-Zero Energy Homes (NZEHs) are homes that consume no more energy than they produce on site during the course of a year. They are well insulated and sealed, use energy efficient appliances, lighting, and mechanical equipment, are designed to maximize the benefits from day lighting, and most often use a combination of solar hot water, passive solar and photovoltaic (PV) panels to produce their on-site energy. To date, NZEHs make up a miniscule percentage of homes in the United States, and of those, few have had their actual performance measured and analyzed once built and occupied. This research focused on 19 NZEHs and near net-zero energy homes (NNZEHs) built in New England. This set of homes had varying designs, numbers of occupants, and installed technologies for energy production, space heating and cooling, and domestic hot water systems. The author worked with participating homeowners to collect construction and systems specifications, occupancy information, and twelve months of energy consumption, production and cost measurements, in order to determine whether the homes reached their respective energy performance design goals. The author found that six out of ten NZEHs achieved net-zero energy or better, while all nine of the NNZEHs achieved an energy density (kWh/ft 2/person) at least half as low as the control house, also built in New England. The median construction cost for the 19 homes was 155/ft 2 vs. 110/ft2 for the US average, their average monthly energy cost was 84% below the average for homes in New England, and their estimated CO2 emissions averaged 90% below estimated CO2 emissions from the control house. Measured energy consumption averaged 14% below predictions for the NZEHs and 38% above predictions for the NNZEHs, while generated energy was within +/- 10% of predicted for 17 out of 18 on-site PV systems. Based on these results, the author concludes that these types of homes can meet or exceed their designed energy performance (depending on

  5. Smart polymer fibers with shape memory effect

    NASA Astrophysics Data System (ADS)

    Ji, Feng Long; Zhu, Yong; Lian Hu, Jin; Liu, Yan; Yeung, Lap-Yan; Dou Ye, Guang

    2006-12-01

    In this study, a series of smart polymer fibers with a shape memory effect were developed. Firstly, a set of shape memory polyurethanes with varying hard-segment content were synthesized. Then, the solutions of the shape memory polyurethanes were spun into fibers through wet spinning. The thin films of the polyurethanes were considered to represent the nature of the polyurethanes. Differential scanning calorimetry tests were performed on both the thin films and the fibers to compare their thermal properties. Wide angle x-ray diffraction and small angle x-ray scattering techniques were applied to investigate the structure of the thin films and the fibers, and the structure change taking place in the spinning process was therefore revealed. The spinning process resulted in the polyurethane molecules being partially oriented in the direction of the fiber axis. The molecular orientation prompted the aggregation of the hard segments and the formation of hard-segment microdomains. The mechanical properties of the fibers were examined through tensile tests. The shape memory effect of the thin films and the fibers was investigated through a series of thermomechanical cyclic tensile tests. It was found that the fibers showed less shape fixity but more shape recovery compared with the thin films. Further investigations revealed that the recovery stress of the fibers was higher than that of the thin films. The smart fibers may exert the recovery force of shape memory polymers to an extreme extent in the direction of the fiber axis and therefore provide a possibility for producing high-performance actuators.

  6. Shape memory effect in Cu nanowires.

    PubMed

    Liang, Wuwei; Zhou, Min; Ke, Fujiu

    2005-10-01

    A rubber-like pseudoelastic behavior is discovered in single-crystalline face-centered-cubic (FCC) Cu nanowires in atomistic simulations. Nonexistent in bulk Cu, this phenomenon is associated primarily with a reversible crystallographic lattice reorientation driven by the high surface-stress-induced internal stresses due to high surface-to-volume ratios at the nanoscale level. The temperature-dependence of this behavior leads to a shape memory effect (SME). Under tensile loading and unloading, the nanowires exhibit recoverable strains up to over 50%, well beyond the typical recoverable strains of 5-8% for most bulk shape memory alloys (SMAs). This behavior is well-defined for wires between 1.76 and 3.39 nm in size over the temperature range of 100-900 K.

  7. Molecular Shape and the Hydrophobic Effect

    NASA Astrophysics Data System (ADS)

    Hillyer, Matthew B.; Gibb, Bruce C.

    2016-05-01

    This review focuses on papers published since 2000 on the topic of the properties of solutes in water. More specifically, it evaluates the state of the art of our understanding of the complex relationship between the shape of a hydrophobe and the hydrophobic effect. To highlight this, we present a selection of references covering both empirical and molecular dynamics studies of small (molecular-scale) solutes. These include empirical studies of small molecules, synthetic hosts, crystalline monolayers, and proteins, as well as in silico investigations of entities such as idealized hard and soft spheres, small solutes, hydrophobic plates, artificial concavity, molecular hosts, carbon nanotubes and spheres, and proteins.

  8. Mechanocaloric effects in shape memory alloys.

    PubMed

    Mañosa, Lluís; Planes, Antoni

    2016-08-13

    Shape memory alloys (SMA) are a class of ferroic materials which undergo a structural (martensitic) transition where the associated ferroic property is a lattice distortion (strain). The sensitiveness of the transition to the conjugated external field (stress), together with the latent heat of the transition, gives rise to giant mechanocaloric effects. In non-magnetic SMA, the lattice distortion is mostly described by a pure shear and the martensitic transition in this family of alloys is strongly affected by uniaxial stress, whereas it is basically insensitive to hydrostatic pressure. As a result, non-magnetic alloys exhibit giant elastocaloric effects but negligible barocaloric effects. By contrast, in a number of magnetic SMA, the lattice distortion at the martensitic transition involves a volume change in addition to the shear strain. Those alloys are affected by both uniaxial stress and hydrostatic pressure and they exhibit giant elastocaloric and barocaloric effects. The paper aims at providing a critical survey of available experimental data on elastocaloric and barocaloric effects in magnetic and non-magnetic SMA.This article is part of the themed issue 'Taking the temperature of phase transitions in cool materials'.

  9. The Effect of Shape Memory on Red Blood Cell Motions

    NASA Astrophysics Data System (ADS)

    Niu, Xiting; Shi, Lingling; Pan, Tsorng-Whay; Glowinski, Roland

    2013-11-01

    An elastic spring model is applied to study the effect of the shape memory on the motion of red blood cell in flows. In shear flow, shape memory also plays an important role to obtain all three motions: tumbling, swinging, and tank-treading. In Poiseuille flow, cell has an equilibrium shape as a slipper or parachute depending on capillary number. To ensure the tank-treading motion while in slippery shape, a modified model is proposed by introducing a shape memory coefficient which describes the degree of shape memory in cells. The effect of the coefficient on the cell motion of red blood cell will be presented.

  10. Shape memory effect of the Ni-Ti-Hf high temperature shape memory alloy

    SciTech Connect

    Wu, K.H.; Pu, Z.; Tseng, H.K.; Biancaniello, F.S.

    1995-11-17

    The one-way shape memory effect of the newly-developed TiNi-Hf high temperature shape memory alloys has been investigated. The results of the study show that TiNi-Hf high temperature alloys possess a relatively high shape memory effect. All the alloys, even those with an Hf content as high as 30at%, exhibit complete strain recovery behavior. However, as the Hf content increases, the fully reversible strain of the alloys decreases. The increase of the second phase as the Hf content increases is the primary reason for the deterioration of the shape memory effect and ductility. The shape memory properties also deteriorate as the deformation temperature increases.

  11. Solvent-driven temperature memory and multiple shape memory effects.

    PubMed

    Xiao, Rui; Guo, Jingkai; Safranski, David L; Nguyen, Thao D

    2015-05-28

    Thermally-activated temperature memory and multiple shape memory effects have been observed in amorphous polymers with a broad glass transition. In this work, we demonstrate that the same shape recovery behaviors can also be achieved through solvent absorption. We investigate the recovery behaviors of programmed Nafion membranes in various solvents and compare the solvent-driven and temperature-driven shape recovery response. The results show that the programming temperature and solvent type have a corresponding strong influence on the shape recovery behavior. Specifically, lower programming temperatures induce faster initial recovery rates and larger recovery, which is known as the temperature memory effect. The temperature memory effect can be used to achieve multi-staged and multiple shape recovery of specimens programmed at different temperatures. Different solvents can also induce different shape recovery, analogous to the temperature memory effect, and can also provide a mechanism for multi-staged and multiple shape memory recovery.

  12. On quantitative effects of RNA shape abstraction.

    PubMed

    Nebel, Markus E; Scheid, Anika

    2009-11-01

    Over the last few decades, much effort has been taken to develop approaches for identifying good predictions of RNA secondary structure. This is due to the fact that most computational prediction methods based on free energy minimization compute a number of suboptimal foldings and we have to identify the native folding among all these possible secondary structures. Using the abstract shapes approach as introduced by Giegerich et al. (Nucleic Acids Res 32(16):4843-4851, 2004), each class of similar secondary structures is represented by one shape and the native structures can be found among the top shape representatives. In this article, we derive some interesting results answering enumeration problems for abstract shapes and secondary structures of RNA. We compute precise asymptotics for the number of different shape representations of size n and for the number of different shapes showing up when abstracting from secondary structures of size n under a combinatorial point of view. A more realistic model taking primary structures into account remains an open challenge. We give some arguments why the present techniques cannot be applied in this case.

  13. 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.

  14. 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.

  15. Whole-Word Shape Effect in Dyslexia

    ERIC Educational Resources Information Center

    Lavidor, Michal

    2011-01-01

    The research question here was whether whole-word shape cues might facilitate reading in dyslexia following reports of how normal-reading children benefit from using this cue when learning to read. We predicted that adults with dyslexia would tend to rely more on orthographic rather than other cues when reading, and therefore would be more…

  16. Shape memory effect of laser welded NiTi plates

    NASA Astrophysics Data System (ADS)

    Oliveira, J. P.; Fernandes, F. M. Braz; Schell, N.; Miranda, R. M.

    2015-07-01

    Laser welding is a suitable joining technique for shape memory alloys (SMAs). This paper reports the existence of shape memory effect (SME) on laser welded NiTi joints, subjected to bending tests, and correlates this effect with the microstructural analysis performed with X-ray diffraction (XRD). All welded samples were able to recover their initial shape after bending to 180°, which is a remarkable result for industrial applications of NiTi involving laser welding.

  17. New shape memory effects in semicrystalline polymeric networks

    NASA Astrophysics Data System (ADS)

    Chung, Taekwoong

    Shape memory polymers (SMPs) have attracted much research interest as a type of smart material that possesses the capacity to undergo rapid changes of their shape and size under a specific or tailored environment. Herein, we prepared semicrystalline polymers-based networks such as poly (cyclooctene) (PCO), poly (e-caprolactone) (PCL) and poly (ethylene glycol) (PEG) networks in order to explore their shape memory effects and thermomechanical properties as well as the possibilities for their applications. Interestingly, besides so-called one-shape memory effect that can be manipulated and fixed to a temporary shape under specific conditions of temperature and stress, and subsequently relax to the original shape on heating, the semicrystalline polymer networks exhibit a reversible two-way shape memory effect, revealing crystallization-induced elongation on cooling and melting-induced contraction on heating. These thermally induced reversible two-way shape memory effects were systematically explored with respect to the crosslinking density of networks and the applied stress. In order to develop a shape memory network with temperature sensing capability, we incorporated appropriately tailored chromogenic cyano-OPVs into cross-linked PCO via guest-diffusion to create phase-separated blends in which the dye's emission properties are dominated by excimer fluorescence. Heatng to the temperature above melting temperature and cooling below the crystallization temperature of PCO led to reversible optical changes through dissolution or agregation of the dye molecules. These optical changes happened in conjuction with shape changes of PCO networks. For an application of shape memory network in bone tissue engineering, we fabricated novel shape memory nanocomposite scaffolds base on PCL and nano-hydroxyapatite (nano-HAP) using thiol-ene photopolymerization and salt leaching technique. The shape memory property, morphologies and biomineralization of the scaffolds were

  18. Effectiveness and Efficiency of Different Shapes of Food Guides

    ERIC Educational Resources Information Center

    Hess, Rebecca; Visschers, Vivianne H. M.; Siegrist, Michael

    2012-01-01

    Objective: To compare the influence of a food guide's shape on its effectiveness and efficiency to convey nutritional information. Methods: A between-subjects experiment was conducted by manipulating the graph's shape (circle, pyramid, or rainbow). Nutrition tasks were used to assess the effectiveness and eye-movement data (number/duration of…

  19. The quintuple-shape memory effect in electrospun nanofiber membranes

    NASA Astrophysics Data System (ADS)

    Zhang, Fenghua; Zhang, Zhichun; Liu, Yanju; Lu, Haibao; Leng, Jinsong

    2013-08-01

    Shape memory fibrous membranes (SMFMs) are an emerging class of active polymers, which are capable of switching from a temporary shape to their permanent shape upon appropriate stimulation. Quintuple-shape memory membranes based on the thermoplastic polymer Nafion, with a stable fibrous structure, are achieved via electrospinning technology, and possess a broad transition temperature. The recovery of multiple temporary shapes of electrospun membranes can be triggered by heat in a single triple-, quadruple-, quintuple-shape memory cycle, respectively. The fiber morphology and nanometer size provide unprecedented design flexibility for the adjustable morphing effect. SMFMs enable complex deformations at need, having a wide potential application field including smart textiles, artificial intelligence robots, bio-medical engineering, aerospace technologies, etc in the future.

  20. Shape memory effects of molded flexible polyurethane foam

    NASA Astrophysics Data System (ADS)

    Lee, Sung Ho; Jang, Moon Kyoung; Kim, Sung Hee; Kim, Byung Kyu

    2007-12-01

    Polyurethane flexible foam having shape memory effects has been synthesized from polyester polyol and 4,4'-diphenylmethane diisocyanate (MDI) following the quasi-prepolymer method in the presence of water as the blowing agent, and the effect of the organometallic catalyst and the molecular weight of polyol has been studied. It was found that the closed cell content, foam density, rubbery modulus, compression set, and shape fixability increased with increasing amounts of organometallic catalyst and decreasing molecular weight of polyol, whereas the cell size showed the opposite tendency. On the other hand, the shape recoverability of the foam was over 99% regardless of the catalyst content and molecular weight of polyol.

  1. Martensite transformation and shape memory effect on NiTi-Zr high temperature shape memory alloys

    SciTech Connect

    Pu, Z.; Tseng, H.; Wu, K.

    1995-10-17

    NiTi-Zr high temperature alloys possess relatively poor shape memory properties and ductility in comparison with NiTi-Hf and NiTi-Pd alloys. During martensite transformation of the newly-developed NiTi-Zr high temperature shape memory alloys (SMAs) the temperature increases along with Zr content when the Zr content is more than 10 at%. As the Zr content increases, the fully reversible strain of the alloys decreases. However, complete strain recovery behavior is exhibited by all the alloys studied in this paper, even those with a Zr content of 20 at%. Stability of the NiTi-Zr alloys during thermal cycling was also tested and results indicate that the NiTi-Zr alloys have poor stability against thermal cycling. The reasons for the deterioration of the shape memory effect and stability have yet to be determined.

  2. Various shape memory effects of stimuli-responsive shape memory polymers

    NASA Astrophysics Data System (ADS)

    Meng, Harper; Mohamadian, Habib; Stubblefield, Michael; Jerro, Dwayne; Ibekwe, Samuel; Pang, Su-Seng; Li, Guoqiang

    2013-09-01

    One-step dual-shape memory polymers (SMPs) recover their original (permanent) shape upon small variation of environmental conditions such as temperature, electric field, light, magnetic field, and solvent/chemicals. For advanced applications such as aerospace and medical devices, complicated, multiple-step, spatially controllable, and two-way shape memory effects (SMEs) are required. In the past decade, researchers have devoted great effort to improve the versatility of the SME of SMPs to meet the needs of advanced applications. This paper is intended to review the up-to-date research endeavors on advanced SMEs. The problems facing the various SMPs are discussed. The challenges and opportunities for future research are discussed.

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

    NASA Astrophysics Data System (ADS)

    Cheng, Hongchang; Wang, Jingyi; Ke, Jun

    2016-06-01

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

  4. Effects of velocity averaging on the shapes of absorption lines

    NASA Technical Reports Server (NTRS)

    Pickett, H. M.

    1980-01-01

    The velocity averaging of collision cross sections produces non-Lorentz line shapes, even at densities where Doppler broadening is not apparent. The magnitude of the effects will be described using a model in which the collision broadening depends on a simple velocity power law. The effect of the modified profile on experimental measures of linewidth, shift and amplitude will be examined and an improved approximate line shape will be derived.

  5. Martensitic transformation, shape memory effects, and other curious mechanical effects

    SciTech Connect

    Vandermeer, R.A.

    1982-01-08

    The objective of this paper is to review tutorially the subject of martensitic transformations in uranium alloys emphasizing their role in the shape memory effect (SME). We examine first what a martensitic transformation is, illustrating some of its characteristics with specific examples. As well as being athermal in nature, as expected, data are presented indicating that martensitic transformations in some uranium alloys also have a strong isothermal component. In addition, a few alloys are known to exhibit thermoelastic martensitic reactions. The SME, which is associated with these, is defined and demonstrated graphically with data from a uranium-6 wt % niobium alloy. Some of the important variables influencing SME behavior are described. Specifically, these are reheat temperature, amount of deformation, crystal structure, and composition. A mechanism for SME is postulated and the association with martensitic transformation is detailed. A self-induced shape instability in the uranium-7.5 wt % niobium-2.5 wt % zirconium alloy with a rationalization of the behavior in terms of texture and lattice parameter change during aging is reviewed and discussed. 24 figures.

  6. The effect of ice crystal shape on aircraft contrails

    NASA Astrophysics Data System (ADS)

    Meza Castillo, Omar E.

    Aircraft contrails are a common phenomenon observed in the sky. They are formed mainly of water, from the ambient atmosphere and as a by-product of the combustion process, in the form of ice crystals. They have been identified as a potential contributor to global warming. Some contrails can be long-lived and create man-made cloud cover, thus possibly altering the radiative balance of the earth. There has been a great deal of research on various aspects of contrail development, but to date, little has been done on the influence of ice crystal shapes on the contrail evolution. In-situ studies have reported that young contrails are mainly quasi-spherical crystals while older contrails can have a much more diverse spectrum of possible shapes. The most common shapes found in contrails are quasi-spherical, hexagonal columns, hexagonal plates, and bullet rosettes. Numerical simulations of contrails to date typically have assumed "spherical" as the default ice shape. This work simulated contrail development with a large eddy simulation (LES) model that implemented both spherical and non-spherical shapes to examine the effects. The included shape effect parameters, such as capacitance coefficient, ventilation factor, Kelvin effect, fall velocity and ice crystal surface area, help to establish the shape difference in the results. This study also investigated initial sensitivities to an additional ice parameter, the ice deposition coefficient. The literature shows conflicting values for this coefficient over a wide range. In the course of this investigation a comparison of various ice metrics was made for simulations with different assumed crystal shapes (spheres, hexagonal columns, hexagonal plates, bullet rosettes and combination of shapes). The simulations were performed at early and late contrail time, with a range of ice crystal sizes, and with/without coupled radiation. In young and older contrails and without coupled radiation, the difference from the shape effect in

  7. Beam Shape Effects on Grating Spectrometer Resolution

    NASA Technical Reports Server (NTRS)

    Erickson, Edwin F.; Rabanus, David; DeVincenzi, Donald L. (Technical Monitor)

    2000-01-01

    The collimated optical beam in a grating spectrometer may be circular or elliptical in cross section, so that different parts of the beam illuminate different numbers of grooves on the grating. Here we estimate the consequent loss in spectral resolution relative to that obtained with a beam which illuminates a fixed number of grooves. For representative diffraction resolution functions, the effect is to reduce the intrinsic resolving power of the spectrometer by about 13%, exclusive of other contributions such as finite entrance slit width.

  8. Threshold hadronic event shapes with effective field theory

    SciTech Connect

    Kelley, Randall; Schwartz, Matthew D.

    2011-02-01

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

  9. Wake shape and its effects on aerodynamic characteristics

    NASA Technical Reports Server (NTRS)

    Emdad, H.; Lan, C. E.

    1986-01-01

    The wake shape under symmetrical flight conditions and its effects on aerodynamic characteristics are examined. In addition, the effect of wake shape in sideslip and discrete vortices such as strake or forebody vortex on lateral characteristics is presented. The present numerical method for airplane configurations, which is based on discretization of the vortex sheet into vortex segments, verified the symmetrical and asymmetrical roll-up process of the trailing vortices. Also, the effect of wing wake on tail planes is calculated. It is concluded that at high lift the assumption of flat wake for longitudinal and lateral-directional characteristics should be reexamined.

  10. Blocked Shape Memory Effect in Negative Poisson's Ratio Polymer Metamaterials.

    PubMed

    Boba, Katarzyna; Bianchi, Matteo; McCombe, Greg; Gatt, Ruben; Griffin, Anselm C; Richardson, Robert M; Scarpa, Fabrizio; Hamerton, Ian; Grima, Joseph N

    2016-08-10

    We describe a new class of negative Poisson's ratio (NPR) open cell PU-PE foams produced by blocking the shape memory effect in the polymer. Contrary to classical NPR open cell thermoset and thermoplastic foams that return to their auxetic phase after reheating (and therefore limit their use in technological applications), this new class of cellular solids has a permanent negative Poisson's ratio behavior, generated through multiple shape memory (mSM) treatments that lead to a fixity of the topology of the cell foam. The mSM-NPR foams have Poisson's ratio values similar to the auxetic foams prior their return to the conventional phase, but compressive stress-strain curves similar to the ones of conventional foams. The results show that by manipulating the shape memory effect in polymer microstructures it is possible to obtain new classes of materials with unusual deformation mechanisms. PMID:27377708

  11. Blocked Shape Memory Effect in Negative Poisson's Ratio Polymer Metamaterials.

    PubMed

    Boba, Katarzyna; Bianchi, Matteo; McCombe, Greg; Gatt, Ruben; Griffin, Anselm C; Richardson, Robert M; Scarpa, Fabrizio; Hamerton, Ian; Grima, Joseph N

    2016-08-10

    We describe a new class of negative Poisson's ratio (NPR) open cell PU-PE foams produced by blocking the shape memory effect in the polymer. Contrary to classical NPR open cell thermoset and thermoplastic foams that return to their auxetic phase after reheating (and therefore limit their use in technological applications), this new class of cellular solids has a permanent negative Poisson's ratio behavior, generated through multiple shape memory (mSM) treatments that lead to a fixity of the topology of the cell foam. The mSM-NPR foams have Poisson's ratio values similar to the auxetic foams prior their return to the conventional phase, but compressive stress-strain curves similar to the ones of conventional foams. The results show that by manipulating the shape memory effect in polymer microstructures it is possible to obtain new classes of materials with unusual deformation mechanisms.

  12. Brain potentials associated with the shape Stroop effect.

    PubMed

    Xiao, Xiao; Xie, Peng; Zhang, Qinglin

    2016-03-23

    Event-related potentials (ERPs) were recorded to explore, for the first time, the electrophysiological correlates of the shape Stroop effect. Fifteen healthy individuals were presented with a frame and a name of an object with a typical shape in life and asked to categorize the object's typical shape in life as a 'circle', a 'square,' or a 'triangle' by pressing the relevant button as quickly as possible. Accurate categorization of the name of an object was faster when it was presented with a congruent shape frame (e.g. name of a tyre/circle frame) than with an incongruent one (e.g. name of a tyre/square frame). Scalp ERPs analysis showed that the incongruent condition elicited a more negative component N430 and a more late positive component LPC than the congruent condition. N430 is a critical sign of conflict detection in the early stage, whereas late positive component reflects the response conflict in the late stage. The results provided evidence for the dissociation between conflict detection and conflict resolution in the shape Stroop effect. PMID:26862935

  13. Brain potentials associated with the shape Stroop effect.

    PubMed

    Xiao, Xiao; Xie, Peng; Zhang, Qinglin

    2016-03-23

    Event-related potentials (ERPs) were recorded to explore, for the first time, the electrophysiological correlates of the shape Stroop effect. Fifteen healthy individuals were presented with a frame and a name of an object with a typical shape in life and asked to categorize the object's typical shape in life as a 'circle', a 'square,' or a 'triangle' by pressing the relevant button as quickly as possible. Accurate categorization of the name of an object was faster when it was presented with a congruent shape frame (e.g. name of a tyre/circle frame) than with an incongruent one (e.g. name of a tyre/square frame). Scalp ERPs analysis showed that the incongruent condition elicited a more negative component N430 and a more late positive component LPC than the congruent condition. N430 is a critical sign of conflict detection in the early stage, whereas late positive component reflects the response conflict in the late stage. The results provided evidence for the dissociation between conflict detection and conflict resolution in the shape Stroop effect.

  14. Effects of Plasma Shaping on Nonlinear Gyrokinetic Turbulence

    SciTech Connect

    E. A. Belli; Hammett, G. W.; Dorland, W.

    2008-08-01

    The effects of flux surface shape on the gyrokinetic stability and transport of tokamak plasmas are studied using the GS2 code [M. Kotschenreuther, G. Rewoldt, and W.M. Tang, Comput. Phys. Commun. 88, 128 (1995); W. Dorland, F. Jenko, M. Kotschenreuther, and B.N. Rogers, Phys. Rev. Lett. 85, 5579 (2000)]. Studies of the scaling of nonlinear turbulence with shaping parameters are performed using analytic equilibria based on interpolations of representative shapes of the Joint European Torus (JET) [P.H. Rebut and B.E. Keen, Fusion Technol. 11, 13 (1987)]. High shaping is found to be a stabilizing influence on both the linear ion-temperature-gradient (ITG) instability and the nonlinear ITG turbulence. For the parameter regime studied here, a scaling of the heat flux with elongation of χ ~ κ-1.5 or κ-2.0, depending on the triangularity, is observed at fixed average temperature gradient. While this is not as strong as empirical elongation scalings, it is also found that high shaping results in a larger Dimits upshift of the nonlinear critical temperature gradient due to an enhancement of the Rosenbluth-Hinton residual zonal flows.

  15. Effects of magnetic field on the shape memory behavior of single and polycrystalline magnetic shape memory alloys

    NASA Astrophysics Data System (ADS)

    Turabi, Ali Sadi

    Shape memory alloys and polymers have been extensively researched recently because of their unique ability to recover large deformations. Shape memory polymers (SMPs) are able to recover large deformations compared to shape memory alloys (SMAs), although SMAs have higher strength and are able to generate more stress during recovery. This project focuses on procedure for fabrication and Finite Element Modeling (FEM) of a shape memory composite actuator. First, SMP was characterized to reveal its mechanical properties. Specifically, glass transition temperature, the effects of temperature and strain rate on compressive response and recovery properties of shape memory polymer were studied. Then, shape memory properties of a NiTi wire, including transformation temperatures and stress generation, were investigated. SMC actuator was fabricated by using epoxy based SMP and NiTi SMA wire. Experimental tests confirmed the reversible behavior of fabricated shape memory composites. (Abstract shortened by ProQuest.).

  16. Investigations of Shape Conundra Using Reorientation-Effect Measurements

    NASA Astrophysics Data System (ADS)

    Orce, J. N.

    2015-11-01

    A recent Coulomb-excitation reorientation-effect measurement at TRIUMF has enabled information on diagonal matrix elements for the 3.368 MeV high-lying first excited state in 10Be from γ-ray data. The result allows for a comparison with state-of-the-art no-core-shell-model calculations and questions our knowledge of the spin-orbit interaction. Similar experiments using 12C beams at TRIUMF are aimed at measuring the diagonal matrix element for the first 2+ state at 4.439 MeV, which is currently determined as oblate, but presents an uncertainty of over 50%. Nuclear clustering effects are also being investigated using 20Ne beams at iThemba LABS--the first `safe' reorientation-effect measurement with 20Ne beams. In addition, the occurrence of oblate shapes and shape coexistence will also be studied using 70Se beams at 5.5 MeV/u at HIE-ISOLDE. These studies will shed light on nuclear shapes and resolved some of the timely shape conundra found in nuclei.

  17. Particle shape effects on the stress response of granular packings.

    PubMed

    Athanassiadis, Athanasios G; Miskin, Marc Z; Kaplan, Paul; Rodenberg, Nicholas; Lee, Seung Hwan; Merritt, Jason; Brown, Eric; Amend, John; Lipson, Hod; Jaeger, Heinrich M

    2014-01-01

    We present measurements of the stress response of packings formed from a wide range of particle shapes. Besides spheres these include convex shapes such as the Platonic solids, truncated tetrahedra, and triangular bipyramids, as well as more complex, non-convex geometries such as hexapods with various arm lengths, dolos, and tetrahedral frames. All particles were 3D-printed in hard resin. Well-defined initial packing states were established through preconditioning by cyclic loading under given confinement pressure. Starting from such initial states, stress-strain relationships for axial compression were obtained at four different confining pressures for each particle type. While confining pressure has the largest overall effect on the mechanical response, we find that particle shape controls the details of the stress-strain curves and can be used to tune packing stiffness and yielding. By correlating the experimentally measured values for the effective Young's modulus under compression, yield stress and energy loss during cyclic loading, we identify trends among the various shapes that allow for designing a packing's aggregate behavior.

  18. Effects of memory on the shapes of simple outbreak trees

    PubMed Central

    Plazzotta, Giacomo; Kwan, Christopher; Boyd, Michael; Colijn, Caroline

    2016-01-01

    Genomic tools, including phylogenetic trees derived from sequence data, are increasingly used to understand outbreaks of infectious diseases. One challenge is to link phylogenetic trees to patterns of transmission. Particularly in bacteria that cause chronic infections, this inference is affected by variable infectious periods and infectivity over time. It is known that non-exponential infectious periods can have substantial effects on pathogens’ transmission dynamics. Here we ask how this non-Markovian nature of an outbreak process affects the branching trees describing that process, with particular focus on tree shapes. We simulate Crump-Mode-Jagers branching processes and compare different patterns of infectivity over time. We find that memory (non-Markovian-ness) in the process can have a pronounced effect on the shapes of the outbreak’s branching pattern. However, memory also has a pronounced effect on the sizes of the trees, even when the duration of the simulation is fixed. When the sizes of the trees are constrained to a constant value, memory in our processes has little direct effect on tree shapes, but can bias inference of the birth rate from trees. We compare simulated branching trees to phylogenetic trees from an outbreak of tuberculosis in Canada, and discuss the relevance of memory to this dataset. PMID:26888437

  19. The shape--memory effect in trans--polyisoprene

    NASA Astrophysics Data System (ADS)

    Safarik, Douglas; Gofryk, Krystof; Llobet, Anna; Lashley, Jason

    2013-03-01

    Polyisoprene, (-CH2C(CH3)CH =CH2 -)n, consists of isoprene (2-methyl-1,3-butadiene) molecules that are linked end-to-end to form long chains. There are two different isomers, cis and trans, with respect to configuration about the C =C double bond. Cis-polyisoprene, the main component in natural rubber derived originally from the Pará rubber tree, is a non-crystalline elastomer at room temperature. In contrast, trans-polyisoprene, derived originally from the gutta percha tree, is a crystalline solid that is rigid and tough. More interestingly, the trans isomer exhibits shape-memory properties, whereas the cis isomer does not. As for shape-memory transformations in alloys, trans-polyisoprene exhibits clear Af and Mf temperatures, with values 338 K and 300 K, respectively. Here we report thermodynamic and structural measurements of the shape-memory effect in trans-polyisoprene. We discuss our results in terms of the mechanism of shape-memory.

  20. Excited Spectator Electron Effects on Spectral Line Shapes

    SciTech Connect

    Iglesias, C A

    2009-10-12

    Excited spectator electron effects on Stark broadened spectral line shapes of transitions involving tightly bound electrons are investigated. It is shown that the interference terms in the electron impact broadening are essential to describe the overlapping lines generated by these configurations (e.g.; dielectronic satellite lines). The main impact is narrower spectral features and reduced far wing intensities compared to calculations neglecting the interference terms.

  1. Acoustic emission and shape memory effect in the martensitic transformation.

    PubMed

    Sreekala, S; Ananthakrishna, G

    2003-04-01

    Acoustic emission signals are known to exhibit a high degree of reproducibility in time and show correlations with the growth and shrinkage of martensite domains when athermal martensites are subjected to repeated thermal cycling in a restricted temperature range. We show that a recently introduced two dimensional model for the martensitic transformation mimics these features. We also show that these features are related to the shape memory effect where near full reversal of morphological features are seen under these thermal cycling conditions.

  2. Orbital Debris Shape and Orientation Effects on Ballistic Limits

    NASA Technical Reports Server (NTRS)

    Evans, Steven W.; Williamsen, Joel E.

    2005-01-01

    The SPHC hydrodynamic code was used to evaluate the effects of orbital debris particle shape and orientation on penetration of a typical spacecraft dual-wall shield. Impacts were simulated at near-normal obliquity at 12 km/sec. Debris cloud characteristics and damage potential are compared with those from impacts by spherical projectiles. Results of these simulations indicate the uncertainties in the predicted ballistic limits due to modeling uncertainty and to uncertainty in the impactor orientation.

  3. Plot shape effects on plant species diversity measurements

    USGS Publications Warehouse

    Keeley, Jon E.; Fotheringham, C.J.

    2005-01-01

    Abstract. Question: Do rectangular sample plots record more plant species than square plots as suggested by both empirical and theoretical studies?Location: Grasslands, shrublands and forests in the Mediterranean-climate region of California, USA.Methods: We compared three 0.1-ha sampling designs that differed in the shape and dispersion of 1-m2 and 100-m2 nested subplots. We duplicated an earlier study that compared the Whittaker sample design, which had square clustered subplots, with the modified Whittaker design, which had dispersed rectangular subplots. To sort out effects of dispersion from shape we used a third design that overlaid square subplots on the modified Whittaker design. Also, using data from published studies we extracted species richness values for 400-m2 subplots that were either square or 1:4 rectangles partially overlaid on each other from desert scrub in high and low rainfall years, chaparral, sage scrub, oak savanna and coniferous forests with and without fire.Results: We found that earlier empirical reports of more than 30% greater richness with rectangles were due to the confusion of shape effects with spatial effects, coupled with the use of cumulative number of species as the metric for comparison. Average species richness was not significantly different between square and 1:4 rectangular sample plots at either 1- or 100-m2. Pairwise comparisons showed no significant difference between square and rectangular samples in all but one vegetation type, and that one exhibited significantly greater richness with squares. Our three intensive study sites appear to exhibit some level of self-similarity at the scale of 400 m2, but, contrary to theoretical expectations, we could not detect plot shape effects on species richness at this scale.Conclusions: At the 0.1-ha scale or lower there is no evidence that plot shape has predictable effects on number of species recorded from sample plots. We hypothesize that for the mediterranean

  4. Plot shape effects on plant species diversity measurements

    USGS Publications Warehouse

    Keeley, J.E.; Fotheringham, C.J.

    2005-01-01

    Question: Do rectangular sample plots record more plant species than square plots as suggested by both empirical and theoretical studies? Location: Grasslands, shrublands and forests in the Mediterranean-climate region of California, USA. Methods: We compared three 0.1-ha sampling designs that differed in the shape and dispersion of 1-m2 and 100-m2 nested subplots. We duplicated an earlier study that compared the Whittaker sample design, which had square clustered subplots, with the modified Whittaker design, which had dispersed rectangular subplots. To sort out effects of dispersion from shape we used a third design that overlaid square subplots on the modified Whittaker design. Also, using data from published studies we extracted species richness values for 400-m2 subplots that were either square or 1:4 rectangles partially overlaid on each other from desert scrub in high and low rainfall years, chaparral, sage scrub, oak savanna and coniferous forests with and without fire. Results: We found that earlier empirical reports of more than 30% greater richness with rectangles were due to the confusion of shape effects with spatial effects, coupled with the use of cumulative number of species as the metric for comparison. Average species richness was not significantly different between square and 1:4 rectangular sample plots at either 1-or 100-m2. Pairwise comparisons showed no significant difference between square and rectangular samples in all but one vegetation type, and that one exhibited significantly greater richness with squares. Our three intensive study sites appear to exhibit some level of self-similarity at the scale of 400 m2, but, contrary to theoretical expectations, we could not detect plot shape effects on species richness at this scale. Conclusions: At the 0.1-ha scale or lower there is no evidence that plot shape has predictable effects on number of species recorded from sample plots. We hypothesize that for the mediterranean-climate vegetation types

  5. Pulsed laser interactions with space debris: Target shape effects

    DOE PAGES

    Liedahl, D. A.; Rubenchik, A.; Libby, S. B.; Nikolaev, S.; Phipps, C. R.

    2013-05-24

    Among the approaches to the proposed mitigation and remediation of the space debris problem is the de-orbiting of objects in low Earth orbit through irradiation by ground-based high-intensity pulsed lasers. Laser ablation of a thin surface layer causes target recoil, resulting in the depletion of orbital angular momentum and accelerated atmospheric re-entry. However, both the magnitude and direction of the recoil are shape dependent, a feature of the laser-based remediation concept that has received little attention. Since the development of a predictive capability is desirable, we have investigated the dynamical response to ablation of objects comprising a variety of shapes.more » We derive and demonstrate a simple analytical technique for calculating the ablation-driven transfer of linear momentum, emphasizing cases for which the recoil is not exclusively parallel to the incident beam. For the purposes of comparison and contrast, we examine one case of momentum transfer in the low-intensity regime, where photon pressure is the dominant momentum transfer mechanism, showing that shape and orientation effects influence the target response in a similar, but not identical, manner. As a result, we address the related problem of target spin and, by way of a few simple examples, show how ablation can alter the spin state of a target, which often has a pronounced effect on the recoil dynamics.« less

  6. Pulsed laser interactions with space debris: Target shape effects

    SciTech Connect

    Liedahl, D. A.; Rubenchik, A.; Libby, S. B.; Nikolaev, S.; Phipps, C. R.

    2013-05-24

    Among the approaches to the proposed mitigation and remediation of the space debris problem is the de-orbiting of objects in low Earth orbit through irradiation by ground-based high-intensity pulsed lasers. Laser ablation of a thin surface layer causes target recoil, resulting in the depletion of orbital angular momentum and accelerated atmospheric re-entry. However, both the magnitude and direction of the recoil are shape dependent, a feature of the laser-based remediation concept that has received little attention. Since the development of a predictive capability is desirable, we have investigated the dynamical response to ablation of objects comprising a variety of shapes. We derive and demonstrate a simple analytical technique for calculating the ablation-driven transfer of linear momentum, emphasizing cases for which the recoil is not exclusively parallel to the incident beam. For the purposes of comparison and contrast, we examine one case of momentum transfer in the low-intensity regime, where photon pressure is the dominant momentum transfer mechanism, showing that shape and orientation effects influence the target response in a similar, but not identical, manner. As a result, we address the related problem of target spin and, by way of a few simple examples, show how ablation can alter the spin state of a target, which often has a pronounced effect on the recoil dynamics.

  7. Effect of geometric shape on two-dimensional finite elements

    SciTech Connect

    Cook, W.A.

    1981-01-01

    Three quadrilateral elements are defined. These are an eight-nodal-point serendipity element (QUAD8s), a nine-nodal-point serendipity element (QUAD9s), and a nine-nodal-point quadrilateral element composed of two six-nodal-point triangular elements (QUAD9t). The effect that the geometric shape of the element has on the approximation function of each element is discussed. Two beam problems demonstrate that when the shape of the elements becomes skewed, the QUAD9t element significantly improves the calculated results. Finally, a recommendation is made for the QUAD8s and QUAD9t to be used together for the most efficient and accurate results.

  8. Effect of piston second land shape on oil consumption

    SciTech Connect

    Yoshida, Hideki; Kusama, Kazunori; Sugihara, Hiroyuki; Ariga, Susumu

    1996-12-31

    Focusing on the oil flow characteristics in piston land areas, the authors measured variables affecting oil flow in an actual engine and conducted computer-aided analysis in order to develop a technique to reduce oil consumption. Since volume of the second land influences piston ring behavior, the volume has to be determined so that blow-up gas flow is reduced. As a means of sizing the second land volume, a V-shaped groove may be made in the second land. This particular groove shape made it possible to prevent the flow of oil into the combustion chamber. The behavior of oil on the piston land was observed through a glass cylinder installed on the engine. The effect of the land design on the oil flow was analyzed by using a computational-fluid-dynamics (CFD) code.

  9. The effect of temporal pulse shape on optical damage

    SciTech Connect

    Carr, C W; Trenholme, J B; Spaeth, M L

    2006-08-15

    The conditions under which optical materials are susceptible to laser-induced damage is a topic which has been the subject of considerable study. Laser parameters such as wavelength and temporal pulse duration have been studied extensively. Until this work the effect of temporal pulse shape has not been considered. We present here data from a simple single-parameter model and a supporting experiment which predicts that a Flat-In-Time-pulse will produce damage at approximately 80% of the fluence of a Gaussian pulse of the same FWHM duration.

  10. HYDROGEN EFFECTS ON LASER ENGINEERED NET SHAPE (LENS) REPAIRED WELDMENTS

    SciTech Connect

    Korinko, P; Thad Adams, T

    2006-10-06

    New methods of repairing mis-machined components are always of interest. In this study, an innovative method using Laser Engineered Net Shape{trademark} (LENS{reg_sign}) forming was used to repair intentionally mis-machined test articles. The components were repaired and subsequently hydrogen charged and burst tested. The LENS repair did not have an adverse effect on the solid state weld process that was used to repair the components. Hydrogen charged samples failed in a similar manner to the uncharged samples. Overall, the prospects for LENS repairing similar products are favorable and further work is encouraged.

  11. Studies of Standard Heat Treatment Effects on Microstructure and Mechanical Properties of Laser Net Shape Manufactured INCONEL 718

    NASA Astrophysics Data System (ADS)

    Qi, H.; Azer, M.; Ritter, A.

    2009-10-01

    Laser net shape manufacturing (LNSM) is a laser cladding/deposition based technology, which can fabricate and repair near-net-shape high-performance components directly from metal powders. Characterizing mechanical properties of the laser net shape manufactured components is prerequisite to the applications of LNSM in aircraft engine industrial productions. Nickel-based superalloys such as INCONEL 718 are the most commonly used metal materials in aircraft engine high-performance components. In this study, the laser deposition process is optimized through a set of designed experiments to reduce the porosity to less than 0.03 pct. It is found that the use of plasma rotating electrode processed (PREP) powder and a high energy input level greater than 80 J/mm are necessary conditions to minimize the porosity. Material microstructure and tensile properties of laser-deposited INCONEL 718 are studied and compared under heat treatment conditions of as deposited, direct aged, solution treatment and aging (STA), and full homogenization followed by STA. Tensile test results showed that the direct age heat treatment produces the highest tensile strength equivalent to the wrought material, which is followed by the STA-treated and the homogenization-treated tensile strengths, while the ductility exhibits the reverse trend. Finally, failure modes of the tensile specimens were analyzed with fractography.

  12. Effects of Setup Errors and Shape Changes on Breast Radiotherapy

    SciTech Connect

    Mourik, Anke van; Kranen, Simon van; Hollander, Suzanne den; Sonke, Jan-Jakob; Herk, Marcel van; Vliet-Vroegindeweij, Corine van

    2011-04-01

    Purpose: The purpose of the present study was to quantify the robustness of the dose distributions from three whole-breast radiotherapy (RT) techniques involving different levels of intensity modulation against whole patient setup inaccuracies and breast shape changes. Methods and Materials: For 19 patients (one computed tomography scan and five cone beam computed tomography scans each), three treatment plans were made (wedge, simple intensity-modulated RT [IMRT], and full IMRT). For each treatment plan, four dose distributions were calculated. The first dose distribution was the original plan. The other three included the effects of patient setup errors (rigid displacement of the bony anatomy) or breast errors (e.g., rotations and shape changes of the breast with respect to the bony anatomy), or both, and were obtained through deformable image registration and dose accumulation. Subsequently, the effects of the plan type and error sources on target volume coverage, mean lung dose, and excess dose were determined. Results: Systematic errors of 1-2 mm and random errors of 2-3 mm (standard deviation) were observed for both patient- and breast-related errors. Planning techniques involving glancing fields (wedge and simple IMRT) were primarily affected by patient errors ({approx}6% loss of coverage near the dorsal field edge and {approx}2% near the skin). In contrast, plan deterioration due to breast errors was primarily observed in planning techniques without glancing fields (full IMRT, {approx}2% loss of coverage near the dorsal field edge and {approx}4% near the skin). Conclusion: The influences of patient and breast errors on the dose distributions are comparable in magnitude for whole breast RT plans, including glancing open fields, rendering simple IMRT the preferred technique. Dose distributions from planning techniques without glancing open fields were more seriously affected by shape changes of the breast, demanding specific attention in partial breast

  13. The effect of knife handle shape on stabbing performance.

    PubMed

    Horsfall, Ian; Watson, Celia; Champion, Steve; Prosser, Philip; Ringrose, Trevor

    2005-07-01

    A quantitative knowledge of stabbing ability is a pre-requisite to establishing protection standards for stab resistant body armour. In order to determine the validity of measurements it is necessary to understand all the mechanisms that determine performance. This paper describes a series of tests that were performed in order to determine the effect of handle size and shape on the forces and impact energy that could be produced during stabbing of an armoured target. It was found that the single largest variable was that of the test participants with all other variables such as handle size and shape having only slight effects on the magnitude of impact energy. The use of a finger guard or hilt was shown to increase the mean energy delivered to the target by approximately 5J compared to a handle having no guard. It was also found that the characteristics of energy delivery were strongly influenced by the position of the grip relative to this guard. This reinforces the conclusions of previous work (Horsfall et al., 1999; Chadwick et al., 1999) on the serial nature of momentum transfer during a stabbing impact.

  14. Shaping cancer nanomedicine: The effect of particle shape on the in vivo journey of nanoparticles

    PubMed Central

    Toy, Randall; Peiris, Pubudu M.; Ghaghada, Ketan B.; Karathanasis, Efstathios

    2014-01-01

    Summary Recent advances in nanoparticle technology have enabled the fabrication of nanoparticle classes with unique size, shape, and materials, which in turn has facilitated major advancements in the field of nanomedicine. More specifically, in the last decade, nanoscientists have recognized that nanomedicine exhibits a highly engineerable nature that makes it a mainstream scientific discipline, which is governed by its own distinctive principles in terms of interactions with cells and intravascular, transvascular and interstitial transport. This review focuses on recent developments and understanding of the relation between the shape of a nanoparticle and its navigation through different biological processes. Importantly, we seek to illustrate that the shape of a nanoparticle can govern its in vivo journey and destination dictating its biodistribution, intravascular and transvascular transport, and ultimately targeting of difficult-to-reach cancer sites. PMID:24354814

  15. Leidenfrost effect: Accurate drop shape modeling and refined scaling laws.

    PubMed

    Sobac, B; Rednikov, A; Dorbolo, S; Colinet, P

    2014-11-01

    We here present a simple fitting-parameter-free theory of the Leidenfrost effect (droplet levitation above a superheated plate) covering the full range of stable shapes, i.e., from small quasispherical droplets to larger puddles floating on a pocketlike vapor film. The geometry of this film is found to be in excellent quantitative agreement with the interferometric measurements of Burton et al. [Phys. Rev. Lett. 109, 074301 (2012)PRLTAO0031-900710.1103/PhysRevLett.109.074301]. We also obtain new scalings generalizing classical ones derived by Biance et al. [Phys. Fluids 15, 1632 (2003)PHFLE61070-663110.1063/1.1572161] as far as the effect of plate superheat is concerned and highlight the relative role of evaporation, gravity, and capillarity in the vapor film. To further substantiate these findings, a treatment of the problem by matched asymptotic expansions is also presented. PMID:25493885

  16. Leidenfrost effect: Accurate drop shape modeling and refined scaling laws

    NASA Astrophysics Data System (ADS)

    Sobac, B.; Rednikov, A.; Dorbolo, S.; Colinet, P.

    2014-11-01

    We here present a simple fitting-parameter-free theory of the Leidenfrost effect (droplet levitation above a superheated plate) covering the full range of stable shapes, i.e., from small quasispherical droplets to larger puddles floating on a pocketlike vapor film. The geometry of this film is found to be in excellent quantitative agreement with the interferometric measurements of Burton et al. [Phys. Rev. Lett. 109, 074301 (2012), 10.1103/PhysRevLett.109.074301]. We also obtain new scalings generalizing classical ones derived by Biance et al. [Phys. Fluids 15, 1632 (2003), 10.1063/1.1572161] as far as the effect of plate superheat is concerned and highlight the relative role of evaporation, gravity, and capillarity in the vapor film. To further substantiate these findings, a treatment of the problem by matched asymptotic expansions is also presented.

  17. Fast-Response-Time Shape-Memory-Effect Foam Actuators

    NASA Technical Reports Server (NTRS)

    Jardine, Peter

    2010-01-01

    Bulk shape memory alloys, such as Nitinol or CuAlZn, display strong recovery forces undergoing a phase transformation after being strained in their martensitic state. These recovery forces are used for actuation. As the phase transformation is thermally driven, the response time of the actuation can be slow, as the heat must be passively inserted or removed from the alloy. Shape memory alloy TiNi torque tubes have been investigated for at least 20 years and have demonstrated high actuation forces [3,000 in.-lb (approximately equal to 340 N-m) torques] and are very lightweight. However, they are not easy to attach to existing structures. Adhesives will fail in shear at low-torque loads and the TiNi is not weldable, so that mechanical crimp fits have been generally used. These are not reliable, especially in vibratory environments. The TiNi is also slow to heat up, as it can only be heated indirectly using heater and cooling must be done passively. This has restricted their use to on-off actuators where cycle times of approximately one minute is acceptable. Self-propagating high-temperature synthesis (SHS) has been used in the past to make porous TiNi metal foams. Shape Change Technologies has been able to train SHS derived TiNi to exhibit the shape memory effect. As it is an open-celled material, fast response times were observed when the material was heated using hot and cold fluids. A methodology was developed to make the open-celled porous TiNi foams as a tube with integrated hexagonal ends, which then becomes a torsional actuator with fast response times. Under processing developed independently, researchers were able to verify torques of 84 in.-lb (approximately equal to 9.5 Nm) using an actuator weighing 1.3 oz (approximately equal to 37 g) with very fast (less than 1/16th of a second) initial response times when hot and cold fluids were used to facilitate heat transfer. Integrated structural connections were added as part of the net shape process, eliminating

  18. Effects of wave shape on sheet flow sediment transport

    USGS Publications Warehouse

    Hsu, T.-J.; Hanes, D.M.

    2004-01-01

    A two-phase model is implemented to study the effects of wave shape on the transport of coarse-grained sediment in the sheet flow regime. The model is based on balance equations for the average mass, momentum, and fluctuation energy for both the fluid and sediment phases. Model simulations indicate that the responses of the sheet flow, such as the velocity profiles, the instantaneous bed shear stress, the sediment flux, and the total amount of the mobilized sediment, cannot be fully parameterized by quasi-steady free-stream velocity and may be correlated with the magnitude of local horizontal pressure gradient (or free-stream acceleration). A net sediment flux in the direction of wave advance is obtained for both skewed and saw-tooth wave shapes typical of shoaled and breaking waves. The model further suggests that at critical values of the horizontal pressure gradient, there is a failure event within the bed that mobilizes more sediment into the mobile sheet and enhances the sediment flux. Preliminary attempts to parameterize the total bed shear stress and the total sediment flux appear promising. Copyright 2004 by the American Geophysical Union.

  19. The Effect of Pulse Shaping QPSK on Bandwidth Efficiency

    NASA Technical Reports Server (NTRS)

    Purba, Josua Bisuk Mubyarto; Horan, Shelia

    1997-01-01

    This research investigates the effect of pulse shaping QPSK on bandwidth efficiency over a non-linear channel. This investigation will include software simulations and the hardware implementation. Three kinds of filters: the 5th order Butterworth filter, the 3rd order Bessel filter and the Square Root Raised Cosine filter with a roll off factor (alpha) of 0.25,0.5 and 1, have been investigated as pulse shaping filters. Two different high power amplifiers, one a Traveling Wave Tube Amplifier (TWTA) and the other a Solid State Power Amplifier (SSPA) have been investigated in the hardware implementation. A significant improvement in the bandwidth utilization (rho) for the filtered data compared to unfiltered data through the non-linear channel is shown in the results. This method promises strong performance gains in a bandlimited channel when compared to unfiltered systems. This work was conducted at NMSU in the Center for Space Telemetering, and Telecommunications Systems in the Klipsch School of Electrical and Computer Engineering Department and is supported by a grant from the National Aeronautics and Space Administration (NASA) NAG5-1491.

  20. Shape effects in optical properties of composite dust particles

    NASA Astrophysics Data System (ADS)

    Botet, Robert S.; Rai, Rakesh K.

    2013-10-01

    We present optical features characteristic of the shape of composite dust particles, such as grain-aggregates formed under cosmic or atmospheric conditions. The discussion develops along two examples of realistic models for the formation of the composite particles, and constant refractive indices. That way, particular features exhibited in the optical cross section behaviors result from the particle structure only. The role of the ratio between optical particle cross section and the corresponding cross section of the coated sphere of same composition and volume is highlighted. Limited wavelength ranges are defined where the coated sphere model can be used to obtain the effective radius or the volume composition of the particle. Other wavelength domains are very dependent on the particle formation mechanisms, then giving constraints on the possible formation processes. Therefore, such an approach is able to provide inverse methods to obtain the actual values of physical parameters from definite features of optical quantities.

  1. Simulation of grain size effects in nanocrystalline shape memory alloys

    NASA Astrophysics Data System (ADS)

    Ahluwalia, Rajeev; Quek, Siu Sin; Wu, David T.

    2015-06-01

    Recently, it has been demonstrated that martensitic transformation in nanocrystalline shape memory alloys can be suppressed for small grain sizes. Motivated by these results, we study the grain size dependence of martensitic transformations and stress-strain response of nanocrystalline shape memory alloys within the framework of the Ginzburg-Landau (GL) theory. A GL model for a square to rectangle transformation in polycrystals is extended to account for grain boundary effects. We propose that an inhibition of the transformation in grain boundary regions can occur, if the grain boundary energy of the martensite is higher than that of the austenite phase. We show that this inhibition of transformation in grain boundary regions has a strong influence on domain patterns inside grains. Although the transformation is inhibited only at the grain boundaries, it leads to a suppression of the transformation even inside the grains as grain size is decreased. In fact, below a critical grain size, the transformation can be completely suppressed. We explain these results in terms of the extra strain gradient cost associated with grain boundaries, when the transformation is inhibited at grain boundaries. On the other hand, no significant size effects are observed when transformation is not inhibited at grain boundaries. We also study the grain size dependence of the stress strain curve. It is found that when the transformation is inhibited at grain boundaries, a significant reduction in the hysteresis associated with stress-strain curves during the loading-unloading cycles is observed. The hysteresis for this situation reduces even further as the grain size is reduced, which is consistent with recent experiments. The simulations also demonstrate that the mechanical behavior is influenced by inter-granular interactions and the local microstructural neighbourhood of a grain has a stronger influence than the orientation of the grain itself.

  2. Effect of shaping sensor data on pilot response

    NASA Technical Reports Server (NTRS)

    Bailey, Roger M.

    1990-01-01

    The pilot of a modern jet aircraft is subjected to varying workloads while being responsible for multiple, ongoing tasks. The ability to associate the pilot's responses with the task/situation, by modifying the way information is presented relative to the task, could provide a means of reducing workload. To examine the feasibility of this concept, a real time simulation study was undertaken to determine whether preprocessing of sensor data would affect pilot response. Results indicated that preprocessing could be an effective way to tailor the pilot's response to displayed data. The effects of three transformations or shaping functions were evaluated with respect to the pilot's ability to predict and detect out-of-tolerance conditions while monitoring an electronic engine display. Two nonlinear transformations, on being the inverse of the other, were compared to a linear transformation. Results indicate that a nonlinear transformation that increases the rate-or-change of output relative to input tends to advance the prediction response and improve the detection response, while a nonlinear transformation that decreases the rate-of-change of output relative to input tends to lengthen the prediction response and make detection more difficult.

  3. Underwater Sliding Properties: Effect of Slider Shape and Surface Wettability

    NASA Astrophysics Data System (ADS)

    Kirveslahti, A.; Mielonen, K.; Ikonen, K.; Cui, W.; Suvanto, M.; Pakkanen, T. A.

    2016-04-01

    A dynamic test method for the measurement of the underwater sliding properties of model boats has been developed. Surface-modified model boats were examined to assess how the surface wettability properties affect sliding. Along with the surface properties, the influence of the boat shape was considered. We studied various coatings in the contact angle range of 3-162∘ with two model boat shapes. The hydrophobicity of the surfaces influenced the sliding speed of the model boat depending on the boat shape. The method is applicable to study sliding properties of model boats with different surfaces in variable flow conditions.

  4. Effects of contact shape on the scaling of biological attachments

    NASA Astrophysics Data System (ADS)

    Spolenak, Ralph; Gorb, Stanislav; Gao, Huajian; Arzt, Eduard

    2005-02-01

    Adhesion of biological systems has recently received much research attention: the survival of organisms ranging from single cells and mussels to insects, spiders and geckos relies crucially on their mechanical interaction with their environments. For spiders, lizards and possible other 'dry' adhesive systems, explanations for adhesion are based on van der Waals interaction, and the adhesion of single-contact elements has been described by the classical Johnson-Kendall-Roberts (JKR) model derived for spherical contacts. However, real biological contacts display a variety of shapes and only rarely resemble a hemisphere. Here, we theoretically assess the influence of various contact shapes on the pull-off force for single contacts as well as their scaling potential in contact arrays. It is concluded that other shapes, such as a toroidal contact geometry, should lead to better attachment; such geometries are observed in our microscopic investigations of hair-tip shapes in beetles and flies.

  5. Effect of droplet shape on ring stains from dried liquid

    NASA Astrophysics Data System (ADS)

    Santiago, Melvin; Brown, Katherine; Mathur, Harsh

    A landmark experimental paper on coffee stains by Deegan et al included a simple theoretical analysis of circular droplets. The analysis was based on a model informally called the Maxwell House equations. It describes the evolving height profile of the droplet, the evaporation of the solvent and the outflow of solute to the rim of the droplet. Since typical droplets are not circles, here we extend the analysis to more general shapes. We find that for thin droplets the height profile may be determined by solving Poisson's equation in a domain corresponding to the footprint of the droplet. Evaporation is treated in a simple approximation via an electrostatic analogy and is dominated by the sharp edges of the droplet. Assuming zero vorticity allows us to analyze the solvent flow in droplets of arbitrary shape. We compare circular droplets to other shapes including long linear droplets, ring shaped droplets and droplets with an elliptical footprint

  6. EFFECTS OF FORSTERITE GRAIN SHAPE ON INFRARED SPECTRA

    SciTech Connect

    Koike, C.; Imai, Y.; Chihara, H.; Murata, K.; Tsuchiyama, A.; Suto, H.; Tachibana, S.; Ohara, S.

    2010-02-01

    The Infrared Space Observatory (ISO) detected several sharp infrared features around young stars, comets, and evolved stars. These sharp features were identified as Mg-rich crystalline silicates of forsterite and enstatite by comparison with spectra from laboratory data. However, certain infrared emission bands in the observed spectra cannot be identified because they appear at slightly shorter wavelengths than the peaks in forsterite laboratory spectra, where the shapes of forsterite particles are irregular. To solve this problem, we measured infrared spectra of forsterite grains of various shapes (irregular, plate-like with no sharp edges, elliptical, cauliflower, and spherical) in the infrared spectral region between 5 and 100 mum. The spectra depend on particle shape. The spectra of the 11, 19, 23, and 33 mum bands, in particular, are extremely sensitive to particle shape, whereas some peaks such as the 11.9, 49, and 69 mum bands remained almost unchanged despite different particle shapes. This becomes most evident from the spectra of near-spherical particles produced by annealing an originally amorphous silicate sample at temperature from 600 to 1150 deg. C. The spectra of these samples differ strongly from those of other ones, showing peaks at much shorter wavelengths. At a higher annealing temperature of 1200 deg. C, the particle shapes changed drastically from spherical to irregular and the spectra became similar to those of forsterite particles with irregular shapes. Based on ISO data and other observational data, the spectra of outflow sources and disk sources may correspond to differences in forsterite shape, and further some unidentified peaks, such as those at 32.8 or 32.5 mum, may be due to spherical or spherical-like forsterite.

  7. Effects of Forsterite Grain Shape on Infrared Spectra

    NASA Astrophysics Data System (ADS)

    Koike, C.; Imai, Y.; Chihara, H.; Suto, H.; Murata, K.; Tsuchiyama, A.; Tachibana, S.; Ohara, S.

    2010-02-01

    The Infrared Space Observatory (ISO) detected several sharp infrared features around young stars, comets, and evolved stars. These sharp features were identified as Mg-rich crystalline silicates of forsterite and enstatite by comparison with spectra from laboratory data. However, certain infrared emission bands in the observed spectra cannot be identified because they appear at slightly shorter wavelengths than the peaks in forsterite laboratory spectra, where the shapes of forsterite particles are irregular. To solve this problem, we measured infrared spectra of forsterite grains of various shapes (irregular, plate-like with no sharp edges, elliptical, cauliflower, and spherical) in the infrared spectral region between 5 and 100 μm. The spectra depend on particle shape. The spectra of the 11, 19, 23, and 33 μm bands, in particular, are extremely sensitive to particle shape, whereas some peaks such as the 11.9, 49, and 69 μm bands remained almost unchanged despite different particle shapes. This becomes most evident from the spectra of near-spherical particles produced by annealing an originally amorphous silicate sample at temperature from 600 to 1150°C. The spectra of these samples differ strongly from those of other ones, showing peaks at much shorter wavelengths. At a higher annealing temperature of 1200°C, the particle shapes changed drastically from spherical to irregular and the spectra became similar to those of forsterite particles with irregular shapes. Based on ISO data and other observational data, the spectra of outflow sources and disk sources may correspond to differences in forsterite shape, and further some unidentified peaks, such as those at 32.8 or 32.5 μm, may be due to spherical or spherical-like forsterite.

  8. Effect of enclosure shape on natural convection velocities

    NASA Technical Reports Server (NTRS)

    Robertson, S. J.; Nicholson, L. A.

    1982-01-01

    A numerical analysis was performed to compare natural convection velocities in two dimensional enclosures of various shape. The following shapes were investigated: circle, square, horizontal and upright 2 x 1 aspect ratio rectangles, horizontal and upright half circles, diamond. In all cases, the length scale in the various dimensionless parameters, such as Rayleigh number, is defined as the diameter of the equal area circle. Natural convection velocities were calculated for Rayleigh numbers of 1000 and 5000 with the temperature difference taken to be across (1) the maximum horizontal dimension, (2) the median horizontal line (line through centroid) and (3) the horizontal distance such that the temperature gradient is the same for shapes of equal area. For the class of shapes including the square, upright half circle and upright rectangle, the computed velocities were found to agree very closely with that of the equal area circle when the temperature difference is taken to be across the maximum horizontal dimension (condition (a)). The velocities for the horizontal rectangle and half circle were found to be approximately one half that of the equal area circle for the same condition. Better overall agreement among all shapes was obtained by setting the temperature difference across a distance such that the temperature gradients were equal for shapes of equal area.

  9. Relationship among grain size, annealing twins and shape memory effect in Fe–Mn–Si based shape memory alloys

    NASA Astrophysics Data System (ADS)

    Wang, Gaixia; Peng, Huabei; Zhang, Chengyan; Wang, Shanling; Wen, Yuhua

    2016-07-01

    In order to clarify the relationship among grain size, annealing twins and the shape memory effect in Fe–Mn–Si based shape memory alloys, the Fe–21.63Mn–5.60Si–9.32Cr–5.38Ni (weight %) alloy with a grain size ranging from 48.9 μm–253.6 μm was obtained by adjusting the heating temperature or heating time after 20% cold-rolling. The densities of grain boundaries and annealing twins increase with a decrease in grain size, whereas the volume fraction and width of stress-induced ε martensite after 9% deformation at Ms + 10 K decrease. This result indicates that grain refinement raises the constraint effects of grain boundaries and annealing twins upon martensitic transformation. In this case, the ability to suppress the plastic deformation and facilitate the stress-induced ε martensite transformation deteriorates after grain refinement owing to the enhancement of the constraint effects. It is demonstrated by the result that the difference at Ms + 10 K between the critical stress for plastic yielding and that for inducing martensitic transformation is smaller for the specimen with a grain size of 48.9 μm than for the specimen with a grain size of 253.6 μm. Therefore, the shape memory effect declined by decreasing the grain size.

  10. Relationship among grain size, annealing twins and shape memory effect in Fe-Mn-Si based shape memory alloys

    NASA Astrophysics Data System (ADS)

    Wang, Gaixia; Peng, Huabei; Zhang, Chengyan; Wang, Shanling; Wen, Yuhua

    2016-07-01

    In order to clarify the relationship among grain size, annealing twins and the shape memory effect in Fe-Mn-Si based shape memory alloys, the Fe-21.63Mn-5.60Si-9.32Cr-5.38Ni (weight %) alloy with a grain size ranging from 48.9 μm-253.6 μm was obtained by adjusting the heating temperature or heating time after 20% cold-rolling. The densities of grain boundaries and annealing twins increase with a decrease in grain size, whereas the volume fraction and width of stress-induced ɛ martensite after 9% deformation at Ms + 10 K decrease. This result indicates that grain refinement raises the constraint effects of grain boundaries and annealing twins upon martensitic transformation. In this case, the ability to suppress the plastic deformation and facilitate the stress-induced ɛ martensite transformation deteriorates after grain refinement owing to the enhancement of the constraint effects. It is demonstrated by the result that the difference at Ms + 10 K between the critical stress for plastic yielding and that for inducing martensitic transformation is smaller for the specimen with a grain size of 48.9 μm than for the specimen with a grain size of 253.6 μm. Therefore, the shape memory effect declined by decreasing the grain size.

  11. Typicality effects in contingency-shaped generalized equivalence classes.

    PubMed Central

    Galizio, Mark; Stewart, Katherine L; Pilgrim, Carol

    2004-01-01

    Two experiments were conducted using match-to-sample methodologies in an effort to model lexical classes, which include both arbitrary and perceptual relations between class members. Training in both experiments used a one-to-many mapping procedure with nonsense syllables as samples and eight sets of abstract stimuli as comparisons. These abstract stimuli differed along a number of dimensions, four of which were critical to the experimenter-defined class membership. Stimuli in some comparison sets included only one of the class-defining features, but stimuli in other sets included two, three, or all four of the critical features. After mastery of the baseline training, three types of probe tests were conducted: symmetry, transitivity/equivalence, and novel probe tests in which the training nonsense syllables served as samples, and comparisons were novel abstract stimuli that included one or more of the class-defining features. Symmetry and transitivity/equivalence probe tests showed that the stimuli used in training became members of equivalence classes. The novel stimuli also became class members on the basis of inclusion of any of the critical features. Thus these probe tests revealed the formation of open-ended generalized equivalence classes. In addition, typicality effects were observed such that comparison sets with more critical features were learned with fewer errors, responded to more rapidly, and judged to be better exemplars of the class. Contingency-shaped stimulus classes established through a match-to-sample procedure thus show several important behavioral similarities to natural lexical categories. PMID:15693522

  12. Temperature memory effect in amorphous shape memory polymers.

    PubMed

    Yu, Kai; Qi, H Jerry

    2014-12-21

    Temperature memory effect (TME) refers to the ability of shape memory polymers (SMPs) to memorize the temperature at which pre-deformation was conducted. In the past few years, this TME was experimentally demonstrated by comparing the applied programming temperature (Td) with a characteristic recovery temperature (Tc), which corresponds to either the maximum recovery stress or free recovery speed. In these well-designed experiments, Tc was observed to be close to Td, which is consistent with the intuitive understanding of 'memorization'. However, since the polymer recovery behavior has been proved to be strongly dependent on various programming and recovery conditions, a new question that whether Tc is always equal to Td in any thermo-temporal conditions remains to be addressed. In this paper, we answered this question by examining the free recovery profile of an acrylate based amorphous SMP. The recovery Tc, which is the temperature with the maximum recovery speed, versus the recovery temperature is shown to be strongly dependent on both programming and recovery conditions. Their detailed influence could be explained by using the reduced time. During a thermomechanical working cycle of SMPs, in addition to the Td, any other thermo-temporal conditions, such as the holding time (th), cooling rate, recovery heating rate (q), etc., can affect the observed Tc by changing the reduced programming or recovery time. In this manner, the relationship between Tc and Td is not uniquely determined. Besides, the TME in SMPs can only be achieved within a given temperature range. Both onset and offset of this temperature range are shown to be influenced by the programming history, but are independent of the recovery conditions.

  13. The effects of 3-D shaping on ITG stability

    NASA Astrophysics Data System (ADS)

    Rorvig, Mordechai; Hegna, Chris

    2012-03-01

    In this work we seek to understand how 3-D shaping can be used to improve ion temperature gradient stability. Part of the difficulty in deducing the role of 3-D shaping is the generation of 3-D MHD equilibria necessary for the calculations. In this work, MHD equilibrium surfaces are generated using local 3-D magnetostatic equilibrium theory [1]. We distinguish three different types of toroidal magnetic surface shaping: axisymmetric shaping, toroidal rotation of the cross section, and toroidal translation of the magnetic axis. We study these types of shaping independently and in combination to look for improvements. Linear growth rates for ITG modes are calculated using the gyrokinetics code GENE [2]. The geometric interface package GIST [3] accepts the equilibrium input data from the local equilibrium calculation. Growth rates for both axisymmetric and 3-D equilibrium calculations are presented. [4pt] [1] C. C. Hegna, Physics of Plasmas 7, 3921 (2000).[0pt] [2] F. Jenko, W. Dorland, M. Kotschenreuther, and B. N. Rogers, Physical Review Letters 7, 1904 (2000).[0pt] [3] P. Xanthopoulos, W. A. Cooper, F. Jenko, Yu. Turkin, A. Runov, and J. Geiger, Physics of Plasmas 16, 082303 (2009).

  14. Dome-shaped PDC cutters drill harder rock effectively

    SciTech Connect

    Moran, D.P. )

    1992-12-14

    This paper reports that rock mechanics and sonic travel time log data indicate that bits with convex-shaped polycrystalline diamond compact (PDC) cutters can drill harder rock formations than comparable bits with flat PDC cutters. The Dome-shaped cutters have drilled carbonate formations with sonic travel times as small as 50 [mu]sec/ft, compared to the standard cutoff of 75 [mu]sec/ft for flat PCD cutters. Recent field data from slim hole wells drilled in the Permian basin have shown successful applications of the 3/8-in. Dome cutter in the Grayburg dolomite with its sonic travel times as low as 50-55 [mu]sec/ft and compressive strengths significantly greater than the standard operating range for PDC bit applications. These field data indicate that the Dome cutters can successfully drill hard rock. The convex cutter shape as good impact resistance, cuttings removal, heat dissipation, and wear resistance.

  15. Effects of pulse shape on indirect drive ICF capsule robustness

    NASA Astrophysics Data System (ADS)

    Fetterman, Abe; Haan, Steve; Herrmann, Mark; Salmonson, Jay; Marinak, Michael

    2004-11-01

    The pulse shape incident on an ICF capsule plays an important role in determining the capsule's performance. Keeping the capsule on a low adiabat maximizes its compressibility and reduces the energy required for ignition. However, 2D studies of direct drive designs suggest that capsules with high adiabats are more robust with respect to the growth of perturbations than capsules with lower adiabats. The question arises, what is the optimal adiabat and pulse shape for an indirect drive inertial confinement fusion capsule? Is there any advantage in having the adiabat above the absolute minimum? To answer these questions we have developed an automated pulse shaper for the HYDRA computer codefootnote[2]Marinak, M. M. et. al. ``Three-dimensional HYDRA simulations of National Ignition Facility targets'' Phys. Plasmas 8, 2275 (2001). and used it to study the sensitivity of indirect drive capsules to various pulse shapes.

  16. Scoliosis surgery and its effect on back shape.

    PubMed

    Jefferson, R J; Weisz, I; Turner-Smith, A R; Harris, J D; Houghton, G R

    1988-03-01

    Thirty-four patients with adolescent idiopathic scoliosis were assessed by radiography and the integrated shape imaging system (ISIS) both before and after spinal surgery. Twenty-seven patients underwent Harrington instrumentation, after which lateral indices of curvature were significantly improved, but changes in the transverse plane were less pronounced. Sublaminar wiring was carried out in two patients whose thoracic lordosis was corrected by the surgery. Five patients whose severe deformity had persisted after previous spinal surgery underwent costoplasty, which resulted in a significant improvement in back shape measurements. We conclude that the cosmetic deformity of the back in scoliosis is only partially corrected by operations on the spine itself, whilst costoplasty addresses the problem directly, and improves the surface shape. PMID:3346300

  17. Word Superiority and Word Shape Effects in Beginning Readers.

    ERIC Educational Resources Information Center

    Feitelson, Dina; Razel, Micha

    1984-01-01

    Examines the notion that words are sometimes perceived with greater ease than letters and that word shape sometimes plays a role in the perception of words. The data collected from 40 Israeli kindergarteners revealed that beginning readers found it easier to identify single letters than whole words, thus refuting the above notion. (Author/AS)

  18. The piston ring shape and its effects on engine performance

    SciTech Connect

    Ma, J.; Ryan, T.W.; Winter, J.; Dixon, R.

    1996-09-01

    The paper presents the latest research results on the piston ring free shape. A new free shape measurement method with optical gauging was developed. Three numerical models to compute the contact force distribution of piston ring were developed using finite element analysis (FEA). These numerical methods have been compared with each other, and validated with the experimental results of ring deformation in a ring gage. The contact force distribution of a piston ring at working condition was also studied. It consists of the ring thermal boundary conditions (RTBC) validation, 3-D FEA thermal analysis and thermal contact force computation based on validated wire-cable element model. The RTBC for heavy duty diesel engine has been validated for the first time using a CUMMINS L10 engine test. Three different free shapes have been tested. The wear band measurements of tested rings all show tremendous improvements over the standard top ring. It was found that the tip contact concentration is a key factor of tip scuffing during break-in. A procedure to define a free shape producing uniform contact force distribution at working condition was developed.

  19. Shared Learning Shapes Human Performance: Transfer Effects in Task Sharing

    ERIC Educational Resources Information Center

    Milanese, Nadia; Iani, Cristina; Rubichi, Sandro

    2010-01-01

    We investigated whether performing a task with a co-actor shapes the way a subsequent task is performed. In four experiments participants were administered a Simon task after practicing a spatial compatibility task with an incompatible S-R mapping. In Experiment 1 they performed both tasks alongside another person; in Experiment 2 they performed…

  20. Effect of systematic dental shape modification in bitemarks.

    PubMed

    Holtkötter, Hannah; Sheets, H David; Bush, Peter J; Bush, Mary A

    2013-05-10

    Studies on human cadaver models have reported significant levels of distortion of bitemarks in skin, indicating that tooth characteristics are not reliably transferred and recorded in the bitten subject. Moreover, matches among the anterior biting dentition in open population studies have been found. This prompts the question as to what degree of difference in shape will distinguish one dentition from another as reflected in a bitemark. In order to understand how these variables appear on skin, 10 dental casts with systematic variations in tooth positions were produced. The height of the lateral incisors was systematically altered in 1mm increments up to 3mm and lateral incisor/canines were altered in facial/lingual displacement in 1mm increments up to 5mm. Each of the models was used to produce a series of 10 repeated bites, distributed over arms and legs of un-embalmed cadavers. Landmark-based geometric morphometrics were used for analysis of digital images of the bitemarks. Results indicate that alterations of height and displacement of particular teeth affected the position of impressions created by the adjacent teeth. Displacement of one lateral incisor/canine led to a relative shift in impressions of the central incisors and unaltered canines, while height alteration of the lateral incisors led to a shift in relative position of central incisors as recorded in the bitemark. The prominence of displacements was more pronounced in the bitemarks than in images of the dentition used to make the bites, thus the bitemarks tended to exaggerate the differences. It was found that a displacement of 5mm between teeth allowed for reliable distinction between bitemarks. No such threshold of distinction could be established for differences in height of teeth under these experimental conditions. The effect of distortion was more significant in the mandibular than maxillary arch, suggesting that the mandible exhibits higher variation than the maxilla, as impressed in skin

  1. Unambiguous observation of shape effects on cellular fate of nanoparticles

    NASA Astrophysics Data System (ADS)

    Chu, Zhiqin; Zhang, Silu; Zhang, Bokai; Zhang, Chunyuan; Fang, Chia-Yi; Rehor, Ivan; Cigler, Petr; Chang, Huan-Cheng; Lin, Ge; Liu, Renbao; Li, Quan

    2014-03-01

    Cellular fate of nanoparticles is vital to application of nanoparticles to cell imaging, bio-sensing, drug delivery, suppression of drug resistance, gene delivery, and cytotoxicity analysis. However, the current studies on cellular fate of nanoparticles have been controversial due to complications of interplay between many possible factors. By well-controlled experiments, we demonstrated unambiguously that the morphology of nanoparticles independently determined their cellular fate. We found that nanoparticles with sharp shapes, regardless of their surface chemistry, size, or composition, could pierce the membranes of endosomes that carried them into the cells and escape to the cytoplasm, which in turn significantly reduced the cellular excretion rate of the nanoparticles. Such features of sharp-shaped nanoparticles are essential for drug delivery, gene delivery, subcellular targeting, and long-term tracking. This work opens up a controllable, purely geometrical and hence safe, degree of freedom for manipulating nanoparticle-cell interaction, with numerous applications in medicine, bio-imaging, and bio-sensing.

  2. Ion shape effect on dynamics of ionic liquids

    NASA Astrophysics Data System (ADS)

    Liu, Hongjun; Maginn, Edward

    2012-02-01

    Ionic liquids (ILs) are a group of salts composing of an organic cation and organic or inorganic anion with melting points below 100 ^oC and have many suitable properties, such as negligible vapor pressure, low flammability, high ionic conductivity and high thermal stability for various applications. Moreover, a great number of ILs with a variety of physical and chemical properties can be synthesized from a combination of different cations (most differently substituted imidazolium, pyridinium, and quaternary ammonium or phosphonium ions) and anions. One can judiciously select from a multitude of ILs to suit a specific application, where the concept of designer solvent comes from. To expedite the development process of target ILs, it is crucial to understand the relationship between ion shape and dynamics of ILs. We studied a wide range of ILs with different ion shape pairings and found the planar-planar paired ILs have a better dynamics as a whole.

  3. Effect of illite particle shape on cesium sorption

    USGS Publications Warehouse

    Rajec, P.; Sucha, V.; Eberl, D.D.; Srodon, J.; Elsass, F.

    1999-01-01

    Samples containing illite and illite-smectite, having different crystal shapes (plates, "barrels", and filaments), were selected for sorption experiments with cesium. There is a positive correlation between total surface area and Cs-sorption capacity, but no correlation between total surface area and the distribution coefficient, Kd. Generally Kd increases with the edge surface area, although "hairy" (filamentous) illite does not fit this pattern, possibly because elongation of crystals along one axis reduces the number of specific sorption sites.

  4. Effect of quench on alpha/beta pulse shape discrimination of liquid scintillation cocktails.

    PubMed

    DeVol, Timothy A; Theisen, Christopher D; DiPrete, David P

    2007-05-01

    The objectives of this paper are (1) to illustrate that knowledge of the external quench parameter is insufficient to properly setup a pulse shape discriminating liquid scintillation counter (LSC) for quantitative measurement, (2) to illustrate dependence on pulse shape discrimination on the radionuclide (more than just radiation and energy), and (3) to compare the pulse shape discrimination (PSD) of two commercial instruments. The effects various quenching agents, liquid scintillation cocktails, radionuclides, and LSCs have on alpha/beta pulse shape discriminating liquid scintillation counting were quantified. Alpha emitting radionuclides (239)Pu and (241)Am and beta emitter (90)Sr/(90)Y were investigated to quantify the nuclide dependence on alpha/beta pulse shape discrimination. Also, chemical and color quenching agents, nitromethane, nitric acid, and yellow dye impact on alpha/beta pulse shape discrimination using PerkinElmer Optiphase "HiSafe" 2 and 3, and Ultima Gold AB liquid scintillation cocktails were determined. The prepared samples were counted on the PerkinElmer Wallac WinSpectral 1414 alpha/beta pulse shape discriminating LSC. It was found that for the same level of quench, as measured by the external quench parameter, different quench agents influenced the pulse shape discrimination and the pulse shape discrimination parameters differently. The radionuclide also affects alpha/beta pulse shape discrimination. By comparison with the PerkinElmer Tri-carb 3150 TR/AB, the Wallac 1414 exhibited better pulse shape discrimination capability under the same experimental conditions. PMID:17440321

  5. Prediction of ice shapes and their effect on airfoil performance

    NASA Technical Reports Server (NTRS)

    Shin, Jaiwon; Berkowitz, Brian; Chen, Hsun H.; Cebeci, Tuncer

    1991-01-01

    Calculations of ice shapes and the resulting drag increases are presented for experimental data on an NACA 0012 airfoil. They were made with a combination of LEWICE and interactive boundary-layer codes for a wide range of conditions which include airspeed and temperature, the droplet size and liquid water content of the cloud, and the angle of attack of the airfoil. In all cases the calculated results account for the drag increase due to ice accretion and, in general, show good agreement with data.

  6. Prediction of ice shapes and their effect on airfoil performance

    NASA Technical Reports Server (NTRS)

    Shin, Jaiwon; Berkowitz, Brian; Chen, Hsun; Cebeci, Tuncer

    1991-01-01

    Calculations of ice shapes and the resulting drag increases are presented for experimental data on a NACA 0012 airfoil. They were made with a combination of LEWICE and interactive boundary-layer codes for a wide range of conditions which include air speed and temperature, the droplet size and liquid water content of the cloud, and the angle of attack of the airfoil. In all cases, the calculated results account for the drag increase due to ice accretion and, in general, show good agreement.

  7. Carrier-wave shape effects in optical filamentation.

    PubMed

    Brown, J M; Shanor, C; Wright, E M; Kolesik, M

    2016-03-01

    Strong-field ionization in optical filaments created by ultrashort pulses with sub-cycle engineered waveforms is studied theoretically. To elucidate the physics of the recently demonstrated enhanced ionization yield and spatial control of the optical filament core in two color pulses, we employ two types of quantum models integrated into spatially resolved pulse-propagation simulations. We show that the dependence of the ionization on the shape of the excitation carrier is adiabatic in nature, and is driven by local temporal peaks of the electric field. Implications for the modeling of light-matter interactions in multicolor optical fields are also discussed. PMID:26974064

  8. Size effects on pull-out of bone shaped fibers

    SciTech Connect

    Tippetts, T. B.; Beyerlein, Irene J.; Zhu, Y. T.

    2001-01-01

    Recent work has demonstrated that ductile bone shaped short (BSS) fibers, i.e. fibers with enlarged ends, can significantly increase toughness of brittle materials over that of conventional short fibers (CSS) [1]. In this work, we apply a recently developed micromechanical model for the pull-out force vs. displacement response of a ductile BSS fiber as it pulls completely out of a brittle matrix material. The pull-out process of BSS fibers absorbs more energy than that of CSS fibers, largely due to nonlinear deformation of the fiber end and surrounding matrix.

  9. Flux-surface shaping effects on tokamak edge turbulence and flows

    SciTech Connect

    Kendl, Alexander; Scott, Bruce D.

    2006-01-15

    Shaping of magnetic flux surfaces is found to have a strong impact on turbulence and transport in tokamak edge plasmas. A series of axisymmetric equilibria, with varying elongation and triangularity, and a divertor configuration are implemented into a computational gyrofluid turbulence model. The mechanisms of shaping effects on turbulence and flows are identified. Transport is mainly reduced by local magnetic shearing and an enhancement of zonal shear flows induced by elongation and X-point shaping.

  10. [Effects of canopy shapes of grape on canopy microenvironment, leaf and fruit quality in greenhouse].

    PubMed

    Shi, Xiang-bin; Liu, Feng-zhi; Cheng, Cun-gang; Wang, Xiao-di; Wang, Bao-liang; Zheng, Xiao-cui; Wang, Hai-bo

    2015-12-01

    The effects of three canopy shapes, i.e., vertical canopy, V-shaped canopy and horizontal canopy, on canopy microenvironment, quality of leaves and fruits were studied in the 3-year-old grape 'Jingmi' grafted on ' Beta' in greenhouse. The results showed that gap fraction and openness of vertical canopy were significantly higher than that of V-shaped canopy and horizontal canopy, and leaf area index, light interception rate and canopy temperature difference between day and night were significantly lower than those of V-shaped canopy and horizontal canopy. There was no significant difference between the latter two treatments. The palisade thickness of V-shaped canopy was significantly greater than that of vertical canopy, and horizontal canopy was in the middle. The chlorophyll and carotenoid contents of V-shaped canopy were significantly higher than those of vertical canopy and horizontal canopy, and those in the latter two treatments had no significant difference. The fruit quality of V-shaped canopy was the best, and that of horizontal canopy was the worst. The results of GC-MS analysis showed that 29 types of volatile aroma compounds were detected in V-shaped canopy, but just 17 and 16 in vertical canopy and horizontal canopy, respectively. In V-shaped canopy, the characteristic aroma in grape 'Jingmi' was higher, except ethanol, trans-2- hexene-1-alcohol, 2-octyl ketone and formic acid ester. The linalool content in vertical canopy and V-shaped canopy was higher than that in horizontal canopy. The nerol content in V-shaped canopy was higher than that in vertical canopy and horizontal canopy, and the leaf alcohol content in V-shaped canopy and horizontal canopy was higher than that in vertical canopy. The citronellol was de-tected only in V-shaped canopy. In greenhouse, the fruit aroma of V-shaped canopy grape was stronger, and well reflected the variety characteristics. PMID:27112012

  11. [Effects of canopy shapes of grape on canopy microenvironment, leaf and fruit quality in greenhouse].

    PubMed

    Shi, Xiang-bin; Liu, Feng-zhi; Cheng, Cun-gang; Wang, Xiao-di; Wang, Bao-liang; Zheng, Xiao-cui; Wang, Hai-bo

    2015-12-01

    The effects of three canopy shapes, i.e., vertical canopy, V-shaped canopy and horizontal canopy, on canopy microenvironment, quality of leaves and fruits were studied in the 3-year-old grape 'Jingmi' grafted on ' Beta' in greenhouse. The results showed that gap fraction and openness of vertical canopy were significantly higher than that of V-shaped canopy and horizontal canopy, and leaf area index, light interception rate and canopy temperature difference between day and night were significantly lower than those of V-shaped canopy and horizontal canopy. There was no significant difference between the latter two treatments. The palisade thickness of V-shaped canopy was significantly greater than that of vertical canopy, and horizontal canopy was in the middle. The chlorophyll and carotenoid contents of V-shaped canopy were significantly higher than those of vertical canopy and horizontal canopy, and those in the latter two treatments had no significant difference. The fruit quality of V-shaped canopy was the best, and that of horizontal canopy was the worst. The results of GC-MS analysis showed that 29 types of volatile aroma compounds were detected in V-shaped canopy, but just 17 and 16 in vertical canopy and horizontal canopy, respectively. In V-shaped canopy, the characteristic aroma in grape 'Jingmi' was higher, except ethanol, trans-2- hexene-1-alcohol, 2-octyl ketone and formic acid ester. The linalool content in vertical canopy and V-shaped canopy was higher than that in horizontal canopy. The nerol content in V-shaped canopy was higher than that in vertical canopy and horizontal canopy, and the leaf alcohol content in V-shaped canopy and horizontal canopy was higher than that in vertical canopy. The citronellol was de-tected only in V-shaped canopy. In greenhouse, the fruit aroma of V-shaped canopy grape was stronger, and well reflected the variety characteristics.

  12. Platinum nanoparticle shape effects on benzene hydrogenation selectivity.

    PubMed

    Bratlie, Kaitlin M; Lee, Hyunjoo; Komvopoulos, Kyriakos; Yang, Peidong; Somorjai, Gabor A

    2007-10-01

    Benzene hydrogenation was investigated in the presence of a surface monolayer consisting of Pt nanoparticles of different shapes (cubic and cuboctahedral) and tetradecyltrimethylammonium bromide (TTAB). Infrared spectroscopy indicated that TTAB binds to the Pt surface through a weak C-H...Pt bond of the alkyl chain. The catalytic selectivity was found to be strongly affected by the nanoparticle shape. Both cyclohexane and cyclohexene product molecules were formed on cuboctahedral nanoparticles, whereas only cyclohexane was produced on cubic nanoparticles. These results are the same as the product selectivities obtained on Pt(111) and Pt(100) single crystals in earlier studies. The apparent activation energy for cyclohexane production on cubic nanoparticles is 10.9 +/- 0.4 kcal/mol, while for cuboctahedral nanoparticles, the apparent activation energies for cyclohexane and cyclohexene production are 8.3 +/- 0.2 and 12.2 +/- 0.4 kcal/mol, respectively. These activation energies are lower, and corresponding turnover rates are three times higher than those obtained with single-crystal Pt surfaces.

  13. Effect of silver on the shape of palladium nanoparticles

    NASA Astrophysics Data System (ADS)

    Gupta, Dikshita; Barman, P. B.; Hazra, S. K.

    2016-05-01

    We report a facile route to prepare palladium-silver nanoparticles at considerably low temperature. First the controlled synthesis of palladium nanoparticles was performed via reduction of sodium tetrachloropalladate (II) in ethylene glycol in the presence of PVP(polyvinylpyrrolidone) as capping agent. The reaction was carried out at three different temperatures-80°C, 100°C and 120°C for one hour. Short reaction time and low synthesis temperature adds advantage to this method over others. Formed palladium nanoparticles were nearly spherical with the average particle size of 7.5±0.5 nm, 9.5±0.5 nm and 10.5±0.5 nm at 80°C, 100°C and 120°C respectively. Secondly, the palladium-silver nanoparticles were prepared by the simultaneous reduction of palladium and silver from their respective precursors in ethylene glycol at 100°C (optimized temperature). The shape and size distribution was studied by TEM (Transmission Electron Microscopy). The role of silver in transforming the shape of palladium nanoparticles from spherical to triangular has been discussed. Spherical symmetry of palladium nanoparticles is disturbed by the interaction of silver ions on the crystal facets of palladium nanoparticles. From UV-vis spectra, the absorption maxima of palladium nanoparticles at 205 nm and absorption maxima of palladium-silver nanoparticles at 272 nm revealed the partial evidence of their formation.

  14. Unambiguous observation of shape effects on cellular fate of nanoparticles

    PubMed Central

    Chu, Zhiqin; Zhang, Silu; Zhang, Bokai; Zhang, Chunyuan; Fang, Chia-Yi; Rehor, Ivan; Cigler, Petr; Chang, Huan-Cheng; Lin, Ge; Liu, Renbao; Li, Quan

    2014-01-01

    Cellular fate of nanoparticles is vital to application of nanoparticles to cell imaging, bio-sensing, drug delivery, suppression of drug resistance, gene delivery, and cytotoxicity analysis. However, the current studies on cellular fate of nanoparticles have been controversial due to complications of interplay between many possible factors. By well-controlled experiments, we demonstrated unambiguously that the morphology of nanoparticles independently determined their cellular fate. We found that nanoparticles with sharp shapes, regardless of their surface chemistry, size, or composition, could pierce the membranes of endosomes that carried them into the cells and escape to the cytoplasm, which in turn significantly reduced the cellular excretion rate of the nanoparticles. Such features of sharp-shaped nanoparticles are essential for drug delivery, gene delivery, subcellular targeting, and long-term tracking. This work opens up a controllable, purely geometrical and hence safe, degree of freedom for manipulating nanoparticle-cell interaction, with numerous applications in medicine, bio-imaging, and bio-sensing. PMID:24675513

  15. Unambiguous observation of shape effects on cellular fate of nanoparticles.

    PubMed

    Chu, Zhiqin; Zhang, Silu; Zhang, Bokai; Zhang, Chunyuan; Fang, Chia-Yi; Rehor, Ivan; Cigler, Petr; Chang, Huan-Cheng; Lin, Ge; Liu, Renbao; Li, Quan

    2014-01-01

    Cellular fate of nanoparticles is vital to application of nanoparticles to cell imaging, bio-sensing, drug delivery, suppression of drug resistance, gene delivery, and cytotoxicity analysis. However, the current studies on cellular fate of nanoparticles have been controversial due to complications of interplay between many possible factors. By well-controlled experiments, we demonstrated unambiguously that the morphology of nanoparticles independently determined their cellular fate. We found that nanoparticles with sharp shapes, regardless of their surface chemistry, size, or composition, could pierce the membranes of endosomes that carried them into the cells and escape to the cytoplasm, which in turn significantly reduced the cellular excretion rate of the nanoparticles. Such features of sharp-shaped nanoparticles are essential for drug delivery, gene delivery, subcellular targeting, and long-term tracking. This work opens up a controllable, purely geometrical and hence safe, degree of freedom for manipulating nanoparticle-cell interaction, with numerous applications in medicine, bio-imaging, and bio-sensing. PMID:24675513

  16. Development of Superelastic Effect in Ferrous Shape Memory Alloy

    NASA Astrophysics Data System (ADS)

    Olson, Scott

    Shape memory alloys (SMAs) with high levels of superelasticity are used where there is a need for the application of large levels of force, or high damping. Current commercially available SMAs require expensive fabrication and lack sufficient ductility for many applications. There is a need for a superelastic material with better properties and easier processing. Y. Tanaka et al. have developed a novel iron based shape memory alloy, NCATB. This alloy still requires complex thermomechanical processing, and does not utilize lessons learned in optimizing Nitinol. To develop the properties of this alloy, it was synthesized in lab from its constituent elements, and thermomechanically processed. Samples were prepared for analysis using conventional metallographic techniques, and investigated with light optical microscopy, scanning electron microscopy equipped with energy dispersive spectroscopy, X-ray diffraction, and mechanical testing. The recrystallization following cold rolling, as well as aging heat treatments, were determined to be critical to increasing the hardness of the NCATB. Overall, smaller grains and longer aging times increased the hardness. The as-cast microstructure exhibits significant tantalum segregation along the dendrite boundaries. Incomplete homogenization of the as-cast microstructure leads to a propensity for a Tarich phase to form along subsequent recrystallized grain boundaries. This phase lead to alloy embrittlement, preventing the NCATB as processed from having the desired superelasticity. An additional high temperature thermomechanical treatment following casting solutionized the tantalum from the dendrite boundaries, and further improved the NCATB hardenability.

  17. Effects of aging on the characteristics of TiNiPd shape memory alloy thin films

    SciTech Connect

    Zhang Congchun

    2008-07-15

    TiNiPd thin films have been deposited on glass substrate using R.F. magnetron sputtering. Effects of annealing and aging on the microstructure, phase transformation behaviors and shape memory effects of these thin films have been studied by X-ray diffractometry, differential scanning calorimeter, tensile tests and internal friction characteristics. The TiNiPd thin films annealed at 750 deg. C exhibit uniform martensite/austenite transformations and shape memory effect. Aging at 450 deg. C for 1 h improved the uniformity of transformations and shape memory effect. Long time aging decreased transformation temperatures and increased the brittleness of TiNiPd thin films.

  18. Cruising the rain forest floor: butterfly wing shape evolution and gliding in ground effect.

    PubMed

    Cespedes, Ann; Penz, Carla M; DeVries, Philip J

    2015-05-01

    Flight is a key innovation in the evolutionary success of insects and essential to dispersal, territoriality, courtship and oviposition. Wing shape influences flight performance and selection likely acts to maximize performance for conducting essential behaviours that in turn results in the evolution of wing shape. As wing shape also contributes to fitness, optimal shapes for particular flight behaviours can be assessed with aerodynamic predictions and placed in an ecomorphological context. Butterflies in the tribe Haeterini (Nymphalidae) are conspicuous members of understorey faunas in lowland Neotropical forests. Field observations indicate that the five genera in this clade differ in flight height and behaviour: four use gliding flight at the forest floor level, and one utilizes flapping flight above the forest floor. Nonetheless, the association of ground level gliding flight behaviour and wing shape has never been investigated in this or any other butterfly group. We used landmark-based geometric morphometrics to test whether wing shapes in Haeterini and their close relatives reflected observed flight behaviours. Four genera of Haeterini and some distantly related Satyrinae showed significant correspondence between wing shape and theoretical expectations in performance trade-offs that we attribute to selection for gliding in ground effect. Forewing shape differed between sexes for all taxa, and male wing shapes were aerodynamically more efficient for gliding flight than corresponding females. This suggests selection acts differentially on male and female wing shapes, reinforcing the idea that sex-specific flight behaviours contribute to the evolution of sexual dimorphism. Our study indicates that wing shapes in Haeterini butterflies evolved in response to habitat-specific flight behaviours, namely gliding in ground effect along the forest floor, resulting in ecomorphological partitions of taxa in morphospace. The convergent flight behaviour and wing morphology

  19. Shape-memory effect in amorphous potato starch: The influence of local orders and paracrystallinity.

    PubMed

    Chevigny, Chloé; Foucat, Loïc; Rolland-Sabaté, Agnès; Buléon, Alain; Lourdin, Denis

    2016-08-01

    In this paper, a detailed characterization of the mechanisms at the origin of the shape-memory effect in amorphous potato starch is presented. Using different treatments (annealing) and preparation methods (hot casting and extrusion), the local structures responsible for the shape-memory were disrupted, as evidenced in the first part of the article detailing the macroscopic properties: mechanical, calorimetric and shape-memory. In the second part the macromolecular scale is investigated using X-rays diffraction and CP-MAS NMR, and thus allows making the link between the structural differences and the macroscopic properties. Finally we discuss the origin of shape-memory in amorphous starch. PMID:27112891

  20. Shape-memory effect in amorphous potato starch: The influence of local orders and paracrystallinity.

    PubMed

    Chevigny, Chloé; Foucat, Loïc; Rolland-Sabaté, Agnès; Buléon, Alain; Lourdin, Denis

    2016-08-01

    In this paper, a detailed characterization of the mechanisms at the origin of the shape-memory effect in amorphous potato starch is presented. Using different treatments (annealing) and preparation methods (hot casting and extrusion), the local structures responsible for the shape-memory were disrupted, as evidenced in the first part of the article detailing the macroscopic properties: mechanical, calorimetric and shape-memory. In the second part the macromolecular scale is investigated using X-rays diffraction and CP-MAS NMR, and thus allows making the link between the structural differences and the macroscopic properties. Finally we discuss the origin of shape-memory in amorphous starch.

  1. Fast Response, Open-Celled Porous, Shape Memory Effect Actuators with Integrated Attachments

    NASA Technical Reports Server (NTRS)

    Jardine, Andrew Peter (Inventor)

    2015-01-01

    This invention relates to the exploitation of porous foam articles exhibiting the Shape Memory Effect as actuators. Each foam article is composed of a plurality of geometric shapes, such that some geometric shapes can fit snugly into or around rigid mating connectors that attach the Shape Memory foam article intimately into the load path between a static structure and a moveable structure. The foam is open-celled, composed of a plurality of interconnected struts whose mean diameter can vary from approximately 50 to 500 microns. Gases and fluids flowing through the foam transfer heat rapidly with the struts, providing rapid Shape Memory Effect transformations. Embodiments of porous foam articles as torsional actuators and approximately planar structures are disposed. Simple, integral connection systems exploiting the ability to supply large loads to a structure, and that can also supply hot and cold gases and fluids to effect rapid actuation are also disposed.

  2. Investigation of the effects of inlet shapes on fan noise radiation

    NASA Astrophysics Data System (ADS)

    Clark, T. L.; Slotboom, D. R.; Vaidya, P. G.

    1981-04-01

    The effect of inlet shape on forward radiated fan tone noise directivities was investigated under experimentally simplified zero flow conditions. Simulated fan tone noise was radiated to the far field through various shaped zero flow inlets. Baseline data were collected for the simplest baffled and unbaffled straight pipe inlets. These data compared well with prediction. The more general inlet shapes tested were the conical, circular, and exponential surfaces of revolution and an asymmetric inlet achieved by cutting a straight pipe inlet at an acute angle. Approximate theories were developed for these general shapes and some comparisons with data are presented. The conical and exponential shapes produced directivities that differed considerably from the baseline data while the circular shape produced directivities similar to the baseline data. The asymmetric inlet produced asymmetric directivities with significant reductions over the straight pipe data for some angles.

  3. Dynamic shape effect in {sup 126}Ba at low spin

    SciTech Connect

    Dewald, A.; Weil, D.; Kruecken, R.; Kuehn, R.; Peusquens, R.; Tiesler, H.; Vogel, O.; Zell, K.O.; von Brentano, P.; Bazzacco, D.; Rossi-Alvarez, C.; Pavan, P.; DeAcuna, D.; De Angelis, G.; De Poli, M. ||

    1996-11-01

    Lifetimes of excited states in {sup 126}Ba have been measured with high precision by means of the GASP spectrometer using the coincidence recoil distance technique. The reaction {sup 100}Mo({sup 30}Si,4{ital n}) {sup 126}Ba at a beam energy of 130 MeV was used. The data were analyzed with the differential decay-curve method (DDCM). The obtained transition quadrupole moments disagree with the predictions of the asymmetric rotor model (ARM), the interacting boson model (IBM), and the general collective model (GCM). They give evidence for a sudden dynamic shape change in {sup 126}Ba between the 4{sup +} and 10{sup +} levels of the ground-state band. {copyright} {ital 1996 The American Physical Society.}

  4. Effects of Caricaturing in Shape or Color on Familiarity Decisions for Familiar and Unfamiliar Faces

    PubMed Central

    Itz, Marlena L.; Schweinberger, Stefan R.; Kaufmann, Jürgen M.

    2016-01-01

    Recent evidence suggests that while reflectance information (including color) may be more diagnostic for familiar face recognition, shape may be more diagnostic for unfamiliar face identity processing. Moreover, event-related potential (ERP) findings suggest an earlier onset for neural processing of facial shape compared to reflectance. In the current study, we aimed to explore specifically the roles of facial shape and color in a familiarity decision task using pre-experimentally familiar (famous) and unfamiliar faces that were caricatured either in shape-only, color-only, or both (full; shape + color) by 15%, 30%, or 45%. We recorded accuracies, mean reaction times, and face-sensitive ERPs. Performance data revealed that shape caricaturing facilitated identity processing for unfamiliar faces only. In the ERP data, such effects of shape caricaturing emerged earlier than those of color caricaturing. Unsurprisingly, ERP effects were accentuated for larger levels of caricaturing. Overall, our findings corroborate the importance of shape for identity processing of unfamiliar faces and demonstrate an earlier onset of neural processing for facial shape compared to color. PMID:26900690

  5. Effects of Caricaturing in Shape or Color on Familiarity Decisions for Familiar and Unfamiliar Faces.

    PubMed

    Itz, Marlena L; Schweinberger, Stefan R; Kaufmann, Jürgen M

    2016-01-01

    Recent evidence suggests that while reflectance information (including color) may be more diagnostic for familiar face recognition, shape may be more diagnostic for unfamiliar face identity processing. Moreover, event-related potential (ERP) findings suggest an earlier onset for neural processing of facial shape compared to reflectance. In the current study, we aimed to explore specifically the roles of facial shape and color in a familiarity decision task using pre-experimentally familiar (famous) and unfamiliar faces that were caricatured either in shape-only, color-only, or both (full; shape + color) by 15%, 30%, or 45%. We recorded accuracies, mean reaction times, and face-sensitive ERPs. Performance data revealed that shape caricaturing facilitated identity processing for unfamiliar faces only. In the ERP data, such effects of shape caricaturing emerged earlier than those of color caricaturing. Unsurprisingly, ERP effects were accentuated for larger levels of caricaturing. Overall, our findings corroborate the importance of shape for identity processing of unfamiliar faces and demonstrate an earlier onset of neural processing for facial shape compared to color.

  6. Light-, pH- and thermal-responsive hydrogels with the triple-shape memory effect.

    PubMed

    Xiao, Yao-Yu; Gong, Xiao-Lei; Kang, Yang; Jiang, Zhi-Chao; Zhang, Sheng; Li, Bang-Jing

    2016-08-23

    Light-, pH- and thermal-responsive hydrogels were prepared by introducing dansyl-aggregations and azo-cyclodextrin inclusion complexes as switches. The resulting material showed dual shape memory behavior in response to light, pH or temperature, respectively, and exhibits the triple-shape memory effect in response to light and pH sequentially.

  7. Effects of Microstimulation in the Anterior Intraparietal Area during Three-Dimensional Shape Categorization

    PubMed Central

    Verhoef, Bram-Ernst; Vogels, Rufin; Janssen, Peter

    2015-01-01

    The anterior intraparietal area (AIP) of rhesus monkeys is part of the dorsal visual stream and contains neurons whose visual response properties are commensurate with a role in three-dimensional (3D) shape perception. Neuronal responses in AIP signal the depth structure of disparity-defined 3D shapes, reflect the choices of monkeys while they categorize 3D shapes, and mirror the behavioral variability across different stimulus conditions during 3D-shape categorization. However, direct evidence for a role of AIP in 3D-shape perception has been lacking. We trained rhesus monkeys to categorize disparity-defined 3D shapes and examined AIP's contribution to 3D-shape categorization by microstimulating in clusters of 3D-shape selective AIP neurons during task performance. We find that microstimulation effects on choices (monkey M1) and reaction times (monkey M1 and M2) depend on the 3D-shape preference of the stimulated site. Moreover, electrical stimulation of the same cells, during either the 3D-shape-categorization task or a saccade task, could affect behavior differently. Interestingly, in one monkey we observed a strong correlation between the strength of choice-related AIP activity (choice probabilities) and the influence of microstimulation on 3D-shape-categorization behavior (choices and reaction time). These findings propose AIP as part of the network responsible for 3D-shape perception. The results also show that the anterior intraparietal cortex contains cells with different tuning properties, i.e. 3D-shape- or saccade-related, that can be dynamically read out depending on the requirements of the task at hand. PMID:26295941

  8. Facile and sustainable synthesis of shaped iron oxide nanoparticles: effect of iron precursor salts on the shapes of iron oxides.

    PubMed

    Sayed, Farheen N; Polshettiwar, Vivek

    2015-05-05

    A facile and sustainable protocol for synthesis of six different shaped iron oxides is developed. Notably, all the six shapes of iron oxides can be synthesised using exactly same synthetic protocol, by simply changing the precursor iron salts. Several of the synthesised shapes are not reported before. This novel protocol is relatively easy to implement and could contribute to overcome the challenge of obtaining various shaped iron oxides in economical and sustainable manner.

  9. Facile and Sustainable Synthesis of Shaped Iron Oxide Nanoparticles: Effect of Iron Precursor Salts on the Shapes of Iron Oxides

    PubMed Central

    Sayed, Farheen N.; Polshettiwar, Vivek

    2015-01-01

    A facile and sustainable protocol for synthesis of six different shaped iron oxides is developed. Notably, all the six shapes of iron oxides can be synthesised using exactly same synthetic protocol, by simply changing the precursor iron salts. Several of the synthesised shapes are not reported before. This novel protocol is relatively easy to implement and could contribute to overcome the challenge of obtaining various shaped iron oxides in economical and sustainable manner. PMID:25939969

  10. Shape and Effective Spring Constant of Liquid Interfaces Probed at the Nanometer Scale: Finite Size Effects.

    PubMed

    Dupré de Baubigny, Julien; Benzaquen, Michael; Fabié, Laure; Delmas, Mathieu; Aimé, Jean-Pierre; Legros, Marc; Ondarçuhu, Thierry

    2015-09-15

    We investigate the shape and mechanical properties of liquid interfaces down to nanometer scale by atomic force microscopy (AFM) and scanning electron microscopy (SEM) combined with in situ micromanipulation techniques. In both cases, the interface is probed with a cylindrical nanofiber with radius R of the order of 25-100 nm. The effective spring constant of the nanomeniscus oscillated around its equilibrium position is determined by static and frequency-modulation (FM) AFM modes. In the case of an unbounded meniscus, we find that the effective spring constant k is proportional to the surface tension γ of the liquid through k = (0.51 ± 0.06)γ, regardless of the excitation frequency from quasi-static up to 450 kHz. A model based on the equilibrium shape of the meniscus reproduces well the experimental data. Electron microscopy allowed to visualize the meniscus profile around the fiber with a lateral resolution of the order of 10 nm and confirmed its catenary shape. The influence of a lateral confinement of the interface is also investigated. We showed that the lateral extension L of the meniscus influences the effective spring constant following a logarithmic evolution k ∼ 2πγ/ln(L/R) deduced from the model. This comprehensive study of liquid interface properties over more than 4 orders of magnitude in meniscus size shows that advanced FM-AFM and SEM techniques are promising tools for the investigation of mechanical properties of liquids down to nanometer scale. PMID:26295187

  11. Shape and Effective Spring Constant of Liquid Interfaces Probed at the Nanometer Scale: Finite Size Effects.

    PubMed

    Dupré de Baubigny, Julien; Benzaquen, Michael; Fabié, Laure; Delmas, Mathieu; Aimé, Jean-Pierre; Legros, Marc; Ondarçuhu, Thierry

    2015-09-15

    We investigate the shape and mechanical properties of liquid interfaces down to nanometer scale by atomic force microscopy (AFM) and scanning electron microscopy (SEM) combined with in situ micromanipulation techniques. In both cases, the interface is probed with a cylindrical nanofiber with radius R of the order of 25-100 nm. The effective spring constant of the nanomeniscus oscillated around its equilibrium position is determined by static and frequency-modulation (FM) AFM modes. In the case of an unbounded meniscus, we find that the effective spring constant k is proportional to the surface tension γ of the liquid through k = (0.51 ± 0.06)γ, regardless of the excitation frequency from quasi-static up to 450 kHz. A model based on the equilibrium shape of the meniscus reproduces well the experimental data. Electron microscopy allowed to visualize the meniscus profile around the fiber with a lateral resolution of the order of 10 nm and confirmed its catenary shape. The influence of a lateral confinement of the interface is also investigated. We showed that the lateral extension L of the meniscus influences the effective spring constant following a logarithmic evolution k ∼ 2πγ/ln(L/R) deduced from the model. This comprehensive study of liquid interface properties over more than 4 orders of magnitude in meniscus size shows that advanced FM-AFM and SEM techniques are promising tools for the investigation of mechanical properties of liquids down to nanometer scale.

  12. Shape memory effect associated with a deformation at a temperature just below A[sub S] in a Fe-Mn-Cr-Si-Ni shape memory alloy

    SciTech Connect

    Federzoni, L.; Guenin, G. )

    1994-07-01

    The shape memory effect of Fe-Mn based shape memory alloys is due to the formation of stress-induced [var epsilon]-martensite by deformation and to its reversion by heating over A[sub f], which permit it to recover a part of the original shape. The shape memory effect is directly associated with the [gamma][yields][var epsilon] transformation. For this reason, the authors have established the best conditions to induce the [var epsilon]-martensite inside an austenitic matrix: the deformation must take place at a temperature close to the M[sub s]. It has been established that a deformation made at a higher temperature degrades the shape memory effect. The purpose of this paper is to evaluate the shape memory effect in the case of a deformation applied at a relatively high temperature (just below A[sub s]) on samples containing a high volume fraction of [var epsilon]-martensite before the deformation. It is shown that an other mechanism of shape memory effect occurs in these conditions and allows to reach an interesting shape memory effect ([approximately]2%).

  13. Joint effects of illumination geometry and object shape in the perception of surface reflectance

    PubMed Central

    Olkkonen, Maria; Brainard, David H

    2011-01-01

    Surface properties provide useful information for identifying objects and interacting with them. Effective utilization of this information, however, requires that the perception of object surface properties be relatively constant across changes in illumination and changes in object shape. Such constancy has been studied separately for changes in these factors. Here we ask whether the separate study of the illumination and shape effects is sufficient, by testing whether joint effects of illumination and shape changes can be predicted from the individual effects in a straightforward manner. We found large interactions between illumination and object shape in their effects on perceived glossiness. In addition, analysis of luminance histogram statistics could not account for the interactions. PMID:23145259

  14. Effect of diffuser vane shape on the performance of a centrifugal compressor stage

    NASA Astrophysics Data System (ADS)

    Reddy, T. Ch Siva; Ramana Murty, G. V.; Prasad, M. V. S. S. S. M.

    2014-04-01

    The present paper reports the results of experimental investigations on the effect of diffuser vane shape on the performance of a centrifugal compressor stage. These studies were conducted on the chosen stage having a backward curved impeller of 500 mm tip diameter and 24.5 mm width and its design flow coefficient is ϕd=0.0535. Three different low solidity diffuser vane shapes namely uncambered aerofoil, constant thickness flat plate and circular arc cambered constant thickness plate were chosen as the variants for diffuser vane shape and all the three shapes have the same thickness to chord ratio (t/c=0.1). Flow coefficient, polytropic efficiency, total head coefficient, power coefficient and static pressure recovery coefficient were chosen as the parameters for evaluating the effect of diffuser vane shape on the stage performance. The results show that there is reasonable improvement in stage efficiency and total head coefficient with the use of the chosen diffuser vane shapes as compared to conventional vaneless diffuser. It is also noticed that the aero foil shaped LSD has shown better performance when compared to flat plate and circular arc profiles. The aerofoil vane shape of the diffuser blade is seen to be tolerant over a considerable range of incidence.

  15. Tubular Scaffold with Shape Recovery Effect for Cell Guide Applications

    PubMed Central

    Hossain, Kazi M. Zakir; Zhu, Chenkai; Felfel, Reda M.; Sharmin, Nusrat; Ahmed, Ifty

    2015-01-01

    Tubular scaffolds with aligned polylactic acid (PLA) fibres were fabricated for cell guide applications by immersing rolled PLA fibre mats into a polyvinyl acetate (PVAc) solution to bind the mats. The PVAc solution was also mixed with up to 30 wt % β-tricalcium phosphate (β-TCP) content. Cross-sectional images of the scaffold materials obtained via scanning electron microscopy (SEM) revealed the aligned fibre morphology along with a significant number of voids in between the bundles of fibres. The addition of β-TCP into the scaffolds played an important role in increasing the void content from 17.1% to 25.3% for the 30 wt % β-TCP loading, which was measured via micro-CT (µCT) analysis. Furthermore, µCT analyses revealed the distribution of aggregated β-TCP particles in between the various PLA fibre layers of the scaffold. The compressive modulus properties of the scaffolds increased from 66 MPa to 83 MPa and the compressive strength properties decreased from 67 MPa to 41 MPa for the 30 wt % β-TCP content scaffold. The scaffolds produced were observed to change into a soft and flexible form which demonstrated shape recovery properties after immersion in phosphate buffered saline (PBS) media at 37 °C for 24 h. The cytocompatibility studies (using MG-63 human osteosarcoma cell line) revealed preferential cell proliferation along the longitudinal direction of the fibres as compared to the control tissue culture plastic. The manufacturing process highlighted above reveals a simple process for inducing controlled cell alignment and varying porosity features within tubular scaffolds for potential tissue engineering applications. PMID:26184328

  16. Effects of airfoil shape, thickness, camber, and angle of attack on calculated transonic unsteady airloads

    NASA Technical Reports Server (NTRS)

    Batina, J. T.

    1985-01-01

    The effects of airfoil shape, thickness, camber, and mean angle of attack on transonic unsteady airloads were investigated as calculated by the transonic small-disturbance computer code XTRAN2L. Shape effects were investigated by examining the pressure distributions, shock locations, and unsteady airloads for three 10 percent thick airfoils. NACA 0010, NACA 64A010, and parabolic arc. Thickness effects were determined by studying a single airfoil shape with three different thicknesses: NACA 0008, NACA 0010, and NACA 0012. Angle of attack and camber effects were studied by including mean angle of attack or by adding a simple parabolic camber distribution to the originally symmetric airfoils. Comparisons of unsteady airloads for different airfoil configurations show similar results caused by variations in airfoil shape, thickness, camber, or mean angle of attack. Computer costs can be reduced by limiting the number of transonic unsteady aerodynamic calculations for small changes in airfoil geometry or angle of attack.

  17. Effect of surface charge convection and shape deformation on the dielectrophoretic motion of a liquid drop.

    PubMed

    Mandal, Shubhadeep; Bandopadhyay, Aditya; Chakraborty, Suman

    2016-04-01

    The dielectrophoretic motion and shape deformation of a Newtonian liquid drop in an otherwise quiescent Newtonian liquid medium in the presence of an axisymmetric nonuniform dc electric field consisting of uniform and quadrupole components is investigated. The theory put forward by Feng [J. Q. Feng, Phys. Rev. E 54, 4438 (1996)10.1103/PhysRevE.54.4438] is generalized by incorporating the following two nonlinear effects-surface charge convection and shape deformation-towards determining the drop velocity. This two-way coupled moving boundary problem is solved analytically by considering small values of electric Reynolds number (ratio of charge relaxation time scale to the convection time scale) and electric capillary number (ratio of electrical stress to the surface tension) under the framework of the leaky dielectric model. We focus on investigating the effects of charge convection and shape deformation for different drop-medium combinations. A perfectly conducting drop suspended in a leaky (or perfectly) dielectric medium always deforms to a prolate shape and this kind of shape deformation always augments the dielectrophoretic drop velocity. For a perfectly dielectric drop suspended in a perfectly dielectric medium, the shape deformation leads to either increase (for prolate shape) or decrease (for oblate shape) in the dielectrophoretic drop velocity. Both surface charge convection and shape deformation affect the drop motion for leaky dielectric drops. The combined effect of these can significantly increase or decrease the dielectrophoretic drop velocity depending on the electrohydrodynamic properties of both the liquids and the relative strength of the electric Reynolds number and electric capillary number. Finally, comparison with the existing experiments reveals better agreement with the present theory. PMID:27176410

  18. Effect of surface charge convection and shape deformation on the dielectrophoretic motion of a liquid drop.

    PubMed

    Mandal, Shubhadeep; Bandopadhyay, Aditya; Chakraborty, Suman

    2016-04-01

    The dielectrophoretic motion and shape deformation of a Newtonian liquid drop in an otherwise quiescent Newtonian liquid medium in the presence of an axisymmetric nonuniform dc electric field consisting of uniform and quadrupole components is investigated. The theory put forward by Feng [J. Q. Feng, Phys. Rev. E 54, 4438 (1996)10.1103/PhysRevE.54.4438] is generalized by incorporating the following two nonlinear effects-surface charge convection and shape deformation-towards determining the drop velocity. This two-way coupled moving boundary problem is solved analytically by considering small values of electric Reynolds number (ratio of charge relaxation time scale to the convection time scale) and electric capillary number (ratio of electrical stress to the surface tension) under the framework of the leaky dielectric model. We focus on investigating the effects of charge convection and shape deformation for different drop-medium combinations. A perfectly conducting drop suspended in a leaky (or perfectly) dielectric medium always deforms to a prolate shape and this kind of shape deformation always augments the dielectrophoretic drop velocity. For a perfectly dielectric drop suspended in a perfectly dielectric medium, the shape deformation leads to either increase (for prolate shape) or decrease (for oblate shape) in the dielectrophoretic drop velocity. Both surface charge convection and shape deformation affect the drop motion for leaky dielectric drops. The combined effect of these can significantly increase or decrease the dielectrophoretic drop velocity depending on the electrohydrodynamic properties of both the liquids and the relative strength of the electric Reynolds number and electric capillary number. Finally, comparison with the existing experiments reveals better agreement with the present theory.

  19. Experimental comparison of ring and diamond shaped planar Hall effect bridge magnetic field sensors

    NASA Astrophysics Data System (ADS)

    Henriksen, Anders Dahl; Rizzi, Giovanni; Hansen, Mikkel Fougt

    2015-09-01

    Planar Hall effect magnetic field sensors with ring and diamond shaped geometries are experimentally compared with respect to their magnetic field sensitivity and total signal variation. Theoretically, diamond shaped sensors are predicted to be 41% more sensitive than corresponding ring shaped sensors for negligible shape anisotropy. To experimentally validate this, we have fabricated both sensor geometries in the exchange-biased stack Ni80Fe20(tFM)/Cu(tCu)/Mn80Ir20(10 nm) with tFM=10 , 20, and 30 nm and tCu=0 , 0.3, and 0.6 nm. Sensors from each stack were characterized by external magnetic field sweeps, which were analyzed in terms of a single domain model. The total signal variation of the diamond sensors was generally found to be about 40% higher than that for the ring sensors in agreement with theoretical predictions. However, for the low-field sensitivity, the corresponding improvement varied from 0% to 35% where the largest improvement was observed for sensor stacks with comparatively strong exchange bias. This is explained by the ring sensors being less affected by shape anisotropy than the diamond sensors. To study the effect of shape anisotropy, we also characterized sensors that were surrounded by the magnetic stack with a small gap of 3 μm. These sensors were found to be less affected by shape anisotropy and thus showed higher low-field sensitivities.

  20. Shape effect in cellular uptake of PEGylated nanoparticles: comparison between sphere, rod, cube and disk

    NASA Astrophysics Data System (ADS)

    Li, Ying; Kröger, Martin; Liu, Wing Kam

    2015-10-01

    The size, shape, surface property and material composition of polymer-coated nanoparticles (NPs) are four important parameters in designing efficient NP-based carriers for targeted drug delivery. However, due to the complex interplay between size, shape and surface property, most studies lead to ambiguous descriptions of the relevance of shape. To clarify its influence on the cellular uptake of PEGylated NPs, large scale molecular simulations have been performed to study differently shaped convex NPs, such as sphere, rod, cube and disk. Comparing systems with identical NP surface area, ligand-receptor interaction strength, and grafting density of the polyethylene glycol, we find that the spherical NPs exhibit the fastest internalization rate, followed by the cubic NPs, then rod- and disk-like NPs. The spherical NPs thus demonstrate the highest uptake among these differently shaped NPs. Based on a detailed free energy analysis, the NP shape effect is found to be mainly induced by the different membrane bending energies during endocytosis. The spherical NPs need to overcome a minimal membrane bending energy barrier, compared with the non-spherical counterparts, while the internalization of disk-like NPs involves a strong membrane deformation, responsible for a large free energy barrier. Besides, the free energy change per tethered chain is about a single kBT regardless of NP shape, as revealed by our self-consistent field theory calculations, where kB and T denote Boltzmann constant and temperature, respectively. Thus, the NP shape only plays the secondary role in the free energy change of grafted PEG polymers during internalization. We also find that star-shaped NPs can be quickly wrapped by the cell membrane, similar to their spherical counterparts, indicating star-shaped NPs can be used for drug delivery with high efficacy. Our findings seem to provide useful guidance in the molecular design of PEGylated NPs for controllable cellular uptake and help establish

  1. How the Intrinsic Shapes of Galaxy Clusters Influence Distance Determinations using the SZ Effect

    NASA Astrophysics Data System (ADS)

    Hughes, J. P.

    1999-05-01

    The intrinsic 3-D shape of the hot gas in clusters of galaxies has a critical influence on the interpretation of X-ray and Sunyaev-Zel'dovich (SZ) effect data for cosmological parameter estimation. I present a study of the intrinsic shapes of galaxy clusters under the axisymmetric hypothesis based on two X-ray cluster samples, using a nonparametric approach and the technique of ``maximum penalized likelihood'' for function estimation. In this talk, the uncertainty in H_0 from unknown geometry for any observed cluster axial ratio is quantified. I conclude with some general comments on the intrinsic shape of X-ray galaxy clusters.

  2. Fast Response Shape Memory Effect Titanium Nickel (TiNi) Foam Torque Tubes

    NASA Technical Reports Server (NTRS)

    Jardine, Peter

    2014-01-01

    Shape Change Technologies has developed a process to manufacture net-shaped TiNi foam torque tubes that demonstrate the shape memory effect. The torque tubes dramatically reduce response time by a factor of 10. This Phase II project matured the actuator technology by rigorously characterizing the process to optimize the quality of the TiNi and developing a set of metrics to provide ISO 9002 quality assurance. A laboratory virtual instrument engineering workbench (LabVIEW'TM')-based, real-time control of the torsional actuators was developed. These actuators were developed with The Boeing Company for aerospace applications.

  3. Effect of shape and size of lung and chest wall on stresses in the lung

    NASA Technical Reports Server (NTRS)

    Vawter, D. L.; Matthews, F. L.; West, J. B.

    1975-01-01

    To understand better the effect of shape and size of lung and chest wall on the distribution of stresses, strains, and surface pressures, we analyzed a theoretical model using the technique of finite elements. First we investigated the effects of changing the chest wall shape during expansion, and second we studied lungs of a variety of inherent shapes and sizes. We found that, in general, the distributions of alveolar size, mechanical stresses, and surface pressures in the lungs were dominated by the weight of the lung and that changing the shape of the lung or chest wall had relatively little effect. Only at high states of expansion where the lung was very stiff did changing the shape of the chest wall cause substantial changes. Altering the inherent shape of the lung generally had little effect but the topographical differences in stresses and surface pressures were approximately proportional to lung height. The results are generally consistent with those found in the dog by Hoppin et al (1969).

  4. Poly(glycerol sebacate urethane)-cellulose nanocomposites with water-active shape-memory effects.

    PubMed

    Wu, Tongfei; Frydrych, Martin; O'Kelly, Kevin; Chen, Biqiong

    2014-07-14

    Biodegradable and biocompatible materials with shape-memory effects (SMEs) are attractive for use as minimally invasive medical devices. Nanocomposites with SMEs were prepared from biodegradable poly(glycerol sebacate urethane) (PGSU) and renewable cellulose nanocrystals (CNCs). The effects of CNC content on the structure, water absorption, and mechanical properties of the PGSU were studied. The water-responsive mechanically adaptive properties and shape-memory performance of PGSU-CNC nanocomposites were observed, which are dependent on the content of CNCs. The PGSU-CNC nanocomposite containing 23.2 vol % CNCs exhibited the best SMEs among the nanocomposites investigated, with the stable shape fixing and shape recovery ratios being 98 and 99%, respectively, attributable to the formation of a hydrophilic, yet strong, CNC network in the elastomeric matrix. In vitro degradation profiles of the nanocomposites were assessed with and without the presence of an enzyme.

  5. Poly(glycerol sebacate urethane)-cellulose nanocomposites with water-active shape-memory effects.

    PubMed

    Wu, Tongfei; Frydrych, Martin; O'Kelly, Kevin; Chen, Biqiong

    2014-07-14

    Biodegradable and biocompatible materials with shape-memory effects (SMEs) are attractive for use as minimally invasive medical devices. Nanocomposites with SMEs were prepared from biodegradable poly(glycerol sebacate urethane) (PGSU) and renewable cellulose nanocrystals (CNCs). The effects of CNC content on the structure, water absorption, and mechanical properties of the PGSU were studied. The water-responsive mechanically adaptive properties and shape-memory performance of PGSU-CNC nanocomposites were observed, which are dependent on the content of CNCs. The PGSU-CNC nanocomposite containing 23.2 vol % CNCs exhibited the best SMEs among the nanocomposites investigated, with the stable shape fixing and shape recovery ratios being 98 and 99%, respectively, attributable to the formation of a hydrophilic, yet strong, CNC network in the elastomeric matrix. In vitro degradation profiles of the nanocomposites were assessed with and without the presence of an enzyme. PMID:24877559

  6. Effects of damping on mode shapes, volume 1

    NASA Technical Reports Server (NTRS)

    Gates, R. M.

    1977-01-01

    Displacement, velocity, and acceleration admittances were calculated for a realistic NASTRAN structural model of space shuttle for three conditions: liftoff, maximum dynamic pressure and end of solid rocket booster burn. The realistic model of the orbiter, external tank, and solid rocket motors included the representation of structural joint transmissibilities by finite stiffness and damping elements. Methods developed to incorporate structural joints and their damping characteristics into a finite element model of the space shuttle, to determine the point damping parameters required to produce realistic damping in the primary modes, and to calculate the effect of distributed damping on structural resonances through the calculation of admittances.

  7. Shaping risky choices: Ethics and the effects of organizational decisions.

    PubMed

    Warren, Marika

    2016-07-01

    Choices to live "at risk" are complex and challenging and can be structured by organizational policy. Some individuals genuinely wish to live in situations that are, or are perceived to be, high risk because this affords them an important benefit. However, it is likely that these choices are significantly affected by context and might not be made under different circumstances. The following argues for a responsibility to be attentive to the effects of organizational decisions on choices to live at risk and the overall distribution of risk.

  8. Effect of surface charge convection and shape deformation on the dielectrophoretic motion of a liquid drop

    NASA Astrophysics Data System (ADS)

    Mandal, Shubhadeep; Bandopadhyay, Aditya; Chakraborty, Suman

    2016-04-01

    The dielectrophoretic motion and shape deformation of a Newtonian liquid drop in an otherwise quiescent Newtonian liquid medium in the presence of an axisymmetric nonuniform dc electric field consisting of uniform and quadrupole components is investigated. The theory put forward by Feng [J. Q. Feng, Phys. Rev. E 54, 4438 (1996), 10.1103/PhysRevE.54.4438] is generalized by incorporating the following two nonlinear effects—surface charge convection and shape deformation—towards determining the drop velocity. This two-way coupled moving boundary problem is solved analytically by considering small values of electric Reynolds number (ratio of charge relaxation time scale to the convection time scale) and electric capillary number (ratio of electrical stress to the surface tension) under the framework of the leaky dielectric model. We focus on investigating the effects of charge convection and shape deformation for different drop-medium combinations. A perfectly conducting drop suspended in a leaky (or perfectly) dielectric medium always deforms to a prolate shape and this kind of shape deformation always augments the dielectrophoretic drop velocity. For a perfectly dielectric drop suspended in a perfectly dielectric medium, the shape deformation leads to either increase (for prolate shape) or decrease (for oblate shape) in the dielectrophoretic drop velocity. Both surface charge convection and shape deformation affect the drop motion for leaky dielectric drops. The combined effect of these can significantly increase or decrease the dielectrophoretic drop velocity depending on the electrohydrodynamic properties of both the liquids and the relative strength of the electric Reynolds number and electric capillary number. Finally, comparison with the existing experiments reveals better agreement with the present theory.

  9. Effects of buffer size and shape on associations between the built environment and energy balance.

    PubMed

    James, Peter; Berrigan, David; Hart, Jaime E; Hipp, J Aaron; Hoehner, Christine M; Kerr, Jacqueline; Major, Jacqueline M; Oka, Masayoshi; Laden, Francine

    2014-05-01

    Uncertainty in the relevant spatial context may drive heterogeneity in findings on the built environment and energy balance. To estimate the effect of this uncertainty, we conducted a sensitivity analysis defining intersection and business densities and counts within different buffer sizes and shapes on associations with self-reported walking and body mass index. Linear regression results indicated that the scale and shape of buffers influenced study results and may partly explain the inconsistent findings in the built environment and energy balance literature.

  10. Multifunctional hybrid nanocomposites with magnetically controlled reversible shape-memory effect.

    PubMed

    Razzaq, Muhammad Yasar; Behl, Marc; Kratz, Karl; Lendlein, Andreas

    2013-10-25

    Magneto-sensitivity and a thermo-sensitive reversible shape-memory effect have been successfully integrated into a hybrid nanocomposite, resulting in a magnetically controlled actuator. The complex requirements for gaining this multifunctionality are fulfilled by combining netpoints on the molecular and nano level in a polyesterurethane network prepared from hydroxyl group decorated magnetic nanoparticles, crystallizable star-shaped poly(ω-pentadecalactone) precursors, and a diisocyanate.

  11. Effect of resin rheology on macro- and micro-flows in resin transfer molding

    SciTech Connect

    Chih-Hsin Shih; Lee, L.J.; Koelling, K.

    1996-12-31

    Resin transfer molding (RTM) is a relatively new and high potential process for near net shape composite manufacturing because of its short cycle time, low labor requirements and low equipment cost. The major material variables in the RTM process are the resin rheology and the fiber reinforcement structure. The presence of low profile additives or fillers tends to change the resin mixture from a Newtonian fluid to a Non-Newtonian fluid. Different fiber architectures may result in different flow patterns that will influence the mold filling and curing processes. This paper will discuss how the resin rheology and fiber structure effect the resin transfer molding process.

  12. Angle-resolved effective potentials for disk-shaped molecules

    NASA Astrophysics Data System (ADS)

    Heinemann, Thomas; Palczynski, Karol; Dzubiella, Joachim; Klapp, Sabine H. L.

    2014-12-01

    We present an approach for calculating coarse-grained angle-resolved effective pair potentials for uniaxial molecules. For integrating out the intramolecular degrees of freedom we apply umbrella sampling and steered dynamics techniques in atomistically-resolved molecular dynamics (MD) computer simulations. Throughout this study we focus on disk-like molecules such as coronene. To develop the methods we focus on integrating out the van der Waals and intramolecular interactions, while electrostatic charge contributions are neglected. The resulting coarse-grained pair potential reveals a strong temperature and angle dependence. In the next step we fit the numerical data with various Gay-Berne-like potentials to be used in more efficient simulations on larger scales. The quality of the resulting coarse-grained results is evaluated by comparing their pair and many-body structure as well as some thermodynamic quantities self-consistently to the outcome of atomistic MD simulations of many-particle systems. We find that angle-resolved potentials are essential not only to accurately describe crystal structures but also for fluid systems where simple isotropic potentials start to fail already for low to moderate packing fractions. Further, in describing these states it is crucial to take into account the pronounced temperature dependence arising in selected pair configurations due to bending fluctuations.

  13. Angle-resolved effective potentials for disk-shaped molecules

    SciTech Connect

    Heinemann, Thomas Klapp, Sabine H. L.; Palczynski, Karol Dzubiella, Joachim

    2014-12-07

    We present an approach for calculating coarse-grained angle-resolved effective pair potentials for uniaxial molecules. For integrating out the intramolecular degrees of freedom we apply umbrella sampling and steered dynamics techniques in atomistically-resolved molecular dynamics (MD) computer simulations. Throughout this study we focus on disk-like molecules such as coronene. To develop the methods we focus on integrating out the van der Waals and intramolecular interactions, while electrostatic charge contributions are neglected. The resulting coarse-grained pair potential reveals a strong temperature and angle dependence. In the next step we fit the numerical data with various Gay-Berne-like potentials to be used in more efficient simulations on larger scales. The quality of the resulting coarse-grained results is evaluated by comparing their pair and many-body structure as well as some thermodynamic quantities self-consistently to the outcome of atomistic MD simulations of many-particle systems. We find that angle-resolved potentials are essential not only to accurately describe crystal structures but also for fluid systems where simple isotropic potentials start to fail already for low to moderate packing fractions. Further, in describing these states it is crucial to take into account the pronounced temperature dependence arising in selected pair configurations due to bending fluctuations.

  14. Angle-resolved effective potentials for disk-shaped molecules.

    PubMed

    Heinemann, Thomas; Palczynski, Karol; Dzubiella, Joachim; Klapp, Sabine H L

    2014-12-01

    We present an approach for calculating coarse-grained angle-resolved effective pair potentials for uniaxial molecules. For integrating out the intramolecular degrees of freedom we apply umbrella sampling and steered dynamics techniques in atomistically-resolved molecular dynamics (MD) computer simulations. Throughout this study we focus on disk-like molecules such as coronene. To develop the methods we focus on integrating out the van der Waals and intramolecular interactions, while electrostatic charge contributions are neglected. The resulting coarse-grained pair potential reveals a strong temperature and angle dependence. In the next step we fit the numerical data with various Gay-Berne-like potentials to be used in more efficient simulations on larger scales. The quality of the resulting coarse-grained results is evaluated by comparing their pair and many-body structure as well as some thermodynamic quantities self-consistently to the outcome of atomistic MD simulations of many-particle systems. We find that angle-resolved potentials are essential not only to accurately describe crystal structures but also for fluid systems where simple isotropic potentials start to fail already for low to moderate packing fractions. Further, in describing these states it is crucial to take into account the pronounced temperature dependence arising in selected pair configurations due to bending fluctuations.

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

    SciTech Connect

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

    2010-02-15

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

  16. Gravity effect on lymphocyte deformation through cell shape change.

    PubMed

    Hung, R J; Tsao, Y D; Spauling, G F

    1995-01-01

    The effects on human cells (lymphocyte) immersed in a culture liquid under microgravity environment has been investigated. The study was based on the numerical simulation of the Morphology of human cells affected by the time dependent variation of gravity acceleration ranging from 10(-3) to 2 g(o) (g(o) = 9.81 m/s2) in 15 s. Both the free floating cells and the cells which came into contact with the upper and lower inclined walls imposed by the time-dependent reduced gravity acceleration were considered in this study. The results show that, when the gravity acceleration increased, the cell morphology changed from spherical to horizontally elongated ellipsoid for both the free floating cells and the stationary cells on the lower inclined wall while the cell morphology varied from spherical to vertically-elongated ellipsoid for the cells hanging on the upper inclined wall. A test of the deformation of human cells exposed to the variation of gravity levels, carried out in the KC-135 free fall aircraft, show that the results of experimental observations agree exactly with the theoretical model computation described in this paper. These results will be useful for study of the behavior and morphology of cells in space.

  17. Effect of Graphene Addition on Shape Memory Behavior of Epoxy Resins

    NASA Technical Reports Server (NTRS)

    Williams, Tiffany; Meador, Michael; Miller, Sandi; Scheiman, Daniel

    2011-01-01

    Shape memory polymers (SMPs) and composites are a special class of smart materials known for their ability to change size and shape upon exposure to an external stimulus (e.g. light, heat, pH, or magnetic field). These materials are commonly used for biomedical applications; however, recent attempts have been made towards developing SMPs and composites for use in aircraft and space applications. Implementing SMPs and composites to create a shape change effect in some aircraft structures could potentially reduce drag, decrease fuel consumption, and improve engine performance. This paper discusses the development of suitable materials to use in morphing aircraft structures. Thermally responsive epoxy SMPs and nanocomposites were developed and the shape memory behavior and thermo-mechanical properties were studied. Overall, preliminary results from dynamic mechanical analysis (DMA) showed that thermally actuated shape memory epoxies and nanocomposites possessed Tgs near approximately 168 C. When graphene nanofiller was added, the storage modulus and crosslinking density decreased. On the other hand, the addition of graphene enhanced the recovery behavior of the shape memory nanocomposites. It was assumed that the addition of graphene improved shape memory recovery by reducing the crosslinking density and increasing the elasticity of the nanocomposites.

  18. Spin Rate Distribution of Small Asteroids Shaped by YORP Effect

    NASA Astrophysics Data System (ADS)

    Pravec, Petr

    2008-09-01

    We studied a distribution of spin rates of main belt/Mars crossing (MB/MC) asteroids with diameters 3-15 km using data obtained within the Photometric Survey of Asynchronous Binary Asteroids (Pravec et al. 2008). We found that the spin distribution of the small asteroids is uniform in the range from f = 1 to 9.5 d-1, and there is an excess of slow rotators with f < 1 d-1. The observed distribution appears to be controlled by the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect. The magnitude of the excess of slow rotators is related to the residence time of slowed down asteroids in the excess and the rate of spin rate change outside the excess. We estimated a median YORP spin rate change of 0.022 d-1/Myr for asteroids in our sample (i.e., a median time in which the spin rate changes by 1 d-1 is 45 Myr), thus the residence time of slowed down asteroids in the excess is 110 Myr. The spin rate distribution of near-Earth asteroids (NEAs) with sizes in the range 0.2-3 km ( 5-times smaller in median diameter than the MB/MC asteroids sample) shows a similar excess of slow rotators, but there is also a concentration of NEAs at fast spin rates with f = 9-10 d-1. The concentration at fast spin rates is correlated with a narrower distribution of spin rates of primaries of binary systems among NEAs; the difference may be due to the apparently more evolved population of binaries among MB/MC asteroids. Reference: Pravec, P., and 30 colleagues, 2008. Spin rate distribution of small asteroids. Icarus, in press. DOI: http://dx.doi.org/10.1016/j.icarus.2008.05.012

  19. Comparison of the effectiveness of alternative feature sets in shape retrieval of multicomponent images

    NASA Astrophysics Data System (ADS)

    Eakins, John P.; Edwards, Jonathan D.; Riley, K. Jonathan; Rosin, Paul L.

    2001-01-01

    Many different kinds of features have been used as the basis for shape retrieval from image databases. This paper investigates the relative effectiveness of several types of global shape feature, both singly and in combination. The features compared include well-established descriptors such as Fourier coefficients and moment invariants, as well as recently-proposed measures of triangularity and ellipticity. Experiments were conducted within the framework of the ARTISAN shape retrieval system, and retrieval effectiveness assessed on a database of over 10,000 images, using 24 queries and associated ground truth supplied by the UK Patent Office . Our experiments revealed only minor differences in retrieval effectiveness between different measures, suggesting that a wide variety of shape feature combinations can provide adequate discriminating power for effective shape retrieval in multi-component image collections such as trademark registries. Marked differences between measures were observed for some individual queries, suggesting that there could be considerable scope for improving retrieval effectiveness by providing users with an improved framework for searching multi-dimensional feature space.

  20. Comparison of the effectiveness of alternative feature sets in shape retrieval of multicomponent images

    NASA Astrophysics Data System (ADS)

    Eakins, John P.; Edwards, Jonathan D.; Riley, K. Jonathan; Rosin, Paul L.

    2000-12-01

    Many different kinds of features have been used as the basis for shape retrieval from image databases. This paper investigates the relative effectiveness of several types of global shape feature, both singly and in combination. The features compared include well-established descriptors such as Fourier coefficients and moment invariants, as well as recently-proposed measures of triangularity and ellipticity. Experiments were conducted within the framework of the ARTISAN shape retrieval system, and retrieval effectiveness assessed on a database of over 10,000 images, using 24 queries and associated ground truth supplied by the UK Patent Office . Our experiments revealed only minor differences in retrieval effectiveness between different measures, suggesting that a wide variety of shape feature combinations can provide adequate discriminating power for effective shape retrieval in multi-component image collections such as trademark registries. Marked differences between measures were observed for some individual queries, suggesting that there could be considerable scope for improving retrieval effectiveness by providing users with an improved framework for searching multi-dimensional feature space.

  1. Degradation of the shape memory effect in copper-base alloys

    SciTech Connect

    Stalmans, R.; Van Humbeeck, J.; Delaey, L. . Dept. of Metallurgy and Materials Science)

    1994-12-01

    The reversible transformation of the parent phase (austenite) to the product phase (martensite) is the basis of several shape memory properties in specific Cu-base alloys. In this respect, the two-way memory effect (TWME) refers the reversible, spontaneous shape change from a hot austenitic shape to a cold martensitic shape during cooling and heating without the application of external stresses. It is known that the magnitude of the TWME decrease during thermal or thermomechanical cycling, in particular in Cu-base shape memory alloys. It is however important to remark that this decrease, indicated as degradation of the TWME, can be caused as well by a decrease of the spontaneous martensitic strain, i.e. a degradation of the cold shape, as by an increase of the residual austenitic strain, i.e. a degradation of the hot shape, or by a combination of both. The degradation of the TWME, and of the hot and cold shape is influenced by a number of factors including the alloy composition, the processing, the heat treatment, the training procedure and the parameters of the thermal or thermomechanical cycling. The knowledge of the degradation phenomena is still limited. In a subsequent study of the relationships between training and the two-way memory behavior, the authors have shown that the degradation of the hot shape already starts during training. It was found that the residual austenitic strain [gamma][sub a] increases gradually during training cycling; [gamma][sub a] is also in the case of training composed of a recoverable residual strain [gamma][sub ar] and a non-recoverable residual strain [gamma][sub anr]. The present paper reports the results of the specific experiments which were designed based upon the results described above. The evolutions during thermal cycling of the TWME, of the martensitic strain and austenitic strain, and of the recoverable and non-recoverable austenitic strain are presented and discussed.

  2. Thermal analysis and evolution of shape loss phenomena during polymer burnout in powder metal processing

    NASA Astrophysics Data System (ADS)

    Enneti, Ravi Kumar

    2005-07-01

    Powder metallurgy technology involves manufacturing of net shape or near net shape components starting from metal powders. Polymers are used to provide lubrication during shaping and handling strength to the shaped component. After shaping, the polymers are removed from the shaped components by providing thermal energy to burnout the polymers. Polymer burnout is one of the most critical step in powder metal processing. Improper design of the polymer burnout cycle will result in formation of defects, shape loss, or carbon contamination of the components. The effect of metal particles on polymer burnout and shape loss were addressed in the present research. The study addressing the effect of metal powders on polymer burnout was based on the hypothesis that metal powders act to catalyze polymer burnout. Thermogravimetric analysis (TGA) on pure polymer, ethylene vinyl acetate (EVA), and on admixed powders of 316L stainless steel and 1 wt. % EVA were carried out to verify the hypothesis. The effect of metal powders additions was studied by monitoring the onset temperature for polymer degradation and the temperature at which maximum rate of weight loss occurred from the TGA data. The catalytic behavior of the powders was verified by varying the particle size and shape of the 316L stainless powder. The addition of metal particles lowered the polymer burnout temperatures. The onset temperature for burnout was found to be sensitive to the surface area of the metal particle as well as the polymer distribution. Powders with low surface area and uniform distribution of polymer showed a lower burnout temperature. The evolution of shape loss during polymer burnout was based on the hypothesis that shape loss occurs during the softening of the polymer and depends on the sequence of chemical bonding in the polymer during burnout. In situ observation of shape loss was carried out on thin beams compacted from admixed powders of 316L stainless steel and 1 wt. % ethylene vinyl acetate

  3. Thermoresponsive fibers containing n-stearyl acrylate groups for shape memory effect

    NASA Astrophysics Data System (ADS)

    Chen, L.; Yu, X.; Feng, X.; Han, Y. L.; Liu, M.; Lin, T. X.

    2007-07-01

    A novel kind of thermoresponsive shape memory fiber was prepared by mixing the P(SA-co-AA) copolymers of stearyl acrylate (SA), and acrylic acid (AA), with PVA polyvinyl alcohol through chemically crosslinking after spinning. The molecular structure, thermomechanical properties and shape memory behaviors were investigated. It was found that the mixed P(SA-co-AA)/PVA fibers had crystalline structures and showed a dramatic change in Young's modulus at melting temperature (Tm) due to the reversible order-disorder transition. The mixed P(SA-co-AA)/PVA fibers also showed a good shape memory effect, through which the deformed fibers could recover to their original shapes and sizes within 40 seconds after they were heated above their Tm again.

  4. Quantifying the effect of rheology on plan-view shapes of lava flows

    NASA Technical Reports Server (NTRS)

    Bruno, B. C.; Taylor, G. J.; Lopes-Gautier, R. M. C.

    1993-01-01

    This study aims at quantifying the effect of rheology on the plan-view shapes of lava flows. Plan-view shapes of lava flows are important because they reflect the processes governing flow emplacement and may provide insight into lava flow rheology and dynamics. In our earlier investigation, it was reported that plan-view shapes of tholeite basalts are fractal, having a characteristic shape regardless of scale. It was also found one could use the fractal dimension (a parameter which quantifies flow margin convolution) to distinguish between the two major types of basalts: a'a and pahoehoe. Encouraged by these earlier results, a similar method for use on silicic flows are being developed and our preliminary work is presented.

  5. Optimal Geometry Aspect Ratio of Ellipse-Shaped- Surrounding-Gate Nanowire Field Effect Transistors.

    PubMed

    Li, Yiming

    2016-01-01

    Theoretically ideally round shape of the surrounding gate may not always guarantee because of limitations of the fabrication process in surrounding-gate nanowire field effect transistors (FETs). These limitations may lead to the formation of an ellipse-shaped surrounding gate with major and minor axes of different lengths. In this paper, we for the first time study the electrical characteristics of ellipse-shaped-surrounding-gate silicon nanowire FETs with different ratio of the major and minor axes. By simultaneously simulating engineering acceptable magnitudes of the threshold voltage roll-off, the drain induced barrier lowering, the subthreshold swing, and the on-/off-state current ratio, an optimal geometry aspect ratio between the channel length and the major and minor axes of the ellipse-shaped-surrounding-gate nanowire FET is concluded. PMID:27398546

  6. Additional Study of Water Droplet Median Volume Diameter (MVD) Effects on Ice Shapes

    NASA Technical Reports Server (NTRS)

    Tsao, Jen-Ching; Anderson, David N.

    2005-01-01

    This paper reports the result of an experimental study in the NASA Glenn Icing Research Tunnel (IRT) to evaluate how well the MVD-independent effect identified previously might apply to SLD conditions in rime icing situations. Models were NACA 0012 wing sections with chords of 53.3 and 91.4 cm. Tests were conducted with a nominal airspeed of 77 m/s (150 kt) and a number of MVD's ranging from 15 to 100 m with LWC of 0.5 to 1 g/cu m. In the present study, ice shapes recorded from past studies and recent results at SLD and Appendix-C conditions are reviewed to show that droplet diameter is not important to rime ice shape for MVD of 30 microns or larger, but for less than 30 m drop sizes a rime ice shape transition from convex to wedge to spearhead type ice shape is observed.

  7. Micromagnetic simulations on the grain shape effect in Nd-Fe-B magnets

    NASA Astrophysics Data System (ADS)

    Yi, Min; Gutfleisch, Oliver; Xu, Bai-Xiang

    2016-07-01

    Micromagnetic simulations were performed to study the effect of grain shape and defect layer in Nd-Fe-B magnets. It was found that the coercivity can be increased by a factor of ˜2 by changing the grain shape from the triangular prism to the spheroid. Both the anisotropy field contribution and the shape contribution to the coercivity, and thus also the final coercivity, were found to decrease in the order: spheroid > circular prism > hexagonal prism > square prism > triangular prism. Sputtered columnar grains and hot-deformed platelet grains with a constant volume were also considered. Results show that the coercivity initially increases with the aspect ratio and then nearly saturates above the ratio of ˜4. Simulations of multigrain ensembles showed that depending on the grain shape, compared to the case of single grain, a further decrease of ˜10%-45% in the coercivity is induced by magnetostatic coupling.

  8. Effect of Base Shape on Damping of Rocking of Rigid Body

    NASA Astrophysics Data System (ADS)

    Imanishi, Nozomu; Inoue, Yoshio; Shibata, Kyoko; Sato, Kazutomo; Yamasaki, Yoshihiko

    Effect of base shape on damping characteristics of rocking of rigid body is presented. We pay attention to the fact that free vibration amplitude of rigid body decreases rapidly without dampers or damping materials. We consider rocking of rigid body is very attractive as a low cost dynamic vibration absorber. At first, damping characteristics of rocking of typical rigid body with flat base shape is discussed theoretically. Next, we propose new type rigid body which base shape is polygon in order to design damping characteristics of rigid body in wide range. Theoretical method to calculate damping characteristics of rigid body is derived. Experiment of free vibration of the rigid body is carried out and the calculated results of the proposed method agree well with the experimental results. By calculating damping ratio of proposed rigid body using derived equations, it can be seen polygon base shape is very useful to design damping characteristics of rigid body.

  9. Coherent Backscattering Effect in Saturnian vs. Uranian Satellites: Effects on Band Depths and Shapes

    NASA Astrophysics Data System (ADS)

    Pitman, Karly M.; Kolokolova, Ludmilla; Verbiscer, Anne J.; Gulotta, Charles; Joseph, Emily C. S.; Mackowski, Daniel W.; Buratti, Bonnie J.; Momary, Thomas W.

    2015-11-01

    In this work, we examine the changes in depth and shape of individual absorption bands as a function of solar phase angle that are caused by the coherent backscattering effect (CBE) in near-IR spectra of saturnian and uranian satellites. We have quantified band depths and shapes for real-world data (from Cassini Visual & Infrared Mapping Spectrometer (VIMS) and TripleSpec at Apache Point Observatory) and also modeled spectra of densely packed icy particulate surfaces with the MSTM (multisphere T-matrix) version 4.0 code specifically developed to model light scattering in regolith layers. MSTM4 allows us to calculate the brightness for thick fluffy layers on order of 20,000 particles (compared to 1000 with previous code versions). We have now obtained good matches between model and real-world data at specific bands for several higher albedo moons. We are finding that the normalized depth of the absorption band can increase or decrease with solar phase angle depending on the albedo at the wavelength of normalization; this is seen in all the data (VIMS, ground-based, and model spectra). We model the change in the phase-angle-dependent band depth in response to varying the size and packing of the constituent icy particles. Indeed, the coherent backscattering effect can be observed at some wavelengths and entirely disappear at others because CBE requires a specific range of size and packing (cf. Muinonen et al. 2014); we see this effect as well.This work is supported by NASA’s Outer Planets Research program (NNX12AM76G; PI Pitman), Planetary Astronomy program (NNX09AD06G; PI Verbiscer), and NASA’s Advanced Supercomputing Division. Calibrated Cassini VIMS data cubes appear courtesy of the Cassini VIMS team and the PDS.

  10. Large-scale experimental landscapes reveal distinctive effects of patch shape and connectivity on arthropod communities.

    SciTech Connect

    Orrock, John, L.; Curler, Gregory, R.; Danielson, Brent, J.; Coyle, David. R.

    2011-09-14

    The size, shape, and isolation of habitat patches can affect organism behavior and population dynamics, but little is known about the relative role of shape and connectivity in affecting ecological communities at large spatial scales. Using six sampling sessions from July 2001 until August 2002, we collected 33,685 arthropods throughout seven 12-ha experimental landscapes consisting of clear-cut patches surrounded by a matrix of mature pine forest. Patches were explicitly designed to manipulate connectivity (via habitat corridors) independently of area and edge effects. We found that patch shape, rather than connectivity, affected ground-dwelling arthropod richness and beta diversity (i.e. turnover of genera among patches). Arthropod communities contained fewer genera and exhibited less turnover in high-edge connected and high-edge unconnected patches relative to low-edge unconnected patches of similar area. Connectivity, rather than patch shape, affected the evenness of ground-dwelling arthropod communities; regardless of patch shape, high-edge connected patches had lower evenness than low- or high-edge unconnected patches. Among the most abundant arthropod orders, increased richness in low-edge unconnected patches was largely due to increased richness of Coleoptera, whereas Hymenoptera played an important role in the lower evenness in connected patches and patterns of turnover. These findings suggest that anthropogenic habitat alteration can have distinct effects on ground-dwelling arthropod communities that arise due to changes in shape and connectivity. Moreover, this work suggests that corridors, which are common conservation tools that change both patch shape and connectivity, can have multiple effects on arthropod communities via different mechanisms, and each effect may alter components of community structure.

  11. Sensitivity of the shortwave radiative effect of dust on particle shape: Comparison of spheres and spheroids

    NASA Astrophysics Data System (ADS)

    Haapanala, PäIvi; RäIsäNen, Petri; Kahnert, Michael; Nousiainen, Timo

    2012-04-01

    The sensitivity of direct shortwave radiative effects of dust (DRE) to assumed particle shape is investigated. Radiative transfer simulations are conducted using optical properties of either spheres, mass-equivalent spheroids (mass-conserving case), or (mass-equivalent) spheroids whose number concentration is modified so that they have the same midvisible optical thickness (τ(545 nm)) as spheres (τ-conserving case). The impact of particle shape on DRE is investigated for different dust particle effective radii, optical thickness of the dust cloud, solar zenith angle, and spectral surface albedo (ocean, grass, and desert). It is found that the influence of particle shape on the DRE is strongest over ocean. It also depends very strongly on the shape distribution of spheroids used, to a degree that the results for two distributions of spheroids may deviate more from each other than from those for spheres. Finally, the effects of nonsphericity largely depend on whether the mass- orτ-conserving case is considered. For example, when using a shape distribution of spheroids recommended in a recent study for approximating the single-scattering properties of dust, the DRE at the surface differs at most 5% from that from spherical particles in the mass-conserving case. This stems from compensating nonsphericity effects on optical thickness, asymmetry parameter, and single-scattering albedo. However, in theτ-conserving case, the negative DRE at the surface can be up to 15% weaker for spheroids than spheres.

  12. Effects of colchicine on the shape of chick neuroepithelial cells during neurulation.

    PubMed

    Fernandez, J G; de Paz, P; Chamorro, C A

    1987-11-01

    We have analyzed the effects of colchicine on the cell shapes in chick neuroepithelium. Cell shapes were ascertained by the position of the nucleus in plastic serial sections. We tested three colchicine doses (5 X 10(-5) M, 5 X 10(-6) M, and 5 X 10(-7) M) by two experimental treatments (in ovo and in vitro). Colchicine treatment in vitro is always effective in depolymerizing microtubules of neuroepithelial cells and reduces the percentages of wedge-shaped cells in the median area of neuroepithelium. The same effect can be observed when the embryos are treated with 5 X 10(-5) M or 5 X 10(-6) M colchicine in ovo. A concentration of colchicine of 5 X 10(-7) M in ovo cannot disrupt microtubules in stage 8 and stage 10 embryos, and the percentage of wedge-shaped cells is the same as that of the untreated cells. In stage 6 embryos this colchicine dose effects the microtubules and the percentages of wedge-shaped cells. These facts are interpreted in respect to variations in microtubular resistance to microtubular-disrupting agents that are shown by the neuroepithelial cells from different developmental stages.

  13. Remarkable shape memory effect of a natural biopolymer in aqueous environment.

    PubMed

    Liu, Z Q; Jiao, D; Zhang, Z F

    2015-10-01

    Remarkable water-stimulated shape memory effect was revealed in a natural biopolymer of peacock's tail covert feathers of which the innate shape can almost be fully recovered after severe deformation by a short hydration step. The shape memory effect manifests a good stability of high recovery rate and ratio during cycles of deformation and subsequent recovery. Both strength and energy absorption efficiency of medullary foam can be recovered despite the apparent decrease in the first deformation stroke caused by structural damage. A kinetic model developed from non-equilibrium thermodynamic fluctuation theory was adopted to describe the shape recovery process by considering the viscoelastic relaxation. The effects of hydration on mechanical properties, recovery kinetics, activation process and dynamic mechanical behaviors were also evaluated. Mechanisms were explored based on the lubrication, swelling effect and structural changes of macromolecular chains or segments in terms of their mobility. This study is expected to aid in understanding the responses of natural biological materials to environmental stimuli and to provide useful information for synthetic shape memory materials from the bio-inspiration perspective.

  14. Effects of irradiation of energetic heavy ions on digital pulse shape analysis with silicon detectors

    NASA Astrophysics Data System (ADS)

    Barlini, S.; Carboni, S.; Bardelli, L.; Le Neindre, N.; Bini, M.; Borderie, B.; Bougault, R.; Casini, G.; Edelbruck, P.; Olmi, A.; Pasquali, G.; Poggi, G.; Rivet, M. F.; Stefanini, A. A.; Baiocco, G.; Berjillos, R.; Bonnet, E.; Bruno, M.; Chbihi, A.; Cruceru, I.; Degerlier, M.; Dueñas, J. A.; Galichet, E.; Gramegna, F.; Kordyasz, A.; Kozik, T.; Kravchuk, V. L.; Lopez, O.; Marchi, T.; Martel, I.; Morelli, L.; Parlog, M.; Piantelli, S.; Petrascu, H.; Rosato, E.; Seredov, V.; Vient, E.; Vigilante, M.; Fazia Collaboration

    2013-04-01

    The next generation of 4π detector arrays for heavy ion studies will largely use Pulse Shape Analysis to push the performance of silicon detectors with respect to ion identification. Energy resolution and pulse shape identification capabilities of silicon detectors under prolonged irradiation by energetic heavy ions have thus become a major issue. In this framework, we have studied the effects of irradiation by energetic heavy ions on the response of neutron transmutation doped (nTD) silicon detectors. Sizeable effects on the amplitude and the risetime of the charge signal have been found for detectors irradiated with large fluences of stopped heavy ions, while much weaker effects were observed by punching-through ions. The robustness of ion identification based on digital pulse shape techniques has been evaluated.

  15. Understanding the shape effect on the plasmonic response of small ligand coated nanoparticles

    NASA Astrophysics Data System (ADS)

    Chen, Xing; Jensen, Lasse

    2016-07-01

    The plasmonic properties of metallic nanoparticles typically depend strongly on their shapes and local environment. However, not much is known about the shape effects on the plasmonic response in small metallic nanoparticles when quantum size effects become important. In this work, we use atomistic electrodynamics models incorporated with quantum size effects to study the optical properties of both bare and ligand coated Ag nanoparticles in different shapes. Using classical electrodynamics, we find that the plasmonic response of bare metallic nanoparticles depends strongly on the morphology of the nanoparticles due to the presence of higher-order plasmon modes. By including quantum size effects in the simulations, we find a significant blue-shift of the dipole plasmon as well as the smearing-out of the multipole plasmon modes, and both lead to a weak shape dependence. The ligand effects on the nanoparticles cause a significant red-shift of the plasmon resonance arising from the reduction of the conductivity of the Ag atoms where the ligands bind. In contrast to the bare nanoparticles, we find several higher-order plasmon modes in the ligand coated nanoparticles, that are likely caused by the weak electron spill-out effect and the symmetry breaking at the surface in the presence of the ligands. Furthermore, we show that the ligand layer strongly modify the near-field distribution due to the screening of the ligands. This work highlights the importance of quantum size and ligand effects on the optical properties of small metallic nanoparticles.

  16. The Effect of Shape Model Uncertainty on the Geophysical Predictions of Binary Asteroids

    NASA Astrophysics Data System (ADS)

    McMahon, Jay W.; Scheeres, Daniel

    2014-11-01

    Recent work by Jacobson and Scheeres (ApJ Vol. 736, L19) have shown that for a binary asteroid system in and equilibrium between tides and the binary YORP effect, the ratio Q/k can be determined, where Q is the tidal dissipation number and k is the tidal Love number. In their work, the value for B (the binary YORP coefficient) was that computed by McMahon and Scheeres (Icarus Vol. 209, pp 494-509, 2010) for binary asteroid 1999 KW4. Using this value, it was shown that the geophysical parameters Q/k can be estimated. Furthermore, we can similarly compute μQ based on the relationship between μ and k (where μ is the rigidity parameter), as discussed by Scheirich et al (ACM, Niigata, Japan, 2012, No. 1667, id.6123). These geophysical predictions, however, depend directly on the value of the binary YORP coefficient used, which is uncertain due to the limited shape model accuracy.In this study, we analyze the effect of shape model uncertainty on the predictions of Q/k and μQ. The 1999 KW4 secondary shape model is stochastically perturbed based on the radar observation accuracy (Ostro et al, Science Vol. 314, pp 1276-1280, 2006). Furthermore the detail of the topography is varied by adding more vertices to create a higher resolution shape model. For each newly perturbed shape model, the binary YORP coefficient is computed using our most advanced modeling software, and is used to derive new values for the geophysical parameter relationships. Furthermore we compute the B for a variety of known asteroid shape models as investigated by McMahon and Scheeres (44th AAS DPS, Reno, NV, 2012. Abstract No. 105.08). The results give effective error bounds on the Q/k (and derived μQ) predictions based on the shape model uncertainties.

  17. Effect of weld line shape on material flow during friction stir welding of aluminum and steel

    NASA Astrophysics Data System (ADS)

    Yasui, Toshiaki; Ando, Naoyuki; Morinaka, Shinpei; Mizushima, Hiroki; Fukumoto, Masahiro

    2014-08-01

    The effect of weld line shape on material flow during the friction stir welding of aluminum and steel was investigated. The material flow velocity was evaluated with simulated experiments using plasticine as the simulant material. The validity of the simulated experiments was verified by the marker material experiments on aluminum. The circumferential velocity of material around the probe increased with the depth from the weld surface. The effect is significant in cases where the advancing side is located on the outside of curve and those with higher curvature. Thus, there is an influence of weld line shape on material flow.

  18. Effect of plasma shaping on performance in the National Spherical Torus Experiment

    SciTech Connect

    Gates, D. A.; Maingi, R.; Menard, J.; Kaye, S.; Sabbagh, S. A.; Taylor, G.; Wilson, J. R.; Bell, M. G.; Bell, R. E.; Bernabei, S.; Bialek, J.; Biewer, T.; Blanchard, W.; Boedo, J.; Bush, C.; Carter, M. D.; Choe, W.; Crocker, N.; Darrow, D. S.; Davis, W.; Delgado-Aparicio, L.; Diem, S.; Ferron, J.; Field, A.; Foley, J.; Fredrickson, E. D.; Harvey, R.; Hatcher, R. E.; Heidbrink, W.; Hill, K.; Hosea, J. C.; Jarboe, T. R.; Johnson, D. W.; Kaita, R.; Kessel, C.; Kubota, S.; Kugel, H. W.; Lawson, J.; LeBlanc, B. P.; Lee, K. C.; Levinton, F.; Manickam, J.; Maqueda, R.; Marsala, R.; Mastrovito, D.; Mau, T. K.; Medley, S. S.; Meyer, H.; Mikkelsen, D. R.; Mueller, D.; Munsat, T.; Nelson, B. A.; Neumeyer, C.; Nishino, N.; Ono, M.; Park, H.; Park, W.; Paul, S.; Peebles, W.; Peng, M.; Phillips, C.; Pigarov, A.; Pinsker, R.; Ram, A.; Ramakrishnan, S.; Raman, R.; Rasmussen, D.; Redi, M.; Rensink, M.; Rewoldt, G.; Robinson, J.; Roney, P.; Roquemore, L.; Ruskov, E.; Ryan, P.; Schneider, H.; Skinner, C. H.; Smith, D. R.; Sontag, A.; Soukhanovskii, V.; Stevenson, T.; Stotler, D.; Stratton, B.; Stutman, D.; Swain, D.; Synakowski, E.; Takase, Y.; Tritz, K.; Halle, A. von; Wade, M.; White, R.; Wilgen, J.; Williams, M.; Zhu, W.; Zweben, S. J.; Akers, R.; Beiersdorfer, P.; Betti, R.; Bigelow, T.

    2006-01-01

    The National Spherical Torus Experiment (NSTX) has explored the effects of shaping on plasma performance as determined by many diverse topics including the stability of global magnetohydrodynamic (MHD) modes (e.g., ideal external kinks and resistive wall modes), edge localized modes (ELMs), bootstrap current drive, divertor flux expansion, and heat transport. Improved shaping capability has been crucial to achieving βt ~ 40%. Precise plasma shape control has been achieved on NSTX using real-time equilibrium reconstruction. NSTX has simultaneously achieved elongation κ ~ 2.8 and triangularity delta ~ 0.8. Ideal MHD theory predicts increased stability at high values of shaping factor S equivalent to q95Ip/(aBt), which has been observed at large values of the S ~ 37[MA/(m • T)] on NSTX. The behavior of ELMs is observed to depend on plasma shape. A description of the ELM regimes attained as shape is varied will be presented. Increased shaping is predicted to increase the bootstrap fraction at fixed Ip. The achievement of strong shaping has enabled operation with 1 s pulses with Ip=1 MA, and for 1.6 s for Ip=700 kA. Analysis of the noninductive current fraction as well as empirical analysis of the achievable plasma pulse length as elongation is varied will be presented. Data are presented showing a reduction in peak divertor heat load due to increasing in flux expansion.

  19. Effects of Angular Shapes on Optical properties of Martian Dust and Ice grains

    NASA Astrophysics Data System (ADS)

    Scarnato, B. V.; Colaprete, A.; Iraci, L. T.

    2012-12-01

    Dust, ice clouds and their interaction are now recognized as playing important roles in atmospheric thermal heating, in driving atmospheric dynamics and therefore in affecting martian climate and weather. However, simulation results depend strongly on dust and cloud optical properties, which depend on assumptions made on particle size, shape, number and composition (e.g. ice impurities). In radiative transfer calculations which are used to interpret space or ground-based observations of Mars, various assumptions are made regarding the aerosol optical properties; it is common to approximate aerosol shape to homogeneous spherical particles. The optical properties of spherical particles can, however, differ significantly from those of irregularly shaped particles, even if their composition and/or size distribution is the same. Therefore, assuming spherical instead of irregularly shaped angular particles in radiative transfer calculations can lead to significant errors in climate modeling and in retrieved atmospheric parameters, such as the aerosol type, optical thickness and particle size distributions. For irregularly shaped particles, which are very common in nature, the optical properties can be calculated with numerical methods such as the Discrete Dipole Approximation (DDA) method. We present a sensitivity study of the effect of angular shapes on optical properties of suspended dust aerosol and water ice particles (type 1 and 2) with and without a dust inclusion. We assess a plausible range of variability of the optical properties (e.g., mass extinction, scattering and absorption coefficients, single scattering albedo, phase function and polarization) over an extended spectral range, between 200 nm and 50 microns. Optical properties of dust and water ice grains with different angular shapes are also compared with more commonly used shapes like spheres, spheres with a concentric spherical inclusion (core-shell) and spheroids.

  20. A review of modeling techniques for advanced effects in shape memory alloy behavior

    NASA Astrophysics Data System (ADS)

    Cisse, Cheikh; Zaki, Wael; Ben Zineb, Tarak

    2016-10-01

    micro, micro-macro and macro scales focusing pseudoelastic and shape memory effects. The paper reviews and discusses various techniques used in the literature for modeling complex behaviors observed in shape memory alloys (SMAs) that go beyond the core pseudoelastic and shape memory effects. These behaviors, which will be collectively referred to herein as ‘secondary effects’, include mismatch between austenite and martensite moduli, martensite reorientation under nonproportional multiaxial loading, slip and transformation-induced plasticity and their influence on martensite transformation, strong thermomechanical coupling and the influence of loading rate, tensile-compressive asymmetry, and the formation of internal loops due to incomplete phase transformation. In addition, because of their importance for practical design considerations, the paper discusses functional and structural fatigue, and fracture mechanics of SMAs.

  1. Effects of window size and shape on accuracy of subpixel centroid estimation of target images

    NASA Technical Reports Server (NTRS)

    Welch, Sharon S.

    1993-01-01

    A new algorithm is presented for increasing the accuracy of subpixel centroid estimation of (nearly) point target images in cases where the signal-to-noise ratio is low and the signal amplitude and shape vary from frame to frame. In the algorithm, the centroid is calculated over a data window that is matched in width to the image distribution. Fourier analysis is used to explain the dependency of the centroid estimate on the size of the data window, and simulation and experimental results are presented which demonstrate the effects of window size for two different noise models. The effects of window shape were also investigated for uniform and Gaussian-shaped windows. The new algorithm was developed to improve the dynamic range of a close-range photogrammetric tracking system that provides feedback for control of a large gap magnetic suspension system (LGMSS).

  2. Shape-memory effect of nanocomposites based on liquid-crystalline elastomers

    NASA Astrophysics Data System (ADS)

    Marotta, A.; Lama, G. C.; Gentile, G.; Cerruti, P.; Carfagna, C.; Ambrogi, V.

    2016-05-01

    In this work, nanocomposites based on liquid crystalline (LC) elastomers were prepared and characterized in their shape memory properties. For the synthesis of materials, p-bis(2,3-epoxypropoxy)-α-methylstilbene (DOMS) was used as mesogenic epoxy monomer, sebacic acid (SA) as curing agent and multi-walled carbon nanotubes (MWCNT) and graphene oxide (GO) as fillers. First, an effective compatibilization methodology was set up to improve the interfacial adhesion between the matrix and the carbonaceous nanofillers, thus obtaining homogeneous distribution and dispersion of the nanofillers within the polymer phase. Then, the obtained nanocomposite films were characterized in their morphological and thermal properties. In particular, the effect of the addition of the nanofillers on liquid crystalline behavior, as well as on shape-memory properties of the realized materials was investigated. It was found that both fillers were able to enhance the thermomechanical response of the LC elastomers, making them good candidates as shape memory materials.

  3. Quantitative separation of the influence of copper (II) chloride mass migration on the chemo-responsive shape memory effect in polyurethane shape memory polymer

    NASA Astrophysics Data System (ADS)

    Lu, Haibao; Lu, Chunrui; Huang, Wei Min; Leng, Jinsong

    2016-10-01

    Chemo-responsive shape memory effect in polyurethane shape memory polymer (SMP) composite triggered by mass migration of copper (II) chloride (CuCl2) has been experimentally demonstrated. In this study, we present a comprehensive study on quantitative separation of the effect of CuCl2 particle mass migration on the chemo-responsive shape recovery behavior of polyurethane SMP composites with different concentrations of CuCl2 particles. It is found that the SMP is featured with a critical release rate of the mechanical energy storage associated with the shape recovery behavior due to mass migration of the CuCl2 particle. A sequence of molecular interactions among CuCl2 particles, polyurethane macromolecules and water molecules, i.e., assembly of the CuCl2 particle with polyurethane macromolecules, and then disassembly and dissolution of the CuCl2 particle in water, results in an acceleration of water-induced shape recovery of polyurethane SMP. This study focuses on the quantitative separation of the influence of mass migration on the chemo-responsive shape recovery behavior of polyurethane SMP in response to water. It is expected to promote and achieve the actuation of chemo-responsive SMPs in a fully controllable manner.

  4. The effects of particle shape, size, and interaction on colloidal glasses and gels

    NASA Astrophysics Data System (ADS)

    Kramb, Ryan C.

    Using multiple step seeded emulsion polymerization reactions, colloid particles of tunable shape are synthesized from polystyrene. In all, four particle shapes are studied referred to as spheres (S), heteronuclear dicolloids (hDC), symmetric homonuclear dicolloids (sDC), and tricolloids (TC). Two size ranges of particles are studied with approximate diameters in the range of 200-300nm and 1.1-1.3mum. The solvent ionic strength is varied from 10 -3M to 1M resulting in particle interaction potentials that range from repulsive to attractive. The effect of anisotropic shape is found to increase the glass transition volume fraction (φg) in good agreement with activated naive Mode Coupling Theory (nMCT) calculations. Differences in φg and the linear elastic modulus (G0') due to particle shape can be understood in terms of the Random Close Packed volume fraction (φRCP ) for each shape; φRCP- φg is a constant. In addition, a reentrant phase diagram is found for S and sDC particles with a maximum in the fluid state volume fraction found at weakly attractive interaction potential, in agreement well with theoretical calculations. Nonlinear rheology and yielding behavior of repulsive and attractive spheres and anisotropic particles are examined and understood in terms of barriers constraining motion. The barriers are due to interparticle bonds or cages constraining translational or rotational motion. Yield stress has similar volume fraction dependence as G 0' and a similar framework is used to understand differences due to particle shape and interaction. For larger particles, the effects of shape and interaction are studied with respect to dynamic yielding and shear thickening. The dynamic yield stress is found to increase with volume fraction while the stress at thickening is constant. The intersection of these indicates a possible jamming point below φRCP.

  5. Tumbling in Turbulence: How much does particle shape effect particle motion?

    NASA Astrophysics Data System (ADS)

    Variano, E. A.; Andersson, H. I.; Zhao, L.; Byron, M.

    2014-12-01

    Natural particles suspended in surface water are often non-spherical. We explore the ways in which particle shape effects particle motion, focusing specifically on how particle rotation is divided into spinning and tumbling components. This, in turn, will effect particle collision, clustering, and settling rates. We focus on idealized axisymmetric particles shaped as rods, discs, and spheroids. They are chosen so as to explain the physics of aspherical-particle motion that will be relevant for natural particles such as plankton, sediment, or aggregates (e.g. oil-mineral aggregates, clay flocs, or bio-sediment aggregates held together by TEP). Our work begins with laboratory measurements of particle motion in a turbulence tank built to mimic the flow found in rivers, estuaries, and the ocean surface mixed layer. We then proceed to direct numerical simulation of particle-flow interactions in sheared turbulence similar to that which is found in the surface water of creeks and rivers. We find that shape has only a very weak effect on particle angular velocity, which is a quantity calculated with respect the global reference frame (i.e. east/north/up). If we analyze rotation in a particle's local frame (i.e. the particle's principle axes of rotation), then particle shape has a strong effect on rotation. In the local frame, rotation is described by two components: tumbling and spinning. We find that rod-shaped particles spin more than they tumble, and we find that disc-shaped particles tumble more than they spin. Such behavior is indicative of how particles respond the the directional influence of vortex tubes in turbulence, and such response has implications for particle motion other than rotation. Understanding particle alignment is relevant for predicting particle-particle collision rates, particle-wall collision rates, and the shear-driven breakup of aggregates. We discuss these briefly in the context of what can be concluded from the rotation data discussed above.

  6. Effect of cathode shape on vertical buffered electropolishing for niobium SRF cavities

    NASA Astrophysics Data System (ADS)

    Jin, S.; Wu, A. T.; Lu, X. Y.; Rimmer, R. A.; Lin, L.; Zhao, K.; Mammosser, J.; Gao, J.

    2013-09-01

    This paper reports the research results of the effect of cathode shape during vertical buffered electropolishing (BEP) by employing a demountable single cell niobium (Nb) superconducting radio frequency (SRF) cavity. Several different cathode shapes such as, for instance, bar, ball, ellipsoid, and wheels of different diameters have been tested. Detailed electropolishing parameters including I-V characteristic, removal rate, surface roughness, and polishing uniformity at different locations inside the demountable cavity are measured. Similar studies are also done on conventional electropolishing (EP) for comparison. It is revealed that cathode shape has dominant effects for BEP especially on the obtaining of a suitable polishing condition and a uniform polishing rate in an Nb SRF single cell cavity. EP appears to have the same tendency. This paper demonstrates that a more homogeneous polishing result can be obtained by optimizing the electric field distribution inside the cavity through the modification of the cathode shape given the conditions that temperature and electrolyte flow are kept constant. Electric field distribution and electrolyte flow patterns inside the cavity are simulated via Poisson-Superfish and Solidworks respectively. With the optimal cathode shape, BEP shows a much faster polishing rate of ∼2.5 μm/min and is able to produce a smoother surface finish in the treatments of single cell cavities in comparison with EP.

  7. Shape effects on the random-packing density of tetrahedral particles.

    PubMed

    Zhao, Jian; Li, Shuixiang; Jin, Weiwei; Zhou, Xuan

    2012-09-01

    Regular tetrahedra have been demonstrated recently giving high packing density in random configurations. However, it is unknown whether the random-packing density of tetrahedral particles with other shapes can reach an even higher value. A numerical investigation on the random packing of regular and irregular tetrahedral particles is carried out. Shape effects of rounded corner, eccentricity, and height on the packing density of tetrahedral particles are studied. Results show that altering the shape of tetrahedral particles by rounding corners and edges, by altering the height of one vertex, or by lateral displacement of one vertex above its opposite face, all individually have the effect of reducing the random-packing density. In general, the random-packing densities of irregular tetrahedral particles are lower than that of regular tetrahedra. The ideal regular tetrahedron should be the shape which has the highest random-packing density in the family of tetrahedra, or even among convex bodies. An empirical formula is proposed to describe the rounded corner effect on the packing density, and well explains the density deviation of tetrahedral particles with different roundness ratios. The particles in the simulations are verified to be randomly packed by studying the pair correlation functions, which are consistent with previous results. The spherotetrahedral particle model with the relaxation algorithm is effectively applied in the simulations.

  8. Effect of Using Logo on Pupils' Learning in Two-Dimensional Shapes

    ERIC Educational Resources Information Center

    Yi, Boo Jia; Eu, Leong Kwan

    2016-01-01

    The integration of technology in mathematics instruction is an important step in the 21st century learning style. At the primary level, some studies have explored how technology could help in mathematics learning. The purpose of this study is to determine the effect of using Logo on pupils' learning of the properties of two-dimensional shapes. A…

  9. Effect of various shapes and materials on the generated power for piezoelectric energy harvesting system

    NASA Astrophysics Data System (ADS)

    Kaur, Sarabjeet; Graak, Pinki; Gupta, Ankita; Chhabra, Priya; Kumar, Dinesh; Shetty, Arjun

    2016-04-01

    Piezoelectric energy harvesting systems are used to convert vicinity vibrations into useful electrical energy. Effect of various shapes and materials open the gateway towards the choice of maximum power generation for the micro and nano world. Comsol Multiphysics was used to simulate the four designed shapes named as Pi, E, Rectangular and T in the size range of less than 1mm but greater than 1 micron. Designed shapes worked under the impact of ambient vibrations using few piezoelectric materials for the maximum power generation so that traditional power sources can be replaced with such piezoelectric energy harvester. A layer of piezoelectric material (PZT-5H, AlN, BaTiO3) of thickness 0.5 µm is added to the cantilever and the base material is silicon of thickness 1.5 µm. Simulations were performed using the piezoelectric device module of Comsol Multiphysics. All three materials were studied for the all four cantilever geometries. The generated power was observed maximum as 382.5 µW in case of the barium titanate material with rectangular shape geometry but the displacement is 0.132 µm which is very less whereas E shape cantilever shows the maximum displacement of 0.6078 µm in case of PZT-5H, Hence rectangular shape with barium titanate material is concluded to be good for maximum power generation but the displacement factor cannot be neglected, hence the cantilever with E shape geometry is considered as the best with a generated power of 49.005 µW and a displacement of 0.6078 µm.

  10. Effects of Lowering Cerebrospinal Fluid Pressure on the Shape of the Peripapillary Retina in Intracranial Hypertension

    PubMed Central

    Sibony, Patrick; Kupersmith, Mark J.; Honkanen, Robert; Rohlf, F. James; Torab-Parhiz, Ali

    2014-01-01

    Purpose. To analyze the deformations of the peripapillary retinal pigment epithelium–basement membrane (ppRPE/BM) layer in response to procedures that lower intracranial pressure (ICP). Second, to demonstrate how shape changes may complement the mean retinal nerve fiber layer (RNFL) thickness as a measure of intracranial hypertension (ICH) and papilledema. Methods. We used geometric morphometrics on spectral-domain optical coherence tomography images to analyze shape change of the ppRPE/BM layer after several interventions that lower cerebrospinal fluid (CSF) pressure. We also evaluated the effects of pressure-lowering interventions on both the anterior–posterior displacement of ppRPE/BM and the mean RNFL thickness. Forty-one patients with ICH and papilledema were studied before and after lumbar puncture (20), CSF shunt (9), and medical treatment of idiopathic ICH (23). We also compared the shape of 30 normal subjects to 23 patients whose papilledema resolved after medical treatment. Results. The ppRPE/BM-layer in ICH and papilledema is characterized by an asymmetric anterior deformation that moves posteriorly and becomes more V-shaped after each pressure-lowering intervention. The differences were statistically significant for all three groups. These shape changes also occur in patients with ongoing ICH who have secondary optic atrophy (without papilledema). Posterior displacement at the margin of the ppRPE/BM layer correlated strongly with overall shape changes. Conclusions. The subsurface contour of the ppRPE/BM layer is a dynamic property that changes with CSF pressure-lowering interventions. It can supplement the RNFL thickness as an indirect gauge of ICP and is particularly helpful in patients with secondary optic atrophy. Direct measurements of displacement at the basement membrane opening may serve as a more convenient office-based surrogate for shape analysis. PMID:25406288

  11. Effect of crash pulse shape on seat stroke requirements for limiting loads on occupants of aircraft

    NASA Technical Reports Server (NTRS)

    Carden, Huey D.

    1992-01-01

    An analytical study was made to provide comparative information on various crash pulse shapes that potentially could be used to test seats under conditions included in Federal Regulations Part 23 Paragraph 23.562(b)(1) for dynamic testing of general aviation seats, show the effects that crash pulse shape can have on the seat stroke requirements necessary to maintain a specified limit loading on the seat/occupant during crash pulse loadings, compare results from certain analytical model pulses with approximations of actual crash pulses, and compare analytical seat results with experimental airplace crash data. Structural and seat/occupant displacement equations in terms of the maximum deceleration, velocity change, limit seat pan load, and pulse time for five potentially useful pulse shapes were derived; from these, analytical seat stroke data were obtained for conditions as specified in Federal Regulations Part 23 Paragraph 23.562(b)(1) for dynamic testing of general aviation seats.

  12. Effects of target shape and reflection on laser radar cross sections.

    PubMed

    Steinvall, O

    2000-08-20

    Laser radar cross sections have been evaluated for a number of ideal targets such as cones, spheres, paraboloids, and cylinders by use of different reflection characteristics. The time-independent cross section is the ratio of the cross section of one of these forms to that of a plate with the same maximum radius. The time-dependent laser radar cross section involves the impulse response from the object shape multiplied by the beam's transverse profile and the surface bidirectional reflection distribution function. It can be clearly seen that knowledge of the combined effect of object shape and reflection characteristics is important for determining the shape and the magnitude of the laser radar return. The results of this study are of interest for many laser radar applications such as ranging, three-dimensional imaging-modeling, tracking, antisensor lasers, and target recognition.

  13. The Effect of Nose Shape on Water-Entry Cavity Formation

    NASA Astrophysics Data System (ADS)

    Ellis, Jeremy; Truscott, Tadd

    2014-11-01

    We examine the effect of nose shape and wetting angle on the threshold velocity at which an underwater cavity will form in the wake of a slender axisymmetric rigid body. The study covers a range of Reynolds numbers (1 E 4 < Re < 1 . 5 E 5), wetting surface conditions (hydrophilic, hydrophobic and super-hydrophobic), and impacting nose shapes (cone, ogive, flat, and two concave profiles: cusp and hemisphere). Cavity formation is visualized using high-speed cameras and impact forces were determined using an embedded inertial measurement unit (IMU). More streamlined nose shapes require higher impact velocities in order to form a cavity. However, the concave profiles generate a uniquely different cavity due to a strong vortex ring formed in front of the nose at impact. Additional results of this experiment and variable dependence on threshold velocity will be presented during the water entry of rigid slender bodies.

  14. The effect of particle shape on mixing in a high shear mixer

    NASA Astrophysics Data System (ADS)

    Sinnott, Matthew D.; Cleary, Paul W.

    2016-11-01

    Discrete element method modelling is used to study the effect of particle shape on the flow dynamics and mixing in a high shear mixer. The blade generates strong flow over its top surface while compacting and pushing forward particles that are directly in front of the blade. A complex three dimensional flow is established with vertical and radial flow components that are shape dependent and which control the nature of the mixing. Mixing was found to be fast in the azimuthal direction, of intermediate speed in the vertical direction and comparatively slow in the radial mixing. Diffusive mixing is characterised using the granular temperature which shows that the regions of higher granular temperature are larger for round particles than non-round ones leading to stronger diffusive mixing. The spatial distribution of the convective component of mixing is identified using novel calculation of shear strain rate. This size and shape of the high shear region is found to be only slightly sensitive to the particle shape indicating that the convective mixing is relatively independent of shape, except in the middle of the mixer. The blockiness of the particles has the strongest impact on flow and mixing while the mixing has only a weak dependence on the particle aspect ratio.

  15. The effect of particle shape on mixing in a high shear mixer

    NASA Astrophysics Data System (ADS)

    Sinnott, Matthew D.; Cleary, Paul W.

    2015-09-01

    Discrete element method modelling is used to study the effect of particle shape on the flow dynamics and mixing in a high shear mixer. The blade generates strong flow over its top surface while compacting and pushing forward particles that are directly in front of the blade. A complex three dimensional flow is established with vertical and radial flow components that are shape dependent and which control the nature of the mixing. Mixing was found to be fast in the azimuthal direction, of intermediate speed in the vertical direction and comparatively slow in the radial mixing. Diffusive mixing is characterised using the granular temperature which shows that the regions of higher granular temperature are larger for round particles than non-round ones leading to stronger diffusive mixing. The spatial distribution of the convective component of mixing is identified using novel calculation of shear strain rate. This size and shape of the high shear region is found to be only slightly sensitive to the particle shape indicating that the convective mixing is relatively independent of shape, except in the middle of the mixer. The blockiness of the particles has the strongest impact on flow and mixing while the mixing has only a weak dependence on the particle aspect ratio.

  16. Performance of AlGaN/GaN Nanowire Omega-Shaped-Gate Fin-Shaped Field-Effect Transistor.

    PubMed

    Lee, Dong-Gi; Sindhuri, V; Jo, Young-Woo; Son, Dong-Hyeok; Kang, Hee-Sung; Lee, Jae-Hong; Lee, Jae-Hoon; Cristoloveanu, Sorin; Im, Ki-Sik; Lee, Jung-Hee

    2016-05-01

    The AlGaN/GaN nanowire omega-shaped-gate FinFET have been successfully fabricated demonstrating much improved performance compared to conventional AlGaN/GaN MISHFET. The AlGaN/GaN omega-shaped-gate FinFET exhibited the remarkable on-state performances, such as maximum drain current of 1.1 A/mm, low on-resistance, and low current collapse compared to that of the conventional device structure. In addition, the excellent off-state performances were measured: low off-state leakage current as low as -10(-10) mA, the theoretical SS value of -62 mV/dec, and high I(ON)/I(OFF) ratio (-10(9)). Improved dc performances were obtained for omega-shaped-gate structure due to the fully depletion of the active fin body and perfectly separation of the depleted fin from the underlying thick GaN buffer layer. Furthermore, the additional reason for the enhanced device performance of the proposed device is the improved gate controllability compared to the conventional MISHFET. The proposed nano-structure device is very promising candidate for the steep switching device applications.

  17. Performance of AlGaN/GaN Nanowire Omega-Shaped-Gate Fin-Shaped Field-Effect Transistor.

    PubMed

    Lee, Dong-Gi; Sindhuri, V; Jo, Young-Woo; Son, Dong-Hyeok; Kang, Hee-Sung; Lee, Jae-Hong; Lee, Jae-Hoon; Cristoloveanu, Sorin; Im, Ki-Sik; Lee, Jung-Hee

    2016-05-01

    The AlGaN/GaN nanowire omega-shaped-gate FinFET have been successfully fabricated demonstrating much improved performance compared to conventional AlGaN/GaN MISHFET. The AlGaN/GaN omega-shaped-gate FinFET exhibited the remarkable on-state performances, such as maximum drain current of 1.1 A/mm, low on-resistance, and low current collapse compared to that of the conventional device structure. In addition, the excellent off-state performances were measured: low off-state leakage current as low as -10(-10) mA, the theoretical SS value of -62 mV/dec, and high I(ON)/I(OFF) ratio (-10(9)). Improved dc performances were obtained for omega-shaped-gate structure due to the fully depletion of the active fin body and perfectly separation of the depleted fin from the underlying thick GaN buffer layer. Furthermore, the additional reason for the enhanced device performance of the proposed device is the improved gate controllability compared to the conventional MISHFET. The proposed nano-structure device is very promising candidate for the steep switching device applications. PMID:27483869

  18. Swelling effect actuation of shape-memory polymer: mechanism and demonstration

    NASA Astrophysics Data System (ADS)

    Lu, Haibao; Leng, Jinsong; Liu, Yanju; Du, Shanyi

    2009-03-01

    Recently, there is increasing interest in triggering shape recovery of shape-memory polymers (SMPs) by novel inductive effect. In this paper, many hard works have been carried out to make SMP induced while along with swelling effect. Based on the Free-volume theory, Rubber Elasticity Theory and Mooney-Rivlin Equation, it is theoretically and experimentally demonstrated the feasibility of SMP activated by swelling effect. The mechanism behind it is solvent acting as plasticizer, to reduce the glass transition temperature (Tg) and melting temperature (Tm) of polymers, make them softer and more flexible, facilitating the diffusion of the molecules to polymer chains, and then separating them. In addition to this physical action, the intermolecular interactions among the chains are weakened, because interactions are hindered at the points where the plasticizer is located. Finally, the Dynamic mechanical analysis (DMA), FTIR study and glass transition temperature measurement tests were used to exemplify the feasibility of SMP driven by swelling effect. And it is qualitatively identified the role of swelling effect playing in influencing the transition temperature. Swelling effect occurs due to the interaction between macromolecules and solvent molecules, leading to free volume of polymeric chains increasing (namely the flexibility of polymer chains increasing), resulting in the Tg decreasing. All above mentioned investigation can be used to confirm that the shape recovery is induced by swelling effect. This actuation almost is applicable for all the SMP and SMP composite, as the swelling theory is almost applicable for all the polymeric materials.

  19. Free drainage of aqueous foams: Container shape effects on capillarity and vertical gradients

    NASA Astrophysics Data System (ADS)

    Saint-Jalmes, A.; Vera, M. U.; Durian, D. J.

    2000-06-01

    The standard drainage equation applies only to foam columns of constant cross-sectional area. Here, we generalize to include the effects of arbitrary container shape and develop an exact solution for an exponential, "Eiffel Tower", sample. This geometry largely eliminates vertical wetness gradients, and hence capillary effects, and should permit a clean test of dissipation mechanisms. Agreement with experiment is not achieved at late times, however, highlighting the importance of both boundary conditions and coarsening.

  20. Clarification of effects of DDE on shell thickness, size, mass, and shape of avian eggs.

    PubMed

    Blus, L J; Wiemeyer, S N; Bunck, C M

    1997-01-01

    Moriarty et al. (1986) used field data to conclude that DDE decreased the size or altered the shape of avian eggs; therefore, they postulated that decreased eggshell thickness was a secondary effect because, as a general rule, thickness and egg size are positively correlated. To further test this relationship, the present authors analyzed data from eggs of captive American kestrels. Falco sparverius given DDT- or DDE-contaminated or clean diets and from wild brown pelicans Pelecanus occidentalis collected both before (pre-1946) and after (post-1945) DDT was introduced into the environment. Pertinent data from other field and laboratory studies were also summarized. DDE was not related to and did not affect size, mass, or shape of eggs of the brown pelican or American kestrel; but the relationship of DDE to eggshell thinning held true. Size and shape of eggs of brown pelicans from the post-1945 era and those of kestrels, on DDT-contaminated diets showed some significant, but inconsistent, changes compared to brown pelican data from the pre-1946 era or kestrels on clean diets. In contrast, nearly all samples of eggs of experimental kestrels given DDT-contaminated diets and those of wild brown pelicans from the post-1945 era exhibited significant eggshell thinning. Pertinent experimental studies with other sensitive avian species indicated no effects of DDE on the size or shape of eggs, even though the high dietary concentrations caused extreme eggshell thinning and mortality of some adult mallards (Anas platyrhynchos) in one study. These findings essentially controvert the argument that decreased eggshell thickness is a secondary effect resulting from the primary effect of DDE-induced changes in the size or shape of eggs. PMID:15093475

  1. Clarification of effects of DDE on shell thickness, size, mass, and shape of avian eggs

    USGS Publications Warehouse

    Blus, L.J.; Wiemeyer, Stanley N.; Bunck, C.M.

    1997-01-01

    Moriarty et al. (1986) used field data to conclude that DDE decreased the size or altered the shape of avian eggs; therefore, they postulated that decreased eggshell thickness was a secondary effect because, as a general rule, thickness and egg size are positively correlated. To further test this relationship, the present authors analyzed data from eggs of captive American kestrels. Falco sparverius given DDT- or DDE-contaminated or clean diets and from wild brown pelicans Pelecanus occidentalis collected both before (pre-1946) and after (post-1945) DDT was introduced into the environment. Pertinent data from other field and laboratory studies were also summarized. DDE was not related to and did not affect size, mass, or shape of eggs of the brown pelican or American kestrel; but the relationship of DDE to eggshell thinning held true. Size and shape of eggs of brown pelicans from the post-1945 era and those of kestrels, on DDT-contaminated diets showed some significant, but inconsistent, changes compared to brown pelican data from the pre-1946 era or kestrels on clean diets. In contrast, nearly all samples of eggs of experimental kestrels given DDT-contaminated diets and those of wild brown pelicans from the post-1945 era exhibited significant eggshell thinning. Pertinent experimental studies with other sensitive avian species indicated no effects of DDE on the size or shape of eggs, even though the high dietary concentrations caused extreme eggshell thinning and mortality of some adult mallards (Anas platyrhynchos) in one study. These findings essentially controvert the argument that decreased eggshell thickness is a secondary effect resulting from the primary effect of DDE-induced changes in the size or shape of eggs.

  2. Shape effect in cellular uptake of PEGylated nanoparticles: comparison between sphere, rod, cube and disk

    NASA Astrophysics Data System (ADS)

    Li, Ying; Kröger, Martin; Liu, Wing Kam

    2015-10-01

    The size, shape, surface property and material composition of polymer-coated nanoparticles (NPs) are four important parameters in designing efficient NP-based carriers for targeted drug delivery. However, due to the complex interplay between size, shape and surface property, most studies lead to ambiguous descriptions of the relevance of shape. To clarify its influence on the cellular uptake of PEGylated NPs, large scale molecular simulations have been performed to study differently shaped convex NPs, such as sphere, rod, cube and disk. Comparing systems with identical NP surface area, ligand-receptor interaction strength, and grafting density of the polyethylene glycol, we find that the spherical NPs exhibit the fastest internalization rate, followed by the cubic NPs, then rod- and disk-like NPs. The spherical NPs thus demonstrate the highest uptake among these differently shaped NPs. Based on a detailed free energy analysis, the NP shape effect is found to be mainly induced by the different membrane bending energies during endocytosis. The spherical NPs need to overcome a minimal membrane bending energy barrier, compared with the non-spherical counterparts, while the internalization of disk-like NPs involves a strong membrane deformation, responsible for a large free energy barrier. Besides, the free energy change per tethered chain is about a single kBT regardless of NP shape, as revealed by our self-consistent field theory calculations, where kB and T denote Boltzmann constant and temperature, respectively. Thus, the NP shape only plays the secondary role in the free energy change of grafted PEG polymers during internalization. We also find that star-shaped NPs can be quickly wrapped by the cell membrane, similar to their spherical counterparts, indicating star-shaped NPs can be used for drug delivery with high efficacy. Our findings seem to provide useful guidance in the molecular design of PEGylated NPs for controllable cellular uptake and help establish

  3. Effect of shaped filter design on dose and image quality in breast CT.

    PubMed

    Lück, Ferdinand; Kolditz, Daniel; Hupfer, Martin; Kalender, Willi A

    2013-06-21

    The purpose of this study was to investigate the effect of shaped filters specifically designed for dedicated breast computed tomography (CT) scanners on dose and image quality. Optimization of filter shape and material in fan direction was performed using two different design methods, one aiming at homogeneous noise distributions in the CT images and the other aiming at a uniform dose distribution in the breast. The optimal filter thickness as a function of fan angle was determined iteratively to fulfil the above mentioned criteria for each breast diameter. Different filter materials (aluminium, copper, carbon, polytetrafluoroethylene) and breast phantoms with diameters between 80-180 mm were investigated. Noise uniformity in the reconstructed images, obtained from CT simulations based on ray-tracing methods, and dose in the breast, calculated with a Monte Carlo software tool, were used as figure of merit. Furthermore, CT-value homogeneity, the distribution of noise in cone direction, spatial resolution from centre to periphery and the contrast-to-noise ratio weighted by dose (CNRD) were evaluated. In addition, the decrease of scatter due to shaped filters was investigated. Since only few or one filter are practical in clinical CT systems, the effects of one shaped filter for different breast diameters were also investigated. In this case the filter, designed for the largest breast diameter, was simulated at variable source-to-filter distances depending on breast diameter. With the filter design method aiming at uniform noise distribution best results were obtained for aluminium as the filter material. Noise uniformity improved from 20} down to 5} and dose was reduced by about 30-40} for all breast diameters. No decrease of noise uniformity in cone direction, CT-value homogeneity, spatial resolution and the CNRD was detected with the shaped filter. However, a small improvement of CNRD was observed. Furthermore, a scatter reduction of about 20-30} and a more

  4. Effect of shaped filter design on dose and image quality in breast CT

    NASA Astrophysics Data System (ADS)

    Lück, Ferdinand; Kolditz, Daniel; Hupfer, Martin; Kalender, Willi A.

    2013-06-01

    The purpose of this study was to investigate the effect of shaped filters specifically designed for dedicated breast computed tomography (CT) scanners on dose and image quality. Optimization of filter shape and material in fan direction was performed using two different design methods, one aiming at homogeneous noise distributions in the CT images and the other aiming at a uniform dose distribution in the breast. The optimal filter thickness as a function of fan angle was determined iteratively to fulfil the above mentioned criteria for each breast diameter. Different filter materials (aluminium, copper, carbon, polytetrafluoroethylene) and breast phantoms with diameters between 80-180 mm were investigated. Noise uniformity in the reconstructed images, obtained from CT simulations based on ray-tracing methods, and dose in the breast, calculated with a Monte Carlo software tool, were used as figure of merit. Furthermore, CT-value homogeneity, the distribution of noise in cone direction, spatial resolution from centre to periphery and the contrast-to-noise ratio weighted by dose (CNRD) were evaluated. In addition, the decrease of scatter due to shaped filters was investigated. Since only few or one filter are practical in clinical CT systems, the effects of one shaped filter for different breast diameters were also investigated. In this case the filter, designed for the largest breast diameter, was simulated at variable source-to-filter distances depending on breast diameter. With the filter design method aiming at uniform noise distribution best results were obtained for aluminium as the filter material. Noise uniformity improved from 20} down to 5} and dose was reduced by about 30-40} for all breast diameters. No decrease of noise uniformity in cone direction, CT-value homogeneity, spatial resolution and the CNRD was detected with the shaped filter. However, a small improvement of CNRD was observed. Furthermore, a scatter reduction of about 20-30} and a more

  5. Electric Field Induced Reversible Phase Transition in Li Doped Phosphorene: Shape Memory Effect and Superelasticity.

    PubMed

    Deng, Junkai; Chang, Zhenyue; Zhao, Tong; Ding, Xiangdong; Sun, Jun; Liu, Jefferson Zhe

    2016-04-13

    Phosphorene, the single-layer form of black phosphorus, as a new member of atomically thin material family, has unique puckered atomistic structure and remarkable physical and chemical properties. In this paper, we report a discovery of an unexpected electromechanical energy conversion phenomenon-shape memory effect-in Li doped phosphorene P4Li2, using ab initio density functional theory simulations. Two stable phases are found for the two-dimensional (2D) P4Li2 crystal. Applying an external electric field can turn on or off the unique adatom switches in P4Li2 crystals, leading to a reversible structural phase transition and thereby the shape memory effect with an tunable strain output as high as 2.06%. Our results demonstrate that multiple temporary shapes are attainable in one piece of P4Li2 material, offering programmability that is particularly useful for device designs. Additionally, the P4Li2 displays superelasticity that can generate a pseudoelastic tensile strain up to 6.2%. The atomic thickness, superior flexibility, excellent electromechanical strain output, the special shape memory phenomenon, and the programmability feature endow P4Li2 with great application potential in high-efficient energy conversion at nanoscale and flexible nanoelectromechanical systems. PMID:27043220

  6. Electric Field Induced Reversible Phase Transition in Li Doped Phosphorene: Shape Memory Effect and Superelasticity.

    PubMed

    Deng, Junkai; Chang, Zhenyue; Zhao, Tong; Ding, Xiangdong; Sun, Jun; Liu, Jefferson Zhe

    2016-04-13

    Phosphorene, the single-layer form of black phosphorus, as a new member of atomically thin material family, has unique puckered atomistic structure and remarkable physical and chemical properties. In this paper, we report a discovery of an unexpected electromechanical energy conversion phenomenon-shape memory effect-in Li doped phosphorene P4Li2, using ab initio density functional theory simulations. Two stable phases are found for the two-dimensional (2D) P4Li2 crystal. Applying an external electric field can turn on or off the unique adatom switches in P4Li2 crystals, leading to a reversible structural phase transition and thereby the shape memory effect with an tunable strain output as high as 2.06%. Our results demonstrate that multiple temporary shapes are attainable in one piece of P4Li2 material, offering programmability that is particularly useful for device designs. Additionally, the P4Li2 displays superelasticity that can generate a pseudoelastic tensile strain up to 6.2%. The atomic thickness, superior flexibility, excellent electromechanical strain output, the special shape memory phenomenon, and the programmability feature endow P4Li2 with great application potential in high-efficient energy conversion at nanoscale and flexible nanoelectromechanical systems.

  7. Effects of star-shape poly(alkyl methacrylate) arm uniformity on lubricant properties

    DOE PAGES

    Robinson, Joshua W.; Qu, Jun; Erck, Robert; Cosimbescu, Lelia; Zhou, Yan

    2016-03-29

    Star-shaped poly(alkyl methacrylate)s (PAMAs) were prepared and blended into an additive-free engine oil to assess the structure property relationship between macromolecular structure and lubricant performance. These additives were designed with a comparable number of repeating units per arm and the number of arms was varied between 3 and 6. Well-defined star-shaped PAMAs were synthesized by atom transfer radical polymerization (ATRP) via a core-first strategy from multi-functional headgroups. Observations of the polymer-oil blends suggest that stars with less than four arms are favorable as a viscosity index improver (VII), and molecular weight dominates viscosity-related effects over other structural features. Star-shaped PAMAs,more » as oil additives, effectively reduce the friction coefficient in both mixed and boundary lubrication regime. Several analogs outperformed commercial VIIs in both viscosity and friction performance. Furthermore, increased wear rates were observed for these star-shaped PAMAs in the boundary lubrication regime suggesting pressure-sensitive conformations may exist.« less

  8. Temperature dependence and shape effect in high-temperature microwave heating of nickel oxide powders

    NASA Astrophysics Data System (ADS)

    Sugawara, H.; Kashimura, K.; Hayashi, M.; Matsumuro, T.; Watanabe, T.; Mitani, T.; Shinohara, N.

    2015-02-01

    The temperature dependence of microwave absorption was investigated for Ni1-yO particles over the frequency range 2.0-13.5 GHz and temperature range 25-1000 °C. Using a coaxial transmission line method with a network analyzer, both the real and imaginary parts of the relative permittivity (ε‧r and ε″r, respectively) and permeability (μ‧r and μ″r, respectively) were measured; finding that both are largely dependent on the temperature at all frequencies. Furthermore, permeability loss factors related to shape effects were observed at high frequencies, indicating an increase in the microwave-absorption properties. A modified form of Mie's theory was applied to discuss these effects, wherein a spherical model demonstrating a close fit to the shape effect data suggests a more complex microwave-absorption behavior at increased temperature.

  9. Effect of liquid bridge shape on the oscillatory thermal Marangoni convection

    NASA Astrophysics Data System (ADS)

    Yano, T.; Nishino, K.

    2015-03-01

    The effect of liquid bridge shape on the instability and associated oscillation mode of Marangoni convection due to the temperature gradient along the free surface is experimentally studied. Although the onset condition of oscillatory state is known to depend on the liquid bridge shape, this effect is not completely understood yet. Onset conditions are measured for various combinations of the aspect ratio ( AR) and the volume ratio ( VR) of liquid bridges. It is found that the convection becomes most stabilized at a certain combination of AR and VR and also that the oscillation mode changes at this most stabilized condition. To account for the effects of AR and VR in a simple way, a new dimensionless parameter SDR (i.e., the ratio of the surface length to the neck diameter) is proposed. It is shown that all the onset conditions measured presently are well correlated with SDR.

  10. Particle shape effects on thermo-physical properties of alumina nanofluids.

    SciTech Connect

    Timofeeva, E.; Routbort, J.; Singh, D.

    2009-07-06

    The thermal conductivity and viscosity of various shapes of alumina nanoparticles in a fluid consisting of equal volumes of ethylene glycol and water were investigated. Experimental data were analyzed and accompanied by theoretical modeling. Enhancements in the effective thermal conductivities due to particle shape effects expected from Hamilton-Crosser equation are strongly diminished by interfacial effects proportional to the total surface area of nanoparticles. On the other hand, the presence of nanoparticles and small volume fractions of agglomerates with high aspect ratios strongly increases viscosity of suspensions due to structural constrains. Nanoparticle surface charge also plays an important role in viscosity. It is demonstrated that by adjusting pH of nanofluid, it is possible to reduce viscosity of alumina nanofluid without significantly affecting thermal conductivity. Efficiency of nanofluids (ratio of thermal conductivity and viscosity increase) for real-life cooling applications is evaluated in both the laminar and turbulent flow regimes using the experimental values of thermal conductivity and viscosity.

  11. Shape effects of filaments versus spherical particles in flow and drug delivery

    NASA Astrophysics Data System (ADS)

    Geng, Yan; Dalhaimer, Paul; Cai, Shenshen; Tsai, Richard; Tewari, Manorama; Minko, Tamara; Discher, Dennis E.

    2007-04-01

    Interaction of spherical particles with cells and within animals has been studied extensively, but the effects of shape have received little attention. Here we use highly stable, polymer micelle assemblies known as filomicelles to compare the transport and trafficking of flexible filaments with spheres of similar chemistry. In rodents, filomicelles persisted in the circulation up to one week after intravenous injection. This is about ten times longer than their spherical counterparts and is more persistent than any known synthetic nanoparticle. Under fluid flow conditions, spheres and short filomicelles are taken up by cells more readily than longer filaments because the latter are extended by the flow. Preliminary results further demonstrate that filomicelles can effectively deliver the anticancer drug paclitaxel and shrink human-derived tumours in mice. Although these findings show that long-circulating vehicles need not be nanospheres, they also lend insight into possible shape effects of natural filamentous viruses.

  12. Periodic Cellular Structure Technology for Shape Memory Alloys

    NASA Technical Reports Server (NTRS)

    Chen, Edward Y.

    2015-01-01

    Shape memory alloys are being considered for a wide variety of adaptive components for engine and airframe applications because they can undergo large amounts of strain and then revert to their original shape upon heating or unloading. Transition45 Technologies, Inc., has developed an innovative periodic cellular structure (PCS) technology for shape memory alloys that enables fabrication of complex bulk configurations, such as lattice block structures. These innovative structures are manufactured using an advanced reactive metal casting technology that offers a relatively low cost and established approach for constructing near-net shape aerospace components. Transition45 is continuing to characterize these structures to determine how best to design a PCS to better exploit the use of shape memory alloys in aerospace applications.

  13. Effects of X-shaped reduction-sensitive amphiphilic block copolymer on drug delivery

    PubMed Central

    Xiao, Haijun; Wang, Lu

    2015-01-01

    To study the effects of X-shaped amphiphilic block copolymers on delivery of docetaxel (DTX) and the reduction-sensitive property on drug release, a novel reduction-sensitive amphiphilic copolymer, (PLGA)2-SS-4-arm-PEG2000 with a Gemini-like X-shape, was successfully synthesized. The formation of nanomicelles was proved with respect to the blue shift of the emission fluorescence as well as the fluorescent intensity increase of coumarin 6-loaded particles. The X-shaped polymers exhibited a smaller critical micelle concentration value and possessed higher micellar stability in comparison with those of linear ones. The size of X-shaped (PLGA)2-SS-4-arm-PEG2000 polymer nanomicelles (XNMs) was much smaller than that of nanomicelles prepared with linear polymers. The reduction sensitivity of polymers was confirmed by the increase of micellar sizes as well as the in vitro drug release profile of DTX-loaded XNMs (DTX/XNMs). Cytotoxicity assays in vitro revealed that the blank XNMs were nontoxic against A2780 cells up to a concentration of 50 µg/mL, displaying good biocompatibility. DTX/XNMs were more toxic against A2780 cells than other formulations in both dose- and time-dependent manners. Cellular uptake assay displayed a higher intracellular drug delivery efficiency of XNMs than that of nanomicelles prepared with linear polymers. Besides, the promotion of tubulin polymerization induced by DTX was visualized by immunofluorescence analysis, and the acceleration of apoptotic process against A2780 cells was also imaged using a fluorescent staining method. Therefore, this X-shaped reduction-sensitive (PLGA)2-SS-4-arm-PEG2000 copolymer could effectively improve the micellar stability and significantly enhance the therapeutic efficacy of DTX by increasing the cellular uptake and selectively accelerating the drug release inside cancer cells. PMID:26346880

  14. Effects of X-shaped reduction-sensitive amphiphilic block copolymer on drug delivery.

    PubMed

    Xiao, Haijun; Wang, Lu

    2015-01-01

    To study the effects of X-shaped amphiphilic block copolymers on delivery of docetaxel (DTX) and the reduction-sensitive property on drug release, a novel reduction-sensitive amphiphilic copolymer, (PLGA)2-SS-4-arm-PEG2000 with a Gemini-like X-shape, was successfully synthesized. The formation of nanomicelles was proved with respect to the blue shift of the emission fluorescence as well as the fluorescent intensity increase of coumarin 6-loaded particles. The X-shaped polymers exhibited a smaller critical micelle concentration value and possessed higher micellar stability in comparison with those of linear ones. The size of X-shaped (PLGA)2-SS-4-arm-PEG2000 polymer nanomicelles (XNMs) was much smaller than that of nanomicelles prepared with linear polymers. The reduction sensitivity of polymers was confirmed by the increase of micellar sizes as well as the in vitro drug release profile of DTX-loaded XNMs (DTX/XNMs). Cytotoxicity assays in vitro revealed that the blank XNMs were nontoxic against A2780 cells up to a concentration of 50 µg/mL, displaying good biocompatibility. DTX/XNMs were more toxic against A2780 cells than other formulations in both dose- and time-dependent manners. Cellular uptake assay displayed a higher intracellular drug delivery efficiency of XNMs than that of nanomicelles prepared with linear polymers. Besides, the promotion of tubulin polymerization induced by DTX was visualized by immunofluorescence analysis, and the acceleration of apoptotic process against A2780 cells was also imaged using a fluorescent staining method. Therefore, this X-shaped reduction-sensitive (PLGA)2-SS-4-arm-PEG2000 copolymer could effectively improve the micellar stability and significantly enhance the therapeutic efficacy of DTX by increasing the cellular uptake and selectively accelerating the drug release inside cancer cells. PMID:26346880

  15. Hydrodynamic drag of diving birds: effects of body size, body shape and feathers at steady speeds.

    PubMed

    Lovvorn, J; Liggins, G A; Borstad, M H; Calisal, S M; Mikkelsen, J

    2001-05-01

    For birds diving to depths where pressure has mostly reduced the buoyancy of air spaces, hydrodynamic drag is the main mechanical cost of steady swimming. Drag is strongly affected by body size and shape, so such differences among species should affect energy costs. Because flow around the body is complicated by the roughness and vibration of feathers, feathers must be considered in evaluating the effects of size and shape on drag. We investigated the effects of size, shape and feathers on the drag of avian divers ranging from wing-propelled auklets weighing 75 g to foot-propelled eiders weighing up to 2060 g. Laser scanning of body surfaces yielded digitized shapes that were averaged over several specimens per species and then used by a milling machine to cut foam models. These models were fitted with casts of the bill area, and their drag was compared with that of frozen specimens. Because of the roughness and vibration of the feathers, the drag of the frozen birds was 2-6 times that of the models. Plots of drag coefficient (C(D)) versus Reynolds number (Re) differed between the model and the frozen birds, with the pattern of difference varying with body shape. Thus, the drag of cast models or similar featherless shapes can differ both quantitatively and qualitatively from that of real birds. On the basis of a new towing method with no posts or stings that alter flow or angles of attack, the dimensionless C(D)/Re curves differed among a size gradient of five auklet species (75-100g) with similar shapes. Thus, extrapolation of C(D)/Re curves among related species must be performed with caution. At lower speeds, the C(D) at a given Re was generally higher for long-necked birds that swim with their neck extended (cormorants, grebes, some ducks) than for birds that swim with their head retracted (penguins, alcids), but this trend was reversed at high speeds. Because swimming birds actually travel at a range of instantaneous speeds during oscillatory strokes, species

  16. The Effect of Caudal Fin Shape on the Hydrodynamics of Swimming

    NASA Astrophysics Data System (ADS)

    Daghooghi, Mohsen; Borazjani, Iman

    2011-11-01

    The caudal fin is thought to be the main thrust generator in body/caudal fin swimmers because the largest undulations occur at the caudal fin. The shape of the fin could possibly be one of the most important factors in thrust generation for such swimmers. However, investigating this experimentally is quite challenging due to the issues in controlling and measuring forces on different appendages of live fish. We can investigate the effect of caudal fin shape through controlled numerical simulations. We construct virtual swimmers with different caudal fin shapes but with the same projected area. We attach trapezoidal and heterocercal shapes of caudal fins (e.g. observed in trouts and sharks, respectively) to a mackerel body and test these swimmers beside the original mackerel with a hemocercal tail. We prescribe the same carangiform kinematics to all virtual swimmers and carry out self-propelled simulations under similar conditions, i.e., the undulations are prescribed while motion of the center of mass is calculated. The simulations are continued until the quasi-steady state is reached, in which the swimmers are compared in terms of different performance measures. This work was partly supported by the Center for Computational Research at the University at Buffalo.

  17. Aging effects in a Cu-12Al-5Ni-2Mn-1Ti shape memory alloy

    SciTech Connect

    Wei, Z.G.; Peng, H.Y.; Yang, D.Z.; Zou, W.H.

    1997-04-01

    The isothermal aging effects in an as-quenched Cu-11.88Al-5.06Ni-1.65Mn-0.96Ti (wt pct) shape memory alloy at temperatures in the range 250 C to 400 C were investigated. The changes in the state of atomic order and microstructural evolutions were traced by means of in situ X-ray diffraction and electrical resistivity measurements, as well as transmission electron microscopy (TEM) and optical observations. The kinetics of the aging process, i.e., the temperature and time dependence of the properties including hardness, resistivity, martensitic transformation temperatures, and shape memory capacity were characterized, and at least three temperature-dependent aging stages were distinguished: (1) D0{sub 3} or L2{sub 1} atomic reordering, which causes the martensic transformation temperatures to shift upward and leads the M18R martensite to tend to be a N18R type structure; (2) formation of solute-depleted bainite which results in a drastic depression in martensitic transformation temperatures and loss of the shape memory capacity, accompanied by the atomic disordering in both the remaining parent phase and bainite; and (3) precipitation of the equilibrium {alpha} and {gamma}{sub 2} phases and destruction of the shape memory capacity.

  18. Effect of size polydispersity versus particle shape in dense granular media.

    PubMed

    Nguyen, Duc-Hanh; Azéma, Emilien; Radjai, Farhang; Sornay, Philippe

    2014-07-01

    We present a detailed analysis of the morphology of granular systems composed of frictionless pentagonal particles by varying systematically both the size span and particle shape irregularity, which represent two polydispersity parameters of the system. The microstructure is characterized in terms of various statistical descriptors such as global and local packing fractions, radial distribution functions, coordination number, and fraction of floating particles. We find that the packing fraction increases with the two parameters of polydispersity, but the effect of shape polydispersity for all the investigated structural properties is significant only at low size polydispersity where the positional and/or orientational ordering of the particles prevail. We focus in more detail on the class of side/side contacts, which is the interesting feature of our system as compared to a packing of disks. We show that the proportion of such contacts has weak dependence on the polydispersity parameters. The side- side contacts do not percolate but they define clusters of increasing size as a function of size polydispersity and decreasing size as a function of shape polydispersity. The clusters have anisotropic shapes but with a decreasing aspect ratio as polydispersity increases. This feature is argued to be a consequence of strong force chains (forces above the mean), which are mainly captured by side-side contacts. Finally, the force transmission is intrinsically multiscale, with a mean force increasing linearly with particle size.

  19. Simulation of time-dependent pool shape during laser spot welding: Transient effects

    NASA Astrophysics Data System (ADS)

    Ehlen, Georg; Ludwig, Andreas; Sahm, Peter R.

    2003-12-01

    The shape and depth of the area molten during a welding process is of immense technical importance. This study investigates how the melt pool shape during laser welding is influenced by Marangoni convection and tries to establish general qualitative rules of melt pool dynamics. A parameter study shows how different welding powers lead to extremely different pool shapes. Special attention is paid to transient effects that occur during the melting process as well as after switching off the laser source. It is shown that the final pool shape can depend strongly on the welding duration. The authors use an axisymmetric two-dimensional (2-D) control-volume-method (CVM) code based on the volume-averaged two-phase model of alloy solidification by Ni and Beckermann[1] and the SIMPLER algorithm by Patankar.[2] They calculate the transient distribution of temperatures, phase fractions, flow velocities, pressures, and concentrations of alloying elements in the melt and two solid phases (peritectic solidification) for a stationary laser welding process. Marangoni flow is described using a semiempirical model for the temperature-dependent surface tension gradient. The software was parallelized using the shared memory standard OpenMP.

  20. Mechanical properties and shape memory effect of 3D-printed PLA-based porous scaffolds.

    PubMed

    Senatov, F S; Niaza, K V; Zadorozhnyy, M Yu; Maksimkin, A V; Kaloshkin, S D; Estrin, Y Z

    2016-04-01

    In the present work polylactide (PLA)/15wt% hydroxyapatite (HA) porous scaffolds with pre-modeled structure were obtained by 3D-printing by fused filament fabrication. Composite filament was obtained by extrusion. Mechanical properties, structural characteristics and shape memory effect (SME) were studied. Direct heating was used for activation of SME. The average pore size and porosity of the scaffolds were 700μm and 30vol%, respectively. Dispersed particles of HA acted as nucleation centers during the ordering of PLA molecular chains and formed an additional rigid fixed phase that reduced molecular mobility, which led to a shift of the onset of recovery stress growth from 53 to 57°C. A more rapid development of stresses was observed for PLA/HA composites with the maximum recovery stress of 3.0MPa at 70°C. Ceramic particles inhibited the growth of cracks during compression-heating-compression cycles when porous PLA/HA 3D-scaffolds recovered their initial shape. Shape recovery at the last cycle was about 96%. SME during heating may have resulted in "self-healing" of scaffold by narrowing the cracks. PLA/HA 3D-scaffolds were found to withstand up to three compression-heating-compression cycles without delamination. It was shown that PLA/15%HA porous scaffolds obtained by 3D-printing with shape recovery of 98% may be used as self-fitting implant for small bone defect replacement owing to SME.

  1. Effect of blockage ratio on pressure drag and heat transfer of a cam-shaped tube

    NASA Astrophysics Data System (ADS)

    Lavasani, Arash Mirabdolah; Maarefdoost, Taher; Bayat, Hamidreza

    2016-09-01

    An experimental investigation has been conducted to clarify the effects of blockage ratio on forced convective heat transfer and pressure drag of an isothermal cam-shaped tube in cross-flow of air. The blockage ratio varies between 1.5 ≤ H/Deq ≤ 7 and Reynolds number based on equivalent diameter varies in range of 7.5 × 103 to 17.5 × 103. Results show that by increasing blockage ratio from 1.5 to 7, drag coefficient of the cam-shaped tube decreases about 55 % and increasing Reynolds number from 7.5 × 103 to 17.5 × 103 results in 40-48 % increment in Nusselt number. For better comparison, ratio of pressure drag over heat transfer of cam-shaped tube is compared with circular tube. In all ranges of Reynolds number and blockage ratios, thermal-hydraulic of cam-shaped tube is about 40-171 % greater than circular tube.

  2. Effects of IGF-binding protein 5 in dysregulating the shape of human hair.

    PubMed

    Sriwiriyanont, Penkanok; Hachiya, Akira; Pickens, William L; Moriwaki, Shigeru; Kitahara, Takashi; Visscher, Marty O; Kitzmiller, William J; Bello, Alexander; Takema, Yoshinori; Kobinger, Gary P

    2011-02-01

    The hair follicle has a unique dynamic property to cyclically regenerate throughout life. Despite significant progress in hair structure and hair shape determination using animal models, the mechanisms controlling the architecture and the shape of the human hair remain largely unexplored. In this study, comparison of the genetic expression of several human genes, especially those involved in growth, development, and differentiation, between Caucasian curly hair and naturally straight hair was performed. Thereafter, analyses using human recombinant and lentiviral vector technologies were conducted to further dissect and elucidate a molecular mechanism that regulates hair growth and development, particularly in controlling the shape of the hair shaft. Overexpression of IGF-binding protein 5 (IGFBP-5) in the human hair xenografts obtained from straight- and curly-haired individuals was found to result in the decreased expression of several extracellular matrix proteins and disassembly of adhesional junctions, resulting in twisted hair shafts as well as an unusual deposition of hair cuticle that may be derived from the disturbance of normal proliferation and differentiation. This study provides evidence that IGFBP-5 has an effect on human hair shape, and that lentiviral transduction regimen can be used for functional analysis of genes involved in human hair morphogenesis.

  3. Effect of Marangoni Flows on the Shape of Thin Sessile Droplets Evaporating into Air

    NASA Astrophysics Data System (ADS)

    Tsoumpas, Yannis; Dehaeck, Sam; Rednikov, Alexey; Colinet, Pierre

    2015-11-01

    With the help of Mach-Zehnder interferometry, we study the (largely) axisymmetric shapes of freely receding evaporating sessile droplets of various HFE liquids. The droplets evaporate into ambient air and, although the liquids are perfectly wetting, possess small finite contact angles reckoned to be evaporation-induced. The experimentally determined droplet profiles are shown here to deviate, under some conditions, from the classical macroscopic static profile of a sessile droplet, as this is determined by gravity and capillarity. These deviations are attributed to a Marangoni flow, due to evaporation-induced thermal gradients along the liquid-air interface, and are mostly observed in conditions of high evaporation. Unlike the classical static shapes, the distorted experimental profiles exhibit an inflection point at the contact line area. When a poorly volatile liquid is considered, however, the temperature differences and the Marangoni stresses are weak, and the measurements are found to be in a good agreement with the classical static shape. Overall, the experimental findings are quantitatively confirmed by the predictions of a lubrication model accounting for the impact of the Marangoni effect on the droplet shape. Financial support of FP7 Marie Curie MULTIFLOW Network (PITNGA-2008-214919), ESA/BELSPO-PRODEX, BELSPO- μMAST (IAP 7/38) & FRS-FNRS is gratefully acknowledged.

  4. Repetitive transcranial magnetic stimulation decreases the kindling induced synaptic potentiation: effects of frequency and coil shape.

    PubMed

    Yadollahpour, Ali; Firouzabadi, Seyed Mohammad; Shahpari, Marzieh; Mirnajafi-Zadeh, Javad

    2014-02-01

    The present study was aimed to investigate the effects of repetitive transcranial magnetic stimulation (rTMS) on kindling-induced synaptic potentiation and to study the effect of frequency and coil shape on rTMS effectiveness. Seizures were induced in rats by perforant path stimulation in a rapid kindling manner (12 stimulations/day). rTMS was applied at different frequencies (0.5, 1 and 2 Hz), using either figure-8 shaped or circular coils at different times (during or before kindling stimulations). rTMS had antiepileptogenic effect at all frequencies and imposed inhibitory effects on enhancement of population excitatory postsynaptic potential slope and population spike amplitude when applied during kindling acquisition. Furthermore, it prevented the kindling-induced changes in paired pulse indices. The inhibitory effect of rTMS was higher at the frequency of 1 Hz compared to 0.5 and 2 Hz. Application of rTMS 1Hz by circular coil imposed a weaker inhibitory action compared with the figure-8 coil. In addition, the results showed that pretreatment of animals by both coils had similar preventing effect on kindling acquisition as well as kindling-induced synaptic potentiation. Obtained results demonstrated that the antiepileptogenic effect of low frequency rTMS is accompanied with the preventing of the kindling induced potentiation. This effect is dependent on rTMS frequency and slightly on coil-type.

  5. Singular observation of the polarization-conversion effect for a gammadion-shaped metasurface

    PubMed Central

    Lin, Chu-En; Yen, Ta-Jen; Yu, Chih-Jen; Hsieh, Cheng-Min; Lee, Min-Han; Chen, Chii-Chang; Chang, Cheng-Wei

    2016-01-01

    In this article, the polarization-conversion effects of a gammadion-shaped metasurface in transmission and reflection modes are discussed. In our experiment, the polarization-conversion effect of a gammadion-shaped metasurface is investigated because of the contribution of the phase and amplitude anisotropies. According to our experimental and simulated results, the polarization property of the first-order transmitted diffraction is dominated by linear anisotropy and has weak depolarization; the first-order reflected diffraction exhibits both linear and circular anisotropies and has stronger depolarization than the transmission mode. These results are different from previously published research. The Mueller matrix ellipsometer and polar decomposition method will aid in the investigation of the polarization properties of other nanostructures. PMID:26915332

  6. Singular observation of the polarization-conversion effect for a gammadion-shaped metasurface.

    PubMed

    Lin, Chu-En; Yen, Ta-Jen; Yu, Chih-Jen; Hsieh, Cheng-Min; Lee, Min-Han; Chen, Chii-Chang; Chang, Cheng-Wei

    2016-01-01

    In this article, the polarization-conversion effects of a gammadion-shaped metasurface in transmission and reflection modes are discussed. In our experiment, the polarization-conversion effect of a gammadion-shaped metasurface is investigated because of the contribution of the phase and amplitude anisotropies. According to our experimental and simulated results, the polarization property of the first-order transmitted diffraction is dominated by linear anisotropy and has weak depolarization; the first-order reflected diffraction exhibits both linear and circular anisotropies and has stronger depolarization than the transmission mode. These results are different from previously published research. The Mueller matrix ellipsometer and polar decomposition method will aid in the investigation of the polarization properties of other nanostructures. PMID:26915332

  7. Precipitation-hardening stainless steels with a shape-memory effect

    NASA Astrophysics Data System (ADS)

    Sagaradze, V. V.; Afanasiev, S. V.; Volkova, E. G.; Zavalishin, V. A.

    2016-02-01

    The possibility of obtaining the shape-memory effect as a result of the γ → ɛ → γ transformations in aging stainless steels strengthened by VC carbides has been investigated. Regimes are given for strengthening aging (at 650 and 720°C) for stainless steels that predominantly contain (in wt %) 0.06-0.45C, 1-2V, 2-5Si, 9 and 13-14Cr. The values of reversible deformation e (amount of shape-memory effect) determined after heating to 400°C in samples preliminarily deformed to 3.5-4% vary from 0.15 to 2.7%, depending on the composition of the steels and regimes of stabilizing and destabilizing aging.

  8. Shape and Composition Effects on Photocatalytic Hydrogen Production for Pt-Pd Alloy Cocatalysts.

    PubMed

    Luo, Muhua; Lu, Pan; Yao, Weifeng; Huang, Cunping; Xu, Qunjie; Wu, Qiang; Kuwahara, Yasutaka; Yamashita, Hiromi

    2016-08-17

    The shape and composition effects of platinum-palladium (Pt-Pd) alloy nanoparticle cocatalysts on visible-light photocatalytic hydrogen evolution from an aqueous ammonium sulphite solution have been reported and discussed. The activity of Pt-Pd nanoparticles loaded Pt-Pd/CdS photocatalysts are affected based on both the Pt-Pd alloy nanoparticles' shape and their compositions. In this research, two shapes of Pt-Pd nanoparticles have been studied. One is Pt-Pd nanocubes enclosed by {100} crystal planes and the other is nano-octahedra covered with {111} crystal facets. Results show that the photocatalytic turnover frequency (TOF), defined as moles of hydrogen produced per surface mole of Pt-Pd metal atom per second, for Pt-Pd nanocubes/CdS (Pt-Pd NCs/CdS) photocatalyst can be 3.4 times more effective than Pt-Pd nano-octahedra/CdS (Pt-Pd NOTa/CdS) nanocomposite photocatalyst. Along with the shape effect, the atomic ratio of Pt to Pd can also impact the efficiency of Pt-Pd/CdS photocatalysts. When the Pt to Pd atomic ratio changes from 1:0 to about 2:1, the rate of hydrogen production increases from 900 μmol/h for Pt NCs/CdS catalyst to 1837 μmol/h for Pt-Pd (2:1) NCs/CdS photocatalyst-a 104% rate increase. This result suggests that the 33 mol % of more expensive Pt can be replaced with less costly Pd, resulting in a more than 100% hydrogen production rate increase. The finding of this research will lead to the research and development of highly effective catalysts for photocatalytic hydrogen production using solar photonic energy. PMID:27439590

  9. Entropic effects, shape, and size of mixed micelles formed by copolymers with complex architectures.

    PubMed

    Kalogirou, Andreas; Gergidis, Leonidas N; Moultos, Othonas; Vlahos, Costas

    2015-11-01

    The entropic effects in the comicellization behavior of amphiphilic AB copolymers differing in the chain size of solvophilic A parts were studied by means of molecular dynamics simulations. In particular, mixtures of miktoarm star copolymers differing in the molecular weight of solvophilic arms were investigated. We found that the critical micelle concentration values show a positive deviation from the analytical predictions of the molecular theory of comicellization for chemically identical copolymers. This can be attributed to the effective interactions between copolymers originated from the arm size asymmetry. The effective interactions induce a very small decrease in the aggregation number of preferential micelles triggering the nonrandom mixing between the solvophilic moieties in the corona. Additionally, in order to specify how the chain architecture affects the size distribution and the shape of mixed micelles we studied star-shaped, H-shaped, and homo-linked-rings-linear mixtures. In the first case the individual constituents form micelles with preferential and wide aggregation numbers and in the latter case the individual constituents form wormlike and spherical micelles. PMID:26651715

  10. Measured Effects of Turbulence on the Loudness and Waveforms of Conventional and Shaped Minimized Sonic Booms

    NASA Technical Reports Server (NTRS)

    Plotkin, Kenneth J.; Maglieri, Domenic J.; Sullivan, Brenda M.

    2005-01-01

    Turbulence has two distinctive effects on sonic booms: there is distortion in the form of random perturbations that appear behind the shock waves, and shock rise times are increased randomly. A first scattering theory by S.C. Crow in the late 1960s quantified the random distortions, and Crow's theory was shown to agree with available flight test data. A variety of theories for the shock thickness have been presented, all supporting the role of turbulence in increasing rise time above that of a basic molecular-relaxation structure. The net effect of these phenomena on the loudness of shaped minimized booms is of significant interest. Initial analysis suggests that there would be no change to average loudness, but this had not been experimentally investigated. The January 2004 flight test of the Shaped Sonic Boom Demonstrator (SSBD), together with a reference unmodified F-5E, included a 12500- foot linear ground sensor array with 28 digitally recorded sensor sites. This data set provides an opportunity to re-test Crow's theory for the post-shock perturbations, and to examine the net effect of turbulence on the loudness of shaped sonic booms.

  11. Effect of Protuberance Shape and Orientation on Space Shuttle Orbiter Boundary-Layer Transition

    NASA Technical Reports Server (NTRS)

    King, RUdolph A.; Berry, Scott A.; Kegerise, Michael A.

    2008-01-01

    This document describes an experimental study conducted to examine the effects of protuberances on hypersonic boundary-layer transition. The experiment was conducted in the Langley 20-Inch Mach 6 Tunnel on a series of 0.9%-scale Shuttle Orbiter models. The data were acquired to complement the existing ground-based boundary-layer transition database that was used to develop Version 1.0 of the boundary-layer transition RTF (return-to-flight) tool. The existing ground-based data were all acquired on 0.75%-scale Orbiter models using diamond-shaped ( pizza-box ) trips. The larger model scale facilitated in manufacturing higher fidelity protuberances. The end use of this experimental database will be to develop a technical basis (in the form of a boundary-layer transition correlation) to assess representative protrusion shapes, e.g., gap fillers and protrusions resulting from possible tile repair concepts. The primary objective of this study is to investigate the effects of protuberance-trip location and geometry on Shuttle Orbiter boundary-layer transition. Secondary goals are to assess the effects of gap-filler orientation and other protrusion shapes on boundary-layer transition. Global heat-transfer images using phosphor thermography of the Orbiter windward surface and the corresponding streamwise and spanwise heating distributions were used to infer the state of the boundary layer, i.e., laminar, transitional, or turbulent.

  12. Precipitation Effects on the Martensitic Transformation in a Cu-Al-Ni Shape Memory Alloy

    NASA Astrophysics Data System (ADS)

    Suru, Marius-Gabriel; Lohan, Nicoleta-Monica; Pricop, Bogdan; Mihalache, Elena; Mocanu, Mihai; Bujoreanu, Leandru-Gheorghe

    2016-04-01

    This paper describes the effects of precipitation of α-phase on a Cu-Al-Ni shape memory alloy (SMA) with chemical composition bordering on β region. By differential scanning calorimetry, a series of reproducible heat flow fluctuations was determined on heating a hot-rolled martensitic Cu-Al-Ni SMA, which was associated with the precipitation of α-phase. Two heat treatments were given to the SMA so as to "freeze" its states before and after the thermal range for precipitation, respectively. The corresponding microstructures of the two heat-treated states were observed by optical and scanning electron microscopy and were compared with the initial martensitic state. Energy dispersive spectroscopy experiments were carried out to determine the chemical compositions of the different phases formed in heat-treated specimens. The initial as well as the heat-treated specimens with a lamellar shape were further comparatively investigated by dynamic mechanical analysis and two-way shape memory effect (TWSME) tests comprising heating-cooling cycles under a bending load. Temperature scans were applied to the three types of specimens (initial and heat-treated states), so as to bring out the effects of heat treatment. The storage modulus increased, corresponding to the reversion of thermoelastic martensite and disappeared with the formation of precipitates. These features are finally discussed in association with TWSME under bending.

  13. The effects of particle shape, orientation and size distribution on the conductivity of granular media

    NASA Astrophysics Data System (ADS)

    Friedman, S. P.; Jones, S. B.; Robinson, D. A.

    2003-04-01

    Understanding the relationship between the effective electrical conductivity and dielectric permittivity of soils and rocks and their porosity and volumetric water content is important because measurements of electrical properties are used to determine porosity and water content. In this lecture we are going to report experimental and theoretical studies aimed at improving our understanding of the way the geometrical attributes of granular materials determine their effective conductivity and permittivity (2--5). In order to avoid surface conductivity and bound water effects we have used coarse granular materials of low surface area such as glass beads, quartz sand grains, tuff and mica particles. Accurate measurements of the effective conductivity (4,5) and permittivity (2,3,5) of anisotropic packings of mica particles (2,4) and isotropic packings of glass beads, sand grains and tuff particles (3,5) have demonstrated: 1, an alteration of the directional effective conductivities and permittivities of anisotropic packings attributed to particle shape and orientation; 2, a reduction in the permittivity of isotropic packings due to deviation from a spherical particle shape and an increased broadness of particle size distribution. The measured effective conductivities and permittivities are predicted reasonably well by modified classical mixing formulas (2,3,5), reviewed in e.g. (1), and by percolation concepts (4). (1) Sihvola, A., Electromagnetic mixing formulas and applications, IEE Electromagnetic Waves Series No. 47., Institution of Electrical Engineers, Stevenage, Herts. UK., 1999. (2) Jones, S. B. and Friedman, S. P., Particle shape effects on the effective permittivity of anisotropic or isotropic media consisting of aligned o randomly oriented ellipsoidal particles, Water Resour. Res., 36:2821--2833, 2000. (3) Robinson, D.A. and Friedman, S. P., Effect of particle size distribution on the effective dielectric permittivity of saturated granular media. Water

  14. Effect of Micro Porous Shape on Mechanical Properties in Polypropylene Syntactic Foams

    NASA Astrophysics Data System (ADS)

    Mae, Hiroyuki; Omiya, Masaki; Kishimoto, Kikuo

    The objective is to characterize the effect of the microstructure of the micro pores inside the matrix on the mechanical properties of the thermoplastic syntactic polypropylene (PP) foams at the intermediate and high strain rates. Tensile tests are conducted at the nominal strain rates from 3 x 10-1 to 102 s-1. In addition, the dart impact tests are conducted at the impact velocities of 0.1, 1 and 10 m/s. Then, the constitutive law with craze evolution is modified by introducing the relative density, the stress concentration coefficient and the volume fraction of cell edge, and then applied to the dart impact test mode for simulating the macroscopic load displacement history of the dart impact process. Moreover, the microstructural finite element analysis is conducted to characterize the local stress states in the microstructure. In the tensile loading, the elastic modulus is not influenced by the shape of the micro pores in the PP matrix while the yield stress and the strain energy up to failure are relatively influenced by the shape of micro pores. The microstructural finite element analysis shows that the magnitudes of the localized stresses at the edges and the ligaments of the elliptical-shape micro pores are larger than those at the spherical micro pores, leading to the early yielding and the small material ductility. In the case of the dart impact loading, the microstructure of pores has strong effect on the absorbed energy. This is because the elliptical-shape micro pores are very sensitive to the shear deformation, which is revealed by the microstructural finite element analysis. The modified constitutive law with the stress concentration coefficient and the volume fraction of the cell edges successfully predicts the load-displacement curve of the dart impact loading in the spherical micro-porous PP foam. It is concluded that the micro porous shape has strong effect on the material ductility especially in the dart impact test, leading to the possibility to

  15. Bend sweep angle and Reynolds number effects on hemodynamics of s-shaped arteries.

    PubMed

    Niazmand, H; Rajabi Jaghargh, E

    2010-09-01

    The purpose of this study is to investigate the effects of the Reynolds number and the bend sweep angle on the blood flow patterns of S-shaped bends. The numerical simulations of steady flows in S-shaped bends with sweep angles of 45 degrees , 90 degrees , and 135 degrees are performed at Reynolds numbers of 125, 500, and 960. Hemodynamic characteristics such as secondary flows, vorticity, and axial velocity profiles are analyzed in detail. Flow patterns in S-shaped bends are strongly dependent on both Reynolds number and bend sweep angle, which can be categorized into three groups based on the first bend secondary flow effects on the transverse flow of the second bend. For low Reynolds numbers and any sweep angles, secondary flows in the second bend eliminate the first bend effects in the early sections of the second bend and therefore the axial velocity profile is consistent with the bend curvature, while for high Reynolds numbers depending on the bend sweep angles the secondary vortex pattern of the first bend may persist partially or totally throughout the second bend leading to a four-vortex secondary structure. Moreover, an interesting flow feature observed at the Reynolds number of 960 is that the secondary flow asymmetrical behavior occurred around the second bend exit and along the outflow straight section. This symmetry-breaking phenomenon which has not been reported in the previous studies is shown to be more pronounced in the 90 degrees S-shaped bend as compared to other models considered here. The probability of flow separation as one of the important flow features contributing to the onset and development of arterial wall diseases is also studied. It is observed that the second bend outer wall of gentle bends with sweep angles from 20 degrees to 30 degrees at high enough Reynolds numbers are prone to flow separation.

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

    NASA Astrophysics Data System (ADS)

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

    2006-04-01

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

  17. The shape and size effects of polycation functionalized silica nanoparticles on gene transfection.

    PubMed

    Lin, Xinyi; Zhao, Nana; Yan, Peng; Hu, Hao; Xu, Fu-Jian

    2015-01-01

    Silica nanoparticles are attractive candidates for the development of safe and efficient non-viral gene carriers, owing to their controlled morphologies, potential of facile surface modification and excellent biocompatibility as well as in vivo biodegradability. Conversely, the size and shape of nanoparticles are considered to have an intense influence on their interaction with cells and biological systems, but the effects of particle size and shape on gene transfection are poorly understood. In this work, a series of novel gene carriers were designed employing polycation modified silica nanoparticles with five different morphologies, while keeping uniform zeta potential and surface functionality. Then the effects of particle size and shape of these five different carriers on gene transfection were investigated. The morphology of silica nanoparticles is demonstrated to play an important role in gene transfection, especially when the amount of polycation is low. Chiral nanorods with larger aspect ratio were found to fabricate the most efficient gene carriers with compromised cytotoxicity. It was also noted that hollow nanosphere-based carriers exhibited better gene transfection performance than did solid counterparts. These results may provide new strategies to develop promising gene carriers and useful information for the application of nanoparticles in biomedical areas. PMID:25219349

  18. Effect of steaming on shape memory polyurethane fibers with various hard segment contents

    NASA Astrophysics Data System (ADS)

    Zhu, Yong; Hu, Jinlian; Yeung, Lap-Yan; Lu, Jing; Meng, Qinghao; Chen, Shaojun; Yeung, Kwok-wing

    2007-08-01

    To illustrate the effect of post-treatment high-pressure steaming and hard segment content on shape memory polyurethane (SMPU) fiber, a series of shape memory polyurethane having various hard segment contents was synthesized with the pre-polymerization method, spun with a wet spinning process and treated with high pressure saturated water vapor. Differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), wide angle x-ray diffraction (WAXD), mechanical testing and cyclic tensile testing were conducted to investigate the particular thermal/mechanical properties, crystallization of hard segments and shape memory properties of SMPU fibers. In addition, in the light of a comparison between the original and the treated SMPU fiber, the effect of steaming post-treatment in SMPU fibers with various hard segment contents was illustrated. The steaming treatment gives rise to a higher elongation ratio at break, lower tenacity and initial modulus. Hard segment crystallization can be induced, especially in fiber with higher hard segment content after treatment. The glass transition temperature of the soft segment of SMPU fibers was decreased after steaming and the trends are most likely significant in high hard segment content specimens. Steaming with high pressure saturated water vapor can eliminate the thermal shrinkage and provide dimensional stability to the original SMPU fibers. The recoverability remains well in all treated specimens, but the fixity ability decreases with the decrease of hard segment content.

  19. Interstellar cloud shapes - A minimum-hypothesis account involving a purely gravitational effect

    NASA Technical Reports Server (NTRS)

    Fleck, Robert C., Jr.

    1992-01-01

    The effect produced by the anisotropic gravitational field on the shape of a nonspherical, self-gravitating interstellar cloud is examined. The projected axial ratios observed for molecular clouds can be accounted for if clouds are not generally in a state of strict dynamical equilibrium. For clouds having spectral line widths dominated by supersonic turbulent motions, this purely gravitational effect predicts a mean true axial ratio q about 0.3 for both oblate and prolate cloud geometries. Clouds having p less than about 0.3 are likely to be prolate and quite elongated. The observational data on molecular cloud cores, which have essentially thermal line widths, can be fitted equally well to either oblate or prolate spheroids having q between 0.1 and 0.4 with q about 0.2 providing the best match: highly elongated cores are again more likely to be prolate. While other processes certainly operate throughout the Galaxy to influence cloud shape, it appears plausible that at least some clouds may be shaped principally by their anisotropic gravitational field.

  20. Inlet Shape Effects on the Far-Field Sound of a Model Fan

    NASA Technical Reports Server (NTRS)

    Clark, L. R.; Thomas, R. H.; Dougherty, R. P.; Farassat, F.; Gerhold, C. H.

    1997-01-01

    A wind tunnel test was conducted to determine the effects of inlet shape on fan radiated noise. Four inlet geometries, which included a long standard flight type inlet, a short, aggressive flight inlet a scarf inlet, and an elliptical inlet were investigated in the study. The fan model used in the study was a 0.1 scale of the Pratt and Whitney Advanced Ducted Propeller (ADP), an ultra high bypass ratio turbofan engine. Acoustic data are presented for a fan speed of 70% (12,000 rpm) and a tunnel speed of 0.10 Mach number, The fan was configured with a 16-bladed rotor and a 40 stator vane set that were separated by 2.0 chord lengths. The radiated noise was measured with 15 microphones on a boom that traversed the length of the tunnel test section. Data from these microphones are presented in the form of sideline angle directivity plots. Noise associated with the test inlets was also predicted using a ray acoustics code. Inlet shape has been found to have a significant effect on both tone and broadband noise, and the non-axisymmetric inlet shape can be used for a noise reduction method.

  1. Using an Effective Charges Method to extract Λ from event shape moments in ee annihilation

    NASA Astrophysics Data System (ADS)

    Maxwell, C. J.; Morgan, K. E.

    2012-05-01

    We use an Effective Charges (ECH) method to extract Λ, and hence α(M), from event shape moments in ee annihilation. We compare these results with ones obtained using standard MS¯ perturbation theory. The ECH method at NLO is found to perform better than standard MS¯ perturbation theory when applied to means of event shape observables. For example, when we apply the NLO ECH method to <1-T> we get α(M)=0.1193±0.0003. However ECH at NNLO is found to work less well than ECH at NLO, and the ECH method also fails to describe data for higher moments of event shapes. We attempt to explain this by considering the ECH β-function as an asymptotic series. We also examine the effect of adding two different models for non-perturbative power corrections to the perturbative approximation given by the ECH method and MS¯ perturbation theory. Whilst only small power corrections are required when using ECH at NLO, it is found that these models are insufficient to counteract the undesirable behaviour of ECH at NNLO.

  2. Ion current rectification in funnel-shaped nanochannels: Hysteresis and inversion effects.

    PubMed

    Rosentsvit, Leon; Wang, Wei; Schiffbauer, Jarrod; Chang, Hsueh-Chia; Yossifon, Gilad

    2015-12-14

    Ion current rectification inversion is observed in a funnel-shaped nanochannel above a threshold voltage roughly corresponding to the under-limiting to over-limiting current transition. Previous experimental studies have examined rectification at either low-voltages (under-limiting current region) for conical nanopores/funnel-shaped nanochannels or at high-voltages (over-limiting region) for straight nanochannels with asymmetric entrances or asymmetric interfacing microchannels. The observed rectification inversion occurs because the system resistance is shifted, beyond a threshold voltage, from being controlled by intra-channel ion concentration-polarization to that controlled by external concentration-polarization. Additionally, strong hysteresis effects, due to residual concentration-polarization, manifest themselves through the dependence of the transient current rectification on voltage scan rate.

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

    PubMed

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

    2009-03-30

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

  4. Particle shape effect on heat transfer performance in an oscillating heat pipe

    PubMed Central

    2011-01-01

    The effect of alumina nanoparticles on the heat transfer performance of an oscillating heat pipe (OHP) was investigated experimentally. A binary mixture of ethylene glycol (EG) and deionized water (50/50 by volume) was used as the base fluid for the OHP. Four types of nanoparticles with shapes of platelet, blade, cylinder, and brick were studied, respectively. Experimental results show that the alumina nanoparticles added in the OHP significantly affect the heat transfer performance and it depends on the particle shape and volume fraction. When the OHP was charged with EG and cylinder-like alumina nanoparticles, the OHP can achieve the best heat transfer performance among four types of particles investigated herein. In addition, even though previous research found that these alumina nanofluids were not beneficial in laminar or turbulent flow mode, they can enhance the heat transfer performance of an OHP. PMID:21711830

  5. Effects of contact cap dimension on dry adhesion of bioinspired mushroom-shaped surfaces

    NASA Astrophysics Data System (ADS)

    Wang, Yue; Shao, Jinyou; Ding, Yucheng; Li, Xiangming; Tian, Hongmiao; Hu, Hong

    2015-03-01

    Dry adhesion observed in small creatures, such as spiders, insects, and geckos, has many great advantages such as repeatability and strong adhesiveness. In order to mimic these unique performances, fibrillar surface with a mushroom shaped end has drawn lots of attentions because of its advantage in efficiently enhancing adhesion compared with other sphere or simple flat ends. Here, in order to study the effects of contact cap dimension on adhesion strength, patterned surfaces of mushroom-shaped micropillars with differing cap diameters are fabricated based on the conventional photolithography and molding. The normal adhesion strength of these dry adhesives with varying cap diameters is measured with home-built equipment. The strength increases with the rise of cap diameter, and interestingly it becomes strongest when the mushroom caps join together.

  6. Unveiling the photonic spin Hall effect of freely propagating fan-shaped cylindrical vector vortex beams.

    PubMed

    Zhang, Yi; Li, Peng; Liu, Sheng; Zhao, Jianlin

    2015-10-01

    An intriguing photonic spin Hall effect (SHE) for a freely propagating fan-shaped cylindrical vector (CV) vortex beam in a paraxial situation is theoretically and experimentally studied. A developed model to describe this kind of photonic SHE is proposed based on angular spectrum diffraction theory. With this model, the close dependences of spin-dependent splitting on the azimuthal order of polarization, the topological charge of the spiral phase, and the propagation distance are accurately revealed. Furthermore, it is demonstrated that the asymmetric spin-dependent splitting of a fan-shaped CV beam can be consciously managed, even with a constant azimuthal order of polarization. Such a controllable photonic SHE is experimentally verified by measuring the Stokes parameters.

  7. Effect of Local Junction Losses in the Optimization of T-shaped Flow Channels

    NASA Astrophysics Data System (ADS)

    Kosaraju, Srinivas

    2015-11-01

    T-shaped channels are extensively used in flow distribution applications such as irrigation, chemical dispersion, gas pipelines and space heating and cooling. The geometry of T-shaped channels can be optimized to reduce the overall pressure drop in stem and branch sections. Results of such optimizations are in the form of geometric parameters such as the length and diameter ratios of the stem and branch sections. The traditional approach of this optimization accounts for the pressure drop across the stem and branch sections, however, ignores the pressure drop in the T-junction. In this paper, we conduct geometry optimization while including the effect of local junction losses in laminar flows. From the results, we are able to identify a non-dimensional parameter that can be used to predict the optimal geometric configurations. This parameter can also be used to identify the conditions in which the local junction losses can be ignored during the optimization.

  8. Effect of counterface roughness on adhesion of mushroom-shaped microstructure

    PubMed Central

    Kasem, Haytam; Varenberg, Michael

    2013-01-01

    In this study, the effect of the substrate roughness on adhesion of mushroom-shaped microstructure was experimentally investigated. To do so, 12 substrates having different isotropic roughness were prepared from the same material by replicating topography of different surfaces. The pull-off forces generated by mushroom-shaped microstructure in contact with the tested substrates were measured and compared with the pull-off forces generated by a smooth reference. It was found that classical roughness parameters, such as average roughness (Ra) and others, cannot be used to explain topography-related variation in pull-off force. This has led us to the development of an integrated roughness parameter capable of explaining results of pull-off measurements. Using this parameter, we have also found that there is a critical roughness, above which neither smooth nor microstructured surface could generate any attachment force, which may have important implications on design of both adhesive and anti-adhesive surfaces. PMID:23925984

  9. Wavelength effect on hole shapes and morphology evolution during ablation by picosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Zhao, Wanqin; Wang, Wenjun; Li, Ben Q.; Jiang, Gedong; Mei, Xuesong

    2016-10-01

    An experimental study is presented of the effect of wavelength on the shape and morphology evolution of micro holes ablated on stainless steel surface by a 10 ps Q-switched Nd:VAN pulsed laser. Two routes of hole development are associated with the visible (532 nm) and near-infrared (1064 nm) laser beams, respectively. The evolution of various geometric shapes and morphological characteristics of the micro holes ablated with the two different wavelengths is comparatively studied for other given processing conditions such as a laser power levels and the number of pulses applied. Plausible explanations, based on the light-materials interaction associated with laser micromachining, are also provided for the discernable paths of geometric and morphological development of holes under laser ablation.

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

    PubMed

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

    2009-03-30

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

  11. Color appearance of familiar objects: effects of object shape, texture, and illumination changes.

    PubMed

    Olkkonen, Maria; Hansen, Thorsten; Gegenfurtner, Karl R

    2008-05-26

    People perceive roughly constant surface colors despite large changes in illumination. The familiarity of colors of some natural objects might help achieve this feat through direct modulation of the objects' color appearance. Research on memory colors and color appearance has yielded controversial results and due to the employed methods has often confounded perceptual with semantic effects. We studied the effect of memory colors on color appearance by presenting photographs of fruit on a monitor under various simulated illuminations and by asking observers to make either achromatic or typical color settings without placing demands on short-term memory or semantic processing. In a control condition, we presented photographs of 3D fruit shapes without texture and 2D outline shapes. We found that (1) achromatic settings for fruit were systematically biased away from the gray point toward the opposite direction of a fruit's memory color; (2) the strength of the effect depended on the degree of naturalness of the stimuli; and (3) the effect was evident under all tested illuminations, being strongest for illuminations whose chromaticity was closest to the stimulus chromaticity. We conclude that the visual identity of an object has a measurable effect on color perception, and that this effect is robust under illuminant changes, indicating its potential significance as an additional mechanism for color constancy.

  12. An improved quasistatic line-shape theory: The effects of molecular motion on the line wings

    NASA Technical Reports Server (NTRS)

    Ma, Q.; Tipping, Richard H.

    1994-01-01

    A theory is presented for the modification of the line-shape functions and absorption coefficient due to the breakdown of the quasistatic approximation. This breakdown arises from the effects of molecular motion and increases the absorption in the near wings. Numerical calculations for the high-frequency wing of the nu(sub 3) band of CO2 broadened by Ar are reported and it is shown that these effects are significant near the bandhead. The importance of such corrections in other spectral regions and for other systems is discussed briefly.

  13. Galilean symmetry in the effective theory of inflation: new shapes of non-Gaussianity

    SciTech Connect

    Creminelli, Paolo; Musso, Marcello; D'Amico, Guido; Noreña, Jorge; Trincherini, Enrico E-mail: gda2@nyu.edu E-mail: jorge.norena@gmail.com

    2011-02-01

    We study the consequences of imposing an approximate Galilean symmetry on the Effective Theory of Inflation, the theory of small perturbations around the inflationary background. This approach allows us to study the effect of operators with two derivatives on each field, which can be the leading interactions due to non-renormalization properties of the Galilean Lagrangian. In this case cubic non-Gaussianities are given by three independent operators, containing up to six derivatives, two with a shape close to equilateral and one peaking on flattened isosceles triangles. The four-point function is larger than in models with small speed of sound and potentially observable with the Planck satellite.

  14. Shape effect on the antibacterial activity of silver nanoparticles synthesized via a microwave-assisted method.

    PubMed

    Hong, Xuesen; Wen, Junjie; Xiong, Xuhua; Hu, Yongyou

    2016-03-01

    Silver nanoparticles (AgNPs) are used as sustained-release bactericidal agents for water treatment. Among the physicochemical characteristics of AgNPs, shape is an important parameter relevant to the antibacterial activity. Three typically shaped AgNPs, nanocubes, nanospheres, and nanowires, were prepared via a microwave-assisted method and characterized by TEM, UV-vis, and XRD. The antibacterial activity of AgNPs was determined by OD growth curves tests, MIC tests, and cell viability assay against Escherichia coli. The interaction between AgNPs and bacterial cells was observed by TEM. The results showed that the three differently shaped AgNPs were nanoscale, 55 ± 10 nm in edge length for nanocubes, 60 ± 15 nm in diameter for nanospheres, 60 ± 10 nm in diameter and 2-4 μm in length for nanowires. At the bacterial concentration of 10(4) CFU/mL, the MIC of nanocubes, nanospheres, and nanowires were 37.5, 75, and 100 μg/mL, respectively. Due to the worst contact with bacteria, silver nanowires exhibited the weakest antibacterial activity compared with silver nanocubes and silver nanospheres. Besides, silver nanocubes mainly covered by {100} facets showed stronger antibacterial activity than silver nanospheres covered by {111} facets. It suggests that the shape effect on the antibacterial activity of AgNPs is attributed to the specific surface areas and facets reactivity; AgNPs with larger effective contact areas and higher reactive facets exhibit stronger antibacterial activity.

  15. The effect of glass shape on alcohol consumption in a naturalistic setting: a feasibility study

    PubMed Central

    Troy, David M.; Maynard, Olivia M.; Hickman, Matthew; Attwood, Angela S.; Munafò, Marcus R.

    2016-01-01

    Background Alcohol-related harms are a major public health concern, and population-level interventions are needed to reduce excessive alcohol consumption. Glass shape is an easily modifiable target for public health intervention. Laboratory findings show beer is consumed slower from a straight glass compared to a curved glass, but these findings have not been replicated in a naturalistic setting. The purpose of this study is to investigate the feasibility of conducting a randomised controlled trial investigating the effect of glass shape on alcohol consumption in public houses. Methods Straight and curved half-pint and pint glasses were delivered to three public houses over two weekends. Glass type was counterbalanced over the two weekends and between the public houses. Monetary takings were recorded as an indirect measure of consumption. Results Replacing stocks of glassware in public houses was feasible and can be enacted in a short space of time. One landlord found the study too disruptive, possibly due to a laborious exchange of glassware and complaints about the new glassware from some customers. One public house’s dishwasher could not accommodate the supplied curved full-pint glasses. Obtaining monetary takings from public house staff was a feasible and efficient way of measuring consumption, although reporting absolute amounts may be commercially sensitive. Monetary takings were reduced by 24 % (95 % confidence interval 77 % reduction to 29 % increase) when straight glasses were used compared to curved glasses. Conclusions This study shows that it is feasible to carry out a trial investigating glass shape in a naturalistic environment, although a number of challenges were encountered. Brewery owners and landlords are willing to engage with public health research in settings where alcohol is consumed, such as public houses. Good communication with stakeholders was vital to acquire good data, and highlighting the potential commercial benefits of

  16. Effects of grain shape on packing and dilatancy of sheared granular materials.

    PubMed

    Wegner, Sandra; Stannarius, Ralf; Boese, Axel; Rose, Georg; Szabó, Balázs; Somfai, Ellák; Börzsönyi, Tamás

    2014-07-28

    A granular material exposed to shear shows a variety of unique phenomena: Reynolds dilatancy, positional order and orientational order effects may compete in the shear zone. We study granular packing consisting of macroscopic prolate, oblate and spherical grains and compare their behaviour. X-ray tomography is used to determine the particle positions and orientations in a cylindrical split bottom shear cell. Packing densities and the arrangements of individual particles in the shear zone are evaluated. For anisometric particles, we observe the competition of two opposite effects. On the one hand, the sheared granules are dilated, on the other hand the particles reorient and align with respect to the streamlines. Even though aligned cylinders in principle may achieve higher packing densities, this alignment compensates for the effect of dilatancy only partially. The complex rearrangements lead to a depression of the surface above the well oriented region while neighbouring parts still show the effect of dilation in the form of heaps. For grains with isotropic shapes, the surface remains rather flat. Perfect monodisperse spheres crystallize in the shear zone, whereby positional order partially overcompensates dilatancy effects. However, even slight deviations from the ideal monodisperse sphere shape inhibit crystallization. PMID:24911156

  17. Effects of grain shape on packing and dilatancy of sheared granular materials.

    PubMed

    Wegner, Sandra; Stannarius, Ralf; Boese, Axel; Rose, Georg; Szabó, Balázs; Somfai, Ellák; Börzsönyi, Tamás

    2014-07-28

    A granular material exposed to shear shows a variety of unique phenomena: Reynolds dilatancy, positional order and orientational order effects may compete in the shear zone. We study granular packing consisting of macroscopic prolate, oblate and spherical grains and compare their behaviour. X-ray tomography is used to determine the particle positions and orientations in a cylindrical split bottom shear cell. Packing densities and the arrangements of individual particles in the shear zone are evaluated. For anisometric particles, we observe the competition of two opposite effects. On the one hand, the sheared granules are dilated, on the other hand the particles reorient and align with respect to the streamlines. Even though aligned cylinders in principle may achieve higher packing densities, this alignment compensates for the effect of dilatancy only partially. The complex rearrangements lead to a depression of the surface above the well oriented region while neighbouring parts still show the effect of dilation in the form of heaps. For grains with isotropic shapes, the surface remains rather flat. Perfect monodisperse spheres crystallize in the shear zone, whereby positional order partially overcompensates dilatancy effects. However, even slight deviations from the ideal monodisperse sphere shape inhibit crystallization.

  18. Antibacterial effect of various shapes of silver nanoparticles monitored by SERS.

    PubMed

    El-Zahry, Marwa R; Mahmoud, Amer; Refaat, Ibrahim H; Mohamed, Horria A; Bohlmann, Holger; Lendl, Bernhard

    2015-06-01

    A comparative evaluation of antimicrobial effect of synthesized silver nanoparticles (AgNPs) of different shapes using different methods was performed. Spherical, triangular and hexagonal AgNPs with an average size of 40 nm were chemically prepared and characterized by transmission electron microscope (TEM) and UV-visible spectroscopy. The antimicrobial effect of these different AgNPs against the gram negative bacterium Escherichia coli (E. coli) was studied by surface enhanced Raman spectroscopy (SERS), the evaluation of growth curves and inhibition zones. SERS proved to be sensitive to monitor the changes that occurred in the bacterial cells upon interaction with AgNPs, which qualitatively compared well with the data provided by the reference methods. However, as SERS is already sensitive to initial changes in the chemistry of bacteria due to the antibacterial effect of the AgNPs, fast and detailed information is provided by SERS as opposed to the classical reference methods based on the evaluation of growth curves and inhibition zones. The results of this work also demonstrate that hexagonal AgNPs display the highest antibacterial effect when compared to other NPs shapes, with triangular AgNPs exhibiting no antibacterial effect under the adopted conditions.

  19. Thermodynamics of multicaloric effects in multiferroic materials: application to metamagnetic shape-memory alloys and ferrotoroidics.

    PubMed

    Planes, Antoni; Castán, Teresa; Saxena, Avadh

    2016-08-13

    We develop a general thermodynamic framework to investigate multicaloric effects in multiferroic materials. This is applied to the study of both magnetostructural and magnetoelectric multiferroics. Landau models with appropriate interplay between the corresponding ferroic properties (order parameters) are proposed for metamagnetic shape-memory and ferrotoroidic materials, which, respectively, belong to the two classes of multiferroics. For each ferroic property, caloric effects are quantified by the isothermal entropy change induced by the application of the corresponding thermodynamically conjugated field. The multicaloric effect is obtained as a function of the two relevant applied fields in each class of multiferroics. It is further shown that multicaloric effects comprise the corresponding contributions from caloric effects associated with each ferroic property and the cross-contribution arising from the interplay between these ferroic properties.This article is part of the themed issue 'Taking the temperature of phase transitions in cool materials'.

  20. Shape-memory effect for self-healing and biodegradable photonic systems

    NASA Astrophysics Data System (ADS)

    Espinha, André; Concepción Serrano, Maria; Blanco, Álvaro; López, Cefe

    2013-05-01

    Photonic systems with the capability to respond to different stimuli are more and more desirable for achieving multifunctionality and higher levels of performance. They demand materials with responsivity that may eventually be used for integrating sensing and actuating functions, a feature highly pursued in technological applications. A notable property which is being gradually incorporated in this kind of multifunctional materials is the shape memory effect (SME). In this work, a material system consisting of a two-dimensional photonic crystal (PC) imprinted in the surface of a shape memory polymer (SMP) is reported. It integrates several interesting features such as elasticity, thermoresponsivity and shape memory. The referred PC is composed of a hexagonal lattice of nanobowls, transferred to the SMP surface using replica molding. Good quality and large extensions of PC were achieved. Differential scanning calorimetry studies confirmed a melting transition responsible for the SME in these materials. From the structural point of view, their surfaces were characterized by atomic force and scanning electron microscopies. From the optical point of view, the characterization of the first order Bragg diffraction angle was carried out. A full programmable character of the structures, derived from the SME, was demonstrated. The reported material system presents some interesting additional features. In particular, the SMP selected for replicating the PC belongs to the family of polydiolcitrates, which are known to be biocompat- ible and biodegradable elastomers. The PC described herein is thus attractive for the development of disposable devices or for temporal usage in biomedicine or biophotonics.

  1. Effects of d-band shape on the surface reactivity of transition-metal alloys

    NASA Astrophysics Data System (ADS)

    Xin, Hongliang; Vojvodic, Aleksandra; Voss, Johannes; Nørskov, Jens K.; Abild-Pedersen, Frank

    2014-03-01

    The d-band shape of a metal site, governed by the local geometry and composition of materials, plays an important role in determining trends of the surface reactivity of transition-metal alloys. We discuss this phenomenon using the chemisorption of various adsorbates such as C, N, O, and their hydrogenated species on Pd bimetallic alloys as an example. For many alloys, the d-band center, even with consideration of the d-band width and sp electrons, can not describe variations in reactivity from one surface to another. We investigate the effect of the d-band shape, represented by higher moments of the d band, on the local electronic structure of adsorbates, e.g., energy and filling of adsorbate-metal antibonding states. The upper d-band edge ɛu, defined as the highest peak position of the Hilbert transform of the density of states projected onto d orbitals of an active metal site, is identified as an electronic descriptor for the surface reactivity of transition metals and their alloys, regardless of variations in the d-band shape. The utilization of the upper d-band edge with scaling relations enables a considerable reduction of the parameter space in search of improved alloy catalysts and further extends our understanding of the relationship between the electronic structure and chemical reactivity of metal surfaces.

  2. Laboratory study of effects of sonic boom shaping on subjective loudness and acceptability

    NASA Technical Reports Server (NTRS)

    Leatherwood, Jack D.; Sullivan, Brenda M.

    1992-01-01

    A laboratory study was conducted to determine the effects of sonic boom signature shaping on subjective loudness and acceptability. The study utilized the sonic boom simulator at the Langley Research Center. A wide range of symmetrical, front-shock-minimized signature shapes were investigated together with a limited number of asymmetrical signatures. Subjective loudness judgments were obtained from 60 test subjects by using an 11-point numerical category scale. Acceptability judgments were obtained using the method of constant stimuli. Results were used to assess the relative predictive ability of several noise metrics, determine the loudness benefits of detailed boom shaping, and derive laboratory sonic boom acceptability criteria. These results indicated that the A-weighted sound exposure level, the Stevens Mark 7 Perceived Level, and the Zwicker Loudness Level metrics all performed well. Significant reductions in loudness were obtained by increasing front-shock rise time and/or decreasing front-shock overpressure of the front-shock minimized signatures. In addition, the asymmetrical signatures were rated to be slightly quieter than the symmetrical front-shock-minimized signatures of equal A-weighted sound exposure level. However, this result was based on a limited number of asymmetric signatures. The comparison of laboratory acceptability results with acceptability data obtained in more realistic situations also indicated good agreement.

  3. Effect of Gravity Level on the Particle Shape and Size During Zeolite Crystal Growth

    NASA Technical Reports Server (NTRS)

    Song, Hong-Wei; Ilebusi, Olusegun J.; Sacco, Albert, Jr.

    2003-01-01

    A microscopic diffusion model is developed to represent solute transport in the boundary layer of a growing zeolite crystal. This model is used to describe the effect of gravity on particle shape and solute distribution. Particle dynamics and crystal growth kinetics serve as the boundary conditions of flow and convection-diffusion equations. A statistical rate theory is used to obtain the rate of solute transport across the growing interface, which is expressed in terms of concentration and velocity of solute species. Microgravity can significantly decrease the solute velocity across the growing interface compared to its earth-based counterpart. The extent of this reduction highly depends on solute diffusion constant in solution. Under gravity, the flow towards the crystal enhances solute transport rate across the growing interface while the flow away from crystals reduces this rate, suggesting a non-uniform growth rate and thus an elliptic final shape. However, microgravity can significantly reduce the influence of flow and obtain a final product with perfect spherical shape. The model predictions compare favorably with the data of space experiment of zeolites grown in space.

  4. Effect of Particle Shape on Mechanical Behaviors of Rocks: A Numerical Study Using Clumped Particle Model

    PubMed Central

    Rong, Guan; Liu, Guang; Zhou, Chuang-bing

    2013-01-01

    Since rocks are aggregates of mineral particles, the effect of mineral microstructure on macroscopic mechanical behaviors of rocks is inneglectable. Rock samples of four different particle shapes are established in this study based on clumped particle model, and a sphericity index is used to quantify particle shape. Model parameters for simulation in PFC are obtained by triaxial compression test of quartz sandstone, and simulation of triaxial compression test is then conducted on four rock samples with different particle shapes. It is seen from the results that stress thresholds of rock samples such as crack initiation stress, crack damage stress, and peak stress decrease with the increasing of the sphericity index. The increase of sphericity leads to a drop of elastic modulus and a rise in Poisson ratio, while the decreasing sphericity usually results in the increase of cohesion and internal friction angle. Based on volume change of rock samples during simulation of triaxial compression test, variation of dilation angle with plastic strain is also studied. PMID:23997677

  5. Mitigation of Adverse Effects Caused by Shock Wave Boundary Layer Interactions Through Optimal Wall Shaping

    NASA Technical Reports Server (NTRS)

    Liou, May-Fun; Lee, Byung Joon

    2013-01-01

    It is known that the adverse effects of shock wave boundary layer interactions in high speed inlets include reduced total pressure recovery and highly distorted flow at the aerodynamic interface plane (AIP). This paper presents a design method for flow control which creates perturbations in geometry. These perturbations are tailored to change the flow structures in order to minimize shock wave boundary layer interactions (SWBLI) inside supersonic inlets. Optimizing the shape of two dimensional micro-size bumps is shown to be a very effective flow control method for two-dimensional SWBLI. In investigating the three dimensional SWBLI, a square duct is employed as a baseline. To investigate the mechanism whereby the geometric elements of the baseline, i.e. the bottom wall, the sidewall and the corner, exert influence on the flow's aerodynamic characteristics, each element is studied and optimized separately. It is found that arrays of micro-size bumps on the bottom wall of the duct have little effect in improving total pressure recovery though they are useful in suppressing the incipient separation in three-dimensional problems. Shaping sidewall geometry is effective in re-distributing flow on the side wall and results in a less distorted flow at the exit. Subsequently, a near 50% reduction in distortion is achieved. A simple change in corner geometry resulted in a 2.4% improvement in total pressure recovery.

  6. Shaping the composition profiles in heteroepitaxial quantum dots: Interplay of thermodynamic and kinetic effects

    SciTech Connect

    Georgiou, C.; Leontiou, T.; Kelires, P. C.

    2014-07-15

    Atomistic Monte Carlo simulations, coupling thermodynamic and kinetic effects, resolve a longstanding controversy regarding the origin of composition profiles in heteroepitaxial SiGe quantum dots. It is shown that profiles with cores rich in the unstrained (Si) component derive from near-equilibrium processes and intraisland diffusion. Profiles with cores rich in the strained (Ge) component are of nonequilibrium nature, i.e., they are strain driven but kinetically limited. They are shaped by the distribution of kinetic barriers of atomic diffusion in the islands. The diffusion pathways are clearly revealed for the first time. Geometrical kinetics play a minor role.

  7. Simulation studies of ion dynamic effects on dense plasma line shapes

    SciTech Connect

    Pollock, E.L.

    1986-12-01

    Computer simulations have been widely used in studying dense plasma properties including the local field properties important in spectral line broadening calculations. We will review here a more recent use of simulation, possibly less familiar to this audience, where the time dependent ionic microfield generated by computer simulation of a plasma is used directly as a time dependent external potential for the evolution of the electronic structure of an ion. This permits calculation of the dipole correlation function and thus line shapes with the inclusion of ion dynamic effects. 12 refs., 7 figs.

  8. The effect of particle aggregate shape on ultrasonic anisotropy in concentrated magnetic fluids

    NASA Astrophysics Data System (ADS)

    Hornowski, T.; Józefczak, A.; Kołodziejczyk, B.; Timko, M.; Skumiel, A.; Rajnak, M.

    2015-05-01

    The effect of aggregate shape on the ultrasonic anisotropy in magnetic fluid was studied. Experimental results were compared with the theory of Ahuja and Hendee. Analysis of experimental results in terms of the theoretical model show the formation of ellipsoidal aggregates composed of several particles. The chain-like aggregates (h = b/a >> 1 a and b being minor and major axis lengths, respectively) are most conspicuous in diluted ferrofluids while dense ferrofluids are characterized by a more homogeneous drop-like (h = b/a > 1) structure. This finding is supported by some theoretical simulations.

  9. Development of a polymer stent with shape memory effect as a drug delivery system.

    PubMed

    Wache, H M; Tartakowska, D J; Hentrich, A; Wagner, M H

    2003-02-01

    The article presents a new concept for vascular endoprothesis (stent). Almost all commercially available stents are made of metallic materials. A common after effect of stent implantation is restenosis. Several studies on metal stents coated with drug show, that the use of a drug delivery system may reduce restenosis. The purpose of this work is to develop a new stent for the drug delivery application. The shape memory properties of thermoplastic polyurethane allow to design a new fully polymeric self-expandable stent. The possibility to use the stent as a drug delivery system is described.

  10. Sexual Dimorphism and Allometric Effects Associated With the Wing Shape of Seven Moth Species of Sphingidae (Lepidoptera: Bombycoidea)

    PubMed Central

    de Camargo, Nícholas Ferreira; Corrêa, Danilo do Carmo Vieira; de Camargo, Amabílio J. Aires; Diniz, Ivone Rezende

    2015-01-01

    Sexual dimorphism is a pronounced pattern of intraspecific variation in Lepidoptera. However, moths of the family Sphingidae (Lepidoptera: Bombycoidea) are considered exceptions to this rule. We used geometric morphometric techniques to detect shape and size sexual dimorphism in the fore and hindwings of seven hawkmoth species. The shape variables produced were then subjected to a discriminant analysis. The allometric effects were measured with a simple regression between the canonical variables and the centroid size. We also used the normalized residuals to assess the nonallometric component of shape variation with a t-test. The deformations in wing shape between sexes per species were assessed with a regression between the nonreduced shape variables and the residuals. We found sexual dimorphism in both wings in all analyzed species, and that the allometric effects were responsible for much of the wing shape variation between the sexes. However, when we removed the size effects, we observed shape sexual dimorphism. It is very common for females to be larger than males in Lepidoptera, so it is expected that the shape of structures such as wings suffers deformations in order to preserve their function. However, sources of variation other than allometry could be a reflection of different reproductive flight behavior (long flights in search for sexual mates in males, and flight in search for host plants in females). PMID:26206895

  11. Sexual Dimorphism and Allometric Effects Associated With the Wing Shape of Seven Moth Species of Sphingidae (Lepidoptera: Bombycoidea).

    PubMed

    de Camargo, Willian Rogers Ferreira; de Camargo, Nícholas Ferreira; Corrêa, Danilo do Carmo Vieira; de Camargo, Amabílio J Aires; Diniz, Ivone Rezende

    2015-01-01

    Sexual dimorphism is a pronounced pattern of intraspecific variation in Lepidoptera. However, moths of the family Sphingidae (Lepidoptera: Bombycoidea) are considered exceptions to this rule. We used geometric morphometric techniques to detect shape and size sexual dimorphism in the fore and hindwings of seven hawkmoth species. The shape variables produced were then subjected to a discriminant analysis. The allometric effects were measured with a simple regression between the canonical variables and the centroid size. We also used the normalized residuals to assess the nonallometric component of shape variation with a t-test. The deformations in wing shape between sexes per species were assessed with a regression between the nonreduced shape variables and the residuals. We found sexual dimorphism in both wings in all analyzed species, and that the allometric effects were responsible for much of the wing shape variation between the sexes. However, when we removed the size effects, we observed shape sexual dimorphism. It is very common for females to be larger than males in Lepidoptera, so it is expected that the shape of structures such as wings suffers deformations in order to preserve their function. However, sources of variation other than allometry could be a reflection of different reproductive flight behavior (long flights in search for sexual mates in males, and flight in search for host plants in females). PMID:26206895

  12. Effect of magnetic nanoparticle shape on flux amplification in inductive coil magnetic resonance detection

    NASA Astrophysics Data System (ADS)

    Barbic, Mladen; ElBidweihy, Hatem

    2016-09-01

    We model and analyze the effect of particle shape on the signal amplification in inductive coil magnetic resonance detection using the reversible transverse magnetic susceptibility of oriented magnetic nanostructures. Utilizing the single magnetic domain Stoner-Wohlfarth model of uniform magnetization rotation, we reveal that different ellipsoidal particle shapes can have a pronounced effect on the magnetic flux enhancement in detection configurations typical of magnetic resonance settings. We compare and contrast the prolate ellipsoids, oblate ellipsoids, and exchange-biased spheres and show that the oblate ellipsoids and exchange-biased spheres have a significantly higher flux amplification effect than the prolate ellipsoids considered previously. In addition, oblate ellipsoids have a much broader polarizing magnetic field range over which their transverse flux amplification is significant. We show the dependence of transverse flux amplification on magnetic resonance bias field and discuss the resulting signal-to-noise ratio of inductive magnetic resonance detection due to the magnetic nanoparticle-filled core of the magnetic resonance detection coil.

  13. Shape and solar phase angle effects on the taxonomic classification of asteroids

    NASA Astrophysics Data System (ADS)

    Carvano, J. M.

    2015-12-01

    Asteroid taxonomy groups asteroids into classes based on similarities of their observational properties, of which the most commonly used are measurments of spectral reflectance in the visible and geometric albedo. It is a commonly used proxy for asteroid composition, since it can be derived from observations that are available for a large number of objects. However, the correspondence between asteroid taxonomy and asteroid composition is not univocal, for two main reasons: 1) not all compositions produce spectra with diagnostic features in the range used to derive the taxonomy; and 2) both the spectra and albedos of asteroids are also affected by other factors that are not directly related to composition. The main effect of the first reason is that asteroids with very different compositions may end up in a same taxonomic class, while the second reason may produce situations where asteroids of a given composition are classified into several different taxonomic groups. The physical causes for this later effect include the properties of the top regolith layer that cover the asteroid surface ( grain size distribution, porosity and rugosity) and processes that operate in this layer (space wethering by solar wind implatation and micro-meteorite bombardment). These are intrinsic properties of each body. Other causes however are linked to the particular geometry at the time of the observations, like solar phase angle, aspect angle and shape. In this work I review how solar phase angle and shape effects may affect the taxonomic classification of asteroids.

  14. Shape matters: effects of silver nanospheres and wires on human alveolar epithelial cells

    PubMed Central

    2011-01-01

    Background In nanotoxicology, the exact role of particle shape, in relation to the composition, on the capacity to induce toxicity is largely unknown. We investigated the toxic and immunotoxic effects of silver wires (length: 1.5 - 25 μm; diameter 100 - 160 nm), spherical silver nanoparticles (30 nm) and silver microparticles (<45 μm) on alveolar epithelial cells (A549). Methods Wires and nanoparticles were synthesized by wet-chemistry methods and extensively characterized. Cell viability and cytotoxicity were assessed and potential immunotoxic effects were investigated. To compare the effects on an activated and a resting immune system, cells were stimulated with rhTNF-α or left untreated. Changes in intracellular free calcium levels were determined using calcium imaging. Finally, ion release from the particles was assessed by ICP-MS and the effects of released ions on cell viability and cytotoxicity were tested. Results No effects were observed for the spherical particles, whereas the silver wires significantly reduced cell viability and increased LDH release from A549 cells. Cytokine promoter induction and NF-κB activation decreased in a concentration dependent manner similar to the decrease seen in cell viability. In addition, a strong increase of intracellular calcium levels within minutes after addition of wires was observed. This toxicity was not due to free silver ions, since the samples with the highest ion release did not induce toxicity and ion release control experiments with cells treated with pre-incubated medium did not show any effects either. Conclusions These data showed that silver wires strongly affect the alveolar epithelial cells, whereas spherical silver particles had no effect. This supports the hypothesis that shape is one of the important factors that determine particle toxicity. PMID:22208550

  15. On the effect of considering more realistic particle shape and mass parameters in MMOD risk assessments

    NASA Astrophysics Data System (ADS)

    Williamsen, Joel E.; Schonberg, William P.; Jenkin, Alan B.

    2011-03-01

    One of the primary mission risks tracked in the development of all spacecraft is that due to micro-meteoroids and orbital debris (MMOD). Both types of particles, especially those larger than 0.1 mm in diameter, contain sufficient kinetic energy due to their combined mass and velocities to cause serious damage to crew members and spacecraft. The process used to assess MMOD risk consists of three elements: environment, damage prediction, and damage tolerance. Orbital debris risk assessments for the Orion vehicle, as well as the Shuttle, Space Station and other satellites use ballistic limit equations (BLEs) that have been developed using high speed impact test data and results from numerical simulations that have used spherical projectiles. However, spheres are not expected to be a common shape for orbital debris; rather, orbital debris fragments might be better represented by other regular or irregular solids. In this paper we examine the general construction of NASA’s current orbital debris (OD) model, explore the potential variations in orbital debris mass and shape that are possible when using particle characteristic length to define particle size (instead of assuming spherical particles), and, considering specifically the Orion vehicle, perform an orbital debris risk sensitivity study taking into account variations in particle mass and shape as noted above. While the results of the work performed for this study are preliminary, they do show that continuing to use aluminum spheres in spacecraft risk assessments could result in an over-design of its MMOD protection systems. In such a case, the spacecraft could be heavier than needed, could cost more than needed, and could cost more to put into orbit than needed. The results obtained in this study also show the need to incorporate effects of mass and shape in mission risk assessment prior to first flight of any spacecraft as well as the need to continue to develop/refine BLEs so that they more accurately reflect

  16. Shape distortions induced by convective effect on hot object in visible, near infrared and infrared bands

    NASA Astrophysics Data System (ADS)

    Delmas, Anthony; Maoult, Yannick Le; Buchlin, Jean-Marie; Sentenac, Thierry; Orteu, Jean-José

    2013-04-01

    The goal of this study is to examine the perturbation induced by the convective effect (or mirage effect) on shape measurement and to give an estimation of the error induced. This work explores the mirage effect in different spectral bands and single wavelengths. A numerical approach is adopted and an original setup has been developed in order to investigate easily all the spectral bands of interest with the help of a CCD camera (Si, 0.35-1.1 μm), a near infrared camera (VisGaAs, 0.8-1.7 μm) or infrared cameras (8-12 μm). Displacements due to the perturbation for each spectral band are measured and finally some hints about how to correct them are given.

  17. U-shaped, double-tapered, fiber-optic sensor for effective biofilm growth monitoring.

    PubMed

    Zhong, Nianbing; Zhao, Mingfu; Li, Yishan

    2016-02-01

    To monitor biofilm growth on polydimethylsiloxane in a photobioreactor effectively, the biofilm cells and liquids were separated and measured using a sensor with two U-shaped, double-tapered, fiber-optic probes (Sen. and Ref. probes). The probes' Au-coated hemispherical tips enabled double-pass evanescent field absorption. The Sen. probe sensed the cells and liquids inside the biofilm. The polyimide-silica hybrid-film-coated Ref. probe separated the liquids from the biofilm cells and analyzed the liquid concentration. The biofilm structure and active biomass were also examined to confirm the effectiveness of the measurement using a simulation model. The sensor was found to effectively respond to the biofilm growth in the adsorption through exponential phases at thicknesses of 0-536 μm.

  18. U-shaped, double-tapered, fiber-optic sensor for effective biofilm growth monitoring.

    PubMed

    Zhong, Nianbing; Zhao, Mingfu; Li, Yishan

    2016-02-01

    To monitor biofilm growth on polydimethylsiloxane in a photobioreactor effectively, the biofilm cells and liquids were separated and measured using a sensor with two U-shaped, double-tapered, fiber-optic probes (Sen. and Ref. probes). The probes' Au-coated hemispherical tips enabled double-pass evanescent field absorption. The Sen. probe sensed the cells and liquids inside the biofilm. The polyimide-silica hybrid-film-coated Ref. probe separated the liquids from the biofilm cells and analyzed the liquid concentration. The biofilm structure and active biomass were also examined to confirm the effectiveness of the measurement using a simulation model. The sensor was found to effectively respond to the biofilm growth in the adsorption through exponential phases at thicknesses of 0-536 μm. PMID:26977344

  19. U-shaped, double-tapered, fiber-optic sensor for effective biofilm growth monitoring

    PubMed Central

    Zhong, Nianbing; Zhao, Mingfu; Li, Yishan

    2016-01-01

    To monitor biofilm growth on polydimethylsiloxane in a photobioreactor effectively, the biofilm cells and liquids were separated and measured using a sensor with two U-shaped, double-tapered, fiber-optic probes (Sen. and Ref. probes). The probes’ Au-coated hemispherical tips enabled double-pass evanescent field absorption. The Sen. probe sensed the cells and liquids inside the biofilm. The polyimide–silica hybrid-film-coated Ref. probe separated the liquids from the biofilm cells and analyzed the liquid concentration. The biofilm structure and active biomass were also examined to confirm the effectiveness of the measurement using a simulation model. The sensor was found to effectively respond to the biofilm growth in the adsorption through exponential phases at thicknesses of 0–536 μm. PMID:26977344

  20. Studies of numerical algorithms for gyrokinetics and the effects of shaping on plasma turbulence

    NASA Astrophysics Data System (ADS)

    Belli, Emily Ann

    Advanced numerical algorithms for gyrokinetic simulations are explored for more effective studies of plasma turbulent transport. The gyrokinetic equations describe the dynamics of particles in 5-dimensional phase space, averaging over the fast gyromotion, and provide a foundation for studying plasma microturbulence in fusion devices and in astrophysical plasmas. Several algorithms for Eulerian/continuum gyrokinetic solvers are compared. An iterative implicit scheme based on numerical approximations of the plasma response is developed. This method reduces the long time needed to set-up implicit arrays, yet still has larger time step advantages similar to a fully implicit method. Various model preconditioners and iteration schemes, including Krylov-based solvers, are explored. An Alternating Direction Implicit algorithm is also studied and is surprisingly found to yield a severe stability restriction on the time step. Overall, an iterative Krylov algorithm might be the best approach for extensions of core tokamak gyrokinetic simulations to edge kinetic formulations and may be particularly useful for studies of large-scale ExB shear effects. The effects of flux surface shape on the gyrokinetic stability and transport of tokamak plasmas are studied using the nonlinear GS2 gyrokinetic code with analytic equilibria based on interpolations of representative JET-like shapes. High shaping is found to be a stabilizing influence on both the linear ITG instability and nonlinear ITG turbulence. A scaling of the heat flux with elongation of chi ˜ kappa-1.5 or kappa-2 (depending on the triangularity) is observed, which is consistent with previous gyrofluid simulations. Thus, the GS2 turbulence simulations are explaining a significant fraction, but not all, of the empirical elongation scaling. The remainder of the scaling may come from (1) the edge boundary conditions for core turbulence, and (2) the larger Dimits nonlinear critical temperature gradient shift due to the

  1. Effects of surface reflectance on local second order shape estimation in dynamic scenes.

    PubMed

    Dövencioğlu, Dicle N; Wijntjes, Maarten W A; Ben-Shahar, Ohad; Doerschner, Katja

    2015-10-01

    In dynamic scenes, relative motion between the object, the observer, and/or the environment projects as dynamic visual information onto the retina (optic flow) that facilitates 3D shape perception. When the object is diffusely reflective, e.g. a matte painted surface, this optic flow is directly linked to object shape, a property found at the foundations of most traditional shape-from-motion (SfM) schemes. When the object is specular, the corresponding specular flow is related to shape curvature, a regime change that challenges the visual system to determine concurrently both the shape and the distortions of the (sometimes unknown) environment reflected from its surface. While human observers are able to judge the global 3D shape of most specular objects, shape-from-specular-flow (SFSF) is not veridical. In fact, recent studies have also shown systematic biases in the perceived motion of such objects. Here we focus on the perception of local shape from specular flow and compare it to that of matte-textured rotating objects. Observers judged local surface shape by adjusting a rotation and scale invariant shape index probe. Compared to shape judgments of static objects we find that object motion decreases intra-observer variability in local shape estimation. Moreover, object motion introduces systematic changes in perceived shape between matte-textured and specular conditions. Taken together, this study provides a new insight toward the contribution of motion and surface material to local shape perception.

  2. Effect of the tool influence function shape of the semirigid bonnet to the tool path ripple error

    NASA Astrophysics Data System (ADS)

    Lin, Jin; Wang, Chunjin; Ye, Hui; Yang, Wei; Guo, Yinbiao

    2015-11-01

    To suppress the medium-high spatial frequency, error on optical surfaces is still a challenging work to date, and the tool path ripple (TPR) error is the main reason for these errors. With this in view, the effect of the tool influence function (TIF) shape of the semirigid (SR) bonnet to the TPR error is analyzed. The SR bonnet is a recently developed bonnet tool for high efficiency polishing. This tool can generate three kinds of TIF including Gaussian-like shape, trapezoidal shape, and "M" shape. Experimental studies have been conducted to analyze their effect to the root mean square/peak-to-valley value of the TPR error, and discussions have been made on those results. It is found that different shapes of TIF can be implemented through controlling its inflated pressure. The Gaussian-like shape has the highest probability to generate lower TPR error than the trapezoidal shape and "M" shape TIFs, which have been proven by the verification experiments.

  3. Chemo-responsive shape memory effect in shape memory polyurethane triggered by inductive release of mechanical energy storage undergoing copper (II) chloride migration

    NASA Astrophysics Data System (ADS)

    Lu, Haibao; Lu, Chunrui; Huang, Wei Min; Leng, Jinsong

    2015-03-01

    In this study, 10% weight fraction of copper (II) chloride (CuCl2) was embedded into shape memory polyurethane (SMPU) by dissolving it in a solvent mixture of tetrahydrofuran and N,N-dimethyl formamide. It is found that CuCl2 particles migrate; they are released from the polymer in the water-driven shape recovery process of SMPU composites. SMPU composites, after various immersion times in water, were characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. Experimental results support that hydrogen bonding between polyurethane macromolecules and water molecules is the driving force, resulting from the inductive decrease in the glass transition temperature. Furthermore, the release of the stored mechanical energy in SMPU is demonstrated by means of tracking the migration of CuCl2 particles via x-ray diffraction and scanning electron microscopy tests. This study focuses on the mechanism of release of the stored mechanical energy of a polymer, which is identified as the driving force for the chemo-responsive shape memory effect and inductive decrease in glass transition temperature of SMPU in response to the water.

  4. Effects of Elevator Nose Shape, Gap, Balance, and Tabs on the Aerodynamic Characteristics of a Horizontal Tail Surface

    NASA Technical Reports Server (NTRS)

    Goett, Harry J; Reeder, J P

    1939-01-01

    Results are presented showing the effects of gap, elevator, nose shape, balance, cut-out, and tabs on the aerodynamic characteristics of a horizontal tail surface tested in the NACA full-scale tunnel.

  5. Effect of diffuse layer and pore shapes in mesoporous carbon supercapacitors

    SciTech Connect

    Huang, Jingsong; Sumpter, Bobby G; Meunier, Vincent; Qiao, Rui

    2010-01-01

    In the spirit of the theoretical evolution from the Helmholtz model to the Gouy Chapman Stern model for electric double-layer capacitors, we explored the effect of a diffuse layer on the capacitance of mesoporous carbon supercapacitors by solving the Poisson Boltzmann (PB) equation in mesopores of diameters from 2 to 20 nm. To evaluate the effect of pore shape, both slit and cylindrical pores were considered. We found that the diffuse layer does not affect the capacitance significantly. For slit pores, the area-normalized capacitance is nearly independent of pore size, which is not experimentally observed for template carbons. In comparison, for cylindrical pores, PB simulations produce a trend of slightly increasing area-normalized capacitance with pore size, similar to that depicted by the electric double-cylinder capacitor model proposed earlier. These results indicate that it is appropriate to approximate the pore shape of mesoporous carbons as being cylindrical and the electric double-cylinder capacitor model should be used for mesoporous carbons as a replacement of the traditional Helmholtz model.

  6. Trapezoidal-shaped detector to reduce edge effects in small gamma camera

    NASA Astrophysics Data System (ADS)

    Chung, Yong Hyun; Hwang, Ji Yeon; Baek, Cheol-Ha; An, Su Jung; Kim, Hyun-Il; Kim, Kwang Hyun

    2011-08-01

    In recent years, there has been a growing interest in compact and high resolution small gamma cameras for the early detection of breast cancer and thyroid diseases. We proposed a new detector consisting of a trapezoidal-shaped crystal and a position-sensitive photomultiplier tube (PSPMT) to reduce the edge effect. In this study, the imaging performance of the proposed detector was evaluated by DETECT2000 simulation. Trapezoidal-shaped NaI(Tl) and CsI(Tl) crystals were modeled and the 2-dimensional event positions were calculated using Anger-logic. 99mTc (140 keV) and 131I (364 keV) gamma rays were generated on evenly spaced points with 3.0 mm spacing in the X-Y plane starting 1.0 mm away from the corner surface and 10,000 gamma events were simulated at each location. The simulated results demonstrated that all the 99mTc and 131I point sources were clearly identified in the NaI(Tl) crystal. CsI(Tl) crystal could image 131I sources without edge effect but did not distinguish 99mTc points at the periphery region due to low light yield. In conclusion, our new detector with an enlarged FOV without increasing crystal size could be a useful tool in breast as well as thyroid imaging.

  7. Effect of tumor shape and size on drug delivery to solid tumors

    PubMed Central

    2012-01-01

    Tumor shape and size effect on drug delivery to solid tumors are studied, based on the application of the governing equations for fluid flow, i.e., the conservation laws for mass and momentum, to physiological systems containing solid tumors. The discretized form of the governing equations, with appropriate boundary conditions, is developed for predefined tumor geometries. The governing equations are solved using a numerical method, the element-based finite volume method. Interstitial fluid pressure and velocity are used to show the details of drug delivery in a solid tumor, under an assumption that drug particles flow with the interstitial fluid. Drug delivery problems have been most extensively researched in spherical tumors, which have been the simplest to examine with the analytical methods. With our numerical method, however, more complex shapes of the tumor can be studied. The numerical model of fluid flow in solid tumors previously introduced by our group is further developed to incorporate and investigate non-spherical tumors such as prolate and oblate ones. Also the effects of the surface area per unit volume of the tissue, vascular and interstitial hydraulic conductivity on drug delivery are investigated. PMID:22534172

  8. Effect of Interface Shape and Magnetic Field on the Microstructure of Bulk Ge:Ga

    NASA Technical Reports Server (NTRS)

    Cobb, S. D.; Szofran, F. R.; Volz, M. P.

    1999-01-01

    Thermal and compositional gradients induced during the growth process contribute significantly to the development of defects in the solidified boule. Thermal gradients and the solid-liquid interface shape can be greatly effected by ampoule material. Compositional gradients are strongly influenced by interface curvature and convective flow in the liquid. Results of this investigation illustrate the combined influences of interface shape and convective fluid flow. An applied magnetic field was used to reduce the effects of convective fluid flow in the electrically conductive melt during directional solidification. Several 8 mm diameter boules of Ga-doped Ge were grown at different field strengths, up to 5 Tesla, in four different ampoule materials. Compositional profiles indicate mass transfer conditions ranged from completely mixed to diffusion controlled. The influence of convection in the melt on the developing crystal microstructure and defect density was investigated as a function of field strength and ampoule material. Chemical etching and electron backscattered electron diffraction were used to map the crystal structure of each boule along the center plane. Dislocation etch pit densities were measured for each boule. Results show the influence of magnetic field strength and ampoule material on overall crystal quality.

  9. Subsonic Maneuvering Effectiveness of High Performance Aircraft Which Employ Quasi-Static Shape Change Devices

    NASA Technical Reports Server (NTRS)

    Montgomery, Raymond C.; Scott, Michael A.; Weston, Robert P.

    1998-01-01

    This paper represents an initial study on the use of quasi-static shape change devices in aircraft maneuvering. The macroscopic effects and requirements for these devices in flight control are the focus of this study. Groups of devices are postulated to replace the conventional leading-edge flap (LEF) and the all-moving wing tip (AMT) on the tailless LMTAS-ICE (Lockheed Martin Tactical Aircraft Systems - Innovative Control Effectors) configuration. The maximum quasi-static shape changes are 13.8% and 7.7% of the wing section thickness for the LEF and AMT replacement devices, respectively. A Computational Fluid Dynamics (CFD) panel code is used to determine the control effectiveness of groups of these devices. A preliminary design of a wings-leveler autopilot is presented. Initial evaluation at 0.6 Mach at 15,000 ft. altitude is made through batch simulation. Results show small disturbance stability is achieved, however, an increase in maximum distortion is needed to statically offset five degrees of sideslip. This only applies to the specific device groups studied, encouraging future research on optimal device placement.

  10. The combined effects on fluid flow during compression of piston bowl shape and offset, and swirl ratio

    SciTech Connect

    Watkins, A.P.; Dessipris, S.; Khaleghi, H.

    1987-01-01

    Computational results are presented of air flow during the compression stroke of three engines with differently shaped piston bowls. The three dimensional computer code uses orthogonal curvilinear coordinate systems to body fit the engine shapes. A parametric variation of bowl offset position and swirl ratio is performed to assess their effects on the mean flow and the turbulence parameters. The bowl shape and swirl ratio are found to be most influential. Bowl offset is less important except when combined with swirl in which case significant effects are made on the mean flow and to a lesser extent on the turbulence.

  11. The effects of syllabic compression and frequency shaping on speech intelligibility in hearing impaired people.

    PubMed

    Verschuure, H; Prinsen, T T; Dreschler, W A

    1994-02-01

    The effect of syllabic compression on speech intelligibility is rarely positive and in those cases that positive effects have been found, the same positive results could in general be obtained by frequency shaping of the frequency response curve. We programmed a syllabic compressor on a digital processor; the compressor differed from a conventional syllabic compressor by incorporating a delay in the signal path to suppress overshoots and thus minimize transient distortion. Furthermore, the time constants were short: attack time of 5 msec and release time of 15 msec. The compressor was only active in the high-frequency band. An essentially linear signal was added to deliver the low-frequency speech components. The processing resulted in a frequency response that mirrored the hearing loss near threshold and became much flatter for higher level input signals. Speech intelligibility scores for nonsense consonant-vowel-consonant words embedded in carrier phrases were determined for hearing-impaired persons with sloping audiograms and discrimination losses for speech. Results showed little additional effect of frequency shaping to the existing improved speech score for compressed speech. Optimum results were found for a compression ratio 2 with lower speech scores for linear amplification and for compression ratio 8. We next determined the effect of providing high-frequency emphasis to the speech signal and/or to the compression control signal to compensate for the upward spread of masking. The frequency response at the root-mean-square level was adjusted according to the half-gain rule. The positive effects of moderate compression could be found again; the high-frequency emphasis, however, was positive for the vowels but made consonant recognition poorer.(ABSTRACT TRUNCATED AT 250 WORDS)

  12. Effects of target shape and impact speed on the outcome of catastrophic disruptions

    NASA Astrophysics Data System (ADS)

    Campo~Bagatin, A.; Durda, D.; Alemañ, R.; Flynn, G.; Strait, M.; Clayton, A.; Patmore, E.

    2014-07-01

    Because of the propensity of previous laboratory investigations to focus on idealized spherical targets, there is a bit of ambiguity in decoupling the relative importance/influence of low speed or spherical shape in producing the 'onion shell' fragment shape outcomes found in impacts into spherical targets [1,2]. If due primarily to impact speed/energy density as suggested by [3], this could play an important role in main-belt impacts due to the presence of non-spherical targets and non-negligible probability of low-speed (i.e., below about 3-4 km/s, subsonic in rock) impacts [4]. Also, [5] and [6] suggested that the shape of targets may affect the outcome of shattering processes, both in terms of fragment shape and mass distribution. To examine explicitly the effects of target shape in impact outcomes, we chose to conduct impact experiments on both spherical and naturally-occurring irregularly-shaped basalt targets. We impacted a total of six targets (two spheres and four irregular targets). We focused on shots with impact speeds in the ˜4 to 6 km/s range by 3/16th-inch diameter Al-sphere projectiles fired at the NASA AVGR. Following each shot, the debris were recovered (>95 %) and large fragments (>0.20 g) were individually weighed, allowing us to carefully measure the mass-frequency distribution from each impact experiment. The 36 largest fragments of each shot were photographed and their largest axes accurately measured by the program ''ImageJ''. Their shortest axes were measured by means of a digital caliber. High-speed video of each impact was obtained to aid interpretation of the fragmentation mode of the targets. Images clearly show that shell-like fragments can be produced in shattering events not in the target's surface. Instead, those fragments may form around the core, well inside the target structure, independently on the target shape itself. This is a feature not reported to date. In order to understand what the bulk macro-porosity of a non

  13. Dilution dependent magnetorheological effect of flake-shaped particle suspensions—destructive friction effects

    NASA Astrophysics Data System (ADS)

    Siebert, Erik; Laherisheth, Zarana; Upadhyay, Ramesh V.

    2015-07-01

    The increase in viscosity as well as yield stress induced by an applied magnetic field were measured in dependence on the particle volume fraction of a magnetorheological fluid with flake-shaped particles. Five suspensions were synthesized, with particle volume concentrations varying from 7.45 vol.% to 17.74 vol.%. A drastic change in the behaviour of the relative viscosities was observed, which was related to a critical volume fraction. The yield stress showed similar characteristics and its origins were studied in more detail using a special analysis method which allows one to distinguish between the magnetic and friction components of yield stress. The hypothesis of ‘destructive friction’ is presented, which describes damped structure formation due to the dissipation of energy through multibody interactions.

  14. Effect of rheology on the equilibrium shape and thickness of dykes: a numerical modelling perspective.

    NASA Astrophysics Data System (ADS)

    Vachon, Rémi; Hieronymus, Christoph

    2015-04-01

    The size and thickness of dykes is of fundamental importance for volcano dynamics because dykes are the primary path for magma transport, and because large numbers of dykes often comprise a large portion of the volcanic edifice and of the underlying crust. Standard elastic models predict dyke geometry to be elliptic in cross-section, whereas observations show that dyke thickness is typically more nearly constant with a sharp taper at the ends. Moreover, the predicted overpressures required to inflate dykes in a purely elastic medium is much higher (>650 Mpa) than those estimated by other means (about 20-50 Mpa). In this study, we use 2-D finite element models to test whether other host-rock rheologies lead to more realistic dyke shapes and overpressures. We examine 3 different rheologies, each of which is affected by the presence of the dyke itself: (1) elasticity with reduced moduli in regions of overall tension; (2) elasto-plasticity with plastic failure near the dyke tips; (3) visco-elasticity with a viscosity decrease due to the heat from the dyke. We use realistic rheological parameters whenever possible, and assume static conditions for the final dyke shape. We thus neglect the dynamic effects of magma flow, an assumption that is probably justified because flow ceases well before the dyke solidifies. We find that all 3 rheologies tend to make the dyke more rectangular relative to the ellipse resulting from the linearly elastic models. The change in shape is due to enhanced deformation in the high-stress zone surrounding the dyke tip. We also find that the overpressure required to inflate an initially thin dyke to a given thickness is reduced for all 3 rheologies. The greatest decrease in overpressure is observed for the elasto-plastic model. We discuss our results with respect to dyke observations from the Rum Island (Scotland) and use these as a guide to evaluate our models.

  15. Magnetocaloric effect and its relation to shape-memory properties in ferromagnetic Heusler alloys.

    PubMed

    Planes, Antoni; Mañosa, Lluís; Acet, Mehmet

    2009-06-10

    Magnetic Heusler alloys which undergo a martensitic transition display interesting functional properties. In the present review, we survey the magnetocaloric effects of Ni-Mn-based Heusler alloys and discuss their relation with the magnetic shape-memory and magnetic superelasticity reported in these materials. We show that all these effects are a consequence of a strong coupling between structure and magnetism which enables a magnetic field to rearrange martensitic variants as well as to provide the possibility to induce the martensitic transition. These two features are respectively controlled by the magnetic anisotropy of the martensitic phase and by the difference in magnetic moments between the structural phases. The relevance of each of these contributions to the magnetocaloric properties is analysed.

  16. Pulse shape dependence in the dynamically assisted Sauter-Schwinger effect

    NASA Astrophysics Data System (ADS)

    Linder, Malte F.; Schneider, Christian; Sicking, Joachim; Szpak, Nikodem; Schützhold, Ralf

    2015-10-01

    While the Sauter-Schwinger effect describes nonperturbative electron-positron pair creation from vacuum by a strong and slowly varying electric field Estrong via tunneling, the dynamically assisted Sauter-Schwinger effect corresponds to a strong (exponential) enhancement of the pair-creation probability by an additional weak and fast electric or electromagnetic pulse Eweak. Using the WKB and worldline instanton method, we find that this enhancement mechanism strongly depends on the shape of the fast pulse. For the Sauter profile 1 /cosh2(ω t ) considered previously, the threshold frequency ωcrit (where the enhancement mechanism sets in) is basically independent of the magnitude Eweak of the weak pulse—whereas for a Gaussian pulse exp (-ω2t2), an oscillating profile cos (ω t ) or a standing wave cos (ω t )cos (k x ) , the value of ωcrit does depend (logarithmically) on Eweak/Estrong.

  17. Effects of erodant particle shape and various heat treatments on erosion resistance of plain carbon steel

    NASA Technical Reports Server (NTRS)

    Salik, J.; Buckley, D. H.

    1981-01-01

    Erosion tests were conducted on 1045 steel samples which had been subjected to different heat treatments. The weight of material removed upon erosion with glass beads and crushed glass was measured. The data show that there is no correlation between hardness and erosion resistance. The erosion rate was strongly dependent on the shape of erodant particles, being an order of magnitude higher for erosion with crushed glass than with glass beads. Heat treatment had a profound effect on the erosion resistance when the erodant particles were glass beads but little or no effect when the particles were crushed glass. It is thus concluded that different mechanisms of material removal are involved with these two erodants. This conclusion is supported by the surface morphology of annealed 1045 steel samples which had been eroded by these two types of erodant particles. SEM micrographs of the eroded surfaces show that for erosion with glass beads it is deformation induced fracture of surface layers.

  18. The effects of overall robot shape on the emotions invoked in users and the perceived personalities of robot.

    PubMed

    Hwang, Jihong; Park, Taezoon; Hwang, Wonil

    2013-05-01

    The affective interaction between human and robots could be influenced by various aspects of robots, which are appearance, countenance, gesture, voice, etc. Among these, the overall shape of robot could play a key role in invoking desired emotions to the users and bestowing preferred personalities to robots. In this regard, the present study experimentally investigates the effects of overall robot shape on the emotions invoked in users and the perceived personalities of robot with an objective of deriving guidelines for the affective design of service robots. In so doing, 27 different shapes of robot were selected, modeled and fabricated, which were combinations of three different shapes of head, trunk and limb (legs and arms) - rectangular-parallelepiped, cylindrical and human-like shapes. For the experiment, visual images and real prototypes of these robot shapes were presented to participants, and emotions invoked and personalities perceived from the presented robots were measured. The results showed that the overall shape of robot arouses any of three emotions named 'concerned', 'enjoyable' and 'favorable', among which 'concerned' emotion is negatively correlated with the 'big five personality factors' while 'enjoyable' and 'favorable' emotions are positively correlated. It was found that the 'big five personality factors', and 'enjoyable' and 'favorable' emotions are more strongly perceived through the real prototypes than through the visual images. It was also found that the robot shape consisting of cylindrical head, human-like trunk and cylindrical head is the best for 'conscientious' personality and 'favorable' emotion, the robot shape consisting of cylindrical head, human-like trunk and human-like limb for 'extroverted' personality, the robot shape consisting of cylindrical head, cylindrical trunk and cylindrical limb for 'anti-neurotic' personality, and the robot shape consisting of rectangular-parallelepiped head, human-like trunk and human-like limb

  19. Effect of Cold Rolling on Phase Transformation Temperatures of NiTi Shape Memory Alloy

    NASA Astrophysics Data System (ADS)

    Pattabi, Manjunatha; Murari, M. S.

    2015-02-01

    The effect of cold rolling and heat treatment on the phase transformation behavior of NiTi shape memory alloy (SMA) heat treated at 660 °C has been investigated. Four sets of samples were cold rolled after heat treatment. The austenite-to-martensite and martensite-to-austenite transformation temperatures for samples without any cold rolling are determined through differential scanning calorimetry (DSC). The austenitic start temperature gets shifted to the higher temperature side with increase in the percentage of the cold rolling up to 12.5%. Austenitic finish temperature could not be detected in cold-rolled samples. Martensitic start temperature increases slightly with increased cold rolling while martensitc finish temperature slightly decreases. Beyond 12.5% cold work, the shape memory effect (SME) is completely lost. The evolution of austenitic phase in SMA subjected to cold rolling was studied through powder x-ray diffraction (XRD) at different temperatures in the range 25 to 160 °C at intervals of 10 °C, during heating and cooling. The XRD results agree with those of DSC. Two sets of cold-rolled samples were again heat treated to 300 and 500 °C and the transformation behavior was studied using DSC. Heat treatment at 300 °C brings back the SME, but with the presence of an intermediate R-Phase due to the additional dislocations present. Even with a heat treatment at 500 °C, the effect of cold work is not completely removed and a single-step transformation is not observed. Another set of samples subjected to cold work were heat treated at 660 °C and the transformation is studied. The effect of cold work even up to 25% is completely removed with this heat treatment as indicated by DSC. The complete regaining of the SME is further confirmed by electrical resistivity measurements also.

  20. Nanoparticle shape evolution and proximity effects during tip-induced electrochemical processes

    DOE PAGES

    Yang, Sangmo; Paranthaman, Mariappan Parans; Noh, Tae Won; Kalinin, Sergei V.; Strelcov, Evgheni

    2016-01-08

    The voltage spectroscopies in scanning probe microscopy (SPM) techniques are widely used to investigate the electrochemical processes in nanoscale volumes, which are important for current key applications, such as batteries, fuel cells, catalysts, and memristors. The spectroscopic measurements are commonly performed on a grid of multiple points to yield spatially resolved maps of reversible and irreversible electrochemical functionalities. Hence, the spacing between measurement points is an important parameter to be considered, especially for irreversible electrochemical processes. Here, we report nonlocal electrochemical dynamics in chains of Ag particles fabricated by the SPM tip on a silver ion solid electrolyte. When themore » grid spacing is small compared with the size of the formed Ag particles, anomalous chains of unequally sized particles with double periodicity evolve. This behavior is ascribed to a proximity effect during the tip-induced electrochemical process, specifically, size-dependent silver particle growth following the contact between the particles. In addition, fractal shape evolution of the formed Ag structures indicates that the growth-limiting process changes from Ag+/Ag redox reaction to Ag+-ion diffusion with the increase in the applied voltage and pulse duration. Our study shows that characteristic shapes of the electrochemical products are good indicators for determining the underlying growth-limiting process, and emergence of complex phenomena during spectroscopic mapping of electrochemical functionalities.« less

  1. Triple shape memory effects of cross-linked polyethylene/polypropylene blends with cocontinuous architecture.

    PubMed

    Zhao, Jun; Chen, Min; Wang, Xiaoyan; Zhao, Xiaodong; Wang, Zhenwen; Dang, Zhi-Min; Ma, Lan; Hu, Guo-Hua; Chen, Fenghua

    2013-06-26

    In this paper, the triple shape memory effects (SMEs) observed in chemically cross-linked polyethylene (PE)/polypropylene (PP) blends with cocontinuous architecture are systematically investigated. The cocontinuous window of typical immiscible PE/PP blends is the volume fraction of PE (v(PE)) of ca. 30-70 vol %. This architecture can be stabilized by chemical cross-linking. Different initiators, 2,5-dimethyl-2,5-di(tert-butylperoxy)-hexane (DHBP), dicumylperoxide (DCP) coupled with divinylbenzene (DVB) (DCP-DVB), and their mixture (DHBP/DCP-DVB), are used for the cross-linking. According to the differential scanning calorimetry (DSC) measurements and gel fraction calculations, DHBP produces the best cross-linking and DCP-DVB the worst, and the mixture, DHBP/DCP-DVB, is in between. The chemical cross-linking causes lower melting temperature (Tm) and smaller melting enthalpy (ΔHm). The prepared triple shape memory polymers (SMPs) by cocontinuous immiscible PE/PP blends with v(PE) of 50 vol % show pronounced triple SMEs in the dynamic mechanical thermal analysis (DMTA) and visual observation. This new strategy of chemically cross-linked immiscible blends with cocontinuous architecture can be used to design and prepare new SMPs with triple SMEs.

  2. Shape Memory Effect in Cast Versus Deformation-Processed NiTiNb Alloys

    NASA Astrophysics Data System (ADS)

    Hamilton, Reginald F.; Lanba, Asheesh; Ozbulut, Osman E.; Tittmann, Bernhard R.

    2015-06-01

    The shape memory effect (SME) response of a deformation-processed NiTiNb shape memory alloy is benchmarked against the response of a cast alloy. The insoluble Nb element ternary addition is known to widen the hysteresis with respect to the binary NiTi alloy. Cast microstructures naturally consist of a cellular arrangement of characteristic eutectic microconstituents surrounding primary matrix regions. Deformation processing typically aligns the microconstituents such that the microstructure resembles discontinuous fiber-reinforced composites. Processed alloys are typically characterized for heat-to-recover applications and thus deformed at constant temperature and subsequently heated for SME recovery, and the critical stress levels are expected to facilitate plastic deformation of the microconstituents. The current work employs thermal cycling under constant bias stresses below those critical levels. This comparative study of cast versus deformation-processed NiTiNb alloys contrasts the strain-temperature responses in terms of forward Δ T F = M s - M f and reverse Δ T R = A f - A s temperature intervals, the thermal hysteresis, and the recovery ratio. The results underscore that the deformation-processed microstructure inherently promotes irreversibility and differential forward and reverse transformation pathways.

  3. Effects of Adhesion Dynamics and Substrate Compliance on the Shape and Motility of Crawling Cells

    PubMed Central

    Ziebert, Falko; Aranson, Igor S.

    2013-01-01

    Computational modeling of eukaryotic cells moving on substrates is an extraordinarily complex task: many physical processes, such as actin polymerization, action of motors, formation of adhesive contacts concomitant with both substrate deformation and recruitment of actin etc., as well as regulatory pathways are intertwined. Moreover, highly nontrivial cell responses emerge when the substrate becomes deformable and/or heterogeneous. Here we extended a computational model for motile cell fragments, based on an earlier developed phase field approach, to account for explicit dynamics of adhesion site formation, as well as for substrate compliance via an effective elastic spring. Our model displays steady motion vs. stick-slip transitions with concomitant shape oscillations as a function of the actin protrusion rate, the substrate stiffness, and the rates of adhesion. Implementing a step in the substrate’s elastic modulus, as well as periodic patterned surfaces exemplified by alternating stripes of high and low adhesiveness, we were able to reproduce the correct motility modes and shape phenomenology found experimentally. We also predict the following nontrivial behavior: the direction of motion of cells can switch from parallel to perpendicular to the stripes as a function of both the adhesion strength and the width ratio of adhesive to non-adhesive stripes. PMID:23741334

  4. Nanoparticle Shape Evolution and Proximity Effects During Tip-Induced Electrochemical Processes.

    PubMed

    Yang, Sang Mo; Paranthaman, Mariappan Parans; Noh, Tae Won; Kalinin, Sergei V; Strelcov, Evgheni

    2016-01-26

    Voltage spectroscopies in scanning probe microscopy (SPM) techniques are widely used to investigate the electrochemical processes in nanoscale volumes, which are important for current key applications, such as batteries, fuel cells, catalysts, and memristors. The spectroscopic measurements are commonly performed on a grid of multiple points to yield spatially resolved maps of reversible and irreversible electrochemical functionalities. Hence, the spacing between measurement points is an important parameter to be considered, especially for irreversible electrochemical processes. Here, we report nonlocal electrochemical dynamics in chains of Ag particles fabricated by the SPM tip on a silver ion solid electrolyte. When the grid spacing is small compared with the size of the formed Ag particles, anomalous chains of unequally sized particles with double periodicity evolve. This behavior is ascribed to a proximity effect during the tip-induced electrochemical process, specifically, size-dependent silver particle growth following the contact between the particles. In addition, fractal shape evolution of the formed Ag structures indicates that the growth-limiting process changes from Ag(+)/Ag redox reaction to Ag(+)-ion diffusion with the increase in the applied voltage and pulse duration. This study shows that characteristic shapes of the electrochemical products are good indicators for determining the underlying growth-limiting process, and emergence of complex phenomena during spectroscopic mapping of electrochemical functionalities. PMID:26743324

  5. Effect of mitral orifice shape on intra-ventricular filling fluid dynamics

    NASA Astrophysics Data System (ADS)

    Okafor, Ikechukwu; Angirish, Yagna; Yoganathan, Ajit; Santhanakrishnan, Arvind

    2013-11-01

    The natural geometry of the mitral orifice is D-shaped. However, most current designs of prosthetic valves employ O-shaped orifice geometry. The goal of this study was to compare the effect of geometrical modification between the D and O orifice on the intra-ventricular fluid dynamics during diastolic filling. The different mitral orifice geometries were incorporated into an in vitro left heart simulator consisting of a flexible-walled anatomical left ventricle (LV) physical model enclosed in an acrylic housing. Physiological flow rates and pressures were obtained via tuning systemic resistance and compliance elements in the flow loop. A programmable piston pump was used to generate the LV model wall motion. 2D Particle image velocimetry measurements were conducted along multiple longitudinal planes perpendicular to the annulus plane. During peak diastole, the incoming jet width at the LV central plane was smaller for the D-orifice than that of the O-orifice. Further, the core of the vortex ring in the D-orifice was reduced in size compared to that of the O-orifice. The spatiotemporal spreading of the inflow jet as well as the propagation of the vortex ring will be discussed. This study was funded by a grant from the National Heart, Lung and Blood Institute (RO1HL70262).

  6. Nanoparticle Shape Evolution and Proximity Effects During Tip-Induced Electrochemical Processes.

    PubMed

    Yang, Sang Mo; Paranthaman, Mariappan Parans; Noh, Tae Won; Kalinin, Sergei V; Strelcov, Evgheni

    2016-01-26

    Voltage spectroscopies in scanning probe microscopy (SPM) techniques are widely used to investigate the electrochemical processes in nanoscale volumes, which are important for current key applications, such as batteries, fuel cells, catalysts, and memristors. The spectroscopic measurements are commonly performed on a grid of multiple points to yield spatially resolved maps of reversible and irreversible electrochemical functionalities. Hence, the spacing between measurement points is an important parameter to be considered, especially for irreversible electrochemical processes. Here, we report nonlocal electrochemical dynamics in chains of Ag particles fabricated by the SPM tip on a silver ion solid electrolyte. When the grid spacing is small compared with the size of the formed Ag particles, anomalous chains of unequally sized particles with double periodicity evolve. This behavior is ascribed to a proximity effect during the tip-induced electrochemical process, specifically, size-dependent silver particle growth following the contact between the particles. In addition, fractal shape evolution of the formed Ag structures indicates that the growth-limiting process changes from Ag(+)/Ag redox reaction to Ag(+)-ion diffusion with the increase in the applied voltage and pulse duration. This study shows that characteristic shapes of the electrochemical products are good indicators for determining the underlying growth-limiting process, and emergence of complex phenomena during spectroscopic mapping of electrochemical functionalities.

  7. Phase effects in masking by harmonic complexes: detection of bands of speech-shaped noise.

    PubMed

    Deroche, Mickael L D; Culling, John F; Chatterjee, Monita

    2014-11-01

    When phase relationships between partials of a complex masker produce highly modulated temporal envelopes on the basilar membrane, listeners may detect speech information from temporal dips in the within-channel masker envelopes. This source of masking release (MR) is however located in regions of unresolved masker partials and it is unclear how much of the speech information in these regions is really needed for intelligibility. Also, other sources of MR such as glimpsing in between resolved masker partials may provide sufficient information from regions that disregard phase relationships. This study simplified the problem of speech recognition to a masked detection task. Target bands of speech-shaped noise were restricted to frequency regions containing either only resolved or only unresolved masker partials, as a function of masker phase relationships (sine or random), masker fundamental frequency (F0) (50, 100, or 200 Hz), and masker spectral profile (flat-spectrum or speech-shaped). Although masker phase effects could be observed in unresolved regions at F0s of 50 and 100 Hz, it was only at 50-Hz F0 that detection thresholds were ever lower in unresolved than in resolved regions, suggesting little role of envelope modulations for harmonic complexes with F0s in the human voice range and at moderate level. PMID:25373972

  8. How to best smash a snail: the effect of tooth shape on crushing load

    PubMed Central

    Crofts, S. B.; Summers, A. P.

    2014-01-01

    Organisms that are durophagous, hard prey consumers, have a diversity of tooth forms. To determine why we see this variation, we tested whether some tooth forms break shells better than others. We measured the force needed with three series of aluminium tooth models, which varied in concavity and the morphology of a stress concentrating cusp, to break a shell. We created functionally identical copies of two intertidal snail shells: the thicker shelled Nucella ostrina and the more ornamented Nucella lamellosa using a three-dimensional printer. In this way, we reduced variation in material properties between test shells, allowing us to test only the interaction of the experimental teeth with the two shell morphologies. We found that for all tooth shapes, thicker shells are harder to break than the thinner shells and that increased ornamentation has no discernible effect. Our results show that for both shell morphologies, domed and flat teeth break shells better than cupped teeth, and teeth with tall or skinny cusps break shells best. While our results indicate that there is an ideal tooth form for shell breaking, we do not see this shape in nature. This suggests a probable trade-off between tooth function and the structural integrity of the tooth. PMID:24430124

  9. Phase effects in masking by harmonic complexes: Detection of bands of speech-shaped noise

    PubMed Central

    Deroche, Mickael L. D.; Culling, John F.; Chatterjee, Monita

    2014-01-01

    When phase relationships between partials of a complex masker produce highly modulated temporal envelopes on the basilar membrane, listeners may detect speech information from temporal dips in the within-channel masker envelopes. This source of masking release (MR) is however located in regions of unresolved masker partials and it is unclear how much of the speech information in these regions is really needed for intelligibility. Also, other sources of MR such as glimpsing in between resolved masker partials may provide sufficient information from regions that disregard phase relationships. This study simplified the problem of speech recognition to a masked detection task. Target bands of speech-shaped noise were restricted to frequency regions containing either only resolved or only unresolved masker partials, as a function of masker phase relationships (sine or random), masker fundamental frequency (F0) (50, 100, or 200 Hz), and masker spectral profile (flat-spectrum or speech-shaped). Although masker phase effects could be observed in unresolved regions at F0s of 50 and 100 Hz, it was only at 50-Hz F0 that detection thresholds were ever lower in unresolved than in resolved regions, suggesting little role of envelope modulations for harmonic complexes with F0s in the human voice range and at moderate level. PMID:25373972

  10. How to best smash a snail: the effect of tooth shape on crushing load.

    PubMed

    Crofts, S B; Summers, A P

    2014-03-01

    Organisms that are durophagous, hard prey consumers, have a diversity of tooth forms. To determine why we see this variation, we tested whether some tooth forms break shells better than others. We measured the force needed with three series of aluminium tooth models, which varied in concavity and the morphology of a stress concentrating cusp, to break a shell. We created functionally identical copies of two intertidal snail shells: the thicker shelled Nucella ostrina and the more ornamented Nucella lamellosa using a three-dimensional printer. In this way, we reduced variation in material properties between test shells, allowing us to test only the interaction of the experimental teeth with the two shell morphologies. We found that for all tooth shapes, thicker shells are harder to break than the thinner shells and that increased ornamentation has no discernible effect. Our results show that for both shell morphologies, domed and flat teeth break shells better than cupped teeth, and teeth with tall or skinny cusps break shells best. While our results indicate that there is an ideal tooth form for shell breaking, we do not see this shape in nature. This suggests a probable trade-off between tooth function and the structural integrity of the tooth.

  11. Effect of temper rolling on final shape defects in a V-section roll forming process

    NASA Astrophysics Data System (ADS)

    Abvabi, Akbar; Rolfe, Bernard; Hodgson, Peter D.; Weiss, Matthias

    2013-12-01

    Roll forming is a continuous process in which a flat strip is shaped to the desired profile by sequential bending in a series of roll stands. Because of the large variety of applications of roll forming in the industry, Finite Element Analysis (FEA) is increasingly utilized for roll forming process design. Bending is the dominant deformation mode in roll forming. Sheet materials used in this process are generally temper rolled, roller- or tension- leveled. These processes introduce residual stresses into the material, and recent studies have shown that those affect the material behavior in bending. In this study a numerical model of the temper rolling (skin passing) process was used to determine a residual stress distribution in a dual phase, DP780, steel strip. A 5-stand roll forming process for the forming of a V-section was modeled, and the effect of various thickness reduction levels in the temper rolling process on the final shape defects was analyzed. The results show that a small thickness reduction in the temper rolling process decreases the maximum bow height but the final springback angle increases. It is also shown that reasonable model accuracy can be achieved by including the residual stress information due to temper rolling as initial condition in the numerical modeling of a roll forming process.

  12. Effects of high pressure strength of rock material on penetration by shaped charge jet

    NASA Astrophysics Data System (ADS)

    Huang, Hongfa

    2012-03-01

    Perforating of oil/gas well creates communication tunnel between reservoir and wellbore. Shaped charges are widely used as perforators in oilfield industry. The liners of the charges are mostly made of powder metal to prevent solid slug clogging the entrance hole of well casing or locking the hole in perforating gun. High speed jet from the shaped charge pierces through perforating gun, well fluid, well casing, and then penetrates into reservoir formation. Prediction of jet penetration in reservoir rock is critical in modeling of well production. An analytical penetration model developed for solid rod by Tate and Alekseevskii is applied in this work. For better results, strength of formation rock at high pressure needs to be measured. Lateral stress gauge measurements in plate impact tests are conducted. Piezoelectric pressure gauges are imbedded in samples to measure the longitudinal and transverse stress simultaneously. The two stresses provide Hugoniot and material compressive strength. Indiana limestone, a typical rock in perforation testing, is selected as target sample material in the plate impact tests. Since target strength effect on penetration is more important in late stage of penetration when the strength of material becomes significant compared to the impact pressure, all the impact tests are focused on lower impact pressure up to 9 GPa. The measurements show that the strength increases with impact pressure. The results are applied in the penetration calculations. The final penetration matches testing data very well.

  13. The effects of patch shape on indigo buntings. Evidence for an ecological trap

    SciTech Connect

    Weldon, Aimee J.; Haddad, Nick M.

    2005-01-01

    Weldon, Aimee, J., and Nick M. Haddad. 2005. The effect of patch shape on indigo buntings: Evidence for an ecological trap. Ecology 86(6):1422-1431. Abstract. Habitat loss and fragmentation have led to a widespread increase in the proportion of edge habitat in the landscape. Disturbance-dependent bird species are widely assumed to benefit from these edges. However, anthropogenic edges may concentrate nest predators while retaining habitat cues that birds use to select breeding habitat. This may lead birds to mistakenly select dangerous habitat a phenomenon known as an ecological trap. We experimentally demonstrated how habitat shape, and thus amount of edge, can adversely affect nest site selection and reproductive success of a disturbance-dependent bird species, the Indigo Bunting (Passerina cyanea). We did so within a landscape-scale experiment composed of equal-area habitat patches that differed in their amount of edge. Indigo Buntings preferentially selected edgy patches, which contained 50% more edge than more compact rectangular patches. Further, buntings fledged significantly fewer young per pair in edgy patches than in rectangular patches. These results provide the first experimental evidence that edges can function as ecological traps.

  14. Density and Shape Effects in the Acoustic Propulsion of Bimetallic Nanorod Motors.

    PubMed

    Ahmed, Suzanne; Wang, Wei; Bai, Lanjun; Gentekos, Dillon T; Hoyos, Mauricio; Mallouk, Thomas E

    2016-04-26

    Bimetallic nanorods are propelled without chemical fuels in megahertz (MHz) acoustic fields, and exhibit similar behaviors to single-metal rods, including autonomous axial propulsion and organization into spinning chains. Shape asymmetry determines the direction of axial movement of bimetallic rods when there is a small difference in density between the two metals. Movement toward the concave end of these rods is inconsistent with a scattering mechanism that we proposed earlier for acoustic propulsion, but is consistent with an acoustic streaming model developed more recently by Nadal and Lauga ( Phys. Fluids 2014 , 26 , 082001 ). Longer rods were slower at constant power, and their speed was proportional to the square of the power density, in agreement with the acoustic streaming model. The streaming model was further supported by a correlation between the disassembly of spinning chains of rods and a sharp decrease in the axial speed of autonomously moving motors within the levitation plane of the cylindrical acoustic cell. However, with bimetallic rods containing metals of different densities, a consistent polarity of motion was observed with the lighter metal end leading. Speed comparisons between single-metal rods of different densities showed that those of lower density are propelled faster. So far, these density effects are not explained in the streaming model. The directionality of bimetallic rods in acoustic fields is intriguing and offers some new possibilities for designing motors in which shape, material, and chemical asymmetry might be combined for enhanced functionality. PMID:26991933

  15. Biomedical engineering in design and application of nitinol stents with shape memory effect

    NASA Astrophysics Data System (ADS)

    Ryklina, E. P.; Khmelevskaya, I. Y.; Morozova, Tamara V.; Prokoshkin, S. D.

    1996-04-01

    Our studies in the field of endosurgery in collaboration with the physicians of the National Research Center of Surgery of the Academy of Medical Sciences are carried out beginning in 1983. These studies laid the foundation for the new direction of X-ray surgery--X-ray Nitinol stenting of vessels and tubular structures. X-ray nitinol stents are unique self-fixing shells based on the shape memory effect and superelasticity of nickel-titanium alloys self- reconstructed under human body temperature. Applied for stenting of arteries in cases of stenosis etc., bile ducts in cases of benign and malignant stenoses, digestive tract in cases of oesophageal cancer and cervical canal uterus in cases of postsurgical atresiss and strictures of uterine. The purpose of stenting is restoration of the shape of artery or tubular structure by a cylinder frame formation. The especially elaborated original method of stenting allows to avoid the traditional surgical operation, i.e. the stenting is performed without blood, narcosis and surgical knife. The stent to be implanted is transported into the affected zone through the puncture under the X-ray control. Clinical applications of X-ray endovascular stenting has been started in March 1984. During this period nearly 400 operations on stenting have been performed on femoral, iliac, brachio-cephalic, subclavian arteries, bile ducts, tracheas, digestive tract and cervical canal uterus.

  16. The tail effect on the shape of an electrical double layer differential capacitance curve

    NASA Astrophysics Data System (ADS)

    Henderson, Douglas; Lamperski, Stanisław; Bari Bhuiyan, Lutful; Wu, Jianzhong

    2013-04-01

    The differential capacitance curve for the double layer formed by an electrolyte dissolved in a solvent is commonly believed to be parabolic-like with a minimum at low electrolyte charge concentration and low electrode surface charge density, and independent of electrolyte concentration at high electrolyte concentrations and high electrode charge and would be, in the absence of solvent effects, featureless at these latter conditions. This is the prediction of the popular Gouy-Chapman-Stern theory. In contrast, for an ionic liquid this curve can have a single or a double hump (or a bell or camel shape). Fedorov et al. [Electrochem. Commun. 12, 296 (2010)], 10.1016/j.elecom.2009.12.019 have related these humps, particularly the double hump, to the neutral tails of ions in many ionic liquids. Evidence presented here shows, however, that such humps are general features of the differential capacitance of a double layer, whether it be formed by ions with or without a neutral tail. The presence of a double or single hump results from the magnitude of the electrolyte charge concentration. For both spherical ions or non-spherical ions consisting of charged heads and neutral tails, the shape of the differential capacitance transforms continuously from a double hump to a single hump as the electrolyte concentration is increased.

  17. Density and Shape Effects in the Acoustic Propulsion of Bimetallic Nanorod Motors.

    PubMed

    Ahmed, Suzanne; Wang, Wei; Bai, Lanjun; Gentekos, Dillon T; Hoyos, Mauricio; Mallouk, Thomas E

    2016-04-26

    Bimetallic nanorods are propelled without chemical fuels in megahertz (MHz) acoustic fields, and exhibit similar behaviors to single-metal rods, including autonomous axial propulsion and organization into spinning chains. Shape asymmetry determines the direction of axial movement of bimetallic rods when there is a small difference in density between the two metals. Movement toward the concave end of these rods is inconsistent with a scattering mechanism that we proposed earlier for acoustic propulsion, but is consistent with an acoustic streaming model developed more recently by Nadal and Lauga ( Phys. Fluids 2014 , 26 , 082001 ). Longer rods were slower at constant power, and their speed was proportional to the square of the power density, in agreement with the acoustic streaming model. The streaming model was further supported by a correlation between the disassembly of spinning chains of rods and a sharp decrease in the axial speed of autonomously moving motors within the levitation plane of the cylindrical acoustic cell. However, with bimetallic rods containing metals of different densities, a consistent polarity of motion was observed with the lighter metal end leading. Speed comparisons between single-metal rods of different densities showed that those of lower density are propelled faster. So far, these density effects are not explained in the streaming model. The directionality of bimetallic rods in acoustic fields is intriguing and offers some new possibilities for designing motors in which shape, material, and chemical asymmetry might be combined for enhanced functionality.

  18. Dilution rates for tailpipe emissions: effects of vehicle shape, tailpipe position, and exhaust velocity.

    PubMed

    Chang, Victor W C; Hildemann, Lynn M; Chang, Cheng-hisn

    2009-06-01

    The rate at which motor vehicle exhaust undergoes dilution with ambient air will greatly affect the size distribution characteristics of the particulate emissions. Wind tunnel experiments were conducted to investigate the impacts of vehicle shape, tailpipe orientation, and exhaust exit velocity on the dilution profiles under steady driving conditions for three model vehicles: a light-duty truck, a passenger car, and a heavy-duty tractor head. A three dimensional array of 60 sensors provided simultaneous measurements of dilution ratios for the emissions in the near- and far-wake regions downstream of the vehicle. The processes underlying the observations were investigated via nondimensionalization. Many of the trends seen substantially downstream can be well generalized using a simple nondimensionalization technique; however, this is not true in the near-wake region (within a downstream distance equivalent to a few vehicle heights). In the near-wake region, using the vehicle width and length to normalize for the vehicle shape is not enough to fully account for the variations seen. Including the exhaust flow rate in the nondimensionalization process is effective further downwind but does not adequately capture the complexity in the near-wake region. Tailpipe orientation and location are also shown to be influential factors affecting the near-wake dilution characteristics.

  19. Effect of particle shape on dust shortwave direct radiative forcing calculations based on MODIS observations for a case study

    NASA Astrophysics Data System (ADS)

    Feng, Qian; Cui, Songxue; Zhao, Wei

    2015-09-01

    Assuming spheroidal and spherical particle shapes for mineral dust aerosols, the effect of particle shape on dust aerosol optical depth retrievals, and subsequently on instantaneous shortwave direct radiative forcing (SWDRF) at the top of the atmosphere (TOA), is assessed based on Moderate Resolution Imaging Spectroradiometer (MODIS) data for a case study. Specifically, a simplified aerosol retrieval algorithm based on the principle of the Deep Blue aerosol retrieval method is employed to retrieve dust aerosol optical depths, and the Fu-Liou radiative transfer model is used to derive the instantaneous SWDRF of dust at the TOA for cloud-free conditions. Without considering the effect of particle shape on dust aerosol optical depth retrievals, the effect of particle shape on the scattering properties of dust aerosols (e.g., extinction efficiency, single scattering albedo and asymmetry factor) is negligible, which can lead to a relative difference of at most 5% for the SWDRF at the TOA. However, the effect of particle shape on the SWDRF cannot be neglected provided that the effect of particle shape on dust aerosol optical depth retrievals is also taken into account for SWDRF calculations. The corresponding results in an instantaneous case study show that the relative differences of the SWDRF at the TOA between spheroids and spheres depend critically on the scattering angles at which dust aerosol optical depths are retrieved, and can be up to 40% for low dust-loading conditions.

  20. Strong neutral spatial effects shape tree species distributions across life stages at multiple scales.

    PubMed

    Hu, Yue-Hua; Lan, Guo-Yu; Sha, Li-Qing; Cao, Min; Tang, Yong; Li, Yi-De; Xu, Da-Ping

    2012-01-01

    Traditionally, ecologists use lattice (regional summary) count data to simulate tree species distributions to explore species coexistence. However, no previous study has explicitly compared the difference between using lattice count and basal area data and analyzed species distributions at both individual species and community levels while simultaneously considering the combined scenarios of life stage and scale. In this study, we hypothesized that basal area data are more closely related to environmental variables than are count data because of strong environmental filtering effects. We also address the contribution of niche and the neutral (i.e., solely dependent on distance) factors to species distributions. Specifically, we separately modeled count data and basal area data while considering life stage and scale effects at the two levels with simultaneous autoregressive models and variation partitioning. A principal coordinates of neighbor matrix (PCNM) was used to model neutral spatial effects at the community level. The explained variations of species distribution data did not differ significantly between the two types of data at either the individual species level or the community level, indicating that the two types of data can be used nearly identically to model species distributions. Neutral spatial effects represented by spatial autoregressive parameters and the PCNM eigenfunctions drove species distributions on multiple scales, different life stages and individual species and community levels in this plot. We concluded that strong neutral spatial effects are the principal mechanisms underlying the species distributions and thus shape biodiversity spatial patterns. PMID:22666497

  1. Effect of chain architecture on the size, shape, and intrinsic viscosity of chains in polymer solutions: A molecular simulation study

    NASA Astrophysics Data System (ADS)

    Khabaz, Fardin; Khare, Rajesh

    2014-12-01

    Effect of chain architecture on the chain size, shape, and intrinsic viscosity was investigated by performing molecular dynamics simulations of polymer solutions in a good solvent. Four types of chains - linear, comb shaped, H-shaped, and star - were studied for this purpose using a model in which the solvent particles were considered explicitly. Results indicated that the chain length (N) dependence of the mean squared radius of gyration of the chains followed a power-law behavior < {R_g^2 } rangle ^{1/2} ˜ N^\\upsilon with scaling exponents of υ = 0.605, 0.642, 0.602, and 0.608, for the linear, comb shaped, H-shaped, and star shaped chains, respectively. The simulation results for the geometrical shrinking factor were higher than the prior theoretical predictions for comb shaped chains. Analysis of chain shape demonstrated that the star chains were significantly smaller and more spherical than the others, while the comb and H-shaped polymer chains showed a more cylindrical shape. It is shown that the intrinsic viscosity of the chains can be calculated by plotting the specific viscosity determined from simulations against the solution concentration. The intrinsic viscosity exhibited linear behavior with the reciprocal of the overlap concentration for all chain architectures studied. The molecular weight dependence of the intrinsic viscosity followed the Mark-Houwink relation, [η] = KMa, for all chain architectures. When comparing the calculated values of exponent a with the literature experimental values, agreement was found only for the H and star chains, and a disagreement for the linear and comb chains. The viscosity shrinking factor of the branched chains was compared with the available experimental data and the theoretical predictions and a general agreement was found.

  2. Effect of various shapes of ZnO nanoparticles on cotton fabric via electrospinning for UV-blocking.

    PubMed

    Neamjan, Natthawut; Sricharussin, Wimonrat; Threepopnatkul, Poonsub

    2012-01-01

    Various shapes of ZnO; multi-petals, rod and spherical were prepared and then applied on cotton fabric for UV-blocking. The ZnO particles were investigated by XRD and SEM. The mixture solution of ZnO with polyvinyl alcohol was applied onto cotton fabrics via electrospinning. The characteristics of the fabric coating were investigated by SEM, XRD, Tensile testing and Atomic absorption spectroscopy (AAS). UV-blocking property was determined by UV-vis spectrophotometer. The results of XRD and SEM on the ZnO powders show that we can produce various shape of ZnO. The investigation by SEM and AAS clearly revealed that ZnO in polyvinyl alcohol nanofibers was effectively deposited on the cotton surface. The sphericals-shaped ZnO coated fabrics show excellent UV-blocking properties. The shape of ZnO shows no considerable effect on the tensile strength of the samples.

  3. Shape memory alloy nanostructures with coupled dynamic thermo-mechanical effects

    NASA Astrophysics Data System (ADS)

    Dhote, R. P.; Gomez, H.; Melnik, R. N. V.; Zu, J.

    2015-07-01

    Employing the Ginzburg-Landau phase-field theory, a new coupled dynamic thermo-mechanical 3D model has been proposed for modeling the cubic-to-tetragonal martensitic transformations in shape memory alloy (SMA) nanostructures. The stress-induced phase transformations and thermo-mechanical behavior of nanostructured SMAs have been investigated. The mechanical and thermal hysteresis phenomena, local non-uniform phase transformations and corresponding non-uniform temperatures and deformations' distributions are captured successfully using the developed model. The predicted microstructure evolution qualitatively matches with the experimental observations. The developed coupled dynamic model has provided a better understanding of underlying martensitic transformation mechanisms in SMAs, as well as their effect on the thermo-mechanical behavior of nanostructures.

  4. Effect of roller shapes on strip buckling in a continuous annealing furnace

    NASA Astrophysics Data System (ADS)

    Yang, Jing; Tang, Di; Su, Lan; Jiang, Hai-Tao; Yang, Quan

    2011-06-01

    The effect of roller shapes on strip buckling in a continuous annealing furnace was focused on. The tensile stress distribution, the transverse compressive stress, and the critical buckling stress of the strip were studied by the finite element method (FEM) when the flat roller, crown roller, single taper roller, and double taper roller were used, respectively. Simulation results show that strip buckling is most likely to occur with the crown roller, then the double taper roller, and finally the single taper roller. Also, strip buckling can not occur when the flat roller is used. Considering strip snaking, the single taper roller and double taper roller are suggested in the continuous annealing furnace. The double taper roller with a better strip snaking-prevention ability should be applied in the sections with high strip temperature, and the single taper roller with a better buckling-prevention ability should be used in the sections with low strip temperature.

  5. The wineglass effect shapes particle export to the deep ocean in mesoscale eddies

    NASA Astrophysics Data System (ADS)

    Waite, Anya M.; Stemmann, Lars; Guidi, Lionel; Calil, Paulo H. R.; Hogg, Andrew Mc C.; Feng, Ming; Thompson, Peter A.; Picheral, Marc; Gorsky, Gaby

    2016-09-01

    Mesoscale eddies in the ocean strongly impact the distribution of planktonic particles, mediating carbon fluxes over ~1/3 of the world ocean. However, mechanisms controlling particle transport through eddies are complex and challenging to measure in situ. Here we show the subsurface distribution of eddy particles funneled into a wineglass shape down to 1000 m, leading to a sevenfold increase of vertical carbon flux in the eddy center versus the eddy flanks, the "wineglass effect". We show that the slope of the wineglass (R) is the ratio of particle sinking velocity to the radially inward velocity, such that R represents a tool to predict radial particle movement (here 0.05 m s-1). A simple model of eddy spindown predicts such an ageostrophic flow concentrating particles in the eddy center. We explore how size-specific particle flux toward the eddy center impacts eddies' biogeochemistry and export fluxes.

  6. Full-Scale Wind-Tunnel Study of the Effect of Nacelle Shape on Cooling Drag

    NASA Technical Reports Server (NTRS)

    Corsiglia, Victor R.; Katz, Joseph; Kroeger, Richard A.

    1981-01-01

    Tests were made in the Ames 40 by 80 ft Wind Tunnel of a semispan wing with a nacelle (no propeller) from a typical, general aviation twin-engine aircraft. Measurements were made of the effect on drag of the flow of cooling air through the nacelle. Internal and external nacelle pressures were measured. It was found that the cooling airflow accounts for about 13% of the total estimated airplane drag during both cruise and climb. The now of cooling air through the nacelle accounts for 30% of the airflow drag component during cruise and 42% during climb; the balance, in both cruise and climb, is attributed to [he external shape of the nacelle. It was suggested that improvements could possibly be made by relocating both the inlet and the outlet for the cooling air.

  7. Effective dynamics of cold atoms flowing in two ring-shaped optical potentials with tunable tunneling

    NASA Astrophysics Data System (ADS)

    Aghamalyan, Davit; Amico, Luigi; Kwek, L. C.

    2013-12-01

    We study the current dynamics of coupled atomic condensates flowing in two ring-shaped optical potentials. We provide a specific setup where the ring-ring coupling can be tuned in an experimentally feasible way. It is demonstrated that the imaginary time effective action of the system in a weak coupling regime provides a two-level-system dynamics for the phase slip across the two rings. Through two-mode Gross- Pitaevskii mean-field equations, the real-time dynamics of the population imbalance and the phase difference between the two condensates is thoroughly analyzed analytically, as a function of the relevant physical parameters of the system. In particular, we find that the macroscopic quantum self-trapping phenomenon is induced in the system if the flowing currents assume a nonvanishing difference.

  8. Effects of finite poloidal gyroradius, shaping, and collisions on the zonal flow residual

    SciTech Connect

    Xiao Yong; Catto, Peter J.; Dorland, William

    2007-05-15

    Zonal flow helps reduce and regulate the turbulent transport level in tokamaks. Rosenbluth and Hinton have shown that zonal flow damps to a nonvanishing residual level in collisionless [M. Rosenbluth and F. Hinton, Phys. Rev. Lett. 80, 724 (1998)] and collisional [F. Hinton and M. Rosenbluth, Plasma Phys. Control. Fusion 41, A653 (1999)] banana regime plasmas. Recent zonal flow advances are summarized including the evaluation of the effects on the zonal flow residual by plasma cross-section shaping, shorter wavelengths including those less than an electron gyroradius, and arbitrary ion collisionality relative to the zonal low frequency. In addition to giving a brief summary of these new developments, the analytic results are compared with GS2 numerical simulations [M. Kotschenreuther, G. Rewoldt, and W. Tang, Comput. Phys. Commun. 88, 128 (1991)] to demonstrate their value as benchmarks for turbulence codes.

  9. Effect of hourglass-shaped nanopore length on osmotic water transport

    NASA Astrophysics Data System (ADS)

    Shahbabaei, Majid; Kim, Daejoong

    2016-09-01

    In the present research, molecular dynamic (MD) simulations are utilized in order to examine the water transport properties through hourglass-shaped pore structures with various lengths. The length elongates in a range of 100-200 Å, while the size of the narrowest diameter remains constant at 3 Å. The results show that the defect effect can be substantially diminished as the length increases, so that the fluctuations of the energy barrier reaches zero inside 200 Å pore structure, which is an indication of rapid increase of water transport rate. The flux increases with length, suggesting a reduction in hydrodynamic resistance, that water molecules are able to easily enter the pore. The axial diffusivity and permeability are increased once the length increments, which indicate a fast water transport. It is concluded that the thermal fluctuations of water molecules inside reservoir affect the motion of water molecules inside the pore as length decreases.

  10. Effect of shape of elastic beam hair on its adhesion with wavy surfaces

    NASA Astrophysics Data System (ADS)

    Hemthavy, Pasomphone; Yazaki, Takehiko; Wang, Boqing; Sekiguchi, Yu; Takahashi, Kunio

    2014-08-01

    An analysis on a tapered elastic beam whose side surface partially adhered to a rigid surface was carried out to study the effect of the beam shape on the gripping force. Considering the total energy of the system, the relation between the gripping force and the displacement was obtained analytically in closed form. The analytical result is significant because it provides an intuitive picture of the gripping force. Although, an individually tapered beam can generate less gripping force for flat or slightly wavy surfaces, compared to a rectangular beam, the analysis result suggests that the tapered beam has more ability to absorb surface waviness. This result can be applied to a multi-beam structure.

  11. Eating attitudes and body shape perceptions among elite rowers: effects of age, gender and weight category.

    PubMed

    Terry, P C; Waite, J

    1996-03-01

    This study examined the influence of age, gender and weight category upon measures associated with eating disorders. Elite rowers (N = 124) participating in the 1994 Great Britain National Squad trials, completed the Eating Attitude Test (EAT) and the Body Shape Questionnaire (BSQ). Subjects were grouped according to whether they competed in the Lightweight (Female: < 59 kg, N = 31; Male: < 72.5 kg, N = 31) or Heavyweight (Female: N = 31; Male: N = 31) category. Results revealed significantly higher EAT and BSQ scores among the Lightweight group, 16.2% of whom showed EAT scores above the threshold associated with eating disorders. Females showed significantly higher BSQ scores than males. The interaction effect was significant for BSQ, indicating a much greater increase in scores from heavyweight to lightweight for females than for males. EAT and BSQ scores were inversely correlated with age. These results suggest that the risk of eating disorders among elite rowers is mediated by age, gender and weight category.

  12. Projectile shape and material effects in hypervelocity impact response of dual-wall structures

    NASA Technical Reports Server (NTRS)

    Schonberg, William P.; Darzi, Kent

    1992-01-01

    All large spacecraft are susceptible to impacts by meteoroids and pieces of orbiting space debris. These impacts occur at extremely high speeds and can damage flight-critical systems, which can in turn lead to catastrophic failure of the spacecraft. A long-duration spacecraft developed for a mission into this environment must include adequate protection against perforation of pressurized components by such impacts. This paper presents the results of an investigation into the effects of projectile shape and material on the perforation of aluminum dual-wall structural systems. Impact damage is characterized according to the extent of perforation, crater, and spall damage in the structural systems as a result of hypervelocity projectile impact loadings. Analysis of the damage data shows that there are distinct differences in impact damage from cylindrical and spherical projectiles. Projectile density is also found to affect the type and extent of damage sustained by dual-wall structural systems.

  13. Arterial pulse shape measurement using self-mixing effect in a diode laser

    SciTech Connect

    Hast, J; Myllylae, Risto; Sorvoja, H; Miettinen, J

    2002-11-30

    The self-mixing effect in a diode laser and the Doppler technique are used for quantitative measurements of the cardiovascular pulses from radial arteries of human individuals. 738 cardiovascular pulses from 10 healthy volunteers were studied. The Doppler spectrograms reconstructed from the Doppler signal, which is measured from the radial displacement of the radial artery, are compared to the first derivative of the blood pressure signals measured from the middle finger by the Penaz technique. The mean correlation coefficient between the Doppler spectrograms and the first derivative of the blood pressure signals was 0.84, with a standard deviation of 0.05. Pulses with the correlation coefficient less than 0.7 were neglected in the study. Percentage of successfully detected pulses was 95.7%. It is shown that cardiovascular pulse shape from the radial artery can be measured noninvasively by using the self-mixing interferometry. (laser biology and medicine)

  14. The effects of prosthetic foot roll-over shape arc length on the gait of trans-tibial prosthesis users.

    PubMed

    Hansen, Andrew H; Meier, Margrit R; Sessoms, Pinata H; Childress, Dudley S

    2006-12-01

    The Shape&Roll prosthetic foot was used to examine the effect of roll-over shape arc length on the gait of 14 unilateral trans-tibial prosthesis users. Simple modifications to the prosthetic foot were used to alter the effective forefoot rocker length, leaving factors such as alignment, limb length, and heel and mid-foot characteristics unchanged. Shortening the roll-over shape arc length caused a significant reduction in the maximum external dorsiflexion moment on the prosthetic side at all walking speeds (p < 0.001 for main effect of arc length), due to a reduction in forefoot leverage (moment arm) about the ankle. Roll-over shape arc length significantly affected the initial loading on the sound limb at normal and fast speeds (p = 0.001 for the main effect of arc length), with participants experiencing larger first peaks of vertical ground reaction forces on their sound limbs when using the foot with the shortest effective forefoot rocker arc length. Additionally, the difference between step lengths on the sound and prosthetic limbs was larger with the shortest arc length condition, although this difference was not statistically significant (p = 0.06 for main effect). It appears that prosthesis users may experience a drop-off effect at the end of single limb stance on prosthetic feet with short roll-over shape arc lengths, leading to increased loading and/or a shortened step on the contralateral limb.

  15. Biophysical feedback mediates effects of invasive grasses on coastal dune shape.

    PubMed

    Zarnetske, Phoebe L; Hacker, Sally D; Seabloom, Eric W; Ruggiero, Peter; Killian, Jason R; Maddux, Timothy B; Cox, Daniel

    2012-06-01

    Vegetation at the aquatic-terrestrial interface can alter landscape features through its growth and interactions with sediment and fluids. Even similar species may impart different effects due to variation in their interactions and feedbacks with the environment. Consequently, replacement of one engineering species by another can cause significant change in the physical environment. Here we investigate the species-specific ecological mechanisms influencing the geomorphology of U.S. Pacific Northwest coastal dunes. Over the last century, this system changed from open, shifting sand dunes with sparse vegetation (including native beach grass, Elymus mollis), to densely vegetated continuous foredune ridges resulting from the introduction and subsequent invasions of two nonnative grass species (Ammophila arenaria and Ammophila breviligulata), each of which is associated with different dune shapes and sediment supply rates along the coast. Here we propose a biophysical feedback responsible for differences in dune shape, and we investigate two, non-mutually exclusive ecological mechanisms for these differences: (1) species differ in their ability to capture sand and (2) species differ in their growth habit in response to sand deposition. To investigate sand capture, we used a moveable bed wind tunnel experiment and found that increasing tiller density increased sand capture efficiency and that, under different experimental densities, the native grass had higher sand capture efficiency compared to the Ammophila congeners. However, the greater densities of nonnative grasses under field conditions suggest that they have greater potential to capture more sand overall. We used a mesocosm experiment to look at plant growth responses to sand deposition and found that, in response to increasing sand supply rates, A. arenaria produced higher-density vertical tillers (characteristic of higher sand capture efficiency), while A. breviligulata and E. mollis responded with lower

  16. Effect of irregularity in shape and boundary of a macro-texture region in titanium

    NASA Astrophysics Data System (ADS)

    Na, Jeong K.; Blackshire, James L.; Freed, Shaun L.

    2016-02-01

    Peak amplitudes of mode converted shear wave signals back scattered from macro-texture regions (MTRs) in an aerospace grade titanium alloy material are measured to be about the same level as corner trapped shear wave signals. In addition to the abnormally high shear wave responses, the time of flight data indicates that the MTR signals are back scattered from a location deep in the sample so that the round trip travel time is close to that of corner trapped signals. In this work, these two ultrasonic properties of an MTR in a test specimen cut from a titanium jet engine disk are closely studied to understand the root cause of abnormally high shear wave responses. Based on the amplitude and time of flight data collected in a laboratory condition, a decision has been made to investigate further experimentally and computationally how surface irregularity of an acoustically reflective surface affects incoming shear waves upon reflection. Attempts are made to correlate the localized back scattered signal response of the MTR in the test specimen to the beam focusing effect of a non-planar surface of an acoustically impedance mismatched boundary layer such as a fatigue crack face. From the current experimental and computational results on the reflection of corner trapped shear waves from a concave shaped section of a non-planar crack face and the time of flight data, it is speculated that the root cause of the abnormally high peak amplitude MTR signal is possibly due to the beam focusing effect caused by the shape of the MTR.

  17. Photophysics of fulvene under the non-resonant stark effect. Shaping the conical intersection seam.

    PubMed

    Ruiz-Barragan, Sergi; Blancafort, Lluís

    2013-01-01

    We introduce a mechanistic strategy to control the excited state lifetime of fulvene based on shaping the topography of an extended seam of intersection with the non-resonant dynamic Stark effect. Fulvene has a very short excited state lifetime due to an energetically accessible seam of intersection which lies along the methylene torsion coordinate, and the initial decay occurs at the seam segment around the planar conical intersection structure. We have followed a three-step approach to simulate the control. First, we have calculated the effect of a non-resonant electric field on the potential energy surface at the ab initio level, including the field in a self-consistent way. The relative energy of the planar segment of the seam is increased by the non-resonant field. In the second step we simulate the control carrying out MCTDH quantum dynamics propagations under a static non-resonant field to derive the main control mechanisms. At moderately intense fields (epsilon < or = 0.03 a.u.) the decay is faster as compared to the field free case because the vibrational overlap between the excited and ground state vibrational functions is increased. However, at more intense fields (epsilon = 0.04 a.u.) the planar conical intersection is energetically inaccessible and the decay occurs at a slower time scale, at the segment of the seam with more twisted geometries. In the third step, the control over the dynamics is exerted with a non-resonant dynamic field. The acceleration of the decay due to the improved vibrational overlap does not occur, but the decay can be made slower with a dynamic field of 0.08 a.u. The results show the viability of our approach to control the photophysics shaping the topology of the conical intersection seam, and they prove that the extended nature of the seam is crucial for simulating and understanding the control.

  18. Effects of nozzle exit geometry and pressure ratio on plume shape for nozzles exhausting into quiescent air

    NASA Technical Reports Server (NTRS)

    Scallion, William I.

    1991-01-01

    The effects of varying the exit geometry on the plume shapes of supersonic nozzles exhausting into quiescent air at several exit-to-ambient pressure ratios are given. Four nozzles having circular throat sections and circular, elliptical and oval exit cross sections were tested and the exit plume shapes are compared at the same exit-to-ambient pressure ratios. The resulting mass flows were calculated and are also presented.

  19. Effects of twin boundary mobility on domain microstructure evolution in magnetic shape memory alloys: Phase field simulation

    SciTech Connect

    Jin, Yongmei M.

    2009-02-09

    Effects of twin boundary mobility on domain microstructure evolution during magnetic field-induced deformation in magnetic shape memory alloys are studied by phase field micromagnetic microelastic modeling. The simulations show that different twin boundary mobilities lead to drastically different domain microstructures and evolution pathways, yielding very different magnetization and strain responses, even with opposite signs. The study also reveals complex domain phenomena in magnetic shape memory alloys.

  20. Large reversible magnetocaloric effect in a Ni-Co-Mn-In magnetic shape memory alloy

    NASA Astrophysics Data System (ADS)

    Huang, L.; Cong, D. Y.; Ma, L.; Nie, Z. H.; Wang, Z. L.; Suo, H. L.; Ren, Y.; Wang, Y. D.

    2016-01-01

    Reversibility of the magnetocaloric effect in materials with first-order magnetostructural transformation is of vital significance for practical magnetic refrigeration applications. Here, we report a large reversible magnetocaloric effect in a Ni49.8Co1.2Mn33.5In15.5 magnetic shape memory alloy. A large reversible magnetic entropy change of 14.6 J/(kg K) and a broad operating temperature window of 18 K under 5 T were simultaneously achieved, correlated with the low thermal hysteresis (˜8 K) and large magnetic-field-induced shift of transformation temperatures (4.9 K/T) that lead to a narrow magnetic hysteresis (1.1 T) and small average magnetic hysteresis loss (48.4 J/kg under 5 T) as well. Furthermore, a large reversible effective refrigeration capacity (76.6 J/kg under 5 T) was obtained, as a result of the large reversible magnetic entropy change, broad operating temperature window, and small magnetic hysteresis loss. The large reversible magnetic entropy change and large reversible effective refrigeration capacity are important for improving the magnetocaloric performance, and the small magnetic hysteresis loss is beneficial to reducing energy dissipation during magnetic field cycle in potential applications.

  1. The effect of moisture absorption on the physical properties of polyurethane shape memory polymer foams

    PubMed Central

    Yu, Ya-Jen; Hearon, Keith; Wilson, Thomas S.; Maitland, Duncan J.

    2011-01-01

    The effect of moisture absorption on the glass transition temperature (Tg) and stress/strain behavior of network polyurethane shape memory polymer (SMP) foams has been investigated. With our ultimate goal of engineering polyurethane SMP foams for use in blood contacting environments, we have investigated the effects of moisture exposure on the physical properties of polyurethane foams. To our best knowledge, this study is the first to investigate the effects of moisture absorption at varying humidity levels (non-immersion and immersion) on the physical properties of polyurethane SMP foams. The SMP foams were exposed to differing humidity levels for varying lengths of time, and they exhibited a maximum water uptake of 8.0% (by mass) after exposure to 100% relative humidity for 96 h. Differential scanning calorimetry results demonstrated that water absorption significantly decreased the Tg of the foam, with a maximum water uptake shifting the Tg from 67 °C to 5 °C. Samples that were immersed in water for 96 h and immediately subjected to tensile testing exhibited 100% increases in failure strains and 500% decreases in failure stresses; however, in all cases of time and humidity exposure, the plasticization effect was reversible upon placing moisture-saturated samples in 40% humidity environments for 24 h. PMID:21949469

  2. Effects of shape parameters on the attractiveness of a female body.

    PubMed

    Fan, J; Dai, W; Qian, X; Chau, K P; Liu, Q

    2007-08-01

    Various researchers have suggested that certain anthropometric ratios can be used to measure female body attractiveness, including the waist to hip ratio, Body Mass Index (BMI), and the body volume divided by the square of the height (Volume-Height Index). Based on a wide range of female subjects and virtual images of bodies with different ratios, Volume-Height Index was found to provide the best fit with female body attractiveness, and the effect of Volume-Height Index can be fitted with two half bell-shaped exponential curves with an optimal Volume-Height Index at 14.2 liter/m2. It is suggested that the general trend of the effect of Volume-Height Index may be culturally invariant, but the optimal value of Volume-Height Index may vary from culture to culture. In addition to Volume-Height Index, other body parameters or ratios which reflect body proportions and the traits of feminine characteristics had smaller but significant effects on female body attractiveness, and such effects were stronger at optimum Volume-Height Index. PMID:17918555

  3. Effect of Inductive Coil Shape on Sensing Performance of Linear Displacement Sensor Using Thin Inductive Coil and Pattern Guide

    PubMed Central

    Misron, Norhisam; Ying, Loo Qian; Firdaus, Raja Nor; Abdullah, Norrimah; Mailah, Nashiren Farzilah; Wakiwaka, Hiroyuki

    2011-01-01

    This paper discusses the effect of inductive coil shape on the sensing performance of a linear displacement sensor. The linear displacement sensor consists of a thin type inductive coil with a thin pattern guide, thus being suitable for tiny space applications. The position can be detected by measuring the inductance of the inductive coil. At each position due to the change in inductive coil area facing the pattern guide the value of inductance is different. Therefore, the objective of this research is to study various inductive coil pattern shapes and to propose the pattern that can achieve good sensing performance. Various shapes of meander, triangular type meander, square and circle shape with different turn number of inductive coils are examined in this study. The inductance is measured with the sensor sensitivity and linearity as a performance evaluation parameter of the sensor. In conclusion, each inductive coil shape has its own advantages and disadvantages. For instance, the circle shape inductive coil produces high sensitivity with a low linearity response. Meanwhile, the square shape inductive coil has a medium sensitivity with higher linearity. PMID:22346656

  4. Effect of inductive coil shape on sensing performance of linear displacement sensor using thin inductive coil and pattern guide.

    PubMed

    Misron, Norhisam; Ying, Loo Qian; Firdaus, Raja Nor; Abdullah, Norrimah; Mailah, Nashiren Farzilah; Wakiwaka, Hiroyuki

    2011-01-01

    This paper discusses the effect of inductive coil shape on the sensing performance of a linear displacement sensor. The linear displacement sensor consists of a thin type inductive coil with a thin pattern guide, thus being suitable for tiny space applications. The position can be detected by measuring the inductance of the inductive coil. At each position due to the change in inductive coil area facing the pattern guide the value of inductance is different. Therefore, the objective of this research is to study various inductive coil pattern shapes and to propose the pattern that can achieve good sensing performance. Various shapes of meander, triangular type meander, square and circle shape with different turn number of inductive coils are examined in this study. The inductance is measured with the sensor sensitivity and linearity as a performance evaluation parameter of the sensor. In conclusion, each inductive coil shape has its own advantages and disadvantages. For instance, the circle shape inductive coil produces high sensitivity with a low linearity response. Meanwhile, the square shape inductive coil has a medium sensitivity with higher linearity.

  5. Trapped fermionic clouds distorted from the trap shape due to many-body effects.

    PubMed

    Haque, Masudul; Stoof, H T C

    2007-06-29

    We present a general approach for describing trapped Fermi gases, when the cloud shape is distorted with respect to the trap shape. Our approach provides a consistent way to explore physics beyond the local density approximation, if this is necessary due to the distortion. We illustrate this by analyzing in detail experimentally observed distortions in a trapped imbalanced Fermi mixture. In particular, we demonstrate in that case dramatic deviations from ellipsoidal cloud shapes arising from the competition between surface and bulk energies.

  6. Shape-memory effect of micro-/nanoparticles from thermoplastic multiblock copolymers.

    PubMed

    Wischke, Christian; Schossig, Michael; Lendlein, Andreas

    2014-01-15

    The miniaturization and retained full shape-memory functionality with particle switching to different predefined shapes is reported for semi-crystalline multiblock copolymer matrices with all dimensions in the low micrometer-range. A matrix size-induced reduction of crystallinity suggests limitations of functionality in the low nanometer range. Applications as actuators in microdevices or as microcarriers with switchable shapes for modulated biorecognition are suggested.

  7. Effect of piano-key shape inlet on critical submergence at a vertical pipe intake

    NASA Astrophysics Data System (ADS)

    Shemshi, R.; Kabiri-Samani, A.

    2012-11-01

    Intake vortices are the result of angular momentum conservation at the flow constriction, where angular velocity increases with a decrease in the cross sectional area. The common solution for avoiding air-entrainment and swirl is to provide sufficient submergence to the intake. If the required approach flow conditions can not be met to avoid swirl and air entrainment, other approaches for preventing vortices at water intakes are considered. There are several means of avoiding air-entrainment, where the most cost-effective option is often determined by a physical model study. Among the most economical and common measures of reducing the effect of air-entrainment and swirl strength, is the optimized shape of inlet for instance by installing a Piano-Key inlet over the pipe intake. If Piano-Key inlet is used, then, its' optimum geometry should be studied experimentally. Since there is not any realized guidance for the use of Piano-Key inlets in pipe intakes, hence, a comprehensive set of model experiments have been carried out using Piano-Key inlets with different dimensions, with respect to the vertical pipe intakes, and four different pipe diameters of (D=) 75, 100, 125 and 150 mm. Results showed that by employing a Piano-Key inlet over the vertical pipe intake, the critical submergence reduces significantly. Fianally, according to the results, the effect of Piano-Key inlet geometry on critical submergence were evaluated in the form of realized relationships which would be of practical interest for design engineers.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  9. Control of gas phase nanoparticle shape and its effect on MRI relaxivity

    NASA Astrophysics Data System (ADS)

    Aktaş, Sıtkı; Thornton, Stuart C.; Binns, Chris; Lari, Leonardo; Pratt, Andrew; Kröger, Roland; Horsfield, Mark A.

    2015-03-01

    We have used a sputtering gas aggregation source to produce Fe@FeO nanoparticles with different shapes, by annealing them at different temperatures in the gas phase. Without annealing, the most common shape found for the nanoparticles is cubic but annealing the nanoparticles at 1129 °C transforms the cubes into cuboctahedra. Measurements of the MRI relaxivity show that the cubic nanoparticles have a higher performance by a factor of two, which is attributed to a higher saturation magnetization for this shape. This indicates that the shape-control enabled by gas-phase synthesis is important for obtaining optimal performance in applications.

  10. The shape effects of nanoparticles suspended in HFE-7100 over wedge with entropy generation and mixed convection

    NASA Astrophysics Data System (ADS)

    Ellahi, R.; Hassan, M.; Zeeshan, A.; Khan, Ambreen A.

    2016-06-01

    The flow of mixed convection nanofluid over wedge under the effects of porous medium is investigated. The HFE-7100 Engineered Fluid having Nimonic 80a metal nanoparticles of spherical and non-spherical shapes with different sizes is used. The particle shape effects on Bejan number and entropy generation are taken into account. The system of partial differential equations is first written in terms of ordinary differential equations using adequate similarity transformations and then solved analytically. Analytical solutions of the resulting equations are obtained for the velocity and temperature profiles. Simultaneous effects of porous medium, particle volume friction, mixed convection parameter, and angle of wedge in the presence of different shapes nanoparticles are demonstrated graphically. Effects of particle concentrations, sizes on wall stress, heat transfer coefficient of Skin friction, and Nusselt are discussed in the form of tables.

  11. Shape and surface effects on the cytotoxicity of nanoparticles: Gold nanospheres versus gold nanostars.

    PubMed

    Favi, Pelagie Marlene; Gao, Ming; Johana Sepúlveda Arango, Liuda; Ospina, Sandra Patricia; Morales, Mariana; Pavon, Juan Jose; Webster, Thomas Jay

    2015-11-01

    Gold nanoparticles are materials with unique optical properties that have made them very attractive for numerous biomedical applications. With the increasing discovery of techniques to synthesize novel nanoparticles such as star-shaped gold nanoparticles for biomedical applications, the safety and performance of these new nanomaterials must be systematically assessed before use. In this study, gold nanostars (AuNSTs) with multibranched surface structures were synthesized, and their influence on the cytotoxicity of human skin fibroblasts and rat fat pad endothelial cells (RFPECs) were assessed and compared with that of gold nanospheres (AuNSPs) with unbranched surfaces. Results showed that the AuNSPs with diameters of approximately 61.46 nm showed greater toxicity with fibroblast cells and RFPECs compared with the synthesized AuNSTs with diameters of approximately 33.69 nm. The AuNSPs were lethal at concentrations of 40 μg/mL for both cell lines, whereas the AuNSTs were less toxic at higher concentrations (400 μg/mL). The calculated IC50 (50% inhibitory concentration) values of the AuNSPs exposed to fibroblast cells were greater at 1 and 4 days of culture (26.4 and 27.7 μg/mL, respectively) compared with the RFPECs (13.6 and 13.8 μg/mL, respectively), indicating that the AuNSPs have a greater toxicity to endothelial cells. It was proposed that possible factors that could be promoting the reduced toxicity effects of the AuNSTs to fibroblast cells and RFPECs, compared with the AuNSPs may be size, surface chemistry, and shape of the gold nanoparticles. The reduced cell toxicity observed with the AuNSTs suggests that AuNSTs may be a promising material for use in biomedical applications. PMID:25904210

  12. The effect of the shape parameters of a sample on the hydraulic conductivity

    NASA Astrophysics Data System (ADS)

    Kucza, Jarosław; Ilek, Anna

    2016-03-01

    The present study is a complement to the research investigating a laboratory method for measuring the saturated hydraulic conductivity of mountain forest soils, the results of which were presented in a paper by Ilek and Kucza (2014). The aim of the study is to analyse the influence of variation of particular cross-sections of samples and their enlarged side surface on the hydraulic conductivity measurement. The results show that a narrowing in the upper section of the sample results in an approximately twice lower disturbance of the laminar water flow than the narrowing occurring inside the sample. For that reason, the extent of the effect of the cross-section narrowing on the hydraulic conductivity measurement error is dependent on the location of the narrowing. An enlarged side surface of a sample, as described by the coefficient of side surface development, is on average 30% larger than the surface of a sample having the same volume and the same average cross-sectional area but a regular shape. The values of the coefficient of side surface development for a given sample were adopted in the range of 1.10-1.56. Among the shape parameters of the analysed irregular soil samples, the greatest impact on the measurement error is exerted by their enlarged lateral surface, which almost entirely explains the whole error of hydraulic conductivity measurement. The variability of successive cross-sectional areas of samples appears to be of marginal importance for the occurrence of this error, whose mean value was 1.15%.

  13. Shape and surface effects on the cytotoxicity of nanoparticles: Gold nanospheres versus gold nanostars.

    PubMed

    Favi, Pelagie Marlene; Gao, Ming; Johana Sepúlveda Arango, Liuda; Ospina, Sandra Patricia; Morales, Mariana; Pavon, Juan Jose; Webster, Thomas Jay

    2015-11-01

    Gold nanoparticles are materials with unique optical properties that have made them very attractive for numerous biomedical applications. With the increasing discovery of techniques to synthesize novel nanoparticles such as star-shaped gold nanoparticles for biomedical applications, the safety and performance of these new nanomaterials must be systematically assessed before use. In this study, gold nanostars (AuNSTs) with multibranched surface structures were synthesized, and their influence on the cytotoxicity of human skin fibroblasts and rat fat pad endothelial cells (RFPECs) were assessed and compared with that of gold nanospheres (AuNSPs) with unbranched surfaces. Results showed that the AuNSPs with diameters of approximately 61.46 nm showed greater toxicity with fibroblast cells and RFPECs compared with the synthesized AuNSTs with diameters of approximately 33.69 nm. The AuNSPs were lethal at concentrations of 40 μg/mL for both cell lines, whereas the AuNSTs were less toxic at higher concentrations (400 μg/mL). The calculated IC50 (50% inhibitory concentration) values of the AuNSPs exposed to fibroblast cells were greater at 1 and 4 days of culture (26.4 and 27.7 μg/mL, respectively) compared with the RFPECs (13.6 and 13.8 μg/mL, respectively), indicating that the AuNSPs have a greater toxicity to endothelial cells. It was proposed that possible factors that could be promoting the reduced toxicity effects of the AuNSTs to fibroblast cells and RFPECs, compared with the AuNSPs may be size, surface chemistry, and shape of the gold nanoparticles. The reduced cell toxicity observed with the AuNSTs suggests that AuNSTs may be a promising material for use in biomedical applications.

  14. Quantifying the effects of hydrograph shape and flow transience on coarse sediment bed load transport

    NASA Astrophysics Data System (ADS)

    Phillips, Colin; Hill, Kimberly; Paola, Chris

    2016-04-01

    The rate of bed load transport under steady flow is known to vary both spatially and temporally due to various hydrologic and granular phenomena. Grain size distributions and riverbed properties (packing, armoring, imbrication, etc.) have been observed to affect flux for a particular value of applied flow stress while hydrology is mainly assumed to control the magnitude of the applied bed stress above the threshold for bed material entrainment. The prediction and measurement of bed load sediment transport in field settings are further complicated by the inherent transience in the flood hydrograph, but relatively little is known about how flood transience differs from a steady flow. Here we investigate the role of flood transience for gravel bed load transport through controlled laboratory experiments in a 28 m long 0.5-meter wide flume. We explore transient flow through the use of short duration hydrographs as the combination of unsteady and intermittent flow, where unsteady flow varies in magnitude over a given duration, and intermittent flow is characterized by turning the flow on and off. Experimental runs consist of sequences of steady and unsteady flood hydrographs of various shapes, but equivalent integrated excess transport capacity. These flood sequences are run for a variety of competent flow durations and peak stress magnitudes. We find that even for a narrow unimodal grain size distribution and constant sediment supply we observe clockwise hysteresis in bed load flux, different thresholds for entrainment and distrainment for the rising and falling limbs of a flood, and a threshold of entrainment that can vary from one flood hydrograph to the next. Despite complex transport phenomena at the particle scale, we find that the total bed load transported for each flood plots along a linear trend with the integrated excess transport capacity, in agreement with prior field results. These experiments indicate that while the effects of transient flow and

  15. Effect of Individual Layer Shape on the Mechanical Properties of Dissimilar Al Alloys Laminated Metal Composite Sheets

    NASA Astrophysics Data System (ADS)

    Chen, Zejun; Wu, Xia; Hu, Hongbo; Chen, Quanzhong; Liu, Qing

    2014-03-01

    For the dissimilar laminated metal composite sheets (LMCS) fabricated by roll bonding technology, the great differences of mechanical properties between the constituent metals lead to the non-uniform deformation and individual layer necking. The individual layer shape affects the mechanical properties and microstructure of dissimilar LMCS. The Al/Al alloy (1100/7075) LMCS with the same thickness and ratio of dissimilar metals, but different individual layer shapes, have been successfully fabricated by hot accumulative roll bonding in conjunction with cold rolling technology. Some effective methods (such as sheet crown, warp degree, and slant angle) were presented to quantitatively evaluate the individual layer shape and necking of constituent metals. The microstructure and mechanical properties of 1100/7075 LMCS with different individual layer shapes were investigated. The effects of bonding interface on the mechanical properties were obtained based on the assessment of individual layer shapes and necking. The strength and elongation of LMCS decrease with the increase of variation of individual layer shapes and necking when the number of layers keeps constant. The research results offer some theoretical guides and references for adjusting the control measures of compatibility deformation, optimizing the hot roll bonding technologies, and designing the novel high-performance dissimilar LMCS.

  16. Effects of altitude versus economic status on birth weight and body shape at birth.

    PubMed

    Giussani, D A; Phillips, P S; Anstee, S; Barker, D J

    2001-04-01

    The compelling evidence linking small size at birth with later cardiovascular disease has renewed and amplified a clinical and scientific interest in the determinants of fetal growth. Although the effects of maternal nutrition on fetal growth have been extensively studied, comparatively little is known about the effects of maternofetal hypoxia. This study tested the hypothesis that in highland regions, high altitude rather than maternal economic status is associated with reduced and altered fetal growth by investigating the effects of high altitude versus economic status on birth weight and body shape at birth in Bolivia. Bolivia is geographically and socioeconomically unique. It contains several highland (>3500 m above sea level) and lowland (<500 m) cities that are inhabited by very economically divergent populations. Birth weight, body length, and head circumference were compared between a high- (n = 100) and low- (n = 100) income region of La Paz (3649 m; largest high-altitude city) and a high- (n = 100) and low- (n = 100) income region of Santa Cruz (437 m; largest low-altitude city). In addition, the frequency distribution across the continuum of birth weights was plotted for babies born from high- and low-income families in La Paz and Santa Cruz. Mean birth weights were lower in babies from La Paz than in babies from Santa Cruz in both high- and low-income groups. The cumulative frequency curve across all compiled birth weights was shifted to the left in babies from La Paz compared with those from Santa Cruz, regardless of economic status. The frequency of low birth weight (<2500 g) was higher in babies from La Paz than from Santa Cruz in both high- and low-income groups. In addition, at high altitude but not at low altitude, high income was associated with an increase in the head circumference:birth weight ratio. These findings suggest that high altitude rather than economic status is associated with low birth weight and altered body shape at birth in

  17. How Cells Integrate Complex Stimuli: The Effect of Feedback from Phosphoinositides and Cell Shape on Cell Polarization and Motility

    PubMed Central

    Edelstein-Keshet, Leah

    2012-01-01

    To regulate shape changes, motility and chemotaxis in eukaryotic cells, signal transduction pathways channel extracellular stimuli to the reorganization of the actin cytoskeleton. The complexity of such networks makes it difficult to understand the roles of individual components, let alone their interactions and multiple feedbacks within a given layer and between layers of signalling. Even more challenging is the question of if and how the shape of the cell affects and is affected by this internal spatiotemporal reorganization. Here we build on our previous 2D cell motility model where signalling from the Rho family GTPases (Cdc42, Rac, and Rho) was shown to organize the cell polarization, actin reorganization, shape change, and motility in simple gradients. We extend this work in two ways: First, we investigate the effects of the feedback between the phosphoinositides (PIs) , and Rho family GTPases. We show how that feedback increases heights and breadths of zones of Cdc42 activity, facilitating global communication between competing cell “fronts”. This hastens the commitment to a single lamellipodium initiated in response to multiple, complex, or rapidly changing stimuli. Second, we show how cell shape feeds back on internal distribution of GTPases. Constraints on chemical isocline curvature imposed by boundary conditions results in the fact that dynamic cell shape leads to faster biochemical redistribution when the cell is repolarized. Cells with frozen cytoskeleton, and static shapes, consequently respond more slowly to reorienting stimuli than cells with dynamic shape changes, the degree of the shape-induced effects being proportional to the extent of cell deformation. We explain these concepts in the context of several in silico experiments using our 2D computational cell model. PMID:22396633

  18. The effect of ethnicity and age on palatal size and shape: a study in a northern Chilean healthy population.

    PubMed

    Ferrario, V F; Sforza, C; Colombo, A; Tartaglia, G M; Carvajal, R; Palomino, H

    2000-01-01

    Race and ethnicity influence the form of the human craniofacial complex in varying ways. The aim of the present investigation was to quantify the effects of ethnicity (mestizos, Aymara, non-Aymara), age (adolescents and adults), and sex on the form (size and shape) of the hard palate in normal Native American individuals. From the dental casts of 51 individuals with a complete permanent dentition, the x, y, and z coordinates of several standardized palatal landmarks were obtained with a computerized 3-dimensional digitizer. Palatal landmarks were used to derive a mathematical equation for palatal shape in the frontal and sagittal planes. Palatal width and length, frontal and sagittal heights, sagittal slope, and deviation of the raphe from the midline were also calculated. In the Aymara subjects, there was no effect of sex on palatal size, but there was an effect on palatal shape independent of size, especially with respect to male growth. Indeed, female palates apparently did not change their shape between adolescence and adulthood, while male palates increased their posterior "height." Overall, the 3 ethnic groups appeared to possess similar palatal size, with small significant differences. In the adult individuals, ethnicity did not seem to influence palatal shape. In contrast, adolescent males showed differences: non-Aymara subjects had the "highest" palatal shape, Aymara the "lowest," and mestizos an intermediate position. In conclusion, ethnicity does not seem to be a factor of major variability of human hard palate morphology, at least in the present 3 northern Chilean groups, as already found for dental arch shape. Age probably has a larger effect, particularly in the posterior part of the palate, where the eruption of the second and third molars between adolescence and young adulthood may play a role. A further development of the present investigation may involve larger samples of individuals from different ethnic groups.

  19. The Effects of Verbal Instruction and Shaping to Improve Tackling by High School Football Players

    ERIC Educational Resources Information Center

    Harrison, Antonio M.; Pyles, David A.

    2013-01-01

    We evaluated verbal instruction and shaping using TAG (teaching with acoustical guidance) to improve tackling by 3 high school football players. Verbal instruction and shaping improved tackling for all 3 participants. In addition, performance was maintained as participants moved more quickly through the tackling procedure.

  20. Study of the Lasting Effects of Attending: A LeaderShape Program

    ERIC Educational Resources Information Center

    Stoker, Daniel J.

    2010-01-01

    This exploratory study investigated the long-term learning resulting from participation in a LeaderShape program. The research examined LeaderShape graduates' current practices and definitions of leadership to see if they remain consistent with the program's learning goals. Graduates with five or more years since attendance were studied to provide…

  1. Effect of Deformation Mode on the Wear Behavior of NiTi Shape Memory Alloys

    NASA Astrophysics Data System (ADS)

    Yan, Lina; Liu, Yong

    2016-06-01

    Owing to good biocompatibility, good fatigue resistance, and excellent superelasticity, various types of bio-medical devices based on NiTi shape memory alloy (SMA) have been developed. Due to the complexity in deformation mode in service, for example NiTi implants, accurate assessment/prediction of the surface wear process is difficult. This study aims at providing a further insight into the effect of deformation mode on the wear behavior of NiTi SMA. In the present study, two types of wear testing modes were used, namely sliding wear mode and reciprocating wear mode, to investigate the effect of deformation mode on the wear behavior of NiTi SMA in both martensitic and austenitic states. It was found that, when in martensitic state and under high applied loads, sliding wear mode resulted in more surface damage as compared to that under reciprocating wear mode. When in austenitic state, although similar trends in the coefficient of friction were observed, the coefficient of friction and surface damage in general is less under reciprocating mode than under sliding mode. These observations were further discussed in terms of different deformation mechanisms involved in the wear tests, in particular, the reversibility of martensite variant reorientation and stress-induced phase transformation, respectively.

  2. Thermal emission spectroscopy of microcrystalline sedimentary phases: Effects of natural surface roughness on spectral feature shape

    NASA Astrophysics Data System (ADS)

    Hardgrove, C. J.; Rogers, A. D.; Glotch, T. D.; Arnold, J. A.

    2016-03-01

    Distinguishing between microcrystalline and macrocrystalline mineral phases can help constrain the conditions under which those minerals formed or the degree of postdepositional alteration. This study demonstrates the effects of crystal size and surface roughness on thermal infrared emission spectra of micro and macrocrystalline phases of the two most common minerals on Earth, quartz and calcite. Given the characteristic depositional and environmental conditions under which microcrystalline minerals form, and the recent observations of high-silica deposits on Mars, it is important to understand how these unique materials can be identified using remote infrared spectroscopy techniques. We find that (a) microcrystalline minerals exhibit naturally rough surfaces compared to their macrocrystalline counterparts at the 10 µm scale; and that (b) this roughness causes distinct spectral differences within the Reststrahlen bands of each mineral. These spectral differences occur for surfaces that are rough on the wavelength scale, where the absorption coefficient (k) is large. Specifically, the wavelength positions of the Reststrahlen features for microcrystalline phases are narrowed and shifted compared to macrocrystalline counterparts. The spectral shape differences are small enough that the composition of the material is still recognizable, but large enough such that a roughness effect could be detected. Petrographic and topographic analyses of microcrystalline samples suggest a relationship between crystal size and surface roughness. Together, these observations suggest it may be possible to make general inferences about microcrystallinity from the thermal infrared spectral character of samples, which could aid in reconstructions of sedimentary rock diagenesis where corresponding petrographic or microimaging is not available.

  3. Effect of Film-Hole Shape on Turbine Blade Film Cooling Performance

    NASA Technical Reports Server (NTRS)

    Han, J. C.; Teng, S.

    2000-01-01

    The detailed heat transfer coefficient and film cooling effectiveness distributions as well as tile detailed coolant jet temperature profiles on the suction side of a gas turbine blade A,ere measured using a transient liquid crystal image method and a traversing cold wire and a traversing thermocouple probe, respectively. The blade has only one row of film holes near the gill hole portion on the suction side of the blade. The hole geometries studied include standard cylindrical holes and holes with diffuser shaped exit portion (i.e. fanshaped holes and laidback fanshaped holes). Tests were performed on a five-blade linear cascade in a low-speed wind tunnel. The mainstream Reynolds number based on cascade exit velocity was 5.3 x 10(exp 5). Upstream unsteady wakes were simulated using a spoke-wheel type wake generator. The wake Strouhal number was kept at 0 or 0.1. Coolant blowing ratio was varied from 0.4 to 1.2. Results show that both expanded holes have significantly improved thermal protection over the surface downstream of the ejection location, particularly at high blowing ratios. However, the expanded hole injections induce earlier boundary layer transition to turbulence and enhance heat transfer coefficients at the latter part of the blade suction surface. In general, the unsteady wake tends to reduce film cooling effectiveness.

  4. Building academic health centers' capacity to shape and respond to comparative effectiveness research policy.

    PubMed

    VanLare, Jordan M; Conway, Patrick H; Rowe, John W

    2011-06-01

    In recent years, the focus on comparative effectiveness research (CER), the funding available to support it, and the range of possible effects of CER policy on academic health centers (AHCs) have increased substantially. CER has implications for the research, education, and clinical care components of AHCs' missions. The current funding and policy environment have created specific opportunities for AHCs to shape and respond to CER policies across the four dimensions of the CER enterprise: research, human and scientific capital, data infrastructure, and translation and dissemination. Characteristics such as the degree of physician-hospital integration, the status of a health information technology infrastructure, and the presence of a well-developed cross-functional health services research capacity linked to the care delivery enterprise could help AHCs respond to these opportunities and influence future policies. AHCs are also essential to the development of methodologies and the training of the next cadre of researchers. Further, a focus on understanding what works in health care and increasing adoption of evidence-based practice must become embedded in the fabric of AHCs. Those AHCs most successful in responding to the CER challenge may leverage it as a point of differentiation in the marketplace for health care and lead transformational improvements in health. PMID:21512371

  5. Size and shape effects on the order-disorder phase transition in CoPt nanoparticles

    NASA Astrophysics Data System (ADS)

    Alloyeau, D.; Ricolleau, C.; Mottet, C.; Oikawa, T.; Langlois, C.; Le Bouar, Y.; Braidy, N.; Loiseau, A.

    2009-12-01

    Chemically ordered bimetallic nanoparticles are promising candidates for magnetic-storage applications. However, the use of sub-10nm nanomagnets requires further study of possible size effects on their physical properties. Here, the effects of size and morphology on the order-disorder phase transition temperature of CoPt nanoparticles (TCNP) have been investigated experimentally, using transmission electron microscopy, and theoretically, with canonical Monte Carlo simulations. For 2.4-3-nm particles, TCNP is found to be 325-175∘C lower than the bulk material transition temperature, consistent with our Monte Carlo simulations. Furthermore, we establish that TCNP is also sensitive to the shape of the nanoparticles, because only one dimension of the particle (that is, in-plane size or thickness) smaller than 3nm is sufficient to induce a considerable depression of TCNP. This work emphasizes the necessity of taking into account the three-dimensional morphology of nano-objects to understand and control their structural properties.

  6. The effects of rotational flow, viscosity, thickness, and shape on transonic flutter dip phenomena

    NASA Technical Reports Server (NTRS)

    Reddy, T. S. R.; Srivastava, Rakesh; Kaza, Krishna Rao V.

    1988-01-01

    The transonic flutter dip phenomena on thin airfoils, which are employed for propfan blades, is investigated using an integrated Euler/Navier-Stokes code and a two degrees of freedom typical section structural model. As a part of the code validation, the flutter characteristics of the NACA 64A010 airfoil are also investigated. In addition, the effects of artificial dissipation models, rotational flow, initial conditions, mean angle of attack, viscosity, airfoil thickness and shape on flutter are investigated. The results obtained with a Euler code for the NACA 64A010 airfoil are in reasonable agreement with published results obtained by using transonic small disturbance and Euler codes. The two artificial dissipation models, one based on the local pressure gradient scaled by a common factor and the other based on the local pressure gradient scaled by a spectral radius, predicted the same flutter speeds except in the recovery region for the case studied. The effects of rotational flow, initial conditions, mean angle of attack, and viscosity for the Reynold's number studied seem to be negligible or small on the minima of the flutter dip.

  7. Cluster Plasmonics: Dielectric and Shape Effects on DNA-Stabilized Silver Clusters.

    PubMed

    Copp, Stacy M; Schultz, Danielle; Swasey, Steven M; Faris, Alexis; Gwinn, Elisabeth G

    2016-06-01

    This work investigates the effects of dielectric environment and cluster shape on electronic excitations of fluorescent DNA-stabilized silver clusters, AgN-DNA. We first establish that the longitudinal plasmon wavelengths predicted by classical Mie-Gans (MG) theory agree with previous quantum calculations for excitation wavelengths of linear silver atom chains, even for clusters of just a few atoms. Application of MG theory to AgN-DNA with 400-850 nm cluster excitation wavelengths indicates that these clusters are characterized by a collective excitation process and suggests effective cluster thicknesses of ∼2 silver atoms and aspect ratios of 1.5 to 5. To investigate sensitivity to the surrounding medium, we measure the wavelength shifts produced by addition of glycerol. These are smaller than reported for much larger gold nanoparticles but easily detectable due to narrower line widths, suggesting that AgN-DNA may have potential for fluorescence-reported changes in dielectric environment at length scales of ∼1 nm.

  8. Shape-dependent effects of dielectrically nonlinear inclusions in heterogeneous media

    NASA Astrophysics Data System (ADS)

    Giordano, Stefano; Rocchia, Walter

    2005-11-01

    In this work the electrical response of a mixture composed of dielectrically nonlinear ellipsoids dispersed in a linear matrix is modeled. The inclusions may be randomly oriented. The aim is both to set up a methodology apt to deal with this kind of system and to use it to study the effect of marked nonsphericity of inclusions on the global behavior of a mixture. The results are quite interesting from both these points of view. The method here developed extends the Maxwell-Garnett theory [A Treatise on Electricity and Magnetism (Clarendon, Oxford, 1881)], which deals with dielectrically linear inclusions, and it allows, inter alia, to obtain a closed-form expression for the hypersusceptibility ratio of the mixture to the dispersed inclusions. These latter can range from cylinders to spheres, already present in the literature, to "penny-shaped" particles. The theoretical framework is based on the assumption that the dispersion is very dilute. We were able to show that in a specific case, when oblate particles such as elliptic lamellae are dispersed in a matrix having dielectric constant lower than the linear term of inclusion permittivity, a remarkable nonlinear effect occurs. This theory finds application in fields such as nonlinear optics and, more broadly, in many branches of material science.

  9. Three-Dimensional Mapping of Gyral Shape and Cortical Surface Asymmetries in Schizophrenia: Gender Effects

    PubMed Central

    Narr, Katherine L.; Thompson, Paul M.; Sharma, Tonmoy; Moussai, Jacob; Zoumalan, Chris; Rayman, Janice; Toga, Arthur W.

    2008-01-01

    Objective People with schizophrenia exhibit abnormalities in brain structure, often in the left hemisphere. Disturbed structural lateralization is controversial, however, and effects appear mediated by gender. The authors mapped differences between schizophrenic and normal subjects in gyral asymmetries, complexity, and variability across the entire cortex. Method Asymmetry and shape profiles for 25 schizophrenic patients (15 men) and 28 demographically similar normal subjects (15 men) were obtained for 38 gyral regions, including the sylvian fissure and temporal and postcentral gyri, by using magnetic resonance data and a novel surface-based mesh-modeling approach. Cortical complexity was examined for sex and diagnosis effects in lobar regions. Intragroup variability was quantified and visualized to assess regional group abnormalities at the cortical surface. Results The patients showed greater variability in frontal areas than the comparison subjects. They also had significant deviations in gyral complexity asymmetry in the superior frontal cortex. In temporoparietal regions, significant gyral asymmetries were present in both groups. Sex differences were apparent in superior temporal gyral measures, and cortical complexity in inferior frontal regions was significantly greater in men. Conclusions Cortical variability and complexity show regional abnormalities in the frontal cortex potentially specific to schizophrenia. The results indicate highly significant temporoparietal gyral asymmetries in both diagnostic groups, contrary to reports of less lateralization in schizophrenia. Substantially larger study groups are necessary to isolate smaller deviations in surface asymmetries, if present in schizophrenia, suggesting their diagnostic value is minimal. PMID:11156807

  10. The effect of spatial light modulator (SLM) dependent dispersion on spatial beam shaping

    NASA Astrophysics Data System (ADS)

    Spangenberg, Dirk-Mathys; Dudley, Angela; Neethling, Pieter; Forbes, Andrew; Rohwer, Erich

    2013-09-01

    SLMs used for spatial modulation of lasers are often used in conjunction with very narrow bandwidth laser light where diffractive dispersion could be approximated as a constant. It is known that diffractive dispersion is inversely proportional to wavelength and this effect can be compensated for depending on the optical set-up. SLMs use birefringent liquid crystal (LC) pixels each with an adjustable refractive index at a specific polarization. The range of the adjustable refractive index is wavelength dependent. This adds an additional SLM dependent dispersion. Note that we distinguish between diffractive dispersion and SLM dependent dispersion. SLMs are therefore calibrated in order to have linearly adjustable phase retardation of light incident on the pixels between zero and two pi for a specific wavelength. It is therefore unavoidable when using the same SLM, to do beam shaping of a source which emits multiple wavelengths or a wide bandwidth, that the device will not modulate all wavelengths between zero and two pi. We numerically and experimentally investigate the effect of SLM dependent dispersion on spatial modulation of light incident on a 2D SLM. We further discuss why it is possible to modulate multiple wavelengths between zero and two pi despite SLM dependent dispersion.

  11. Effect of Quarterly Element Addition of Cobalt on Phase Transformation Characteristics of Cu-Al-Ni Shape Memory Alloys

    NASA Astrophysics Data System (ADS)

    Saud, Safaa Najah; Abu Bakar, Tuty Asma; Hamzah, Esah; Ibrahim, Mustafa Khaleel; Bahador, Abollah

    2015-08-01

    In the current study, a new type of Cu-based shape memory alloys with the function of shape memory effect was successfully produced with the introduction of high-purity Co precipitates between the phases of Cu-Al-Ni shape memory alloy. The microstructure, transformation characteristics, and mechanical properties were systematically investigated by means of differential scanning calorimetry, field emission scanning electron microscopy, energy dispersive spectroscopy (EDS), transmission electron microscopy, X-ray diffraction (XRD), a tensile test, a hardness test, and a shape memory effect test. The typical microstructures show that a new phase was formed, known as the γ 2 phase, and the volume friction and the size of this phase were gradually increased with the increasing Co content. According to the results of the XRD and EDS, it was confirmed that the γ 2 phase represents a compound of Al75Co22Ni3. However, the presence of γ 2 phase in the modified alloys was found to result in an increase of the transformation temperatures in comparison with the unmodified alloy. Nevertheless, it was found that with 1 wt pct of Co addition, a maximum ductility of 7 pct was achieved, corresponding to an increase in the strain recovery by the shape memory effect to 95 pct with respect to the unmodified alloy of 50 pct.

  12. Early discrimination of Atlantic salmon smolt age: Time course of the relative effectiveness of body size and shape

    USGS Publications Warehouse

    Pearlstein, J.H.; Letcher, B.H.; Obedzinski, M.

    2007-01-01

    The goal of this study was to test the relative effectiveness of morphological measurements and body size in predicting the smolt age of Atlantic salmon Salmo salar and to determine the time course of body size and shape differences between smolt ages. Analyses were conducted on age-0 to age-2 fish that were stocked as fry in the West Brook, Massachusetts and on laboratory-raised age-0 to age-1 fish. Using both body size and shape, we could partition the age-0 fish collected during fall into future early or late smolts, although the predictive ability of body shape was somewhat weaker than that of body size, especially in the laboratory. Classification success averaged 81% (size) and 79% (shape) in the field and 85% (size) and 73% (shape) in the laboratory. Despite differences in smolt age between the field and the laboratory, the relative timing of growth rate differences between future early and late smolts was similar in the field and the laboratory and peaked at 50-60% of development from fry to smolt. While body shape differed between early and late smolts well before smoltification, it did not improve classification based on size alone.

  13. Classification of particle effective shape ratios in cirrus clouds based on the lidar depolarization ratio.

    PubMed

    Noel, Vincent; Chepfer, Helene; Ledanois, Guy; Delaval, Arnaud; Flamant, Pierre H

    2002-07-20

    A shape classification technique for cirrus clouds that could be applied to future spaceborne lidars is presented. A ray-tracing code has been developed to simulate backscattered and depolarized lidar signals from cirrus clouds made of hexagonal-based crystals with various compositions and optical depth, taking into account multiple scattering. This code was used first to study the sensitivity of the linear depolarization rate to cloud optical and microphysical properties, then to classify particle shapes in cirrus clouds based on depolarization ratio measurements. As an example this technique has been applied to lidar measurements from 15 mid-latitude cirrus cloud cases taken in Palaiseau, France. Results show a majority of near-unity shape ratios as well as a strong correlation between shape ratios and temperature: The lowest temperatures lead to high shape ratios. The application of this technique to space-borne measurements would allow a large-scale classification of shape ratios in cirrus clouds, leading to better knowledge of the vertical variability of shapes, their dependence on temperature, and the formation processes of clouds.

  14. Shape-memory effect by specific biodegradable polymer blending for biomedical applications.

    PubMed

    Cha, Kook Jin; Lih, Eugene; Choi, Jiyeon; Joung, Yoon Ki; Ahn, Dong Jun; Han, Dong Keun

    2014-05-01

    Specific biodegradable polymers having shape-memory properties through "polymer-blend" method are investigated and their shape-switching in body temperature (37 °C) is characterized. Poly(L-lactide-co-caprolactone) (PLCL) and poly(L-lactide-co-glycolide) (PLGA) are dissolved in chloroform and the films of several blending ratios of PLCL/PLGA are prepared by solvent casting. The shape-memory properties of films are also examined using dynamic mechanical analysis (DMA). Among the blending ratios, the PLCL50/PLGA50 film shows good performance of shape-fixity and shape-recovery based on glass transition temperature. It displays that the degree of shape recovery is 100% at 37 °C and the shape recovery proceeds within only 15 s. In vitro biocompatibility studies are shown to have good blood compatibility and cytocompatibility for the PLCL50/PLGA50 films. It is expected that this blended biodegradable polymer can be potentially used as a material for blood-contacting medical devices such as a self-expended vascular polymer stents and vascular closure devices in biomedical applications.

  15. Modeling size effects on the transformation behavior of shape memory alloy micropillars

    NASA Astrophysics Data System (ADS)

    Peraza Hernandez, Edwin A.; Lagoudas, Dimitris C.

    2015-07-01

    The size dependence of the thermomechanical response of shape memory alloys (SMAs) at the micro and nano-scales has gained increasing attention in the engineering community due to existing and potential uses of SMAs as solid-state actuators and components for energy dissipation in small scale devices. Particularly, their recent uses in microelectromechanical systems (MEMS) have made SMAs attractive options as active materials in small scale devices. One factor limiting further application, however, is the inability to effectively and efficiently model the observed size dependence of the SMA behavior for engineering applications. Therefore, in this work, a constitutive model for the size-dependent behavior of SMAs is proposed. Experimental observations are used to motivate the extension of an existing thermomechanical constitutive model for SMAs to account for the scale effects. It is proposed that such effects can be captured via characteristic length dependent material parameters in a power-law manner. The size dependence of the transformation behavior of NiFeGa micropillars is investigated in detail and used as model prediction cases. The constitutive model is implemented in a finite element framework and used to simulate and predict the response of SMA micropillars with different sizes. The results show a good agreement with experimental data. A parametric study performed using the calibrated model shows that the influence of micropillar aspect ratio and taper angle on the compression response is significantly smaller than that of the micropillar average diameter. It is concluded that the model is able to capture the size dependent transformation response of the SMA micropillars. In addition, the simplicity of the calibration and implementation of the proposed model make it practical for the design and numerical analysis of small scale SMA components that exhibit size dependent responses.

  16. Particle-specific toxic effects of differently shaped zinc oxide nanoparticles to zebrafish embryos (Danio rerio).

    PubMed

    Hua, Jing; Vijver, Martina G; Richardson, Michael K; Ahmad, Farooq; Peijnenburg, Willie J G M

    2014-12-01

    A general approach is proposed that allows for quantifying the relative toxic contribution of ions released from metallic nanoparticles and of the particles themselves, as exemplified for the case of differently shaped zinc oxide (ZnO) nanoparticles (NPs) exposed to zebrafish embryos. First of all, the toxicity of suspensions of ZnO nanoparticles (NP(total))--nanospheres, nanosticks, cuboidal submicron particles (SMPs), and Zn(NO3)2--to the embryos was assessed. The observed toxicity of ZnO NP(total) is assumed to result from the combined effect of the particles present in the suspensions (NP(particle)) and of the dissolved Zn(2+) ions released from the particles (NP(ion)). Different addition models were used to explicitly account for the toxicity of NP(particle). The median lethal concentrations (LC50) of NP(particle) of nanospheres, nanosticks, and SMPs were found to range between 7.1 mg Zn/L and 11.9 mg Zn/L (i.e., to differ by a factor of 1.7). Behavioral performance showed no significant differences among all types of the NP(particle). The median effective concentrations (EC50) of the particles were found to range between 1.0 mg Zn/L and 2.2 mg Zn/L. At the LC50 of each particle suspension, the main contribution to lethality to zebrafish embryos was from the NP(particle) (52%-72%). For hatching inhibition, the NP(particle) was responsible for 38% to 83% of the adverse effects observed. The ZnO nanosticks were more toxic than any of the other NPs with regard to the endpoints mortality and hatching inhibition. The main contribution to toxicity to zebrafish embryos was from the NP(particle) at the LC50 and EC50 of each particle suspension.

  17. A thermo dynamical model for the shape and size effect on melting of boron carbide nanoparticles.

    PubMed

    Antoniammal, Paneerselvam; Arivuoli, Dakshanamoorthy

    2012-02-01

    The size and shape dependence of the melting temperature of Boron Carbide (B4C) nanoparticles has been investigated with a numerical thermo dynamical approach. The problem considered in this paper is the inward melting of nanoparticles with spherical and cylindrical geometry. The cylindrical Boron Carbide (B4C) nanoparticles, whose melting point has been reported to decrease with decreasing particle radius, become larger than spherical shaped nanoparticle. Comparative investigation of the size dependence of the melting temperature with respect to the two shapes is also been done. The melting temperature obtained in the present study is approximately a dealing function of radius, in a good agreement with prediction of thermo dynamical model.

  18. Effect of Cargo Size and Shape on the Transport Efficiency of the Bacterial Tat Translocase

    PubMed Central

    Whitaker, Neal; Bageshwar, Umesh; Musser, Siegfried M.

    2013-01-01

    The Tat machinery translocates fully-folded and oligomeric substrates. The passage of large, bulky cargos across an ion-tight membrane suggests the need to match pore and cargo size, and therefore that Tat transport efficiency may depend on both cargo size and shape. A series of cargos of different sizes and shapes were generated using the natural Tat substrate pre-SufI as a base. Four (of 17) cargos transported with significant (>20% of wild-type) efficiencies. These results indicate that cargo size and shape significantly influences Tat transportability. PMID:23422074

  19. Effects of laser parameters on the geometrical characteristics of peg-shaped bionic coupling unit

    NASA Astrophysics Data System (ADS)

    Zhang, Baoyu; Zhang, Zhihui; Liang, Yunhong; Yan, Qiongqiong; Ren, Luquan

    2014-12-01

    Peg-shaped bionic coupling unit (PBCU) processed by pulse laser is effective in anti-adhesion, anti-drag, anti-wear and anti-fatigue application. To obtain desired structural and morphological characteristics of the PBCU for industrial manufacturing, selection of proper processing parameters gradually becomes a growing important problem. Traditionally, the procedure of parameter selecting is often cost-plus and time-consuming. In this work, a statistical analysis of fabricating PBCU on the surface of medium carbon steel was conducted. The laser processing parameters utilized in the experiment and analysis are peak power 4-8 kW, pulse duration 6-16 ms and defocusing amount 6-10 mm. A series of mathematical models regarding the relationship between geometrical characteristics of PBCU and laser processing parameters were developed and checked. The results indicate that the developed models can be adequately used to control the structural and morphological characteristics of PBCU within the scope of analysis. Based on the models, the formation mechanism of the structural and morphological characteristics under different laser parameters were analyzed and discussed.

  20. Effects of nacelle position and shape on performance of subsonic cruise aircraft

    NASA Technical Reports Server (NTRS)

    Bangert, L. H.; Krivec, D. K.; Segall, R. N.

    1983-01-01

    The reduction of installed-propulsion-system drag by installing circular and D-shaped-cross-section nacelles in an underwing-aft position is investigated experimentally in the NASA-Langley 16-foot transonic wind tunnel. Measurements were made at Mach 0.70 to 0.85, -2.5 to 4.1-deg angle of attack, and 3.4 to 4.0 million/ft Reynolds numbers using the NASA USB full-span transonic transport model; and results were compared with those for the wing-body and underwing-forward/pylon-mounted-nacelle (UTW) configurations. While all nacelle configurations are found to have interference drag, which can probably be reduced by eliminating supersonic flows, both aft configurations are shown to reduce drag relative to UTW and increase lift coefficients. The aft D-nacelle had the lowest drag, 6.8 percent of airplane drag lower than UTW at Mach 8.0 and lift coefficient 0.45. Wing pressure distributions and the effects of deflectors are discussed.

  1. Modeling and design of a vibration energy harvester using the magnetic shape memory effect

    NASA Astrophysics Data System (ADS)

    Saren, A.; Musiienko, D.; Smith, A. R.; Tellinen, J.; Ullakko, K.

    2015-09-01

    In this study, a vibration energy harvester is investigated which uses a Ni-Mn-Ga sample that is mechanically strained between 130 and 300 Hz while in a constant biasing magnetic field. The crystallographic reorientation of the sample during mechanical actuation changes its magnetic properties due to the magnetic shape memory (MSM) effect. This leads to an oscillation of the magnetic flux in the yoke which generates electrical energy by inducing an alternating current within the pick-up coils. A power of 69.5 mW (with a corresponding power density of 1.37 mW mm-3 compared to the active volume of the MSM element) at 195 Hz was obtained by optimizing the biasing magnetic field, electrical resistance and electrical resonance. The optimization of the electrical resonance increased the energy generated by nearly a factor of four when compared to a circuit with no resonance. These results are strongly supported by a theoretical model and simulation which gives corresponding values with an error of approximately 20% of the experimental data. This model will be used in the design of future MSM energy harvesters and their optimization for specific frequencies and power outputs.

  2. Molecular Orientation in Two Component Vapor-Deposited Glasses: Effect of Substrate Temperature and Molecular Shape

    NASA Astrophysics Data System (ADS)

    Powell, Charles; Jiang, Jing; Walters, Diane; Ediger, Mark

    Vapor-deposited glasses are widely investigated for use in organic electronics including the emitting layers of OLED devices. These materials, while macroscopically homogenous, have anisotropic packing and molecular orientation. By controlling this orientation, outcoupling efficiency can be increased by aligning the transition dipole moment of the light-emitting molecules parallel to the substrate. Light-emitting molecules are typically dispersed in a host matrix, as such, it is imperative to understand molecular orientation in two-component systems. In this study we examine two-component vapor-deposited films and the orientations of the constituent molecules using spectroscopic ellipsometry, UV-vis and IR spectroscopy. The role of temperature, composition and molecular shape as it effects molecular orientation is examined for mixtures of DSA-Ph in Alq3 and in TPD. Deposition temperature relative to the glass transition temperature of the two-component mixture is the primary controlling factor for molecular orientation. In mixtures of DSA-Ph in Alq3, the linear DSA-Ph has a horizontal orientation at low temperatures and slight vertical orientation maximized at 0.96Tg,mixture, analogous to one-component films.

  3. The effects of window shape and reticle presence on performance in a vertical alignment task.

    PubMed

    Rosenberg, E L; Haines, R F; Jordan, K

    1989-06-01

    This study was conducted to evaluate the effect of selected interior work-station orientational cuing upon the ability to align a target image with local vertical in the frontal plane. Angular error from gravitational vertical in an alignment task was measured for 20 observers viewing through two window shapes (square, round), two initial orientations of a computer-generated space shuttle image, and the presence or absence of a stabilized optical alignment reticle. In terms of overall accuracy, it was found that observer error was significantly smaller for the square window and reticle-present conditions than for the round window and reticle-absent conditions. Response bias data reflected an overall tendency to undershoot and greater variability of response in the round window/no reticle condition. These results suggest that environmental cuing information, such as that provided by square window frames and alignment reticles, may aid in subjective orientation and increase accuracy of response in a space station proximity operations alignment task. PMID:2751584

  4. The effects of window shape and reticle presence on performance in a vertical alignment task

    NASA Technical Reports Server (NTRS)

    Rosenberg, Erika L.; Haines, Richard F.; Jordan, Kevin

    1989-01-01

    This study was conducted to evaluate the effect of selected interior work-station orientational cuing upon the ability to align a target image with local vertical in the frontal plane. Angular error from gravitational vertical in an alignment task was measured for 20 observers viewing through two window shapes (square, round), two initial orientations of a computer-generated space shuttle image, and the presence or absence of a stabilized optical alignment reticle. In terms of overall accuracy, it was found that observer error was significantly smaller for the square window and reticle-present conditions than for the round window and reticle-absent conditions. Response bias data reflected an overall tendency to undershoot and greater variability of response in the round window/no reticle condition. These results suggest that environmental cuing information, such as that provided by square window frames and alignment reticles, may aid in subjective orientation and increase accuracy of response in a Space Station proximity operations alignment task.

  5. An internal charge transfer-dependent solvent effect in V-shaped azacyanines.

    PubMed

    Tasior, Mariusz; Bald, Ilko; Deperasińska, Irena; Cywiński, Piotr J; Gryko, Daniel T

    2015-12-28

    New V-shaped non-centrosymmetric dyes, possessing a strongly electron-deficient azacyanine core, have been synthesized based on a straightforward two-step approach. The key step in this synthesis involves palladium-catalysed cross-coupling of dibromo-N,N'-methylene-2,2'-azapyridinocyanines with arylacetylenes. The resulting strongly polarized π-expanded heterocycles exhibit green to orange fluorescence and they strongly respond to changes in solvent polarity. We demonstrate that differently electron-donating peripheral groups have a significant influence on the internal charge transfer, hence on the solvent effect and fluorescence quantum yield. TD-DFT calculations confirm that, in contrast to the previously studied bis(styryl)azacyanines, the proximity of S1 and T2 states calculated for compounds bearing two 4-N,N-dimethylaminophenylethynyl moieties establishes good conditions for efficient intersystem crossing and is responsible for its low fluorescence quantum yield. Non-linear properties have also been determined for new azacyanines and the results show that depending on peripheral groups, the synthesized dyes exhibit small to large two-photon absorption cross sections reaching 4000 GM.

  6. The role of experience during childhood in shaping the other-race effect.

    PubMed

    de Heering, Adélaïde; de Liedekerke, Claire; Deboni, Malorie; Rossion, Bruno

    2010-01-01

    It is well known that adults' face recognition is characterized by an 'other-race effect' (ORE; see Meissner & Brigham, 2001), but few studies have investigated this ORE during the development of the face processing system. Here we examined the role of experience with other-race faces during childhood by testing a group of 6- to 14-year-old Asian children adopted between 2 and 26 months in Caucasian families living in Western Europe, as well as a group of age-matched Caucasian children. The latter group showed a strong ORE in favour of own-race faces that was stable from 6 to 14 years of age. The adopted participants did not show a significant reversal of the ORE, unlike a recently reported study (Sangrigoli et al., 2005), but rather comparable results with Asian and Caucasian faces. Their pattern of performance was neither influenced by their age of adoption, nor by the amount of experience they accumulated during childhood with other-race faces. These results indicate that the balance of performance with Asian and Caucasian faces can be modulated, but not completely reversed, in children whose exposure to own- and other-race faces changes drastically during the period of maturation of the face recognition system, depending on the length of exposure to the new face race. Overall, experience appears to be crucial during childhood to shape the face recognition system towards the most predominant morphologies of faces present in the environment. PMID:20121874

  7. Subjective Significance Shapes Arousal Effects on Modified Stroop Task Performance: A Duality of Activation Mechanisms Account.

    PubMed

    Imbir, Kamil K

    2016-01-01

    Activation mechanisms such as arousal are known to be responsible for slowdown observed in the Emotional Stroop and modified Stroop tasks. Using the duality of mind perspective, we may conclude that both ways of processing information (automatic or controlled) should have their own mechanisms of activation, namely, arousal for an experiential mind, and subjective significance for a rational mind. To investigate the consequences of both, factorial manipulation was prepared. Other factors that influence Stroop task processing such as valence, concreteness, frequency, and word length were controlled. Subjective significance was expected to influence arousal effects. In the first study, the task was to name the color of font for activation charged words. In the second study, activation charged words were, at the same time, combined with an incongruent condition of the classical Stroop task around a fixation point. The task was to indicate the font color for color-meaning words. In both studies, subjective significance was found to shape the arousal impact on performance in terms of the slowdown reduction for words charged with subjective significance. PMID:26869974

  8. Variational self-consistent estimates for cubic viscoplastic polycrystals: the effects of grain anisotropy and shape

    NASA Astrophysics Data System (ADS)

    Nebozhyn, Michael V.; Gilormini, Pierre; Ponte Castañeda, Pedro

    2001-02-01

    A fundamental problem in mechanics of materials is the computation of the macroscopic response of polycrystalline aggregates from the properties of their constituent single-crystal grains and the microstructure. In this work, the nonlinear homogenization method of deBotton and Ponte Castañeda (1995) [deBotton, G., Ponte Castañeda, P., 1995. Variational estimates for the creep behavior of polycrystals. Proc. R. Soc. Lond. A 448, 121-142] is used to compute "variational" self-consistent estimates for the effective behavior of various types of cubic viscoplastic polycrystals. In contrast with earlier estimates of the self-consistent type, such as those arising from the "incremental" and "tangent" schemes, the new estimates are found to satisfy all known bounds, even in the strongly nonlinear, rate-insensitive limit, and to exhibit a more realistic scaling law at large grain anisotropy. Also, unlike the Taylor and Reuss estimates, they are able to account for grain shape in a rigorous statistical sense. For these reasons, they can be shown to be significantly more accurate than earlier estimates. Thus, for example, the new self-consistent estimates can be less than half the corresponding Taylor estimates for ionic polycrystals with highly anisotropic "flat" grains.

  9. Femtosecond pulse shaping enables detection of optical Kerr-effect (OKE) dynamics for molecular imaging

    PubMed Central

    Robles, Francisco E.; Fischer, Martin C.; Warren, Warren S.

    2014-01-01

    We apply femtosecond pulse shaping to generate optical pulse trains that directly access a material’s nonlinear refractive index (n2) and can thus determine time-resolved optical Kerr-effect (OKE) dynamics. Two types of static pulse trains are discussed: The first uses two identical fields delayed in time, plus a pump field at a different wavelength. Time-resolved OKE dynamics are retrieved by monitoring the phase of the interference pattern produced by the two identical fields in the Fourier-domain (FD) as a function of pump–probe–time–delay (where the probe is one of the two identical fields). The second pulse train uses three fields with equal time delays, but with the center field phase shifted by π/2. In this pulse scheme, changes on a sample’s nonlinear refractive index produce a new frequency in the FD signal, which in turn yields background-free intensity changes in the conjugate (time) domain and provides superior signal-to-noise ratios. The demonstrated sensitivity improvements enable, for the first time to our knowledge, molecular imaging based on OKE dynamics. PMID:25121875

  10. Numerical study of mixing viscous fluids in T-shaped micro-channels with compressibility effects

    NASA Astrophysics Data System (ADS)

    Yang, Junfeng; Matar, Omar; Harrison, Christopher; Sullivan, Matthew

    2015-11-01

    We study numerically the mixing processes of two miscible fluids in T-shaped micro-channels in the presence of compressibility effects. Three mixing modes are considered: `passive' mixing, which relies on the molecular diffusion and chaotic advection; `active' mixing relies on external disturbances, e.g. due to periodic compression; and a combination of these modes. In all cases considered, one of the fluids, fluid `A', is initially present in the dead-end region of the micro-channel. In the `passive' mixing case, the other fluid, fluid `B', flows through the open part of the channel at a constant flow rate. In the `active' case, this fluid is initially at rest but is then set in motion through pressure cycling. The combined case, involves the flow of fluid `B' in the presence of compression-decompression cycles. Numerical simulations are carried out for three different fluids, accounting for their compressibility, and their pressure-dependent e.g. density, viscosity, and diffusivity; a simple mixing rule is used to model the properties of the mixed fluids. Our results indicate that the vortices in the dead-end zone, engendered by the relative motion of the fluids leads to their mixing; the combination of mixing modes is shown to promote mixing efficiency significantly. Schlumberger-Doll Research.

  11. Calculated Effects of Body Shape on the Bow-Shock Overpressures in the Far Field of Bodies in Supersonic Flow

    NASA Technical Reports Server (NTRS)

    Lansing, Donald L.

    1960-01-01

    A theory for the supersonic flow about bodies in uniform flight in a homogeneous medium is reviewed and an integral which expresses the effect of body shape upon the flow parameters in the far field is reduced to a form which may be readily evaluated for arbitrary body shapes. This expression is then used to investigate the effect of nose angle, fineness ratio, and location of maximum body cross section upon the far-field pressure jump across the bow-shock of slender bodies. Curves are presented showing the variation of the shock strength with each of these parameters. It is found that, for a wide variety of shapes having equal fineness ratios, the integral has nearly a constant value.

  12. Investigation of screening effects on the shape resonances in the electron-hydrogen system using the complex-scaling method

    NASA Astrophysics Data System (ADS)

    Jiao, Li-Guang; Ho, Y. K.

    2013-05-01

    In the present work we study the effects of screened Coulomb potentials on shape resonances in the electron-hydrogen system. Here we concentrate on the 1Se and 1Po shape resonances associated with and lying above, respectively, the H (N = 2), (N =3), (N =4), and (N = 5) thresholds. The complex-scaling method is used to extract resonance poles, together with employing correlated Hylleraas-type wave functions up to 1078 and 1771 terms for the S- and P-wave states, respectively, to represent the two-electron system. To model the screening effect we replace the pure Coulomb interaction term for any pair of charged particles by a screened Coulomb (or Yukawa-type) interaction term. Our un-screened shape resonances agree well with those in the literature. We will present our latest results for the screened cases at the meeting. Supported by the National Science Council of Taiwan.

  13. Trajectory perception and object continuity: effects of shape and color change on 4-month-olds' perception of object identity.

    PubMed

    Bremner, J Gavin; Slater, Alan M; Mason, Uschi C; Spring, Jo; Johnson, Scott P

    2013-06-01

    Previous work has demonstrated that infants use object trajectory continuity as a cue to the constant identity of an object, but results are equivocal regarding the role of object features, with some work suggesting that a change in the appearance of an object does not cue a change in identity. In an experiment involving 72 participants, we investigated the effects of changing object shape and color, singly and in combination, on 4-month-olds' perception of object continuity. A change in the shape of an object while it passed behind an occluder had no effect on perception of continuity, whereas a change in shape and color led to perception of discontinuity, and a change in color led to no clear percept regarding continuity or discontinuity. These results are discussed in terms of a perceptual learning model of development of object identity.

  14. Effect of Size, Content and Shape of Reinforcements on the Behavior of Metal Matrix Composites (MMCs) Under Tension

    NASA Astrophysics Data System (ADS)

    Paknia, A.; Pramanik, A.; Dixit, A. R.; Chattopadhyaya, S.

    2016-08-01

    The objective of this research was to investigate the mechanical behavior of metal matrix composites (MMCs) 6061 aluminum, reinforced with silicon carbide particles, under unidirectional tensile loading by finite element analysis. The effects of particle's shape, size and content on the tensile properties of the composites were studied and compared with each other. In addition, stress and strain distributions and possible particle fracture or debonding were investigated. It was found that, among different shapes, a certain shape of reinforcement particle provided better tensile properties for MMCs and, within each shape category, composites with smaller particle size and higher particle content (20%) also showed better properties. It was also found that when the reinforcement content was 10%, the effects of shape and size of the particles were negligible. Not only interfacial length between the reinforcement and matrix materials, but also state of matrix material, due to the presence of the reinforcement particles, affected the stiffness of the MMCs. In almost all of the cases, except for MMCs with triangular particles, when the stress increased, with the increase in the applied positive displacement, the stress distributions remained unchanged.

  15. Sexual dimorphism in the size and shape of the os coxae and the effects of microevolutionary processes.

    PubMed

    Betti, Lia

    2014-02-01

    Sexual dimorphism in the human pelvis has been studied widely for forensic purposes, but it is still unclear to what extent it varies among human populations. There is evidence that microevolutionary processes, both neutral (i.e., population history) and selective (e.g., thermoregulatory adaptation and size-related obstetrical constraints) contribute to explain pelvic variation among populations, but the extent to which these factors affect pelvic sexual dimorphism is unknown. In this study, I analyze sexual dimorphism of the os coxae in 20 globally distributed human populations, using 3D morphometric data to separate the size and shape components of sexual differences. After evaluating population differences in the degree and pattern of sexual dimorphism, I test for the effect of population history, climate, and body size in shaping global diversity. The results show that size and shape dimorphism follow different patterns. Coxal size dimorphism is generally quite consistent through populations, with males bigger than females, but it appears to be reduced in small-bodied populations, possibly in relation to obstetrically-related selective pressures for a spacious birth canal. Beyond a general species-wide pattern of shape dimorphism, commonly used for forensic sex determination, other aspects of sexual differences in coxal shape vary among human populations, reflecting the effects of neutral demographic processes and climatic adaptation. PMID:24222471

  16. The effect of stent porosity and strut shape on saccular aneurysm and its numerical analysis with lattice Boltzmann method.

    PubMed

    Kim, Yong Hyun; Xu, Xiaofeng; Lee, Joon Sang

    2010-07-01

    The analysis of a flow pattern in cerebral aneurysms and the effect of stent strut shapes are presented in this article. The treatment of cerebral aneurisms with a porous stent has recently been proposed as a minimally invasive way to prevent rupture and favor coagulation mechanism inside the aneurism. The efficiency of stent is related to several parameters, including porosity and stent strut shapes. The goal of this article is to study the effect of the stent strut shape and porosity on the hemodynamic properties of the flow inside an aneurysm using a numerical analysis. In this study, we use the concept of flow reduction to characterize the stent efficiency. Also, we use the lattice Boltzmann method (LBM) of a non-Newtonian blood flow. To resolve the characteristics of a highly complex flow, we use an extrapolation method for the wall and stent boundary. To ease the code development and facilitate the incorporation of new physics, a scientific programming strategy based on object-oriented concepts is developed. Reduced velocity, smaller average vorticity magnitude, smaller average shear rate, and increased viscosity are observed when the proposed stent shapes and porosities are used. The rectangular stent is observed to be optimal and to decrease the magnitude of the velocity by 89.25% in the 2D model and 53.92% in the 3D model in the aneurysm sac. Our results show the role of the porosity and stent strut shape and help us to understand the characteristics of stent strut design. PMID:20300847

  17. Effect of Size, Content and Shape of Reinforcements on the Behavior of Metal Matrix Composites (MMCs) Under Tension

    NASA Astrophysics Data System (ADS)

    Paknia, A.; Pramanik, A.; Dixit, A. R.; Chattopadhyaya, S.

    2016-10-01

    The objective of this research was to investigate the mechanical behavior of metal matrix composites (MMCs) 6061 aluminum, reinforced with silicon carbide particles, under unidirectional tensile loading by finite element analysis. The effects of particle's shape, size and content on the tensile properties of the composites were studied and compared with each other. In addition, stress and strain distributions and possible particle fracture or debonding were investigated. It was found that, among different shapes, a certain shape of reinforcement particle provided better tensile properties for MMCs and, within each shape category, composites with smaller particle size and higher particle content (20%) also showed better properties. It was also found that when the reinforcement content was 10%, the effects of shape and size of the particles were negligible. Not only interfacial length between the reinforcement and matrix materials, but also state of matrix material, due to the presence of the reinforcement particles, affected the stiffness of the MMCs. In almost all of the cases, except for MMCs with triangular particles, when the stress increased, with the increase in the applied positive displacement, the stress distributions remained unchanged.

  18. Tree branch-shaped cupric oxide for highly effective photoelectrochemical water reduction.

    PubMed

    Jang, Youn Jeong; Jang, Ji-Wook; Choi, Sun Hee; Kim, Jae Young; Kim, Ju Hun; Youn, Duck Hyun; Kim, Won Yong; Han, Suenghoon; Sung Lee, Jae

    2015-05-01

    Highly efficient tree branch-shaped CuO photocathodes are fabricated using the hybrid microwave annealing process with a silicon susceptor within 10 minutes. The unique hierarchical, one-dimensional structure provides more facile charge transport, larger surface areas, and increased crystallinity and crystal ordering with less defects compared to irregular-shaped CuO prepared by conventional thermal annealing. As a result, the photocathode fabricated with the tree branch-shaped CuO produces an unprecedently high photocurrent density of -4.4 mA cm(-2) at 0 VRHE under AM 1.5 G simulated sunlight compared to -1.44 mA cm(-2) observed for a photocathode fabricated by thermal annealing. It is also confirmed that stoichiometric hydrogen and oxygen are produced from photoelectrochemical water splitting on the tree branch-shaped CuO photocathode and a platinum anode.

  19. Origin of shape anisotropy effects in solution-phase synthesized FePt nanomagnets

    SciTech Connect

    Ferrer, D. A.; Guchhait, S.; Liu, H.; Ferdousi, F.; Corbet, C.; Xu, H.; Saha, S.; Ramon, M.; Banerjee, S. K.; Doczy, M.; Bourianoff, G.; Mathew, L.; Rao, R.; Ganguly, S.; Markert, J. T.

    2011-07-01

    Controlling the morphology of inorganic nanocrystals is important because many of their electronic attributes are highly sensitive to shape and aspect ratio. FePt nanocrystals have potential as advanced magnetic materials for ultrahigh-density memory. This is due to their high shape and/or magnetocrystalline anisotropy, which allows bits as small as 3 nm to be thermally stable over typical data storage periods of 10 years. Herein, nanocrystals were simply fabricated by simultaneous reduction of platinum acetylacetonate and thermal decomposition of iron pentacarbonyl in properly chosen conditions of solvent/surfactant proportions and temperature for rational design of their shape and magnetic properties. This work has combined magnetometry measurements and micromagnetic simulations to illustrate the role of the external shape on the rotation of the magnetization vector for colloidal assemblies.

  20. Influences of Substrate Adhesion and Particle Size on the Shape Memory Effect of Polystyrene Particles.

    PubMed

    Cox, Lewis M; Killgore, Jason P; Li, Zhengwei; Long, Rong; Sanders, Aric W; Xiao, Jianliang; Ding, Yifu

    2016-04-19

    Formulations and applications of micro- and nanoscale polymer particles have proliferated rapidly in recent years, yet knowledge of their mechanical behavior has not grown accordingly. In this study, we examine the ways that compressive strain, substrate surface energy, and particle size influence the shape memory cycle of polystyrene particles. Using nanoimprint lithography, differently sized particles are programmed into highly deformed, temporary shapes in contact with substrates of differing surface energies. Atomic force microscopy is used to obtain in situ measurements of particle shape recovery kinetics, and scanning electron microscopy is employed to assess differences in the profiles of particles at the conclusion of the shape memory cycle. Finally, finite element models are used to investigate the growing impact of surface energies at smaller length scales. Results reveal that the influence of substrate adhesion on particle recovery is size-dependent and can become dominating at submicron length scales.

  1. Passive mechanical models of fish caudal fins: effects of shape and stiffness on self-propulsion.

    PubMed

    Feilich, Kara L; Lauder, George V

    2015-06-01

    Fishes are found in a great variety of body forms with tail shapes that vary from forked tuna-like tails to the square-shaped tails found in some deep-bodied species. Hydrodynamic theory suggests that a fish's body and tail shape affects undulatory swimming performance. For example, a narrow caudal peduncle is believed to reduce drag, and a tuna-like tail to increase thrust. Despite the prevalence of these assertions, there is no experimental verification of the hydrodynamic mechanisms that may confer advantages on specific forms. Here, we use a mechanically-actuated flapping foil model to study how two aspects of shape, caudal peduncle depth and presence or absence of a forked caudal fin, may affect different aspects of swimming performance. Four different foil shapes were each made of plastics of three different flexural stiffnesses, permitting us to study how shape might interact with stiffness to produce swimming performance. For each foil, we measured the self-propelling swimming speed. In addition, we measured the forces, torques, cost of transport and power coefficient of each foil swimming at its self-propelling speed. There was no single 'optimal' foil exhibiting the highest performance in all metrics, and for almost all measures of swimming performance, foil shape and flexural stiffness interacted in complicated ways. Particle image velocimetry of several foils suggested that stiffness might affect the relative phasing of the body trailing edge and the caudal fin leading edge, changing the flow incident to the tail, and affecting hydrodynamics of the entire foil. The results of this study of a simplified model of fish body and tail morphology suggest that considerable caution should be used when inferring a swimming performance advantage from body and tail shape alone. PMID:25879846

  2. Effects of shielding coatings on the anode shaping process during counter-rotating electrochemical machining

    NASA Astrophysics Data System (ADS)

    Wang, Dengyong; Zhu, Zengwei; Wang, Ningfeng; Zhu, Di

    2016-06-01

    Electrochemical machining (ECM) has been widely used in the aerospace, automotive, defense and medical industries for its many advantages over traditional machining methods. However, the machining accuracy in ECM is to a great extent limited by the stray corrosion of the unwanted material removal. Many attempts have been made to improve the ECM accuracy, such as the use of a pulse power, passivating electrolytes and auxiliary electrodes. However, they are sometimes insufficient for the reduction of the stray removal and have their limitations in many cases. To solve the stray corrosion problem in CRECM, insulating and conductive coatings are respectively used. The different implement processes of the two kinds of coatings are introduced. The effects of the two kinds of shielding coatings on the anode shaping process are investigated. Numerical simulations and experiments are conducted for the comparison of the two coatings. The simulation and experimental results show that both the two kinds of coatings are valid for the reduction of stray corrosion on the top surface of the convex structure. However, for insulating coating, the convex sidewall becomes concave when the height of the convex structure is over 1.26 mm. In addition, it is easy to peel off by the high-speed electrolyte. In contrast, the conductive coating has a strong adhesion, and can be well reserved during the whole machining process. The convex structure fabricated by using a conductive iron coating layer presents a favorable sidewall profile. It is concluded that the conductive coating is more effective for the improvement of the machining quality in CRECM. The proposed shielding coatings can also be employed to reduce the stray corrosion in other schemes of ECM.

  3. Tract shape modeling detects changes associated with preterm birth and neuroprotective treatment effects

    PubMed Central

    Anblagan, Devasuda; Bastin, Mark E.; Sparrow, Sarah; Piyasena, Chinthika; Pataky, Rozalia; Moore, Emma J.; Serag, Ahmed; Wilkinson, Alastair Graham; Clayden, Jonathan D.; Semple, Scott I.; Boardman, James P.

    2015-01-01

    Preterm birth is associated with altered connectivity of neural circuits. We developed a tract segmentation method that provides measures of tract shape and integrity (probabilistic neighborhood tractography, PNT) from diffusion MRI (dMRI) data to test the hypotheses: 1) preterm birth is associated with alterations in tract topology (R), and tract-averaged mean diffusivity (〈D〉) and fractional anisotropy (FA); 2) neural systems are separable based on tract-averaged dMRI parameters; and 3) PNT can detect neuroprotective treatment effects. dMRI data were collected from 87 preterm infants (mean gestational age 29+1 weeks, range 23+2 –34+6) at term equivalent age and 24 controls (mean gestational age 39+6 weeks). PNT was used to segment eight major fasciculi, characterize topology, and extract tract-averaged 〈D〉 and FA. Tract topology was altered by preterm birth in all tracts except the splenium (p < 0.05, false discovery rate [FDR] corrected). After adjustment for age at scan, tract-averaged 〈D〉 was increased in the genu and splenium, right corticospinal tract (CST) and the left and right inferior longitudinal fasciculi (ILF) in preterm infants compared with controls (p < 0.05, FDR), while tract-averaged FA was decreased in the splenium and left ILF (p < 0.05, FDR). Specific fasciculi were separable based on tract-averaged 〈D〉 and FA values. There was a modest decrease in tract-averaged 〈D〉 in the splenium of preterm infants who had been exposed to antenatal MgSO4 for neuroprotection (p = 0.002). Tract topology is a biomarker of preterm brain injury. The data provide proof of concept that tract-averaged dMRI parameters have utility for evaluating tissue effects of perinatal neuroprotective strategies. PMID:26106527

  4. Vibration shape effects on the power output in piezoelectric vibro-impact energy harvesters

    NASA Astrophysics Data System (ADS)

    Twiefel, Jens

    2013-04-01

    Vibro-Impcact harvesting devices are one concept to increase the bandwidth of resonant operated piezoelectric vibration generators. The fundamental setup is a piezoelectric bending element, where the deflection is limited by two stoppers. After starting the system in resonance operation the bandwidth increases towards higher frequencies as soon the deflection reach the stopper. If the stoppers are rigid, the frequency response gives constant amplitude for increasing frequencies, as long the system is treated as ideal one-DOF system with symmetric stoppers. In consequence, the bandwidth is theoretically unlimited large. However, such a system also has two major drawbacks, firstly the complicated startup mechanism and secondly the tendency to drop from the high constant branch in the frequency response on the much smaller linear branch if the system is disturbed. Nevertheless, the system has its application wherever the startup problem can be solved. Most modeling approaches utilize modal one-DOF models to describe the systems behavior and do not tread the higher harmonics of the beam. This work investigates the effects of the stoppers on the vibration shape of the piezoelectric beam, wherefore a finite element model is used. The used elements are one-dimensional two node elements based on the Timoshenko-beam theory. The finite element code is implemented in Matlab. The model is calculated utilizing time step integration for simulation, to reduce the computation time an auto-resonant calculation method is implemented. A control loop including positive feedback and saturation is used to create a self-excited system. Therefore, the system is always operated in resonance (on the backbone curve) and the frequency is a direct result of the computation. In this case tip velocity is used as feedback. This technique allows effective parametric studies. Investigated parameters include gap, excitation amplitude, tip mass as well as the stiffness of the stopper. The stress and

  5. Effects of surface characteristics on the plantar shape of feet and subjects' perceived sensations.

    PubMed

    Witana, Channa P; Goonetilleke, Ravindra S; Xiong, Shuping; Au, Emily Y L

    2009-03-01

    Orthotics and other types of shoe inserts are primarily designed to reduce injury and improve comfort. The interaction between the plantar surface of the foot and the load-bearing surface contributes to foot and surface deformations and hence to perceived comfort, discomfort or pain. The plantar shapes of 16 participants' feet were captured when standing on three support surfaces that had different cushioning properties in the mid-foot region. Foot shape deformations were quantified using 3D laser scans. A questionnaire was used to evaluate the participant's perceptions of perceived shape and perceived feeling. The results showed that the structure in the mid-foot could change shape, independent of the rear-foot and forefoot regions. Participants were capable of identifying the shape changes with distinct preferences towards certain shapes. The cushioning properties of the mid-foot materials also have a direct influence on perceived feelings. This research has strong implications for the design and material selection of orthotics, insoles and footwear.

  6. Shape Beyond Recognition: Form-derived Directionality and its Effects on Visual Attention and Motion Perception

    PubMed Central

    Sigurdardottir, Heida M.; Michalak, Suzanne M.; Sheinberg, David L.

    2013-01-01

    The shape of an object restricts its movements and therefore its future location. The rules governing selective sampling of the environment likely incorporate any available data, including shape, that provide information about where important things are going to be in the near future so that the object can be located, tracked, and sampled for information. We asked people to assess in which direction several novel objects pointed or directed them. With independent groups of people, we investigated whether their attention and sense of motion were systematically biased in this direction. Our work shows that nearly any novel object has intrinsic directionality derived from its shape. This shape information is swiftly and automatically incorporated into the allocation of overt and covert visual orienting and the detection of motion, processes which themselves are inherently directional. The observed connection between form and space suggests that shape processing goes beyond recognition alone and may help explain why shape is a relevant dimension throughout the visual brain. PMID:23565670

  7. Elastic poly(ε-caprolactone)-polydimethylsiloxane copolymer fibers with shape memory effect for bone tissue engineering.

    PubMed

    Kai, Dan; Prabhakaran, Molamma P; Chan, Benjamin Qi Yu; Liow, Sing Shy; Ramakrishna, Seeram; Xu, Fujian; Loh, Xian Jun

    2016-02-01

    A porous shape memory scaffold with biomimetic architecture is highly promising for bone tissue engineering applications. In this study, a series of new shape memory polyurethanes consisting of organic poly(ε-caprolactone) (PCL) segments and inorganic polydimethylsiloxane (PDMS) segments in different ratios (9 : 1, 8 : 2 and 7 : 3) was synthesised. These PCL-PDMS copolymers were further engineered into porous fibrous scaffolds by electrospinning. With different ratios of PCL: PDMS, the fibers showed various fiber diameters, thermal behaviour and mechanical properties. Even after being processed into fibrous structures, these PCL-PDMS copolymers maintained their shape memory properties, and all the fibers exhibited excellent shape recovery ratios of  >90% and shape fixity ratios of  >92% after 7 thermo-mechanical cycles. Biological assay results corroborated that the fibrous PCL-PDMS scaffolds were biocompatible by promoting osteoblast proliferation, functionally enhanced biomineralization-relevant alkaline phosphatase expression and mineral deposition. Our study demonstrated that the PCL-PDMS fibers with excellent shape memory properties are promising substrates as bioengineered grafts for bone regeneration.

  8. Effects of parallelogram-shaped pavement markings on vehicle speed and safety of pedestrian crosswalks on urban roads in China.

    PubMed

    Guo, Yanyong; Liu, Pan; Liang, Qiyu; Wang, Wei

    2016-10-01

    The primary objective of this study was to evaluate the effects of parallelogram-shaped pavement markings on vehicle speed and crashes in the vicinity of urban pedestrian crosswalks. The research team measured speed data at twelve sites, and crash data at eleven sites. Observational cross-sectional studies were conducted to identify if the effects of parallelogram-shaped pavement markings on vehicle speeds and speed violations were statistically significant. The results showed that parallelogram-shaped pavement markings significantly reduced vehicle speeds and speed violations in the vicinity of pedestrian crosswalks. More specifically, the speed reduction effects varied from 1.89km/h to 4.41km/h with an average of 3.79km/h. The reduction in the 85th percentile speed varied from 0.81km/h to 5.34km/h with an average of 4.19km/h. Odds ratios (OR) showed that the parallelogram-shaped pavement markings had effects of a 7.1% reduction in the mean speed and a 6.9% reduction in the 85th percentile speed at the pedestrian crosswalks. The reduction of proportion of drivers exceeding the speed limit varied from 8.64% to 14.15% with an average of 11.03%. The results of the crash data analysis suggested that the use of parallelogram-shaped pavement markings reduced both the frequency and severity of crashes at pedestrian crosswalks. The parallelogram-shaped pavement markings had a significant effect on reducing the vehicle-pedestrian crashes. Two crash prediction models were developed for vehicle-pedestrian crashes and rear-end crashes. According to the crash models, the presence of parallelogram-shaped pavement markings reduced vehicle-pedestrian crashes at pedestrian crosswalks by 24.87% with a 95% confidence interval of [10.06-30.78%]. However, the model results also showed that the presence of parallelogram-shaped pavement markings increased rear-end crashes at pedestrian crosswalks by 5.4% with a 95% confidence interval of [0-11.2%]. PMID:26164705

  9. Effects of parallelogram-shaped pavement markings on vehicle speed and safety of pedestrian crosswalks on urban roads in China.

    PubMed

    Guo, Yanyong; Liu, Pan; Liang, Qiyu; Wang, Wei

    2016-10-01

    The primary objective of this study was to evaluate the effects of parallelogram-shaped pavement markings on vehicle speed and crashes in the vicinity of urban pedestrian crosswalks. The research team measured speed data at twelve sites, and crash data at eleven sites. Observational cross-sectional studies were conducted to identify if the effects of parallelogram-shaped pavement markings on vehicle speeds and speed violations were statistically significant. The results showed that parallelogram-shaped pavement markings significantly reduced vehicle speeds and speed violations in the vicinity of pedestrian crosswalks. More specifically, the speed reduction effects varied from 1.89km/h to 4.41km/h with an average of 3.79km/h. The reduction in the 85th percentile speed varied from 0.81km/h to 5.34km/h with an average of 4.19km/h. Odds ratios (OR) showed that the parallelogram-shaped pavement markings had effects of a 7.1% reduction in the mean speed and a 6.9% reduction in the 85th percentile speed at the pedestrian crosswalks. The reduction of proportion of drivers exceeding the speed limit varied from 8.64% to 14.15% with an average of 11.03%. The results of the crash data analysis suggested that the use of parallelogram-shaped pavement markings reduced both the frequency and severity of crashes at pedestrian crosswalks. The parallelogram-shaped pavement markings had a significant effect on reducing the vehicle-pedestrian crashes. Two crash prediction models were developed for vehicle-pedestrian crashes and rear-end crashes. According to the crash models, the presence of parallelogram-shaped pavement markings reduced vehicle-pedestrian crashes at pedestrian crosswalks by 24.87% with a 95% confidence interval of [10.06-30.78%]. However, the model results also showed that the presence of parallelogram-shaped pavement markings increased rear-end crashes at pedestrian crosswalks by 5.4% with a 95% confidence interval of [0-11.2%].

  10. NEUTRON-PROTON EFFECTIVE RANGE PARAMETERS AND ZERO-ENERGY SHAPE DEPENDENCE.

    SciTech Connect

    HACKENBURG, R.W.

    2005-06-01

    A completely model-independent effective range theory fit to available, unpolarized, np scattering data below 3 MeV determines the zero-energy free proton cross section {sigma}{sub 0} = 20.4287 {+-} 0.0078 b, the singlet apparent effective range r{sub s} = 2.754 {+-} 0.018{sub stat} {+-} 0.056{sub syst} fm, and improves the error slightly on the parahydrogen coherent scattering length, a{sub c} = -3.7406 {+-} 0.0010 fm. The triplet and singlet scattering lengths and the triplet mixed effective range are calculated to be a{sub t} = 5.4114 {+-} 0.0015 fm, a{sub s} = -23.7153 {+-} 0.0043 fm, and {rho}{sub t}(0,-{epsilon}{sub t}) = 1.7468 {+-} 0.0019 fm. The model-independent analysis also determines the zero-energy effective ranges by treating them as separate fit parameters without the constraint from the deuteron binding energy {epsilon}{sub t}. These are determined to be {rho}{sub t}(0,0) = 1.705 {+-} 0.023 fm and {rho}{sub s}(0,0) = 2.665 {+-} 0.056 fm. This determination of {rho}{sub t}(0,0) and {rho}{sub s}(0,0) is most sensitive to the sparse data between about 20 and 600 keV, where the correlation between the determined values of {rho}{sub t}(0,0) and {rho}{sub s}(0,0) is at a minimum. This correlation is responsible for the large systematic error in r{sub s}. More precise data in this range are needed. The present data do not event determine (with confidence) that {rho}{sub t}(0,0) {ne} {rho}{sub t}(0, -{epsilon}{sub t}), referred to here as ''zero-energy shape dependence''. The widely used measurement of {sigma}{sub 0} = 20.491 {+-} 0.014 b from W. Dilg, Phys. Rev. C 11, 103 (1975), is argued to be in error.

  11. The Effect of Prosthetic Ankle Units on Roll-Over Shape Characteristics During Walking in Persons with Bilateral Transtibial Amputations

    PubMed Central

    Gard, Steven A.; Su, Po-Fu; Lipschutz, Robert D.; Hansen, Andrew H.

    2015-01-01

    Some important functions of walking are adversely affected or eliminated in prosthesis users due to reduced or absent ankle motion. The purpose of this retrospective data analysis was to determine the effect of prosthetic ankle units on the characteristics of the ankle-foot roll-over shape in persons with bilateral transtibial amputations. Seventeen subjects were fitted with Endolite Multiflex Ankles to provide ankle plantar/dorsiflexion during the stance phase of gait. Two quantitative gait analyses were performed as subjects walked with (1) Seattle Lightfoot II feet (baseline condition) and (2) with the prosthetic ankle units added. Roll-over shape radii and effective foot length ratio were calculated and compared for the two prosthetic configurations. When subjects walked with the ankle units, ankle motion increased (p<0.001), peak ankle plantarflexion moment during stance decreased slightly, and ankle-foot roll-over shape radii were significantly less (p<0.001) compared to the baseline condition. The effective foot length ratio of the roll-over shape was found to increase with walking speed (p<0.001), but it was not significantly affected by the prosthetic ankle units (p=0.066). Prosthetists and manufacturers are encouraged to consider the effect of combining prosthetic components on the overall characteristics of the prosthesis and the functions they impart to the user. PMID:22234709

  12. Effects of Anticaricaturing vs. Caricaturing and Their Neural Correlates Elucidate a Role of Shape for Face Learning

    ERIC Educational Resources Information Center

    Schulz, Claudia; Kaufmann, Jurgen M.; Walther, Lydia; Schweinberger, Stefan R.

    2012-01-01

    To assess the role of shape information for unfamiliar face learning, we investigated effects of photorealistic spatial anticaricaturing and caricaturing on later face recognition. We assessed behavioural performance and event-related brain potential (ERP) correlates of recognition, using different images of anticaricatures, veridical faces, or…

  13. New system for manipulation of nanoobjects based on composite Ti2NiCu/Pt nanotweezers with shape memory effect

    NASA Astrophysics Data System (ADS)

    Zhikharev, A. M.; Irzhak, A. V.; Beresin, M. Y.; Lega, P. V.; Koledov, V. V.; Kasyanov, N. N.; Martynov, G. S.

    2016-08-01

    We report the new system for manipulation of nanoobjects based on composite Ti2NiCu/Pt nanotweezers with shape memory effect. The design consists of the bimetallic Ti2NiCu/Pt shape memory nanotweezers placed on a tip of electrochemically etched tungsten needle. The semiconductor diode placed on the tip of the needle plays both role of resistive element of the heater and temperature sensor for feedback control loop closing. The device is compatible with existing positioning systems like OmniProbe®, Kleindiek®, etc. and may find numerous practical applications in various tasks of nanotechnology connected with 3D manipulation.

  14. Effect of external tank nose shape on the Rockwell International space shuttle vehicle 3, integrated configuration (IA37B)

    NASA Technical Reports Server (NTRS)

    Allen, E. C.

    1974-01-01

    Tests of several tank nose shapes were conducted as a part of the investigation of configuration changes to reduce drag for the integrated vehicle. The effect on the integrated vehicle aerodynamic characteristics of several tank nose shapes was investigated. The tank nose shapes investigated were the 600 inch (baseline) and 1204 inch radius ogives, and the 600 inch ogive plus a spike 360 inches long and 12.0 inches in diameter. Data were obtained over a Mach number range of 0.6 through 4.96 and for angles-of-attack and sideslip from -10 through +10 degrees. The model used was the 0.004-scale integrated vehicle model number 34-OTS.

  15. Size effects on magnetic actuation in Ni-Mn-Ga shape-memory alloys.

    PubMed

    Dunand, David C; Müllner, Peter

    2011-01-11

    The off-stoichiometric Ni(2)MnGa Heusler alloy is a magnetic shape-memory alloy capable of reversible magnetic-field-induced strains (MFIS). These are generated by twin boundaries moving under the influence of an internal stress produced by a magnetic field through the magnetocrystalline anisotropy. While MFIS are very large (up to 10%) for monocrystalline Ni-Mn-Ga, they are near zero (<0.01%) in fine-grained polycrystals due to incompatibilities during twinning of neighboring grains and the resulting internal geometrical constraints. By growing the grains and/or shrinking the sample, the grain size becomes comparable to one or more characteristic sample sizes (film thickness, wire or strut diameter, ribbon width, particle diameter, etc), and the grains become surrounded by free space. This reduces the incompatibilities between neighboring grains and can favor twinning and thus increase the MFIS. This approach was validated recently with very large MFIS (0.2-8%) measured in Ni-Mn-Ga fibers and foams with bamboo grains with dimensions similar to the fiber or strut diameters and in thin plates where grain diameters are comparable to plate thickness. Here, we review processing, micro- and macrostructure, and magneto-mechanical properties of (i) Ni-Mn-Ga powders, fibers, ribbons and films with one or more small dimension, which are amenable to the growth of bamboo grains leading to large MFIS, and (ii) "constructs" from these structural elements (e.g., mats, laminates, textiles, foams and composites). Various strategies are proposed to accentuate this geometric effect which enables large MFIS in polycrystalline Ni-Mn-Ga by matching grain and sample sizes.

  16. Forces and shapes as determinants of micro-swimming: effect on synchronisation and the utilisation of drag.

    PubMed

    Pande, Jayant; Smith, Ana-Sunčana

    2015-03-28

    In this analytical study we demonstrate the richness of behaviour exhibited by bead-spring micro-swimmers, both in terms of known yet not fully explained effects such as synchronisation, and hitherto undiscovered phenomena such as the existence of two transport regimes where the swimmer shape has fundamentally different effects on the velocity. For this purpose we employ a micro-swimmer model composed of three arbitrarily-shaped rigid beads connected linearly by two springs. By analysing this swimmer in terms of the forces on the different beads, we determine the optimal kinematic parameters for sinusoidal driving, and also explain the pusher/puller nature of the swimmer. Moreover, we show that the phase difference between the swimmer's arms automatically attains values which maximise the swimming speed for a large region of the parameter space. Apart from this, we determine precisely the optimal bead shapes that maximise the velocity when the beads are constrained to be ellipsoids of a constant volume or surface area. On doing so, we discover the surprising existence of the aforementioned transport regimes in micro-swimming, where the motion is dominated by either a reduction of the drag force opposing the beads, or by the hydrodynamic interaction amongst them. Under some conditions, these regimes lead to counter-intuitive effects such as the most streamlined shapes forming locally the slowest swimmers.

  17. Effects of test sample shape and surface production method on the fatigue behaviour of PMMA bone cement.

    PubMed

    Sheafi, E M; Tanner, K E

    2014-01-01

    There is no consensus over the optimal criterion to define the fatigue life of bone cement in vitro. Fatigue testing samples have been made into various shapes using different surface preparation techniques with little attention being paid to the importance of these variations on the fatigue results. The present study focuses on the effect of test sample shape and surface production method on the fatigue results. The samples were manufactured with two cross sectional shapes: rectangular according to ISO 527 and circular according to ASTM F2118. Each shape was produced using two methods: direct moulding of the cement dough and machining from oversized rods. Testing was performed using two different bone cements: SmartSet GHV and DePuy CMW1. At least 10 samples of each category were tested, under fully reversed tension-compression fatigue stress at ±20MPa, to allow for Weibull analysis to compare results. The growth of fatigue cracks was observed by means of the changes in the absorbed energy and apparent modulus. It was found that fatigue crack growth can be altered by the sample shape and production method; however it is also dependent on the chemical composition of the cement. The results revealed that moulded samples, particularly those based on the ASTM F2118 standard, can lead to up to 5.5 times greater fatigue lives compared to the machined samples of the same cement. It is thus essential, when comparing the fatigue results of bone cement, to consider the effect of production method along with the shape of the test sample. PMID:24070780

  18. Effect of panel shape of soccer ball on its flight characteristics

    NASA Astrophysics Data System (ADS)

    Hong, Sungchan; Asai, Takeshi

    2014-05-01

    Soccer balls are typically constructed from 32 pentagonal and hexagonal panels. Recently, however, newer balls named Cafusa, Teamgeist 2, and Jabulani were respectively produced from 32, 14, and 8 panels with shapes and designs dramatically different from those of conventional balls. The newest type of ball, named Brazuca, was produced from six panels and will be used in the 2014 FIFA World Cup in Brazil. There have, however, been few studies on the aerodynamic properties of balls constructed from different numbers and shapes of panels. Hence, we used wind tunnel tests and a kick-robot to examine the relationship between the panel shape and orientation of modern soccer balls and their aerodynamic and flight characteristics. We observed a correlation between the wind tunnel test results and the actual ball trajectories, and also clarified how the panel characteristics affected the flight of the ball, which enabled prediction of the trajectory.

  19. Effect of panel shape of soccer ball on its flight characteristics

    PubMed Central

    Hong, Sungchan; Asai, Takeshi

    2014-01-01

    Soccer balls are typically constructed from 32 pentagonal and hexagonal panels. Recently, however, newer balls named Cafusa, Teamgeist 2, and Jabulani were respectively produced from 32, 14, and 8 panels with shapes and designs dramatically different from those of conventional balls. The newest type of ball, named Brazuca, was produced from six panels and will be used in the 2014 FIFA World Cup in Brazil. There have, however, been few studies on the aerodynamic properties of balls constructed from different numbers and shapes of panels. Hence, we used wind tunnel tests and a kick-robot to examine the relationship between the panel shape and orientation of modern soccer balls and their aerodynamic and flight characteristics. We observed a correlation between the wind tunnel test results and the actual ball trajectories, and also clarified how the panel characteristics affected the flight of the ball, which enabled prediction of the trajectory. PMID:24875291

  20. Study of temporal pulse shape effects on W using simulations and laser heating

    NASA Astrophysics Data System (ADS)

    Yu, J. H.; De Temmerman, G.; Doerner, R. P.; van den Berg, M. A.

    2016-02-01

    Transient heat pulses with triangular, square, and ELM-like temporal shapes are investigated in order to further understand how transient plasma instabilities will affect plasma facing components in tokamaks. A solution to the 1D heat equation for triangular pulses allows the peak surface temperature to be written analytically for arbitrary rise times. The solution as well as ANSYS simulations reveal that a positive ramp (maximum rise time) triangular pulse has a higher peak surface temperature by a factor of \\sqrt{2} compared to that from a negative ramp (rise time = 0) pulse shape with equal energy density, peak power, and pulse width. Translating the results to ITER, an ELM or disruption pulse with the shortest rise time is the most benign compared to other pulse shapes with the same peak heat flux and same energy density.

  1. Monte Carlo - Metropolis Investigations of Shape and Matrix Effects in 2D and 3D Spin-Crossover Nanoparticles

    NASA Astrophysics Data System (ADS)

    Guerroudj, Salim; Caballero, Rafael; De Zela, Francisco; Jureschi, Catalin; Linares, Jorge; Boukheddaden, Kamel

    2016-08-01

    The Ising like model, taking into account short-, long-range interaction as well as surface effects is used to investigate size and shape effects on the thermal behaviour of 2D and 3D spin crossover (SCO) nanoparticles embedded in a matrix. We analyze the role of the parametert, representing the ratio between the number of surface and volume molecules, on the unusual thermal hysteresis behaviour (appearance of the hysteresis and a re-entrance phase transition) at small scales.

  2. Strain characterization of fin-shaped field effect transistors with SiGe stressors using nanobeam electron diffraction

    SciTech Connect

    Kim, Sun-Wook; Byeon, Dae-Seop; Jang, Hyunchul; Koo, Sang-Mo; Ko, Dae-Hong; Lee, Hoo-Jeong

    2014-08-25

    This study undertook strain analysis on fin-shaped field effect transistor structures with epitaxial Si{sub 1−x}Ge{sub x} stressors, using nano-beam electron diffraction and finite elements method. Combining the two methods disclosed dynamic strain distribution in the source/drain and channel region of the fin structure, and the effects of dimensional factors such as the stressor thickness and fin width, offering valuable information for device design.

  3. Effect of ocular shape and vascular geometry on retinal hemodynamics: a computational model.

    PubMed

    Dziubek, Andrea; Guidoboni, Giovanna; Harris, Alon; Hirani, Anil N; Rusjan, Edmond; Thistleton, William

    2016-08-01

    A computational model for retinal hemodynamics accounting for ocular curvature is presented. The model combines (i) a hierarchical Darcy model for the flow through small arterioles, capillaries and small venules in the retinal tissue, where blood vessels of different size are comprised in different hierarchical levels of a porous medium; and (ii) a one-dimensional network model for the blood flow through retinal arterioles and venules of larger size. The non-planar ocular shape is included by (i) defining the hierarchical Darcy flow model on a two-dimensional curved surface embedded in the three-dimensional space; and (ii) mapping the simplified one-dimensional network model onto the curved surface. The model is solved numerically using a finite element method in which spatial domain and hierarchical levels are discretized separately. For the finite element method, we use an exterior calculus-based implementation which permits an easier treatment of non-planar domains. Numerical solutions are verified against suitably constructed analytical solutions. Numerical experiments are performed to investigate how retinal hemodynamics is influenced by the ocular shape (sphere, oblate spheroid, prolate spheroid and barrel are compared) and vascular architecture (four vascular arcs and a branching vascular tree are compared). The model predictions show that changes in ocular shape induce non-uniform alterations of blood pressure and velocity in the retina. In particular, we found that (i) the temporal region is affected the least by changes in ocular shape, and (ii) the barrel shape departs the most from the hemispherical reference geometry in terms of associated pressure and velocity distributions in the retinal microvasculature. These results support the clinical hypothesis that alterations in ocular shape, such as those occurring in myopic eyes, might be associated with pathological alterations in retinal hemodynamics. PMID:26445874

  4. Effect of higher-order multipole moments on the Stark line shape

    NASA Astrophysics Data System (ADS)

    Gomez, T. A.; Nagayama, T.; Kilcrease, D. P.; Montgomery, M. H.; Winget, D. E.

    2016-08-01

    Spectral line shapes are sensitive to plasma conditions and are often used to diagnose electron density of laboratory plasmas as well as astrophysical plasmas. Stark line-shape models take into account the perturbation of the radiator's energy structure due to the Coulomb interaction with the surrounding charged particles. Solving this Coulomb interaction is challenging and is commonly approximated via a multipole expansion. However, most models include only up to the second term of the expansion (the dipole term). While there have been studies on the higher-order terms due to one of the species (i.e., either ions or electrons), there is no model that includes the terms beyond dipole from both species. Here, we investigate the importance of the higher-order multipole terms from both species on the Hβ line shape. First, we find that it is important to include higher-order terms consistently from both ions and electrons to reproduce measured line-shape asymmetry. Next, we find that the line shape calculated with the dipole-only approximation becomes inaccurate as density increases. It is necessary to include up to the third (quadrupole) term to compute the line shape accurately within 2%. Since most existing models include only up to the dipole terms, the densities inferred with such models are in question. We find that the model without the quadrupole term slightly underestimates the density, and the discrepancy becomes as large as 12% at high densities. While the case of study is limited to Hβ, we expect similar impact on other lines.

  5. Effect of the defect initial shape on the fatigue lifetime of a continuous casting machine roll

    NASA Astrophysics Data System (ADS)

    Yasniy, Oleh P.; Lapusta, Yuri

    2016-08-01

    The article deals with the influence of the defect initial shape on the residual lifetime of a continuous casting machine roll made of 25Cr1MoV steel. Based on this approach, previously proposed by some authors, the growth of the surface fatigue crack was modeled in a roll under loading and temperature conditions that are close to operational ones, taking into account the statistical distribution of the C parameter of Paris' equation. Dependencies of the continuous casting machines roll fatigue lifetime on the initial defect shape and critical defect sizes are obtained.

  6. Effects of Processing Parameters on the Forming Quality of C-Shaped Thermosetting Composite Laminates in Hot Diaphragm Forming Process

    NASA Astrophysics Data System (ADS)

    Bian, X. X.; Gu, Y. Z.; Sun, J.; Li, M.; Liu, W. P.; Zhang, Z. G.

    2013-10-01

    In this study, the effects of processing temperature and vacuum applying rate on the forming quality of C-shaped carbon fiber reinforced epoxy resin matrix composite laminates during hot diaphragm forming process were investigated. C-shaped prepreg preforms were produced using a home-made hot diaphragm forming equipment. The thickness variations of the preforms and the manufacturing defects after diaphragm forming process, including fiber wrinkling and voids, were evaluated to understand the forming mechanism. Furthermore, both interlaminar slipping friction and compaction behavior of the prepreg stacks were experimentally analyzed for showing the importance of the processing parameters. In addition, autoclave processing was used to cure the C-shaped preforms to investigate the changes of the defects before and after cure process. The results show that the C-shaped prepreg preforms with good forming quality can be achieved through increasing processing temperature and reducing vacuum applying rate, which obviously promote prepreg interlaminar slipping process. The process temperature and forming rate in hot diaphragm forming process strongly influence prepreg interply frictional force, and the maximum interlaminar frictional force can be taken as a key parameter for processing parameter optimization. Autoclave process is effective in eliminating voids in the preforms and can alleviate fiber wrinkles to a certain extent.

  7. Analysis of stationary roving mass effect for damage detection in beams using wavelet analysis of mode shapes

    NASA Astrophysics Data System (ADS)

    Solís, Mario; Benjumea, Antonio J.; Algaba, Mario; Galvín, Pedro

    2015-07-01

    One of the main challenges in damage detection techniques is sensitivity to damage. During the last years, a large number of papers have used wavelet analysis as a sensitive mathematical tool for identifying changes in mode shapes induced by damage. This paper analyzes the effect of adding a mass to the structure at different positions. Depending on the location and severity of damage, the presence of the mass affects the natural frequencies and mode shapes in a different way. The paper applies a damage detection methodology proposed by the authors, although it has been modified in order to consider the addition of the mas. This methodology is based on a wavelet analysis of the difference of mode shapes of a damaged and a reference state. The singular behavior of a normalized weighted addition of wavelet coefficients is used as an indicator of damage. The presence of damage is detected by combining all the information provided by mode shapes and natural frequencies for different positions of the roving mass. A continuous wavelet transform is used to detect the difference between the response of a healthy state and a damaged one. The paper shows the results obtained for a beam with different cracks. The paper analyzes the sensitivity to damage of the proposed methodology by considering some practical issues such as the size of the crack, the number of measuring points and the effect of experimental noise.

  8. Effect of shape and thickness of asbestos bundles and fibres on EDS microanalysis: A Monte Carlo simulation

    NASA Astrophysics Data System (ADS)

    Moro, D.; Valdre, G.

    2016-02-01

    Quantitative microanalysis of tiny asbestos mineral fibres by scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy (SEM-EDS) still represents a complex analytical issue. This complexity arises from the variable fibre shape and small thickness (< 5 μm) compared with the penetration of the incident electron beam. Here, we present the results of Monte Carlo simulations of chrysotile, crocidolite and amosite fibres (and bundles of fibres) of circular and square section and thicknesses from 0.1 μm to 10 μm, to investigate the effect of shape and thickness on SEM-EDS microanalysis. The influence of shape and thickness on the simulated spectrum was investigated for electron beam energies of 5, 15 and 25 keV, respectively. A strong influence of the asbestos bundles and fibres shape and thickness on the detected EDS X-ray intensity was observed. The X-ray intensity trends as a function of fibre thickness showed a non-linear dependence for all the elements and minerals. In general, the X-ray intensities showed a considerable reduction for thicknesses below about 5 μm at 5 keV, 2 μm at 15 keV, and 5 μm at 25 keV. Correction parameters, k-ratios, for the asbestos fibre thickness effect, are reported.

  9. Influence of aging and thermomechanical cycling on the magnetostriction and magnetic shape memory effect in martensitic alloy

    NASA Astrophysics Data System (ADS)

    L'vov, Victor A.; Kosogor, Anna; Barandiaran, Jose M.; Chernenko, Volodymyr A.

    2015-10-01

    An influence of internal stress created by the crystal defects on the magnetically induced reorientation (MIR) of martensite variants in the ferromagnetic shape memory alloy (FSMA) has been analyzed. Using the internal stress conception, a noticeable influence of the spatial reconfiguration of crystal defects on the ordinary magnetostriction of FSMA and magnetic shape memory (MSM) effect has been predicted. It has been shown that the defect reconfiguration, which stabilizes the martensitic phase during martensite aging, increases the shear elastic modulus. The increase of shear modulus reduces the magnetostriction value and in this way suppresses the MSM effect. The magneto-thermo-mechanical training of aged alloys destabilizes the martensitic phase, restores the initial magnetostriction value, and promotes the MSM effect.

  10. The Effect of Aerodynamic Heating on Air Penetration by Shaped Charge Jets and Their Particles

    NASA Astrophysics Data System (ADS)

    Backofen, Joseph

    2009-06-01

    The goal of this paper is to present recent work modeling thermal coupling between shaped charge jets and their particles with air while it is being penetrated to form a crater that subsequently collapses back onto the jet. This work complements research published at International Symposia on Ballistics: 1) 1987 - Shaped Charge Jet Aerodynamics, Particulation and Blast Field Modeling; and 2) 2007 - Air Cratering by Eroding Shaped Charge Jets. The current work shows how and when a shaped charge jet's tip and jet particles are softened enough that they can erode in a hydrodynamic manner as modeled in these papers. This paper and its presentation includes models for heat transfer from shocked air as a function of jet velocity as well as heat flow within the jet or particle. The work is supported by an extensive bibliographic search including publications on meteors and ballistic missile re-entry vehicles. The modeling shows that a jet loses its strength to the depth required to justify hydrodynamic erosion when its velocity is above a specific velocity related to the shock properties of air and the jet material's properties. As a result, the portion of a jet's kinetic energy converted at the aerodynamic shock into heating transferred back onto the jet affects the energy deposited into the air through drag and ablation which in turn affect air crater expansion and subsequent collapse back onto the jet and its particles as shown in high-speed photography.

  11. Effects of Interresponse-Time Shaping on Multiple-Schedule Performance

    ERIC Educational Resources Information Center

    Bejarano, Rafael

    2004-01-01

    The experiment reported herein was conducted to determine whether interresponse-time (IRT) shaping can produce different response rates in 2 components of a multiple schedule that are equated with respect to reinforcement rate. To this end, pigeons' key pecks were reinforced with food, if they terminated IRTs that were more extreme (shorter in 1…

  12. Shape effect of torsional resonance mode AFM cantilevers operated in fluids

    NASA Astrophysics Data System (ADS)

    Haochih Liu, Bernard; Chuang, Sheng-Kai; Lowai Huang, Allison

    2014-09-01

    Nanoscale resolution, high scanning rate, and non-destructive measurement are highly desirable attributes for imagining living cells in fluids. Torsional resonance (TR) mode is a promising approach that can satisfy these requirements. In this study, we have fabricated scanning probes with suitable cantilever designs for use in TR mode in fluids, using computer simulation as an aid in the design and fabrication iterations. Several geometrical parameters of cantilevers were considered and simulated for mechanical properties and dynamic characteristics, and selected designs were fabricated for performance evaluation. The influences of design parameters on scan performance were investigated by statistical analysis. Based on this approach, we designed and fabricated optimal cantilevers that can be operated in TR mode in water with high quality (Q) factor (˜60), high resonance frequency (˜240 kHz), and low spring constant (˜0.14 N m-1). Overall, O-shape cantilevers have demonstrated superior Q factors to typical rectangular shape, A-shape and V-shape designs.

  13. Effects of pore-size and shape distributions on diffusion pore imaging by nuclear magnetic resonance

    NASA Astrophysics Data System (ADS)

    Kuder, Tristan Anselm; Laun, Frederik Bernd

    2015-08-01

    In medical imaging and porous media research, NMR diffusion measurements are extensively used to investigate the structure of diffusion restrictions such as cell membranes. Recently, several methods have been proposed to unambiguously determine the shape of arbitrary closed pores or cells filled with an NMR-visible medium by diffusion experiments. The first approach uses a combination of a long and a short diffusion-weighting gradient pulse, while the other techniques employ short gradient pulses only. While the eventual aim of these methods is to determine pore-size and shape distributions, the focus has been so far on identical pores. Thus, the aim of this work is to investigate the ability of these different methods to resolve pore-size and orientation distributions. Simulations were performed comparing the various pore imaging techniques employing different distributions of pore size and orientation and varying timing parameters. The long-narrow gradient profile is most advantageous to investigate pore distributions, because average pore images can be directly obtained. The short-gradient methods suppress larger pores or induce a considerable blurring. Moreover, pore-shape-specific artifacts occur; for example, the central part of a distribution of cylinders may be largely underestimated. Depending on the actual pore distribution, short-gradient methods may nonetheless yield good approximations of the average pore shape. Furthermore, the application of short-gradient methods can be advantageous to differentiate whether pore-size distributions or intensity distributions, e.g., due to surface relaxation, are predominant.

  14. Listening to Families: The Role of Values in Shaping Effective Social Policy.

    ERIC Educational Resources Information Center

    Sylvester, Kathleen

    Noting that the American public's concern for children is shaped by complicated and sometimes conflicting beliefs about family life, this paper examines the policy debates surrounding child care, early childhood development, family leave, and children's health insurance, and analyzes how well advocates have adapted to the new realities. Part 1 of…

  15. Temporal Intraspeech Masking of Plosive Bursts: Effects of Hearing Loss and Frequency Shaping

    ERIC Educational Resources Information Center

    Mackersie, Carol L.

    2007-01-01

    Purpose: The purposes were (a) to compare masking of consonant bursts by adjacent vowels for listeners with and without hearing loss and (b) to determine the extent to which the temporal intraspeech masking can be reduced by a simulated hearing-aid frequency-response shaping. Method: Fourteen adults with sensorineural hearing loss and 10 with…

  16. Martensite aging effect in a Ti{sub 50}Pd{sub 50} high temperature shape memory alloy

    SciTech Connect

    Cai, W.; Otsuka, Kazuhiro

    1999-11-19

    Ti-Pd alloy system is one of the potential high temperature shape memory alloys due to its high martensitic transformation temperatures. Thus, many researches including shape memory characteristics, martensitic transformations and mechanical behavior of the alloys have been done in recent yeas. However, martensite aging effect in the alloy, which is an important issue as to the stability of martensite at high temperature, has not been reported yet. Ti{sub 50}Pd{sub 50} transforms from B2 parent phase to B19 martensite upon cooling, and M{sub s} is 823 K (25) and T{sub m} is 1,673 K (26). Thus M{sub s}/T{sub m} ratio of the alloy is about 0.49, and the alloy may show strong martensite aging effect according to the above proposal. It is now of interest to examine whether the Ti{sub 50}Pd{sub 50} alloy show martensite aging effect. As will be shown, the Ti{sub 50}Pd{sub 50} alloy indeed shows the aging effect, as expected; however, the aging effect of this alloy exhibits a unique feature, which is not found in other shape memory alloys.

  17. Integration of tomato reproductive developmental landmarks and expression profiles, and the effect of SUN on fruit shape

    PubMed Central

    Xiao, Han; Radovich, Cheryll; Welty, Nicholas; Hsu, Jason; Li, Dongmei; Meulia, Tea; van der Knaap, Esther

    2009-01-01

    Background Universally accepted landmark stages are necessary to highlight key events in plant reproductive development and to facilitate comparisons among species. Domestication and selection of tomato resulted in many varieties that differ in fruit shape and size. This diversity is useful to unravel underlying molecular and developmental mechanisms that control organ morphology and patterning. The tomato fruit shape gene SUN controls fruit elongation. The most dramatic effect of SUN on fruit shape occurs after pollination and fertilization although a detailed investigation into the timing of the fruit shape change as well as gene expression profiles during critical developmental stages has not been conducted. Results We provide a description of floral and fruit development in a red-fruited closely related wild relative of tomato, Solanum pimpinellifolium accession LA1589. We use established and propose new floral and fruit landmarks to present a framework for tomato developmental studies. In addition, gene expression profiles of three key stages in floral and fruit development are presented, namely floral buds 10 days before anthesis (floral landmark 7), anthesis-stage flowers (floral landmark 10 and fruit landmark 1), and 5 days post anthesis fruit (fruit landmark 3). To demonstrate the utility of the landmarks, we characterize the tomato shape gene SUN in fruit development. SUN controls fruit shape predominantly after fertilization and its effect reaches a maximum at 8 days post-anthesis coinciding with fruit landmark 4 representing the globular embryo stage of seed development. The expression profiles of the NILs that differ at sun show that only 34 genes were differentially expressed and most of them at a less than 2-fold difference. Conclusion The landmarks for flower and fruit development in tomato were outlined and integrated with the effect of SUN on fruit shape. Although we did not identify many genes differentially expressed in the NILs that differ at

  18. Environmental effects on the shape variation of male ultraviolet patterns in the Brimstone butterfly ( Gonepteryx rhamni, Pieridae, Lepidoptera)

    NASA Astrophysics Data System (ADS)

    Pecháček, Pavel; Stella, David; Keil, Petr; Kleisner, Karel

    2014-12-01

    The males of the Brimstone butterfly ( Gonepteryx rhamni) have ultraviolet pattern on the dorsal surfaces of their wings. Using geometric morphometrics, we have analysed correlations between environmental variables (climate, productivity) and shape variability of the ultraviolet pattern and the forewing in 110 male specimens of G. rhamni collected in the Palaearctic zone. To start with, we subjected the environmental variables to principal component analysis (PCA). The first PCA axis (precipitation, temperature, latitude) significantly correlated with shape variation of the ultraviolet patterns across the Palaearctic. Additionally, we have performed two-block partial least squares (PLS) analysis to assess co-variation between intraspecific shape variation and the variation of 11 environmental variables. The first PLS axis explained 93 % of variability and represented the effect of precipitation, temperature and latitude. Along this axis, we observed a systematic increase in the relative area of ultraviolet colouration with increasing temperature and precipitation and decreasing latitude. We conclude that the shape variation of ultraviolet patterns on the forewings of male Brimstones is correlated with large-scale environmental factors.

  19. A parametric study of effect of forebody shape on flow angularity at Mach 8. [for hypersonic aircraft

    NASA Technical Reports Server (NTRS)

    Johnson, C. B.; Marcum, D. C., Jr.

    1974-01-01

    Flow angularity and static pressure measurements have been made on the lower surface of nine forebody models that simulate the bottom forward surface of a hypersonic aircraft. Measurements were made in an area of the forebody that represents the location of an inlet of a scramjet engine. A parametric variation of the forebody surface investigated the effect of: (1) spanwise curvature; (2) longitudinal curvature; and (3) planform shape on both flow angularity and static pressure distribution. Results of each of the three parametric variations of geometry were compared to those for the same flat delta forebody. Spanwise curvature results showed that a concave shape and the flat delta had the lowest flow angularity and lowest rate of increase in flow angularity with angle of attack. Longitudinal curvature results showed a convex surface to give the better flow at the higher angles of attack. The better of the two planform shapes tested was a convex elliptical shape. Limited flow field calculations were made at angles of attack using a three dimensional, method-of-characteristics program. In general, at all angles of attack there was agreement between data and theory.

  20. Do studies reporting 'U'-shaped serum 25-hydroxyvitamin D-health outcome relationships reflect adverse effects?

    PubMed

    Grant, William B; Karras, Spyridon N; Bischoff-Ferrari, Heike A; Annweiler, Cedric; Boucher, Barbara J; Juzeniene, Asta; Garland, Cedric F; Holick, Michael F

    2016-01-01

    Several reports describe U-shaped 25-hydroxyvitamin D [25(OH)D] concentration-health outcomes, including musculo-skeletal disorders such as falls and fractures, several cancers, cardiovascular disease (CVD), cognitive function, all-cause mortality rates, birth outcomes, allergic reactions, frailty, and some other disorders. This paper reviews reports of U-shaped outcome associations with vitamin D status for evidence of underlying pathophysiological processes, or of confounding, finding that some U-shaped associations appear to be biologically meaningful, but that many could well reflect confounding by factors such as lifestyle, or hypovitaminosis D-related disease onset being masked by self-supplementation that was begun too late to correct developing health problems but before baseline vitamin D status assessment. However, the various U-shaped associations for allergic reactions may be due to vitamin D modulation of the phenotype of the immune response, shifting the Th1-Th2 balance toward Th2 formation. For prostate cancer, there seems to be little effect of 25(OH)D concentration on incidence; however, there is an inverse correlation between 25(OH)D concentration and mortality rates. Future observational studies, and randomized controlled trial data analyses, should include adjustment for data collected on prior long-term vitamin D supplementation and solar UVB exposure, as well as other potential confounders. PMID:27489574

  1. Do studies reporting ‘U’-shaped serum 25-hydroxyvitamin D–health outcome relationships reflect adverse effects?

    PubMed Central

    Grant, William B.; Karras, Spyridon N.; Bischoff-Ferrari, Heike A.; Annweiler, Cedric; Boucher, Barbara J.; Juzeniene, Asta; Garland, Cedric F.; Holick, Michael F.

    2016-01-01

    ABSTRACT Several reports describe U-shaped 25-hydroxyvitamin D [25(OH)D] concentration–health outcomes, including musculo-skeletal disorders such as falls and fractures, several cancers, cardiovascular disease (CVD), cognitive function, all-cause mortality rates, birth outcomes, allergic reactions, frailty, and some other disorders. This paper reviews reports of U-shaped outcome associations with vitamin D status for evidence of underlying pathophysiological processes, or of confounding, finding that some U-shaped associations appear to be biologically meaningful, but that many could well reflect confounding by factors such as lifestyle, or hypovitaminosis D-related disease onset being masked by self-supplementation that was begun too late to correct developing health problems but before baseline vitamin D status assessment. However, the various U-shaped associations for allergic reactions may be due to vitamin D modulation of the phenotype of the immune response, shifting the Th1-Th2 balance toward Th2 formation. For prostate cancer, there seems to be little effect of 25(OH)D concentration on incidence; however, there is an inverse correlation between 25(OH)D concentration and mortality rates. Future observational studies, and randomized controlled trial data analyses, should include adjustment for data collected on prior long-term vitamin D supplementation and solar UVB exposure, as well as other potential confounders. PMID:27489574

  2. Bioaccumulation and effects of different-shaped copper oxide nanoparticles in the deposit-feeding snail Potamopyrgus antipodarum.

    PubMed

    Ramskov, Tina; Selck, Henriette; Banta, Gary; Misra, Superb K; Berhanu, Deborah; Valsami-Jones, Eugenia; Forbes, Valery E

    2014-09-01

    Copper oxide (CuO) nanoparticles (NPs) are among the most widely used engineered NPs and are thus likely to end up in the environment, predominantly in sediments. Copper oxide NPs have been found to be toxic to a variety of (mainly pelagic) organisms, but to differing degrees. In the present study, the influence of CuO NP shape on bioavailability and toxicity in the sediment-dwelling freshwater gastropod Potamopyrgus antipodarum was examined. In 2 separate studies, snails were exposed to either clean sediment or sediment spiked with either aqueous Cu or CuO NPs of different shapes (rods, spheres, or platelets) at 240 µg Cu/g dry weight of sediment (nominal). In neither of the studies was survival found to be related to Cu form (i.e., free ion vs particle) or shape, whereas snail growth was severely influenced by both form and shape. Reproduction was affected (by CuO NP spheres and aqueous Cu) only when estimated as the total number (live plus dead) of juveniles produced per snail per week. Both the aqueous and particulate forms of Cu were available for uptake by snails when mixed into sediment. However, Cu body burden was not directly related to observed effects. The present study stresses the need for both a better understanding of uptake mechanisms and internal distribution pathways of NPs and an assessment of long-term consequences of NP exposure.

  3. Enhanced magnetic hysteresis in Ni-Mn-Ga single crystal and its influence on magnetic shape memory effect

    SciTech Connect

    Heczko, O. Drahokoupil, J.; Straka, L.

    2015-05-07

    Enhanced magnetic hysteresis due to boron doping in combination with magnetic shape memory effect in Ni-Mn-Ga single crystal results in new interesting functionality of magnetic shape memory (MSM) alloys such as mechanical demagnetization. In Ni{sub 50.0}Mn{sub 28.5}Ga{sub 21.5} single crystal, the boron doping increased magnetic coercivity from few Oe to 270 Oe while not affecting the transformation behavior and 10 M martensite structure. However, the magnetic field needed for MSM effect also increased in doped sample. The magnetic behavior is compared to undoped single crystal of similar composition. The evidence from the X-ray diffraction, magnetic domain structure, magnetization loops, and temperature evolution of the magnetic coercivity points out that the enhanced hysteresis is caused by stress-induced anisotropy.

  4. Infrared thermography videos of the elastocaloric effect for shape memory alloys NiTi and Ni2FeGa

    PubMed Central

    Pataky, Garrett J.; Ertekin, Elif; Sehitoglu, Huseyin

    2015-01-01

    Infrared thermogrpahy was utilized to record the temperature change during tensile loading cycles of two shape memory alloy single crystals with pseudoelastic behavior. During unloading, a giant temperature drop was measured in the gage section due to the elastocaloric effect. This data article provides a video of a [001] oriented Ni2FeGa single crystal, including the corresponding stress–strain curve, shows the temperature drop over one cycle. The second video of a [148] oriented NiTi single crystal depicts the repeatability of the elastocaloric effect by showing two consecutive cycles. The videos are supplied in this paper. For further analysis and enhanced discussion of large temperature change in shape memory alloys, see Pataky et al. [1] PMID:26380838

  5. Infrared thermography videos of the elastocaloric effect for shape memory alloys NiTi and Ni2FeGa.

    PubMed

    Pataky, Garrett J; Ertekin, Elif; Sehitoglu, Huseyin

    2015-12-01

    Infrared thermogrpahy was utilized to record the temperature change during tensile loading cycles of two shape memory alloy single crystals with pseudoelastic behavior. During unloading, a giant temperature drop was measured in the gage section due to the elastocaloric effect. This data article provides a video of a [001] oriented Ni2FeGa single crystal, including the corresponding stress-strain curve, shows the temperature drop over one cycle. The second video of a [148] oriented NiTi single crystal depicts the repeatability of the elastocaloric effect by showing two consecutive cycles. The videos are supplied in this paper. For further analysis and enhanced discussion of large temperature change in shape memory alloys, see Pataky et al. [1].

  6. Effect of porcelain shape for strain behavior of strengthened porcelain in impact test

    NASA Astrophysics Data System (ADS)

    Hayashi, Akemi; Kurachi, Kazumasa; Mizuno, Masatoshi; Ota, Toshitaka

    2011-10-01

    Four types of strengthened porcelains were evaluated by an impact examination machine based on ASTM C368-88. The waveform of strain developed on impact was measured by a strain gauge pasted on the inside surface and the outside surface, vertical and horizontal direction of porcelain. In minute scales, procelain deformed into an oval shape as a whole by an impact onto the rim, where the higher tensile strain occurred in the horizontal direction on the inside surface of porcelain. The maximum tensile strain occurred at the impact point. The waveform of strain, that showed two remarkable peaks, was greatly affected by porcelain shape. In addition it was more or less affected by measurement conditions such as impact energy, weight or speed of hammer, weight for holding, and position of backstops.

  7. Effect of Molecular Structure on Rheological Behavior of Nearly Monodisperse H-Shaped Polybutadienes

    NASA Astrophysics Data System (ADS)

    Li, Si Wan; Park, Hee Eon; Dealy, John M.; Maric, Milan; Rahman, M. Shahinur; Mays, Jimmy; Chen, Xue; Larson, Ronald G.

    2008-07-01

    Nearly monodisperse H-shaped Polybutadiene (PBD) with high 1,4 microstructure (˜90%) were synthesized by a novel synthesis strategy of living anionic polymerization. Linear viscoelastic properties over a broad frequency range of a linear PBD and an H-shaped PBD were studied by frequency sweep and creep/recovery experiments. The dynamic moduli of all samples were found to obey the time-temperature superposition. Primary attention was given to properties that depend on chain microstructure: the plateau modulus QN0, the steady state compliance Js0, and the horizontal and vertical temperature shift factors for the frequency and modulus, aT and bT. The data are compared with the predictions of a hierarchical model developed by Larson.

  8. Effects of molecular noise on bistable protein distributions in rod-shaped bacteria

    PubMed Central

    Wettmann, L.; Bonny, M.; Kruse, K.

    2014-01-01

    The distributions of many proteins in rod-shaped bacteria are far from homogeneous. Often they accumulate at the cell poles or in the cell centre. At the same time, the copy number of proteins in a single cell is relatively small making the patterns noisy. To explore limits to protein patterns due to molecular noise, we studied a generic mechanism for spontaneous polar protein assemblies in rod-shaped bacteria, which are based on cooperative binding of proteins to the cytoplasmic membrane. For mono-polar assemblies, we find that the switching time between the two poles increases exponentially with the cell length and with the protein number. This feature could be beneficial to organelle maintenance in ageing bacteria. PMID:25485085

  9. The effect of cross linker concentration in the physical properties of shape memory gel

    NASA Astrophysics Data System (ADS)

    Kabir, M. Hasnat; Ahmed, Kumkum; Gong, Jin; Furukawa, Hidemitsu

    2015-04-01

    The shape memory hydrogels were synthesized and studied the physical properties. The gels were made by a hydrophilic monomer named N, N-dimethyl acrylamide (DMAAm) and a hydrophobic monomer named stearyl acrylate (SA). The water-swollen hydrogels show well transparency and shape memory property while gels absorb large water content. The properties were characterized by varying the cross-link concentration, whereas the concentration of other chemical components was remained constant. In this study, the DMAAm and the SA ratio was 3:1 to make one mole solution. It is observed that the swelling ratio slightly depends on the cross-link concentration at certain amount. However, mechanical properties strongly depend on the cross-link concentration. Thermal properties were investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). DSC spactra of dried samples exhibits complex crystalline nature, while swollen samples show homogeneous crystallinity. A well thermal stability is observed regard less of cross-link concentration.

  10. Kinetic depth effect and optic flow--I. 3D shape from Fourier motion.

    PubMed

    Dosher, B A; Landy, M S; Sperling, G

    1989-01-01

    Fifty-three different 3D shapes were defined by sequences of 2D views (frames) of dots on a rotating 3D surface. (1) Subjects' accuracy of shape identifications dropped from over 90% to less than 10% when either the polarity of the stimulus dots was alternated from light-on-gray to dark-on-gray on successive frames or when neutral gray interframe intervals were interposed. Both manipulations interfere with motion extraction by spatio-temporal (Fourier) and gradient first-order detectors. Second-order (non-Fourier) detectors that use full-wave rectification are unaffected by alternating-polarity but disrupted by interposed gray frames. (2) To equate the accuracy of two-alternative forced-choice (2AFC) planar direction-of-motion discrimination in standard and polarity-alternated stimuli, standard contrast was reduced. 3D shape discrimination survived contrast reduction in standard stimuli whereas it failed completely with polarity-alternation even at full contrast. (3) When individual dots were permitted to remain in the image sequence for only two frames, performance showed little loss compared to standard displays where individual dots had an expected lifetime of 20 frames, showing that 3D shape identification does not require continuity of stimulus tokens. (4) Performance in all discrimination tasks is predicted (up to a monotone transformation) by considering the quality of first-order information (as given by a simple computation on Fourier power) and the number of locations at which motion information is required. Perceptual first-order analysis of optic flow is the primary substrate for structure-from-motion computations in random dot displays because only it offers sufficient quality of perceptual motion at a sufficient number of locations.

  11. Size effects in the magnetic anisotropy of embedded cobalt nanoparticles: from shape to surface

    PubMed Central

    Oyarzún, Simón; Tamion, Alexandre; Tournus, Florent; Dupuis, Véronique; Hillenkamp, Matthias

    2015-01-01

    Strong size-dependent variations of the magnetic anisotropy of embedded cobalt clusters are evidenced quantitatively by combining magnetic experiments and advanced data treatment. The obtained values are discussed in the frame of two theoretical models that demonstrate the decisive role of the shape in larger nanoparticles and the predominant role of the surface anisotropy in clusters below 3 nm diameter. PMID:26439626

  12. Evidence for cluster shape effects on the kinetic energy spectrum in thermionic emission.

    PubMed

    Calvo, F; Lépine, F; Baguenard, B; Pagliarulo, F; Concina, B; Bordas, C; Parneix, P

    2007-11-28

    Experimental kinetic energy release distributions obtained for the thermionic emission from C(n) (-) clusters, 10< or =n< or =20, exhibit significant non-Boltzmann variations. Using phase space theory, these different features are analyzed and interpreted as the consequence of contrasting shapes in the daughter clusters; linear and nonlinear isomers have clearly distinct signatures. These results provide a novel indirect structural probe for atomic clusters associated with their thermionic emission spectra.

  13. Effects of surface reflectance and 3D shape on perceived rotation axis.

    PubMed

    Doerschner, Katja; Yilmaz, Ozgur; Kucukoglu, Gizem; Fleming, Roland W

    2013-09-10

    Surface specularity distorts the optic flow generated by a moving object in a way that provides important cues for identifying surface material properties (Doerschner, Fleming et al., 2011). Here we show that specular flow can also affect the perceived rotation axis of objects. In three experiments, we investigate how three-dimensional shape and surface material interact to affect the perceived rotation axis of unfamiliar irregularly shaped and isotropic objects. We analyze observers' patterns of errors in a rotation axis estimation task under four surface material conditions: shiny, matte textured, matte untextured, and silhouette. In addition to the expected large perceptual errors in the silhouette condition, we find that the patterns of errors for the other three material conditions differ from each other and across shape category, yielding the largest differences in error magnitude between shiny and matte, textured isotropic objects. Rotation axis estimation is a crucial implicit computational step to perceive structure from motion; therefore, we test whether a structure from a motion-based model can predict the perceived rotation axis for shiny and matte, textured objects. Our model's predictions closely follow observers' data, even yielding the same reflectance-specific perceptual errors. Unlike previous work (Caudek & Domini, 1998), our model does not rely on the assumption of affine image transformations; however, a limitation of our approach is its reliance on projected correspondence, thus having difficulty in accounting for the perceived rotation axis of smooth shaded objects and silhouettes. In general, our findings are in line with earlier research that demonstrated that shape from motion can be extracted based on several different types of optical deformation (Koenderink & Van Doorn, 1976; Norman & Todd, 1994; Norman, Todd, & Orban, 2004; Pollick, Nishida, Koike, & Kawato, 1994; Todd, 1985).

  14. Effects of chitosan on the alignment, morphology and shape of calcite crystals nucleating under Langmuir monolayers

    SciTech Connect

    Kim, Kyungil; Uysal, Ahmet; Kewalramani, Sumit; Stripe, Benjamin; Dutta, Pulak

    2009-04-22

    The growth of calcium carbonate crystals under Langmuir monolayers was investigated in the presence of chitosan, a soluble derivative of chitin added to the subphase to better simulate the polyelectrolyte-containing in vivo environment. Chitosan causes distinct concentration-dependent changes in the orientation, shape and morphology of the calcite crystals nucleating under acid and sulfate monolayers. Our results suggest that polyelectrolytes may play essential roles in controlling the growth of biogenic calcite crystals.

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

    SciTech Connect

    Tang, Jau; Dikshit, S.N.; Norris, J.R. |

    1997-08-01

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

  16. DDA Computations of Porous Aggregates with Forsterite Crystals: Effects of Crystal Shape and Crystal Mass Fraction

    NASA Technical Reports Server (NTRS)

    Wooden, Diane H.; Lindsay, Sean S.; Harker, David; Woodward, Charles; Kelley, Michael S.; Kolokolova, Ludmilla

    2015-01-01

    Porous aggregate grains are commonly found in cometary dust samples and are needed to model cometary IR spectral energy distributions (SEDs). Models for thermal emissions from comets require two forms of silicates: amorphous and crystalline. The dominant crystal resonances observed in comet SEDs are from Forsterite (Mg2SiO4). The mass fractions that are crystalline span a large range from 0.0 < or = fcrystal < or = 0.74. Radial transport models that predict the enrichment of the outer disk (>25 AU at 1E6 yr) by inner disk materials (crystals) are challenged to yield the highend-range of cometary crystal mass fractions. However, in current thermal models, Forsterite crystals are not incorporated into larger aggregate grains but instead only are considered as discrete crystals. A complicating factor is that Forsterite crystals with rectangular shapes better fit the observed spectral resonances in wavelength (11.0-11.15 microns, 16, 19, 23.5, 27, and 33 microns), feature asymmetry and relative height (Lindley et al. 2013) than spherically or elliptically shaped crystals. We present DDA-DDSCAT computations of IR absorptivities (Qabs) of 3 micron-radii porous aggregates with 0.13 < or = fcrystal < or = 0.35 and with polyhedral-shaped Forsterite crystals. We can produce crystal resonances with similar appearance to the observed resonances of comet Hale- Bopp. Also, a lower mass fraction of crystals in aggregates can produce the same spectral contrast as a higher mass fraction of discrete crystals; the 11micron and 23 micron crystalline resonances appear amplified when crystals are incorporated into aggregates composed otherwise of spherically shaped amorphous Fe-Mg olivines and pyroxenes. We show that the optical properties of a porous aggregate is not linear combination of its monomers, so aggregates need to be computed. We discuss the consequence of lowering comet crystal mass fractions by modeling IR SEDs with aggregates with crystals, and the implications for radial

  17. Serial position effects in the identification of letters, digits, symbols, and shapes in peripheral vision.

    PubMed

    Chanceaux, Myriam; Grainger, Jonathan

    2012-10-01

    Three experiments measured serial position functions for character-in-string identification in peripheral vision. In Experiment 1, random strings of five letters (e.g., P F H T M) or five symbols (e.g., λ Б Þ Ψ ¥) were briefly presented to the left or to the right of fixation, and identification accuracy was measured at each position in the string using a post-cued two-alternative forced-choice task (e.g., was there a T or a B at the 4th position). In Experiment 2 the performance to letter stimuli was compared with familiar two-dimensional shapes (e.g., square, triangle, circle), and in Experiment 3 we compared digit strings (e.g., 6 3 7 9 2) with a set of keyboard symbols (e.g., % § @ < ?). Eye-movements were monitored to ensure central fixation. The results revealed a triple interaction between the nature of the stimulus (letters/digits vs. symbols/shapes), eccentricity, and visual field. In all experiments this interaction reflected a selective left visual field advantage for letter or digit stimuli compared with symbol or shape stimuli for targets presented at the greatest eccentricity. The results are in line with the predictions of the modified receptive field hypothesis proposed by Tydgat and Grainger (2009), and the predictions of the SERIOL2 model of letter string encoding. PMID:22964055

  18. Using shape effects to target antibody-coated nanoparticles to lung and brain endothelium.

    PubMed

    Kolhar, Poornima; Anselmo, Aaron C; Gupta, Vivek; Pant, Kapil; Prabhakarpandian, Balabhaskar; Ruoslahti, Erkki; Mitragotri, Samir

    2013-06-25

    Vascular endothelium offers a variety of therapeutic targets for the treatment of cancer, cardiovascular diseases, inflammation, and oxidative stress. Significant research has been focused on developing agents to target the endothelium in diseased tissues. This includes identification of antibodies against adhesion molecules and neovascular expression markers or peptides discovered using phage display. Such targeting molecules also have been used to deliver nanoparticles to the endothelium of the diseased tissue. Here we report, based on in vitro and in vivo studies, that the specificity of endothelial targeting can be enhanced further by engineering the shape of ligand-displaying nanoparticles. In vitro studies performed using microfluidic systems that mimic the vasculature (synthetic microvascular networks) showed that rod-shaped nanoparticles exhibit higher specific and lower nonspecific accumulation under flow at the target compared with their spherical counterparts. Mathematical modeling of particle-surface interactions suggests that the higher avidity and specificity of nanorods originate from the balance of polyvalent interactions that favor adhesion and entropic losses as well as shear-induced detachment that reduce binding. In vivo experiments in mice confirmed that shape-induced enhancement of vascular targeting is also observed under physiological conditions in lungs and brain for nanoparticles displaying anti-intracellular adhesion molecule 1 and anti-transferrin receptor antibodies.

  19. Growth of Au nanoparticle films and the effect of nanoparticle shape on plasmon peak wavelength

    SciTech Connect

    Horikoshi, S. Matsumoto, N.; Kato, T.; Omata, Y.

    2014-05-21

    Metal nanoparticles (NPs) exhibit localized surface plasmon resonance (LSPR) and thus have potential for use in a wide range of applications. A facile technique for the preparation of NP films using an electron-cyclotron-resonance plasma sputtering method without a dewetting process is described. Field emission scanning electron microscopy (FE-SEM) observations revealed that the Au NPs grew independently as island-like particles during the first stage of sputtering and then coalesced with one another as sputtering time increased to ultimately form a continuous film. A plasmon absorption peak was observed via optical measurement of absorption efficiency. The LSPR peak shifted toward longer wavelengths (red shift) with an increase in sputtering time. The cause of this plasmon peak shift was theoretically investigated using the finite-difference time-domain calculation method. A realistic statistical distribution of the particle shapes based on FE-SEM observations was applied for the analysis, which has not been previously reported. It was determined that the change in the shape of the NPs from spheroidal to oval or slender due to coalescence with neighbouring NPs caused the LSPR peak shift. These results may enable the design of LSPR devices by controlling the characteristics of the nanoparticles, such as their size, shape, number density, and coverage.

  20. Effects of chamber shape and fiber orientation on relations between fiber dynamics and chamber dynamics.

    PubMed

    Regen, D M

    1988-01-01

    The function of a chamber depends on its hydrodynamic properties: isometric pressures it can exert in the operating range of distensions, compliances in the operating range of distensions, and wall-displacement resistances in the operating range of distensions. Wall-displacement resistance is the departure of pressure from isometric pressure relative to rate of cavity-volume change. The dependence of pressure on average stress and wall/cavity volume ratio is indifferent to chamber shape, which suggests that the volume-based compliance-elastance and resistance-viscosity equations would be only moderately shape dependent. The present study shows that this supposition is correct. If the wall is thin, these relations are shape indifferent. At higher wall/cavity volume ratio, cylindricity increases slightly the P-V-curve slope relative to elastance and either increases slightly or does not affect resistance relative to viscosity. The compliance-elastance and resistance-viscosity relations also depend only slightly on fiber orientation. Therefore, with the sphere equations, one can account accurately for normal and abnormal function of a prolate spheroid in terms of volume dimensions of the wall and apparent average fiber properties.

  1. Icing flight research: Aerodynamic effects of ice and ice shape documentation with stereo photography

    NASA Technical Reports Server (NTRS)

    Mikkelsen, K. L.; Mcknight, R. C.; Ranaudo, R. J.; Perkins, P. J., Jr.

    1985-01-01

    Aircraft icing flight research was performed in natural icing conditions. A data base consisting of icing cloud measurements, ice shapes, and aerodynamic measurements is being developed. During research icing encounters the icing cloud was continuously measured. After the encounter, the ice accretion shapes on the wing were documented with a stereo camera system. The increase in wing section drag was measured with a wake survey probe. The overall aircraft performance loss in terms of lift and drag coefficient changes was obtained by steady level speed/power measurements. Selective deicing of the airframe components was performed to determine their contributions to the total drag increase. Engine out capability in terms of power available was analyzed for the iced aircraft. It was shown that the stereo photography system can be used to document ice shapes in flight and that the wake survey probe can measure increases in wing section drag caused by ice. On one flight, the wing section drag coefficient (c sub d) increased approximately 120 percent over the uniced baseline at an aircraft angle of attack of 6 deg. On another flight, the aircraft darg coefficient (c sub d) increased by 75 percent over the uniced baseline at an aircraft lift coefficient (C sub d) of 0.5.

  2. Triple-shape effect in polymer-based composites by cleverly matching geometry of active component with heating method.

    PubMed

    Razzaq, M Y; Behl, M; Kratz, K; Lendlein, A

    2013-10-11

    A triple-shape effect is created for a segmented device consisting of an active component encapsulated in a highly flexible polymer network. Segments with the same composition but different interface areas can be recovered independently either at specific field strengths (Hsw ) during inductive heating, at a specific time during environmentally heating, or at different airflow during inductive heating at constant H. Herein the type of heating method regulates the sequence order.

  3. A numerical investigation of grain shape and crystallographic texture effects on the plastic strain localization in friction stir weld zones

    NASA Astrophysics Data System (ADS)

    Romanova, V.; Balokhonov, R.; Batukhtina, E.; Shakhidjanov, V.

    2015-10-01

    Crystal plasticity approaches were adopted to build models accounting for the microstructure and texture observed in different friction stir weld zones. To this end, a numerical investigation of crystallographic texture and grain shape effects on the plastic strain localization in a friction stir weld of an aluminum-base alloy was performed. The presence of texture was found to give rise to pronounced mesoscale plastic strain localization.

  4. Hypocycloid-shaped hollow-core photonic crystal fiber Part II: cladding effect on confinement and bend loss.

    PubMed

    Alharbi, M; Bradley, T; Debord, B; Fourcade-Dutin, C; Ghosh, D; Vincetti, L; Gérôme, F; Benabid, F

    2013-11-18

    We report on numerical and experimental studies on the influence of cladding ring-number on the confinement and bend loss in hypocycloid-shaped Kagome hollow core photonic crystal fiber. The results show that beyond the second ring, the ring number has a minor effect on confinement loss whereas the bend loss is strongly reduced with the ring-number increase. Finally, the results show that the increase in the cladding ring-number improves the modal content of the fiber.

  5. The VIMOS Public Extragalactic Redshift Survey (VIPERS). Environmental effects shaping the galaxy stellar mass function

    NASA Astrophysics Data System (ADS)

    Davidzon, I.; Cucciati, O.; Bolzonella, M.; De Lucia, G.; Zamorani, G.; Arnouts, S.; Moutard, T.; Ilbert, O.; Garilli, B.; Scodeggio, M.; Guzzo, L.; Abbas, U.; Adami, C.; Bel, J.; Bottini, D.; Branchini, E.; Cappi, A.; Coupon, J.; de la Torre, S.; Di Porto, C.; Fritz, A.; Franzetti, P.; Fumana, M.; Granett, B. R.; Guennou, L.; Iovino, A.; Krywult, J.; Le Brun, V.; Le Fèvre, O.; Maccagni, D.; Małek, K.; Marulli, F.; McCracken, H. J.; Mellier, Y.; Moscardini, L.; Polletta, M.; Pollo, A.; Tasca, L. A. M.; Tojeiro, R.; Vergani, D.; Zanichelli, A.

    2016-02-01

    We exploit the first public data release of VIPERS to investigate environmental effects in the evolution of galaxies between z ~ 0.5 and 0.9. The large number of spectroscopic redshifts (more than 50 000) over an area of about 10 deg2 provides a galaxy sample with high statistical power. The accurate redshift measurements (σz = 0.00047(1 + zspec)) allow us to robustly isolate galaxies living in the lowest and highest density environments (δ< 0.7 and δ> 4, respectively) as defined in terms of spatial 3D density contrast δ. We estimate the stellar mass function of galaxies residing in these two environments and constrain the high-mass end (ℳ ≳ 1011 ℳ⊙) with unprecedented precision. We find that the galaxy stellar mass function in the densest regions has a different shape than was measured at low densities, with an enhancement of massive galaxies and a hint of a flatter (less negative) slope at z< 0.8. We normalise each mass function to the comoving volume occupied by the corresponding environment and relate estimates from different redshift bins. We observe an evolution of the stellar mass function of VIPERS galaxies in high densities, while the low-density one is nearly constant. We compare these results to semi-analytical models and find consistent environmental signatures in the simulated stellar mass functions. We discuss how the halo mass function and fraction of central/satellite galaxies depend on the environments considered, making intrinsic and environmental properties of galaxies physically coupled, hence difficult to disentangle. The evolution of our low-density regions is described well by the formalism introduced by Peng et al. (2010, ApJ, 721, 193), and is consistent with the idea that galaxies become progressively passive because of internal physical processes. The same formalism could also describe the evolution of the mass function in the high density regions, but only if a significant contribution from dry mergers is considered. Based on

  6. The effects of ice crystal shape on the evolution of optically thin cirrus clouds in the tropics

    NASA Astrophysics Data System (ADS)

    Russotto, Rick

    Thin cirrus clouds in the tropical tropopause layer (TTL) play potentially important roles in Earth's radiation budget and in the transport of water into the stratosphere. Radiative heating of these clouds results in mesoscale circulations that maintain them against sedimentation and redistribute water vapor. In this study, the System for Atmospheric Modeling (SAM) cloud-resolving model is modified in order to calculate the fall speeds, growth rates, and radiative absorption coefficients of non-spherical ice crystals. This extended model is used in simulations that aim to constrain the effects of ice crystal shape on the time evolution of thin cirrus clouds and to identify the physical processes responsible. Model runs assuming spheroidal crystals result in a higher center of cloud ice mass than in the control, spherical case, which is roughly 60% due to a reduction in fall speeds and 40% due to stronger updrafts caused by stronger radiative heating. Other effects of ice crystal shape on the cloud evolution include faster growth and sublimation in supersaturated and subsaturated environments, respectively, and local temperature increases caused by diabatic heating. Effects of ice crystal shape on the total and mean ice crystal masses are within about 10% but do not appear to be entirely negligible. Comparisons of modeled ice crystal size distributions with recent airborne observations of TTL cirrus show that incorporating non-spherical shape has the potential to bring the model closer to observations. It is hoped that this work will eventually lead towards a more realistic physical representation of thin tropical cirrus in global climate models.

  7. The sex-limited effects of mutations in the EGFR and TGF-β signaling pathways on shape and size sexual dimorphism and allometry in the Drosophila wing.

    PubMed

    Testa, Nicholas D; Dworkin, Ian

    2016-06-01

    Much of the morphological diversity in nature-including among sexes within a species-is a direct consequence of variation in size and shape. However, disentangling variation in sexual dimorphism for both shape (SShD), size (SSD), and their relationship with one another remains complex. Understanding how genetic variation influences both size and shape together, and how this in turn influences SSD and SShD, is challenging. In this study, we utilize Drosophila wing size and shape as a model system to investigate how mutations influence size and shape as modulated by sex. Previous work has demonstrated that mutations in epidermal growth factor receptor (EGFR) and transforming growth factor-β (TGF-β) signaling components can influence both wing size and shape. In this study, we re-analyze this data to specifically address how they impact the relationship between size and shape in a sex-specific manner, in turn altering the pattern of sexual dimorphism. While most mutations influence shape overall, only a subset have a genotypic specific effect that influences SShD. Furthermore, while we observe sex-specific patterns of allometric shape variation, the effects of most mutations on allometry tend to be small. We discuss this within the context of using mutational analysis to understand sexual size and shape dimorphism.

  8. The sex-limited effects of mutations in the EGFR and TGF-β signaling pathways on shape and size sexual dimorphism and allometry in the Drosophila wing.

    PubMed

    Testa, Nicholas D; Dworkin, Ian

    2016-06-01

    Much of the morphological diversity in nature-including among sexes within a species-is a direct consequence of variation in size and shape. However, disentangling variation in sexual dimorphism for both shape (SShD), size (SSD), and their relationship with one another remains complex. Understanding how genetic variation influences both size and shape together, and how this in turn influences SSD and SShD, is challenging. In this study, we utilize Drosophila wing size and shape as a model system to investigate how mutations influence size and shape as modulated by sex. Previous work has demonstrated that mutations in epidermal growth factor receptor (EGFR) and transforming growth factor-β (TGF-β) signaling components can influence both wing size and shape. In this study, we re-analyze this data to specifically address how they impact the relationship between size and shape in a sex-specific manner, in turn altering the pattern of sexual dimorphism. While most mutations influence shape overall, only a subset have a genotypic specific effect that influences SShD. Furthermore, while we observe sex-specific patterns of allometric shape variation, the effects of most mutations on allometry tend to be small. We discuss this within the context of using mutational analysis to understand sexual size and shape dimorphism. PMID:27038022

  9. Shape and surface chemistry effects on the cytotoxicity and cellular uptake of metallic nanorods and nanospheres.

    PubMed

    Favi, Pelagie Marlene; Valencia, Mariana Morales; Elliott, Paul Robert; Restrepo, Alejandro; Gao, Ming; Huang, Hanchen; Pavon, Juan Jose; Webster, Thomas Jay

    2015-12-01

    Metallic nanoparticles (such as gold and silver) have been intensely studied for wound healing applications due to their ability to be easily functionalized, possess antibacterial properties, and their strong potential for targeted drug release. In this study, rod-shaped silver nanorods (AgNRs) and gold nanorods (AuNRs) were fabricated by electron beam physical vapor deposition (EBPVD), and their cytotoxicity toward human skin fibroblasts were assessed and compared to sphere-shaped silver nanospheres (AgNSs) and gold nanospheres (AuNSs). Results showed that the 39.94 nm AgNSs showed the greatest toxicity with fibroblast cells followed by the 61.06 nm AuNSs, ∼556 nm × 47 nm (11.8:1 aspect ratio) AgNRs, and the ∼534 nm × 65 nm (8.2:1 aspect ratio) AuNRs demonstrated the least amount of toxicity. The calculated IC50 (50% inhibitory concentration) value for the AgNRs exposed to fibroblasts was greater after 4 days of exposure (387.3 μg mL(-1)) compared to the AgNSs and AuNSs (4.3 and 23.4 μg mL(-1), respectively), indicating that these spherical metallic nanoparticles displayed a greater toxicity to fibroblast cells. The IC50 value could not be measured for the AuNRs due to an incomplete dose response curve. The reduced cell toxicity with the presently developed rod-shaped nanoparticles suggests that they may be promising materials for use in numerous biomedical applications.

  10. Shape and surface chemistry effects on the cytotoxicity and cellular uptake of metallic nanorods and nanospheres.

    PubMed

    Favi, Pelagie Marlene; Valencia, Mariana Morales; Elliott, Paul Robert; Restrepo, Alejandro; Gao, Ming; Huang, Hanchen; Pavon, Juan Jose; Webster, Thomas Jay

    2015-12-01

    Metallic nanoparticles (such as gold and silver) have been intensely studied for wound healing applications due to their ability to be easily functionalized, possess antibacterial properties, and their strong potential for targeted drug release. In this study, rod-shaped silver nanorods (AgNRs) and gold nanorods (AuNRs) were fabricated by electron beam physical vapor deposition (EBPVD), and their cytotoxicity toward human skin fibroblasts were assessed and compared to sphere-shaped silver nanospheres (AgNSs) and gold nanospheres (AuNSs). Results showed that the 39.94 nm AgNSs showed the greatest toxicity with fibroblast cells followed by the 61.06 nm AuNSs, ∼556 nm × 47 nm (11.8:1 aspect ratio) AgNRs, and the ∼534 nm × 65 nm (8.2:1 aspect ratio) AuNRs demonstrated the least amount of toxicity. The calculated IC50 (50% inhibitory concentration) value for the AgNRs exposed to fibroblasts was greater after 4 days of exposure (387.3 μg mL(-1)) compared to the AgNSs and AuNSs (4.3 and 23.4 μg mL(-1), respectively), indicating that these spherical metallic nanoparticles displayed a greater toxicity to fibroblast cells. The IC50 value could not be measured for the AuNRs due to an incomplete dose response curve. The reduced cell toxicity with the presently developed rod-shaped nanoparticles suggests that they may be promising materials for use in numerous biomedical applications. PMID:26053238

  11. The effects of the J3-harmonic (pear shape) on the orbits of a satellite.

    NASA Astrophysics Data System (ADS)

    Broucke, R. A.

    The object of the present article is a detailed numerical investigation of the perturbation on the orbit of a satellite, caused by the pear-shape or J3-harmonic of the central body. The author uses in this study concepts from the general theory of periodic orbits, such as Poincaré surfaces of section, stability theory, characteristic exponents and bifurcations. He finds several new families of periodic orbits in the J3-problem. The orbital characteristics of five principal families are decribed in detail. The orbits of these families are periodic only in the rotating meridian plane which contains the satellite. They are not symmetric with respect to the equator.

  12. Effects of interface treatment on the fatigue behaviour of shape memory alloy reinforced polymer composites

    NASA Astrophysics Data System (ADS)

    Hiremath, S. R.; Harish, K.; Vasireddi, Ramakrishna; Benal, M. M.; Mahapatra, D. R.

    2015-04-01

    Interfacial properties of Shape Memory Alloy (SMA) reinforced polymer matrix composites can be enhanced by improving the interfacial bonding. This paper focuses on studying the interfacial stresses developed in the SMAepoxy interface due to various laser shot penning conditions. Fiber-pull test-setup is designed to understand the role of mechanical bias stress cycling and thermal actuation cycling. Phase transformation is tracked over mechanical and thermal fatigue cycles. A micromechanics based model developed earlier based on shear lag in SMA and energy based consistent homogenization is extended here to incorporate the stress-temperature phase diagram parameters for modeling fatigue.

  13. Shape effects on dynamics of inertia-free spheroids in wall turbulence

    SciTech Connect

    Challabotla, Niranjan Reddy; Zhao, Lihao; Andersson, Helge I.

    2015-06-15

    The rotational motion of inertia-free spheroids has been studied in a numerically simulated turbulent channel flow. Although inertia-free spheroids were translated as tracers with the flow, neither the disk-like nor the rod-like particles adapted to the fluid rotation. The flattest disks preferentially aligned their symmetry axes normal to the wall, whereas the longest rods were parallel with the wall. The shape-dependence of the particle orientations carried over to the particle rotation such that the mean spin was reduced with increasing departure from sphericity. The streamwise spin fluctuations were enhanced due to asphericity, but substantially more for prolate than for oblate spheroids.

  14. DDA Computations of Porous Aggregates with Forsterite Crystals: Effects of Crystal Shape and Crystal Mass Fraction

    NASA Astrophysics Data System (ADS)

    Wooden, Diane H.; Lindsay, Sean S.; Harker, David; Woodward, Charles; Kelley, Michael S. P.; Kolokolova, Ludmilla

    2015-08-01

    Porous aggregate grains are commonly found in cometary dust samples and are needed to model cometary IR spectral energy distributions (SEDs). Models for thermal emissions from comets require two forms of silicates: amorphous and crystalline. The dominant crystal resonances observed in comet SEDs are from Forsterite (Mg2SiO4). The mass fractions that are crystalline span a large range from 0.0 ≤ fcrystal ≤ 0.74. Radial transport models that predict the enrichment of the outer disk (>25 AU at 1E6 yr) by inner disk materials (crystals) are challenged to yield the highend-range of cometary crystal mass fractions. However, in current thermal models, Forsterite crystals are not incorporated into larger aggregate grains but instead only are considered as discrete crystals. A complicating factor is that Forsterite crystals with rectangular shapes better fit the observed spectral resonances in wavelength (11.0-11.15 μm, 16, 19, 23.5, 27, and 33 μm), feature asymmetry and relative height (Lindley et al. 2013) than spherically or elliptically shaped crystals. We present DDA-DDSCAT computations of IR absorptivities (Qabs) of 3 μm-radii porous aggregates with 0.13 ≤ fcrystal ≤ 0.35 and with polyhedral-shaped Forsterite crystals. We can produce crystal resonances with similar appearance to the observed resonances of comet Hale-Bopp. Also, a lower mass fraction of crystals in aggregates can produce the same spectral contrast as a higher mass fraction of discrete crystals; the 11µm and 23 µm crystalline resonances appear amplified when crystals are incorporated into aggregates composed otherwise of spherically shaped amorphous Fe-Mg olivines and pyroxenes. We show that the optical properties of a porous aggregate is not linear combination of its monomers, so aggregates need to be computed. We discuss the consequence of lowering comet crystal mass fractions by modeling IR SEDs with aggregates with crystals, and the implications for radial transport models of our

  15. The effect of nanoparticle size, shape, and surface chemistry on biological systems.

    PubMed

    Albanese, Alexandre; Tang, Peter S; Chan, Warren C W

    2012-01-01

    An understanding of the interactions between nanoparticles and biological systems is of significant interest. Studies aimed at correlating the properties of nanomaterials such as size, shape, chemical functionality, surface charge, and composition with biomolecular signaling, biological kinetics, transportation, and toxicity in both cell culture and animal experiments are under way. These fundamental studies will provide a foundation for engineering the next generation of nanoscale devices. Here, we provide rationales for these studies, review the current progress in studies of the interactions of nanomaterials with biological systems, and provide a perspective on the long-term implications of these findings.

  16. Skin Effect Modeling in Conductors of Arbitrary Shape Through a Surface Admittance Operator and the Contour Integral Method

    NASA Astrophysics Data System (ADS)

    Patel, Utkarsh R.; Triverio, Piero

    2016-09-01

    An accurate modeling of skin effect inside conductors is of capital importance to solve transmission line and scattering problems. This paper presents a surface-based formulation to model skin effect in conductors of arbitrary cross section, and compute the per-unit-length impedance of a multiconductor transmission line. The proposed formulation is based on the Dirichlet-Neumann operator that relates the longitudinal electric field to the tangential magnetic field on the boundary of a conductor. We demonstrate how the surface operator can be obtained through the contour integral method for conductors of arbitrary shape. The proposed algorithm is simple to implement, efficient, and can handle arbitrary cross-sections, which is a main advantage over the existing approach based on eigenfunctions, which is available only for canonical conductor's shapes. The versatility of the method is illustrated through a diverse set of examples, which includes transmission lines with trapezoidal, curved, and V-shaped conductors. Numerical results demonstrate the accuracy, versatility, and efficiency of the proposed technique.

  17. The Effect of Geometric Parameters of Conical Cups on the Preform Shape in Two-Stage Superplastic Forming Process

    NASA Astrophysics Data System (ADS)

    Shamsi-Sarband, Asghar; Hosseinipour, Seyed Jamal; Bakhshi-Jooybari, Mohammad; Shakeri, Mohsen

    2013-12-01

    A combination of sensitivity analysis and finite element simulation has been developed for the preform design in two-stage superplastic forming process. The aim is to present a simple approach to generate an estimate for the preform shape. In this respect, the commercial finite element software ABAQUS/Standard 6.8 was used as a computational tool and sensitivity analysis was used for preform design by minimizing the mean fractional deviation from the target thickness as an objective function. The predicted preform was verified through comparison with experimental results by investigating the deformation of AA5083 sheet at temperature of 500 °C. The effect of the geometric parameters of conical cups on the preform shape was examined. The results showed that the geometric parameters have a significant effect on the preform shape. By increasing the height and the cone angle of the final cup, the depth of the preform in the inner cavity decreases and the dome region is approached to the center of the preform cup. By increasing the corner radius of the final-die, only the height of the dome region decreases.

  18. Effects of Side Walls on Pipe Inlet Flow(Drag Reduction by Separated Flow Control Using Ring Shaped Small Obstacle)

    NASA Astrophysics Data System (ADS)

    Ando, Toshitake; Shakouchi, Toshihiko; Yamamoto, Hiroyuki; Tsujimoto, Koichi

    The flow from a wide space into a pipe has a large annular separated vortex region just after the inlet corner. This vortex region produces large flow resistance, or drag, in this kind of flow. To reduce the drag, a means to control flow in order to suppress the vortex region is needed. In this study, a simple method to reduce the drag of the pipe inlet flow by mounting a small ring-shaped obstacle instead of a bell-mouth has been proposed and examined. The effects of the side-walls and their offset distance on drag reduction were also examined. The small offset distance corresponds to the case in which the pipe inlet is placed near the bottom or corner of the tank. The distributions of pressure and velocity components in the axial direction at several cross-sections were measured, and a visualized flow pattern of the water flow just after the pipe inlet was examined. The effects of the small ring-shaped obstacle on drag reduction were also examined. It was clarified that the inlet loss (drag) coefficient was reduced by a maximum of about 90 percent by mounting the ring-shaped obstacle.

  19. The relevance of molecular weight in the design of amorphous biodegradable polymers with optimized shape memory effect.

    PubMed

    Petisco-Ferrero, S; Fernández, J; Fernández San Martín, M M; Santamaría Ibarburu, P A; Sarasua Oiz, J R

    2016-08-01

    The shape memory effect (SME) has long been the focus of interest of many research groups that have studied many facets of it, yet to the authors' knowledge some molecular parameters, such as the molecular weight, have been skipped. Thus, the aim of this work is to offer further insight into the shape memory effect, by disclosing the importance of the molecular weight as the relevant parameter dictating the extension of the rubbery plateau, which is the scenario where the entropic network of entanglements manifests. For this, a set of biodegradable amorphous poly(rac-d,l)lactides have been synthesised by ring opening copolymerization of a racemic mixture of L-and D-lactide. The analysis performed on the synthesised enantiomeric copolylactides includes the determination of molecular weights by means of Gel Permeation Chromatography (GPC), thermal properties by Differential Scanning Calorimetry (DSC), dynamic mechanical analysis (DMA) and rheological tests using small amplitude oscillatory flow analysis. Shape memory properties have been determined by means of specific cyclic thermo-mechanic test protocol. It has been shown that the recovery capacity of amorphous PDLLA is linked to the disentanglement time through an exponential law.

  20. Influence of crystal-orientation effects on pulse-shape-based identification of heavy-ions stopped in silicon detectors

    NASA Astrophysics Data System (ADS)

    Bardelli, L.; Bini, M.; Casini, G.; Pasquali, G.; Poggi, G.; Barlini, S.; Becla, A.; Berjillos, R.; Borderie, B.; Bougault, R.; Bruno, M.; Cinausero, M.; D'Agostino, M.; de Sanctis, J.; Dueñas, J. A.; Edelbruck, P.; Geraci, E.; Gramegna, F.; Kordyasz, A.; Kozik, T.; Kravchuk, V. L.; Lavergne, L.; Marini, P.; Nannini, A.; Negoita, F.; Olmi, A.; Ordine, A.; Piantelli, S.; Rauly, E.; Rivet, M. F.; Rosato, E.; Scian, C.; Stefanini, A. A.; Vannini, G.; Velica, S.; Vigilante, M.; Fazia Collaboration

    2009-07-01

    Current and charge signals have been collected for Se ions at 408 MeV, S at 160 MeV and Ni at 703 MeV, all stopped in silicon detectors. Some detectors were cut 0∘ off the <1 1 1> axis and some off the <1 0 0> axis. Important effects on the shape of the silicon current and charge signals have been observed, depending on the orientation of the impinging ion relative to the crystal axes and planes. A degradation of the energy and risetime resolution of about a factor ˜3 with respect to the measured optimal values (for example 7∘ off-axis orientation) is observed for ion impinging directions close to crystal axes and/or planes, i.e. the common scenario for normal incidence on 0∘ cut detectors. For Pulse Shape Analysis applications, the necessity of using such "random" oriented silicon detectors is demonstrated.