Science.gov

Sample records for plane load-bearing structures

  1. Ceramic Fiber Structures for Cryogenic Load-Bearing Applications

    NASA Technical Reports Server (NTRS)

    Jaskowiak, Martha H.; Eckel, Andrew J.

    2009-01-01

    This invention is intended for use as a load-bearing device under cryogenic temperatures and/or abrasive conditions (i.e., during missions to the Moon). The innovation consists of small-diameter, ceramic fibers that are woven or braided into devices like ropes, belts, tracks, or cables. The fibers can be formed from a variety of ceramic materials like silicon carbide, carbon, aluminosilicate, or aluminum oxide. The fiber architecture of the weave or braid is determined by both the fiber properties and the mechanical requirements of the application. A variety of weave or braid architectures is possible for this application. Thickness of load-bearing devices can be achieved by using either a 3D woven structure, or a layered, 2D structure. For the prototype device, a belt approximately 0.10 in. (0.25 cm) thick, and 3.0 in. (7.6 cm) wide was formed by layering and stitching a 2D aluminosilicate fiber weave.

  2. Composite load bearing outer skin for an arctic structure and a method for erecting same

    SciTech Connect

    Chen, J.; Birdy, J. N.; Watt, B. J.

    1985-08-27

    The load bearing outer skin contains an inner assembly and an outer assembly. Both the inner and outer assemblies include a skin plate member which is stiffened by stiffeners welded to one side of the skin plate member. The stiffeners are located at spaced intervals from each other and are disposed substantially perpendicular to the skin plate member. The inner and outer assembly are placed substantially parallel to each other to form a composite structure having an internal cavity defined by the inner and outer plates. The stiffeners of the inner assembly and the outer assembly are disposed in the cavity at a spaced relation to each other and extend partly into the cavity. A cementitious material substantially fills the cavity thereby completing the load bearing outer skin structure. The stiffeners may be flat steel plates or may have the profile of structural shapes such as angles or T's among others.

  3. Conformal load-bearing antenna structures (CLAS): initiative for multiple military and commercial applications

    NASA Astrophysics Data System (ADS)

    Lockyer, Allen J.; Alt, Kevin H.; Kudva, Jayanth N.; Kinslow, Robert W.; Goetz, Allan C.

    1997-06-01

    The Structures Division of the Air Force's Wright Laboratory is sponsoring the development and demonstration of a new high pay-off technology termed CLAS--Conformal Load Bearing Antenna Structures. Northrop Grumman Corporation and TRW/ASD are developing the technology under the `Smart-Skin Structure Technology Demonstration (S3D)' program, contract, No. F33615-93-C-3200. The program goal is to design, develop, fabricate, and test a CLAS component and lay the foundation for future work where potential benefits from structurally integrated antennas may be realized. Key issues will focus but are not limited to the design, structures, and manufacturing aspects of antenna embedment into load bearing aircraft structures. Results from Phase 1 of the program have been previously reported, where initial pay-offs in reducing overall airframe acquisition and support cost, weight, signature, and drag were quantitatively and qualitatively identified. A full-sized CLAS component, featuring a broadband multi-arm spiral embedded in sandwich stiffened structure, will be fabricated and tested for static strength, durability, and damage tolerance. Basic electrical performance, (e.g., radiation patterns, gain, and impedance) will also be verified; however, extensive electrical validation will be the subject of further work. Key aspects of the work and progress to date are detailed below. Also covered are future projections of CLAS technology expansion beyond tactical aircraft into other military products highlighting ships, army vehicles, and `spin-off' commercial applications to civil aircraft and the automotive industry.

  4. Influence of structural load-bearing scaffolds on mechanical load- and BMP-2-mediated bone regeneration.

    PubMed

    McDermott, Anna M; Mason, Devon E; Lin, Angela S P; Guldberg, Robert E; Boerckel, Joel D

    2016-09-01

    A common design constraint in functional tissue engineering is that scaffolds intended for use in load-bearing sites possess similar mechanical properties to the replaced tissue. Here, we tested the hypothesis that in vivo loading would enhance bone morphogenetic protein-2 (BMP-2)-mediated bone regeneration in the presence of a load-bearing PLDL scaffold, whose pores and central core were filled with BMP-2-releasing alginate hydrogel. First, we evaluated the effects of in vivo mechanical loading on bone regeneration in the structural scaffolds. Second, we compared scaffold-mediated bone regeneration, independent of mechanical loading, with alginate hydrogel constructs, without the structural scaffold, that have been shown previously to facilitate in vivo mechanical stimulation of bone formation. Contrary to our hypothesis, mechanical loading had no effect on bone formation, distribution, or biomechanical properties in structural scaffolds. Independent of loading, the structural scaffolds reduced bone formation compared to non-structural alginate, particularly in regions in which the scaffold was concentrated, resulting in impaired functional regeneration. This is attributable to a combination of stress shielding by the scaffold and inhibition of cellular infiltration and tissue ingrowth. Collectively, these data question the necessity of scaffold similarity to mature tissue at the time of implantation and emphasize development of an environment conducive to cellular activation of matrix production and ultimate functional regeneration.

  5. Structure design and manufacturing of layered bioceramic scaffolds for load-bearing bone reconstruction.

    PubMed

    Yang, Jing-Zhou; Hu, Xiao-Zhi; Sultana, Rumana; Edward Day, Robert; Ichim, Paul

    2015-07-08

    Bioceramic scaffolds with desired bone regeneration functions have the potential to become real alternatives to autologous bone grafts for reconstruction of load-bearing and critical-sized segmental bone defects. The aim of this paper was to develop a layered scaffold structure that has the biodegradable function of common monolithic scaffolds and adequate mechanical function for surgical fixing and after surgery support. The exemplary case of this study is assumed to be a large-segment tibia or femur bone repair. The layered scaffold structure consists of a macro porous hydroxyapatite-wollastonite layer and a strong dense zirconia matrix dense layer. The bio-functional scaffold layer with interconnected freeze-dried porous structures shows excellent apatite formation, cell attachment, and cell proliferation capabilities. The mechanical functional layer provides a bending strength matching that of the compact bone.

  6. Network structure of the mussel plaque and its significance for load bearing and adhesion

    NASA Astrophysics Data System (ADS)

    Filippidi, Emmanouela; Kim, Juntae; Waite, J. Herbert; Helgeson, Matthew; Valentine, Megan T.

    2015-03-01

    Marine mussels attach to rocks, each other, and a variety of surfaces via a flat, wide plaque that is interpenetrated by the collagen fibers of a thin, long thread that connects the plaque to the mussel body. The unusually strong adhesion of the plaque has long been attributed to the molecular design of its adhesive proteins that can form a variety of strong chemical bonds. However, the molecular energies for de-adhesion are orders of magnitude smaller than the macroscopic energies measured. We propose that the mesoscopic design of the plaque is critical in enhancing load bearing and eventually adhesion. We present new results on the structure of the plaque studied via electron microscopy and neutron scattering that exhibit a plaque geometry reminiscent of structural foams. Our studies reveal a collection of pores with an inner network, further connected with an outer network. The final structure can be described by two length scales. A synthetic soft system is constructed in an effort to mimic the two-lengthscale structure of the natural plaques. The structure of the native and synthetic systems is compared with the ultimate goal of evaluating the importance of the mesoscopic structure to mechanics and adhesion. NSF MRSEC IRG-I.

  7. Active load path adaption in a simple kinematic load-bearing structure due to stiffness change in the structure's supports

    NASA Astrophysics Data System (ADS)

    Gehb, C. M.; Platz, R.; Melz, T.

    2016-09-01

    Load-bearing structures with kinematic functions enable and disable degrees of freedom and are part of many mechanical engineering applications. The relative movement between a wheel and the body of a car or a landing gear and an aircraft fuselage are examples for load-bearing systems with defined kinematics. In most cases, the load is transmitted through a predetermined load path to the structural support interfaces. However, unexpected load peaks or varying health condition of the system's supports, which means for example varying damping and stiffness characteristics, may require an active adjustment of the load path. However, load paths transmitted through damaged or weakened supports can be the reason for reduced comfort or even failure. In this paper a simplified 2D two mass oscillator with two supports is used to numerically investigate the potential of controlled adaptive auxiliary kinematic guidance elements in a load-bearing structure to adapt the load path depending on the stiffness change, representing damage of the supports. The aim is to provide additional forces in the auxiliary kinematic guidance elements for two reasons. On the one hand, one of the two supports that may become weaker through stiffness change will be relieved from higher loading. On the other hand, tilting due to different compliance in the supports will be minimized. Therefore, shifting load between the supports during operation could be an effective option.

  8. Bioinspired structure of bioceramics for bone regeneration in load-bearing sites.

    PubMed

    Zhang, Faming; Chang, Jiang; Lu, Jianxi; Lin, Kaili; Ning, Congqin

    2007-11-01

    The major problem with the use of porous bioceramics as bone regeneration grafts is their weak mechanical strength, which has not been overcome to date. Here we described a novel way to solve this problem. Beta-tricalcium phosphate (beta-TCP) bioceramics with a bioinspired structure were designed and prepared with a porous cancellous core (porosity: 70-90%) inside and a dense compact shell (porosity: 5-10%) outside that mimics the characteristics of natural bone. They showed excellent mechanical properties, with a compressive strength of 10-80MPa and an elastic modulus of 180MPa-1.0GPa, which could be tailored by the dense/porous cross-sectional area ratio obeying the rule of exponential growth. The in vitro degradation of the bioinspired bioceramics was faster than that of dense bioceramics but slower than that of porous counterparts. The changes in mechanical properties of the bioinspired ceramics during in vitro degradation were also investigated. A concept of the bioinspired macrostructure design of natural bone was proposed which provided a simple but effective way to increase the mechanical properties of porous bioceramics for load-bearing bone regeneration applications. It should be readily applicable to other porous materials.

  9. Conformal Load-Bearing Antenna Structure for Australian Defence Force Aircraft

    DTIC Science & Technology

    2007-03-01

    transport a thermal transfer media ( coolant ). Directed energy weapons Directed energy weapons such as lasers and microwaves are being developed for on... Dielectric substrate Separating core Load-bearing face-sheet Absorber pan Absorber Aircraft OML Figure: 1 Typical CLAS components, after...the volume/size constraints and produce the desired radiation pattern could be considered for any specific application. Dielectric substrate

  10. Application of laser engineered net shaping (LENS) to manufacture porous and functionally graded structures for load bearing implants.

    PubMed

    Bandyopadhyay, Amit; Krishna, B V; Xue, Weichang; Bose, Susmita

    2009-12-01

    Fabrication of net shape load bearing implants with complex anatomical shapes to meet desired mechanical and biological performance is still a challenge. In this article, an overview of our research activities is discussed focusing on application of Laser Engineered Net Shaping (LENS) toward load bearing implants to increase in vivo life time. We have demonstrated that LENS can fabricate net shape, complex metallic implants with designed porosities up to 70 vol.% to reduce stress-shielding. The effective modulus of Ti, NiTi, and other alloys was tailored to suit the modulus of human cortical bone by introducing 12-42 vol.% porosity. In addition, laser processed porous NiTi alloy samples show a 2-4% recoverable strain, a potentially significant result for load bearing implants. To minimize the wear induced osteolysis, unitized structures with functionally graded Co-Cr-Mo coating on porous Ti6Al4V were also made using LENS, which showed high hardness with excellent bone cell-materials interactions. Finally, LENS is also being used to fabricate porous, net shape implants with a functional gradation in porosity characteristics.

  11. Development of the Enhanced Load-Tree Apparatus for Structural Resistance Measurement of Modern Load-Bearing Construction Techniques (PREPRINT)

    DTIC Science & Technology

    2015-07-15

    Antiterrorism/Force Protection (AT/FP) applications are defined by the U.S. Army Corps of Engi- neers (COE). Levels of Protection ( LOP ) are specified for...these damage levels are associated with building LOP . A primary structural component is defined by the PDC-TR 06-08 [6] criteria as “members whose...the building in the area of loss.” Therefore, any load-bearing structural component would be considered primary. When determining the building LOP

  12. Compliant load-bearing skins and structures for morphing aircraft applications

    NASA Astrophysics Data System (ADS)

    Olympio, Kingnide Raymond

    Aircraft morphing has the potential to significantly improve the performance of an aircraft over its flight envelope and expand its ight capability to allow it to perform dramatically different missions. The multiple projects carried on in the past three decades have considerably helped improve the designing of actuation systems and the utilization of smart materials for morphing aircraft structures. However, morphing aircraft and especially aircraft undergoing large shape change still face some significant technical issues. Among them, the skin covering the morphing structure must meet challenging requirements that no current conventional material fully satisfy. The design of such skin, which should be able to undergo large deformations and to carry air-loads, has received some attention in the last several years but no satisfactory solution has been found yet. In the current study, the design of compliant cellular structures and flexible skins for morphing aircraft structures is investigated for two different morphing deformations. The first morphing deformation considered corresponds to one-dimensional morphing which is representative of a wing or blade changing its chord or span. The second morphing deformation considered is shear-compression morphing which can be found in some morphing wing undergoing change in area, sweep and chord such as NextGen Aeronautics' morphing wing. Topologies of compliant cellular structures which can be used for these two types of structures are first calculated using a multi-objective approach. These topologies are calculated based on linear kinematics but the effect of geometric nonlinearities is also investigated. Then, ways to provide a smooth surface were investigated by considering a general honeycomb substructure with infill, bonded face-sheet or scales. This allowed justifying an overall skin concept made of a cellular substructure with a bonded face-sheet. Lastly, the design of an improved skin for NextGen Aeronautics

  13. Spider silk as a load bearing biomaterial: tailoring mechanical properties via structural modifications

    NASA Astrophysics Data System (ADS)

    Brown, Cameron P.; Rosei, Federico; Traversa, Enrico; Licoccia, Silvia

    2011-03-01

    Spider silk shows great potential as a biomaterial: in addition to biocompatibility and biodegradability, its strength and toughness are greater than native biological fibres (e.g. collagen), with toughness exceeding that of synthetic fibres (e.g. nylon). Although the ultimate tensile strength and toughness at failure are unlikely to be limiting factors, its yield strain of 2% is insufficient, particularly for biomedical application because of the inability to mimic the complex ultrastructure of natural tissues with current tissue engineering approaches. To harness the full potential of spider silk as a biomaterial, it is therefore necessary to increase its yield strain. In this paper, we discuss the means by which the mechanical properties of spider silk, particularly the yield strain, can be optimized through structural modifications.

  14. Effects of load-bearing exercise on skeletal structure and mechanics differ between outbred populations of mice.

    PubMed

    Wallace, Ian J; Judex, Stefan; Demes, Brigitte

    2015-03-01

    Effects of load-bearing exercise on skeletal structure and mechanical properties can vary between inbred strains of mice. Here, we examine whether such variation also exists at the population level. An experiment was performed with two outbred mouse stocks that have been reproductively isolated for >120 generations (Hsd:ICR, Crl:CD1). Growing females from each stock were either treated with a treadmill-running regimen for 1 month or served as controls. Limb forces were recorded with a force plate and cage activity monitored to verify that they were similar between stocks. After the experiment, femoral cortical and trabecular bone structure were quantified with micro-CT in the mid-diaphysis and distal metaphysis, respectively, and diaphyseal structural strength was determined with mechanical testing. Among Hsd:ICR mice, running led to significant improvements in diaphyseal bone quantity, structural geometry, and mechanical properties, as well as enhanced trabecular morphology. In contrast, among Crl:CD1 mice, the same running regimen had little effect on cortical and trabecular structure and significantly reduced diaphyseal resistance to fracture. In neither stock was body mass, muscle mass, or cage activity level different between runners and controls. Given that most environmental variables were controlled in this study, the differential effects of exercise on Hsd:ICR and Crl:CD1 bones were likely due to genetic differences between stocks. These results suggest that the benefits of loading for bone may vary between human populations (e.g., ethnic groups), in which case exercise programs and technologies designed to promote bone health with mechanical signals may be more advantageous to certain populations than others.

  15. Development of a structurally integrated conformal load-bearing multifunction antenna: overview of the Air Force Smart Skin Structures Technology Demonstration Program

    NASA Astrophysics Data System (ADS)

    Lockyer, Allen J.; Alt, Kevin H.; Kinslow, Robert W.; Kan, Han-Pin; Kudva, Jayanth N.; Tuss, James; Goetz, Allan C.

    1996-05-01

    The Structures Division of the Air Force's Wright Laboratory is sponsoring the development and demonstration of a new high pay-off technology termed CLAS--Conformal Load Bearing Antenna Structures. Northrop Grumman Corporation and TRW/ASD are developing the technology under the `Smart-Skin Structure Technology Demonstration (S3D)' program, contract, No. F33615-93-C-3200. The program goal is to design, develop, fabricate, and test a CLAS component and lay the foundation for future work where potential benefits from structurally integrated antennas may be realized. Key issues will focus but are not limited to the design, structures, and manufacturing aspects of antenna embedment into load bearing aircraft structures. Results from Phase I of the program have been previously reported, where initial pay-offs in reducing overall airframe acquisition and support cost, weight, signature, and drag were quantitatively and qualitatively identified. A full-sized CLAS component, featuring a broadband multi-arm spiral embedded in sandwich stiffened structure, will be fabricated and tested for static strength, durability, and damage tolerance. Basic electrical performance, (e.g. radiation patterns, gain, and impedance) will also be verified; however, extensive electrical validation will be the subject of further work. Key aspects of the work and progress to date are detailed below.

  16. Novel class of collector in electrospinning device for the fabrication of 3D nanofibrous structure for large defect load-bearing tissue engineering application.

    PubMed

    Hejazi, Fatemeh; Mirzadeh, Hamid; Contessi, Nicola; Tanzi, Maria Cristina; Faré, Silvia

    2017-05-01

    Adequate porosity, appropriate pore size, and 3D-thick shape are crucial parameters in the design of scaffolds, as they should provide the right space for cell adhesion, spreading, migration, and growth. In this work, a novel design for fabricating a 3D nanostructured scaffold by electrospinning was taken into account. Helical spring-shaped collector was purposely designed and used for electrospinning PCL fibers. Improved morphological properties and more uniform diameter distribution of collected nanofibers on the turns of helical spring-shaped collector are confirmed by SEM analysis. SEM images elaboration showed 3D pores with average diameter of 4 and 5.5 micrometer in x-y plane and z-direction, respectively. Prepared 3D scaffold possessed 99.98% porosity which led to the increased water uptake behavior in PBS at 37°C up to 10 days, and higher degradation rate compared to 2D flat structure. Uniaxial compression test on 3D scaffolds revealed an elastic modulus of 7 MPa and a stiffness of 10(2) MPa, together with very low hysteresis area and residual strain. In vitro cytocompatibility test with MG-63 osteoblast-like cells using AlamarBlue(™) colorimetric assay, indicated a continuous increase in cell viability for the 3D structure over the test duration. SEM observation showed enhanced cells spreading and diffusion into the underneath layers for 3D scaffold. Accelerated calcium deposition in 3D substrate was confirmed by EDX analysis. Obtained morphological, physical, and mechanical properties together with in vitro cytocompatibility results, suggest this novel technique as a proper method for the fabrication of 3D nanofibrous scaffolds for the regeneration of critical-size load bearing defects. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1535-1548, 2017.

  17. Structural finite-element modeling strategies for conformal load-bearing antenna structure (CLAS) (Air Force contract F33615-C-93-3200)

    NASA Astrophysics Data System (ADS)

    Lockyer, Allen J.; Alt, Kevin H.; Kudva, Jayanth N.; Kinslow, Robert W.; Goetz, Allan C.

    1997-06-01

    As the Wright Lab Air Force military contrast `Smart Skin Structures Technology Demonstration' (S3TD) Contract No. F33615-C-93-3200 draws toward conclusion, pertinent features of the program finite element modeling are presented. Analysis was performed to predict the structural performance of a complex multilayered composite panel that will be tested structurally (and electrically) for the final program deliverable. Application of finite element modeling to predict component load path and strain distribution in sandwich panel construction has been reported elsewhere in the literature for more standard applications. However, the unauthordox sandwich configuration lay-up posed by the quite revolutionary S3TD CLAS aircraft fuselage panel demonstration article merits further discussion. Difficulties with material selection, the stumbling block for many programs, are further exacerbated by conflicting material properties required to support simultaneous electrical and structural performance roles. The structural analysis challenge derives from S3TD's unique program goal, namely, to investigate load bearing antennas structural configurations, rather than conventional structurally inefficient `bolt in' installations, that have been the modus operandi for tactical aircraft antenna installations to date. Discussed below is a cost saving strategy where use of linear finite element analysis has been employed in the prediction of key structural parameters, and validated with risk reduction sub panel measurements, before proceeding to the final fabrication of a full scale 36 by 36 inch CLAS panel demonstration article.

  18. Mechanical characterization of structurally porous biomaterials built via additive manufacturing: experiments, predictive models, and design maps for load-bearing bone replacement implants.

    PubMed

    Melancon, D; Bagheri, Z S; Johnston, R B; Liu, L; Tanzer, M; Pasini, D

    2017-09-18

    Porous biomaterials can be additively manufactured with micro-architecture tailored to satisfy the stringent mechano-biological requirements imposed by bone replacement implants. In a previous investigation, we introduced structurally porous biomaterials, featuring strength five times stronger than commercially available porous materials, and confirmed their bone ingrowth capability in an in vivo canine model. While encouraging, the manufactured biomaterials showed geometric mismatches between their internal porous architecture and that of its as-designed counterpart, as well as discrepancies between predicted and tested mechanical properties, issues not fully elucidated. In this work, we propose a systematic approach integrating computed tomography, mechanical testing, and statistical analysis of geometric imperfections to generate statistical based numerical models of high-strength additively manufactured porous biomaterials. The method is used to develop morphology and mechanical maps that illustrate the role played by pore size, porosity, strut thickness, and topology on the relations governing their elastic modulus and compressive yield strength. Overall, there are mismatches between the mechanical properties of ideal-geometry models and as-manufactured porous biomaterials with average errors of 49% and 41% respectively for compressive elastic modulus and yield strength. The proposed methodology gives more accurate predictions for the compressive stiffness and the compressive strength properties with a reduction of the average error to 11% and 7.6%. The implications of the results and the methodology here introduced are discussed in the relevant biomechanical and clinical context, with insight that highlights promises and limitations of additively manufactured porous biomaterials for load-bearing bone replacement implants. In this work, we perform mechanical characterization of load-bearing porous biomaterials for bone replacement over their entire design

  19. Design and development of a conformal load-bearing smart skin antenna: overview of the AFRL Smart Skin Structures Technology Demonstration (S3TD)

    NASA Astrophysics Data System (ADS)

    Lockyer, Allen J.; Alt, Kevin H.; Coughlin, Daniel P.; Durham, Michael D.; Kudva, Jayanth N.; Goetz, Allan C.; Tuss, James

    1999-07-01

    Documented herein is a review of progress for the recently completed 'Smart Skin Structure Technology Demonstration' (S3TD) contract number F33615-93-C-3200 performed by Northrop Grumman Corporation, Hawthorne, California and TRW/ASD, Rancho Bernardo, San Diego, California under the Air Force Research Laboratory, Flight Dynamics Directorate, Structures Division's direction and sponsorship. S3TD was conceived as the first serious attempt, to made a complex antenna become a bone fide aircraft structural panel, without loss of overall structural integrity or electrical performance. The program successfully demonstrated the design, fabrication, and structural validation of a load bearing multifunction antenna component panel subjected to realistic aircraft flight load conditions. The final demonstration article was a structurally effective 36 by 36 inch curved multifunction antenna component panel that withstood running loads of 4,000 pounds per inch, and principal strain levels of 4,700 microstrain. Testing the structural component to ultimate, the panel failed at the predicted limit of 148 kips equating to 150 percent design limit load, after successfully completing one lifetime of fatigue. The load conditions were representative of a mid-fuselage F-18 class fighter component panel installation. The panel was designed not to buckle at ultimate failure, and the dominant failure mode was face sheet pull off, as predicted. Structural test data correlated closely with analysis. Wide band electrical performance for the component antenna panel was validated using anechoic chamber measurements and near field probing techniques, covering avionics communication navigation and identification and electronic warfare functions in the 0.15 to 2.2 GHz frequency regimes.

  20. Carbon-Nanotube-Based Epoxy Matrix Thermal Interface Materials for Thermal Management in Load Bearing Aerospace Structures

    DTIC Science & Technology

    2012-01-12

    anharmonic processes , namely three-phonon processes that can contribute a significant additional channel for the transport of heat by altering phonon...Since tin has lower melting point, the target was procured with a copper back plate for dissipating heat during the deposition process . The thickness...conductivities in single -walled and multi-walled carbon nanotubes as well as other graphite materials [3-11], suggests that these nano- structured

  1. Load Bearing Innovative Construction from Glass

    NASA Astrophysics Data System (ADS)

    Kalamar, R.; Eliášová, M.

    2015-11-01

    Glass plays an exceptional role in the modern architecture due to the optical properties and transparency. Structural elements from glass like beams, facades and roofs are relatively frequent in common practice [1]. Although glass has significantly higher compressive strength in comparison with tensile strength, load bearing glass elements are relatively rare. This opens up new opportunities for application of glass in such structures as transparent columns loaded by the axial force. This paper summarizes the experimental results of the tests on glass columns loaded by centric pressure, which were performed in the laboratories of the CTU in Prague, Faculty of Civil Engineering. The first set of experiments was composed of three specimens in a reduced scale 1:2 to verify real behaviour of the specimens with enclosed hollow cross-section. The main goal of the experiment was to determine force at the first breakage and consequently the maximal force at the collapse of this element.

  2. Nanogel Aerogel as Load Bearing Insulation for Cryogenic Systems

    NASA Astrophysics Data System (ADS)

    Koravos, J. J.; Miller, T. M.; Fesmire, J. E.; Coffman, B. E.

    2010-04-01

    Load support structures in cryogenic storage, transport and processing systems are large contributors to the total heat leak of the system. Conventional insulation systems require the use of these support members in order to stabilize the process fluid enclosure and prevent degradation of insulation performance due to compression. Removal of these support structures would substantially improve system efficiency. Nanogel aerogel insulation performance is tested at vacuum pressures ranging from high vacuum to atmospheric pressure and under loads from loosely packed to greater than 10,000 Pa. Insulation performance is determined using boil-off calorimetry with liquid nitrogen as the latent heat recipient. Two properties of the aerogel insulation material suit it to act as a load bearing "structure" in a process vessel: (1) Ability to maintain thermal performance under load; (2) Elasticity when subjected to load. Results of testing provide positive preliminary indication that these properties allow Nanogel aerogel to effectively be used as a load bearing insulation in cryogenic systems.

  3. Load Bearing Equipment for Bone and Muscle

    NASA Technical Reports Server (NTRS)

    Shackelford, Linda; Griffith, Bryan

    2015-01-01

    Resistance exercise on ISS has proven effective in maintaining bone mineral density and muscle mass. Exploration missions require exercise with similar high loads using equipment with less mass and volume and greater safety and reliability than resistance exercise equipment used on ISS (iRED, ARED, FWED). Load Bearing Equipment (LBE) uses each exercising person to create and control the load to the partner.

  4. Designing functionally graded materials with superior load-bearing properties

    PubMed Central

    Zhang, Yu; Sun, Ming-jie; Zhang, Denzil

    2011-01-01

    Ceramic prostheses often fail from fracture and wear. We hypothesize that these failures may be substantially mitigated by an appropriate grading of elastic modulus at the ceramic surface. In this study, we elucidate the effect of elastic modulus profile on the flexural damage resistance of functionally graded materials (FGMs), providing theoretical guidlines for designing FGM with superior load-bearing property. The Young's modulus of the graded structure is assumed to vary in a power-law relation with a scaling exponent n; this is in accordance with experimental observations from our laboratory and elsewhere. Based on the theory for bending of graded beams, we examine the effect of n value and bulk-to-surface modulus ratio (Eb/Es) on stress distribution through the graded layer. Theory predicts that a low exponent (0.15 < n < 0.5), coupled with a relatively small modulus ratio (3 < Eb/Es < 6), is most desirable for reducing the maximum stress and transferring it into the interior, while keeping the surface stress low. Experimentally, we demonstrate that elastically graded materials with various n values and Eb/Es ratios can be fabricated by infiltrating alumina and zirconia with a low-modulus glass. Flexural tests show that graded alumina and zirconia with suitable values of these parameters exhibit superior load-bearing capacity, 20% to 50% higher than their homogeneous counterparts. Improving load-bearing capacity of ceramic materials could have broad impacts on biomedical, civil, structural, and an array of other engineering applications. PMID:22178651

  5. Failure tolerance of load-bearing hierarchical networks

    NASA Astrophysics Data System (ADS)

    Kachhvah, Ajay Deep; Gupte, Neelima

    2011-03-01

    We investigate the statistics and dynamics of failure in a two-dimensional load-bearing network with branching hierarchical structure, and its variants. The variants strengthen the original lattice by using connectivity strategies which add new sites to the maximal cluster in top-to-bottom or bottom-to-top versions. We study the load-bearing capacity and the failure tolerance of all versions, as well as that of the strongest realization of the original lattice, the V lattice. The average number of failures as a function of the test load shows power-law behavior with power 5/2 for the V lattice, but sigmoidal behavior for all other versions. Thus the V lattice turns out to be the critical case of the load-bearing lattices. The distribution of failures is Gaussian for the original lattice, the V lattice, and the bottom-to-top strategy, but is non-Gaussian for the top-to-bottom one. The bottom-to-top strategy leads to stable and strong lattices, and can resist failure even when tested with weights which greatly exceed the capacity of its backbone. We also examine the behavior of asymmetric lattices and discover that the mean failure rates are minimized if the probability of connection p is symmetric with respect to both neighbors. Our results can be of relevance in the context of realistic networks.

  6. A multifunctional load-bearing solid-state supercapacitor.

    PubMed

    Westover, Andrew S; Tian, John W; Bernath, Shivaprem; Oakes, Landon; Edwards, Rob; Shabab, Farhan N; Chatterjee, Shahana; Anilkumar, Amrutur V; Pint, Cary L

    2014-06-11

    A load-bearing, multifunctional material with the simultaneous capability to store energy and withstand static and dynamic mechanical stresses is demonstrated. This is produced using ion-conducting polymers infiltrated into nanoporous silicon that is etched directly into bulk conductive silicon. This device platform maintains energy densities near 10 W h/kg with Coulombic efficiency of 98% under exposure to over 300 kPa tensile stresses and 80 g vibratory accelerations, along with excellent performance in other shear, compression, and impact tests. This demonstrates performance feasibility as a structurally integrated energy storage material broadly applicable across renewable energy systems, transportation systems, and mobile electronics, among others.

  7. A Broadband High-Gain Bi-Layer Log-Periodic Dipole Array (LPDA) for Ultra High Frequency (UHF) Conformal Load Bearing Antenna Structures (CLAS) Applications

    DTIC Science & Technology

    2014-08-01

    AFRL-RQ-WP-TR-2014-0212 University of South Carolina Department of Electrical Engineering Columbia, SC 29208 Structures Technology Branch...S2603-04-C01. Cleared for Public Release - Case Number: . Nicholas Bishop and M. Ali are with the Department of Electrical Engineering, University of...that is stiff and light weight. The sandwich composite panel has a greatly increased strength -to-weight ratio when compared to a similar RF

  8. The nebulin SH3 domain is dispensable for normal skeletal muscle structure but is required for effective active load bearing in mouse.

    PubMed

    Yamamoto, Daniel L; Vitiello, Carmen; Zhang, Jianlin; Gokhin, David S; Castaldi, Alessandra; Coulis, Gerald; Piaser, Fabio; Filomena, Maria Carmela; Eggenhuizen, Peter J; Kunderfranco, Paolo; Camerini, Serena; Takano, Kazunori; Endo, Takeshi; Crescenzi, Marco; Luther, Pradeep K L; Lieber, Richard L; Chen, Ju; Bang, Marie-Louise

    2013-12-01

    Nemaline myopathy (NM) is a congenital myopathy with an estimated incidence of 150,000 live births. It is caused by mutations in thin filament components, including nebulin, which accounts for about 50% of the cases. The identification of NM cases with nonsense mutations resulting in loss of the extreme C-terminal SH3 domain of nebulin suggests an important role of the nebulin SH3 domain, which is further supported by the recent demonstration of its role in IGF-1-induced sarcomeric actin filament formation through targeting of N-WASP to the Z-line. To provide further insights into the functional significance of the nebulin SH3 domain in the Z-disk and to understand the mechanisms by which truncations of nebulin lead to NM, we took two approaches: (1) an affinity-based proteomic screening to identify novel interaction partners of the nebulin SH3 domain; and (2) generation and characterization of a novel knockin mouse model with a premature stop codon in the nebulin gene, eliminating its C-terminal SH3 domain (NebΔSH3 mouse). Surprisingly, detailed analyses of NebΔSH3 mice revealed no structural or histological skeletal muscle abnormalities and no changes in gene expression or localization of interaction partners of the nebulin SH3 domain, including myopalladin, palladin, zyxin and N-WASP. Also, no significant effect on peak isometric stress production, passive tensile stress or Young's modulus was found. However, NebΔSH3 muscle displayed a slightly altered force-frequency relationship and was significantly more susceptible to eccentric contraction-induced injury, suggesting that the nebulin SH3 domain protects against eccentric contraction-induced injury and possibly plays a role in fine-tuning the excitation-contraction coupling mechanism.

  9. The nebulin SH3 domain is dispensable for normal skeletal muscle structure but is required for effective active load bearing in mouse

    PubMed Central

    Yamamoto, Daniel L.; Vitiello, Carmen; Zhang, Jianlin; Gokhin, David S.; Castaldi, Alessandra; Coulis, Gerald; Piaser, Fabio; Filomena, Maria Carmela; Eggenhuizen, Peter J.; Kunderfranco, Paolo; Camerini, Serena; Takano, Kazunori; Endo, Takeshi; Crescenzi, Marco; Luther, Pradeep K. L.; Lieber, Richard L.; Chen, Ju; Bang, Marie-Louise

    2013-01-01

    Summary Nemaline myopathy (NM) is a congenital myopathy with an estimated incidence of 1∶50,000 live births. It is caused by mutations in thin filament components, including nebulin, which accounts for about 50% of the cases. The identification of NM cases with nonsense mutations resulting in loss of the extreme C-terminal SH3 domain of nebulin suggests an important role of the nebulin SH3 domain, which is further supported by the recent demonstration of its role in IGF-1-induced sarcomeric actin filament formation through targeting of N-WASP to the Z-line. To provide further insights into the functional significance of the nebulin SH3 domain in the Z-disk and to understand the mechanisms by which truncations of nebulin lead to NM, we took two approaches: (1) an affinity-based proteomic screening to identify novel interaction partners of the nebulin SH3 domain; and (2) generation and characterization of a novel knockin mouse model with a premature stop codon in the nebulin gene, eliminating its C-terminal SH3 domain (NebΔSH3 mouse). Surprisingly, detailed analyses of NebΔSH3 mice revealed no structural or histological skeletal muscle abnormalities and no changes in gene expression or localization of interaction partners of the nebulin SH3 domain, including myopalladin, palladin, zyxin and N-WASP. Also, no significant effect on peak isometric stress production, passive tensile stress or Young's modulus was found. However, NebΔSH3 muscle displayed a slightly altered force–frequency relationship and was significantly more susceptible to eccentric contraction-induced injury, suggesting that the nebulin SH3 domain protects against eccentric contraction-induced injury and possibly plays a role in fine-tuning the excitation–contraction coupling mechanism. PMID:24046450

  10. Morphogenic Peptides in Regeneration of Load Bearing Tissues.

    PubMed

    Moeinzadeh, Seyedsina; Jabbari, Esmaiel

    2015-01-01

    Morphogenic proteins due to their short half-life require high doses of growth factors in regeneration of load bearing tissues which leads to undesirable side effects. These side effects include bone overgrowth, tumor formation and immune reaction. An alternative approach to reduce undesirable side effects of proteins in regenerative medicine is to use morphogenic peptides derived from the active domains of morphogenic proteins or soluble and insoluble components of the extracellular matrix of mineralized load bearing tissues to induce differentiation of progenitor cells, mineralization, maturation and bone formation. In that regard, many peptides with osteogenic activity have been discovered. These include peptides derived from bone morphogenic proteins (BMPs), those based on interaction with integrin and heparin-binding receptors, collagen derived peptides, peptides derived from other soluble ECM proteins such as bone sialoprotein and enamel matrix proteins, and those peptides derived from vasculoinductive and neuro-inductive proteins. Although these peptides show significant osteogenic activity in vitro and increase mineralization and bone formation in animal models, they are not widely used in clinical orthopedic applications as an alternative to morphogenic proteins. This is partly due to the limited availability of data on structure and function of morphogenic peptides in physiological medium, particularly in tissue engineered scaffolds. Due to their amphiphilic nature, peptides spontaneously self-assemble and aggregate into micellar structures in physiological medium. Aggregation alters the sequence of amino acids in morphogenic peptides that interact with cell surface receptors thus affecting osteogenic activity of the peptide. Aggregation and micelle formation can dramatically reduce the active concentration of morphogenic peptides with many-fold increase in peptide concentration in physiological medium. Other factors that affect bioactivity are the non

  11. Load-Bearing Capacity of Fiber-Reinforced Composite Abutments and One-Piece Implants.

    PubMed

    Etxeberria, Marina; Abdulmajeed, Aous A; Escuin, Tomas; Vinas, Miguel; Lassila, Lippo V J; Närhi, Timo O

    2015-06-01

    Fiber-reinforced composites (FRC) can potentially help in a physiologic stress transmission due to its excellent biomechanical matching with living tissues. Novel one-piece FRC implants and abutments with two different fiber orientations were loaded until failure to assess the load-bearing capacity, fracture patterns, and precision of fit. The one-piece FRC implants showed significantly higher load-bearing capacity compared to FRC abutments regardless of the fiber orientation (p < 0.001). For FRC abutments, bidirectional abutments showed significantly higher loads compared to unidirectional abutments (p < 0.001). The type of structure and fiber orientation are strong determinant factors of the load-bearing capacity of FRC implants and abutments.

  12. Fracture behaviors of ceramic tissue scaffolds for load bearing applications

    NASA Astrophysics Data System (ADS)

    Entezari, Ali; Roohani-Esfahani, Seyed-Iman; Zhang, Zhongpu; Zreiqat, Hala; Dunstan, Colin R.; Li, Qing

    2016-07-01

    Healing large bone defects, especially in weight-bearing locations, remains a challenge using available synthetic ceramic scaffolds. Manufactured as a scaffold using 3D printing technology, Sr-HT-Gahnite at high porosity (66%) had demonstrated significantly improved compressive strength (53 ± 9 MPa) and toughness. Nevertheless, the main concern of ceramic scaffolds in general remains to be their inherent brittleness and low fracture strength in load bearing applications. Therefore, it is crucial to establish a robust numerical framework for predicting fracture strengths of such scaffolds. Since crack initiation and propagation plays a critical role on the fracture strength of ceramic structures, we employed extended finite element method (XFEM) to predict fracture behaviors of Sr-HT-Gahnite scaffolds. The correlation between experimental and numerical results proved the superiority of XFEM for quantifying fracture strength of scaffolds over conventional FEM. In addition to computer aided design (CAD) based modeling analyses, XFEM was conducted on micro-computed tomography (μCT) based models for fabricated scaffolds, which took into account the geometric variations induced by the fabrication process. Fracture strengths and crack paths predicted by the μCT-based XFEM analyses correlated well with relevant experimental results. The study provided an effective means for the prediction of fracture strength of porous ceramic structures, thereby facilitating design optimization of scaffolds.

  13. Fracture behaviors of ceramic tissue scaffolds for load bearing applications

    PubMed Central

    Entezari, Ali; Roohani-Esfahani, Seyed-Iman; Zhang, Zhongpu; Zreiqat, Hala; Dunstan, Colin R.; Li, Qing

    2016-01-01

    Healing large bone defects, especially in weight-bearing locations, remains a challenge using available synthetic ceramic scaffolds. Manufactured as a scaffold using 3D printing technology, Sr-HT-Gahnite at high porosity (66%) had demonstrated significantly improved compressive strength (53 ± 9 MPa) and toughness. Nevertheless, the main concern of ceramic scaffolds in general remains to be their inherent brittleness and low fracture strength in load bearing applications. Therefore, it is crucial to establish a robust numerical framework for predicting fracture strengths of such scaffolds. Since crack initiation and propagation plays a critical role on the fracture strength of ceramic structures, we employed extended finite element method (XFEM) to predict fracture behaviors of Sr-HT-Gahnite scaffolds. The correlation between experimental and numerical results proved the superiority of XFEM for quantifying fracture strength of scaffolds over conventional FEM. In addition to computer aided design (CAD) based modeling analyses, XFEM was conducted on micro-computed tomography (μCT) based models for fabricated scaffolds, which took into account the geometric variations induced by the fabrication process. Fracture strengths and crack paths predicted by the μCT-based XFEM analyses correlated well with relevant experimental results. The study provided an effective means for the prediction of fracture strength of porous ceramic structures, thereby facilitating design optimization of scaffolds. PMID:27403936

  14. Fracture behaviors of ceramic tissue scaffolds for load bearing applications.

    PubMed

    Entezari, Ali; Roohani-Esfahani, Seyed-Iman; Zhang, Zhongpu; Zreiqat, Hala; Dunstan, Colin R; Li, Qing

    2016-07-12

    Healing large bone defects, especially in weight-bearing locations, remains a challenge using available synthetic ceramic scaffolds. Manufactured as a scaffold using 3D printing technology, Sr-HT-Gahnite at high porosity (66%) had demonstrated significantly improved compressive strength (53 ± 9 MPa) and toughness. Nevertheless, the main concern of ceramic scaffolds in general remains to be their inherent brittleness and low fracture strength in load bearing applications. Therefore, it is crucial to establish a robust numerical framework for predicting fracture strengths of such scaffolds. Since crack initiation and propagation plays a critical role on the fracture strength of ceramic structures, we employed extended finite element method (XFEM) to predict fracture behaviors of Sr-HT-Gahnite scaffolds. The correlation between experimental and numerical results proved the superiority of XFEM for quantifying fracture strength of scaffolds over conventional FEM. In addition to computer aided design (CAD) based modeling analyses, XFEM was conducted on micro-computed tomography (μCT) based models for fabricated scaffolds, which took into account the geometric variations induced by the fabrication process. Fracture strengths and crack paths predicted by the μCT-based XFEM analyses correlated well with relevant experimental results. The study provided an effective means for the prediction of fracture strength of porous ceramic structures, thereby facilitating design optimization of scaffolds.

  15. Design Methods for Load-bearing Elements from Crosslaminated Timber

    NASA Astrophysics Data System (ADS)

    Vilguts, A.; Serdjuks, D.; Goremikins, V.

    2015-11-01

    Cross-laminated timber is an environmentally friendly material, which possesses a decreased level of anisotropy in comparison with the solid and glued timber. Cross-laminated timber could be used for load-bearing walls and slabs of multi-storey timber buildings as well as decking structures of pedestrian and road bridges. Design methods of cross-laminated timber elements subjected to bending and compression with bending were considered. The presented methods were experimentally validated and verified by FEM. Two cross-laminated timber slabs were tested at the action of static load. Pine wood was chosen as a board's material. Freely supported beam with the span equal to 1.9 m, which was loaded by the uniformly distributed load, was a design scheme of the considered plates. The width of the plates was equal to 1 m. The considered cross-laminated timber plates were analysed by FEM method. The comparison of stresses acting in the edge fibres of the plate and the maximum vertical displacements shows that both considered methods can be used for engineering calculations. The difference between the results obtained experimentally and analytically is within the limits from 2 to 31%. The difference in results obtained by effective strength and stiffness and transformed sections methods was not significant.

  16. Protein-based materials in load-bearing tissue-engineering applications.

    PubMed

    Sayin, Esen; Baran, Erkan Türker; Hasirci, Vasif

    2014-01-01

    Proteins such as collagen and elastin are robust molecules that constitute nanocomponents in the hierarchically organized ultrastructures of bone and tendon as well as in some of the soft tissues that have load-bearing functions. In the present paper, the macromolecular structure and function of the proteins are reviewed and the potential of mammalian and non-mammalian proteins in the engineering of load-bearing tissue substitutes are discussed. Chimeric proteins have become an important structural biomaterial source and their potential in tissue engineering is highlighted. Processing of proteins challenge investigators and in this review rapid prototyping and microfabrication are proposed as methods for obtaining precisely defined custom-built tissue engineered structures with intrinsic microarchitecture.

  17. 3D Printing and Biofabrication for Load Bearing Tissue Engineering.

    PubMed

    Jeong, Claire G; Atala, Anthony

    2015-01-01

    Cell-based direct biofabrication and 3D bioprinting is becoming a dominant technological platform and is suggested as a new paradigm for twenty-first century tissue engineering. These techniques may be our next step in surpassing the hurdles and limitations of conventional scaffold-based tissue engineering, and may offer the industrial potential of tissue engineered products especially for load bearing tissues. Here we present a topically focused review regarding the fundamental concepts, state of the art, and perspectives of this new technology and field of biofabrication and 3D bioprinting, specifically focused on tissue engineering of load bearing tissues such as bone, cartilage, osteochondral and dental tissue engineering.

  18. Thermal coupon testing of Load-Bearing Multilayer Insulation

    NASA Astrophysics Data System (ADS)

    Johnson, W. L.; Heckle, K. W.; Hurd, J.

    2014-01-01

    Advanced liquid hydrogen storage concepts being considered for long duration space travel incorporate refrigeration systems and cryocoolers to lower the heat load. Using a refrigeration loop to intercept the energy flowing through MLI to a liquid hydrogen tank at a temperature between the environment and the liquid hydrogen can lower the heat load on the propellant system by as much as 50%. However, the refrigeration loop requires structural integration into the MLI. Use of a more traditional concept of MLI underneath this refrigeration loop requires that a structural system be put in place to support the loop. Such structures, even when thermally optimized, present a relatively large parasitic heat load into the tank. Through NASA small business innovation research funding, Quest Thermal Group and Ball Aerospace have been developing a structural MLI based insulation system. These systems are designed with discrete polymeric spacers between reflective layers instead of either dacron or silk netting. The spacers (or posts) have an intrinsic structural capability that is beyond that of just supporting the internal insulation mechanical loads. This new MLI variant called Load Bearing MLI (LB-MLI) has been developed specifically for the application of supporting thermal shields within the insulation system. Test articles (coupons) of the new LB-MLI product were fabricated for thermal performance testing using liquid nitrogen at Kennedy Space Center (KSC) and using cryocooler based calorimetry at Florida State University. The test results and analysis are presented. Thermal models developed for correlation with the thermal testing results both at KSC and testing that was performed at Florida State University are also discussed.

  19. Out of plane analysis for composite structures

    NASA Technical Reports Server (NTRS)

    Paul, P. C.; Saff, C. R.; Sanger, Kenneth B.; Mahler, M. A.; Kan, Han Pin; Kautz, Edward F.

    1990-01-01

    Simple two dimensional analysis techniques were developed to aid in the design of strong joints for integrally stiffened/bonded composite structures subjected to out of plane loads. It was found that most out of plane failures were due to induced stresses arising from rapid changes in load path direction or geometry, induced stresses due to changes in geometry caused by buckling, or direct stresses produced by fuel pressure or bearing loads. While the analysis techniques were developed to address a great variety of out of plane loading conditions, they were primarily derived to address the conditions described above. The methods were developed and verified using existing element test data. The methods were demonstrated using the data from a test failure of a high strain wingbox that was designed, built, and tested under a previous program. Subsequently, a set of design guidelines were assembled to assist in the design of safe, strong integral composite structures using the analysis techniques developed.

  20. Load-bearing capacity of fiber reinforced fixed composite bridges.

    PubMed

    Göncü Başaran, Emine; Ayna, Emrah; Üçtaşli, Sadullah; Vallittu, Pekka K; Lassila, Lippo V J

    2013-01-01

    The aim of this study was to evaluate the reinforcing effect of differently oriented fibers on the load-bearing capacity of three-unit fixed dental prostheses (FDPs). Forty-eight composite FDPs were fabricated. Specimens were divided into eight groups (n = 6/group; codes 1-8). Groups 1 and 5 were plain restorative composites (Grandio and Z100) without fiber reinforcement, groups 2 and 6 were reinforced with a continuous unidirectional fiber substructure, groups 3 and 7 were reinforced with a continuous bidirectional fiber and groups 4 and 8 were reinforced with a continuous bidirectional fiber substructure and continuous unidirectional fiber. FDPs were polymerized incrementally with a handheld light curing unit for 40 s and statically loaded until final fracture. Kruskal-Wallis analysis revealed that all groups had significantly different load-bearing capacities. Group 4 showed the highest mean load-bearing capacity and Group 7 the lowest. The results of this study suggest that continuous unidirectional fiber increased the mechanical properties of composite FDPs and bidirectional reinforcement slowed crack propagation on abutments.

  1. Structure analysis for plane geometry figures

    NASA Astrophysics Data System (ADS)

    Feng, Tianxiao; Lu, Xiaoqing; Liu, Lu; Li, Keqiang; Tang, Zhi

    2013-12-01

    As there are increasing numbers of digital documents for education purpose, we realize that there is not a retrieval application for mathematic plane geometry images. In this paper, we propose a method for retrieving plane geometry figures (PGFs), which often appear in geometry books and digital documents. First, detecting algorithms are applied to detect common basic geometry shapes from a PGF image. Based on all basic shapes, we analyze the structural relationships between two basic shapes and combine some of them to a compound shape to build the PGF descriptor. Afterwards, we apply matching function to retrieve candidate PGF images with ranking. The great contribution of the paper is that we propose a structure analysis method to better describe the spatial relationships in such image composed of many overlapped shapes. Experimental results demonstrate that our analysis method and shape descriptor can obtain good retrieval results with relatively high effectiveness and efficiency.

  2. Load Bearing Equipment for Bone and Muscle Project

    NASA Technical Reports Server (NTRS)

    Terrier, Douglas; Clayton, Ronald G.; Shackelford, Linda

    2015-01-01

    Axial skeletal loads coupled with muscle torque forces around joints maintain bone. Astronauts working in pairs to exercise can provide high eccentric loads for each other that are most effective. A prototype of load bearing equipment that will allow astronauts to perform exercises using each other for counter force generation in a controlled fashion and provide eccentric overload is proposed. A frame and attachments that can be rapidly assembled for use and easily stored will demonstrate feasibility of a design that can be adapted for ISS testing and Orion use.

  3. Evacuated load-bearing high performance insulation study

    NASA Technical Reports Server (NTRS)

    Parmley, R. T.; Cunnington, G. R.

    1977-01-01

    A light weight, vacuum jacketed, load bearing cryogenic insulation system was developed and tested on a 1.17-m (46-in.) spherical test tank. The vacuum jacket consists of 0.08 mm (0.003 in.) thick 321 stainless steel formed into a wedge design that allows elastic jacket movements as the tank shrinks (cools) or expands (warms up or is pressurized). Hollow glass spheres, approximately 80 micrometers in diameter with a bulk density of 0.069 g/cc (4.3 lb cubic foot), provide the insulating qualities and one atmosphere load bearing capability required. The design, fabrication, and test effort developed the manufacturing methods and engineering data needed to scale the system to other tank sizes, shapes, and applications. The program demonstrated that thin wall jackets can be formed and welded to maintain the required vacuum level of .013 Pa yet flex elastically for multiple reuses. No significant shifting or breakage of the microspheres occurred after 13 simulated Space Tug flight cycles on the test tank and a hundred 1 atmosphere load cycles in a flat plate calorimeter. The test data were then scaled to the Space Tug LO2 and LH2 tanks, and weight, thermal performance, payload performance, and costs were compared with a helium purged multilayer insulation system.

  4. Human Footprint Variation while Performing Load Bearing Tasks

    PubMed Central

    Wall-Scheffler, Cara M.; Wagnild, Janelle; Wagler, Emily

    2015-01-01

    Human footprint fossils have provided essential evidence about the evolution of human bipedalism as well as the social dynamics of the footprint makers, including estimates of speed, sex and group composition. Generally such estimates are made by comparing footprint evidence with modern controls; however, previous studies have not accounted for the variation in footprint dimensions coming from load bearing activities. It is likely that a portion of the hominins who created these fossil footprints were carrying a significant load, such as offspring or foraging loads, which caused variation in the footprint which could extend to variation in any estimations concerning the footprint’s maker. To identify significant variation in footprints due to load-bearing tasks, we had participants (N = 30, 15 males and 15 females) walk at a series of speeds carrying a 20kg pack on their back, side and front. Paint was applied to the bare feet of each participant to create footprints that were compared in terms of foot length, foot width and foot area. Female foot length and width increased during multiple loaded conditions. An appreciation of footprint variability associated with carrying loads adds an additional layer to our understanding of the behavior and morphology of extinct hominin populations. PMID:25738496

  5. Load-bearing properties of minimal-invasive monolithic lithium disilicate and zirconia occlusal onlays: finite element and theoretical analyses

    PubMed Central

    Ma, Li; Guess, Petra C.; Zhang, Yu

    2013-01-01

    Objectives The aim of this study was to test the hypothesis that monolithic lithium disilicate glass-ceramic occlusal onlay can exhibit a load-bearing capacity that approaches monolithic zirconia, due to a smaller elastic modulus mismatch between the lithium disilicate and its supporting tooth structure relative to zirconia. Methods Ceramic occlusal onlays of various thicknesses cemented to either enamel or dentin were considered. Occlusal load was applied through an enamel-like deformable indenter or a control rigid indenter. Flexural tensile stress at the ceramic intaglio (cementation) surface—a cause for bulk fracture of occlusal onlays—was rigorously analyzed using finite element analysis and classical plate-on-foundation theory. Results When bonded to enamel (supported by dentin), the load-bearing capacity of lithium disilicate can approach 75% of that of zirconia, despite the flexural strength of lithium disilicate (400 MPa) being merely 40% of zirconia (1000 MPa). When bonded to dentin (with the enamel completely removed), the load-bearing capacity of lithium disilicate is about 57% of zirconia, still significantly higher than the anticipated value based on its strength. Both ceramics show slightly higher load-bearing capacity when loaded with a deformable indenter (enamel, glass-ceramic, or porcelain) rather than a rigid indenter. Significance When supported by enamel, the load-bearing property of minimally invasive lithium disilicate occlusal onlays (0.6 to 1.4 mm thick) can exceed 70% of that of zircona. Additionally, a relatively weak dependence of fracture load on restoration thickness indicates that a 1.2 mm thin lithium disilicate onlay can be as fracture resistant as its 1.6 mm counterpart. PMID:23683531

  6. Plane mixing layer vortical structure kinematics

    NASA Technical Reports Server (NTRS)

    Leboeuf, Richard L.

    1993-01-01

    The objective of the current project was to experimentally investigate the structure and dynamics of the streamwise vorticity in a plane mixing layer. The first part of this research program was intended to clarify whether the observed decrease in mean streamwise vorticity in the far-field of mixing layers is due primarily to the 'smearing' caused by vortex meander or to diffusion. Two-point velocity correlation measurements have been used to show that there is little spanwise meander of the large-scale streamwise vortical structure. The correlation measurements also indicate a large degree of transverse meander of the streamwise vorticity which is not surprising since the streamwise vorticity exists in the inclined braid region between the spanwise vortex core regions. The streamwise convection of the braid region thereby introduces an apparent transverse meander into measurements using stationary probes. These results corroborated with estimated secondary velocity profiles in which the streamwise vorticity produces a signature which was tracked in time.

  7. Muscle force regulates bone shaping for optimal load-bearing capacity during embryogenesis.

    PubMed

    Sharir, Amnon; Stern, Tomer; Rot, Chagai; Shahar, Ron; Zelzer, Elazar

    2011-08-01

    The vertebrate skeleton consists of over 200 individual bones, each with its own unique shape, size and function. We study the role of intrauterine muscle-induced mechanical loads in determining the three-dimensional morphology of developing bones. Analysis of the force-generating capacity of intrauterine muscles in mice revealed that developing bones are subjected to significant and progressively increasing mechanical challenges. To evaluate the effect of intrauterine loads on bone morphogenesis and the contribution of the emerging shape to the ability of bones to withstand these loads, we monitored structural and mineral changes during development. Using daily micro-CT scans of appendicular long bones we identify a developmental program, which we term preferential bone growth, that determines the specific circumferential shape of each bone by employing asymmetric mineral deposition and transient cortical thickening. Finite element analysis demonstrates that the resulting bone structure has optimal load-bearing capacity. To test the hypothesis that muscle forces regulate preferential bone growth in utero, we examine this process in a mouse strain (mdg) that lacks muscle contractions. In the absence of mechanical loads, the stereotypical circumferential outline of each bone is lost, leading to the development of mechanically inferior bones. This study identifies muscle force regulation of preferential bone growth as the module that shapes the circumferential outline of bones and, consequently, optimizes their load-bearing capacity during development. Our findings invoke a common mechanism that permits the formation of different circumferential outlines in different bones.

  8. A detailed study of homogeneous agarose/hydroxyapatite nanocomposites for load-bearing bone tissue.

    PubMed

    Hu, Jingxiao; Zhu, Youjia; Tong, Hua; Shen, Xinyu; Chen, Li; Ran, Jiabing

    2016-01-01

    Agarose/hydroxyapatite (agar/HA) nanocomposites for load-bearing bone substitutes were successfully fabricated via a novel in situ precipitation method. Observation via SEM and TEM revealed that the spherical inorganic nanoparticles of approximately 50 nm were well dispersed in the organic matrix, and the crystallographic area combined closely with the amorphous area. The uniform dispersion of HA nanoparticles had prominent effect on improving the mechanical properties of the agar/HA nanocomposites (the highest elastic modulus: 1104.42 MPa; the highest compressive strength: 400.039 MPa), which proved to be potential load-bearing bone substitutes. The thermal stability of agarose and nanocomposites was also studied. The MG63 osteoblast-like cells on the composite disks displayed fusiform and polygonal morphology in the presence of HA, suggesting that the cell maturation was promoted. The results of cell proliferation and cell differentiation indicated that the cells cultured on the agar/HA composite disks significantly increased the alkaline phosphatase activity and calcium deposition. The structural role of agarose in the composite system was investigated to better understand the effect of biopolymer on structure and properties of the composites. The optimal properties were the result of a comprehensive synergy of the components.

  9. Mesenchymal stem cell proliferation and differentiation on load-bearing trabecular Nitinol scaffolds.

    PubMed

    Gotman, Irena; Ben-David, Dror; Unger, Ronald E; Böse, Thomas; Gutmanas, Elazar Y; Kirkpatrick, C James

    2013-09-01

    Bone tissue regeneration in load-bearing regions of the body requires high-strength porous scaffolds capable of supporting angiogenesis and osteogenesis. 70% porous Nitinol (NiTi) scaffolds with a regular 3-D architecture resembling trabecular bone were produced from Ni foams using an original reactive vapor infiltration technique. The "trabecular Nitinol" scaffolds possessed a high compressive strength of 79 MPa and high permeability of 6.9×10(-6) cm2. The scaffolds were further modified to produce a near Ni-free surface layer and evaluated in terms of Ni ion release and human mesenchymal stem cell (hMSC) proliferation (AlamarBlue), differentiation (alkaline phosphatase activity, ALP) and mineralization (Alizarin Red S staining). Scanning electron microscopy was employed to qualitatively corroborate the results. hMSCs were able to adhere and proliferate on both as-produced and surface-modified trabecular NiTi scaffolds, to acquire an osteoblastic phenotype and produce a mineralized extracellular matrix. Both ALP activity and mineralization were increased on porous scaffolds compared to control polystyrene plates. Experiments in a model coculture system of microvascular endothelial cells and hMSCs demonstrated the formation of prevascular structures in trabecular NiTi scaffolds. These data suggest that load-bearing trabecular Nitinol scaffolds could be effective in regenerating damaged or lost bone tissue.

  10. The influence of operating loads on the state of stress and strain in selected load-bearing elements of a tower-type headgear structure / Wpływ obciążeń eksploatacyjnych na stan naprężenia oraz przemieszczenia wybranych elementów nośnych konstrukcji basztowej wieży szybowych

    NASA Astrophysics Data System (ADS)

    Wolny, Stanisław

    2012-12-01

    The headgear structure allows the conveyance to be moved over the shaft top to the loading (unloading) point, at the same time it keeps in place the rope pulleys while tower-type headgear structures also accommodate the entire winder installations. The headgear is where the final stage of the hoisting installation is located and where the surface transport systems begin. These aspects strongly impact the actual shape of the tower, its height and in some cases determine the design of the entire winding gear. In order that all the headgear functions should be provided, it is required that the ultimate state conditions should be maintained throughout its entire service life. In order to assess the critical service conditions, the computation procedure should be applied based on design loads and fatigue endurance parameters. The computations of characteristic loads acting on the headgear structure use the developed model of the system based on the dynamic analysis carried out for a specific case: a hoisting installation operated in one of the underground collieries in Poland. The maximal and minimal loads acting on a Koepe pulley and those required for the system operation are determined accordingly. The laws of dynamics provide a background for finding the forces and moments of forces acting in the components of the driving system (including the electric motors and pulley blocks) for the specified loading of the Koepe pulley. Underlying the numerical FEM model of the tower-type headgear structure are the technical specifications of the analysed object and FEM calculations followed by endurance analysis to find the state of stress in structural elements of the headgear under the typical service conditions. The results help in assessing how the design of the hoisting installation should impact on safety features of load-bearing elements in the headgear structure.

  11. Novel Concepts for Conformal Load-Bearing Antenna Structure

    DTIC Science & Technology

    2008-02-01

    liquid moulding techniques of Vacuum Assisted Resin Transfer Moulding ( VARTM ) or Resin Transfer Moulding ( RTM ). Latter specimens were prepared using... VARTM ) 4 Resin Transfer Moulding ( RTM ) 5 Meter resin onto dry fibre then stage in an autoclave 7 Mandrel Number 0 As-received 25.4 mm x 12.7 mm...r Spiral slot radius RF Radio Frequency RFID Radio Frequency Identification Rs Surface resistivity RTM Resin Transfer Moulding S11 Reflection S

  12. Three-dimensional printing of porous load-bearing bioceramic scaffolds.

    PubMed

    Mancuso, Elena; Alharbi, Naif; Bretcanu, Oana A; Marshall, Martyn; Birch, Mark A; McCaskie, Andrew W; Dalgarno, Kenneth W

    2016-12-01

    This article reports on the use of the binder jetting three-dimensional printing process combined with sintering to process bioceramic materials to form micro- and macroporous three-dimensional structures. Three different glass-ceramic formulations, apatite-wollastonite and two silicate-based glasses, have been processed using this route to create porous structures which have Young's modulus equivalent to cortical bone and average bending strengths in the range 24-36 MPa. It is demonstrated that a range of macroporous geometries can be created with accuracies of ±0.25 mm over length scales up to 40 mm. Hot-stage microscopy is a valuable tool in the definition of processing parameters for the sintering step of the process. Overall, it is concluded that binder jetting followed by sintering offers a versatile process for the manufacture of load-bearing bioceramic components for bone replacement applications.

  13. Bending strength of piezoelectric ceramics and single crystals for multifunctional load-bearing applications.

    PubMed

    Anton, Steven R; Erturk, Alper; Inman, Daniel

    2012-06-01

    The topic of multifunctional material systems using active or smart materials has recently gained attention in the research community. Multifunctional piezoelectric systems present the ability to combine multiple functions into a single active piezoelectric element, namely, combining sensing, actuation, or energy conversion ability with load-bearing capacity. Quantification of the bending strength of various piezoelectric materials is, therefore, critical in the development of load-bearing piezoelectric systems. Three-point bend tests are carried out on a variety of piezoelectric ceramics including soft monolithic piezoceramics (PZT-5A and PZT-5H), hard monolithic ceramics (PZT-4 and PZT-8), single-crystal piezoelectrics (PMN-PT and PMN-PZT), and commercially packaged composite devices (which contain active PZT-5A layers). A common 3-point bend test procedure is used throughout the experimental tests. The bending strengths of these materials are found using Euler-Bernoulli beam theory to be 44.9 MPa for PMN-PZT, 60.6 MPa for PMN-PT, 114.8 MPa for PZT- 5H, 123.2 MPa for PZT-4, 127.5 MPa for PZT-8, 140.4 MPa for PZT-5A, and 186.6 MPa for the commercial composite. The high strength of the commercial configuration is a result of the composite structure that allows for shear stresses on the surfaces of the piezoelectric layers, whereas the low strength of the single-crystal materials is due to their unique crystal structure, which allows for rapid propagation of cracks initiating at flaw sites. The experimental bending strength results reported, which are linear estimates without nonlinear ferroelastic considerations, are intended for use in the design of multifunctional piezoelectric systems in which the active device is subjected to bending loads.

  14. Biomimetic nanocomposites of carboxymethyl cellulose-hydroxyapatite: novel three dimensional load bearing bone grafts.

    PubMed

    Garai, Subhadra; Sinha, Arvind

    2014-03-01

    An innovative biomimetic synthesis of novel three dimensional micro/macro porous carboxymethyl cellulose (CMC)-hydroxyapatite (HA) nanocomposites having four systematically different compositions has been established for its possible application as a load bearing synthetic bone graft. Our process, being in situ, involves a simple and cost effective route akin to a matrix mediated biomineralization process. Developed synthesis route not only controls the size of HA particles in the range of 15-50 nm, embedded in CMC matrix, but also assists in the formation of a mechanically strong three dimensional nanocomposite structures due to physical cross linking of HA impregnated CMC matrix. The process does not involve any toxic cross linker and works at near ambient conditions. The nanocomposites are systematically structurally and mechanically characterized using various techniques like scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform IR (FTIR), solid state (13)C nuclear magnetic resonance ((13)C NMR), thermo-gravimetric analysis (TGA) and Universal mechanical test. It reveals that the ionic/polar or electrostatic interactions are the main driving force for formation of load bearing three dimensional nanocomposites via a process similar to matrix mediated biomineralization. Compressive strength and compressive modulus of nanocomposites, being in the range of 1.74-12 MPa and 157-330 MPa, respectively, meet the desired range of compressive strength for the synthetic grafts used in cancellous bone. An increase in the compressive strength with increase in the porosity has been an interesting observation in the present study. In vitro cytotoxicity of the synthesized nanocomposites has been evaluated using bone marrow mesenchymal stem cells (BMSC) isolated from Wistar rat.

  15. High strength, surface porous polyether-ether-ketone for load-bearing orthopaedic implants

    PubMed Central

    Evans, Nathan T.; Torstrick, F. Brennan; Lee, Christopher S.D.; Dupont, Kenneth M.; Safranski, David L.; Chang, W. Allen; Macedo, Annie E.; Lin, Angela; Boothby, Jennifer M.; Whittingslow, Daniel C.; Carson, Robert A.; Guldberg, Robert E.; Gall, Ken

    2015-01-01

    Despite its widespread clinical use in load-bearing orthopaedic implants, polyether-ether-ketone (PEEK) is often associated with poor osseointegration. In this study, a surface porous PEEK material (PEEK-SP) was created using a melt extrusion technique. The porous layer thickness was 399.6±63.3 µm and possessed a mean pore size of 279.9±31.6 µm, strut spacing of 186.8±55.5 µm, porosity of 67.3±3.1%, and interconnectivity of 99.9±0.1%. Monotonic tensile tests showed that PEEK-SP preserved 73.9% of the strength (71.06±2.17 MPa) and 73.4% of the elastic modulus (2.45±0.31 GPa) of as-received, injection molded PEEK. PEEK-SP further demonstrated a fatigue strength of 60.0 MPa at one million cycles, preserving 73.4% of the fatigue resistance of injection molded PEEK. Interfacial shear testing showed the pore layer shear strength to be 23.96±2.26 MPa. An osseointegration model in the rat revealed substantial bone formation within the pore layer at 6 and 12 weeks via µCT and histological evaluation. Ingrown bone was more closely apposed to the pore wall and fibrous tissue growth was reduced in PEEK-SP when compared to non-porous PEEK controls. These results indicate that PEEK-SP could provide improved osseointegration while maintaining the structural integrity necessary for load-bearing orthopaedic applications. PMID:25463499

  16. Assessment of the transportation route of oversize and excessive loads in relation to the load-bearing capacity of existing bridges

    NASA Astrophysics Data System (ADS)

    Doležel, Jiří; Novák, Drahomír; Petrů, Jan

    2017-09-01

    Transportation routes of oversize and excessive loads are currently planned in relation to ensure the transit of a vehicle through critical points on the road. Critical points are level-intersection of roads, bridges etc. This article presents a comprehensive procedure to determine a reliability and a load-bearing capacity level of the existing bridges on highways and roads using the advanced methods of reliability analysis based on simulation techniques of Monte Carlo type in combination with nonlinear finite element method analysis. The safety index is considered as a main criterion of the reliability level of the existing construction structures and the index is described in current structural design standards, e.g. ISO and Eurocode. An example of a single-span slab bridge made of precast prestressed concrete girders of the 60 year current time and its load bearing capacity is set for the ultimate limit state and serviceability limit state. The structure’s design load capacity was estimated by the full probability nonlinear MKP analysis using a simulation technique Latin Hypercube Sampling (LHS). Load-bearing capacity values based on a fully probabilistic analysis are compared with the load-bearing capacity levels which were estimated by deterministic methods of a critical section of the most loaded girders.

  17. Application of a load-bearing passive and active vibration isolation system in hydraulic drives

    NASA Astrophysics Data System (ADS)

    Unruh, Oliver; Haase, Thomas; Pohl, Martin

    2016-09-01

    Hydraulic drives are widely used in many engineering applications due to their high power to weight ratio. The high power output of the hydraulic drives produces high static and dynamic reaction forces and moments which must be carried by the mounts and the surrounding structure. A drawback of hydraulic drives based on rotating pistons consists in multi-tonal disturbances which propagate through the mounts and the load bearing structure and produce structure borne sound at the surrounding structures and cavities. One possible approach to overcome this drawback is to use an optimised mounting, which combines vibration isolation in the main disturbance direction with the capability to carry the reaction forces and moments. This paper presents an experimental study, which addresses the vibration isolation performance of an optimised mounting. A dummy hydraulic drive is attached to a generic surrounding structure with optimised mounting and excited by multiple shakers. In order to improve the performance of the passive vibration isolation system, piezoelectric transducers are applied on the mounting and integrated into a feed-forward control loop. It is shown that the optimised mounting of the hydraulic drive decreases the vibration transmission to the surrounding structure by 8 dB. The presented study also reveals that the use of the active control system leads to a further decrease of vibration transmission of up to 14 dB and also allows an improvement of the vibration isolation in an additional degree of freedom and higher harmonic frequencies.

  18. Out-of-plane chiral domain wall spin-structures in ultrathin in-plane magnets

    DOE PAGES

    Chen, Gong; Kang, Sang Pyo; Ophus, Colin; ...

    2017-05-19

    Chiral spin textures in ultrathin films, such as skyrmions or chiral domain walls, are believed to offer large performance advantages in the development of novel spintronics technologies. While in-plane magnetized films have been studied extensively as media for current- and field-driven domain wall dynamics with applications in memory or logic devices, the stabilization of chiral spin textures in in-plane magnetized films has remained rare. Here we report a phase of spin structures in an in-plane magnetized ultrathin film system where out-of-plane spin orientations within domain walls are stable. Moreover, while domain walls in in-plane films are generally expected to bemore » non-chiral, we show that right-handed spin rotations are strongly favoured in this system, due to the presence of the interfacial Dzyaloshinskii-Moriya interaction. These results constitute a platform to explore unconventional spin dynamics and topological phenomena that may enable high-performance in-plane spin-orbitronics devices.« less

  19. Out-of-plane chiral domain wall spin-structures in ultrathin in-plane magnets

    NASA Astrophysics Data System (ADS)

    Chen, Gong; Kang, Sang Pyo; Ophus, Colin; N'diaye, Alpha T.; Kwon, Hee Young; Qiu, Ryan T.; Won, Changyeon; Liu, Kai; Wu, Yizheng; Schmid, Andreas K.

    2017-05-01

    Chiral spin textures in ultrathin films, such as skyrmions or chiral domain walls, are believed to offer large performance advantages in the development of novel spintronics technologies. While in-plane magnetized films have been studied extensively as media for current- and field-driven domain wall dynamics with applications in memory or logic devices, the stabilization of chiral spin textures in in-plane magnetized films has remained rare. Here we report a phase of spin structures in an in-plane magnetized ultrathin film system where out-of-plane spin orientations within domain walls are stable. Moreover, while domain walls in in-plane films are generally expected to be non-chiral, we show that right-handed spin rotations are strongly favoured in this system, due to the presence of the interfacial Dzyaloshinskii-Moriya interaction. These results constitute a platform to explore unconventional spin dynamics and topological phenomena that may enable high-performance in-plane spin-orbitronics devices.

  20. Out-of-plane chiral domain wall spin-structures in ultrathin in-plane magnets

    PubMed Central

    Chen, Gong; Kang, Sang Pyo; Ophus, Colin; N'Diaye, Alpha T.; Kwon, Hee Young; Qiu, Ryan T.; Won, Changyeon; Liu, Kai; Wu, Yizheng; Schmid, Andreas K.

    2017-01-01

    Chiral spin textures in ultrathin films, such as skyrmions or chiral domain walls, are believed to offer large performance advantages in the development of novel spintronics technologies. While in-plane magnetized films have been studied extensively as media for current- and field-driven domain wall dynamics with applications in memory or logic devices, the stabilization of chiral spin textures in in-plane magnetized films has remained rare. Here we report a phase of spin structures in an in-plane magnetized ultrathin film system where out-of-plane spin orientations within domain walls are stable. Moreover, while domain walls in in-plane films are generally expected to be non-chiral, we show that right-handed spin rotations are strongly favoured in this system, due to the presence of the interfacial Dzyaloshinskii–Moriya interaction. These results constitute a platform to explore unconventional spin dynamics and topological phenomena that may enable high-performance in-plane spin-orbitronics devices. PMID:28524875

  1. Out-of-plane chiral domain wall spin-structures in ultrathin in-plane magnets.

    PubMed

    Chen, Gong; Kang, Sang Pyo; Ophus, Colin; N'Diaye, Alpha T; Kwon, Hee Young; Qiu, Ryan T; Won, Changyeon; Liu, Kai; Wu, Yizheng; Schmid, Andreas K

    2017-05-19

    Chiral spin textures in ultrathin films, such as skyrmions or chiral domain walls, are believed to offer large performance advantages in the development of novel spintronics technologies. While in-plane magnetized films have been studied extensively as media for current- and field-driven domain wall dynamics with applications in memory or logic devices, the stabilization of chiral spin textures in in-plane magnetized films has remained rare. Here we report a phase of spin structures in an in-plane magnetized ultrathin film system where out-of-plane spin orientations within domain walls are stable. Moreover, while domain walls in in-plane films are generally expected to be non-chiral, we show that right-handed spin rotations are strongly favoured in this system, due to the presence of the interfacial Dzyaloshinskii-Moriya interaction. These results constitute a platform to explore unconventional spin dynamics and topological phenomena that may enable high-performance in-plane spin-orbitronics devices.

  2. 8. Interior of Building 1015 (land plane hangar), structural detail, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    8. Interior of Building 1015 (land plane hangar), structural detail, looking northeast - Naval Air Station Chase Field, Building 1015, Byrd Street, .82 mile South-southeast of intersection of Texas State Highway 202 & Independence Street, Beeville, Bee County, TX

  3. 7. Interior of Building 1015 (land plane hangar), structural detail, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    7. Interior of Building 1015 (land plane hangar), structural detail, looking northeast - Naval Air Station Chase Field, Building 1015, Byrd Street, .82 mile South-southeast of intersection of Texas State Highway 202 & Independence Street, Beeville, Bee County, TX

  4. Tank Applied Testing of Load-Bearing Multilayer Insulation (LB-MLI)

    NASA Technical Reports Server (NTRS)

    Johnson, Wesley L.; Valenzuela, Juan G.; Feller, Jerr; Plachta, Dave

    2014-01-01

    The development of long duration orbital cryogenic storage systems will require the reduction of heat loads into the storage tank. In the case of liquid hydrogen, complete elimination of the heat load at 20 K is currently impractical due to the limitations in lift available on flight cryocoolers. In order to reduce the heat load, without having to remove heat at 20 K, the concept of Reduced Boil-Off uses cooled shields within the insulation system at approximately 90 K. The development of Load-Bearing Multilayer Insulation (LB-MLI) allowed the 90 K shield with tubing and cryocooler attachments to be suspended within the MLI and still be structurally stable. Coupon testing both thermally and structurally were performed to verify that the LB-MLI should work at the tank applied level. Then tank applied thermal and structural (acoustic) testing was performed to demonstrate the functionality of the LB-MLI as a structural insulation system. The LB-MLI showed no degradation of thermal performance due to the acoustic testing and showed excellent thermal performance when integrated with a 90 K class cryocooler on a liquid hydrogen tank.

  5. Tank Applied Testing of Load-Bearing Multilayer Insulation (LB-MLI)

    NASA Technical Reports Server (NTRS)

    Johnson, Wesley L.; Valenzuela, Juan G.; Feller, Jeffrey R.; Plachta, David W.

    2014-01-01

    The development of long duration orbital cryogenic storage systems will require the reduction of heat loads into the storage tank. In the case of liquid hydrogen, complete elimination of the heat load at 20 K is currently impractical due to the limitations in lift available on flight cryocoolers. In order to reduce the heat load, without having to remove heat at 20 K, the concept of Reduced Boil-Off uses cooled shields within the insulation system at approximately 90 K. The development of Load-Bearing Multilayer Insulation (LB-MLI) allowed the 90 K shield with tubing and cryocooler attachments to be suspended within the MLI and still be structurally stable. Coupon testing, both thermal and structural was performed to verify that the LB-MLI should work at the tank applied level. Then tank applied thermal and structural (acoustic) testing was performed to demonstrate the functionality of the LB-MLI as a structural insulation system. The LB-MLI showed no degradation of thermal performance due to the acoustic testing and showed excellent thermal performance when integrated with a 90 K class cryocooler on a liquid hydrogen tank.

  6. Protein viscosity, mineral fraction and staggered architecture cooperatively enable the fastest stress wave decay in load-bearing biological materials.

    PubMed

    Qwamizadeh, Mahan; Zhang, Zuoqi; Zhou, Kun; Zhang, Yong Wei

    2016-07-01

    One of the key functions of load-bearing biological materials, such as bone, dentin and sea shell, is to protect their inside fragile organs by effectively damping dynamic impact. How those materials achieve this remarkable function remains largely unknown. Using systematic finite element analyses, we study the stress wave propagation and attenuation in cortical bone at the nanoscale as a model material to examine the effects of protein viscosity, mineral fraction and staggered architecture on the elastic wave decay. It is found that the staggered arrangement, protein viscosity and mineral fraction work cooperatively to effectively attenuate the stress wave. For a typical mineral volume fraction and protein viscosity, an optimal staggered nanostructure with specific feature sizes and layouts is able to give rise to the fastest stress wave decay, and the optimal aspect ratio and thickness of mineral platelets are in excellent agreement with experimental measurements. In contrary, as the mineral volume fraction or the protein viscosity goes much higher, the structural arrangement is seen having trivial effect on the stress wave decay, suggesting that the damping properties of the composites go into the structure-insensitive regime from the structure-sensitive regime. These findings not only significantly add to our understanding of the structure-function relationship of load-bearing biological materials, and but also provide useful guidelines for the design of bio-inspired materials with superior resistance to impact loading.

  7. ON THE BIOMECHANICAL FUNCTION OF SCAFFOLDS FOR ENGINEERING LOAD BEARING SOFT TISSUES

    PubMed Central

    Stella, John A.; D’Amore, Antonio; Wagner, William R.; Sacks, Michael S.

    2010-01-01

    Replacement or regeneration of load bearing soft tissues has long been the impetus for the development bioactive materials. While maturing, current efforts continue to be confounded by our lack of understanding of the intricate multi-scale hierarchical arrangements and interactions typically found in native tissues. The current state of the art in biomaterial processing enables a degree of controllable microstructure that can be used for the development of model systems to deduce fundamental biological implications of matrix morphologies on cell function. Furthermore, the development of computational frameworks which allow for the simulation of experimentally derived observations represents a positive departure from what has mostly been an empirically driven field, enabling a deeper understanding of the highly complex biological mechanisms we wish to ultimately emulate. Ongoing research is actively pursuing new materials and processing methods to control material structure down to the micro-scale to sustain or improve cell viability, guide tissue growth, and provide mechanical integrity all while exhibiting the capacity to degrade in a controlled manner. The purpose of this review is not to focus solely on material processing but to assess the ability of these techniques to produce mechanically sound tissue surrogates, highlight the unique structural characteristics produced in these materials, and discuss how this translates to distinct macroscopic biomechanical behaviors. PMID:20060509

  8. Tissue Changes During Operational Load Bearing in UH-60 Aircrew Using Magnetic Resonance Imaging.

    PubMed

    Games, Kenneth E; Kollock, Roger O; Windham, Jerrod; Fischer, Gregory S; Sefton, JoEllen M

    2015-09-01

    Warfighters involved in mounted operations often experience prolonged periods of tissue loading, leading to injury. Determining how anatomical structures are affected during loading aids in the prevention and treatment of injury. The purpose of this study was to develop a magnetic resonance imaging (MRI) compatible seat system that simulates a UH-60 Blackhawk in-flight sitting posture. Eight men were scanned with a 3.0 Tesla MRI. Scans were collected with and without 6.38 psi of pressure applied to the buttocks via two air bladders and an MRI-compatible robot controller system. Scans revealed that 6.38 psi of pressure applied to the buttocks significantly decreases total soft-tissue thickness beneath the left and right ischial tuberosities by 3.6 and 3.8 mm, respectively. At operational load bearing pressures seen in the UH-60, the soft tissue structures of the buttocks are compressed. These findings aid in our understanding of the etiology of repetitive trauma disorders in aircrew due to prolonged sitting. This study serves as the foundation for future work examining the anatomical changes associated with prolonged restricted sitting and other operational activities. A better understanding of the anatomical characteristics associated with mounted operations is invaluable to the prevention and treatment of injuries reported by warfighters and civilian populations.

  9. Two-plane symmetry in the structural organization of man.

    PubMed

    Ermolenko, A E

    2005-01-01

    Manifestations of symmetry in the human structural organization in ontogenesis and phylogenetic development are analysed. A concept of macrobiocrystalloid with inherent complex symmetry is proposed for the description of the human organism in its integrity. The symmetry can be characterized as two-plane radial (quadrilateral), where the planar symmetry is predominant while the layout of organs of radial symmetry is subordinated to it. Out of the two planes of symmetry (sagittal and horizontal), the sagittal plane is predominant: (a) the location of the organs is governed by two principles: in compliance with the symmetry planes and in compliance with the radial symmetry around cavities; (b) the location of the radial symmetry organs is also governed by the principle of two-plane symmetry; (c) out of the four antimeres of two-plane symmetry, two are paired while the other two have merged into one organ; (d) some organs which are antimeres relative to the horizontal plane are located at the cranial end of the organism (sensory organs, cerebrum-cerebellum, heart-spleen and others). The two-plane symmetry is formed by two mechanisms--(a) the impact of morphogenetic fields of the whole crystalloid organism during embriogenesis and (b) genetic mechanisms of the development of chromosomes having two-plane symmetry. When comparing mineral and biological entities we should consider not the whole immobile crystal but only the active superficial part of a growing or dissolving crystal, the interface between the crystal surface and the crystal-forming environment which directly controls crystal growth and adapts itself to it, as well as crystal feed stock expressed in the structure of concentration flows. The symmetry of the chromosome, of the embrion at the early stages of cell cleavage as well as of some organs and systems in their phylogenetic development is described.

  10. Glide planes symmetry in the organization of some sulfide structures

    NASA Astrophysics Data System (ADS)

    Borisov, S. V.; Magarill, S. A.; Pervukhina, N. V.

    2016-03-01

    The role of glide planes in the organization of structures is shown based on a crystallographic analysis of the monoclinic structures of TlAs3S5 and Tl2(As,Sb)3S13 sulfides. In the first structure, cations and anions form systems (with identical geometries) of two face-centered sublattices, linked by the c plane, with the effect of unified "two-dimensional" (2D) ordering. The second structure, exhibiting signs of order-disorder (OD) type, is interpreted as a superposition of two noncentrosymmetric components with independent cation and anion sublattices, which, however, also form a regular 2D order due to the n plane. The stabilizing role of Tl cations in the geometry of cation matrices is indicated.

  11. Characterization of load bearing metrological parameters in reptilian exuviae in comparison to precision-finished cylinder liner surfaces

    NASA Astrophysics Data System (ADS)

    Abdel-Aal, H. A.; El Mansori, M.

    2014-10-01

    Design of precise functional surfaces is essential for many future applications. In the technological realm, the accumulated experience with construction of such surfaces is not sufficient. Nature provides many examples of dynamic surfaces worthy of study and adoption, at least in concept, within human engineering. This work probes the load-bearing metrological features of the ventral skin in snakes. We examine the structure of two snake species that mainly move by rectilinear locomotion. These are Python regius (Pythonidae) and Bitis gabonica (Vipridae). To this end, we focus on the load-bearing characteristics of the ventral skin surface (i.e., the Sk family of parameters). Therefore, detailed comparison is drawn between the metrological structure of the reptilian surfaces and two sets of technological data. The first set pertains to an actual commercial cylinder liner, whereas the second set is a summary of recommended surface finish metrological values for several commercial cylinder liner manufacturers. The results highlight several similarities between the two types of surfaces. In particular, it is shown that there is a striking correspondence between the sense of texture morphology within both surfaces (although their construction evolved along entirely different paths). It is also shown that reptilian surfaces manifest a high degree of specialization with respect to habitat constraints on wear resistance and adhesive effects. In particular, their surface displays a high degree of pre-conditioning to functional requirements, which eliminates the need for a running-in period.

  12. Load bearing and stiffness tailored NiTi implants produced by additive manufacturing: a simulation study

    NASA Astrophysics Data System (ADS)

    Rahmanian, Rasool; Shayesteh Moghaddam, Narges; Haberland, Christoph; Dean, David; Miller, Michael; Elahinia, Mohammad

    2014-03-01

    Common metals for stable long-term implants (e.g. stainless steel, Titanium and Titanium alloys) are much stiffer than spongy cancellous and even stiffer than cortical bone. When bone and implant are loaded this stiffness mismatch results in stress shielding and as a consequence, degradation of surrounding bony structure can lead to disassociation of the implant. Due to its lower stiffness and high reversible deformability, which is associated with the superelastic behavior, NiTi is an attractive biomaterial for load bearing implants. However, the stiffness of austenitic Nitinol is closer to that of bone but still too high. Additive manufacturing provides, in addition to the fabrication of patient specific implants, the ability to solve the stiffness mismatch by adding engineered porosity to the implant. This in turn allows for the design of different stiffness profiles in one implant tailored to the physiological load conditions. This work covers a fundamental approach to bring this vision to reality. At first modeling of the mechanical behavior of different scaffold designs are presented as a proof of concept of stiffness tailoring. Based on these results different Nitinol scaffolds can be produced by additive manufacturing.

  13. Purdue Plane Structures Analyzer II : a computerized wood engineering system

    Treesearch

    S. K. Suddarth; R. W. Wolfe

    1984-01-01

    The Purdue Plane Structures Analyzer (PPSA) is a computer program developed specifically for the analysis of wood structures. It uses recognized analysis procedures, in conjunction with recommendations of the 1982 National Design Specification for Wood Construction, to determine stresses and deflections of wood trusses and frames. The program offers several options for...

  14. Design, fabrication and test of Load Bearing multilayer insulation to support a broad area cooled shield

    NASA Astrophysics Data System (ADS)

    Dye, S. A.; Johnson, W. L.; Plachta, D. W.; Mills, G. L.; Buchanan, L.; Kopelove, A. B.

    2014-11-01

    Improvements in cryogenic propellant storage are needed to achieve reduced or Zero Boil Off of cryopropellants, critical for long duration missions. Techniques for reducing heat leak into cryotanks include using passive multi-layer insulation (MLI) and vapor cooled or actively cooled thermal shields. Large scale shields cannot be supported by tank structural supports without heat leak through the supports. Traditional MLI also cannot support shield structural loads, and separate shield support mechanisms add significant heat leak. Quest Thermal Group and Ball Aerospace, with NASA SBIR support, have developed a novel Load Bearing multi-layer insulation (LBMLI) capable of self-supporting thermal shields and providing high thermal performance. We report on the development of LBMLI, including design, modeling and analysis, structural testing via vibe and acoustic loading, calorimeter thermal testing, and Reduced Boil-Off (RBO) testing on NASA large scale cryotanks. LBMLI uses the strength of discrete polymer spacers to control interlayer spacing and support the external load of an actively cooled shield and external MLI. Structural testing at NASA Marshall was performed to beyond maximum launch profiles without failure. LBMLI coupons were thermally tested on calorimeters, with superior performance to traditional MLI on a per layer basis. Thermal and structural tests were performed with LBMLI supporting an actively cooled shield, and comparisons are made to the performance of traditional MLI and thermal shield supports. LBMLI provided a 51% reduction in heat leak per layer over a previously tested traditional MLI with tank standoffs, a 38% reduction in mass, and was advanced to TRL5. Active thermal control using LBMLI and a broad area cooled shield offers significant advantages in total system heat flux, mass and structural robustness for future Reduced Boil-Off and Zero Boil-Off cryogenic missions with durations over a few weeks.

  15. Direct ink writing of highly porous and strong glass scaffolds for load-bearing bone defects repair and regeneration.

    PubMed

    Fu, Qiang; Saiz, Eduardo; Tomsia, Antoni P

    2011-10-01

    The quest for synthetic materials to repair load-bearing bone lost because of trauma, cancer, or congenital bone defects requires the development of porous, high-performance scaffolds with exceptional mechanical strength. However, the low mechanical strength of porous bioactive ceramic and glass scaffolds, compared with that of human cortical bone, has limited their use for these applications. In the present work bioactive 6P53B glass scaffolds with superior mechanical strength were fabricated using a direct ink writing technique. The rheological properties of Pluronic® F-127 (referred to hereafter simply as F-127) hydrogel-based inks were optimized for the printing of features as fine as 30 μm and of three-dimensional scaffolds. The mechanical strength and in vitro degradation of the scaffolds were assessed in a simulated body fluid (SBF). The sintered glass scaffolds showed a compressive strength (136 ± 22 MPa) comparable with that of human cortical bone (100-150 MPa), while the porosity (60%) was in the range of that of trabecular bone (50-90%). The strength is ~100-times that of polymer scaffolds and 4-5-times that of ceramic and glass scaffolds with comparable porosities. Despite the strength decrease resulting from weight loss during immersion in SBF, the value (77 MPa) is still far above that of trabecular bone after 3 weeks. The ability to create both porous and strong structures opens a new avenue for fabricating scaffolds for load-bearing bone defect repair and regeneration.

  16. Fiber-reinforced composite substructure: load-bearing capacity of an onlay restoration.

    PubMed

    Garoushi, Sufyan K; Lassila, Lippo V J; Vallittu, Pekka K

    2006-10-01

    To determine the static load-bearing capacity of composite resin onlay restorations made of particulate filler composite (PFC) with two different types of fiber-reinforced composite (FRC) substructures. Specimens were prepared to simulate an onlay restoration, composed of a 2 to 3 mm FRC layer as the substructure (short random and continuous bidirectional fiber orientation) and a 1 mm surface layer of PFC. Control specimens were prepared from plain PFC. The specimens were incrementally polymerized with a hand-light curing unit for 40 s and then post-cured in a light-curing oven for 15 min. The specimens were cemented on dentin substrate of extracted human molars using a standard adhesive resin cementation technique. The specimens (n=8/group) were water stored either for 24 h at room temperature or for 4 weeks at 37 degrees C before they were statically loaded until fracture using a universal testing machine. Failure modes were visually examined. ANOVA revealed that all specimens with FRC substructures had higher values of static load-bearing capacity than those obtained with plain PFC (p<0.001). The load-bearing capacity of all the specimens decreased after water storage (p<0.001). Restorations made from a combination of FRC and PFC showed better load-bearing capacity than those obtained with PFC alone.

  17. Load-bearing capacity and fracture behavior of glass fiber-reinforced composite cranioplasty implants.

    PubMed

    Piitulainen, Jaakko M; Mattila, Riina; Moritz, Niko; Vallittu, Pekka K

    2017-08-11

    Glass fiber-reinforced composites (FRCs) have been adapted for routine clinical use in various dental restorations and are presently also used in cranial implants. The aim of this study was to measure the load-bearing capacity and failure type of glass FRC implants during static loading with and without interconnective bars and with different fixation modes. Load-bearing capacities of 2 types of FRC implants with 4 different fixation modes were experimentally tested. The sandwich-like FRC implants were made of 2 sheets of woven FRC fabric, which consisted of silanized, woven E-glass fiber fabrics impregnated in BisGMA-TEGDMA monomer resin matrix. The space between the outer and inner surfaces was filled with glass particles. All FRC implants were tested up to a 10-mm deflection with load-bearing capacity determined at 6-mm deflection. The experimental groups were compared using nonparametric Kruskal-Wallis analysis with Steel-Dwass post hoc test. FRC implants underwent elastic and plastic deformation until 6-mm deflection. The loading test did not demonstrate any protrusions of glass fibers or cut fiber even at 10-mm deflection. An elastic and plastic deformation of the implant occurred until the FRC sheets were separated from each other. In the cases of the free-standing setup (no fixation) and the fixation with 6 screws, the FRC implants with 2 interconnective bars showed a significantly higher load-bearing capacity compared with the implant without interconnective bars. FRC implants used in this study showed a load-bearing capacity which may provide protection for the brain after cranial bone defect reconstruction.

  18. Load-bearing capacity of all-ceramic posterior inlay-retained fixed dental prostheses.

    PubMed

    Puschmann, Djamila; Wolfart, Stefan; Ludwig, Klaus; Kern, Matthias

    2009-06-01

    The purpose of this in vitro study was to compare the quasi-static load-bearing capacity of all-ceramic resin-bonded three-unit inlay-retained fixed dental prostheses (IRFDPs) made from computer-aided design/computer-aided manufacturing (CAD/CAM)-manufactured yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) frameworks with two different connector dimensions, with and without fatigue loading. Twelve IRFDPs each were made with connector dimensions 3 x 3 mm(2) (width x height) (control group) and 3 x 2 mm(2) (test group). Inlay-retained fixed dental prostheses were adhesively cemented on identical metal-models using composite resin cement. Subgroups of six specimens each were fatigued with maximal 1,200,000 loading cycles in a chewing simulator with a weight load of 25 kg and a load frequency of 1.5 Hz. The load-bearing capacity was tested in a universal testing machine for IRFDPs without fatigue loading and for IRFDPs that had not already fractured during fatigue loading. During fatigue testing one IRFDP (17%) of the test group failed. Under both loading conditions, IRFDPs of the control group exhibited statistically significantly higher load-bearing capacities than the test group. Fatigue loading reduced the load-bearing capacity in both groups. Considering the maximum chewing forces in the molar region, it seems possible to use zirconia ceramic as a core material for IRFDPs with a minimum connector dimension of 9 mm(2). A further reduction of the connector dimensions to 6 mm(2) results in a significant reduction of the load-bearing capacity.

  19. Plane and hemispherical potential structures in magnetically expanding plasmas

    SciTech Connect

    Takahashi, Kazunori; Igarashi, Yuichi; Fujiwara, Tamiya

    2010-07-26

    Two-dimensional potential structures are measured for different gas pressure in expanding argon plasma using permanent magnets, where the magnetic field is about 100 G in the source and several gauss in the diffusion chamber. The plane potential drop is observed near the source exit for 0.35 mTorr, while the potential structure becomes hemispherical when increasing up to 1 mTorr; the hemispherical structure results in the radial divergence of the ion beam. It is found that the trajectories of the accelerated ions and the electrons overcoming the potential drop are dominated by the potential structure and magnetic-field lines, respectively.

  20. Influence of preliminary damage on the load-bearing capacity of zirconia fixed dental prostheses.

    PubMed

    Kohorst, Philipp; Butzheinen, Lutz Oliver; Dittmer, Marc Philipp; Heuer, Wieland; Borchers, Lothar; Stiesch, Meike

    2010-12-01

    The objective of this investigation was to evaluate the influence of differently shaped preliminary cuts in combination with artificial aging on the load-bearing capacity of four-unit zirconia fixed dental prostheses (FDPs). Forty frameworks were fabricated from white-stage zirconia blanks (InCeram YZ, Vita) by means of a computer-aided design/computer-aided manufacturing system (Cerec inLab, Sirona). Frameworks were divided into four homogeneous groups with ten specimens each. Prior to veneering, frameworks of two groups were "damaged" by defined saw cuts of different dimensions, to simulate accidental flaws generated during shape cutting. After the veneering process, FDPs, with the exception of a control group without preliminary damage, were subjected to thermal and mechanical cycling (TMC) during 200 days storage in distilled water at 36°C. Following the aging procedure, all specimens were loaded until fracture, and forces at fracture were recorded. The statistical analysis of force at fracture data was performed using two-way ANOVA, with the level of significance chosen at 0.05. Neither type of preliminary mechanical damage significantly affected the load-bearing capacity of FDPs. In contrast, artificial aging by TMC proved to have a significant influence on the load-bearing capacity of both the undamaged and the predamaged zirconia restorations (p < 0.001); however, even though load-bearing capacity decreased by about 20% due to simulated aging, the FDPs still showed mean load-bearing capacities of about 1600 N. The results of this study reveal that zirconia restorations have a high tolerance regarding mechanical damages. Irrespective of these findings, damage to zirconia ceramics during production or finishing should be avoided, as this may nevertheless lead to subcritical crack growth and, eventually, catastrophic failure. Furthermore, to ensure long-term clinical success, the design of zirconia restorations has to accommodate the decrease in load-bearing

  1. Calibration of structured light stripe system using plane with slits

    NASA Astrophysics Data System (ADS)

    Ha, Jong-Eun; Her, Kang-Wook

    2013-01-01

    Structured light stripe systems are widely used in industrial applications for acquiring three-dimensional (3-D) information. Calibration is the first necessary step and traditional algorithms compute the 4×3 transformation matrix from image to world. Therefore, 3-D information can be obtained with respect to the camera's coordinate system, and it cannot be transformed into the laser coordinate system. We propose a new calibration algorithm of a structured light system that can compute the relative pose of the laser coordinate system with respect to the camera coordinate system. We can convert 3-D information either to the laser coordinate system or to the camera coordinate system. The proposed algorithm uses two planes where one plane with multiple slits is set perpendicular to the other plane. We can easily compute the position and rotation of the laser coordinate system using proposed calibration structure. Also, we can solve the extrinsic calibration using just one shot of an image while conventional algorithms require more than two images under different poses. Experiments under various configurations show the feasibility of proposed algorithm.

  2. Load-Bearing Biomedical Applications of Diamond-Like Carbon Coatings - Current Status

    PubMed Central

    Alakoski, Esa; Tiainen, Veli-Matti; Soininen, Antti; Konttinen, Yrjö T

    2008-01-01

    The current status of diamond-like carbon (DLC) coatings for biomedical applications is reviewed with emphasis on load-bearing coatings. Although diamond-like carbon coating materials have been studied for decades, no indisputably successful commercial biomedical applications for high load situations exist today. High internal stress, leading to insufficient adhesion of thick coatings, is the evident reason behind this delay of the break-through of DLC coatings for applications. Excellent adhesion of thick DLC coatings is of utmost importance for load-bearing applications. According to this review superior candidate material for articulating implants is thick and adherent DLC on both sliding surfaces. With the filtered pulsed arc discharge method, all the necessary requirements for the deposition of thick and adherent DLC are fulfilled, provided that the substrate material is selected properly. PMID:19478929

  3. Effect of thickness ratio on load-bearing capacity of bilayered dental ceramics.

    PubMed

    Wang, Gaoqi; Zhang, Song; Bian, Cuirong; Kong, Hui

    2015-01-01

    The aims of this study were to reveal the mechanism of failure of bilayered beams and to assess the thickness ratio effect on the load-bearing capacity of the bilayered beams. Both analytical and finite element analysis methods were used to analyze the stress distributions of bilayered beams subjected to three-point bending test and the residual thermal stresses due to coefficient of thermal expansion mismatch. Then, the ideal load-bearing capacity of the beams as a function of core thickness was evaluated based on the mechanical models. Finally, three-point bending tests were performed on Cercon Zirconia /IPS e.max Ceram beams to verify the mechanical models. The failure load as a function of core thickness was obtained. For the materials employed in this study, the thickness ratio did not significantly affect the load-bearing capacity of bilayered beams when the thickness ratio changed from 1:2 to 2:1. The residual thermal stresses in the core layer have slightly beneficial effects on the strength of the beams. The first strength theory can be used to explain the mechanism of failure, which can be described as the failure is interpreted by tensile stress and ultimate strength of the material. Based on the relationship between the thickness ratio and load-bearing capacity, the core/veneer thickness ratio of the connector of a fixed partial denture could be relatively small to about 1:2 to obtain a good appearance. © 2014 by the American College of Prosthodontists.

  4. Reinforcement Size Dependence of Load Bearing Capacity in Ultrafine-Grained Metal Matrix Composites

    NASA Astrophysics Data System (ADS)

    Yang, Hanry; Jiang, Lin; Balog, Martin; Krizik, Peter; Schoenung, Julie M.

    2017-09-01

    The length-scale effects on the load bearing capacity of reinforcement particles in an ultrafine-grained metal matrix composite (MMC) were studied, paying particular attention to the nanoscale effects. We observed that the nanoparticles provide the MMCs with a higher strength but a lower stiffness compared to equivalent materials reinforced with submicron particles. The reduction in stiffness is attributed to ineffective load transfer of the local stresses to the small and equiaxed nanoparticles.

  5. (GameChanger) Multifunctional Design of Hybrid Composites of Load Bearing Antennas

    DTIC Science & Technology

    2011-06-01

    and Hydroethyl Cellulose ", Nov 2009, AICHE Annual Meeting 24. June 2009:Gordon Research Conference, “ Carbon Nanotube Nanostructures E. Jan, N...Volakis, “Polymer- Carbon Nanotube Sheets for Conformal Load Bearing Antennas,” IEEE Trans. Antenn. Propag., vol. 58, no. 7, pp. 2169- 2175, Jul. 2010...Propagation, Toronto, Canada, July, 2010. 7. Y. Bayram, Feng Du, L. Dai, J.L. Volakis, “Surface Conditioned Carbon Nanotube Conductive Sheet for Flexible and

  6. Reinforcement Size Dependence of Load Bearing Capacity in Ultrafine-Grained Metal Matrix Composites

    NASA Astrophysics Data System (ADS)

    Yang, Hanry; Jiang, Lin; Balog, Martin; Krizik, Peter; Schoenung, Julie M.

    2017-07-01

    The length-scale effects on the load bearing capacity of reinforcement particles in an ultrafine-grained metal matrix composite (MMC) were studied, paying particular attention to the nanoscale effects. We observed that the nanoparticles provide the MMCs with a higher strength but a lower stiffness compared to equivalent materials reinforced with submicron particles. The reduction in stiffness is attributed to ineffective load transfer of the local stresses to the small and equiaxed nanoparticles.

  7. Fiber reinforced calcium phosphate cements -- on the way to degradable load bearing bone substitutes?

    PubMed

    Krüger, Reinhard; Groll, Jürgen

    2012-09-01

    Calcium phosphate cements (CPC) are well-established materials for the repair of bone defects with excellent biocompatibility and bioactivity. However, brittleness and low flexural/tensile strength so far restrict their application to non-load bearing areas. Reinforcement of CPC with fibers can substantially improve its strength and toughness and has been one major strategy to overcome the present mechanical limitations of CPC. Fiber reinforced calcium phosphate cements (FRCPC) thus bear the potential to facilitate the use of degradable bone substitutes in load bearing applications. This review recapitulates the state of the art of FRCPC research with focus on their mechanical properties and their biological evaluation in vitro and in vivo, including the clinical data that has been generated so far. After an overview on FRCPC constitutes and processing, some general aspects of fracture mechanics of reinforced cementitious composites are introduced, and their importance for the mechanical properties of FRCPC are highlighted. So far, fiber reinforcement leads to a toughness increase of up to two orders of magnitude. FRCPC have extensively been examined in vitro and in vivo with generally good results. While first clinical products focus on the improved performance of FRCPC with regard to secondary processing after injection such as fixation of screws and plates, first animal studies in load bearing applications show improved performance as compared to pure CPCs. Aside of the accomplished results, FRCPC bear a great potential for future development and optimization. Future research will have to focus on the selection and tailoring of FRCPC components, fiber-matrix compatibilization, integral composite design and the adjusted degradation behavior of the composite components to ensure successful long term behavior and make the composites strong enough for application in load bearing defects. Copyright © 2012 Elsevier Ltd. All rights reserved.

  8. Direct Ink Writing of Highly Porous and Strong Glass Scaffolds for Load-bearing Bone Defects Repair and Regeneration

    PubMed Central

    Fu, Qiang; Saiz, Eduardo; Tomsia, Antoni P.

    2011-01-01

    The quest for synthetic materials to repair load-bearing bone lost because of trauma, cancer, or congenital bone defects requires development of porous and high-performance scaffolds with exceptional mechanical strength. However, the low mechanical strength of porous bioactive ceramic and glass scaffolds, compared with that of human cortical bone, has limited their use for these applications. In the present work, bioactive 6P53B glass scaffolds with superior mechanical strength were fabricated using a direct ink writing technique. The rheological properties of Pluronic® F-127 (referred to hereafter simply as F-127) hydrogel-based inkswere optimized for the printing of features as fine as 30 μm and of the three-dimensional scaffolds. The mechanical strength and in vitro degradation of the scaffolds were assessed in a simulated body fluid (SBF). The sintered glass scaffolds show a compressive strength (136 ± 22 MPa) comparable to that of human cortical bone (100-150 MPa), while the porosity (60%) is in the range of that of trabecular bone (50-90%).The strength is ~100 times that of polymer scaffolds and 4–5 times that of ceramic and glass scaffolds with comparable porosities. Despite the strength decrease resulting from weight loss during immersion in an SBF, the value (77 MPa) is still far above that of trabecular bone after three weeks. The ability to create both porous and strong structures opens a new avenue for fabricating scaffolds for load-bearing bone defect repair and regeneration. PMID:21745606

  9. Carbon structures and defect planes in diamond at high pressure

    NASA Astrophysics Data System (ADS)

    Botti, Silvana; Amsler, Maximilian; Flores-Livas, José A.; Ceria, Paul; Goedecker, Stefan; Marques, Miguel A. L.

    2013-07-01

    We performed a systematic structural search of high-pressure carbon allotropes for unit cells containing from 6 to 24 atoms using the minima hopping method. We discovered a series of new structures that are consistently lower in enthalpy than the ones previously reported. Most of these include (5+7)- or (4+8)-membered rings and can therefore be placed in the families proposed by H. Niu [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.108.135501 108, 135501 (2012)]. However, we also found three more families with competitive enthalpies that contain (5+5+8)-membered rings, sp2 motives, or buckled hexagons. These structures are likely to play an important role in dislocation planes and structural defects of diamond and hexagonal diamond.

  10. Surface modification and fatigue behavior of nitinol for load bearing implants

    NASA Astrophysics Data System (ADS)

    Bernard, Sheldon A.

    Musculoskeletal disorders are recognized amongst the most significant human health problems that exist today. Even though considerable research and development has gone towards understanding musculoskeletal disorders, there is still lack of bone replacement materials that are appropriate for restoring lost structures and functions, particularly for load-bearing applications. Many materials on the market today, such as titanium and stainless steel, suffer from significantly higher modulus than natural bone and low bioactivity leading to stress shielding and implant loosening over longer time use. Nitinol (NiTi) is an equiatomic intermetallic compound of nickel and titanium whose unique biomechanical and biological properties contributed to its increasing use as a biomaterial. An innovative method for creating dense and porous net shape NiTi alloy parts has been developed to improve biological properties while maintaining comparable or better mechanical properties than commercial materials that are currently in use. Laser engineered net shaping (LENS(TM)) and surface electrochemistry modification was used to create dense/porous samples and micro textured surfaces on NiTi parts, respectively. Porous implants are known to promote cell adhesion and have a low elastic modulus, a combination that can significantly increase the life of an implant. However, porosity can significantly reduce the fatigue life of an implant, and very little work has been reported on the fatigue behavior of bulk porous metals, specifically on porous nitinol alloy. High-cycle rotating bending and compression-compression fatigue behavior of porous NiTi fabricated using LENS(TM) were studied. In cyclic compression loading, plastic strain increased with increasing porosity and it was evident that maximum strain was achieved during the first 50000 cycles and remained constant throughout the remaining loading. No failures were observed due to loading up to 150% of the yield strength. When subjected

  11. The structure of sheared turbulence near a plane boundary

    NASA Technical Reports Server (NTRS)

    Lee, Moon J.; Hunt, J. C. R.

    1988-01-01

    An analysis is presented of how a plane boundary affects the structure of turbulence in a sheared free stream. A uniform-shear boundary layer (USBL) is formulated with slip velocity condition at the surface, and inhomogeneous rapid distortion theory is applied. The effects of blocking by the surface on the turbulence structure in USBL is compared with those in the shear-free boundary layer (SFBL). Shear produces highly anisotropic eddies elongated in the flow direction. The vertical velocity variance is reduced with shear at all heights, roughly in proportion to the reduction in the homogeneous value, but the shape of the profile remains unchanged only near the surface. The streamwise integral scales increase with shear, indicating elongation of the streamwise extent of eddies.

  12. Strained layer superlattice focal plane array having a planar structure

    DOEpatents

    Kim, Jin K; Carroll, Malcolm S; Gin, Aaron; Marsh, Phillip F; Young, Erik W; Cich, Michael J

    2012-10-23

    An infrared focal plane array (FPA) is disclosed which utilizes a strained-layer superlattice (SLS) formed of alternating layers of InAs and In.sub.xGa.sub.1-xSb with 0.ltoreq.x.ltoreq.0.5 epitaxially grown on a GaSb substrate. The FPA avoids the use of a mesa structure to isolate each photodetector element and instead uses impurity-doped regions formed in or about each photodetector for electrical isolation. This results in a substantially-planar structure in which the SLS is unbroken across the entire width of a 2-D array of the photodetector elements which are capped with an epitaxially-grown passivation layer to reduce or eliminate surface recombination. The FPA has applications for use in the wavelength range of 3-25 .mu.m.

  13. Geometric structure of pseudo-plane quadratic flows

    NASA Astrophysics Data System (ADS)

    Sun, Che

    2017-03-01

    Quadratic flows have the unique property of uniform strain and are commonly used in turbulence modeling and hydrodynamic analysis. While previous applications focused on two-dimensional homogeneous fluid, this study examines the geometric structure of three-dimensional quadratic flows in stratified fluid by solving a steady-state pseudo-plane flow model. The complete set of exact solutions reveals that steady quadratic flows have an invariant conic type in the non-rotating frame and a non-rotatory vertical structure in the rotating frame. Three baroclinic solutions with vertically non-aligned formulation disprove an earlier conjecture. All elliptic and hyperbolic solutions, except for the inertial ones, exhibit vertical concentricity. The rich geometry of quadratic flows stands in contrast to the depleted geometry of high-degree polynomial flows. A paradox in the steady solutions of shallow-water reduced-gravity models is also explained.

  14. Plane shock wave structure in a dilute granular gas

    NASA Astrophysics Data System (ADS)

    Reddy, M. H. Lakshminarayana; Alam, Meheboob

    2016-11-01

    We analyse the early time evolution of the Riemann problem of planar shock wave structures for a dilute granular gas by solving Navier-Stokes equations numerically. The one-dimensional reduced Navier-Stokes equations for plane shock wave problem are solved numerically using a relaxation-type numerical scheme. The results on the shock structures in granular gases are presented for different Mach numbers and restitution coefficients. Based on our analysis on early time shock dynamics we conclude that the density and temperature profiles are "asymmetric"; the density maximum and the temperature maximum occur within the shock layer; the absolute magnitudes of longitudinal stress and heat flux which are initially zero at both end states attain maxima in a very short time and thereafter decrease with time.

  15. Mechanical behaviour of Bioactive Glass granules and morselized cancellous bone allograft in load bearing defects.

    PubMed

    Hulsen, D J W; Geurts, J; van Gestel, N A P; van Rietbergen, B; Arts, J J

    2016-05-03

    Bioactive Glass (BAG) granules are osteoconductive and possess unique antibacterial properties for a synthetic biomaterial. To assess the applicability of BAG granules in load-bearing defects, the aim was to compare mechanical behaviour of graft layers consisting of BAG granules and morselized cancellous bone allograft in different volume mixtures under clinically relevant conditions. The graft layers were mechanically tested, using two mechanical testing modalities with simulated physiological loading conditions: highly controllable confined compression tests (CCT) and more clinically realistic in situ compression tests (ISCT) in cadaveric porcine bone defects. Graft layer impaction strain, residual strain, aggregate modulus, and creep strain were determined in CCT. Graft layer porosity was determined using micro computed tomography. The ISCT was used to determine graft layer subsidence in bone environment. ANOVA showed significant differences (p<0.001) between different graft layer compositions. True strains absolutely decreased for increasing BAG content: impaction strain -0.92 (allograft) to -0.39 (BAG), residual strain -0.12 to -0.01, and creep strain -0.09 to 0.00 respectively. Aggregate modulus increased with increasing BAG content from 116 to 653MPa. Porosity ranged from 66% (pure allograft) to 15% (pure BAG). Subsidence was highest for allograft, and remarkably low for a 1:1 BAG-allograft volume mixture. Both BAG granules and allograft morsels as stand-alone materials exhibit suboptimal mechanical behaviour for load-bearing purpose. BAG granules are difficult to handle and less porous, whereas allograft subsides and creeps. A 1:1 volume mixture of BAG and allograft is therefore proposed as the best graft material in load-bearing defects.

  16. Load bearing capacity of fibre-reinforced and particulate filler composite resin combination.

    PubMed

    Garoushi, Sufyan; Lassila, Lippo V J; Tezvergil, Arzu; Vallittu, Pekka K

    2006-03-01

    Longevity of particulate filler resin (PFR) is controversial for large restorations with high occlusal-stresses. The aim of this study was to reinforce PFR with fiber reinforced composite (FRC) and to evaluate the effect of thickness of FRC substructure and thickness of overlaying PFR, on the static load-bearing capacity of the material combination. A total of 336 test specimens having a FRC substructure (short random or continuous bidirectional fibre orientation) and layer of restorative PFR were prepared for this study. In Group A, the specimens contained short random oriented fibres (length: 2-3mm) and in Group B, there were continuous bidirectionally oriented fibres. The specimens (n = 12/group) were polymerized with a hand light-curing unit and were either dry-stored or thermocycled before they were statically loaded with a steel ball until fracture, using a universal testing machine. Increase the volume fraction of the short random FRC versus the fraction of PFR, the load-bearing capacity of the specimen increased (p < 0.001). Short random FRC revealed significantly different behavior than the bidirectionally oriented FRC (p < 0.001). By combining the FRC layer of 0.5mm in thickness with a layer of 2.5mm of PFR gave load values of 1462N and 1196N, which were considerably higher than values for plain PFR of 3mm in thickness (782N and 729N). The results suggest that by adding a FRC substructure under the PFR, the load-bearing capacity of the material combination was increased.

  17. Static load bearing exercises of individuals with transfemoral amputation fitted with an osseointegrated implant: Loading compliance.

    PubMed

    Vertriest, Sofie; Coorevits, Pascal; Hagberg, Kerstin; Brånemark, Rickard; Häggström, Eva Elisabet; Vanderstraeten, Guy; Frossard, Laurent Alain

    2017-08-01

    Load-bearing exercises are performed by transfemoral amputees fitted with an osseointegrated implant to facilitate bone remodelling. This study presents the loading compliance comparing loads prescribed and applied on the three axes of the implant during static load-bearing exercises with a specific emphasis on axial and vectorial comparisons. Cohort study. A total of 11 fully rehabilitated unilateral transfemoral amputees fitted with an osseointegrated implant performed five trials in four loading conditions using a static standing frame. The load prescribed was monitored using a vertical single-axis strain gauge connected to an electronic display. The tri-axial forces applied on the implant were measured directly with an instrumented pylon including a six-channel transducer. The analysis included 'axial' and 'vectorial' comparisons corresponding to the difference between the force applied on the long axis of the implant and the load prescribed as well as the resultant of the three components of the load applied and the load prescribed, respectively. The results demonstrated that axial and vectorial differences were significant in all conditions ( p < 0.05), except for the vectorial difference for the 40 kg condition ( p = 0.182). The significant lack of axial compliance led to systematic underloading of the long axis of the implant. Clinical relevance This study contributes to a better understanding of the load applied on an osseointegrated implant during the static load-bearing exercises that could contribute to improve the design of apparatus to monitor loading exercises as well as clinical guidelines for the loading progression during rehabilitation.

  18. Stretchable and transparent electrodes based on in-plane structures

    NASA Astrophysics Data System (ADS)

    Kim, Kukjoo; Kim, Joohee; Hyun, Byung Gwan; Ji, Sangyoon; Kim, So-Yun; Kim, Sungwon; An, Byeong Wan; Park, Jang-Ung

    2015-08-01

    Stretchable electronics has attracted great interest with compelling potential applications that require reliable operation under mechanical deformation. Achieving stretchability in devices, however, requires a deeper understanding of nanoscale materials and mechanics beyond the success of flexible electronics. In this regard, tremendous research efforts have been dedicated toward developing stretchable electrodes, which are one of the most important building blocks for stretchable electronics. Stretchable transparent thin-film electrodes, which retain their electrical conductivity and optical transparency under mechanical deformation, are particularly important for the favourable application of stretchable devices. This minireview summarizes recent advances in stretchable transparent thin-film electrodes, especially employing strategies based on in-plane structures. Various approaches using metal nanomaterials, carbon nanomaterials, and their hybrids are described in terms of preparation processes and their optoelectronic/mechanical properties. Some challenges and perspectives for further advances in stretchable transparent electrodes are also discussed.

  19. HERSCHEL GALACTIC PLANE SURVEY OF [N ii] FINE STRUCTURE EMISSION

    SciTech Connect

    Goldsmith, Paul F.; Yıldız, Umut A.; Langer, William D.; Pineda, Jorge L.

    2015-12-01

    We present the first large-scale high angular resolution survey of ionized nitrogen in the Galactic Plane through emission of its two fine structure transitions ([N ii]) at 122 and 205 μm. The observations were largely obtained with the PACS instrument onboard the Herschel Space Observatory. The lines of sight were in the Galactic plane, following those of the Herschel OTKP project GOT C+. Both lines are reliably detected at the 10{sup −8}–10{sup −7} Wm{sup −2} sr{sup −1} level over the range –60° ≤ l ≤ 60°. The rms of the intensity among the 25 PACS spaxels of a given pointing is typically less than one third of the mean intensity, showing that the emission is extended. [N ii] is produced in gas in which hydrogen is ionized, and collisional excitation is by electrons. The ratio of the two fine structure transitions provides a direct measurement of the electron density, yielding n(e) largely in the range 10–50 cm{sup −3} with an average value of 29 cm{sup −3} and N{sup +} column densities 10{sup 16}–10{sup 17} cm{sup −2}. [N ii] emission is highly correlated with that of [C ii], and we calculate that between 1/3 and 1/2 of the [C ii] emission is associated with the ionized gas. The relatively high electron densities indicate that the source of the [N ii] emission is not the warm ionized medium (WIM), which has electron densities more than 100 times smaller. Possible origins of the observed [N ii] include the ionized surfaces of dense atomic and molecular clouds, the extended low-density envelopes of H ii regions, and low-filling factor high-density fluctuations of the WIM.

  20. Herschel Galactic Plane Survey of [NII] Fine Structure Emission

    NASA Astrophysics Data System (ADS)

    Goldsmith, Paul F.; Yıldız, Umut A.; Langer, William D.; Pineda, Jorge L.

    2015-12-01

    We present the first large-scale high angular resolution survey of ionized nitrogen in the Galactic Plane through emission of its two fine structure transitions ([N ii]) at 122 and 205 μm. The observations were largely obtained with the PACS instrument onboard the Herschel Space Observatory. The lines of sight were in the Galactic plane, following those of the Herschel OTKP project GOT C+. Both lines are reliably detected at the 10-8-10-7 Wm-2 sr-1 level over the range -60° ≤ l ≤ 60°. The rms of the intensity among the 25 PACS spaxels of a given pointing is typically less than one third of the mean intensity, showing that the emission is extended. [N ii] is produced in gas in which hydrogen is ionized, and collisional excitation is by electrons. The ratio of the two fine structure transitions provides a direct measurement of the electron density, yielding n(e) largely in the range 10-50 cm-3 with an average value of 29 cm-3 and N+ column densities 1016-1017 cm-2. [N ii] emission is highly correlated with that of [C ii], and we calculate that between 1/3 and 1/2 of the [C ii] emission is associated with the ionized gas. The relatively high electron densities indicate that the source of the [N ii] emission is not the warm ionized medium (WIM), which has electron densities more than 100 times smaller. Possible origins of the observed [N ii] include the ionized surfaces of dense atomic and molecular clouds, the extended low-density envelopes of H ii regions, and low-filling factor high-density fluctuations of the WIM.

  1. Silk as a biocohesive sacrificial binder in the fabrication of hydroxyapatite load bearing scaffolds

    PubMed Central

    McNamara, Stephanie L.; Rnjak-Kovacina, Jelena; Schmidt, Daniel; Lo, Tim J.; Kaplan, David L.

    2014-01-01

    Limitations of current clinical methods for bone repair continue to fuel the demand for a high strength, bioactive bone replacement material. Recent attempts to produce porous scaffolds for bone regeneration have been limited by the intrinsic weakness associated with high porosity materials. In this study, ceramic scaffold fabrication techniques for potential use in load-bearing bone repairs have been developed using naturally derived silk from Bombyx mori. Silk was first employed for ceramic grain consolidation during green body formation, and later as a sacrificial polymer to impart porosity during sintering. These techniques allowed preparation of hydroxyapatite (HA) scaffolds that exhibited a wide range of mechanical and porosity profiles, with some displaying unusually high compressive strength up to 152.4 ± 9.1 MPa. Results showed that the scaffolds exhibited a wide range of compressive strengths and moduli (8.7 ± 2.7 MPa to 152.4 ± 9.1 MPa and 0.3 ± 0.1 GPa to 8.6 ± 0.3 GPa) with total porosities of up to 62.9 ± 2.7% depending on the parameters used for fabrication. Moreover, HA-silk scaffolds could be molded into large, complex shapes, and further machined post-sinter to generate specific three-dimensional geometries. Scaffolds supported bone marrow-derived mesenchymal stem cell attachment and proliferation, with no signs of cytotoxicity. Therefore, silk-fabricated HA scaffolds show promise for load bearing bone repair and regeneration needs. PMID:24881027

  2. Biodynamic feedback training to assure learning partial load bearing on forearm crutches.

    PubMed

    Krause, Daniel; Wünnemann, Martin; Erlmann, Andre; Hölzchen, Timo; Mull, Melanie; Olivier, Norbert; Jöllenbeck, Thomas

    2007-07-01

    To examine how biodynamic feedback training affects the learning of prescribed partial load bearing (200N). Three pre-post experiments. Biomechanics laboratory in a German university. A volunteer sample of 98 uninjured subjects who had not used crutches recently. There were 24 subjects in experiment 1 (mean age, 23.2y); 64 in experiment 2 (mean age, 43.6y); and 10 in experiment 3 (mean age, 40.3y), parallelized by arm force. Video instruction and feedback training: In experiment 1, 2 varied instruction videos and reduced feedback frequency; in experiment 2, varied frequencies of changing tasks (contextual interference); and in experiment 3, feedback training (walking) and transfer (stair tasks). Vertical ground reaction force. Absolute error of practiced tasks was significantly reduced for all samples (P<.050). Varied contextual interference conditions did not significantly affect retention (P=.798) or transfer (P=.897). Positive transfer between tasks was significant in experiment 2 (P<.001) and was contrary to findings in experiment 3 (P=.071). Biodynamic feedback training is applicable for learning prescribed partial load bearing. The frequency of changing tasks is irrelevant. Despite some support for transfer effects, additional practice in climbing and descending stairs might be beneficial.

  3. Study on Load-Bearing Characteristics of a New Pile Group Foundation for an Offshore Wind Turbine

    PubMed Central

    Liu, Run; Lian, Jijian; Ding, Hongyan

    2014-01-01

    Because offshore wind turbines are high-rise structures, they transfer large horizontal loads and moments to their foundations. One of the keys to designing a foundation is determining the sensitivities and laws affecting its load-bearing capacity. In this study, this procedure was carried out for a new high-rise cap pile group foundation adapted to the loading characteristics of offshore wind turbines. The sensitivities of influential factors affecting the bearing properties were determined using an orthogonal test. Through a combination of numerical simulations and model tests, the effects of the inclination angle, length, diameter, and number of side piles on the vertical bearing capacity, horizontal bearing capacity, and bending bearing capacity were determined. The results indicate that an increase in the inclination angle of the side piles will increase the vertical bearing capacity, horizontal bearing capacity, and bending bearing capacity. An increase in the length of the side piles will increase the vertical bearing capacity and bending bearing capacity. When the length of the side piles is close to the central pile, the increase is more apparent. Finally, increasing the number of piles will increase the horizontal bearing capacity; however, the growth rate is small because of the pile group effect. PMID:25250375

  4. Study on load-bearing characteristics of a new pile group foundation for an offshore wind turbine.

    PubMed

    Lang, Ruiqing; Liu, Run; Lian, Jijian; Ding, Hongyan

    2014-01-01

    Because offshore wind turbines are high-rise structures, they transfer large horizontal loads and moments to their foundations. One of the keys to designing a foundation is determining the sensitivities and laws affecting its load-bearing capacity. In this study, this procedure was carried out for a new high-rise cap pile group foundation adapted to the loading characteristics of offshore wind turbines. The sensitivities of influential factors affecting the bearing properties were determined using an orthogonal test. Through a combination of numerical simulations and model tests, the effects of the inclination angle, length, diameter, and number of side piles on the vertical bearing capacity, horizontal bearing capacity, and bending bearing capacity were determined. The results indicate that an increase in the inclination angle of the side piles will increase the vertical bearing capacity, horizontal bearing capacity, and bending bearing capacity. An increase in the length of the side piles will increase the vertical bearing capacity and bending bearing capacity. When the length of the side piles is close to the central pile, the increase is more apparent. Finally, increasing the number of piles will increase the horizontal bearing capacity; however, the growth rate is small because of the pile group effect.

  5. Stress analysis of the space telescope focal plane structure joint

    NASA Technical Reports Server (NTRS)

    Foster, W. A., Jr.; Shoemaker, W. L.

    1985-01-01

    Two major efforts were begun concerning the Space Telescope focal plane structure joint. The 3-D solid finite element modeling of the bipod flexure plate was carried out. Conceptual models were developed for the load transfer through the three major bolts to the flexure plate. The flexure plate drawings were reconstructed using DADAM for the purpose of developing a file from which the coordinates of any point on the flexure plate could be determined and also to locate the attachment points of the various components which connect with the flexure plate. For modeling convenience the CADAM drawing of the flexure plate has been divided into several regions which will be subdivided into finite elements using MSGMESH, which is a finite element mesh generator available with MSC/NASTRAN. In addition to the CADAM work on the flexure plate, an effort was also begun to develop computer aided drawings of the peripheral beam which will be used to assist in modeling the connection between it and the flexure plate.

  6. Microfabrication of Cell-Laden Hydrogels for Engineering Mineralized and Load Bearing Tissues.

    PubMed

    Li, Chia-Cheng; Kharaziha, Mahshid; Min, Christine; Maas, Richard; Nikkhah, Mehdi

    2015-01-01

    Microengineering technologies and advanced biomaterials have extensive applications in the field of regenerative medicine. In this chapter, we review the integration of microfabrication techniques and hydrogel-based biomaterials in the field of dental, bone, and cartilage tissue engineering. We primarily discuss the major features that make hydrogels attractive candidates to mimic extracellular matrix (ECM), and we consider the benefits of three-dimensional (3D) culture systems for tissue engineering applications. We then focus on the fundamental principles of microfabrication techniques including photolithography, soft lithography and bioprinting approaches. Lastly, we summarize recent research on microengineering cell-laden hydrogel constructs for dental, bone and cartilage regeneration, and discuss future applications of microfabrication techniques for load-bearing tissue engineering.

  7. Tuning the Hydration and Lubrication of the Embedded Load-Bearing Hydrogel Fibers.

    PubMed

    Zhang, Ran; Feng, Yange; Ma, Shuanhong; Cai, Meirong; Yang, Jun; Yu, Bo; Zhou, Feng

    2017-03-07

    One of the most prominent properties of hydrogels is their excellent hydrolubrication that derives from the strong hydration of the gel network. However, excessive hydration makes hydrogels exhibit a very poor mechanical property, which limits their practical applications. Here, we prepared a novel composite surface of hydrogel nanofibers embedded in an anodic aluminum oxide substrate which exhibited both excellent lubrication and a high load-bearing capacity. Through the copolymerization of acrylic acid and 3-sulfopropyl methacrylate potassium salt, the gel network swelled sufficiently in aqueous solution and caused high osmotic pressure repulsion to bear heavy loads and hence exhibited excellent aqueous lubrication (μ ≈ 0.01). Notably, the friction coefficient of gels showed no dependence on the load in the experiment, whereas it was strongly influenced by the sliding velocity. Additionally, both electrolyte solution and ionic surfactants affect the conformation of the polymer chains, which results in a significant impact on the friction properties of hydrogel fibers.

  8. Growth and Crystal Orientation of ZnTe on m-Plane Sapphire with Nanofaceted Structure

    NASA Astrophysics Data System (ADS)

    Nakasu, Taizo; Sun, Wei-Che; Kobayashi, Masakazu; Asahi, Toshiaki

    2017-04-01

    ZnTe thin films on sapphire substrate with nanofaceted structure have been studied. The nanofaceted structure of the m-plane (10-10) sapphire was obtained by heating the substrate at above 1100°C in air, and the r-plane (10-12) and S-plane (1-101) were confirmed. ZnTe layers were prepared on the nanofaceted m-plane sapphire substrates by molecular beam epitaxy (MBE). The effect of the nanofaceted structure on the orientation of the thin films was examined based on x-ray diffraction (XRD) pole figures. Transmission electron microscopy (TEM) was also employed to characterize the interface structures. The ZnTe layer on the nanofaceted m-plane sapphire substrate exhibited (331)-plane orientation, compared with (211)-plane without the nanofaceted structure. After thermal treatment, the m-plane surface vanished and (211) layer could not be formed because of the lack of surface lattice matching. On the other hand, (331)-plane thin film was formed on the nanofaceted m-plane sapphire substrate, since the (111) ZnTe domains were oriented on the S-facet. The orientation of the ZnTe epilayer depended on the atomic ordering on the surface and the influence of the S-plane.

  9. Localized and chaotic folding: the role of axial plane structures.

    PubMed

    Hobbs, Bruce E; Ord, Alison

    2012-04-28

    Most natural fold systems are not sinusoidal in profile. A widely held view is that such irregularity derives solely from inherited initial geometrical perturbations. Although, undoubtedly, initial perturbations can contribute to irregularity, we explore a different (but complementary) view in which the irregular geometry results from some material or system softening process. This arises because the buckling response of a layer (or layers) embedded in a weaker matrix is controlled in a sensitive manner by the nature of the reaction forces exerted by the deforming matrix on the layer. In many theoretical treatments of the folding problem, this reaction force is assumed to be a linear function of some measure of the deformation or deformation rate. This paper is concerned with the influence of nonlinear reaction forces such as arise from nonlinear elasticity or viscosity. Localized folds arising from nonlinearity form in a fundamentally different way than the Biot wavelength selection process. As a particular example of nonlinear behaviour, we examine the influence of axial plane structures made up of layers of different mineralogy formed by chemical differentiation processes accompanying the deformation; they are referred to as metamorphic layering. The alternating mineralogical composition in the metamorphic layers means that the embedding matrix exerts a reaction force on the folded layers that varies not only with the deflection or the velocity of deflection of the layer, but also in a periodic manner along the length of the folded layers. The influence of this spatially periodic reaction force on the development of localized and chaotic folding is explored numerically.

  10. Three-Dimensional Structure of Plane Mixing Layers.

    NASA Astrophysics Data System (ADS)

    Bell, James Horatio

    Recent studies have shown the existence of an organized and persistent streamwise vortex structure in plane mixing layers, which is believed to take the form of a row of alternating-sign streamwise vortices. So far, this streamwise vortex structure has been studied mostly through flow-visualization at relatively low Reynolds numbers. The main objective of the present work was to obtain quantitative measurements of the streamwise vorticity at Reynolds numbers more comparable to those commonly found in practical applications. In the first experiment, the artificially induced streamwise vortex was observed to decay as approximately 1/X^2 within the mixing layer. The effect of the vortex was to locally distort the mean strain distribution in the mixing layer, thus altering the production of the Reynolds stresses. Peak values of the normal stresses were increased by about 20% over the undisturbed case in the region of the streamwise vortex. In particular a strong, pronounced peak was generated in the secondary shear stress, (overline{u^' w^ '}).. In the second experiment, "naturally-occurring" streamwise vorticity was clearly observed in a two-stream mixing layer. Concentrated streamwise vortices appeared just downstream of the first roll-up of the spanwise vorticity, with an initial circulation which was roughly half that of the spanwise vortex circulation. The streamwise vortices first appeared in "clusters", the positions of which seemed to be related to small disturbances in one of the upstream boundary layers. The clusters quickly reorganized into a single row of alternating-sign vortices under the influence of vortex dynamics and changes in the normal stress anisotropy. The streamwise vortex spacing increased in a stepwise fashion, at least partially through the amalgamation of like-sign vortices. The wavelength of the streamwise vortices increased approximately as the mixing layer vorticity thickness, while their strength decayed as roughly 1/X^ {1.5}. In the

  11. Proteins in load-bearing junctions: the histidine-rich metal-binding protein of mussel byssus.

    PubMed

    Zhao, Hua; Waite, J Herbert

    2006-11-28

    Building complex load-bearing scaffolds depends on effective ways of joining functionally different biomacromolecules. The junction between collagen fibers and foamlike adhesive plaques in mussel byssus is robust despite the strikingly dissimilar connected structures. mcfp-4, the matrix protein from this junction, and its presecreted form from the foot tissue of Mytilus californianus were isolated and characterized. mcfp-4 has a mass of approximately 93 kDa as determined by MALDI-TOF mass spectrometry. Its composition is dominated by histidine (22 mol %), but levels of lysine, arginine, and aspartate are also significant. A small amount of 3,4-dihydroxyphenyl-l-alanine (2 mol %) can be detected by amino acid analysis and redox cycling assays. The cDNA-deduced sequence of mcfp-4 reveals multiple variants with highly repetitive internal structures, including approximately 36 tandemly repeated His-rich decapeptides (e.g., HVHTHRVLHK) in the N-terminal half and 16 somewhat more degenerate aspartate-rich undecapeptides (e.g., DDHVNDIAQTA) in the C-terminal half. Incubation of a synthetic peptide based on the His-rich decapeptide with Fe3+, Co2+, Ni2+, Zn2+, and Cu2+ indicates that only Cu is strongly bound. MALDI-TOF mass spectrometry of the peptide modified with diethyl pyrocarbonate before and after Cu binding suggests that histidine residues dominate Cu binding. In contrast, the aspartate-rich undecapeptides preferentially bind Ca2+. mcfp-4 is strategically positioned to function as a macromolecular bifunctional linker by using metal ions to couple its own His-rich domains to the His-rich termini of the preCOLs. Ca2+ may mediate coupling of the C-terminus to other calcium-binding plaque proteins.

  12. Tailored complex 3D vortex lattice structures by perturbed multiples of three-plane waves.

    PubMed

    Xavier, Jolly; Vyas, Sunil; Senthilkumaran, Paramasivam; Joseph, Joby

    2012-04-20

    As three-plane waves are the minimum number required for the formation of vortex-embedded lattice structures by plane wave interference, we present our experimental investigation on the formation of complex 3D photonic vortex lattice structures by a designed superposition of multiples of phase-engineered three-plane waves. The unfolding of the generated complex photonic lattice structures with higher order helical phase is realized by perturbing the superposition of a relatively phase-encoded, axially equidistant multiple of three noncoplanar plane waves. Through a programmable spatial light modulator assisted single step fabrication approach, the unfolded 3D vortex lattice structures are experimentally realized, well matched to our computer simulations. The formation of higher order intertwined helices embedded in these 3D spiraling vortex lattice structures by the superposition of the multiples of phase-engineered three-plane waves interference is also studied.

  13. Thermal and structural analyses of variable thickness plane problems

    SciTech Connect

    Wang, Zhibi; Kuzay, T.M.

    1995-07-01

    Finite difference formulations for variable thickness thermal analysis and variable thickness plane stress analysis are presented. In heat transfer analysis, radiation effects and temperature-dependent thermal conductivity are taken into account. While in thermal stress analysis, the thermal expansion coefficient is considered as temperature dependent. An application of the variable thickness window for synchrotron radiation beamline under very strong X-ray is provided.

  14. Lubrication and load-bearing properties of human salivary pellicles adsorbed ex vivo on molecularly smooth substrata.

    PubMed

    Harvey, Neale M; Yakubov, Gleb E; Stokes, Jason R; Klein, Jacob

    2012-01-01

    In a series of Surface Force Balance experiments, material from human whole saliva was adsorbed to molecularly smooth mica substrata (to form an 'adsorbed salivary film'). Measurements were taken of normal (load bearing, F (n)) and shear (frictional, F (s)*) forces between two interacting surfaces. One investigation involved a salivary film formed by overnight adsorption from undiluted, centrifuged saliva, with the adsorbed film rinsed with pure water before measurement. Measurements were taken under pure water and 70 mM NaNO(3). In a second investigation, a film was formed from and measured under a solution of 7% filtered saliva in 10 mM NaNO(3). F (n) results for both systems showed purely repulsive layers, with an uncompressed thickness of 35-70 nm for the diluted saliva investigation and, prior to the application of shear, 11 nm for the rinsed system. F (s)* was essentially proportional to F (n) for all systems and independent of shear speed (in the range 100-2000 nm s(-1)), with coefficients of friction μ ≈ 0.24 and μ ≈ 0.46 for the unrinsed and rinsed systems, respectively. All properties of the rinsed system remained similar when the pure water measurement environment was changed to 70 mM NaNO(3). For all systems studied, shear gave rise to an approximately threefold increase in the range of normal forces, attributed to the ploughing up of adsorbed material during shear to form debris that stood proud of the adsorbed layer. The results provide a microscopic demonstration of the wear process for a salivary film under shear and may be of particular interest for understanding the implications for in vivo oral lubrication under conditions such as rinsing of the mouth cavity. The work is interpreted in light of earlier studies that showed a structural collapse and increase in friction for an adsorbed salivary film in an environment of low ionic strength.

  15. In Vivo Response of Laser Processed Porous Titanium Implants for Load-Bearing Implants.

    PubMed

    Bandyopadhyay, Amit; Shivaram, Anish; Tarafder, Solaiman; Sahasrabudhe, Himanshu; Banerjee, Dishary; Bose, Susmita

    2017-01-01

    Applications of porous metallic implants to enhance osseointegration of load-bearing implants are increasing. In this work, porous titanium implants, with 25 vol.% porosity, were manufactured using Laser Engineered Net Shaping (LENS™) to measure the influence of porosity towards bone tissue integration in vivo. Surfaces of the LENS™ processed porous Ti implants were further modified with TiO2 nanotubes to improve cytocompatibility of these implants. We hypothesized that interconnected porosity created via additive manufacturing will enhance bone tissue integration in vivo. To test our hypothesis, in vivo experiments using a distal femur model of male Sprague-Dawley rats were performed for a period of 4 and 10 weeks. In vivo samples were characterized via micro-computed tomography (CT), histological imaging, scanning electron microscopy, and mechanical push-out tests. Our results indicate that porosity played an important role to establish early stage osseointegration forming strong interfacial bonding between the porous implants and the surrounding tissue, with or without surface modification, compared to dense Ti implants used as a control.

  16. Load-bearing capacity of human incisor restored with various fiber-reinforced composite posts.

    PubMed

    Le Bell-Rönnlöf, Anna-Maria; Lassila, Lippo V J; Kangasniemi, Ilkka; Vallittu, Pekka K

    2011-06-01

    The aim of this study was to evaluate the load-bearing capacity and microstrain of incisors restored with posts of various kinds. Both prefabricated titanium posts and different fiber-reinforced composite posts were tested. The crowns of human incisors were cut and post preparation was carried out. The roots were divided into groups: (1) prefabricated serrated titanium posts, (2) prefabricated carbon fiber-reinforced composite posts, (3) individually formed glass fiber-reinforced composite posts with the canal full of fibers, and (4) individually formed "split" glass fiber-reinforced composite posts. The posts were cemented and composite crowns were made. Intact human incisors were used as reference. All roots were embedded in acrylic resin cylinders and stored at room temperature in water. Static load was applied under a loading angle of 45° using a universal testing machine. On half of the specimens microstrain was measured with strain gages and an acoustic emission analysis was carried out. Failure mode assessment was also made. The group with titanium posts showed highest number of unfavorable failures compared to the groups with fiber-reinforced composite posts. With fiber-reinforced composite posts the failures may more often be favorable compared to titanium posts, which clinically means repairable failures. Copyright © 2011 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  17. Development of composite scaffolds for load-bearing segmental bone defects.

    PubMed

    Pilia, Marcello; Guda, Teja; Appleford, Mark

    2013-01-01

    The need for a suitable tissue-engineered scaffold that can be used to heal load-bearing segmental bone defects (SBDs) is both immediate and increasing. During the past 30 years, various ceramic and polymer scaffolds have been investigated for this application. More recently, while composite scaffolds built using a combination of ceramics and polymeric materials are being investigated in a greater number, very few products have progressed from laboratory benchtop studies to preclinical testing in animals. This review is based on an exhaustive literature search of various composite scaffolds designed to serve as bone regenerative therapies. We analyzed the benefits and drawbacks of different composite scaffold manufacturing techniques, the properties of commonly used ceramics and polymers, and the properties of currently investigated synthetic composite grafts. To follow, a comprehensive review of in vivo models used to test composite scaffolds in SBDs is detailed to serve as a guide to design appropriate translational studies and to identify the challenges that need to be overcome in scaffold design for successful translation. This includes selecting the animal type, determining the anatomical location within the animals, choosing the correct study duration, and finally, an overview of scaffold performance assessment.

  18. An Investigation on Load Bearing Capacities of Cement and Resin Grouted Rock Bolts Installed in Weak Rocks

    NASA Astrophysics Data System (ADS)

    Kalyoncu Erguler, Guzide; Abiddin Erguler, Zeynal

    2015-04-01

    Rock bolts have been considered one of indispensable support method to improve load bearing capacity of many underground engineering projects, and thus, various types of them have been developed until now for different purposes. Although mechanically anchored rock bolts can be successfully installed to prevent structurally controlled instabilities in hard rocks, in comparison with cement and resin grouted rock bolts, these types of anchors are not so effective in weak rocks characterized by relatively low mechanical properties. In order to investigate the applicability and to measure relative performance of cement and resin grouted rock bolts into weak and heavily jointed rock mass, a research program mainly consisting of pull-out tests was performed in a metal mine in Turkey. The rock materials excavated in this underground mining were described as basalt, tuff, ore dominated volcanic rocks and dacite. To achieve more representative results for rock materials found in this mining and openings excavated in varied dimensions, the pull-out tests were conducted on rock bolts used in many different locations where more convergences were measured and deformation dependent instability was expected to cause greater engineering problems. It is well known that the capacity of rock bolts depends on the length, diameter and density of the bolt pattern, and so considering the thickness of plastic zone in the studied openings, the length and diameter of rock bolts were taken as 2.4 m. and 25 mm., respectively. The spacing between rows changed between 70 and 180 cm. In this study, totally twenty five pull-out tests were performed to have a general understanding about axial load bearing capacity and support reaction curves of cement and resin grouted rock bolts. When pull load-displacement curves belongs to cement and resin grouted rock bolts were compared with each other, it was determined that cement grouted rock bolts carry more load ranging between 115.6 kN and 127.5 kN with

  19. Effect of a novel load-bearing trabecular Nitinol scaffold on rabbit radius bone regeneration

    NASA Astrophysics Data System (ADS)

    Gotman, Irena; Zaretzky, Asaph; Psakhie, Sergey G.; Gutmanas, Elazar Y.

    2015-10-01

    The research aim was to evaluate the bone regeneration capability of novel load-bearing NiTi alloy (Nitinol) scaffolds in a critical-size defect (CSD) model. High strength "trabecular Nitinol" scaffolds were prepared by PIRAC (Powder Immersion Reaction Assisted Coating) annealing of the highly porous Ni foam in Ti powder at 900°C. This was followed by PIRAC nitriding to mitigate the release of potentially toxic Ni ions. Scaffolds phase composition and microstructure were characterized by X-ray diffraction and scanning electron microscopy (SEM/EDS), and their mechanical properties were tested in compression. New Zealand white rabbits received bone defect in right radius and were divided in four groups randomly. In the control group, nothing was placed in the defect. In other groups, NiTi scaffolds were implanted in the defect: (i) as produced, (ii) loaded with bone marrow aspirate (BMA), and (iii) biomimetically CaP-coated. The animals were sacrificed after 12 weeks. The forelimbs with scaffolds were resected, fixed, sectioned and examined in SEM. New bone formation inside the scaffold was studied by EDS analysis and by the processing of backscattered electron images. Bone ingrowth into the scaffold was observed in all implant groups, mostly next to the ulna. New bone formation was strongly enhanced by BMA loading and biomimeatic CaP coating, the bone penetrating as much as 1-1.5 mm into the scaffold. The results of this preliminary study demonstrate that the newly developed high strength trabecular Nitinol scaffolds can be successfully used for bone regeneration in critical size defects.

  20. Effect of a novel load-bearing trabecular Nitinol scaffold on rabbit radius bone regeneration

    SciTech Connect

    Gotman, Irena Gutmanas, Elazar Y.; Zaretzky, Asaph; Psakhie, Sergey G.

    2015-10-27

    The research aim was to evaluate the bone regeneration capability of novel load-bearing NiTi alloy (Nitinol) scaffolds in a critical-size defect (CSD) model. High strength “trabecular Nitinol” scaffolds were prepared by PIRAC (Powder Immersion Reaction Assisted Coating) annealing of the highly porous Ni foam in Ti powder at 900°C. This was followed by PIRAC nitriding to mitigate the release of potentially toxic Ni ions. Scaffolds phase composition and microstructure were characterized by X-ray diffraction and scanning electron microscopy (SEM/EDS), and their mechanical properties were tested in compression. New Zealand white rabbits received bone defect in right radius and were divided in four groups randomly. In the control group, nothing was placed in the defect. In other groups, NiTi scaffolds were implanted in the defect: (i) as produced, (ii) loaded with bone marrow aspirate (BMA), and (iii) biomimetically CaP-coated. The animals were sacrificed after 12 weeks. The forelimbs with scaffolds were resected, fixed, sectioned and examined in SEM. New bone formation inside the scaffold was studied by EDS analysis and by the processing of backscattered electron images. Bone ingrowth into the scaffold was observed in all implant groups, mostly next to the ulna. New bone formation was strongly enhanced by BMA loading and biomimeatic CaP coating, the bone penetrating as much as 1–1.5 mm into the scaffold. The results of this preliminary study demonstrate that the newly developed high strength trabecular Nitinol scaffolds can be successfully used for bone regeneration in critical size defects.

  1. Calcium phosphate-titanium composites for articulating surfaces of load-bearing implants.

    PubMed

    Bandyopadhyay, Amit; Dittrick, Stanley; Gualtieri, Thomas; Wu, Jeffrey; Bose, Susmita

    2016-04-01

    Calcium phosphate (CaP)-titanium (Ti) composites were processed using a commercial laser engineered net shaping (LENS™) machine to increase wear resistance of articulating surfaces of load-bearing implants. Such composites could be used to cover the surface of titanium implants and potentially increase the lifetime of a joint replacement. It was hypothesized that adding calcium phosphate to commercially pure titanium (CP-Ti) and Ti6Al4V alloy via laser processing would decrease the material loss when subjected to wear. This added protection would be due to the in situ formation of a CaP tribofilm. Different amounts of CaP were mixed by weight with pure Ti and Ti6Al4V powders. The mixed powders were then made into cylindrical samples using a commercial LENS™-750 system. Microstructures were observed and it was found the CaP had integrated into the titanium metal matrix. Compression test revealed that CaP significantly increased the 0.2% offset yield strength as well as the ultimate compressive strength of CP-Ti. It was found that the addition of CaP to pure titanium reduced the material loss and increased wear resistance. This was due to the formation of CaP tribofilm on the articulating surface. The in situ formed tribofilm also lowered the coefficient of friction and acted as a solid lubricant between the two interacting metal surfaces. Overall, CaP addition to Ti and its alloy Ti6Al4V show an effective way to minimize wear induced damage due to the formation of in situ tribofilm at the articulating surface, a strategy that can be utilized in various biomedical devices.

  2. Reduction of load-bearing capacity of all-ceramic crowns due to cement aging.

    PubMed

    Lu, Chenglin; Wang, Raorao; Mao, Shuangshuang; Arola, Dwayne; Zhang, Dongsheng

    2013-01-01

    The purpose of this study was to investigate how water aging of the resin cement influences the stress distribution in all-ceramic crowns and if there is an increase in the propensity for crown failure. The failure of all-ceramic crowns attributed to cement degradation was explored using a combination of experimental and numerical methods. Sectioned all-ceramic crown specimens were fabricated of IPS e.max Ceram/e.max Press (CP) and Vita VM9/Cercon zirconia (VZ), and then stored in either air or distilled water for 30 days. Monotonic contact loads were applied to fracture near the buccal cusp ridge of each sample. Deformation within the crown layers during loading was analyzed by means of Digital Image Correlation (DIC). A 3D finite element model of the restoration including veneer, core, cement and tooth substrate was developed to evaluate the stress distribution in the crowns before and after cement degradation. There was a significant decrease (p<0.001) in the critical fracture load and a change in the fracture mode after cement water absorption in the CP crowns. In contrast, there was no significant influence of cement aging on fracture modes and fracture loads (p>0.05) in the VZ crowns. Finite element analysis showed that regardless of the crown types, the stress distribution is identical by degradation in Young's modulus of the cement. However, core/substrate debonding results in a change of the stress distribution and a significant increase in the magnitude. Water aging causes reduction of stiffness and bonding strength of cement agents. Degradation in bonding strength and stiffness could potentially lead to stress redistribution in the restored crown and reduce the load-bearing capacity of all-ceramic restorations after years of service. Copyright © 2012 Elsevier Ltd. All rights reserved.

  3. Geometric Structure of 3D Spinal Curves: Plane Regions and Connecting Zones

    PubMed Central

    Berthonnaud, E.; Hilmi, R.; Dimnet, J.

    2012-01-01

    This paper presents a new study of the geometric structure of 3D spinal curves. The spine is considered as an heterogeneous beam, compound of vertebrae and intervertebral discs. The spine is modeled as a deformable wire along which vertebrae are beads rotating about the wire. 3D spinal curves are compound of plane regions connected together by zones of transition. The 3D spinal curve is uniquely flexed along the plane regions. The angular offsets between adjacent regions are concentrated at level of the middle zones of transition, so illustrating the heterogeneity of the spinal geometric structure. The plane regions along the 3D spinal curve must satisfy two criteria: (i) a criterion of minimum distance between the curve and the regional plane and (ii) a criterion controlling that the curve is continuously plane at the level of the region. The geometric structure of each 3D spinal curve is characterized by the sizes and orientations of regional planes, by the parameters representing flexed regions and by the sizes and functions of zones of transition. Spinal curves of asymptomatic subjects show three plane regions corresponding to spinal curvatures: lumbar, thoracic and cervical curvatures. In some scoliotic spines, four plane regions may be detected. PMID:25031873

  4. Load-bearing masonry system adoption and performance: A case study of construction company in a developing country

    NASA Astrophysics Data System (ADS)

    Ramli, Nor Azlinda; Abdullah, Che Sobry; Nawi, Mohd Nasrun Mohd; Bahaudin, Ahmad Yusni

    2016-08-01

    This study addresses the factors that influence the adoption of load-bearing masonry (LBM) system. A case study of the load-bearing masonry (LBM) system adoption is conducted through an interview to explore the situation of the technology adoption in a construction company. The finding indicates the factors influence the adoption of LBM system for the construction company are: organizational resources, usefulness, less maintenance, reduce construction time and cost. From the findings, these factors consistent with previous literature. Furthermore, the performance of the company was measured by looking into the financial and non-financial aspects. The LBM system brings good performance as it increased the profits of the company, a good quality of product and attracts more demand from customers. Thus, these factors should be considered for the other companies that are interested in implementing the LBM system in their projects.

  5. Grain Boundary Plane Orientation Fundamental Zones and Structure-Property Relationships.

    PubMed

    Homer, Eric R; Patala, Srikanth; Priedeman, Jonathan L

    2015-10-26

    Grain boundary plane orientation is a profoundly important determinant of character in polycrystalline materials that is not well understood. This work demonstrates how boundary plane orientation fundamental zones, which capture the natural crystallographic symmetries of a grain boundary, can be used to establish structure-property relationships. Using the fundamental zone representation, trends in computed energy, excess volume at the grain boundary, and temperature-dependent mobility naturally emerge and show a strong dependence on the boundary plane orientation. Analysis of common misorientation axes even suggests broader trends of grain boundary energy as a function of misorientation angle and plane orientation. Due to the strong structure-property relationships that naturally emerge from this work, boundary plane fundamental zones are expected to simplify analysis of both computational and experimental data. This standardized representation has the potential to significantly accelerate research in the topologically complex and vast five-dimensional phase space of grain boundaries.

  6. Grain boundary plane orientation fundamental zones and structure-property relationships

    SciTech Connect

    Homer, Eric R.; Patala, Srikanth; Priedeman, Jonathan L.

    2015-10-26

    Grain boundary plane orientation is a profoundly important determinant of character in polycrystalline materials that is not well understood. This work demonstrates how boundary plane orientation fundamental zones, which capture the natural crystallographic symmetries of a grain boundary, can be used to establish structure-property relationships. Using the fundamental zone representation, trends in computed energy, excess volume at the grain boundary, and temperature-dependent mobility naturally emerge and show a strong dependence on the boundary plane orientation. Analysis of common misorientation axes even suggests broader trends of grain boundary energy as a function of misorientation angle and plane orientation. Due to the strong structure-property relationships that naturally emerge from this work, boundary plane fundamental zones are expected to simplify analysis of both computational and experimental data. This standardized representation has the potential to significantly accelerate research in the topologically complex and vast five-dimensional phase space of grain boundaries.

  7. Grain Boundary Plane Orientation Fundamental Zones and Structure-Property Relationships

    PubMed Central

    Homer, Eric R.; Patala, Srikanth; Priedeman, Jonathan L.

    2015-01-01

    Grain boundary plane orientation is a profoundly important determinant of character in polycrystalline materials that is not well understood. This work demonstrates how boundary plane orientation fundamental zones, which capture the natural crystallographic symmetries of a grain boundary, can be used to establish structure-property relationships. Using the fundamental zone representation, trends in computed energy, excess volume at the grain boundary, and temperature-dependent mobility naturally emerge and show a strong dependence on the boundary plane orientation. Analysis of common misorientation axes even suggests broader trends of grain boundary energy as a function of misorientation angle and plane orientation. Due to the strong structure-property relationships that naturally emerge from this work, boundary plane fundamental zones are expected to simplify analysis of both computational and experimental data. This standardized representation has the potential to significantly accelerate research in the topologically complex and vast five-dimensional phase space of grain boundaries. PMID:26498715

  8. Grain boundary plane orientation fundamental zones and structure-property relationships

    DOE PAGES

    Homer, Eric R.; Patala, Srikanth; Priedeman, Jonathan L.

    2015-10-26

    Grain boundary plane orientation is a profoundly important determinant of character in polycrystalline materials that is not well understood. This work demonstrates how boundary plane orientation fundamental zones, which capture the natural crystallographic symmetries of a grain boundary, can be used to establish structure-property relationships. Using the fundamental zone representation, trends in computed energy, excess volume at the grain boundary, and temperature-dependent mobility naturally emerge and show a strong dependence on the boundary plane orientation. Analysis of common misorientation axes even suggests broader trends of grain boundary energy as a function of misorientation angle and plane orientation. Due to themore » strong structure-property relationships that naturally emerge from this work, boundary plane fundamental zones are expected to simplify analysis of both computational and experimental data. This standardized representation has the potential to significantly accelerate research in the topologically complex and vast five-dimensional phase space of grain boundaries.« less

  9. Load bearing capacity of fiber-reinforced and unreinforced composite resin CAD/CAM-fabricated fixed dental prostheses.

    PubMed

    Başaran, Emine Göncü; Ayna, Emrah; Vallittu, Pekka K; Lassila, Lippo V J

    2013-02-01

    It is unclear if fiber-reinforced fixed dental prostheses can be fabricated with physical properties that make them suitable for definitive prostheses. The purpose of this study was to compare the load bearing capacity of fiber-reinforced and unreinforced computer-aided design/computer-aided manufacturing (CAD/CAM) fabricated fixed dental prostheses. Fixed dental prostheses were fabricated with CAD/CAM from 3 experimental fiber-reinforced composite resin blocks, 1 experimental composite resin block, and 1 commercially available composite resin block. The experimental fiber-reinforced composite resin was prepared by mixing dimethacrylate resin with filler particles of BaO silicate and E-glass fiber. Different ratios of resin, filler, and fiber were used to fabricate specimens measuring 15.5 × 19 × 39 mm, which were allocated to 5 different groups (n=8) and statically loaded until final fracture. Statistical analyses were calculated according to final fracture values. A 1-way ANOVA and the Tukey post hoc multiple comparison test were used (α=.05). All groups showed significantly different load-bearing capacities (P<.001). Experimental randomly oriented fiber-reinforced composite resin blocks revealed the highest load-bearing capacity (2163 ±246 N), whereas commercial composite resin blocks showed the lowest (1290 ±172 N). Fixed partial dental prostheses consisting of experimental fiber-reinforced composite resin blocks showed higher load-bearing capacities than did unreinforced composite resin blocks. Copyright © 2013 The Editorial Council of the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.

  10. An automatic recognition and parameter extraction method for structural planes in borehole image

    NASA Astrophysics Data System (ADS)

    Wang, Chuanying; Zou, Xianjian; Han, Zengqiang; Wang, Yiteng; Wang, Jinchao

    2016-12-01

    As a breakthrough in borehole imaging technology, digital panoramic borehole camera technology has been widely employed. The high-resolution panoramic borehole images can accurately reproduce the geometric features of structural planes. However, the detection of these features is usually done manually, which is both time-consuming and introduces human errors. To solve this problem, this paper presents a method for the automatic recognition and parameter extraction of borehole geometric features of camera images. In this method, the image's gray and gradient level, and also their projection on the depth axis are used to identify the locations of structural planes. Afterwards, iterative matching is employed by using a template of sinusoidal function to search for structural planes in the identified image blocks. Finally, optimal sine curves are selected as the feature curves of structural planes, and their related parameters are converted into structural plane parameters required for engineering, such as their positions, dip directions, dip angles and fracture widths. The method can automatically identify all of structural planes throughout the whole borehole camera image in a continuous and rapid manner, and obtain the corresponding structural parameters. It has proven highly reliable, accurate and efficient.

  11. Fiber-reinforced composite substructure: load-bearing capacity of an onlay restoration and flexural properties of the material.

    PubMed

    Garoushi, Sufyan K; Lassila, Lippo V J; Tezvergil, Arzu; Vallittu, Pekka K

    2006-09-01

    The aim of this study was to determine the static load-bearing capacity of composite resin onlay restorations made of particulate filler composite (PFC) with two different types of fiber-reinforced composite (FRC) substructures. In addition, flexural properties of the material combination and the effect of polymerization devices were tested. Specimens were prepared to simulate an onlay restoration, which consisted of 2 to 3 mm of FRC layer as a substructure (short random and continuous bidirectional fiber orientation) and a 1 mm surface layer of PFC. Control specimens were prepared from plain PFC. In Group A the specimens were incrementally polymerized only with a hand-light curing unit for 40 s, while in Group B the specimens were post-cured in a light-curing oven for 15 min before they were statically loaded with a steel ball. Bar-shaped test specimens were prepared to measure the flexural properties of material combination using a three-point bending test (ISO 10477). Analysis of variance (ANOVA) revealed all specimens with a FRC substructure have higher values of static load-bearing capacity and flexural properties than those obtained with plain PFC (p<0.001). The load-bearing capacity of all the specimens decreased after post-curing and water storage. Restorations made from a material combination of FRC and PFC showed better mechanical properties than those obtained with plain PFC.

  12. Out-of-plane free vibration analysis of a cable-arch structure

    NASA Astrophysics Data System (ADS)

    Kang, H. J.; Zhao, Y. Y.; Zhu, H. P.

    2013-02-01

    Cable-arch structure has been widely used in many long-span structures such as cable roofs and cable-stayed arch bridges, but its dynamics is still not well understood. In this paper, the out-of-plane dynamic behavior of a cable-arch structure is investigated. The equations governing the out-of-plane free vibration of the structure are derived using d'Alembert's principle. A transfer matrix method is used to solve the governing equations and determine the frequencies of the out-of-plane vibration. The theories are then used to study two specific cases: free vibration of a model cable-arch and simulation of an arch erection process. The effects of some key parameters of cable and arch, such as tension of cable and radius, open-angle and shape of arch, are examined. The results indicate that in-plane and spatial cables can largely improve the out-of-plane dynamic behavior of arch structures, which are further verified by analyzing the out-of-plane buckling of cable-arch structures. The present work should be valuable and significant not only for the fundamental research but also engineering design of roofs and bridges.

  13. A FUNDAMENTAL PLANE OF SPIRAL STRUCTURE IN DISK GALAXIES

    SciTech Connect

    Davis, Benjamin L.; Kennefick, Daniel; Kennefick, Julia; Shields, Douglas W.; Flatman, Russell; Hartley, Matthew T.; Berrier, Joel C.; Martinsson, Thomas P. K.; Swaters, Rob A.

    2015-03-20

    Spiral structure is the most distinctive feature of disk galaxies and yet debate persists about which theory of spiral structure is correct. Many versions of the density wave theory demand that the pitch angle be uniquely determined by the distribution of mass in the bulge and disk of the galaxy. We present evidence that the tangent of the pitch angle of logarithmic spiral arms in disk galaxies correlates strongly with the density of neutral atomic hydrogen in the disk and with the central stellar bulge mass of the galaxy. These three quantities, when plotted against each other, form a planar relationship that we argue should be fundamental to our understanding of spiral structure in disk galaxies. We further argue that any successful theory of spiral structure must be able to explain this relationship.

  14. Out-of-plane structural flexibility of phosphorene.

    PubMed

    Wang, Gaoxue; Loh, G C; Pandey, Ravindra; Karna, Shashi P

    2016-02-05

    Phosphorene has been rediscovered recently, establishing itself as one of the most promising two-dimensional group-V elemental monolayers with direct band gap, high carrier mobility, and anisotropic electronic properties. In this paper, surface buckling and its effect on its electronic properties are investigated by using molecular dynamics simulations together with density functional theory calculations. We find that phosphorene shows superior structural flexibility along the armchair direction allowing it to have large curvatures. The semiconducting and direct band gap nature are retained with buckling along the armchair direction; the band gap decreases and transforms to an indirect band gap with buckling along the zigzag direction. The structural flexibility and electronic robustness along the armchair direction facilitate the fabrication of devices with complex shapes, such as folded phosphorene and phosphorene nano-scrolls, thereby offering new possibilities for the application of phosphorene in flexible electronics and optoelectronics.

  15. Formation of Deformation Band Structures Normal to the Shear Plane

    NASA Astrophysics Data System (ADS)

    Balasko, C. M.; Schultz, R. A.

    2001-12-01

    Recent fieldwork has shown that many of the geometric relationships previously observed in cataclastic deformation bands are based on a two dimensional view of a three dimensional structure. When the bands are viewed in the shear direction lenses and inosculating bands are seen, as first noted by Aydin [1978] and later by many others. When viewed normal to the shear direction "ladder structures" (linked mode II echelon stepovers or duplexes) and conjugate structures are seen [Davis, 1999]. Davis [1999] grouped these two geometries as different classes of deformation bands and many have interpreted the duplexes as strain localization in Riedel shear zones. Here we demonstrate an alternative explanation. When viewed normal to the shear direction, deformation bands display either mutually crosscutting ("conjugate") sets or contractional stepovers ("duplexes") between interacting mode-II bands. Our field observations reveal that the principal difference between the two is the relative distance separating the parallel echelon bands. Bands that are sufficiently close interact mechanically to promote linking bands within the stepovers. These linking bands are younger than the bounding echelon bands. Because the orientations of bands within the stepovers are the same as that of "conjugate" bands that are more widely spaced, we infer that the magnitude of stress within the stepovers was increased somewhat over background values, but that stress rotations within the stepovers were negligible. To accomplish this, the echelon deformation bands must be strong relative to the host rock and accommodate only small offsets, leading to only minor perturbations of the local stress state in their vicinity. Ladder structure, "radiator rock" [Davis, 1999], and linked echelon stepovers demonstrate a progression from distributed to more localized strain of the sandstone, with the scale dependent on the size and offset magnitude of individual bands. Occurrence of linked echelon stepovers

  16. VLA structure of variable radio sources in the Galactic plane

    NASA Astrophysics Data System (ADS)

    Duric, Nebojsa; Gregory, P. C.

    1988-04-01

    VLA observations of 17 new variable and three nonvariable radio sources from the Galactic Patrol Survey of Gregory and Taylor (1981) are presented. The variable-source morphologies range from unresolved point sources to doubles and triples with jet-lobe structures. No optical counterparts were found for the variable sources to the plate limits of the Palomar Sky Survey, but a 15th-magnitude stellar-like object was found for the nonvariable source GT 0007 + 635. The new observations are combined with previous data to study the collective properties of 28 variable sources. Their spectra, morphologies, and variability characteristics suggest that they fall into two broad categories. The first category consists of 15 unresolved point sources which are characterized by flat inverted spectra between 6 and 20 cm and strong variability. The second category consists of a heterogeneous mixture of resolved sources having varying degrees of structure. The bimodal distribution of variability properties of the patrol sources, reported by Gregory and Taylor, can, in part, be explained by these results. The presence or absence of nonvariable extended emission, resolved in the VLA observations but not in the Patrol observations, appears to regulate the variabilities of these sources.

  17. The effect of short fiber composite base on microleakage and load-bearing capacity of posterior restorations

    PubMed Central

    Garoushi, Sufyan K.; Hatem, Marwa; Lassila, Lippo V. J.; Vallittu, Pekka K.

    2015-01-01

    Abstract Objectives: To determine the marginal microleakage of Class II restorations made with different composite base materials and the static load-bearing capacity of direct composite onlay restorations. Methods: Class II cavities were prepared in 40 extracted molars. They were divided into five groups (n = 8/group) depending on composite base material used (everX Posterior, SDR, Tetric EvoFlow). After Class II restorations were completed, specimens were sectioned mid-sagitally. For each group, sectioned restorations were immersed in dye. Specimens were viewed under a stereo-microscope and the percentage of cavity leakage was calculated. Ten groups of onlay restorations were fabricated (n = 8/group); groups were made with composite base materials (everX Posterior, SDR, Tetric EvoFlow, Gradia Direct LoFlo) and covered by 1 mm layer of conventional (Tetric N-Ceram) or bulk fill (Tetric EvoCeram Bulk Fill) composites. Groups made only from conventional, bulk fill and short fiber composites were used as control. Specimens were statically loaded until fracture. Data were analyzed using ANOVA (p = 0.05). Results: Microleakage of restorations made of plain conventional composite or short fiber composite base material showed statistically (p < 0.05) lower values compared to other groups. ANOVA revealed that onlay restorations made from short fiber-reinforced composite (FRC) as base or plain restoration had statistically significant higher load-bearing capacity (1593 N) (p < 0.05) than other restorations. Conclusion: Restorations combining base of short FRC and surface layer of conventional composite displayed promising performance related to microleakage and load-bearing capacity. PMID:28642894

  18. Compressive neuropathy of long thoracic nerve and accessory nerve secondary to heavy load bearing. A case report.

    PubMed

    Sahin, F; Yilmaz, F; Esit, N; Aysal, F; Kuran, B

    2007-03-01

    Carrying heavy loads that compress the shoulders is a possible etiological factor for both accessory and long thoracic nerve entrapment. In our patient, shouldering heavy loads damaged both nerves. A 27-year-old right-hand-dominant man was referred because of difficulty in raising his arms after a brief period of painful episodes due to heavy load bearing on both shoulders. Atrophic muscles around the shoulders, depressed and winged scapula were noted. An EMG confirmed entrapment of long thoracic and accessory nerves. An exercise program was instituted; 16 months after initial referral, though winged scapula was still noted, manual muscular strength had returned without functional limitation.

  19. Effect of weave tightness and structure on the in-plane and through-plane air permeability of woven carbon fibers for gas diffusion layers

    NASA Astrophysics Data System (ADS)

    Caston, Terry B.; Murphy, Andrew R.; Harris, Tequila A. L.

    In this study, woven gas diffusion layers (GDLs) with varying weave type and tightness are investigated. Plain and twill weave patterns were manufactured in-house. The in-plane and through-plane air permeability of the woven samples were tested, and mercury intrusion porosimetry (MIP) tests were performed to study the pore structure. It was found that the twill weave has a higher permeability than the plain weave, which is consistent with literature. Like non-woven carbon papers, woven GDLs have higher in-plane permeability than through-plane permeability; however it has been shown that it is possible to manufacture a GDL with higher through-plane permeability than in-plane permeability. It was also concluded that the percentage of macropores in the weave is the driving factor in determining the through-plane air permeability. This work lays the groundwork for future studies to attempt to characterize the relationship between the weave structure and the air permeability in woven GDLs.

  20. The influence of the atomic structure of basal planes on interplanar distance in pyrolytic carbon materials

    NASA Astrophysics Data System (ADS)

    Borgardt, N. I.; Prihodko, A. S.; Seibt, M.

    2016-12-01

    The atomic structure of carbon materials is studied using the example of pyrocarbon and boronrich pyrocarbon by means of the method of reconstruction of the wave function in transmission electron microscopy. It is shown that the digital processing of the phase distributions of these functions allows us to find the average distance between the basal planes. Using the method of molecular dynamics for the formation of the test structures and obtaining for them the calculated phase distributions, the effect of depletion of the basal planes of the carbon atoms on the interplanar distance in the pyrocarbon materials is quantified.

  1. Effect of fiber crosslinking on collagen-fiber reinforced collagen-chondroitin-6-sulfate materials for regenerating load-bearing soft tissues.

    PubMed

    Shepherd, J H; Ghose, S; Kew, S J; Moavenian, A; Best, S M; Cameron, R E

    2013-01-01

    Porous collagen-glycosaminoglycan structures are bioactive and exhibit a pore architecture favorable for both cellular infiltration and attachment; however, their inferior mechanical properties limit use, particularly in load-bearing situations. Reinforcement with collagen fibers may be a feasible route for enhancing the mechanical characteristics of these materials, providing potential for composites used for the repair and regeneration of soft tissue such as tendon, ligaments, and cartilage. Therefore, this study investigates the reinforcement of collagen-chondroitin-6-sulfate (C6S) porous structures with bundles of extruded, reconstituted type I collagen fibers. Fiber bundles were produced through extrusion and then, where applicable, crosslinked using a solution of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide/N-hydroxysuccinimide. Fibers were then submerged in the collagen-C6S matrix slurry before being lyophilized. A second 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and N-hydroxysuccinimide crosslinking process was then applied to the composite material before a secondary lyophilization cycle. Where bundles had been previously crosslinked, composites withstood a load of approximately 60 N before failure, the reinforcing fibers remained dense and a favorable matrix pore structure resulted, with good interaction between fiber and matrix. Fibers that had not been crosslinked before lyophilization showed significant internal porosity and a channel existed between them and the matrix. Mechanical properties were significantly reduced, but the additional porosity could prove favorable for cell migration and has potential for directing aligned tissue growth.

  2. Influence of cyclic fatigue in water on the load-bearing capacity of dental bridges made of zirconia.

    PubMed

    Kohorst, Philipp; Dittmer, Marc Philipp; Borchers, Lothar; Stiesch-Scholz, Meike

    2008-09-01

    The humid atmosphere and permanent occurrence of chewing forces in the oral environment lead to degradation of ceramics used for prosthetic restorations. The aim of this in vitro study was to evaluate the influence of artificial aging on the load-bearing capacity of four-unit bridges, with both undamaged and predamaged zirconia frameworks. Additionally, different parameters for chewing simulation have been investigated and a finite element analysis was made to predict the location of highest tensile stresses within the bridges. A total of 60 frameworks were milled from presintered zirconia and divided into six homogeneous groups. Prior to veneering, frameworks of two groups were "damaged" by a defined saw cut similar to an accidental flaw generated during shape cutting. After veneering, FPDs were subjected to thermal and mechanical cycling - with the exception of control groups. The load-bearing capacity of tested FPDs was significantly reduced by artificial aging. In comparison to unaged specimens, fracture resistance decreased by about 40%, whereas preliminary damage did not have a significant effect. Increasing number of cycles and increasing upper load limit failed to show any additional effect on fracture force. To predict the progression of degradation under the terms of in vitro simulation for even longer periods, further aging experiments are required.

  3. Evaluation of a hybrid scaffold/cell construct in repair of high-load-bearing osteochondral defects in rabbits.

    PubMed

    Shao, Xin Xin; Hutmacher, Dietmar W; Ho, Saey Tuan; Goh, James C H; Lee, Eng Hin

    2006-03-01

    The objective of this study was to evaluate the feasibility and potential of a hybrid scaffold system in large- and high-load-bearing osteochondral defects repair. The implants were made of medical-grade PCL (mPCL) for the bone compartment whereas fibrin glue was used for the cartilage part. Both matrices were seeded with allogenic bone marrow-derived mesenchymal cells (BMSC) and implanted in the defect (4 mm diameter x 5 mm depth) on medial femoral condyle of adult New Zealand White rabbits. Empty scaffolds were used at the control side. Cell survival was tracked via fluorescent labeling. The regeneration process was evaluated by several techniques at 3 and 6 months post-implantation. Mature trabecular bone regularly formed in the mPCL scaffold at both 3 and 6 months post-operation. Micro-Computed Tomography showed progression of mineralization from the host-tissue interface towards the inner region of the grafts. At 3 months time point, the specimens showed good cartilage repair. In contrast, the majority of 6 months specimens revealed poor remodeling and fissured integration with host cartilage while other samples could maintain good cartilage appearance. In vivo viability of the transplanted cells was demonstrated for the duration of 5 weeks. The results demonstrated that mPCL scaffold is a potential matrix for osteochondral bone regeneration and that fibrin glue does not inherit the physical properties to allow for cartilage regeneration in a large and high-load-bearing defect site.

  4. Optical polarization characteristics of m-plane GaN/AlGaN quantum well structures grown on m-plane SiC substrate

    NASA Astrophysics Data System (ADS)

    Park, Seoung-Hwan; Ahn, Doyeol

    2015-12-01

    Optical polarization characteristics of m-plane GaN/AlGaN QW structures grown on m-plane SiC substrate were theoretically investigated using the multiband effective-mass theory. The QW structure grown on SiC substrate shows much larger in-plane optical polarization than that grown on GaN substrate. This is attributed to the fact that the QW structure grown on SiC substrate has larger y‧-polarized optical emission and smaller x‧-polarized optical emission than the QW structure grown on GaN substrate. Also, the magnitude of the optical polarization is found to depend on the carrier density and decrease gradually with increasing carrier density. This can be explained by the fact that, with increasing k∥, the x‧-polarized matrix element increases while the y‧-polarized matrix element rapidly decreases.

  5. Women with late whiplash syndrome have greatly reduced load-bearing of the cervical spine. In vivo biomechanical, cross-sectional, lateral radiographic study.

    PubMed

    Kristjansson, Eythor; Gislason, Magnus K

    2017-07-17

    No study has been conducted to ascertain whether the load-bearing capacity of the cervical spine is reduced in vivo in late whiplash syndrome (LWS). To compare the segmental cervical angular values across C0-C6, between two conditions: without versus with external axial load upon the head in three groups of women. A single-blind, age-Body Mass Index (BMI) matched, radiographic, cross-sectional study. Radiographic Department at a University Hospital. One hundred eighty-two women, aged between 18-50 years were enrolled. Participants were divided into 3 groups: a group with LWS (N=62) and two control groups: a chronic insidious neck pain (IONP) group (N=60) and an asymptomatic group (N=60). Prior to and on the same day as the radiographic examination took place, BMI in kg/m2 was recorded and all participants answered the Neck Disability Index (NDI). The two symptomatic groups answered also three other pain and disability questionnaires. Analysis of variance (mixed-model ANOVA) for repeated measures was used for comparison. Significant differences between groups, and the two conditions tested was revealed, but only within the asymptomatic and the IONP groups (p<0.0001), but not within the LWS group (p= 0.9433). Unexpectedly the women with LWS adopted a rigid horizontal translation strategy when external load was applied upon their head. The inter-rater and intra-rater segmental measurements were highly reliable. Women with LWS scored significantly higher on all questionnaires. The results of this study strongly indicate that the load-bearing capacity of the cervical spine is reduced in vivo in women with LWS. The study shows, for the first time, that the cervical spine in women with LWS predominately functions such as a rigid cylinder when loaded. The study implies that the cervical column is extremely weak in the LWS and that the superficial neck muscles, which are designed to move the head-neck, must compensate and act as rigid stabilizers. This causes great joint

  6. Population analysis of plane-wave electronic structure calculations of bulk materials

    SciTech Connect

    Segall, M.D.; Shah, R.; Pickard, C.J.; Payne, M.C.

    1996-12-01

    {ital Ab} {ital initio} plane-wave electronic structure calculations are widely used in the study of bulk materials. A technique for the projection of plane-wave states onto a localized basis set is used to calculate atomic charges and bond populations by means of Mulliken analysis. We analyze a number of simple bulk crystals and find correlations of overlap population with covalency of bonding and bond strength, and effective valence charge with ionicity of bonding. Thus, we show that the techniques described in this paper may be usefully applied in the field of solid state physics. {copyright}{ital 1996 The American Physical Society.}

  7. Dwarf galaxy planes: the discovery of symmetric structures in the Local Group

    NASA Astrophysics Data System (ADS)

    Pawlowski, Marcel S.; Kroupa, Pavel; Jerjen, Helmut

    2013-11-01

    Both major galaxies in the Local Group (LG) are surrounded by thin planes of mostly co-orbiting satellite galaxies, the vast polar structure (VPOS) around the Milky Way (MW) and the Great Plane of Andromeda (GPoA) around M31. We summarize the current knowledge concerning these structures and compare their relative orientations by re-determining their properties in a common coordinate system. The existence of similar, coherent structures around both major LG galaxies motivates an investigation of the distribution of the more distant non-satellite galaxies in the LG. This results in the discovery of two planes (diameters of 1-2 Mpc) which contain almost all nearby non-satellite galaxies. The two LG planes are surprisingly symmetric. They are inclined by only 20° relative to the galactic disc of M31, are similarly thin (heights of ≈60 kpc) and have near-to-identical offsets from the MW and from M31. They are inclined relative to each other by 35°. Comparing the plane orientations with each other and with additional features reveals indications for an intimate connection between the VPOS and the GPoA. They are both polar with respect to the MW, have similar orbital directions and are inclined by about 45°±7° relative to each other. The Magellanic Stream approximately aligns with the VPOS and the GPoA, but also shares its projected position and line-of-sight velocity trend with a part of the dominating structure of non-satellite dwarf galaxies. In addition, the recent proper motion measurement of M31 indicates a prograde orbit of the MW-M31 system, the VPOS and the GPoA. The alignment with other features such as the Supergalactic Plane and the overdensity in hypervelocity stars are discussed as well. We end with a short summary of the currently proposed scenarios trying to explain the LG galaxy structures as either originating from cosmological structures or from tidal debris of a past galaxy encounter. We emphasize that there currently exists no full detailed

  8. Role of shear along horizontal plane in the formation of helicoidal structures

    NASA Astrophysics Data System (ADS)

    Koronovsky, N. V.; Gogonenkov, G. N.; Goncharov, M. A.; Timurziev, A. I.; Frolova, N. S.

    2009-09-01

    An unusual structural paragenesis, complicated by brachyanticlines, is revealed for the first time in the sedimentary cover of the West Siberian Plate by 3D seismic surveying. These are linear (in plan view) systems of en-echelon arranged low-amplitude normal faults related to wrench faults in the basement. On different sides off a wrench fault, the planes of normal faults dip in opposite directions, forming a helicoidal structure that resembles the blades of a propeller. In the section parallel to the wrench fault, the boundaries of the beds and normal fault planes dip in opposite directions as well. In the section across the strike of the normal faults converging toward the basement, the beds take the shape of an antiform with a crest sagged along the normal faults (flower structure). This structural assembly was formed as a result of interference of stress fields of horizontal shear in the vertical plane (induced by faulting in the basement) and in the horizontal plane (caused by gravity resistance of the cover). In this case, the displacements along the normal faults develop in both the vertical and, to a greater extent, horizontal directions, so that the faults in cover are actually characterized by normal-strike-slip kinematics. The regional N-S-trending compression of the West Siberian Plate is the main cause of shearing along the NW- and NE-trending faults in the basement, which make up a rhomb-shaped system in plan view. Petroliferous brachyanticlines, whose axes, notwithstanding tectonophysical laws, are oriented in the direction close to the maximum compression axis, are known in the large wrench fault zones of Western Siberia. Our experiments with equivalent materials showed that a local stress field arising at the ends of echeloned Riedel shears within a wrench fault zone may be a cause of the formation of such brachyanticlines. The progressive elongation of Riedel shears leads to the corresponding elongation of the brachyanticlines located between

  9. Excess iron undermined bone load-bearing capacity through tumor necrosis factor-α-dependent osteoclastic activation in mice.

    PubMed

    Li, Junping; Hou, Yanli; Zhang, Shuping; Ji, Hong; Rong, Haiqin; Qu, Guangbo; Liu, Sijin

    2013-01-01

    Iron overload has been associated with bone mass loss. To elucidate the effects of excess iron on bone metabolism, an iron-overloading mouse model was established by administering iron-dextran at 250 mg/kg to female BALB/c mice. After 4 weeks, the mice were sacrificed and the biomechanical properties of the femurs were examined. The results suggested a notable decrease of the maximal bending stress and the modulus of bending elasticity in the femurs obtained from the excess iron-treated mice compared to the control mice. The levels of the serum osteocalcin, C-telopeptide of type I collagen (CTX-1) and tumor necrosis factor-α (TNF-α) were measured in order to investigate the underlying mechanism responsible for the excess iron-induced bone strength reduction. Overall, the results suggested that iron overload resulted in a marked reduction of bone load-bearing capacity through a TNF-triggered osteoclast differentiation and resorption mechanism.

  10. Performance of bioactive PMMA-based bone cement under load-bearing conditions: an in vivo evaluation and FE simulation.

    PubMed

    Fottner, Andreas; Nies, Berthold; Kitanovic, Denis; Steinbrück, Arnd; Mayer-Wagner, Susanne; Schröder, Christian; Heinemann, Sascha; Pohl, Ulrich; Jansson, Volkmar

    2016-09-01

    In the past, bioactive bone cement was investigated in order to improve the durability of cemented arthroplasties by strengthening the bone-cement interface. As direct bone-cement bonding may theoretically lead to higher stresses within the cement, the question arises, whether polymethylmethacrylate features suitable mechanical properties to withstand altered stress conditions? To answer this question, in vivo experiments and finite element simulations were conducted. Twelve rabbits were divided into two groups examining either bioactive polymethylmethacrylate-based cement with unchanged mechanical properties or commercially available polymethylmethacrylate cement. The cements were tested under load-bearing conditions over a period of 7 months, using a spacer prosthesis cemented into the femur. For the finite element analyses, boundary conditions of the rabbit femur were simulated and analyses were performed with respect to different loading scenarios. Calculations of equivalent stress distributions within the cements were applied, with a completely bonded cement surface for the bioactive cement and with a continuously interfering fibrous tissue layer for the reference cement. The bioactive cement revealed good in vivo bioactivity. In the bioactive cement group two failures (33 %), with complete break-out of the prosthesis occurred, while none in the reference group. Finite element analyses of simulated bioactive cement fixation showed an increase in maximal equivalent stress by 49.2 to 109.4 % compared to the simulation of reference cement. The two failures as well as an increase in calculated equivalent stress highlight the importance of fatigue properties of polymethylmethacrylate in general and especially when developing bioactive cements designated for load-bearing conditions.

  11. Development of hydroxyapatite/calcium silicate composites addressed to the design of load-bearing bone scaffolds.

    PubMed

    Sprio, Simone; Tampieri, Anna; Celotti, Giancarlo; Landi, Elena

    2009-04-01

    This work deals with the preparation of bioactive ceramic composites to be employed for the development of load-bearing bone substitutes, made of hydroxyapatite (Ca(10)(PO(4))(6)(OH)(2), HA) and bioactive dicalcium silicate (Ca(2)SiO(4), C(2)S) as a reinforcing phase. The composite materials were prepared by Fast Hot-Pressing (FHP), which allowed the rapid sintering of monolithic ceramics at temperatures up to 1500 degrees C, well above the commonly adopted temperatures for the consolidation of hydroxyapatite (1200-1300 degrees C). The purpose was to achieve the grain coalescence of both HA and the strengthening phase, so that to obtain a homogeneous ceramic material characterized by controlled phase composition and improved mechanical strength; the dwell time was reduced as much as possible to prevent HA decomposition and excessive grain growth. The most remarkable result, in terms of phase composition, was the absence of any secondary phases in the final ceramics other than HA and C(2)S, even after sintering at 1500 degrees C. The flexure strength of the composite materials was found to be much higher than that of HA alone. Further mechanical characterization was also carried out on HA and composites, sintered in different conditions, to evaluate the elastic properties and fracture toughness, and properties close to those of mineral bone were found. These preliminary results confirmed that composites of HA and Ca(2)SiO(4) are promising for the development of bioactive load-bearing ceramic bone substitutes with controlled phase composition.

  12. A Search for Narrow Vertical Structures in the Canadian Galactic Plane Survey

    NASA Astrophysics Data System (ADS)

    Asgekar, Ashish; English, Jayanne; Safi-Harb, Samar; Kothes, Roland

    2005-08-01

    Worms are defined to be dusty, atomic hydrogen (H I) structures that are observed in low-resolution data to rise perpendicular to the Galactic plane. Data from the 1' resolution Canadian Galactic Plane Survey (CGPS) were systematically searched for narrow vertical H I structures that could be resolved worms. Another motivation for the search was to explore the scenario in which mushroom-shaped worms such as GW 123.4-1.5, studied by English and collaborators, could be generated by a single supernova. However, no other vertical structures of mushroom-shape morphology were found. We also examined objects previously classified as worm candidates by Koo and collaborators; only seven have a significant portion of their structure falling in the CGPS range of l=74deg-147deg, -3.5dstructures that extend toward the Milky Way's halo. However, a list of 10 narrow vertical structures found in our search is furnished; one structure is >~500 pc tall, thus extending from the Galactic plane into the halo. We provide details about these narrow vertical structures, including comparisons between H I, radio continuum, IR, and CO observations. Our search was conducted by visual inspection, and we describe the limitations of this approach since it indicates that only six disk-halo features may exist throughout the Milky Way. We also discuss the possible origins of structures at high latitudes and the relationship between mushroom-shaped clouds and old supernova remnants.

  13. Measurements of the streamwise vortical structures in a plane mixing layer

    NASA Technical Reports Server (NTRS)

    Bell, James H.; Mehta, Rabindra D.

    1992-01-01

    The 3D structure of a plane two-stream mixing layer of velocity ratio 0.6 and originating from laminar initial boundary layers was investigated through direct measurements made in a specially constructed mixing-layer wind tunnel. The main objective of the study was to establish quantitatively the presence and the role of the secondary streamwise vortex structure (of the kind that has been shown in past flow visualization investigations to ride among the primary spanwise vortices) in the development of a plane turbulent mixing layer at relatively high Reynolds numbers. Results indicate that the instability leading to the formation of streamwise vortices is initially amplified just downstream of the first spanwise roll-up. The streamwise vortices, which first appear in clusters containing vorticity of both signs, realign further downstream to form counterrotating pairs. Due to the amalgamation of like-sign vortices, the streamwise vortex spacing increases in a stepwise fashion.

  14. Structural phase transitions and out-of-plane dust lattice instabilities in vertically confined plasma crystals

    NASA Astrophysics Data System (ADS)

    Qiao, K.; Hyde, T. W.

    2005-02-01

    The formation of plasma crystals confined in an external one-dimensional parabolic potential well is simulated for a normal experimental environment employing a computer code called BOX&barbelow;TREE. Under appropriate conditions, crystals were found to form layered systems. The system’s structural phase transitions, including transitions between crystals with differing numbers of layers and the same number of layers but different intralayer structures, were investigated and found to agree with previous theoretical and experimental research results. One- to two-layer transitions were examined in detail and shown to start at the point where the out-of-plane lattice instability appears. The resulting three layer system caused by this instability was observed at the center of the system. Finally, growth rates for this out-of-plane lattice instability were obtained using the BOX&barbelow;TREE simulation with these results shown to agree with those obtained from analytical theory.

  15. Plane of elastic non-resisting tension material under foundation structures

    NASA Astrophysics Data System (ADS)

    Baratta, A.; Corbi, I.

    2004-05-01

    In the frame of 2D-static problems one approaches the problem of elastic-NRT (not-resisting tension) semi-plane loaded on its limit line. This problem is intended to model the stress situation induced in the soil by a foundation structure. The solution, in terms of activated stress field, is searched for in the class of stress fields satisfying equilibrium and admissibility conditions, by applying an energy approach. Copyright

  16. Structural Properties of Lanthanide and Actinide Compounds within the Plane Wave Pseudopotential Approach

    NASA Astrophysics Data System (ADS)

    Pickard, Chris J.; Winkler, Björn; Chen, Roger K.; Payne, M. C.; Lee, M. H.; Lin, J. S.; White, J. A.; Milman, V.; Vanderbilt, David

    2000-12-01

    We show that plane wave ultrasoft pseudopotential methods readily extend to the calculation of the structural properties of lanthanide and actinide containing compounds. This is demonstrated through a series of calculations performed on UO, UO2, UO3, U3O8, UC2, α-CeC2, CeB6, CeSe, CeO2, NdB6, TmOI, LaBi, LaTiO3, YbO, and elemental Lu.

  17. Structural properties of lanthanide and actinide compounds within the plane wave pseudopotential approach

    PubMed

    Pickard; Winkler; Chen; Payne; Lee; Lin; White; Milman; Vanderbilt

    2000-12-11

    We show that plane wave ultrasoft pseudopotential methods readily extend to the calculation of the structural properties of lanthanide and actinide containing compounds. This is demonstrated through a series of calculations performed on UO, UO2, UO3, U3O8, UC2, alpha-CeC2, CeB6, CeSe, CeO2, NdB6, TmOI, LaBi, LaTiO3, YbO, and elemental Lu.

  18. Designing stable finite state machine behaviors using phase plane analysis and variable structure control

    SciTech Connect

    Feddema, J.T.; Robinett, R.D.; Driessen, B.J.

    1998-03-10

    This paper discusses how phase plane analysis can be used to describe the overall behavior of single and multiple autonomous robotic vehicles with finite state machine rules. The importance of this result is that one can begin to design provably asymptotically stable group behaviors from a set of simple control laws and appropriate switching points with decentralized variable structure control. The ability to prove asymptotically stable group behavior is especially important for applications such as locating military targets or land mines.

  19. Crystallographic tilt and in-plane anisotropies of an a-plane InGaN/GaN layered structure grown by MOCVD on r-plane sapphire using a ZnO buffer

    NASA Astrophysics Data System (ADS)

    Liu, H. F.; Liu, W.; Guo, S.; Chi, D. Z.

    2016-03-01

    High-resolution x-ray diffraction (HRXRD) was used to investigate the crystallographic tilts and structural anisotropies in epitaxial nonpolar a-plane InGaN/GaN grown by metal-organic chemical vapor deposition on r-plane sapphire using a ZnO buffer. The substrate had an unintentional miscut of 0.14° towards its [-4 2 2 3] axis. However, HRXRD revealed a tilt of 0.26° (0.20°) between the ZnO (GaN) (11-20) and the Al2O3 (1-102) atomic planes, with the (11-20) axis of ZnO (GaN) tilted towards its c-axis, which has a difference of 163° in azimuth from that of the substrate’s miscut. Excess broadenings in the GaN/ZnO (11-20) rocking curves (RCs) were observed along its c-axis. Specific analyses revealed that partial dislocations and anisotropic in-plane strains, rather than surface-related effects, wafer curvature or stacking faults, are the dominant factors for the structural anisotropy. The orientation of the partial dislocations is most likely affected by the miscut of the substrate, e.g. via tilting of the misfit dislocation gliding planes created during island coalescences. Their Burgers vector components in the growth direction, in turn, gave rise to crystallographic tilts in the same direction as that of the excess RC-broadenings.

  20. A novel dual-frequency loading system for studying mechanobiology of load-bearing tissue.

    PubMed

    Zhang, Chunqiu; Qiu, Lulu; Gao, Lilan; Guan, Yinjie; Xu, Qiang; Zhang, Xizheng; Chen, Qian

    2016-12-01

    In mechanobiological research, an appropriate loading system is an essential tool to mimic mechanical signals in a native environment. To achieve this goal, we have developed a novel loading system capable of applying dual-frequency loading including both a low-frequency high-amplitude loading and a high-frequency low-amplitude loading, according to the mechanical conditions experienced by bone and articular cartilage tissues. The low-frequency high-amplitude loading embodies the main force from muscular contractions and/or reaction forces while the high-frequency low-amplitude loading represents an assistant force from small muscles, ligaments and/or other tissue in order to maintain body posture during human activities. Therefore, such dual frequency loading system may reflect the natural characteristics of complex mechanical load on bone or articular cartilage than the single frequency loading often applied during current mechanobiological experiments. The dual-frequency loading system is validated by experimental tests using precision miniature plane-mirror interferometers. The dual-frequency loading results in significantly more solute transport in articular cartilage than that of the low-frequency high-amplitude loading regiment alone, as determined by quantitative fluorescence microscopy of tracer distribution in articular cartilage. Thus, the loading system can provide a new method to mimic mechanical environment in bone and cartilage, thereby revealing the in vivo mechanisms of mechanosensation, mechanotransduction and mass-transport, and improving mechanical conditioning of cartilage and/or bone constructs for tissue engineering. Copyright © 2016 Elsevier B.V. All rights reserved.

  1. Structural anisotropic properties of a-plane GaN epilayers grown on r-plane sapphire by molecular beam epitaxy

    SciTech Connect

    Lotsari, A.; Kehagias, Th.; Katsikini, M.; Arvanitidis, J.; Ves, S.; Komninou, Ph.; Dimitrakopulos, G. P.; Tsiakatouras, G.; Tsagaraki, K.; Georgakilas, A.; Christofilos, D.

    2014-06-07

    Heteroepitaxial non-polar III-Nitride layers may exhibit extensive anisotropy in the surface morphology and the epilayer microstructure along distinct in-plane directions. The structural anisotropy, evidenced by the “M”-shape dependence of the (112{sup ¯}0) x-ray rocking curve widths on the beam azimuth angle, was studied by combining transmission electron microscopy observations, Raman spectroscopy, high resolution x-ray diffraction, and atomic force microscopy in a-plane GaN epilayers grown on r-plane sapphire substrates by plasma-assisted molecular beam epitaxy (PAMBE). The structural anisotropic behavior was attributed quantitatively to the high dislocation densities, particularly the Frank-Shockley partial dislocations that delimit the I{sub 1} intrinsic basal stacking faults, and to the concomitant plastic strain relaxation. On the other hand, isotropic samples exhibited lower dislocation densities and a biaxial residual stress state. For PAMBE growth, the anisotropy was correlated to N-rich (or Ga-poor) conditions on the surface during growth, that result in formation of asymmetric a-plane GaN grains elongated along the c-axis. Such conditions enhance the anisotropy of gallium diffusion on the surface and reduce the GaN nucleation rate.

  2. Anti-plane transverse waves propagation in nanoscale periodic layered piezoelectric structures.

    PubMed

    Chen, A-Li; Yan, Dong-Jia; Wang, Yue-Sheng; Zhang, Chuanzeng

    2016-02-01

    In this paper, anti-plane transverse wave propagation in nanoscale periodic layered piezoelectric structures is studied. The localization factor is introduced to characterize the wave propagation behavior. The transfer matrix method based on the nonlocal piezoelectricity continuum theory is used to calculate the localization factor. Additionally, the stiffness matrix method is applied to compute the wave transmission spectra. A cut-off frequency is found, beyond which the elastic waves cannot propagate through the periodic structure. The size effect or the influence of the ratio of the internal to external characteristic lengths on the cut-off frequency and the wave propagation behavior are investigated and discussed.

  3. Out-of-Plane Measurements of the Fifth Structure Function of the Deuteron

    NASA Astrophysics Data System (ADS)

    Gilfoyle, Gerard

    2006-10-01

    We have measured the asymmetry ALT^' associated with the fifth structure function in quasi-elastic kinematics at beam energies of 2.56 GeV and 4.23 GeV over a Q^2 range 0.1 - 2.0 (GeV/c)^2 with the CLAS detector at Jefferson Lab. The differential cross section of the D(e,e^'p)n reaction with a polarized beam and unpolarized target has a component that is the imaginary part of the interference term between the longitudinal and transverse parts of the nuclear current. This fifth structure function is non-zero only for protons ejected out of the scattering plane defined by the incoming and outgoing electron and is sensitive to final-state interactions. Only limited measurements have been made of this quantity before now. We extract ALT^' using quasi-elastic, missing momentum (pm) spectra weighted by (φpq) where φpq is the angle between the scattering plane and the plane defined by the ejected proton and neutron. We will present event selection criteria, calibrations, and consistency checks of the analysis. We will show results for measurements of ALT^' that explore different Q^2 regions and different W ranges near the quasi-elastic peak. The data agree with theoretical calculations at low pm, but diverge at higher missing momenta.

  4. Chiral nematic self-assembly of minimally surface damaged chitin nanofibrils and its load bearing functions.

    PubMed

    Oh, Dongyeop X; Cha, Yun Jeong; Nguyen, Hoang-Linh; Je, Hwa Heon; Jho, Yong Seok; Hwang, Dong Soo; Yoon, Dong Ki

    2016-03-18

    Chitin is one of the most abundant biomaterials in nature, with 10(10) tons produced annually as hierarchically organized nanofibril fillers to reinforce the exoskeletons of arthropods. This green and cheap biomaterial has attracted great attention due to its potential application to reinforce biomedical materials. Despite that, its practical use is limited since the extraction of chitin nanofibrils requires surface modification involving harsh chemical treatments, leading to difficulties in reproducing their natural prototypal hierarchical structure, i.e. chiral nematic phase. Here, we develop a chemical etching-free approach using calcium ions, called "natural way", to disintegrate the chitin nanofibrils while keeping the essential moiety for the self-assembly, ultimately resulting in the reproduction of chitin's natural chiral structure in a polymeric matrix. This chiral chitin nanostructure exceptionally toughens the composite. Our resultant chiral nematic phase of chitin materials can contribute to the understanding and use of the reinforcing strategy in nature.

  5. Chiral nematic self-assembly of minimally surface damaged chitin nanofibrils and its load bearing functions

    NASA Astrophysics Data System (ADS)

    Oh, Dongyeop X.; Cha, Yun Jeong; Nguyen, Hoang-Linh; Je, Hwa Heon; Jho, Yong Seok; Hwang, Dong Soo; Yoon, Dong Ki

    2016-03-01

    Chitin is one of the most abundant biomaterials in nature, with 1010 tons produced annually as hierarchically organized nanofibril fillers to reinforce the exoskeletons of arthropods. This green and cheap biomaterial has attracted great attention due to its potential application to reinforce biomedical materials. Despite that, its practical use is limited since the extraction of chitin nanofibrils requires surface modification involving harsh chemical treatments, leading to difficulties in reproducing their natural prototypal hierarchical structure, i.e. chiral nematic phase. Here, we develop a chemical etching-free approach using calcium ions, called “natural way”, to disintegrate the chitin nanofibrils while keeping the essential moiety for the self-assembly, ultimately resulting in the reproduction of chitin’s natural chiral structure in a polymeric matrix. This chiral chitin nanostructure exceptionally toughens the composite. Our resultant chiral nematic phase of chitin materials can contribute to the understanding and use of the reinforcing strategy in nature.

  6. Chiral nematic self-assembly of minimally surface damaged chitin nanofibrils and its load bearing functions

    PubMed Central

    Oh, Dongyeop X.; Cha, Yun Jeong; Nguyen, Hoang-Linh; Je, Hwa Heon; Jho, Yong Seok; Hwang, Dong Soo; Yoon, Dong Ki

    2016-01-01

    Chitin is one of the most abundant biomaterials in nature, with 1010 tons produced annually as hierarchically organized nanofibril fillers to reinforce the exoskeletons of arthropods. This green and cheap biomaterial has attracted great attention due to its potential application to reinforce biomedical materials. Despite that, its practical use is limited since the extraction of chitin nanofibrils requires surface modification involving harsh chemical treatments, leading to difficulties in reproducing their natural prototypal hierarchical structure, i.e. chiral nematic phase. Here, we develop a chemical etching-free approach using calcium ions, called “natural way”, to disintegrate the chitin nanofibrils while keeping the essential moiety for the self-assembly, ultimately resulting in the reproduction of chitin’s natural chiral structure in a polymeric matrix. This chiral chitin nanostructure exceptionally toughens the composite. Our resultant chiral nematic phase of chitin materials can contribute to the understanding and use of the reinforcing strategy in nature. PMID:26988392

  7. Engineering of optical polarization based on electronic band structures of A-plane ZnO layers under biaxial strains

    SciTech Connect

    Matsui, Hiroaki Tabata, Hitoshi; Hasuike, Noriyuki; Harima, Hiroshi

    2014-09-21

    In-plane anisotropic strains in A-plane layers on the electronic band structure of ZnO were investigated from the viewpoint of optical polarization anisotropy. Investigations utilizing k·p perturbation theory revealed that energy transitions and associated oscillation strengths were dependent on in-plane strains. The theoretical correlation between optical polarizations and in-plane strains was experimentally demonstrated using A-plane ZnO layers with different in-plane strains. Finally, optical polarization anisotropy and its implications for in-plane optical properties are discussed in relation to the energy shift between two orthogonal directions. Higher polarization rotations were obtained in an A-plane ZnO layer with in-plane biaxially compressive strains as compared to strain-free ZnO. This study provides detailed information concerning the role played by in-plane strains in optically polarized applications based on nonpolar ZnO in the ultra-violet region.

  8. Domain overlap matrices from plane-wave-based methods of electronic structure calculation

    NASA Astrophysics Data System (ADS)

    Golub, Pavlo; Baranov, Alexey I.

    2016-10-01

    Plane waves are one of the most popular and efficient basis sets for electronic structure calculations of solids; however, their delocalized nature makes it difficult to employ for them classical orbital-based methods of chemical bonding analysis. The quantum chemical topology approach, introducing chemical concepts via partitioning of real space into chemically meaningful domains, has no difficulties with plane-wave-based basis sets. Many popular tools employed within this approach, for instance delocalization indices, need overlap integrals over these domains—the elements of the so called domain overlap matrices. This article reports an efficient algorithm for evaluation of domain overlap matrix elements for plane-wave-based calculations as well as evaluation of its implementation for one of the most popular projector augmented wave (PAW) methods on the small set of simple and complex solids. The stability of the obtained results with respect to PAW calculation parameters has been investigated, and the comparison of the results with the results from other calculation methods has also been made.

  9. Controlling the Electronic Structures and Properties of in-Plane Transition-Metal Dichalcogenides Quantum Wells.

    PubMed

    Wei, Wei; Dai, Ying; Niu, Chengwang; Huang, Baibiao

    2015-11-30

    In-plane transition-metal dichalcogenides (TMDs) quantum wells have been studied on the basis of first-principles density functional calculations to reveal how to control the electronic structures and the properties. In collection of quantum confinement, strain and intrinsic electric field, TMD quantum wells offer a diverse of exciting new physics. The band gap can be continuously reduced ascribed to the potential drop over the embedded TMD and the strain substantially affects the band gap nature. The true type-II alignment forms due to the coherent lattice and strong interface coupling suggesting the effective separation and collection of excitons. Interestingly, two-dimensional quantum wells of in-plane TMD can enrich the photoluminescence properties of TMD materials. The intrinsic electric polarization enhances the spin-orbital coupling and demonstrates the possibility to achieve topological insulator state and valleytronics in TMD quantum wells. In-plane TMD quantum wells have opened up new possibilities of applications in next-generation devices at nanoscale.

  10. Controlling the Electronic Structures and Properties of in-Plane Transition-Metal Dichalcogenides Quantum Wells

    PubMed Central

    Wei, Wei; Dai, Ying; Niu, Chengwang; Huang, Baibiao

    2015-01-01

    In-plane transition-metal dichalcogenides (TMDs) quantum wells have been studied on the basis of first-principles density functional calculations to reveal how to control the electronic structures and the properties. In collection of quantum confinement, strain and intrinsic electric field, TMD quantum wells offer a diverse of exciting new physics. The band gap can be continuously reduced ascribed to the potential drop over the embedded TMD and the strain substantially affects the band gap nature. The true type-II alignment forms due to the coherent lattice and strong interface coupling suggesting the effective separation and collection of excitons. Interestingly, two-dimensional quantum wells of in-plane TMD can enrich the photoluminescence properties of TMD materials. The intrinsic electric polarization enhances the spin-orbital coupling and demonstrates the possibility to achieve topological insulator state and valleytronics in TMD quantum wells. In-plane TMD quantum wells have opened up new possibilities of applications in next-generation devices at nanoscale. PMID:26616013

  11. Role of isostaticity and load-bearing microstructure in the elasticity of yielded colloidal gels

    PubMed Central

    Hsiao, Lilian C.; Newman, Richmond S.; Glotzer, Sharon C.; Solomon, Michael J.

    2012-01-01

    We report a simple correlation between microstructure and strain-dependent elasticity in colloidal gels by visualizing the evolution of cluster structure in high strain-rate flows. We control the initial gel microstructure by inducing different levels of isotropic depletion attraction between particles suspended in refractive index matched solvents. Contrary to previous ideas from mode coupling and micromechanical treatments, our studies show that bond breakage occurs mainly due to the erosion of rigid clusters that persist far beyond the yield strain. This rigidity contributes to gel elasticity even when the sample is fully fluidized; the origin of the elasticity is the slow Brownian relaxation of rigid, hydrodynamically interacting clusters. We find a power-law scaling of the elastic modulus with the stress-bearing volume fraction that is valid over a range of volume fractions and gelation conditions. These results provide a conceptual framework to quantitatively connect the flow-induced microstructure of soft materials to their nonlinear rheology. PMID:22988067

  12. On load paths and load bearing topology from finite element analysis

    NASA Astrophysics Data System (ADS)

    Kelly, D.; Reidsema, C.; Lee, M.

    2010-06-01

    Load paths can be mapped from vector plots of 'pointing stress vectors'. They define a path along which a component of load remains constant as it traverses the solution domain. In this paper the theory for the paths is first defined. Properties of the plots that enable a designer to interpret the structural behavior from the contours are then identified. Because stress is a second order tensor defined on an orthogonal set of axes, the vector plots define separate paths for load transfer in each direction of the set of axes. An algorithm is therefore presented that combines the vectors to define a topology to carry the loads. The algorithm is shown to straighten the paths reducing bending moments and removing stress concentration. Application to a bolted joint, a racing car body and a yacht hull demonstrate the usefulness of the plots.

  13. Anodized titania: Processing and characterization to improve cell-materials interactions for load bearing implants

    NASA Astrophysics Data System (ADS)

    Das, Kakoli

    The objective of this study is to investigate in vitro cell-materials interactions using human osteoblast cells on anodized titanium. Titanium is a bioinert material and, therefore, gets encapsulated after implantation into the living body by a fibrous tissue that isolates them from the surrounding tissues. In this work, bioactive nonporous and nanoporous TiO2 layers were grown on commercially pure titanium substrate by anodization process using different electrolyte solutions namely (1) H3PO 4, (2) HF and (3) H2SO4, (4) aqueous solution of citric acid, sodium fluoride and sulfuric acid. The first three electrolytes produced bioactive TiO2 films with a nonporous structure showing three distinctive surface morphologies. Nanoporous morphology was obtained on Ti-surfaces from the fourth electrolyte at 20V for 4h. Cross-sectional view of the nanoporous surface reveals titania nanotubes of length 600 nm. It was found that increasing anodization time initially increased the height of the nanotubes while maintaining the tubular array structure, but beyond 4h, growth of nanotubes decreased with a collapsed array structure. Human osteoblast (HOB) cell attachment and growth behavior were studied using an osteoprecursor cell line (OPC 1) for 3, 7 and 11 days. Colonization of the cells was noticed with distinctive cell-to-cell attachment on HF anodized surfaces. TiO2 layer grown in H2SO4 electrolyte did not show significant cell growth on the surface, and some cell death was also noticed. Good cellular adherence with extracellular matrix extensions in between the cells was noticed for samples anodized with H3PO 4 electrolyte and nanotube surface. Cell proliferation was excellent on anodized nanotube surfaces. An abundant amount of extracellular matrix (ECM) between the neighboring cells was also noticed on nanotube surfaces with filopodia extensions coming out from cells to grasp the nanoporous surface for anchorage. To better understand and compare cell-materials interactions

  14. Planarized triarylboranes: stabilization by structural constraint and their plane-to-bowl conversion.

    PubMed

    Zhou, Zhiguo; Wakamiya, Atsushi; Kushida, Tomokatsu; Yamaguchi, Shigehiro

    2012-03-14

    Triphenylborane and 9,10-diphenyl-9,10-dihydro-9,10-diboraanthracene, constrained to a planar arrangement with methylene tethers, were synthesized by intramolecular multi-fold Friedel-Crafts cyclization. These compounds were stable toward air, water, and amines, despite the absence of steric protection in the vertical direction with respect to the B atoms, and showed characteristic structural, electronic, and photophysical properties. In addition, upon treatment with a fluoride ion, these compounds underwent a plane-to-bowl conversion in a controlled manner.

  15. Effect of in-plane density on the structural and elastic properties of graphite intercalation compounds

    SciTech Connect

    Woo, K.C.; Kamitakahara, W.A.; DiVincenzo, D.P.; Robinson, D.S.; Mertwoy, H.; Milliken, J.W.; Fischer, J.E.

    1983-01-17

    Dramatic differences in structure, elastic properties, and order-disorder temperatures are observed for stage-2 Li-graphite of different in-plane density, indicating the importance of long-range interactions in cohesive properties. LiC/sub 12/ is three-dimensionally ordered up to approx.500 K with ..sqrt..3 x ..sqrt..3 Li superlattice and AA graphite stacking, whereas LiC/sub 18/ is disordered at 300 K and has AB staking. LO and LA (00l) phonon energies are 30% greater in the former, which can be understood in terms of electrostatic effects.

  16. Complex band structure under plane-wave nonlocal pseudopotential Hamiltonian of metallic wires and electrodes

    SciTech Connect

    Yang, Chao

    2009-07-17

    We present a practical approach to calculate the complex band structure of an electrode for quantum transport calculations. This method is designed for plane wave based Hamiltonian with nonlocal pseudopotentials and the auxiliary periodic boundary condition transport calculation approach. Currently there is no direct method to calculate all the evanescent states for a given energy for systems with nonlocal pseudopotentials. On the other hand, in the auxiliary periodic boundary condition transport calculation, there is no need for all the evanescent states at a given energy. The current method fills this niche. The method has been used to study copper and gold nanowires and bulk electrodes.

  17. Load-bearing capacity of all-ceramic posterior four-unit fixed partial dentures with different zirconia frameworks.

    PubMed

    Kohorst, Philipp; Herzog, Timo J; Borchers, Lothar; Stiesch-Scholz, Meike

    2007-04-01

    The aim of this in vitro study was to compare the load-bearing capacity of posterior four-unit fixed partial dentures (FPDs) produced with two different yttria-stabilized polycrystalline tetragonal zirconia (Y-TZP) ceramics, one being a presintered material, the other a fully sintered, hot isostatically pressed material. Additionally, as a novel approach, the influence of preliminary mechanical damage upon the fracture force of an FPD has been investigated. A total of 20 frameworks each were milled from presintered zirconia and from fully sintered zirconia. Prior to veneering, 10 frameworks of each material were 'damaged' by a defined saw cut similar to an accidental flaw generated during shape cutting. Before fracture testing, all FPDs were subjected to thermal and mechanical cycling. Additionally, scanning electron microscopy was used to investigate fracture surfaces. Statistical analysis showed that FPDs milled from fully sintered zirconia had a significantly higher fracture resistance compared with specimens made from presintered material, whereas preliminary damage did not have a significant effect. After aging, FPDs made from both materials were capable of withstanding occlusal forces reported in the literature. Therefore, both types of Y-TZP may be suitable for posterior four-unit all-ceramic FPDs, although further prolonged aging experiments and prospective clinical trials are required to prove their fitness for clinical use.

  18. Nonlocal axial load-bearing capacity of two neighboring perpendicular single-walled carbon nanotubes accounting for shear deformation

    NASA Astrophysics Data System (ADS)

    Kiani, Keivan

    2015-11-01

    This study is devoted to examine load-bearing capacity of a nanosystem composed of two adjacent perpendicular single-walled carbon nanotubes (SWCNTs) which are embedded in an elastic matrix. Accounting for the nonlocality and the intertube van der Waals forces, the governing equations are established based on the nonlocal Euler-Bernoulli, Timoshenko, and higher-order beam theories. These are sets of coupled integro-ordinary differential equations whose analytical solutions are unavailable. Hence, an efficient meshless methodology is proposed and the discrete governing equations are obtained via Galerkin approach. By solving the resulting set of eigenvalue equations, the axial buckling load of the elastically embedded nanosystem is evaluated. The roles of the radius and slenderness ratio of the constitutive SWCNTs, free distance between two tubes, small-scale parameter, aspect ratio, transverse and rotational stiffness of the surrounding matrix on the axial buckling load of the nanosystem are comprehensively addressed. The obtained results can be regarded as a pivotal step for better understanding the mechanism of elastic buckling of more complex systems such as elastically embedded-orthogonal membranes or even forests of SWCNTs.

  19. Static load bearing exercises of individuals with transfemoral amputation fitted with an osseointegrated implant: reliability of kinetic data.

    PubMed

    Vertriest, Sofie; Coorevits, Pascal; Hagberg, Kerstin; Brånemark, Rickard; Häggström, Eva; Vanderstraeten, Guy; Frossard, Laurent

    2015-05-01

    This study aimed at presenting the intra-tester reliability of the static load bearing exercises (LBEs) performed by individuals with transfemoral amputation (TFA) fitted with an osseointegrated implant to stimulate the bone remodeling process. There is a need for a better understanding of the implementation of these exercises particularly the reliability. The intra-tester reliability is discussed with a particular emphasis on inter-load prescribed, inter-axis and inter-component reliabilities as well as the effect of body weight normalization. Eleven unilateral TFAs fitted with an OPRA implant performed five trials in four loading conditions. The forces and moments on the three axes of the implant were measured directly with an instrumented pylon including a six-channel transducer. Reliability of loading variables was assessed using intraclass correlation coefficients (ICCs) and percentage standard error of measurement values ( %SEMs ). The ICCs of all variables were above 0.9 and the %SEM values ranged between 0 and 87%. This study showed a high between-participants' variance highlighting the lack of loading consistency typical of symptomatic population as well as a high reliability between the loading sessions indicating a plausible correct repetition of the LBE by the participants. However, these outcomes must be understood within the framework of the proposed experimental protocol.

  20. Effect of a self-adhesive coating on the load-bearing capacity of tooth-coloured restorative materials.

    PubMed

    Bagheri, R; Palamara, Jea; Mese, A; Manton, D J

    2017-03-01

    The aim of this study was to compare the flexural strength and Vickers hardness of tooth-coloured restorative materials with and without applying a self-adhesive coating for up to 6 months. Specimens were prepared from three resin composites (RC), two resin-modified glass-ionomer cements (RM-GIC) and two conventional glass-ionomer cements (CGIC). All materials were tested both with and without applying G-Coat Plus (GCP). Specimens were conditioned in 37 °C distilled deionized water for 24 h, and 1, 3 and 6 months. The specimens were strength tested using a four-point bend test jig in a universal testing machine. The broken specimen's halves were used for Vickers hardness testing. Representative specimens were examined under an environmental scanning electron microscope. Data analysis showed that regardless of time and materials, generally the surface coating was associated with a significant increase in the flexural strength of the materials. Applying the GCP decreased the hardness of almost all materials significantly (P < 0.05) and effect of time intervals on hardness was material dependent. The load-bearing capacity of the restorative materials was affected by applying self-adhesive coating and ageing. The CGIC had significantly higher hardness but lower flexural strength than the RM-GIC and RC. © 2016 Australian Dental Association.

  1. High load-bearing multi-material-joints of metal sheets and composites by incremental in-situ forming processes

    NASA Astrophysics Data System (ADS)

    Seidlitz, Holger; Fritzsche, Sebastian; Bambach, Markus; Gerstenberger, Colin

    2016-10-01

    Thermo-mechanically flow-formed joints (FDJ) are an appropriate joining technology to realize high load-bearing multi-material-joints between fiber reinforced thermoplastics and sheet metals, without additional joining components. As in the automotive industry new vehicle and lightweight designs with one-sided accessibility joints are required, the technology which so far requires a two-sided accessibility of the joint, is examined for the ability to be performed with one-sided accessibility. The main part of the paper are therefore experimental studies on the one-sided manufacturing of FDJ-joints without an additional forming tool and their examination with head pull test and tension shear test according to DIN EN ISO 14272 and DIN EN ISO 14273. In this context, a tool and an experimental setup were designed to provide a corresponding joint production of a material combination of continuous glass fiber reinforced polypropylene (Plytron) and an aluminum alloy (EN AW-6082 T6). In the experiment, the novel joints bear maximum forces of 291 N in the head pull test and 708 N in the tension shear test.

  2. Fracture toughness, compressive strength and load-bearing capacity of short glass fibre-reinforced composite resin.

    PubMed

    Garoushi, Sufyan; Vallittu, Pekka K; Lassila, Lippo V

    2011-01-01

    To investigate the reinforcing effect of short E-glass fibre fillers on fracture related mechanical properties of dental composite resin with a semi-interpenetrating polymer network (IPN) polymer matrix. Experimental short fibre composite (FC) resin was prepared by mixing 22.5 wt% of short E-glass fibres, 22.5 wt% of IPN-resin and 55 wt% of silane treated silica fillers using a high speed mixing machine. Test specimens were made bar shaped (3 × 6 × 25 mm3), cylindrical (6 mm length × 3 mm diameter) and cubic (9.5 × 5.5 × 3 mm3) from the experimental FC resin and conventional particulate composite resin (Grandio) as control. The test specimens (n = 8) were either dry stored or water stored (37°C for 30 days) before the mechanical tests. A three-point loading test and compression test were carried out according to ISO 10477 and a static loading test was carried out using a steel ball (Ø 3.0 mm) with a speed of 1.0 mm/min until fracture. Experimental fibre composite had a significantly higher mechanical performance for fracture toughness (14 MNm-1.5), compression strength (129 MPa) and static load-bearing capacity (1584 N) than the control composite (2 MNm-1.5, 112 MPa and 1031 N). The resin with short E-glass fibre fillers and IPN-polymer matrix yielded improved mechanical performance compared to the conventional particulate composite resin.

  3. Influence of cyclic loading on the fracture toughness and load bearing capacities of all-ceramic crowns

    PubMed Central

    Wang, Rao-Rao; Lu, Cheng-Lin; Wang, Gang; Zhang, Dong-Sheng

    2014-01-01

    The purpose of this study was to investigate how cyclic loading influenced the fracture toughness of hot-press lithium disilicate and zirconia core materials and whether there was an increase in the propensity for crown failure. Two types of all-ceramic crowns including the IPS e.max Press system (n=24) and the Lava zirconia system (n=24), were selected. Sectioned specimens were subjected to cyclic loading with the maximum magnitude of 200 N (R=0.1) until two million cycles. The material properties including Young's modulus (E) and hardness (H) and the fracture toughness (KIC) of the core materials were evaluated using indentation methods (n=12 each). The load-bearing capacities of the specimens were examined by means of monotonic load to fracture (n=12 each). It was found that the material properties, including E, H and KIC, of the two types of dental ceramics, were reduced. Statistical analysis indicated that there were no significant influences of fatigue loading on material properties E and H for both types of dental ceramics or KIC for zirconia, while for the IPS e.max Press core, KIC, which was parallel to the direction of the lithium disilicate crystals, was significantly reduced (P=0.001). A conclusion was drawn that zirconia possesses high mechanical reliability and sustainable capacity to resist fatigue loading, while fatigue loading remarkably degraded the anisotropic mechanical behaviour of hot-press lithium disilicate ceramics. PMID:24335786

  4. Excess iron undermined bone load-bearing capacity through tumor necrosis factor-α-dependent osteoclastic activation in mice

    PubMed Central

    LI, JUNPING; HOU, YANLI; ZHANG, SHUPING; JI, HONG; RONG, HAIQIN; QU, GUANGBO; LIU, SIJIN

    2013-01-01

    Iron overload has been associated with bone mass loss. To elucidate the effects of excess iron on bone metabolism, an iron-overloading mouse model was established by administering iron-dextran at 250 mg/kg to female BALB/c mice. After 4 weeks, the mice were sacrificed and the biomechanical properties of the femurs were examined. The results suggested a notable decrease of the maximal bending stress and the modulus of bending elasticity in the femurs obtained from the excess iron-treated mice compared to the control mice. The levels of the serum osteocalcin, C-telopeptide of type I collagen (CTX-1) and tumor necrosis factor-α (TNF-α) were measured in order to investigate the underlying mechanism responsible for the excess iron-induced bone strength reduction. Overall, the results suggested that iron overload resulted in a marked reduction of bone load-bearing capacity through a TNF-triggered osteoclast differentiation and resorption mechanism. PMID:24648899

  5. Load-bearing evaluation of spinal posterior column by measuring surface strain from lumbar pedicles. An in vitro study.

    PubMed

    Sun, Peidong; Zhao, Weidong; Bi, Zhenyu; Wu, Changfu; Ouyang, Jun

    2012-01-01

    An understanding of the load transfer within spinal posterior column of lumbar spine is necessary to determine the influence of mechanical factors on potential mechanisms of the motion-sparing implant such as artificial intervertebral disc and the dynamic spine stabilization systems. In this study, a new method has been developed for evaluating the load bearing of spinal posterior column by the surface strain of spinal pedicle response to the loading of spinal segment. Six cadaveric lumbar spine segments were biomechanically evaluated between levels L1 and L5 in intact condition and the strain gauges were pasted to an inferior surface of L2 pedicles. Multidirectional flexibility testing used the Panjabi testing protocol; pure moments for the intact condition with overall spinal motion and unconstrained intact moments of ±8 Nm were used for flexion-extension and lateral bending testing. High correlation coefficient (0.967-0.998) indicated a good agreement between the load of spinal segment and the surface strain of pedicle in all loading directions. Principal compressive strain could be observed in flexion direction and tensile strain in extension direction, respectively. In conclusion, the new method seems to be effective for evaluating posterior spinal column loads using pedicles' surface strain data collected during biomechanical testing of spine segments.

  6. Three-dimensional vortical structures of transition in plane channel flow

    NASA Technical Reports Server (NTRS)

    Biringen, S.

    1987-01-01

    Three-dimensional visualization of flwo field structures in transitional plane channel flow obtained from a numerical simulation are presented at two Reynolds numbers. It is revealed that at the one-spike stage, independent of Reynolds number, the flow is characterized by a multi-layer vortex system. In the upper layer, total vorticity vector plots indicate a high-shear layer dominated by spanwise vorticity, whereas the middle layer (corresponding approximately to the critical layer) forms a vortex loop (alpha-vortex) consisting of strong streamwise and spanwise vorticity components. At the three-spike stage, the breakdown of the vortical structure proceeds in a manner similar to frontal relaminarization of turbulent spots. This process is accompanied by intense vortex lift-up activity near the wall which seems to originate at the legs of the vortex loop trailing the high-shear layer. Finally, at the five-spike stage, it is shown that high-vorticity regions (vortical structures) develop into horseshow eddies in planes inclined to the main flow direction.

  7. Woven silk fabric-reinforced silk nanofibrous scaffolds for regenerating load-bearing soft tissues.

    PubMed

    Han, F; Liu, S; Liu, X; Pei, Y; Bai, S; Zhao, H; Lu, Q; Ma, F; Kaplan, D L; Zhu, H

    2014-02-01

    Although three-dimensional (3-D) porous regenerated silk scaffolds with outstanding biocompatibility, biodegradability and low inflammatory reactions have promising application in different tissue regeneration, the mechanical properties of regenerated scaffolds, especially suture retention strength, must be further improved to satisfy the requirements of clinical applications. This study presents woven silk fabric-reinforced silk nanofibrous scaffolds aimed at dermal tissue engineering. To improve the mechanical properties, silk scaffolds prepared by lyophilization were reinforced with degummed woven silk fabrics. The ultimate tensile strength, elongation at break and suture retention strength of the scaffolds were significantly improved, providing suitable mechanical properties strong enough for clinical applications. The stiffness and degradation behaviors were then further regulated by different after-treatment processes, making the scaffolds more suitable for dermal tissue regeneration. The in vitro cell culture results indicated that these scaffolds maintained their excellent biocompatibility after being reinforced with woven silk fabrics. Without sacrifice of porous structure and biocompatibility, the fabric-reinforced scaffolds with better mechanical properties could facilitate future clinical applications of silk as matrices in skin repair.

  8. Electronic and crystal structure changes induced by in-plane oxygen vacancies in multiferroic YMnO3

    DOE PAGES

    Cheng, Shaobo; Meng, Qingping; Li, Mengli; ...

    2016-02-08

    Here, the widely spread oxygen vacancies (VO) in multiferroic materials can strongly affect their physical properties. However, their exact influence has rarely been identified in hexagonal manganites. Here, with the combined use of transmission electron microscopy (TEM) and first-principles calculations, we have systematically studied the electronic and crystal structure modifications induced by VO located at the same Mn atomic plane (in-plane VO). Our TEM experiments reveal that the easily formed in-plane VO not only influence the electronic structure of YMnO3 but alter the in-plane Wyckoff positions of Mn ions, which may subsequently affect the intraplane and interplane exchange interaction ofmore » Mn ions. The ferroelectricity is also impaired due to the introduction of VO. Further calculations confirm these electronic and structural changes and modifications. Our results indicate that the electronic and crystal structure of YMnO3 can be manipulated by the creation of VO.« less

  9. Design, characterization and testing of Ti-based multicomponent coatings for load-bearing medical applications.

    PubMed

    Shtansky, D V; Gloushankova, N A; Sheveiko, A N; Kharitonova, M A; Moizhess, T G; Levashov, E A; Rossi, F

    2005-06-01

    A comparative investigation of multicomponent thin films based on the systems Ti-Ca-C-O-(N), Ti-Zr-C-O-(N), Ti-Si-Zr-O-(N) and Ti-Nb-C-(N) is presented. TiC(0.5) + 10%CaO, TiC0.5 + 20%CaO, TiC0.5 + 10%ZrO2, TiC0.5 + 20%ZrO2, Ti5Si3 + 10%ZrO2, TiC0.5 + 10%Nb2C and TiC0.5 + 30%Nb2C composite targets were manufactured by means of self-propagating high-temperature synthesis, followed by DC magnetron sputtering in an atmosphere of argon or in a gaseous mixture of argon and nitrogen. The films were characterized in terms of their structure, chemical composition, surface topography, hardness, elastic modulus, elastic recovery, surface charge, friction coefficient, and wear rate. The biocompatibility of the films was evaluated by both in vitro and in vivo experiments. In vitro studies involved the investigation of the proliferation of Rat-1 fibroblasts and IAR-2 epithelial cells on the tested films, morphometric analysis and actin cytoskeleton staining of the cells cultivated on the films. In vivo studies were fulfilled by subcutaneous implantation of Teflon plates coated with the tested films in mice and analysis of the population of cells on the surfaces. The films deposited under optimal conditions showed high hardness in the range of 30-37 GPa, significant reduced Young's modulus, low friction coefficient down to 0.1-0.2 and low wear rate in comparison with conventional magnetron-sputtered TiC and TiN films. The surface of all films was negatively charged with an outstanding shift between the Ar and Ar + N2 Zeta potential curves that reaches 5 mV at the highest pH values. We did not detect statistically significant differences in the attachment, spreading and cell shape of cultured IAR-2 and Rat-1 cells on the Ti-Ca-C-O-(N), Ti-Zr-C-O-(N) (TiC0.5 + 10%ZrO2 target), Ti-Si-Zr-O-(N) films and the uncoated substrata. The adhesion and proliferation of cultured cells in vitro was perfect at all investigated films. Assessment of the population of cells covering on the Teflon

  10. Simulated ΛCDM analogues of the thin plane of satellites around the Andromeda galaxy are not kinematically coherent structures

    NASA Astrophysics Data System (ADS)

    Buck, Tobias; Dutton, Aaron A.; Macciò, Andrea V.

    2016-08-01

    A large fraction of the dwarf satellites orbiting the Andromeda galaxy are surprisingly aligned in a thin, extended and apparently kinematically coherent planar structure. Such a structure is not easily found in simulations based on the cold dark matter model (ΛCDM). Using 21 high-resolution cosmological simulations, we analyse the kinematics of planes of satellites similar to the one around Andromeda. We find good agreement when co-rotation is characterized by the line-of-sight velocity. At the same time, when co-rotation is inferred by the angular momenta of the satellites, the planes are in agreement with the plane around our Galaxy. We find such planes to be common in our high-concentration haloes. The number of co-rotating satellites obtained from the sign of the line-of-sight velocity shows large variations depending on the viewing angle and is consistent with that obtained from a sample with random velocities. We find that the clustering of angular momentum vectors of the satellites in the plane is a better measure of the kinematic coherence. Thus we conclude that the line-of-sight velocity is not well suited as a proxy for the kinematical coherence of the plane. Analysis of the kinematics of our planes shows a fraction of ˜30 per cent chance-aligned satellites. Tracking the satellites in the plane back in time reveals that these planes are a transient feature and not kinematically coherent as would appear at first sight. Thus we expect some of the satellites in the plane around Andromeda to have high velocities perpendicular to the plane.

  11. Vortex structure of a plane impinging jet with spanwise periodic forcing

    NASA Astrophysics Data System (ADS)

    Sakakibara, Jun; Anzai, Tomokuni

    1999-11-01

    Vortex structure of a plane impinging jet of water with spanwise periodic forcing has been experimentally measured using PIV. A plane nozzle, having a width of ( B=30 ) mm and aspect ratio of 10, issued water jet vertically and impinged on a plate set at a distance ( H=5.5B ) from the nozzle exit. Sixty rectangular slots (1mm (×) 4mm cross-section) aligned in spanwise direction are installed both side of the nozzle exit with 5mm interval. Each slots are connected via vinyl tubes to four of speaker boxes to add suction/blowing perturbations to the initial shear layer of the jet. The perturbation added by successive 3 slots, 15mm in spanwise length, have a phase lag (α) behind the perturbation by next 3 slots, and repeated in whole row of the slots. This configuration could make spanwise periodic perturbations, which have a wave length (λ=30)mm, to excite the secondary instability of the shear layer. As increasing phase lag (α) the intensity of the vorticity of the streamwise counter-rotating vortices on the stagnation plate was increased, and maximum intensity was achieved at (α=π). Time and spatial evolution of the vortex structures will be shown in the presentation.

  12. Dense ionic fluids confined in planar capacitors: in- and out-of-plane structure from classical density functional theory

    NASA Astrophysics Data System (ADS)

    Härtel, Andreas; Samin, Sela; van Roij, René

    2016-06-01

    The ongoing scientific interest in the properties and structure of electric double layers (EDLs) stems from their pivotal role in (super)capacitive energy storage, energy harvesting, and water treatment technologies. Classical density functional theory (DFT) is a promising framework for the study of the in- and out-of-plane structural properties of double layers. Supported by molecular dynamics simulations, we demonstrate the adequate performance of DFT for analyzing charge layering in the EDL perpendicular to the electrodes. We discuss charge storage and capacitance of the EDL and the impact of screening due to dielectric solvents. We further calculate, for the first time, the in-plane structure of the EDL within the framework of DFT. While our out-of-plane results already hint at structural in-plane transitions inside the EDL, which have been observed recently in simulations and experiments, our DFT approach performs poorly in predicting in-plane structure in comparison to simulations. However, our findings isolate fundamental issues in the theoretical description of the EDL within the primitive model and point towards limitations in the performance of DFT in describing the out-of-plane structure of the EDL at high concentrations and potentials.

  13. Dense ionic fluids confined in planar capacitors: in- and out-of-plane structure from classical density functional theory.

    PubMed

    Härtel, Andreas; Samin, Sela; van Roij, René

    2016-06-22

    The ongoing scientific interest in the properties and structure of electric double layers (EDLs) stems from their pivotal role in (super)capacitive energy storage, energy harvesting, and water treatment technologies. Classical density functional theory (DFT) is a promising framework for the study of the in- and out-of-plane structural properties of double layers. Supported by molecular dynamics simulations, we demonstrate the adequate performance of DFT for analyzing charge layering in the EDL perpendicular to the electrodes. We discuss charge storage and capacitance of the EDL and the impact of screening due to dielectric solvents. We further calculate, for the first time, the in-plane structure of the EDL within the framework of DFT. While our out-of-plane results already hint at structural in-plane transitions inside the EDL, which have been observed recently in simulations and experiments, our DFT approach performs poorly in predicting in-plane structure in comparison to simulations. However, our findings isolate fundamental issues in the theoretical description of the EDL within the primitive model and point towards limitations in the performance of DFT in describing the out-of-plane structure of the EDL at high concentrations and potentials.

  14. Heat resistant soy adhesives for structural wood products

    Treesearch

    Christopher G. Hunt; Charles Frihart; Jane O' Dell

    2009-01-01

    Because load-bearing bonded wood assemblies must support the structure during a fire, the limited softening and depolymerization of biobased polymers at elevated temperatures should be an advantage of biobased adhesives compared to fossil fuel-based adhesives. Because load-bearing bonded wood assemblies must support the structure during a fire, the limited softening...

  15. Strained-layer superlattice focal plane array having a planar structure

    DOEpatents

    Kim, Jin K [Albuquerque, NM; Carroll, Malcolm S [Albuquerque, NM; Gin, Aaron [Albuquerque, NM; Marsh, Phillip F [Lowell, MA; Young, Erik W [Albuquerque, NM; Cich, Michael J [Albuquerque, NM

    2010-07-13

    An infrared focal plane array (FPA) is disclosed which utilizes a strained-layer superlattice (SLS) formed of alternating layers of InAs and In.sub.xGa.sub.1-xSb with 0.ltoreq.x.ltoreq.0.5 epitaxially grown on a GaSb substrate. The FPA avoids the use of a mesa structure to isolate each photodetector element and instead uses impurity-doped regions formed in or about each photodetector for electrical isolation. This results in a substantially-planar structure in which the SLS is unbroken across the entire width of a 2-D array of the photodetector elements which are capped with an epitaxially-grown passivation layer to reduce or eliminate surface recombination. The FPA has applications for use in the wavelength range of 3-25 .mu.m.

  16. Dynamics of the spatial structure of pulsed discharges in dense gases in point cathode−plane anode gaps and their erosion effect on the plane electrode surface

    SciTech Connect

    Baksht, E. Kh.; Blinova, O. M.; Erofeev, M. V.; Karelin, V. I.; Ripenko, V. S.; Tarasenko, V. F.; Trenkin, A. A.; Shibitov, Yu. M.; Shulepov, M. A.

    2016-09-15

    The dynamics of the spatial structure of the plasma of pulsed discharges in air and nitrogen in a nonuniform electric field and their erosion effect on the plane anode surface were studied experimentally. It is established that, at a nanosecond front of the voltage pulse, a diffuse discharge forms in the point cathode–plane anode gap due to the ionization wave propagating from the cathode. As the gap length decreases, the diffuse discharge transforms into a spark. A bright spot on the anode appears during the diffuse discharge, while the spark channel forms in the later discharge stage. The microstructure of autographs of anode spots and spark channels in discharges with durations of several nanoseconds is revealed. The autographs consist of up to 100 and more microcraters 5–100 μm in diameter. It is shown that, due to the short duration of the voltage pulse, a diffuse discharge can be implemented, several pulses of which do not produce appreciable erosion on the plane anode or the soot coating deposited on it.

  17. Bioresorbable β-TCP-FeAg nanocomposites for load bearing bone implants: High pressure processing, properties and cell compatibility.

    PubMed

    Swain, S K; Gotman, I; Unger, R; Gutmanas, E Y

    2017-09-01

    In this paper, the processing and properties of iron-toughened bioresorbable β-tricalcium phosphate (β-TCP) nanocomposites are reported. β-TCP is chemically similar to bone mineral and thus a good candidate material for bioresorbable bone healing devices; however intrinsic brittleness and low bending strength make it unsuitable for use in load-bearing sites. Near fully dense β-TCP-matrix nanocomposites containing 30vol% Fe, with and without addition of silver, were produced employing high energy attrition milling of powders followed by high pressure consolidation/cold sintering at 2.5GPa. In order to increase pure iron's corrosion rate, 10 to 30vol% silver were added to the metal phase. The degradation behavior of the developed composite materials was studied by immersion in Ringer's and saline solutions for up to 1month. The mechanical properties, before and after immersion, were tested in compression and bending. All the compositions exhibited high mechanical strength, the strength in bending being several fold higher than that of polymer toughened β-TCP-30PLA nanocomposites prepared by the similar procedure of attrition milling and cold sintering, and of pure high-temperature sintered β-TCP. Partial substitution of iron with silver led to an increase in both strength and ductility. Furthermore, the galvanic action of silver particles dispersed in the iron phase significantly accelerated in vitro degradation of β-TCP-30(Fe-Ag) nanocomposites. After 1month immersion, the composites retained about 50% of their initial bending strength. In cell culture experiments, β-TCP-27Fe3Ag nanocomposites exhibited no signs of cytotoxicity towards human osteoblasts suggesting that they can be used as an implant material. Copyright © 2017 Elsevier B.V. All rights reserved.

  18. Preparation of three-dimensional braided carbon fiber-reinforced PEEK composites for potential load-bearing bone fixations. Part I. Mechanical properties and cytocompatibility.

    PubMed

    Luo, Honglin; Xiong, Guangyao; Yang, Zhiwei; Raman, Sudha R; Li, Qiuping; Ma, Chunying; Li, Deying; Wang, Zheren; Wan, Yizao

    2014-01-01

    In this study, we focused on fabrication and characterization of three-dimensional carbon fiber-reinforced polyetheretherketone (C3-D/PEEK) composites for orthopedic applications. We found that pre-heating of 3-D fabrics before hot-pressing could eliminate pores in the composites prepared by 3-D co-braiding and hot-pressing techniques. The manufacturing process and the processing variables were studied and optimum parameters were obtained. Moreover, the carbon fibers were surface treated by the anodic oxidization and its effect on mechanical properties of the composites was determined. Preliminary cell studies with mouse osteoblast cells were also performed to examine the cytocompatibility of the composites. Feasibility of the C3-D/PEEK composites as load-bearing bone fixation materials was evaluated. Results suggest that the C3-D/PEEK composites show good promising as load-bearing bone fixations.

  19. Structure and mechanism of turbulence under dynamical restriction in plane Poiseuille flow

    NASA Astrophysics Data System (ADS)

    Constantinou, Navid; Farrell, Brian; Ioannou, Petros; Jimenez, Javier; Lozano-Duran, Adrian; Nikolaidis, Marios-Andreas

    2016-11-01

    The perspective of Statistical State Dynamics (SSD) is used to investigate plane Poiseuille turbulence at moderately high Reynolds numbers (Reτ 940). Simulations of a quasi-linear restricted nonlinear dynamics (RNL), which is an approximation to the full SSD, provide insight into the mechanism and structure of turbulent flow. RNL dynamics spontaneously limits the support of its turbulence to a small set of streamwise Fourier components giving rise to a natural minimal representation of its turbulence dynamics. Although greatly simplified, this RNL turbulence exhibits natural-looking structures and turbulent statistics. RNL turbulence at the Reynolds numbers studied is dominated by the roll/streak structure in the buffer layer and similar very-large-scale structure (VLSM) in the outer layer. Diagnostics of the structure, spectrum and energetics of RNL and DNS turbulence are used to demonstrate that the roll/streak dynamics supporting the turbulence in the buffer and logarithmic layer is essentially similar in RNL and DNS. This mechanism, which has analytical expression in the SSD, comprises a cooperative interaction between the coherent streamwise mean flow and the incoherent turbulent perturbations.

  20. Optical Fourier transform based in-plane vibration characterization for MEMS comb structure.

    PubMed

    Gao, Yongfeng; Cao, Liangcai; You, Zheng; Zhao, Jiahao; Zhang, Zichen; Yang, Jianzhong

    2013-02-25

    On-line and on-wafer characterizations of mechanical properties of Micro-Electro-Mechanical-System (MEMS) with efficiency are very important to the mass production of MEMS foundry in the near future. However, challenges still remain. In this paper, we present an in-plane vibration characterizing method for MEMS comb using optical Fourier transform (OFT). In the experiment, the intensity distribution at the focal plane was captured to characterize the displacement of the vibrator in the MEMS comb structure. A typical MEMS comb was tested to verify the principle. The shape and the movement of MEMS comb was imitated and tested to calibrate the measurement by using a spatial light modulator (SLM). The relative standard deviations (RSD) of the measured displacements were better than 5%, where the RSD is defined as the ratio of the standard deviation to the mean. It is convinced that the presented method is feasible for on-line and on-wafer characterizations for MEMS with great convenience, high efficiency and low cost.

  1. Principles of Z-plane technology and on-sensor processing for photoelectric structures with memory

    NASA Astrophysics Data System (ADS)

    Vinogradov, Sergey L.; Shubin, Vitaly E.

    1996-06-01

    Novel integrated intelligent videosensor and its possible application using on-FPA real-time parallel processing are discussed. This solid-state single-chip sensor is photoelectric structure with memory (PESM), which consists of semiconductor, insulator and metal layers, wherein optical information are detected, recorded and stored in the form of 2D charge and potential patterns, and then processed due to internal interaction of these patterns in a normal direction to the input plane. Thus, such Z-plane technology allows the PESM to operate as multifunctional device utilizing massively parallel processing with high effective operational speed (up to 10(superscript 14) operation/bit/s) without additional electronic and computing units. Except reading, writing and storing, PESM performs such parallel image processing as summation, subtraction, contouring, convolution and correlation, which may be effectively applied to numerous tasks of diverse optoelectronic systems. Two image operations--subtraction and correlation, which seems to us of high importance, are demonstrated as an example of the PESM performance. It allows one to solve in a real time the main problems concerned with background subtraction, moving object selection, target tracking and pointing, recognition of extended objects and so on. As we suppose, the possible applications of the PESM as an intellectual `supersensor', which combines a high-quality imager and a high-capacity multifunctional processor, would provide substantially lower prime cost of the designed systems in comparison with the now-existing ones and may be widely extended.

  2. Coherent structure interactions in a two-stream plane turbulent mixing layer with impulsive acoustic excitation

    NASA Astrophysics Data System (ADS)

    Latigo, Ben O.

    1989-10-01

    Periodic plane acoustic waves consisting of four discrete pulses are used to trigger the Kelvin-Helmholtz (KH) instability at the origin of an initially laminar plane mixing layer. The resulting coherent large-scale structures (CLSS) which grow and interact with their neighbors are followed downstream with hot-wire probes traversed across the mixing layer to a Reynolds number Re=1.5×106. The Reynolds number here is based on downstream distance x and the velocity difference (U1-U2). The continuous hot-wire time record is conditionally sampled with respect to the tone bursts and the samples are phase averaged to reveal the CLSS footprints. Optimum phase averages are obtained using an iterative correlation technique that corrects for phase jitters due to turbulence. An enhanced study of the CLSS is therefore made possible. The ensembles reveal a vivid picture of vortex pairing between the initial eddies as well as the significant role played by the CLSS in momentum transport; hence turbulence mixing.

  3. Coherent structure interactions in a two-stream plane turbulent mixing layer with impulsive acoustic excitation

    NASA Astrophysics Data System (ADS)

    Latigo, Ben O.

    1989-10-01

    Periodic plane acoustic waves consisting of four discrete pulses are used to trigger the Kelvin-Helmholtz (KH) instability at the origin of an initially laminar plane mixing layer. The resulting coherent large-scale structures (CLSS), which grow and interact with their neighbors, are followed downstream with hot-wire probes traversed across the mixing layer to a Reynolds number Re = 1.5 x 10 to the 6th. The Reynolds number here is based on downstream distance x and the velocity difference (U1-U2). The continuous hot-wire time record is conditionally sampled with respect to the tone bursts and the samples are phase averaged to reveal the CLSS footprints. Optimum phase averages are obtained using an iterative correlation technique that corrects for phase jitters due to turbulence. An enhanced study of the CLSS is therefore made possible. The ensembles reveal a vivid picture of vortex pairing between the initial eddies as well as the significant role played by the CLSS in momentum transport; hence turbulence mixing.

  4. Turbulent rotating plane Couette flow: Reynolds and rotation number dependency of flow structure and momentum transport

    NASA Astrophysics Data System (ADS)

    Kawata, Takuya; Alfredsson, P. Henrik

    2016-07-01

    Plane Couette flow under spanwise, anticyclonic system rotation [rotating plane Couette flow (RPCF)] is studied experimentally using stereoscopic particle image velocimetry for different Reynolds and rotation numbers in the fully turbulent regime. Similar to the laminar regime, the turbulent flow in RPCF is characterized by roll cells, however both instantaneous snapshots of the velocity field and space correlations show that the roll cell structure varies with the rotation number. All three velocity components are measured and both the mean flow and all four nonzero Reynolds stresses are obtained across the central parts of the channel. This also allows us to determine the wall shear stress from the viscous stress and the Reynolds stress in the center of the channel, and for low rotation rates the wall shear stress increases with increasing rotation rate as expected. The results show that zero absolute vorticity is established in the central parts of the channel of turbulent RPCF for high enough rotation rates, but also that the mean velocity profile for certain parameter ranges shows an S shape giving rise to a negative velocity gradient in the center of the channel. We find that from an analysis of the Reynolds stress transport equation using the present data there is a transport of the Reynolds shear stress towards the center of the channel, which may then result in a negative mean velocity gradient there.

  5. Analysis of Out-of-Plane Measurments of the Fifth Structure Function of the Deuteron

    NASA Astrophysics Data System (ADS)

    Jordan, Matthew; Gilfoyle, Gerard

    2008-10-01

    We have measured the D(e,e^'p)n reaction and the asymmetry ALT^' associated with the fifth structure function in quasi-elastic electron scattering from deuterium at a beam energy of 2.56 GeV and over the range Q^2 = 0.1-2.0 GeV^2 with the CLAS detector at Jefferson Lab. The data were collected using both magnet polarities to explore different Q^2 regions. We extracted ALT^' as a function of missing momentum (pm) using spectra weighted by φpq where φpq is the angle between the electron scattering plane and the plane defined by the ejected proton and 3-momentum transfer. We compared the measured ALT^' with a calculation by Jeschonnek and Van Orden by averaging over the Q^2 distribution of the CLAS data. The theoretical curves largely agree with the 2.56-GeV data at Q^2=0.6-2.0 GeV^2, but diverge from the data for low Q^2 (0.1-1.0 GeV^2) and high pm (greater than 0.4 GeV). To understand the systematic uncertainties on ALT^' we varied the positions of the kinematic cuts used to define quasielastic scattering and the final state proton. The results showed systematic uncertainties of about 1% or less in regions of high statistics.

  6. Systematic Uncertainties of Out-of-Plane Measurements of the Fifth Structure Function of the Deuteron

    NASA Astrophysics Data System (ADS)

    Jordan, Matthew; Gilfoyle, Gerard

    2009-10-01

    We have measured the 2H( e ,e^'p)n reaction and the asymmetry ALT^' associated with the fifth structure function in quasi-elastic electron scattering from deuterium at a beam energy of 2.56 GeV and over the range Q^2 = 0.2-2.0 GeV^2 with the CLAS detector at Jefferson Lab. The data were collected using both magnet polarities to explore different Q^2 regions. We extracted ALT^' as a function of missing momentum (pm) using spectra weighted by φpq where φpq is the angle between the electron scattering plane and the plane defined by the ejected proton and 3-momentum transfer. To understand the systematic uncertainties on ALT' we varied the positions of the cuts placed on the data used to define the position of the deuterium target, the active region of the electromagnetic calorimeters (EC), the sampling fraction of the EC, and the production of photoelectrons in the Cherenkov counters. These results show a systematic uncertainty of less than 1% in regions of high statistics and much lower than the statistical uncertainty across the full pm range. We combined these results with our previous study of systematic uncertainties on our identification of the proton and neutron. Work supported by US Department of Energy contract DE-FG02-96ER40980.

  7. Investigation of flaw geometry and loading effects on plane strain fracture in metallic structures

    NASA Technical Reports Server (NTRS)

    Hall, L. R.; Finger, R. W.

    1971-01-01

    The effects on fracture and flaw growth of weld-induced residual stresses, combined bending and tension stresses, and stress fields adjacent to circular holes in 2219-T87 aluminum and 5AI-2.5Sn(ELI) titanium alloys were evaluated. Static fracture tests were conducted in liquid nitrogen; fatigue tests were performed in room air, liquid nitrogen, and liquid hydrogen. Evaluation of results was based on linear elastic fracture mechanics concepts and was directed to improving existing methods of estimating minimum fracture strength and fatigue lives for pressurized structure in spacecraft and booster systems. Effects of specimen design in plane-strain fracture toughness testing were investigated. Four different specimen types were tested in room air, liquid nitrogen and liquid hydrogen environments using the aluminum and titanium alloys. Interferometry and holograph were used to measure crack-opening displacements in surface-flawed plexiglass test specimens. Comparisons were made between stress intensities calculated using displacement measurements, and approximate analytical solutions.

  8. A substrate-free optical readout focal plane array with a heat sink structure

    NASA Astrophysics Data System (ADS)

    Rmwen, Liu; Yanmei, Kong; Binbin, Jiao; Zhigang, Li; Haiping, Shang; Dike, Lu; Chaoqun, Gao; Dapeng, Chen; Qingchuan, Zhang

    2013-02-01

    A substrate-free optical readout focal plane array (FPA) operating in 8-12 μm with a heat sink structure (HSS) was fabricated and its performance was tested. The temperature distribution of the FPA with an HSS investigated by using a commercial FLIR IR camera shows excellent uniformity. The thermal cross-talk effect existing in traditional substrate-free FPAs was eliminated effectively. The heat sink is fabricated successfully by electroplating copper, which provides high thermal capacity and high thermal conductivity, on the frame of substrate-free FPA. The FPA was tested in the optical-readout system, the results show that the response and NETD are 13.6 grey/K (F / # = 0.8) and 588 mK, respectively.

  9. Use of 3X3 integrated optic polarizer/splitters for a smart aerospace plane structure

    NASA Astrophysics Data System (ADS)

    Seshamani, Ramani; Alex, T. K.

    1991-10-01

    A fiber-optic/integrated optic optoelectronic neural computer approach to the design of an 'intelligent' aerospace structure is described, and the methodology of the approach is defined. A source consisting of a strained-layer QW laser emitting 100 micro-W at 978 nm and an Er-doped single-mode polarization preserving fiber laser with a gain of 3.9 dB/mW is assumed. The SNR for the aerospace plane is calculated with 49 sensing arms. A 441-path splitter is required; this is designed using an eight-stage multipath coupler based on a 3X3 polarizer/splitter as the basic repeating element. A surface-mounted implementation is suggested, which includes a 448-path switch, an integrated-optic coupler, a detector, an ADC, and a processor.

  10. Load-bearing capacity of screw-retained CAD/CAM-produced titanium implant frameworks (I-Bridge®2) before and after cyclic mechanical loading

    PubMed Central

    DITTMER, Marc Philipp; NENSA, Moritz; STIESCH, Meike; KOHORST, Philipp

    2013-01-01

    Implant-supported screw-retained fixed dental prostheses (FDPs) produced by CAD/ CAM have been introduced in recent years for the rehabilitation of partial or total endentulous jaws. However, there is a lack of data about the long-term mechanical characteristics. Objective The aim of this study was to investigate the failure mode and the influence of extended cyclic mechanical loading on the load-bearing capacity of these frameworks. Material and Methods Ten five-unit FDP frameworks simulating a free-end situation in the mandibular jaw were manufactured according to the I-Bridge®2-concept (I-Bridge®2, Biomain AB, Helsingborg, Sweden) and each was screw-retained on three differently angulated Astra Tech implants (30º buccal angulation/0º angulation/30º lingual angulation). One half of the specimens was tested for static load-bearing capacity without any further treatment (control), whereas the other half underwent five million cycles of mechanical loading with 100 N as the upper load limit (test). All specimens were loaded until failure in a universal testing machine with an occlusal force applied at the pontics. Load-displacement curves were recorded and the failure mode was macro- and microscopically analyzed. The statistical analysis was performed using a t-test (p=0.05). Results All the specimens survived cyclic mechanical loading and no obvious failure could be observed. Due to the cyclic mechanical loading, the load-bearing capacity decreased from 8,496 N±196 N (control) to 7,592 N±901 N (test). The cyclic mechanical loading did not significantly influence the load-bearing capacity (p=0.060). The failure mode was almost identical in all specimens: large deformations of the framework at the implant connection area were obvious. Conclusion The load-bearing capacity of the I-Bridge®2 frameworks is much higher than the clinically relevant occlusal forces, even with considerably angulated implants. However, the performance under functional loading in vivo

  11. The generalized scattering coefficient method for plane wave scattering in layered structures

    NASA Astrophysics Data System (ADS)

    Liu, Yu; Li, Chao; Wang, Huai-Yu; Zhou, Yun-Song

    2017-02-01

    The generalized scattering coefficient (GSC) method is pedagogically derived and employed to study the scattering of plane waves in homogeneous and inhomogeneous layered structures. The numerical stabilities and accuracies of this method and other commonly used numerical methods are discussed and compared. For homogeneous layered structures, concise scattering formulas with clear physical interpretations and strong numerical stability are obtained by introducing the GSCs. For inhomogeneous layered structures, three numerical methods are employed: the staircase approximation method, the power series expansion method, and the differential equation based on the GSCs. We investigate the accuracies and convergence behaviors of these methods by comparing their predictions to the exact results. The conclusions are as follows. The staircase approximation method has a slow convergence in spite of its simple and intuitive implementation, and a fine stratification within the inhomogeneous layer is required for obtaining accurate results. The expansion method results are sensitive to the expansion order, and the treatment becomes very complicated for relatively complex configurations, which restricts its applicability. By contrast, the GSC-based differential equation possesses a simple implementation while providing fast and accurate results.

  12. Computational studies of the structure of monolayers of chlorine physisorbed on the basal plane of graphite

    NASA Astrophysics Data System (ADS)

    Hammonds, Kenton D.; McDonald, Ian R.; Tildesley, Dominic J.

    Results are reported of energy minimizations and molecular-dynamics calculations for chlorine physisorbed on the basal plane of graphite. The dispersion-repulsion component of the intermolecular potential is modelled by an anisotropic site-site potential and the permanent electrostatic potential is represented by distributed multipoles at the atomic nuclei. The molecule-surface interaction includes the anisotropic polarizability of the graphite, image-multipole interactions and substrate mediation of the dispersion interaction. The energy minimizations show that the adsorbed molecules are likely to favour a two-sublattice, herringbone structure; a four-sublattice pinwheel arrangement is also a possibility if image interactions play a sufficiently important role. Difficulties in reproducing the experimental X-ray scattering pattern are discussed. The molecular-dynamics calculations suggest that the low-symmetry structure postulated by Klee et al., (1986, Surf. Sci., 171, 103) is unstable, and melting of the simulated monolayers occurs at temperatures at least 100K below the claimed experimental value. There is a clear need for further thermodynamic and structural studies of this system.

  13. Inertial effects on thin-film wave structures with imposed surface shear on an inclined plane

    NASA Astrophysics Data System (ADS)

    Sivapuratharasu, M.; Hibberd, S.; Hubbard, M. E.; Power, H.

    2016-06-01

    This study provides an extended approach to the mathematical simulation of thin-film flow on a flat inclined plane relevant to flows subject to high surface shear. Motivated by modelling thin-film structures within an industrial context, wave structures are investigated for flows with moderate inertial effects and small film depth aspect ratio ε. Approximations are made assuming a Reynolds number, Re ∼ O(ε-1) and depth-averaging used to simplify the governing Navier-Stokes equations. A parallel Stokes flow is expected in the absence of any wave disturbance and a generalisation for the flow is based on a local quadratic profile. This approach provides a more general system which includes inertial effects and is solved numerically. Flow structures are compared with studies for Stokes flow in the limit of negligible inertial effects. Both two-tier and three-tier wave disturbances are used to study film profile evolution. A parametric study is provided for wave disturbances with increasing film Reynolds number. An evaluation of standing wave and transient film profiles is undertaken and identifies new profiles not previously predicted when inertial effects are neglected.

  14. Structural Affects on the Slamming Pressures of High-Speed Planing Craft

    NASA Astrophysics Data System (ADS)

    Ikeda, Christine; Taravella, Brandon; Judge, Carolyn

    2015-11-01

    High-speed planing craft are subjected to repeated slamming events in waves that can be very extreme depending on the wave topography, impact angle of the ship, forward speed of the ship, encounter angle, and height out of the water. The current work examines this fluid-structure interaction problem through the use of wedge drop experiments and a CFD code. In the first set of experiments, a rigid 20-degree deadrise angle wedge was dropped from a range of heights (0 <= H <= 0 . 6 m) and while pressures and accelerations of the slam even were measured. The second set of experiments involved a flexible-bottom 15-degree deadrise angle wedge that was dropped from from the same range of heights. In these second experiments, the pressures, accelerations, and strain field were measured. Both experiments are compared with a non-linear boundary value flat cylinder theory code in order to compare the pressure loading. The code assumes a rigid structure, therefore, the results between the code and the first experiment are in good agreement. The second experiment shows pressure magnitudes that are lower than the predictions due to the energy required to deform the structure. Funding from University of New Orleans Office of Research and Sponsored Programs and the Office of Naval Research.

  15. Dynamics of a passive micro-vibration isolator based on a pretensioned plane cable net structure and fluid damper

    NASA Astrophysics Data System (ADS)

    Chen, Yanhao; Lu, Qi; Jing, Bo; Zhang, Zhiyi

    2016-09-01

    This paper addresses dynamic modelling and experiments on a passive vibration isolator for application in the space environment. The isolator is composed of a pretensioned plane cable net structure and a fluid damper in parallel. Firstly, the frequency response function (FRF) of a single cable is analysed according to the string theory, and the FRF synthesis method is adopted to establish a dynamic model of the plane cable net structure. Secondly, the equivalent damping coefficient of the fluid damper is analysed. Thirdly, experiments are carried out to compare the plane cable net structure, the fluid damper and the vibration isolator formed by the net and the damper, respectively. It is shown that the plane cable net structure can achieve substantial vibration attenuation but has a great amplification at its resonance frequency due to the light damping of cables. The damping effect of fluid damper is acceptable without taking the poor carrying capacity into consideration. Compared to the plane cable net structure and the fluid damper, the isolator has an acceptable resonance amplification as well as vibration attenuation.

  16. Adhesive strength of bone-implant interfaces and in-vivo degradation of PHB composites for load-bearing applications.

    PubMed

    Meischel, M; Eichler, J; Martinelli, E; Karr, U; Weigel, J; Schmöller, G; Tschegg, E K; Fischerauer, S; Weinberg, A M; Stanzl-Tschegg, S E

    2016-01-01

    Aim of this study was to evaluate the response of bone to novel biodegradable polymeric composite implants in the femora of growing rats. Longitudinal observation of bone reaction at the implant site (BV/TV) as well as resorption of the implanted pins were monitored using in vivo micro-focus computed tomography (µCT). After 12, 24 and 36 weeks femora containing the implants were explanted, scanned with high resolution ex vivo µCT, and the surface roughness of the implants was measured to conclude on the ingrowth capability for bone tissue. Scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDX) were used to observe changes on the surface of Polyhydroxybutyrate (PHB) during degradation and cell ingrowth. Four different composites with zirconium dioxide (ZrO2) and Herafill(®) were compared. After 36 weeks in vivo, none of the implants did show significant degradation. The PHB composite with ZrO2 and a high percentage (30%) of Herafill® as well as the Mg-alloy WZ21 showed the highest values of bone accumulation (increased BV/TV) around the implant. The lowest value was measured in PHB with 3% ZrO2 containing no Herafill®. Roughness measurements as well as EDX and SEM imaging could not reveal any changes on the PHB composites׳ surfaces. Biomechanical parameters, such as the adhesion strength between bone and implant were determined by measuring the shear strength as well as push-out energy of the bone-implant interface. The results showed that improvement of these mechanical properties of the studied PHBs P3Z, P3Z10H and P3Z30H is necessary in order to obtain appropriate load-bearing material. The moduli of elasticity, tensile strength and strain properties of the PHB composites are close to that of bone and thus promising. Compared to clinically used PLGA, PGA and PLA materials, their additional benefit is an unchanged local pH value during degradation, which makes them well tolerated by cells and immune system. They might be used

  17. Anatomical sector analysis of load-bearing tibial bone structure during 90-day bed rest and 1-year recovery.

    PubMed

    Cervinka, Tomas; Rittweger, Jörn; Hyttinen, Jari; Felsenberg, Dieter; Sievänen, Harri

    2011-07-01

    The aim of this study was to investigate whether the bone response to long bed rest-related immobility and during subsequent recovery differed at anatomically different sectors of tibial epiphysis and diaphysis. For this study, peripheral quantitative tomographic (pQCT) scans obtained from a previous 90-day 'Long Term Bed Rest' intervention were preprocessed with a new method based on statistical approach and re-analysed sector-wise. The pQCT was performed on 25 young healthy males twice before the bed rest, after the bed rest and after 1-year follow-up. All men underwent a strict bed rest intervention, and in addition, seven of them received pamidronate treatment and nine did flywheel exercises as countermeasures against disuse-related bone loss. Clearly, 3-9% sector-specific losses in trabecular density were observed at the tibial epiphysis on average. Similarly, cortical density decreased in a sector-specific way being the largest at the anterior sector of tibial diaphysis. During recovery, the bed rest-induced bone losses were practically restored and no consistent sector-specific modulation was observed in any subgroup. It is concluded that the sector-specific analysis of bone cross-sections has potential to reveal skeletal responses to various interventions that cannot be inferred from the average analysis of the whole bone cross-section. This approach is considered also useful for evaluating the bone responses from the biomechanical point of view.

  18. Prognosis of Long-Term Load-Bearing Capability in Aerospace Structures: Quantification of Microstructurally Short Crack Growth

    DTIC Science & Technology

    2013-07-31

    stress ratio, R 0.05 frequency 10 Hz temperature 23 ◦C number of cycles, N 37,500 2.2 Characterization 2.2.1 Automated EBSD and High...Energy Diffraction Microscopy Automated electron backscatter diffraction ( EBSD ) and high energy diffraction microscopy (HEDM) were used to...characterize the samples. EBSD is a now-standard technique performed in the SEM to probe the surface of a specimen and provide lattice orientation information

  19. Supramolecular structures of peptide assemblies in membranes by neutron off-plane scattering: method of analysis

    PubMed Central

    Yang, L; Weiss, TM; Harroun, TA; Heller, WT; Huang, HW

    1999-01-01

    In a previous paper (Yang et al., Biophys. J. 75:641-645, 1998), we showed a simple, efficient method of recording the diffraction patterns of supramolecular peptide assemblies in membranes where the samples were prepared in the form of oriented multilayers. Here we develop a method of analysis based on the diffraction theory of two-dimensional liquids. Gramicidin was used as a prototype model because its pore structure in membrane in known. At full hydration, the diffraction patterns of alamethicin and magainin are similar to gramicidin except in the scale of q (the momentum transfer of scattering), clearly indicating that both alamethicin and magainin form pores in membranes but of different sizes. When the hydration of the multilayer samples was decreased while the bilayers were still fluid, the in-plane positions of the membrane pores became correlated from one bilayer to the next. We believe that this is a new manifestation of the hydration force. The effect is most prominent in magainin patterns, which are used to demonstrate the method of analysis. When magainin samples were further dehydrated or cooled, the liquid-like diffraction turned into crystal-like patterns. This discovery points to the possibility of investigating the supramolecular structures with high-order diffraction. PMID:10545365

  20. Electronic structure, properties, and phase stability of inorganic crystals: A pseudopotential plane-wave study

    SciTech Connect

    Milman, V.; Winkler, B.; White, J.A.; Pickard, C.J.; Payne, M.C.; Akhmatskaya, E.V.; Nobes, R.H.

    2000-04-20

    Recent developments in density functional theory (DFT) methods applicable to studies of large periodic systems are outlined. During the past three decades, DFT has become an essential part of computational materials science, addressing problems in materials design and processing. The theory allows one to interpret experimental data and to generate property data (such as binding energies of molecules on surfaces) for known materials, and also serves as an aid in the search for and design of novel materials and processes. A number of algorithmic implementations are currently being used, including ultrasoft pseudopotentials, efficient iterative schemes for solving the one-electron DFT equations, and computationally efficient codes for massively parallel computers. The first part of this article provides an overview of plane-wave pseudopotential DFT methods. Their capabilities are subsequently illustrated by examples including the prediction of crystal structures, the study of the compressibility of minerals, and applications to pressure-induced phase transitions. Future theoretical and computational developments are expected to lead to improved accuracy and to treatment of larger systems with a higher computational efficiency.

  1. Turbulent statistics and flow structures in spanwise-rotating turbulent plane Couette flows

    NASA Astrophysics Data System (ADS)

    Gai, Jie; Xia, Zhenhua; Cai, Qingdong; Chen, Shiyi

    2016-09-01

    A series of direct numerical simulations of spanwise-rotating turbulent plane Couette flows at a Reynolds number of 1300 with rotation numbers Ro between 0 and 0.9 is carried out to investigate the effects of anticyclonic rotation on turbulent statistics and flow structures. Several typical turbulent statistics are presented, including the mean shear rate at the centerline, the wall-friction Reynolds number, and volume-averaged kinetic energies with respect to the secondary flow field, turbulent field, and total fluctuation field. Our results show that the rotation changes these quantities in different manners. Volume-averaged balance equations for kinetic energy are analyzed and it turns out that the interaction term acts as a kinetic energy bridge that transfers energy from the secondary flow to the turbulent fluctuations. Several typical flow regimes are identified based on the correlation functions across the whole channel and flow visualizations. The two-dimensional roll cells are observed at weak rotation Ro=0.01 , where alternant clustering of vortices appears. Three-dimensional roll cells emerge around Ro≈0.02 , where the clustering of vortices shows the meandering and bifurcating behavior. For moderate rotation 0.07 ≲Ro≲0.36 , well-organized structures are observed, where the herringbonelike vortices are clustered between streaks from the top view of three-dimensional flow visualization and form annuluses. More importantly, the vortices are rather confined to one side of the walls when Ro≤0.02 and are inclined from the bottom to upper walls when Ro≥0.07 .

  2. Evaluation of the Load-bearing Capacity of Fractured Incisal Edge of Maxillary Permanent Central Incisors restored with a Glass Fiber-reinforced Nanocomposite: An in vitro Study

    PubMed Central

    Srilatha, KT; Nandlal, B; Dhull, Kanika Singh

    2015-01-01

    ABSTRACT Objectives: The aim of this study was to evaluate and compare the load-bearing capacity of fractured incisal edge of maxillary permanent central incisors restored with a nanocomposite and a glass fiber-reinforced nanocomposite. Materials and methods: Thirty-six extracted sound maxillary central incisors randomly divided in three groups were used for the present study. Group I (control) contained untreated teeth. Samples in experimental groups II and III were prepared by cutting the incisal (one-third) part of the crown horizontally and subjected to enamel preparations and restored with a nanocomposite and a glass fiber-reinforced nanocomposite respectively. All restored teeth were stored in distilled water at room temperature for 24 hours. Fracture resistance was evaluated as peak load at failure (Newton) for samples tested in a cantilever-bending test using Hounsfield universal testing machine. Failure modes were microscopically examined. Results: Highest mean peak failure load (Newton) among experimental groups was observed in glass fiber-reinforced nano composite group (863.50 ± 76.12 N) followed by nanocomposite group (633.67 ± 40.14 N). One-way analysis of variance (ANOVA) revealed that the restoration technique significantly affected the load-bearing capacity (p < 0.001). Scheffe’s post-hoc comparison test (subset for α = 0.05) revealed that there was significant difference in the mean peak failure load values of nanocomposite and glass fiber-reinforced nanocomposite groups when considered together (p < 0.001). Experimental groups showed similar types of failure modes with majority occurring ascohesive and mixed type. Fifty-eight percent of the teeth in glass fiber-reinforced nanocomposite group fractured below the cementoenamel junction. Conclusion: By using fiber-reinforced composite substructure under conventional composites in the repair of fractured incisors, the load-bearing capacity of the restored incisal edge could be substantially

  3. Evaluation of the Load-bearing Capacity of Fractured Incisal Edge of Maxillary Permanent Central Incisors restored with a Glass Fiber-reinforced Nanocomposite: An in vitro Study.

    PubMed

    Kumar, Ps Praveen; Srilatha, K T; Nandlal, B; Dhull, Kanika Singh

    2015-01-01

    The aim of this study was to evaluate and compare the load-bearing capacity of fractured incisal edge of maxillary permanent central incisors restored with a nanocomposite and a glass fiber-reinforced nanocomposite. Thirty-six extracted sound maxillary central incisors randomly divided in three groups were used for the present study. Group I (control) contained untreated teeth. Samples in experimental groups II and III were prepared by cutting the incisal (one-third) part of the crown horizontally and subjected to enamel preparations and restored with a nanocomposite and a glass fiber-reinforced nanocomposite respectively. All restored teeth were stored in distilled water at room temperature for 24 hours. Fracture resistance was evaluated as peak load at failure (Newton) for samples tested in a cantilever-bending test using Hounsfield universal testing machine. Failure modes were microscopically examined. Highest mean peak failure load (Newton) among experimental groups was observed in glass fiber-reinforced nano composite group (863.50 ± 76.12 N) followed by nanocomposite group (633.67 ± 40.14 N). One-way analysis of variance (ANOVA) revealed that the restoration technique significantly affected the load-bearing capacity (p < 0.001). Scheffe's post-hoc comparison test (subset for α = 0.05) revealed that there was significant difference in the mean peak failure load values of nanocomposite and glass fiber-reinforced nanocomposite groups when considered together (p < 0.001). Experimental groups showed similar types of failure modes with majority occurring ascohesive and mixed type. Fifty-eight percent of the teeth in glass fiber-reinforced nanocomposite group fractured below the cementoenamel junction. By using fiber-reinforced composite substructure under conventional composites in the repair of fractured incisors, the load-bearing capacity of the restored incisal edge could be substantially increased. How to cite this article: Kumar PSP, Srilatha KT, Nandlal B

  4. Electronic and crystal structure changes induced by in-plane oxygen vacancies in multiferroic YMnO3

    SciTech Connect

    Cheng, Shaobo; Meng, Qingping; Li, Mengli; Duan, Wenhui; Zhao, Y. G.; Sun, X. F.; Zhu, Yimei; Zhu, Jing

    2016-02-08

    Here, the widely spread oxygen vacancies (VO) in multiferroic materials can strongly affect their physical properties. However, their exact influence has rarely been identified in hexagonal manganites. Here, with the combined use of transmission electron microscopy (TEM) and first-principles calculations, we have systematically studied the electronic and crystal structure modifications induced by VO located at the same Mn atomic plane (in-plane VO). Our TEM experiments reveal that the easily formed in-plane VO not only influence the electronic structure of YMnO3 but alter the in-plane Wyckoff positions of Mn ions, which may subsequently affect the intraplane and interplane exchange interaction of Mn ions. The ferroelectricity is also impaired due to the introduction of VO. Further calculations confirm these electronic and structural changes and modifications. Our results indicate that the electronic and crystal structure of YMnO3 can be manipulated by the creation of VO.

  5. Detection of trans–cis flips and peptide-plane flips in protein structures

    SciTech Connect

    Touw, Wouter G.; Joosten, Robbie P.; Vriend, Gert

    2015-07-28

    A method is presented to detect peptide bonds that need either a trans–cis flip or a peptide-plane flip. A coordinate-based method is presented to detect peptide bonds that need correction either by a peptide-plane flip or by a trans–cis inversion of the peptide bond. When applied to the whole Protein Data Bank, the method predicts 4617 trans–cis flips and many thousands of hitherto unknown peptide-plane flips. A few examples are highlighted for which a correction of the peptide-plane geometry leads to a correction of the understanding of the structure–function relation. All data, including 1088 manually validated cases, are freely available and the method is available from a web server, a web-service interface and through WHAT-CHECK.

  6. Structure and magnetism of bulk Fe and Cr: from plane waves to LCAO methods.

    PubMed

    Soulairol, R; Fu, Chu-Chun; Barreteau, C

    2010-07-28

    Magnetic, structural and energetic properties of bulk Fe and Cr were studied using first-principles calculations within density functional theory (DFT). We aimed to identify the dependence of these properties on key approximations of DFT, namely the exchange-correlation functional, the pseudopotential and the basis set. We found a smaller effect of pseudopotentials (PPs) on Fe than on Cr. For instance, the local magnetism of Cr was shown to be particularly sensitive to the potentials representing the core electrons, i.e. projector augmented wave and Vanderbilt ultrasoft PPs predict similar results, whereas standard norm-conserving PPs tend to overestimate the local magnetic moments of Cr in bcc Cr and in dilute bcc FeCr alloys. This drawback is suggested to be closely correlated to the overestimation of Cr solution energy in the latter system. On the other hand, we point out that DFT methods with very reduced localized basis sets (LCAO: linear combination of atomic orbitals) give satisfactory results compared with more robust plane-wave approaches. A minimal-basis representation of '3d' electrons comes to be sufficient to describe non-trivial magnetic phases including spin spirals in both fcc Fe and bcc Cr, as well as the experimental magnetic ground state of bcc Cr showing a spin density wave (SDW) state. In addition, a magnetic 'spd' tight binding model within the Stoner formalism was proposed and validated for Fe and Cr. The respective Stoner parameters were obtained by fitting to DFT data. This efficient semiempirical approach was shown to be accurate enough for studying various collinear and non-collinear phases of bulk Fe and Cr. It also enabled a detailed investigation of different polarization states of SDW in bcc Cr, where the longitudinal state was suggested to be the ground state, consistent with existing experimental data.

  7. Simultaneous in-plane and out-of-plane displacement measurement based on a dual-camera imaging system and its application to inspection of large-scale space structures

    NASA Astrophysics Data System (ADS)

    Ri, Shien; Tsuda, Hiroshi; Yoshida, Takeshi; Umebayashi, Takashi; Sato, Akiyoshi; Sato, Eiichi

    2015-07-01

    Optical methods providing full-field deformation data have potentially enormous interest for mechanical engineers. In this study, an in-plane and out-of-plane displacement measurement method based on a dual-camera imaging system is proposed. The in-plane and out-of-plane displacements are determined simultaneously using two measured in-plane displacement data observed from two digital cameras at different view angles. The fundamental measurement principle and experimental results of accuracy confirmation are presented. In addition, we applied this method to the displacement measurement in a static loading and bending test of a solid rocket motor case (CFRP material; 2.2 m diameter and 2.3 m long) for an up-to-date Epsilon rocket developed by JAXA. The effectiveness and measurement accuracy is confirmed by comparing with conventional displacement sensor. This method could be useful to diagnose the reliability of large-scale space structures in the rocket development.

  8. Repair of segmental load-bearing bone defect by autologous mesenchymal stem cells and plasma-derived fibrin impregnated ceramic block results in early recovery of limb function.

    PubMed

    Ng, Min Hwei; Duski, Suryasmi; Tan, Kok Keong; Yusof, Mohd Reusmaazran; Low, Kiat Cheong; Rose, Isa Mohamed; Mohamed, Zahiah; Bin Saim, Aminuddin; Idrus, Ruszymah Bt Hj

    2014-01-01

    Calcium phosphate-based bone substitutes have not been used to repair load-bearing bone defects due to their weak mechanical property. In this study, we reevaluated the functional outcomes of combining ceramic block with osteogenic-induced mesenchymal stem cells and platelet-rich plasma (TEB) to repair critical-sized segmental tibial defect. Comparisons were made with fresh marrow-impregnated ceramic block (MIC) and partially demineralized allogeneic bone block (ALLO). Six New Zealand White female rabbits were used in each study group and three rabbits with no implants were used as negative controls. By Day 90, 4/6 rabbits in TEB group and 2/6 in ALLO and MIC groups resumed normal gait pattern. Union was achieved significantly faster in TEB group with a radiological score of 4.50 ± 0.78 versus ALLO (1.06 ± 0.32), MIC (1.28 ± 0.24), and negative controls (0). Histologically, TEB group scored the highest percentage of new bone (82% ± 5.1%) compared to ALLO (5% ± 2.5%) and MIC (26% ± 5.2%). Biomechanically, TEB-treated tibiae achieved the highest compressive strength (43.50 ± 12.72 MPa) compared to those treated with ALLO (15.15 ± 3.57 MPa) and MIC (23.28 ± 6.14 MPa). In conclusion, TEB can repair critical-sized segmental load-bearing bone defects and restore limb function.

  9. Evaluation of Bernese periacetabular osteotomy: prospective studies examining projected load-bearing area, bone density, cartilage thickness and migration.

    PubMed

    Mechlenburg, Inger

    2008-06-01

    The typical dysplastic hip joint is characterised by maldirection of the acetabulum and femoral neck, insufficient coverage of the femoral head focally and globally and erosions of the limbus acetabuli (1). An unknown number of persons with hip dysplasia will suffer from pain in hip or groin, decreased hip function and development of osteoarthritis at a young age. The Bernese periacetabular osteotomy is performed to prevent osteoarthritis in patients with hip dysplasia and has been carried out at Aarhus University Hospital, Denmark since 1996 with more than 500 osteotomies performed. Throughout the years, research and quality improvement of the treatment has taken place and this PhD thesis is part of that process. The aims of this PhD thesis were to evaluate outcome aspects after periacetabular osteotomy in terms of I) estimating the projected loadbearing surface before and after periacetabular osteotomy, II) estimating bone density changes in the acetabulum after periacetabular osteotomy, III) developing a technique to precisely and efficiently estimate the thickness of the articular cartilage in the hip joint and IV) examining the stability of the re-orientated acetabulum after periacetabular osteotomy. In study I, we applied a stereologic method based on 3D computed tomography (CT) to estimate the projected loadbearing surface in six normal hip joints and in six dysplastic hips. The dysplastic hips were CT scanned before and after periacetabular osteotomy. We found that the average area of the projected loadbearing surface of the femoral head preoperatively was 7.4 (range 6.5-8.4) cm2 and postoperatively 11 (9.8-14.3) cm2. The area of the projected loadbearing surface was increased significantly with a mean of 49% (34-70%) postoperatively and thus comparable with the load-bearing surface in the normal control group. Double measurements were performed and the error variance of the mean was estimated to be 1.6%. The effect of overprojection, on the projected

  10. Line-feature-based calibration method of structured light plane parameters for robot hand-eye system

    NASA Astrophysics Data System (ADS)

    Qi, Yuhan; Jing, Fengshui; Tan, Min

    2013-03-01

    For monocular-structured light vision measurement, it is essential to calibrate the structured light plane parameters in addition to the camera intrinsic parameters. A line-feature-based calibration method of structured light plane parameters for a robot hand-eye system is proposed. Structured light stripes are selected as calibrating primitive elements, and the robot moves from one calibrating position to another with constraint in order that two misaligned stripe lines are generated. The images of stripe lines could then be captured by the camera fixed at the robot's end link. During calibration, the equations of two stripe lines in the camera coordinate system are calculated, and then the structured light plane could be determined. As the robot's motion may affect the effectiveness of calibration, so the robot's motion constraints are analyzed. A calibration experiment and two vision measurement experiments are implemented, and the results reveal that the calibration accuracy can meet the precision requirement of robot thick plate welding. Finally, analysis and discussion are provided to illustrate that the method has a high efficiency fit for industrial in-situ calibration.

  11. Octupolar out-of-plane magnetic field structure generation during collisionless magnetic reconnection in a stressed X-point collapse

    SciTech Connect

    Graf von der Pahlen, J.; Tsiklauri, D.

    2014-06-15

    The out-of-plane magnetic field, generated by fast magnetic reconnection, during collisionless, stressed X-point collapse, was studied with a kinetic, 2.5D, fully electromagnetic, relativistic particle-in-cell numerical code, using both closed (flux conserving) and open boundary conditions on a square grid. It was discovered that the well known quadrupolar structure in the out-of-plane magnetic field gains four additional regions of opposite magnetic polarity, emerging near the corners of the simulation box, moving towards the X-point. The emerging, outer, magnetic field structure has opposite polarity to the inner quadrupolar structure, leading to an overall octupolar structure. Using Ampere's law and integrating electron and ion currents, defined at grid cells, over the simulation domain, contributions to the out-of-plane magnetic field from electron and ion currents were determined. The emerging regions of opposite magnetic polarity were shown to be the result of ion currents. Magnetic octupolar structure is found to be a signature of X-point collapse, rather than tearing mode, and factors relating to potential discoveries in experimental scenarios or space-craft observations are discussed.

  12. Fabrication of interface-modified ramp-edge junction on YBCO ground plane with multilayer structure

    NASA Astrophysics Data System (ADS)

    Wakana, H.; Adachi, S.; Kamitani, A.; Sugiyama, H.; Sugano, T.; Horibe, M.; Ishimaru, Y.; Tarutani, Y.; Tanabe, K.

    2003-10-01

    We examined the fabrication conditions to obtain high-quality ramp-edge Josephson junctions on a liquid-phase-epitaxy YBa 2Cu 3O y (LPE-YBCO) ground plane, in particular, focusing on the fabrication of a suitable insulating layer on the ground plane and the post-annealing conditions to load oxygen to the ground plane. A (LaAlO 3) 0.3-(SrAl 0.5Ta 0.5O 3) 0.7 (LSAT) insulating film on the ground planes exhibited a conductance ranging from 10 -4 to 10 -8 S after deposition of an upper superconducting film, suggesting existence of some leak paths through the LSAT insulating layer. By introducing approximately 30 nm thick SrTiO 3 (STO) buffer layers on both side of the LSAT insulating layer. We reproducibly obtained a conductance lower than 10 -8 S. The dielectric constant of the STO/LSAT/STO layer was 32, which was slightly larger than that of the single LSAT layer. It was found that a very slow cooling rate of 1.0 °C/h in oxygen was needed to fully oxidize the ground plane through the STO/LSAT/STO insulating layers, while the oxidation time could be effectively reduced by introducing via holes in the insulating layer at an interval of 200 μm. Ramp-edge junctions on LPE-YBCO ground planes with STO/LSAT/STO insulating layers exhibited a 1 σ-spread in Ic of 8% for 100-junction series-arrays and a sheet inductance of 0.7 pH/□ at 4.2 K.

  13. Mobile offshore structure for arctic exploratory drilling

    SciTech Connect

    Hale, D. R.; Orndorff Jr., J. A.; Owen, W. A.

    1985-04-23

    An offshore exploratory drilling floatable structure ballastable to rest on a sea floor but to extend above water level when so supported and adapted to withstand arctic ice loads, comprising a substantially vertical wall capable of withstanding arctic ice loads; a structural load bearing bottom rigidly connected to a lower portion of the wall; and a floatable vertically displaceable load bearing structural deck inside the wall.

  14. In-Plane Structure of Underpotentially Deposited Copper on Gold (111) Determined by Surface EXAFS (Extended X-Ray Absorption Fine Structure).

    DTIC Science & Technology

    1988-01-28

    D-Al 263 INN-PLANE STRUCTURE OF UNDERPOTENTIALLY DEPOSITED COPPER /. ON GOLD (Iii) DET (U) PUERTO RICO UNIV RIO PIEDRAS DEPT OF PHVS I CS 0 R...051-0776 TECHNICAL REPORT #33 In-Plane Structure of Underpotentially Deposited Copper on Gold (111) Determined by Surface EXAFS by O.R. Melroy*, M.G...Strueture of Underpotentially Deposited Copper on Gold ( 11) determincd hv Surface EXAFS 0. R. Melroy*, N1. G. Samant, G. L. Borges. and J. G. Gordon

  15. Study of the in-plane magnetic structure of a layered system using polarized neutron scattering under grazing incidence geometry

    NASA Astrophysics Data System (ADS)

    Maruyama, R.; Bigault, T.; Wildes, A. R.; Dewhurst, C. D.; Soyama, K.; Courtois, P.

    2016-05-01

    The in-plane magnetic structure of a layered system with a polycrystalline grain size less than the ferromagnetic exchange length was investigated using polarized neutron off-specular scattering and grazing incidence small angle scattering measurements to gain insight into the mechanism that controls the magnetic properties which are different from the bulk. These complementary measurements with different length scales and the data analysis based on the distorted wave Born approximation revealed the lateral correlation on a length scale of sub- μm due to the fluctuating orientation of the magnetization in the layer. The obtained in-plane magnetic structure is consistent with the random anisotropy model, i.e. competition between the exchange interactions between neighboring spins and the local magnetocrystalline anisotropy.

  16. Planes formed with four intron-positions in tertiary structures of retinol binding protein and calpain domain VI.

    PubMed

    Nosaka, Michiko; Hirata, Katsuki; Tsuji, Ryotarou; Sunaba, Syunya

    2014-01-07

    Eukaryotic genes have intervening sequences, introns, in their coding regions. Since introns are spliced out from m-RNA before translation, they are considered to have no effect on the protein structure. Here, we report a novel relationship between introns and the tertiary structures of retinol binding protein and calpain domain VI. We identified "intron-positions" as amino acid residues on which or just after which introns are found in their corresponding nucleotide sequences, and then found that four intron-positions form a plane. We also found that the four intron-positions of retinol-binding protein encloses its ligand retinol. The tertiary structure of calpain domain VI changes after Ca(2+) binding, and the four intron-positions form a plane that includes its ligand calpastatin. To evaluate the statistical significance of the planarity, we calculated the mean distance of each intron-position from the plane defined by the other three intron-positions, and showed that it is significantly smaller than the one calculated for randomly generated locations based on exon size distribution. On the basis of this finding, we discuss the evolution of retinol binding protein and the origin of introns.

  17. In-plane chemical pressure essential for superconductivity in BiCh2-based (Ch: S, Se) layered structure

    PubMed Central

    Mizuguchi, Yoshikazu; Miura, Akira; Kajitani, Joe; Hiroi, Takafumi; Miura, Osuke; Tadanaga, Kiyoharu; Kumada, Nobuhiro; Magome, Eisuke; Moriyoshi, Chikako; Kuroiwa, Yoshihiro

    2015-01-01

    BiCh2-based compounds (Ch: S, Se) are a new series of layered superconductors, and the mechanisms for the emergence of superconductivity in these materials have not yet been elucidated. In this study, we investigate the relationship between crystal structure and superconducting properties of the BiCh2-based superconductor family, specifically, optimally doped Ce1−xNdxO0.5F0.5BiS2 and LaO0.5F0.5Bi(S1−ySey)2. We use powder synchrotron X-ray diffraction to determine the crystal structures. We show that the structure parameter essential for the emergence of bulk superconductivity in both systems is the in-plane chemical pressure, rather than Bi-Ch bond lengths or in-plane Ch-Bi-Ch bond angle. Furthermore, we show that the superconducting transition temperature for all REO0.5F0.5BiCh2 superconductors can be determined from the in-plane chemical pressure. PMID:26447333

  18. The existence and behavior of viscous structure for plane detonation waves

    NASA Astrophysics Data System (ADS)

    Wagner, David H.

    1989-09-01

    A necessary condition and a sufficient condition are proved for the existence of steady plane wave solutions to the Navier-Stokes equations for a reacting gas. These solutions represent plane detonation waves, and converge to ZND detonation waves as the viscosity, heat conductivity, and species diffusion rates tend to zero. It is assumed that the Prandtl number is 3/4, but arbitrary Lewis numbers are permitted. No assumption is made concerning the activation energy. It is shown that the stagnation enthalpy and the entropy flux are always monotone for such solutions, and that the mass density and pressure are nearly always not monotone, as predicted by the ZND theory. In certain parameter ranges, typically that of large diffusion, many of these waves have the appearance of a weak detonation followed by an inert shock wave. This confirms a phenomenon observed in numerical calculations and in a model system by Colella, Majda, and Roytburd (1986).

  19. Heat transfer and vortical structures of a plane impinging jet excited by spanwise periodic disturbances

    NASA Astrophysics Data System (ADS)

    Miyoshi, Yoshifumi; Kaneko, Jun-Ichi; Sakakibara, Jun

    2001-11-01

    Wall temperature and vorticity distribution of a stagnation region of a plane impinging jet with spanwise and temporal periodic disturbances has been measured by using thermochromic liquid crystal (TLC) and PIV. The plane jet of water was excited in time and space by adding suction/blowing type disturbances produced by servomotor-driven injectors. Stainless foil heaters with TLC coating glued on a Plexiglass plate was used as a heated impingement wall. The TLC surface was observed by 3 monochrome CCD cameras through RGB filters to acquire color distribution, and the velocity and vorticity field in a center-plane of the jet have been measured by PIV. Strouhal and Reynolds number were set respectively at St=0.45 and Re=2300. Surface temperature distribution showed unsteady streaks in parallel with a wall jet direction. It was evident from the PIV results that these streaks were caused by counter-rotating vortices induced on the wall. The vorticity magnitude and heat transfer rate could be modified by the temporal phase angle between disturbances added in adjacent spanwise locations.

  20. Structural analysis of FAST reflector supporting system

    NASA Astrophysics Data System (ADS)

    Luo, Y. F.; Deng, C. G.; Li, G. Q.; He, Y. M.

    According to the deformation and movement requirements of the FAST reflector, a multi-purpose analysis, including the load-bearing behavior, deformation, construction costs of the reflector supporting structure and its model, is presented in this paper. The advantages and disadvantages of steel and aluminum alloy structures are also discussed and compared through detailed design calculations under load-bearing capacity and normal working conditions.

  1. Strain and water effects on the electronic structure and chemical activity of in-plane graphene/silicene heterostructure

    NASA Astrophysics Data System (ADS)

    Kistanov, Andrey A.; Cai, Yongqing; Zhang, Yong-Wei; Dmitriev, Sergey V.; Zhou, Kun

    2017-03-01

    By using first-principles calculations, the electronic structure of planar and strained in-plane graphene/silicene heterostructure is studied. The heterostructure is found to be metallic in a strain range from  ‑7% (compression) to  +7% (tension). The effect of compressive/tensile strain on the chemical activity of the in-plane graphene/silicene heterostructure is examined by studying its interaction with the H2O molecule. It shows that compressive/tensile strain is able to increase the binding energy of H2O compared with the adsorption on a planar surface, and the charge transfer between the water molecule and the graphene/silicene sheet can be modulated by strain. Moreover, the presence of the boron-nitride (BN)-substrate significantly influences the chemical activity of the graphene/silicene heterostructure upon its interaction with the H2O molecule and may cause an increase/decrease of the charge transfer between the H2O molecule and the heterostructure. These findings provide insights into the modulation of electronic properties of the in-plane free-standing/substrate-supported graphene/silicene heterostructure, and render possible ways to control its electronic structure, carrier density and redox characteristics, which may be useful for its potential applications in nanoelectronics and gas sensors.

  2. In-Plane Magnetic Field Effect on the Transport Properties in a Quasi-3D Quantum Well Structure

    SciTech Connect

    Brooks, J.; Clark, R.; Lumpkin, N.; O'Brien, J.; Reno, J.; Simmons, J.; Wang, Z.; Zhang, B.

    1999-05-25

    The transport properties of a quasi-three-dimensional, 200 layer quantum well structure are investigated at integer filling in the quantum Hall state. We find that the transverse magnetoresistance Rxx, the Hall resistance Rxy, and the vertical resistance Rzz all follow a similar behavior with both temperature and in-plane magnetic field. A general feature of the influence of increasing in-plane field Bin is that the Hall conductance quantization first improves, but above a characteristic value BCin, the quantization is systematically removed. We consider the interplay of the chid edge state transport and the bulk (quantum Hall) transport properties. This mechanism may arise from the competition of the cyclotron energy with the superlattice band structure energies. A comparison of the resuIts with existing theories of the chiral edge state transport with in-plane field is also discussed.

  3. Direct spontaneous growth and interfacial structural properties of inclined GaN nanopillars on r-plane sapphire

    SciTech Connect

    Adikimenakis, A.; Aretouli, K. E.; Tsagaraki, K.; Androulidaki, M.; Georgakilas, A.; Lotsari, A.; Dimitrakopulos, G. P. Kehagias, Th.; Komninou, Ph.

    2015-06-28

    The spontaneous growth of GaN nanopillars (NPs) by direct plasma-assisted molecular beam epitaxy on nitridated r-plane sapphire substrates has been studied. The emanation of metal-polarity NPs from inside an a-plane nonpolar GaN film was found to depend on both the substrate nitridation and the growth conditions. The density of NPs increased with increasing the duration of the nitridation process and the power applied on the radio-frequency plasma source, as well as the III/V flux ratio, while variation of the first two parameters enhanced the roughness of the substrate's surface. Transmission electron microscopy (TEM) techniques were employed to reveal the structural characteristics of the NPs and their nucleation mechanism from steps on the sapphire surface and/or interfacial semipolar GaN nanocrystals. Lattice strain measurements showed a possible Al enrichment of the first 5–6 monolayers of the NPs. By combining cross-sectional and plan-view TEM observations, the three-dimensional model of the NPs was constructed. The orientation relationship and interfacial accommodation between the NPs and the nonpolar a-plane GaN film were also elucidated. The NPs exhibited strong and narrow excitonic emission, suggesting an excellent structural quality.

  4. Direct spontaneous growth and interfacial structural properties of inclined GaN nanopillars on r-plane sapphire

    NASA Astrophysics Data System (ADS)

    Adikimenakis, A.; Lotsari, A.; Dimitrakopulos, G. P.; Kehagias, Th.; Aretouli, K. E.; Tsagaraki, K.; Androulidaki, M.; Komninou, Ph.; Georgakilas, A.

    2015-06-01

    The spontaneous growth of GaN nanopillars (NPs) by direct plasma-assisted molecular beam epitaxy on nitridated r-plane sapphire substrates has been studied. The emanation of metal-polarity NPs from inside an a-plane nonpolar GaN film was found to depend on both the substrate nitridation and the growth conditions. The density of NPs increased with increasing the duration of the nitridation process and the power applied on the radio-frequency plasma source, as well as the III/V flux ratio, while variation of the first two parameters enhanced the roughness of the substrate's surface. Transmission electron microscopy (TEM) techniques were employed to reveal the structural characteristics of the NPs and their nucleation mechanism from steps on the sapphire surface and/or interfacial semipolar GaN nanocrystals. Lattice strain measurements showed a possible Al enrichment of the first 5-6 monolayers of the NPs. By combining cross-sectional and plan-view TEM observations, the three-dimensional model of the NPs was constructed. The orientation relationship and interfacial accommodation between the NPs and the nonpolar a-plane GaN film were also elucidated. The NPs exhibited strong and narrow excitonic emission, suggesting an excellent structural quality.

  5. Repair of Segmental Load-Bearing Bone Defect by Autologous Mesenchymal Stem Cells and Plasma-Derived Fibrin Impregnated Ceramic Block Results in Early Recovery of Limb Function

    PubMed Central

    Ng, Min Hwei; Duski, Suryasmi; Tan, Kok Keong; Yusof, Mohd Reusmaazran; Low, Kiat Cheong; Mohamed Rose, Isa; Mohamed, Zahiah; Bin Saim, Aminuddin; Idrus, Ruszymah Bt Hj

    2014-01-01

    Calcium phosphate-based bone substitutes have not been used to repair load-bearing bone defects due to their weak mechanical property. In this study, we reevaluated the functional outcomes of combining ceramic block with osteogenic-induced mesenchymal stem cells and platelet-rich plasma (TEB) to repair critical-sized segmental tibial defect. Comparisons were made with fresh marrow-impregnated ceramic block (MIC) and partially demineralized allogeneic bone block (ALLO). Six New Zealand White female rabbits were used in each study group and three rabbits with no implants were used as negative controls. By Day 90, 4/6 rabbits in TEB group and 2/6 in ALLO and MIC groups resumed normal gait pattern. Union was achieved significantly faster in TEB group with a radiological score of 4.50 ± 0.78 versus ALLO (1.06 ± 0.32), MIC (1.28 ± 0.24), and negative controls (0). Histologically, TEB group scored the highest percentage of new bone (82% ± 5.1%) compared to ALLO (5% ± 2.5%) and MIC (26% ± 5.2%). Biomechanically, TEB-treated tibiae achieved the highest compressive strength (43.50 ± 12.72 MPa) compared to those treated with ALLO (15.15 ± 3.57 MPa) and MIC (23.28 ± 6.14 MPa). In conclusion, TEB can repair critical-sized segmental load-bearing bone defects and restore limb function. PMID:25165699

  6. In vivo evaluation of bioactive PMMA-based bone cement with unchanged mechanical properties in a load-bearing model on rabbits.

    PubMed

    Fottner, Andreas; Nies, Berthold; Kitanovic, Denis; Steinbrück, Arnd; Hausdorf, Jörg; Mayer-Wagner, Susanne; Pohl, Ulrich; Jansson, Volkmar

    2015-07-01

    Polymethylmethacrylate-based bone cements are widely used for fixation of joint replacements. To improve the long-term outcome, bioactive bone cements are aspired to advance the bone-cement interface. This study evaluated the in vivo properties of a new polymethylmethacrylate-based bioactive bone cement with addition of amphiphilic phosphorylated 2-hydroxyethylmethacrylate. Previous in vitro studies confirmed bioactive properties in cell culture, as well as unchanged mechanical properties are tests according to ISO 5833:2002.Three different variations of the cement (polymethylmethacrylate + phosphorylated 2-hydroxyethylmethacrylate, polymethylmethacrylate + phosphorylated 2-hydroxyethylmethacrylate + CaCl2 and polymethylmethacrylate + phosphorylated 2-hydroxyethylmethacrylate + CaCl2 + Na2CO3) were compared to conventional polymethylmethacrylate cement. To evaluate the properties under load-bearing conditions, a spacer prosthesis was implanted into the femoral diaphysis of 24 rabbits. Additionally, a cement plug was installed into the proximal tibia. After three months, polished sections with Giemsa surface staining were prepared. The bioactivity was determined using the bone affinity index.The sections showed a good osseointegration of the bioactive bone cement without cement cracks under load-bearing conditions. Regarding the bone affinity index, the bioactive bone cement revealed a significantly higher value in the proximal tibia (25.9-37.7%) and around the spacer prosthesis (36.8-58.9%) compared to the conventional polymethylmethacrylate cement (12.8-17.0%).The results confirm the in vivo bioactivity of this bone cement. The absence of cement cracks indicates a sufficient mechanical stability to fix prostheses with this bioactive cement, but for a final assessment long-term tests are necessary.

  7. Electronic states in low-dimensional nano-structures: Comparison between the variational and plane wave basis method

    NASA Astrophysics Data System (ADS)

    Hu, Min; Wang, Hailong; Gong, Qian; Wang, Shumin

    2017-04-01

    A comparison is made between the plane wave basis and variational method. Within the framework of effective-mass approximation theory, the variational and plane wave basis method are used to calculate ground state energy and ground state binding energy in low-dimensional nano-structures under the external electric field. Comparing calculation results, the donor binding energies of ground state display the consistent trend, both of them are strongly dependent on the quantum size, impurity position and external electric field. However, the impurity ground state energy calculated using variational method may be larger than the real value and it results in the smaller binding energy for variational method. In addition, the binding energy is more sensitive to the external electric field for the variational method, which can be seen more clearly from Stark shift.

  8. Voltage-Driven In-Plane Magnetization Easy Axis Switching in FeNi/Piezoelectric Actuator Hybrid Structure

    NASA Astrophysics Data System (ADS)

    Xi, Li; Guo, Xiaobin; Wang, Zhen; Li, Yue; Yao, Yuelin; Zuo, Yalu; Xue, Desheng

    2013-01-01

    FeNi thin films with the in-plane uniaxial anisotropy were fabricated by direct current magnetron sputtering. An FeNi/piezoelectric actuator hybrid structure was used to investigate the voltage-controlled magnetization switching. A theoretical calculation was performed to provide a simplified vision of the magnetoelastic contribution to the magnetic anisotropy. Magneto-optical Kerr effect measurements were performed and the rotation of the magnetization easy axis in the FeNi film upon application of a voltage with or without the application of a magnetic field was demonstrated. A film-thickness dependent in-plane magnetization easy axis rotation angle was observed and explained by the variation of the magnetostriction.

  9. Magnonic band structures in two-dimensional bi-component magnonic crystals with in-plane magnetization

    NASA Astrophysics Data System (ADS)

    Krawczyk, M.; Mamica, S.; Mruczkiewicz, M.; Klos, J. W.; Tacchi, S.; Madami, M.; Gubbiotti, G.; Duerr, G.; Grundler, D.

    2013-12-01

    We investigate the magnonic band structure of in-plane magnetized two-dimensional magnonic crystals composed of cobalt dots embedded into a permalloy antidot lattice. Our analysis is based on the results of numerical calculations carried out by the plane wave method. The complex magnonic band structure found in square-lattice magnonic crystals is explained on the basis of the spin wave dispersion relations calculated in the empty lattice model. We show that four principal effects influence the formation of a magnonic band structure in planar two-dimensional bi-component magnonic crystals: a folding effect, Bragg scattering, hybridization between various spin wave modes, and a demagnetizing field. While the first two effects are found for other types of waves in periodic composites, the third one exists in an anisotropic medium and the last one is specific to spin waves propagating in magnonic crystals with magnetization in the film plane. The strong anisotropy in the dispersion relation of spin waves in thin ferromagnetic films results in the crossing and anti-crossing of the fast, Damon-Eshbach-like mode with a number of other spin waves folded to the first Brillouin zone. The demagnetizing field can induce the formation of channels for spin waves which are propagating perpendicular to the external magnetic field direction, but this property exists only in the limiting range of the thicknesses and the lattice constants of the bi-component magnonic crystals. Based on the model analysis we propose a modification of the magnonic crystal structure by changing its thickness, lattice constant and aspect ratio along the direction of the applied magnetic field to significantly modify the magnonic band structure and obtain partial magnonic band gaps.

  10. Splitting of the neutral mechanical plane depends on the length of the multi-layer structure of flexible electronics.

    PubMed

    Li, Shuang; Su, Yewang; Li, Rui

    2016-06-01

    Multi-layer structures with soft (compliant) interlayers have been widely used in flexible electronics and photonics as an effective design for reducing interactions among the hard (stiff) layers and thus avoiding the premature failure of an entire device. The analytic model for bending of such a structure has not been well established due to its complex mechanical behaviour. Here, we present a rational analytic model, without any parameter fitting, to study the bending of a multi-layer structure on a cylinder, which is often regarded as an important approach to mechanical reliability testing of flexible electronics and photonics. For the first time, our model quantitatively reveals that, as the key for accurate strain control, the splitting of the neutral mechanical plane depends not only on the relative thickness of the middle layer, but also on the length-to-thickness ratio of the multi-layer structure. The model accurately captures the key quantities, including the axial strains in the top and bottom layers, the shear strain in the middle layer and the locations of the neutral mechanical planes of the top and bottom layers. The effects of the length of the multi-layer and the thickness of the middle layer are elaborated. This work is very useful for the design of multi-layer structure-based flexible electronics and photonics.

  11. Splitting of the neutral mechanical plane depends on the length of the multi-layer structure of flexible electronics

    NASA Astrophysics Data System (ADS)

    Li, Shuang; Su, Yewang; Li, Rui

    2016-06-01

    Multi-layer structures with soft (compliant) interlayers have been widely used in flexible electronics and photonics as an effective design for reducing interactions among the hard (stiff) layers and thus avoiding the premature failure of an entire device. The analytic model for bending of such a structure has not been well established due to its complex mechanical behaviour. Here, we present a rational analytic model, without any parameter fitting, to study the bending of a multi-layer structure on a cylinder, which is often regarded as an important approach to mechanical reliability testing of flexible electronics and photonics. For the first time, our model quantitatively reveals that, as the key for accurate strain control, the splitting of the neutral mechanical plane depends not only on the relative thickness of the middle layer, but also on the length-to-thickness ratio of the multi-layer structure. The model accurately captures the key quantities, including the axial strains in the top and bottom layers, the shear strain in the middle layer and the locations of the neutral mechanical planes of the top and bottom layers. The effects of the length of the multi-layer and the thickness of the middle layer are elaborated. This work is very useful for the design of multi-layer structure-based flexible electronics and photonics.

  12. The effect of design parameters of dynamic pedicle screw systems on kinematics and load bearing: an in vitro study

    PubMed Central

    Krüger, S.; Grupp, T. M.; Duda, G. N.; Blömer, W.; Rohlmann, A.

    2010-01-01

    As an alternative treatment for chronic back pain due to disc degeneration motion preserving techniques such as posterior dynamic stabilization (PDS) has been clinically introduced, with the intention to alter the load transfer and the kinematics at the affected level to delay degeneration. However, up to the present, it remains unclear when a PDS is clinically indicated and how the ideal PDS mechanism should be designed to achieve this goal. Therefore, the objective of this study was to compare different PDS devices against rigid fixation to investigate the biomechanical impact of PDS design on stabilization and load transfer in the treated and adjacent cranial segment. Six human lumbar spine specimens (L3–L5) were tested in a spine loading apparatus. In vitro flexibility testing was performed by applying pure bending moments of 7.5 Nm without and with additional preload of 400 N in the three principal motion planes. Four PDS devices, “DYN” (Dynesys®, Zimmer GmbH, Switzerland), “DSS™” (Paradigm Spine, Wurmlingen, Germany), and two prototypes of dynamic rods, “LSC” with a leaf spring, and “STC” with a spring tube (Aesculap AG, Tuttlingen, Germany), were tested in comparison to a rigid fixation device S4 (Aesculap AG, Tuttlingen, Germany) “RIG”, to the native situation “NAT” and to a defect situation “DEF” of the specimens. The instrumented level was L4–L5. The tested PDS devices comprising a stiffness range for axial stiffness of 10 N/mm to 230 N/mm and for bending stiffness of 3 N/mm to 15 N/mm. Range of motion (ROM), neutral zone (NZ), and intradiscal pressure (IDP) were analyzed for all instrumentation steps and load cases of the instrumented and non-instrumented level. In flexion, extension, and lateral bending, all systems, except STC, showed a significant reduction of ROM and NZ compared to the native situation (p < 0.05). Furthermore, we found no significant difference between DYN and RIG (p > 0.1). In axial

  13. Iterative diagonalization in augmented plane wave based methods in electronic structure calculations

    SciTech Connect

    Blaha, P.; Laskowski, R.; Schwarz, K.

    2010-01-20

    Due to the increased computer power and advanced algorithms, quantum mechanical calculations based on Density Functional Theory are more and more widely used to solve real materials science problems. In this context large nonlinear generalized eigenvalue problems must be solved repeatedly to calculate the electronic ground state of a solid or molecule. Due to the nonlinear nature of this problem, an iterative solution of the eigenvalue problem can be more efficient provided it does not disturb the convergence of the self-consistent-field problem. The blocked Davidson method is one of the widely used and efficient schemes for that purpose, but its performance depends critically on the preconditioning, i.e. the procedure to improve the search space for an accurate solution. For more diagonally dominated problems, which appear typically for plane wave based pseudopotential calculations, the inverse of the diagonal of (H - ES) is used. However, for the more efficient 'augmented plane wave + local-orbitals' basis set this preconditioning is not sufficient due to large off-diagonal terms caused by the local orbitals. We propose a new preconditioner based on the inverse of (H - {lambda}S) and demonstrate its efficiency for real applications using both, a sequential and a parallel implementation of this algorithm into our WIEN2k code.

  14. Synthesis, crystal structure, and properties of new lead barium borate with B3O6 plane hexagonal rings

    NASA Astrophysics Data System (ADS)

    Zhao, Wenwu

    2017-08-01

    A new lead barium borate Ba8.02Pb0.98(B3O6)6 with B3O6 plane hexagonal rings was synthesized through spontaneous nucleation from a high-temperature solution utilizing PbO, H3BO3, and BaF2 as reagents. Its crystal structure was determined from single-crystal X-ray diffraction data and further characterized by FT-IR. It crystallizes in space group R32 and the crystallographic structure of Ba8.02Pb0.98(B3O6)6 can be described as a layer-like structure, there is stacking along the c-axis of B3O6 plane hexagonal rings with the Ba2 and Pb/Ba1 atoms alternately occupying sites between the B3O6 sheets. A comparison of the structures of Ba8.02Pb0.98(B3O6)6, PbBa2(B3O6)2 and α-BaB2O4 is presented. UV-Vis-NIR diffuse-reflectance spectrum indicates that the absorption edge of Ba8.02Pb0.98(B3O6)6 is about 399 nm.

  15. Glide-plane symmetry and superconducting gap structure of iron-based superconductors

    DOE PAGES

    Wang, Yan; Berlijn, Tom; Hirschfeld, Peter J.; ...

    2015-03-10

    We consider the effect of glide-plane symmetry of the Fe-pnictogen/chalcogen layer in Fe-based superconductors on pairing in spin fluctuation models. Recent theories propose that so-called η-pairing states with nonzero total momentum can be realized and possess such exotic properties as odd parity spin singlet symmetry and time-reversal symmetry breaking. Here we show that when there is orbital weight at the Fermi level from orbitals with even and odd mirror reflection symmetry in z, η pairing is inevitable; however, we conclude from explicit calculation that the gap function appearing in observable quantities is identical to that found in earlier pseudocrystal momentummore » calculations with 1 Fe per unit cell.« less

  16. Glide-plane symmetry and superconducting gap structure of iron-based superconductors

    SciTech Connect

    Wang, Yan; Berlijn, Tom; Hirschfeld, Peter J.; Scalapino, Douglas J.; Maier, Thomas A.

    2015-03-10

    We consider the effect of glide-plane symmetry of the Fe-pnictogen/chalcogen layer in Fe-based superconductors on pairing in spin fluctuation models. Recent theories propose that so-called η-pairing states with nonzero total momentum can be realized and possess such exotic properties as odd parity spin singlet symmetry and time-reversal symmetry breaking. Here we show that when there is orbital weight at the Fermi level from orbitals with even and odd mirror reflection symmetry in z, η pairing is inevitable; however, we conclude from explicit calculation that the gap function appearing in observable quantities is identical to that found in earlier pseudocrystal momentum calculations with 1 Fe per unit cell.

  17. The mixing mechanism by organised turbulence structures in a plane jet excited by a novel method

    NASA Technical Reports Server (NTRS)

    Badri Narayanan, M. A.; Platzer, Max F.

    1988-01-01

    The effect on a plane subsonic turbulent jet of controlled high-amplitude periodic oscillations applied to the nozzle is investigated experimentally. A variable-speed motor and a gear-cam mechanism are used to make the lips of the nozzle reciprocate in opposite directions at the desired frequency. Velocity profiles, flow visualizations, and pressure-signal traces are presented and analyzed in detail. The complex vortex processes involved in the oscillation-induced spreading and entrainment of the jet are explored, and a critical Strouhal number for vortex formation and amplification is determined. The oscillation technique is found to augment the thrust of a jet/duct-diffuser configuration by a factor of 1.20; the thrust increases with oscillation frequency up to 20 Hz and remains constant if the frequency is further increased.

  18. TIGHT CORRELATIONS BETWEEN MASSIVE GALAXY STRUCTURAL PROPERTIES AND DYNAMICS: THE MASS FUNDAMENTAL PLANE WAS IN PLACE BY z ∼ 2

    SciTech Connect

    Bezanson, Rachel; Van Dokkum, Pieter G.; Leja, Joel; Van de Sande, Jesse; Franx, Marijn; Kriek, Mariska

    2013-12-20

    The fundamental plane (FP) is an empirical relation between the size, surface brightness, and velocity dispersion of early-type galaxies. This relation has been studied extensively for early-type galaxies in the local universe to constrain galaxy formation mechanisms. The evolution of the zero point of this plane has been extended to high redshifts to study the luminosity evolution of massive galaxies, under the assumption of structural homology. In this work, we assess this assumption by replacing surface brightness with stellar mass density and present the evolution of the ''mass FP'' for massive, quiescent galaxies since z ∼ 2. By accounting for stellar populations, we thereby isolate and trace structural and dynamical evolution. Despite the observed dramatic evolution in the sizes and morphologies of massive galaxies since z ∼ 3, we find that quiescent galaxies lie on the mass FP out to z ∼ 2. In contrast with ∼1.4 dex evolution in the luminosity FP, average residuals from the z ∼ 0 mass FP are less than ∼0.15 dex since z ∼ 2. Assuming the Hyde and Bernardi mass FP slope, we find that this minimal offset scales as (1 + z){sup –0.095} {sup ±} {sup 0.043}. This result lends credence to previous studies that derived luminosity evolution from the FP. Therefore, despite their compact sizes and suggestions that massive galaxies are more disk-like at z ∼ 2, the relationship between their dynamics and structural properties are consistent with local early-type galaxies. Finally, we find no strong evidence for a tilt of the mass FP relative to the virial plane, but emphasize the need for full models including selection biases to fully investigate this issue.

  19. Tight Correlations between Massive Galaxy Structural Properties and Dynamics: The Mass Fundamental Plane was in Place by z ~ 2

    NASA Astrophysics Data System (ADS)

    Bezanson, Rachel; van Dokkum, Pieter G.; van de Sande, Jesse; Franx, Marijn; Leja, Joel; Kriek, Mariska

    2013-12-01

    The fundamental plane (FP) is an empirical relation between the size, surface brightness, and velocity dispersion of early-type galaxies. This relation has been studied extensively for early-type galaxies in the local universe to constrain galaxy formation mechanisms. The evolution of the zero point of this plane has been extended to high redshifts to study the luminosity evolution of massive galaxies, under the assumption of structural homology. In this work, we assess this assumption by replacing surface brightness with stellar mass density and present the evolution of the "mass FP" for massive, quiescent galaxies since z ~ 2. By accounting for stellar populations, we thereby isolate and trace structural and dynamical evolution. Despite the observed dramatic evolution in the sizes and morphologies of massive galaxies since z ~ 3, we find that quiescent galaxies lie on the mass FP out to z ~ 2. In contrast with ~1.4 dex evolution in the luminosity FP, average residuals from the z ~ 0 mass FP are less than ~0.15 dex since z ~ 2. Assuming the Hyde & Bernardi mass FP slope, we find that this minimal offset scales as (1 + z)-0.095 ± 0.043. This result lends credence to previous studies that derived luminosity evolution from the FP. Therefore, despite their compact sizes and suggestions that massive galaxies are more disk-like at z ~ 2, the relationship between their dynamics and structural properties are consistent with local early-type galaxies. Finally, we find no strong evidence for a tilt of the mass FP relative to the virial plane, but emphasize the need for full models including selection biases to fully investigate this issue.

  20. Real-space and plane-wave hybrid method for electronic structure calculations for two-dimensional materials

    NASA Astrophysics Data System (ADS)

    Do, V. Nam; Le, H. Anh; Vu, V. Thieu

    2017-04-01

    We propose a computational approach to combining the plane-wave method and the real-space treatment to describe the periodic variation in the material plane and the decay of wave functions from the material surfaces. The proposed approach is natural for two-dimensional material systems and thus may circumvent some intrinsic limitations involving the artificial replication of material layers in traditional supercell methods. In particular, we show that the proposed method is easy to implement and, especially, computationally effective since low-cost computational algorithms, such as iterative and recursive techniques, can be used to treat matrices with block tridiagonal structure. Using this approach we show first-principles features that supplement the current knowledge of some fundamental issues in bilayer graphene systems, including the coupling between the two graphene layers, the preservation of the σ band of monolayer graphene in the electronic structure of the bilayer system, and the differences in low-energy band structure between the AA- and AB-stacked configurations.

  1. Focal plane array detectors with micro-bolometer structure and its application in IR and THz imaging

    NASA Astrophysics Data System (ADS)

    Wang, Jun; Mou, Wenchao; Gou, Jun; Jiang, Yadong

    2016-10-01

    Focal Plane Array (FPA) detector has characteristics of low cost, operating at room temperature, compatibility with the silicon CMOS technology, and high detecting performance, therefore it becomes a hot spot in infrared (IR) or terahertz (THz) detect field recently. However, the tradition structure of micro-bolometer has the conflict of the pixel size and thermal performance. In order to improve the detecting performance of small pixel size bolometer, high fill factor and low thermal conductance design should be considered. In IR detecting, double layers structure is an efficient method to improve the absorption of micro-bolometer and reduce thermal conductance. The three-dimension model of small size micro-bolometer was built in this article. The thermal and mechanical characters of those models were simulated and optimized, and finally the double layer structure micro-bolometer was fabricated with multifarious semiconductor recipes on the readout integrated chip wafer. For THz detecting, to improve the detecting performance, different dimension THz detectors based on micro-bridge structure were designed and fabricated to get optimizing micro-bolometer parameters from the test results of membrane deformation. A nanostructured titanium thin film absorber is integrated in the micro-bridge structure of the VOx micro-bolometer to enhance the absorption of THz radiation. Continuous-wave THz detection and imaging are demonstrated with a 2.52 THz far infrared CO2 laser and fabricated 320×240 vanadium oxide micro-bolometer focal plane array with optimized cell structure. With this detecting system, THz imaging of metal concealed in wiping cloth and envelope is demonstrated.

  2. Glide plane symmetry and gap structure in the iron-based superconductors

    NASA Astrophysics Data System (ADS)

    Wang, Yan; Berlijn, Tom; Hirschfeld, Peter; Scalapino, Douglas; Maier, Thomas

    2015-03-01

    We consider the effect of glide plane symmetry of the Fe-pnictogen/chalcogen layer in Fe-based superconductors for pairing in spin fluctuation models. Recent theories have proposed that so-called η-pairing states with nonzero total momentum can be realized and possess exotic properties such as odd parity spin singlet symmetry and time-reversal symmetry breaking. Here we show that η-pairing is inevitable when there is orbital weight at the Fermi level from orbitals with even and odd mirror reflection symmetry in z; however, by explicit calculation, we conclude that the gap function that appears in observable quantities is identical to that found in earlier, 1 Fe per unit cell pseudo-crystal momentum calculations. P.J.H. and Y.W. were supported by Grant No. DOE DE-FG02-05ER46236 and T.B. was supported as a Wigner Fellow at the Oak Ridge National Laboratory. A portion of this research was conducted at the Center for Nanophase Materials Sciences, which is sponsored at Oak Ridge National Laboratory by the Scientific User Facilities Division, Office of Basic Energy Sciences, US Department of Energy.

  3. Functional fatigue behavior of superelastic beta Ti-22Nb-6Zr(at%) alloy for load-bearing biomedical applications.

    PubMed

    Sheremetyev, V; Brailovski, V; Prokoshkin, S; Inaekyan, K; Dubinskiy, S

    2016-01-01

    Ti-22Nb-6Zr (at.%) alloy with different processing-induced microstructures (highly-dislocated partially recovered substructure, polygonized nanosubgrained (NSS) dislocation substructure, and recrystallized structure) was subjected to strain-controlled tension-tension fatigue testing in the 0.2...1.5% strain range (run-out at 10^6 cycles). The NSS alloy obtained after cold-rolling with 0.3 true strain and post-deformation annealing at 600 °C showed the lowest Young's modulus and globally superior fatigue performance due to the involvement of reversible stress-induced martensitic transformation in the deformation process. This NSS structure appears to be suitable for biomedical applications with an extended variation range of loading conditions (orthopedic implants). Copyright © 2015 Elsevier B.V. All rights reserved.

  4. Predicting the Influence of Nano-Scale Material Structure on the In-Plane Buckling of Orthotropic Plates

    NASA Technical Reports Server (NTRS)

    Gates, Thomas S.; Odegard, Gregory M.; Nemeth, Michael P.; Frankland, Sarah-Jane V.

    2004-01-01

    A multi-scale analysis of the structural stability of a carbon nanotube-polymer composite material is developed. The influence of intrinsic molecular structure, such as nanotube length, volume fraction, orientation and chemical functionalization, is investigated by assessing the relative change in critical, in-plane buckling loads. The analysis method relies on elastic properties predicted using the hierarchical, constitutive equations developed from the equivalent-continuum modeling technique applied to the buckling analysis of an orthotropic plate. The results indicate that for the specific composite materials considered in this study, a composite with randomly orientated carbon nanotubes consistently provides the highest values of critical buckling load and that for low volume fraction composites, the non-functionalized nanotube material provides an increase in critical buckling stability with respect to the functionalized system.

  5. In-plane structural and electronic anisotropy in de-twinned (Ba1-xKx)Fe2As2

    NASA Astrophysics Data System (ADS)

    Blomberg, Erick; Tanatar, M. A.; Straszheim, W. E.; Shen, B.; Wen, H. H.; Prozorov, R.

    2012-02-01

    The iron-pnictides undergo a tetragonal to orthorhombic structural transition below a doping - dependent temperature Ts. In the absence of external stress or strain, the orthorhombic phase is divided into four degenerate, equally populated, ``twin'' structural domains, obscuring direct measurement of in-plane anisotropy. This degeneracy may be broken through mild mechanical stress or strain leaving the sample de-twinned. The properties of detwinned (Ba1-xKx)Fe2As2 with x=0.1, 0.18 (hole under-doped) were discussed previously [1]. Here we report polarized-light microscopy and AC transport measurements of strain-detwinned (Ba1-xKx)Fe2As2 with a dopping range from x=0.15 to x=0.35. Our results provide new insight into a region of coexisting magnetic and superconducting order parameters. [4pt] [1] J. J. Ying, et al. Phys. Rev. Lett. 107 067001 (2011).

  6. Stress-induced formation of structural defects on the [l brace]311[r brace] planes of silicon

    SciTech Connect

    Weng-Sieh, Z. ); Krulevitch, P. ); Gronsky, R. ); Johnson, G.C. )

    1994-08-01

    Structural defects occurring on the [l brace]311[r brace] planes of single crystal silicon have been observed near the bottom oxide corner in silicon-on-insulator structures formed by selective epitaxial growth. These [l brace]311[r brace] defects exhibit a preferential orientation and are clustered near the silicon/silicon dioxide interface. This new observation provides an opportunity to study the mechanism of [l brace]311[r brace] defect generation in a system with discernible microstructure and stress state. High resolution electron microscopy combined with analytical and numerical three-dimensional stress modeling are used to show the dependence of these [l brace]311[r brace] defects on the local stress field, and to establish their origin in terms of the homogeneous dislocation nucleation model.

  7. Mechanical properties and in vivo performance of load-bearing fiber-reinforced composite intramedullary nails with improved torsional strength.

    PubMed

    Moritz, N; Strandberg, N; Zhao, D S; Mattila, R; Paracchini, L; Vallittu, P K; Aro, H T

    2014-12-01

    Fiber-reinforced composites (FRC) could be feasible materials for fracture fixation devices if the mechanical properties of the composites are congruent with the local structural properties of bone. In a recently developed FRC implant, bisphenol A dimethacrylate (BisGMA) and triethylene glycol dimethacrylate (TEGDMA) resin was reinforced with unidirectional E-glass fibers. The addition of a braided glass fiber sleeving to the unidirectional fibers increased the torsional strength (99.5MPa) of the FRC implants at the expense of the flexural strength (602.0MPa). The flexural modulus was 15.3GPa. Two types of FRC intramedullary nails were prepared; first type was FRC as such, second type was FRC with a surface layer of bioactive glass (BG) granules. Experimental oblong subtrochanteric defect was created in 14 rabbits. The defect, which reduced the torsional strength of the bones by 66%, was fixed with an FRC intramedullary nail of either type. The contralateral intact femur served as the control. This model simulated surgical stabilization of bone metastasis. After 12 weeks of follow-up, the femurs were harvested and analyzed by torsional testing, micro-CT and hard tissue histology. Healed undisplaced peri-implant fractures were noticed in half of the animals irrespective of the type of FRC implant. Torsional testing showed no significant differences between the implantation groups. The torsional strength of the bones stabilized by either type of FRC implant was 83% of that of the contralateral femurs. In histological analysis, no implant debris and no adverse tissue reactions were observed. While the mechanical properties of the modified FRCs were suboptimal, the FRC intramedullary nails supported the femurs without structural failure, even in the cases of peri-implant fractures.

  8. Influence of fatigue testing and cementation mode on the load-bearing capability of bovine incisors restored with crowns and FRC posts.

    PubMed

    Nothdurft, Frank P; Schmitt, Thomas; Rupf, Stefan; Pospiech, Peter R

    2011-01-01

    The aim of the study was to evaluate the influence of fatigue and cementation mode on the fracture behaviour of endodontically treated bovine incisors restored with fiber-reinforced-composite (FRC) posts and crowns. Forty-eight endodontically treated incisors were restored with FRC posts, composite build-ups, and cast crowns. In 16 teeth, each of the posts were cemented conventionally with KetacCem (3M Espe) or adhesively with Panavia F (Kuraray) or RelyXUniCem (3M Espe). One-half of the specimens in each group were subjected to thermal cycling with 10,000 cycles at 5-55°C and mechanical aging, loading the specimens in 1,200,000 cycles with 50 N. Fracture resistance was determined by loading the specimens until fracture at an angle of 45°. The loading test showed that cementation mode and fatigue testing had an influence on the load bearing capability. Before fatigue testing no statistically significant differences between the different cementation modes could be detected. After fatigue testing, conventionally cemented FRC posts lead to statistically significant higher fracture loads compared to adhesively luted posts. Most specimens fractured in a favourable way, independent from the type of cementation.

  9. The role of heat treatment on microstructure and mechanical properties of Ti-13Zr-13Nb alloy for biomedical load bearing applications.

    PubMed

    Majumdar, P; Singh, S B; Chakraborty, M

    2011-10-01

    The suitability of heat treated Ti-13Zr-13Nb (TZN) alloy for biomedical load bearing applications has been investigated. Depending upon the heat treatment conditions, the microstructure of TZN alloy mainly consists of α, β or α" martensite phases. In general, for all the deformation and solution treatment temperatures the variation of the hardness and tensile strength with cooling rate is similar. The elastic modulus of TZN alloy decreases with an increase in cooling rate from the solution treatment temperature. Relatively fine α+β microstructure increases the hardness and tensile strength. The presence of martensite and/or retained β in the microstructure decreases the hardness and elastic modulus and increases the ductility substantially whereas higher amount of α phase in the matrix increases the elastic modulus. Decomposition of martensite and retained β into α phase during aging increases the hardness, elastic modulus and tensile strength and decreases the ductility. Among the samples studied, the aged TZN sample, which was deformed and solution treated at 800 °C followed by water quenching, is a promising candidate for the application as implant material.

  10. Influence of fatigue testing and cementation mode on the load-bearing capability of bovine incisors restored with crowns and zirconium dioxide posts.

    PubMed

    Nothdurft, F P; Schmitt, T; Motter, P J; Pospiech, P R

    2008-12-01

    The aim of the study was to evaluate the influence of fatigue and cementation mode on the fracture behavior of endodontically treated bovine incisors restored with zirconium dioxide posts and crowns. Forty-eight endodontically treated bovine primary incisors were restored with zirconium dioxide posts (Cerapost, Brasseler), composite build-ups, and crowns cast from a chromium cobalt alloy. In 16 teeth, each of the posts was cemented conventionally with KetacCem (3M ESPE) or adhesively with Panavia F (Kuraray) or RelyX UniCem (3M ESPE). One-half of the specimens in each group were subjected to thermocycling with 10,000 cycles at 5-55 degrees C and mechanical aging, loading the specimens at an angle of 45 degrees in 1,200,000 cycles with 50 N. Fracture resistance was determined by loading the specimens until fracture at an angle of 45 degrees to the long axis of the teeth. The loading test showed that neither cementation mode nor fatigue testing had an influence on the load bearing capability. Most specimens fractured in a favorable way, independent from the type of cementation.

  11. Silk coating on a bioactive ceramic scaffold for bone regeneration: effective enhancement of mechanical and in vitro osteogenic properties towards load-bearing applications.

    PubMed

    Li, Jiao Jiao; Roohani-Esfahani, Seyed-Iman; Kim, Kyungsook; Kaplan, David L; Zreiqat, Hala

    2017-06-01

    Bioactive ceramic scaffolds represent competitive choices for clinical bone reconstruction, but their widespread use is restricted by inherent brittleness and weak mechanical performance under load. This study reports the development of strong and tough bioactive scaffolds suitable for use in load-bearing bone reconstruction. A strong and bioactive ceramic scaffold (strontium-hardystonite-gahnite) is combined with single and multiple coating layers of silk fibroin to enhance its toughness, producing composite scaffolds which match the mechanical properties of cancellous bone and show enhanced capacity to promote in vitro osteogenesis. Also reported for the first time is a comparison of the coating effects obtained when a polymeric material is coated on ceramic scaffolds with differing microstructures, namely the strontium-hardystonite-gahnite scaffold with high-density struts as opposed to a conventional ceramic scaffold, such as biphasic calcium phosphate, with low-density struts. The results show that silk coating on a unique ceramic scaffold can lead to simple and effective enhancement of its mechanical and biological properties to suit a wider range of applications in clinical bone reconstruction, and also establish the influence of ceramic microstructure on the effectiveness of silk coating as a method of reinforcement when applied to different types of ceramic bone graft substitutes. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

  12. Use of passive scalar tagging for the study of coherent structures in the plane mixing layer

    NASA Technical Reports Server (NTRS)

    Ramaprian, B. R.; Sandham, N. D.; Mungal, M. G.; Reynolds, W. C.

    1988-01-01

    Data obtained from the numerical simulation of a 2-D mixing layer were used to study the feasibility of using the instantaneous concentration of a passive scalar for detecting the typical coherent structures in the flow. The study showed that this technique works quite satisfactorily and yields results similar to those that can be obtained by using the instantaneous vorticity for structure detection. Using the coherent events educed by the scalar conditioning technique, the contribution of the coherent events to the total turbulent momentum and scalar transport was estimated. It is found that the contribution from the typical coherent events is of the same order as that of the time-mean value. However, the individual contributions become very large during the pairing of these structures. The increase is particularly spectacular in the case of the Reynolds shear stress.

  13. Resorbable composites with bioresorbable glass fibers for load-bearing applications. In vitro degradation and degradation mechanism.

    PubMed

    Lehtonen, Timo J; Tuominen, Jukka U; Hiekkanen, Elina

    2013-01-01

    An in vitro degradation study of three bioresorbable glass fiber-reinforced poly(l-lactide-co-dl-lactide) (PLDLA) composites was carried out in simulated body fluid (SBF), to simulate body conditions, and deionized water, to evaluate the nature of the degradation products. The changes in mechanical and chemical properties were systematically characterized over 52 weeks dissolution time to determine the degradation mechanism and investigate strength retention by the bioresorbable glass fiber-reinforced PLDLA composite. The degradation mechanism was found to be a combination of surface and bulk erosion and does not follow the typical core-accelerated degradation mechanism of poly(α-hydroxyacids). Strength retention by bioresorbable glass fiber-reinforced PLDLA composites can be tailored by changing the oxide composition of the glass fibers, but the structure-property relationship of the glass fibers has to be understood and controlled so that the phenomenon of ion leaching can be utilized to control the degradation rate. Therefore, these high performance composites are likely to open up several new possibilities for utilizing resorbable materials in clinical applications which could not be realized in the past.

  14. Modeling and performance of two types of piston-like out-of-plane motion micromechanical structures

    NASA Astrophysics Data System (ADS)

    Lim, Si-Hyung; Horowitz, Roberto; Majumdar, Arunava

    2006-07-01

    We have modeled and analyzed the performance of two types of piston-like out-of-plane motion micromechanical structures: a conventional microstructure, which has a single bimorph region, and a flip-over-bimaterial (FOB) microstructure, which has two bimorph regions respectively located on the top and bottom sides of the structure. For both structures, simple analytical expressions of their end-point deflections have been established to facilitate parametric studies in sensor or actuator designs. These structures can be used in several applications such as temperature and chemical sensors, or as actuators for micromirrors. The derived analytical deflection predictions are in good agreement with those made using finite element (FE) models. For a micro-opto-mechanical sensor using interconnected FOB microstructures, these analytical and FE predictions agree with the experimental results within about 25%. Discrepancies can be attributed to uncertainties in the material properties of the specimen being tested. Both the analytically derived deflection expressions and the FE models predict that the FOB microstructures are capable of achieving up to two times higher deflection than conventional microstructures that have a single bimorph region. When compared to a cantilever design, a sensor design having interconnected FOB structures has a higher signal-to-noise ratio for the same device footprint. The analytical modeling and performance analysis presented in this paper can be useful to predict the device performance as well as optimize design parameters.

  15. In-plane current induced domain wall nucleation and its stochasticity in perpendicular magnetic anisotropy Hall cross structures

    NASA Astrophysics Data System (ADS)

    Sethi, P.; Murapaka, C.; Lim, G. J.; Lew, W. S.

    2015-11-01

    Hall cross structures in magnetic nanowires are commonly used for electrical detection of magnetization reversal in which a domain wall (DW) is conventionally nucleated by a local Oersted field. In this letter, we demonstrate DW nucleation in Co/Ni perpendicular magnetic anisotropy nanowire at the magnetic Hall cross junction. The DWs are nucleated by applying an in-plane pulsed current through the nanowire without the need of a local Oersted field. The change in Hall resistance, detected using anomalous Hall effect, is governed by the magnetic volume switched at the Hall junction, which can be tuned by varying the magnitude of the applied current density and pulse width. The nucleated DWs are driven simultaneously under the spin transfer torque effect when the applied current density is above a threshold. The possibility of multiple DW generation and variation in magnetic volume switched makes nucleation process stochastic in nature. The in-plane current induced stochastic nature of DW generation may find applications in random number generation.

  16. In-plane current induced domain wall nucleation and its stochasticity in perpendicular magnetic anisotropy Hall cross structures

    SciTech Connect

    Sethi, P.; Murapaka, C.; Lim, G. J.; Lew, W. S.

    2015-11-09

    Hall cross structures in magnetic nanowires are commonly used for electrical detection of magnetization reversal in which a domain wall (DW) is conventionally nucleated by a local Oersted field. In this letter, we demonstrate DW nucleation in Co/Ni perpendicular magnetic anisotropy nanowire at the magnetic Hall cross junction. The DWs are nucleated by applying an in-plane pulsed current through the nanowire without the need of a local Oersted field. The change in Hall resistance, detected using anomalous Hall effect, is governed by the magnetic volume switched at the Hall junction, which can be tuned by varying the magnitude of the applied current density and pulse width. The nucleated DWs are driven simultaneously under the spin transfer torque effect when the applied current density is above a threshold. The possibility of multiple DW generation and variation in magnetic volume switched makes nucleation process stochastic in nature. The in-plane current induced stochastic nature of DW generation may find applications in random number generation.

  17. Determination of three-dimensional structured objects, vascular structures, and imaging geometry from single-plane and biplane projection images

    NASA Astrophysics Data System (ADS)

    Nazareth, Daryl P.

    Three-dimensional (3D) vessel trees can provide useful visual and quantitative information during interventional procedures. To calculate the 3D vasculature and improve these measurements, we have developed methods for the determination of geometric parameters from single-plane and biplane projection images. Our single-plane technique provides an accurate estimation of the magnification and orientation of objects of known dimensions in vessels by comparing measurements in the images with those in simulated images of modeled objects. Our biplane technique calculates the transformation relating the imaging systems (i.e., the rotation matrix R and the translation vector t) and requires only the identification of approximately corresponding vessel regions in the two images. Initial estimates of R and t are refined using an optimization method. The objective function to be minimized is based on the amount of overlap of corresponding vessel regions in the two images. The 3D vasculature is then obtained from the optimal R and t using triangulation. The accuracy of the 3D vasculature calculations may be further improved when a calibration object, such as a stent, is present in the vasculature and the biplane images, if the required user-indicated points in the stent are highly accurate. We have modified the above biplane technique to incorporate information provided by the stent, by including three additional terms in the objective function. These techniques were evaluated using simulated and phantom images. The single-plane technique provided accuracies of 1% in magnification and 2 degrees in orientation. The biplane technique provided accuracies of 1% and 1 degree, respectively, which was reduced to 0.3% and 0.5 degrees in simulations when a calibration object was present. The results of the biplane technique applied to the phantom indicated that inaccuracies in user indication of the calibration object may propagate into the errors in the 3D vessel tree reconstruction

  18. Slicing the perovskite structure with crystallographic shear planes: the A(n)B(n)O(3n-2) homologous series.

    PubMed

    Abakumov, Artem M; Hadermann, Joke; Batuk, Maria; D'Hondt, Hans; Tyablikov, Oleg A; Rozova, Marina G; Pokholok, Konstantin V; Filimonov, Dmitry S; Sheptyakov, Denis V; Tsirlin, Alexander A; Niermann, Daniel; Hemberger, Joachim; Van Tendeloo, Gustaaf; Antipov, Evgeny V

    2010-10-18

    A new A(n)B(n)O(3n-2) homologous series of anion-deficient perovskites has been evidenced by preparation of the members with n = 5 (Pb(2.9)Ba(2.1)Fe(4)TiO(13)) and n = 6 (Pb(3.8)Bi(0.2)Ba(2)Fe(4.2)Ti(1.8)O(16)) in a single phase form. The crystal structures of these compounds were determined using a combination of transmission electron microscopy and X-ray and neutron powder diffraction (S.G. Ammm, a = 5.74313(7), b = 3.98402(4), c = 26.8378(4) Å, R(I) = 0.035, R(P) = 0.042 for Pb(2.9)Ba(2.1)Fe(4)TiO(13) and S.G. Imma, a = 5.7199(1), b = 3.97066(7), c = 32.5245(8) Å, R(I) = 0.032, R(P) = 0.037 for Pb(3.8)Bi(0.2)Ba(2)Fe(4.2)Ti(1.8)O(16)). The crystal structures of the A(n)B(n)O(3n-2) homologues are formed by slicing the perovskite structure with (101)(p) crystallographic shear (CS) planes. The shear planes remove a layer of oxygen atoms and displace the perovskite blocks with respect to each other by the 1/2[110](p) vector. The CS planes introduce edge-sharing connections of the transition metal-oxygen polyhedra at the interface between the perovskite blocks. This results in intrinsically frustrated magnetic couplings between the perovskite blocks due to a competition of the exchange interactions between the edge- and the corner-sharing metal-oxygen polyhedra. Despite the magnetic frustration, neutron powder diffraction and Mössbauer spectroscopy reveal that Pb(2.9)Ba(2.1)Fe(4)TiO(13) and Pb(3.8)Bi(0.2)Ba(2)Fe(4.2)Ti(1.8)O(16) are antiferromagnetically ordered below T(N) = 407 and 343 K, respectively. The Pb(2.9)Ba(2.1)Fe(4)TiO(13) and Pb(3.8)Bi(0.2)Ba(2)Fe(4.2)Ti(1.8)O(16) compounds are in a paraelectric state in the 5-300 K temperature range.

  19. Enabling technologies research and development structures. [for National Aerospace Plane Program

    NASA Technical Reports Server (NTRS)

    Davis, John G., Jr.; Murrow, Harold N.

    1989-01-01

    The technology-development areas of most critical importance to the definition of the NASP vehicle's airframe and integrated propulsion systems are discussed with a view to the progress made to date and the prospects for the expansion of a definitive NASP design data base on materials, structures, etc. It is necessary to achieve a very low structural-mass fraction, to withstand 6000 F radiation equilibrium fuselage nosecap temperatures, to manage an extensive active cooling network for both airframe and propulsion system capable of dissipating 10,000 BTU/sq ft-sec thermal fluxes, to maintain effective hot-gas sealing, and to manufacture high temperature effectiveness-retaining control surfaces. An account is given of successes thus far achieved.

  20. Scanning transmission X-ray microscopy study of the stretched magnetic-domain structure of Co/Pt multilayers under an in-plane field

    NASA Astrophysics Data System (ADS)

    Handoko, Djati; Quach, Duy-Truong; Lee, Sang-Hyuk; Shim, Je-Ho; Kim, Dong-Hyun; Lee, Kyung-Min; Jeong, Jong-Ryul; Kim, Namdong; Shin, Hyun-Joon

    2015-06-01

    We report our investigation on the magnetic-domain structure of a Co/Pt multilayer with perpendicular magnetic anisotropy under a horizontal in-plane field by using a high-resolution scanning transmission X-ray microscope (STXM) developed at Pohang Accelerator Laboratory. The ruggedshaped striped magnetic-domain structure that was initially formed under a field cycle along the out-of-the plane magnetic easy axis was found to be stretched and elongated along the direction of the horizontal in-plane field. As the in-plane field was strengthened, the striped pattern exhibited an anisotropic domain growth with further stretching and aligning, as well as with a modification of the magnetic-domain's width.

  1. Ab initio electronic structure of quasi-two-dimensional materials: A "native" Gaussian-plane wave approach.

    PubMed

    Trevisanutto, Paolo E; Vignale, Giovanni

    2016-05-28

    Ab initio electronic structure calculations of two-dimensional layered structures are typically performed using codes that were developed for three-dimensional structures, which are periodic in all three directions. The introduction of a periodicity in the third direction (perpendicular to the layer) is completely artificial and may lead in some cases to spurious results and to difficulties in treating the action of external fields. In this paper we develop a new approach, which is "native" to quasi-2D materials, making use of basis function that are periodic in the plane, but atomic-like in the perpendicular direction. We show how some of the basic tools of ab initio electronic structure theory - density functional theory, GW approximation and Bethe-Salpeter equation - are implemented in the new basis. We argue that the new approach will be preferable to the conventional one in treating the peculiarities of layered materials, including the long range of the unscreened Coulomb interaction in insulators, and the effects of strain, corrugations, and external fields.

  2. Compact Test Structure to Measure All Thermophysical Properties for the In-Plane Figure of Merit ZT of Thin Films

    NASA Astrophysics Data System (ADS)

    Moser, Dominik; Mueller, David; Paul, Oliver

    2016-11-01

    This paper reports a versatile thermophysical test structure to measure all material properties contributing to the in-plane thermoelectric figure of merit ZT=S^2Tκ ^{-1} ρ ^{-1} from a single thin film sample of only about 0.5 mm^2. These properties are the Seebeck coefficient S of the sample against aluminum (Al), its thermal conductivity κ , and its resistivity ρ. The thermal membrane-based test structure is produced using standard thin film deposition and structuring processes followed by silicon micromachining. It can be used to characterize thin films deposited at high temperature, such as doped polycrystalline silicon (poly-Si), as well as films deposited at low temperature, e.g., sputtered metals. We present the measurement of all components of the ZT of low-pressure, chemical vapor-deposited n- and p-doped poly-Si thin films in the temperature range from 300 K to 380 K. Values of 1.46 × 10-2 and 0.95 × 10-2 were found at room temperature (RT) for the ZT of n- and p-doped poly-Si films, respectively. Furthermore, the test structure was used to extract ρ and κ of a sputtered aluminum film in the same temperature range. The respective RT values are 48.7 × 10-9 Ω {m} and 154 W m-1 K-1.

  3. Magnetization reversal induced by in-plane current in Ta/CoFeB/MgO structures with perpendicular magnetic easy axis

    SciTech Connect

    Zhang, C.; Yamanouchi, M. Ikeda, S.; Sato, H.; Fukami, S.; Matsukura, F.; Ohno, H.

    2014-05-07

    We investigate in-plane current-induced magnetization reversal under an in-plane magnetic field in Hall bar shaped devices composed of Ta/CoFeB/MgO structures with perpendicular magnetic easy axis. The observed relationship between the directions of current and magnetization switching and Ta thickness dependence of magnetization switching current are accordance with those for magnetization reversal by spin transfer torque originated from the spin Hall effect in the Ta layer.

  4. Electronic structure of hole centers in CuO2 planes of cuprates

    NASA Astrophysics Data System (ADS)

    Moskvin, A. S.; Panov, Yu. D.

    2011-03-01

    A theoretical analysis and a large amount of experimental data indicate that the structure of the valence hole states in doped cuprates is more complicated than assumed in the simple Zhang-Rice singlet model. In fact, we are dealing with a competition between a hybrid Cu3d -O2pb1g∝dx2-y2-state and purely oxygen nonbonding states with a2g- and eux ,y∝px ,y-symmetries. Thus, as a cluster analog of a Cu3+ ion, the ground state of a non-Zhang-Rice CuO45- hole center of this sort should be described by complicated A1g1-B2g1,3-Eu1,3 multiplet with a set of charge, orbital, and spin order parameters, some of which are well known (e.g., spin moment or "ferromagnetic" Ising orbital momentum localized on oxygen ions) while others are unconventional or hidden (e.g., "antiferromagnetic" ordering of Ising orbital momenta localized on four oxygen atoms or a combined spin-orbital-quadrupole ordering). The non-Zhang-Rice CuO45- centers are actually singlet-triplet pseudo-Jahn-Teller centers with strong vibron coupling to the lattice. The complicated structure of the ground-state multiplet of the hole centers shows up in many of the unusual properties of doped cuprates, in particular, their pseudo-gap phase.

  5. Structural analysis of the 3C|4H boundaries formed on prismatic planes in 4H-SiC epitaxial films

    NASA Astrophysics Data System (ADS)

    Yamashita, T.; Matsuhata, H.; Naijo, T.; Momose, K.; Osawa, H.

    2016-12-01

    The boundaries between 3C and 4H-SiC domains on the prismatic planes of hexagonal lattices formed in a 4H-SiC epitaxial film were investigated using both transmission and scanning transmission electron microscopy. These observations determined that the boundaries have a periodic structure, in which each unit cell consists of 12 basal planes of the hexagonal lattice. Six Shockley partial dislocations are situated in each unit cell of the boundary structure. Burgers vectors and core structures of these partial dislocations are discussed.

  6. Low elastic modulus Ti-Ta alloys for load-bearing permanent implants: enhancing the biodegradation resistance by electrochemical surface engineering.

    PubMed

    Kesteven, Jazmin; Kannan, M Bobby; Walter, Rhys; Khakbaz, Hadis; Choe, Han-Choel

    2015-01-01

    In this study, the in vitro degradation behaviour of titanium-tantalum (Ti-Ta) alloys (10-30 wt.% Ta) was investigated and compared with conventional implant materials, i.e., commercially pure titanium (Cp-Ti) and titanium-aluminium-vanadium (Ti6Al4V) alloy. Among the three Ti-Ta alloys studied, the Ti20Ta (6.3×10(-4) mm/y) exhibited the lowest degradation rate, followed by Ti30Ta (1.2×10(-3) mm/y) and Ti10Ta (1.4×10(-3) mm/y). All the Ti-Ta alloys exhibited lower degradation rate than that of Cp-Ti (1.8×10(-3) mm/y), which suggests that Ta addition to Ti is beneficial. As compared to Ti6Al4V alloy (8.1×10(-4) mm/y), the degradation rate of Ti20Ta alloy was lower by ~22%. However, the Ti30Ta alloy, which has closer elastic modulus to that of natural bone, showed ~48% higher degradation rate than that of Ti6Al4V alloy. Hence, to improve the degradation performance of Ti30Ta alloy, an intermediate thin porous layer was formed electrochemically on the alloy followed by calcium phosphate (CaP) electrodeposition. The coated Ti30Ta alloy (3.8×10(-3) mm/y) showed ~53% lower degradation rate than that of Ti6Al4V alloy. Thus, the study suggests that CaP coated Ti30Ta alloy can be a viable material for load-bearing permanent implants.

  7. Mechanics, degradability, bioactivity, in vitro, and in vivo biocompatibility evaluation of poly(amino acid)/hydroxyapatite/calcium sulfate composite for potential load-bearing bone repair.

    PubMed

    Fan, Xiaoxia; Ren, Haohao; Luo, Xiaoman; Wang, Peng; Lv, Guoyu; Yuan, Huipin; Li, Hong; Yan, Yonggang

    2016-03-01

    A ternary composite of poly(amino acid), hydroxyapatite, and calcium sulfate (PAA/HA/CS) was prepared using in situ melting polycondensation method and evaluated in terms of mechanical strengths, in vitro degradability, bioactivity, as well as in vitro and in vivo biocompatibility. The results showed that the ternary composite exhibited a compressive strength of 147 MPa, a bending strength of 121 MPa, a tensile strength of 122 MPa, and a tensile modulus of 4.6 GPa. After immersion in simulated body fluid, the compressive strength of the composite decreased from 147 to 98 MPa for six weeks and the bending strength decreased from 121 to 75 MPa for eight weeks, and both of them kept stable in the following soaking period. The composite could be slowly degraded with 7.27 wt% loss of initial weight after soaking in phosphate buffered solution for three weeks when started to keep stable weight in the following days. The composite was soaked in simulated body fluid solution and the hydroxyapatite layer, as flower-like granules, formed on the surface of the composite samples, showing good bioactivity. Moreover, it was found that the composite could promote proliferation of MG-63 cells, and the cells with normal phenotype extended and spread well on the composite surface. The implantation of the composite into the ulna of sheep confirmed that the composite was biocompatible and osteoconductive in vivo, and offered the PAA/HA/CS composite promising material for load-bearing bone substitutes for clinical application. © The Author(s) 2015.

  8. Fabrication and characterization of titanium-matrix composite with 20 vol% hydroxyapatite for use as heavy load-bearing hard tissue replacement.

    PubMed

    Chu, Chenglin; Xue, Xiaoyan; Zhu, Jingchuan; Yin, Zhongda

    2006-03-01

    Titanium-matrix composite with 20 vol% HA ceramic was fabricated by hot pressing technique and the microstructure of the composite was studied by transmission electron microscope (TEM). The mechanical and biological properties of the composite were investigated by mechanical and in vivo studies. The experimental results by TEM observation show the bonding state of Ti/HA interface in Ti-20 vol% HA composite with the relative density of 97.86% is good, however, there exists an interfacial transition zone between Ti and HA. In Ti matrix of the composite and pure Ti metal, an interesting substructure comprised of screw dislocations with Burgers vectors b of 1/3 < 11 20> was found. Screw dislocations are straight and regularly distributed, and cross slip can be observed. The subgrain boundaries consist of dislocation network walls with equidistant dislocation lines in the same direction. Elastic modulus and Vicker's hardness of Ti-20 vol%HA composite are 102.6 GPa and 3.41 GPa respectively. Owing to the existence of 20 vol% HA ceramic, bending strength and fracture toughness of the composite decrease sharply to 170.1 MPa and 3.57 MPa.m(1/2) respectively, which are only about 17.5 and 12% of those of pure Ti metal. In vivo studies indicate Ti-20 vol% HA composite has good biocompatibility, and even better osteointegration ability than pure titanium, especially in the early stage after the implantation. In conclusion, Ti-20 vol% HA composite is suitable for heavy load-bearing hard tissue replacement from the point of view of both mechanical properties and biocompatibility.

  9. Axial load-bearing capacity of an osteochondral autograft stabilized with a resorbable osteoconductive bone cement compared with a press-fit graft in a bovine model.

    PubMed

    Kiss, Marc-Olivier; Levasseur, Annie; Petit, Yvan; Lavigne, Patrick

    2012-05-01

    Osteochondral autografts in mosaicplasty are inserted in a press-fit fashion, and hence, patients are kept nonweightbearing for up to 2 months after surgery to allow bone healing and prevent complications. Very little has been published regarding alternative fixation techniques of those grafts. Osteochondral autografts stabilized with a resorbable osteoconductive bone cement would have a greater load-bearing capacity than standard press-fit grafts. Controlled laboratory study. Biomechanical testing was conducted on 8 pairs of cadaveric bovine distal femurs. For the first 4 pairs, 6 single osteochondral autografts were inserted in a press-fit fashion on one femur. On the contralateral femur, 6 grafts were stabilized with a calcium triglyceride osteoconductive bone cement. For the 4 remaining pairs of femurs, 4 groups of 3 adjacent press-fit grafts were inserted on one femur, whereas on the contralateral femur, grafts were cemented. After a maturation period of 48 hours, axial loading was applied on all single grafts and on the middle graft of each 3-in-a-row series. For the single-graft configuration, median loads required to sink the press-fit and cemented grafts by 2 and 3 mm were 281.87 N versus 345.56 N (P = .015) and 336.29 N versus 454.08 N (P = .018), respectively. For the 3-in-a-row configuration, median loads required to sink the press-fit and cemented grafts by 2 and 3 mm were 260.31 N versus 353.47 N (P = .035) and 384.83 N versus 455.68 N (P = .029), respectively. Fixation of osteochondral grafts using bone cement appears to improve immediate stability over the original mosaicplasty technique for both single- and multiple-graft configurations. Achieving greater primary stability of osteochondral grafts could potentially accelerate postoperative recovery, allowing early weightbearing and physical therapy.

  10. Improved performance of HgCdTe infrared detector focal plane arrays by modulating light field based on photonic crystal structure

    SciTech Connect

    Liang, Jian; Hu, Weida Ye, Zhenhua; Li, Zhifeng; Chen, Xiaoshuang Lu, Wei; Liao, Lei

    2014-05-14

    An HgCdTe long-wavelength infrared focal plane array photodetector is proposed by modulating light distributions based on the photonic crystal. It is shown that a promising prospect of improving performance is better light harvest and dark current limitation. To optimize the photon field distributions of the HgCdTe-based photonic crystal structure, a numerical method is built by combining the finite-element modeling and the finite-difference time-domain simulation. The optical and electrical characteristics of designed HgCdTe mid-wavelength and long-wavelength photon-trapping infrared detector focal plane arrays are obtained numerically. The results indicate that the photon crystal structure, which is entirely compatible with the large infrared focal plane arrays, can significantly reduce the dark current without degrading the quantum efficiency compared to the regular mesa or planar structure.

  11. Off-easy-plane antiferromagnetic spin canting in coupled FePt/NiO bilayer structure with perpendicular exchange bias

    NASA Astrophysics Data System (ADS)

    Gao, Tenghua; Itokawa, Nobuhide; Wang, Jian; Yu, Youxing; Harumoto, Takashi; Nakamura, Yoshio; Shi, Ji

    2016-08-01

    We report on the investigation of perpendicular exchange bias in FePt (001 ) /NiO (1 ¯1 ¯1 ) orthogonal exchange couple with FePt partially L 10 ordered. From initial magnetization curve measurement and magnetic domain imaging, we find that, for the as-grown bilayer structure, the FePt layer experiences a small-angle magnetization rotation when it is magnetized near to saturation in film normal direction. After field cooling, the bilayer structure shows a significant enhancement of perpendicular magnetic anisotropy, indicating the field mediated coupling between the spins across the FePt/NiO interface. According to Koon's theoretical calculation on the basis of lowest energy ferromagnetic/antiferromagnetic coupling configuration for compensated spins at antiferromagnetic side, we consider slightly slanted Ni spins at the interface off the (1 ¯1 ¯1 ) easy plane can stabilize the spin coupling between FePt and NiO and result in the observed exchange bias in this paper. This consideration was further confirmed by stripe domain width calculation.

  12. The vertical photoconductor: A novel device structure suitable for HgCdTe two-dimensional infrared focal plane arrays

    NASA Astrophysics Data System (ADS)

    Siliquini, J. F.; Faraone, L.

    1997-06-01

    A novel photoconductive device structure is proposed and described that has been designed specifically as a sensing element for high density two-dimensional infrared focal plane array (IRFPA) applications. Although the design concept can be applied to a variety of epitaxially grown HgCdTe material, optimum performance can be achieved using n-type HgCdTe semiconductor material consisting of epitaxially grown heterostructure layers in which a two-dimensional mosaic of vertical design photoconductors are fabricated. The heterostructure layers provide high performance devices at greatly reduced power dissipation levels, while the vertical design allows for the high density integration of photoconductors in a two-dimensional array geometry with high fill factor. The salient feature of the proposed device structure is that the bias field is applied in the vertical direction such that it is parallel to the impinging infrared radiation. A comprehensive one-dimensional model is presented for the vertical design photoconductor, which is subsequently used to determine the optimum design parameters in order to achieve maximum responsivity at the lowest possible power dissipation level. It is found that the proposed device structure has the potential to be used in the fabrication of long wavelength IRFPAs approaching 10 6 pixels using 25 × 25 μm 2 detector elements. Furthermore, this is achieved with individual device detectivities that are background limited and for a total array power dissipation of less than 0.1 W using a pulsed biasing scheme. Performance issues such as response uniformity, pixel yield, fill factor, crosstalk, power dissipation, detector impedance, array architecture, and maximum array size are discussed in relation to the suitability of the proposed vertical photoconductor structure for use in IRFPA modules. When considering IRFPA operability, it is found that in many cases the proposed technology has the potential to deliver significant advantages, such

  13. Accessible length scale of the in-plane structure in polarized neutron off-specular and grazing-incidence small-angle scattering measurements

    NASA Astrophysics Data System (ADS)

    Maruyama, R.; Bigault, T.; Wildes, A. R.; Dewhurst, C. D.; Saerbeck, T.; Honecker, D.; Yamazaki, D.; Soyama, K.; Courtois, P.

    2017-06-01

    Polarized neutron off-specular and grazing-incidence small-angle scattering measurements are useful methods to investigate the in-plane structure and its correlation of layered systems. Although these measurements give information on complementary and overlapping length scale, the different characteristics between them need to be taken into account when performed. In this study, the difference in the accessible length scale of the in-plane structure, which is one of the most important characteristics, was discussed using an Fe/Si multilayer together with simulations based on the distorted wave Born approximation.

  14. Determination of the effect of initial inner-core structure on tropical cyclone intensification and track on a beta plane

    NASA Astrophysics Data System (ADS)

    Chen, Guanghua

    2016-08-01

    The sensitivity of TC intensification and track to the initial inner-core structure on a β plane is investigated using a numerical model. The results show that the vortex with large inner-core winds (CVEX-EXP) experiences an earlier intensification than that with small inner-core winds (CCAVE-EXP), but they have nearly the same intensification rate after spin-up. In the early stage, the convective cells associated with surface heat flux are mainly confined within the inner-core region in CVEX-EXP, whereas the vortex in CCAVE-EXP exhibits a considerably asymmetric structure with most of the convective vortices being initiated to the northeast in the outer-core region due to the β effect. The large inner-core inertial stability in CVEX-EXP can prompt a high efficiency in the conversion from convective heating to kinetic energy. In addition, much stronger straining deformation and PBL imbalance in the inner-core region outside the primary eyewall ensue during the initial development stage in CVEX-EXP than in CCAVE-EXP, which is conducive to the rapid axisymmetrization and early intensification in CVEX-EXP. The TC track in CVEX-EXP sustains a northwestward displacement throughout the integration, whereas the TC in CCAVE-EXP undergoes a northeastward recurvature when the asymmetric structure is dominant. Due to the enhanced asymmetric convection to the northeast of the TC center in CCAVE-EXP, a pair of secondary gyres embedded within the large-scale primary β gyres forms, which modulates the ventilation flow and thus steers the TC to move northeastward.

  15. Dual Character of the Electronic Structure of YBa2Cu4O8: The Conduction Bands of CuO2 Planes and CuO Chains

    NASA Astrophysics Data System (ADS)

    Kondo, T.; Khasanov, R.; Karpinski, J.; Kazakov, S. M.; Zhigadlo, N. D.; Ohta, T.; Fretwell, H. M.; Palczewski, A. D.; Koll, J. D.; Mesot, J.; Rotenberg, E.; Keller, H.; Kaminski, A.

    2007-04-01

    We use microprobe angle-resolved photoemission spectroscopy (μARPES) to separately investigate the electronic properties of CuO2 planes and CuO chains in the high temperature superconductor, YBa2Cu4O8. For the CuO2 planes, a two-dimensional (2D) electronic structure is observed and, in contrast to Bi2Sr2CaCu2O8+δ, the bilayer splitting is almost isotropic and 50% larger, which strongly suggests that bilayer splitting has no direct effect on the superconducting properties. In addition, the scattering rate for the bonding band is about 1.5 times stronger than the antibonding band and is independent of momentum. For the CuO chains, the electronic structure is quasi-one-dimensional and consists of a conduction and insulating band. Finally, we find that the conduction electrons are well confined within the planes and chains with a nontrivial hybridization.

  16. Liquid crystal-gated-organic field-effect transistors with in-plane drain-source-gate electrode structure.

    PubMed

    Seo, Jooyeok; Nam, Sungho; Jeong, Jaehoon; Lee, Chulyeon; Kim, Hwajeong; Kim, Youngkyoo

    2015-01-14

    We report planar liquid crystal-gated-organic field-effect transistors (LC-g-OFETs) with a simple in-plane drain-source-gate electrode structure, which can be cost-effectively prepared by typical photolithography/etching processes. The LC-g-OFET devices were fabricated by forming the LC layer (4-cyano-4'-pentylbiphenyl, 5CB) on top of the channel layer (poly(3-hexylthiophene), P3HT) that was spin-coated on the patterned indium-tin oxide (ITO)-coated glass substrates. The LC-g-OFET devices showed p-type transistor characteristics, while a current saturation behavior in the output curves was achieved for the 50-150 nm-thick P3HT (channel) layers. A prospective on/off ratio (>1 × 10(3)) was obtained regardless of the P3HT thickness, whereas the resulting hole mobility (0.5-1.1 cm(2)/(V s)) at a linear regime was dependent on the P3HT thickness. The tilted ordering of 5CB at the LC-P3HT interfaces, which is induced by the gate electric field, has been proposed as a core point of working mechanism for the present LC-g-OFETs.

  17. 4H-SiC(0001) Basal Plane Stability during the Growth of Epitaxial Graphene on Inverted-Mesa Structures

    NASA Astrophysics Data System (ADS)

    Ushio, Shoji; Kutsuma, Yasunori; Yoshii, Arata; Tamai, Naoto; Ohtani, Noboru; Kaneko, Tadaaki

    2011-07-01

    The epitaxial graphene growth at the 4H-SiC(0001) surface with intentionally inserted step-free basal plane regions was performed by high temperature annealing in the range of 1600-1900 °C under ultrahigh vacuum. For fabricating inverted-mesa structures with the step-free regions at SiC surfaces, a combined process consisting of a direct laser digging and a Si-vapor etching at 1900 °C was utilized. The graphitized surfaces were characterized by atomic force microscopy, low acceleration voltage (0.1-1.0 kV) scanning electron microscopy and Raman spectroscopy. It was found that the graphene thickness at the SiC step-free surface tends to be suppressed compared with the thickness at background SiC step-terrace surfaces where the steps are intrinsically introduced from intentional/unintentional substrate miscut angles. From the characterization by Raman mapping, 1 ML graphene was obtained at the SiC step-free surface at 1600 °C graphitization in contrast to the case that multilayer graphene was grown at SiC step-terrace surfaces.

  18. Multilayer out-of-plane overlap electrostatic energy harvesting structure actuated by blood pressure for powering intra-cardiac implants

    NASA Astrophysics Data System (ADS)

    Deterre, M.; Risquez, S.; Bouthaud, B.; Dal Molin, R.; Woytasik, M.; Lefeuvre, E.

    2013-12-01

    We present an innovative multilayer out-of-plane electrostatic energy harvesting device conceived in view of scavenging energy from regular blood pressure in the heart. This concept involves the use of a deformable packaging for the implant in order to transmit the blood pressure to the electrostatic transducer. As shown in previous work, this is possible by using thin metal micro-bellows structure, providing long term hermeticity and high flexibility. The design of the electrostatic device has overcome several challenges such as the very low frequency of the mechanical excitation (1 to 2 Hz) and the small available room in the medical implant. Analytical and numerical models have been used to maximize the capacitance variation, and hence to optimize the energy conversion. We have theoretically shown that a 25-layer transducer with 6-mm diameter and 1-mm thickness could harvest at least 20 mJ per heart beat in the left ventricle under a maximum voltage of 75 V. These results show that the proposed concept is promising and could power the next generation of leadless pacemakers.

  19. Trade-offs and difficulties of the vertical photoconductor: a novel device structure suitable for HgCdTe two-dimensional infrared focal plane arrays

    NASA Astrophysics Data System (ADS)

    Bhan, R. K.; Dhar, V.; Mittal, Vandana

    1999-10-01

    Recently Siliquini and Faraone [J.F. Siliquini, L. Faraone, Infrared Phys. Technol. 38 (1997) 205] have proposed vertical photoconductive device (PC) based two-dimensional long wavelength infrared region focal plane arrays (LWIR FPAs). In this note, we examine some trade-offs and difficulties of this proposed structure.

  20. Structure and switching of in-plane ferroelectric nano-domains in strained Pb(x)Sr(1-x)TiO(3) thin films

    NASA Astrophysics Data System (ADS)

    Matzen, Sylvia; Nesterov, Oleksiy; Rispens, Gijsbert; Heuver, Jeroen; Noheda, Beatriz; Biegalski, Michael; Christen, Hans

    2014-03-01

    Understanding and controlling domain formation in nanoscale ferroelectrics is interesting from a fundamental point of view and of great technological importance. Increasing miniaturization allows creating complex domain structures, offering novel functionalities that could be particularly useful for the development of nanoelectronic devices. While most studies in thin films focus on domain patterns with up/down polarization for ferroelectric memories, domain structures with purely in-plane polarization have not been much investigated. However, such structures are potentially useful in optical devices or to avoid depolarization fields in ultra-thin films, as long as the domains can be addressed and switched. We use a combination of compositional substitutions and epitaxial growth on a substrate in order to tune the domain configuration. The substitution of Pb by Sr in PbxSr1-xTiO3 thin films grown epitaxially on (110)-DyScO3, stabilizes a domain structure with purely in-plane polarization. In this work, we show that it is possible to stabilize and control a complex domain architecture at two different length scales, yielding periodic ferroelectric nano-domains with purely in-plane polarization. Most importantly, these in-plane domains can be switched by a scanning probe.

  1. Domain structure and in-plane switching in a highly strained Bi0.9Sm0.1FeO3 film

    NASA Astrophysics Data System (ADS)

    Chen, Weigang; Ren, Wei; You, Lu; Yang, Yurong; Chen, Zuhuang; Qi, Yajun; Zou, Xi; Wang, Junling; Sritharan, Thirumany; Yang, Ping; Bellaiche, L.; Chen, Lang

    2011-11-01

    We report the domain structure and ferroelectric properties of a 32 nm-thick Bi0.9Sm0.1FeO3 film epitaxially grown on a LaAlO3 (LAO) substrate. This film exhibits a monoclinic Mc phase, with its monoclinic distortion and anisotropy of in-plane (IP) lattice parameters being both smaller than those of pure BiFeO3 (BFO) grown on LaAlO3. Polarization hysteresis loops measured using a quasi-planar capacitor show an in-plane polarization up to 30 μC/cm2. Piezoresponse force microcopy demonstrates that a 180° in-plane polarization switching accompanied by a 90° domain wall rotation takes place after electric poling. First-principles calculations suggest the differences between highly strained Sm-substituted and pure BiFeO3.

  2. Plane wave density functional theory studies of the structural and the electronic properties of amino acids attached to graphene oxide via peptide bonding

    NASA Astrophysics Data System (ADS)

    Min, Byeong June; Jeong, Hae Kyung; Lee, ChangWoo

    2015-08-01

    We studied via plane wave pseudopotential total-energy calculations within the local spin density approximation (LSDA) the electronic and the structural properties of amino acids (alanine, glycine, and histidine) attached to graphene oxide (GO) by peptide bonding. The HOMO-LUMO gap, the Hirshfeld charges, and the equilibrium geometrical structures exhibit distinctive variations that depend on the species of the attached amino acid. The GO-amino acid system appears to be a good candidate for a biosensor.

  3. In-plane structural order of domain engineered La0.7Sr0.3MnO3 thin films

    NASA Astrophysics Data System (ADS)

    Boschker, J. E.; Monsen, Å. F.; Nord, M.; Mathieu, R.; Grepstad, J. K.; Holmestad, R.; Wahlström, E.; Tybell, T.

    2013-05-01

    We present a detailed structural study of tensile-strained La0.7Sr0.3MnO3 thin films. We use the substrate miscut to control the number of rhombohedral variants in the films and study the in-plane order and structural distortions. Using high-resolution X-ray diffraction, we demonstrate that step-edge induced lattice modulations occur in 4-variant films, whereas periodic twinning is the dominant in-plane order for 2-variant films. We show that the in-plane twinning angle is almost completely relaxed. However, the relaxation of shear strain by the out-of-plane twinning angle and the monoclinic distortion is only partial. Furthermore, the film thickness dependence of the domain width reveals that domain formation is a universal mechanism for shear strain relaxation. Finally, we show that the structural response to the transition from the paramagnetic to the ferromagnetic phase of La0.7Sr0.3MnO3 at 345 K is smaller in 4-variant films compared to 2-variant films.

  4. Vibration and acoustic properties of honeycomb sandwich structures subject to variable incident plane-wave angle pressure loads

    NASA Astrophysics Data System (ADS)

    Yan, Jiaxue

    Honeycomb structures are widely used in many areas for their material characteristics such as high strength-to-weight ratio, stiffness-to-weight, sound transmission, and other properties. Honeycomb structures are generally constructed from periodically spaced tessellations of unit cells. It can be shown that the effective stiffness and mass properties of honeycomb are controlled by the local geometry and wall thickness of the particular unit cells used. Of particular interest are regular hexagonal (6-sided) honeycomb unit cell geometries which exhibit positive effective Poisson's ratio, and modified 6-sided auxetic honeycomb unit cells with Poisson's ratio which is effectively negative; a property not found in natural materials. One important honeycomb meta-structure is sandwich composites designed with a honeycomb core bonded between two panel layers. By changing the geometry of the repetitive unit cell, and overall depth and material properties of the honeycomb core, sandwich panels with different vibration and acoustic properties can be designed to shift resonant frequencies and improve intensity and Sound Transmission Loss (STL). In the present work, a honeycomb finite element model based on beam elements is programmed in MATLAB and verified with the commercial finite element software ABAQUS for frequency extraction and direct frequency response analysis. The MATLAB program was used to study the vibration and acoustic properties of different kinds of honeycomb sandwich panels undergoing in-plane loading with different incident pressure wave angles and frequency. Results for the root mean square intensity IRMS based on normal velocity on the transmitted side of the panel measure vibration magnitude are reported for frequencies between 0 and 1000 Hz. The relationship between the sound transmission loss computed with ABAQUS and the inverse of the intensity of surface velocity is established. In the present work it is demonstrated that the general trend between the

  5. Fermions on the low-buckled honey-comb structured lattice plane and classical Casimir-Polder force

    NASA Astrophysics Data System (ADS)

    Goswami, Partha

    2016-05-01

    We start with the well-known expression for the vacuum polarization and suitably modify it for 2+1-dimensional spin-orbit coupled (SOC) fermions on the low-buckled honey-comb structured lattice plane described by the low-energy Liu-Yao-Feng-Ezawa (LYFE) model Hamiltonian involving the Dirac matrices in the chiral representation obeying the Clifford algebra. The silicene and germanene fit this description suitably. They have the Dirac cones similar to those of graphene and SOC is much stronger. The system could be normal or ferromagnetic in nature. The silicene turns into the latter type if there is exchange field arising due to the proximity coupling to a ferromagnet (FM) such as depositing Fe atoms to the silicene surface. For the silicene, we find that the many-body effects considerably change the bare Coulomb potential by way of the dependence of the Coulomb propagator on the real-spin, iso-spin and the potential due to an electric field applied perpendicular to the silicene plane. The computation aspect of the Casimir-Polder force (CPF) needs to be investigated in this paper. An important quantity in this process is the dielectric response function (DRF) of the material. The plasmon branch was obtained by finding the zeros of DRF in the long-wavelength limit. This leads to the plasmon frequencies. We find that the collective charge excitations at zero doping, i.e., intrinsic plasmons, in this system, are absent in the Dirac limit. The valley-spin-split intrinsic plasmons, however, come into being in the case of the massive Dirac particles with characteristic frequency close to 10 THz. Our scheme to calculate the Casimir-Polder interaction (CPI) of a micro-particle with a sheet involves replacing the dielectric constant of the sample in the CPI expression obtained on the basis of the Lifshitz theory by the static DRF obtained using the expressions for the polarization function we started with. Though the approach replaces a macroscopic constant by a microscopic

  6. System and method of designing a load bearing layer that interfaces to a structural pass-through of an inflatable vessel

    NASA Technical Reports Server (NTRS)

    Spexarth, Gary R. (Inventor)

    2010-01-01

    A method for determining a design of an inflatable module including a rigid member disposed in a restraint layer, wherein the restraint layer includes orthogonal straps, includes modeling a strap adjacent to the rigid member and a strap connected to the rigid member. The adjacent strap and the member strap extend in a first direction. The method further includes selecting a first length of the member strap such that the adjacent strap carries load before the member strap during pressurization of the inflatable module, modeling tensions in the member strap with the first length and the adjacent strap during pressurization of the inflatable model, and outputting the modeled tensions in the member strap with the first length and the adjacent strap. An inflatable module includes a member strap having a length such that an adjacent strap carries load before the member strap during pressurization of the inflatable module.

  7. Plane Jane(s).

    ERIC Educational Resources Information Center

    Greenman, Geri

    2001-01-01

    Describes an assignment that was used in an advanced drawing class in which the students created self-portraits, breaking up their images using planes and angles to suggest their bone structure. Explains that the students also had to include three realistic portions in their drawings. (CMK)

  8. Enhanced plane wave expansion analysis for the band structure of bulk modes in two-dimensional high-contrast solid-solid phononic crystals

    NASA Astrophysics Data System (ADS)

    Baboly, Mohammadhosein Ghasemi; Soliman, Yasser; Su, Mehmet F.; Reinke, Charles M.; Leseman, Zayd C.; El-Kady, Ihab

    2014-11-01

    Plane wave expansion analyses that use the inverse rule to obtain the Fourier coefficients of the elastic tensor instead of the more conventional Laurent's rule, exhibit faster convergence rates for solid-solid phononic crystals. In this work, the band structure convergence of calculations using the inverse rule is investigated and applied to the case of high acoustic impedance contrast solid-solid phononic crystals, previously known for convergence difficulties. Results are contrasted to those obtained with the conventional plane wave expansion method. The inverse rule is found to converge at a much rate for all ranges of impedance contrast, and the ratio between the computational times needed to obtain a convergent band structure for a high-contrast solid-solid phononic crystal with the conventional plane wave expansion method using 1369 reciprocal lattice vectors is as large as 6800:1. This ratio decreases for material sets with lower impedance contrast; however, the inverse rule is still faster for a given error threshold for even the lowest impedance contrast phononic crystals reported in the literature. This convergence enhancement is a major factor in reconsidering the plane wave expansion method as an important tool in obtaining propagating elastic modes in phononic crystals.

  9. Axial Plane Optical Microscopy

    PubMed Central

    Li, Tongcang; Ota, Sadao; Kim, Jeongmin; Wong, Zi Jing; Wang, Yuan; Yin, Xiaobo; Zhang, Xiang

    2014-01-01

    We present axial plane optical microscopy (APOM) that can, in contrast to conventional microscopy, directly image a sample's cross-section parallel to the optical axis of an objective lens without scanning. APOM combined with conventional microscopy simultaneously provides two orthogonal images of a 3D sample. More importantly, APOM uses only a single lens near the sample to achieve selective-plane illumination microscopy, as we demonstrated by three-dimensional (3D) imaging of fluorescent pollens and brain slices. This technique allows fast, high-contrast, and convenient 3D imaging of structures that are hundreds of microns beneath the surfaces of large biological tissues. PMID:25434770

  10. THE CANADA-FRANCE ECLIPTIC PLANE SURVEY-FULL DATA RELEASE: THE ORBITAL STRUCTURE OF THE KUIPER BELT

    SciTech Connect

    Petit, J.-M.; Rousselot, P.; Mousis, O.; Kavelaars, J. J.; Gladman, B. J.; Jones, R. L.; Van Laerhoven, C.; Parker, J. Wm.; Bieryla, A.; Nicholson, P.; Mars, G.; Marsden, B.; Ashby, M. L. N.; Taylor, M.; Bernabeu, G.; Benavidez, P.; Campo Bagatin, A.

    2011-10-15

    We report the orbital distribution of the trans-Neptunian objects (TNOs) discovered during the Canada-France Ecliptic Plane Survey (CFEPS), whose discovery phase ran from early 2003 until early 2007. The follow-up observations started just after the first discoveries and extended until late 2009. We obtained characterized observations of 321 deg{sup 2} of sky to depths in the range g {approx} 23.5-24.4 AB mag. We provide a database of 169 TNOs with high-precision dynamical classification and known discovery efficiency. Using this database, we find that the classical belt is a complex region with sub-structures that go beyond the usual splitting of inner (interior to 3:2 mean-motion resonance [MMR]), main (between 3:2 and 2:1 MMR), and outer (exterior to 2:1 MMR). The main classical belt (a = 40-47 AU) needs to be modeled with at least three components: the 'hot' component with a wide inclination distribution and two 'cold' components (stirred and kernel) with much narrower inclination distributions. The hot component must have a significantly shallower absolute magnitude (H{sub g} ) distribution than the other two components. With 95% confidence, there are 8000{sup +1800}{sub -1600} objects in the main belt with H{sub g} {<=} 8.0, of which 50% are from the hot component, 40% from the stirred component, and 10% from the kernel; the hot component's fraction drops rapidly with increasing H{sub g} . Because of this, the apparent population fractions depend on the depth and ecliptic latitude of a trans-Neptunian survey. The stirred and kernel components are limited to only a portion of the main belt, while we find that the hot component is consistent with a smooth extension throughout the inner, main, and outer regions of the classical belt; in fact, the inner and outer belts are consistent with containing only hot-component objects. The H{sub g} {<=} 8.0 TNO population estimates are 400 for the inner belt and 10,000 for the outer belt to within a factor of two (95

  11. A theoretical study of the local electronic structure of two adjacent CuOplanes in YBa 2Cu 3O 7

    NASA Astrophysics Data System (ADS)

    Suter, H. U.; Stoll, E. P.; Hüsser, P.; Schafroth, S.; Meier, P. F.

    1997-08-01

    To reveal the local electronic structure of the two adjacent CuOplanes in YBa 2Cu 3O 7, ab initio studies on a small cluster (Cu 2Y 4O 8) were performed. Electron correlation was investigated with both density functional theory and Møller-Plesset theory. The ionisation energies, electron affinities adn the singlet-triplet differences are discussed with respect to model Hamiltonians of high-T c compounds.

  12. A combined three-dimensional finite element and scattering matrix method for the analysis of plane wave diffraction by bi-periodic, multilayered structures

    SciTech Connect

    Dossou, Kokou B.; Botten, Lindsay C.

    2012-08-15

    A three-dimensional finite element method (FEM) for the analysis of plane wave diffraction by a bi-periodic slab is described and implemented. A scattering matrix formalism based on the FEM allows the efficient treatment of light reflection and transmission by multilayer bi-periodic structures, and the computation of Bloch modes of three-dimensional arrays. Numerical simulations, which show the accuracy and flexibility of the FEM, are presented.

  13. The Camel Rhinarium: A Study Revealing the Presence of the Nasal Plane in Dromedary Camel (Camelus dromedarius), with Special Reference to Its Epidermal Structure.

    PubMed

    Eshrah, E A

    2017-02-01

    The aim of this study was to prove that the nasal plane (Planum nasale) present in camel (Camelus dromedarius). Furthermore, it was the first description of the gross and primary microscopic anatomy as well as the epidermal ultrastructure of the camel nasal plane. Grossly, the camel rhinarium was formed of the glabrous grayish-black skin that extended to cover the philtrum and the medial nasal angles. It was composed of two perinasal parts and an inter-labial part. A shallow groove was passed across its middle. A dermatoglyphic pattern of epidermal ridges with primary and secondary fissures in between was revealed by scanning electron microscopy. The nasal plane was very small in relation to the camel head size. In general, the morphological appearance of the camel rhinarium was greatly similar to that of the proboscis-bearing mammals. The basic histological structure as well as the epidermal ultrastructure of the camel nasal plane was observed to resemble very closely the common type. Few differences were found, including indistinct or absent hypodermal layer, thinner stratum corneum and some basal cells have unusual sinuous bases. © 2016 Blackwell Verlag GmbH.

  14. Futurepath: The Story of Research and Technology at NASA Lewis Research Center. Structures for Flight Propulsion, ARC Sprayed Monotape, National Aero-Space Plane

    NASA Technical Reports Server (NTRS)

    1989-01-01

    The story of research and technology at NASA Lewis Research Center's Structures Division is presented. The job and designs of the Structures Division needed for flight propulsion is described including structural mechanics, structural dynamics, fatigue, and fracture. The video briefly explains why properties of metals used in structural mechanics need to be tested. Examples of tests and simulations used in structural dynamics (bodies in motion) are briefly described. Destructive and non-destructive fatigue/fracture analysis is also described. The arc sprayed monotape (a composite material) is explained, as are the programs in which monotape plays a roll. Finally, the National Aero-Space Plane (NASP or x-30) is introduced, including the material development and metal matrix as well as how NASP will reduce costs for NASA.

  15. Continuum dynamics of the formation, migration and dissociation of self-locked dislocation structures on parallel slip planes

    NASA Astrophysics Data System (ADS)

    Zhu, Yichao; Niu, Xiaohua; Xiang, Yang

    2016-11-01

    In continuum models of dislocations, proper formulations of short-range elastic interactions of dislocations are crucial for capturing various types of dislocation patterns formed in crystalline materials. In this article, the continuum dynamics of straight dislocations distributed on two parallel slip planes is modelled through upscaling the underlying discrete dislocation dynamics. Two continuum velocity field quantities are introduced to facilitate the discrete-to-continuum transition. The first one is the local migration velocity of dislocation ensembles which is found fully independent of the short-range dislocation correlations. The second one is the decoupling velocity of dislocation pairs controlled by a threshold stress value, which is proposed to be the effective flow stress for single slip systems. Compared to the almost ubiquitously adopted Taylor relationship, the derived flow stress formula exhibits two features that are more consistent with the underlying discrete dislocation dynamics: (i) the flow stress increases with the in-plane component of the dislocation density only up to a certain value, hence the derived formula admits a minimum inter-dislocation distance within slip planes; (ii) the flow stress smoothly transits to zero when all dislocations become geometrically necessary dislocations. A regime under which inhomogeneities in dislocation density grow is identified, and is further validated through comparison with discrete dislocation dynamical simulation results. Based on the findings in this article and in our previous works, a general strategy for incorporating short-range dislocation correlations into continuum models of dislocations is proposed.

  16. Analysis of the Structure of the Torso in the Frontal Plane in Girls with Rett Syndrome Taking into Account Their Functional Status.

    PubMed

    Małachowska-Sobieska, Monika; Barczyk-Pawelec, Katarzyna; Marcmiszyn, Zuzanna; Demczuk-Włodarczyk, Ewa; Skolimowska, Beata; Maćków, Anna; Miler, Agnieszka

    2016-03-23

    Rett syndrome is a rare developmental disorder with a genetic background, and scoliosis is one of its many complications. The aim of the present study was to assess the structure of the torso in the frontal plane in RTT. It was assumed that asymmetry of the structure of the torso in the frontal plane would be smaller in girls who are able to maintain a vertical body position. The study included 14 girls previously diagnosed with RTT aged between 3 and 15 years, who were divided into 2 groups. Group 1 comprised 5 girls who were not able to maintain a vertical position. Group 2 comprised 9 girls who were able to maintain a vertical position. Body mass and weight were measured with an electronic scales and a height measuring device. The Body Mass Index was calculated. Photogrammetry was used to assess the structure of the torso in the frontal plane. The study results were subjected to a statistical analysis involving the calculation of the arithmetic mean (x), standard deviation (sd), coefficient of variation (v%) and significance of differences (p). Left-sided asymmetries were most common in both groups. All angles and linear values were higher in Group 1. 80% of the subjects in Group 1 demonstrated significant asymmetry of the pelvic tilt angle (PTA). There were no statistically significant differences between Group 1 and 2 regarding all study indices. 1. The study demonstrated that asymmetry of the torso in the frontal plane was common in the girls with RTT. 2. Torso asymmetry was more pronounced in girls with a poorer functional status. 3. Analysis of BMI values demonstrated a poor nutritional status of the girls.

  17. Magnon-driven longitudinal spin Seebeck effect in F | N and N | F | N structures: Role of asymmetric in-plane magnetic anisotropy

    NASA Astrophysics Data System (ADS)

    Chotorlishvili, L.; Toklikishvili, Z.; Etesami, S. R.; Dugaev, V. K.; Barnaś, J.; Berakdar, J.

    2015-12-01

    The influence of an asymmetric in-plane magnetic anisotropy Kx ≠Ky on the thermally activated spin current is studied theoretically for two different systems: (i) the F | N system consisting of a ferromagnetic insulator (F) in a direct contact with a nonmagnetic metal (N) and (ii) the sandwich structure N | F | N consisting of a ferromagnetic insulating part sandwiched between two nonmagnetic metals. It is shown that when the difference between the temperatures of the two nonmagnetic metals in a N | F | N structure is not large, the spin pumping currents from the magnetic part to the nonmagnetic ones are equal in amplitude and have opposite directions, so only the spin torque current contributes to the total spin current. The spin current flows then from the nonmagnetic metal with the higher temperature to the nonmagnetic metal having a lower temperature. Its amplitude varies linearly with the difference in temperatures. In addition, we have found that if the magnetic anisotropy is in the layer plane, then the spin current increases with the magnon temperature, while in the case of an out-of-plane magnetic anisotropy the spin current decreases when the magnon temperature enhances. Enlarging the difference between the temperatures of the nonmagnetic metals, the linear response becomes important, as confirmed by analytical expressions inferred from the Fokker-Planck approach and by the results obtained upon a full numerical integration of the stochastic Landau-Lifshitz-Gilbert equation.

  18. Dual character of the electronic structure in YBa2Cu4O8: conduction bands of CuO2 planes and CuO chains

    NASA Astrophysics Data System (ADS)

    Kaminski, A.; Kondo, T.; Khasanov, R.; Karpinski, J.; Kazakov, S. M.; Zhigadlo, N. D.; Ohta, T.; Fretwell, H. M.; Palczewski, A. D.; Koll, J. D.; Mesot, J.; Rotenberg, E.; Keller, H.

    2007-03-01

    We use microprobe Angle-Resolved Photoemission Spectroscopy (μARPES) to separately investigate the electronic properties of CuO2 planes and CuO chains in the high temperature superconductor, YBa2Cu4O8. In the CuO2 planes, a two dimensional (2D) electronic structure with nearly momentum independent bilayer splitting is observed. The splitting energy is 150 meV at (π,0), almost 50% larger than in Bi2Sr2CaCu2O8+δ and the electron scattering at the Fermi level in the bonding band is about 1.5 times stronger than in the antibonding band. The CuO chains have a quasi one dimensional (1D) electronic structure. We observe two 1D bands separated by ˜ 550meV: a conducting band and an insulating band with an energy gap of ˜240meV. We find that the conduction electrons are well confined within the planes and chains with a non-trivial hybridization.

  19. Development of a fatigue-life methodology for composite structures subjected to out-of-plane load components

    NASA Technical Reports Server (NTRS)

    Sumich, Mark; Kedward, Keith T.

    1991-01-01

    The efforts to identify and implement a fatigue life methodology applicable to demonstrate delamination failures for use in certifying composite rotor blades are presented. The RSRA/X-Wing vehicle was a proof-of-concept stopped rotor aircraft configuration which used rotor blades primarily constructed of laminated carbon fiber. Delamination of the main spar during ground testing demonstrated that significant interlaminar stresses were produced. Analysis confirmed the presence of out-of-plane load components. The wear out (residual strength) methodology and the requirements for its implementation are discussed.

  20. Prediction of fatigue crack growth kinetics in the plane structural elements of aircraft in the biaxial stress state

    NASA Astrophysics Data System (ADS)

    Shanyavskij, A. A.; Karaev, K. Z.; Grigor'ev, V. M.; Koronov, M. Z.; Orlov, E. F.

    1991-07-01

    The kinetics of fatigue crack growth in the case of a complex stress state is investigated with particular reference to D16T aluminum alloy. By using simulation models in the form of plane cruciform specimens, the characteristics of fatigue crack growth are investigated under conditions of uniaxial and biaxial tension-compression, with the ratio of the main stresses varying from -1 to 1.5. An algorithm is developed which makes it possible to predict the kinetics of fatigue crack growth and the equivalent stress level under conditions of multiparametric loading.

  1. Comparison tests and experimental compliance calibration of the proposed standard round compact plane strain fracture toughness specimen

    NASA Technical Reports Server (NTRS)

    Fisher, D. M.; Buzzard, R. J.

    1979-01-01

    Standard round specimen fracture test results compared satisfactorily with results from standard rectangular compact specimens machined from the same material. The location of the loading pin holes was found to provide adequate strength in the load bearing region for plane strain fracture toughness testing. Excellent agreement was found between the stress intensity coefficient values obtained from compliance measurements and the analytic solution proposed for inclusion in the standard test method. Load displacement measurements were made using long armed displacement gages and hollow loading cylinders. Gage points registered on the loading hole surfaces through small holes in the walls of the loading cylinders.

  2. Quasiparticle density of states in layered superconductors under a magnetic field parallel to the ab plane: Determination of the gap structure of Sr2 Ru O4

    NASA Astrophysics Data System (ADS)

    Udagawa, Masafumi; Yanase, Youichi; Ogata, Masao

    2004-11-01

    We study the vortex state of a layered superconductor with vertical line nodes on its Fermi surface when a magnetic field is applied in the ab -plane direction. We rotate the magnetic field within the plane, and analyze the change of low-energy excitation spectrum. Our analysis is based on the microscopic Bogoliubov-de Gennes equation and a convenient approximate analytical method invented by Pesch and developed by Dahm Both methods give consistent results. Near the upper critical field Hc2 , we observe a larger zero-energy density of states (ZEDOS) when the magnetic field is applied in the nodal direction, while much below Hc2 , larger ZEDOS is observed under a field in the anti-nodal direction. We give a natural interpretation to this crossover behavior in terms of contributions of quasiparticles propagating parallel and perpendicular to the applied field in the plane. We examine the recent field angle variation experiments of thermal conductivity and specific heat. Comparisons with our results suggest that special care should be taken to derive the position of line nodes from the experimental data. Combining the experimental data of the specific heat and our analyses, we conclude that Sr2RuO4 has a vertical-line-node-like structure in the direction of the a axis and the b axis.

  3. Electronic structure of cerium hydrides: Augmented-plane-wave linear-combination-of-atomic-orbitals energy bands

    NASA Astrophysics Data System (ADS)

    Fujimori, A.; Minami, F.; Tsuda, N.

    1980-10-01

    Electronic energy bands have been calculated for CeH2 and CeH3 using the augmented-plane-wave method and have been fitted by the linear-combination-of-atomic-orbitals interpolation scheme. The partial densities of states and the numbers of electrons on atomic orbitals indicate that hydrogen in CeH2 is almost anionlike. When going from CeH2 to CeH3, shallow bonding levels are found to form between the third hydrogen state and conduction electrons of CeH2, other features of CeH2 being little affected by it. Thus the rare-earth dihydrides are regarded as ionic compounds similar to the saline-element dihydrides except for the presence of d-like conduction electrons.

  4. On the Structure Dependence of CO Oxidation over CeO2 Nanocrystals with Well-Defined Surface Planes

    SciTech Connect

    Wu, Zili; Li, Meijun; Overbury, Steven {Steve} H

    2012-01-01

    CO oxidation is a model reaction for probing the redox property of ceria-based catalysts. In this study, CO oxidation was investigated over ceria nanocrystals with defined surface planes (nanoshapes) including rods ({110} + {100}), cubes ({100}), and octahedra ({111}). To understand the strong dependence of CO oxidation observed on these different ceria nanoshapes, in situ techniques including infrared and Raman spectroscopy coupled with online mass spectrometer, and temperature-programmed reduction (TPR) were employed to reveal how CO interacts with the different ceria surfaces, while the mobility of ceria lattice oxygen was investigated via oxygen isotopic exchange experiment. CO adsorption at room temperature leads to strongly bonded carbonate species on the more reactive surfaces of rods and cubes but weakly bonded ones on the rather inert octahedra surface. CO-TPR, proceeding via several channels including CO removal of lattice oxygen, surface water-gas shift reaction and CO disproportionation reaction, reveals that the reducibility of these ceria nanoshapes is in line with their CO oxidation activity, i.e., rods > cubes > octahedra. The mobility of lattice oxygen also shows similar dependence. It is suggested that defect sites and coordinatively unsaturated sites on ceria play a direct role in facilitating both CO interaction with ceria surface and the reactivity and mobility of lattice oxygen. The nature and amount of the defect and low coordination sites are intrinsically affected by the surface planes of the ceria nanoshapes. Several reaction pathways for CO oxidation over the ceria nanoshapes are proposed and certain types of carbonates, especially those associated with reduced ceria surface, are considered among the reaction intermediates to form CO2, while the majority of carbonate species observed under CO oxidation condition are believed to be spectators.

  5. Structural properties of Al-rich AlInN grown on c-plane GaN substrate by metal-organic chemical vapor deposition

    PubMed Central

    2014-01-01

    The attractive prospect for AlInN/GaN-based devices for high electron mobility transistors with advanced structure relies on high-quality AlInN epilayer. In this work, we demonstrate the growth of high-quality Al-rich AlInN films deposited on c-plane GaN substrate by metal-organic chemical vapor deposition. X-ray diffraction, scanning electron microscopy, and scanning transmission electron microscopy show that the films lattice-matched with GaN can have a very smooth surface with good crystallinity and uniform distribution of Al and In in AlInN. PMID:25489282

  6. Structure and switching of in-plane ferroelectric nano-domains in strained PbxSr1-xTiO3 thin films

    SciTech Connect

    Matzen, Sylivia; Nesterov, Okeksiy; Rispens, Gregory; Heuver, J. A.; Bark, C; Biegalski, Michael D; Christen, Hans M; Noheda, Beatriz

    2014-01-01

    Nanoscale ferroelectrics, the active elements of a variety of nanoelectronic devices, develop denser and richer domain structures than the bulk counterparts. With shrinking device sizes understanding and controlling domain formation in nanoferroelectrics is being intensely studied. Here we show that a precise control of the epitaxy and the strain allows stabilizing a hierarchical domain architecture in PbxSr1-xTiO3 thin films, showing periodic, purely in-plane polarized, ferroelectric nano-domains that can be switched by a scanning probe.

  7. Shear-strain-induced structural and electronic modifications of the molecular crystal 1,1-diamino-2,2-dinitroethylene: Slip-plane flow and band gap relaxation

    NASA Astrophysics Data System (ADS)

    Kuklja, Maija M.; Rashkeev, Sergey N.

    2007-03-01

    First-principles calculations of the structural and electronic properties of the deformed molecular crystal 1,1-diamino-2,2-dinitroethylene (FOX-7) under shear-strain loading are presented. The reaction of the crystal to applied shear-strain loading is found to be highly anisotropic. When the external loading is removed, the relaxation of the system is mainly defined by stretching, bending, and rotations of the NO2 groups of neighboring molecules from the two adjacent zigzag-shaped crystalline planes that were initially shifted. In general, the deformed molecular crystal relaxes to its initial, ideal crystalline FOX-7 structure. However, different planes remain shifted relatively to each other on vectors, which are typically incommensurated with any translational vector of the ideal crystal. This fact makes an existence of ideal crystals of this material quite problematic. We also found that no metallization occurs under shear-strain loading. We suggest that the considered mechanisms of the shear-strain relaxation of the structural and electronic degrees of freedom are typical for layered anisotropic molecular crystals, and that they should significantly affect their chemical reactivity, conductivity, optical properties, and initiation of detonation in energetic materials.

  8. Statistics of the fractal structure and phase singularity of a plane light wave propagation in atmospheric turbulence.

    PubMed

    Rao, Ruizhong

    2008-01-10

    Numerical experiments are carried out for a plane wave propagating in the atmospheric turbulence for a weak to strong fluctuation condition, i.e., the Rytov index being in a large range of 2x10(-3) to 20. Mainly two categories of propagation events are explored for the same range of Rytov index. In one category the propagation distance and also the Fresnel length are kept fixed with the turbulence strength changing. In the other the turbulence strength is kept fixed with the distance changing. The statistical characteristics of the scintillation index, the maximum and minimum of the intensity, the fractal dimension of the intensity image, and the number density of the phase singularity are analyzed. The behaviors of the fractal dimension and the density of the phase singularity present obvious differences for the two categories of propagation. The fractal dimension depends both on the Rytov index and the Fresnel length. In both weak and strong fluctuation conditions the dimension generally increases with the Rytov index, but is at minimum at the onset region. The phase singularity density is coincident with the theoretical results under a weak fluctuation condition, and has a slowly increasing manner with the Rytov index in the strong fluctuation condition. The dependence on the Fresnel size is confident and there is no saturation for the phase singularity.

  9. Anisotropic structural and optical properties of semi-polar (11–22) GaN grown on m-plane sapphire using double AlN buffer layers

    PubMed Central

    Zhao, Guijuan; Wang, Lianshan; Yang, Shaoyan; Li, Huijie; Wei, Hongyuan; Han, Dongyue; Wang, Zhanguo

    2016-01-01

    We report the anisotropic structural and optical properties of semi-polar (11–22) GaN grown on m-plane sapphire using a three-step growth method which consisted of a low temperature AlN buffer layer, followed by a high temperature AlN buffer layer and GaN growth. By introducing double AlN buffer layers, we substantially improve the crystal and optical qualities of semi-polar (11–22) GaN, and significantly reduce the density of stacking faults and dislocations. The high resolution x-ray diffraction measurement revealed that the in-plane anisotropic structural characteristics of GaN layer are azimuthal dependent. Transmission electron microscopy analysis showed that the majority of dislocations in the GaN epitaxial layer grown on m-sapphire are the mixed-type and the orientation of GaN layer was rotated 58.4° against the substrate. The room temperature photoluminescence (PL) spectra showed the PL intensity and wavelength have polarization dependence along parallel and perpendicular to the [1–100] axis (polarization degrees ~ 0.63). The realization of a high polarization semi-polar GaN would be useful to achieve III-nitride based lighting emission device for displays and backlighting. PMID:26861595

  10. Validation of the k-filtering technique for a signal composed of random phase plane waves and non-random coherent structures

    NASA Astrophysics Data System (ADS)

    Roberts, O. W.; Li, X.; Jeska, L.

    2014-08-01

    Recent observations of astrophysical magnetic fields have shown the presence of fluctuations being wave-like (propagating in the plasma frame) and those described as being structure-like (advected by the plasma bulk velocity). Typically with single spacecraft missions it is impossible to differentiate between these two fluctuations, due to the inherent spatio-temporal ambiguity associated with a single point measurement. However missions such as Cluster which contain multiple spacecraft have allowed temporal and spatial changes to be resolved, with techniques such as the k-filtering technique. While this technique does not assume Taylor's hypothesis as is necessary with single spacecraft missions, it does require weak stationarity of the time series, and that the fluctuations can be described by a superposition of plane waves with random phase. In this paper we test whether the method can cope with a synthetic signal which is composed of a combination of non-random phase coherent structures with a mean radius d and a mean separation λ, as well as plane waves with random phase.

  11. Validation of the k-filtering technique for a signal composed of random-phase plane waves and non-random coherent structures

    NASA Astrophysics Data System (ADS)

    Roberts, O. W.; Li, X.; Jeska, L.

    2014-12-01

    Recent observations of astrophysical magnetic fields have shown the presence of fluctuations being wave-like (propagating in the plasma frame) and those described as being structure-like (advected by the plasma bulk velocity). Typically with single-spacecraft missions it is impossible to differentiate between these two fluctuations, due to the inherent spatio-temporal ambiguity associated with a single point measurement. However missions such as Cluster which contain multiple spacecraft have allowed for temporal and spatial changes to be resolved, using techniques such as k filtering. While this technique does not assume Taylor's hypothesis it requires both weak stationarity of the time series and that the fluctuations can be described by a superposition of plane waves with random phases. In this paper we test whether the method can cope with a synthetic signal which is composed of a combination of non-random-phase coherent structures with a mean radius d and a mean separation λ, as well as plane waves with random phase.

  12. Molecular crowding of collagen: a pathway to produce highly-organized collagenous structures.

    PubMed

    Saeidi, Nima; Karmelek, Kathryn P; Paten, Jeffrey A; Zareian, Ramin; DiMasi, Elaine; Ruberti, Jeffrey W

    2012-10-01

    Collagen in vertebrate animals is often arranged in alternating lamellae or in bundles of aligned fibrils which are designed to withstand in vivo mechanical loads. The formation of these organized structures is thought to result from a complex, large-area integration of individual cell motion and locally-controlled synthesis of fibrillar arrays via cell-surface fibripositors (direct matrix printing). The difficulty of reproducing such a process in vitro has prevented tissue engineers from constructing clinically useful load-bearing connective tissue directly from collagen. However, we and others have taken the view that long-range organizational information is potentially encoded into the structure of the collagen molecule itself, allowing the control of fibril organization to extend far from cell (or bounding) surfaces. We here demonstrate a simple, fast, cell-free method capable of producing highly-organized, anistropic collagen fibrillar lamellae de novo which persist over relatively long-distances (tens to hundreds of microns). Our approach to nanoscale organizational control takes advantage of the intrinsic physiochemical properties of collagen molecules by inducing collagen association through molecular crowding and geometric confinement. To mimic biological tissues which comprise planar, aligned collagen lamellae (e.g. cornea, lamellar bone or annulus fibrosus), type I collagen was confined to a thin, planar geometry, concentrated through molecular crowding and polymerized. The resulting fibrillar lamellae show a striking resemblance to native load-bearing lamellae in that the fibrils are small, generally aligned in the plane of the confining space and change direction en masse throughout the thickness of the construct. The process of organizational control is consistent with embryonic development where the bounded planar cell sheets produced by fibroblasts suggest a similar confinement/concentration strategy. Such a simple approach to nanoscale

  13. KrF resists for implant layers patterning extreme high-aspect ratio structures with a double focal plane exposure technique

    NASA Astrophysics Data System (ADS)

    Rafaelli, Giorgio; Ferri, Fabio; Volpi, Stefano; Hong, Chisun

    2012-03-01

    The design rules for advanced image sensor applications are requiring continuous CD shrinkage, and increasing aspect ratios which resulting in major challenges associated with using KrF technology. For the implant photo layers in particular, the need to block high-energy boron implants (well above 2 MeV) with extremely localized implant profiles requires an aspect ratio of deep well structures greater than 10:1. Other desirable attributes of a good photoresist for such demanding applications are high transparency, a steep wall profile consistent throughout the entire film, good adhesion with no structure collapse, and a wide process window. In this paper, we will discuss the role of a chemically amplified, ESCAP-type of resist in meeting these design criteria using a double focal plane exposure technique.

  14. THE CANADA-FRANCE ECLIPTIC PLANE SURVEY-L3 DATA RELEASE: THE ORBITAL STRUCTURE OF THE KUIPER BELT

    SciTech Connect

    Kavelaars, J. J.; Jones, R. L.; Murray, I.; Gladman, B. J.; Petit, J.-M.; Van Laerhoven, C.; Parker, Joel Wm.; Bieryla, A.; Nicholson, P.; Margot, J. L.; Rousselot, P.; Mousis, O.; Scholl, H.; Marsden, B.; Benavidez, P.; Campo Bagatin, A.; Doressoundiram, A.; Veillet, C.

    2009-06-15

    We report the orbital distribution of the trans-Neptunian comets discovered during the first discovery year of the Canada-France Ecliptic Plane Survey (CFEPS). CFEPS is a Kuiper Belt object survey based on observations acquired by the Very Wide component of the Canada-France-Hawaii Telescope Legacy Survey (LS-VW). The first year's detections consist of 73 Kuiper Belt objects, 55 of which have now been tracked for three years or more, providing precise orbits. Although this sample size is small compared to the world-wide inventory, because we have an absolutely calibrated and extremely well-characterized survey (with known pointing history) we are able to de-bias our observed population and make unbiased statements about the intrinsic orbital distribution of the Kuiper Belt. By applying the (publically available) CFEPS Survey Simulator to models of the true orbital distribution and comparing the resulting simulated detections to the actual detections made by the survey, we are able to rule out several hypothesized Kuiper Belt object orbit distributions. We find that the main classical belt's so-called 'cold' component is confined in semimajor axis (a) and eccentricity (e) compared to the more extended 'hot' component; the cold component is confined to lower e and does not stretch all the way out to the 2:1 resonance but rather depletes quickly beyond a = 45 AU. For the cold main classical belt population we find a robust population estimate of N(H{sub g} < 10) = 50 {+-} 5 x 10{sup 3} and find that the hot component of the main classical belt represents {approx}60% of the total population. The inner classical belt (sunward of the 3:2 mean-motion resonance) has a population of roughly 2000 trans-Neptunian objects with absolute magnitudes H{sub g} < 10, and may not share the inclination distribution of the main classical belt. We also find that the plutino population lacks a cold low-inclination component, and so, the population is somewhat larger than recent estimates

  15. Atomic-scale investigation of structural defects in GaN layer on c-plane sapphire substrate during initial growth stage

    NASA Astrophysics Data System (ADS)

    Matsubara, Tohoru; Sugimoto, Kohei; Okada, Narihito; Tadatomo, Kazuyuki

    2016-04-01

    Structural defects in the initial growth stages of GaN on sapphire, including stacking faults (SFs), threading dislocations (TDs), and mosaic structure containing grain boundaries, are investigated at the atomic scale. Individual grains in the as-deposited low temperature-GaN buffer layer are found to have twists correlated with those of the adjacent grains. These grains have little similarity on the stacking sequences, and the atomic arrangement on each side of the grain boundaries may be rearranged by annealing to achieve higher similarity in the stacking sequence. The TD identified as a-type at the top of the SFs-rich interfacial region is thought to originate from Frank partial dislocations. The Frank partial dislocation produces a distorted wurtzite-type structure. At the intermediate region of the basal-plane stacking fault between Frank and Shockley partial dislocations, the TD relieves the distortion in the wurtzite-type structure. In the TD, the wurtzite structure slips relative to the surrounding wurtzite.

  16. SiGe/Si quantum structures as a thermistor material for low cost IR microbolometer focal plane arrays

    NASA Astrophysics Data System (ADS)

    Andersson, J. Y.; Ericsson, P.; Radamson, H. H.; Wissmar, S. G. E.; Kolahdouz, M.

    2011-06-01

    Uncooled microbolometer thermal infrared detector technology is presently revolutionizing the infrared technology field. Essential improvement of the cost/performance ratio would be achieved by microbolometer arrays with higher sensitivity, since this allows the use of simpler and less costly camera optics, which implies a lower cost of the complete IR camera. The sensitivity of the microbolometers depends critically on the signal-to-noise ratio of the integrated thermistor material, which is set by its temperature coefficient of resistance (TCR) and noise characteristics. In this work we have investigated the use of epitaxial silicon-germanium/silicon (SiGe/Si) quantum well (QW) structures as a thermistor material. Si 0.68Ge 0.32/Si QW structures typically give a TCR of 3.0%/K and low noise values. A calculation of the noise equivalent temperature NETD of a bolometer gives 25 mK using the following assumptions: f-number = 1, 30 Hz video frame rate for a 640 × 480 array, with a pixel size 25 × 25 μm. Higher TCR values are foreseen for SiGe/Si quantum dot structures, and the noise is expected to be similar to the QW based structures.

  17. A statistical state dynamics-based study of the structure and mechanism of large-scale motions in plane Poiseuille flow

    NASA Astrophysics Data System (ADS)

    Farrell, Brian F.; Ioannou, Petros J.; Jiménez, Javier; Constantinou, Navid C.; Lozano-Durán, Adrián; Nikolaidis, Marios-Andreas

    2016-12-01

    The perspective of statistical state dynamics (SSD) has recently been applied to the study of mechanisms underlying turbulence in various physical systems. An example implementation of SSD is the second order closure referred to as stochastic structural stability theory (S3T), which has provided insight into the dynamics of wall turbulence and specifically the emergence and maintenance of the roll/streak structure. This closure eliminates nonlinear interactions among the perturbations has been removed, restricting nonlinearity in the dynamics to that of the mean equation and the interaction between the mean and perturbation covariance. Here, this quasi-linear restriction of the dynamics is used to study the structure and dynamics of turbulence in plane Poiseuille flow at moderately high Reynolds numbers in a closely related dynamical system, referred to as the restricted nonlinear (RNL) system. RNL simulations reveal that the essential features of wall-turbulence dynamics are retained. Remarkably, the RNL system spontaneously limits the support of its turbulence to a small set of streamwise Fourier components giving rise to a naturally minimal representation of its turbulence dynamics. Although greatly simplified, this RNL turbulence exhibits natural-looking structures and statistics. Surprisingly, even when further truncation of the perturbation support to a single streamwise component is imposed the RNL system continues to produce self-sustaining turbulent structure and dynamics. RNL turbulence at the Reynolds numbers studied is dominated by the roll/streak structure in the buffer layer and similar very-large-scale structure (VLSM) in the outer layer. Diagnostics of the structure, spectrum and energetics of RNL and DNS turbulence are used to demonstrate that the roll/streak dynamics supporting the turbulence in the buffer and logarithmic layer is essentially similar in RNL and DNS.

  18. Out-of-plane (SH) soil-structure interaction: a shear wall with rigid and flexible ring foundation

    NASA Astrophysics Data System (ADS)

    Le, Thang; Lee, Vincent W.; Luo, Hao

    2016-02-01

    Soil-structure interaction (SSI) of a building and shear wall above a foundation in an elastic half-space has long been an important research subject for earthquake engineers and strong-motion seismologists. Numerous papers have been published since the early 1970s; however, very few of these papers have analytic closed-form solutions available. The soil-structure interaction problem is one of the most classic problems connecting the two disciplines of earthquake engineering and civil engineering. The interaction effect represents the mechanism of energy transfer and dissipation among the elements of the dynamic system, namely the soil subgrade, foundation, and superstructure. This interaction effect is important across many structure, foundation, and subgrade types but is most pronounced when a rigid superstructure is founded on a relatively soft lower foundation and subgrade. This effect may only be ignored when the subgrade is much harder than a flexible superstructure: for instance a flexible moment frame superstructure founded on a thin compacted soil layer on top of very stiff bedrock below. This paper will study the interaction effect of the subgrade and the superstructure. The analytical solution of the interaction of a shear wall, flexible-rigid foundation, and an elastic half-space is derived for incident SH waves with various angles of incidence. It found that the flexible ring (soft layer) cannot be used as an isolation mechanism to decouple a superstructure from its substructure resting on a shaking half-space.

  19. Atomic structure characterization of stacking faults on the { 1 1 ¯00 } plane in α-alumina by scanning transmission electron microscopy

    NASA Astrophysics Data System (ADS)

    Tochigi, Eita; Findlay, Scott D.; Okunishi, Eiji; Mizoguchi, Teruyasu; Nakamura, Atsutomo; Shibata, Naoya; Ikuhara, Yuichi

    2016-08-01

    The structure of a b =<1 1 ¯00 > dislocation formed in the { 1 1 ¯00 } /<112 ¯0> 2° low-angle grain boundary of alumina was observed by scanning transmission electron microscopy (STEM). It was found that the <1 1 ¯00 > dislocation dissociate-s into 1/3<1 1 ¯00 > partial-dislocation triplets with two stacking faults on the { 1 1 ¯00 } plane. The atomic structure of the { 1 1 ¯00 } stacking faults was characterized by annular bright field STEM (ABF-STEM). The two stacking faults were found to have a stacking sequence of …ABCCABC… and …ABCBCAB…, wh-ich is consistent with a former report. ABF-STEM image simulation was performed using structure models with the { 1 1 ¯00 } stacking faults optimized by first-principles calculations. The overall features of the experimental and the simulated results agree with each other. However, slight differences in contrast were recognized in the vicinity of the stacking faults, suggesting that there are small differences between the observed structures and the theoretical models.

  20. Structural, electronic, and optical properties of m -plane InGaN/GaN quantum wells: Insights from experiment and atomistic theory

    NASA Astrophysics Data System (ADS)

    Schulz, S.; Tanner, D. P.; O'Reilly, E. P.; Caro, M. A.; Martin, T. L.; Bagot, P. A. J.; Moody, M. P.; Tang, F.; Griffiths, J. T.; Oehler, F.; Kappers, M. J.; Oliver, R. A.; Humphreys, C. J.; Sutherland, D.; Davies, M. J.; Dawson, P.

    2015-12-01

    In this paper we present a detailed analysis of the structural, electronic, and optical properties of an m -plane (In,Ga)N/GaN quantum well structure grown by metal organic vapor phase epitaxy. The sample has been structurally characterized by x-ray diffraction, scanning transmission electron microscopy, and 3D atom probe tomography. The optical properties of the sample have been studied by photoluminescence (PL), time-resolved PL spectroscopy, and polarized PL excitation spectroscopy. The PL spectrum consisted of a very broad PL line with a high degree of optical linear polarization. To understand the optical properties we have performed atomistic tight-binding calculations, and based on our initial atom probe tomography data, the model includes the effects of strain and built-in field variations arising from random alloy fluctuations. Furthermore, we included Coulomb effects in the calculations. Our microscopic theoretical description reveals strong hole wave function localization effects due to random alloy fluctuations, resulting in strong variations in ground state energies and consequently the corresponding transition energies. This is consistent with the experimentally observed broad PL peak. Furthermore, when including Coulomb contributions in the calculations we find strong exciton localization effects which explain the form of the PL decay transients. Additionally, the theoretical results confirm the experimentally observed high degree of optical linear polarization. Overall, the theoretical data are in very good agreement with the experimental findings, highlighting the strong impact of the microscopic alloy structure on the optoelectronic properties of these systems.

  1. Novel slanted incidence air-coupled ultrasound method for delamination assessment in individual bonding planes of structural multi-layered glued timber laminates.

    PubMed

    Sanabria, Sergio J; Furrer, Roman; Neuenschwander, Jürg; Niemz, Peter; Sennhauser, Urs

    2013-09-01

    Non-destructive assessment of delaminations in glued laminated timber structures is required during their full life cycle. A novel air-coupled ultrasound (ACU) method has been developed, which is able to separately detect delaminations in individual bonding planes of arbitrarily high and long laminated stacks and typically 200 mm wide. The 120 kHz ACU transmitter-receiver pair is positioned at two opposite lateral faces of the sample, with a small inclination with respect to the inspected bonding planes, so that an ultrasound beam is excited at a user-defined refraction angle within the sample, interacting with defects in a limited height portion of the stack. The attenuation of the ultrasound beam transmitted across the defect (negative detection) provided better sensitivity to defects than the scattered fields (positive detection), which are masked by spurious fields. Dedicated finite-difference time-domain (FDTD) simulations provided understanding on the wave propagation and defect detectability limits, with respect to the heterogeneous anisotropic material structure introduced by the curvature of the annual rings in individual timber lamellas. A simplified analytical expression was derived to calculate refraction angles in timber in function of insonification angle and ring angle. Experimental results show that the method is able to detect >20% wide defects in both isotropic material and in glulam with straight year rings, and >50% wide and 100mm long defects in commercial glulam beams. The discrimination of defects from background variability is optimized by normalizing the images with respect to reference defect-free sample sections (normalization) or previous measurements (difference imaging), and by combining readings obtained with distinct ultrasound beam refraction angles (spatial diversity). Future work aims at the development of a tomographic defect inspection by combining the described theoretical and experimental methods. Copyright © 2013 Elsevier B

  2. Study of defect structures in 6H-SiC a/m-plane pseudofiber crystals grown by hot-wall CVD epitaxy

    SciTech Connect

    Goue, Ouloide Y.; Raghothamachar, Balaji; Yang, Yu; Guo, Jianqiu; Dudley, Michael; Kisslinger, Kim; Trunek, Andrew J.; Neudeck, Philip G.; Spry, David J.; Woodworth, Andrew A.

    2015-11-25

    Structural perfection of silicon carbide (SiC) single crystals is essential to achieve high-performance power devices. A new bulk growth process for SiC proposed by researchers at NASA Glenn Research Center, called large tapered crystal (LTC) growth, based on axial fiber growth followed by lateral expansion, could produce SiC boules with potentially as few as one threading screw dislocation per wafer. In this study, the lateral expansion aspect of LTC growth is addressed through analysis of lateral growth of 6H-SiC a/m-plane seed crystals by hot-wall chemical vapor deposition. Preliminary synchrotron white-beam x-ray topography (SWBXT) indicates that the as-grown boules match the polytype structure of the underlying seed and have a faceted hexagonal morphology with a strain-free surface marked by steps. SWBXT Laue diffraction patterns of transverse and axial slices of the boules reveal streaks suggesting the existence of stacking faults/polytypes, and this is confirmed by micro-Raman spectroscopy. Transmission x-ray topography of both transverse and axial slices reveals inhomogeneous strains at the seed–epilayer interface and linear features propagating from the seed along the growth direction. Micro-Raman mapping of an axial slice reveals that the seed contains high stacking disorder, while contrast extinction analysis (g·b and g·b×l) of the linear features reveals that these are mostly edge-type basal plane dislocations. Further high-resolution transmission electron microscopy investigation of the seed–homoepilayer interface also reveals nanobands of different SiC polytypes. A model for their formation mechanism is proposed. Lastly, the implication of these results for improving the LTC growth process is addressed.

  3. Study of defect structures in 6H-SiC a/m-plane pseudofiber crystals grown by hot-wall CVD epitaxy

    DOE PAGES

    Goue, Ouloide Y.; Raghothamachar, Balaji; Yang, Yu; ...

    2015-11-25

    Structural perfection of silicon carbide (SiC) single crystals is essential to achieve high-performance power devices. A new bulk growth process for SiC proposed by researchers at NASA Glenn Research Center, called large tapered crystal (LTC) growth, based on axial fiber growth followed by lateral expansion, could produce SiC boules with potentially as few as one threading screw dislocation per wafer. In this study, the lateral expansion aspect of LTC growth is addressed through analysis of lateral growth of 6H-SiC a/m-plane seed crystals by hot-wall chemical vapor deposition. Preliminary synchrotron white-beam x-ray topography (SWBXT) indicates that the as-grown boules match themore » polytype structure of the underlying seed and have a faceted hexagonal morphology with a strain-free surface marked by steps. SWBXT Laue diffraction patterns of transverse and axial slices of the boules reveal streaks suggesting the existence of stacking faults/polytypes, and this is confirmed by micro-Raman spectroscopy. Transmission x-ray topography of both transverse and axial slices reveals inhomogeneous strains at the seed–epilayer interface and linear features propagating from the seed along the growth direction. Micro-Raman mapping of an axial slice reveals that the seed contains high stacking disorder, while contrast extinction analysis (g·b and g·b×l) of the linear features reveals that these are mostly edge-type basal plane dislocations. Further high-resolution transmission electron microscopy investigation of the seed–homoepilayer interface also reveals nanobands of different SiC polytypes. A model for their formation mechanism is proposed. Lastly, the implication of these results for improving the LTC growth process is addressed.« less

  4. In-plane commensurate GaN/AlN junctions: Single-layer composite structures, single and multiple quantum wells and quantum dots

    NASA Astrophysics Data System (ADS)

    Onen, A.; Kecik, D.; Durgun, E.; Ciraci, S.

    2017-04-01

    In-plane composite structures constructed of the stripes or core/shells of single-layer GaN and AlN, which are joined commensurately, display a diversity of electronic properties that can be tuned by the size of their constituents. In heterostructures, the dimensionality of the electrons changes from two dimensional (2D) to one dimensional (1D) upon their confinements in wide constituent stripes, leading to the type-I band alignment and hence multiple quantum well structure in the direct space. The δ doping of one wide stripe by another narrow stripe results in local narrowing or widening of the band gap. A single quantum well structure is acquired from the finite-size AlN-GaN-AlN junctions. In a patterned array of GaN/AlN core/shells, the dimensionality of the electronic states is reduced from two dimensional to zero dimensional, forming multiple quantum dots in large GaN cores, while 2D electrons propagate in multiply connected AlN shell as if they are in a supercrystal. A consistent and detailed discussion of the effects of confinement in momentum and direct spaces is provided. As a result of confinement, the variation of the band gap in the direct space is found to be rather different from the edges of the conduction and valence bands inferred from the band edges of constituent 2D single-layer GaN and AlN. Even if all the results in this study pertain to the free-standing single-layer composite structures, the effects of the different substrates over which these composites can grow are examined in detail. This study unveils the potential of composite structures in designing novel nanomaterials. These predictions are obtained from first-principles calculations based on density functional theory on 2D GaN and AlN compound semiconductors which were synthesized recently.

  5. Variational theory of complex rays applied to shell structures: in-plane inertia, quasi-symmetric ray distribution, and orthotropic materials

    NASA Astrophysics Data System (ADS)

    Cattabiani, Alessandro; Barbarulo, Andrea; Riou, Hervé; Ladevèze, Pierre

    2015-12-01

    Recently, interest of aerospace and automotive industries on medium-frequency vibrational behavior of composite shell structures has grown due to their high specific stiffness and fatigue resistance. Conventional methods such as the finite element method and the statistical energy analysis are not suitable for the medium-frequency bandwidth. Conversely, the variational theory of complex rays (VTCR) is taking place as an ad-hoc technique to tackle such frequency band. It is a Trefftz method based on a weak variational formulation. Equilibrium equations are met using exact solutions as shape functions. The variational problem imposes boundary conditions in weak form. The present paper extends VTCR to orthotropic shell structures. Moreover, several new enhancements are introduced. Now, we use a quasi-symmetric ray distribution which can greatly reduce computational costs, and addresses in-plane inertia which was neglected in previous works. Some relevant numerical examples are presented to show the strategy and results are compared with a FEM reference to study performances.

  6. Simple quasi-analytical holonomic homogenization model for the non-linear analysis of in-plane loaded masonry panels: Part 2, structural implementation and validation

    NASA Astrophysics Data System (ADS)

    Milani, G.; Bertolesi, E.

    2017-07-01

    The simple quasi analytical holonomic homogenization approach for the non-linear analysis of in-plane loaded masonry presented in Part 1 is here implemented at a structural leveland validated. For such implementation, a Rigid Body and Spring Mass model (RBSM) is adopted, relying into a numerical modelling constituted by rigid elements interconnected by homogenized inelastic normal and shear springs placed at the interfaces between adjoining elements. Such approach is also known as HRBSM. The inherit advantage is that it is not necessary to solve a homogenization problem at each load step in each Gauss point, and a direct implementation into a commercial software by means of an external user supplied subroutine is straightforward. In order to have an insight into the capabilities of the present approach to reasonably reproduce masonry behavior at a structural level, non-linear static analyses are conducted on a shear wall, for which experimental and numerical data are available in the technical literature. Quite accurate results are obtained with a very limited computational effort.

  7. Optimum design of phononic crystal perforated plate structures for widest bandgap of fundamental guided wave modes and maximized in-plane stiffness

    NASA Astrophysics Data System (ADS)

    Hedayatrasa, Saeid; Abhary, Kazem; Uddin, Mohammad; Ng, Ching-Tai

    2016-04-01

    This paper presents a topology optimization of single material phononic crystal plate (PhP) to be produced by perforation of a uniform background plate. The primary objective of this optimization study is to explore widest exclusive bandgaps of fundamental (first order) symmetric or asymmetric guided wave modes as well as widest complete bandgap of mixed wave modes (symmetric and asymmetric). However, in the case of single material porous phononic crystals the bandgap width essentially depends on the resultant structural integration introduced by achieved unitcell topology. Thinner connections of scattering segments (i.e. lower effective stiffness) generally lead to (i) wider bandgap due to enhanced interfacial reflections, and (ii) lower bandgap frequency range due to lower wave speed. In other words higher relative bandgap width (RBW) is produced by topology with lower effective stiffness. Hence in order to study the bandgap efficiency of PhP unitcell with respect to its structural worthiness, the in-plane stiffness is incorporated in optimization algorithm as an opposing objective to be maximized. Thick and relatively thin Polysilicon PhP unitcells with square symmetry are studied. Non-dominated sorting genetic algorithm NSGA-II is employed for this multi-objective optimization problem and modal band analysis of individual topologies is performed through finite element method. Specialized topology initiation, evaluation and filtering are applied to achieve refined feasible topologies without penalizing the randomness of genetic algorithm (GA) and diversity of search space. Selected Pareto topologies are presented and gradient of RBW and elastic properties in between the two Pareto front extremes are investigated. Chosen intermediate Pareto topology, even not extreme topology with widest bandgap, show superior bandgap efficiency compared with the results reported in other works on widest bandgap topology of asymmetric guided waves, available in the literature

  8. 24 CFR 3280.305 - Structural design requirements.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... extend beneath load-bearing walls that are fastened to the floor structure. (b) Design loads—(1) Design... Wabasha Brown St. Louis Chippewa Winona Redwood Lake Yellow Medicine Fillmore Lyon Cook Mille Lacs Mower... Wind Zone II and Wind Zone III, roof framing members must be securely fastened at the vertical bearing...

  9. 24 CFR 3280.305 - Structural design requirements.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... extend beneath load-bearing walls that are fastened to the floor structure. (b) Design loads—(1) Design... Wabasha Brown St. Louis Chippewa Winona Redwood Lake Yellow Medicine Fillmore Lyon Cook Mille Lacs Mower... Wind Zone II and Wind Zone III, roof framing members must be securely fastened at the vertical bearing...

  10. 24 CFR 3280.305 - Structural design requirements.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... extend beneath load-bearing walls that are fastened to the floor structure. (b) Design loads—(1) Design... Wabasha Brown St. Louis Chippewa Winona Redwood Lake Yellow Medicine Fillmore Lyon Cook Mille Lacs Mower... Wind Zone II and Wind Zone III, roof framing members must be securely fastened at the vertical bearing...

  11. 24 CFR 3280.305 - Structural design requirements.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... extend beneath load-bearing walls that are fastened to the floor structure. (b) Design loads—(1) Design... Wabasha Brown St. Louis Chippewa Winona Redwood Lake Yellow Medicine Fillmore Lyon Cook Mille Lacs Mower... Wind Zone II and Wind Zone III, roof framing members must be securely fastened at the vertical bearing...

  12. Rayleigh-wave phase-velocity maps and three-dimensional shear velocity structure of the western US from local non-plane surface wave tomography

    USGS Publications Warehouse

    Pollitz, F.F.; Snoke, J. Arthur

    2010-01-01

    We utilize two-and-three-quarter years of vertical-component recordings made by the Transportable Array (TA) component of Earthscope to constrain three-dimensional (3-D) seismic shear wave velocity structure in the upper 200 km of the western United States. Single-taper spectral estimation is used to compile measurements of complex spectral amplitudes from 44 317 seismograms generated by 123 teleseismic events. In the first step employed to determine the Rayleigh-wave phase-velocity structure, we implement a new tomographic method, which is simpler and more robust than scattering-based methods (e.g. multi-plane surface wave tomography). The TA is effectively implemented as a large number of local arrays by defining a horizontal Gaussian smoothing distance that weights observations near a given target point. The complex spectral-amplitude measurements are interpreted with the spherical Helmholtz equation using local observations about a succession of target points, resulting in Rayleigh-wave phase-velocity maps at periods over the range of 18–125 s. The derived maps depend on the form of local fits to the Helmholtz equation, which generally involve the nonplane-wave solutions of Friederich et al. In a second step, the phase-velocity maps are used to derive 3-D shear velocity structure. The 3-D velocity images confirm details witnessed in prior body-wave and surface-wave studies and reveal new structures, including a deep (>100 km deep) high-velocity lineament, of width ∼200 km, stretching from the southern Great Valley to northern Utah that may be a relic of plate subduction or, alternatively, either a remnant of the Mojave Precambrian Province or a mantle downwelling. Mantle seismic velocity is highly correlated with heat flow, Holocene volcanism, elastic plate thickness and seismicity. This suggests that shallow mantle structure provides the heat source for associated magmatism, as well as thinning of the thermal lithosphere, leading to relatively high

  13. Physiological Determinants of Load Bearing Capacity

    DTIC Science & Technology

    1987-06-01

    less than a 2 ml increase of oxygen uptake with a 2% increase in grade. Gas volumes were measured by a Collins 120 liter chain-compensated spirometer ...and/or commanders. Participation by the chain of command In the performance trial, while desirable, may not be feasible. Incentives such as weekend

  14. High density load bearing insulation peg

    DOEpatents

    Nowobilski, J.J.; Owens, W.J.

    1985-01-29

    A high density peg is disclosed which can support a large load and exhibits excellent thermal resistance produced by a method wherein the peg is made in compliance with specified conditions of time, temperature and pressure. 4 figs.

  15. High density load bearing insulation peg

    DOEpatents

    Nowobilski, Jeffert J.; Owens, William J.

    1985-01-01

    A high density peg which can support a large load and exhibits excellent thermal resistance produced by a method wherein the peg is made in compliance with specified conditions of time, temperature and pressure.

  16. TEMP-STRESS---A thermomechanical finite element program for the analysis of plane and axisymmetric reinforced/prestressed concrete structures: User`s manual

    SciTech Connect

    Kennedy, J. M.; Pfeiffer, P. A.; Marchertas, A. H.

    1989-01-01

    TEMP-STRESS has been developed to improve the understanding of the behavior of concrete subjected to mechanical loadings and high temperatures simulating the effects of coolant spills, molten debris, etc. The capability to model concrete structures subjected to static and dynamic overpressures, such as LWR and LMR containments with complex axisymmetric geometries, can be solved. The computer code is a finite element program which has a weakly coupled thermomechanical formulation. It can handle transient and steady state problems through the use of explicit time integration and dynamic relaxation. There is a plane or axisymmetric continuum element and flexural beam and shell elements for concrete discretization. The continuum element is a four node quadrilateral using numerical integration and elastic hourglass control. Variable material properties as a function of temperature are available. Thermal and/or mechanical loading can be handled. The concrete material model has the following characteristics: (a) elastic-plastic response, (b) variable loading surface capability, (c) cracking normal to maximum principal strain at specified failure surface, (d) post-failure element treatment, and (e) variable temperature dependence. Concrete can be reinforced and/or prestressed. 15 refs., 33 figs., 24 tabs.

  17. Angular emission from 1D and 2D meso- and nano-structures: Probed by dual-channel Fourier-plane microscopy

    NASA Astrophysics Data System (ADS)

    Singh, Danveer; Sharma, Deepak Kumar; Chaubey, Shailendra Kumar; Kumar, G. V. Pavan

    2017-09-01

    The optical emission characteristics from individual nanostructures such as organic waveguides, plasmonic nanowires and 2D materials such as MoS2 can vary depending on the nature of interface on which they are grown or deposited. We constructed a dual-channel Fourier-plane microscopy, and studied the directional emission characteristics of an individual organic mesowires, Ag nanowires and MoS2 nanolayers through the glass substrate or air superstrate. Specifically, we show the ability of our microscope to quantitatively probe the radial and azimuthal angular spread in the waveguided PL from the distal ends of the mesowire across the interface without changing its position or orientation. Furthermore, from the guided PL spectral signatures, we show that the finesse of the waveguided Fabry-Perot resonance depends on whether the measurement was performed through the substrate or superstrate. To reveal the versatility of our microscope, we have quantified angular distribution of directional light scattering from the distal end of Ag nanowire at an interface, and angular distribution of excitonic emission from MoS2 nanolayers through a glass substrate. Our work highlights the capability of dual-channel Fourier microscope in quantifying the angular emission characteristics from individual optical antenna structures at an interface, and can be extrapolated to nonlinear organic nanophotonic regimes.

  18. Electronic structure of the ingredient planes of the cuprate superconductor Bi2Sr2CuO6 +δ : A comparison study with Bi2Sr2CaCu2O8 +δ

    NASA Astrophysics Data System (ADS)

    Lv, Yan-Feng; Wang, Wen-Lin; Ding, Hao; Wang, Yang; Ding, Ying; Zhong, Ruidan; Schneeloch, John; Gu, G. D.; Wang, Lili; He, Ke; Ji, Shuai-Hua; Zhao, Lin; Zhou, Xing-Jiang; Song, Can-Li; Ma, Xu-Cun; Xue, Qi-Kun

    2016-04-01

    By means of low-temperature scanning tunneling microscopy, we report on the electronic structures of the BiO and SrO planes of the Bi2Sr2CuO6 +δ (Bi-2201) superconductor prepared by argon-ion bombardment and annealing. Depending on post annealing conditions, the BiO planes exhibit either a pseudogap (PG) with sharp coherence peaks and an anomalously large gap magnitude of 49 meV or van Hove singularity (vHS) near the Fermi level, while the SrO is always characteristic of a PG-like feature. This contrasts with the Bi2Sr2CaCu2O8 +δ (Bi-2212) superconductor where vHS occurs solely on the SrO plane. We disclose the interstitial oxygen dopants (δ in the formulas) as a primary cause for the occurrence of vHS, which are located dominantly around the BiO and SrO planes, respectively, in Bi-2201 and Bi-2212. This is supported by the contrasting structural buckling amplitude of the BiO and SrO planes in the two superconductors. Our findings provide solid evidence for the irrelevance of PG to the superconductivity in the two superconductors, as well as insights into why Bi-2212 can achieve a higher superconducting transition temperature than Bi-2201, and by implication, the mechanism of cuprate superconductivity.

  19. Electronic structure of the ingredient planes of the cuprate superconductor Bi2Sr2CuO6+δ: A comparison study with Bi2Sr2CaCu2O8+δ

    DOE PAGES

    Yan -Feng Lv; Gu, G. D.; Wang, Wen -Lin; ...

    2016-04-15

    By means of low-temperature scanning tunneling microscopy, we report on the electronic structures of the BiO and SrO planes of the Bi2Sr2CuO6+δ (Bi-2201) superconductor prepared by argon-ion bombardment and annealing. Depending on post annealing conditions, the BiO planes exhibit either a pseudogap (PG) with sharp coherence peaks and an anomalously large gap magnitude of 49 meV or van Hove singularity (vHS) near the Fermi level, while the SrO is always characteristic of a PG-like feature. This contrasts with the Bi2Sr2CaCu2O8+δ (Bi-2212) superconductor where vHS occurs solely on the SrO plane. We disclose the interstitial oxygen dopants (δ in the formulas)more » as a primary cause for the occurrence of vHS, which are located dominantly around the BiO and SrO planes, respectively, in Bi-2201 and Bi-2212. This is supported by the contrasting structural buckling amplitude of the BiO and SrO planes in the two superconductors. Furthermore, our findings provide solid evidence for the irrelevance of PG to the superconductivity in the two superconductors, as well as insights into why Bi-2212 can achieve a higher superconducting transition temperature than Bi-2201, and by implication, the mechanism of cuprate superconductivity.« less

  20. THE BOLOCAM GALACTIC PLANE SURVEY. XII. DISTANCE CATALOG EXPANSION USING KINEMATIC ISOLATION OF DENSE MOLECULAR CLOUD STRUCTURES WITH {sup 13}CO(1-0)

    SciTech Connect

    Ellsworth-Bowers, Timothy P.; Glenn, Jason; Rosolowsky, Erik; Ginsburg, Adam; Evans II, Neal J.; Battersby, Cara; Shirley, Yancy L.; Svoboda, Brian

    2015-01-20

    We present an expanded distance catalog for 1710 molecular cloud structures identified in the Bolocam Galactic Plane Survey (BGPS) version 2, representing a nearly threefold increase over the previous BGPS distance catalog. We additionally present a new method for incorporating extant data sets into our Bayesian distance probability density function (DPDF) methodology. To augment the dense-gas tracers (e.g., HCO{sup +}(3-2), NH{sub 3}(1,1)) used to derive line-of-sight velocities for kinematic distances, we utilize the Galactic Ring Survey (GRS) {sup 13}CO(1-0) data to morphologically extract velocities for BGPS sources. The outline of a BGPS source is used to select a region of the GRS {sup 13}CO data, along with a reference region to subtract enveloping diffuse emission, to produce a line profile of {sup 13}CO matched to the BGPS source. For objects with a HCO{sup +}(3-2) velocity, ≈95% of the new {sup 13}CO(1-0) velocities agree with that of the dense gas. A new prior DPDF for kinematic distance ambiguity (KDA) resolution, based on a validated formalism for associating molecular cloud structures with known objects from the literature, is presented. We demonstrate this prior using catalogs of masers with trigonometric parallaxes and H II regions with robust KDA resolutions. The distance catalog presented here contains well-constrained distance estimates for 20% of BGPS V2 sources, with typical distance uncertainties ≲ 0.5 kpc. Approximately 75% of the well-constrained sources lie within 6 kpc of the Sun, concentrated in the Scutum-Centaurus arm. Galactocentric positions of objects additionally trace out portions of the Sagittarius, Perseus, and Outer arms in the first and second Galactic quadrants, and we also find evidence for significant regions of interarm dense gas.

  1. The Bolocam Galactic Plane Survey. XII. Distance Catalog Expansion Using Kinematic Isolation of Dense Molecular Cloud Structures with 13CO(1-0)

    NASA Astrophysics Data System (ADS)

    Ellsworth-Bowers, Timothy P.; Rosolowsky, Erik; Glenn, Jason; Ginsburg, Adam; Evans, Neal J., II; Battersby, Cara; Shirley, Yancy L.; Svoboda, Brian

    2015-01-01

    We present an expanded distance catalog for 1710 molecular cloud structures identified in the Bolocam Galactic Plane Survey (BGPS) version 2, representing a nearly threefold increase over the previous BGPS distance catalog. We additionally present a new method for incorporating extant data sets into our Bayesian distance probability density function (DPDF) methodology. To augment the dense-gas tracers (e.g., HCO^+(3-2), NH3(1,1)) used to derive line-of-sight velocities for kinematic distances, we utilize the Galactic Ring Survey (GRS) 13CO(1-0) data to morphologically extract velocities for BGPS sources. The outline of a BGPS source is used to select a region of the GRS 13CO data, along with a reference region to subtract enveloping diffuse emission, to produce a line profile of 13CO matched to the BGPS source. For objects with a HCO^+(3-2) velocity, ≈95% of the new 13CO(1-0) velocities agree with that of the dense gas. A new prior DPDF for kinematic distance ambiguity (KDA) resolution, based on a validated formalism for associating molecular cloud structures with known objects from the literature, is presented. We demonstrate this prior using catalogs of masers with trigonometric parallaxes and H II regions with robust KDA resolutions. The distance catalog presented here contains well-constrained distance estimates for 20% of BGPS V2 sources, with typical distance uncertainties <~ 0.5 kpc. Approximately 75% of the well-constrained sources lie within 6 kpc of the Sun, concentrated in the Scutum-Centaurus arm. Galactocentric positions of objects additionally trace out portions of the Sagittarius, Perseus, and Outer arms in the first and second Galactic quadrants, and we also find evidence for significant regions of interarm dense gas.

  2. Evidence for a collinear easy-plane magnetic structure of multiferroic EuF e3(BO3) 4 : Spectroscopic and theoretical studies

    NASA Astrophysics Data System (ADS)

    Popova, M. N.; Malkin, B. Z.; Boldyrev, K. N.; Stanislavchuk, T. N.; Erofeev, D. A.; Temerov, V. L.; Gudim, I. A.

    2016-11-01

    We performed high-resolution polarized optical transmission spectroscopy and theoretical studies of multiferroic EuF e3(BO3) 4 single crystals in the three phases: paramagnetic R 32 (T >Ts=84 K ) and P 3121 ( Ts>T >TN=34 K ) , and antiferromagnetic (T structure, namely, a collinear arrangement of the iron magnetic moments along the C2 symmetry axis in the a b crystallographic plane of EuF e3(BO3) 4 below TN. Spectral signatures of the phase transitions and the spin-phonon interaction are observed and discussed. Reliable crystal-field and exchange-interaction parameters are obtained and used to model the magnetic susceptibility of the compound. The results of detailed calculations of the electric polarization of EuF e3(BO3) 4 in the R 32 phase are presented, and mechanisms of the magnetoelectric response are discussed. We detect a strong effect of impurities (that enter the crystal from a flux in the course of the crystal growth) on the structural phase-transition temperature and demonstrate a coexistence of both R 32 and P 3121 phases down to the lowest temperatures in a EuF e3(BO3) 4 crystal grown with the B i2M o3O12 based flux, due to inhomogeneous distribution of impurity B i3 + ions. Our study can be considered as a demonstration of the abilities of optical spectroscopy in delivering new information on a magnetic compound, even in the case when other methods fail.

  3. Nanostructured carbon films with oriented graphitic planes

    SciTech Connect

    Teo, E. H. T.; Kalish, R.; Kulik, J.; Kauffmann, Y.; Lifshitz, Y.

    2011-03-21

    Nanostructured carbon films with oriented graphitic planes can be deposited by applying energetic carbon bombardment. The present work shows the possibility of structuring graphitic planes perpendicular to the substrate in following two distinct ways: (i) applying sufficiently large carbon energies for deposition at room temperature (E>10 keV), (ii) utilizing much lower energies for deposition at elevated substrate temperatures (T>200 deg. C). High resolution transmission electron microscopy is used to probe the graphitic planes. The alignment achieved at elevated temperatures does not depend on the deposition angle. The data provides insight into the mechanisms leading to the growth of oriented graphitic planes under different conditions.

  4. Experiments with Planing Surfaces

    NASA Technical Reports Server (NTRS)

    Sottorf, W

    1934-01-01

    A previous report discusses the experimental program of a systematic exploration of all questions connected with the planing problem as well as the first fundamental results of the investigation of a flat planing surface. The present report is limited to the conversion of the model test data to full scale.

  5. Effect of out-of-plane directional intra-layer coupling from graphene monolayer on sp3 type defect with gap-plasmonic structures

    NASA Astrophysics Data System (ADS)

    Park, Won-Hwa

    2016-09-01

    The author investigates an intra-layer coupling effect through transverse acoustic (TA) phonon modes along the z-direction at Au nanoparticle (NP)-graphene monolayer (GM)-Au thin film (TF) plasmonic junctions in regard with sp3 type defect effect. The oxidation and resulting disorder of GM with breaking of six-fold symmetry have been explored. Because a Raman-forbidden D peak can be activated due to unwanted single-phonon inter-valley and intra-valley scattering processes, the quantitative estimation of the sp3 type defect is being performed by the intensity ratio between G and D peaks. By exploring the difference of the maximum peak position (TA3-TA1) and the intensity ratio, (TA1/TA3) the author can reveal that a lower z-protruded GM accompanied with weak intra-coupling and a weaker RBLM intensity show relatively high D/G. It means that larger surface area of a GM to be functionalized by oxidization can secure more easily than the higher z-protruded. This investigation presents the importance of controlling the degree of z-protrusion of GM surface in terms of not only the presence of high D/G but also its related and detailed nano-structural surface shape, leading to the enhancement of electrical properties such as a carrier mobility and sheet resistance value. The out-of-plane phonon modes will be considered as a key factor in further exploring nano-physical deformation of 2D materials in sync with its electrical performance.

  6. Fourier plane imaging microscopy

    SciTech Connect

    Dominguez, Daniel Peralta, Luis Grave de; Alharbi, Nouf; Alhusain, Mdhaoui; Bernussi, Ayrton A.

    2014-09-14

    We show how the image of an unresolved photonic crystal can be reconstructed using a single Fourier plane (FP) image obtained with a second camera that was added to a traditional compound microscope. We discuss how Fourier plane imaging microscopy is an application of a remarkable property of the obtained FP images: they contain more information about the photonic crystals than the images recorded by the camera commonly placed at the real plane of the microscope. We argue that the experimental results support the hypothesis that surface waves, contributing to enhanced resolution abilities, were optically excited in the studied photonic crystals.

  7. Single-chain magnets constructed by using the strict orthogonality of easy-planes: use of structural flexibility to control the magnetic properties.

    PubMed

    Kajiwara, Takashi; Tanaka, Hiroki; Nakano, Motohiro; Takaishi, Shinya; Nakazawa, Yasuhiro; Yamashita, Masahiro

    2010-09-20

    A family of single-chain magnets (SCMs), of which the SCM character originated from the spatial arrangement of high spin Fe(II) ions with easy-plane anisotropy, was synthesized, and their magnetic properties were investigated. The chain complexes including alternating high-spin Fe(II) ions and low-spin Fe(III) ions, catena-[Fe(II)(ClO(4))(2){Fe(III)(bpca)(2)}]ClO(4)·3MeNO(2) (1·3MeNO(2)), catena-[Fe(II)(ClO(4))(H(2)O){Fe(III)((Me)L)(2)}](ClO(4))(2)·2MeNO(2)·H(2)O (2·2MeNO(2)·H(2)O), catena-[Fe(II)(ClO(4))(H(2)O){Fe(III)((Bu)L)(2)}](ClO(4))(2)·3.5MeNO(2) (3·3.5MeNO(2)), and catena-[{Fe(II)(ClO(4))(H(2)O)Fe(II)(H(2)O)(2)}(0.5){Fe(III)((Ph)L)(2)}](ClO(4))(2.5)·4EtNO(2) (4·4EtNO(2)), were synthesized with the use of bridging ligand Hbpca (bis-(2-pyridylcarbonyl)amine)) and its derivatives of H(Me)L, H(Bu)L, and H(Ph)L each incorporating methyl, tert-butyl, or phenyl group on the 4-position of pyridyl ring. These complexes showed a typical ferrimagnetic behavior on direct current (dc) susceptibility data, and from an alternating current (ac) susceptibility measurements, SCM or superparamagnetic behaviors were confirmed with the Δ/k(B) values of 22.5(4), 21.8(18), and 28.8(3) K for 1·3MeNO(2), 2·2MeNO(2)·H(2)O, and 3·3.5MeNO(2), of which the easy-axis anisotropy was originated from the orthogonal arrangement of easy-planes of Fe(II) ions. In the crystal structures, cylindrical voids were formed along the chain axis being surrounded by four chains in 1·3MeNO(2), 2·2MeNO(2)·H(2)O, and 4·4EtNO(2) and two chains in 3·3.5MeNO(2), and solvent molecules as well as coordination-free perchlorate anions occupied these voids in a slightly different fashion depending on the complexes. 2·2MeNO(2)·H(2)O maintains its chemical composition in a dried condition, whereas 1·3MeNO(2), 3·3.5MeNO(2), and 4·4EtNO(2) easily release solvent molecules to give 1, 3, and 4, respectively. 1 and 3 maintain the crystalline character showing slightly different X-ray diffraction

  8. Controlling the threshold voltage of SnO2 nanowire transistors with dual in-plane-gate structures gated by chitosan proton conductors

    NASA Astrophysics Data System (ADS)

    Liu, Huixuan; Tan, Rongri

    2017-05-01

    We fabricated novel dual in-plane-gate electric-double-layer (EDL) SnO2 nanowire transistors gated by chitosan using only one transmission electron microscopy (TEM) nickel grid mask at room temperature, and we successfully controlled its threshold voltage. By changing the second in-plane gate bias from 1.0 to -1.0 V, we tuned the threshold voltage of these transistors from -0.35 to 0.21 V. Their operation voltage was 1.0 V, because the EDL gate dielectric can lead to high gate dielectric capacitance (4.24 µF/cm2). These dual in-plane-gate nanowire transistors could pave the way to useful low-voltage nanoelectronic devices.

  9. Fixed Sagittal Plane Imbalance

    PubMed Central

    Savage, Jason W.; Patel, Alpesh A.

    2014-01-01

    Study Design Literature review. Objective To discuss the evaluation and management of fixed sagittal plane imbalance. Methods A comprehensive literature review was performed on the preoperative evaluation of patients with sagittal plane malalignment, as well as the surgical strategies to address sagittal plane deformity. Results Sagittal plane imbalance is often caused by de novo scoliosis or iatrogenic flat back deformity. Understanding the etiology and magnitude of sagittal malalignment is crucial in realignment planning. Objective parameters have been developed to guide surgeons in determining how much correction is needed to achieve favorable outcomes. Currently, the goals of surgery are to restore a sagittal vertical axis < 5 cm, pelvic tilt < 20 degrees, and lumbar lordosis equal to pelvic incidence ± 9 degrees. Conclusion Sagittal plane malalignment is an increasingly recognized cause of pain and disability. Treatment of sagittal plane imbalance varies according to the etiology, location, and severity of the deformity. Fixed sagittal malalignment often requires complex reconstructive procedures that include osteotomy correction. Reestablishing harmonious spinopelvic alignment is associated with significant improvement in health-related quality-of-life outcome measures and patient satisfaction. PMID:25396111

  10. Fixed sagittal plane imbalance.

    PubMed

    Savage, Jason W; Patel, Alpesh A

    2014-12-01

    Study Design Literature review. Objective To discuss the evaluation and management of fixed sagittal plane imbalance. Methods A comprehensive literature review was performed on the preoperative evaluation of patients with sagittal plane malalignment, as well as the surgical strategies to address sagittal plane deformity. Results Sagittal plane imbalance is often caused by de novo scoliosis or iatrogenic flat back deformity. Understanding the etiology and magnitude of sagittal malalignment is crucial in realignment planning. Objective parameters have been developed to guide surgeons in determining how much correction is needed to achieve favorable outcomes. Currently, the goals of surgery are to restore a sagittal vertical axis < 5 cm, pelvic tilt < 20 degrees, and lumbar lordosis equal to pelvic incidence ± 9 degrees. Conclusion Sagittal plane malalignment is an increasingly recognized cause of pain and disability. Treatment of sagittal plane imbalance varies according to the etiology, location, and severity of the deformity. Fixed sagittal malalignment often requires complex reconstructive procedures that include osteotomy correction. Reestablishing harmonious spinopelvic alignment is associated with significant improvement in health-related quality-of-life outcome measures and patient satisfaction.

  11. Structure and Function of the Superior Temporal Plane in Adult Males with Cleft Lip and Palate: Pathologic Enlargement with No Relationship to Childhood Hearing Deficits

    ERIC Educational Resources Information Center

    Shriver, A. S.; Canady, J.; Richman, L.; Andreasen, N. C.; Nopoulos, P.

    2006-01-01

    Background: In a previous study from our lab, adult males with non-syndromic cleft lip and/or palate (NSCLP) were shown to have significantly lower temporal lobe gray matter volume than matched controls. The current study was designed to begin a regional analysis of specific subregions of the temporal lobe. The superior temporal plane (STP) is a…

  12. Structure and Function of the Superior Temporal Plane in Adult Males with Cleft Lip and Palate: Pathologic Enlargement with No Relationship to Childhood Hearing Deficits

    ERIC Educational Resources Information Center

    Shriver, A. S.; Canady, J.; Richman, L.; Andreasen, N. C.; Nopoulos, P.

    2006-01-01

    Background: In a previous study from our lab, adult males with non-syndromic cleft lip and/or palate (NSCLP) were shown to have significantly lower temporal lobe gray matter volume than matched controls. The current study was designed to begin a regional analysis of specific subregions of the temporal lobe. The superior temporal plane (STP) is a…

  13. Building Technology Forecast and Evaluation (BTFE). Volume 2. Evaluation of Two Structural Systems

    DTIC Science & Technology

    1990-11-01

    insulative foam ( expanded polystyrene ) strips between each truss. The assembly is held together with 14-gauge wires welded to the trusses on 2-in. centers...structural load bearing qualities expanded polystyrene . No taping and mudding. Ar. ~J~ .wplrtpd( at each irllnfrnPllo Tile I hin- set or float over

  14. A Displacive Structural Transformation in the CuO{sub 2} Planes of YBa{sub 2}Cu{sub 3}O{sub {ital x}} at the Underdoped-Overdoped Phase Separation Line

    SciTech Connect

    Kaldis, E.; Conder, K.; Roehler, J.; Liarokapis, E.; Poulakis, N.; Loeffen, P.W.

    1997-12-01

    A structural phase transformation in the CuO{sub 2} planes of YBa{sub 2}Cu {sub 3}O{sub x} has been observed at the onset of the overdoped regime, x=6.95 . We have measured as a function of x the dimpling in the CuO{sub 2} planes by EXAFS, and the O(2,3) in-phase (A{sub 1g}) mode by Raman scattering. The data show for x{ge}6.95 anomalously large static displacements of the Cu(2) atoms off the O(2,3) layer and a gap in the distribution of the O(2,3) in-phase Raman shifts. We conclude the structure of overdoped YBa{sub 2}Cu {sub 3}O{sub x} to be a martensitic form of the optimum doped crystal. {copyright} {ital 1997} {ital The American Physical Society}

  15. Structure and Composition of Air-Plane Soots and Surrogates Analyzed by Raman Spectroscopy and Laser/Ions Desorption Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Ortega, Ismael; Chazallon, Bertrand; Carpentier, Yvain; Irimiea, Cornelia; Focsa, Cristian; Ouf, François-Xavier; Salm, François; Delhaye, David; Gaffié, Daniel; Yon, Jérôme

    2015-04-01

    Aviation alters the composition of the atmosphere globally and can thus drive climate change and ozone depletion [1]. An aircraft exhaust plume contains species emitted by the engines, species formed in the plume from the emitted species and atmospheric species that become entrained into the plume. The majority of emitted species (gases and soot particles) are produced by the combustion of kerosene with ambient air in the combustion chamber of the engine. Emissions of soot particles by air-planes produce persistent contrails in the upper troposphere in ice-supersaturated air masses that contribute to cloudiness and impact the radiative properties of the atmosphere. These aerosol-cloud interactions represent one of the largest sources of uncertainty in global climate models [2]. Though the formation of atmospheric ice particles has been studied since many years [3], there are still numerous opened questions on nucleation properties of soot particles [4], as the ice nucleation experiments showed a large spread in results depending on the nucleation mode chosen and origin of the soot produced. Most likely one of the reasons behind these discrepancies resides in the different physico-chemical properties (composition, structure) of soot particles produced in different conditions, e.g. with respect to fuel or combustion techniques. In this work, we use Raman microscopy (266, 514 and 785 nm excitation) and ablation techniques (SIMS, Secondary Ions Mass Spectrometry, and Laser Desorption Mass Spectrometry) to characterize soot particles produced from air-plane at different engine regimes simulating a landing and taking-off (LTO) cycle. First, the spectral parameters of the first-order Raman band of various soot samples, collected from three different sources in the frame of the MERMOSE project (http://mermose.onera.fr/): PowerJet SaM-146 turbofan (four engine regimes), CAST generator (propane fuel, four different global equivalence ratios), and Kerosene laboratory flame

  16. Spin-orbit torque induced magnetization switching in Ta/Co{sub 20}Fe{sub 60}B{sub 20}/MgO structures under small in-plane magnetic fields

    SciTech Connect

    Cao, Jiangwei Zheng, Yuqiang; Su, Xianpeng; Hao, Liang; Wang, Ying; Bai, Jianmin; Wei, Fulin

    2016-04-25

    Spin-orbit torque (SOT)-induced magnetization switching under small in-plane magnetic fields in as-deposited and annealed Ta/CoFeB/MgO structures is studied. For the as-deposited samples, partial SOT-induced switching behavior is observed under an in-plane field of less than 100 Oe. Conversely, for the annealed samples, an in-plane field of 10 Oe is large enough to achieve full deterministic magnetization switching. The Dzyaloshinskii-Moriya interaction at the Ta/CoFeB interface is believed to be the main reason for the discrepancy of the requisite in-plane magnetic fields for switching in the as-deposited and annealed samples. In addition, asymmetric field dependence behavior of SOT-induced magnetization switching is observed in the annealed samples. Deterministic magnetization switching in the absence of an external magnetic field is obtained in the annealed samples, which is extremely important to develop SOT-based magnetoresistive random access memory.

  17. Eight plane IPND mechanical testing.

    SciTech Connect

    Zhao, A.; Guarino, V.; Wood, K.; Nephew, T.; Ayres, D.; Lee, A.; High Energy Physics; FNAL

    2008-03-18

    A mechanical test of an 8 plane IPND mechanical prototype, which was constructed using extrusions from the testing/tryout of the 16 cell prototype extrusion die in Argonne National Laboratory, was conducted. There were 4 vertical and 4 horizontal planes in this 8 plane IPND prototype. Each vertical plane had four 16 cell extrusions, while each horizontal plane had six 16 cell extrusions. Each plane was glued together using the formulation of Devcon adhesive, Devcon 60. The vertical extrusions used in the vertical planes shares the same dimensions as the horizontal extrusions in the horizontal planes with the average web thickness of 2.1 mm and the average wall thickness of 3.1 mm. This mechanical prototype was constructed with end-seals on the both ends of the vertical extrusions. The gaps were filled with epoxy between extrusions and end-seals. The overall dimension of IPND is 154.8 by 103.1 by 21.7 inches with the weight of approximately 1200 kg, as shown in a figure. Two similar mechanical tests of 3 layer and 11 layer prototypes have been done in order to evaluate the strength of the adhesive joint between extrusions in the NOvA detector. The test showed that the IPND prototype was able to sustain under the loading of weight of itself and scintillator. Two FEA models were built to verify the measurement data from the test. The prediction from FEA slice model seems correlated reasonably well to the test result, even under a 'rough' estimated condition for the wall thickness (from an untuned die) and an unknown property of 'garage type' extrusion. A full size of FEA 3-D model also agrees very well with the test data from strain gage readings. It is worthy to point out that the stress distribution of the structure is predominantly determined by the internal pressure, while the buckling stability relies more on the loading weight from the extrusions themselves and scintillate. Results of conducted internal pressure tests, including 3- cell, 11-cell and the IPND

  18. Core structure, dislocation energy and Peierls stress for 1/3?11 0? edge dislocations with (0001) and {1 00} slip planes in α-Zr.

    SciTech Connect

    Voskoboinikov, Roman E; Osetskiy, Yury N; Bacon, David J

    2005-01-01

    Atomic-scale simulations of edge dislocations of the 1/3<11{bar 2}0> (0001) and 1/3<11{bar 2}0> {l_brace}1{bar 1}00{r_brace} slip systems have been carried out using a Finnis-Sinclair-type interatomic potential for {alpha}-zirconium. The distribution of atomic displacements in the dislocation core shows that in this model the edge dislocation in the basal plane dissociates into two Shockley partials whereas the dislocation in the prism plane remains undissociated. The effective core radius and core energy are estimated, and dislocation response to increasing applied shear strain is investigated. The core properties and the critical stress for dislocation glide (Peierls stress) depend sensitively on whether the core extends or not.

  19. Structural and electronic properties of InN epitaxial layer grown on c-plane sapphire by chemical vapor deposition technique

    SciTech Connect

    Barick, Barun Kumar Prasad, Nivedita; Saroj, Rajendra Kumar; Dhar, Subhabrata

    2016-09-15

    Growth of InN epilayers on c-plane sapphire substrate by chemical vapor deposition technique using pure indium metal and ammonia as precursors has been systematically explored. It has been found that [0001] oriented indium nitride epitaxial layers with smooth surface morphology can be grown on c-plane sapphire substrates by optimizing the growth conditions. Bandgap of the film is observed to be Burstein–Moss shifted likely to be due to high background electron concentration. It has been found that the concentration of this unintentional doping decreases with the increase in the growth temperature and the ammonia flux. Epitaxial quality on the other hand deteriorates as the growth temperature increases. Moreover, the morphology of the deposited layer has been found to change from flat top islands to faceted mounds as the flow rate of ammonia increases. This phenomenon is expected to be related to the difference in surface termination character at low and high ammonia flow rates.

  20. SNAP focal plane

    SciTech Connect

    Lampton, Michael L.; Kim, A.; Akerlof, C.W.; Aldering, G.; Amanullah, R.; Astier, P.; Barrelet, E.; Bebek, C.; Bergstrom, L.; Berkovitz, J.; Bernstein, G.; Bester, M.; Bonissent, A.; Bower, C.; Carithers Jr., W.C.; Commins, E.D.; Day, C.; Deustua, S.E.; DiGennaro,R.; Ealet, A.; Ellis, R.S.; Eriksson, M.; Fruchter, A.; Genat, J.-F.; Goldhaber, G.; Goobar, A.; Groom, D.; Harris, S.E.; Harvey, P.R.; Heetderks, H.D.; Holland, S.E.; Huterer, D.; Karcher, A.; Kolbe, W.; Krieger, B.; Lafever, R.; Lamoureux, J.; Levi, M.E.; Levin, D.S.; Linder,E.V.; Loken, S.C.; Malina, R.; Massey, R.; McKay, T.; McKee, S.P.; Miquel, R.; Mortsell, E.; Mostek, N.; Mufson, S.; Musser, J.; Nugent, P.; Oluseyi, H.; Pain, R.; Palaio, N.; Pankow, D.; Perlmutter, S.; Pratt, R.; Prieto, E.; Refregier, A.; Rhodes, J.; Robinson, K.; Roe, N.; Sholl, M.; Schubnell, M.; Smadja, G.; Smoot, G.; Spadafora, A.; Tarle, G.; Tomasch,A.; von der Lippe, H.; Vincent, R.; Walder, J.-P.; Wang, G.

    2002-07-29

    The proposed SuperNova/Acceleration Probe (SNAP) mission will have a two-meter class telescope delivering diffraction-limited images to an instrumented 0.7 square-degree field sensitive in the visible and near-infrared wavelength regime. We describe the requirements for the instrument suite and the evolution of the focal plane design to the present concept in which all the instrumentation--visible and near-infrared imagers, spectrograph, and star guiders--share one common focal plane.

  1. Anisotropy in geometrically rough structure of ice prismatic plane interface during growth: Development of a modified six-site model of H2O and a molecular dynamics simulation.

    PubMed

    Nada, Hiroki

    2016-12-28

    This paper presents a modified version of the six-site model of H2O [H. Nada and J. P. J. M. van der Eerden, J. Chem. Phys. 118, 7401 (2003)]. Although the original six-site model was optimized by assuming the cut-off of the Coulomb interaction at an intermolecular distance of 10 Å, the modified model is optimized by using the Ewald method for estimating the Coulomb interaction. Molecular dynamics (MD) simulations of an ice-water interface suggest that the melting point of ice at 1 atm in the modified model is approximately 274.5 K, in good agreement with the real melting point of 273.15 K. MD simulations of bulk ice and water suggest that the modified model reproduces not only the structures and density curves of ice and water, but also the diffusion coefficient of water molecules in water near the melting point at 1 atm. Using the modified model, a large-scale MD simulation of the growth at an ice-water interface of the prismatic plane is performed to elucidate the anisotropy in the interface structure during growth. Simulation results indicate that the geometrical roughness of the ice growth front at the interface is greater in the c-axis direction than in the direction normal to the c-axis when it is analyzed along the axes parallel to the prismatic plane. In addition, during the growth at the interface, the transient appearance of specific crystallographic planes, such as a {202¯1} pyramidal plane, occurs preferentially at the ice growth front. The effect of different ensembles with different simulation systems on the anisotropy in the interface structure is also investigated.

  2. Anisotropy in geometrically rough structure of ice prismatic plane interface during growth: Development of a modified six-site model of H2O and a molecular dynamics simulation

    NASA Astrophysics Data System (ADS)

    Nada, Hiroki

    2016-12-01

    This paper presents a modified version of the six-site model of H2O [H. Nada and J. P. J. M. van der Eerden, J. Chem. Phys. 118, 7401 (2003)]. Although the original six-site model was optimized by assuming the cut-off of the Coulomb interaction at an intermolecular distance of 10 Å, the modified model is optimized by using the Ewald method for estimating the Coulomb interaction. Molecular dynamics (MD) simulations of an ice-water interface suggest that the melting point of ice at 1 atm in the modified model is approximately 274.5 K, in good agreement with the real melting point of 273.15 K. MD simulations of bulk ice and water suggest that the modified model reproduces not only the structures and density curves of ice and water, but also the diffusion coefficient of water molecules in water near the melting point at 1 atm. Using the modified model, a large-scale MD simulation of the growth at an ice-water interface of the prismatic plane is performed to elucidate the anisotropy in the interface structure during growth. Simulation results indicate that the geometrical roughness of the ice growth front at the interface is greater in the c-axis direction than in the direction normal to the c-axis when it is analyzed along the axes parallel to the prismatic plane. In addition, during the growth at the interface, the transient appearance of specific crystallographic planes, such as a {20 2 ¯ 1 } pyramidal plane, occurs preferentially at the ice growth front. The effect of different ensembles with different simulation systems on the anisotropy in the interface structure is also investigated.

  3. In-plane orientation and composition dependences of crystal structure and electrical properties of {100}-oriented Pb(Zr,Ti)O3 films grown on (100) Si substrates by metal organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Okamoto, Shoji; Sankara Rama Krishnan, P. S.; Okamoto, Satoshi; Yokoyama, Shintaro; Akiyama, Kensuke; Funakubo, Hiroshi

    2017-10-01

    In-plane orientation-controlled Pb(Zr x ,Ti1‑ x )O3 (PZT) films with a thickness of approximately 2 µm and a Zr/(Zr + Ti) ratio of 0.39–0.65 were grown on (100) Si substrates by pulsed metal–organic chemical vapor deposition (MOCVD). In-plane-oriented epitaxial PZT films and in-plane random fiber-textured PZT films with {100} out-of-plane orientation were grown on (100)c SrRuO3//(100)c LaNiO3//(100) CeO2//(100) YSZ//(100) Si and (100)c SrRuO3/(100)c LaNiO3/(111) Pt/TiO2/SiO2/(100) Si substrates, respectively. The effects of Zr/(Zr + Ti) ratio and in-plane orientation on the crystal structure, dielectric, ferroelectric, and piezoelectric properties of the films were systematically investigated. The X-ray diffraction measurement showed that the epitaxial PZT films had a higher volume fraction of (100) orientation than the fiber-textured PZT films in the tetragonal Zr/(Zr + Ti) ratio region. A large difference was not detected between the epitaxial films and the fiber-textured films for Zr/(Zr + Ti) ratio dependence of the dielectric constant, and remanent polarization. However, in the rhombohedral phase region [Zr/(Zr + Ti) = 0.65], coercive field was found to be 1.5-fold different between the epitaxial and fiber-textured PZT films. The maximum field-induced strains measured at 0–100 kV/cm by scanning atomic force microscopy were obtained at approximately Zr/(Zr + Ti) = 0.50 and were about 0.5 and 0.3% for the epitaxial and fiber-textured PZT films, respectively.

  4. Structural components of nuclear integrity with gene regulatory potential.

    PubMed

    Fenelon, Kelli D; Hopyan, Sevan

    2017-10-01

    The nucleus is a mechanosensitive and load-bearing structure. Structural components of the nucleus interact to maintain nuclear integrity and have become subjects of exciting research that is relevant to cell and developmental biology. Here we outline the boundaries of what is known about key architectural elements within the nucleus and highlight their potential structural and transcriptional regulatory functions. Copyright © 2017. Published by Elsevier Ltd.

  5. Precise measurement of planeness.

    PubMed

    Schulz, G; Schwider, J

    1967-06-01

    Interference methods are reviewed-particularly those developed at the German Academy of Sciences in Berlin-with which the deviations of an optically flat surface from the ideal plane can be measured with a high degree of exactness. One aid to achieve this is the relative methods which measure the differences in planeness between two surfaces. These are then used in the absolute methods which determine the absolute planeness of a surface. This absolute determination can be effected in connection with a liquid surface, or (as done by the authors) only by suitable evaluation of relative measurements between unknown plates in various positional combinations. Experimentally, one uses two- or multiple-beam interference fringes of equal thickness(1) or of equal inclination. The fringes are observed visually, scanned, or photographed, and in part several wavelengths or curves of equal density (Aquidensiten) are employed. The survey also brings the following new methods: a relative method, where, with the aid of fringes of superposition, the fringe separation is subdivided equidistantly thus achieving an increase of measuring precision, and an absolute method which determines the deviations of a surface from ideal planeness along arbitrary central sections, without a liquid surface, from four relative interference photographs.

  6. Effect of CuO2 planes on the structural and superconducting transport properties of [CuTl - 12(n - 1)n;n = 2,3,4] superconductor family

    NASA Astrophysics Data System (ADS)

    Muzaffar, M. Usman; Khan, Nawazish A.

    2016-06-01

    Cu0.5Tl0.5Ba2Can-1CunO2n+4-δ (n = 2, 3, 4) superconducting bulk samples have been synthesized by using two-step solid state reaction method. We investigated the effects of CuO2 planes on the structural and superconducting transport properties of [CuTl - 12(n - 1)n; n = 2, 3, 4] superconducting family. These samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) absorption spectroscopy and DC-resistivity (ρ) measurements. These samples are c-axis length oriented and have shown orthorhombic crystal structure. All the samples have shown metallic variations of resistivity from room temperature down to onset of superconductivity. The zero resistivity critical temperature Tc(R = 0) increases with the increase in superconducting planes and normal state resistivity systematically decreases, which show the density of inadvertent defects decreases in the final compound. The apical oxygen phonon modes are hardened as observed in the FTIR absorption measurements. The intrinsic microscopic superconducting parameters, such as the cross-over temperatures, coherence length along c-axis (ξc(0)) at 0 K, inter-layer coupling (J), inter-grain coupling (α) and fermi velocity (VF), were extracted from the fluctuation-induced conductivity (FIC) analysis. FIC analysis also showed the improvement in superconductivity with the increase in CuO2 planes.

  7. Influence of edge-grown HVPE GaN on the structural quality of c-plane oriented HVPE-GaN grown on ammonothermal GaN substrates

    NASA Astrophysics Data System (ADS)

    Domagala, J. Z.; Smalc-Koziorowska, J.; Iwinska, M.; Sochacki, T.; Amilusik, M.; Lucznik, B.; Fijalkowski, M.; Kamler, G.; Grzegory, I.; Kucharski, R.; Zajac, M.; Bockowski, M.

    2016-12-01

    Study on the sources of stress in HVPE-GaN layer crystallized on 1-in. ammonothermally grown GaN seed is presented in this paper. Characterization by means of X-ray diffraction and transmission electron microscopy is performed. HVPE-GaN samples of high quality and those with visible quality deterioration are investigated on c-plane and m-plane cross-sections. Special attention is paid to HVPE material growing in semi-polar and non-polar directions on the edges of the seed and the growing layer. It is shown that this material generates significant stress leading to a structural deterioration of HVPE-GaN growing in the c-direction.

  8. Augmented-plane-wave forces

    NASA Astrophysics Data System (ADS)

    Soler, José M.; Williams, Arthur R.

    1990-11-01

    Results are presented that demonstrate the effectiveness of a calculational method of electronic-structure theory. The method combines the power (tractable basis-set size) and flexibility (transition and first-row elements) of the augmented-plane-wave method with the computational efficiency of the Car-Parrinello method of molecular dynamics and total-energy minimization. Equilibrium geometry and vibrational frequencies in agreement with experiment are presented for Si, to demonstrate agreement with existing methods and for Cu, N2, and H2O to demonstrate the broader applicability of the approach.

  9. Foam rigidized inflatable structural assemblies

    NASA Technical Reports Server (NTRS)

    Tinker, Michael L. (Inventor); Schnell, Andrew R. (Inventor)

    2010-01-01

    An inflatable and rigidizable structure for use as a habitat or a load bearing structure is disclosed. The structure consists of an outer wall and an inner wall defining a containment member and a bladder. The bladder is pressurized to erect the structure from an initially collapsed state. The containment member is subsequently injected with rigidizable fluid through an arrangement of injection ports. Exhaust gases from the curing rigidizable fluid are vented through an arrangement of exhaust ports. The rate of erection can be controlled by frictional engagement with a container or by using a tether. A method for fabricating a tubular structure is disclosed.

  10. Complete assignment of the hydrogen out-of-plane wagging vibrations of bathorhodopsin: chromophore structure and energy storage in the primary photoproduct of vision.

    PubMed

    Palings, I; van den Berg, E M; Lugtenburg, J; Mathies, R A

    1989-02-21

    Resonance Raman vibrational spectra of the retinal chromophore in bathorhodopsin have been obtained after regenerating bovine visual pigments with an extensive series of 13C- and deuterium-labeled retinals. A low-temperature spinning cell technique was used to produce high-quality bathorhodopsin spectra exhibiting resolved hydrogen out-of-plane wagging vibrations at 838, 850, 858, 875, and 921 cm-1. The isotopic shifts and a normal coordinate analysis permit the assignment of these lines to the HC7 = C8H Bg, C14H, C12H, C10H, and C11H hydrogen out-of-plane wagging modes, respectively. The coupling constant between the C11H and C12H wags as well as the C12H wag force constant are unusually low compared to those of retinal model compounds. This quantitatively confirms the lack of coupling between the C11H and C12H wags and the low C12H wag vibrational frequency noted earlier by Eyring et al. [(1982) Biochemistry 21, 384]. The force constants for the C10H and C14H wags are also significantly below the values observed in model compounds. We suggest that the perturbed hydrogen out-of-plane wagging and C-C stretching force constants for the C10-C11 = C12-C13 region of the chromophore in bathorhodopsin result from electrostatic interactions with a charged protein residue. This interaction may also contribute to the 33 kcal/mol energy storage in bathorhodopsin.

  11. Dielectric response and structure of in-plane tensile strained BaTiO3 thin films grown on the LaNiO3 buffered Si substrate

    NASA Astrophysics Data System (ADS)

    Qiao, Liang; Bi, Xiaofang

    2008-02-01

    Highly (001)-textured BaTiO3 films were grown epitaxially on the LaNiO3 buffered Si substrate. A strong in-plane tensile strain has been revealed by using x-ray diffraction and high resolution transmission electron microscopy. The BaTiO3 film has exhibited a small remnant polarization, indicating the presence of ca1/ca2/ca1/ca2 polydomain state in the film. Temperature dependent dielectric permittivity has demonstrated that two phase transitions occurred at respective temperatures of 170 and 30°C. The result was discussed in detail based on the misfit strain-temperature phase diagrams theory.

  12. Double plane wave reverse time migration with plane wave Green's function

    NASA Astrophysics Data System (ADS)

    Zhao, Z.; Sen, M. K.; Stoffa, P. L.

    2015-12-01

    Reverse time migration (RTM) is effective in obtaining complex subsurface structures from seismic data. By solving the two-way wave equation, RTM can use entire wavefield for imaging. Although powerful computer are becoming available, the conventional pre-stack shot gather RTM is still computationally expensive. Solving forward and backward wavefield propagation for each source location and shot gather is extremely time consuming, especially for large seismic datasets. We present an efficient, accurate and flexible plane wave RTM in the frequency domain where we utilize a compressed plane wave dataset, known as the double plane wave (DPW) dataset. Provided with densely sampled seismic dataset, shot gathers can be decomposed into source and receiver plane wave components with minimal artifacts. The DPW RTM is derived under the Born approximation and utilizes frequency domain plane wave Green's function for imaging. Time dips in the shot profiles can help to estimate the range of plane wave components present in shot gathers. Therefore, a limited number of plane wave Green's functions are needed for imaging. Plane wave Green's functions can be used for imaging both source and receiver plane waves. Source and receiver reciprocity can be used for imaging plane wave components at no cost and save half of the computation time. As a result, the computational burden for migration is substantially reduced. Plane wave components can be migrated independently to recover specific targets with given dips, and ray parameter common image gathers (CIGs) can be generated after migration directly. The ray parameter CIGs can be used to justify the correctness of velocity models. Subsurface anisotropy effects can also be included in our imaging condition, provided with plane wave Green's functions in the anisotropic media.

  13. Self-accommodation of B19' martensite in Ti-Ni shape memory alloys - Part II. Characteristic interface structures between habit plane variants

    NASA Astrophysics Data System (ADS)

    Nishida, M.; Okunishi, E.; Nishiura, T.; Kawano, H.; Inamura, T.; S., Ii; Hara, T.

    2012-06-01

    Four characteristic interface microstructures between habit plane variants (HPVs) in the self-accommodation morphologies of B19‧ martensite in Ti-Ni alloys have been investigated by scanning transmission electron microscopy (STEM). The straight interface of a ? B19‧ type I twin is present at interface I. The relaxation of the transformation strain at interface II is achieved by a volume reduction of the minor correspondence variants (CVs) in the relevant habit plane variants (HPVs). The relaxation of the transformation strain at interface III is mainly due to the formation of a ? B19‧ type I twin between the two major CVs. Subsequently, local strain around the tips of the minor CVs perpendicular to the interface is released by the formation of micro-twins with the ⟨011⟩B19‧ type II and/or ? B19‧ type I relation. The major and minor CVs in each HPV are alternately connected through fine variants with the ? B19‧ type I twin relation parallel to interface IV. The results are compared with macroscopic observations and the predictions of PTMC analysis.

  14. Space plane navigation simulation

    NASA Astrophysics Data System (ADS)

    Matsushima, Koichi; Murata, Masaaki; Shingu, Hirokimi; Shimizu, Tetsuo; Mikami, Tatsuo; Hashida, Yoshikazu

    A simulation program for a future Japanese space-plane (SP) considered for development is presented along with the results of the analysis of a candidate navigation configuration, focused on the terminal area energy management phase and the approach/landing phase of SP. The guidance laws and aerodynamic parameters which are applied to the program for the analysis are modeled using the laws and parameters of the U.S. Space Suttle, assuming typical values for the accuracy of sensors.

  15. Parameter Plane Design Method

    DTIC Science & Technology

    1989-03-01

    Th usr a toente aninteer a thca sms b esta 1 Fp-ocsing 2. Enter P1 values, lwgt, ldig - > 9 Table I give us proper values. Table 1. PARAMETER TABLE...necessary and identify by block number) In this thesis a control systems analysis package is developed using parameter plane methods. It is an interactive...designer is able to choose values of the parameters which provide a good compromise between cost and dynamic behavior. 20 Distribution Availability of

  16. The tail plane

    NASA Technical Reports Server (NTRS)

    Munk, Max M

    1923-01-01

    This report deals with the calculation of the equilibrium, statistical stability, and damping of the tail plane. The author has simplified the present theory of longitudinal stability for the particular purpose of obtaining one definite coefficient characteristics of the effect of the tail plane. This coefficient is obtained by substituting certain aerodynamic characteristics and some dimensions of the airplane in a comparatively simple mathematical expression. Care has been taken to confine all aerodynamical information necessary for the calculation of the coefficient to the well-known curves representing the qualities of the wing section. This is done by making use of the present results of modern aerodynamics. All formulas and relations necessary for the calculation are contained in the paper. They give in some cases only an approximation of the real values. An example of calculation is added in order to illustrate the application of the method. The coefficient indicates not only whether the effect of the tail plane is great enough, but also whether it is not too great. It appears that the designer has to avoid a certain critical length of the fuselage, which inevitably gives rise to periodical oscillations of the airplane. The discussion also shows the way and in what direction to carry out experimental work.

  17. Structural Characterization of Lateral-grown 6H-SiC am-plane Seed Crystals by Hot Wall CVD Epitaxy

    NASA Technical Reports Server (NTRS)

    Goue, Ouloide Yannick; Raghothamachar, Balaji; Dudley, Michael; Trunek, Andrew J.; Neudeck, Philip G.; Woodworth, Andrew A.; Spry, David J.

    2014-01-01

    The performance of commercially available silicon carbide (SiC) power devices is limited due to inherently high density of screw dislocations (SD), which are necessary for maintaining polytype during boule growth and commercially viable growth rates. The NASA Glenn Research Center (GRC) has recently proposed a new bulk growth process based on axial fiber growth (parallel to the c-axis) followed by lateral expansion (perpendicular to the c-axis) for producing multi-faceted m-plane SiC boules that can potentially produce wafers with as few as one SD per wafer. In order to implement this novel growth technique, the lateral homoepitaxial growth expansion of a SiC fiber without introducing a significant number of additional defects is critical. Lateral expansion is being investigated by hot wall chemical vapor deposition (HWCVD) growth of 6H-SiC am-plane seed crystals (0.8mm x 0.5mm x 15mm) designed to replicate axially grown SiC single crystal fibers. The post-growth crystals exhibit hexagonal morphology with approximately 1500 m (1.5 mm) of total lateral expansion. Preliminary analysis by synchrotron white beam x-ray topography (SWBXT) confirms that the growth was homoepitaxial, matching the polytype of the respective underlying region of the seed crystal. Axial and transverse sections from the as grown crystal samples were characterized in detail by a combination of SWBXT, transmission electron microscopy (TEM) and Raman spectroscopy to map defect types and distribution. X-ray diffraction analysis indicates the seed crystal contained stacking disorders and this appears to have been reproduced in the lateral growth sections. Analysis of the relative intensity for folded transverse acoustic (FTA) and optical (FTO) modes on the Raman spectra indicate the existence of stacking faults. Further, the density of stacking faults is higher in the seed than in the grown crystal. Bundles of dislocations are observed propagating from the seed in m-axis lateral directions

  18. Full-scale testing and numerical modeling of a multistory masonry structure subjected to internal blast loading

    NASA Astrophysics Data System (ADS)

    Zapata, Brian Jarvis

    As military and diplomatic representatives of the United States are deployed throughout the world, they must frequently make use of local, existing facilities; it is inevitable that some of these will be load bearing unreinforced masonry (URM) structures. Although generally suitable for conventional design loads, load bearing URM presents a unique hazard, with respect to collapse, when exposed to blast loading. There is therefore a need to study the blast resistance of load bearing URM construction in order to better protect US citizens assigned to dangerous locales. To address this, the Department of Civil and Environmental Engineering at the University of North Carolina at Charlotte conducted three blast tests inside a decommissioned, coal-fired, power plant prior to its scheduled demolition. The power plant's walls were constructed of URM and provided an excellent opportunity to study the response of URM walls in-situ. Post-test analytical studies investigated the ability of existing blast load prediction methodologies to model the case of a cylindrical charge with a low height of burst. It was found that even for the relatively simple blast chamber geometries of these tests, simplified analysis methods predicted blast impulses with an average net error of 22%. The study suggested that existing simplified analysis methods would benefit from additional development to better predict blast loads from cylinders detonated near the ground's surface. A hydrocode, CTH, was also used to perform two and three-dimensional simulations of the blast events. In order to use the hydrocode, Jones Wilkins Lee (JWL) equation of state (EOS) coefficients were developed for the experiment's Unimax dynamite charges; a novel energy-scaling technique was developed which permits the derivation of new JWL coefficients from an existing coefficient set. The hydrocode simulations were able to simulate blast impulses with an average absolute error of 34.5%. Moreover, the hydrocode simulations

  19. Submillimeter wavelength survey of the galactic plane from l = -5 deg to l = +62 deg: Structure and energetics of the inner disk

    NASA Technical Reports Server (NTRS)

    Hauser, M. G.; Silverberg, R. F.; Stier, M. T.; Kelsall, T.; Gezari, D. Y.; Dwek, E.; Walser, D.; Mather, J. C.; Cheung, L. H.

    1984-01-01

    Results from a large scale survey of the first quadrant of the Milky Way galactic plane at wavelengths of 150, 250, and 300 microns with a 10x10 arcmin beam are presented. The emission detected in the survey arises from compact sources, most of which are identified with known peaks of 5 GHz and/or CO emission, and from an underlying diffuse background with a typical angular width of approximately 0.9 deg (FWHM) which accounts for most of the emission. A total of 80 prominent discrete sources were identified and characterized, of which about half were not previously reported at far infrared wavelengths. The total infrared luminosity within the solar circle is approximately 1 to 2x10 to the 10th power L sub 0, and is probably emitted by dust that resides in molecular clouds.

  20. Submillimeter wavelength survey of the galactic plane from l = -5 deg to l = +62 deg - Structure and energetics of the inner disk

    NASA Technical Reports Server (NTRS)

    Hauser, M. G.; Silverberg, R. F.; Stier, M. T.; Kelsall, T.; Gezari, D. Y.; Dwek, E.; Walser, D.; Mather, J. C.; Cheung, L. H.

    1984-01-01

    Observational results are presented from a new large-scale survey of the first quadrant of the galactic plane at wavelengths of 150, 250, and 300 microns, with a 10 x 10 arcmin beam. The emission detected in the survey arises from compact sources, most of which are identified with known peaks of 5 GHz or CO emission, or both, and from an underlying diffuse background with a typical angular width of about 0.9 deg (FWHM) which accounts for most of the emission. A total of 80 prominent discrete sources are identified and characterized, of which about half have not previously been reported at far-infrared wavelengths. The total infrared luminosity within the solar circle is about 1 to 2 x 10 to the 10th solar luminosity, and is probably emitted by dust that resides in molecular clouds.

  1. Chlamydia trachomatis protein CT009 is a structural and functional homolog to the key morphogenesis component RodZ and interacts with division septal plane localized MreB

    SciTech Connect

    Kemege, Kyle E.; Hickey, John M.; Barta, Michael L.; Wickstrum, Jason; Balwalli, Namita; Lovell, Scott; Battaile, Kevin P.; Hefty, P. Scott

    2014-11-10

    Cell division in Chlamydiae is poorly understood as apparent homologs to most conserved bacterial cell division proteins are lacking and presence of elongation (rod shape) associated proteins indicate non-canonical mechanisms may be employed. The rod-shape determining protein MreB has been proposed as playing a unique role in chlamydial cell division. In other organisms, MreB is part of an elongation complex that requires RodZ for proper function. A recent study reported that the protein encoded by ORF CT009 interacts with MreB despite low sequence similarity to RodZ. The studies in this paper expand on those observations through protein structure, mutagenesis and cellular localization analyses. Structural analysis indicated that CT009 shares high level of structural similarity to RodZ, revealing the conserved orientation of two residues critical for MreB interaction. Substitutions eliminated MreB protein interaction and partial complementation provided by CT009 in RodZ deficient Escherichia coli. Cellular localization analysis of CT009 showed uniform membrane staining in Chlamydia. This was in contrast to the localization of MreB, which was restricted to predicted septal planes. Finally, MreB localization to septal planes provides direct experimental observation for the role of MreB in cell division and supports the hypothesis that it serves as a functional replacement for FtsZ in Chlamydia.

  2. Chlamydia trachomatis protein CT009 is a structural and functional homolog to the key morphogenesis component RodZ and interacts with division septal plane localized MreB

    DOE PAGES

    Kemege, Kyle E.; Hickey, John M.; Barta, Michael L.; ...

    2014-11-10

    Cell division in Chlamydiae is poorly understood as apparent homologs to most conserved bacterial cell division proteins are lacking and presence of elongation (rod shape) associated proteins indicate non-canonical mechanisms may be employed. The rod-shape determining protein MreB has been proposed as playing a unique role in chlamydial cell division. In other organisms, MreB is part of an elongation complex that requires RodZ for proper function. A recent study reported that the protein encoded by ORF CT009 interacts with MreB despite low sequence similarity to RodZ. The studies in this paper expand on those observations through protein structure, mutagenesis andmore » cellular localization analyses. Structural analysis indicated that CT009 shares high level of structural similarity to RodZ, revealing the conserved orientation of two residues critical for MreB interaction. Substitutions eliminated MreB protein interaction and partial complementation provided by CT009 in RodZ deficient Escherichia coli. Cellular localization analysis of CT009 showed uniform membrane staining in Chlamydia. This was in contrast to the localization of MreB, which was restricted to predicted septal planes. Finally, MreB localization to septal planes provides direct experimental observation for the role of MreB in cell division and supports the hypothesis that it serves as a functional replacement for FtsZ in Chlamydia.« less

  3. The Aerodynamic Plane Table

    NASA Technical Reports Server (NTRS)

    Zahm, A F

    1924-01-01

    This report gives the description and the use of a specially designed aerodynamic plane table. For the accurate and expeditious geometrical measurement of models in an aerodynamic laboratory, and for miscellaneous truing operations, there is frequent need for a specially equipped plan table. For example, one may have to measure truly to 0.001 inch the offsets of an airfoil at many parts of its surface. Or the offsets of a strut, airship hull, or other carefully formed figure may require exact calipering. Again, a complete airplane model may have to be adjusted for correct incidence at all parts of its surfaces or verified in those parts for conformance to specifications. Such work, if but occasional, may be done on a planing or milling machine; but if frequent, justifies the provision of a special table. For this reason it was found desirable in 1918 to make the table described in this report and to equip it with such gauges and measures as the work should require.

  4. Fourier plane image amplifier

    DOEpatents

    Hackel, L.A.; Hermann, M.R.; Dane, C.B.; Tiszauer, D.H.

    1995-12-12

    A solid state laser is frequency tripled to 0.3 {micro}m. A small portion of the laser is split off and generates a Stokes seed in a low power oscillator. The low power output passes through a mask with the appropriate hole pattern. Meanwhile, the bulk of the laser output is focused into a larger stimulated Brillouin scattering (SBS) amplifier. The low power beam is directed through the same cell in the opposite direction. The majority of the amplification takes place at the focus which is the fourier transform plane of the mask image. The small holes occupy large area at the focus and thus are preferentially amplified. The amplified output is now imaged onto the multichip module where the holes are drilled. Because of the fourier plane amplifier, only about 1/10th the power of a competitive system is needed. This concept allows less expensive masks to be used in the process and requires much less laser power. 1 fig.

  5. Fourier plane image amplifier

    DOEpatents

    Hackel, Lloyd A.; Hermann, Mark R.; Dane, C. Brent; Tiszauer, Detlev H.

    1995-01-01

    A solid state laser is frequency tripled to 0.3 .mu.m. A small portion of the laser is split off and generates a Stokes seed in a low power oscillator. The low power output passes through a mask with the appropriate hole pattern. Meanwhile, the bulk of the laser output is focused into a larger stimulated Brillouin scattering (SBS) amplifier. The low power beam is directed through the same cell in the opposite direction. The majority of the amplification takes place at the focus which is the fourier transform plane of the mask image. The small holes occupy large area at the focus and thus are preferentially amplified. The amplified output is now imaged onto the multichip module where the holes are drilled. Because of the fourier plane amplifier, only .about.1/10th the power of a competitive system is needed. This concept allows less expensive masks to be used in the process and requires much less laser power.

  6. Structures Technology for Future Aerospace Systems

    NASA Technical Reports Server (NTRS)

    Noor, Ahmed K.; Venneri, Samuel L.; Paul, Donald B.; Hopkins, Mark A.

    2000-01-01

    An overview of structures technology for future aerospace systems is given. Discussion focuses on developments in component technologies that will improve the vehicle performance, advance the technology exploitation process, and reduce system life-cycle costs. The component technologies described are smart materials and structures, multifunctional materials and structures, affordable composite structures, extreme environment structures, flexible load bearing structures, and computational methods and simulation-based design. The trends in each of the component technologies are discussed and the applicability of these technologies to future aerospace vehicles is described.

  7. Structural TEM study of nonpolar a-plane gallium nitride grown on(112_0) 4H-SiC by organometallic vapor phase epitaxy

    SciTech Connect

    Zakharov, Dmitri N.; Liliental-Weber, Zuzanna; Wagner, Brian; Reitmeier,Zachary J.; Preble, Edward A.; Davis, Robert F.

    2005-04-05

    Conventional and high resolution electron microscopy havebeen applied for studying lattice defects in nonpolar a-plane GaN grownon a 4H-SiC substrate with an AlN buffer layer. Samples in plan-view andcross-section configurations have been investigated. Basal and prismaticstacking faults together with Frank and Shockley partial dislocationswere found to be the main defects in the GaN layers. High resolutionelectron microscopy in combination with image simulation supported Drum smodel for the prismatic stacking faults. The density of basal stackingfaults was measured to be ~;1.6_106cm-1. The densities of partialdislocations terminating I1 and I2 types of intrinsic basal stackingfaults were ~;4.0_1010cm-2 and ~;0.4_1010cm-2, respectively. The energyof the I2 stacking fault in GaN was estimated to be (40+-4) erg/cm2 basedon the separation of Shockley partial dislocations. To the best of ourknowledge, the theoretically predicted I3 basal stacking fault in GaN wasobserved experimentally for the first time.

  8. Frictional contact behaviour of the tyre: the effect of tread slip on the in-plane structural deformation and stress field development

    NASA Astrophysics Data System (ADS)

    Tsotras, Achillefs; Mavros, George

    2010-08-01

    The analysis of the in-plane deformation of the tyre in relation to the frictional contact between the road and the tread is a crucial first step in the understanding of its contribution to the longitudinal dynamics of a vehicle. In this work, the physical mechanism of the generation of the two-dimensional contact pressure distribution for a non-rolling tyre is studied. Towards this aim, a physical tyre model is constructed, consisting of an analytical ring under pretension, a non-linear sidewall foundation, and a discretised foundation of viscoelastic elements representing the tread. Tread behaviour is examined first, with focus on the development of shear micro-slip. The tread simulation is enhanced with the combination of radial and tangential tread elements and the benefits of such an approach are identified. Subsequently, the contact of the complete model is examined by implementing an algorithm for transient simulations in the time domain. The effects of the imposed vertical load and sidewall non-linearity on the contact stress and strain fields are identified. The modelling approach is validated by comparison with published experimental results. The physical mechanism that couples the torsional and horizontal/vertical deformations of the carcass with the frictional forces at the tread is identified and discussed in detail. The proposed modelling approach is found appropriate for the description of the development of the two-dimensional contact pressure field as a function of the frictional potential of the contact.

  9. Integrated focal-plane array /IFPA/ approach to large-area infrared focal plane architecture

    NASA Astrophysics Data System (ADS)

    Warren, R. E.

    1980-01-01

    A modular approach to IFPA design is presented which makes it possible to obtain a high-density infrared focal plane amendable to parallel manufacturing techniques as well as to serial plane integration and test. The percent fill factor of the design is dependent on the dimension of the individual detectors; each submodule is manufactured from identical components. The technologies including cables, interconnects, multilayer interconnect structures, and subassembly test requirements, which have direct application to scanning as well as staring integrated focal plane arrays, are discussed.

  10. Transformation from an easy-plane to an easy-axis antiferromagnetic structure in the mixed rare-earth ferroborates Pr x Y1-x Fe3(BO3)4: magnetic properties and crystal field calculations.

    PubMed

    Pankrats, A I; Demidov, A A; Ritter, C; Velikanov, D A; Semenov, S V; Tugarinov, V I; Temerov, V L; Gudim, I A

    2016-10-05

    The magnetic structure of the mixed rare-earth system Pr x Y1-x Fe3(BO3)4 (x  =  0.75, 0.67, 0.55, 0.45, 0.25) was studied via magnetic and resonance measurements. These data evidence the successive spin reorientation from the easy-axis antiferromagnetic structure formed in PrFe3(BO3)4 to the easy-plane one of YFe3(BO3)4 associated with the weakening of the magnetic anisotropy of the Pr subsystem due to its diamagnetic dilution by nonmagnetic Y. This reorientation occurs through the formation of an inclined magnetic structure, as was confirmed by our previous neutron research in the range of x  =  0.67 ÷ 0.45. In the compounds with x  =  0.75 and 0.67 whose magnetic structure is close to the easy-axis one, a two-step spin reorientation takes place in the magnetic field H||c. Such a peculiarity is explained by the formation of an interjacent inclined magnetic structure with magnetic moments of Fe ions located closer to the basal plane than in the initial state, with these intermediate states remaining stable in some ranges of the magnetic field. An approach based on a crystal field model for the Pr(3+) ion and the molecular-field approximation is used to describe the magnetic characteristics of the system Pr x Y1-x Fe3(BO3)4. With the parameters of the d-d and f-d exchange interactions, of the magnetic anisotropy of the iron subsystem and of the crystal field parameters of praseodymium thus determined, it is possible to achieve a good agreement between the experimental and calculated temperature and field dependences of the magnetization curves (up to 90 kOe) and magnetic susceptibilities (2-300 K).

  11. Thermodynamics of black plane solution

    NASA Astrophysics Data System (ADS)

    Rodrigues, Manuel E.; Jardim, Deborah F.; Houndjo, Stéphane J. M.; Myrzakulov, Ratbay

    2013-11-01

    We obtain a new phantom black plane solution in D of the Einstein-Maxwell theory coupled with a cosmological constant. We analyse their basic properties, as well as its causal structure, and obtain the extensive and intensive thermodynamic variables, as well as the specific heat and the first law. Through the specific heat and the so-called geometric methods, we analyse in detail their thermodynamic properties, the extreme and phase transition limits, as well as the local and global stabilities of the system. The normal case is shown with an extreme limit and the phantom one with a phase transition only for null mass, which is physically inaccessible. The systems present local and global stabilities for certain values of the entropy density with respect to the electric charge, for the canonical and grand canonical ensembles.

  12. Focal plane polarimeter design

    SciTech Connect

    McClelland, J.B.

    1983-10-12

    Measurement of polarization transfer or so-called triple-scattering parameters have been made recently for proton-nucleon scattering at TRIUMF, SIN, and LAMPF using carbon polarimeters and have been essential in determining the proton-nucleon amplitudes up to 800 MeV. An extension to the case is described where the scattered proton polarization is analyzed after passage through some type of spectrometer. Most of the experience with this type of focal plane polarimeter (FPP) has been gained in the field of proton-nucleus scattering at intermediate energies but is certainly not confined to such specific cases. The salient features of an FPP are emphasized by describing a minimal system which includes all the necessary components then go on to a more complete system. 10 references. (WHK)

  13. NASA Connect: 'Plane Weather'

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Excerpt from the NASA Connect show 'Plane Weather' This clip explains what high and low pressure weather systems are, and how these affect weather patterns. Weather affects our daily lives. The elements of weather: rain, wind, fog, ice and snow affect the operation and flight of an airplane. In this program, NASA and FAA researchers will introduce students to math, science, and weather; demonstrate how these elements influence flight; and show how NASA and FAA research is used to limit the effects of these elements on flight. Students will examine: the tools, techniques, and technologies used by engineers and scientists to detect these and other climatological factors affecting aircraft in flight. The lesson and classroom experiment will involve students in the scientific process and emphasizing problem solving, measurement, and reasoning skills.

  14. Small angle neutron scattering study to determine the structure of high strength hydrogels.

    NASA Astrophysics Data System (ADS)

    Tominaga, Taiki; Tirumala, Vijay R.; Lin, Eric K.; Wu, Wen-Li; Gong, Jian Ping; Furukawa, Hidemitsu; Osada, Yoshihito

    2006-03-01

    Hydrogels are swollen polymer networks containing more than 90% water. Most hydrogels, however, are mechanically too weak to be used as load bearing devices. Gong et al. have overcome this problem by synthesizing hydrogels with a double network (DN) structure. Modifying the polyelectrolyte network structure by polymerization of high molecular weight uncharged polymer in situ, resulted in orders of magnitude increase in their load bearing ability. Despite 90% water, these tough gels exhibit a fracture stress of 170 kg/cm^2, similar to that of articular cartilage found in the bone-joints of human body. In this work, we determined the structure of DN-gels using small angle neutron scattering. Structural origins for high toughness found in DN-gels were then examined by comparing the structure of DN-gels with that of pure polyelectrolyte network and polyacrylamide solution.

  15. Spin-polarized semiconductors: tuning the electronic structure of graphene by introducing a regular pattern of sp3 carbons on the graphene plane.

    PubMed

    Jing, Long; Huang, Ping; Zhu, Huarui; Gao, Xueyun

    2013-01-28

    First-principles calculations (generalized gradient approximation, density functional therory (DFT) with dispersion corrections, and DFT plus local atomic potential) are carried out on the stability and electronic structures of superlattice configurations of nitrophenyl diazonium functionalized graphene with different coverage. In the calculations, the stabilities of these structures are strengthened significantly since van der Waals interactions between nitrophenyl groups are taken into account. Furthermore, spin-polarized and wider-bandgap electronic structures are obtained when the nitrophenyl groups break the sublattice symmetry of the graphene. The unpaired quasi-localized p electrons are responsible for this itinerant magnetism. The results provide a novel approach to tune graphene's electronic structures as well as to form ferromagnetic semiconductive graphene. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Structural materials for breeder reactor cores and coolant circuits

    SciTech Connect

    Diercks, D.R.

    1984-02-01

    The structural components of principal interest in LMFBR cores and cooling circuits include the reactor vessel, primary and secondary piping, intermediate heat exchanger (IHX), and steam generator. Load-bearing components inside the vessel, among these the fuel cladding and duct, are also included. The operating conditions present in a fast-breeder nuclear reactor impose a number of requirements on the mechanical, physical, and neutronic properties of the materials used to construct these components.

  17. Stabilization of endangered part of structures by building dry brunt brick buttressing, critical case study of plane wall in DKG-North Area, Mohenjo daro

    NASA Astrophysics Data System (ADS)

    Shaikh, J. M.; Park, J.

    2013-07-01

    'World Heritage Sites' are places or buildings of outstanding universal value recognized as constituting a world heritage 'for whose protection it is the duty of the international community as a whole to co-operate'. The concept of World Heritage is at the core of the World Heritage Convention, adopted by Heritage List as a means of identifying, protecting, conserving and presenting those parts of the world's natural and cultural heritage that are of sufficient 'outstanding universal value' to be the responsibility of the international community as a whole. By joining the Convention, nation states are pledged to safeguard the WH S by protecting their national heritage. UNESCO in 1972, to which 160 nations have now been adhered. The Convention came into force in 1975 and established a Site in their territory as part of a universally agreed policy for World. Moenjodaro site covering an area of 555 Acres out of which only 10 % of it has been excavated by exposing 50 Kilometer standing walls. The wall of the main street of DK G Area, Mohen jo Daro partially deformed, due to the torque effects this is studied here on a lateral cross wall in the chief house. Furthermore, the resulting behaviour of the bucking wall demonstrates the significant loadbearing capacity of the structure under service conditions and its high sensitivity to imposed changes of the geometry. Although the tensile stresses exceeded the flexural strength at the vertices and the length of the wall, hence both the geometry and condition of this area are critical for the safety of the wall. The results of this study can improve the assessment and thus help in the preservation of many important structures of the metropolitan city. Here the hydrous characteristic of the brick is studied as a general phenomenon, it is observed that the remains of the sites located in Sindh suffered a lot mostly due to age, human neglect variations of atmospheric condition, severe temperature and natural disasters. The main

  18. Fourier plane filters

    NASA Technical Reports Server (NTRS)

    Oliver, D. S.; Aldrich, R. E.; Krol, F. T.

    1972-01-01

    An electrically addressed liquid crystal Fourier plane filter capable of real time optical image processing is described. The filter consists of two parts: a wedge filter having forty 9 deg segments and a ring filter having twenty concentric rings in a one inch diameter active area. Transmission of the filter in the off (transparent) state exceeds fifty percent. By using polarizing optics, contrast as high as 10,000:1 can be achieved at voltages compatible with FET switching technology. A phenomenological model for the dynamic scattering is presented for this special case. The filter is designed to be operated from a computer and is addressed by a seven bit binary word which includes an on or off command and selects any one of the twenty rings or twenty wedge pairs. The overall system uses addressable latches so that once an element is in a specified state, it will remain there until a change of state command is received. The drive for the liquid crystal filter is ? 30 V peak at 30 Hz to 70 Hz. These parameters give a rise time for the scattering of 20 msec and a decay time of 80 to 100 msec.

  19. Visualization of microvascular proliferation as a tumor infiltration structure in rat glioma specimens using the diffraction-enhanced imaging in-plane CT technique

    NASA Astrophysics Data System (ADS)

    Seo, Seung-Jun; Sunaguchi, Naoki; Yuasa, Tetsuya; Huo, Qingkai; Ando, Masami; Choi, Gi-Hwan; Kim, Hong-Tae; Kim, Ki-Hong; Jeong, Eun-Ju; Chang, Won-Seok; Kim, Jong-Ki

    2012-03-01

    In order to study potent microenvironments of malignant gliomas with a high- resolution x-ray imaging technique, an injection orthotopic glioma model was made using the Sprague-Dawley rat. Total brain tissue, taken out as an ex vivo model, was examined with diffraction-enhanced imaging (DEI) computed tomography (CT) acquired with a 35 keV monochromatic x-ray. In the convolution-reconstructed 2D/3D images with a spatial resolution of 12.5 × 12.5 × 25 µm, distinction among necrosis, typical ring-shaped viable tumors, edemas and healthy tissues was clearly observed near the frontal lobe in front of the rat's caudate nucleus. Multiple microvascular proliferations (MVPs) were observed surrounding peritumoral edemas as a tumor infiltration structure. Typical dimensions of tubular MVPs were 130 (diameter) ×250 (length) µm with a partial sprout structure revealed in the 3D reconstructed image. Hyperplasia of cells around vessel walls was revealed with tumor cell infiltration along the perivascular space in microscopic observations of mild MVP during histological analysis. In conclusion, DEI-CT is capable of imaging potent tumor-infiltrating MVP structures surrounding high-grade gliomas.

  20. Structural, mechanical and electronic properties of in-plane 1T/2H phase interface of MoS{sub 2} heterostructures

    SciTech Connect

    Guo, Xiaoyan; Yang, Guohui; Zhang, Junfeng; Xu, Xiaohong

    2015-09-15

    Two-dimensional (2D) molybdenum disulfide (MoS{sub 2}) phase hybrid system composed by 2H and 1T phase is a natural metal/semiconductor heterostructures and promised a wide range of potential applications. Here, we report the first principle investigations on the structural, mechanical and electronic properties of hybrid system with armchair (AC) and zigzag (ZZ) interfaces. The ZZ type 1T/2H interface are more energy favorable than AC type interface with 3.39 eV/nm. Similar with that of bulked 1T MoS{sub 2}, the intrinsic strengths of the heterostructures are lower than that of the bulk 2H, especially for that with ZZ interface. Analysis of density of states shows that the electronic properties gradually transmitted from the metallic 1T phase to the semiconducting 2H phase for the structural abrupt interface. The present theoretical results constitute a useful picture for the 2D electronic devices using current MoS{sub 2} 1T/2H heterostructures and provide vital insights into the other 2D hybrid materials.

  1. Plane Smoothers for Multiblock Grids: Computational Aspects

    NASA Technical Reports Server (NTRS)

    Llorente, Ignacio M.; Diskin, Boris; Melson, N. Duane

    1999-01-01

    Standard multigrid methods are not well suited for problems with anisotropic discrete operators, which can occur, for example, on grids that are stretched in order to resolve a boundary layer. One of the most efficient approaches to yield robust methods is the combination of standard coarsening with alternating-direction plane relaxation in the three dimensions. However, this approach may be difficult to implement in codes with multiblock structured grids because there may be no natural definition of global lines or planes. This inherent obstacle limits the range of an implicit smoother to only the portion of the computational domain in the current block. This report studies in detail, both numerically and analytically, the behavior of blockwise plane smoothers in order to provide guidance to engineers who use block-structured grids. The results obtained so far show alternating-direction plane smoothers to be very robust, even on multiblock grids. In common computational fluid dynamics multiblock simulations, where the number of subdomains crossed by the line of a strong anisotropy is low (up to four), textbook multigrid convergence rates can be obtained with a small overlap of cells between neighboring blocks.

  2. Enhancement of current-perpendicular-to-plane giant magnetoresistance by insertion of amorphous ferromagnetic underlayer in Heusler alloy-based spin-valve structures

    NASA Astrophysics Data System (ADS)

    Choi, Young-suk; Nakatani, Tomoya; Read, John C.; Carey, Matthew J.; Stewart, Derek A.; Childress, Jeffrey R.

    2017-01-01

    We report an improved method for depositing Heusler alloy thin films, which reduces the B2-ordering temperature, and demonstrate its effect on improving spin-polarization and ΔR/R in CPP-GMR sensors. The insertion of a CoFeBTa or CoBTi amorphous ferromagnetic underlayer induced the formation of an amorphous Co2(Mn,Fe)Ge Heusler alloy film, reducing the B2-ordering temperature to ∼220 °C, which is significantly lower than the value of 500 °C for an epitaxial system and 400 °C for a polycrystalline system. This novel approach allows the fabrication of spin-valve sensor structures with ΔR/R of 18% after post-deposition annealing at temperatures less than 300 °C and is thus compatible with standard recording read-head sensor production.

  3. SAS-2 gamma-ray results from the galactic plane and their implications for galactic structure and galactic cosmic-ray dynamics

    NASA Technical Reports Server (NTRS)

    Fichtel, C. E.; Kniffen, D. A.; Thompson, D. J.

    1977-01-01

    The final SAS-2 results related to high energy galactic gamma-ray emission show a strong correlation with galactic structural features seen at other wavelenghts, when the known gamma-ray sources are subtracted. Theoretical considerations and analysis of the gamma-ray data suggest that the galactic cosmic rays are dynamically coupled to the interstellar matter through the magnetic fields, and hence the cosmic ray density is enhanced where the matter density is greatest on the scale of the galactic arms. This concept has been explored in a galactic model that assumes: (1) cosmic rays are galactic and not universal; (2)on the scale of the galactic arms, the cosmic ray column (surface) density is proportional to the total interstellar gas column density; (3)the cosmic ray scale height is significantly larger than the scale height to the matter; and (4) ours is a spiral galaxy characterized by an arm to interarm density ratio of over 2:1.

  4. Plane Transformations in a Complex Setting I: Homotheties-Translations

    ERIC Educational Resources Information Center

    Dana-Picard, T.

    2006-01-01

    A previous note described how complex numbers can be used for elementary analytic geometry in the plane, describing lines, circles and their intersections using complex Cartesian equations. In the present note, a description of elementary plane transformations, namely homotheties and translations, their group structure and their operations on…

  5. Basal-plane metallography of deformed pyrolytic carbon

    NASA Technical Reports Server (NTRS)

    Adkins, J. M.; Fischbach, D. B.

    1969-01-01

    Cleavage technique is recommended over the normal polishing technique in preparing pyrolytic carbon for metallographic examination of basal-plane surfaces. After careful removal of torn basal-plane fragments and other cleavage debris with cellulose tape, the true structure is clearly revealed.

  6. Viewing Saturn from the Plane

    NASA Image and Video Library

    2006-04-19

    This view of the ringed planet shows its tilt relative to the plane of its orbit around the Sun. The planet tilts nearly 27 degrees relative to the ecliptic plane giving rise to seasons in which the rings shadow each hemisphere in its respective winter

  7. The structural and in-plane dielectric/ferroelectric properties of the epitaxial (Ba, Sr)(Zr, Ti)O{sub 3} thin films

    SciTech Connect

    Chan, N. Y. Wang, Y.; Chan, H. L. W.; Wang, D. Y.; Dai, J. Y.

    2014-06-21

    Epitaxial (Ba{sub 1-x}Sr{sub x})(Zr{sub 0.1}Ti{sub 0.9})O{sub 3} (BSZT, x = 0 – 0.45) thin films were deposited on (LaAlO{sub 3}){sub 0.3}(Sr{sub 2}AlTaO{sub 6}){sub 0.35} (LSAT) substrates by pulsed laser deposition. The experimental results demonstrate that the structural, dielectric, and ferroelectric properties of the BSZT thin films were greatly dependent on the strontium content. The BSZT thin films transformed from tetragonal to cubic phase when x ≥ 0.35 at room temperature. The Curie temperature and room-temperature remnant polarization decrease with increasing strontium concentration. The optimal dielectric properties were found in (Ba{sub 0.55}Sr{sub 0.45})(Zr{sub 0.1}Ti{sub 0.9})O{sub 3} thin films which is in paraelectric state, having tunability of 47% and loss tangent of 0.0338 under an electric field of 20 MV/m at 1 MHz. This suggests that BSZT thin film is a promising candidate for tunable microwave device applications.

  8. Effect of Out-of-Plane Alkyl Group's Position in Dye-Sensitized Solar Cell Efficiency: A Structure-Property Relationship Utilizing Indoline-Based Unsymmetrical Squaraine Dyes.

    PubMed

    Alagumalai, Ananthan; M K, Munavvar Fairoos; Vellimalai, Punitharasu; Sil, Manik Chandra; Nithyanandhan, Jayaraj

    2016-12-28

    Squaraine dyes are promising chromophores to harvest visible and near-infrared (NIR) photons. A series of indoline-based unsymmetrical squaraine (SQ) dyes that contain alkyl chains at sp(3) C- and N- atoms of indoline moieties with a carboxylic acid anchoring group were synthesized. The optical and electrochemical properties of the SQ dyes in solution were nearly identical as there was no change in the D-A-D SQ framework; however, remarkable changes with respect to the power conversion efficiencies (PCE) were observed depending upon the position of alkyl groups in the dye. Introduction of alkyl groups to the indoline unit that was away from anchoring unit were helped in more dye loading with controlled organization of dyes on surface, increased charge transfer resistance, long electron lifetime, and hence higher PCE than that of the corresponding isomer in which the alkyl groups funtionalized indoline unit contains the carboxylic acid anchoring group. Careful analysis of incident photon-to-current conversion efficiency (IPCE) profiles indicated the presence of aggregated structure on the TiO2 surface that contributes to the charge injection in the presence of a coadsorbent. A dye-sensitized solar cell (DSSC) device made out of SQ5 was achieved an efficiency of 9.0%, with an open-circuit potential (Voc) of 660 mV and short-circuit current density (Jsc) of 19.82 mA/cm(2), under simulated AM 1.5G illumination (100 mW/cm(2)). The IPCE profile of SQ5 shows an onset near to 750 nm with a good quantum efficiency (>80%) in the range of 550-700 nm, indicating the importance of self-organization of dyes on the TiO2 surface for an efficient charge injection. This present investigation revealed the importance of position of alkyl groups in the squaraine-based dyes for the better PCE.

  9. Galactic plane gamma-radiation

    NASA Technical Reports Server (NTRS)

    Hartman, R. C.; Kniffen, D. A.; Thompson, D. J.; Fichtel, C. E.; Ogelman, H. B.; Tumer, T.; Ozel, M. E.

    1979-01-01

    Analysis of the SAS 2 data together with the COS B results shows that the distribution of galactic gamma-radiation has several similarities to that of other large-scale tracers of galactic structure. The radiation is primarily confined to a thin disc which exhibits offsets from b = 0 degrees similar to warping at radio frequencies. The principal distinction of the gamma-radiation is a stronger contrast in intensity between the region from 310 to 45 degrees in longitude and the regions away from the center that can be attributed to a variation in cosmic-ray density as a function of position in Galaxy. The diffuse galactic gamma-ray energy spectrum shows no significant variation in direction, and the spectrum seen along the plane is the same as that for the galactic component of the gamma-radiation at high altitudes. The uniformity of the galactic gamma-ray spectrum, the smooth decrease in intensity as a function of altitude, and the absence of any galactic gamma-ray sources at high altitudes indicate a diffuse origin for bulk of the galactic gamma-radiation rather than a collection of localized sources.

  10. Plane reconstruction ultrasound tomography device

    SciTech Connect

    Hassler, D.

    1984-10-23

    An ultrasound tomography device for scanning an object under examination from a plurality of directions. Coronal slice images of the plane areas near or at the female breast wall are obtained. Ultrasound lobes from ultrasound transducers are electronically directed or mechanically positioned to obliquely strike the coronal slice located at or near the breast wall. A full image of the coronal slice plane is reconstructed through section by section combination of the images obtained from the several ultrasound lobes.

  11. Dynamically variable negative stiffness structures

    PubMed Central

    Churchill, Christopher B.; Shahan, David W.; Smith, Sloan P.; Keefe, Andrew C.; McKnight, Geoffrey P.

    2016-01-01

    Variable stiffness structures that enable a wide range of efficient load-bearing and dexterous activity are ubiquitous in mammalian musculoskeletal systems but are rare in engineered systems because of their complexity, power, and cost. We present a new negative stiffness–based load-bearing structure with dynamically tunable stiffness. Negative stiffness, traditionally used to achieve novel response from passive structures, is a powerful tool to achieve dynamic stiffness changes when configured with an active component. Using relatively simple hardware and low-power, low-frequency actuation, we show an assembly capable of fast (<10 ms) and useful (>100×) dynamic stiffness control. This approach mitigates limitations of conventional tunable stiffness structures that exhibit either small (<30%) stiffness change, high friction, poor load/torque transmission at low stiffness, or high power active control at the frequencies of interest. We experimentally demonstrate actively tunable vibration isolation and stiffness tuning independent of supported loads, enhancing applications such as humanoid robotic limbs and lightweight adaptive vibration isolators. PMID:26989771

  12. Dynamically variable negative stiffness structures.

    PubMed

    Churchill, Christopher B; Shahan, David W; Smith, Sloan P; Keefe, Andrew C; McKnight, Geoffrey P

    2016-02-01

    Variable stiffness structures that enable a wide range of efficient load-bearing and dexterous activity are ubiquitous in mammalian musculoskeletal systems but are rare in engineered systems because of their complexity, power, and cost. We present a new negative stiffness-based load-bearing structure with dynamically tunable stiffness. Negative stiffness, traditionally used to achieve novel response from passive structures, is a powerful tool to achieve dynamic stiffness changes when configured with an active component. Using relatively simple hardware and low-power, low-frequency actuation, we show an assembly capable of fast (<10 ms) and useful (>100×) dynamic stiffness control. This approach mitigates limitations of conventional tunable stiffness structures that exhibit either small (<30%) stiffness change, high friction, poor load/torque transmission at low stiffness, or high power active control at the frequencies of interest. We experimentally demonstrate actively tunable vibration isolation and stiffness tuning independent of supported loads, enhancing applications such as humanoid robotic limbs and lightweight adaptive vibration isolators.

  13. Relation of Rib Spacing to Stress in Wing Planes

    NASA Technical Reports Server (NTRS)

    Zahm, A F

    1920-01-01

    The stress relations to the fabric and the rib consequent upon a change of spacing between ribs in a wing plane are discussed. Considering the wing plane as a static structure, and ignoring the question of aerodynamic efficiency, it appears that the unit stress in the rib and fabric will remain constant for constant p if the linear dimensions of both rib and fabric are increased alike, viz., if wing and fabric remain geometrically similar. Since the bulge and the structural dimensions remain geometrically similar, the whole distended plane remains so, and hence should have the same pressure distribution and efficiency. If therefore the Burgess rule of making the rib spacing always one-fifth of the chord of the plane be valid, it must be valid for all others that are mechanically similar in structure and covering.

  14. Computational insight into the capacitive performance of graphene edge planes

    DOE PAGES

    Zhan, Cheng; Zhang, Yu; Cummings, Peter T.; ...

    2017-02-01

    Recent experiments have shown that electric double-layer capacitors utilizing electrodes consisting of graphene edge plane exhibit higher capacitance than graphene basal plane. However, theoretical understanding of this capacitance enhancement is still limited. Here we applied a self-consistent joint density functional theory calculation on the electrode/electrolyte interface and found that the capacitance of graphene edge plane depends on the edge type: zigzag edge has higher capacitance than armchair edge due to the difference in their electronic structures. We further examined the quantum, dielectric, and electric double-layer (EDL) contributions to the total capacitance of the edge-plane electrodes. Classical molecular dynamics simulation foundmore » that the edge planes have higher EDL capacitance than the basal plane due to better adsorption of counter-ions and higher solvent accessible surface area. Finally, our work therefore has elucidated the capacitive energy storage in graphene edge planes that take into account both the electrode's electronic structure and the EDL structure.« less

  15. The Fundamental Plane of evolving red nuggets

    NASA Astrophysics Data System (ADS)

    Oldham, Lindsay; Auger, Matthew; Fassnacht, Christopher D.; Treu, Tommaso; Koopmans, L. V. E.; Lagattuta, David; McKean, John; Vegetti, Simona

    2017-09-01

    We present an exploration of the mass structure of a sample of 12 strongly lensed massive, compact early-type galaxies at redshifts z ∼ 0.6 to provide further possible evidence for their inside-out growth. We obtain new Echelette Spectrograph and Imager/Keck spectroscopy and infer the kinematics of both lens and source galaxies, and combine these with existing photometry to construct (a) the Fundamental Plane (FP) of the source galaxies and (b) physical models for their dark and luminous mass structure. We find their FP to be tilted towards the virial plane relative to the local FP, and attribute this to their unusual compactness, which causes their kinematics to be totally dominated by the stellar mass as opposed to their dark matter; that their FP is nevertheless still inconsistent with the virial plane implies that both the stellar and dark structure of early-type galaxies is non-homologous. We also find the intrinsic scatter of their FP to be comparable to the local value, indicating that variations in the stellar mass structure outweigh variations in the dark halo in the central regions of early-type galaxies. Finally, we show that inference on the dark halo structure - and, in turn, the underlying physics - is sensitive to assumptions about the stellar initial mass function (IMF), but that physically motivated assumptions about the IMF imply haloes with sub-Navarro-Frenk-White inner density slopes, and may present further evidence for the inside-out growth of compact early-type galaxies via minor mergers and accretion.

  16. The Laplace Planes of Uranus and Pluto

    NASA Technical Reports Server (NTRS)

    Dobrovolskis, Anthony R.

    1993-01-01

    Satellite orbits close to an oblate planet precess about its equatorial plane, while distant satellites precess around the plane of the planet's heliocentric orbit. In between, satellites in nearly circular orbits precess about a warped intermediate surface called the Laplace 'plane.' Herein we derive general formulas for locating the Laplace plane. Because Uranus and Pluto have high obliquities, their Laplace planes are severely warped. We present maps of these Laplace planes, of interest in telescopic searches for new satellites. The Laplace plane of the Solar System as a whole is similarly distorted, but comets in the inner Oort cloud precess too slowly to sense the Laplace plane.

  17. Plane waves as tractor beams

    NASA Astrophysics Data System (ADS)

    Forgács, Péter; Lukács, Árpád; Romańczukiewicz, Tomasz

    2013-12-01

    It is shown that in a large class of systems, plane waves act as tractor beams: i.e., an incident plane wave can exert a pulling force on the scatterer. The underlying physical mechanism for the pulling force is due to the sufficiently strong scattering of the incoming wave into another mode carrying more momentum, in which case excess momentum is created behind the scatterer. This tractor beam or negative radiation pressure (NRP) effect, is found to be generic in systems with multiple scattering channels. In a birefringent medium, electromagnetic plane waves incident on a thin plate exert NRP of the same order of magnitude as optical radiation pressure, while in artificial dielectrics (metamaterials), the magnitude of NRP can even be macroscopic. In two dimensions, we study various scattering situations on vortices, and NRP is shown to occur by the scattering of heavy baryons into light leptons off cosmic strings, and by neutron scattering off vortices in the XY model.

  18. Explosive plane-wave lens

    DOEpatents

    Marsh, S.P.

    1988-03-08

    An explosive plane-wave air lens which enables a spherical wave form to be converted to a planar wave without the need to specially machine or shape explosive materials is described. A disc-shaped impactor having a greater thickness at its center than around its periphery is used to convert the spherical wave into a plane wave. When the wave reaches the impactor, the center of the impactor moves first because the spherical wave reaches the center of the impactor first. The wave strikes the impactor later in time as one moves radially along the impactor. Because the impactor is thinner as one moves radially outward, the velocity of the impactor is greater at the periphery than at the center. An acceptor explosive is positioned so that the impactor strikes the acceptor simultaneously. Consequently, a plane detonation wave is propagated through the acceptor explosive. 4 figs.

  19. Explosive plane-wave lens

    DOEpatents

    Marsh, Stanley P.

    1988-01-01

    An explosive plane-wave air lens which enables a spherical wave form to be converted to a planar wave without the need to specially machine or shape explosive materials is described. A disc-shaped impactor having a greater thickness at its center than around its periphery is used to convert the spherical wave into a plane wave. When the wave reaches the impactor, the center of the impactor moves first because the spherical wave reaches the center of the impactor first. The wave strikes the impactor later in time as one moves radially along the impactor. Because the impactor is thinner as one moves radially outward, the velocity of the impactor is greater at the periphery than at the center. An acceptor explosive is positioned so that the impactor strikes the acceptor simultaneously. Consequently, a plane detonation wave is propagated through the acceptor explosive.

  20. Explosive plane-wave lens

    DOEpatents

    Marsh, S.P.

    1987-03-12

    An explosive plane-wave air lens which enables a spherical wave form to be converted to a planar wave without the need to specially machine or shape explosive materials is described. A disc-shaped impactor having a greater thickness at its center than around its periphery is used to convert the spherical wave into a plane wave. When the wave reaches the impactor, the center of the impactor moves first because the spherical wave reaches the center of the impactor first. The wave strikes the impactor later in time as one moves radially along the impactor. Because the impactor is thinner as one moves radially outward, the velocity of the impactor is greater at the periphery than at the center. An acceptor explosive is positioned so that the impactor strikes the acceptor simultaneously. Consequently, a plane detonation wave is propagated through the acceptor explosive. 3 figs., 3 tabs.

  1. Space-Plane Spreadsheet Program

    NASA Technical Reports Server (NTRS)

    Mackall, Dale

    1993-01-01

    Basic Hypersonic Data and Equations (HYPERDATA) spreadsheet computer program provides data gained from three analyses of performance of space plane. Equations used to perform analyses derived from Newton's second law of physics, derivation included. First analysis is parametric study of some basic factors affecting ability of space plane to reach orbit. Second includes calculation of thickness of spherical fuel tank. Third produces ratio between volume of fuel and total mass for each of various aircraft. HYPERDATA intended for use on Macintosh(R) series computers running Microsoft Excel 3.0.

  2. Space-Plane Spreadsheet Program

    NASA Technical Reports Server (NTRS)

    Mackall, Dale

    1993-01-01

    Basic Hypersonic Data and Equations (HYPERDATA) spreadsheet computer program provides data gained from three analyses of performance of space plane. Equations used to perform analyses derived from Newton's second law of physics, derivation included. First analysis is parametric study of some basic factors affecting ability of space plane to reach orbit. Second includes calculation of thickness of spherical fuel tank. Third produces ratio between volume of fuel and total mass for each of various aircraft. HYPERDATA intended for use on Macintosh(R) series computers running Microsoft Excel 3.0.

  3. Concentric Nested Toroidal Inflatable Structures

    NASA Technical Reports Server (NTRS)

    Johnson, Christopher J.; Raboin, Jasen L.; Spexarth, Gary R.

    2010-01-01

    Assemblies comprising multiple limited- height toroidal inflatable structures nested in a concentric arrangement have been invented to obtain more design flexibility than can be obtained in single taller, wider toroidal inflatable structures (see figure). Originally intended for use as containers for habitats for humans in outer space or on remote planets, these and related prior inflatable structures could also be useful on Earth as lightweight, compactly stowable, portable special-purpose buildings that could be transported to remote locations and there inflated to full size and shape. In the case of a single inflatable toroidal structure, one important source of lack of design flexibility is the fact that an increase in outer diameter (which is sometimes desired) is necessarily accompanied by an increase in height (which is sometimes undesired). Increases in diameter and height can also cause difficulty in utilization of the resulting larger volume, in that it can become necessary to partition the volume by means of walls and floors, and features (e.g., stairs or ladders) must be added to enable vertical movement between floors. Moreover, ascending and descending between floors in a gravitational environment could pose unacceptable difficulty for the inhabitants under some circumstances. Another source of lack of design flexibility in a single toroidal inflatable structure is that for a given inflation pressure, an increase in the outer diameter of the structure necessarily entails an increase in the maximum stress in the structure. Because it is necessary to keep the maximum stress within the load-bearing capability of the structural materials, consistent with other aspects of the design, this may translate to a limit on the outer diameter. In an assembly comprising concentric nested toroidal structures, an increase in outer diameter does not necessarily entail an increase in height or a maximum stress in excess of the load-bearing capability of the structural

  4. Radiation enhanced basal plane dislocation glide in GaN

    NASA Astrophysics Data System (ADS)

    Yakimov, Eugene B.; Vergeles, Pavel S.; Polyakov, Alexander Y.; Lee, In-Hwan; Pearton, Stephen J.

    2016-05-01

    A movement of basal plane segments of dislocations in GaN films grown by epitaxial lateral overgrowth under low energy electron beam irradiation (LEEBI) was studied by the electron beam induced current (EBIC) method. Only a small fraction of the basal plane dislocation segments were susceptible to irradiation and the movement was limited to relatively short distances. The effect is explained by the radiation enhanced dislocation glide (REDG) in the structure with strong pinning. A dislocation velocity under LEEBI with a beam current lower than 1 nA was estimated as about 10 nm/s. The results assuming the REDG for prismatic plane dislocations were presented.

  5. Cleavage plane determination in amphibian eggs.

    PubMed

    Sawai, T; Yomota, A

    1990-01-01

    In the present study using eggs of Cynops pyrrhogaster and Xenopus laevis, we examined (1) structural changes in the cytoplasm before the appearance of the cleavage furrow using a cytochemical method, (2) the time of cleavage plane determination depending on the mitotic apparatus (MA), by changing the shape of the eggs, and (3) the time of arrival of the "cleavage stimulus" at the cortex, by injecting colchicine solution or removing cytoplasm. Results were as follows: (1) In amphibian eggs the diastema was formed after development of the MA, appearing between the two asters after the MA had begun to degenerate. (2) The cleavage plane was preliminarily determined by the MA in the meta- to anaphase of karyokinesis. At this time, however, the egg cortex had not yet received the "cleavage stimulus" indispensable for furrow formation. (3) The egg cortex was really prepared to establish the furrow just after the edge of the diastema arrived at the cortex, when the MA had already degenerated. These results imply that the cleavage plane of the amphibian eggs is determined in two steps: the first, depending on the MA, is the determination of the direction of the growth of the diastema, and the second is the arrival of the "cleavage stimulus" at the cortex in association with the diastema.

  6. Bi3+/M2+ oxyphosphate: a continuous series of polycationic species from the 1D single chain to the 2D planes. Part 2: Crystal structure of three original structural types showing a combination of new ribbonlike polycations.

    PubMed

    Colmont, Marie; Huvé, Marielle; Mentré, Olivier

    2006-08-21

    With the assistance of structural models deduced from the high-resolution electron microscope (HREM) investigation presented in Part 1 of this work, three new structural types were pointed out in Bi2O3-MO-P2O5 ternary systems. Their crystal structures are built on the arrangement of 2D polycationic ribbons formed of edge-sharing O(Bi,M)4 tetrahedra and isolated by PO4 groups. Prior to this study, materials with ribbons up to n = 3 tetrahedra wide have been discovered. The original structures presented here display longer n = 4-6 cases, which suggests a possible continuous series of polycationic entities that range from the single chain (one tetrahedron wide) to the infinite [Bi2O2]2+ Aurivillius layer. The ribbons with n > 3 show strong structural modifications that are able to bring a good ribbon-phosphate cohesion. In addition to these fascinating structural results, this work fully confirms the validity of the decoding established from HREM images of a single crystallite in inhomogeneous mixtures.

  7. Two Polymorphic Forms of a Six-Coordinate Mononuclear Cobalt(II) Complex with Easy-Plane Anisotropy: Structural Features, Theoretical Calculations, and Field-Induced Slow Relaxation of the Magnetization.

    PubMed

    Roy, Subhadip; Oyarzabal, Itziar; Vallejo, Julia; Cano, Joan; Colacio, Enrique; Bauza, Antonio; Frontera, Antonio; Kirillov, Alexander M; Drew, Michael G B; Das, Subrata

    2016-09-06

    A mononuclear cobalt(II) complex [Co(3,5-dnb)2(py)2(H2O)2] {3,5-Hdnb = 3,5-dinitrobenzoic acid; py = pyridine} was isolated in two polymorphs, in space groups C2/c (1) and P21/c (2). Single-crystal X-ray diffraction analyses reveal that 1 and 2 are not isostructural in spite of having equal formulas and ligand connectivity. In both structures, the Co(II) centers adopt octahedral {CoN2O4} geometries filled by pairs of mutually trans terminal 3,5-dnb, py, and water ligands. However, the structures of 1 and 2 disclose distinct packing patterns driven by strong intermolecular O-H···O hydrogen bonds, leading to their 0D→2D (1) or 0D→1D (2) extension. The resulting two-dimensional layers and one-dimensional chains were topologically classified as the sql and 2C1 underlying nets, respectively. By means of DFT theoretical calculations, the energy variations between the polymorphs were estimated, and the binding energies associated with the noncovalent interactions observed in the crystal structures were also evaluated. The study of the direct-current magnetic properties, as well as ab initio calculations, reveal that both 1 and 2 present a strong easy-plane magnetic anisotropy (D > 0), which is larger for the latter polymorph (D is found to exhibit values between +58 and 117 cm(-1) depending on the method). Alternating current dynamic susceptibility measurements show that these polymorphs exhibit field-induced slow relaxation of the magnetization with Ueff values of 19.5 and 21.1 cm(-1) for 1 and 2, respectively. The analysis of the whole magnetic data allows the conclusion that the magnetization relaxation in these polymorphs mainly takes place through a virtual excited state (Raman process). It is worth noting that despite the notable difference between the supramolecular networks of 1 and 2, they exhibit almost identical magnetization dynamics. This fact suggests that the relaxation process is intramolecular in nature and that the virtual state involved in the

  8. Affine Contractions on the Plane

    ERIC Educational Resources Information Center

    Celik, D.; Ozdemir, Y.; Ureyen, M.

    2007-01-01

    Contractions play a considerable role in the theory of fractals. However, it is not easy to find contractions which are not similitudes. In this study, it is shown by counter examples that an affine transformation of the plane carrying a given triangle onto another triangle may not be a contraction even if it contracts edges, heights or medians.…

  9. Affine Contractions on the Plane

    ERIC Educational Resources Information Center

    Celik, D.; Ozdemir, Y.; Ureyen, M.

    2007-01-01

    Contractions play a considerable role in the theory of fractals. However, it is not easy to find contractions which are not similitudes. In this study, it is shown by counter examples that an affine transformation of the plane carrying a given triangle onto another triangle may not be a contraction even if it contracts edges, heights or medians.…

  10. Testing the two planes of satellites in the Centaurus group

    NASA Astrophysics Data System (ADS)

    Müller, Oliver; Jerjen, Helmut; Pawlowski, Marcel S.; Binggeli, Bruno

    2016-11-01

    Context. The existence of satellite galaxy planes poses a major challenge for the standard picture of structure formation with non-baryonic dark matter. Recently Tully et al. (2015, ApJ, 802, L25) reported the discovery of two almost parallel planes in the nearby Cen A group using mostly high-mass galaxies (MB< -10 mag) in their analysis. Aims: Our team detected a large number of new group member candidates in the Cen A group. This dwarf galaxy sample, combined with other recent results from the literature, enables us to test the galaxy distribution in the direction of the Cen A group and to determine the statistical significance of the geometric alignment. Methods: Taking advantage of the fact that the two galaxy planes lie almost edge-on along the line of sight, the newly found group members can be assigned relative to the two planes. We used various statistical methods to test whether the distribution of galaxies follows a single normal distribution or shows evidence of bimodality as has been reported earlier. Results: We confirm that the data used for the Tully et al. study support the picture of a bimodal structure. When the new galaxy samples are included, however, the gap between the two galaxy planes is closing and the significance level of the bimodality is reduced. Instead, the plane that contains Cen A becomes more prominent. Conclusions: We found evidence that the galaxy system around Cen A is made up of only one plane of satellites. This plane is almost orthogonal to the dust plane of Cen A. Accurate distances to the new dwarf galaxies will be required to measure the precise 3D distribution of the galaxies around Cen A.

  11. Braiding patterns on an inclined plane.

    PubMed

    Mertens, Keith; Putkaradze, Vakhtang; Vorobieff, Peter

    2004-07-08

    A jet of fluid flowing down a partially wetting, inclined plane usually meanders but--by maintaining a constant flow rate--meandering can be suppressed, leading to the emergence of a beautiful braided structure. Here we show that this flow pattern can be explained by the interplay between surface tension, which tends to narrow the jet, and fluid inertia, which drives the jet to widen. These observations dispel misconceptions about the relationship between braiding and meandering that have persisted for over 20 years.

  12. Fourier Plane Image Combination by Feathering

    NASA Astrophysics Data System (ADS)

    Cotton, W. D.

    2017-09-01

    Astronomical objects frequently exhibit structure over a wide range of scales whereas many telescopes, especially interferometer arrays, only sample a limited range of spatial scales. To properly image these objects, images from a set of instruments covering the range of scales may be needed. These images then must be combined in a manner to recover all spatial scales. This paper describes the feathering technique for image combination in the Fourier transform plane. Implementations in several packages are discussed and example combinations of single dish and interferometric observations of both simulated and celestial radio emission are given.

  13. Experiments with unilateral bite planes in rabbits.

    PubMed

    Sergl, H G; Farmland, M

    1975-04-01

    1. Insertion of bite planes on the right mandibular lateral teeth of eight young rabbits caused load changes in the masticatory system. Eight other animals served as controls. 2. The induced changes were equilibrated during the nine-week experimental period by adapation processes. At the end of the period all teeth were in occlusion and the glenoid fossa-condylar process distance was equal on both sides. 3. The adaptation was the result of several mechanisms working together. We found changes in the alveolar region and at distant growth structures. Cranial scolioses were observed. 4. Masticatory functional loading is a factor which regulates growth in the region of the facial skeleton.

  14. Changes in load bearing in the rheumatoid foot.

    PubMed Central

    Sharma, M; Dhanendran, M; Hutton, W C; Corbett, M

    1979-01-01

    A study of peak force exerted under areas of the foot was made in 27 patients with rheumatoid disease and in 30 normal persons. Patients were found to exert considerably less force under their toes and under the first metatarsal head and more force under the 3 outer metatarsal heads. It was possible to correlate these changes with increasing clinical and radiological severity. Images PMID:539846

  15. Development of Composite Scaffolds for Load Bearing Segmental Bone Defects

    DTIC Science & Technology

    2013-07-01

    progressed from laboratory benchtop studies to preclinical testing in animals. This review is based on an exhaustive literature search of various...follow, a comprehensive review of in vivo models used to test composite scaffolds in SBDs is detailed to serve as a guide to design appropriate...related to fractures, sport and blast injuries. Diseases include bone cancer (osteosarcoma), tumor resection and reconstruction, osteoporosis

  16. Material Characterization for Composite Materials in Load Bearing Wave Guides

    DTIC Science & Technology

    2012-03-01

    in their thermal expansions. Fiber composites offer high internal damping, which leads to better "vibrational energy absorption within the material... internal stresses. Composites are normally coated or painted to prevent moisture absorption. Composites first started seeing use in military... internal protons and electrons. The additional energy from EM waves excites the electrons allowing them to potentially jump into higher energy bands or

  17. Mechanical Impedance of the Non-loaded Lower Leg with Relaxed Muscles in the Transverse Plane

    PubMed Central

    Ficanha, Evandro Maicon; Ribeiro, Guilherme Aramizo; Rastgaar, Mohammad

    2015-01-01

    This paper describes the protocols and results of the experiments for the estimation of the mechanical impedance of the humans’ lower leg in the External–Internal direction in the transverse plane under non-load bearing condition and with relaxed muscles. The objectives of the estimation of the lower leg’s mechanical impedance are to facilitate the design of passive and active prostheses with mechanical characteristics similar to the humans’ lower leg, and to define a reference that can be compared to the values from the patients suffering from spasticity. The experiments were performed with 10 unimpaired male subjects using a lower extremity rehabilitation robot (Anklebot, Interactive Motion Technologies, Inc.) capable of applying torque perturbations to the foot. The subjects were in a seated position, and the Anklebot recorded the applied torques and the resulting angular movement of the lower leg. In this configuration, the recorded dynamics are due mainly to the rotations of the ankle’s talocrural and the subtalar joints, and any contribution of the tibiofibular joints and knee joint. The dynamic mechanical impedance of the lower leg was estimated in the frequency domain with an average coherence of 0.92 within the frequency range of 0–30 Hz, showing a linear correlation between the displacement and the torques within this frequency range under the conditions of the experiment. The mean magnitude of the stiffness of the lower leg (the impedance magnitude averaged in the range of 0–1 Hz) was determined as 4.9 ± 0.74 Nm/rad. The direct estimation of the quasi-static stiffness of the lower leg results in the mean value of 5.8 ± 0.81 Nm/rad. An analysis of variance shows that the estimated values for the stiffness from the two experiments are not statistically different. PMID:26697424

  18. Apparatus for integrating a rigid structure into a flexible wall of an inflatable structure

    NASA Technical Reports Server (NTRS)

    Johnson, Christopher J. (Inventor); Patterson, Ross M. (Inventor); Spexarth, Gary R. (Inventor)

    2009-01-01

    For an inflatable structure having a flexible outer shell or wall structure having a flexible restraint layer comprising interwoven, load-bearing straps, apparatus for integrating one or more substantially rigid members into the flexible shell. For each rigid member, a corresponding opening is formed through the flexible shell for receiving the rigid member. A plurality of connection devices are mounted on the rigid member for receiving respective ones of the load-bearing straps. In one embodiment, the connection devices comprise inner connecting mechanisms and outer connecting mechanisms, the inner and outer connecting mechanisms being mounted on the substantially rigid structure and spaced along a peripheral edge portion of the structure in an interleafed array in which respective outer connecting mechanisms are interposed between adjacent pairs of inner connecting mechanisms, the outer connecting mechanisms projecting outwardly from the peripheral edge portion of the substantially rigid structure beyond the adjacent inner connecting mechanisms to form a staggered array of connecting mechanisms extending along the panel structure edge portion. In one embodiment, the inner and outer connecting mechanisms form part of an integrated, structure rotatably mounted on the rigid member peripheral edge portion.

  19. The primal sagittal plane of the head: a new concept.

    PubMed

    Gateno, J; Jajoo, A; Nicol, M; Xia, J J

    2016-03-01

    To assess facial form, one has to determine the size, position, orientation, shape, and symmetry of the different facial units. Many of these assessments require a frame of reference. The customary coordinate system used for these assessments is the 'standard anatomical frame of reference', a three-dimensional Cartesian system made by three planes: the sagittal, the axial, and the coronal. Constructing the sagittal plane seems simple, but because of universal facial asymmetry, it is complicated. Depending on the method one selects, one can build hundreds of different planes, never knowing which one is correct. This conundrum can be solved by estimating the sagittal plane a patient would have had if his or her face had developed symmetrically. We call this the 'primal sagittal plane'. To estimate this plane we have developed a mathematical algorithm called LAGER (Landmark Geometric Routine). In this paper, we explain the concept of the primal sagittal plane and present the structure of the LAGER algorithm. Copyright © 2015 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.

  20. Epitaxial growth, electrical and optical properties of a-plane InN on r-plane sapphire

    SciTech Connect

    Ajagunna, A. O.; Iliopoulos, E.; Tsiakatouras, G.; Tsagaraki, K.; Androulidaki, M.; Georgakilas, A.

    2010-01-15

    The heteroepitaxy of a-plane (1120) InN films on r-plane (1102) sapphire substrates, by nitrogen radio frequency plasma-assisted molecular beam epitaxy, has been investigated and compared to that of c-plane (0001) InN. The epitaxial growth of a-plane InN proceeded through the nucleation, growth, and coalescence of three-dimensional islands, resulting in surface roughness that increased monotonically with epilayer thickness. The full width at half maximum of (1120) x-ray diffraction rocking curves decreased significantly with increasing InN thickness, characteristic of structural improvement, and it reached the value of 24 arcmin for a 1 {mu}m thick film. Hall-effect measurements exhibited a similar dependence of electron concentration and mobility on thickness for both the a- and c-plane InN films. The analysis of the Hall-effect measurements, by considering the contribution of two conducting layers, indicates a similar accumulation of low mobility electrons with N{sub s}>10{sup 14} cm{sup -2} at the films' surface/interfacial region for both the a- and c-plane InN films. From optical transmittance measurements, the absorption edge of 0.768 eV was determined for the 1 {mu}m a-plane film, consistent with the expected Burstein-Moss effect. Photoluminescence spectra exhibited a lower energy peak at 0.631 eV, suggesting defect-related transitions.

  1. SETI in the Ecliptic Plane

    NASA Astrophysics Data System (ADS)

    Conn Henry, Richard; Kilston, S.; Shostak, S.

    2008-05-01

    The strong advantages of SETI searches in the ecliptic plane have been pointed out by Kilston, Shostak, and Henry (2008). In our poster we show one possible history of civilizations in the galaxy, from birth, through galactic colonization, up to death - and even beyond. Should this scenario be correct, the pattern suggests that the best hope for success in SETI is exploration of the possibility that there are a few extremely ancient but non-colonizing civilizations; civilizations that, aeons ago, detected the existence of Earth (oxygen, and hence life) and of its Moon (stabilizing Earth's rotation) via observations of transits of the Sun (hence, ecliptic, which is stable over millions of years [Laskar et al. 2004]), and have been beaming voluminous information in our direction ever since, in their faint hope (now realized) that a technological "receiving” species would appear. To maintain such a targeted broadcast would be extremely cheap for an advanced civilization. A search of a swath centered on our ecliptic plane should easily find such civilizations, if they exist. We hope to carry out such a search, using the Allen Telescope Array. http://henry.pha.jhu.edu/poster.SETI.pdf References: Kilston, Steven; Shostak, Seth; & Henry, Richard Conn; "Who's Looking at You, Kid?: SETI Advantages near the Ecliptic Plane," AbSciCon 2008, April 14-17, Santa Clara, CA.; Laskar, J., et al., A&A 428, 261, 2004 This work was supported by Maryland Space Grant Consortium.

  2. Symmetry in finite phase plane

    NASA Astrophysics Data System (ADS)

    Zak, J.

    2010-03-01

    The known symmetries in one-dimensional systems are inversion and translations. These symmetries persist in finite phase plane, but a novel symmetry arises in view of the discrete nature of the coordinate xi and the momentum pi : xi and pi can undergo permutations. Thus, if xi assumes M discrete values, i = 0, 1,2,..., M - 1, a permutation will change the order of the set x0,x1,..., xM-1 into a new ordered set. Such a symmetry element does not exist for a continuous x-coordinate in an infinite phase plane. Thus, in a finite phase plane, translations can be replaced by permutations. This is also true for the inversion operator. The new permutation symmetry has been used for the construction of conjugate representations and for the splitting of the M-dimensional vector space into independent subspaces. This splitting is exhaustive in the sense that if M = iMi with Mi being prime numbers, the M-dimensional space splits into M1,M2,...Mn-dimensional independent subspaces. It is shown that following this splitting one can design new potentials with appropriate constants of motion. A related problem is the Weyl-Heisenberg group in the M-dimensional space which turns into a direct product of its subgroups in the Mi-dimensional subspaces. As an example we consider the case of M = 8.

  3. Orbital Space Plane (OSP) Program

    NASA Technical Reports Server (NTRS)

    McKenzie, Patrick M.

    2003-01-01

    Lockheed Martin has been an active participant in NASA's Space Launch Initiative (SLI) programs over the past several years. SLI, part of NASA's Integrated Space Transportation Plan (ISTP), was restructured in November of 2002 to focus the overall theme of safer, more afford-able space transportation along two paths - the Orbital Space Plane Program and the Next Generation Launch Technology programs. The Orbital Space Plane Program has the goal of providing rescue capability from the International Space Station by 2008 and transfer capability for crew (and limited cargo) by 2012. The Next Generation Launch Technology program is combining research and development efforts from the 2nd Generation Reusable Launch Vehicle (2GRLV) program with cutting-edge, advanced space transportation programs (previously designated 3rd Generation) into one program aimed at enabling safe, reliable, cost-effective reusable launch systems by the middle of the next decade. Lockheed Martin is one of three prime contractors working to bring Orbital Space Plane system concepts to a system definition level of maturity by December of 2003. This paper and presentation will update the international community on the progress of the' OSP program, from an industry perspective, and provide insights into Lockheed Martin's role in enabling the vision of a safer, more affordable means of taking people to and from space.

  4. Does monocular visual space contain planes?

    PubMed

    Koenderink, Jan J; Albertazzi, Liliana; van Doorn, Andrea J; van Ee, Raymond; van de Grind, Wim A; Kappers, Astrid M L; Lappin, Joe S; Norman, J Farley; Stijn Oomes, A H J; te Pas, Susan P; Phillips, Flip; Pont, Sylvia C; Richards, Whitman A; Todd, James T; Verstraten, Frans A J; de Vries, Sjoerd

    2010-05-01

    The issue of the existence of planes-understood as the carriers of a nexus of straight lines-in the monocular visual space of a stationary human observer has never been addressed. The most recent empirical data apply to binocular visual space and date from the 1960s (Foley, 1964). This appears to be both the first and the last time this basic issue was addressed empirically. Yet the question is of considerable conceptual interest. Here we report on a direct empirical test of the existence of planes in monocular visual space for a group of sixteen experienced observers. For the majority of these observers monocular visual space lacks a projective structure, albeit in qualitatively different ways. This greatly reduces the set of viable geometrical models. For example, it rules out all the classical homogeneous spaces (the Cayley-Klein geometries) such as the familiar Luneburg model. The qualitatively different behavior of experienced observers implies that the generic population might well be inhomogeneous with respect to the structure of visual space. Copyright 2009 Elsevier B.V. All rights reserved.

  5. A method of plane geometry primitive presentation

    NASA Astrophysics Data System (ADS)

    Jiao, Anbo; Luo, Haibo; Chang, Zheng; Hui, Bin

    2014-11-01

    Point feature and line feature are basic elements in object feature sets, and they play an important role in object matching and recognition. On one hand, point feature is sensitive to noise; on the other hand, there are usually a huge number of point features in an image, which makes it complex for matching. Line feature includes straight line segment and curve. One difficulty in straight line segment matching is the uncertainty of endpoint location, the other is straight line segment fracture problem or short straight line segments joined to form long straight line segment. While for the curve, in addition to the above problems, there is another difficulty in how to quantitatively describe the shape difference between curves. Due to the problems of point feature and line feature, the robustness and accuracy of target description will be affected; in this case, a method of plane geometry primitive presentation is proposed to describe the significant structure of an object. Firstly, two types of primitives are constructed, they are intersecting line primitive and blob primitive. Secondly, a line segment detector (LSD) is applied to detect line segment, and then intersecting line primitive is extracted. Finally, robustness and accuracy of the plane geometry primitive presentation method is studied. This method has a good ability to obtain structural information of the object, even if there is rotation or scale change of the object in the image. Experimental results verify the robustness and accuracy of this method.

  6. Planes of satellite galaxies: when exceptions are the rule

    NASA Astrophysics Data System (ADS)

    Cautun, Marius; Bose, Sownak; Frenk, Carlos S.; Guo, Qi; Han, Jiaxin; Hellwing, Wojciech A.; Sawala, Till; Wang, Wenting

    2015-10-01

    The detection of planar structures within the satellite systems of both the Milky Way (MW) and Andromeda (M31) has been reported as being in stark contradiction to the predictions of the standard cosmological model (Λ cold dark matter - ΛCDM). Given the ambiguity in defining a planar configuration, it is unclear how to interpret the low incidence of the MW and M31 planes in ΛCDM. We investigate the prevalence of satellite planes around galactic mass haloes identified in high-resolution cosmological simulations. We find that planar structures are very common, and that ˜10 per cent of ΛCDM haloes have even more prominent planes than those present in the Local Group. While ubiquitous, the planes of satellite galaxies show a large diversity in their properties. This precludes using one or two systems as small-scale probes of cosmology, since a large sample of satellite systems is needed to obtain a good measure of the object-to-object variation. This very diversity has been misinterpreted as a discrepancy between the satellite planes observed in the Local Group and ΛCDM predictions. In fact, ˜10 per cent of ΛCDM galactic haloes have planes of satellites that are as infrequent as the MW and M31 planes. The look-elsewhere effect plays an important role in assessing the detection significance of satellite planes and accounting for it leads to overestimating the significance level by a factor of 30 and 100 for the MW and M31 systems, respectively.

  7. Point-to-plane and plane-to-plane electrostatic charge injection atomization for insulating liquids

    NASA Astrophysics Data System (ADS)

    Malkawi, Ghazi

    An electrostatic charge injection atomizer was fabricated and used to introduce and study the electrostatic charge injection atomization methods for highly viscous vegetable oils and high conductivity low viscosity aviation fuel, JP8. The total, spray and leakage currents and spray breakup characteristics for these liquids were investigated and compared with Diesel fuel data. Jet breakup and spray atomization mechanism showed differences for vegetable oils and lower viscosity hydrocarbon fuels. For vegetable oils, a bending/spinning instability phenomenon was observed similar to the phenomenon found in liquid jets of high viscosity polymer solutions. The spray tip lengths and cone angles were presented qualitatively and quantitatively and correlated with the appropriate empirical formulas. The different stages of the breakup mechanisms for such oils, as a function of specific charges and flow rates, were discussed. In order to make this method of atomization more suitable for practical use in high flow rate applications, a blunt face electrode (plane-to-plane) was used as the charge emitter in place of a single pointed electrode (point-to-plane). This allowed the use of a multi-orifice emitter that maintained a specific charge with the flow rate increase which could not be achieved with the needle electrode. The effect of the nozzle geometry, liquid physical properties and applied bulk flow on the spray charge, total charge, maximum critical spray specific charge and electrical efficiency compared with the needle point-to-plane atomizer results was presented. Our investigation revealed that the electrical efficiency of the atomizer is dominated by the charge forced convection rate rather than charge transport by ion motilities and liquid motion by the electric field. As a result of the electric coulomb forces between the electrified jets, the multi-orifice atomizer provided a unique means of dispersing the fuel in a hollow cone with wide angles making the new

  8. Electronic structure of the ingredient planes of the cuprate superconductor Bi2Sr2CuO6+δ: A comparison study with Bi2Sr2CaCu2O8+δ

    SciTech Connect

    Yan -Feng Lv; Gu, G. D.; Wang, Wen -Lin; Ding, Hao; Wang, Yang; Ding, Ying; Zhong, Ruidan; Schneeloch, John; Wang, Lili; He, Ke; Ji, Shuai -Hua; Zhao, Lin; Zhou, Xing -Jiang; Song, Can -Li; Ma, Xu -Cun; Xue, Qi -Kun

    2016-04-15

    By means of low-temperature scanning tunneling microscopy, we report on the electronic structures of the BiO and SrO planes of the Bi2Sr2CuO6+δ (Bi-2201) superconductor prepared by argon-ion bombardment and annealing. Depending on post annealing conditions, the BiO planes exhibit either a pseudogap (PG) with sharp coherence peaks and an anomalously large gap magnitude of 49 meV or van Hove singularity (vHS) near the Fermi level, while the SrO is always characteristic of a PG-like feature. This contrasts with the Bi2Sr2CaCu2O8+δ (Bi-2212) superconductor where vHS occurs solely on the SrO plane. We disclose the interstitial oxygen dopants (δ in the formulas) as a primary cause for the occurrence of vHS, which are located dominantly around the BiO and SrO planes, respectively, in Bi-2201 and Bi-2212. This is supported by the contrasting structural buckling amplitude of the BiO and SrO planes in the two superconductors. Furthermore, our findings provide solid evidence for the irrelevance of PG to the superconductivity in the two superconductors, as well as insights into why Bi-2212 can achieve a higher superconducting transition temperature than Bi-2201, and by implication, the mechanism of cuprate superconductivity.

  9. Electronic structure of the ingredient planes of the cuprate superconductor Bi2Sr2CuO6+δ: A comparison study with Bi2Sr2CaCu2O8+δ

    SciTech Connect

    Yan -Feng Lv; Gu, G. D.; Wang, Wen -Lin; Ding, Hao; Wang, Yang; Ding, Ying; Zhong, Ruidan; Schneeloch, John; Wang, Lili; He, Ke; Ji, Shuai -Hua; Zhao, Lin; Zhou, Xing -Jiang; Song, Can -Li; Ma, Xu -Cun; Xue, Qi -Kun

    2016-04-15

    By means of low-temperature scanning tunneling microscopy, we report on the electronic structures of the BiO and SrO planes of the Bi2Sr2CuO6+δ (Bi-2201) superconductor prepared by argon-ion bombardment and annealing. Depending on post annealing conditions, the BiO planes exhibit either a pseudogap (PG) with sharp coherence peaks and an anomalously large gap magnitude of 49 meV or van Hove singularity (vHS) near the Fermi level, while the SrO is always characteristic of a PG-like feature. This contrasts with the Bi2Sr2CaCu2O8+δ (Bi-2212) superconductor where vHS occurs solely on the SrO plane. We disclose the interstitial oxygen dopants (δ in the formulas) as a primary cause for the occurrence of vHS, which are located dominantly around the BiO and SrO planes, respectively, in Bi-2201 and Bi-2212. This is supported by the contrasting structural buckling amplitude of the BiO and SrO planes in the two superconductors. Furthermore, our findings provide solid evidence for the irrelevance of PG to the superconductivity in the two superconductors, as well as insights into why Bi-2212 can achieve a higher superconducting transition temperature than Bi-2201, and by implication, the mechanism of cuprate superconductivity.

  10. Eta Carinae: Orientation of The Orbital Plane

    NASA Technical Reports Server (NTRS)

    Gull, T. R.; Nielsen, K. E.; Ivarsson, S.; Corcoran, M. F.; Verner, E.; Hillier, J. D.

    2006-01-01

    Evidence continues to build that Eta Carinae is a massive binary system with a hidden hot companion in a highly elliptical orbit. We present imaging and spectroscopic evidence that provide clues to the orientation of the orbital plane. The circumstellar ejecta, known as the Homunculus and Little Homunculus, are hourglass-shaped structures, one encapsulated within the other, tilted at about 45 degrees from the sky plane. A disk region lies between the bipolar lobes. Based upon their velocities and proper motions, Weigelt blobs B, C and D, very bright emission clumps 0.1 to 0.3" Northwest from Eta Carinae, lie in the disk. UV flux from the hot companion, Eta Car B, photoexcites the Weigelt blobs. Other clumps form a complete chain around the star, but are not significantly photoexcited. The strontium filament, a 'neutral' emission structure, lies in the same general direction as the Weigelt blobs and exhibits peculiar properties indicative that much mid-UV, but no hydrogen-ionizing radiation impinges on this structure. It is shielded by singly-ionized iron. P Cygni absorptions in Fe I I lines, seen directly in line of sight from Eta Carinae, are absent in the stellar light scattered by the Weigelt blobs. Rather than a strong absorption extending to -600 km/s, a low velocity absorption feature extends from -40 to -150 km/s. No absorbing Fe II exists between Eta Carinae and Weigelt D, but the outer reaches of the wind are intercepted in line of sight from Weigelt D to the observer. This indicates that the UV radiation is constrained by the dominating wind of Eta Car A to a small cavity carved out by the weaker wind of Eta Car B. Since the high excitation nebular lines are seen in the Weigelt blobs at most phases, the cavity, and hence the major axis of the highly elliptical orbit, must lie in the general direction of the Weigelt blobs. The evidence is compelling that the orbital major axis of Eta Carinae is projected at -45 degrees position angle on the sky. Moreover

  11. Eta Carinae: Orientation of The Orbital Plane

    NASA Technical Reports Server (NTRS)

    Gull, T. R.; Nielsen, K. E.; Ivarsson, S.; Corcoran, M. F.; Verner, E.; Hillier, J. D.

    2006-01-01

    Evidence continues to build that Eta Carinae is a massive binary system with a hidden hot companion in a highly elliptical orbit. We present imaging and spectroscopic evidence that provide clues to the orientation of the orbital plane. The circumstellar ejecta, known as the Homunculus and Little Homunculus, are hourglass-shaped structures, one encapsulated within the other, tilted at about 45 degrees from the sky plane. A disk region lies between the bipolar lobes. Based upon their velocities and proper motions, Weigelt blobs B, C and D, very bright emission clumps 0.1 to 0.3" Northwest from Eta Carinae, lie in the disk. UV flux from the hot companion, Eta Car B, photoexcites the Weigelt blobs. Other clumps form a complete chain around the star, but are not significantly photoexcited. The strontium filament, a 'neutral' emission structure, lies in the same general direction as the Weigelt blobs and exhibits peculiar properties indicative that much mid-UV, but no hydrogen-ionizing radiation impinges on this structure. It is shielded by singly-ionized iron. P Cygni absorptions in Fe I I lines, seen directly in line of sight from Eta Carinae, are absent in the stellar light scattered by the Weigelt blobs. Rather than a strong absorption extending to -600 km/s, a low velocity absorption feature extends from -40 to -150 km/s. No absorbing Fe II exists between Eta Carinae and Weigelt D, but the outer reaches of the wind are intercepted in line of sight from Weigelt D to the observer. This indicates that the UV radiation is constrained by the dominating wind of Eta Car A to a small cavity carved out by the weaker wind of Eta Car B. Since the high excitation nebular lines are seen in the Weigelt blobs at most phases, the cavity, and hence the major axis of the highly elliptical orbit, must lie in the general direction of the Weigelt blobs. The evidence is compelling that the orbital major axis of Eta Carinae is projected at -45 degrees position angle on the sky. Moreover

  12. Kauffman bracket of plane curves

    NASA Astrophysics Data System (ADS)

    Chmutov, S.; Goryunov, V.

    1996-12-01

    We lower the Kauffman bracket for links in a solid torus (see [16]) to generic plane fronts. It turns out that the bracket can be entirely defined in terms of a front itself without using the Legendrian lifting. We show that all the coefficients of the lowered bracket are in fact Vassilev type invariants of Arnold's J +-theory [3, 4]. We calculate their weight systems. As a corollary we obtain that the first coefficient is essentially the quantum deformation of the Bennequin invariant introduced recently by M. Polyak [19].

  13. SNAP Satellite Focal Plane Development

    SciTech Connect

    Bebek, C.; Akerlof, C.; Aldering, G.; Amanullah, R.; Astier, P.; Baltay, C.; Barrelet, E.; Basa, S.; Bercovitz, J.; Bergstrom, L.; Berstein, G.P.; Bester, M.; Bohlin, R.; Bonissent, A.; Bower, C.; Campbell, M.; Carithers, W.; Commins, E.; Day, C.; Deustua, S.; DiGennaro, R.; Ealet, A.; Ellis, R.; Emmett, W.; Eriksson, M.; Fouchez,D.; Fruchter, A.; Genat, J-F.; Goldhaber, G.; Goobar, A.; Groom, D.; Heetderks, H.; Holland, S.; Huterer, D.; Johnson, W.; Kadel, R.; Karcher,A.; Kim, A.; Kolbe, W.; Lafever, R.; Lamoureaux, J.; Lampton, M.; Lefevre, O.; Levi, M.; Levin, D.; Linder, E.; Loken, S.; Malina, R.; Mazure, A.; McKay, T.; McKee, S.; Miquel, R.; Morgan, N.; Mortsell, E.; Mostek, N.; Mufson, S.; Musser, J.; Roe, N.; Nugent, P.; Oluseyi, H.; Pain, R.; Palaio, N.; Pankow, D.; Perlmutter, S.; Prieto, E.; Rabinowitz,D.; Refregier, A.; Rhodes, J.; Schubnell, M.; Sholl, M.; Smadja, G.; Smith, R.; Smoot, G.; Snyder, J.; Spadafora, A.; Szymkowiak, A.; Tarle,G.; Taylor, K.; Tilquin, A.; Tomasch, A.; Vincent, D.; von der Lippe, H.; Walder, J-P.; Wang, G.

    2003-07-07

    The proposed SuperNova/Acceleration Probe (SNAP) mission will have a two-meter class telescope delivering diffraction-limited images to an instrumented 0.7 square degree field in the visible and near-infrared wavelength regime. The requirements for the instrument suite and the present configuration of the focal plane concept are presented. A two year R&D phase, largely supported by the Department of Energy, is just beginning. We describe the development activities that are taking place to advance our preparedness for mission proposal in the areas of detectors and electronics.

  14. Orbital Space Plane Cost Credibility

    NASA Technical Reports Server (NTRS)

    Creech, Steve

    2003-01-01

    NASA's largest new start development program is the Orbital Space Plane (OSP) Program. The program is currently in the formulation stage. One of the critical issues to be resolved, prior to initiating full-scale development, is establishing cost credibility of NASA s budget estimates for development, production, and operations of the OSP. This paper will discuss the processes, tools, and methodologies that NASA, along with its industry partners, are implementing to assure cost credibility for the OSP program. Results of benchmarking of current tools and the development of new cost estimating capabilities and approaches will be discussed.

  15. Thermomechanical architecture of the VIS focal plane for Euclid

    NASA Astrophysics Data System (ADS)

    Martignac, Jérôme; Carty, Michaël.; Tourette, Thierry; Bachet, Damien; Berthé, Michel; Augueres, Jean-Louis; Amiaux, Jérôme; Fontignie, Jean; Horeau, Benoît; Renaud, Diana; Pottinger, Sabrina; Denniston, James; Winter, Berend; Guttridge, Phillip; Cole, Richard; Cropper, Mark; Niemi, Sami; Coker, John; Hunt, Thomas

    2014-08-01

    One of the main challenges for current and near future space experiments is the increase of focal plane complexity in terms of amount of pixels. In the frame work of the ESA Euclid mission to be launched in 2020, the Euclid Consortium is developing an extremely large and stable focal plane for the VIS instrument. CEA has developed the thermomechanical architecture of that Focal Plane taking into account all the very stringent performance and mission related requirements. The VIS Focal Plane Assembly integrates 36 CCDs (operated at 150K) connected to their front end electronics (operated at 280K) as to obtain one of the largest focal plane (˜0.6 billion pixels) ever built for space application after the GAIA one. The CCDs are CCD273 type specially designed and provided by the e2v company under ESA contract, front end electronics is studied and provided by MSSL. In this paper we first recall the specific requirements that have driven the overall architecture of the VIS-FPA and especially the solutions proposed to cope with the scientific needs of an extremely stable focal plane, both mechanically and thermally. The mechanical structure based on SiC material used for the cold sub assembly supporting the CCDs is detailed. We describe also the modular architecture concept that we have selected taking into account AIT-AIV and programmatic constraints.

  16. A new twist on the geometry of gravitational plane waves

    NASA Astrophysics Data System (ADS)

    Shore, Graham M.

    2017-09-01

    The geometry of twisted null geodesic congruences in gravitational plane wave spacetimes is explored, with special focus on homogeneous plane waves. The rôle of twist in the relation of the Rosen coordinates adapted to a null congruence with the fundamental Brinkmann coordinates is explained and a generalised form of the Rosen metric describing a gravitational plane wave is derived. The Killing vectors and isometry algebra of homogeneous plane waves (HPWs) are described in both Brinkmann and twisted Rosen form and used to demonstrate the coset space structure of HPWs. The van Vleck-Morette determinant for twisted congruences is evaluated in both Brinkmann and Rosen descriptions. The twisted null congruences of the Ozsváth-Schücking, `anti-Mach' plane wave are investigated in detail. These developments provide the necessary geometric toolkit for future investigations of the rôle of twist in loop effects in quantum field theory in curved spacetime, where gravitational plane waves arise generically as Penrose limits; in string theory, where they are important as string backgrounds; and potentially in the detection of gravitational waves in astronomy.

  17. Fundamentals of the dwarf fundamental plane

    NASA Astrophysics Data System (ADS)

    McCall, M. L.; Vaduvescu, O.; Pozo Nunez, F.; Barr Dominguez, A.; Fingerhut, R.; Unda-Sanzana, E.; Li, B.; Albrecht, M.

    2012-04-01

    Aims: Star-forming dwarfs are studied to elucidate the physical underpinnings of their fundamental plane. Processes controlling dynamics are evaluated, connections between quiescent and bursting dwarfs are examined, and the viability of using structural properties of dwarfs to determine distances is assessed. Methods: Deep surface photometry in Ks is presented for 19 star-forming dwarfs. The data are amalgamated with previously published observations to create a sample of 66 galaxies suitable for exploring how global properties and kinematics are connected. Results: It is confirmed that residuals in the Tully-Fisher relation are correlated with surface brightness, but that even after accomodating the surface brightness dependence through the dwarf fundamental plane, residuals in absolute magnitude are far larger than expected from observational errors. Rather, a morefundamental plane is identified which connects the potential to HI line width and surface brightness. Residuals correlate with the axis ratio in a way which can be accommodated by recognizing the galaxies to be oblate spheroids viewed at varying angles. Correction of surface brightnesses to face-on leads to a correlation among the potential, line width, and surface brightness for which residuals are entirely attributable to observational uncertainties. The mean mass-to-light ratio of the diffuse component of the galaxies is constrained to be 0.88 ± 0.20 in Ks. Blue compact dwarfs lie in the same plane as dwarf irregulars. The dependence of the potential on line width is less strong than expected for virialized systems, but this may be because surface brightness is acting as a proxy for variations in the mass-to-light ratio from galaxy to galaxy. Altogether, the observations suggest that gas motions are predominantly disordered and isotropic, that they are a consequence of gravity, not turbulence, and that the mass and scale of dark matter haloes scale with the amount and distribution of luminous matter

  18. Stokes problems for moving half-planes.

    PubMed

    Zeng, Y; Weinbaum, S

    1995-01-01

    New exact solutions of the Navier-Stokes equations are obtained for the unbounded and bounded oscillatory and impulsive tangential edgewise motion of touching half-infinite plates in their own plane. In contrast to Stokes classical solutions for the harmonic and impulsive motion of an infinite plane wall, where the solutions are separable or have a simple similarity form, the present solutions have a two-dimensional structure in the near region of the contact between the half-infinite plates. Nevertheless, it is possible to obtain relatively simple closed-form solutions for the flow field in each case by defining new variables which greatly simplify the r- and theta- dependence of the solutions in the vicinity of the contact region. These solutions for flow in a half-infinite space are then extended to bounded flows in a channel using an image superposition technique. The impulsive motion has application to the motion near geophysical faults, whereas the oscillatory motion has arisen in the design of a novel oscillating half-plate flow chamber for examining the effect of fluid shear stress on cultured cell monolayers.

  19. The Bolocam Galactic Plane Survey

    NASA Technical Reports Server (NTRS)

    Glenn, Jason; Aguirre, James; Bally, John; Battersby, Cara; Bradley, Eric Todd; Cyganowski, Claudia; Dowell, Darren; Drosback, Meredith; Dunham, Miranda K.; Evans, Neal J., II; hide

    2009-01-01

    The Bolocam Galactic Plane Survey (BGPS) is a 1.1 millimeter continuum survey of the northern Galactic Plane made with Bolocam and the Caltech Submillimeter Observatory. The coverage totals 170 square degrees, comprised of a contiguous range from -10.5 deg is less than or equal to 90.5 deg, 0.5 deg is less than or equal to b is less than or equal to 0.5 deg, with extended coverage in b in selected regions, and four targeted regions in the outer Galaxy, including: IC1396, toward the Perseus arm at l is approximately 111 deg, W3/4/5, and Gem OB1. Depths of the maps range from 30 to 60 mJy beam (sup 1). Approximately 8,400 sources were detected and the maps and source catalog have been made publicly available. Millimeter-wave thermal dust emission reveals dense regions within molecular clouds, thus the BGPS serves as a database for studies of the dense interstellar medium and star formation within the Milky Way.

  20. The Bolocam Galactic Plane Survey

    NASA Technical Reports Server (NTRS)

    Glenn, Jason; Aguirre, James; Bally, John; Battersby, Cara; Bradley, Eric Todd; Cyganowski, Claudia; Dowell, Darren; Drosback, Meredith; Dunham, Miranda K.; Evans, Neal J., II; Ginsburg, Adam; Harvey, Paul; Rosolowsky, Erik; Schlingman, Wayne; Shirley, Yancy L.; Stringfellow, Guy S.; Walawender, Josh; Williams, Jonathan

    2009-01-01

    The Bolocam Galactic Plane Survey (BGPS) is a 1.1 millimeter continuum survey of the northern Galactic Plane made with Bolocam and the Caltech Submillimeter Observatory. The coverage totals 170 square degrees, comprised of a contiguous range from -10.5 deg is less than or equal to 90.5 deg, 0.5 deg is less than or equal to b is less than or equal to 0.5 deg, with extended coverage in b in selected regions, and four targeted regions in the outer Galaxy, including: IC1396, toward the Perseus arm at l is approximately 111 deg, W3/4/5, and Gem OB1. Depths of the maps range from 30 to 60 mJy beam (sup 1). Approximately 8,400 sources were detected and the maps and source catalog have been made publicly available. Millimeter-wave thermal dust emission reveals dense regions within molecular clouds, thus the BGPS serves as a database for studies of the dense interstellar medium and star formation within the Milky Way.

  1. Image plane sweep volume illumination.

    PubMed

    Sundén, Erik; Ynnerman, Anders; Ropinski, Timo

    2011-12-01

    In recent years, many volumetric illumination models have been proposed, which have the potential to simulate advanced lighting effects and thus support improved image comprehension. Although volume ray-casting is widely accepted as the volume rendering technique which achieves the highest image quality, so far no volumetric illumination algorithm has been designed to be directly incorporated into the ray-casting process. In this paper we propose image plane sweep volume illumination (IPSVI), which allows the integration of advanced illumination effects into a GPU-based volume ray-caster by exploiting the plane sweep paradigm. Thus, we are able to reduce the problem complexity and achieve interactive frame rates, while supporting scattering as well as shadowing. Since all illumination computations are performed directly within a single rendering pass, IPSVI does not require any preprocessing nor does it need to store intermediate results within an illumination volume. It therefore has a significantly lower memory footprint than other techniques. This makes IPSVI directly applicable to large data sets. Furthermore, the integration into a GPU-based ray-caster allows for high image quality as well as improved rendering performance by exploiting early ray termination. This paper discusses the theory behind IPSVI, describes its implementation, demonstrates its visual results and provides performance measurements.

  2. Singularities from colliding plane gravitational waves

    NASA Astrophysics Data System (ADS)

    Tipler, Frank J.

    1980-12-01

    A simple geometrical argument is given which shows that a collision between two plane gravitational waves must result in singularities. The argument suggests that these singularities are a peculiar feature of plane waves, because singularities are also a consequence of a collision between self-gravitating plane waves of other fields with arbitrarily small energy density.

  3. Crisis bifurcations in plane Poiseuille flow

    NASA Astrophysics Data System (ADS)

    Zammert, Stefan; Eckhardt, Bruno

    2015-04-01

    Many shear flows follow a route to turbulence that has striking similarities to bifurcation scenarios in low-dimensional dynamical systems. Among the bifurcations that appear, crisis bifurcations are important because they cause global transitions between open and closed attractors, or indicate drastic increases in the range of the state space that is covered by the dynamics. We here study exterior and interior crisis bifurcations in direct numerical simulations of transitional plane Poiseuille flow in a mirror-symmetric subspace. We trace the state space dynamics from the appearance of the first three-dimensional exact coherent structures to the transition from an attractor to a chaotic saddle in an exterior crisis. For intermediate Reynolds numbers, the attractor undergoes several interior crises, in which new states appear and intermittent behavior can be observed. The bifurcations contribute to increasing the complexity of the dynamics and to a more dense coverage of state space.

  4. On turbulent spots in plane Poiseuille flow

    NASA Technical Reports Server (NTRS)

    Henningson, Dan S.; Kim, John

    1991-01-01

    Turbulence characteristics inside a turbulent spot in plane Poiseuille flow are investigated by analyzing a database obtained from a direct numerical simulation. The spot is found to consist of two distinct regions - a turbulent area and a wave area. The flow inside the turbulent area has a strong resemblance to that found in the fully developed turbulent channel. Suitably defined mean and r.m.s. fluctuations as well as the internal shear-layer structures are found to be similar to the turbulent counterpart. In the wave area the inflexional mean spanwise profiles cause a rapid growth of oblique waves, which break down to turbulence. The breakdown process of the oblique waves is reminiscent of the secondary instability observed during transition to turbulence in channel and boundary-layer flows. Other detailed characteristics associated with the Poiseuille spot are presented and are compared with experimental results.

  5. Empirically Derived Strength of Residential Roof Structures for Solar Installations.

    SciTech Connect

    Dwyer, Stephen F.; Sanchez, Alfred; Campos, Ivan A.; Gerstle, Walter H.

    2014-12-01

    Engineering certification for the installation of solar photovoltaic (PV) modules on wood roofs is often denied because existing wood roofs do not meet structural design codes. This work is intended to show that many roofs are actually sufficiently strong given the conservatism in codes, documented allowable strengths, roof structure system effects, and beam composite action produced by joist-sheathing interaction. This report provides results from a testing program to provide actual load carrying capacity of residential rooftops. The results reveal that the actual load carrying capacity of structural members and systems tested are significantly stronger than allowable loads provided by the International Residential Code (IRC 2009) and the national structural code found in Minimum Design Loads for Buildings and Other Structures (ASCE 7-10). Engineering analysis of residential rooftops typically ignores the system affects and beam composite action in determining rooftop stresses given a potential PV installation. This extreme conservatism combined with conservatism in codes and published allowable stress values for roof building materials (NDS 2012) lead to the perception that well built homes may not have adequate load bearing capacity to enable a rooftop PV installation. However, based on the test results presented in this report of residential rooftop structural systems, the actual load bearing capacity is several times higher than published values (NDS 2012).

  6. Toward structurally integrated locally resonant metamaterials for vibration attenuation

    NASA Astrophysics Data System (ADS)

    Schmied, Jascha U.; Sugino, Christopher; Bergamini, Andrea; Ermanni, Paolo; Ruzzene, Massimo; Erturk, Alper

    2017-04-01

    In this contribution, we explore the use of locally resonant metamaterials for multi-functional structural load- bearing concepts using analytical, numerical, and experimental techniques. Locally resonant metamaterials exhibit bandgaps at wavelengths much larger than the lattice dimension. This is a promising feature for low- frequency vibration attenuation. The presented work aims to investigate highly integrated structural concepts and experimentally validated prototypes for vibration reduction in load-bearing applications. The goal is to explore and extend the design space of lightweight structural systems, by designing multi-functional periodic structural elements, preserving structural stiffness while concurrently enabling sufficiently wideband damping performance over a target frequency range of interest. Following a generalized theoretical modeling framework for bandgap design and analysis in finite structures, the focus is placed on the design, fabrication, and analysis of a load-carrying frame development with internally resonant components. Finite-element modeling is employed to design and analyze the frequency response of the frame and simplified analytical solution is compared with this numerical solution. Experimental validations are presented for a 3D-printed prototype. The effects of various parameters are reported both based on numerical and experimental findings.

  7. Broken chiral symmetry on a null plane

    SciTech Connect

    Beane, Silas R.

    2013-10-15

    On a null-plane (light-front), all effects of spontaneous chiral symmetry breaking are contained in the three Hamiltonians (dynamical Poincaré generators), while the vacuum state is a chiral invariant. This property is used to give a general proof of Goldstone’s theorem on a null-plane. Focusing on null-plane QCD with N degenerate flavors of light quarks, the chiral-symmetry breaking Hamiltonians are obtained, and the role of vacuum condensates is clarified. In particular, the null-plane Gell-Mann–Oakes–Renner formula is derived, and a general prescription is given for mapping all chiral-symmetry breaking QCD condensates to chiral-symmetry conserving null-plane QCD condensates. The utility of the null-plane description lies in the operator algebra that mixes the null-plane Hamiltonians and the chiral symmetry charges. It is demonstrated that in a certain non-trivial limit, the null-plane operator algebra reduces to the symmetry group SU(2N) of the constituent quark model. -- Highlights: •A proof (the first) of Goldstone’s theorem on a null-plane is given. •The puzzle of chiral-symmetry breaking condensates on a null-plane is solved. •The emergence of spin-flavor symmetries in null-plane QCD is demonstrated.

  8. Smov Baseline Focal Plane Check

    NASA Astrophysics Data System (ADS)

    Gilmozzi, Roberto

    1994-01-01

    This test will be executed during the period after the servicing mission and before the extension of the COSTAR assembly. Its purpose is to verify that the FOS, HRS, and FOC focal planes have not been altered by the activities performed by Story and the Astronauts during the servicing mission. A large unknown deviation in aperture position would severly impact subsequent COSTAR alignment activities. If this test reveals a deviation, we may be able to compensate for any offsets prior to the complex and delicate COSTAR alignment calibrations. This enhanced version of the Heptathlon is designed to verify course alignments and measure relative aperture positions to within a few arcsecs. SPECIAL REQUIREMENTS: ***This test uses pre-servicing parameters for HRS, FOS, and FOC and the Cycle 4 parameters for WFPC2.*** ***This test requires special alignment and special guide stars.** ***This test requires special commanding for telemetry setups.**

  9. Snakes Out of the Plane

    NASA Astrophysics Data System (ADS)

    McCormick, Andrew; Young, Bruce A.; Mahadevan, L.

    2012-02-01

    We develop a new computational model of elastic rods, taking into account shear and full rotational dynamics, as well as friction, adhesion, and collision. This model is used to study the movement of snakes in different environments. By applying different muscular activation patterns to the snake, we observe many different patterns of motion, from planar undulation to sudden strikes. Many of the most interesting behaviors involve the snake rising out of the horizontal plane in the vertical direction. Such behaviors include a sand snake sidewinding over the hot desert sand and a cobra rearing up into a defensive striking position. Experimental videos of live snakes are analyzed and compared with computational results. We identify and explain a new form of movement previously unobserved: ``collateral locomotion.''

  10. Functional Aesthetic Occlusal Plane (FAOP)

    PubMed Central

    Câmara, Carlos Alexandre; Martins, Renato Parsekian

    2016-01-01

    ABSTRACT Introduction: A reasonable exposure of incisors and gingival tissues is generally considered more attractive than excess or lack of exposure. A reasonable gingival exposure is considered to be around 0 to 2 mm when smiling and 2-4 mm exposure of the maxillary incisor edge when the lips are at rest. Objective: The aim of this paper is to present the Functional Aesthetic Occlusal Plane (FAOP), which aims to help in the diagnosis of the relationships established among molars, incisors and the upper lip. Conclusion: FAOP can complement an existing and established orthodontic treatment plan, facilitating the visualization of functional and aesthetic demands by giving a greater focus on the position of incisors in the relationship established among the incisors, molars and the upper lip stomion. PMID:27653271

  11. P-Wave and S-Wave Velocity Structure of Submarine Landslide Associated With Gas Hydrate Layer on Frontal Ridge of Northern Cascadia Margin

    NASA Astrophysics Data System (ADS)

    He, T.; Lu, H.; Yelisetti, S.; Spence, G.

    2015-12-01

    The submarine landslide associated with gas hydrate is a potential risk for environment and engineering projects, and thus from long time ago it has been a hot topic of hydrate research. The study target is Slipstream submarine landslide, one of the slope failures observed on the frontal ridges of the Northern Cascadia accretionary margin off Vancouver Island. The previous studies indicated a possible connection between this submarine landslide feature and gas hydrate, whose occurrence is indicated by a prominent bottom-simulating reflector (BSR), at a depth of ~265-275 m beneath the seafloor (mbsf). The OBS (Ocean Bottom Seismometer) data collected during SeaJade (Seafloor Earthquake Array - Japan Canada Cascadia Experiment) project were used to derive the subseafloor velocity structure for both P- and S-wave using travel times picked from refraction and reflection events. The P-wave velocity structure above the BSR showed anomalous high velocities of about 2.0 km/s at shallow depths of 100 mbsf, closely matching the estimated depth of the glide plane (100 ± 10 m). Forward modelling of S-waves was carried out using the data from the OBS horizontal components. The S-wave velocities, interpreted in conjunction with the P-wave results, provide the key constraints on the gas hydrate distribution within the pores. The hydrate distribution in the pores is important for determining concentrations, and also for determining the frame strength which is critical for controlling slope stability of steep frontal ridges. The increase in S-wave velocity suggests that the hydrate is distributed as part of the load-bearing matrix to increase the rigidity of the sediment.

  12. TCS-CAIN: NIR survey of the Galactic plane

    NASA Astrophysics Data System (ADS)

    González-Fernández, C.; Cabrera-Lavers, A.; Garzón, F.; Hammersley, P. L.; López-Corredoira, M.; Vicente, B.

    2007-03-01

    We present TCS-CAIN, a NIR survey of the Galactic plane, recently made public at the Instituto de Astrofísica de Canarias, and some results derived from it: with star counts derived directly the structure of the inner the Milky Way can be dissected, obtaining also estimations for the extinction toward the inner MW.

  13. Thermoelectric characterization and fabrication of nanostructured p-type Bi0.5Sb1.5Te3 and n-type Bi2Te3 thin film thermoelectric energy generator with an in-plane planar structure

    NASA Astrophysics Data System (ADS)

    Park, No-Won; Park, Tae-Hyun; Ahn, Jay-Young; Kang, So-Hyeon; Lee, Won-Yong; Yoon, Young-Gui; Yoon, Soon-Gil; Lee, Sang-Kwon

    2016-06-01

    This paper presents in-plane bismuth-telluride-based thermoelectric (TE) energy generators fabricated using metal-shadow and radio-frequency sputtering methods at room temperature. The TE energy generators consist of four couples of 300-nm-thick nanostructured Bi2Te3 (n-BT) and Bi0.5Sb1.5Te3 (p-BST) thin films used as n-type and p-type materials, respectively, on a Si substrate for the p/n junctions of the TE energy generators. Furthermore, the effect of annealing treatment of both n-BT and p-BST thin films on the electrical and TE properties as well as the TE performance of the TE energy generators is discussed. By varying the temperature between the hot and cold junction legs of the n-BT/p-BST in-plane TE energy generators annealed at 200 °C, the maximum output voltage and power are determined to be ˜3.6 mV and ˜1.1 nW, respectively, at a temperature difference of 50 K. The output powers increased by ˜590% compared to that of the as-grown TE generator at a temperature difference of 90 K. This improvement in the TE performance is attributed to the enhancement of the electrical conductivity after heat treatment. From a numerical simulation conducted using a commercial software (COMSOL), we are confident that it plays a crucial role in determining the dimension (i.e., thickness of each leg) and material properties of both n-BT and p-BST materials of the in-plane TE energy generators.

  14. Active TLCGD control of plane asymmetric buildings under earthquake excitation

    NASA Astrophysics Data System (ADS)

    Fu, Chuan

    2011-10-01

    The sealed, tuned liquid column gas damper (TLCGD) with gas-spring effect extends the frequency range of application and efficiently increases the modal structural damping. Active tuned liquid column gas damper (ATLCGD) is developed for the vibration control of plane asymmetric buildings subjected to earthquake excitation, improving the performance of the passive control scheme. The active behaviour is obtained by adjusting the pressure at the end of the liquid column using a pressurised reservoir. The classical linear quadratic regulator (LQR) design is presented as a straightforward approach to optimal control. Numerical simulations indicate a significant vibration reduction of plane asymmetric buildings by active control within the strong motion of the dynamic response.

  15. Plasmonic Airy beam generated by in-plane diffraction.

    PubMed

    Li, L; Li, T; Wang, S M; Zhang, C; Zhu, S N

    2011-09-16

    We report an experimental realization of a plasmonic Airy beam, which is generated thoroughly on a silver surface. With a carefully designed nanoarray structure, such Airy beams come into being from an in-plane propagating surface plasmon polariton wave, exhibiting nonspreading, self-bending, and self-healing properties. Besides, a new phase-tuning method based on nonperfectly matched diffraction processes is proposed to generate and modulate the beam almost at will. This unique plasmonic Airy beam as well as the generation method would significantly promote the evolutions in in-plane surface plasmon polariton manipulations and indicate potential applications in lab-on-chip photonic integrations.

  16. Tilted planes in 3D image analysis

    NASA Astrophysics Data System (ADS)

    Pargas, Roy P.; Staples, Nancy J.; Malloy, Brian F.; Cantrell, Ken; Chhatriwala, Murtuza

    1998-03-01

    Reliable 3D wholebody scanners which output digitized 3D images of a complete human body are now commercially available. This paper describes a software package, called 3DM, being developed by researchers at Clemson University and which manipulates and extracts measurements from such images. The focus of this paper is on tilted planes, a 3DM tool which allows a user to define a plane through a scanned image, tilt it in any direction, and effectively define three disjoint regions on the image: the points on the plane and the points on either side of the plane. With tilted planes, the user can accurately take measurements required in applications such as apparel manufacturing. The user can manually segment the body rather precisely. Tilted planes assist the user in analyzing the form of the body and classifying the body in terms of body shape. Finally, titled planes allow the user to eliminate extraneous and unwanted points often generated by a 3D scanner. This paper describes the user interface for tilted planes, the equations defining the plane as the user moves it through the scanned image, an overview of the algorithms, and the interaction of the tilted plane feature with other tools in 3DM.

  17. Artificial impedance ground planes for low profile antenna applications

    NASA Astrophysics Data System (ADS)

    McMichael, Ian T.

    Recent interest in artificial impedance surfaces for low-profile antennas has led to extensive research with the goal of optimizing the ground plane's characteristics for a given antenna configuration and broadening the operational bandwidth, or alternatively creating a multi-band functionality. A method of determining the optimal reflection phase for a low-profile dipole antenna over an electromagnetic band gap (EBG) ground plane has been developed based on image theory and is presented with experimental and numerical validation. A new artificial impedance surface has also been developed, which is composed of an annular slot ring on a thin grounded dielectric. The main difference between the proposed ground plane and a conventional EBG is that the high impedance condition exists only in the vicinity of the slot and is therefore best suited for antennas with a current distribution that has a similar shape as the annular slot ring. It is shown that a loop antenna positioned closely over an annular slot loaded ground plane exhibits approximately the same gain as a loop antenna over a conventional EBG ground plane. The advantage of the new structure is its lack of periodicity, which significantly eases manufacturing. Additionally, it is shown that multiple concentric slot rings can be designed into the ground plane, which excites multiple resonances in low-profile wideband antennas. The result is a multi-band high impedance ground plane constructed using a simple arrangement of annular slots. Finally, a manufacturing technique is presented for the application of arbitrarily configured EBG antennas to handheld dual-sensor landmine detection systems. It is shown that creating an EBG antenna using very thin layers of metal will enable it to be used for ground penetrating radar (GPR) when it is co-located with a low frequency metal detector without compromising the operation of the metal detector. The potential benefit of such an antenna would be a lower profile sensor

  18. The hybrid solution for the Fundamental Plane

    NASA Astrophysics Data System (ADS)

    D'Onofrio, M.; Fasano, G.; Moretti, A.; Marziani, P.; Bindoni, D.; Fritz, J.; Varela, J.; Bettoni, D.; Cava, A.; Poggianti, B.; Gullieuszik, M.; Kjærgaard, P.; Moles, M.; Vulcani, B.; Omizzolo, A.; Couch, W. J.; Dressler, A.

    2013-10-01

    By exploiting the data base of early-type galaxy (ETG) members of the WINGS survey of nearby clusters, we address here the long debated question of the origin and shape of the Fundamental Plane (FP). Our data suggest that different physical mechanisms concur in shaping and `tilting' the FP with respect to the virial plane (VP) expectation. In particular, a `hybrid solution' in which the structure of galaxies and their stellar population are the main contributors to the FP tilt seems to be favoured. We find that the bulk of the tilt should be attributed to structural non-homology, while stellar population effects play an important but less crucial role. In addition, our data indicate that the differential FP tilt between the V and K band is due to a sort of entanglement between structural and stellar population effects, for which the inward steepening of colour profiles (V - K) tends to increase at increasing the stellar mass of ETGs. The same kind of analysis applied to the ATLAS3D and Sloan Digital Sky Survey (SDSS) data in common with WINGS (WSDSS throughout the paper) confirms our results, the only remarkable difference being the less important role that our data attribute to the stellar mass-to-light-ratio (stellar populations) in determining the FP tilt. The ATLAS3D data also suggest that the FP tilt depends as well on the dark matter (DM) fraction and on the rotational contribution to the kinetic energy (Vrot/σ), thus again pointing towards the above-mentioned `hybrid solution'. We show that the global properties of the FP, i.e. its tilt and tightness, can be understood in terms of the underlying correlation among mass, structure and stellar population of ETGs, for which, at increasing the stellar mass, ETGs become (on average) `older' and more centrally concentrated. Finally, we show that a Malmquist-like selection effect may mimic a differential evolution of the mass-to-light ratio for galaxies of different masses. This should be taken into account in the

  19. The UKIDSS Galactic Plane Survey

    NASA Astrophysics Data System (ADS)

    Lucas, P. W.; Hoare, M. G.; Longmore, A.; Schröder, A. C.; Davis, C. J.; Adamson, A.; Bandyopadhyay, R. M.; de Grijs, R.; Smith, M.; Gosling, A.; Mitchison, S.; Gáspár, A.; Coe, M.; Tamura, M.; Parker, Q.; Irwin, M.; Hambly, N.; Bryant, J.; Collins, R. S.; Cross, N.; Evans, D. W.; Gonzalez-Solares, E.; Hodgkin, S.; Lewis, J.; Read, M.; Riello, M.; Sutorius, E. T. W.; Lawrence, A.; Drew, J. E.; Dye, S.; Thompson, M. A.

    2008-11-01

    The UKIDSS Galactic Plane Survey (GPS) is one of the five near-infrared Public Legacy Surveys that are being undertaken by the UKIDSS consortium, using the Wide Field Camera on the United Kingdom Infrared Telescope. It is surveying 1868 deg2 of the northern and equatorial Galactic plane at Galactic latitudes -5° < b < 5° in the J, H and K filters and a ~200-deg2 area of the Taurus-Auriga-Perseus molecular cloud complex in these three filters and the 2.12 μm (1-0) H2 filter. It will provide data on ~2 × 109 sources. Here we describe the properties of the data set and provide a user's guide for its exploitation. We also present brief Demonstration Science results from DR2 and from the Science Verification programme. These results illustrate how GPS data will frequently be combined with data taken in other wavebands to produce scientific results. The Demonstration Science comprises six studies. (1) A GPS-Spitzer-GLIMPSE cross-match for the star formation region G28.983-0.603 to identify YSOs. This increases the number of YSOs identified by a factor of 10 compared to GLIMPSE alone. (2) A wide-field study of the M17 nebula, in which an extinction map of the field is presented and the effect of source confusion on luminosity functions in different subregions is noted. (3) H2 emission in the ρ Ophiuchi dark cloud. All the molecular jets are traced back to a single active clump containing only a few protostars, which suggests that the duration of strong jet activity and associated rapid accretion in low-mass protostars is brief. (4) X-ray sources in the nuclear bulge. The GPS data distinguishes local main-sequence counterparts with soft X-ray spectra from nuclear bulge giant counterparts with hard X-ray spectra. (5) External galaxies in the zone of avoidance. The galaxies are clearly distinguished from stars in fields at longitudes l > 90°. (6) IPHAS-GPS optical-infrared spectrophotometric typing. The (i' - J) versus (J - H) diagram is used to distinguish A-F type

  20. Out-of-plane properties

    NASA Technical Reports Server (NTRS)

    Jackson, Wade C.; Portanova, Marc A.

    1995-01-01

    This paper summarizes three areas of research which were performed to characterize out-of-plane properties of composite materials. In the first investigation, a series of tests was run to characterize the through-the-thickness tensile strength for a variety of composites that included 2D braids, 2D and 3D weaves, and prepreg tapes. A new test method based on a curved beam was evaluated. Failures were significantly different between the 2D materials and the 3D weaves. The 2D materials delaminated between layers due to out-of-plane tensile stresses while the 3D weaves failed due to the formation of radial cracks between the surface plies caused by high circumferential stresses along the inner radius. The strength of the 2D textile composites did not increase relative to the tapes. Final failure in the 3D weaves was caused by a circumferential crack similar to the 2D materials and occurred at a lower bending moment than in other materials. The early failures in the 3D weaves were caused by radial crack formation rather than a low through-the-thickness strength. The second investigation focused on the development of a standard impact test method to measure impact damage resistance. The only impact tests that currently exist are compression after impact (CAI) tests which incorporate elements of both damage resistance and damage tolerance. A new impact test method is under development which uses a quasi-static indentation (QSI) test to directly measure damage resistance. Damage resistance is quantified in terms of the contact force to produce a unit of damage where a metric for damage may be area in C-scan, depth of residual dent , penetration, damage growth, etc. A final draft of an impact standard that uses a QSI test method will be presented to the ASTM Impact Task Group on impact. In the third investigation, the impact damage resistance behavior of a variety of textile materials was studied using the QSI test method. In this study, the force where large damage