Science.gov

Sample records for additional structural elements

  1. Addition of three-dimensional isoparametric elements to NASA structural analysis program (NASTRAN)

    NASA Technical Reports Server (NTRS)

    Field, E. I.; Johnson, S. E.

    1973-01-01

    Implementation is made of the three-dimensional family of linear, quadratic and cubic isoparametric solid elements into the NASA Structural Analysis program, NASTRAN. This work included program development, installation, testing, and documentation. The addition of these elements to NASTRAN provides a significant increase in modeling capability particularly for structures requiring specification of temperatures, material properties, displacements, and stresses which vary throughout each individual element. Complete program documentation is presented in the form of new sections and updates for direct insertion to the three NASTRAN manuals. The results of demonstration test problems are summarized. Excellent results are obtained with the isoparametric elements for static, normal mode, and buckling analyses.

  2. Effects of additions of small amounts of fourth elements on structure, crystal structure and shape recovery of Cu-Zn-Al shape memory alloys

    SciTech Connect

    Zhang, M.R. |; Yang, D.Z.; Tadaki, T.; Hirotsu, Y.

    1997-01-15

    Cu-based shape memory alloys (SMAs) are particularly interesting, compared to Ni-Ti SMAs because of their low cost and relatively ease process. However, there are important problems to be solved, such as intergranular fracture due to large grain size, stabilization of martensite, etc. In the present work, the influences of additions only less than 1 mass% of several fourth elements, such as Mn, Fe, Co, Ni, and Y, to two kinds of Cu-Zn-Al SMAs, i.e., Cu-30Zn-4Al and Cu-25Zn-7Al on their structure, crystal structure and shape recovery have been examined in order to know what elements are the most effective for the thermal stability of the parent and martensite phases and the shape memory capacity.

  3. Effect of additional elements on compositional modulated atomic layered structure of hexagonal Co80Pt20 alloy films with superlattice diffraction

    NASA Astrophysics Data System (ADS)

    Hinata, Shintaro; Yamane, Akira; Saito, Shin

    2016-05-01

    The effect of additional element on compositionally modulated atomic layered structure of hexagonal Co80Pt20 alloy films with superlattice diffraction was investigated. In this study it is found that the addition of Cr or W element to Co80Pt20 alloy film shows less deterioration of hcp stacking structure and compositionally modulated atomic layer stacking structure as compared to Si or Zr or Ti with Ku of around 1.4 or 1.0 × 107 erg/cm3 at 5 at.% addition. Furthermore, for O2 addition of O2 ≥ 5.0 × 10-3 Pa to CoPt alloy, compositionally modulated atomic layer stacking structure will be deteriorated with enhancement of formation of hcp stacking structure which leads higher Ku of 1.0 × 107 erg/cm3.

  4. Effect of Additional 3d Elements M (M = Fe and Ni) on Atomic Ordered Structure in Cu-M-Pd alloy

    NASA Astrophysics Data System (ADS)

    Ahmad, Naseeb; Takahashi, Miwako; Bashir Ziya, Amer; Ohshima, Ken-ichi

    X-ray diffraction measurements were performed to elucidate the effect of ternary addition of Fe and Ni elements to Cu-rich Cu-Pd binary alloy system on the structure and an atomic ordering. X-ray polycrystalline diffraction patterns of the specimens quenched from 900 °C have shown that a single phase with face-centered cubic (fcc) structure is formed in all the specimens for Ni system and in specimens with Pd composition xPd (at. %) more than 10 for Fe system. After appropriate heat treatment, the Fe system a fcc single phase forms fcc-based Cu3Au-type ordered structure for xPd around 20, and body-centered-cubic based CsCl-type ordered structure xPd for around 40. Assuming that Fe atoms simply substitute for Cu atoms in the ordered structures, the atomic phase coincides well with that of Cu-Pd alloys for the Cu3Au-type structure, but there is a discrepancy for the CsCl-type structure on that it does not appear as a single phase in Cu-Fe-Pd alloys. As for Ni system, no ordered structures are formed except for the alloys with xPd more than 35, in which fcc and CsCl-type structures are found to coexist.

  5. Addition of higher order plate and shell elements into NASTRAN computer program

    NASA Technical Reports Server (NTRS)

    Narayanaswami, R.; Goglia, G. L.

    1976-01-01

    Two higher order plate elements, the linear strain triangular membrane element and the quintic bending element, along with a shallow shell element, suitable for inclusion into the NASTRAN (NASA Structural Analysis) program are described. Additions to the NASTRAN Theoretical Manual, Users' Manual, Programmers' Manual and the NASTRAN Demonstration Problem Manual, for inclusion of these elements into the NASTRAN program are also presented.

  6. Elements of Regolith Simulant's Cost Structure

    NASA Technical Reports Server (NTRS)

    Rickman, Douglas L.

    2009-01-01

    The cost of lunar regolith simulants is much higher than many users anticipate. After all, it is nothing more than broken rock. This class will discuss the elements which make up the cost structure for simulants. It will also consider which elements can be avoided under certain circumstances and which elements might be altered by the application of additional research and development.

  7. Endjoints For Structural Elements

    NASA Technical Reports Server (NTRS)

    Bush, Harold G.; Mikulas, Martin M.; Wallsom, Richard E.

    1989-01-01

    Endjoint and connecting-node system designed for use in erection of frames. System structurally sound and simple to operate. All nodes and struts interchangeable. Nodes and struts attach to form cubic cell structures to produce beams, platforms, towers, or combinations of these. Design suitable for use in construction of space structures and such terrestrial skeletal frameworks as antenna-reflector supports, roof structures for large buildings, lookout towers, radio-transmitter towers, powerline pylons, and scaffolds.

  8. Automatic Element Addition and Deletion in Lens Optimization

    NASA Astrophysics Data System (ADS)

    Cheng, Xuemin; Wang, Yongtian; Hao, Qun; Sasian, Jose

    2003-03-01

    A mechanism is established for the automatic addition and deletion of optical elements during the course of lens optimization. Two lens-form parameters, quantifying the symmetry of the optical system and the optical-power distribution among the individual lens elements, are used as criteria in this automatic procedure. Design examples are provided that demonstrate the practicability of the scheme.

  9. Biobased extreme pressure additives: Structure-property considerations

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Extreme pressure additives are widely used in lubricant formulations for engine oils, hydraulic fluids, gear oils, metalworking fluids, and many others. Extreme pressure additives contain selected elements such as sulfur, phosphorus, and halogens in their structures. These elements, under extreme tr...

  10. Structural Truss Elements and Forces

    ERIC Educational Resources Information Center

    Troyer, Steve; Griffis, Kurt; Shackelford, Ray

    2005-01-01

    In the field of construction, most structures are supported by several groups of truss systems working together synergistically. A "truss" is a group of centered and balanced elements combined to carry a common load (Warner, 2003). Trusses provide strength against loads and forces within a structure. Though a complex field of study, structural…

  11. Methanogenesis from wastewater stimulated by addition of elemental manganese

    PubMed Central

    Qiao, Sen; Tian, Tian; Qi, Benyu; Zhou, Jiti

    2015-01-01

    This study presents a novel procedure for accelerating methanogenesis from wastewater by adding elemental manganese into the anaerobic digestion system. The results indicated that elemental manganese effectively enhanced both the methane yield and the production rate. Compared to the control test without elemental manganese, the total methane yield and production rate with 4 g/L manganese addition increased 3.4-fold (from 0.89 ± 0.03 to 2.99 ± 0.37 M/gVSS within 120 h) and 4.4-fold (from 6.2 ± 0.1 to 27.2 ± 2.2 mM/gVSS/h), respectively. Besides, more acetate consumption and less propionate generation were observed during the methanogenesis with manganese. Further studies demonstrated that the elemental manganese served as electron donors for the methanogenesis from carbon dioxide, and the final proportion of methane in the total generated gas with 4 g/L manganese addition reached 96.9%, which was 2.1-fold than that of the control (46.6%). PMID:26244609

  12. Element-by-element Solution Procedures for Nonlinear Structural Analysis

    NASA Technical Reports Server (NTRS)

    Hughes, T. J. R.; Winget, J. M.; Levit, I.

    1984-01-01

    Element-by-element approximate factorization procedures are proposed for solving the large finite element equation systems which arise in nonlinear structural mechanics. Architectural and data base advantages of the present algorithms over traditional direct elimination schemes are noted. Results of calculations suggest considerable potential for the methods described.

  13. Improved finite element methodology for integrated thermal structural analysis

    NASA Technical Reports Server (NTRS)

    Dechaumphai, P.; Thornton, E. A.

    1982-01-01

    An integrated thermal-structural finite element approach for efficient coupling of thermal and structural analyses is presented. New thermal finite elements which yield exact nodal and element temperature for one dimensional linear steady state heat transfer problems are developed. A nodeless variable formulation is used to establish improved thermal finite elements for one dimensional nonlinear transient and two dimensional linear transient heat transfer problems. The thermal finite elements provide detailed temperature distributions without using additional element nodes and permit a common discretization with lower order congruent structural finite elements. The accuracy of the integrated approach is evaluated by comparisons with analytical solutions and conventional finite element thermal-structural analyses for a number of academic and more realistic problems. Results indicate that the approach provides a significant improvement in the accuracy and efficiency of thermal stress analysis for structures with complex temperature distributions.

  14. Open-Section Composite Structural Elements

    NASA Technical Reports Server (NTRS)

    Loftin, T. A.; Smith, C. A.; Raheb, S. J.; Nowitzky, A. M.

    1991-01-01

    Report describes investigation of manufacture and mechanical properties of graphite-fiber/aluminum-matrix open-section structural elements; e.g., channels and angle bars. Conducted with view toward using such elements to build lightweight, thermally stable truss structures in outer space. Other applications transport to, and assembly at, remote or otherwise uninviting locations. Advantages include shapes permitting high packing density during shipment, convenient paths for routing tubes, hoses, and cables; accessibility of both inner and outer surfaces for repair; and ease of attachment of additional hardware. Easier and require less equipment to fabricate, and more amenable to automated fabrication and assembly at remote site. Disadvantages, not as resistant to some kinds of deformation under load.

  15. Evaluation of additive element to improve PZT piezoelectricity by using first-principles calculation

    NASA Astrophysics Data System (ADS)

    Yasoda, Yutaka; Uetsuji, Yasutomo; Tsuchiya, Kazuyoshi

    2015-12-01

    Recently, piezoelectric material has a very important potential for functional material which configure Bio-MEMS (Biological Micro Electro Mechanical Systems) actuator and sensor. Specifically, in implementation of piezoelectric material for Bio-MEMS, thin film fabrication by sputtering method is made from the viewpoint of miniaturization. Furthermore, in piezoelectric material, perovskite type material composed of ABO3 has a high piezoelectricity. Then, PZT (Lead Zirconate Titanate) as the perovskite type piezoelectric material is widely used since it is easy to produce and has high piezoelectricity. PZT has zirconium or titanium in the B site of ABO3 structure. PZT has the features such as physical properties to greatly change by change in the B site composition ratio of zirconium and titanium. Thus, the B site greatly influences physical properties and therefore function improvement by additive element is tried widely. However, experimental method to lack in economy and quantitativeness is mainstream. Therefore, application of the result is difficult and new evaluation method of B site additive element for sputtering fabrication is necessary. Accordingly, in this research, search of an additive element at low cost and quantitative from the viewpoint of energy by first-principles calculation. First of all, the additive elements which capable of substituting for a B site of PZT were searched. Next, change of piezoelectricity was evaluated by change of crystal structure in a PZT system was introduced an additive element that substitution of the B site was possible. As a result, additive elements for the PZT B site capable of improving piezoelectricity were determined.

  16. Where the Periodic Table of Elements Ends? Additional Explanations

    NASA Astrophysics Data System (ADS)

    Khazan, Albert

    2011-03-01

    Already 40 years ago, physicists claimed that the elements with number higher than 110 cannot exist. However at this day, Period 7 has been complete. Experiementalists syntesed 10 new syperheavy elements during only the last because. The method of synthesis is so finely developed that the experimentalists of Dubna tell about element No.150 as the higher limit of theTable of Elements (they do not provide a ground to the calculation). In contrast, our calculation are based neither on calculation of the stability of the electronic shells of the atoms, nor synthesis of the superheavy elements. Our caculation is based on study of the chemical processes, which give a new law of the Periodic Table (Albert Khazan. Upper Limit in Mendeleev's Periodic Table---Element No. 155. Svenska fysikarkivet, Stockholm, 2009). The core of the delusion of numerous scientists was that they, in their calculationsbased on Quantum Mechanics, initially set up the number of the elements (number of the protons) then calculated the atomic mass proceeding from the data. According to our theory, the atomic mass of the last element (411.66) should be calculated first, only then its number (155)!

  17. Providing Structure: The Critical Element.

    ERIC Educational Resources Information Center

    Miller, Judith E.; And Others

    1996-01-01

    Discussion of course structure in active learning at the college level looks at ways level and type of structure can be varied and manipulated to meet challenges presented by a diverse student body. Issues discussed include the relationship of structure to cognitive style and development, fitting structure to content and objectives, and what can…

  18. Finite element analysis of helicopter structures

    NASA Technical Reports Server (NTRS)

    Rich, M. J.

    1978-01-01

    Application of the finite element analysis is now being expanded to three dimensional analysis of mechanical components. Examples are presented for airframe, mechanical components, and composite structure calculations. Data are detailed on the increase of model size, computer usage, and the effect on reducing stress analysis costs. Future applications for use of finite element analysis for helicopter structures are projected.

  19. Enumeration of Secondary Structure Element Bundles

    SciTech Connect

    Brown, William Michael; Faulon, Jean-Loup

    2004-10-26

    A deterministic algorithm for enumeration of transmembrane protein folds is implemented. Using a set of sparse pairwise atomic distance constraints (such as those obtained from chemical cross-linking, FRET, or dipolar EPR experiments), the algorithm performs an exhaustive search of secondary structure element packing conformations distributed throughout the entire conformational space. The end result is a set of distinct protein conformations which can be scored and refined as part of a process designed for computational elucidation of transmembrane protein structures. Algorithm Overview: The ESSEB algorithm works by dividing the conforrnational space of each secondary structure element (SSE) into a set of cells. For each cell there is a representative conformation and for each atom in the SSE for which a distance restraint is available, there is an associated internal error, The internal error for a distance restraint is the maximum distance that the atom, when positioned in any conformation within a cell, can be from the atom in the representative conformation. The algorithm works recursively by positioning one representative conformation of an SSE. AdI distance restraints are checked with a tolerance that includes both the experimental and internal error. If all restraints are satisfied, every representative conformation of the next SSE is checked, otherwise, the program moves on to the next representative conformation of the current SSE. In addition to the distance restraints, other constraints on protein conformation can be enforced. These include the distance of closest approach between SSE axes, a restraint which prevents the crossover of loops connecting adjacent SSEs, and a restriction on the minimum and maximum distances between axis end-points. Any protein conformation satisfying all of the restraints is enumerated for later scoring and possible refinement. Additionally, in order to make run-times feasible, a divide-and-conquer approach is used in which

  20. Bifunctional air electrodes containing elemental iron powder charging additive

    DOEpatents

    Liu, Chia-tsun; Demczyk, Brian G.; Gongaware, Paul R.

    1982-01-01

    A bifunctional air electrode for use in electrochemical energy cells is made, comprising a hydrophilic layer and a hydrophobic layer, where the hydrophilic layer essentially comprises a hydrophilic composite which includes: (i) carbon; (ii) elemental iron particles having a particle size of between about 25 microns and about 700 microns diameter; (iii) an oxygen evolution material; (iv) a nonwetting agent; and (v) a catalyst, where at least one current collector is formed into said composite.

  1. The Electronic Structure of Heavy Element Complexes

    SciTech Connect

    Bursten, Bruce E.

    2000-07-25

    The area of study is the bonding in heavy element complexes, and the application of more sophisticated electronic structure theories. Progress is recounted in several areas: (a) technological advances and current methodologies - Relativistic effects are extremely important in gaining an understanding of the electronic structure of compounds of the actinides, transactinides, and other heavy elements. Therefore, a major part of the continual benchmarking was the proper inclusion of the appropriate relativistic effects for the properties under study. (b) specific applications - These include organoactinide sandwich complexes, CO activation by actinide atoms, and theoretical studies of molecules of the transactinide elements. Finally, specific directions in proposed research are described.

  2. Structure Property Studies for Additively Manufactured Parts

    SciTech Connect

    Milenski, Helen M; Schmalzer, Andrew Michael; Kelly, Daniel

    2015-08-17

    Since the invention of modern Additive Manufacturing (AM) processes engineers and designers have worked hard to capitalize on the unique building capabilities that AM allows. By being able to customize the interior fill of parts it is now possible to design components with a controlled density and customized internal structure. The creation of new polymers and polymer composites allow for even greater control over the mechanical properties of AM parts. One of the key reasons to explore AM, is to bring about a new paradigm in part design, where materials can be strategically optimized in a way that conventional subtractive methods cannot achieve. The two processes investigated in my research were the Fused Deposition Modeling (FDM) process and the Direct Ink Write (DIW) process. The objectives of the research were to determine the impact of in-fill density and morphology on the mechanical properties of FDM parts, and to determine if DIW printed samples could be produced where the filament diameter was varied while the overall density remained constant.

  3. 41 CFR 60-2.17 - Additional required elements of affirmative action programs.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... elements of affirmative action programs. 60-2.17 Section 60-2.17 Public Contracts and Property Management... Action Programs § 60-2.17 Additional required elements of affirmative action programs. In addition to the elements required by § 60-2.10 through § 60-2.16, an acceptable affirmative action program must include...

  4. 41 CFR 60-2.17 - Additional required elements of affirmative action programs.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... elements of affirmative action programs. 60-2.17 Section 60-2.17 Public Contracts and Property Management... Action Programs § 60-2.17 Additional required elements of affirmative action programs. In addition to the elements required by § 60-2.10 through § 60-2.16, an acceptable affirmative action program must include...

  5. 41 CFR 60-2.17 - Additional required elements of affirmative action programs.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... elements of affirmative action programs. 60-2.17 Section 60-2.17 Public Contracts and Property Management... Action Programs § 60-2.17 Additional required elements of affirmative action programs. In addition to the elements required by § 60-2.10 through § 60-2.16, an acceptable affirmative action program must include...

  6. 41 CFR 60-2.17 - Additional required elements of affirmative action programs.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... elements of affirmative action programs. 60-2.17 Section 60-2.17 Public Contracts and Property Management... Action Programs § 60-2.17 Additional required elements of affirmative action programs. In addition to the elements required by § 60-2.10 through § 60-2.16, an acceptable affirmative action program must include...

  7. 41 CFR 60-2.17 - Additional required elements of affirmative action programs.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... elements of affirmative action programs. 60-2.17 Section 60-2.17 Public Contracts and Property Management... Action Programs § 60-2.17 Additional required elements of affirmative action programs. In addition to the elements required by § 60-2.10 through § 60-2.16, an acceptable affirmative action program must include...

  8. Enumeration of Secondary Structure Element Bundles

    2004-10-26

    A deterministic algorithm for enumeration of transmembrane protein folds is implemented. Using a set of sparse pairwise atomic distance constraints (such as those obtained from chemical cross-linking, FRET, or dipolar EPR experiments), the algorithm performs an exhaustive search of secondary structure element packing conformations distributed throughout the entire conformational space. The end result is a set of distinct protein conformations which can be scored and refined as part of a process designed for computational elucidationmore » of transmembrane protein structures. Algorithm Overview: The ESSEB algorithm works by dividing the conforrnational space of each secondary structure element (SSE) into a set of cells. For each cell there is a representative conformation and for each atom in the SSE for which a distance restraint is available, there is an associated internal error, The internal error for a distance restraint is the maximum distance that the atom, when positioned in any conformation within a cell, can be from the atom in the representative conformation. The algorithm works recursively by positioning one representative conformation of an SSE. AdI distance restraints are checked with a tolerance that includes both the experimental and internal error. If all restraints are satisfied, every representative conformation of the next SSE is checked, otherwise, the program moves on to the next representative conformation of the current SSE. In addition to the distance restraints, other constraints on protein conformation can be enforced. These include the distance of closest approach between SSE axes, a restraint which prevents the crossover of loops connecting adjacent SSEs, and a restriction on the minimum and maximum distances between axis end-points. Any protein conformation satisfying all of the restraints is enumerated for later scoring and possible refinement. Additionally, in order to make run-times feasible, a divide-and-conquer approach is used

  9. Laser Additive Manufacturing of Gas Permeable Structures

    NASA Astrophysics Data System (ADS)

    Klahn, C.; Bechmann, F.; Hofmann, S.; Dinkel, M.; Emmelmann, C.

    Laser additive manufacturing offers a variety of new design possibilities. In mold making laser additive manufactured inserts with conformal cooling channels are already state of the art. Pneumatic ejectors for injection molds are a new application for laser additive manufacturing. The pneumatic ejectors require a durable gas permeable material. This material is produced by placing the scan vectors for the laser additive manufacturing process in a defined pattern. Trials with different plastics proofed the function and reliability of the pneumatic ejector concept in the injection molding cycle.

  10. Superheavy Elements -- Synthesis, Structure and Reaction Mechanism

    SciTech Connect

    Ackermann, Dieter

    2006-08-14

    The exciting results search for superheavy elements which have been achieved in the recent years have triggered a broad range of activities. Apart from experiments to attempt the synthesis of new elements, nuclear structure investigations in the transactinide region has become possibly for Z up to 108 or 110. Heavy element chemistry has successfully placed Hs in the periodic table and is no attacking element 112. The development of accelerators and experimental methods promises advances to enable the extension of these investigations in regions closer to the ''island of stability''. Mass measurements using ion traps and neutron rich unstable beam species for the systematic investigation of nuclear structure and reaction mechanisms for heavy neutron rich system are believed to complete the variety of tools in future.

  11. Finite-Element Modeling For Structural Analysis

    NASA Technical Reports Server (NTRS)

    Min, J. B.; Androlake, S. G.

    1995-01-01

    Report presents study of finite-element mathematical modeling as used in analyzing stresses and strains at joints between thin, shell-like components (e.g., ducts) and thicker components (e.g., flanges or engine blocks). First approach uses global/local model to evaluate system. Provides correct total response and correct representation of stresses away from any discontinuities. Second approach involves development of special transition finite elements to model transitions between shells and thicker structural components.

  12. Will Finite Elements Replace Structural Mechanics?

    NASA Astrophysics Data System (ADS)

    Ojalvo, I. U.

    1984-01-01

    This paper presents a personal view regarding the need for a continued interest and activity in structural methods in general, while viewing finite elements and the computer as simply two specific tools for assisting in this endeavor. An attempt is made to provide some insight as to why finite element methods seem to have "won the war," and to give examples of their more (and less) intelligent use. Items addressed include a highlight of unnecessary limitations of many existing standard finite element codes and where it is felt that further development work is needed.

  13. 47 CFR 51.509 - Rate structure standards for specific elements.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 3 2012-10-01 2012-10-01 false Rate structure standards for specific elements... SERVICES (CONTINUED) INTERCONNECTION Pricing of Elements § 51.509 Rate structure standards for specific elements. In addition to the general rules set forth in § 51.507, rates for specific elements shall...

  14. 47 CFR 51.509 - Rate structure standards for specific elements.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 3 2013-10-01 2013-10-01 false Rate structure standards for specific elements... SERVICES (CONTINUED) INTERCONNECTION Pricing of Elements § 51.509 Rate structure standards for specific elements. In addition to the general rules set forth in § 51.507, rates for specific elements shall...

  15. 47 CFR 51.509 - Rate structure standards for specific elements.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 3 2014-10-01 2014-10-01 false Rate structure standards for specific elements... SERVICES (CONTINUED) INTERCONNECTION Pricing of Elements § 51.509 Rate structure standards for specific elements. In addition to the general rules set forth in § 51.507, rates for specific elements shall...

  16. 47 CFR 51.509 - Rate structure standards for specific elements.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 3 2011-10-01 2011-10-01 false Rate structure standards for specific elements... SERVICES (CONTINUED) INTERCONNECTION Pricing of Elements § 51.509 Rate structure standards for specific elements. In addition to the general rules set forth in § 51.507, rates for specific elements shall...

  17. 47 CFR 51.509 - Rate structure standards for specific elements.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 3 2010-10-01 2010-10-01 false Rate structure standards for specific elements... SERVICES (CONTINUED) INTERCONNECTION Pricing of Elements § 51.509 Rate structure standards for specific elements. In addition to the general rules set forth in § 51.507, rates for specific elements shall...

  18. Finite Element Simulation of Smart Structures

    NASA Technical Reports Server (NTRS)

    Cui, Y. Lawrence; Panahandeh, M.

    1996-01-01

    Finite element equations representing the behavior of piezoelectric materials when bounded to a typical structure and used as sensors and actuators were developed. Emphasis was placed on generating sensor output equations of piezoelectric sensors and responses of a typical structure bonded with piezoelectric sensors and actuators on the basis of finite element formulation. The model can predict not only structural responses due to both mechanical and electrical loading but also electrical potential due to mechanical or thermal effects. The resulted finite element equations were then used for simple control design and performance evaluation. In the control algorithm, voltages coming out from piezoelectric sensors, which are proportional to strains at sensing locations, are taken as input. The voltages applied to the piezoelectric actuators are used as output. The feasibility of integrating control algorithm with the element routine developed herein and FEAP was demonstrated. In particular, optimal independent modal space control was implemented in a software package on the basis of finite element formulation. A rudimentary finite element-control algorithm package was also developed to evaluate the performance of candidate control laws. A few numerical simulations using the software package developed herein were given. The integrated software package will provide a design tool to address issues such as how adaptive smart systems will scale to a full size aircraft, the amount of piezoelectric materials and the powers needed to actuate it for desired performance. It will also provide a viable new structural control design concept for practical applications in large flexible structures such as aerospace vehicles and aircraft.

  19. Reporting of NSC Additional (A2) Data Elements. Updated July 29, 2014

    ERIC Educational Resources Information Center

    National Student Clearinghouse, 2014

    2014-01-01

    Since the 2008-09 academic year, the National Student Clearinghouse has provided its participating institutions with the option to include 13 additional data elements in their enrollment submissions. These additional data elements help make Clearinghouse data more comprehensive and enable StudentTracker? participants to utilize a more robust data…

  20. Bioinspired Cellular Structures: Additive Manufacturing and Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Stampfl, J.; Pettermann, H. E.; Liska, R.

    Biological materials (e.g., wood, trabecular bone, marine skeletons) rely heavily on the use of cellular architecture, which provides several advantages. (1) The resulting structures can bear the variety of "real life" load spectra using a minimum of a given bulk material, featuring engineering lightweight design principles. (2) The inside of the structures is accessible to body fluids which deliver the required nutrients. (3) Furthermore, cellular architectures can grow organically by adding or removing individual struts or by changing the shape of the constituting elements. All these facts make the use of cellular architectures a reasonable choice for nature. Using additive manufacturing technologies (AMT), it is now possible to fabricate such structures for applications in engineering and biomedicine. In this chapter, we present methods that allow the 3D computational analysis of the mechanical properties of cellular structures with open porosity. Various different cellular architectures including disorder are studied. In order to quantify the influence of architecture, the apparent density is always kept constant. Furthermore, it is shown that how new advanced photopolymers can be used to tailor the mechanical and functional properties of the fabricated structures.

  1. Finite element structural redesign by large admissible perturbations

    NASA Technical Reports Server (NTRS)

    Bernitsas, Michael M.; Beyko, E.; Rim, C. W.; Alzahabi, B.

    1991-01-01

    In structural redesign, two structural states are involved; the baseline (known) State S1 with unacceptable performance, and the objective (unknown) State S2 with given performance specifications. The difference between the two states in performance and design variables may be as high as 100 percent or more depending on the scale of the structure. A Perturbation Approach to Redesign (PAR) is presented to relate any two structural states S1 and S2 that are modeled by the same finite element model and represented by different values of the design variables. General perturbation equations are derived expressing implicitly the natural frequencies, dynamic modes, static deflections, static stresses, Euler buckling loads, and buckling modes of the objective S2 in terms of its performance specifications, and S1 data and Finite Element Analysis (FEA) results. Large Admissible Perturbation (LEAP) algorithms are implemented in code RESTRUCT to define the objective S2 incrementally without trial and error by postprocessing FEA results of S1 with no additional FEAs. Systematic numerical applications in redesign of a 10 element 48 degree of freedom (dof) beam, a 104 element 192 dof offshore tower, a 64 element 216 dof plate, and a 144 element 896 dof cylindrical shell show the accuracy, efficiency, and potential of PAR to find an objective state that may differ 100 percent from the baseline design.

  2. Fuzzy finite element analysis of smart structures

    NASA Astrophysics Data System (ADS)

    Akpan, Unyime O.; Koko, Tamunoiyala S.; Orisamolu, Irewole R.; Gallant, B. Keith

    2000-06-01

    A fuzzy finite element based approach is developed for modelling smart structures with vague or imprecise uncertainties. Fuzzy sets are used to represent the uncertainties present in the piezoelectric, mechanical, thermal, and physical properties of the smart structure. In order to facilitate efficient computation, a sensitivity analysis procedure is used to streamline the number of input fuzzy variables, and the vertex fuzzy analysis technique is then used to compute the possibility distributions of the responses of the smart structural system. The methodology has been developed within the framework of the SMARTCOM computational tool for the design/analysis of smart composite structures. The methodology developed is found to be accurate and computationally efficient for solution of practical problems.

  3. Study on automatic optical element addition or deletion in lens optimization

    NASA Astrophysics Data System (ADS)

    Cheng, Xuemin; Wang, Yongtian; Hao, Qun

    2002-09-01

    Two lens form parameters, quantifying the symmetry of the optical system and the optical power distribution among the individual lens elements, are used as the criteria for automatic element addition or deletion in lens optimization. The scheme based on the criteria is described in this paper. Design examples are provided, which demonstrate that the scheme is practicable.

  4. 1. Building #3, original structure and first addition, north side, ...

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

    1. Building #3, original structure and first addition, north side, looking south. Photo shows (from left) the original 1911 structure, the 1939 infill addition, and the 1934 structure. - S. W. Shattuck Chemical Company, Incorporated, Building No. 3, 1805 South Bannock Street, Denver, Denver County, CO

  5. 46 CFR 72.01-25 - Additional structural requirements.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 3 2010-10-01 2010-10-01 false Additional structural requirements. 72.01-25 Section 72.01-25 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) PASSENGER VESSELS CONSTRUCTION AND ARRANGEMENT Hull Structure § 72.01-25 Additional structural requirements. (a) Vessels required by part 171 of this chapter to have...

  6. Electronic structure theory of the superheavy elements

    NASA Astrophysics Data System (ADS)

    Eliav, Ephraim; Fritzsche, Stephan; Kaldor, Uzi

    2015-12-01

    High-accuracy calculations of atomic properties of the superheavy elements (SHE) up to element 122 are reviewed. The properties discussed include ionization potentials, electron affinities and excitation energies, which are associated with the spectroscopic and chemical behavior of these elements, and are therefore of considerable interest. Accurate predictions of these quantities require high-order inclusion of relativity and electron correlation, as well as large, converged basis sets. The Dirac-Coulomb-Breit Hamiltonian, which includes all terms up to second order in the fine-structure constant α, serves as the framework for the treatment; higher-order Lamb shift terms are considered in some selected cases. Electron correlation is treated by either the multiconfiguration self-consistent-field approach or by Fock-space coupled cluster theory. The latter is enhanced by the intermediate Hamiltonian scheme, allowing the use of larger model (P) spaces. The quality of the calculations is assessed by applying the same methods to lighter homologs of the SHEs and comparing with available experimental information. Very good agreement is obtained, within a few hundredths of an eV, and similar accuracy is expected for the SHEs. Many of the properties predicted for the SHEs differ significantly from what may be expected by straightforward extrapolation of lighter homologs, demonstrating that the structure and chemistry of SHEs are strongly affected by relativity. The major scientific challenge of the calculations is to find the electronic structure and basic atomic properties of the SHE and assign its proper place in the periodic table. Significant recent developments include joint experimental-computational studies of the excitation spectrum of Fm and the ionization energy of Lr, with excellent agreement of experiment and theory, auguring well for the future of research in the field.

  7. Faxing Structures to the Moon: Freeform Additive Construction System (FACS)

    NASA Technical Reports Server (NTRS)

    Howe, A. Scott; Wilcox, Brian; McQuin, Christopher; Townsend, Julie; Rieber, Richard; Barmatz, Martin; Leichty, John

    2013-01-01

    Using the highly articulated All-Terrain Hex-Limbed Extra-Terrestrial Explorer (ATHLETE) robotic mobility system as a precision positioning tool, a variety of print head technologies can be used to 3D print large-scale in-situ structures on planetary surfaces such as the moon or Mars. In effect, in the same way CAD models can be printed in a 3D printer, large-scale structures such as walls, vaults, domes, berms, paving, trench walls, and other insitu derived elements can be FAXed to the planetary surface and built in advance of the arrival of crews, supplementing equipment and materials brought from earth. This paper discusses the ATHLETE system as a mobility / positioning platform, and presents several options for large-scale additive print head technologies, including tunable microwave "sinterator" approaches and in-situ concrete deposition. The paper also discusses potential applications, such as sintered-in-place habitat shells, radiation shielding, road paving, modular bricks, and prefabricated construction components.

  8. Superheavy Element Synthesis And Nuclear Structure

    SciTech Connect

    Ackermann, D.; Block, M.; Burkhard, H.-G.; Heinz, S.; Hessberger, F. P.; Khuyagbaatar, J.; Kojouharov, I.; Mann, R.; Maurer, J.; Antalic, S.; Saro, S.; Venhart, M.; Hofmann, S.; Leino, M.; Uusitalo, J.; Nishio, K.; Popeko, A. G.; Yeremin, A. V.

    2009-08-26

    After the successful progress in experiments to synthesize superheavy elements (SHE) throughout the last decades, advanced nuclear structure studies in that region have become feasible in recent years thanks to improved accelerator, separation and detection technology. The means are evaporation residue(ER)-alpha-alpha and ER-alpha-gamma coincidence techniques complemented by conversion electron (CE) studies, applied after a separator. Recent examples of interesting physics to be discovered in this region of the chart of nuclides are the studies of K-isomers observed in {sup 252,254}No and in {sup 270}Ds.

  9. Electrical connection structure for a superconductor element

    SciTech Connect

    Lallouet, Nicolas; Maguire, James

    2010-05-04

    The invention relates to an electrical connection structure for a superconductor element cooled by a cryogenic fluid and connected to an electrical bushing, which bushing passes successively through an enclosure at an intermediate temperature between ambient temperature and the temperature of the cryogenic fluid, and an enclosure at ambient temperature, said bushing projecting outside the ambient temperature enclosure. According to the invention, said intermediate enclosure is filled at least in part with a solid material of low thermal conductivity, such as a polyurethane foam or a cellular glass foam. The invention is applicable to connecting a superconductor cable at cryogenic temperature to a device for equipment at ambient temperature.

  10. Finite element analysis of a deployable space structure

    NASA Technical Reports Server (NTRS)

    Hutton, D. V.

    1982-01-01

    To assess the dynamic characteristics of a deployable space truss, a finite element model of the Scientific Applications Space Platform (SASP) truss has been formulated. The model incorporates all additional degrees of freedom associated with the pin-jointed members. Comparison of results with SPAR models of the truss show that the joints of the deployable truss significantly affect the vibrational modes of the structure only if the truss is relatively short.

  11. EVA assembly of large space structure element

    NASA Technical Reports Server (NTRS)

    Bement, L. J.; Bush, H. G.; Heard, W. L., Jr.; Stokes, J. W., Jr.

    1981-01-01

    The results of a test program to assess the potential of manned extravehicular activity (EVA) assembly of erectable space trusses are described. Seventeen tests were conducted in which six "space-weight" columns were assembled into a regular tetrahedral cell by a team of two "space"-suited test subjects. This cell represents the fundamental "element" of a tetrahedral truss structure. The tests were conducted under simulated zero-gravity conditions. Both manual and simulated remote manipulator system modes were evaluated. Articulation limits of the pressure suit and zero gravity could be accommodated by work stations with foot restraints. The results of this study have confirmed that astronaut EVA assembly of large, erectable space structures is well within man's capabilities.

  12. Analysis of synthetic motor oils for additive elements by ICP-AES

    SciTech Connect

    Williams, M.C.; Salmon, S.G.

    1995-12-31

    Standard motor oils are made by blending paraffinic or naphthenic mineral oil base stocks with additive packages containing anti-wear agents, dispersants, corrosion inhibitors, and viscosity index improvers. The blender can monitor the correct addition of the additives by determining the additive elements in samples dissolved in a solvent by ICP-AES. Internal standardization is required to control sample transport interferences due to differences in viscosity between samples and standards. Synthetic motor oils, made with poly-alpha-olefins and trimethylol propane esters, instead of mineral oils, pose an additional challenge since these compounds affect the plasma as well as having sample transport interference considerations. The synthetic lubricant base stocks add significant oxygen to the sample matrix, which makes the samples behave differently than standards prepared in mineral oil. Determination of additive elements in synthetic motor oils will be discussed.

  13. Finite Element Estimation of Meteorite Structural Properties

    NASA Technical Reports Server (NTRS)

    Hart, Kenneth Arthur

    2015-01-01

    The goal of the project titled Asteroid Threat Assessment at NASA Ames Research Center is to develop risk assessment tools. The expertise in atmospheric entry in the Entry Systems and Technology Division is being used to describe the complex physics of meteor breakup in the atmosphere. The breakup of a meteor is dependent on its structural properties, including homogeneity of the material. The present work describes an 11-week effort in which a literature survey was carried for structural properties of meteoritic material. In addition, the effect of scale on homogeneity isotropy was studied using a Monte Carlo approach in Nastran. The properties were then in a static structural response simulation of an irregularly-shape meteor (138-scale version of Asteroid Itokawa). Finally, an early plan was developed for doctoral research work at Georgia Tech. in the structural failure fragmentation of meteors.

  14. A design study for the addition of higher order parametric discrete elements to NASTRAN

    NASA Technical Reports Server (NTRS)

    Stanton, E. L.

    1972-01-01

    The addition of discrete elements to NASTRAN poses significant interface problems with the level 15.1 assembly modules and geometry modules. Potential problems in designing new modules for higher-order parametric discrete elements are reviewed in both areas. An assembly procedure is suggested that separates grid point degrees of freedom on the basis of admissibility. New geometric input data are described that facilitate the definition of surfaces in parametric space.

  15. Effect of lubricant extreme pressure additives on rolling element fatigue life

    NASA Technical Reports Server (NTRS)

    Parker, R. J.; Zaretsky, E. V.

    1973-01-01

    The effects of surface active additives on rolling-element fatigue life were investigated with the five-ball fatigue tester at conditions where classical subsurface initiated rolling-element fatigue is the sole mode of failure. Test balls of AISI 52100, AISI M-50, and AISI 1018 were run with an acid-treated white oil containing either 2.5 percent sulfurized terpene, 1 percent didodecyl phosphite, or 5 percent chlorinated wax. In general, it was found that the influence of surface active additives was detrimental to rolling-element fatigue life. The chlorinated-wax additive significantly reduced fatigue life by a factor of 7. The base oil with the 2.5 percent sulfurized-terpene additive can reduce fatigue life by as much as 50 percent. No statistical change in fatigue life occurred with the base oil having the 1 percent didodecyl-phosphite additive. The additives used with the base oil did not change the ranking of the bearing steels where rolling-element fatigue life was of subsurface origin.

  16. Elements of Regolith Simulant's Cost Structure--Why Rock Is NOT Cheap

    NASA Technical Reports Server (NTRS)

    Rickman, Douglas L.

    2009-01-01

    The cost of lunar regolith simulants is much higher than many users anticipate. After all, it is nothing more than broken rock. This class will discuss the elements which make up the cost structure for simulants. It will also consider which elements can be avoided under certain circumstances and which elements might be altered by the application of additional research and development.

  17. Mineral elements of subtropical tree seedlings in response to elevated carbon dioxide and nitrogen addition.

    PubMed

    Huang, Wenjuan; Zhou, Guoyi; Liu, Juxiu; Zhang, Deqiang; Liu, Shizhong; Chu, Guowei; Fang, Xiong

    2015-01-01

    Mineral elements in plants have been strongly affected by increased atmospheric carbon dioxide (CO2) concentrations and nitrogen (N) deposition due to human activities. However, such understanding is largely limited to N and phosphorus in grassland. Using open-top chambers, we examined the concentrations of potassium (K), calcium (Ca), magnesium (Mg), aluminum (Al), copper (Cu) and manganese (Mn) in the leaves and roots of the seedlings of five subtropical tree species in response to elevated CO2 (ca. 700 μmol CO2 mol(-1)) and N addition (100 kg N ha(-1) yr(-1)) from 2005 to 2009. These mineral elements in the roots responded more strongly to elevated CO2 and N addition than those in the leaves. Elevated CO2 did not consistently decrease the concentrations of plant mineral elements, with increases in K, Al, Cu and Mn in some tree species. N addition decreased K and had no influence on Cu in the five tree species. Given the shifts in plant mineral elements, Schima superba and Castanopsis hystrix were less responsive to elevated CO2 and N addition alone, respectively. Our results indicate that plant stoichiometry would be altered by increasing CO2 and N deposition, and K would likely become a limiting nutrient under increasing N deposition in subtropics. PMID:25794046

  18. Mineral Elements of Subtropical Tree Seedlings in Response to Elevated Carbon Dioxide and Nitrogen Addition

    PubMed Central

    Huang, Wenjuan; Zhou, Guoyi; Liu, Juxiu; Zhang, Deqiang; Liu, Shizhong; Chu, Guowei; Fang, Xiong

    2015-01-01

    Mineral elements in plants have been strongly affected by increased atmospheric carbon dioxide (CO2) concentrations and nitrogen (N) deposition due to human activities. However, such understanding is largely limited to N and phosphorus in grassland. Using open-top chambers, we examined the concentrations of potassium (K), calcium (Ca), magnesium (Mg), aluminum (Al), copper (Cu) and manganese (Mn) in the leaves and roots of the seedlings of five subtropical tree species in response to elevated CO2 (ca. 700 μmol CO2 mol-1) and N addition (100 kg N ha-1 yr-1) from 2005 to 2009. These mineral elements in the roots responded more strongly to elevated CO2 and N addition than those in the leaves. Elevated CO2 did not consistently decrease the concentrations of plant mineral elements, with increases in K, Al, Cu and Mn in some tree species. N addition decreased K and had no influence on Cu in the five tree species. Given the shifts in plant mineral elements, Schima superba and Castanopsis hystrix were less responsive to elevated CO2 and N addition alone, respectively. Our results indicate that plant stoichiometry would be altered by increasing CO2 and N deposition, and K would likely become a limiting nutrient under increasing N deposition in subtropics. PMID:25794046

  19. Hierarchical flux-based thermal-structural finite element analysis method

    NASA Technical Reports Server (NTRS)

    Polesky, Sandra P.

    1992-01-01

    A hierarchical flux-based finite element method is developed for both a one and two dimensional thermal structural analyses. Derivation of the finite element equations is presented. The resulting finite element matrices associated with the flux based formulation are evaluated in a closed form. The hierarchical finite elements include additional degrees of freedom in the approximation of the element variable distributions by the use of nodeless variables. The nodeless variables offer increased solution accuracy without the need for defining actual nodes and rediscretizing the finite element model. Thermal and structural responses are obtained from a conventional linear finite element method and exact solutions. Results show that the hierarchical flux-based method can provide improved thermal and structural solution accuracy with fewer elements when compared to results for the conventional linear element method.

  20. Structural characteristic responses for finite element model updating of structures

    NASA Astrophysics Data System (ADS)

    Zhou, Linren; Wang, Lei; Ou, Jinping

    2014-04-01

    The field measurements of structures are very important to the structural finite element (FE) model updating because the errors and uncertainties of a FE model are corrected directly through closing the discrepancies between the analytical responses from FE model and the measurements from field testing of a structure. Usually, the accurate and reliable field measurements are very limited. Therefore, it is very important to make full use of the limited and valuable field measurements in structural model updating to achieve a best result with the lowest cost. In this paper, structural FE model updating is investigated in the point of view of solving a mathematical problem, and different amount and category of structural dynamic responses and static responses are considered as constraints to explore their effects on the updated results of different degree and types of structural damages. The numerical studies are carried out on a space truss. Accounting for the numerical results, some inherent phenomena and connections taking account of the updating parameters, output responses and the updated results are revealed and discussed. Some useful and practicable suggestions about using the field measurements for FE model updating are provided to achieve efficient and reliable results.

  1. Elements of the cellular metabolic structure

    PubMed Central

    De la Fuente, Ildefonso M.

    2015-01-01

    A large number of studies have demonstrated the existence of metabolic covalent modifications in different molecular structures, which are able to store biochemical information that is not encoded by DNA. Some of these covalent mark patterns can be transmitted across generations (epigenetic changes). Recently, the emergence of Hopfield-like attractor dynamics has been observed in self-organized enzymatic networks, which have the capacity to store functional catalytic patterns that can be correctly recovered by specific input stimuli. Hopfield-like metabolic dynamics are stable and can be maintained as a long-term biochemical memory. In addition, specific molecular information can be transferred from the functional dynamics of the metabolic networks to the enzymatic activity involved in covalent post-translational modulation, so that determined functional memory can be embedded in multiple stable molecular marks. The metabolic dynamics governed by Hopfield-type attractors (functional processes), as well as the enzymatic covalent modifications of specific molecules (structural dynamic processes) seem to represent the two stages of the dynamical memory of cellular metabolism (metabolic memory). Epigenetic processes appear to be the structural manifestation of this cellular metabolic memory. Here, a new framework for molecular information storage in the cell is presented, which is characterized by two functionally and molecularly interrelated systems: a dynamic, flexible and adaptive system (metabolic memory) and an essentially conservative system (genetic memory). The molecular information of both systems seems to coordinate the physiological development of the whole cell. PMID:25988183

  2. The use of elemental powder mixes in laser-based additive manufacturing

    NASA Astrophysics Data System (ADS)

    Clayton, Rodney Michael

    This study examines the use and functionality of laser depositing alloys from mixes of elemental metallic powders. Through the use of laser-based additive manufacturing (LAM), near net-shaped 3-Dimensional metallic parts can be produced in a layer-by-layer fashion. It is customary for pre-alloyed powders to be used in this process. However, mixes of elemental powders can be used to produce alloys that are formed during the deposition process. This alternative technique requires that the elemental powders adequately mix during deposition for a homogeneous deposit to be produced. Cost savings and versatility are among several of the advantages to using elemental powder mixes in LAM. Representative alloys of 316 and 430 Stainless Steel (SS) and Ti-6Al-4V were produced with elemental powder mixes during this research. These deposits were then compared to deposits of the same material manufactured with pre-alloyed powder. Comparison between the two types of samples included; EDS analysis to examine chemical homogeneity, metallography techniques to compare microstructures, and finally hardness testing to observe mechanical properties. The enthalpy of mixing is also discussed as this can impact the resulting homogeneity of deposits produced with mixes of elemental powders. Some differences were observed between the two types of deposits for 430 SS and Ti-6Al-4V. Results indicate that deposits fabricated with mixes of elemental powders can be produced to an equivalent quality of pre-alloyed powder deposits for 316 SS. This research also proposes potential alloys that could be considered for use in an elemental powder mixing technique.

  3. Addition of organic amendments contributes to C sequestration in trace element contaminated soils.

    NASA Astrophysics Data System (ADS)

    del Mar Montiel Rozas, María; Panettier, Marco; Madejón Rodríguez, Paula; Madejón Rodríguez, Engracia

    2015-04-01

    ha ¯¹. Thus, results revealed the effect of amendments. Values of net balance show an increase in C sequestered in amended plots. The retention of carbon in soluble and total forms was reflected in the increase in time. According to the results, application of leonardite (a more stabilized amendment) seems to entail a greater retention of carbon in soil than in the case of biosolid compost. Restoration strategies have multiple benefits for the ecosystem. In our case, the use of organic amendments decreased trace element toxicity, improved soil structure and microbial communities, and contribute to retain C in terrestrial ecosystems.

  4. Additive Manufacturing of Metal Cellular Structures: Design and Fabrication

    NASA Astrophysics Data System (ADS)

    Yang, Li; Harrysson, Ola; Cormier, Denis; West, Harvey; Gong, Haijun; Stucker, Brent

    2015-03-01

    With the rapid development of additive manufacturing (AM), high-quality fabrication of lightweight design-efficient structures no longer poses an insurmountable challenge. On the other hand, much of the current research and development with AM technologies still focuses on material and process development. With the design for additive manufacturing in mind, this article explores the design issue for lightweight cellular structures that could be efficiently realized via AM processes. A unit-cell-based modeling approach that combines experimentation and limited-scale simulation was demonstrated, and it was suggested that this approach could potentially lead to computationally efficient design optimizations with the lightweight structures in future applications.

  5. Additives

    NASA Technical Reports Server (NTRS)

    Smalheer, C. V.

    1973-01-01

    The chemistry of lubricant additives is discussed to show what the additives are chemically and what functions they perform in the lubrication of various kinds of equipment. Current theories regarding the mode of action of lubricant additives are presented. The additive groups discussed include the following: (1) detergents and dispersants, (2) corrosion inhibitors, (3) antioxidants, (4) viscosity index improvers, (5) pour point depressants, and (6) antifouling agents.

  6. Interior detail of structural elements section; camera facing east. ...

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

    Interior detail of structural elements section; camera facing east. - Mare Island Naval Shipyard, Supply Building, Walnut Avenue, southeast corner of Walnut Avenue & Fifth Street, Vallejo, Solano County, CA

  7. Controlling crystallization process and thermal stability of a binary Cu-Zr bulk metallic glass via minor element addition

    NASA Astrophysics Data System (ADS)

    Zhang, S. T.; Wang, Q.; Liu, T. T.; Liu, J. J.

    2015-09-01

    In this paper, the effect of minor element addition on the initial structural evolution during crystallization in a simple binary Cu-Zr bulk metallic glass (BMG) forming liquid has been investigated by using differential scanning calorimetry (DSC) and X-ray diffraction (XRD). Despite no changes in the completely crystallized products, the remarkable opposite impacts on the supercooled liquid region (SLR) and crystallization reaction rate constant Kcr are observed as a result of minor selective additions of an affine element, i.e., Sn and an immiscible element, i.e., Nb into the Cu-Zr BMG alloy, respectively. Furthermore, it is demonstrated that the primary devitrification pathway and crystalline phases are simultaneously modified, which leads to significant changes in kinetics of atomic rearrangement and thus thermal stability of this material. Such a finding offers a promising way to control the type of primary crystalline phases of BMG-forming metallic supercooled liquids to synthesize novel BMGs or BMG matrix composites for structural or functional applications.

  8. Friction Stir Additive Manufacturing: Route to High Structural Performance

    NASA Astrophysics Data System (ADS)

    Palanivel, S.; Sidhar, H.; Mishra, R. S.

    2015-03-01

    Aerospace and automotive industries provide the next big opportunities for additive manufacturing. Currently, the additive industry is confronted with four major challenges that have been identified in this article. These challenges need to be addressed for the additive technologies to march into new frontiers and create additional markets. Specific potential success in the transportation sectors is dependent on the ability to manufacture complicated structures with high performance. Most of the techniques used for metal-based additive manufacturing are fusion based because of their ability to fulfill the computer-aided design to component vision. Although these techniques aid in fabrication of complex shapes, achieving high structural performance is a key problem due to the liquid-solid phase transformation. In this article, friction stir additive manufacturing (FSAM) is shown as a potential solid-state process for attaining high-performance lightweight alloys for simpler geometrical applications. To illustrate FSAM as a high-performance route, manufactured builds of Mg-4Y-3Nd and AA5083 are shown as examples. In the Mg-based alloy, an average hardness of 120 HV was achieved in the built structure and was significantly higher than that of the base material (97 HV). Similarly for the Al-based alloy, compared with the base hardness of 88 HV, the average built hardness was 104 HV. A potential application of FSAM is illustrated by taking an example of a simple stiffener assembly.

  9. Effects of extreme pressure additive chemistry on rolling element bearing surface durability

    SciTech Connect

    Evans, Ryan D.; Nixon, H. P.; Darragh, Craig V.; Howe, Jane Y; Coffey, Dorothy W

    2007-01-01

    Lubricant additives have been known to affect rolling element bearing surface durability for many years. Tapered roller bearings were used in fatigue testing of lubricants formulated with gear oil type additive systems. These systems have sulfur- and phosphoruscontaining compounds used for gear protection as well as bearing lubrication. Several variations of a commercially available base additive formulation were tested having modified sulfur components. The variations represent a range of ''active'' extreme pressure (EP) chemistries. The bearing fatigue test results were compared with respect to EP formulation and test conditions. Inner ring near-surface material in selected test bearings was evaluated on two scales: the micrometer scale using optical metallography and the nanometer scale using transmission electron microscopy (TEM). Focused-ion beam (FIB) techniques were used for TEM specimen preparation. Imaging and chemical analysis of the bearing samples revealed near-surface material and tribofilm characteristics. These results are discussed with respect to the relative fatigue lives.

  10. Chromatin structure and transposable elements in organismal aging

    PubMed Central

    Wood, Jason G.; Helfand, Stephen L.

    2013-01-01

    Epigenetic regulatory mechanisms are increasingly appreciated as central to a diverse array of biological processes, including aging. An association between heterochromatic silencing and longevity has long been recognized in yeast, and in more recent years evidence has accumulated of age-related chromatin changes in Caenorhabditis elegans, Drosophila, and mouse model systems, as well as in the tissue culture-based replicative senescence model of cell aging. In addition, a number of studies have linked expression of transposable elements (TEs), as well as changes in the RNAi pathways that cells use to combat TEs, to the aging process. This review summarizes the recent evidence linking chromatin structure and function to aging, with a particular focus on the relationship of heterochromatin structure to organismal aging. PMID:24363663

  11. Analysis of random structure-acoustic interaction problems using coupled boundary element and finite element methods

    NASA Technical Reports Server (NTRS)

    Mei, Chuh; Pates, Carl S., III

    1994-01-01

    A coupled boundary element (BEM)-finite element (FEM) approach is presented to accurately model structure-acoustic interaction systems. The boundary element method is first applied to interior, two and three-dimensional acoustic domains with complex geometry configurations. Boundary element results are very accurate when compared with limited exact solutions. Structure-interaction problems are then analyzed with the coupled FEM-BEM method, where the finite element method models the structure and the boundary element method models the interior acoustic domain. The coupled analysis is compared with exact and experimental results for a simplistic model. Composite panels are analyzed and compared with isotropic results. The coupled method is then extended for random excitation. Random excitation results are compared with uncoupled results for isotropic and composite panels.

  12. Work of Adhesion in Al/SiC Composites with Alloying Element Addition

    NASA Astrophysics Data System (ADS)

    Fang, Xin; Fan, Tongxiang; Zhang, Di

    2013-11-01

    In the current work, a general methodology was proposed to demonstrate how to calculate the work of adhesion in a reactive multicomponent alloy/ceramic system. Applying this methodology, the work of adhesion of Al alloy/SiC systems and the influence of different alloying elements were predicted. Based on the thermodynamics of interfacial reaction and calculation models for component activities, the equilibrium compositions of the melts in Al alloy/SiC systems were calculated. Combining the work of adhesion models for reactive metal/ceramic systems, the work of adhesion in Al alloy/SiC systems both before and after the reaction was calculated. The results showed that the addition of most alloying elements, such as Mg, Si, and Mn, could increase the initial work of adhesion, while Fe had a slightly decreasing effect. As for the equilibrium state, the additions of Cu, Fe, Mn, Ni, Ti, and La could increase the equilibrium work of adhesion, but the additions of Mg and Zn had an opposite effect. Si was emphasized due to its suppressing effect on the interfacial reaction.

  13. Impact of Zn, Mg, Ni and Co elements on glass alteration: Additive effects

    NASA Astrophysics Data System (ADS)

    Aréna, H.; Godon, N.; Rébiscoul, D.; Podor, R.; Garcès, E.; Cabie, M.; Mestre, J.-P.

    2016-03-01

    The minor elements present in the nuclear glass composition or coming from the groundwater of the future repository may impact glass alteration. In this study, the effects of Zn, Mg, Ni and Co on the International Simple Glass (ISG) alteration were studied throughout 511 days of aqueous leaching experiments. The aim was to determine their additive or competitive effect on glass alteration and the nature of the alteration products. The four elements were introduced separately or altogether in solution as XCl2 chloride salts (X = Zn, Mg, Ni or Co) with monthly additions to compensate for their consumption. The alteration kinetics were determined by leachate analyses (ICP-AES) and alteration products were characterized in terms of composition, morphology and microstructure (SEM, TEM-EDX, ToF-SIMS and XRD). Results indicate that when they are introduced separately, Zn, Mg, Ni and Co have the same qualitative and quantitative effect on glass alteration kinetics and on pH: they form secondary phases leading to a pH decrease and a significant increase in glass alteration. The secondary phases were identified as silicates of the added X element: trioctahedral smectites with a stoichiometry of[(Si(4-a) Ala) (X(3-b) Alb) O10 (OH)2](a+b)- [Xc Nad Cae] (2c+d+2e)+ with a = 0.11 to 0.45, b = 0.00 to 0.29, c = 0, d = 0.19 to 0.74 and e = 0.10 to 0.14. . It was shown that as pH stabilizes at a minimum value, X-silicates no longer precipitate, thus leading to a significant drop in the glass alteration rate. This pH value depends on X and it has been identified as being 8 for Mg-silicates, probably around 7.3 for Ni and Co-silicates and less than 6.2 for Zn-silicates. When tested together, the effects of these four elements on glass alteration are additive and lead to the formation of a mix of X-silicates that precipitate as long as their constitutive elements are available and the pH is above their respective minimum value. This study brings new quantitative information about the

  14. The design of impact absorbing structures for additive manufacture

    NASA Astrophysics Data System (ADS)

    Brennan-Craddock, J.; Brackett, D.; Wildman, R.; Hague, R.

    2012-08-01

    Additive manufacturing (AM) is increasingly becoming a viable manufacturing process due to dramatic advantages that it facilitates in the area of design complexity. This paper investigates the potential of additively manufactured lattice structures for the application of tailored impact absorption specifically for conformal body protection. It explores lattice cell types based on foam microstructures and assesses their suitability for impact absorption. The effect of varying the cell strut edge design is also investigated. The implications of scaling these cells up for AM are discussed as well as the design issues regarding the handling of geometric complexity and the requirement for body conformity. The suitability of AM materials for this application is also discussed.

  15. Multilevel additive Schwarz method for the h-p version of the Galerkin boundary element method

    NASA Astrophysics Data System (ADS)

    Heuer, N.; Stephan, E. P.; Tran, T.

    1998-04-01

    We study a multilevel additive Schwarz method for the h-p version of the Galerkin boundary element method with geometrically graded meshes. Both hypersingular and weakly singular integral equations of the first kind are considered. As it is well known the h-p version with geometric meshes converges exponentially fast in the energy-norm. However, the condition number of the Galerkin matrix in this case blows up exponentially in the number of unknowns M. We prove that the condition number kappa(P) of the multilevel additive Schwarz operator behaves like O(root Mlog(2) M). Asa direct consequence of this we also give the results for the 2-level preconditioner and also for the h-p version with quasi-uniform meshes. Numerical results supporting our theory are presented.

  16. Laser Additive Melting and Solidification of Inconel 718: Finite Element Simulation and Experiment

    NASA Astrophysics Data System (ADS)

    Romano, John; Ladani, Leila; Sadowski, Magda

    2016-03-01

    The field of powdered metal additive manufacturing is experiencing a surge in public interest finding uses in aerospace, defense, and biomedical industries. The relative youth of the technology coupled with public interest makes the field a vibrant research topic. The authors have expanded upon previously published finite element models used to analyze the processing of novel engineering materials through the use of laser- and electron beam-based additive manufacturing. In this work, the authors present a model for simulating fabrication of Inconel 718 using laser melting processes. Thermal transport phenomena and melt pool geometries are discussed and validation against experimental findings is presented. After comparing experimental and simulation results, the authors present two correction correlations to transform the modeling results into meaningful predictions of actual laser melting melt pool geometries in Inconel 718.

  17. The Wavelet Element Method. Part 2; Realization and Additional Features in 2D and 3D

    NASA Technical Reports Server (NTRS)

    Canuto, Claudio; Tabacco, Anita; Urban, Karsten

    1998-01-01

    The Wavelet Element Method (WEM) provides a construction of multiresolution systems and biorthogonal wavelets on fairly general domains. These are split into subdomains that are mapped to a single reference hypercube. Tensor products of scaling functions and wavelets defined on the unit interval are used on the reference domain. By introducing appropriate matching conditions across the interelement boundaries, a globally continuous biorthogonal wavelet basis on the general domain is obtained. This construction does not uniquely define the basis functions but rather leaves some freedom for fulfilling additional features. In this paper we detail the general construction principle of the WEM to the 1D, 2D and 3D cases. We address additional features such as symmetry, vanishing moments and minimal support of the wavelet functions in each particular dimension. The construction is illustrated by using biorthogonal spline wavelets on the interval.

  18. Nuclear microscopy of sperm cell elemental structure

    NASA Astrophysics Data System (ADS)

    Bench, Graham S.; Balhorn, Rod; Friz, Alexander M.

    1995-05-01

    Theories suggest there is a link between protamine concentrations in individual sperm and male fertility. Previously, biochemical analyses have used pooled samples containing millions of sperm to determine protamine concentrations. These methods have not been able to determine what percentage of morphologically normal sperm are biochemically defective and potentially infertile. Nuclear microscopy has been utilized to measure elemental profiles at the single sperm level. By measuring the amount of phosphorus and sulfur, the total DNA and protamine content in individual sperm from fertile bull and mouse semen have been determined. These values agree with results obtained from other biochemical analyses. Nuclear microscopy shows promise for measuring elemental profiles in the chromatin of individual sperm. The technique may be able to resolve theories regarding the importance of protamines to male fertility and identify biochemical defects responsible for certain types of male infertility.

  19. Nuclear microscopy of sperm cell elemental structure

    SciTech Connect

    Bench, G.S.; Balhorn, R.; Friz, A.M.; Freeman, S.P.H.T.

    1994-09-28

    Theories suggest there is a link between protamine concentrations in individual sperm and male fertility. Previously, biochemical analyses have used pooled samples containing millions of sperm to determine protamine concentrations. These methods have not been able to determine what percentage of morphologically normal sperm are biochemically defective and potentially infertile. Nuclear microscopy has been utilized to measure elemental profiles at the single sperm level. By measuring the amount of phosphorus and sulfur, the total DNA and protamine content in individual sperm from fertile bull and mouse semen have been determined. These values agree with results obtained from other biochemical analyses. Nuclear microscopy shows promise for measuring elemental profiles in the chromatin of individual sperm. The technique may be able to resolve theories regarding the importance of protamines to male fertility and identify biochemical defects responsible for certain types of male infertility.

  20. Finite Element Model Development For Aircraft Fuselage Structures

    NASA Technical Reports Server (NTRS)

    Buehrle, Ralph D.; Fleming, Gary A.; Pappa, Richard S.; Grosveld, Ferdinand W.

    2000-01-01

    The ability to extend the valid frequency range for finite element based structural dynamic predictions using detailed models of the structural components and attachment interfaces is examined for several stiffened aircraft fuselage structures. This extended dynamic prediction capability is needed for the integration of mid-frequency noise control technology. Beam, plate and solid element models of the stiffener components are evaluated. Attachment models between the stiffener and panel skin range from a line along the rivets of the physical structure to a constraint over the entire contact surface. The finite element models are validated using experimental modal analysis results.

  1. Seawater-derived rare earth element addition to abyssal peridotites during serpentinization

    NASA Astrophysics Data System (ADS)

    Frisby, Carl; Bizimis, Michael; Mallick, Soumen

    2016-04-01

    Serpentinized abyssal peridotites are evidence for active communication between the Earth's hydrosphere and the upper mantle, where exchange and retention of both major and trace elements occur. Bulk rock Nd isotopes in serpentinized abyssal peridotites imply interaction of seawater with the peridotite. In contrast, the Nd isotopes of clinopyroxenes from serpentinized abyssal peridotites retain their primary magmatic signature. It is currently unclear if, how and where seawater-derived Nd and other REE are being added or exchanged with the mantle peridotite minerals during serpentinization. To remedy this knowledge gap, we present in situ trace and major element concentrations, bulk rock and sequential leaching experiment trace element concentrations as well as Nd, Sr isotope data on refertilized and depleted serpentinized abyssal peridotites from the Southwest Indian Ridge. The secondary serpentine matrix and magnetite veins in these peridotites have elevated LREE concentrations, with variable negative Ce anomalies and large Rb, Sr, Pb and U enrichments that resemble seawater trace element patterns. The LREE concentrations in the serpentine phase are higher than those expected for the primary mantle mineralogy (olivine, orthopyroxene) based on data from relic clinopyroxenes and equilibrium partition coefficients. These data are consistent with seawater-derived REE addition to the peridotite during serpentinization. The bulk rocks have more radiogenic Sr and more unradiogenic Nd isotopes than their clinopyroxene (up to 8 εNd units lower than clinopyroxene). Sequential leaching experiments designed to mobilize secondary carbonates and Fe-oxides show even more unradiogenic Nd isotope ratios in the leachates than the bulk rock and clinopyroxene, approaching seawater compositions (up to 15 εNd units lower than clinopyroxene). Mass balance calculations using trace elements or Nd isotopes suggest that up to 30% of the bulk peridotite Nd budget is of seawater origin and

  2. Structural Elements in Franz Kafka's "The Metamorphosis."

    ERIC Educational Resources Information Center

    Johnson, Scott

    1993-01-01

    Notes that Kafka's "The Metamorphosis" is not only a masterpiece of modern literature but also a work that exemplifies many ideas of structural family therapy. Examines how Kafka's novella embodies concepts such as parentified children, enmeshment, intergenerational boundaries, coalitions and triangles, structural dysfunction, and structural…

  3. Hybrid curved nano-structured micro-optical elements.

    PubMed

    Balčytis, A; Hakobyan, D; Gabalis, M; Žukauskas, A; Urbonas, D; Malinauskas, M; Petruškevičius, R; Brasselet, E; Juodkazis, S

    2016-07-25

    Tailoring the spatial degree of freedom of light is an essential step towards the realization of advanced optical manipulation tools. A topical challenge consists of device miniaturization for improved performance and enhanced functionality at the micron scale. We demonstrate a novel approach that combines the additive three-dimensional (3D) structuring capability of laser polymerization and the subtractive subwavelength resolution patterning of focused ion beam lithography. As a case in point hybrid (dielectric/metallic) micro-optical elements that deliver a well-defined topological shaping of light are produced. Here we report on hybrid 3D binary spiral zone plates with unit and double topological charge. Their optical performances are compared to corresponding 2D counterparts both numerically and experimentally. Cooperative refractive capabilities without compromising topological beam shaping are shown. Realization of advanced designs where the dielectric architecture itself is endowed with singular properties is also discussed. PMID:27464151

  4. Nuclear microscopy of sperm cell elemental structure

    SciTech Connect

    Bench, G.S.

    1994-12-31

    Theories have suggested that there is a link between protamine concentrations in individual sperm and sperm fertility. At present, biochemical analyses have only been performed on bulk populations and existing methods have not been able to determine what percentage of morphologically normal sperm are biochemically defective and potentially infertile. As part of an investigation into male sperm fertility, nuclear microscopy has been utilized to measure elemental profiles at the single sperm level. By measuring the ratio of Phosphorus to Sulfur the authors have been able to determine the amount of protamine 1 and protamine 2 in individual cells from bulk fertile samples of bull and mouse sperm. Preliminary results show that, for each species, the relative amounts of protamine 1 and protamine 2 in morphologically normal sperm agree well with expected values.

  5. Simulation of Powder Layer Deposition in Additive Manufacturing Processes Using the Discrete Element Method

    SciTech Connect

    Herbold, E. B.; Walton, O.; Homel, M. A.

    2015-10-26

    This document serves as a final report to a small effort where several improvements were added to a LLNL code GEODYN-­L to develop Discrete Element Method (DEM) algorithms coupled to Lagrangian Finite Element (FE) solvers to investigate powder-­bed formation problems for additive manufacturing. The results from these simulations will be assessed for inclusion as the initial conditions for Direct Metal Laser Sintering (DMLS) simulations performed with ALE3D. The algorithms were written and performed on parallel computing platforms at LLNL. The total funding level was 3-­4 weeks of an FTE split amongst two staff scientists and one post-­doc. The DEM simulations emulated, as much as was feasible, the physical process of depositing a new layer of powder over a bed of existing powder. The DEM simulations utilized truncated size distributions spanning realistic size ranges with a size distribution profile consistent with realistic sample set. A minimum simulation sample size on the order of 40-­particles square by 10-­particles deep was utilized in these scoping studies in order to evaluate the potential effects of size segregation variation with distance displaced in front of a screed blade. A reasonable method for evaluating the problem was developed and validated. Several simulations were performed to show the viability of the approach. Future investigations will focus on running various simulations investigating powder particle sizing and screen geometries.

  6. Failure location prediction by finite element analysis for an additive manufactured mandible implant.

    PubMed

    Huo, Jinxing; Dérand, Per; Rännar, Lars-Erik; Hirsch, Jan-Michaél; Gamstedt, E Kristofer

    2015-09-01

    In order to reconstruct a patient with a bone defect in the mandible, a porous scaffold attached to a plate, both in a titanium alloy, was designed and manufactured using additive manufacturing. Regrettably, the implant fractured in vivo several months after surgery. The aim of this study was to investigate the failure of the implant and show a way of predicting the mechanical properties of the implant before surgery. All computed tomography data of the patient were preprocessed to remove metallic artefacts with metal deletion technique before mandible geometry reconstruction. The three-dimensional geometry of the patient's mandible was also reconstructed, and the implant was fixed to the bone model with screws in Mimics medical imaging software. A finite element model was established from the assembly of the mandible and the implant to study stresses developed during mastication. The stress distribution in the load-bearing plate was computed, and the location of main stress concentration in the plate was determined. Comparison between the fracture region and the location of the stress concentration shows that finite element analysis could serve as a tool for optimizing the design of mandible implants. PMID:26227805

  7. Viscoelastic structures. [finite element computer programs

    NASA Technical Reports Server (NTRS)

    Gupta, K. K.; Heer, E.

    1974-01-01

    Numerical analysis of viscoelastic problems may be achieved by either a step-by-step solution procedure or by the integral transform approach. However, for complicated loading and material property relationships, the latter method proves ineffective. Programs specifically developed for the analysis of viscoelastic structures are considered along with multipurpose programs with specific viscoelastic analysis capabilities.

  8. Optimum element density studies for finite-element thermal analysis of hypersonic aircraft structures

    NASA Technical Reports Server (NTRS)

    Ko, William L.; Olona, Timothy; Muramoto, Kyle M.

    1990-01-01

    Different finite element models previously set up for thermal analysis of the space shuttle orbiter structure are discussed and their shortcomings identified. Element density criteria are established for the finite element thermal modelings of space shuttle orbiter-type large, hypersonic aircraft structures. These criteria are based on rigorous studies on solution accuracies using different finite element models having different element densities set up for one cell of the orbiter wing. Also, a method for optimization of the transient thermal analysis computer central processing unit (CPU) time is discussed. Based on the newly established element density criteria, the orbiter wing midspan segment was modeled for the examination of thermal analysis solution accuracies and the extent of computation CPU time requirements. The results showed that the distributions of the structural temperatures and the thermal stresses obtained from this wing segment model were satisfactory and the computation CPU time was at the acceptable level. The studies offered the hope that modeling the large, hypersonic aircraft structures using high-density elements for transient thermal analysis is possible if a CPU optimization technique was used.

  9. Additional developments regarding manifest dream structure and function.

    PubMed

    Wolowitz, H

    1998-06-01

    Detailed observation of manifest dream sequences indicated self-advocating occurrences facilitating the dreamer's self interests, opposed by self-adversarial interferences. Further examination of manifest dream syntactical structure additionally suggested a recurrent, four-step, algorithm for personal problem-solving within an interpersonal matrix consisting of the following cycle: (1) an opening scene setting the stage, (2) for the emergence of a self-concern, (3) which evokes a strategy to deal with dreamer's self-concern, (4) that eventuates in a consequence of the strategy. These steps repeat until the dream ends. Observing these manifest dream structural features, attributable to broadening past theorizing with "bottom-up" approaches, clarifies the dream's problem-solving process by providing an empirical, observable framework for dream interpretation and by contributing to their consensual validation. PMID:9656284

  10. Structural order in additive processed bulk heterojunction organic solar cells

    NASA Astrophysics Data System (ADS)

    Rogers, James Thomas

    Considerable academic and industrial efforts have been dedicated to resolving scientific and technological issues associated with the fabrication of efficient plastic solar cells via solution deposition techniques. The most successful strategy used to generate solution processable devices implements a two component donor-acceptor type system composed of a (p-type) narrow bandgap conjugated polymer donor blended with a (n-type) fullerene acceptor. Due to the limited exciton diffusion lengths (~10 nm) inherent to these materials, efficient photoinduced charge generation requires heterojunction formation (i.e. donor/acceptor interfaces) in close proximity to the region of exciton generation. Maximal charge extraction therefore requires that donor and acceptor components form nanoscale phase separated percolating pathways to their respective electrodes. Devices exhibiting these structural characteristics are termed bulk heterojunction devices (BHJ). Although the BHJ architecture highlights the basic characteristics of functional donor-acceptor type organic solar cells, device optimization requires internal order within each phase and proper organization relative to the substrate in order to maximize charge transport efficiencies and minimize charge carrier recombination losses. The economic viability of BHJ solar cells hinges upon the minimization of processing costs; thus, commercially relevant processing techniques should generate optimal structural characteristics during film formation, eliminating the need for additional post deposition processing steps. Empirical optimization has shown that solution deposition using high boiling point additives (e.g. octanedithiol (ODT)) provides a simple and widely used fabrication method for maximizing the power conversion efficiencies of BHJ solar cells. This work will show using x-ray scattering that a small percentage of ODT (~2%) in chlorobenzene induces the nucleation of polymeric crystallites within 2 min of deposition

  11. Nuclear structure notes on element 115 decay chains

    SciTech Connect

    Rudolph, D. Sarmiento, L. G.; Forsberg, U.

    2015-10-15

    Hitherto collected data on more than hundred α-decay chains stemming from element 115 are combined to probe some aspects of the underlying nuclear structure of the heaviest atomic nuclei yet created in the laboratory.

  12. Interior detail of third level structural elements at south end; ...

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

    Interior detail of third level structural elements at south end; camera facing west. - Mare Island Naval Shipyard, Supply Building, Walnut Avenue, southeast corner of Walnut Avenue & Fifth Street, Vallejo, Solano County, CA

  13. 16. DETAIL VIEW OF TYPICAL STRUCTURAL ELEMENTS; CROSSBAY 3 BETWEEN ...

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

    16. DETAIL VIEW OF TYPICAL STRUCTURAL ELEMENTS; CROSSBAY 3 BETWEEN D & E BAYS; LOOKING WSW. (Ryan) - Watervliet Arsenal, Building No. 135, Gillespie Road, South of Parker Road, Watervliet, Albany County, NY

  14. 11. Detail, southeast corner, showing decorative elements of main structure, ...

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

    11. Detail, southeast corner, showing decorative elements of main structure, and window at the second story of the hose tower. - Independent Hose Company No. 3, Nineteenth & Belmont Streets, Bellaire, Belmont County, OH

  15. Interior view of third floor structural elements; camera facing south. ...

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

    Interior view of third floor structural elements; camera facing south. - Mare Island Naval Shipyard, Supply Building, Walnut Avenue, southeast corner of Walnut Avenue & Fifth Street, Vallejo, Solano County, CA

  16. Storage Area (1942 section), looking east, showing concrete structural elements ...

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

    Storage Area (1942 section), looking east, showing concrete structural elements and wall opening to vaults - Fort McNair, Film Store House, Fort Lesley J. McNair, P Street between Third & Fourth Streets, Southwest, Washington, District of Columbia, DC

  17. Effects of nitrate addition and iron speciation on trace element transfer in coastal food webs under phosphate and iron enrichment.

    PubMed

    Li, Shun-Xing; Liu, Feng-Jiao; Zheng, Feng-Ying; Zuo, Yue-Gang; Huang, Xu-Guang

    2013-06-01

    Coastal organisms are often exposed to both iron enrichment and eutrophication. Trace elements transfer in coastal food webs are critical for marine life and therefore influence coastal ecosystem function and the global carbon cycle. However, how these exposures affect algal element uptake and the subsequent element transfer to marine copepods (Tigriopus japonicus) is unknown. Here we investigated the effects of nitrate addition and iron speciation (Fe (OH)3 or EDTA-Fe) on the biological uptake of Cu, Zn, and Se under phosphate and iron enrichment, using Thalassiosira weissflogii, Skeletonema costatum, and Chlorella vulgaris as model marine algae. Algal element adsorption/absorption generally increased with increasing macronutrient concentrations. Algal element assimilation efficiencies depended on iron speciation and marine algae species. Element assimilation efficiencies of copepods were significantly correlated to the intracellular element concentrations in algal cells. Element uptake and transfer were controlled by eutrophication, iron speciation, and algal species in coastal food webs. PMID:23332676

  18. A multi-microprocessor system for finite element structural analysis

    NASA Technical Reports Server (NTRS)

    Jordan, H. F.; Sawyer, P. L.

    1978-01-01

    During the last few years, advances in microprocessor technology have spurred a renewed interest in special-purpose computers. The microprocessor has become small, inexpensive, and powerful enough to be considered as a building block for special-purpose hardware. A description is presented of the architecture of a prototype 'finite element machine' currently being built. Attention is given to details regarding the finite element analysis problem, the arrangement of the processors as finite element nodes in the structural model, the influence of the architecture on the solution algorithm, interprocessor communication primitives, and the performance of the finite element machine.

  19. Structural elements of the Sulu Sea, Philippines

    SciTech Connect

    Hinz, K.; Block, M.; Kudrass, H.R.; Meyer, H. , Hannover )

    1994-07-01

    The structure and tectonic history of the Sulu Sea are described on the basis of seismic reflection data combined with the findings of onshore and offshore geological studies, and the results of ODP Leg 124 drilling. Closing of a hypothetical Mesozoic proto-South China Sea associated with the formation of oceanic crustal splinters in the late Eocene followed by southward subduction and, in turn, progressive collision of the north Palawan continental terrane with the micro-continental Borneo plate since the middle Miocene, resulted in the formation of the structurally complex Sulu-Borneo collision belt. The latter comprises north Sabah, southern and central Palawan, and the northwest Sulu basin. Fracturing of the Borneo micro-continental plate into the Sulu and Cagayan ridges initiated the opening of the southeast Sulu basin during the late Oligocene through the early Miocene. Collision of the north Palawan continental terrane with Cagayan Ridge in the late early Miocene and oblique collision of these blocks with the central Philippines resulted in the still ongoing closing of the southeast Sulu basin since the middle or late Miocene. Closing of the southeast Sulu basin began with the formation of an oceanic crustal slab.

  20. Survey and development of finite elements for nonlinear structural analysis. Volume 2: Nonlinear shell finite elements

    NASA Technical Reports Server (NTRS)

    1976-01-01

    The development of two new shell finite elements for applications to large deflection problems is considered. The elements in question are doubly curved and of triangular and quadrilateral planform. They are restricted to small strains of elastic materials, and can accommodate large rotations. The elements described, which are based on relatively simple linear elements, make use of a new displacement function approach specifically designed for strongly nonlinear problems. The displacement function development for nonlinear applications is based on certain beam element formulations, and the strain-displacement equations are of a shallow shell type. Additional terms were included in these equations in an attempt to avoid the large errors characteristic of shallow shell elements in certain types of problems. An incremental nonlinear solution procedure specifically adopted to the element formulation was developed. The solution procedure is of combined incremental and total Lagrangian type, and uses a new updating scheme. A computer program was written to evaluate the developed formulations. This program can accommodate small element groups in arbitrary arrangements. Two simple programs were successfully solved. The results indicate that this new type of element has definite promise and should be a fruitful area for further research.

  1. Stability of the ω structure of transition elements

    NASA Astrophysics Data System (ADS)

    Ikeda, Yuji; Tanaka, Isao

    2016-03-01

    Properties of the ω structure are investigated for 27 transition elements from the viewpoints of thermodynamical and dynamical stability based on first-principles calculations. The thermodynamical stability of the ω structure is compared with those of the body-centered-cubic, face-centered-cubic, and hexagonal-close-packed structures. Similar to the case of those popular crystal structures, the occupation number for d orbitals is found to roughly determine relative energy and volume of the nonmagnetic ω structure. For the group 4 elements (Ti, Zr, and Hf), the ω structure is almost the lowest in energy among the investigated crystal structures and is also dynamically stable. The ω structure of the group 7 elements (Mn, Tc, and Re) is also dynamically stable. The ω Fe is found to exhibit a magnetic state with antiparallel magnetic moments. This magnetic state is the most favorable among the investigated magnetic states. The ω Fe in this magnetic state is also dynamically stable. Energies of binary alloys composed of the elements in the group 4 and those in the groups 5 and 6 are estimated by linear interpolation, and most of the alloys show concentration ranges where the ω structure is the lowest in energy among the investigated crystal structures.

  2. Tuning structure and mobility of solvation shells surrounding tracer additives

    SciTech Connect

    Carmer, James; Jain, Avni; Bollinger, Jonathan A.; Truskett, Thomas M.; Swol, Frank van

    2015-03-28

    Molecular dynamics simulations and a stochastic Fokker-Planck equation based approach are used to illuminate how position-dependent solvent mobility near one or more tracer particle(s) is affected when tracer-solvent interactions are rationally modified to affect corresponding solvation structure. For tracers in a dense hard-sphere fluid, we compare two types of tracer-solvent interactions: (1) a hard-sphere-like interaction, and (2) a soft repulsion extending beyond the hard core designed via statistical mechanical theory to enhance tracer mobility at infinite dilution by suppressing coordination-shell structure [Carmer et al., Soft Matter 8, 4083–4089 (2012)]. For the latter case, we show that the mobility of surrounding solvent particles is also increased by addition of the soft repulsive interaction, which helps to rationalize the mechanism underlying the tracer’s enhanced diffusivity. However, if multiple tracer surfaces are in closer proximity (as at higher tracer concentrations), similar interactions that disrupt local solvation structure instead suppress the position-dependent solvent dynamics.

  3. Tuning structure and mobility of solvation shells surrounding tracer additives.

    PubMed

    Carmer, James; Jain, Avni; Bollinger, Jonathan A; van Swol, Frank; Truskett, Thomas M

    2015-03-28

    Molecular dynamics simulations and a stochastic Fokker-Planck equation based approach are used to illuminate how position-dependent solvent mobility near one or more tracer particle(s) is affected when tracer-solvent interactions are rationally modified to affect corresponding solvation structure. For tracers in a dense hard-sphere fluid, we compare two types of tracer-solvent interactions: (1) a hard-sphere-like interaction, and (2) a soft repulsion extending beyond the hard core designed via statistical mechanical theory to enhance tracer mobility at infinite dilution by suppressing coordination-shell structure [Carmer et al., Soft Matter 8, 4083-4089 (2012)]. For the latter case, we show that the mobility of surrounding solvent particles is also increased by addition of the soft repulsive interaction, which helps to rationalize the mechanism underlying the tracer's enhanced diffusivity. However, if multiple tracer surfaces are in closer proximity (as at higher tracer concentrations), similar interactions that disrupt local solvation structure instead suppress the position-dependent solvent dynamics. PMID:25833590

  4. Additives Induced Structural Transformation of ABC Triblock Copolymer Particles.

    PubMed

    Xu, Jiangping; Yang, Yi; Wang, Ke; Li, Jingyi; Zhou, Huamin; Xie, Xiaolin; Zhu, Jintao

    2015-10-13

    Here we report the structural control of polystyrene-b-polyisoprene-b-poly(2-vinylpyridine) (PS-b-PI-b-P2VP) asymmetric ABC triblock copolymer particles under 3D confinement by tuning the interactions among blocks. The additives, including 3-n-pentadecylphenol, homopolystyrene, and solvents, which can modulate the interactions among polymer blocks, play significant roles in the particle morphology. Moreover, the structured particles can be disassembled into isolated micellar aggregates with novel morphologies or mesoporous particles with tunable pore shape. Interestingly, the formed pupa-like PS-b-PI-b-P2VP particles display interesting dynamic stretch-retraction behavior when the solvent property is changed after partial cross-linking of the P2VP block. We further prove that such dynamic behavior is closely related to the density of cross-linking. The strategies presented here are believed to be promising routes to rationally design and fabricate block copolymer particles with desirable shape and internal structure. PMID:26388457

  5. Effects of heavy metal and other elemental additives to activated sludge on growth of Eisenia foetida

    SciTech Connect

    Hartenstein, R.; Neuhauser, E.F.; Narahara, A.

    1981-09-01

    The approximate level at which added concentrations of certain elements would cause an activated sludge to induce a toxic effect upon the growth of Eisenia foetida was determined. During 43 trials on sludge samples obtained throughout 1 year of study, earthworms grew from 3 to 10 mg live wt at hatching to 792 mg +- 18% (mean +- C.V.) in 8 weeks, when sludge was 24/sup 0/C and contained no additives. None of several elements commonly used in microbial growth media enhanced the growth rate of the earthworm. At salt concentrations up to about 6.6% on a dry wt basis, none of six anions tested was in and of itself toxic, while five of 15 cations - Co, Hg, Cu, Ni, and Cd - appeared specifically to inhibit growth rate or cause death. Manganese, Cr, and Pb were innocuous even at the highest levels of application - 22,000, 46,000, and 52,000 mg/kg, respectively. Neither the anionic nor cationic component of certain salts, such as NaCl or NH/sub 4/Cl, could be said to inhibit growth, which occurred only at high concentrations of these salts (about 3.3 and/or 6.6%). Below 7 mmho/cm, toxicity could not be correlated with electrolytic conductance, though higher values may help to explain the nonspecific growth inhibitory effects of salts like NaCl and KCl. Nor could toxicity ever be ascribed to hydrogen ion activity, since sludge pH was not altered even at the highest salt dose. It is concluded that except under very extreme conditions, the levels of heavy metals and salts generally found in activated sludges will not have an adverse affect on the growth of E. foetida.

  6. The finite element method for calculating the marine structural design

    NASA Astrophysics Data System (ADS)

    Ion, A.; Ticu, I.

    2015-11-01

    The aim of this paper is to optimally design and dimension marine structures in order for them to fulfil both functional and safety requirements. A master level of structural mechanics is vital in order to check tests and analysis and to develop new structures. This study can improve the calculation and estimation of the effects of hydrodynamics and of other loads; movements, strains and internal forces in fixed and floating platforms and ships. The finite element method (FEM) ensures basic understanding of the finite element model as applied on static cases including beam and plate elements, experience with static analysis of marine structures like platforms and ships, along with the basic understanding of dynamic response of systems with one degree of freedom and simple continuous beams, and also how analysis models can be established for real structures by the use of generalized coordinates and superposition.

  7. Assumed--stress hybrid elements with drilling degrees of freedom for nonlinear analysis of composite structures

    NASA Technical Reports Server (NTRS)

    Knight, Norman F., Jr. (Principal Investigator)

    1996-01-01

    The goal of this research project is to develop assumed-stress hybrid elements with rotational degrees of freedom for analyzing composite structures. During the first year of the three-year activity, the effort was directed to further assess the AQ4 shell element and its extensions to buckling and free vibration problems. In addition, the development of a compatible 2-node beam element was to be accomplished. The extensions and new developments were implemented in the Computational Structural Mechanics Testbed COMET. An assessment was performed to verify the implementation and to assess the performance of these elements in terms of accuracy. During the second and third years, extensions to geometrically nonlinear problems were developed and tested. This effort involved working with the nonlinear solution strategy as well as the nonlinear formulation for the elements. This research has resulted in the development and implementation of two additional element processors (ES22 for the beam element and ES24 for the shell elements) in COMET. The software was developed using a SUN workstation and has been ported to the NASA Langley Convex named blackbird. Both element processors are now part of the baseline version of COMET.

  8. Global-local finite element analysis of composite structures

    SciTech Connect

    Deibler, J.E.

    1992-06-01

    The development of layered finite elements has facilitated analysis of laminated composite structures. However, the analysis of a structure containing both isotropic and composite materials remains a difficult problem. A methodology has been developed to conduct a ``global-local`` finite element analysis. A ``global`` analysis of the entire structure is conducted at the appropriate loads with the composite portions replaced with an orthotropic material of equivalent materials properties. A ``local`` layered composite analysis is then conducted on the region of interest. The displacement results from the ``global`` analysis are used as loads to the ``local`` analysis. the laminate stresses and strains can then be examined and failure criteria evaluated.

  9. Global-local finite element analysis of composite structures

    SciTech Connect

    Deibler, J.E.

    1992-06-01

    The development of layered finite elements has facilitated analysis of laminated composite structures. However, the analysis of a structure containing both isotropic and composite materials remains a difficult problem. A methodology has been developed to conduct a global-local'' finite element analysis. A global'' analysis of the entire structure is conducted at the appropriate loads with the composite portions replaced with an orthotropic material of equivalent materials properties. A local'' layered composite analysis is then conducted on the region of interest. The displacement results from the global'' analysis are used as loads to the local'' analysis. the laminate stresses and strains can then be examined and failure criteria evaluated.

  10. Finite element thermal analysis of convectively-cooled aircraft structures

    NASA Technical Reports Server (NTRS)

    Wieting, A. R.; Thornton, E. A.

    1981-01-01

    The design complexity and size of convectively-cooled engine and airframe structures for hypersonic transports necessitate the use of large general purpose computer programs for both thermal and structural analyses. Generally thermal analyses are based on the lumped-parameter finite difference technique, and structural analyses are based on the finite element technique. Differences in these techniques make it difficult to achieve an efficient interface. It appears, therefore, desirable to conduct an integrated analysis based on a common technique. A summary is provided of efforts by NASA concerned with the development of an integrated thermal structural analysis capability using the finite element method. Particular attention is given to the development of conduction/forced-convection finite element methodology and applications which illustrate the capabilities of the developed concepts.

  11. A comparison of element-by-element preconditioned iterative methods for solid and structural mechanics

    SciTech Connect

    Ferencz, R.M.

    1988-10-01

    Past work with element-by-element (EBE) preconditioned conjugate gradient iterative solution strategies has shown these techniques can be effective for large-scale, three-dimensional calculations in solid and structural mechanics. Significant gains over the profile storage direct solution method traditionally used in implicit finite element codes have been observed for a variety of real engineering analyses, especially in solid mechanics. Structural mechanics applications have proved less successful due to the ill-conditioned linear systems engendered by standard structural discretizations. This lack of robustness has recently motivated reconsideration of Lanczos-based algorithms as alternative iterative drivers. In this paper we compare the relative strengths of the conjugate gradient and Lanczos drivers when coupled with EBE preconditioning. The performance of the two methods is characterized, and compared with direct solution, using a model problem and a number of real engineering meshes. 26 refs., 14 figs., 2 tabs.

  12. Probabilistic Finite Element Analysis & Design Optimization for Structural Designs

    NASA Astrophysics Data System (ADS)

    Deivanayagam, Arumugam

    This study focuses on implementing probabilistic nature of material properties (Kevlar® 49) to the existing deterministic finite element analysis (FEA) of fabric based engine containment system through Monte Carlo simulations (MCS) and implementation of probabilistic analysis in engineering designs through Reliability Based Design Optimization (RBDO). First, the emphasis is on experimental data analysis focusing on probabilistic distribution models which characterize the randomness associated with the experimental data. The material properties of Kevlar® 49 are modeled using experimental data analysis and implemented along with an existing spiral modeling scheme (SMS) and user defined constitutive model (UMAT) for fabric based engine containment simulations in LS-DYNA. MCS of the model are performed to observe the failure pattern and exit velocities of the models. Then the solutions are compared with NASA experimental tests and deterministic results. MCS with probabilistic material data give a good prospective on results rather than a single deterministic simulation results. The next part of research is to implement the probabilistic material properties in engineering designs. The main aim of structural design is to obtain optimal solutions. In any case, in a deterministic optimization problem even though the structures are cost effective, it becomes highly unreliable if the uncertainty that may be associated with the system (material properties, loading etc.) is not represented or considered in the solution process. Reliable and optimal solution can be obtained by performing reliability optimization along with the deterministic optimization, which is RBDO. In RBDO problem formulation, in addition to structural performance constraints, reliability constraints are also considered. This part of research starts with introduction to reliability analysis such as first order reliability analysis, second order reliability analysis followed by simulation technique that

  13. Finite Element Model Development and Validation for Aircraft Fuselage Structures

    NASA Technical Reports Server (NTRS)

    Buehrle, Ralph D.; Fleming, Gary A.; Pappa, Richard S.; Grosveld, Ferdinand W.

    2000-01-01

    The ability to extend the valid frequency range for finite element based structural dynamic predictions using detailed models of the structural components and attachment interfaces is examined for several stiffened aircraft fuselage structures. This extended dynamic prediction capability is needed for the integration of mid-frequency noise control technology. Beam, plate and solid element models of the stiffener components are evaluated. Attachment models between the stiffener and panel skin range from a line along the rivets of the physical structure to a constraint over the entire contact surface. The finite element models are validated using experimental modal analysis results. The increased frequency range results in a corresponding increase in the number of modes, modal density and spatial resolution requirements. In this study, conventional modal tests using accelerometers are complemented with Scanning Laser Doppler Velocimetry and Electro-Optic Holography measurements to further resolve the spatial response characteristics. Whenever possible, component and subassembly modal tests are used to validate the finite element models at lower levels of assembly. Normal mode predictions for different finite element representations of components and assemblies are compared with experimental results to assess the most accurate techniques for modeling aircraft fuselage type structures.

  14. Future Launch Vehicle Structures - Expendable and Reusable Elements

    NASA Astrophysics Data System (ADS)

    Obersteiner, M. H.; Borriello, G.

    2002-01-01

    Further evolution of existing expendable launch vehicles will be an obvious element influencing the future of space transportation. Besides this reusability might be the change with highest potential for essential improvement. The expected cost reduction and finally contributing to this, the improvement of reliability including safe mission abort capability are driving this idea. Although there are ideas of semi-reusable launch vehicles, typically two stages vehicles - reusable first stage or booster(s) and expendable second or upper stage - it should be kept in mind that the benefit of reusability will only overwhelm if there is a big enough share influencing the cost calculation. Today there is the understanding that additional technology preparation and verification will be necessary to master reusability and get enough benefits compared with existing launch vehicles. This understanding is based on several technology and system concepts preparation and verification programmes mainly done in the US but partially also in Europe and Japan. The major areas of necessary further activities are: - System concepts including business plan considerations - Sub-system or component technologies refinement - System design and operation know-how and capabilities - Verification and demonstration oriented towards future mission mastering: One of the most important aspects for the creation of those coming programmes and activities will be the iterative process of requirements definition derived from concepts analyses including economical considerations and the results achieved and verified within technology and verification programmes. It is the intention of this paper to provide major trends for those requirements focused on future launch vehicles structures. This will include the aspects of requirements only valid for reusable launch vehicles and those common for expendable, semi-reusable and reusable launch vehicles. Structures and materials is and will be one of the

  15. Automated Finite Element Modeling of Wing Structures for Shape Optimization

    NASA Technical Reports Server (NTRS)

    Harvey, Michael Stephen

    1993-01-01

    The displacement formulation of the finite element method is the most general and most widely used technique for structural analysis of airplane configurations. Modem structural synthesis techniques based on the finite element method have reached a certain maturity in recent years, and large airplane structures can now be optimized with respect to sizing type design variables for many load cases subject to a rich variety of constraints including stress, buckling, frequency, stiffness and aeroelastic constraints (Refs. 1-3). These structural synthesis capabilities use gradient based nonlinear programming techniques to search for improved designs. For these techniques to be practical a major improvement was required in computational cost of finite element analyses (needed repeatedly in the optimization process). Thus, associated with the progress in structural optimization, a new perspective of structural analysis has emerged, namely, structural analysis specialized for design optimization application, or.what is known as "design oriented structural analysis" (Ref. 4). This discipline includes approximation concepts and methods for obtaining behavior sensitivity information (Ref. 1), all needed to make the optimization of large structural systems (modeled by thousands of degrees of freedom and thousands of design variables) practical and cost effective.

  16. Recent experiences using finite-element-based structural optimization

    NASA Technical Reports Server (NTRS)

    Paul, B. K.; Mcconnell, J. C.; Love, Mike H.

    1989-01-01

    Structural optimization has been available to the structural analysis community as a tool for many years. The popular use of displacement method finite-element techniques to analyze linearly elastic structures has resulted in an ability to calculate the weight and constraint gradients inexpensively for numerical optimization of structures. Here, recent experiences in the investigation and use of structural optimization are discussed. In particular, experience with the commercially available ADS/NASOPT code is addressed. An overview of the ADS/NASOPT procedure and how it was implemented is given. Two example problems are also discussed.

  17. Finite-element-based design tool for smart composite structures

    NASA Astrophysics Data System (ADS)

    Koko, Tamunoiyala S.; Orisamolu, Irewole R.; Smith, Malcolm J.; Akpan, Unyime O.

    1997-06-01

    This paper presents an integrated finite element-control methodology for the design/analysis of smart composite structures. The method forms part of an effort to develop an integrated computational tool that includes finite element modeling; control algorithms; and deterministic, fuzzy and probabilistic optimization and integrity assessment of the structures and control systems. The finite element analysis is based on a 20 node thermopiezoelectric composite element for modeling the composite structure with surface bonded piezoelectric sensors and actuators; and control is based on the linear quadratic regulator and the independent modal space control methods. The method has been implemented in a computer code called SMARTCOM. Several example problems have been used to verify various aspects of the formulations and the analysis results from the present study compare well against other numerical or experimental results. Being based on the finite element method, the present formation can be conveniently used for the analysis and design of smart composite structures with complex geometrical configurations and loadings.

  18. New Ground-State Crystal Structure of Elemental Boron.

    PubMed

    An, Qi; Reddy, K Madhav; Xie, Kelvin Y; Hemker, Kevin J; Goddard, William A

    2016-08-19

    Elemental boron exhibits many polymorphs in nature based mostly on an icosahedral shell motif, involving stabilization of 13 strong multicenter intraicosahedral bonds. It is commonly accepted that the most thermodynamic stable structure of elemental boron at atmospheric pressure is the β rhombohedral boron (β-B). Surprisingly, using high-resolution transmission electron microscopy, we found that pure boron powder contains grains of two different types, the previously identified β-B containing a number of randomly spaced twins and what appears to be a fully transformed twinlike structure. This fully transformed structure, denoted here as τ-B, is based on the Cmcm orthorhombic space group. Quantum mechanics predicts that the newly identified τ-B structure is 13.8  meV/B more stable than β-B. The τ-B structure allows 6% more charge transfer from B_{57} units to nearby B_{12} units, making the net charge 6% closer to the ideal expected from Wade's rules. Thus, we predict the τ-B structure to be the ground state structure for elemental boron at atmospheric pressure. PMID:27588864

  19. New Ground-State Crystal Structure of Elemental Boron

    NASA Astrophysics Data System (ADS)

    An, Qi; Reddy, K. Madhav; Xie, Kelvin Y.; Hemker, Kevin J.; Goddard, William A.

    2016-08-01

    Elemental boron exhibits many polymorphs in nature based mostly on an icosahedral shell motif, involving stabilization of 13 strong multicenter intraicosahedral bonds. It is commonly accepted that the most thermodynamic stable structure of elemental boron at atmospheric pressure is the β rhombohedral boron (β -B ). Surprisingly, using high-resolution transmission electron microscopy, we found that pure boron powder contains grains of two different types, the previously identified β -B containing a number of randomly spaced twins and what appears to be a fully transformed twinlike structure. This fully transformed structure, denoted here as τ -B , is based on the C m c m orthorhombic space group. Quantum mechanics predicts that the newly identified τ -B structure is 13.8 meV /B more stable than β -B . The τ -B structure allows 6% more charge transfer from B57 units to nearby B12 units, making the net charge 6% closer to the ideal expected from Wade's rules. Thus, we predict the τ -B structure to be the ground state structure for elemental boron at atmospheric pressure.

  20. Fluid structure interaction in electrohydraulic servovalve: a finite element approach

    NASA Astrophysics Data System (ADS)

    Hiremath, Somashekhar S.; Singaperumal, M.

    2010-01-01

    Electrohydraulic servovalves (EHSV) promise unique application opportunities and high performance, unmatched by other drive technologies. Typical applications include aerospace, robotic manipulators, motion simulators, injection molding, CNC machines and material testing machines. EHSV available are either a flapper/nozzle type or a jet pipe type. In the present paper an attempt has been made to study the dynamics of jet pipe EHSV with built-in mechanical feedback using Finite Element Method (FEM). In jet pipe EHSV, the dynamics of spool greatly depends on pressure recovery and hence the fluid flow at spool ends. The effect of pressure recovery on spool dynamics is studied using FEM by creating the fluid-structure-interaction. The mechanical parts were created using general purpose finite elements like shell, beam, and solid elements while fluid cavities were created using hydrostatic fluid elements. The analysis was carried out using the commercially available FE code ABAQUS. The jet pipe and spool dynamics are presented in the paper.

  1. Fluid structure interaction in electrohydraulic servovalve: a finite element approach

    NASA Astrophysics Data System (ADS)

    Hiremath, Somashekhar S.; Singaperumal, M.

    2009-12-01

    Electrohydraulic servovalves (EHSV) promise unique application opportunities and high performance, unmatched by other drive technologies. Typical applications include aerospace, robotic manipulators, motion simulators, injection molding, CNC machines and material testing machines. EHSV available are either a flapper/nozzle type or a jet pipe type. In the present paper an attempt has been made to study the dynamics of jet pipe EHSV with built-in mechanical feedback using Finite Element Method (FEM). In jet pipe EHSV, the dynamics of spool greatly depends on pressure recovery and hence the fluid flow at spool ends. The effect of pressure recovery on spool dynamics is studied using FEM by creating the fluid-structure-interaction. The mechanical parts were created using general purpose finite elements like shell, beam, and solid elements while fluid cavities were created using hydrostatic fluid elements. The analysis was carried out using the commercially available FE code ABAQUS. The jet pipe and spool dynamics are presented in the paper.

  2. Picornavirus IRES elements: RNA structure and host protein interactions.

    PubMed

    Martínez-Salas, Encarnación; Francisco-Velilla, Rosario; Fernandez-Chamorro, Javier; Lozano, Gloria; Diaz-Toledano, Rosa

    2015-08-01

    Internal ribosome entry site (IRES) elements were discovered in picornaviruses. These elements are cis-acting RNA sequences that adopt diverse three-dimensional structures and recruit the translation machinery using a 5' end-independent mechanism assisted by a subset of translation initiation factors and various RNA binding proteins termed IRES transacting factors (ITAFs). Many of these factors suffer important modifications during infection including cleavage by picornavirus proteases, changes in the phosphorylation level and/or redistribution of the protein from the nuclear to the cytoplasm compartment. Picornavirus IRES are amongst the most potent elements described so far. However, given their large diversity and complexity, the mechanistic basis of its mode of action is not yet fully understood. This review is focused to describe recent advances on the studies of RNA structure and RNA-protein interactions modulating picornavirus IRES activity. PMID:25617758

  3. Structural similarities between viroids and transposable genetic elements.

    PubMed Central

    Kiefer, M C; Owens, R A; Diener, T O

    1983-01-01

    The primary structures of the tomato planta macho and tomato apical stunt viroids have been determined, and probable secondary structures are proposed. Both viroids can assume the rodlike conformation with extensive base-pairing characteristic of all known viroids. Sequence homologies between the two viroids (75%) and with members of the potato spindle tuber viroid group (73-83%) indicate that they both belong to this group. Comparative sequence analysis of all members of the group reveals striking similarities with the ends of transposable genetic elements. These similarities, the presence of inverted repeats often ending with the dinucleotides U-G and C-A, and flanking imperfect direct repeats suggest that viroids may have originated from transposable elements or retroviral proviruses by deletion of interior portions of the viral (or element) DNA. PMID:6312450

  4. Better Finite-Element Analysis of Composite Shell Structures

    NASA Technical Reports Server (NTRS)

    Clarke, Gregory

    2007-01-01

    A computer program implements a finite-element-based method of predicting the deformations of thin aerospace structures made of isotropic materials or anisotropic fiber-reinforced composite materials. The technique and corresponding software are applicable to thin shell structures in general and are particularly useful for analysis of thin beamlike members having open cross-sections (e.g. I-beams and C-channels) in which significant warping can occur.

  5. A Cost Element Structure for Defense Training. Final Report.

    ERIC Educational Resources Information Center

    Knapp, Mark I.; Orlansky, Jesse

    This paper identifies, structures, and defines a list of cost elements that is intended to describe fully the life-cycle cost of any formal program, course, or device for individual training of Department of Defense personnel. It was developed to provide consistent, comparable, and credible evaluations of the cost-effectiveness of alternative…

  6. Finite element forced vibration analysis of rotating cyclic structures

    NASA Technical Reports Server (NTRS)

    Elchuri, V.; Smith, G. C. C.

    1981-01-01

    A capability was added to the general purpose finite element program NASTRAN Level 17.7 to conduct forced vibration analysis of tuned cyclic structures rotating about their axes of symmetry. The effects of Coriolis and centripetal accelerations together with those due to linear acceleration of the axis of rotation were included. The theoretical development of this capability is presented.

  7. Detail of array structural elements through axis of array, looking ...

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

    Detail of array structural elements through axis of array, looking north-northeast - Over-the-Horizon Backscatter Radar Network, Columbia Falls Radar Site Receive Sector Two Antenna Array, At the end of Shadagee Ridge Road, Columbia Falls, Washington County, ME

  8. Structural optimization of thin shells using finite element method

    NASA Technical Reports Server (NTRS)

    Gotsis, Pascal K.

    1992-01-01

    The objective of the present work was the structural optimization of thin shell structures that are subjected to stress and displacement constraints. In order to accomplish this, the structural optimization computer program DESAP1 was modified and improved. In the static analysis part of the DESAP1 computer program the torsional spring elements, which are used to analyze thin, shallow shell structures, were eliminated by modifying the membrane stiffness matrix of the triangular elements in the local coordinate system and adding a fictitious rotational stiffness matrix. This simplified the DESAP1 program input, improved the accuracy of the analysis, and saved computation time. In the optimization part of the DESAP1 program the stress ratio formula, which redesigns the thickness of each finite element of the structure, was solved by an analytical method. This scheme replaced the iterative solution that was previously used in the DESAP1 program, thus increasing the accuracy and speed of the design. The modified program was used to design a thin, cylindrical shell structure with optimum weight, and the results are reported in this paper.

  9. Using support vector machines to improve elemental ion identification in macromolecular crystal structures

    SciTech Connect

    Morshed, Nader; Echols, Nathaniel; Adams, Paul D.

    2015-05-01

    A method to automatically identify possible elemental ions in X-ray crystal structures has been extended to use support vector machine (SVM) classifiers trained on selected structures in the PDB, with significantly improved sensitivity over manually encoded heuristics. In the process of macromolecular model building, crystallographers must examine electron density for isolated atoms and differentiate sites containing structured solvent molecules from those containing elemental ions. This task requires specific knowledge of metal-binding chemistry and scattering properties and is prone to error. A method has previously been described to identify ions based on manually chosen criteria for a number of elements. Here, the use of support vector machines (SVMs) to automatically classify isolated atoms as either solvent or one of various ions is described. Two data sets of protein crystal structures, one containing manually curated structures deposited with anomalous diffraction data and another with automatically filtered, high-resolution structures, were constructed. On the manually curated data set, an SVM classifier was able to distinguish calcium from manganese, zinc, iron and nickel, as well as all five of these ions from water molecules, with a high degree of accuracy. Additionally, SVMs trained on the automatically curated set of high-resolution structures were able to successfully classify most common elemental ions in an independent validation test set. This method is readily extensible to other elemental ions and can also be used in conjunction with previous methods based on a priori expectations of the chemical environment and X-ray scattering.

  10. The effect of trace element addition to mono-digestion of grass silage at high organic loading rates.

    PubMed

    Wall, David M; Allen, Eoin; Straccialini, Barbara; O'Kiely, Padraig; Murphy, Jerry D

    2014-11-01

    This study investigated the effect of trace element addition to mono-digestion of grass silage at high organic loading rates. Two continuous reactors were compared. The first mono-digested grass silage whilst the second operated in co-digestion, 80% grass silage with 20% dairy slurry (VS basis). The reactors were run for 65weeks with a further 5weeks taken for trace element supplementation for the mono-digestion of grass silage. The co-digestion reactor reported a higher biomethane efficiency (1.01) than mono-digestion (0.90) at an OLR of 4.0kgVSm(-3)d(-1) prior to addition of trace elements. Addition of cobalt, iron and nickel, led to an increase in the SMY in mono-digestion of grass silage by 12% to 404LCH4kg(-1)VS and attained a biomethane efficiency of 1.01. PMID:25280042

  11. The computational structural mechanics testbed generic structural-element processor manual

    NASA Technical Reports Server (NTRS)

    Stanley, Gary M.; Nour-Omid, Shahram

    1990-01-01

    The usage and development of structural finite element processors based on the CSM Testbed's Generic Element Processor (GEP) template is documented. By convention, such processors have names of the form ESi, where i is an integer. This manual is therefore intended for both Testbed users who wish to invoke ES processors during the course of a structural analysis, and Testbed developers who wish to construct new element processors (or modify existing ones).

  12. Probabilistic nonlinear finite element analysis of composite structures

    NASA Technical Reports Server (NTRS)

    Engelstad, S. P.; Reddy, J. N.

    1993-01-01

    A probabilistic finite element analysis procedure for laminated composite shells is developed. A total Lagrangian finite element formulation, employing a degenerated three-dimensional laminated composite shell element with the full Green-Lagrange strains and first-order shear deformable kinematics, is used. The first-order second-moment technique for probabilistic finite element analysis of random fields is employed, and results are presented in the form of mean and variance of the structural response. Reliability calculations are made by using the first-order reliability method combined with sensitivity derivatives from the finite element analysis. Both ply-level and micromechanics-level random variables are incorporated, the latter by means of the Aboudi micromechanics model. Two sample problems are solved to verify the accuracy of the procedures developed and to quantify the variability of certain material type/structure combinations. In general, the procedure is quite effective in determining the response statistics and reliability for linear and geometric nonlinear behavior of laminated composite shells.

  13. Curved Thermopiezoelectric Shell Structures Modeled by Finite Element Analysis

    NASA Technical Reports Server (NTRS)

    Lee, Ho-Jun

    2000-01-01

    "Smart" structures composed of piezoelectric materials may significantly improve the performance of aeropropulsion systems through a variety of vibration, noise, and shape-control applications. The development of analytical models for piezoelectric smart structures is an ongoing, in-house activity at the NASA Glenn Research Center at Lewis Field focused toward the experimental characterization of these materials. Research efforts have been directed toward developing analytical models that account for the coupled mechanical, electrical, and thermal response of piezoelectric composite materials. Current work revolves around implementing thermal effects into a curvilinear-shell finite element code. This enhances capabilities to analyze curved structures and to account for coupling effects arising from thermal effects and the curved geometry. The current analytical model implements a unique mixed multi-field laminate theory to improve computational efficiency without sacrificing accuracy. The mechanics can model both the sensory and active behavior of piezoelectric composite shell structures. Finite element equations are being implemented for an eight-node curvilinear shell element, and numerical studies are being conducted to demonstrate capabilities to model the response of curved piezoelectric composite structures (see the figure).

  14. Finite element solution of transient fluid-structure interaction problems

    NASA Technical Reports Server (NTRS)

    Everstine, Gordon C.; Cheng, Raymond S.; Hambric, Stephen A.

    1991-01-01

    A finite element approach using NASTRAN is developed for solving time-dependent fluid-structure interaction problems, with emphasis on the transient scattering of acoustic waves from submerged elastic structures. Finite elements are used for modeling both structure and fluid domains to facilitate the graphical display of the wave motion through both media. For the liquid, the use of velocity potential as the fundamental unknown results in a symmetric matrix equation. The approach is illustrated for the problem of transient scattering from a submerged elastic spherical shell subjected to an incident tone burst. The use of an analogy between the equations of elasticity and the wave equation of acoustics, a necessary ingredient to the procedure, is summarized.

  15. Finite-element thermo-viscoplastic analysis of aerospace structures

    NASA Technical Reports Server (NTRS)

    Pandey, Ajay; Dechaumphai, Pramote; Thornton, Earl A.

    1990-01-01

    The time-dependent thermo-viscoplastic response of aerospace structures subjected to intense aerothermal loads is predicted using the finite-element method. The finite-element analysis uses the Bodner-Partom unified viscoplastic constitutive relations to determine rate-dependent nonlinear material behavior. The methodology is verified by comparison with experimental data and other numerical results for a uniaxially-loaded bar. The method is then used (1) to predict the structural response of a rectangular plate subjected to line heating along a centerline, and (2) to predict the thermal-structural response of a convectively-cooled engine cowl leading edge subjected to aerodynamic shock-shock interference heating. Compared to linear elastic analysis, the viscoplastic analysis results in lower peak stresses and regions of plastic deformations.

  16. Finite element thermo-viscoplastic analysis of aerospace structures

    NASA Technical Reports Server (NTRS)

    Pandey, Ajay K.; Dechaumphai, Pramote; Thornton, Earl A.

    1990-01-01

    The time-dependent thermo-viscoplastic response of aerospace structures subjected to intense aerothermal loads is predicted using the finite-element method. The finite-element analysis uses the Bodner-Partom unified viscoplastic constitutive relations to determine rate-dependent nonlinear material behavior. The methodology is verified by comparison with experimental data and other numerical results for a uniaxially-loaded bar. The method is then used (1) to predict the structural response of a rectangular plate subjected to line heating along a centerline, and (2) to predict the thermal-structural response of a convectively-cooled engine cowl leading edge subjected to aerodynamic shock-shock interference heating. Compared to linear elastic analysis, the viscoplastic analysis results in lower peak stresses and regions of plastic deformations.

  17. Aircraft wing structural design optimization based on automated finite element modelling and ground structure approach

    NASA Astrophysics Data System (ADS)

    Yang, Weizhu; Yue, Zhufeng; Li, Lei; Wang, Peiyan

    2016-01-01

    An optimization procedure combining an automated finite element modelling (AFEM) technique with a ground structure approach (GSA) is proposed for structural layout and sizing design of aircraft wings. The AFEM technique, based on CATIA VBA scripting and PCL programming, is used to generate models automatically considering the arrangement of inner systems. GSA is used for local structural topology optimization. The design procedure is applied to a high-aspect-ratio wing. The arrangement of the integral fuel tank, landing gear and control surfaces is considered. For the landing gear region, a non-conventional initial structural layout is adopted. The positions of components, the number of ribs and local topology in the wing box and landing gear region are optimized to obtain a minimum structural weight. Constraints include tank volume, strength, buckling and aeroelastic parameters. The results show that the combined approach leads to a greater weight saving, i.e. 26.5%, compared with three additional optimizations based on individual design approaches.

  18. Formal Nuclear and Atomic Structure of the Elements

    NASA Astrophysics Data System (ADS)

    Nduka, Amagh

    2004-05-01

    In the paper "The Space of 4-Operators and the Unification of the Fundamental Interactions" (see APS paper with log number 10016) we discussed the Fundamental Particle Scheme (not the Standard Model). As an application of the theory, we discuss in this paper formal atomic and nuclear structures and (1) deduce the correct periodic table of the elements that accounts for the missing elements of the empirically derived Chancourtois-Newlands-Lothar Meyer-Mendeleev table; and a table of the nuclides, (2) calculate the mass of the electron neutrino, and deduce the missing mass and dark matter of the universe.

  19. Simplified Finite Element Modelling of Acoustically Treated Structures

    NASA Astrophysics Data System (ADS)

    Carfagni, M.; Citti, P.; Pierini, M.

    1997-07-01

    The application of non-optimized damping and phono-absorbent materials to automotive systems has not proved fully satisfactory in abating noise and vibration. The objective of this work was to develop a simple finite element modelling procedure that would allow optimizing structures such as a car body-in-white in terms of vibroacoustic behavior from the design stage. A procedure was developed to determine the modifications to be made in the mass, stiffness and damping characteristics in the finite element (FE) modelling of a metal structure meshed with shell elements so that the model would describe the behavior of the acoustically treated structure. To validate the modifications, a numerical-experimental comparison of the velocities on the vibrating surface was carried out, followed by a numerical-experimental comparison of the sound pressures generated by the vibrating plate. In the comparison a simple monopole model was used, in which each area of vibrating surface could be likened to a point source. The simulation and experimental procedures, previously validated for the metal structure, were then applied to multi-layered panels. Good agreement between the experimental and simulated velocities and sound pressures resulted for all the multi-layered panel configurations examined.

  20. Structural changes in gluten protein structure after addition of emulsifier. A Raman spectroscopy study

    NASA Astrophysics Data System (ADS)

    Ferrer, Evelina G.; Gómez, Analía V.; Añón, María C.; Puppo, María C.

    2011-06-01

    Food protein product, gluten protein, was chemically modified by varying levels of sodium stearoyl lactylate (SSL); and the extent of modifications (secondary and tertiary structures) of this protein was analyzed by using Raman spectroscopy. Analysis of the Amide I band showed an increase in its intensity mainly after the addition of the 0.25% of SSL to wheat flour to produced modified gluten protein, pointing the formation of a more ordered structure. Side chain vibrations also confirmed the observed changes.

  1. Control of Gas Tungsten Arc welding pool shape by trace element addition to the weld pool

    DOEpatents

    Heiple, C.R.; Burgardt, P.

    1984-03-13

    An improved process for Gas Tungsten Arc welding maximizes the depth/width ratio of the weld pool by adding a sufficient amount of a surface active element to insure inward fluid flow, resulting in deep, narrow welds. The process is especially useful to eliminate variable weld penetration and shape in GTA welding of steels and stainless steels, particularly by using a sulfur-doped weld wire in a cold wire feed technique.

  2. Finite Element Based HWB Centerbody Structural Optimization and Weight Prediction

    NASA Technical Reports Server (NTRS)

    Gern, Frank H.

    2012-01-01

    This paper describes a scalable structural model suitable for Hybrid Wing Body (HWB) centerbody analysis and optimization. The geometry of the centerbody and primary wing structure is based on a Vehicle Sketch Pad (VSP) surface model of the aircraft and a FLOPS compatible parameterization of the centerbody. Structural analysis, optimization, and weight calculation are based on a Nastran finite element model of the primary HWB structural components, featuring centerbody, mid section, and outboard wing. Different centerbody designs like single bay or multi-bay options are analyzed and weight calculations are compared to current FLOPS results. For proper structural sizing and weight estimation, internal pressure and maneuver flight loads are applied. Results are presented for aerodynamic loads, deformations, and centerbody weight.

  3. A Curved, Elastostatic Boundary Element for Plane Anisotropic Structures

    NASA Technical Reports Server (NTRS)

    Smeltzer, Stanley S.; Klang, Eric C.

    2001-01-01

    The plane-stress equations of linear elasticity are used in conjunction with those of the boundary element method to develop a novel curved, quadratic boundary element applicable to structures composed of anisotropic materials in a state of plane stress or plane strain. The curved boundary element is developed to solve two-dimensional, elastostatic problems of arbitrary shape, connectivity, and material type. As a result of the anisotropy, complex variables are employed in the fundamental solution derivations for a concentrated unit-magnitude force in an infinite elastic anisotropic medium. Once known, the fundamental solutions are evaluated numerically by using the known displacement and traction boundary values in an integral formulation with Gaussian quadrature. All the integral equations of the boundary element method are evaluated using one of two methods: either regular Gaussian quadrature or a combination of regular and logarithmic Gaussian quadrature. The regular Gaussian quadrature is used to evaluate most of the integrals along the boundary, and the combined scheme is employed for integrals that are singular. Individual element contributions are assembled into the global matrices of the standard boundary element method, manipulated to form a system of linear equations, and the resulting system is solved. The interior displacements and stresses are found through a separate set of auxiliary equations that are derived using an Airy-type stress function in terms of complex variables. The capabilities and accuracy of this method are demonstrated for a laminated-composite plate with a central, elliptical cutout that is subjected to uniform tension along one of the straight edges of the plate. Comparison of the boundary element results for this problem with corresponding results from an analytical model show a difference of less than 1%.

  4. Experimental validation of finite element and boundary element methods for predicting structural vibration and radiated noise

    NASA Technical Reports Server (NTRS)

    Seybert, A. F.; Wu, T. W.; Wu, X. F.

    1994-01-01

    This research report is presented in three parts. In the first part, acoustical analyses were performed on modes of vibration of the housing of a transmission of a gear test rig developed by NASA. The modes of vibration of the transmission housing were measured using experimental modal analysis. The boundary element method (BEM) was used to calculate the sound pressure and sound intensity on the surface of the housing and the radiation efficiency of each mode. The radiation efficiency of each of the transmission housing modes was then compared to theoretical results for a finite baffled plate. In the second part, analytical and experimental validation of methods to predict structural vibration and radiated noise are presented. A rectangular box excited by a mechanical shaker was used as a vibrating structure. Combined finite element method (FEM) and boundary element method (BEM) models of the apparatus were used to predict the noise level radiated from the box. The FEM was used to predict the vibration, while the BEM was used to predict the sound intensity and total radiated sound power using surface vibration as the input data. Vibration predicted by the FEM model was validated by experimental modal analysis; noise predicted by the BEM was validated by measurements of sound intensity. Three types of results are presented for the total radiated sound power: sound power predicted by the BEM model using vibration data measured on the surface of the box; sound power predicted by the FEM/BEM model; and sound power measured by an acoustic intensity scan. In the third part, the structure used in part two was modified. A rib was attached to the top plate of the structure. The FEM and BEM were then used to predict structural vibration and radiated noise respectively. The predicted vibration and radiated noise were then validated through experimentation.

  5. Compatibility conditions of structural mechanics for finite element analysis

    NASA Technical Reports Server (NTRS)

    Patnaik, Surya N.; Berke, Laszlo; Gallagher, Richard H.

    1990-01-01

    The equilibrium equations and the compatibility conditions are fundamental to the analyses of structures. However, anyone who undertakes even a cursory generic study of the compatibility conditions can discover, with little effort, that historically this facet of structural mechanics had not been adequately researched by the profession. Now the compatibility conditions (CC's) have been researched and are understood to a great extent. For finite element discretizations, the CC's are banded and can be divided into three distinct categories: (1) the interface CC's; (2) the cluster or field CC's; and (3) the external CC's. The generation of CC's requires the separating of a local region, then writing the deformation displacement relation (ddr) for the region, and finally, the eliminating of the displacements from the ddr. The procedure to generate all three types of CC's is presented and illustrated through examples of finite element models. The uniqueness of the CC's thus generated is shown.

  6. Torque sensor having a spoked sensor element support structure

    NASA Technical Reports Server (NTRS)

    Lurie, Boris J. (Inventor); Schier, J. Alan (Inventor)

    1990-01-01

    Piezoelectric sensor devices are attached across pairs of circularly arranged spokes arrayed on the periphery of an annular ring. The sensor devices each include a preloaded steel ball mounting arrangement for mounting a piezoelectric sensor element. A first circular interface plate on one side of the sensor structure attaches to alternate one of the spokes, and a circular interface plate on the opposite side of the same diameter as the first interface plate attaches to the remaining spokes.

  7. The effect of selected alloying element additions on properties of Mg-based alloy as bioimplants: A literature review

    NASA Astrophysics Data System (ADS)

    Zhang, Li-Nan; Hou, Zeng-Tao; Ye, Xin; Xu, Zhao-Bin; Bai, Xue-Ling; Shang, Peng

    2013-09-01

    This review investigates the current application limitations of Mg and Mg alloys. The key issues hindering the application of biodegradable Mg alloys as implants are their fast degradation rate and biological consideration. We have discussed the effect of some selected alloying element additions on the properties of the Mg-based alloy, especially the nutrient elements in human (Zn, Mn, Ca, Sr). Different grain sizes, phase constituents and distributions consequently influence the mechanical properties of the Mg alloys. Solution strengthening and precipitation strengthening are enhanced by the addition of alloying elements, generally improving the mechanical properties. Besides, the hot working process can also improve the mechanical properties. Combination of different processing steps is suggested to be adopted in the fabrication of Mg-based alloys. Corrosion properties of these Mg-based alloys have been measured in vitro and in vivo. The degradation mechanism is also discussed in terms of corrosion types, rates, byproducts and response of the surrounding tissues. Moreover, the clinical response and requirements of degradable implants are presented, especially for the nutrient elements (Ca, Mn, Zn, Sr). This review provides information related to different Mg alloying elements and presents the promising candidates for an ideal implant.

  8. Nonlinear structural finite element model updating and uncertainty quantification

    NASA Astrophysics Data System (ADS)

    Ebrahimian, Hamed; Astroza, Rodrigo; Conte, Joel P.

    2015-04-01

    This paper presents a framework for nonlinear finite element (FE) model updating, in which state-of-the-art nonlinear structural FE modeling and analysis techniques are combined with the maximum likelihood estimation method (MLE) to estimate time-invariant parameters governing the nonlinear hysteretic material constitutive models used in the FE model of the structure. The estimation uncertainties are evaluated based on the Cramer-Rao lower bound (CRLB) theorem. A proof-of-concept example, consisting of a cantilever steel column representing a bridge pier, is provided to verify the proposed nonlinear FE model updating framework.

  9. Fuzzy finite-element analysis of smart structures

    NASA Astrophysics Data System (ADS)

    Akpan, U. O.; Koko, T. S.; Orisamolu, I. R.; Gallant, B. K.

    2001-04-01

    A fuzzy finite element based approach is developed for modelling smart structures with vague or imprecise uncertainties. Fuzzy sets are used to represent the uncertainties present in the piezoelectric, mechanical, thermal, and physical properties of the smart structure. In order to facilitate efficient computation, a sensitivity analysis procedure is used to streamline the number of input fuzzy variables, and the vertex fuzzy analysis technique is then used to compute the possibility distributions of the responses of the smart structural system. The methodology has been developed within the framework of the SMARTCOM computational tool for the design/analysis of smart composite structures. The methodology developed is found to be accurate and computationally efficient for the solution of practical problems.

  10. Conductivity and structure of bilinear organic addition compounds

    PubMed Central

    Phillips, J. C.

    1976-01-01

    The relationship between crystal structures and metallic conductivities of linear organic materials such as tetrathiafulvalene-tetracyanoquinodimethane is explained in terms of strong lateral elastic interactions between chains. A microdomain model is presented in which at high temperatures there are, in general, two coexisting phases on each stacked molecular chain. The ordering of (in general, four) phases on two interacting chains leads to a variety of phase transitions at low temperatures. By examining temperature-dependent electrical conductivities and magnetic susceptibilities one can establish the character of each such transition. PMID:16592359

  11. Dynamic Shape Reconstruction of Three-Dimensional Frame Structures Using the Inverse Finite Element Method

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

    A robust and efficient computational method for reconstructing the three-dimensional displacement field of truss, beam, and frame structures, using measured surface-strain data, is presented. Known as shape sensing , this inverse problem has important implications for real-time actuation and control of smart structures, and for monitoring of structural integrity. The present formulation, based on the inverse Finite Element Method (iFEM), uses a least-squares variational principle involving strain measures of Timoshenko theory for stretching, torsion, bending, and transverse shear. Two inverse-frame finite elements are derived using interdependent interpolations whose interior degrees-of-freedom are condensed out at the element level. In addition, relationships between the order of kinematic-element interpolations and the number of required strain gauges are established. As an example problem, a thin-walled, circular cross-section cantilevered beam subjected to harmonic excitations in the presence of structural damping is modeled using iFEM; where, to simulate strain-gauge values and to provide reference displacements, a high-fidelity MSC/NASTRAN shell finite element model is used. Examples of low and high-frequency dynamic motion are analyzed and the solution accuracy examined with respect to various levels of discretization and the number of strain gauges.

  12. Penalty-Based Finite Element Interface Technology for Analysis of Homogeneous and Composite Structures

    NASA Technical Reports Server (NTRS)

    Averill, Ronald C.

    2002-01-01

    An effective and robust interface element technology able to connect independently modeled finite element subdomains has been developed. This method is based on the use of penalty constraints and allows coupling of finite element models whose nodes do not coincide along their common interface. Additionally, the present formulation leads to a computational approach that is very efficient and completely compatible with existing commercial software. A significant effort has been directed toward identifying those model characteristics (element geometric properties, material properties, and loads) that most strongly affect the required penalty parameter, and subsequently to developing simple 'formulae' for automatically calculating the proper penalty parameter for each interface constraint. This task is especially critical in composite materials and structures, where adjacent sub-regions may be composed of significantly different materials or laminates. This approach has been validated by investigating a variety of two-dimensional problems, including composite laminates.

  13. Modeling bistable behaviors in morphing structures through finite element simulations.

    PubMed

    Guo, Qiaohang; Zheng, Huang; Chen, Wenzhe; Chen, Zi

    2014-01-01

    Bistable structures, exemplified by the Venus flytrap and slap bracelets, can transit between different configurations upon certain external stimulation. Here we study, through three-dimensional finite element simulations, the bistable behaviors in elastic plates in the absence of terminate loads, but with pre-strains in one (or both) of the two composite layers. Both the scenarios with and without a given geometric mis-orientation angle are investigated, the results of which are consistent with recent theoretical and experimental studies. This work can open ample venues for programmable designs of plant/shell structures with large deformations, with applications in designing bio-inspired robotics for biomedical research and morphing/deployable structures in aerospace engineering. PMID:24211939

  14. The Effect of Emphasizing Mathematical Structure in the Acquisition of Whole Number Computation Skills (Addition and Subtraction) By Seven- and Eight-Year Olds: A Clinical Investigation.

    ERIC Educational Resources Information Center

    Uprichard, A. Edward; Collura, Carolyn

    This investigation sought to determine the effect of emphasizing mathematical structure in the acquisition of computational skills by seven- and eight-year-olds. The meaningful development-of-structure approach emphasized closure, commutativity, associativity, and the identity element of addition; the inverse relationship between addition and…

  15. Using support vector machines to improve elemental ion identification in macromolecular crystal structures

    DOE PAGESBeta

    Morshed, Nader; Echols, Nathaniel; Adams, Paul D.

    2015-04-25

    In the process of macromolecular model building, crystallographers must examine electron density for isolated atoms and differentiate sites containing structured solvent molecules from those containing elemental ions. This task requires specific knowledge of metal-binding chemistry and scattering properties and is prone to error. A method has previously been described to identify ions based on manually chosen criteria for a number of elements. Here, the use of support vector machines (SVMs) to automatically classify isolated atoms as either solvent or one of various ions is described. Two data sets of protein crystal structures, one containing manually curated structures deposited with anomalousmore » diffraction data and another with automatically filtered, high-resolution structures, were constructed. On the manually curated data set, an SVM classifier was able to distinguish calcium from manganese, zinc, iron and nickel, as well as all five of these ions from water molecules, with a high degree of accuracy. Additionally, SVMs trained on the automatically curated set of high-resolution structures were able to successfully classify most common elemental ions in an independent validation test set. This method is readily extensible to other elemental ions and can also be used in conjunction with previous methods based on a priori expectations of the chemical environment and X-ray scattering.« less

  16. Using support vector machines to improve elemental ion identification in macromolecular crystal structures

    SciTech Connect

    Morshed, Nader; Echols, Nathaniel; Adams, Paul D.

    2015-04-25

    In the process of macromolecular model building, crystallographers must examine electron density for isolated atoms and differentiate sites containing structured solvent molecules from those containing elemental ions. This task requires specific knowledge of metal-binding chemistry and scattering properties and is prone to error. A method has previously been described to identify ions based on manually chosen criteria for a number of elements. Here, the use of support vector machines (SVMs) to automatically classify isolated atoms as either solvent or one of various ions is described. Two data sets of protein crystal structures, one containing manually curated structures deposited with anomalous diffraction data and another with automatically filtered, high-resolution structures, were constructed. On the manually curated data set, an SVM classifier was able to distinguish calcium from manganese, zinc, iron and nickel, as well as all five of these ions from water molecules, with a high degree of accuracy. Additionally, SVMs trained on the automatically curated set of high-resolution structures were able to successfully classify most common elemental ions in an independent validation test set. This method is readily extensible to other elemental ions and can also be used in conjunction with previous methods based on a priori expectations of the chemical environment and X-ray scattering.

  17. Using support vector machines to improve elemental ion identification in macromolecular crystal structures

    PubMed Central

    Morshed, Nader; Echols, Nathaniel; Adams, Paul D.

    2015-01-01

    In the process of macromolecular model building, crystallographers must examine electron density for isolated atoms and differentiate sites containing structured solvent molecules from those containing elemental ions. This task requires specific knowledge of metal-binding chemistry and scattering properties and is prone to error. A method has previously been described to identify ions based on manually chosen criteria for a number of elements. Here, the use of support vector machines (SVMs) to automatically classify isolated atoms as either solvent or one of various ions is described. Two data sets of protein crystal structures, one containing manually curated structures deposited with anomalous diffraction data and another with automatically filtered, high-resolution structures, were constructed. On the manually curated data set, an SVM classifier was able to distinguish calcium from manganese, zinc, iron and nickel, as well as all five of these ions from water molecules, with a high degree of accuracy. Additionally, SVMs trained on the automatically curated set of high-resolution structures were able to successfully classify most common elemental ions in an independent validation test set. This method is readily extensible to other elemental ions and can also be used in conjunction with previous methods based on a priori expectations of the chemical environment and X-ray scattering. PMID:25945580

  18. Validation of finite element and boundary element methods for predicting structural vibration and radiated noise

    NASA Technical Reports Server (NTRS)

    Seybert, A. F.; Wu, X. F.; Oswald, Fred B.

    1992-01-01

    Analytical and experimental validation of methods to predict structural vibration and radiated noise are presented. A rectangular box excited by a mechanical shaker was used as a vibrating structure. Combined finite element method (FEM) and boundary element method (BEM) models of the apparatus were used to predict the noise radiated from the box. The FEM was used to predict the vibration, and the surface vibration was used as input to the BEM to predict the sound intensity and sound power. Vibration predicted by the FEM model was validated by experimental modal analysis. Noise predicted by the BEM was validated by sound intensity measurements. Three types of results are presented for the total radiated sound power: (1) sound power predicted by the BEM modeling using vibration data measured on the surface of the box; (2) sound power predicted by the FEM/BEM model; and (3) sound power measured by a sound intensity scan. The sound power predicted from the BEM model using measured vibration data yields an excellent prediction of radiated noise. The sound power predicted by the combined FEM/BEM model also gives a good prediction of radiated noise except for a shift of the natural frequencies that are due to limitations in the FEM model.

  19. Refinement by shifting secondary structure elements improves sequence alignments.

    PubMed

    Tong, Jing; Pei, Jimin; Otwinowski, Zbyszek; Grishin, Nick V

    2015-03-01

    Constructing a model of a query protein based on its alignment to a homolog with experimentally determined spatial structure (the template) is still the most reliable approach to structure prediction. Alignment errors are the main bottleneck for homology modeling when the query is distantly related to the template. Alignment methods often misalign secondary structural elements by a few residues. Therefore, better alignment solutions can be found within a limited set of local shifts of secondary structures. We present a refinement method to improve pairwise sequence alignments by evaluating alignment variants generated by local shifts of template-defined secondary structures. Our method SFESA is based on a novel scoring function that combines the profile-based sequence score and the structure score derived from residue contacts in a template. Such a combined score frequently selects a better alignment variant among a set of candidate alignments generated by local shifts and leads to overall increase in alignment accuracy. Evaluation of several benchmarks shows that our refinement method significantly improves alignments made by automatic methods such as PROMALS, HHpred and CNFpred. The web server is available at http://prodata.swmed.edu/sfesa. PMID:25546158

  20. Refinement by shifting secondary structure elements improves sequence alignments

    PubMed Central

    Tong, Jing; Pei, Jimin; Otwinowski, Zbyszek; Grishin, Nick V.

    2015-01-01

    Constructing a model of a query protein based on its alignment to a homolog with experimentally determined spatial structure (the template) is still the most reliable approach to structure prediction. Alignment errors are the main bottleneck for homology modeling when the query is distantly related to the template. Alignment methods often misalign secondary structural elements by a few residues. Therefore, better alignment solutions can be found within a limited set of local shifts of secondary structures. We present a refinement method to improve pairwise sequence alignments by evaluating alignment variants generated by local shifts of template-defined secondary structures. Our method SFESA is based on a novel scoring function that combines the profile-based sequence score and the structure score derived from residue contacts in a template. Such a combined score frequently selects a better alignment variant among a set of candidate alignments generated by local shifts and leads to overall increase in alignment accuracy. Evaluation of several benchmarks shows that our refinement method significantly improves alignments made by automatic methods such as PROMALS, HHpred and CNFpred. The web server is available at http://prodata.swmed.edu/sfesa. PMID:25546158

  1. Finite element analysis of piezoelectric thin film membrane structures.

    PubMed

    Choi, Hongsoo; Ding, Jow-Lian; Bandyopadhyay, Amita; Bose, Susmita

    2007-10-01

    Thin film structures have found a wide variety of applications in electromechanical technologies. As the design flexibility for these structures increases, so does the demand for design software that can provide some good insights into the behavior of the structure before it is fabricated. In this study, a finite element code based on a combination of equivalent single-plate theory and classical laminated plate theory was used to predict the dynamic response of thin film structures in micro length scale. As a benchmark for the code development, thin film structures were also fabricated using MEMS technology, and their fundamental frequencies were characterized. It was demonstrated that the model predictions matched fairly well with the experimental data for the small membranes with widths less than 200 microm, but underestimated them for large ones with widths greater than 500 microm. The model also demonstrated that the fundamental frequencies increased with the thickness of the layers. The areas that need to be investigated further in order to improve the predicative capability of the calculations include effects of residual stress, dc bias voltage, parasitic capacitance, interaction of membrane vibration with the supports of the structure, and accurate measurement of the dimensions and material properties of the thin films. PMID:18019241

  2. Oro-facial granulomatosis. Response to elemental diet and provocation by food additives.

    PubMed

    Sweatman, M C; Tasker, R; Warner, J O; Ferguson, M M; Mitchell, D N

    1986-07-01

    We report the case of an 8.5-year-old girl with oro-facial granulomatosis associated with clinical atopy, in whom relapse of her granulomatous disorder was shown to be related to exposure to specific food additives, viz. carmoisine, sunset yellow and monosodium glutamate. Treatment with a restricted diet resulted in considerable regression in the facial swelling which has been maintained for 6 months. A brief account of the histological features, both under light and electron microscopy, is given, together with a description of the use of nuclear magnetic resonance scanning in the assessment of this disease. The patient had no evidence to support a diagnosis of sarcoidosis or Crohn's disease. PMID:3755655

  3. Disentangling Effects of Nuclear Structure in Heavy Element Formation

    SciTech Connect

    Hinde, D. J.; Thomas, R. G.; Rietz, R. du; Diaz-Torres, A.; Dasgupta, M.; Brown, M. L.; Evers, M.; Gasques, L. R.; Rafiei, R.; Rodriguez, M. D.

    2008-05-23

    Forming the same heavy compound nucleus with different isotopes of the projectile and target elements allows nuclear structure effects in the entrance channel (resulting in static deformation) and in the dinuclear system to be disentangled. Using three isotopes of Ti and W, forming {sup 232}Cm, with measurement spanning the capture barrier energies, alignment of the heavy prolate deformed nucleus is shown to be the main reason for the broadening of the mass distribution of the quasifission fragments as the beam energy is reduced. The complex, consistently evolving mass-angle correlations that are observed carry more information than the integrated mass or angular distributions, and should severely test models of quasifission.

  4. SPAR data set contents. [finite element structural analysis system

    NASA Technical Reports Server (NTRS)

    Cunningham, S. W.

    1981-01-01

    The contents of the stored data sets of the SPAR (space processing applications rocket) finite element structural analysis system are documented. The data generated by each of the system's processors are stored in a data file organized as a library. Each data set, containing a two-dimensional table or matrix, is identified by a four-word name listed in a table of contents. The creating SPAR processor, number of rows and columns, and definitions of each of the data items are listed for each data set. An example SPAR problem using these data sets is also presented.

  5. Hybrid Residual Flexibility/Mass-Additive Method for Structural Dynamic Testing

    NASA Technical Reports Server (NTRS)

    Tinker, M. L.

    2003-01-01

    A large fixture was designed and constructed for modal vibration testing of International Space Station elements. This fixed-base test fixture, which weighs thousands of pounds and is anchored to a massive concrete floor, initially utilized spherical bearings and pendulum mechanisms to simulate Shuttle orbiter boundary constraints for launch of the hardware. Many difficulties were encountered during a checkout test of the common module prototype structure, mainly due to undesirable friction and excessive clearances in the test-article-to-fixture interface bearings. Measured mode shapes and frequencies were not representative of orbiter-constrained modes due to the friction and clearance effects in the bearings. As a result, a major redesign effort for the interface mechanisms was undertaken. The total cost of the fixture design, construction and checkout, and redesign was over $2 million. Because of the problems experienced with fixed-base testing, alternative free-suspension methods were studied, including the residual flexibility and mass-additive approaches. Free-suspension structural dynamics test methods utilize soft elastic bungee cords and overhead frame suspension systems that are less complex and much less expensive than fixed-base systems. The cost of free-suspension fixturing is on the order of tens of thousands of dollars as opposed to millions, for large fixed-base fixturing. In addition, free-suspension test configurations are portable, allowing modal tests to be done at sites without modal test facilities. For example, a mass-additive modal test of the ASTRO-1 Shuttle payload was done at the Kennedy Space Center launch site. In this Technical Memorandum, the mass-additive and residual flexibility test methods are described in detail. A discussion of a hybrid approach that combines the best characteristics of each method follows and is the focus of the study.

  6. Multiphase poroelastic finite element models for soft tissue structure

    SciTech Connect

    Simon, B.R.

    1992-06-01

    During the last two decades. biological structures with soft tissue components have been modeled using poroelastic or mixture-based constitutive laws, i.e., the material is viewed as a deformable (porous) solid matrix that is saturated by mobile tissue fluid. These structures exhibit a highly nonlinear, history-dependent material behavior; undergo finite strains-, and may swell or shrink when tissue ionic concentrations are altered. Given the geometric and material complexity of soft tissue structures and that they are subjected to complicated initial and boundary conditions, finite element models (FEMs) have been very useful for quantitative structural analyses. This paper surveys recent applications of poroelastic and mixture-based theories and the associated FEMs for the study of the biomechanics of soft tissues, and indicates future directions for research in this area. Equivalent finite-strain poroelastic and mixture continuum biomechanical models are presented. Special attention is given to the identification of material properties using a porohyperelastic constitutive law and a total Lagrangian view for the formulation. The associated FEMS are then formulated to include this porohyperelastic material response and finite strains. Extensions of the theory are suggested in order to include inherent viscoelasticity, transport phenomena, and swelling in soft tissue structures. A number of biomechanical research areas are identified, and possible applications of the porohyperelastic and mixture-based FEMs are suggested.

  7. Multiphase poroelastic finite element models for soft tissue structures

    SciTech Connect

    Simon, B.R.

    1992-12-01

    During the last two decades, biological structures with soft tissue components have been modeled using poroelastic or mixture-based constitutive laws, i.e., the material is viewed as a deformable (porous) solid matrix that is saturated by mobile tissue fluid. These structures exhibit a highly nonlinear, history-dependent material behavior; undergo finite strains; and may swell or shrink when tissue ionic concentrations are altered. Give the geometric and material complexity of soft tissue structures and that they are subjected to complicated initial and boundary conditions, finite element models (FEMs) have been very useful for quantitative structural analyses. This paper surveys recent applications of poroelastic and mixture-based theories and the associated FEMs for the study of the biomechanics of soft tissues, and indicates future directions for research in this area. Equivalent finite-strain poroelastic and mixture continuum biomechanical models are presented. Special attention is given to the identification of material properties using a porohyperelastic constitutive law ans a total Lagrangian view for the formulation. The associated FEMs are then formulated to include this porohyperelastic material response and finite strains. Extensions of the theory are suggested in order to include inherent viscoelasticity, transport phenomena, and swelling in soft tissue structures. A number of biomechanical research areas are identified, and possible applications of the porohyperelastic and mixture-based FEMs are suggested. 62 refs., 11 figs., 3 tabs.

  8. Finite Element Analysis of Wrinkled Membrane Structures for Sunshield Applications

    NASA Technical Reports Server (NTRS)

    Johnston, John D.; Brodeur, Stephen J. (Technical Monitor)

    2002-01-01

    The deployable sunshield is an example of a gossamer structure envisioned for use on future space telescopes. The basic structure consists of multiple layers of pretensioned, thin-film membranes supported by deployable booms. The prediction and verification of sunshield dynamics has been identified as an area in need of technology development due to the difficulties inherent in predicting nonlinear structural behavior of the membranes and because of the challenges involved. in ground testing of the full-scale structure. This paper describes a finite element analysis of a subscale sunshield that has been subjected to ground testing in support of the Next Generation Space Telescope (NGST) program. The analysis utilizes a nonlinear material model that accounts for wrinkling of the membranes. Results are presented from a nonlinear static preloading analysis and subsequent dynamics analyses to illustrate baseline sunshield structural characteristics. Studies are then described which provide further insight into the effect of membrane. preload on sunshield dynamics and the performance of different membrane modeling techniques. Lastly, a comparison of analytical predictions and ground test results is presented.

  9. Gene regulation by structured mRNA elements.

    PubMed

    Wachter, Andreas

    2014-05-01

    The precise temporal and spatial coordination of gene activity, based on the integration of internal and external signals, is crucial for the accurate functioning of all biological processes. Although the basic principles of gene expression were established some 60 years ago, recent research has revealed a surprising complexity in the control of gene activity. Many of these gene regulatory mechanisms occur at the level of the mRNA, including sophisticated gene control tasks mediated by structured mRNA elements. We now know that mRNA folds can serve as highly specific receptors for various types of molecules, as exemplified by metabolite-binding riboswitches, and interfere with pro- and eukaryotic gene expression at the level of transcription, translation, and RNA processing. Gene regulation by structured mRNA elements comprises versatile strategies including self-cleaving ribozymes, RNA-folding-mediated occlusion or presentation of cis-regulatory sequences, and sequestration of trans-acting factors including other RNAs and proteins. PMID:24780087

  10. Structural and Ferromagnetic Properties of an Orthorhombic Phase of MnBi Stabilized with Rh Additions

    NASA Astrophysics Data System (ADS)

    Taufour, Valentin; Thimmaiah, Srinivasa; March, Stephen; Saunders, Scott; Sun, Kewei; Lamichhane, Tej Nath; Kramer, Matthew J.; Bud'ko, Sergey L.; Canfield, Paul C.

    2015-07-01

    The article addresses the possibility of alloy elements in MnBi which may modify the thermodynamic stability of the NiAs-type structure without significantly degrading the magnetic properties. The addition of small amounts of Rh and Mn provides an improvement in the thermal stability with some degradation of the magnetic properties. The small amounts of Rh and Mn additions in MnBi stabilize an orthorhombic phase whose structural and magnetic properties are closely related to the ones of the previously reported high-temperature phase of MnBi (HT MnBi). To date, the properties of the HT MnBi, which is stable between 613 and 719 K, have not been studied in detail because of its transformation to the stable low-temperature MnBi (LT MnBi), making measurements near and below its Curie temperature difficult. The Rh-stabilized MnBi with chemical formula Mn1.0625 -xRhx Bi [x =0.02 (1 ) ] adopts a new superstructure of the NiAs /Ni2In structure family. It is ferromagnetic below a Curie temperature of 416 K. The critical exponents of the ferromagnetic transition are not of the mean-field type but are closer to those associated with the Ising model in three dimensions. The magnetic anisotropy is uniaxial; the anisotropy energy is rather large, and it does not increase when raising the temperature, contrary to what happens in LT MnBi. The saturation magnetization is approximately 3 μB/f .u . at low temperatures. While this exact composition may not be application ready, it does show that alloying is a viable route to modifying the stability of this class of rare-earth-free magnet alloys.

  11. Structural and ferromagnetic properties of an orthorhombic phase of MnBi stabilized with Rh additions

    DOE PAGESBeta

    Taufour, Valentin; Thimmaiah, Srinivasa; March, Stephen; Saunders, Scott; Sun, Kewei; Lamichhane, Tej Nath; Kramer, Matthew J.; Bud’ko, Sergey L.; Canfield, Paul C.

    2015-07-28

    The article addresses the possibility of alloy elements in MnBi which may modify the thermodynamic stability of the NiAs-type structure without significantly degrading the magnetic properties. The addition of small amounts of Rh and Mn provides an improvement in the thermal stability with some degradation of the magnetic properties. The small amounts of Rh and Mn additions in MnBi stabilize an orthorhombic phase whose structural and magnetic properties are closely related to the ones of the previously reported high-temperature phase of MnBi (HT MnBi). The properties of the HT MnBi, which is stable between 613 and 719 K, have notmore » been studied in detail because of its transformation to the stable low-temperature MnBi (LT MnBi), making measurements near and below its Curie temperature difficult. The Rh-stabilized MnBi with chemical formula Mn1.0625–xRhxBi [x=0.02(1)] adopts a new superstructure of the NiAs/Ni2In structure family. It is ferromagnetic below a Curie temperature of 416 K. The critical exponents of the ferromagnetic transition are not of the mean-field type but are closer to those associated with the Ising model in three dimensions. The magnetic anisotropy is uniaxial; the anisotropy energy is rather large, and it does not increase when raising the temperature, contrary to what happens in LT MnBi. The saturation magnetization is approximately 3μB/f.u. at low temperatures. Thus, while this exact composition may not be application ready, it does show that alloying is a viable route to modifying the stability of this class of rare-earth-free magnet alloys.« less

  12. Structural and ferromagnetic properties of an orthorhombic phase of MnBi stabilized with Rh additions

    SciTech Connect

    Taufour, Valentin; Thimmaiah, Srinivasa; March, Stephen; Saunders, Scott; Sun, Kewei; Lamichhane, Tej Nath; Kramer, Matthew J.; Bud’ko, Sergey L.; Canfield, Paul C.

    2015-07-28

    The article addresses the possibility of alloy elements in MnBi which may modify the thermodynamic stability of the NiAs-type structure without significantly degrading the magnetic properties. The addition of small amounts of Rh and Mn provides an improvement in the thermal stability with some degradation of the magnetic properties. The small amounts of Rh and Mn additions in MnBi stabilize an orthorhombic phase whose structural and magnetic properties are closely related to the ones of the previously reported high-temperature phase of MnBi (HT MnBi). The properties of the HT MnBi, which is stable between 613 and 719 K, have not been studied in detail because of its transformation to the stable low-temperature MnBi (LT MnBi), making measurements near and below its Curie temperature difficult. The Rh-stabilized MnBi with chemical formula Mn1.0625–xRhxBi [x=0.02(1)] adopts a new superstructure of the NiAs/Ni2In structure family. It is ferromagnetic below a Curie temperature of 416 K. The critical exponents of the ferromagnetic transition are not of the mean-field type but are closer to those associated with the Ising model in three dimensions. The magnetic anisotropy is uniaxial; the anisotropy energy is rather large, and it does not increase when raising the temperature, contrary to what happens in LT MnBi. The saturation magnetization is approximately 3μB/f.u. at low temperatures. Thus, while this exact composition may not be application ready, it does show that alloying is a viable route to modifying the stability of this class of rare-earth-free magnet alloys.

  13. Element decoupling of 7T dipole body arrays by EBG metasurface structures: Experimental verification.

    PubMed

    Hurshkainen, Anna A; Derzhavskaya, Tatyana A; Glybovski, Stanislav B; Voogt, Ingmar J; Melchakova, Irina V; van den Berg, Cornelis A T; Raaijmakers, Alexander J E

    2016-08-01

    Metasurfaces are artificial electromagnetic boundaries or interfaces usually implemented as two-dimensional periodic structures with subwavelength periodicity and engineered properties of constituent unit cells. The electromagnetic bandgap (EBG) effect in metasurfaces prevents all surface modes from propagating in a certain frequency band. While metasurfaces provide a number of important applications in microwave antennas and antenna arrays, their features are also highly suitable for MRI applications. In this work we perform a proof-of-principle experiment to study finite structures based on mushroom-type EBG metasurfaces and employ them for suppression of inter-element coupling in dipole transceive array coils for body imaging at 7T. We firstly show experimentally that employment of mushroom structures leads to reduction of coupling between adjacent closely-spaced dipole antenna elements of a 7T transceive body array, which reduces scattering losses in neighboring channels. The studied setup consists of two active fractionated dipole antennas previously designed by the authors for body imaging at 7T. These are placed on top of a body-mimicking phantom and equipped with the manufactured finite-size periodic structure tuned to have EBG properties at the Larmor frequency of 298MHz. To improve the detection range of the B1+ field distribution of the top elements, four additional elements were positioned along the bottom side of the phantom. Bench measurements of a scattering matrix showed that coupling between the two top elements can be considerably reduced depending on the distance to the EBG structure. On the other hand, the measurements performed on a 7T MRI machine indicated redistribution of the B1+ field due to interaction between the dipoles with the structure. When the structure is located just over two closely spaced dipoles, one can reach a very high isolation improvement of -14dB accompanied by a strong field redistribution. In contrast, when put at a

  14. Element decoupling of 7 T dipole body arrays by EBG metasurface structures: Experimental verification

    NASA Astrophysics Data System (ADS)

    Hurshkainen, Anna A.; Derzhavskaya, Tatyana A.; Glybovski, Stanislav B.; Voogt, Ingmar J.; Melchakova, Irina V.; van den Berg, Cornelis A. T.; Raaijmakers, Alexander J. E.

    2016-08-01

    Metasurfaces are artificial electromagnetic boundaries or interfaces usually implemented as two-dimensional periodic structures with subwavelength periodicity and engineered properties of constituent unit cells. The electromagnetic bandgap (EBG) effect in metasurfaces prevents all surface modes from propagating in a certain frequency band. While metasurfaces provide a number of important applications in microwave antennas and antenna arrays, their features are also highly suitable for MRI applications. In this work we perform a proof-of-principle experiment to study finite structures based on mushroom-type EBG metasurfaces and employ them for suppression of inter-element coupling in dipole transceive array coils for body imaging at 7 T. We firstly show experimentally that employment of mushroom structures leads to reduction of coupling between adjacent closely-spaced dipole antenna elements of a 7 T transceive body array, which reduces scattering losses in neighboring channels. The studied setup consists of two active fractionated dipole antennas previously designed by the authors for body imaging at 7 T. These are placed on top of a body-mimicking phantom and equipped with the manufactured finite-size periodic structure tuned to have EBG properties at the Larmor frequency of 298 MHz. To improve the detection range of the B1 + field distribution of the top elements, four additional elements were positioned along the bottom side of the phantom. Bench measurements of a scattering matrix showed that coupling between the two top elements can be considerably reduced depending on the distance to the EBG structure. On the other hand, the measurements performed on a 7 T MRI machine indicated redistribution of the B1 + field due to interaction between the dipoles with the structure. When the structure is located just over two closely spaced dipoles, one can reach a very high isolation improvement of -14 dB accompanied by a strong field redistribution. In contrast, when put

  15. Studies of finite element analysis of composite material structures

    NASA Technical Reports Server (NTRS)

    Douglas, D. O.; Holzmacher, D. E.; Lane, Z. C.; Thornton, E. A.

    1975-01-01

    Research in the area of finite element analysis is summarized. Topics discussed include finite element analysis of a picture frame shear test, BANSAP (a bandwidth reduction program for SAP IV), FEMESH (a finite element mesh generation program based on isoparametric zones), and finite element analysis of a composite bolted joint specimens.

  16. Optimum structural design with plate bending elements - A survey

    NASA Technical Reports Server (NTRS)

    Haftka, R. T.; Prasad, B.

    1981-01-01

    A survey is presented of recently published papers in the field of optimum structural design of plates, largely with respect to the minimum-weight design of plates subject to such constraints as fundamental frequency maximization. It is shown that, due to the availability of powerful computers, the trend in optimum plate design is away from methods tailored to specific geometry and loads and toward methods that can be easily programmed for any kind of plate, such as finite element methods. A corresponding shift is seen in optimization from variational techniques to numerical optimization algorithms. Among the topics covered are fully stressed design and optimality criteria, mathematical programming, smooth and ribbed designs, design against plastic collapse, buckling constraints, and vibration constraints.

  17. Nonlinear analysis of structures. [within framework of finite element method

    NASA Technical Reports Server (NTRS)

    Armen, H., Jr.; Levine, H.; Pifko, A.; Levy, A.

    1974-01-01

    The development of nonlinear analysis techniques within the framework of the finite-element method is reported. Although the emphasis is concerned with those nonlinearities associated with material behavior, a general treatment of geometric nonlinearity, alone or in combination with plasticity is included, and applications presented for a class of problems categorized as axisymmetric shells of revolution. The scope of the nonlinear analysis capabilities includes: (1) a membrane stress analysis, (2) bending and membrane stress analysis, (3) analysis of thick and thin axisymmetric bodies of revolution, (4) a general three dimensional analysis, and (5) analysis of laminated composites. Applications of the methods are made to a number of sample structures. Correlation with available analytic or experimental data range from good to excellent.

  18. Creep deformation and fracture of a Cr/Mo/V bolting steel containing selected trace-element additions

    NASA Astrophysics Data System (ADS)

    Larouk, Z.; Pilkington, R.

    1999-08-01

    The article reports the creep behavior, at 565 °C, of 1Cr1Mo0.75V (Ti, B) (Durehete D1055) steel, in each of two grain sizes and doped with individual trace elements such as P, As, and Sn, in comparison to a reference cast of the base material containing 0.08 wt pct Ti. The addition of the trace elements P, As, or Sn (each <0.045 wt pct) appears to produce no significant effect on creep strength or creep crack-growth resistance at 565 °C. The fine-grained material shows low creep strength but notch strengthening, while the coarse-grained material shows higher creep strength and exhibits notch weakening for test times up to 2750 hours. From creep crack-growth tests, it appears that the C* parameter is not appropriate for correlating the creep crack-growth rate under the present test conditions. The parameters K I or σ net are found to correlate better, but, from the present data, it is not possible to judge which of these parameters is more appropriate for general use. It is suggested that the presence of Ti in CrMoV steels has an inhibiting effect on trace-element embrittlement.

  19. Protein structure prediction: assembly of secondary structure elements by basin-hopping.

    PubMed

    Hoffmann, Falk; Vancea, Ioan; Kamat, Sanjay G; Strodel, Birgit

    2014-10-20

    The prediction of protein tertiary structure from primary structure remains a challenging task. One possible approach to this problem is the application of basin-hopping global optimization combined with an all-atom force field. In this work, the efficiency of basin-hopping is improved by introducing an approach that derives tertiary structures from the secondary structure assignments of individual residues. This approach is termed secondary-to-tertiary basin-hopping and benchmarked for three miniproteins: trpzip, trp-cage and ER-10. For each of the three miniproteins, the secondary-to-tertiary basin-hopping approach successfully and reliably predicts their three-dimensional structure. When it is applied to larger proteins, correctly folded structures are obtained. It can be concluded that the assembly of secondary structure elements using basin-hopping is a promising tool for de novo protein structure prediction. PMID:25056272

  20. Activation of IFN-beta element by IRF-1 requires a posttranslational event in addition to IRF-1 synthesis.

    PubMed Central

    Watanabe, N; Sakakibara, J; Hovanessian, A G; Taniguchi, T; Fujita, T

    1991-01-01

    Expression of the Type I IFN (i.e., IFN-alpha s and IFN-beta) genes is efficiently induced by viruses at the transcriptional level. This induction is mediated by at least two types of positive regulatory elements located in the human IFN-beta gene promoter: (1) the repeated elements which bind both the transcriptional activator IRF-1 and the repressor IRF-2 (IRF-elements; IRF-Es), and (2) the kappa B element (kappa B-E), which binds NF kappa B and is located between the IRF-Es and the TATA box. In this study we demonstrate that a promoter containing synthetic IRF-E, which displays high affinity for the IRFs can be efficiently activated by Newcastle disease virus (NDV). In contrast, such activation was either very weak or nil when cells were treated by IFN-beta or tumor necrosis factor-alpha (TNF-alpha), despite the fact they both efficiently induce de novo synthesis of the short-lived IRF-1 in L929 cells. In fact, efficient activation of the IRF-E apparently requires an event in addition to de novo IRF-1 induction, which can be elicited by NDV even in the presence of protein synthesis inhibitor, cycloheximide. Moreover, efficient activation of the IRF-E by NDV is specifically inhibited by the protein kinase inhibitor, Staurosporin. Hence our results suggest the importance of IRF-1 synthesis and post-translational modification event(s), possibly phosphorylation for the efficient activation of IRF-Es, which are otherwise under negative regulation by IRF-2. Images PMID:1886766

  1. Are additional trace elements necessary in total parenteral nutrition for patients with esophageal cancer receiving cisplatin-based chemotherapy?

    PubMed

    Akutsu, Yasunori; Kono, Tsuguaki; Uesato, Masaya; Hoshino, Isamu; Murakami, Kentaro; Fujishiro, Takeshi; Imanishi, Shunsuke; Endo, Satoshi; Toyozumi, Takeshi; Matsubara, Hisahiro

    2012-12-01

    It is known that cisplatin induces the excretion of zinc from the urine and thereby reduces its serum concentration. However, the fluctuation of these trace elements during or after cisplatin-based chemotherapy has not been evaluated. To answer this question, we performed a clinical study in esophageal cancer patients undergoing cisplatin-based chemotherapy. Eighteen patients with esophageal cancer who were not able to swallow food or water orally due to complete stenosis of the esophagus were evaluated. The patients were divided into a control group [total parenteral nutrition (TPN) alone for 28 days, ten cases] and an intervention group (TPN with additional trace elements for 28 days, eight cases). The serum concentrations of zinc, iron, copper, manganese, triiodothyronin (T3), and thyroxin (T4), as alternative indicators of iodine, were measured on days 0, 14, and 28 of treatment, and statistically analyzed on day 28. In the control group, the serum concentration of copper was significantly decreased from 135.4 (day 0) to 122.1 μg/ml (day 14), and finally to 110.6 μg/ml (day 28, p = 0.015). The concentration of manganese was also significantly decreased from 1.34 (day 0) to 1.17 μg/ml (day 14) and finally to 1.20 (day 28, p = 0.049). The levels of zinc, iron, T3, and T4 were not significantly changed. In the intervention group, the supplementation with trace elements successfully prevented these decreases in their concentrations. TPN with supplementary trace elements is preferable and recommended for patients who are undergoing chemotherapy in order to maintain the patients' nutrient homeostasis. PMID:23054866

  2. Influence of Finite Element Size in Residual Strength Prediction of Composite Structures

    NASA Technical Reports Server (NTRS)

    Satyanarayana, Arunkumar; Bogert, Philip B.; Karayev, Kazbek Z.; Nordman, Paul S.; Razi, Hamid

    2012-01-01

    The sensitivity of failure load to the element size used in a progressive failure analysis (PFA) of carbon composite center notched laminates is evaluated. The sensitivity study employs a PFA methodology previously developed by the authors consisting of Hashin-Rotem intra-laminar fiber and matrix failure criteria and a complete stress degradation scheme for damage simulation. The approach is implemented with a user defined subroutine in the ABAQUS/Explicit finite element package. The effect of element size near the notch tips on residual strength predictions was assessed for a brittle failure mode with a parametric study that included three laminates of varying material system, thickness and stacking sequence. The study resulted in the selection of an element size of 0.09 in. X 0.09 in., which was later used for predicting crack paths and failure loads in sandwich panels and monolithic laminated panels. Comparison of predicted crack paths and failure loads for these panels agreed well with experimental observations. Additionally, the element size vs. normalized failure load relationship, determined in the parametric study, was used to evaluate strength-scaling factors for three different element sizes. The failure loads predicted with all three element sizes provided converged failure loads with respect to that corresponding with the 0.09 in. X 0.09 in. element size. Though preliminary in nature, the strength-scaling concept has the potential to greatly reduce the computational time required for PFA and can enable the analysis of large scale structural components where failure is dominated by fiber failure in tension.

  3. America`s Cup yacht structural design: Finite element analysis and laminate optimization

    SciTech Connect

    Hamilton, J.G.; Patterson, J.M.

    1993-12-31

    Structural design of America`s Cup yachts has evolved to a more sophisticated level than previously due to high performance gains geometry, a stiff, lightweight structural configuration will result in a fast yacht. In addition, crew safety has to be guaranteed under the wind, wave, and heeling forces. Finite elements were utilized to model the entire hull, keel, rig, and mast system: this paper focuses on the finite element techniques used to model the hull and keel. In order to take advantage of advanced composites and their high specific stiffness and strength, the laminates were optimized, Objectives and constraints were determined by naval architects, designers, and stress analysts in a concurrent engineering process. Keel placement and structural attachment into a predetermined hull shape were designed for maximum stiffness, minimum weight, and to minimize the detrimental effects of keel twist and dynamic oscillation. Rig forces (mast compression, shroud tension), keel torque, and wave (hydrostatic) pressure were introduced into the finite element analysis to iteratively improve the structure. These trade studies aided design evolution leading to the `final` blueprints. Following construction of the hull and substructure internals, manufacturing anomalies of the `as built` construction were added to the finite element models to evaluate their severity. During a two month schedule, more than 20 design iterations for the internal substructure and keel were examined. Laminate tailoring and geometric modification provided an optimum design which exhibited fewer peak local strains and lower over-all working strain. Low strain structure and the associated excess weight were eliminated as the global structure was designed to carry more uniform strains. The technology transfer of aerospace design practice to yacht building has resulted in a high performance product.

  4. Alu element-containing RNAs maintain nucleolar structure and function.

    PubMed

    Caudron-Herger, Maïwen; Pankert, Teresa; Seiler, Jeanette; Németh, Attila; Voit, Renate; Grummt, Ingrid; Rippe, Karsten

    2015-11-12

    Non-coding RNAs play a key role in organizing the nucleus into functional subcompartments. By combining fluorescence microscopy and RNA deep-sequencing-based analysis, we found that RNA polymerase II transcripts originating from intronic Alu elements (aluRNAs) were enriched in the nucleolus. Antisense-oligo-mediated depletion of aluRNAs or drug-induced inhibition of RNA polymerase II activity disrupted nucleolar structure and impaired RNA polymerase I-dependent transcription of rRNA genes. In contrast, overexpression of a prototypic aluRNA sequence increased both nucleolus size and levels of pre-rRNA, suggesting a functional link between aluRNA, nucleolus integrity and pre-rRNA synthesis. Furthermore, we show that aluRNAs interact with nucleolin and target ectopic genomic loci to the nucleolus. Our study suggests an aluRNA-based mechanism that links RNA polymerase I and II activities and modulates nucleolar structure and rRNA production. PMID:26464461

  5. The atomic-scale mechanism for the enhanced glass-forming-ability of a Cu-Zr based bulk metallic glass with minor element additions

    PubMed Central

    Wang, Q.; Liu, C. T.; Yang, Y.; Liu, J. B.; Dong, Y. D.; Lu, J.

    2014-01-01

    It is known that the glass forming-ability (GFA) of bulk metallic glasses (BMGs) can be greatly enhanced via minor element additions. However, direct evidence has been lacking to reveal its structural origin despite different theories hitherto proposed. Through the high-resolution transmission-electron-microscopy (HRTEM) analysis, here we show that the content of local crystal-like orders increases significantly in a Cu-Zr-Al BMG after a 2-at% Y addition. Contrasting the previous studies, our current results indicate that the formation of crystal-like order at the atomic scale plays an important role in enhancing the GFA of the Cu-Zr-Al base BMG. PMID:24721927

  6. Finite element-finite difference thermal/structural analysis of large space truss structures

    NASA Technical Reports Server (NTRS)

    Warren, Andrew H.; Arelt, Joseph E.; Eskew, William F.; Rogers, Karen M.

    1992-01-01

    A technique of automated and efficient thermal-structural processing of truss structures that interfaces the finite element and finite difference method was developed. The thermal-structural analysis tasks include development of the thermal and structural math models, thermal analysis, development of an interface and data transfer between the models, and finally an evaluation of the thermal stresses and displacements in the structure. Consequently, the objective of the developed technique was to minimize the model development time, in order to assure an automatic transfer of data between the thermal and structural models as well as to minimize the computer resources needed for the analysis itself. The method and techniques described are illustrated on the thermal/structural analysis of the Space Station Freedom main truss.

  7. Reliable Electronic Structure Calculations for Heavy Element Chemistry: Molecules Containing Actinides, Lanthanides, and Transition Metals

    SciTech Connect

    Marino, Maria, M.; Ermler, Walter C

    2006-01-27

    It is now possible to calculate many properties including the energetics (total bond dissociation energies or heats of formation) of molecules containing light elements to high accuracy by using correlation-consistent basis sets, coupled cluster theory and including additive corrections for core-valence and relativistic effects and careful treatment of the zero point energy. We propose to develop software for ab initio electronic structure calculations based on molecular orbital theory and density functional theory with the proper treatment of relativistic effects to study complexes of heavy elements in order to assist in understanding and predicting the chemistry of the actinides, lanthanides, and heavy transition metals, molecules critical to DOE missions including environmental management. The proposed work will focus on the development of these electronic structure methods and their implementation in software on advanced massively parallel processor (MPP) computer architectures capable of multi-tens of teraflops to petaflops. The core of the software will be developed within the NWChem and Columbus software suites. We propose to make the software broadly available so that other scientists can use these tools to address the complex environmental problems facing the Department of Energy's nuclear production sites as well as other waste sites in the Nation. Our implementation of relativistic quantum chemical methods for massively parallel computers will enable us to simulate the behavior of heavy-element compounds at the same type of level currently available for light-element compounds. In addition, this work will enable us to provide better methods for benchmarks of the additive energetic schemes currently available for light atom compounds. The theoretical and computational methodology so developed will be an invaluable supplement to current, very expensive experimental studies of the actinides, lanthanides, and radioactive heavy transition metal elements

  8. Finite element modeling of multilayered structures of fish scales.

    PubMed

    Chandler, Mei Qiang; Allison, Paul G; Rodriguez, Rogie I; Moser, Robert D; Kennedy, Alan J

    2014-12-01

    The interlinked fish scales of Atractosteus spatula (alligator gar) and Polypterus senegalus (gray and albino bichir) are effective multilayered armor systems for protecting fish from threats such as aggressive conspecific interactions or predation. Both types of fish scales have multi-layered structures with a harder and stiffer outer layer, and softer and more compliant inner layers. However, there are differences in relative layer thickness, property mismatch between layers, the property gradations and nanostructures in each layer. The fracture paths and patterns of both scales under microindentation loads were different. In this work, finite element models of fish scales of A. spatula and P. senegalus were built to investigate the mechanics of their multi-layered structures under penetration loads. The models simulate a rigid microindenter penetrating the fish scales quasi-statically to understand the observed experimental results. Study results indicate that the different fracture patterns and crack paths observed in the experiments were related to the different stress fields caused by the differences in layer thickness, and spatial distribution of the elastic and plastic properties in the layers, and the differences in interface properties. The parametric studies and experimental results suggest that smaller fish such as P. senegalus may have adopted a thinner outer layer for light-weighting and improved mobility, and meanwhile adopted higher strength and higher modulus at the outer layer, and stronger interface properties to prevent ring cracking and interface cracking, and larger fish such as A. spatula and Arapaima gigas have lower strength and lower modulus at the outer layers and weaker interface properties, but have adopted thicker outer layers to provide adequate protection against ring cracking and interface cracking, possibly because weight is less of a concern relative to the smaller fish such as P. senegalus. PMID:25300062

  9. Electronic structure, phase transitions and diffusive properties of elemental plutonium

    NASA Astrophysics Data System (ADS)

    Setty, Arun; Cooper, B. R.

    2003-03-01

    We present a SIC-LDA-LMTO based study of the electronic structure of the delta, alpha and gamma phases of plutonium, and also of the alpha and gamma phases of elemental cerium. We find excellent agreement with the experimental densities and magnetic properties [1]. Furthermore, detailed studies of the computational densities of states for delta plutonium, and comparison with the experimental photoemission spectrum [2], provide evidence for the existence of an unusual fluctuating valence state. Results regarding the vacancy formation and self-diffusion in delta plutonium will be presented. Furthermore, a study of interface diffusion between plutonium and steel (technologically relevant in the storage of spent fuel) or other technologically relevant alloys will be included. Preliminary results regarding gallium stabilization of delta plutonium, and of plutonium alloys will be presented. [1] M. Dormeval et al., private communication (2001). [2] A. J. Arko, J. J. Joyce, L. Morales, J. Wills, and J. Lashley et. al., Phys. Rev. B, 62, 1773 (2000). [3] B. R. Cooper et al, Phil. Mag. B 79, 683 (1999); B.R. Cooper, Los Alamos Science 26, 106 (2000)); B.R. Cooper, A.K. Setty and D.L.Price, to be published.

  10. Parallel Finite Element Domain Decomposition for Structural/Acoustic Analysis

    NASA Technical Reports Server (NTRS)

    Nguyen, Duc T.; Tungkahotara, Siroj; Watson, Willie R.; Rajan, Subramaniam D.

    2005-01-01

    A domain decomposition (DD) formulation for solving sparse linear systems of equations resulting from finite element analysis is presented. The formulation incorporates mixed direct and iterative equation solving strategics and other novel algorithmic ideas that are optimized to take advantage of sparsity and exploit modern computer architecture, such as memory and parallel computing. The most time consuming part of the formulation is identified and the critical roles of direct sparse and iterative solvers within the framework of the formulation are discussed. Experiments on several computer platforms using several complex test matrices are conducted using software based on the formulation. Small-scale structural examples are used to validate thc steps in the formulation and large-scale (l,000,000+ unknowns) duct acoustic examples are used to evaluate the ORIGIN 2000 processors, and a duster of 6 PCs (running under the Windows environment). Statistics show that the formulation is efficient in both sequential and parallel computing environmental and that the formulation is significantly faster and consumes less memory than that based on one of the best available commercialized parallel sparse solvers.

  11. Slave finite elements for nonlinear analysis of engine structures, volume 1

    NASA Technical Reports Server (NTRS)

    Gellin, S.

    1991-01-01

    A 336 degrees of freedom slave finite element processing capability to analyze engine structures under severe thermomechanical loading is presented. Description of the theoretical development and demonstration of that element is presented in this volume.

  12. Improved finite-element methods for rotorcraft structures

    NASA Technical Reports Server (NTRS)

    Hinnant, Howard E.

    1991-01-01

    An overview of the research directed at improving finite-element methods for rotorcraft airframes is presented. The development of a modification to the finite element method which eliminates interelement discontinuities is covered. The following subject areas are discussed: geometric entities, interelement continuity, dependent rotational degrees of freedom, and adaptive numerical integration. This new methodology is being implemented as an anisotropic, curvilinear, p-version, beam, shell, and brick finite element program.

  13. The effect of small additional elements on the precipitation of reduced activation Fe9Cr2W steels

    NASA Astrophysics Data System (ADS)

    Shibayama, T.; Kimura, A.; Kayano, H.

    1996-10-01

    In order to study effects of small additional elements on precipitation of reduced activation Fe9Cr2W steels were irradiated up to 60 dpa at 693 K, 698 K and 733 K in FFTF. Micro-voids were observed in both materials of Fe9Cr2W with or without boron, the density of micro-voids in the steel with boron is larger than without boron, and the mean size of micro-voids is smaller than that without boron. However void swelling was less than 1%. Many precipitates were found to be M 23C 6 which consists of mainly Cr. Several precipitates which were Ti rich including Si and W were also observed at grain boundary at 733 K. Several Y 2O 3 particles was observed in an yttrium containing alloy. No precipitation including Al was observed in an Al containing alloy. Ti addition decreased precipitation of Ta-rich M 6C in 9Cr and 12Cr steels in this irradiation condition.

  14. Structure of a conjugative element in Streptococcus pneumoniae

    SciTech Connect

    Vijayakumar, M.N.; Priebe, S.D.; Guild, W.R.

    1986-06-01

    The authors have cloned and mapped a 69-kilobase (kb) region of the chromosome of Streptococcus pneumoniae DP1322, which carries the conjugative Omega(cat-tet) insertion from S. pneumoniae BM6001. This element proved to be 65.5 kb in size. Location of the junctions was facilitated by cloning a preferred target region from the wild-type strain Rx1 recipient genome. This target site was preferred by both the BM6001 element and the cat-erm-tet element from Streptococcus agalactiae B109. Within the BM6001 element cat and tet were separated by 30 kb, and cat was flanked by two copies of a sequence that was also present in the recipient strain Rx1 DNA. Another sequence at least 2.4 kb in size was found inside the BM6001 element and at two places in the Rx1 genome. Its role is unknown. The ends of the BM6001 element appear to be the same as those of the B109 element, both as seen after transfer to S. pneumoniae and as mapped by others in pDP5 after transposition in Streptococcus faecalis. No homology is seen between the ends of the BM6001 element and no evidence found suggesting that it ever circularizes.

  15. Effects of heavy-element settling on solar neutrino fluxes and interior structure

    NASA Technical Reports Server (NTRS)

    Proffitt, Charles R.

    1994-01-01

    We consider the effects of gravitational settling of both He and heavier elements on the predicted solar neutrino fluxes and interior sound speed and density profiles. We find that while the structural changes that result from the inclusion of both He and heavy-element settling are only slightly larger than the changes resulting from the inclusion of He settling alone, the additional increases in expected neutrino fluxes are of comparable size. Our preferred model with both He and heavy-element settling has neutrino count rates of 9.0 SNU for Cl-37 detectors and 137 SNU for Ga-71 detectors, as compared to 7.1 and 127 SNU for a comparable model without any diffusive separation, or 8.0 and 132 SNU for a model that includes He settling alone. We suggest that the correction factors by which the predicted neutrino fluxes of solar models calculated without including the effects of diffusion should be multiplied are 1.25 +/- 0.08 for Cl detectors, 1.07 +/- 0.02 for Ga detectors, and 1.28 +/- 0.09 for the B-8 flux (1 sigma errors). Comparison of internal sound speed and density profiles strongly suggests that the additional changes in calculated p-mode oscillation frequencies due to the inclusion of heavy-element settling will be small compared to the changes that result from He settling alone, especially for the higher degree modes. All models with diffusive separation give much better agreement with the observed depth of the convection zone than do nondiffusive models. The model that includes both He and heavy-element settling requires an initial He mass fraction Y = 0.280 and has a surface He abundance of Y = 0.251 at the solar age.

  16. Can the Isolated-Elements Strategy Be Improved by Targeting Points of High Cognitive Load for Additional Practice?

    ERIC Educational Resources Information Center

    Ayres, Paul

    2013-01-01

    Reducing problem complexity by isolating elements has been shown to be an effective instructional strategy. Novices, in particular, benefit from learning from worked examples that contain partially interacting elements rather than worked examples that provide full interacting elements. This study investigated whether the isolating-elements…

  17. An atomic view of additive mutational effects in a protein structure

    SciTech Connect

    Skinner, M.M.; Terwilliger, T.C.

    1996-04-01

    Substitution of a single amino acid in a protein will often lead to substantial changes in properties. If these properties could be altered in a rational way then proteins could be readily generated with functions tailored to specific uses. When amino acid substitutions are made at well-separated locations in a single protein, their effects are generally additive. Additivity of effects of amino acid substitutions is very useful because the properties of proteins with any combination of substitutions can be inferred directly from those of the proteins with single changes. It would therefore be of considerable interest to have a means of knowing whether substitutions at a particular pair of sites in a protein are likely to lead to additive effects. The structural basis for additivity of effects of mutations on protein function was examined by determining crystal structures of single and double mutants in the hydrophobic core of gene V protein. Structural effects of mutations were found to be cumulative when two mutations were made in a single protein. Additivity occurs in this case because the regions structurally affected by mutations at the two sites do not overlap even though the sites are separated by only 9 {angstrom}. Structural distortions induced by mutations in gene V protein decrease rapidly, but not isotropically, with distance from the site of mutation. It is anticipated that cases where structural and functional effects of mutations will be additive could be identified simply by examining whether the regions structurally affected by each component mutation overlap.

  18. The structure of the human peripherin gene (PRPH) and identification of potential regulatory elements

    SciTech Connect

    Foley, J.; Ley, C.A.; Parysek, L.M.

    1994-07-15

    The authors determined the complete nucleotide sequence of the coding region of the human peripherin gene (PRPH), as well as 742 bp 5{prime} to the cap site and 584 bp 3{prime} to the stop codon, and compared its structure and sequence to the rat and mouse genes. The overall structure of 9 exons separated by 8 introns is conserved among these three mammalian species. The nucleotide sequences of the human peripherin gene exons were 90% identical to the rat gene sequences, and the predicted human peripherin protein differed from rat peripherin at only 18 of 475 amino acid residues. Comparison of the 5{prime} flanking regions of the human peripherin gene and rodent genes revealed extensive areas of high homology. Additional conserved segments were found in introns 1 and 2. Within the 5{prime} region, potential regulatory sequences, including a nerve growth factor negative regulatory element, a Hox protein binding site, and a heat shock element, were identified in all peripherin genes. The positional conservation of each element suggests that they may be important in the tissue-specific, developmental-specific, and injury-specific expression of the peripherin gene. 24 refs., 2 figs., 1 tab.

  19. A solid-shell Cosserat point element (SSCPE) for elastic thin structures at finite deformation

    NASA Astrophysics Data System (ADS)

    Jabareen, Mahmood; Mtanes, Eli

    2016-04-01

    The objective of this study is to develop a new solid-shell element using the Cosserat point theory for modeling thin elastic structures at finite deformations. The point-wise Green-Lagrange strain tensor is additively decomposed into homogeneous and inhomogeneous parts. Only the latter part of the strain tensor is modified by the assumed natural strain ANS concept to avoid both curvature-thickness locking and transverse shear locking. To the authors' knowledge, such modification has not been applied yet in the literature, and here it is referred to as the assumed natural inhomogeneous strain ANIS concept. Moreover, a new methodology for determining the constitutive coefficients of the strain energy function, which controls the inhomogeneous deformations, is proposed. The resulting coefficients ensure both accuracy, robustness, and elimination of all locking pathologies in the solid-shell Cosserat point element (SSCPE). The performance of the developed SSCPE is verified and tested via various benchmark problems and compared to other solid, shell, and solid-shell elements. These examples demonstrate that the SSCPE is accurate, robust, stable, free of locking, and can be used for modeling thin structures at both small and finite deformations.

  20. A solid-shell Cosserat point element ( SSCPE) for elastic thin structures at finite deformation

    NASA Astrophysics Data System (ADS)

    Jabareen, Mahmood; Mtanes, Eli

    2016-07-01

    The objective of this study is to develop a new solid-shell element using the Cosserat point theory for modeling thin elastic structures at finite deformations. The point-wise Green-Lagrange strain tensor is additively decomposed into homogeneous and inhomogeneous parts. Only the latter part of the strain tensor is modified by the assumed natural strain ANS concept to avoid both curvature-thickness locking and transverse shear locking. To the authors' knowledge, such modification has not been applied yet in the literature, and here it is referred to as the assumed natural inhomogeneous strain ANIS concept. Moreover, a new methodology for determining the constitutive coefficients of the strain energy function, which controls the inhomogeneous deformations, is proposed. The resulting coefficients ensure both accuracy, robustness, and elimination of all locking pathologies in the solid-shell Cosserat point element ( SSCPE). The performance of the developed SSCPE is verified and tested via various benchmark problems and compared to other solid, shell, and solid-shell elements. These examples demonstrate that the SSCPE is accurate, robust, stable, free of locking, and can be used for modeling thin structures at both small and finite deformations.

  1. Genomic and structural organization of Drosophila melanogaster G elements.

    PubMed Central

    Di Nocera, P P; Graziani, F; Lavorgna, G

    1986-01-01

    The properties and the genomic organization of G elements, a moderately repeated DNA family of D. melanogaster, are reported. G elements lack terminal repeats, generate target site duplications at the point of insertion and exhibit at one end a stretch of A residues of variable length. In a large number of recombinant clones analyzed G elements occur in tandem arrays, interspersed with specific ribosomal DNA (rDNA) segments. This arrangement results from the insertion of members of the G family within the nontranscribed spacer (NTS) of rDNA units. Similarity of the site of integration of G elements to that of ribosomal DNA insertions suggests that distinct DNA sequences might have been inserted into rDNA through a partly common pathway. Images PMID:3003691

  2. Trace and Minor Elements in Magmas at High Pressure: In Situ Structural Insights on Partitioning at Depth

    NASA Astrophysics Data System (ADS)

    Sanloup, C.; Cochain, B.; de Grouchy, C.; Leroy, C.; Bureau, H.; Schmidt, B.; Konopkova, Z.; Kantor, I.; Irifune, T.; Daisenberg, D.

    2014-12-01

    Trace element partitioning between crystals and silicate melts has been successfully modelled using crystal-chemistry rules [1], although these models do not explicitly include melt's properties. However, melt composition has been shown to strongly influence element partitioning [2], implying a control from the 'melt-chemistry' as well. Additionally, element partitioning can be pressure-dependent, in which case it is a useful marker of depth for planetary processes such as mantle melting, and crust or core formation. To assess the effect of melt structure on partitioning at depth, we have investigated the local structure around trace and minor elements in melts at high pressure using two in situ techniques, high energy x-ray diffraction and EXAFS. X-ray diffraction data, once converted into pair distribution functions, are straightforward to interpret and give access to the full structure although overlaps between different contributions occur. In contrast, EXAFS is a chemically-sensitive probe that describes the local structure around a given element, but is model-dependent. Both methods will be illustrated by results obtained on two types of elements, some volatiles and some lithophiles. References: [1] Blundy JD and Wood BJ, Nature 372:452, 1999. [2] Schmidt MW et al., Science 312:1646, 2006.

  3. The Least Squares Stochastic Finite Element Method in Structural Stability Analysis of Steel Skeletal Structures

    NASA Astrophysics Data System (ADS)

    Kamiński, M.; Szafran, J.

    2015-05-01

    The main purpose of this work is to verify the influence of the weighting procedure in the Least Squares Method on the probabilistic moments resulting from the stability analysis of steel skeletal structures. We discuss this issue also in the context of the geometrical nonlinearity appearing in the Stochastic Finite Element Method equations for the stability analysis and preservation of the Gaussian probability density function employed to model the Young modulus of a structural steel in this problem. The weighting procedure itself (with both triangular and Dirac-type) shows rather marginal influence on all probabilistic coefficients under consideration. This hybrid stochastic computational technique consisting of the FEM and computer algebra systems (ROBOT and MAPLE packages) may be used for analogous nonlinear analyses in structural reliability assessment.

  4. Formation and finite element analysis of tethered bilayer lipid structures.

    PubMed

    Kwak, Kwang Joo; Valincius, Gintaras; Liao, Wei-Ching; Hu, Xin; Wen, Xuejin; Lee, Andrew; Yu, Bo; Vanderah, David J; Lu, Wu; Lee, L James

    2010-12-01

    Rapid solvent exchange of an ethanolic solution of diphytanoyl phosphatidylcholine (DPhyPC) in the presence of a mixed self-assembled monolayer (SAM) [thiolipid/β-mercaptoethanol (βME) (3/7 mol/mol) on Au] shows a transition from densely packed tethered bilayer lipid membranes [(dp)tBLMs], to loosely packed tethered bilayer lipid membranes [(lp)tBLMs], and tethered bilayer liposome nanoparticles (tBLNs) with decreasing DPhyPC concentration. The tethered lipidic constructs in the aqueous medium were analyzed by atomic force microscopy (AFM) and electrochemical impedance spectroscopy (EIS). Finite element analysis (FEA) was applied to interpret spectral EIS features without referring to equivalent circuit modeling. Using structural data obtained earlier from neutron reflectometry and dielectric constants of lipid bilayers, we reproduced experimentally observed features of the electrochemical impedance (EI) spectra of complex surface constructs involving small pinhole defects, large membrane-free patches, and bound liposomes. We demonstrated by FEA that highly insulating (dp)tBLMs with low-defect density exhibit EI spectra in the shape of a perfect semicircle with or without low-frequency upward "tails" in the Cole-Cole representation. Such EI spectra were observed at DPhyPC concentrations of >5 × 10(-3) mol L(-1). While AFM was not able to visualize very small lateral defects in such films, EI spectra unambiguously signaled their presence by increased low frequency "tails". Using FEA we demonstrate that films with large diameter visible defects (>25 nm by AFM) produce EI spectral features consisting of two semicircles of comparable size. Such films were typically obtained at DPhyPC concentrations of <5 × 10(-3) mol L(-1). At DPhyPC concentrations of <1.0 × 10(-3) mol L(-1) the planar bilayer structures were replaced by ellipsoidal liposomes with diameters ranging from 50 to 500 nm as observed in AFM images. Despite the distinct surface morphology change, the EI

  5. Structural Responses and Finite Element Modeling of Hakka Tulou Rammed Earth Structures

    NASA Astrophysics Data System (ADS)

    Sranislawski, Daniel

    Hakka Tulous are rammed earth structures that have survived the effects of aging and natural elements upwards of even over a thousand years. These structures have housed the Hakka people of the Fujian Province, China in natural yet modern housing that has provided benefits over newer building materials. The key building material, rammed earth, which is used for the walls of the Hakka Tulou structures, has provided structural stability along with thermal comfort to the respective inhabitants of the Hakka Tulous. Through material testing and analysis this study has examined how the Tulou structures have maintained their structural stability while also providing thermal comfort. Reports of self healing cracks in the rammed earth walls were also analyzed for their validity in this study. The study has found that although the story of the self healing crack cannot be validated, there is reason to believe that with the existence of lime, some type of autogenous healing could occur on a small scale. The study has also found, through the use of nondestructive testing, that both the internal wooden systems (flooring, roof, and column support) and the rammed earth walls, are still structurally sound. Also, rammed earth's high thermal mass along with the use of sufficient shading has allowed for a delay release of heat energy from the walls of the Tulous, thus providing thermal comfort that can be felt during both night and day temperatures. The Hakka Tulou structures have been found to resist destruction from natural disasters such as strong earthquakes even when more modern construction has not. Through finite element modeling, this study has shown that the high volume of rammed earth used in the construction of the Hakka Tulous helps dissipate lateral force energy into much lower stresses for the rammed earth wall. This absorption of lateral force energy allows the rammed earth structures to survive even the strongest of earthquakes experienced in the region. The Hakka

  6. An Innovative Structural Mode Selection Methodology: Application for the X-33 Launch Vehicle Finite Element Model

    NASA Technical Reports Server (NTRS)

    Hidalgo, Homero, Jr.

    2000-01-01

    An innovative methodology for determining structural target mode selection and mode selection based on a specific criterion is presented. An effective approach to single out modes which interact with specific locations on a structure has been developed for the X-33 Launch Vehicle Finite Element Model (FEM). We presented Root-Sum-Square (RSS) displacement method computes resultant modal displacement for each mode at selected degrees of freedom (DOF) and sorts to locate modes with highest values. This method was used to determine modes, which most influenced specific locations/points on the X-33 flight vehicle such as avionics control components, aero-surface control actuators, propellant valve and engine points for use in flight control stability analysis and for flight POGO stability analysis. Additionally, the modal RSS method allows for primary or global target vehicle modes to also be identified in an accurate and efficient manner.

  7. Recent advances and progress towards an integrated interdisciplinary thermal-structural finite element technology

    NASA Technical Reports Server (NTRS)

    Namburu, Raju R.; Tamma, Kumar K.

    1993-01-01

    An integrated finite element approach is presented for interdisciplinary thermal-structural problems. Of the various numerical approaches, finite element methods with direct time integration procedures are most widely used for these nonlinear problems. Traditionally, combined thermal-structural analysis is performed sequentially by transferring data between thermal and structural analysis. This approach is generally effective and routinely used. However, to solve the combined thermal-structural problems, this approach results in cumbersome data transfer, incompatible algorithmic representations, and different discretized element formulations. The integrated approach discussed in this paper effectively combines thermal and structural fields, thus overcoming the above major shortcomings. The approach follows Lax-Wendroff type finite element formulations with flux and stress based representations. As a consequence, this integrated approach uses common algorithmic representations and element formulations. Illustrative test examples show that the approach is effective for integrated thermal-structural problems.

  8. FINITE ELEMENT MODELS FOR COMPUTING SEISMIC INDUCED SOIL PRESSURES ON DEEPLY EMBEDDED NUCLEAR POWER PLANT STRUCTURES.

    SciTech Connect

    XU, J.; COSTANTINO, C.; HOFMAYER, C.

    2006-06-26

    PAPER DISCUSSES COMPUTATIONS OF SEISMIC INDUCED SOIL PRESSURES USING FINITE ELEMENT MODELS FOR DEEPLY EMBEDDED AND OR BURIED STIFF STRUCTURES SUCH AS THOSE APPEARING IN THE CONCEPTUAL DESIGNS OF STRUCTURES FOR ADVANCED REACTORS.

  9. Structure-property effects of tantalum additions to nickel-base superalloys

    NASA Technical Reports Server (NTRS)

    Heckel, R. W.; Pletka, B. J.; Koss, D. A.; Jackson, M. R.

    1982-01-01

    The characterization of the effect of Ta on the structure of Ni base superalloys, the determination of the effects of Ta (structure) variations on the mechanical, thermal, and oxidation behavior, and the identification of alloying elements which have potential as substitutes for Ta are investigated. Mar M247 type alloys are emphasized; nominal and analyzed compositions of ten alloys under study are given. X-ray and composition analysis are being used to determine the partitioning of alloying elements between gamma, gamma primes, and MC (cubic) as a function of Ta content. The diffusional interactions of the Mar M247-type alloys with as cast beta + gamma alloys are studied to determine the effects of Ta on alloy/coating degradation.

  10. The Associative Structure of Memory for Multi-Element Events

    PubMed Central

    2013-01-01

    The hippocampus is thought to be an associative memory “convergence zone,” binding together the multimodal elements of an experienced event into a single engram. This predicts a degree of dependency between the retrieval of the different elements comprising an event. We present data from a series of studies designed to address this prediction. Participants vividly imagined a series of person–location–object events, and memory for these events was assessed across multiple trials of cued retrieval. Consistent with the prediction, a significant level of dependency was found between the retrieval of different elements from the same event. Furthermore, the level of dependency was sensitive both to retrieval task, with higher dependency during cued recall than cued recognition, and to subjective confidence. We propose a simple model, in which events are stored as multiple pairwise associations between individual event elements, and dependency is captured by a common factor that varies across events. This factor may relate to between-events modulation of the strength of encoding, or to a process of within-event “pattern completion” at retrieval. The model predicts the quantitative pattern of dependency in the data when changes in the level of guessing with retrieval task and confidence are taken into account. Thus, we find direct behavioral support for the idea that memory for complex multimodal events depends on the pairwise associations of their constituent elements and that retrieval of the various elements corresponding to the same event reflects a common factor that varies from event to event. PMID:23915127

  11. The Use of Additive Manufacturing for Fabrication of Multi-Function Small Satellite Structures

    SciTech Connect

    Horais, Brian J; Love, Lonnie J; Dehoff, Ryan R

    2013-01-01

    The use of small satellites in constellations is limited only by the growing functionality of smallsats themselves. Additive manufacturing provides exciting new design opportunities for development of multifunction CubeSat structures that integrate such functions as propulsion and thermal control into the satellite structures themselves. Manufacturing of these complex multifunction structures is now possible in lightweight, high strength, materials such as titanium by using existing electron beam melting additive manufacturing processes. However, the use of today's additive manufacturing capabilities is often cost-prohibitive for small companies due to the large capital investments required. To alleviate this impediment the U.S. Department of Energy has established a Manufacturing Demonstration Facility (MDF) at their Oak Ridge National Laboratory (ORNL) in Tennessee that provides industry access to a broad range of energy-efficient additive manufacturing equipment for collaborative use by both small and large organizations. This paper presents a notional CubeSat multifunction design that integrates the propulsion system into a three-unit (3U) CubeSat structure. The full-scale structure has been designed and fabricated at the ORNL MDF. The use of additive manufacturing for spacecraft fabrication is opening up many new possibilities in design and fabrication capabilities for what had previously been impossible structures to fabricate.

  12. Experimentally validated finite element model of electrocaloric multilayer ceramic structures

    SciTech Connect

    Smith, N. A. S. E-mail: maciej.rokosz@npl.co.uk Correia, T. M. E-mail: maciej.rokosz@npl.co.uk; Rokosz, M. K. E-mail: maciej.rokosz@npl.co.uk

    2014-07-28

    A novel finite element model to simulate the electrocaloric response of a multilayer ceramic capacitor (MLCC) under real environment and operational conditions has been developed. The two-dimensional transient conductive heat transfer model presented includes the electrocaloric effect as a source term, as well as accounting for radiative and convective effects. The model has been validated with experimental data obtained from the direct imaging of MLCC transient temperature variation under application of an electric field. The good agreement between simulated and experimental data, suggests that the novel experimental direct measurement methodology and the finite element model could be used to support the design of optimised electrocaloric units and operating conditions.

  13. Experimentally validated finite element model of electrocaloric multilayer ceramic structures

    NASA Astrophysics Data System (ADS)

    Smith, N. A. S.; Rokosz, M. K.; Correia, T. M.

    2014-07-01

    A novel finite element model to simulate the electrocaloric response of a multilayer ceramic capacitor (MLCC) under real environment and operational conditions has been developed. The two-dimensional transient conductive heat transfer model presented includes the electrocaloric effect as a source term, as well as accounting for radiative and convective effects. The model has been validated with experimental data obtained from the direct imaging of MLCC transient temperature variation under application of an electric field. The good agreement between simulated and experimental data, suggests that the novel experimental direct measurement methodology and the finite element model could be used to support the design of optimised electrocaloric units and operating conditions.

  14. Finite element methodology for integrated flow-thermal-structural analysis

    NASA Technical Reports Server (NTRS)

    Thornton, Earl A.; Ramakrishnan, R.; Vemaganti, G. R.

    1988-01-01

    Papers entitled, An Adaptive Finite Element Procedure for Compressible Flows and Strong Viscous-Inviscid Interactions, and An Adaptive Remeshing Method for Finite Element Thermal Analysis, were presented at the June 27 to 29, 1988, meeting of the AIAA Thermophysics, Plasma Dynamics and Lasers Conference, San Antonio, Texas. The papers describe research work supported under NASA/Langley Research Grant NsG-1321, and are submitted in fulfillment of the progress report requirement on the grant for the period ending February 29, 1988.

  15. Development of Additive Construction Technologies for Application to Development of Lunar/Martian Surface Structures Using In-Situ Materials

    NASA Technical Reports Server (NTRS)

    Werkheiser, Niki J.; Fiske, Michael R.; Edmunson, Jennifer E.; Khoshnevis, Berokh

    2015-01-01

    For long-duration missions on other planetary bodies, the use of in situ materials will become increasingly critical. As human presence on these bodies expands, so must the breadth of the structures required to accommodate them including habitats, laboratories, berms, radiation shielding for natural radiation and surface reactors, garages, solar storm shelters, greenhouses, etc. Planetary surface structure manufacturing and assembly technologies that incorporate in situ resources provide options for autonomous, affordable, pre-positioned environments with radiation shielding features and protection from micrometeorites, exhaust plume debris, and other hazards. The ability to use in-situ materials to construct these structures will provide a benefit in the reduction of up-mass that would otherwise make long-term Moon or Mars structures cost prohibitive. The ability to fabricate structures in situ brings with it the ability to repair these structures, which allows for the self-sufficiency and sustainability necessary for long-duration habitation. Previously, under the auspices of the MSFC In-Situ Fabrication and Repair (ISFR) project and more recently, under the jointly-managed MSFC/KSC Additive Construction with Mobile Emplacement (ACME) project, the MSFC Surface Structures Group has been developing materials and construction technologies to support future planetary habitats with in-situ resources. One such additive construction technology is known as Contour Crafting. This paper presents the results to date of these efforts, including development of novel nozzle concepts for advanced layer deposition using this process. Conceived initially for rapid development of cementitious structures on Earth, it also lends itself exceptionally well to the automated fabrication of planetary surface structures using minimally processed regolith as aggregate, and binders developed from in situ materials as well. This process has been used successfully in the fabrication of

  16. Finite element analysis of structural engineering problems using a viscoplastic model incorporating two back stresses

    NASA Technical Reports Server (NTRS)

    Arya, Vinod K.; Halford, Gary R.

    1993-01-01

    The feasibility of a viscoplastic model incorporating two back stresses and a drag strength is investigated for performing nonlinear finite element analyses of structural engineering problems. To demonstrate suitability for nonlinear structural analyses, the model is implemented into a finite element program and analyses for several uniaxial and multiaxial problems are performed. Good agreement is shown between the results obtained using the finite element implementation and those obtained experimentally. The advantages of using advanced viscoplastic models for performing nonlinear finite element analyses of structural components are indicated.

  17. Element-by-element model updating of large-scale structures based on component mode synthesis method

    NASA Astrophysics Data System (ADS)

    Yu, Jie-xin; Xia, Yong; Lin, Wei; Zhou, Xiao-qing

    2016-02-01

    Component mode synthesis (CMS) method is developed and applied to the element-by-element model updating of large-scale structures in this study. Several lowest frequencies and mode shapes of the global structure are obtained with the free interface CMS method by employing the several lowest frequencies and mode shapes of each substructure individually. In this process, the removal of higher modes is compensated by the residual modes. The eigensensitivity of the global structure is then assembled from the eigensensitivities of each substructure to the updating element parameters. Subsequently, the global model is updated using the sensitivity-based optimization technique. The application of the present method to an 11-floor frame structure and to a large-scale structure demonstrates its accuracy and efficiency. The computational time required by the substructuring method to calculate the eigensensitivity matrices is significantly reduced, as compared with that consumed by the conventional global-based approach. Selection of the number of master modes is also proposed.

  18. Elemental and structural studies at the bone-cartilage interface

    NASA Astrophysics Data System (ADS)

    Kaabar, W.; Daar, E.; Bunk, O.; Farquharson, M. J.; Laklouk, A.; Bailey, M.; Jeynes, C.; Gundogdu, O.; Bradley, D. A.

    2011-10-01

    Micro-Proton Induced X-ray Emission (μ-PIXE) and Proton Induced Gamma-ray Emission (PIGE) techniques were employed in the investigation of trace and essential elements distribution in normal and diseased human femoral head sections affected by osteoarthritis (OA). PIGE was exploited in the determination of elements of low atomic number z<15 such as Na and F whereas elements with z>15 viz Ca, Z, P and S were determined by PIXE. Accumulations of key elements in the bone and cartilage sections were observed, significant S and Na concentrations being found in the cartilage region particularly in normal tissues. Zn showed enhanced concentrations at the bone-cartilage interface. At a synchrotron facility, small angle X-ray scattering (SAXS) was utilized on a decalcified human femoral head section affected by OA, direct measurements being made of spatial alterations of collagen fibres. The SAXS results showed a slight decrease in the axial periodicity between normal collagen type I and that in diseased tissue in various sites, in contrast with the findings of others.

  19. Modeling the Structure of Complex Aluminosilicate Glasses: The Effect of Zinc Addition.

    PubMed

    Bernasconi, Andrea; Dapiaggi, Monica; Pavese, Alessandro; Agostini, Giovanni; Bernasconi, Maurizio; Bowron, Daniel T

    2016-03-10

    An empirical potential structure refinement of neutron and X-ray diffraction data combined with extended absorption fine structure evidence has been applied to the investigation of two distinct sets of complex aluminosilicate glasses containing different quantities of zinc. Data come from (i) neutron and X-ray total scattering experiments, which have been performed at the ISIS neutron spallation source (SANDALS beamline) and at the European Synchrotron Radiation Facility (ID11 beamline), and (ii) EXAFS experiments which have been performed at the European Synchrotron Radiation Facility (BM23 beamline). By careful examination of the modeled ensemble of atoms, a wide range of structural information has been extracted: coordination numbers, bond distances, cluster sizes, type of oxygen sharing, and the preference of large cations to adopt a charge-compensating role. The first series of glasses, which is characterized by a fixed network modifier element content (i.e., Na), shows how the introduction of Zn at the expense of Si and Al network forming elements does not significantly alter the polymerization degree, as a result of its dominant 4-fold coordination. In the case of the second series, which is characterized by fixed network forming element content (i.e., Si and Al), it is shown how the replacement of a network modifier element (i.e., Ca) with the introduction of Zn does not change the propensity of Zn to be mainly 4-fold coordinated by promoting the network. Where appropriate the experimental results have been compared with classical theoretical approaches such as stoichiometric models based on Zachariasen's rules and computational routines. PMID:26848740

  20. A Procedure for Modeling Structural Component/Attachment Failure Using Transient Finite Element Analysis

    NASA Technical Reports Server (NTRS)

    Lovejoy, Andrew E.; Jegley, Dawn C. (Technical Monitor)

    2007-01-01

    Structures often comprise smaller substructures that are connected to each other or attached to the ground by a set of finite connections. Under static loading one or more of these connections may exceed allowable limits and be deemed to fail. Of particular interest is the structural response when a connection is severed (failed) while the structure is under static load. A transient failure analysis procedure was developed by which it is possible to examine the dynamic effects that result from introducing a discrete failure while a structure is under static load. The failure is introduced by replacing a connection load history by a time-dependent load set that removes the connection load at the time of failure. The subsequent transient response is examined to determine the importance of the dynamic effects by comparing the structural response with the appropriate allowables. Additionally, this procedure utilizes a standard finite element transient analysis that is readily available in most commercial software, permitting the study of dynamic failures without the need to purchase software specifically for this purpose. The procedure is developed and explained, demonstrated on a simple cantilever box example, and finally demonstrated on a real-world example, the American Airlines Flight 587 (AA587) vertical tail plane (VTP).

  1. A unique approach to fabricating precision space structures elements

    NASA Technical Reports Server (NTRS)

    Cohan, H.; Johnson, R. R.

    1981-01-01

    A procedure of fabricating graphite epoxy columns used in the assembly of large space platforms is described. The requirement for precise dimensional control led to a unique hot resin injection process. Dry, high modulus fiber is wound over a vertically mounted steam-heated mandrel. A steam-heated sleeve or caul is slipped over the wound mandrel and resin is injected and cured in place. Approximately 200 column elements have been fabricated using this efficient process.

  2. Mechanical end joint system for structural column elements

    NASA Technical Reports Server (NTRS)

    Bush, H. G.; Wallsom, R. E. (Inventor)

    1982-01-01

    A mechanical end joint system, useful for the transverse connection of strut elements to a common node, comprises a node joint half with a semicircular tongue and groove, and a strut joint half with a semicircular tongue and groove. The two joint halves are engaged transversely and the connection is made secure by the inherent physical property characteristics of locking latches and/or by a spring-actioned shaft. A quick release mechanism provides rapid disengagement of the joint halves.

  3. Application of Finite Element Method to Analyze Inflatable Waveguide Structures

    NASA Technical Reports Server (NTRS)

    Deshpande, M. D.

    1998-01-01

    A Finite Element Method (FEM) is presented to determine propagation characteristics of deformed inflatable rectangular waveguide. Various deformations that might be present in an inflatable waveguide are analyzed using the FEM. The FEM procedure and the code developed here are so general that they can be used for any other deformations that are not considered in this report. The code is validated by applying the present code to rectangular waveguide without any deformations and comparing the numerical results with earlier published results.

  4. Manufacturing processes for fabricating graphite/PMR 15 polyimide structural elements

    NASA Technical Reports Server (NTRS)

    Sheppard, C. H.; Hoggatt, J. T.; Symonds, W. A.

    1979-01-01

    Investigations were conducted to obtain commercially available graphite/PMR-15 polyimide prepreg, develop an autoclave manufacturing process, and demonstrate the process by manufacturing structural elements. Controls were established on polymer, prepreg, composite fabrication, and quality assurance, Successful material quality control and processes were demonstrated by fabricating major structural elements including flat laminates, hat sections, I beam sections, honeycomb sandwich structures, and molded graphite reinforced fittings. Successful fabrication of structural elements and simulated section of the space shuttle aft body flap shows that the graphite/PMR-15 polyimide system and the developed processes are ready for further evaluation in flight test hardware.

  5. Effect of the addition of low rare earth elements (lanthanum, neodymium, cerium) on the biodegradation and biocompatibility of magnesium.

    PubMed

    Willbold, Elmar; Gu, Xuenan; Albert, Devon; Kalla, Katharina; Bobe, Katharina; Brauneis, Maria; Janning, Carla; Nellesen, Jens; Czayka, Wolfgang; Tillmann, Wolfgang; Zheng, Yufeng; Witte, Frank

    2015-01-01

    Rare earth elements are promising alloying element candidates for magnesium alloys used as biodegradable devices in biomedical applications. Rare earth elements have significant effects on the high temperature strength as well as the creep resistance of alloys and they improve magnesium corrosion resistance. We focused on lanthanum, neodymium and cerium to produce magnesium alloys with commonly used rare earth element concentrations. We showed that low concentrations of rare earth elements do not promote bone growth inside a 750 μm broad area around the implant. However, increased bone growth was observed at a greater distance from the degrading alloys. Clinically and histologically, the alloys and their corrosion products caused no systematic or local cytotoxicological effects. Using microtomography and in vitro experiments, we could show that the magnesium-rare earth element alloys showed low corrosion rates, both in in vitro and in vivo. The lanthanum- and cerium-containing alloys degraded at comparable rates, whereas the neodymium-containing alloy showed the lowest corrosion rates. PMID:25278442

  6. Finite Element Analysis of Morphing Piezoelectric Structures Studied

    NASA Technical Reports Server (NTRS)

    Lee, Ho-Jun

    2002-01-01

    The development of morphing aerospace structures that optimize their shape offers the potential to significantly improve the performance of existing airplanes. These morphing vehicles will operate with new capabilities to reduce noise, damp vibrations, manipulate flow, and monitor damage. Piezoelectric materials represent one of the popular materials currently being investigated for applications in morphing structures.

  7. The cyclic oxidation resistance at 1200 C of beta-NiAl, FeAl, and CoAl alloys with selected third element additions

    NASA Technical Reports Server (NTRS)

    Barrett, C. A.; Titran, R. H.

    1992-01-01

    The intermetallic compounds Beta-NiAl, FeAl, and CoAl were tested in cyclic oxidation with selected third element alloy additions. Tests in static air for 200 1-hr cycles at 1200 C indicated by specific weight change/time data and x-ray diffraction analysis that the 5 at percent alloy additions did not significantly improve the oxidation resistance over the alumina forming baseline alloys without the additions. Many of the alloy additions were actually deleterious. Ta and Nb were the only alloy additions that actually altered the nature of the oxide(s) formed and still maintained the oxidation resistance of the protective alumina scale.

  8. Metal aircraft structural elements reinforced with graphite filamentary composites

    NASA Technical Reports Server (NTRS)

    Berg, K. R.; Ramsey, J.

    1972-01-01

    Strain compatibility equations are used to evaluate the thermal stresses existing when unidirectional graphite composites are bonded to aluminum structures. Based on thermal stresses and optimum placement of the composite, skin-stringer aluminum panels are optimized for minimum weight compression panels with selective composite reinforcement. Composite reinforced skin-stringer panels are thermal cycled to determine the effect of thermal fatigue on structural integrity. Both cycled and uncycled panels are tested in compression and tension. Test results are correlated with predicted loads. Use of filamentary graphite composites is an efficient method of reinforcing metal structures, but care must be taken to minimize thermal stresses.

  9. NanoSIMS Reveals New Structural and Elemental Signatures of Early Life

    NASA Technical Reports Server (NTRS)

    Oehler, Dorothy Z.; Mostefaoui, Smail; Meibom, Anders; Selo, Madeleine; Robert, Francois; McKay, David S.

    2006-01-01

    The young technology of NanoSIMS is unlocking new information from organic matter in ancient sediments. We have used this technique to characterize sub-micron scale element composition of Proterozoic organics that are clearly biogenic as a guide for interpreting problematic structures in terrestrial or extraterrestrial samples. We used the NanoSIMS 50 of the National Museum of Natural History in Paris to map carbon, nitrogen (as CN), and sulfur in organic structures from the approximately 0.8 Ga Bitter Springs Formation. We analyzed spheroidal and filamentous microfossils as well as organic laminae that appeared amorphous by optical and scanning electron microscopy. In clear-cut microfossils, a coincidence between optical images and NanoSIMS element maps suggests a biological origin for the mapped carbon, sulfur, and nitrogen; this conclusion is supported by high resolution NanoSIMS maps showing identical spatial distributions of C, CN and S. High resolution images also demonstrate distinctive nano structure of the filaments and spheroids. In the amorphous laminae, NanoSIMS reveals morphologies reminiscent of compressed microfossils. Distinct CN/C ratios of the spheroids, filaments, and laminae may reflect their biological precursors (cell walls, cyanobacterial sheaths, and microbial communities/biofilms, respectively). Similar amorphous laminae comprise a preponderance of the organic matter in many Precambrian deposits. Thus it is possible that NanoSIMS will provide fresh insight into a large body of previously uninterpretable material. Additionally, NanoSIMS analysis may establish new biosignatures that will be helpful for assessing the origin and biogenicity of controversial Archean structures and any organic materials that may occur in Martian or other extraterrestrial samples.

  10. Elemental and structural studies of the rat galactose cataract

    SciTech Connect

    Harding, C.V.; Unakar, N.J.; Bagchi, M.; Chylack, L.T. Jr.; Jampel, R.S.; Bobrowski, W.F.; Dang, L.; Tsui, J.Y.; Harding, D. )

    1989-01-01

    A series of rat galactose lenses, from 1 to 20 days on the 50% galactose diet, were frozen in the whole eye, and fractured from pole to pole in the frozen state. Lyophilized half-lenses were prepared for analysis by energy dispersive spectrometry (EDS). Following elemental analysis, some specimens were embedded and sectioned for histological studies. Elemental X-ray maps, and/or profiles, were made for K, Na, Cl, Ca, P, and S. As early as two days on the galactose diet, a crescent-shaped region (streak) of Cl, Na, and Ca gain, and K loss develops near the equatorial surface. Between this region and the equatorial surface are the nucleated differentiating fiber cells which maintain low Cl, Na, and Ca, and high K (viable equatorial zone, VEZ). With time the streak expands anteriorly, centrally and posteriorly, eventually (by 20 days) including most of the lens. The VEZ, including the epithelium, however, is non-reactive to the galactose diet, which is deleterious to the fully differentiated fiber cells. Eventually, the VEZ undergoes a characteristic morphological change, apparently due in part to changes in its physical environment.

  11. Nondestructive evaluation of critical composite material structural elements

    NASA Astrophysics Data System (ADS)

    Duke, John C., Jr.; Lesko, John J.; Weyers, R.

    1996-11-01

    A small span bridge that has suffered corrosive deterioration of a number of the steel structural members is in the process of being rehabilitated with glass and carbon fiber reinforced, pultruded polymer structural beams. As part of a comprehensive research program to develop methods for modeling long term durability of the composite material, nondestructive evaluation if being used to provide a preliminary assessment of the initial condition of the beams as well as to monitor the deterioration of the beams during service.

  12. Structural evaluation of mixer pump installed in Tank 241-AN-107 for caustic addition project

    SciTech Connect

    Leshikar, G.A.

    1995-06-16

    This report documents the structural analysis and evaluation of a mixer pump and caustic addition system to be used in Tank 107-AN. This pump will be installed in the central pump pit of this double- shell tank for the purpose of bringing the hydroxide ion concentration into compliance with Tank Farm operating specifications.

  13. Effects of small amount of additional elements on control of interstitial impurities and mechanical properties of V?4Cr?4Ti?Si?Al?Y alloys

    NASA Astrophysics Data System (ADS)

    Chuto, Toshinori; Satou, Manabu; Hasegawa, Akira; Abe, Katsunori; Muroga, Takeo; Yamamoto, Norikazu

    2004-03-01

    In order to improve the mechanical properties of low activation vanadium alloys for fusion structural applications, effects of small addition of Si, Al and Y on the control of interstitial impurities (O, C and N) during the fabrication process were examined for several V-4Cr-4Ti-Si-Al-Y alloys produced by the levitation melting method. Charpy impact tests and tensile tests were carried out for five kinds of V-4Cr-4Ti-Si-Al-Y alloys using miniaturized specimens for the purpose of evaluating the effects of these elements on mechanical properties. Oxygen concentration decreased almost linearly with increasing loss of yttrium during melting. This oxygen reduction with yttrium loss during the melting process may have been achieved by two types of mechanisms, they are, (i) suppression of oxygen penetration into the molten materials from the environment and (ii) getting of oxygen from the matrix by forming Y 2O 3, which floats to the surface during the melting. There was no effect of Si and Al addition to control the concentration of interstitial impurities. V-4Cr-4Ti-0.1Si-0.1Al-0.1Y alloy showed the best impact properties out of the alloys investigated. Upper-shelf energy of the alloys decreased with increasing yttrium content. High number density of coarse inclusions containing yttrium could cause the degradation of impact properties, though they hardly affect tensile properties of the alloys. Even at higher yttrium contents, V-4Cr-4Ti-Y alloys without addition of Si and Al showed relatively high upper-shelf energy.

  14. Rapid detection of delamination areas in laminated structural elements by means of optically monitored strain solitons

    NASA Astrophysics Data System (ADS)

    Semenova, I. V.; Belashov, A. V.; Dreiden, G. V.; Petrov, N. V.; Samsonov, A. M.

    2015-05-01

    Modern structural elements are often made of laminated polymer materials or composites on the base of polymer matrices. The proper functioning of these elements may be of vital importance especially in automotive and aerospace industries, in gas and oil transportation. The major problem in their performance is a possibility of a sudden and irreversible delamination caused by various factors. We propose and study a NDT approach aimed to detect delamination areas in adhesively bonded layered structural elements made of different materials. The proposed approach is evaluated by use of holographic detection and monitoring of the evolution of bulk strain solitons generated in such structures.

  15. Structural property of regulatory elements in human promoters

    NASA Astrophysics Data System (ADS)

    Cao, Xiao-Qin; Zeng, Jia; Yan, Hong

    2008-04-01

    The capacity of transcription factors to activate gene expression is encoded in the promoter sequences, which are composed of short regulatory motifs that function as transcription factor binding sites (TFBSs) for specific proteins. To the best of our knowledge, the structural property of TFBSs that controls transcription is still poorly understood. Rigidity is one of the important structural properties of DNA, and plays an important role in guiding DNA-binding proteins to the target sites efficiently. After analyzing the rigidity of 2897 TFBSs in 1871 human promoters, we show that TFBSs are generally more flexible than other genomic regions such as exons, introns, 3' untranslated regions, and TFBS-poor promoter regions. Furthermore, we find that the density of TFBSs is consistent with the average rigidity profile of human promoters upstream of the transcription start site, which implies that TFBSs directly influence the promoter structure. We also examine the local rigid regions probably caused by specific TFBSs such as the DNA sequence TATA(A/T)A(A/T) box, which may inhibit nucleosomes and thereby facilitate the access of transcription factors bound nearby. Our results suggest that the structural property of TFBSs accounts for the promoter structure as well as promoter activity.

  16. A triangular thin shell finite element: Nonlinear analysis. [structural analysis

    NASA Technical Reports Server (NTRS)

    Thomas, G. R.; Gallagher, R. H.

    1975-01-01

    Aspects of the formulation of a triangular thin shell finite element which pertain to geometrically nonlinear (small strain, finite displacement) behavior are described. The procedure for solution of the resulting nonlinear algebraic equations combines a one-step incremental (tangent stiffness) approach with one iteration in the Newton-Raphson mode. A method is presented which permits a rational estimation of step size in this procedure. Limit points are calculated by means of a superposition scheme coupled to the incremental side of the solution procedure while bifurcation points are calculated through a process of interpolation of the determinants of the tangent-stiffness matrix. Numerical results are obtained for a flat plate and two curved shell problems and are compared with alternative solutions.

  17. Mechanical properties and phase composition of potential biodegradable Mg-Zn-Mn-base alloys with addition of rare earth elements

    SciTech Connect

    Stulikova, Ivana; Smola, Bohumil

    2010-10-15

    Mechanical properties and creep resistance of the MgY4Zn1Mn1 alloy in the as cast as well as in the T5 condition were compared to those of the MgCe4Zn1Mn1 alloy in the same conditions. Yield tensile stress and ultimate tensile strength of the MgY4Zn1Mn1 alloy are slightly better in the temperature range 20 deg. C-400 deg. C than these of the MgCe4Zn1Mn1 alloy. Better thermal stability of ultimate tensile strength was observed in the T5 treated MgCe4Zn1Mn1 alloy than in this material in the as cast condition. An outstanding creep resistance at 225 deg. C-350 deg. C found in the MgY4Zn1Mn1 alloy is due to the existence of the 18R long period stacking structure persisting in this alloy even a long heat treatment of 500 deg. C/32 h. No similar stacking effects happen when Ce substitutes Y in approximately the same concentration. The creep resistance deteriorates considerably in the MgCe4Zn1Mn1 alloy. Rectangular particles of the equilibrium Mg{sub 12}Ce phase dominate in the microstructure of as cast as well as of high temperature heat-treated MgCe4Zn1Mn1 alloy. A population of small oval particles containing Mg and Zn develops additionally during annealing of this alloy. These particles pin effectively dislocations and can be responsible for the better thermal stability of the T5 treated material.

  18. sp3-hybridized framework structure of group-14 elements discovered by genetic algorithm

    SciTech Connect

    Nguyen, Manh Cuong; Zhao, Xin; Wang, Cai-Zhuang; Ho, Kai-Ming

    2014-05-01

    Group-14 elements, including C, Si, Ge, and Sn, can form various stable and metastable structures. Finding new metastable structures of group-14 elements with desirable physical properties for new technological applications has attracted a lot of interest. Using a genetic algorithm, we discovered a new low-energy metastable distorted sp3-hybridized framework structure of the group-14 elements. It has P42/mnm symmetry with 12 atoms per unit cell. The void volume of this structure is as large as 139.7Å3 for Si P42/mnm, and it can be used for gas or metal-atom encapsulation. Band-structure calculations show that P42/mnm structures of Si and Ge are semiconducting with energy band gaps close to the optimal values for optoelectronic or photovoltaic applications. With metal-atom encapsulation, the P42/mnm structure would also be a candidate for rattling-mediated superconducting or used as thermoelectric materials.

  19. Structural elements and organization of the ancestral translational machinery

    NASA Technical Reports Server (NTRS)

    Rein, R.; Srinivasan, S.; Mcdonald, J.; Raghunathan, G.; Shibata, M.

    1987-01-01

    The molecular mechanisms of the primitive translational apparatus are discussed in the framework of present-day protein biosynthesis. The structural necessities of an early adaptor and the multipoint recognition properties of such an adaptor are investigated on the basis of structure/function relationships found in a contemporary system and a molecular model of the contemporary transpeptidation complex. A model of the tRNA(Tyr)-tyrosyl tRNA synthetase complex including the positioning of the disordered region is proposed; the model is used to illustrate the required recognition properties of the ancestor aminoacyl synthetase.

  20. Optimal placement of active elements in control augmented structural synthesis

    NASA Technical Reports Server (NTRS)

    Sepulveda, A. E.; Jin, I. M.; Schmit, L. A., Jr.

    1992-01-01

    A methodology for structural/control synthesis is presented in which the optimal location of active members is treated in terms of (0,1) variables. Structural member sizes, control gains and (0,1) placement variables are treated simultaneously as design variables. Optimization is carried out by generating and solving a sequence of explicit approximate problems using a branch and bound strategy. Intermediate design variable and intermediate response quantity concepts are used to enhance the quality of the approximate design problems. Numerical results for example problems are presented to illustrate the efficacy of the design procedure set forth.

  1. Ten-Structure as Strategy of Addition 1-20 by Involving Spatial Structuring Ability for First Grade Students

    ERIC Educational Resources Information Center

    Salmah, Ummy; Putri, Ratu Ilma Indra; Somakim

    2015-01-01

    The aim of this study is to design learning activities that can support students to develop strategies for the addition of number 1 to 20 in the first grade by involving students' spatial structuring ability. This study was conducted in Indonesia by involving 27 students. In this paper, one of three activities is discussed namely ten-box activity.…

  2. Energy flow prediction in built-up structures through a hybrid finite element/wave and finite element approach

    NASA Astrophysics Data System (ADS)

    Fan, Y.; Collet, M.; Ichchou, M.; Li, L.; Bareille, O.; Dimitrijevic, Z.

    2016-01-01

    This paper presents a rapid and accurate numerical tool for the energy flow evaluation in a periodic substructure from the near-field to the far-field domain. Here we suppose that the near-field part contains a point source characterized by the injected power in the structure. The near-field part is then modeled by Finite Element Method (FEM) while the periodic structure and the far-field part are regarded as waveguides and modeled by an enhanced Wave and Finite Element Method (WFEM). Enhancements are made on the eigenvalue scheme, the condensation of the unit cell and the consideration of a reduced wave basis. Efforts are made to adapt substructures modeled by different strategies in a multi-scale manner such that the final matrices dimensions of the built-up structure are largely reduced. The method is then validated numerically and theoretically. An application is presented, where a structural dynamical system coupled with periodic resistive piezoelectric shunts is discussed.

  3. State Children's Cabinets and Councils--Elements of Success Issue 1: Structural Options

    ERIC Educational Resources Information Center

    Gaines, Elizabeth; Faigley, Ian; Pittman, Karen

    2008-01-01

    Elements of Success 1: Structural Options outlines the range of current children's cabinet and council structures in place and offers tips and warnings for getting the most effective structure in place. This issue brief builds heavily on interviews conducted by the Forum and on the detailed documentation work done by Susan Robison for the National…

  4. In Situ Determination of Trace Elements in Fish Otoliths by Laser Ablation Double Focusing Sector Field Inductively Coupled Plasma Mass Spectrometry Using a Solution Standard Addition Calibration Method

    NASA Astrophysics Data System (ADS)

    Chen, Z.; Jones, C. M.

    2002-05-01

    Microchemistry of fish otoliths (fish ear bones) is a very useful tool for monitoring aquatic environments and fish migration. However, determination of the elemental composition in fish otolith by ICP-MS has been limited to either analysis of dissolved sample solution or measurement of limited number of trace elements by laser ablation (LA)- ICP-MS due to low sensitivity, lack of available calibration standards, and complexity of polyatomic molecular interference. In this study, a method was developed for in situ determination of trace elements in fish otoliths by laser ablation double focusing sector field ultra high sensitivity Finnigan Element 2 ICP-MS using a solution standard addition calibration method. Due to the lack of matrix-match solid calibration standards, sixteen trace elements (Na, Mg, P, Cr, Mn, Fe, Ni, Cu, Rb, Sr, Y, Cd, La, Ba, Pb and U) were determined using a solution standard calibration with Ca as an internal standard. Flexibility, easy preparation and stable signals are the advantages of using solution calibration standards. In order to resolve polyatomic molecular interferences, medium resolution (M/delta M > 4000) was used for some elements (Na, Mg, P, Cr, Mn, Fe, Ni, and Cu). Both external calibration and standard addition quantification strategies are compared and discussed. Precision, accuracy, and limits of detection are presented.

  5. Probabilistic structural analysis using a general purpose finite element program

    NASA Astrophysics Data System (ADS)

    Riha, D. S.; Millwater, H. R.; Thacker, B. H.

    1992-07-01

    This paper presents an accurate and efficient method to predict the probabilistic response for structural response quantities, such as stress, displacement, natural frequencies, and buckling loads, by combining the capabilities of MSC/NASTRAN, including design sensitivity analysis and fast probability integration. Two probabilistic structural analysis examples have been performed and verified by comparison with Monte Carlo simulation of the analytical solution. The first example consists of a cantilevered plate with several point loads. The second example is a probabilistic buckling analysis of a simply supported composite plate under in-plane loading. The coupling of MSC/NASTRAN and fast probability integration is shown to be orders of magnitude more efficient than Monte Carlo simulation with excellent accuracy.

  6. Effect of Stitching on Debonding in Composite Structural Elements

    NASA Technical Reports Server (NTRS)

    Raju, I. S.; Glaessgen, E. H.

    2001-01-01

    Stitched multiaxial warp knit materials have been suggested as viable alternatives to laminated prepreg materials for large aircraft structures such as wing skins. Analyses have been developed to quantify the effectiveness of stitching for reducing strain energy release rates in skin-stiffener debond, lap joint and sandwich debond configurations. Strain energy release rates were computed using the virtual crack closure technique. In all configurations, the stitches were shown to significantly reduce the strain energy release rate.

  7. Finite Element Prediction of Acoustic Scattering and Radiation from Submerged Elastic Structures

    NASA Technical Reports Server (NTRS)

    Everstine, G. C.; Henderson, F. M.; Lipman, R. R.

    1984-01-01

    A finite element formulation is derived for the scattering and radiation of acoustic waves from submerged elastic structures. The formulation uses as fundamental unknowns the displacement in the structure and a velocity potential in the field. Symmetric coefficient matrices result. The outer boundary of the fluid region is terminated with an approximate local wave-absorbing boundary condition which assumes that outgoing waves are locally planar. The finite element model is capable of predicting only the near-field acoustic pressures. Far-field sound pressure levels may be determined by integrating the surface pressures and velocities over the wet boundary of the structure using the Helmholtz integral. Comparison of finite element results with analytic results show excellent agreement. The coupled fluid-structure problem may be solved with general purpose finite element codes by using an analogy between the equations of elasticity and the wave equation of linear acoustics.

  8. Characterization of Effect of Support Structures in Laser Additive Manufacturing of Stainless Steel

    NASA Astrophysics Data System (ADS)

    Järvinen, Jukka-Pekka; Matilainen, Ville; Li, Xiaoyun; Piili, Heidi; Salminen, Antti; Mäkelä, Ismo; Nyrhilä, Olli

    Laser additive manufacturing (LAM) of stainless steel is a layer wisetechnology for fabricating 3D parts from metal powder via selectively melting powder with laser beam. Support structures play a significant role in LAM process as they help to remove heat away from the process and on the other hand hold the work piece in its place. A successful design of support structures can help to achievea building process fast and inexpensive with high quality. Aimof this study was to characterize the usability of two types of support structures: web and tube supports. Purpose of this studywas also to analyze how suitable they are in two industrial application cases: case for dental application and case for jewelry application. It was concluded that the removability of web supports was much better than tube supports. It was noticed that support structures are an important part of LAM process and they strongly affect the manufacturability and the end quality of the part.

  9. Recognition on space photographs of structural elements of Baja California

    NASA Technical Reports Server (NTRS)

    Hamilton, W.

    1971-01-01

    Gemini and Apollo photographs provide illustrations of known structural features of the peninsula and some structures not recognized previously. An apparent transform relationship between strike-slip and normal faulting is illustrated by the overlapping vertical photographs of northern Baja California. The active Agua Blanca right-lateral strike-slip fault trends east-southeastward to end at the north end of the Valle San Felipe and Valle Chico. The uplands of the high Sierra San Pedro Martir are a low-relief surface deformed by young faults, monoclines, and warps, which mostly produce west-facing steps and slopes; the topography is basically structural. The Sierra Cucapas of northeasternmost Baja California and the Colorado River delta of northwesternmost Sonora are broken by northwest-trending strike-slip faults. A strike-slip fault is inferred to trend northward obliquely from near Cabo San Lucas to La Paz, thence offshore until it comes ashore again as the Bahia Concepcion strike-slip fault.

  10. Finite Element Analysis of a Deployable Space Structure

    NASA Technical Reports Server (NTRS)

    Weeks, G. E.

    1983-01-01

    The dynamic characteristics of the Solar Array Flight Experiment (SAFE) structure during deployment and retraction are investigated. The SAFE structure consists of a deployable mast with an attached solar blanket designed with accordion type folds to permit packaging in a small volume. The planar form of the blanket geometry during deployment is maintained by a blanket tension/guidewire system. Structurally, the mast is modeled as an Euler beam column with inplane and out of plane bending and finite torsional stiffness. For out of plane motion, the blanket is modeled as a distributed mass uniformly supported by the three guidewires. For inplane motion the blanket displacements are assumed to vary linearly from the mast base to the mast tip. The mathematical model uses a virtual work formulation, required because the axial loading on the mast is nonconservative, combined with assumed beam modes to derive the differential equations of motion. Consideration of the time dependent boundary conditions results in an infinite set of ODE with time dependent coefficients. Finally, correlation of mast tip accelerations to mast base bending moments for specified modal motions are indicated.

  11. Stochastic filtering for damage identification through nonlinear structural finite element model updating

    NASA Astrophysics Data System (ADS)

    Astroza, Rodrigo; Ebrahimian, Hamed; Conte, Joel P.

    2015-03-01

    This paper describes a novel framework that combines advanced mechanics-based nonlinear (hysteretic) finite element (FE) models and stochastic filtering techniques to estimate unknown time-invariant parameters of nonlinear inelastic material models used in the FE model. Using input-output data recorded during earthquake events, the proposed framework updates the nonlinear FE model of the structure. The updated FE model can be directly used for damage identification and further used for damage prognosis. To update the unknown time-invariant parameters of the FE model, two alternative stochastic filtering methods are used: the extended Kalman filter (EKF) and the unscented Kalman filter (UKF). A three-dimensional, 5-story, 2-by-1 bay reinforced concrete (RC) frame is used to verify the proposed framework. The RC frame is modeled using fiber-section displacement-based beam-column elements with distributed plasticity and is subjected to the ground motion recorded at the Sylmar station during the 1994 Northridge earthquake. The results indicate that the proposed framework accurately estimate the unknown material parameters of the nonlinear FE model. The UKF outperforms the EKF when the relative root-mean-square error of the recorded responses are compared. In addition, the results suggest that the convergence of the estimate of modeling parameters is smoother and faster when the UKF is utilized.

  12. The structure of the SOLE element of oskar mRNA

    PubMed Central

    Simon, Bernd; Masiewicz, Pawel; Ephrussi, Anne; Carlomagno, Teresa

    2015-01-01

    mRNA localization by active transport is a regulated process that requires association of mRNPs with protein motors for transport along either the microtubule or the actin cytoskeleton. oskar mRNA localization at the posterior pole of the Drosophila oocyte requires a specific mRNA sequence, termed the SOLE, which comprises nucleotides of both exon 1 and exon 2 and is assembled upon splicing. The SOLE folds into a stem–loop structure. Both SOLE RNA and the exon junction complex (EJC) are required for oskar mRNA transport along the microtubules by kinesin. The SOLE RNA likely constitutes a recognition element for a yet unknown protein, which either belongs to the EJC or functions as a bridge between the EJC and the mRNA. Here, we determine the solution structure of the SOLE RNA by Nuclear Magnetic Resonance spectroscopy. We show that the SOLE forms a continuous helical structure, including a few noncanonical base pairs, capped by a pentanucleotide loop. The helix displays a widened major groove, which could accommodate a protein partner. In addition, the apical helical segment undergoes complex dynamics, with potential functional significance. PMID:26089324

  13. Finite Macro-Element Mesh Deformation in a Structured Multi-Block Navier-Stokes Code

    NASA Technical Reports Server (NTRS)

    Bartels, Robert E.

    2005-01-01

    A mesh deformation scheme is developed for a structured multi-block Navier-Stokes code consisting of two steps. The first step is a finite element solution of either user defined or automatically generated macro-elements. Macro-elements are hexagonal finite elements created from a subset of points from the full mesh. When assembled, the finite element system spans the complete flow domain. Macro-element moduli vary according to the distance to the nearest surface, resulting in extremely stiff elements near a moving surface and very pliable elements away from boundaries. Solution of the finite element system for the imposed boundary deflections generally produces smoothly varying nodal deflections. The manner in which distance to the nearest surface has been found to critically influence the quality of the element deformation. The second step is a transfinite interpolation which distributes the macro-element nodal deflections to the remaining fluid mesh points. The scheme is demonstrated for several two-dimensional applications.

  14. Uranium hydrogeochemical and stream sediment reconnasissance of the Trinidad NTMS Quadrangle, Colorado, including concentrations of forty-two additional elements

    SciTech Connect

    Shannon, S.S. Jr.

    1980-05-01

    Uranium and other elemental data resulting from the Hydrogeochemical and Stream Sediment Reconnaissance (HSSR) of the Trinidad National Topographic Map Series (NTMS) quadrangle, Colorado, by the Los Alamos Scientific Laboratory (LASL) are reported herein. This study was conducted as part of the United States Department of Energy's National Uranium Resource Evaluation (NURE), which is designed to provide improved estimates of the availability and economics of nuclear fuel resources and to make available to industry information for use in exploration and development of uranium resources. The HSSR data will ultimately be integrated with other NURE data (e.g., airborne radiometric surveys and geological investigations) to complete the entire NURE program. This report is a supplement to the HSSR uranium evaluation report for the Trinidad quadrange (Morris et al, 1978), which presented the field and uranium data for the 1060 water and 1240 sediment samples collected from 1768 locations in the quadrangle. The earlier report contains an evaluation of the uranium concentrations of the samples as well as descriptions of the geology, hydrology, climate, and uranium occurrences of the quadrange. This supplement presents the sediment field and uranium data again and the analyses of 42 other elements in the sediments. All uranium samples were redetermined by delayed-neutron counting (DNC) when the sediment samples were analyzed for 31 elements by neutron activation. For 99.6% of the sediment samples analyzed, the differences between the uranium contents first determined (Morris et al, 1978) and the analyses reported herein are less than 10%.

  15. The Application of Quasi-Mean-Element-Method to LEO under Additional Perturbation due to Change of Coordinate System

    NASA Astrophysics Data System (ADS)

    Tang, Jing-shi; Liu, Lin

    2010-10-01

    The perturbation caused by the oscillation of Earth's equator plane must be taken into account when working on the motion of satellite on a low Earth orbit (LEO) in the geocentric celestial coordinate system. Since 1960 s, an intermediate orbit coordinate system using true equator and mean equinox (TEME) is introduced. It effectively solves the problem and has been widely used in various applications till today. But this traditional reference frame is purely conceptual and has always been a headache when performing the transition between these systems especially for those who are unfamiliar with celestial frames. As proved in a previous paper, it is possible to avoid the intermediate TEME frame, and conversions between osculating elements and mean elements can be completed in a consistent geocentric celestial coordinate system where only short-period terms are required. In this paper, after including the improved secular and long-period terms, the quasi-mean-element-method is available to predict the orbit analytically, reaching the accuracy of 10 -6 in Earth's radius. And all these can be done in the same celestial frame. The results suggest that the celestial coordinate system (J2000.0 nowadays) can be used throughout any applications without having to introduce TEME system as intermediate frame any more.

  16. Structural Elements in a Persistent Identifier Infrastructure and Resulting Benefits for the Earth Science Community

    NASA Astrophysics Data System (ADS)

    Weigel, T.; Toussaiant, F.; Stockhause, M.; Höck, H.; Kindermann, S.; Lautenschlager, M.; Ludwig, T.

    2012-12-01

    break if individual links become unavailable. Secondly, a single service cannot interpret links if downstream solutions differ in their implementation schemas. Emerging efforts driven by the European Persistent Identifier Consortium (EPIC) aim to establish a default mechanism for structural elements at the Handle level. We motivate to make applications, which take part in the data lifecycle, aware of data derivation provenance and let them provide additional elements to the provenance graph. Since they are also Handles, DataCite DOIs can act as a corner stone and provide an entry point to discover the provenance graph. References B. Lawrence, C. Jones, B. Matthews, S. Pepler, and S. Callaghan, "Citation and peer review of data: Moving towards formal data publication," Int. J. of Digital Curation, vol. 6, no. 2, 2011. L. Moreau, "The foundations for provenance on the web," Foundations and Trends® in Web Science, vol. 2, no. 2-3, pp. 99-241, 2010. F. Toussaint, T. Weigel, H. Thiemann, H. Höck, M. Stockhause: "Application Examples for Handle System Usage", submitted to AGU 2012 session IN009.

  17. Consistent linearization of the element-independent corotational formulation for the structural analysis of general shells

    NASA Technical Reports Server (NTRS)

    Rankin, C. C.

    1988-01-01

    A consistent linearization is provided for the element-dependent corotational formulation, providing the proper first and second variation of the strain energy. As a result, the warping problem that has plagued flat elements has been overcome, with beneficial effects carried over to linear solutions. True Newton quadratic convergence has been restored to the Structural Analysis of General Shells (STAGS) code for conservative loading using the full corotational implementation. Some implications for general finite element analysis are discussed, including what effect the automatic frame invariance provided by this work might have on the development of new, improved elements.

  18. Adaptive contact elements for three-dimensional fluid-structure interfaces

    SciTech Connect

    Kulak, R.F.

    1985-01-01

    A finite element method is developed for treating the mechanics of contact between two deformable bodies which occurs, for example, at fluid-structure interfaces. The method uses a family of adaptive contact elements, which are based upon the penalty method, to handle all of the possible contact configurations that can occur between the discretized contacting bodies. The contact element's nodal connectivity is allowed to change during the computations in order to accommodate finite sliding. The infusion of these elements in the interface results in satisfying the force equilibrium condition during contact. The methodology has been implemented into the NEPTUNE code. Results are presented for an illustrative problem.

  19. Structured Extended Finite Element Methods of Solids Defined by Implicit Surfaces

    SciTech Connect

    Belytschko, T; Mish, K; Moes, N; Parimi, C

    2002-11-17

    A paradigm is developed for generating structured finite element models from solid models by means of implicit surface definitions. The implicit surfaces are defined by radial basis functions. Internal features, such as material interfaces, sliding interfaces and cracks are treated by enrichment techniques developed in the extended finite element method (X-FEM). Methods for integrating the weak form for such models are proposed. These methods simplify the generation of finite element models. Results presented for several examples show that the accuracy of this method is comparable to standard unstructured finite element methods.

  20. Protein GB1 Folding and Assembly from Structural Elements

    PubMed Central

    Bauer, Mikael C.; Xue, Wei-Feng; Linse, Sara

    2009-01-01

    Folding of the Protein G B1 domain (PGB1) shifts with increasing salt concentration from a cooperative assembly of inherently unstructured subdomains to an assembly of partly pre-folded structures. The salt-dependence of pre-folding contributes to the stability minimum observed at physiological salt conditions. Our conclusions are based on a study in which the reconstitution of PGB1 from two fragments was studied as a function of salt concentrations and temperature using circular dichroism spectroscopy. Salt was found to induce an increase in β-hairpin structure for the C-terminal fragment (residues 41 – 56), whereas no major salt effect on structure was observed for the isolated N-terminal fragment (residues 1 – 41). In line with the increasing evidence on the interrelation between fragment complementation and stability of the corresponding intact protein, we also find that salt effects on reconstitution can be predicted from salt dependence of the stability of the intact protein. Our data show that our variant (which has the mutations T2Q, N8D, N37D and reconstitutes in a manner similar to the wild type) displays the lowest equilibrium association constant around physiological salt concentration, with higher affinity observed both at lower and higher salt concentration. This corroborates the salt effects on the stability towards denaturation of the intact protein, for which the stability at physiological salt is lower compared to both lower and higher salt concentrations. Hence we conclude that reconstitution reports on molecular factors that govern the native states of proteins. PMID:19468325

  1. Erbium-doped fiber amplifier elements for structural analysis sensors

    NASA Technical Reports Server (NTRS)

    Hanna-Hawver, P.; Kamdar, K. D.; Mehta, S.; Nagarajan, S.; Nasta, M. H.; Claus, R. O.

    1992-01-01

    The use of erbium-doped fiber amplifiers (EDFA's) in optical fiber sensor systems for structural analysis is described. EDFA's were developed for primary applications as periodic regenerator amplifiers in long-distance fiber-based communication systems. Their in-line amplification performance also makes them attractive for optical fiber sensor systems which require long effective lengths or the synthesis of special length-dependent signal processing functions. Sensor geometries incorporating EDFA's in recirculating and multiple loop sensors are discussed. Noise and polarization birefringence are also considered, and the experimental development of system components is discussed.

  2. Erbium-doped fiber amplifier elements for structural analysis sensors

    NASA Astrophysics Data System (ADS)

    Hanna-Hawver, P.; Kamdar, K. D.; Mehta, S.; Nagarajan, S.; Nasta, M. H.; Claus, R. O.

    1992-06-01

    The use of erbium-doped fiber amplifiers (EDFA's) in optical fiber sensor systems for structural analysis is described. EDFA's were developed for primary applications as periodic regenerator amplifiers in long-distance fiber-based communication systems. Their in-line amplification performance also makes them attractive for optical fiber sensor systems which require long effective lengths or the synthesis of special length-dependent signal processing functions. Sensor geometries incorporating EDFA's in recirculating and multiple loop sensors are discussed. Noise and polarization birefringence are also considered, and the experimental development of system components is discussed.

  3. Effective Simulation of Delamination in Aeronautical Structures Using Shells and Cohesive Elements

    NASA Technical Reports Server (NTRS)

    Davila, Carlos G.; Camanho, Pedro P.; Turon, Albert

    2007-01-01

    A cohesive element for shell analysis is presented. The element can be used to simulate the initiation and growth of delaminations between stacked, non-coincident layers of shell elements. The procedure to construct the element accounts for the thickness offset by applying the kinematic relations of shell deformation to transform the stiffness and internal force of a zero-thickness cohesive element such that interfacial continuity between the layers is enforced. The procedure is demonstrated by simulating the response and failure of the Mixed Mode Bending test and a skin-stiffener debond specimen. In addition, it is shown that stacks of shell elements can be used to create effective models to predict the inplane and delamination failure modes of thick components. The results indicate that simple shell models can retain many of the necessary predictive attributes of much more complex 3D models while providing the computational efficiency that is necessary for design.

  4. Equivalent Dynamic Stiffness Mapping technique for identifying nonlinear structural elements from frequency response functions

    NASA Astrophysics Data System (ADS)

    Wang, X.; Zheng, G. T.

    2016-02-01

    A simple and general Equivalent Dynamic Stiffness Mapping technique is proposed for identifying the parameters or the mathematical model of a nonlinear structural element with steady-state primary harmonic frequency response functions (FRFs). The Equivalent Dynamic Stiffness is defined as the complex ratio between the internal force and the displacement response of unknown element. Obtained with the test data of responses' frequencies and amplitudes, the real and imaginary part of Equivalent Dynamic Stiffness are plotted as discrete points in a three dimensional space over the displacement amplitude and the frequency, which are called the real and the imaginary Equivalent Dynamic Stiffness map, respectively. These points will form a repeatable surface as the Equivalent Dynamic stiffness is only a function of the corresponding data as derived in the paper. The mathematical model of the unknown element can then be obtained by surface-fitting these points with special functions selected by priori knowledge of the nonlinear type or with ordinary polynomials if the type of nonlinearity is not pre-known. An important merit of this technique is its capability of dealing with strong nonlinearities owning complicated frequency response behaviors such as jumps and breaks in resonance curves. In addition, this technique could also greatly simplify the test procedure. Besides there is no need to pre-identify the underlying linear parameters, the method uses the measured data of excitation forces and responses without requiring a strict control of the excitation force during the test. The proposed technique is demonstrated and validated with four classical single-degree-of-freedom (SDOF) numerical examples and one experimental example. An application of this technique for identification of nonlinearity from multiple-degree-of-freedom (MDOF) systems is also illustrated.

  5. Finite element modeling of truss structures with frequency-dependent material damping

    NASA Technical Reports Server (NTRS)

    Lesieutre, George A.

    1991-01-01

    A physically motivated modelling technique for structural dynamic analysis that accommodates frequency dependent material damping was developed. Key features of the technique are the introduction of augmenting thermodynamic fields (AFT) to interact with the usual mechanical displacement field, and the treatment of the resulting coupled governing equations using finite element analysis methods. The AFT method is fully compatible with current structural finite element analysis techniques. The method is demonstrated in the dynamic analysis of a 10-bay planar truss structure, a structure representative of those contemplated for use in future space systems.

  6. Application of a finite element algorithm for high speed viscous flows using structured and unstructured meshes

    NASA Technical Reports Server (NTRS)

    Vemaganti, Gururaja R.; Wieting, Allan R.

    1990-01-01

    A higher-order streamline upwinding Petrov-Galerkin finite element method is employed for high speed viscous flow analysis using structured and unstructured meshes. For a Mach 8.03 shock interference problem, successive mesh adaptation was performed using an adaptive remeshing method. Results from the finite element algorithm compare well with both experimental data and results from an upwind cell-centered method. Finite element results for a Mach 14.1 flow over a 24 degree compression corner compare well with experimental data and two other numerical algorithms for both structured and unstructured meshes.

  7. STARS: A general-purpose finite element computer program for analysis of engineering structures

    NASA Technical Reports Server (NTRS)

    Gupta, K. K.

    1984-01-01

    STARS (Structural Analysis Routines) is primarily an interactive, graphics-oriented, finite-element computer program for analyzing the static, stability, free vibration, and dynamic responses of damped and undamped structures, including rotating systems. The element library consists of one-dimensional (1-D) line elements, two-dimensional (2-D) triangular and quadrilateral shell elements, and three-dimensional (3-D) tetrahedral and hexahedral solid elements. These elements enable the solution of structural problems that include truss, beam, space frame, plane, plate, shell, and solid structures, or any combination thereof. Zero, finite, and interdependent deflection boundary conditions can be implemented by the program. The associated dynamic response analysis capability provides for initial deformation and velocity inputs, whereas the transient excitation may be either forces or accelerations. An effective in-core or out-of-core solution strategy is automatically employed by the program, depending on the size of the problem. Data input may be at random within a data set, and the program offers certain automatic data-generation features. Input data are formatted as an optimal combination of free and fixed formats. Interactive graphics capabilities enable convenient display of nodal deformations, mode shapes, and element stresses.

  8. Facility for the automatic spray painting of structural elements

    SciTech Connect

    Duggins, B.D.; Goolsby, T.D.; Benham, R.A.

    1989-01-01

    A process has been developed for remote controlled spray painting of structures of various sizes and shapes with a coating of sensitive explosive. The damaging effects of a hostile nuclear burst are simulated when the explosive layer is detonated. The process has evolved from a cumbersome, motor driven carriage assembly, to a facility which employs robotics and automatic positioning hardware. This paper will describe the hardware components which have been introduced into the facility and also the software which is used to control the spray application. The proper use of this hardware/software combination allows the design in advance of operations which deposit uniform or contoured thickness coatings onto complex shapes. 7 refs., 5 figs., 2 tabs.

  9. Development of an active truss element for control of precision structures

    NASA Technical Reports Server (NTRS)

    Anderson, Eric H.; Moore, Donald M.; Fanson, James L.; Ealey, Mark A.

    1990-01-01

    An active structural element for use in precision control of large space structures is described. The active member is intended to replace a passive strut in a truss-like structure. It incorporates an eddy current displacement sensor and an actuator that is either piezoelectric (PZT) or electrostrictive (PMN). The design of the device is summarized. Performance of separate PZT and PMN actuators is compared for several properties relevant to submicrometer control of precision structures.

  10. Osmium-Isotope and Platinum-Group-Element Systematics of Impact-Melt Rocks, Chesapeake Bay Impact Structure, Virginia, USA

    NASA Technical Reports Server (NTRS)

    Lee, Seung Ryeol; Wright Horton, J., Jr.; Walker, Richard J.

    2005-01-01

    Osmium (Os) isotopes and platinum-group elements (PGEs) are useful for geochemically identifying a meteoritic component within impact structures, because meteorites are typically characterized by low (187)Os/(188)Os ratios and high PGE concentrations. In contrast, most types of crustal target rocks have high radiogenic Os and very low PGE concentrations. We have examined Os isotope and PGE systematics of impact-melt rocks and pre-impact target rocks from a 2004 test hole in the late Eocene Chesapeake Bay impact structure and from nearby coreholes. Our goal is to determine the proportion of the projectile component in the melt rock Additional information is included in the original extended abstract.

  11. PLANS; a finite element program for nonlinear analysis of structures. Volume 2: User's manual

    NASA Technical Reports Server (NTRS)

    Pifko, A.; Armen, H., Jr.; Levy, A.; Levine, H.

    1977-01-01

    The PLANS system, rather than being one comprehensive computer program, is a collection of finite element programs used for the nonlinear analysis of structures. This collection of programs evolved and is based on the organizational philosophy in which classes of analyses are treated individually based on the physical problem class to be analyzed. Each of the independent finite element computer programs of PLANS, with an associated element library, can be individually loaded and used to solve the problem class of interest. A number of programs have been developed for material nonlinear behavior alone and for combined geometric and material nonlinear behavior. The usage, capabilities, and element libraries of the current programs include: (1) plastic analysis of built-up structures where bending and membrane effects are significant, (2) three dimensional elastic-plastic analysis, (3) plastic analysis of bodies of revolution, and (4) material and geometric nonlinear analysis of built-up structures.

  12. Mechanical end joint system for connecting structural column elements

    NASA Technical Reports Server (NTRS)

    Bush, Harold G. (Inventor); Mikulas, Martin M., Jr. (Inventor); Wallsom, Richard E. (Inventor)

    1990-01-01

    A mechanical end joint system is presented that eliminates the possibility of free movements between the joint halves during loading or vibration. Both node joint body (NJB) and column end joint body (CEJB) have cylindrical engaging ends. Each of these ends has an integral semicircular tongue and groove. The two joint halves are engaged transversely - the tongue of the NJB mating with the groove of the CEJB and vice versa. The joint system employs a spring loaded internal latch mechanism housed in the CEJB. During mating, this mechanism is pushed away from the NJB and enters the NJB when mating is completed. In order to lock the joint and add a preload across the tongue and groove faces, an operating ring collar is rotated through 45 deg causing an internal mechanism to compress a Belleville washer preload mechanism. This causes an equal and opposite force to be exerted on the latch bolt and the latch plunger. This force presses the two joint halves tightly together. In order to prevent inadvertent disassembly, a secondary lock is also engaged when the joint is closed. Plungers are carried in the operating ring collar. When the joint is closed, the plungers fall into tracks on the CEJB, which allows the joint to be opened only when the operating ring collar and plungers are pushed directly away from the joining end. One application of this invention is the rapid assembly and disassembly of diverse skeletal framework structures which is extremely important in many projects involving the exploration of space.

  13. The effect of quaternary element on the thermodynamic parameters and structure of CuAlMn shape memory alloys

    NASA Astrophysics Data System (ADS)

    Aksu Canbay, C.; Karagoz, Z.

    2013-10-01

    In this study, the Cu-based shape memory alloys were produced by arc melting. We have investigated the effects of the alloying elements on the characteristic transformation temperatures, enthalpy, entropy values, and the structure of Cu-Al-Mn ternary system. The evolution of the transformation temperatures was studied by the differential scanning calorimetry. The characteristic transformation temperatures can be controlled by the variations in the aluminum and manganese content. Additionally, the effect of magnesium and iron on the transformation temperatures and thermodynamic parameters was investigated in the Cu-Al-Mn ternary system. The addition of the magnesium decreases the characteristic transformation temperatures of the Cu-Al-Mn system, but that of the iron increases. The structural changes of the samples were studied by X-ray diffraction measurements and optical microscope observations. Due to the low solubility of the magnesium, the magnesium addition into the Cu-Al-Mn system forms precipitates in the matrix. It is evaluated that the transformation parameters of the CuAlMn shape memory alloys can be controlled by the change of the alloying elements and the weight percentages of alloying elements.

  14. Finite element modeling of composite piezoelectric structures with MSC/NASTRAN

    NASA Astrophysics Data System (ADS)

    Freed, Brian D.; Babuska, Vit

    1997-06-01

    Techniques for modeling structures containing piezoelectric ceramics with MSC/NASTRAN are presented. Unlike other finite element programs such as ANSYS and ABAQUS, MSC/NASTRAN offers no piezoelectric coupled-field elements with which to model smart structures directly. Rather, the analogy between piezoelectric strain and thermally induced strain, which allows temperature change to model piezoelectric voltage actuation, must be used. The application and limitations of this method are discussed. To overcome some of the limitations in modeling piezoelectric effects with the thermal analogy, one and two dimensional finite elements which include piezoelectric coupling were developed and integrated into MSC/NASTRAN as dummy elements. The dummy elements offer an alternative method for modeling piezoelectric structural members. As actuators, the elements support charge and voltage actuation in both static and dynamic analyses. When used as sensors, both strain and strain rate outputs are supported. The elements can be used for modal, transient, and frequency response solutions and facilitate combined thermal and piezoelectric loading.

  15. Measuring Productive Elements of Multi-Word Phrase Vocabulary Knowledge among Children with English as an Additional or Only Language

    ERIC Educational Resources Information Center

    Smith, Sara A.; Murphy, Victoria A.

    2015-01-01

    Vocabulary plays a critical role in language and reading development for children, particularly those learning English as an additional language (EAL) (Stahl & Nagy, 2006). Previous research on vocabulary has mainly focused on measuring individual words without considering multi-word phrase knowledge, despite evidence that these items occur…

  16. Is the structural diversity of tripeptides sufficient for developing functional food additives with satisfactory multiple bioactivities?

    NASA Astrophysics Data System (ADS)

    Wang, Jian-Hui; Liu, Yong-Le; Ning, Jing-Heng; Yu, Jian; Li, Xiang-Hong; Wang, Fa-Xiang

    2013-05-01

    Multifunctional peptides have attracted increasing attention in the food science community because of their therapeutic potential, low toxicity and rapid intestinal absorption. However, previous study demonstrated that the limited structural variations make it difficult to optimize dipeptide molecules in a good balance between desirable and undesirable properties (F. Tian, P. Zhou, F. Lv, R. Song, Z. Li, J. Pept. Sci. 13 (2007) 549-566). In the present work, we attempt to answer whether the structural diversity is sufficient for a tripeptide to have satisfactory multiple bioactivities. Statistical test, structural examination and energetic analysis confirm that peptides of three amino acids long can bind tightly to human angiotensin converting enzyme (ACE) and thus exert significant antihypertensive efficacy. Further quantitative structure-activity relationship (QSAR) modeling and prediction of all 8000 possible tripeptides reveal that their ACE-inhibitory potency exhibits a good (positive) relationship to antioxidative activity, but has only a quite modest correlation with bitterness. This means that it is possible to find certain tripeptide entities possessing the optimal combination of strong ACE-inhibitory potency, high antioxidative activity and weak bitter taste, which are the promising candidates for developing multifunctional food additives with satisfactory multiple bioactivities. The marked difference between dipeptide and tripeptide can be attributed to the fact that the structural diversity of peptides increases dramatically with a slight change in sequence length.

  17. Incommensurate host-guest structures in compressed elements: Hume—Rothery effects as origin

    NASA Astrophysics Data System (ADS)

    Degtyareva, V. F.

    2015-11-01

    Discovery of the incommensurate structure in the element Ba under pressure 15 years ago was followed by findings of a series of similar structures in other compressed elements. Incommensurately modulated structures of the host-guest type consist of a tetragonal host structure and a guest structure. The guest structure forms chains of atoms embedded in the channels of host atoms so that the axial ratio of these subcells along the c axis is not rational. Two types of the host-guest structures have been found so far: with the host cells containing 8 atoms and 16 atoms; in these both types the guest cells contain 2 atoms. These crystal structures contain a non-integer number of atoms in their unit cell: tI11* in Bi, Sb, As, Ba, Sr, Sc and tI19* in Na, K, Rb. We consider here a close structural relationship of these host-guest structures with the binary alloy phase Au3Cd5-tI32. This phase is related to the family of the Hume-Rothery phases that is stabilized by the Fermi sphere-Brillouin zone interaction. From similar considerations for alkali and alkaline-earth elements a necessary condition for structural stability emerges in which the valence electrons band overlaps with the upper core electrons and the valence electron count increases under compression.

  18. A finite element analysis of a 3D auxetic textile structure for composite reinforcement

    NASA Astrophysics Data System (ADS)

    Ge, Zhaoyang; Hu, Hong; Liu, Yanping

    2013-08-01

    This paper reports the finite element analysis of an innovative 3D auxetic textile structure consisting of three yarn systems (weft, warp and stitch yarns). Different from conventional 3D textile structures, the proposed structure exhibits an auxetic behaviour under compression and can be used as a reinforcement to manufacture auxetic composites. The geometry of the structure is first described. Then a 3D finite element model is established using ANSYS software and validated by the experimental results. The deformation process of the structure at different compression strains is demonstrated, and the validated finite element model is finally used to simulate the auxetic behaviour of the structure with different structural parameters and yarn properties. The results show that the auxetic behaviour of the proposed structure increases with increasing compression strain, and all the structural parameters and yarn properties have significant effects on the auxetic behaviour of the structure. It is expected that the study could provide a better understanding of 3D auxetic textile structures and could promote their application in auxetic composites.

  19. Effect of reduction of strategic Columbium addition in 718 Alloy on the structure and properties

    NASA Technical Reports Server (NTRS)

    Ziegler, K. R.; Wallace, J. F.

    1985-01-01

    A series of alloys was developed having a base composition similar to Inconel 718, with reduced Cb levels of 3.00 and 1.10 wt% Cb. Substitutions of 3.0% W, 3.0W + 0.9V or Mo increased from 3.0% to 5.8% were made for the Cb in these alloys. Two additional alloys, one containing 3.49% Cb and 1.10% Ti and another containing 3.89% Cb and 1.29% Ti were also studied. Tensile properties at rooom and elevated temperatures, stress-rupture tests, and an analysis of extracted phases were carried out for each of the alloys. Additions of solid solution elements to a reduced Cb alloy had no significant effect on the properties of the alloys under either process condition. The solution and age alloys with substitutions of 1.27% i at 3.89% Cb had tensile properties similar top hose of the original alloy and stress-rupture properties superior to the original alloy. The improved stress-rupture properties were the result of significant precipitation of Ni3Ti-gamma prime in the alloy, which is more stable than gamma' at the elevated temperatures. At lower temperatures, the new alloy benefits from gamma' strengthening. With more precise control and proper processing, the reduced Cb direct-age alloy could substitute for Alloy 718 in high strength applications.

  20. Finite element based electrostatic-structural coupled analysis with automated mesh morphing

    SciTech Connect

    OWEN,STEVEN J.; ZHULIN,V.I.; OSTERGAARD,D.F.

    2000-02-29

    A co-simulation tool based on finite element principles has been developed to solve coupled electrostatic-structural problems. An automated mesh morphing algorithm has been employed to update the field mesh after structural deformation. The co-simulation tool has been successfully applied to the hysteric behavior of a MEMS switch.

  1. A role of BNLT compound addition on structure and properties of PZT ceramics

    NASA Astrophysics Data System (ADS)

    Jaita, P.; Watcharapasorn, A.; Jiansirisomboon, S.

    2010-09-01

    In this research, effects of lead-free bismuth sodium lanthanum titanate (BNLT) addition on structure and properties of lead zirconate titanate (PZT) ceramics were investigated. PZT ceramics with addition of 0.1-3.0 wt%BNLT were fabricated by a solid-state mixed oxide method and sintering at 1050-1200 °C for 2 h to obtain dense ceramics with at least 96% of theoretical density. X-ray diffraction indicated that complete solid solution occurred for all compositions. Phase identification showed both tetragonal and rhombohedral perovskite structure of PZT with no BNLT phase detected. Scanning electron micrographs of fractured PZT/BNLT ceramics showed equiaxed grain shape with both transgranular and intergranular fracture modes. Addition of BNLT was also found to reduce densification and effectively limited grain growth of PZT ceramic. Optimum Hv and KIC values were found to be 4.85 GPa and 1.56 MPa.m 1/2 for PZT/0.5 wt%BNLT sample. Among PZT/BNLT samples, room temperature dielectric constant seemed to be improved with increasing BNLT content. The maximum piezoelectric coefficient values were observed in pure PZT ceramic and were slightly decreased in BNLT-added samples. Small reduction of remanent polarization and coercive field in hysteresis loops was observed in BNLT-added samples, indicating a slightly suppressed ferroelectric interaction in this material system.

  2. Sensitivity of high strain rate of structural elements in relation to dynamics properties of material

    NASA Astrophysics Data System (ADS)

    Kruszka, Leopold; Vorobiov, Iurii S.; Ovcharova, Nataliia Iu.

    2015-09-01

    Protective structures such as process chambers, protective boxes, facing elements of vehicles, personal protection equipment, motors cases etc. widely used in modern technology has been tested in the following project. Under the influence of impact loads, the three-dimensional dynamic stress-strain state with finite dynamic displacements and deformations has arised. The deformations occur in the elastic- plastic stage. In the analysis of the high-rate deformations, the dynamic properties of the materials, which are determined based on experimental data should be taken into account. The dynamic stress state of structural elements depends essentially on the dynamic properties of the materials used. The problem is solved using the finite element method, which takes into account the specifics of the process. Boundary conditions in the element nodes must satisfy the equality movement as well as derivatives. The formed function allows to describe continuous and smooth stress changes. The numerical analysis of the dynamic stress-strain state of structural elements under impact loads, takes into account different dynamic properties of the materials. A series of numerical calculations allows to reveal the features of high-rate deformation elements of protective structures and makes recommendations to improve their dynamic strength under different loading conditions.

  3. Fast lane recognition based on morphological multi-structure element model

    NASA Astrophysics Data System (ADS)

    Lei, Tao; Fan, Yang-Yu; Huang, Lian-Bing

    2009-07-01

    This paper proposes a lane detection algorithm based on multi-structure element model of morphological. The innovative point of the algorithm lies in the facts that the flexible structure has the multi-structure elements that lane model features have, and that the algorithm adopts the morphological filtering principle to extract the pixels in the image, which is similar to the lane model. In the algorithm, the interested area is extracted by a model of trapezium from original image, which is detected by the operator of Canny, and the lanes are extracted by the structure elements, which have similar characteristics to that of lane model. Several lines are detected by Hough transformation, then the traffic lanes are reconstructed. Experiments show that this algorithm is simple and robust, and can efficiently detect the lane mask accurately and quickly.

  4. An identification method for enclosed voids restriction in manufacturability design for additive manufacturing structures

    NASA Astrophysics Data System (ADS)

    Liu, Shutian; Li, Quhao; Chen, Wenjiong; Tong, Liyong; Cheng, Gengdong

    2015-06-01

    Additive manufacturing (AM) technologies, such as selective laser sintering (SLS) and fused deposition modeling (FDM), have become the powerful tools for direct manufacturing of complex parts. This breakthrough in manufacturing technology makes the fabrication of new geometrical features and multiple materials possible. Past researches on designs and design methods often focused on how to obtain desired functional performance of the structures or parts, specific manufacturing capabilities as well as manufacturing constraints of AM were neglected. However, the inherent constraints in AM processes should be taken into account in design process. In this paper, the enclosed voids, one type of manufacturing constraints of AM, are investigated. In mathematics, enclosed voids restriction expressed as the solid structure is simplyconnected. We propose an equivalent description of simply-connected constraint for avoiding enclosed voids in structures, named as virtual temperature method (VTM). In this method, suppose that the voids in structure are filled with a virtual heating material with high heat conductivity and solid areas are filled with another virtual material with low heat conductivity. Once the enclosed voids exist in structure, the maximum temperature value of structure will be very high. Based upon this method, the simplyconnected constraint is equivalent to maximum temperature constraint. And this method can be easily used to formulate the simply-connected constraint in topology optimization. The effectiveness of this description method is illustrated by several examples. Based upon topology optimization, an example of 3D cantilever beam is used to illustrate the trade-off between manufacturability and functionality. Moreover, the three optimized structures are fabricated by FDM technology to indicate further the necessity of considering the simply-connected constraint in design phase for AM.

  5. Interactive effects between N addition and disturbance on boreal forest ecosystem structure and function

    NASA Astrophysics Data System (ADS)

    Nordin, Annika; Strengbom, Joachim; From, Fredrik

    2014-05-01

    In management of boreal forests, nitrogen (N) enrichment from atmospheric deposition or from forest fertilization can appear in combination with land-use related disturbances, i.e. tree harvesting by clear-felling. Long-term interactive effects between N enrichment and disturbance on boreal forest ecosystem structure and function are, however, poorly known. We investigated effects of N enrichment by forest fertilization done > 25 years ago on forest understory species composition in old-growth (undisturbed) forests, and in forests clear-felled 10 years ago (disturbed). In clear-felled forests we also investigated effects of the previous N addition on growth of tree saplings. The results show that the N enrichment effect on the understory species composition was strongly dependent on the disturbance caused by clear-felling. In undisturbed forests, there were small or no effects on understory species composition from N addition. In contrast, effects were large in forests first exposed to N addition and subsequently disturbed by clear-felling. Effects of N addition differed among functional groups of plants. Abundance of graminoids increased (+232%) and abundance of dwarf shrubs decreased (-44%) following disturbance in N fertilized forests. For vascular plants, the two perturbations had contrasting effects on α-(within forests) and β-diversity (among forests): in disturbed forests, N addition reduced, or had no effect on α-diversity, while β-diversity increased. For bryophytes, negative effects of disturbance on α-diversity were smaller in N fertilized forests than in forests not fertilized, while neither N addition nor disturbance had any effects on β-diversity. Moreover, sapling growth in forests clear-felled 10 years ago was significantly higher in previously N fertilized forests than in forests not fertilized. Our study show that effects of N addition on plant communities may appear small, short-lived, or even absent until exposed to a disturbance. This

  6. Equilibrium Structures of Molecules Featuring Bonds Between Second-Row Elements %STRUCTURES of Molecules Containing More than One 2ND-ROW Elements

    NASA Astrophysics Data System (ADS)

    Thorwirth, Sven; Harding, Michael E.

    2010-06-01

    Equilibrium geometries of a set of molecules containing chemical bonds between second-row elements (Al, Si, P, S, Cl) have been evaluated at the CCSD(T) level of theory in combination with large basis sets. The results of these calculations are compared against equilibrium values from experiment. Purely experimental equilibrium structures are only available for very few molecules of this kind. Consequently, empirical equilibrium structural parameters for the majority of members of the set had to be determined using ground-state rotational constants corrected for zero-point vibrational effects. The latter were obtained by second-order vibrational perturbation theory employing coupled-cluster calculations of anharmonic force fields.

  7. Effect of boron addition on the structure and magnetic properties of CoPt nanoparticles

    SciTech Connect

    Khemjeen, Yutthaya; Pinitsoontorn, Supree Chompoosor, Apiwat

    2015-05-07

    The effect of B addition on CoPt nanoparticles was investigated. The CoPt-B nanoparticles were synthesized by means of the polyol process. Transmission electron microscopy has shown that the as-synthesized particles have a spherical morphology with average size about 2–3 nm. The X-ray absorption spectroscopy and the X-ray diffraction technique showed the effect of B concentration on phase transformation. The addition of B at up to 60% promoted the formation of the L1{sub 0} phase when the nanoparticles were subjected to annealing at 600 °C. If the B content is higher than 60%, the phase transition is suppressed. The evidence of B addition on the structure of CoPt nanoparticles was further supported by the magnetic measurements. The results show that the coercivity of the annealed CoPt-B nanoparticles was enhanced by the B additions from 20% to 60%, with the maximum coercivity of 12 000 Oe for the CoPt-40%B sample.

  8. Uranium hydrogeochemical and stream sediment reconnaissance of the Newcastle NTMS quadrangle, Wyoming, including concentrations of forty-two additional elements

    SciTech Connect

    Goff, S.J.; Sandoval, W.F.; Gallimore, D.L.; Talcott, C.L.; Martinez, R.G.; Minor, M.E.; Mills, C.F.

    1980-06-01

    During the summer and fall of 1977, 533 water and 1226 sediment samples were collected from 1740 locations within the 18,000 km/sup 2/ area of the Newcastle quadrangle, Wyoming. Water samples were collected from wells and springs; sediment samples were collected from stream channels and from springs. Each water sample was analyzed for uranium, and each sediment sample was analyzed for 43 elements, including uranium and thorium. Uranium concentrations in water samples range from below the detection limit of 0.02 ppB to 702.26 ppB and have a median of 1.73 ppB and a mean of 11.76 ppB. Water samples containing high uranium concentrations (>20 ppB) generally are associated with known uranium mining activity or units known to be uranium bearing. About one-third of the water samples containing high uranium concentrations were collected from locations within the Pumpkin Buttes and Turnercrest-Ross Districts. Nearly half of the water samples containing high uranium concentrations were collected from locations just west of the Monument Hill and Highland Flats-Box Creek Districts. Similar anomalous uranium concentrations in this region have been reported updip from Exxon's Highland uranium deposits. High uranium concentrations were also found associated with the Lance Creek-Old Woman Anticline District.

  9. The addition of soft tissue replacement grafts in plastic periodontal and implant surgery: critical elements in design and execution.

    PubMed

    Zuhr, Otto; Bäumer, Daniel; Hürzeler, Markus

    2014-04-01

    Soft tissue replacement grafts have become a substantial element to increase tissue volume in plastic periodontal and implant surgery. Autogenous subepithelial connective tissue grafts are increasingly applied in aesthetic indications like soft tissue thickening, recession treatment, ridge preservation, soft tissue ridge augmentation and papilla re-construction. For the clinical performance of connective tissue graft harvesting and transplantation, a fundamental understanding of the anatomy at the donor sites and a sound knowledge of tissue integration and re-vascularization processes are required. Possible donor sites are the anterior and posterior palate including the maxillary tuberosity, providing grafts of distinct geometric shape and histologic composition. The selective clinical application of different grafts depends on the amount of required tissue, the indication and the personal preference of the treating surgeon. One of the main future challenges is to volumetrically evaluate and compare the efficacy and long-term stability of soft tissue autografts and their prospective substitutes. The aim of this review was to discuss the advantages and shortfalls of different donor sites, substitute materials and harvesting techniques. Although standardized recommendations regarding treatment choice and execution can hardly be given, guidelines for predictable and successful treatment outcomes are provided based on clinical experience and the available scientific data. PMID:24640997

  10. Numerical accuracy of linear triangular finite elements in modeling multi-holed structures

    SciTech Connect

    Sullivan, R.M.; Griffen, J.E.

    1980-06-01

    A study has been performed to quantify the accuracy of linear triangular finite elements for modeling temperature and stress fields in structures with multiple holes. The purpose of the study was to evaluate the use of these elements for the analysis of HTGR fuel blocks, which may contain up to 325 holes. Since an accurate full scale analysis was not feasible with existing methods, a representative small scale benchmark problem containing only seven holes was selected. The finite element codes used in this study were TEPC-2D for thermal analysis and SAFIRE for stress analysis. It was concluded that linear triangular finite elements are too inefficient for this application. An accurate analysis of stresses in HTGR fuel blocks will require the use of higher order elements, such as the 8-node quadrilaterals in the new TWOD code.

  11. Challenges in Integrating Nondestructive Evaluation and Finite Element Methods for Realistic Structural Analysis

    NASA Technical Reports Server (NTRS)

    Abdul-Aziz, Ali; Baaklini, George Y.; Zagidulin, Dmitri; Rauser, Richard W.

    2000-01-01

    Capabilities and expertise related to the development of links between nondestructive evaluation (NDE) and finite element analysis (FEA) at Glenn Research Center (GRC) are demonstrated. Current tools to analyze data produced by computed tomography (CT) scans are exercised to help assess the damage state in high temperature structural composite materials. A utility translator was written to convert velocity (an image processing software) STL data file to a suitable CAD-FEA type file. Finite element analyses are carried out with MARC, a commercial nonlinear finite element code, and the analytical results are discussed. Modeling was established by building MSC/Patran (a pre and post processing finite element package) generated model and comparing it to a model generated by Velocity in conjunction with MSC/Patran Graphics. Modeling issues and results are discussed in this paper. The entire process that outlines the tie between the data extracted via NDE and the finite element modeling and analysis is fully described.

  12. Typical structural elements of seismicity and impact crater morphology identified in GIS ENDDB digital models.

    NASA Astrophysics Data System (ADS)

    Mikheeva, Anna

    2014-05-01

    The subject database of the ENDDB system (Earth's Natural Disasters Database) is a combination of the EISC catalog (Earth's impact structures Catalog [1]) and seismological data of more than 60 earthquake catalogs (EC). ENDDB geographic subsystem uses the NASA ASTER GDEM data arrays to obtain a high-resolution (1 arc-second) shaded relief model, as well as the digital mapping technology, which consists in shading surface points according to their brightness controlled by the illumination angle. For example, the identifying impact craters by means of ENDDB begins with selecting the optimum base colors of the image, the parameters of illumination and shadow depth for constructing a shaded model on a regular grid of values. This procedure allows obtaining precise 3D images of the terrain and gravity patterns, and, moreover, furnishes data for recognizing standard morphological elements according to which impact structures can be visually detected. For constructing a shaded gravity anomaly with the ENDDB tools, Global marine gravity data (of models V16.1 and V18.1 [2]) are embedded into the system. These models, which are arrays of gravity pixel values, are of the resolution increased from the equator to the poles, being 30 arc-seconds per point on average. This resolution is the same as in the more recent V21.1 model. Due to these data, new morphological elements typical of impact structures, which are expressed in the shaded elevation and gravity models (identified using the ENDDB visualization tools) was found and compared in hundreds of craters from the EISC-catalog: tail-shaped asymmetry of relief, heart-shaped geometry of craters, and tail-shaped gravity lows [3] and so on. New diagnostic criteria associated with typical morphological elements revealed with advanced image processing technologies are very important to confirm the impact origin for many potential craters. The basic hypothesis of the impact-explosive tectonics [4] is that meteorite craters on the

  13. Structural Element Testing in Support of the Design of the NASA Composite Crew Module

    NASA Technical Reports Server (NTRS)

    Kellas, Sotiris; Jackson, Wade C.; Thesken, John C.; Schleicher, Eric; Wagner, Perry; Kirsch, Michael T.

    2012-01-01

    In January 2007, the NASA Administrator and Associate Administrator for the Exploration Systems Mission Directorate chartered the NASA Engineering and Safety Center (NESC) to design, build, and test a full-scale Composite Crew Module (CCM). For the design and manufacturing of the CCM, the team adopted the building block approach where design and manufacturing risks were mitigated through manufacturing trials and structural testing at various levels of complexity. Following NASA's Structural Design Verification Requirements, a further objective was the verification of design analysis methods and the provision of design data for critical structural features. Test articles increasing in complexity from basic material characterization coupons through structural feature elements and large structural components, to full-scale structures were evaluated. This paper discusses only four elements tests three of which include joints and one that includes a tapering honeycomb core detail. For each test series included are specimen details, instrumentation, test results, a brief analysis description, test analysis correlation and conclusions.

  14. Probabilistic buckling analysis of the beam steel structures subjected to fire by the stochastic finite element method

    NASA Astrophysics Data System (ADS)

    Świta, P.; Kamiński, M.

    2016-05-01

    The main purpose is to present the stochastic perturbation-based Finite Element Method analysis of the stability in the issues related to the influence of high temperature resulting from a fire directly connected with the reliability analysis of such structures. The thin-walled beam structures with constant cross-sectional thickness are uploaded with typical constant loads, variable loads and, additionally, a temperature increase and we look for the first critical value equivalent to the global stability loss. Such an analysis is carried out in the probabilistic context to determine as precisely as possible the safety margins according to the civil engineering Eurocode statements. To achieve this goal we employ the additional design-oriented Finite Element Method program and computer algebra system to get the analytical polynomial functions relating the critical pressure (or force) and several random design parameters; all the models are state-dependent as we consider an additional reduction of the strength parameters due to the temperature increase. The first four probabilistic moments of the critical forces are computed assuming that the input random parameters have all Gaussian probability functions truncated to the positive values only. Finally, the reliability index is calculated according to the First Order Reliability Method (FORM) by an application of the limit function as a difference in-between critical pressure and maximum compression stress determined in the given structures to verify their durability according to the demands of EU engineering designing codes related to the fire situation.

  15. Memristor memory element based on ZnO thin film structures

    NASA Astrophysics Data System (ADS)

    Poghosyan, A. R.; Elbakyan, E. Y.; Guo, R.; Hovsepyan, R. K.

    2015-08-01

    The memristor element for random access memory (resistance random access memory - ReRAM) was developed and investigated. The developed structure consists of a Schottky diode (1D) based on Pt/ZnO:Ga/ZnO/Pt heterostructure and a memristor (1R) based on Pt/ZnO:Ga/ZnO/ZnO:Li/Pt heterostructure. Thus the unipolar memristor memory element of 1D1R type was obtained. The heterostructures were produced by the electron-beam vacuum deposition method. The laboratory samples of the memory elements were prepared and their characteristics were studied. The proposed device has a high stability and withstands 1000 switching cycles without derating.

  16. Finite element model reduction application to parametric studies and optimization of rotorcraft structures

    NASA Technical Reports Server (NTRS)

    Hashemi-Kia, M.; Toossi, M.

    1990-01-01

    As a result of this work, a reduction procedure has been developed which can be applied to large finite element model of airframe type structures. This procedure, which is tailored to be used with MSC/NASTRAN finite element code, is applied to the full airframe dynamic finite element model of AH-64A Attack Helicopter. The applicability of the resulting reduced model to parametric and optimization studies is examined. Through application of the design sensitivity analysis, the viability and efficiency of this reduction technique has been demonstrated in a vibration reduction study.

  17. A finite element approach for large motion dynamic analysis of multibody structures in space

    NASA Technical Reports Server (NTRS)

    Chang, Che-Wei

    1989-01-01

    A three-dimensional finite element formulation for modeling the transient dynamics of constrained multibody space sructures with truss-like configurations is presented. Convected coordinate systems are used to define rigid-body motion of individual elements in the system. These systems are located at one end of each element and are oriented such that one axis passes through the other end of the element. Deformation of each element, relative to its convected coordinate system, is defined by cubic flexural shape functions as used in finite element methods of structural analysis. The formulation is oriented toward joint dominated structures and places the generalized coordinates at the joint. A transformation matrix is derived to integrate joint degree-of-freedom into the equations of motion of the element. Based on the derivation, a general-purpose code LATDYN (Large Angle Transient DYNamics) was developed. Two examples are presented to illustrate the application of the code. For the spin-up of a flexible beam, results are compared with existing solutions available in the literature. For the deployment of one bay of a deployable space truss (the Minimast), results are verified by the geometric knowledge of the system and converged solution of a successively refined model.

  18. Uranium hydrogeochemical and stream sediment reconnaissance of the Newcastle NTMS Quadrangle, Wyoming, including concentrations of forty-two additional elements

    SciTech Connect

    Goff, S.J.; Sandoval, W.F.; Gallimore, D.L.; Talcott, C.L.; Martinez, R.G.; Minor, M.E.; Mills, C.F.

    1980-06-01

    Water and sediment samples were collected and each water sample was analyzed for U, and each sediment sample was analyzed for 43 elements, including U and Th. Uranium concentrations in water samples range from below the detection limit of 0.02 ppB to 702.26 ppB and have a median of 1.73 ppB and a mean of 11.76 ppB. Water samples containing high uranium concentrations generally are associated with known uranium mining activity or units known to be uranium bearing. About one-third of the water samples containing high uranium concentrations were collected from locations within the Pumpkin Buttes and Turnercrest-Ross Districts. Nearly half of the water samples containing high uranium concentrations were collected from locations just west of the Monument Hill and Highland Flats-Box Creek Districts. Similar anomalous uranium concentrations in this region have been reported updip from Exxon's Highland uranium deposits. High uranium concentrations were also found associated with the Lance Creek-Old Woman Anticline District. Uranium concentrations in sediment samples range from 1.14 to 220.70 ppM and have a median of 3.37 ppM and a mean of 4.03 ppM. Throughout the major uranium mining districts of the Powder River Basin, sediment samples with high uranium concentrations were collected from dry streams located near wells producing water samples with high uranium concentrations. High uranium concentrations were also found associated with the Lance Creek oil field where uranium mineralization is known in the White River formation. High uranium concentrations were also found in sediment samples in areas where uranium mineralization is not known. These samples are from dry streams in areas underlain by the White River formation, the Niobrara formation, and the Pierre, Carlisle, Belle Fourche, and Mowry shales.

  19. Bim from Laser Clouds and Finite Element Analysis: Combining Structural Analysis and Geometric Complexity

    NASA Astrophysics Data System (ADS)

    Barazzetti, L.; Banfi, F.; Brumana, R.; Gusmeroli, G.; Oreni, D.; Previtali, M.; Roncoroni, F.; Schiantarelli, G.

    2015-02-01

    This paper describes the use of BIM models derived from point clouds for structural simulation based on Finite Element Analysis (FEA). Although BIM interoperability has reached a significant level of maturity, the density of laser point clouds provides very detailed BIM models that cannot directly be used in FEA software. The rationalization of the BIM towards a new finite element model is not a simple reduction of the number of nodes. The interconnections between the different elements and their materials require a particular attention: BIM technology includes geometrical aspects and structural considerations that allow one to understand and replicate the constructive elements and their mutual interaction. The information must be accurately investigated to obtain a finite element model suitable for a complete and detailed structural analysis. The aim of this paper is to prove that a drastic reduction of the quality of the BIM model is not necessary. Geometric data encapsulated into dense point clouds can be taken into consideration also for finite element analysis.

  20. Dynamic and thermal response finite element models of multi-body space structural configurations

    NASA Technical Reports Server (NTRS)

    Edighoffer, Harold H.

    1987-01-01

    Presented is structural dynamics modeling of two multibody space structural configurations. The first configuration is a generic space station model of a cylindrical habitation module, two solar array panels, radiator panel, and central connecting tube. The second is a 15-m hoop-column antenna. Discussed is the special joint elimination sequence used for these large finite element models, so that eigenvalues could be extracted. The generic space station model aided test configuration design and analysis/test data correlation. The model consisted of six finite element models, one of each substructure and one of all substructures as a system. Static analysis and tests at the substructure level fine-tuned the finite element models. The 15-m hoop-column antenna is a truss column and structural ring interconnected with tension stabilizing cables. To the cables, pretensioned mesh membrane elements were attached to form four parabolic shaped antennae, one per quadrant. Imposing thermal preloads in the cables and mesh elements produced pretension in the finite element model. Thermal preload variation in the 96 control cables was adjusted to maintain antenna shape within the required tolerance and to give pointing accuracy.

  1. EBSD analysis of magnesium addition on inclusion formation in SS400 structural steel

    SciTech Connect

    Luo, Sin-Jie; Su, Yen-Hao Frank; Lu, Muh-Jung; Kuo, Jui-Chao

    2013-08-15

    In this study, the effect of magnesium addition on the inclusion formation in SS400 steel was investigated. The experimental specimens with and without Mg addition treatment were compared. The microstructure was observed using optical microscopy after etching with 3% nital. The morphology and chemical composition of the inclusions were analyzed via scanning electron microscopy and energy dispersive spectrometry. The lattice structure and orientation of the inclusions were identified by electron backscattering diffraction. The average size of inclusions in SS400 was between 0.67 and 0.75 μm, and between 0.65 and 0.68 μm in SS400 + Mg. The 2 ppm Mg addition resulted in the oxide formation change from Al{sub 2}O{sub 3} to MgO·Al{sub 2}O{sub 3} and in the inclusion formation change from Al{sub 2}O{sub 3}–MnS to MgO·Al{sub 2}O{sub 3}–MnS. Moreover, a simple-phase MnS with an average grain size of 1 μm to 2 μm was observed in rod-like, globular, and polyhedron forms. - Highlights: • The effect of magnesium addition was investigated for SS400 steel. • 2 ppm Mg addition changes the inclusion formation from Al2O3-MnS to MgO·Al2O3-MnS. • MnS observed in inclusions exhibits rod-like, globular, and polyhedron forms.

  2. Dynamic adaptive finite element analysis of acoustic wave propagation due to underwater explosion for fluid-structure interaction problems

    NASA Astrophysics Data System (ADS)

    Emamzadeh, Seyed Shahab; Ahmadi, Mohammad Taghi; Mohammadi, Soheil; Biglarkhani, Masoud

    2015-07-01

    In this paper, an investigation into the propagation of far field explosion waves in water and their effects on nearby structures are carried out. For the far field structure, the motion of the fluid surrounding the structure may be assumed small, allowing linearization of the governing fluid equations. A complete analysis of the problem must involve simultaneous solution of the dynamic response of the structure and the propagation of explosion wave in the surrounding fluid. In this study, a dynamic adaptive finite element procedure is proposed. Its application to the solution of a 2D fluid-structure interaction is investigated in the time domain. The research includes: a) calculation of the far-field scatter wave due to underwater explosion including solution of the time-depended acoustic wave equation, b) fluid-structure interaction analysis using coupled Euler-Lagrangian approach, and c) adaptive finite element procedures employing error estimates, and re-meshing. The temporal mesh adaptation is achieved by local regeneration of the grid using a time-dependent error indicator based on curvature of pressure function. As a result, the overall response is better predicted by a moving mesh than an equivalent uniform mesh. In addition, the cost of computation for large problems is reduced while the accuracy is improved.

  3. Conserved Structural Elements in the V3 Crown of HIV-1 gp120

    SciTech Connect

    Jiang, X.; Burke, V; Totrov, M; Williams, C; Cardozo, T; Gorny, M; Zolla-Pazner, S; Kong, X

    2010-01-01

    Binding of the third variable region (V3) of the HIV-1 envelope glycoprotein gp120 to the cell-surface coreceptors CCR5 or CXCR4 during viral entry suggests that there are conserved structural elements in this sequence-variable region. These conserved elements could serve as epitopes to be targeted by a vaccine against HIV-1. Here we perform a systematic structural analysis of representative human anti-V3 monoclonal antibodies in complex with V3 peptides, revealing that the crown of V3 has four conserved structural elements: an arch, a band, a hydrophobic core and the peptide backbone. These are either unaffected by or are subject to minimal sequence variation. As these regions are targeted by cross-clade neutralizing human antibodies, they provide a blueprint for the design of vaccine immunogens that could elicit broadly cross-reactive protective antibodies.

  4. Focusing and imaging properties of diffractive optical elements with star-ring topological structure

    NASA Astrophysics Data System (ADS)

    Ke, Jie; Zhang, Junyong; Zhang, Yanli; Sun, Meizhi

    2015-08-01

    A kind of diffractive optical elements (DOE) with star-ring topological structure is proposed and their focusing and imaging properties are studied in detail. The so-called star-ring topological structure denotes that a large number of pinholes distributed in many specific zone orbits. In two dimensional plane, this structure can be constructed by two constrains, one is a mapping function, which yields total potential zone orbits, corresponding to the optical path difference (OPD); the other is a switching sequence based on the given encoded seed elements and recursion relation to operate the valid zone orbits. The focusing and imaging properties of DOE with star-ring topological structure are only determined by the aperiodic sequence, and not relevant to the concrete geometry structure. In this way, we can not only complete the traditional symmetrical DOE, such as circular Dammam grating, Fresnel zone plates, photon sieves, and their derivatives, but also construct asymmetrical elements with anisotropic diffraction pattern. Similarly, free-form surface or three dimensional DOE with star-ring topological structure can be constructed by the same method proposed. In consequence of smaller size, lighter weight, more flexible design, these elements may allow for some new applications in micro and nanphotonics.

  5. Shape and Stress Sensing of Multilayered Composite and Sandwich Structures Using an Inverse Finite Element Method

    NASA Technical Reports Server (NTRS)

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

    2013-01-01

    The marked increase in the use of composite and sandwich material systems in aerospace, civil, and marine structures leads to the need for integrated Structural Health Management systems. A key capability to enable such systems is the real-time reconstruction of structural deformations, stresses, and failure criteria that are inferred from in-situ, discrete-location strain measurements. This technology is commonly referred to as shape- and stress-sensing. Presented herein is a computationally efficient shape- and stress-sensing methodology that is ideally suited for applications to laminated composite and sandwich structures. The new approach employs the inverse Finite Element Method (iFEM) as a general framework and the Refined Zigzag Theory (RZT) as the underlying plate theory. A three-node inverse plate finite element is formulated. The element formulation enables robust and efficient modeling of plate structures instrumented with strain sensors that have arbitrary positions. The methodology leads to a set of linear algebraic equations that are solved efficiently for the unknown nodal displacements. These displacements are then used at the finite element level to compute full-field strains, stresses, and failure criteria that are in turn used to assess structural integrity. Numerical results for multilayered, highly heterogeneous laminates demonstrate the unique capability of this new formulation for shape- and stress-sensing.

  6. Soil microbial community structure and nitrogen cycling responses to agroecosystem management and carbon substrate addition

    NASA Astrophysics Data System (ADS)

    Berthrong, S. T.; Buckley, D. H.; Drinkwater, L. E.

    2011-12-01

    Fertilizer application in conventional agriculture leads to N saturation and decoupled soil C and N cycling, whereas organic practices, e.g. complex rotations and legume incorporation, often results in increased SOM and tightly coupled cycles of C and N. These legacy effects of management on soils likely affect microbial community composition and microbial process rates. This project tested if agricultural management practices led to distinct microbial communities and if those communities differed in ability to utilize labile plant carbon substrates and to produce more plant available N. We addressed several specific questions in this project. 1) Do organic and conventional management legacies on similar soils produce distinct soil bacterial and fungal community structures and abundances? 2) How do these microbial community structures change in response to carbon substrate addition? 3) How do the responses of the microbial communities influence N cycling? To address these questions we conducted a laboratory incubation of organically and conventionally managed soils. We added C-13 labelled glucose either in one large dose or several smaller pulses. We extracted genomic DNA from soils before and after incubation for TRFLP community fingerprinting. We measured C in soil pools and respiration and N in soil extracts and leachates. Management led to different compositions of bacteria and fungi driven by distinct components in organic soils. Biomass did not differ across treatments indicating that differences in cycling were due to composition rather than abundance. C substrate addition led to convergence in bacterial communities; however management still strongly influenced the difference in communities. Fungal communities were very distinct between managements and plots with substrate addition not altering this pattern. Organic soils respired 3 times more of the glucose in the first week than conventional soils (1.1% vs 0.4%). Organic soils produced twice as much

  7. Geometric identification and damage detection of structural elements by terrestrial laser scanner

    NASA Astrophysics Data System (ADS)

    Hou, Tsung-Chin; Liu, Yu-Wei; Su, Yu-Min

    2016-04-01

    In recent years, three-dimensional (3D) terrestrial laser scanning technologies with higher precision and higher capability are developing rapidly. The growing maturity of laser scanning has gradually approached the required precision as those have been provided by traditional structural monitoring technologies. Together with widely available fast computation for massive point cloud data processing, 3D laser scanning can serve as an efficient structural monitoring alternative for civil engineering communities. Currently most research efforts have focused on integrating/calculating the measured multi-station point cloud data, as well as modeling/establishing the 3D meshes of the scanned objects. Very little attention has been spent on extracting the information related to health conditions and mechanical states of structures. In this study, an automated numerical approach that integrates various existing algorithms for geometric identification and damage detection of structural elements were established. Specifically, adaptive meshes were employed for classifying the point cloud data of the structural elements, and detecting the associated damages from the calculated eigenvalues in each area of the structural element. Furthermore, kd-tree was used to enhance the searching efficiency of plane fitting which were later used for identifying the boundaries of structural elements. The results of geometric identification were compared with M3C2 algorithm provided by CloudCompare, as well as validated by LVDT measurements of full-scale reinforced concrete beams tested in laboratory. It shows that 3D laser scanning, through the established processing approaches of the point cloud data, can offer a rapid, nondestructive, remote, and accurate solution for geometric identification and damage detection of structural elements.

  8. Structural weights analysis of advanced aerospace vehicles using finite element analysis

    NASA Technical Reports Server (NTRS)

    Bush, Lance B.; Lentz, Christopher A.; Rehder, John J.; Naftel, J. Chris; Cerro, Jeffrey A.

    1989-01-01

    A conceptual/preliminary level structural design system has been developed for structural integrity analysis and weight estimation of advanced space transportation vehicles. The system includes a three-dimensional interactive geometry modeler, a finite element pre- and post-processor, a finite element analyzer, and a structural sizing program. Inputs to the system include the geometry, surface temperature, material constants, construction methods, and aerodynamic and inertial loads. The results are a sized vehicle structure capable of withstanding the static loads incurred during assembly, transportation, operations, and missions, and a corresponding structural weight. An analysis of the Space Shuttle external tank is included in this paper as a validation and benchmark case of the system.

  9. Finite element strategies for the efficient analysis and evaluation of solar collector structures

    SciTech Connect

    Koteras, J. R.

    1980-01-01

    Concentrating or reflecting structures for solar energy systems must be evaluated as to their structural integrity and optical performance. Computer studies can be used as an integral part of these evaluations. The computer studies make use of finite element structural codes coupled with post-processors that calculate optical data. If the analysis of a solar structure is to be carried out in an efficient manner, these computer codes must have certain capabilities. A number of solar energy projects at Sandia National Laboratories have made extensive use of finite element analyses. The analyses have been useful in evaluating design concepts which hold promise for large scale use in solar energy projects. Analysis procedures have been developed for some structures so that evaluations can be carried out in a straightforward manner.

  10. Structural Health Monitoring Using High-Density Fiber Optic Strain Sensor and Inverse Finite Element Methods

    NASA Technical Reports Server (NTRS)

    Vazquez, Sixto L.; Tessler, Alexander; Quach, Cuong C.; Cooper, Eric G.; Parks, Jeffrey; Spangler, Jan L.

    2005-01-01

    In an effort to mitigate accidents due to system and component failure, NASA s Aviation Safety has partnered with industry, academia, and other governmental organizations to develop real-time, on-board monitoring capabilities and system performance models for early detection of airframe structure degradation. NASA Langley is investigating a structural health monitoring capability that uses a distributed fiber optic strain system and an inverse finite element method for measuring and modeling structural deformations. This report describes the constituent systems that enable this structural monitoring function and discusses results from laboratory tests using the fiber strain sensor system and the inverse finite element method to demonstrate structural deformation estimation on an instrumented test article

  11. STARS: An integrated general-purpose finite element structural, aeroelastic, and aeroservoelastic analysis computer program

    NASA Technical Reports Server (NTRS)

    Gupta, Kajal K.

    1991-01-01

    The details of an integrated general-purpose finite element structural analysis computer program which is also capable of solving complex multidisciplinary problems is presented. Thus, the SOLIDS module of the program possesses an extensive finite element library suitable for modeling most practical problems and is capable of solving statics, vibration, buckling, and dynamic response problems of complex structures, including spinning ones. The aerodynamic module, AERO, enables computation of unsteady aerodynamic forces for both subsonic and supersonic flow for subsequent flutter and divergence analysis of the structure. The associated aeroservoelastic analysis module, ASE, effects aero-structural-control stability analysis yielding frequency responses as well as damping characteristics of the structure. The program is written in standard FORTRAN to run on a wide variety of computers. Extensive graphics, preprocessing, and postprocessing routines are also available pertaining to a number of terminals.

  12. Biomechanical investigation into the structural design of porous additive manufactured cages using numerical and experimental approaches.

    PubMed

    Tsai, Pei-I; Hsu, Ching-Chi; Chen, San-Yuan; Wu, Tsung-Han; Huang, Chih-Chieh

    2016-09-01

    Traditional solid cages have been widely used in posterior lumbar interbody fusion (PLIF) surgery. However, solid cages significantly affect the loading mechanism of the human spine due to their extremely high structural stiffness. Previous studies proposed and investigated porous additive manufactured (AM) cages; however, their biomechanical performances were analyzed using oversimplified bone-implant numerical models. Thus, the aim of this study was to investigate the outer shape and inner porous structure of the AM cages. The outer shape of the AM cages was discovered using a simulation-based genetic algorithm; their inner porous structure was subsequently analyzed parametrically using T10-S1 multilevel spine models. Finally, six types of the AM cages, which were manufactured using selective laser melting, were tested to validate the numerical outcomes. The subsidence resistance of the optimum design was superior to the conventional cage designs. A porous AM cage with a pillar diameter of 0.4mm, a pillar angle of 40°, and a porosity of between 69% and 80% revealed better biomechanical performances. Both the numerical and experimental outcomes can help surgeons to understand the biomechanics of PLIF surgery combined with the use of AM cages. PMID:27392226

  13. A finite element method for active vibration control of uncertain structures

    NASA Astrophysics Data System (ADS)

    Morales, A. L.; Rongong, J. A.; Sims, N. D.

    2012-10-01

    This work introduces a fuzzy design method using the finite element procedure to simulate and analyze active vibration control of structures subjected to uncertain parameters. The purpose of this work is to provide a tool for studying the influence of uncertainty propagation on both stability and performance of a vibration control system, whilst avoiding the need for computationally expensive probabilistic methods or complex robust control techniques. The proposed procedure applies a general and efficient strategy for computing fuzzy results to a sequence of finite element calculations. Finally, the applicability of the methodology is illustrated through some realistic case studies related to structural control where spillover instability may arise.

  14. [Developing a finite element model of human head with true anatomic structure mandible].

    PubMed

    Ma, Chunsheng; Zhang, Haizhong; Du, Huiliang; Huang, Shilin; Zhang, Jinhuan

    2005-02-01

    A finite element model of human mandible is developed from CT scan images by the technologies of three-dimensional reconstruction, image processing and meshing. The mandible model is connected to one modified head model of Hybrid III dummy with joint according to the anatomic structure and mechanical characteristics of the temporomandibular joint. Then a finite element model of the human head with the true anatomic structure mandible is developed. This model has been validated with the cadaver test results. It can be used in researches on the mechanism of craniofacial blunt-impact injury and on the assessment of injury severity. PMID:15762115

  15. Applications of a global nuclear-structure model to studies of the heaviest elements

    SciTech Connect

    Moeller, P.; Nix, J.R.

    1993-10-01

    We present some new results on heavy-element nuclear-structure properties calculated on the basis of the finite-range droplet model and folded-Yukawa single-particle potential. Specifically, we discuss calculations of nuclear ground-state masses and microscopic corrections, {alpha}-decay properties, {beta}-decay properties, fission potential-energy surfaces, and spontaneous-fission half-lives. These results, obtained in a global nuclear-structure approach, are particularly reliable for describing the stability properties of the heaviest elements.

  16. Nanoscale Imaging of Buried Structures with Elemental Specificity Using Resonant X-Ray Diffraction Microscopy

    SciTech Connect

    Song, Changyong; Bergstrom, Raymond; Ramunno-Johnson, Damien; Jiang, Huaidong; Miao, Jianwei; Paterson, David; Jonge, Martin D. de; McNulty, Ian; Lee, Jooyoung; Wang, Kang L.

    2008-01-18

    We report the first demonstration of resonant x-ray diffraction microscopy for element specific imaging of buried structures with a pixel resolution of {approx}15 nm by exploiting the abrupt change in the scattering cross section near electronic resonances. We performed nondestructive and quantitative imaging of buried Bi structures inside a Si crystal by directly phasing coherent x-ray diffraction patterns acquired below and above the Bi M{sub 5} edge. We anticipate that resonant x-ray diffraction microscopy will be applied to element and chemical state specific imaging of a broad range of systems including magnetic materials, semiconductors, organic materials, biominerals, and biological specimens.

  17. Survey and development of finite elements for nonlinear structural analysis. Volume 1: Handbook for nonlinear finite elements

    NASA Technical Reports Server (NTRS)

    1976-01-01

    A survey of research efforts in the area of geometrically nonlinear finite elements is presented. The survey is intended to serve as a guide in the choice of nonlinear elements for specific problems, and as background to provide directions for new element developments. The elements are presented in a handbook format and are separated by type as beams, plates (or shallow shells), shells, and other elements. Within a given type, the elements are identified by the assumed displacement shapes and the forms of the nonlinear strain equations. Solution procedures are not discussed except when a particular element formulation poses special problems or capabilities in this regard. The main goal of the format is to provide quick access to a wide variety of element types, in a consistent presentation format, and to facilitate comparison and evaluation of different elements with regard to features, probable accuracy, and complexity.

  18. Numerical simulation of the fatigue behavior of additive manufactured titanium porous lattice structures.

    PubMed

    Zargarian, A; Esfahanian, M; Kadkhodapour, J; Ziaei-Rad, S

    2016-03-01

    In this paper, the effects of cell geometry and relative density on the high-cycle fatigue behavior of Titanium scaffolds produced by selective laser melting and electron beam melting techniques were numerically investigated by finite element analysis. The regular titanium lattice samples with three different unit cell geometries, namely, diamond, rhombic dodecahedron and truncated cuboctahedron, and the relative density range of 0.1-0.3 were analyzed under uniaxial cyclic compressive loading. A failure event based algorithm was employed to simulate fatigue failure in the cellular material. Stress-life approach was used to model fatigue failure of both bulk (struts) and cellular material. The predicted fatigue life and the damage pattern of all three structures were found to be in good agreement with the experimental fatigue investigations published in the literature. The results also showed that the relationship between fatigue strength and cycles to failure obeyed the power law. The coefficient of power function was shown to depend on relative density, geometry and fatigue properties of the bulk material while the exponent was only dependent on the fatigue behavior of the bulk material. The results also indicated the failure surface at an angle of 45° to the loading direction. PMID:26706539

  19. Creating a Test Validated Structural Dynamic Finite Element Model of the X-56A Aircraft

    NASA Technical Reports Server (NTRS)

    Pak, Chan-Gi; Truong, Samson

    2014-01-01

    Small modeling errors in the finite element model will eventually induce errors in the structural flexibility and mass, thus propagating into unpredictable errors in the unsteady aerodynamics and the control law design. One of the primary objectives of the Multi Utility Technology Test-bed, X-56A aircraft, is the flight demonstration of active flutter suppression, and therefore in this study, the identification of the primary and secondary modes for the structural model tuning based on the flutter analysis of the X-56A aircraft. The ground vibration test-validated structural dynamic finite element model of the X-56A aircraft is created in this study. The structural dynamic finite element model of the X-56A aircraft is improved using a model tuning tool. In this study, two different weight configurations of the X-56A aircraft have been improved in a single optimization run. Frequency and the cross-orthogonality (mode shape) matrix were the primary focus for improvement, while other properties such as center of gravity location, total weight, and offdiagonal terms of the mass orthogonality matrix were used as constraints. The end result was a more improved and desirable structural dynamic finite element model configuration for the X-56A aircraft. Improved frequencies and mode shapes in this study increased average flutter speeds of the X-56A aircraft by 7.6% compared to the baseline model.

  20. Creating a Test-Validated Finite-Element Model of the X-56A Aircraft Structure

    NASA Technical Reports Server (NTRS)

    Pak, Chan-Gi; Truong, Samson

    2014-01-01

    Small modeling errors in a finite-element model will eventually induce errors in the structural flexibility and mass, thus propagating into unpredictable errors in the unsteady aerodynamics and the control law design. One of the primary objectives of the X-56A Multi-Utility Technology Testbed aircraft is the flight demonstration of active flutter suppression and, therefore, in this study, the identification of the primary and secondary modes for the structural model tuning based on the flutter analysis of the X-56A aircraft. The ground-vibration test-validated structural dynamic finite-element model of the X-56A aircraft is created in this study. The structural dynamic finite-element model of the X-56A aircraft is improved using a model-tuning tool. In this study, two different weight configurations of the X-56A aircraft have been improved in a single optimization run. Frequency and the cross-orthogonality (mode shape) matrix were the primary focus for improvement, whereas other properties such as c.g. location, total weight, and off-diagonal terms of the mass orthogonality matrix were used as constraints. The end result was an improved structural dynamic finite-element model configuration for the X-56A aircraft. Improved frequencies and mode shapes in this study increased average flutter speeds of the X-56A aircraft by 7.6% compared to the baseline model.

  1. CMB topography and electrical conductivity as additional constraints for the lowermost mantle thermo-chemical structure

    NASA Astrophysics Data System (ADS)

    Deschamps, F.; Yin, Y.; Tackley, P. J.

    2013-12-01

    A variety of seismic observations, including tomographic models, indicate that the lowermost mantle is strongly heterogeneous. Seismic observations further support a thermo-chemical origin for the large scale heterogeneities. In particular, the large low-shear wave velocity provinces (LLSVP) observed by global tomographic images are better explained by a combination of thermal and chemical anomalies. Despite the accuracy of seismic information, uncertainties and trade-off still prevent the determination of a detailed lower mantle thermo-chemical structure. For instance, the nature of chemical heterogeneities and the exact role played by the post-perovskite phase transition are still debated. Additional constraints are needed to discriminate between the possible models of structure and dynamics of the lower mantle. Here, we consider two potential additional constraints, the electrical conductivity and the dynamic topography at the core-mantle boundary (CMB). Unlike density and seismic velocities, electrical conductivity increases with temperature. In addition, it strongly varies with the iron and silicate content. Using appropriate mineral physics data, we calculated a 3D distribution of electrical conductivity in lower mantle from the thermo-chemical structure inferred by probabilistic tomography, which maps iron and silicate excess in the LLSVP. In the lowermost mantle, we observe a belt of high conductivity, with maximum values around 20 S/m located in the LLSVP. Such a belt may trigger electric currents in the lowermost mantle and induce magnetic field variations with period of one year or more. It may thus be seen by global models of electrical conductivity. Unfortunately, such models do not sample yet regions deeper than 2000 km. A second, independent constraint we explored is the dynamic topography at the CMB. We used stagYY to calculate the dynamic topography associated with several models of thermo-chemical convection, and observe strong differences

  2. The central element of the synaptonemal complex in mice is organized as a bilayered junction structure.

    PubMed

    Hernández-Hernández, Abrahan; Masich, Sergej; Fukuda, Tomoyuki; Kouznetsova, Anna; Sandin, Sara; Daneholt, Bertil; Höög, Christer

    2016-06-01

    The synaptonemal complex transiently stabilizes pairing interactions between homologous chromosomes during meiosis. Assembly of the synaptonemal complex is mediated through integration of opposing transverse filaments into a central element, a process that is poorly understood. We have, here, analyzed the localization of the transverse filament protein SYCP1 and the central element proteins SYCE1, SYCE2 and SYCE3 within the central region of the synaptonemal complex in mouse spermatocytes using immunoelectron microscopy. Distribution of immuno-gold particles in a lateral view of the synaptonemal complex, supported by protein interaction data, suggest that the N-terminal region of SYCP1 and SYCE3 form a joint bilayered central structure, and that SYCE1 and SYCE2 localize in between the two layers. We find that disruption of SYCE2 and TEX12 (a fourth central element protein) localization to the central element abolishes central alignment of the N-terminal region of SYCP1. Thus, our results show that all four central element proteins, in an interdependent manner, contribute to stabilization of opposing N-terminal regions of SYCP1, forming a bilayered transverse-filament-central-element junction structure that promotes synaptonemal complex formation and synapsis. PMID:27103161

  3. Wave motion analysis in arch structures via wavelet finite element method

    NASA Astrophysics Data System (ADS)

    Yang, Zhibo; Chen, Xuefeng; Li, Xiang; Jiang, Yongying; Miao, Huihui; He, Zhengjia

    2014-01-01

    The application of B-spline wavelet on interval (BSWI) finite element method for wave motion analysis in arch structures is presented in this paper. Instead of traditional polynomial interpolation, scaling functions at certain scales have been adopted to form the shape functions and construct wavelet-based elements. Different from other wavelet numerical methods adding wavelets directly, the element displacement field represented by the coefficients of wavelets expansions is transformed from wavelet space to physical space via the corresponding transformation matrix. The energy functional of the arch is obtained by the generalized shell theory, and the finite element model for wave motion analysis is constructed according to Hamilton's principle and the central difference method in time domain. Taking the practical application into account, damaged arch waveguides are also investigated. Proper analysis of the responses from structure damages allows one to indicate the location very precisely. This paper mainly focuses on the crack in structures. Based on Castigliano's theorem and the Pairs equation, the local flexibility of crack is formulated for BSWI element. Numerical experiments are performed to study the effect of wave propagations in arch waveguides, that is, frequency dispersion and mode spilt in the arch. The responses of the arch with cracks are simulated under the broad-band, narrow-band and chirp excitations. In order to estimate the spatial, time and frequency concentrations of responses, the reciprocal length, time-frequency transform and correlation coefficient are introduced in this investigation.

  4. Three Dimensional Viscous Finite Element Formulation For Acoustic Fluid Structure Interaction

    PubMed Central

    Cheng, Lei; White, Robert D.; Grosh, Karl

    2010-01-01

    A three dimensional viscous finite element model is presented in this paper for the analysis of the acoustic fluid structure interaction systems including, but not limited to, the cochlear-based transducers. The model consists of a three dimensional viscous acoustic fluid medium interacting with a two dimensional flat structure domain. The fluid field is governed by the linearized Navier-Stokes equation with the fluid displacements and the pressure chosen as independent variables. The mixed displacement/pressure based formulation is used in the fluid field in order to alleviate the locking in the nearly incompressible fluid. The structure is modeled as a Mindlin plate with or without residual stress. The Hinton-Huang’s 9-noded Lagrangian plate element is chosen in order to be compatible with 27/4 u/p fluid elements. The results from the full 3d FEM model are in good agreement with experimental results and other FEM results including Beltman’s thin film viscoacoustic element [2] and two and half dimensional inviscid elements [21]. Although it is computationally expensive, it provides a benchmark solution for other numerical models or approximations to compare to besides experiments and it is capable of modeling any irregular geometries and material properties while other numerical models may not be applicable. PMID:20174602

  5. A finite element approach for the dynamic analysis of joint-dominated structures

    NASA Technical Reports Server (NTRS)

    Chang, Che-Wei; Wu, Shih-Chin

    1991-01-01

    A finite element method to model dynamic structural systems undergoing large rotations is presented. The dynamic systems are composed of rigid joint bodies and flexible beam elements. The configurations of these systems are subject to change due to the relative motion in the joints among interconnected elastic beams. A body fixed reference is defined for each joint body to describe the joint body's displacements. Using the finite element method and the kinematic relations between each flexible element and its corotational reference, the total displacement field of an element, which contains gross rigid as well as elastic effects, can be derived in terms of the translational and rotational displacements of the two end nodes. If one end of an element is hinged to a joint body, the joint body's displacements and the hinge degree of freedom at the end are used to represent the nodal displacements. This results in a highly coupled system of differential equations written in terms of hinge degrees of freedom as well as the rotational and translational displacements of joint bodies and element nodes.

  6. Genomic-scale comparison of sequence- and structure-based methods of function prediction: Does structure provide additional insight?

    PubMed Central

    Fetrow, Jacquelyn S.; Siew, Naomi; Di Gennaro, Jeannine A.; Martinez-Yamout, Maria; Dyson, H. Jane; Skolnick, Jeffrey

    2001-01-01

    A function annotation method using the sequence-to-structure-to-function paradigm is applied to the identification of all disulfide oxidoreductases in the Saccharomyces cerevisiae genome. The method identifies 27 sequences as potential disulfide oxidoreductases. All previously known thioredoxins, glutaredoxins, and disulfide isomerases are correctly identified. Three of the 27 predictions are probable false-positives. Three novel predictions, which subsequently have been experimentally validated, are presented. Two additional novel predictions suggest a disulfide oxidoreductase regulatory mechanism for two subunits (OST3 and OST6) of the yeast oligosaccharyltransferase complex. Based on homology, this prediction can be extended to a potential tumor suppressor gene, N33, in humans, whose biochemical function was not previously known. Attempts to obtain a folded, active N33 construct to test the prediction were unsuccessful. The results show that structure prediction coupled with biochemically relevant structural motifs is a powerful method for the function annotation of genome sequences and can provide more detailed, robust predictions than function prediction methods that rely on sequence comparison alone. PMID:11316881

  7. Modeling of thin structures in eddy current testing with shell elements

    NASA Astrophysics Data System (ADS)

    Ospina, A.; Santandrea, L.; Le Bihan, Y.; Marchand, C.

    2010-11-01

    The modeling and design of eddy currents sensors for non-destructive testing applications, generally, requires numerical methods. Among these methods, the finite element method is one of the most used. Indeed, it presents a great capability to treat a large variety of configurations. However, in the study of eddy current testing problems, the existence of structures that have a geometrical dimension smaller than the others (thin air gaps, coatings...) will lead to difficulties related to the meshing process. The introduction of particular elements such as shell elements allows to simplify the modeling of these problems. In this paper, the shell elements are used in two different 2D axisymmetric formulations, the electric formulation a* and the magnetic formulation t-ϕ in order to simulate the behaviour of the electromagnetic fields. The results obtained with the two formulations are compared with analytical solutions.

  8. Properties of Inconel 625 Mesh Structures Grown by Electron Beam Additive Manufacturing

    SciTech Connect

    List III, Frederick Alyious; Dehoff, Ryan R; Lowe, Larry E; Sames, William J

    2014-01-01

    Relationships between electron beam parameters (beam current, beam speed, and beam focus) and physical properties (mass, diameter, elastic modulus, and yield strength) have been investigated for Inconel 625 mesh cubes fabricated using an additive manufacturing technology based on electron beam melting. The elastic modulus and yield strength of the mesh cubes have been systematically varied by approximately a factor of ten by changing the electron beam parameters. Simple models have been used to understand better these relationships. Structural anisotropies of the mesh associated with the layered build architecture have been observed and may contribute, along with microstructural anisotropies, to the anisotropic mechanical properties of the mesh. Knowledge of this kind is likely applicable to other metal and alloy systems and is essential to rapidly realize the full potential of this burgeoning technology.

  9. Application and testing of additive manufacturing for mirrors and precision structures

    NASA Astrophysics Data System (ADS)

    Sweeney, Michael; Acreman, Martyn; Vettese, Tom; Myatt, Ray; Thompson, Mike

    2015-09-01

    Additive Manufacturing (aka AM, and 3-D printing) is widely touted in the media as the foundation for the next industrial revolution. Beneath the hype, AM does indeed offer profound advantages in lead-time, dramatically reduced consumption of expensive raw materials, while enabling new and innovative design forms that cannot be produced by other means. General Dynamics and their industry partners have begun to embrace this technology for mirrors and precision structures used in the aerospace, defense, and precision optical instrumentation industries. Aggressively lightweighted, open and closed back test mirror designs, 75-150 mm in size, were first produced by AM from several different materials. Subsequent optical finishing and test experiments have exceeded expectations for density, surface finish, dimensional stability and isotropy of thermal expansion on the optical scale of measurement. Materials currently under examination include aluminum, titanium, beryllium, aluminum beryllium, Inconel 625, stainless steel/bronze, and PEKK polymer.

  10. Tailoring of Boehmite-Derived Aluminosilicate Aerogel Structure and Properties: Influence of Ti Addition

    NASA Technical Reports Server (NTRS)

    Hurwitz, Frances I.; Guo, Haiquan; Sheets, Erik J.; Miller, Derek R.; Newlin, Katy N.

    2010-01-01

    Aluminosilicate aerogels offer potential for extremely low thermal conductivities at temperatures greater than 900 C, beyond where silica aerogels reach their upper temperature limits. Aerogels have been synthesized at various Al:Si ratios, including mullite compositions, using Boehmite (AlOOH) as the Al source, and tetraethoxy orthosilicate as the Si precursor. The Boehmite-derived aerogels are found to form by a self-assembly process of AlOOH crystallites, with Si-O groups on the surface of an alumina skeleton. Morphology, surface area and pore size varies with the crystallite size of the starting Boehmite powder, as well as with synthesis parameters. Ternary systems, including Al-Si-Ti aerogels incorporating a soluble Ti precursor, are possible with careful control of pH. The addition of Ti influences sol viscosity, gelation time pore structure and pore size distribution, as well as phase formation on heat treatment.

  11. Finite element thermal-structural analysis of cable-stiffened space structues

    NASA Technical Reports Server (NTRS)

    Thornton, E. A.; Dechaumphai, P.; Pandey, A. K.

    1984-01-01

    Finite element thermal-structural analyses of large, cable-stiffened space structures are presented. A computational scheme for the calculation of prestresses in the cable-stiffened structures is also described. The determination of thermal loads on orbiting space structures due to environment heating is discussed briefly. Three finite element structural analysis techniques are presented for the analysis of prestressed structures. Linear, stress stiffening, and large displacement analysis techniques were investigated. These three techniques were employed for analysis of prestressed cable structures at different prestress levels. The analyses produced similar results at small prestress, but at higher prestress, differences between the results became significant. For the cable-stiffened structures studied, the linear analysis technique may not provide acceptable results. The stress stiffening analysis technique may yield results of acceptable accuracy depending upon the level of prestress. The large displacement analysis technique produced accurate results over a wide range of prestress and is recommended as a general analysis technique for thermal-structural analysis of cable-stiffened space structures.

  12. Structural Anomaly Detection Using Fiber Optic Sensors and Inverse Finite Element Method

    NASA Technical Reports Server (NTRS)

    Quach, Cuong C.; Vazquez, Sixto L.; Tessler, Alex; Moore, Jason P.; Cooper, Eric G.; Spangler, Jan. L.

    2005-01-01

    NASA Langley Research Center is investigating a variety of techniques for mitigating aircraft accidents due to structural component failure. One technique under consideration combines distributed fiber optic strain sensing with an inverse finite element method for detecting and characterizing structural anomalies anomalies that may provide early indication of airframe structure degradation. The technique identifies structural anomalies that result in observable changes in localized strain but do not impact the overall surface shape. Surface shape information is provided by an Inverse Finite Element Method that computes full-field displacements and internal loads using strain data from in-situ fiberoptic sensors. This paper describes a prototype of such a system and reports results from a series of laboratory tests conducted on a test coupon subjected to increasing levels of damage.

  13. Structural elements defining elongation factor Tu mediated suppression of codon ambiguity

    PubMed Central

    Roy, Hervé; Becker, Hubert Dominique; Mazauric, Marie-Hélène; Kern, Daniel

    2007-01-01

    In most prokaryotes Asn-tRNAAsn and Gln-tRNAGln are formed by amidation of aspartate and glutamate mischarged onto tRNAAsn and tRNAGln, respectively. Coexistence in the organism of mischarged Asp-tRNAAsn and Glu-tRNAGln and the homologous Asn-tRNAAsn and Gln-tRNAGln does not, however, lead to erroneous incorporation of Asp and Glu into proteins, since EF-Tu discriminates the misacylated tRNAs from the correctly charged ones. This property contrasts with the canonical function of EF-Tu, which is to non-specifically bind the homologous aa-tRNAs, as well as heterologous species formed in vitro by aminoacylation of non-cognate tRNAs. In Thermus thermophilus that forms the Asp-tRNAAsn intermediate by the indirect pathway of tRNA asparaginylation, EF-Tu must discriminate the mischarged aminoacyl-tRNAs (aa-tRNA). We show that two base pairs in the tRNA T-arm and a single residue in the amino acid binding pocket of EF-Tu promote discrimination of Asp-tRNAAsn from Asn-tRNAAsn and Asp-tRNAAsp by the protein. Our analysis suggests that these structural elements might also contribute to rejection of other mischarged aa-tRNAs formed in vivo that are not involved in peptide elongation. Additionally, these structural features might be involved in maintaining a delicate balance of weak and strong binding affinities between EF-Tu and the amino acid and tRNA moieties of other elongator aa-tRNAs. PMID:17478519

  14. Synthesis of Ti-Ta alloys with dual structure by incomplete diffusion between elemental powders.

    PubMed

    Liu, Yong; Li, Kaiyang; Wu, Hong; Song, Min; Wang, Wen; Li, Nianfeng; Tang, Huiping

    2015-11-01

    In this work, powder metallurgical (PM) Ti-Ta alloys were sintered using blended elemental powders. A dual structure, consisting of Ti-rich and Ta-rich zones, was formed due to the insufficient diffusion between Ti and Ta powders. The microstructure, mechanical properties and in vitro biological properties of the alloys were studied. Results indicated that the alloys have inhomogenous microstructures and compositions, but the grain structures were continuous from the Ti-rich zone to the Ta-rich zone. The Ta-rich zone exhibited a much finer grain size than the Ti-rich zone. The alloys had a high relative density in the range of 95-98%, with the porosity increasing with the content of Ta due to the increased difficulty in sintering and the formation of Kirkendall pores. The alloys had a good combination of low elastic modulus and high tensile strength. The strength of alloys was almost doubled compared to that of the ingot metallurgy alloys with the same compositions. The low elastic modulus was due to the residual pores and the alloying effect of Ta, while the high tensile strength resulted from the strengthening effects of solid solution, fine grain size and α phase. The alloys had a high biocompatibility due to the addition of Ta, and were suitable for the attachment of cells due to the surface porosity. It was also indicated that PM Ti-(20-30)Ta alloys are promising for biomedical applications after the evaluations of both the mechanical and the biological properties. PMID:26275506

  15. Pounding Effects on the Earthquake Response of Adjacent Reinforced Concrete Structures Strengthened by Cable Elements

    NASA Astrophysics Data System (ADS)

    Liolios, Angelos; Liolios, Asterios; Hatzigeorgiou, George; Radev, Stefan

    2014-06-01

    A numerical approach for estimating the effects of pounding (seismic interaction) on the response of adjacent Civil Engineering structures is presented. Emphasis is given to reinforced concrete (RC) frames of existing buildings which are seismically strengthened by cable-elements. A double discretization, in space by the Finite Element Method and in time by a direct incremental approach is used. The unilateral behaviours of both, the cable-elements and the interfaces contact-constraints, are taken strictly into account and result to inequality constitutive conditions. So, in each time-step, a non-convex linear complementarity problem is solved. It is found that pounding and cable strengthening have significant effects on the earthquake response and, hence, on the seismic upgrading of existing adjacent RC structures.

  16. Application of the multi-scale finite element method to wave propagation problems in damaged structures

    NASA Astrophysics Data System (ADS)

    Casadei, F.; Ruzzene, M.

    2011-04-01

    This work illustrates the possibility to extend the field of application of the Multi-Scale Finite Element Method (MsFEM) to structural mechanics problems that involve localized geometrical discontinuities like cracks or notches. The main idea is to construct finite elements with an arbitrary number of edge nodes that describe the actual geometry of the damage with shape functions that are defined as local solutions of the differential operator of the specific problem according to the MsFEM approach. The small scale information are then brought to the large scale model through the coupling of the global system matrices that are assembled using classical finite element procedures. The efficiency of the method is demonstrated through selected numerical examples that constitute classical problems of great interest to the structural health monitoring community.

  17. Novel technique for internal structure and elemental distribution analyses of granular sludge from reactors for wastewater treatment.

    PubMed

    Cao, Xiaolei; Cao, Hongbin; Sheng, Yuxing; You, Haixia; Zhang, Yi

    2013-03-01

    A novel technique for internal structure and elemental distribution analyses of granular sludge is presented. Sludge samples were freeze-dried and embedded in epoxy resin to form a module, which were then ground and polished to obtain sequential cross-sections. The cross-sections were analyzed by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). SEM observations showed that one granule was formed having several cores with different inorganic minerals, rather than a single core. EDX results indicate that the main elements of the granules are O, Ca, Mg, and P. In addition, the distribution areas of calcium and magnesium in the granule do not coincide. PMID:23160739

  18. Effect of calcium chloride addition on ice cream structure and quality.

    PubMed

    Costa, F F; Resende, J V; Abreu, L R; Goff, H D

    2008-06-01

    The influence of calcium fortification by the addition of calcium chloride on quality parameters of ice cream based on physical properties was investigated, as was the effect of kappa-carrageenan at modifying the effects of this calcium fortification. Four ice cream mixes of conventional composition, with added kappa-carrageenan (0 or 0.025%) and added calcium chloride (0 or 4.4 g L(-1) = 40 mM of added Ca(2+)), were prepared. Modulated temperature-differential scanning calorimetry was used to investigate the effect of calcium chloride on the nucleation temperature, enthalpy of melting, and freezing point depression. The protein composition of 15.4% (wt/wt) reconstituted skim milk powder solutions with or without 4.4 g L(-1) added CaCl(2) and in the supernatant after ultracentrifugation was determined. Fat particle size distributions in ice cream were characterized by light scattering. Ice crystal sizes before and after temperature cycling were determined by cold-stage light microscopy. The results demonstrated that the addition of calcium chloride led to a substantial increase in ice crystal sizes and in fat partial coalescence, which were exacerbated by the addition of kappa-carrageenan. These results can be explained by the interaction between Ca(2+) ions and casein micelles, rather than any effects on freezing point depression. The calcium ions led to a more compact micelle, less serum beta-casein, and high fat destabilization, all of which would be expected to reduce macromolecular structure and volume occupancy in the unfrozen phase, which led to increased rates of ice recrystallization. PMID:18487638

  19. Calculation of the hyperfine structure of the superheavy elements Z=119 and Z=120{sup +}

    SciTech Connect

    Dinh, T. H.; Dzuba, V. A.; Flambaum, V. V.

    2009-10-15

    The hyperfine-structure constants of the lowest s and p{sub 1/2} states of superheavy elements Z=119 and Z=120{sup +} are calculated using ab initio approach. Core polarization and dominating correlation effects are included to all orders. Breit and quantum electrodynamic effects are also considered. Similar calculations for Cs, Fr, Ba{sup +}, and Ra{sup +} are used to control the accuracy. The dependence of the hyperfine-structure constants on the nuclear radius is discussed.

  20. Addition of cement to lime-based mortars: Effect on pore structure and vapor transport

    SciTech Connect

    Mosquera, M.J. . E-mail: mariajesus.mosquera@uca.es; Silva, B.; Prieto, B.; Ruiz-Herrera, E.

    2006-09-15

    The main focus of this work is to determine the effect of cement addition, a common practice in many restorations, on the pore structure of lime-based mortars. A second target is to establish correlations between microstructure and water vapor transport across the mortar, which is a key characteristic of building decay. In order to achieve these objectives, we prepared a set of mortars consisting of air-hardening lime with a progressively increasing cement content, as well as a mortar containing hydraulic lime. Several different techniques, most notably mercury intrusion porosimetry and scanning electron microscopy in the backscatter mode, were used to investigate the pore structure. The results from these procedures led to the conclusion that porosity and pore size are progressively reduced as cement content increases. Moreover, an excellent correlation between pore radius parameter and the vapor diffusion coefficient was established. Hydraulic lime mortar exhibited textural parameters and diffusivity values halfway between those of the different lime/cement mixes studied.

  1. Children's Understanding of the Additive Composition of Number and of the Decimal Structure: What Is the Relationship?

    ERIC Educational Resources Information Center

    Krebs, Georgina; Squire, Sarah; Bryant, Peter

    2003-01-01

    Nunes and Bryant (Children doing mathematics, Blackwell, Oxford, 1996) proposed that an understanding of the additive composition of number could be a precursor to an understanding of the decimal structure. If this is so, children should achieve an understanding of additive composition before they can handle the decimal structure. The aim of our…

  2. Simulation of wind effects on tall structures by finite element method

    NASA Astrophysics Data System (ADS)

    Ebrahimi, Masood

    2015-07-01

    In the present study finite element method is used to predict the wind forces on a tall structure. The governing equations of mass and momentum with boundary conditions are solved. The κ-ɛ turbulence model is utilized to calculate the turbulence viscosity. The results are independent from the generated mesh. The numerical results are validated with American Society of Civil Engineering standards.

  3. Simulation of wind effects on tall structures by finite element method

    NASA Astrophysics Data System (ADS)

    Ebrahimi, Masood

    2016-06-01

    In the present study finite element method is used to predict the wind forces on a tall structure. The governing equations of mass and momentum with boundary conditions are solved. The κ- ɛ turbulence model is utilized to calculate the turbulence viscosity. The results are independent from the generated mesh. The numerical results are validated with American Society of Civil Engineering standards.

  4. Aromatization of Propane over Element-Alumosilicate Catalysts with ZSM-5 Structure

    NASA Astrophysics Data System (ADS)

    Vosmerikova, L. N.; Volynkina, A. N.; Vosmerikov, A. V.

    2014-08-01

    A method of hydrothermal crystallization of alkaline alumosilicagels is used to manufacture element-alumosilicates with ZSM-5 structure. Their physicochemical and acid properties are investigated and their catalytic activity in the course of propane conversion to aromatic hydrocarbons is determined. The Ga-alumosilicate is found to be the most efficient zeolite catalyst for propane aromatization.

  5. DYCAST: A finite element program for the crash analysis of structures

    NASA Technical Reports Server (NTRS)

    Pifko, A. B.; Winter, R.; Ogilvie, P.

    1987-01-01

    DYCAST is a nonlinear structural dynamic finite element computer code developed for crash simulation. The element library contains stringers, beams, membrane skin triangles, plate bending triangles and spring elements. Changing stiffnesses in the structure are accounted for by plasticity and very large deflections. Material nonlinearities are accommodated by one of three options: elastic-perfectly plastic, elastic-linear hardening plastic, or elastic-nonlinear hardening plastic of the Ramberg-Osgood type. Geometric nonlinearities are handled in an updated Lagrangian formulation by reforming the structure into its deformed shape after small time increments while accumulating deformations, strains, and forces. The nonlinearities due to combined loadings are maintained, and stiffness variation due to structural failures are computed. Numerical time integrators available are fixed-step central difference, modified Adams, Newmark-beta, and Wilson-theta. The last three have a variable time step capability, which is controlled internally by a solution convergence error measure. Other features include: multiple time-load history tables to subject the structure to time dependent loading; gravity loading; initial pitch, roll, yaw, and translation of the structural model with respect to the global system; a bandwidth optimizer as a pre-processor; and deformed plots and graphics as post-processors.

  6. effect of hydrogen addition and burner diameter on the stability and structure of lean, premixed flames

    NASA Astrophysics Data System (ADS)

    Kaufman, Kelsey Leigh

    Low swirl burners (LSBs) have gained popularity in heating and gas power generation industries, in part due to their proven capacity for reducing the production of NOx, which in addition to reacting to form smog and acid rain, plays a central role in the formation of the tropospheric ozone layer. With lean operating conditions, LSBs are susceptible to combustion instability, which can result in flame extinction or equipment failure. Extensive work has been performed to understand the nature of LSB combustion, but scaling trends between laboratory- and industrial-sized burners have not been established. Using hydrogen addition as the primary method of flame stabilization, the current work presents results for a 2.54 cm LSB to investigate potential effects of burner outlet diameter on the nature of flame stability, with focus on flashback and lean blowout conditions. In the lean regime, the onset of instability and flame extinction have been shown to occur at similar equivalence ratios for both the 2.54 cm and a 3.81 cm LSB and depend on the resolution of equivalence ratios incremented. Investigations into flame structures are also performed. Discussion begins with a derivation for properties in a multicomponent gas mixture used to determine the Reynolds number (Re) to develop a condition for turbulent intensity similarity in differently-sized LSBs. Based on this requirement, operating conditions are chosen such that the global Reynolds number for the 2.54 cm LSB is within 2% of the Re for the 3.81 cm burner. With similarity obtained, flame structure investigations focus on flame front curvature and flame surface density (FSD). As flame structure results of the current 2.54 cm LSB work are compared to results for the 3.81 cm LSB, no apparent relationship is shown to exist between burner diameter and the distribution of flame surface density. However, burner diameter is shown to have a definite effect on the flame front curvature. In corresponding flow conditions, a

  7. Influence of alloying elements Nb, Zr, Sn, and oxygen on structural stability and elastic properties of the Ti2448 alloy

    NASA Astrophysics Data System (ADS)

    Dai, J. H.; Song, Y.; Li, W.; Yang, R.; Vitos, L.

    2014-01-01

    The mechanisms of how alloying elements and oxygen influence the stability and elastic properties of binary Ti-X (X = Nb, Zr, or Sn) and Ti2448 (Ti-24Nb-4Zr-8Sn in wt.%) alloys are studied via first principles calculations. In addition to the fully disordered solid solution phase, we consider 44 quasirandom configurations to search for the possible distributions of the alloying elements in Ti2448. Our results show that all alloying elements considered here are good β-stabilizers for Ti, and the formation energies are greatly affected by their distributions. The site preference of oxygen and its concentration dependence in binary Ti alloys and in Ti2448 are also investigated. Oxygen prefers to occupy the octahedral site regardless of the concentrations of the alloys and strongly interacts with Ti and Nb in Ti-Nb. The elastic properties of Ti2448 alloy and the influence of oxygen on the elastic parameters are evaluated. The calculated polycrystalline Young's modulus of the Ti2448 alloy is very close to that of the human bone (10-40 GPa). We find that oxygen has a weak effect on the elastic moduli of Ti2448. The electronic structures are analyzed to reveal how the alloying elements and oxygen influence the stability of binary Ti-X and Ti2448 alloys.

  8. Simulation of dynamics of beam structures with bolted joints using adjusted Iwan beam elements

    NASA Astrophysics Data System (ADS)

    Song, Y.; Hartwigsen, C. J.; McFarland, D. M.; Vakakis, A. F.; Bergman, L. A.

    2004-05-01

    Mechanical joints often affect structural response, causing localized non-linear stiffness and damping changes. As many structures are assemblies, incorporating the effects of joints is necessary to produce predictive finite element models. In this paper, we present an adjusted Iwan beam element (AIBE) for dynamic response analysis of beam structures containing joints. The adjusted Iwan model consists of a combination of springs and frictional sliders that exhibits non-linear behavior due to the stick-slip characteristic of the latter. The beam element developed is two-dimensional and consists of two adjusted Iwan models and maintains the usual complement of degrees of freedom: transverse displacement and rotation at each of the two nodes. The resulting element includes six parameters, which must be determined. To circumvent the difficulty arising from the non-linear nature of the inverse problem, a multi-layer feed-forward neural network (MLFF) is employed to extract joint parameters from measured structural acceleration responses. A parameter identification procedure is implemented on a beam structure with a bolted joint. In this procedure, acceleration responses at one location on the beam structure due to one known impulsive forcing function are simulated for sets of combinations of varying joint parameters. A MLFF is developed and trained using the patterns of envelope data corresponding to these acceleration histories. The joint parameters are identified through the trained MLFF applied to the measured acceleration response. Then, using the identified joint parameters, acceleration responses of the jointed beam due to a different impulsive forcing function are predicted. The validity of the identified joint parameters is assessed by comparing simulated acceleration responses with experimental measurements. The capability of the AIBE to capture the effects of bolted joints on the dynamic responses of beam structures, and the efficacy of the MLFF parameter

  9. Detection of earthquake-induced damage in a framed structure using a finite element model updating procedure.

    PubMed

    Yu, Eunjong; Kim, Seung-Nam; Park, Taewon; Lee, Sang-Hyun

    2014-01-01

    Damage of a 5-story framed structure was identified from two types of measured data, which are frequency response functions (FRF) and natural frequencies, using a finite element (FE) model updating procedure. In this study, a procedure to determine the appropriate weightings for different groups of observations was proposed. In addition, a modified frame element which included rotational springs was used to construct the FE model for updating to represent concentrated damage at the member ends (a formulation for plastic hinges in framed structures subjected to strong earthquakes). The results of the model updating and subsequent damage detection when the rotational springs (RS model) were used were compared with those obtained using the conventional frame elements (FS model). Comparisons indicated that the RS model gave more accurate results than the FS model. That is, the errors in the natural frequencies of the updated models were smaller, and the identified damage showed clearer distinctions between damaged and undamaged members and was more consistent with observed damage. PMID:24574888

  10. Structural elements of the gills of the shore crab Carcinus mediterraneus

    NASA Astrophysics Data System (ADS)

    Venezia, L. Dalla; Zago, C.; Siebers, D.; Menetto, A.

    1992-12-01

    Fine structural studies were conducted on the gills of the shore crab Carcinus mediterraneus using scanning electron microscopic techniques. The results obtained show the structural organization of crab gills from whole gills including spiny elements over the 150 lamellae to lamellar components such as cuticles, median shaft, marginal canal, afferent and efferent lamellar vessels and hemolymph cells. Enormous surface enlargement is accomplished by a variety of structural elements which allow rapid circulation of hemolymph. In the form of a relatively small organ, the gills fulfill all the necessary exchanges of specific molecules between the crab and its environment. Aggregations of ca 1-μm particles covering the outer cuticular surfaces are considered to be bacterial colonies of unknown properties and functions.

  11. Large scale nonlinear numerical optimal control for finite element models of flexible structures

    NASA Technical Reports Server (NTRS)

    Shoemaker, Christine A.; Liao, Li-Zhi

    1990-01-01

    This paper discusses the development of large scale numerical optimal control algorithms for nonlinear systems and their application to finite element models of structures. This work is based on our expansion of the optimal control algorithm (DDP) in the following steps: improvement of convergence for initial policies in non-convex regions, development of a numerically accurate penalty function method approach for constrained DDP problems, and parallel processing on supercomputers. The expanded constrained DDP algorithm was applied to the control of a four-bay, two dimensional truss with 12 soft members, which generates geometric nonlinearities. Using an explicit finite element model to describe the structural system requires 32 state variables and 10,000 time steps. Our numerical results indicate that for constrained or unconstrained structural problems with nonlinear dynamics, the results obtained by our expanded constrained DDP are significantly better than those obtained using linear-quadratic feedback control.

  12. Using cuttlefish ink as an additive to produce -non-iridescent structural colors of high color visibility.

    PubMed

    Zhang, Yafeng; Dong, Biqin; Chen, Ang; Liu, Xiaohan; Shi, Lei; Zi, Jian

    2015-08-26

    Non-iridescent structural colors of high color visibility are produced by amorphous photonic structures, in which -natural cuttlefish ink is used as an additive to break down the long-range order of the structures. The color hue and its spectral purity can be tuned by adjusting the diameter of the polystyrene (PS) spheres and the proportion of ink particles. PMID:26175211

  13. Structural Basis for Promoter ;#8722;10 Element Recognition by the Bacterial RNA Polymerase [sigma] Subunit

    SciTech Connect

    Feklistov, Andrey; Darst, Seth A.

    2011-12-15

    The key step in bacterial promoter opening is recognition of the -10 promoter element (T-{sub 12}A-{sub 11}T-{sub 10}A-{sub 9}A-{sub 8}T{sub -7} consensus sequence) by the RNA polymerase {alpha} subunit. We determined crystal structures of {alpha} domain 2 bound to single-stranded DNA bearing -10 element sequences. Extensive interactions occur between the protein and the DNA backbone of every -10 element nucleotide. Base-specific interactions occur primarily with A{sub -11} and T{sub -7}, which are flipped out of the single-stranded DNA base stack and buried deep in protein pockets. The structures, along with biochemical data, support a model where the recognition of the -10 element sequence drives initial promoter opening as the bases of the nontemplate strand are extruded from the DNA double-helix and captured by {alpha}. These results provide a detailed structural basis for the critical roles of A{sub -11} and T{sub -7} in promoter melting and reveal important insights into the initiation of transcription bubble formation.

  14. Structural basis for promoter –10 element recognition by the bacterial RNA polymerase σ subunit

    PubMed Central

    Feklistov, Andrey; Darst, Seth A.

    2011-01-01

    SUMMARY The key step in bacterial promoter opening is recognition of the -10 promoter element (T-12A-11T-10A-9A-8T-7 consensus sequence) by the RNA polymerase σ subunit. We determined crystal structures of σ domain 2 bound to single-stranded DNA bearing -10 element sequences. Extensive interactions occur between the protein and the DNA backbone of every -10 element nucleotide. Base-specific interactions occur primarily with A-11, and T-7, which are flipped out of the single-stranded DNA base-stack and buried deep in protein pockets. The structures, along with biochemical data, support a model where the recognition of the -10 element sequence drives initial promoter opening as the bases of the non-template strand are extruded from the DNA double-helix and captured by σ. These results provide a detailed structural basis for the critical roles of A-11 and T-7 in promoter melting, and reveal important insights into the initiation of transcription bubble formation. PMID:22136875

  15. Experimental and Finite Element Study of Guided Ultrasonic Wave Scattering at Structural Features in a Plate

    NASA Astrophysics Data System (ADS)

    Fromme, P.

    2007-03-01

    Many technical structures contain large plate-like components, which can suffer from severe corrosion and the development of fatigue damage during their service life. Permanent monitoring of such structures can be achieved using guided ultrasonic waves, which can propagate over large distances and allow for efficient nondestructive testing of such structures with limited access. Damage often occurs at or close to structural features, e.g., stiffeners welded to the hull plates of a ship. The reflection of the Lamb wave A0 mode at a stiffener welded to a steel plate has been investigated experimentally in the laboratory. The wave propagation and scattering in the vicinity of the stiffener has been measured using a laser vibrometer and compared to Finite Element predictions; good agreement was found. The sensitivity for damage detection close to structural features has been investigated by studying the combined interaction of the guided ultrasonic wave with defects and structural features.

  16. Finite Element Analysis of an Energy Absorbing Sub-floor Structure

    NASA Technical Reports Server (NTRS)

    Moore, Scott C.

    1995-01-01

    As part of the Advanced General Aviation Transportation Experiments program, the National Aeronautics and Space Administration's Langley Research Center is conducting tests to design energy absorbing structures to improve occupant survivability in aircraft crashes. An effort is currently underway to design an Energy Absorbing (EA) sub-floor structure which will reduce occupant loads in an aircraft crash. However, a recent drop test of a fuselage specimen with a proposed EA sub-floor structure demonstrated that the effects of sectioning the fuselage on both the fuselage section's stiffness and the performance of the EA structure were not fully understood. Therefore, attempts are underway to model the proposed sub-floor structure on computers using the DYCAST finite element code to provide a better understanding of the structure's behavior in testing, and in an actual crash.

  17. Finite element analysis of steady and transiently moving/rolling nonlinear viscoelastic structure. I - Theory

    NASA Technical Reports Server (NTRS)

    Padovan, Joe

    1987-01-01

    In a three-part series of papers, a generalized finite element analysis scheme is developed to handle the steady and transient response of moving/rolling nonlinear viscoelastic structure. This paper considers the development of the moving/rolling element strategy, including the effects of large deformation kinematics and viscoelasticity modeled by fractional integrodifferential operators. To improve the solution strategy, a special hierarchical constraint procedure is developed for the case of steady rolling/translating, as well as a transient scheme involving the use of a Grunwaldian representation of the fractional operator.

  18. Layerwise Mechanics and Finite Elements for Smart Composite Structures with Piezoelectric Actuators and Sensors

    NASA Technical Reports Server (NTRS)

    Saravanos, Dimitris A.; Heyliger, Paul R.; Hopkins, Dale A.

    1996-01-01

    Recent developments on layerwise mechanics for the analysis of composite laminates and structures with piezoelectric actuators and sensors are reviewed. The mechanics implement layerwise representations of displacements and electric potential, and can model both the global and local electromechanical response of smart composite structures. The corresponding finite-element implementations for the static and dynamic analysis of smart piezoelectric composite structures are also summarized. Select application illustrate the accuracy, robustness and capability of the developed mechanics to capture the global and local dynamic response of thin and/or thick laminated piezoelectric plates.

  19. An approach to simulation of the finite element machine. [array of microcomputers for structural analysis

    NASA Technical Reports Server (NTRS)

    Sawyer, P. L.

    1980-01-01

    The paper describes the simulation approach for the finite element machine (FEM), a special-purpose computer for structural analysis calculations under development at the NASA-Langley Research Center. The FEM consists of an array (1000 or more) of general-purpose microcomputers performing structural analysis in an asychronous parallel manner. A simulator of sufficient flexibility to model the behavior of the FEM on many levels has been designed and coded, and verification has begun using the experimental FEM hardware. The structure of the simulator is described, and preliminary simulation results are presented.

  20. Simulations of Underground Structures Subjected to Dynamic Loading Using the Distinct Element Method

    SciTech Connect

    Morris, J P; Bonner, M P; Heuze, F E

    2004-08-20

    We present results from an investigation into the stability of underground structures in response to explosive loading. Field tests indicate that structural response can be dominated by the effect of preexisting fractures and faults in the rock mass. Consequently, accurate models of underground structures must take into account plastic deformations across fractures and not simply within the intact portions of the rock mass. The distinct element method (DEM) is naturally suited to simulating such systems because it can explicitly accommodate the blocky nature of natural rock masses. We will discuss details specific to our implementation of the DEM and summarize recent results.

  1. Critical review of the safety assessment of nano-structured silica additives in food.

    PubMed

    Winkler, Hans Christian; Suter, Mark; Naegeli, Hanspeter

    2016-01-01

    The development of nano-materials is viewed as one of the most important technological advances of the 21st century and new applications of nano-sized particles in the production, processing, packaging or storage of food are expected to emerge soon. This trend of growing commercialization of engineered nano-particles as part of modern diet will substantially increase oral exposure. Contrary to the proven benefits of nano-materials, however, possible adverse health effects have generally received less attention. This problem is very well illustrated by nano-structured synthetic amorphous silica (SAS), which is a common food additive since several decades although the relevant risk assessment has never been satisfactorily completed. A no observed adverse effect level of 2500 mg SAS particles/kg body weight per day was derived from the only available long-term administration study in rodents. However, extrapolation to a safe daily intake for humans is problematic due to limitations of this chronic animal study and knowledge gaps as to possible local intestinal effects of SAS particles, primarily on the gut-associated lymphoid system. This uncertainty is aggravated by digestion experiments indicating that dietary SAS particles preserve their nano-sized structure when reaching the intestinal lumen. An important aspect is whether food-borne particles like SAS alter the function of dendritic cells that, embedded in the intestinal mucosa, act as first-line sentinels of foreign materials. We conclude that nano-particles do not represent a completely new threat and that most potential risks can be assessed following procedures established for conventional chemical hazards. However, specific properties of food-borne nano-particles should be further examined and, for that purpose, in vitro tests with decision-making cells of the immune system are needed to complement existing in vivo studies. PMID:27287345

  2. Linear and nonlinear finite-element analysis of laminated composite structures at high temperatures

    SciTech Connect

    Wilt, T.E.

    1992-01-01

    A simple robust finite element which can effectively model the multilayer composite material is developed. This will include thermal gradient capabilities necessary for a complete thermomechanical analysis. In order to integrate the numerically stiff rate-dependent viscoplastic equations, efficient, stable numerical algorithms are developed. In addition, consistent viscoplastic/plastic tangent matrices are also formulated. The finite element is formulated based upon a generalized mixed variational principle with independently assumed displacements and layer-number independent strains. A unique scheme utilizing nodal temperatures is used to model a linear thermal gradient through the thickness of the composite. The numerical-integration algorithms are formulated in the context of a fully implicit backward Euler scheme. The consistent tangent matrices arise directly from the formulation. The multi-layer composite finite element demonstrates good performance in terms of static displacement and stress predictions, and dynamic response.

  3. Elements of the Chicxulub Impact Structure as revealed in SRTM and surface GPS topographic data

    NASA Astrophysics Data System (ADS)

    Kobrick, M.; Kinsland, G. L.; Sanchez, G.; Cardador, M. H.

    2003-04-01

    Pope et al have utilized elevations from the Petroleos Mexicanos (PEMEX) gravity data files to show that the main component of the surface expression of the Chicxu-lub Impact Structure is a roughly semi-circular, low-relief depression about 90 km in diameter. They also identified other topographic features and the elements of the buried impact which possibly led to the development of these features. Kinsland et al presented a connection between these topographic anomalies, small gravity anomalies and buried structure of the impact. Shaded relief images from recently acquired SRTM elevation data clearly show the circular depression of the crater and the moat/cenote ring. In addition we can readily identify Inner trough 1, Inner trough 2 and Outer trough as defined by Pope et al. The agreement between the topographic maps of Pope et al, Kinsland et al and SRTM data are remarkable considering that the distribution and types of data in the sets are so different. We also have ground topographic data collected with a special "autonomous differ-ential GPS" system during summer 2002. Profiles from these data generally agree with both the gravity data based topographic maps and profiles extracted from the SRTM data. Preliminary analyses of our new data, SRTM and GPS, have uncovered features not previously recognized: 1) as shown by the GPS data the moat/cenote ring consists of two distinct depressions separated by about 10 km...perhaps separate ring faults, 2) in the SRTM data over the southern part of the crater and on southward for perhaps 20 km beyond the moat/ cenote ring there exists a pattern, as yet unexplained, of roughly concentric topographic features whose center lies at about 21deg 40min N and 89deg 25min W, about 50km NNE of the moat/cenote ring center. The corroboration and better definition of the previously recognized topographic features yielded by the two new forms of data strengthens the cases for these fea-tures and for their relevance to the underlying

  4. Influencing the structure of block copolymer micelles with small molecule additives

    NASA Astrophysics Data System (ADS)

    Robertson, Megan; Singh, Avantika; Cooksey, Tyler; Kidd, Bryce; Piemonte, Rachele; Wang, Shu; Mai Le, Kim; Madsen, Louis

    Amphiphilic block copolymer micelles in water are under broad exploration for drug delivery applications due to their high loading capacity and targeted drug delivery. We aim to understand the kinetic and thermodynamic processes that underlie the self-assembly of diblock copolymer micelle systems. The present work focuses on diblock copolymers containing poly(ethylene oxide) (a hydrophilic polymer) and polycaprolactone (a hydrophobic polymer), which spontaneously self-assemble into spherical micelles in water. Addition of a common good solvent (a co-solvent) for both of the constituting blocks, such as tetrahydrofuran (THF), reduces the interfacial tension at the core-corona interface. We are currently investigating the effect of this phenomenon on the micelle structural properties, using small-angle scattering and nuclear magnetic resonance. We have characterized the hydrodynamic radius, core radius, corona thickness, aggregation number, degree of swelling of the micelle core with the co-solvent, and unimer (free chain) concentration, as a function of the co-solvent concentration. Fundamental knowledge from these studies will inform design of drug delivery systems by allowing us to tailor micelle properties for optimal cargo loading.

  5. Electronic Structure and Gas-Phase Behaviour of the Heaviest Elements

    SciTech Connect

    Pershina, V.; Anton, J.; Jacob, T.; Borschevsky, A.

    2010-04-30

    Electronic structures and gas-phase adsorption behaviour of the heaviest elements 112, 113 and 114 and of their lighter homologs Hg, Tl and Pb is studied on the basis of ab initio Dirac-Coulomb atomic and four-component Density Functional Theory molecular and cluster calculations. The heaviest elements were shown to have low adsorption enthalpies on Teflon and should, therefore, be well transported through Teflon capillaries from the target chamber to the chemistry set up. Adsorption enthalpies of these elements on the Au(111) surface are predicted as -44.5 kJ/mol, -158.6 kJ/mol and -68.5 kJ/mol, respectively, giving the following sequence in the adsorption temperatures 113>114>112.

  6. Finite element analysis of smart structures and modal testing of a flexible spacecraft arm

    NASA Astrophysics Data System (ADS)

    Trump, James C.

    1994-12-01

    This thesis deals with analytical predictions and experimental determination of the modal frequencies and shapes associated with the arm portion of the Naval Postgraduate School's Flexible Spacecraft Simulator (FSS). A description of how piezoceramic sensors and actuators are incorporated in finite element modeling is presented. A MATLAB (tm) code conducting the finite element modeling of the arm is used to verify the modal frequencies generated via Structural Dynamic Research Corporation's I-DEAS (tm) software. Modal testing is conducted with the I-DEAS test package to determine the first four physical modal frequencies and shapes so that we may compare them with the analytical results. The results of the testing indicated that finite element analysis predicted modes one and three within an average of 23.1%, and modes two and four within an average of 4.4%.

  7. Structural Rearrangements in CHO Cells After Disruption of Individual Cytoskeletal Elements and Plasma Membrane.

    PubMed

    Jokhadar, Špela Zemljič; Derganc, Jure

    2015-04-01

    Cellular structural integrity is provided primarily by the cytoskeleton, which comprises microtubules, actin filaments, and intermediate filaments. The plasma membrane has been also recognized as a mediator of physical forces, yet its contribution to the structural integrity of the cell as a whole is less clear. In order to investigate the relationship between the plasma membrane and the cytoskeleton, we selectively disrupted the plasma membrane and each of the cytoskeletal elements in Chinese hamster ovary cells and assessed subsequent changes in cellular structural integrity. Confocal microscopy was used to visualize cytoskeletal rearrangements, and optical tweezers were utilized to quantify membrane tether extraction. We found that cholesterol depletion from the plasma membrane resulted in rearrangements of all cytoskeletal elements. Conversely, the state of the plasma membrane, as assessed by tether extraction, was affected by disruption of any of the cytoskeletal elements, including microtubules and intermediate filaments, which are located mainly in the cell interior. The results demonstrate that, besides the cytoskeleton, the plasma membrane is an important contributor to cellular integrity, possibly by acting as an essential framework for cytoskeletal anchoring. In agreement with the tensegrity model of cell mechanics, our results support the notion of the cell as a prestressed structure. PMID:25395197

  8. Coupling equivalent plate and finite element formulations in multiple-method structural analyses

    NASA Technical Reports Server (NTRS)

    Giles, Gary L.; Norwood, Keith

    1994-01-01

    A coupled multiple-method analysis procedure for use late in conceptual design or early in preliminary design of aircraft structures is described. Using this method, aircraft wing structures are represented with equivalent plate models, and structural details such as engine/pylon structure, landing gear, or a 'stick' model of a fuselage are represented with beam finite element models. These two analysis methods are implemented in an integrated multiple-method formulation that involves the assembly and solution of a combined set of linear equations. The corresponding solution vector contains coefficients of the polynomials that describe the deflection of the wing and also the components of translations and rotations at the joints of the beam members. Two alternative approaches for coupling the methods are investigated; one using transition finite elements and the other using Lagrange multipliers. The coupled formulation is applied to the static analysis and vibration analysis of a conceptual design model of a fighter aircraft. The results from the coupled method are compared with corresponding results from an analysis in which the entire model is composed of finite elements.

  9. Energy Finite Element Analysis Developments for Vibration Analysis of Composite Aircraft Structures

    NASA Technical Reports Server (NTRS)

    Vlahopoulos, Nickolas; Schiller, Noah H.

    2011-01-01

    The Energy Finite Element Analysis (EFEA) has been utilized successfully for modeling complex structural-acoustic systems with isotropic structural material properties. In this paper, a formulation for modeling structures made out of composite materials is presented. An approach based on spectral finite element analysis is utilized first for developing the equivalent material properties for the composite material. These equivalent properties are employed in the EFEA governing differential equations for representing the composite materials and deriving the element level matrices. The power transmission characteristics at connections between members made out of non-isotropic composite material are considered for deriving suitable power transmission coefficients at junctions of interconnected members. These coefficients are utilized for computing the joint matrix that is needed to assemble the global system of EFEA equations. The global system of EFEA equations is solved numerically and the vibration levels within the entire system can be computed. The new EFEA formulation for modeling composite laminate structures is validated through comparison to test data collected from a representative composite aircraft fuselage that is made out of a composite outer shell and composite frames and stiffeners. NASA Langley constructed the composite cylinder and conducted the test measurements utilized in this work.

  10. Development of an integrated BEM approach for hot fluid structure interaction: BEST-FSI: Boundary Element Solution Technique for Fluid Structure Interaction

    NASA Technical Reports Server (NTRS)

    Dargush, G. F.; Banerjee, P. K.; Shi, Y.

    1992-01-01

    As part of the continuing effort at NASA LeRC to improve both the durability and reliability of hot section Earth-to-orbit engine components, significant enhancements must be made in existing finite element and finite difference methods, and advanced techniques, such as the boundary element method (BEM), must be explored. The BEM was chosen as the basic analysis tool because the critical variables (temperature, flux, displacement, and traction) can be very precisely determined with a boundary-based discretization scheme. Additionally, model preparation is considerably simplified compared to the more familiar domain-based methods. Furthermore, the hyperbolic character of high speed flow is captured through the use of an analytical fundamental solution, eliminating the dependence of the solution on the discretization pattern. The price that must be paid in order to realize these advantages is that any BEM formulation requires a considerable amount of analytical work, which is typically absent in the other numerical methods. All of the research accomplishments of a multi-year program aimed toward the development of a boundary element formulation for the study of hot fluid-structure interaction in Earth-to-orbit engine hot section components are detailed. Most of the effort was directed toward the examination of fluid flow, since BEM's for fluids are at a much less developed state. However, significant strides were made, not only in the analysis of thermoviscous fluids, but also in the solution of the fluid-structure interaction problem.

  11. Crystal Structure of the Lysine Riboswitch Regulatory mRNA Element*S⃞

    PubMed Central

    Garst, Andrew D.; Héroux, Annie; Rambo, Robert P.; Batey, Robert T.

    2008-01-01

    Riboswitches are metabolite-sensitive elements found in mRNAs that control gene expression through a regulatory secondary structural switch. Along with regulation of lysine biosynthetic genes, mutations within the lysine-responsive riboswitch (L-box) play a role in the acquisition of resistance to antimicrobial lysine analogs. To understand the structural basis for lysine binding, we have determined the 2.8Å resolution crystal structure of lysine bound to the Thermotoga maritima asd lysine riboswitch ligand-binding domain. The structure reveals a complex architecture scaffolding a binding pocket completely enveloping lysine. Mutations conferring antimicrobial resistance cluster around this site as well as highly conserved long range interactions, indicating that they disrupt lysine binding or proper folding of the RNA. Comparison of the free and bound forms by x-ray crystallography, small angle x-ray scattering, and chemical probing reveals almost identical structures, indicating that lysine induces only limited and local conformational changes upon binding. PMID:18593706

  12. Crystal structure of the lysine riboswitch regulatory mRNA element.

    PubMed

    Garst, Andrew D; Héroux, Annie; Rambo, Robert P; Batey, Robert T

    2008-08-15

    Riboswitches are metabolite-sensitive elements found in mRNAs that control gene expression through a regulatory secondary structural switch. Along with regulation of lysine biosynthetic genes, mutations within the lysine-responsive riboswitch (L-box) play a role in the acquisition of resistance to antimicrobial lysine analogs. To understand the structural basis for lysine binding, we have determined the 2.8 angstroms resolution crystal structure of lysine bound to the Thermotoga maritima asd lysine riboswitch ligand-binding domain. The structure reveals a complex architecture scaffolding a binding pocket completely enveloping lysine. Mutations conferring antimicrobial resistance cluster around this site as well as highly conserved long range interactions, indicating that they disrupt lysine binding or proper folding of the RNA. Comparison of the free and bound forms by x-ray crystallography, small angle x-ray scattering, and chemical probing reveals almost identical structures, indicating that lysine induces only limited and local conformational changes upon binding. PMID:18593706

  13. Crystal Structure of the Lysine Riboswitch Regulatory mRNA Element

    SciTech Connect

    Garst, A.; Heroux, A; Rambo, R; Batey, R

    2008-01-01

    Riboswitches are metabolite-sensitive elements found in mRNAs that control gene expression through a regulatory secondary structural switch. Along with regulation of lysine biosynthetic genes, mutations within the lysine-responsive riboswitch (L-box) play a role in the acquisition of resistance to antimicrobial lysine analogs. To understand the structural basis for lysine binding, we have determined the 2.8{angstrom} resolution crystal structure of lysine bound to the Thermotoga maritima asd lysine riboswitch ligand-binding domain. The structure reveals a complex architecture scaffolding a binding pocket completely enveloping lysine. Mutations conferring antimicrobial resistance cluster around this site as well as highly conserved long range interactions, indicating that they disrupt lysine binding or proper folding of the RNA. Comparison of the free and bound forms by x-ray crystallography, small angle x-ray scattering, and chemical probing reveals almost identical structures, indicating that lysine induces only limited and local conformational changes upon binding.

  14. Phase Structure and Site Preference Behavior of Ternary Alloying Additions to PdTi and PtTi Shape-Memory Alloys

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo; Mosca, Hugo O.; Noebe, Ronald D.

    2006-01-01

    The phasc structure and concentration dependence of the lattice parameter and energy of formation of ternary Pd-'I-X and Pt-Ti-X alloys for a large number of ternary alloying additions X (X = Na, Mg, Al, Si, Sc. V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Ag, Cd, Hf, Ta, W, Re, Os, Ir) are investigated with an atomistic modeling approach. In addition, a detailed description of the site preference behavior of such additions showing that the elements can be grouped according to their absolute preference for a specific site, regardless of concentration, or preference for available sites in the deficient sublattice is provided.

  15. Development of Finite Elements for Two-Dimensional Structural Analysis Using the Integrated Force Method

    NASA Technical Reports Server (NTRS)

    Kaljevic, Igor; Patnaik, Surya N.; Hopkins, Dale A.

    1996-01-01

    The Integrated Force Method has been developed in recent years for the analysis of structural mechanics problems. This method treats all independent internal forces as unknown variables that can be calculated by simultaneously imposing equations of equilibrium and compatibility conditions. In this paper a finite element library for analyzing two-dimensional problems by the Integrated Force Method is presented. Triangular- and quadrilateral-shaped elements capable of modeling arbitrary domain configurations are presented. The element equilibrium and flexibility matrices are derived by discretizing the expressions for potential and complementary energies, respectively. The displacement and stress fields within the finite elements are independently approximated. The displacement field is interpolated as it is in the standard displacement method, and the stress field is approximated by using complete polynomials of the correct order. A procedure that uses the definitions of stress components in terms of an Airy stress function is developed to derive the stress interpolation polynomials. Such derived stress fields identically satisfy the equations of equilibrium. Moreover, the resulting element matrices are insensitive to the orientation of local coordinate systems. A method is devised to calculate the number of rigid body modes, and the present elements are shown to be free of spurious zero-energy modes. A number of example problems are solved by using the present library, and the results are compared with corresponding analytical solutions and with results from the standard displacement finite element method. The Integrated Force Method not only gives results that agree well with analytical and displacement method results but also outperforms the displacement method in stress calculations.

  16. Distinct Structural Elements Dictate the Specificity of the Type III Pentaketide Synthase from Neurospora crassa

    SciTech Connect

    Rubin-Pitel, Sheryl B.; Zhang, Houjin; Vu, Trang; Brunzelle, Joseph S.; Zhao, Huimin; Nair, Satish K.

    2009-01-15

    The fungal type III polyketide synthase 2'-oxoalkylresorcyclic acid synthase (ORAS) primes with a range of acyl-Coenzyme A thioesters (C{sub 4}--C{sub 20}) and extends using malonyl-Coenzyme A to produce pyrones, resorcinols, and resorcylic acids. To gain insight into this unusual substrate specificity and product profile, we have determined the crystal structures of ORAS to 1.75 {angstrom} resolution, the Phe-252{yields}Gly site-directed mutant to 2.1 {angstrom} resolution, and a binary conplex of ORAS with eicosanoic acid to 2.0 {angstrom} resolution. The structures reveal a distinct rearrangement of structural elements near the active site that allows accomodation of long-chain fatty acid esters and a reorientation of the gating mechanism that controls cyclization and polyketide chain length. The roles of these structural elements are further elucidated by characterization of various structure-based site-directed variants. These studies establish an unexpected plasticity to the PKS fold, unanticipated from structural studies of other members of this enzyme family.

  17. Exact finite element method analysis of viscoelastic tapered structures to transient loads

    NASA Technical Reports Server (NTRS)

    Spyrakos, Constantine Chris

    1987-01-01

    A general method is presented for determining the dynamic torsional/axial response of linear structures composed of either tapered bars or shafts to transient excitations. The method consists of formulating and solving the dynamic problem in the Laplace transform domain by the finite element method and obtaining the response by a numerical inversion of the transformed solution. The derivation of the torsional and axial stiffness matrices is based on the exact solution of the transformed governing equation of motion, and it consequently leads to the exact solution of the problem. The solution permits treatment of the most practical cases of linear tapered bars and shafts, and employs modeling of structures with only one element per member which reduces the number of degrees of freedom involved. The effects of external viscous or internal viscoelastic damping are also taken into account.

  18. Three-dimensionality of space in the structure of the periodic table of chemical elements

    SciTech Connect

    Veremeichik, T. F.

    2006-07-15

    The effect of the dimension of the 3D homogeneous and isotropic Euclidean space, and the electron spin on the self-organization of the electron systems of atoms of chemical elements is considered. It is shown that the finite dimension of space creates the possibility of periodicity in the structure of an electron cloud, while the value of the dimension determines the number of stable systems of electrons at different levels of the periodic table of chemical elements and some characteristics of the systems. The conditions for the stability of systems of electrons and the electron system of an atom as a whole are considered. On the basis of the results obtained, comparison with other hierarchical systems (nanostructures and biological structures) is performed.

  19. Application of Flame-Sprayed Coatings as Heating Elements for Polymer-Based Composite Structures

    NASA Astrophysics Data System (ADS)

    Lopera-Valle, Adrián; McDonald, André

    2015-10-01

    Flame-sprayed nickel-chromium-aluminum-yttrium (NiCrAlY) and nickel-chromium (NiCr) coatings were deposited on fiber-reinforced polymer composites for use as heating elements of structures that were exposed to cold environments. Electrical current was applied to the coatings to increase the surface temperature by way of Joule heating. The surface temperature profiles of the coatings were measured under free and forced convection conditions at different ambient temperatures, ranging from -25 to 23 °C. It was found that at ambient air temperatures below 0 °C, the surface temperature of the coating remained above 0 °C for both the forced and free convection conditions, and there was a nearly homogeneous temperature distribution over the coating surface. This suggests that flame-sprayed coatings could be used as heating elements to mitigate ice accretion on structures, without the presence of areas of localized high temperature.

  20. Structure-acoustic finite element analyses for noise reduction investigations of launcher payload compartment structures made of CFRP sandwich material

    NASA Astrophysics Data System (ADS)

    Faust, M.; Schweickert, G.; Strobel, F.

    1991-10-01

    An investigation of the noise reduction properties of the Ariane 5 Speltra payload compartment structure is reported. The low frequency noise reduction was calculated by the Finite Element Method (FEM) with a formulation for fluid structure interaction (FE code PERMAS-FS). The results of the different analysis steps including uncoupled and coupled analysis are presented. The uncoupled structure and cavity dynamics results were compared to closed form solutions with good agreement. The introduction of external field effects, i.e. radiation damping and scattering, was performed by using closed form solutions for cylinder type structures. The analyses were performed for 2 different test cylinders and the Speltra cylindrical part. The test cylinder results were compared with the measured noise reductions and good agreement was obtained.

  1. Structured additive regression modeling of age of menarche and menopause in a breast cancer screening program.

    PubMed

    Duarte, Elisa; de Sousa, Bruno; Cadarso-Suarez, Carmen; Rodrigues, Vitor; Kneib, Thomas

    2014-05-01

    Breast cancer risk is believed to be associated with several reproductive factors, such as early menarche and late menopause. This study is based on the registries of the first time a woman enters the screening program, and presents a spatio-temporal analysis of the variables age of menarche and age of menopause along with other reproductive and socioeconomic factors. The database was provided by the Portuguese Cancer League (LPCC), a private nonprofit organization dealing with multiple issues related to oncology of which the Breast Cancer Screening Program is one of its main activities. The registry consists of 259,652 records of women who entered the screening program for the first time between 1990 and 2007 (45-69-year age group). Structured Additive Regression (STAR) models were used to explore spatial and temporal correlations with a wide range of covariates. These models are flexible enough to deal with a variety of complex datasets, allowing us to reveal possible relationships among the variables considered in this study. The analysis shows that early menarche occurs in younger women and in municipalities located in the interior of central Portugal. Women living in inland municipalities register later ages for menopause, and those born in central Portugal after 1933 show a decreasing trend in the age of menopause. Younger ages of menarche and late menopause are observed in municipalities with a higher purchasing power index. The analysis performed in this study portrays the time evolution of the age of menarche and age of menopause and their spatial characterization, adding to the identification of factors that could be of the utmost importance in future breast cancer incidence research. PMID:24615881

  2. Testing the Big Bang: Light elements, neutrinos, dark matter and large-scale structure

    NASA Technical Reports Server (NTRS)

    Schramm, David N.

    1991-01-01

    Several experimental and observational tests of the standard cosmological model are examined. In particular, a detailed discussion is presented regarding: (1) nucleosynthesis, the light element abundances, and neutrino counting; (2) the dark matter problems; and (3) the formation of galaxies and large-scale structure. Comments are made on the possible implications of the recent solar neutrino experimental results for cosmology. An appendix briefly discusses the 17 keV thing and the cosmological and astrophysical constraints on it.

  3. A generalized threading model using integer programming that allows for secondary structure element deletion.

    PubMed

    Ellrott, Kyle; Guo, Jun-tao; Olman, Victor; Xu, Ying

    2006-01-01

    Integer programming is a combinatorial optimization method that has been successfully applied to the protein threading problem. We seek to expand the model optimized by this technique to allow for a more accurate description of protein threading. We have developed and implemented an expanded model of integer programming that has the capability to model secondary structure element deletion, which was not possible in previous version of integer programming based optimization. PMID:17503397

  4. A new structure of two-dimensional allotropes of group V elements.

    PubMed

    Li, Ping; Luo, Weidong

    2016-01-01

    The elemental two-dimensional (2D) materials such as graphene, silicene, germanene, and black phosphorus have attracted considerable attention due to their fascinating physical properties. Structurally they possess the honeycomb or distorted honeycomb lattices, which are composed of six-atom rings. Here we find a new structure of 2D allotropes of group V elements composed of eight-atom rings, which we name as the octagonal tiling (OT) structure. First-principles calculations indicate that these allotropes are dynamically stable and are also thermally stable at temperatures up to 600 K. These allotropes are semiconductors with band gaps ranging from 0.3 to 2.0 eV, thus they are potentially useful in near- and mid-infrared optoelectronic devices. OT-Bi is also a 2D topological insulator (TI) with a band gap of 0.33 eV, which is the largest among the reported elemental 2D TIs, and this gap can be increased further by applying compressive strains. PMID:27150010

  5. A new structure of two-dimensional allotropes of group V elements

    NASA Astrophysics Data System (ADS)

    Li, Ping; Luo, Weidong

    2016-05-01

    The elemental two-dimensional (2D) materials such as graphene, silicene, germanene, and black phosphorus have attracted considerable attention due to their fascinating physical properties. Structurally they possess the honeycomb or distorted honeycomb lattices, which are composed of six-atom rings. Here we find a new structure of 2D allotropes of group V elements composed of eight-atom rings, which we name as the octagonal tiling (OT) structure. First-principles calculations indicate that these allotropes are dynamically stable and are also thermally stable at temperatures up to 600 K. These allotropes are semiconductors with band gaps ranging from 0.3 to 2.0 eV, thus they are potentially useful in near- and mid-infrared optoelectronic devices. OT-Bi is also a 2D topological insulator (TI) with a band gap of 0.33 eV, which is the largest among the reported elemental 2D TIs, and this gap can be increased further by applying compressive strains.

  6. A new structure of two-dimensional allotropes of group V elements

    NASA Astrophysics Data System (ADS)

    Li, Ping; Luo, Weidong

    The elemental two-dimensional (2D) materials such as graphene, silicene, germanene, and black phosphorus have attracted considerable attention due to their fascinating physical properties. Structurally they possess the honeycomb or distorted honeycomb lattices, which are composed of six-atom rings. Here we find a new structure of 2D allotropes of group V elements composed of eight-atom rings, which we name as the octagonal tiling (OT) structure. First-principles calculations indicate that these allotropes are dynamically stable and are also thermally stable at temperatures up to 600 K. These allotropes are semiconductors with band gaps ranging from 0.3 to 2.0 eV, thus they are potentially useful in near- and mid-infrared optoelectronic devices. OT-Bi is also a 2D topological insulator (TI) with a band gap of 0.33 eV, which is the largest among the reported elemental 2D TIs, and this gap can be increased further by applying compressive strains.

  7. The influence of doping element on structural and luminescent characteristics of ZnS thin films

    NASA Astrophysics Data System (ADS)

    Kryshtab, T.; Khomchenko, V. S.; Andraca-Adame, J. A.; Rodionov, V. E.; Khachatryan, V. B.; Tzyrkunov, Yu. A.

    2006-10-01

    For the fabrication of green and blue emitting ZnS structures the elements of I, III, and VII groups (Cu, Al, Ga, Cl) are used as dopants. The influence of type of impurity, doping technique, and type of substrate on crystalline structure and surface morphology together with luminescent properties was investigated. The doping of thin films was realized during the growth process and/or post-deposition thermal treatment. ZnS thin films were deposited by physical (EBE) and chemical (MOCVD) methods onto glass or ceramic (BaTiO 3) substrates. Closed spaced evaporation and thermodiffusion methods were used for the post-deposition doping of ZnS films. X-ray diffraction (XRD) techniques, atomic force microscopy (AFM), and measurements of photoluminescent (PL) spectra were used for the investigations. It was shown that the doping by the elements of I (Cu) and III (Al, Ga) groups does not change the crystal structure during the thermal treatment up to 1000 ∘C, whereas simultaneous use of the elements of I (Cu) and VII (Cl) groups leads to decrease of the phase transition temperature to 800 ∘C. The presence of impurities in the growth process leads to a grain size increase. At post-deposition treatment Ga and Cl act as activators of recrystallization process. The transition of ZnS sphalerite lattice to wurtzite one leads to the displacement of the blue emission band position towards the short-wavelength range by 10 nm.

  8. A new structure of two-dimensional allotropes of group V elements

    PubMed Central

    Li, Ping; Luo, Weidong

    2016-01-01

    The elemental two-dimensional (2D) materials such as graphene, silicene, germanene, and black phosphorus have attracted considerable attention due to their fascinating physical properties. Structurally they possess the honeycomb or distorted honeycomb lattices, which are composed of six-atom rings. Here we find a new structure of 2D allotropes of group V elements composed of eight-atom rings, which we name as the octagonal tiling (OT) structure. First-principles calculations indicate that these allotropes are dynamically stable and are also thermally stable at temperatures up to 600 K. These allotropes are semiconductors with band gaps ranging from 0.3 to 2.0 eV, thus they are potentially useful in near- and mid-infrared optoelectronic devices. OT-Bi is also a 2D topological insulator (TI) with a band gap of 0.33 eV, which is the largest among the reported elemental 2D TIs, and this gap can be increased further by applying compressive strains. PMID:27150010

  9. Fuzzy Modal Finite Element Analysis of Structures with Imprecise Material Properties

    NASA Astrophysics Data System (ADS)

    Lallemand, B.; Cherki, A.; Tison, T.; Level, P.

    1999-02-01

    This paper extends the fuzzy set theory to a dynamic finite element analysis of engineering systems which have uncertainties in material properties. A general algorithm which resolves the uncertain eigenvalue problem by using a reanalysis approach is considered. This algorithm is applied to the study of the modal behaviour of structures presenting uncertain material properties. Some indexes which determine the more sensitive eigenvalue to several uncertainty sources are also put forward. Finally, a plate structure as numerical path-test is analysed. The results of such a calculation determine the sensitivity of the modal behaviour to multiple simultaneous material parameters.

  10. Structural characterization and regulatory element analysis of the heart isoform of cytochrome c oxidase VIa

    NASA Technical Reports Server (NTRS)

    Wan, B.; Moreadith, R. W.; Blomqvist, C. G. (Principal Investigator)

    1995-01-01

    In order to investigate the mechanism(s) governing the striated muscle-specific expression of cytochrome c oxidase VIaH we have characterized the murine gene and analyzed its transcriptional regulatory elements in skeletal myogenic cell lines. The gene is single copy, spans 689 base pairs (bp), and is comprised of three exons. The 5'-ends of transcripts from the gene are heterogeneous, but the most abundant transcript includes a 5'-untranslated region of 30 nucleotides. When fused to the luciferase reporter gene, the 3.5-kilobase 5'-flanking region of the gene directed the expression of the heterologous protein selectively in differentiated Sol8 cells and transgenic mice, recapitulating the pattern of expression of the endogenous gene. Deletion analysis identified a 300-bp fragment sufficient to direct the myotube-specific expression of luciferase in Sol8 cells. The region lacks an apparent TATA element, and sequence motifs predicted to bind NRF-1, NRF-2, ox-box, or PPAR factors known to regulate other nuclear genes encoding mitochondrial proteins are not evident. Mutational analysis, however, identified two cis-elements necessary for the high level expression of the reporter protein: a MEF2 consensus element at -90 to -81 bp and an E-box element at -147 to -142 bp. Additional E-box motifs at closely located positions were mutated without loss of transcriptional activity. The dependence of transcriptional activation of cytochrome c oxidase VIaH on cis-elements similar to those found in contractile protein genes suggests that the striated muscle-specific expression is coregulated by mechanisms that control the lineage-specific expression of several contractile and cytosolic proteins.

  11. Multivariate Statistical Analysis of Volatile Trace Elements in H Chondrites: Implications for Parent Body Structure

    NASA Astrophysics Data System (ADS)

    Wolf, S. F.; Lipschutz, M. E.

    1993-07-01

    The perception among meteoriticists is that contents of the volatile trace elements systematically decrease with shock and particularly petrologic type. This perception affects views that investigators have of the early history and structure of the H chondrite parent body. Measurement of a variety of volatile trace elements in a statistically significant number of samples accompanied by chemometric data analysis techniques developed for interpretation of trace- element data [1] should maximize the amount of genetic information available from the volatile trace elements and offer clues to the early thermal history of the H chondrite parent body. Volatile trace-element data exist for 58 H chondrite falls: the complete dataset includes Co, Rb, Ag, Se, Cs, Te, Zn, Cd, Bi, Tl, and In (listed in increasing order of volatility) [2,3]. This dataset includes 13 H4, 32 H5, and 13 H6 chondrites, which cover the full range of shock facies from a through f. To examine the effect that shock has on volatile trace-element concentrations in H4-6 chondrites, we have compared data for the least-shocked samples (shock facies a-b) with the most shocked samples (shock facies c-f) using both univariate (Student's t-test) and multivariate techniques (linear discriminant analysis). The results demonstrate no reason to doubt the null hypothesis of no difference in volatile trace-element composition between shocked and unshocked H4-6 chondrites at any reasonable significance level. This situation contrasts sharply with the strong difference found between shocked and unshocked L chondrites [4]. The role of shock in establishing volatile trace- element contents in H and L chondrites clearly differs. Univariate comparisons between H4, H5, and H6 chondrites demonstrate that only Cs varies significantly with petrologic type (prob. > F 0.0006) with concentration decreasing monotonically with increasing petrographic type. Box- and-whisker plots of volatile trace-element contents reveal a general

  12. Designing synthetic RNAs to determine the relevance of structural motifs in picornavirus IRES elements

    NASA Astrophysics Data System (ADS)

    Fernandez-Chamorro, Javier; Lozano, Gloria; Garcia-Martin, Juan Antonio; Ramajo, Jorge; Dotu, Ivan; Clote, Peter; Martinez-Salas, Encarnacion

    2016-04-01

    The function of Internal Ribosome Entry Site (IRES) elements is intimately linked to their RNA structure. Viral IRES elements are organized in modular domains consisting of one or more stem-loops that harbor conserved RNA motifs critical for internal initiation of translation. A conserved motif is the pyrimidine-tract located upstream of the functional initiation codon in type I and II picornavirus IRES. By computationally designing synthetic RNAs to fold into a structure that sequesters the polypyrimidine tract in a hairpin, we establish a correlation between predicted inaccessibility of the pyrimidine tract and IRES activity, as determined in both in vitro and in vivo systems. Our data supports the hypothesis that structural sequestration of the pyrimidine-tract within a stable hairpin inactivates IRES activity, since the stronger the stability of the hairpin the higher the inhibition of protein synthesis. Destabilization of the stem-loop immediately upstream of the pyrimidine-tract also decreases IRES activity. Our work introduces a hybrid computational/experimental method to determine the importance of structural motifs for biological function. Specifically, we show the feasibility of using the software RNAiFold to design synthetic RNAs with particular sequence and structural motifs that permit subsequent experimental determination of the importance of such motifs for biological function.

  13. A Finite Element Procedure for Calculating Fluid-Structure Interaction Using MSC/NASTRAN

    NASA Technical Reports Server (NTRS)

    Chargin, Mladen; Gartmeier, Otto

    1990-01-01

    This report is intended to serve two purposes. The first is to present a survey of the theoretical background of the dynamic interaction between a non-viscid, compressible fluid and an elastic structure is presented. Section one presents a short survey of the application of the finite element method (FEM) to the area of fluid-structure-interaction (FSI). Section two describes the mathematical foundation of the structure and fluid with special emphasis on the fluid. The main steps in establishing the finite element (FE) equations for the fluid structure coupling are discussed in section three. The second purpose is to demonstrate the application of MSC/NASTRAN to the solution of FSI problems. Some specific topics, such as fluid structure analogy, acoustic absorption, and acoustic contribution analysis are described in section four. Section five deals with the organization of the acoustic procedure flowchart. Section six includes the most important information that a user needs for applying the acoustic procedure to practical FSI problems. Beginning with some rules concerning the FE modeling of the coupled system, the NASTRAN USER DECKs for the different steps are described. The goal of section seven is to demonstrate the use of the acoustic procedure with some examples. This demonstration includes an analytic verification of selected FE results. The analytical description considers only some aspects of FSI and is not intended to be mathematically complete. Finally, section 8 presents an application of the acoustic procedure to vehicle interior acoustic analysis with selected results.

  14. Designing synthetic RNAs to determine the relevance of structural motifs in picornavirus IRES elements

    PubMed Central

    Fernandez-Chamorro, Javier; Lozano, Gloria; Garcia-Martin, Juan Antonio; Ramajo, Jorge; Dotu, Ivan; Clote, Peter; Martinez-Salas, Encarnacion

    2016-01-01

    The function of Internal Ribosome Entry Site (IRES) elements is intimately linked to their RNA structure. Viral IRES elements are organized in modular domains consisting of one or more stem-loops that harbor conserved RNA motifs critical for internal initiation of translation. A conserved motif is the pyrimidine-tract located upstream of the functional initiation codon in type I and II picornavirus IRES. By computationally designing synthetic RNAs to fold into a structure that sequesters the polypyrimidine tract in a hairpin, we establish a correlation between predicted inaccessibility of the pyrimidine tract and IRES activity, as determined in both in vitro and in vivo systems. Our data supports the hypothesis that structural sequestration of the pyrimidine-tract within a stable hairpin inactivates IRES activity, since the stronger the stability of the hairpin the higher the inhibition of protein synthesis. Destabilization of the stem-loop immediately upstream of the pyrimidine-tract also decreases IRES activity. Our work introduces a hybrid computational/experimental method to determine the importance of structural motifs for biological function. Specifically, we show the feasibility of using the software RNAiFold to design synthetic RNAs with particular sequence and structural motifs that permit subsequent experimental determination of the importance of such motifs for biological function. PMID:27053355

  15. A Six-Node Curved Triangular Element and a Four-Node Quadrilateral Element for Analysis of Laminated Composite Aerospace Structures

    NASA Technical Reports Server (NTRS)

    Martin, C. Wayne; Breiner, David M.; Gupta, Kajal K. (Technical Monitor)

    2004-01-01

    Mathematical development and some computed results are presented for Mindlin plate and shell elements, suitable for analysis of laminated composite and sandwich structures. These elements use the conventional 3 (plate) or 5 (shell) nodal degrees of freedom, have no communicable mechanisms, have no spurious shear energy (no shear locking), have no spurious membrane energy (no membrane locking) and do not require arbitrary reduction of out-of-plane shear moduli or under-integration. Artificial out-of-plane rotational stiffnesses are added at the element level to avoid convergence problems or singularity due to flat spots in shells. This report discusses a 6-node curved triangular element and a 4-node quadrilateral element. Findings show that in regular rectangular meshes, the Martin-Breiner 6-node triangular curved shell (MB6) is approximately equivalent to the conventional 8-node quadrilateral with integration. The 4-node quadrilateral (MB4) has very good accuracy for a 4-node element, and may be preferred in vibration analysis because of narrower bandwidth. The mathematical developments used in these elements, those discussed in the seven appendices, have been applied to elements with 3, 4, 6, and 10 nodes and can be applied to other nodal configurations.

  16. Perspectives Of Employment Of Pultruded FRP Structural Elements In Seismic Engineering Field

    SciTech Connect

    Russo, Salvatore; Silvestri, Mirko

    2008-07-08

    Today the employment of FRP material in structural engineering is in common use, with excellent results in term of applications especially as reinforcement of existing structures. This success is related to the very reduced weight of FRP material, to its performance in term of strength and durability and thanks to the easy use in technical application. There is a modern way to use this material disguised as structural pultruded element (with weight equal to 1600-1800 kg/m{sup 3}) in new constructions, local reinforcements and in other seismic applications. Actually the international technical and scientific literature in form of draft, recommendations and researches on this topic is very rich also taking into account Italian contribution. Some interesting applications of all FRP structures in seismic engineering field are showed in this research in real terms and in form of capability.

  17. Hoxb-2 transcriptional activation in rhombomeres 3 and 5 requires an evolutionarily conserved cis-acting element in addition to the Krox-20 binding site.

    PubMed Central

    Vesque, C; Maconochie, M; Nonchev, S; Ariza-McNaughton, L; Kuroiwa, A; Charnay, P; Krumlauf, R

    1996-01-01

    Segmentation is a key feature of the development of the vertebrate hindbrain where it involves the generation of repetitive morphological units termed rhombomeres (r). Hox genes are likely to play an essential role in the specification of segmental identity and we have been investigating their regulation. We show here that the mouse and chicken Hoxb-2 genes are dependent for their expression in r3 and r5 on homologous enhancer elements and on binding to this enhancer of the r3/r5-specific transcriptional activator Krox-20. Among the three Krox-20 binding sites of the mouse Hoxb-2 enhancer, only the high-affinity site is absolutely necessary for activity. In contrast, we have identified an additional cis-acting element, Box1, essential for r3/r5 enhancer activity. It is conserved both in sequence and in position respective to the high-affinity Krox-20 binding site within the mouse and chicken enhancers. Furthermore, a short 44 bp sequence spanning the Box1 and Krox-20 sites can act as an r3/r5 enhancer when oligomerized. Box1 may therefore constitute a recognition sequence for another factor cooperating with Krox-20. Taken together, these data demonstrate the conservation of Hox gene regulation and of Krox-20 function during vertebrate evolution. Images PMID:8895582

  18. A Pilot Study to Examine the Effect of Additional Structured Outdoor Playtime on Preschoolers' Physical Activity Levels

    ERIC Educational Resources Information Center

    Alhassan, Sofiya; Nwaokelemeh, Ogechi; Lyden, Kate; Goldsby, TaShauna; Mendoza, Albert

    2013-01-01

    The impact of additional structured outdoor playtime on preschoolers'; physical activity (PA) level is unclear. The purpose of this pilot study was to explore the effects of increasing structured outdoor playtime on preschoolers'; PA levels. Eight full-day classrooms (n = 134 children) from two preschool programmes were randomised into a treatment…

  19. Theoretical Studies of the Electronic Structure of the Compounds of the Actinide Elements

    SciTech Connect

    Kaltsoyannis, Nikolas; Hay, P. Jeffrey; Li, Jun; Blaudeau, Jean-Philippe; Bursten, Bruce E.

    2006-02-02

    In this chapter, we will present an overview of the theoretical and computational developments that have increased our understanding of the electronic structure of actinide-containing molecules and ions. The application of modern electronic structure methodologies to actinide systems remains one of the great challenges in quantum chemistry; indeed, as will be discussed below, there is no other portion of the periodic table that leads to the confluence of complexity with respect to the calculation of ground- and excited-state energies, bonding descriptions, and molecular properties. But there is also no place in the periodic table in which effective computational modeling of electronic structure can be more useful. The difficulties in creating, isolating, and handling many of the actinide elements provide an opportunity for computational chemistry to be an unusually important partner in developing the chemistry of these elements. The importance of actinide electronic structure begins with the earliest studies of uranium chemistry and predates the discovery of quantum mechanics. The fluorescence of uranyl compounds was observed as early as 1833 (Jørgensen and Reisfeld, 1983), a presage of the development of actinometry as a tool for measuring photochemical quantum yields. Interest in nuclear fuels has stimulated tremendous interest in understanding the properties, including electronic properties, of small actinide-containing molecules and ions, especially the oxides and halides of uranium and plutonium. The synthesis of uranocene in 1968 (Streitwieser and Mu¨ ller-Westerhoff, 1968) led to the flurry of activity in the organometallic chemistry of the actinides that continues today. Actinide organometallics (or organoactinides) are nearly always molecular systems and are often volatile, which makes them amenable to an arsenal of experimental probes of molecular and electronic structure (Marks and Fischer, 1979). Theoretical and computational studies of the electronic

  20. Finite element prediction of seismic response modification of monumental structures utilizing base isolation

    NASA Astrophysics Data System (ADS)

    Spanos, Konstantinos; Anifantis, Nikolaos; Kakavas, Panayiotis

    2015-05-01

    The analysis of the mechanical behavior of ancient structures is an essential engineering task concerning the preservation of architectural heritage. As many monuments of classical antiquity are located in regions of earthquake activity, the safety assessment of these structures, as well as the selection of possible restoration interventions, requires numerical models capable of correctly representing their seismic response. The work presented herein was part of a research project in which a better understanding of the dynamics of classical column-architrave structures was sought by means of numerical techniques. In this paper, the seismic behavior of ancient monumental structures with multi-drum classical columns is investigated. In particular, the column-architrave classical structure under strong ground excitations was represented by a finite element method. This approach simulates the individual rock blocks as distinct rigid blocks interconnected with slidelines and incorporates seismic isolation dampers under the basement of the structure. Sliding and rocking motions of individual stone blocks and drums are modeled utilizing non-linear frictional contact conditions. The seismic isolation is modeled through the application of pad bearings under the basement of the structure. These pads are interpreted by appropriate rubber and steel layers. Time domain analyses were performed, considering the geometric and material non-linear behavior at the joints and the characteristics of pad bearings. The deformation and failure modes of drum columns subject to seismic excitations of various types and intensities were analyzed. The adverse influence of drum imperfections on structural safety was also examined.

  1. Effect of addition of pore expanding agent on changes of structure characteristics of ordered mesoporous silicas

    NASA Astrophysics Data System (ADS)

    Derylo-Marczewska, A.; Marczewski, A. W.; Skrzypek, I.; Pikus, S.; Kozak, M.

    2008-12-01

    A series of mesoporous silica materials were synthesized by applying two types of Pluronic copolymers as pore creating agents. Differentiation of pore structure of the obtained sorbents was attained by changing the amount of trimethylbenzene as pore expander introduced to a reacting mixture. The parameters characterizing porous structure were estimated from nitrogen adsorption/desorption isotherms. The changes of pore arrangement in the synthesized materials were investigated by using X-ray diffraction. The structural transformations were found at the TMB/polymer ratio of 0.8 and 1. Correlations between the values of structure parameters and the content of TMB were found.

  2. Micromechanical analysis and finite element modeling of electromechanical properties of active piezoelectric structural fiber (PSF) composites

    NASA Astrophysics Data System (ADS)

    Dai, Qingli; Ng, Kenny

    2013-04-01

    This paper presents the combined micromechanics analysis and finite element modeling of the electromechanical properties of piezoelectric structural fiber (PSF) composites. The active piezoelectric materials are widely used due to their high stiffness, voltage-dependent actuation capability, and broadband electro-mechanical interactions. However, the fragile nature of piezoceramics limits their sensing and actuating applications. In this study, the active PSF composites were made by deploying the longitudinally poled PSFs into a polymer matrix. The PSF itself consists a silicon carbide (SiC) or carbon core fiber as reinforcement to the fragile piezoceramic shell. To predict the electromechanical properties of PSF composites, the micromechanics analysis was firstly conducted with the dilute approximation model and the Mori-Tanaka approach. The extended Rule of Mixtures was also applied to accurately predict the transverse properties by considering the effects of microstructure including inclusion sizes and geometries. The piezoelectric finite element (FE) modeling was developed with the ABAQUS software to predict the detailed mechanical and electrical field distribution within a representative volume element (RVE) of PSF composites. The simulated energy or deformation under imposed specific boundary conditions was used to calculate each individual property with constitutive laws. The comparison between micromechanical analysis and finite element modeling indicates the combination of the dilute approximation model, the Mori-Tanaka approach and the extended Rule of Mixtures can favorably predict the electromechanical properties of three-phase PSF composites.

  3. Improved accuracy for finite element structural analysis via a new integrated force method

    NASA Technical Reports Server (NTRS)

    Patnaik, Surya N.; Hopkins, Dale A.; Aiello, Robert A.; Berke, Laszlo

    1992-01-01

    A comparative study was carried out to determine the accuracy of finite element analyses based on the stiffness method, a mixed method, and the new integrated force and dual integrated force methods. The numerical results were obtained with the following software: MSC/NASTRAN and ASKA for the stiffness method; an MHOST implementation method for the mixed method; and GIFT for the integrated force methods. The results indicate that on an overall basis, the stiffness and mixed methods present some limitations. The stiffness method generally requires a large number of elements in the model to achieve acceptable accuracy. The MHOST method tends to achieve a higher degree of accuracy for course models than does the stiffness method implemented by MSC/NASTRAN and ASKA. The two integrated force methods, which bestow simultaneous emphasis on stress equilibrium and strain compatibility, yield accurate solutions with fewer elements in a model. The full potential of these new integrated force methods remains largely unexploited, and they hold the promise of spawning new finite element structural analysis tools.

  4. Improved accuracy for finite element structural analysis via an integrated force method

    NASA Technical Reports Server (NTRS)

    Patnaik, S. N.; Hopkins, D. A.; Aiello, R. A.; Berke, L.

    1992-01-01

    A comparative study was carried out to determine the accuracy of finite element analyses based on the stiffness method, a mixed method, and the new integrated force and dual integrated force methods. The numerical results were obtained with the following software: MSC/NASTRAN and ASKA for the stiffness method; an MHOST implementation method for the mixed method; and GIFT for the integrated force methods. The results indicate that on an overall basis, the stiffness and mixed methods present some limitations. The stiffness method generally requires a large number of elements in the model to achieve acceptable accuracy. The MHOST method tends to achieve a higher degree of accuracy for course models than does the stiffness method implemented by MSC/NASTRAN and ASKA. The two integrated force methods, which bestow simultaneous emphasis on stress equilibrium and strain compatibility, yield accurate solutions with fewer elements in a model. The full potential of these new integrated force methods remains largely unexploited, and they hold the promise of spawning new finite element structural analysis tools.

  5. Material properties assignment to finite element models of bone structures: a new method.

    PubMed

    Zannoni, C; Mantovani, R; Viceconti, M

    1998-12-01

    Finite element analysis (FEA) is widely adopted to investigate the mechanical behaviour of bone structures. Computed tomography (CT) data are frequently used to generate FE models of bone. If properly calibrated, CT images are capable of providing accurate information about the bone morphology and tissue density. The aim of this work was to develop a special program able to read a CT data set as well as the FEA mesh generated from it, and to assign to each element of the mesh the material properties derived from the bone tissue density at the element location. The program was tested on phantom data sets and was adopted to evaluate the effects of the discrete description of the bone material properties. A three-dimensional FE model was generated automatically from a 16 bit CT data set of a distal femur acquired in vivo. The strain energy density (SED) was evaluated for each model element for increasing model complexity (number of different material cards assigned to the model). The computed SED were strongly dependent on the material mapping strategy. PMID:10223642

  6. Validating finite element models of composite aerospace structures for damage detection applications

    NASA Astrophysics Data System (ADS)

    Oliver, J. A.; Kosmatka, J. B.; Hemez, François M.; Farrar, Charles R.

    2006-03-01

    Carbon-fiber-reinforced-polymer (CFRP) composites represent the future for advanced lightweight aerospace structures. However, reliable and cost-effective techniques for structural health monitoring (SHM) are needed. Modal and vibration-based analysis, when combined with validated finite element (FE) models, can provide a key tool for SHM. Finite element models, however, can easily give spurious and misleading results if not finely tuned and validated. These problems are amplified in complex structures with numerous joints and interfaces. A small series of all-composite test pieces emulating wings from a lightweight all-composite Unmanned Aerial Vehicle (UAV) have been developed to support damage detection and SHM research. Each wing comprises two CFRP prepreg and Nomex honeycomb co-cured skins and two CFRP prepreg spars bonded together in a secondary process using a structural adhesive to form the complete wings. The first of the set is fully healthy while the rest have damage in the form of disbonds built into the main spar-skin bondline. Detailed FE models were created of the four structural components and the assembled structure. Each wing component piece was subjected to modal characterization via vibration testing using a shaker and scanning laser Doppler vibrometer before assembly. These results were then used to correlate the FE model on a component-basis, through fitting and optimization of polynomial meta-models. Assembling and testing the full wing provided subsequent data that was used to validate the numerical model of the entire structure, assembled from the correlated component models. The correlation process led to the following average percent improvement between experimental and FE frequencies of the first 20 modes for each piece: top skin 10.98%, bottom skin 45.62%, main spar 25.56%, aft spar 10.79%. The assembled wing model with no further correlation showed an improvement of 32.60%.

  7. Impact of zeolite-based nanomodified additive on the structure and strength of the cement stone

    NASA Astrophysics Data System (ADS)

    Egorova, A. D.; Filippova, K. E.

    2015-01-01

    Portland cement is the main binder in the building materials industry; its properties strongly influence properties of mortars and concretes. Some regions experience difficulties with delivery and storage of Portland cement, raising the need to develop an effective additive from the available raw materials. Such materials for the Republic of Sakha (Yakutia) are zeolite-containing rocks. Studies have shown that introducing of dibutylphthalate to the composition of modified additive during mechanochemical activation leads to achievement of up to 11% of total amount particles with the size of 3-30 nm. After introducing 0.5% of the obtained additives, the compressive strength of cement-sand slurry samples increases up to 28%. Positive effect of additives introduction is also observed at high flow rate of water (W / C = 0.7). Gaining strength reaches 23%, allowing the efficient use of additive for movable mixtures with enhanced strength properties. In general, the proposed supplement allows reducing the water flow in the solution without decreasing its mobility, and increasing strength properties, which makes it possible to obtain a whole class of solutions of modified cement binder. The market value of the developed additives is 18 rubles per 1 kg, making sound competition in the market of modifying additives.

  8. Progression of meiotic recombination requires structural maturation of the central element of the synaptonemal complex.

    PubMed

    Hamer, Geert; Wang, Hong; Bolcun-Filas, Ewelina; Cooke, Howard J; Benavente, Ricardo; Höög, Christer

    2008-08-01

    The synaptonemal complex is an elaborate meiosis-specific supramolecular protein assembly that promotes chromosome synapsis and meiotic recombination. We inactivated the meiosis-specific gene Tex12 and found that TEX12 is essential for progression of meiosis in both male and female germ cells. Structural analysis of the synaptonemal complex in Tex12-/- meiocytes revealed a disrupted central element structure, a dense structure residing between the synapsed homologous chromosomes. Chromosome synapsis is initiated at multiple positions along the paired homologous chromosomes in Tex12-/- meiotic cells, but fails to propagate along the chromosomes. Furthermore, although meiotic recombination is initiated in Tex12-/- meiotic cells, these early recombination events do not develop into meiotic crossovers. Hence, the mere initiation of synapsis is not sufficient to support meiotic crossing-over. Our results show that TEX12 is a component of the central element structure of the synaptonemal complex required for propagation of synapsis along the paired homologous chromosomes and maturation of early recombination events into crossovers. PMID:18611960

  9. Superheavy Element Chemistry by Relativistic Density Functional Theory Electronic Structure Modeling

    NASA Astrophysics Data System (ADS)

    Zaitsevskii, A. V.; Polyaev, A. V.; Demidov, Yu. A.; Mosyagin, N. S.; Lomachuk, Yu. V.; Titov, A. V.

    2015-06-01

    Two-component density functional theory in its non-collinear formulation combined with the accurate relativistic electronic structure model defined by shape-consistent small-core pseudopotentials (PP/RDFT) provides a robust basis of efficient computational schemes for predicting energetic and structural properties of complex polyatomic systems including superheavy elements (SHEs). Because of the exceptional role of thermochromatography in the experiments on the "chemical" identification of SHEs with atomic numbers Z ≥ 112, we focus on the description of the adsorption of single SHE atoms on the surfaces of solids through cluster modeling of adsorption complexes. In some cases our results differ significantly from those of previous theoretical studies. The results of systematic comparative studies on chemical bonding in simple molecules of binary compounds of SHEs and their nearest homologs with most common light elements, obtained at the PP/RDFT level and visualized through the "chemical graphs", provide the understanding of the general chemistry of SHEs which at present cannot be derived from the experimental data. These results are used to discuss the main trends in changing chemical properties of the elements in the given group of the periodic table and demonstrate the specificity of SHEs.

  10. Integrated force method - Compatibility conditions of structural mechanics for finite element analysis

    NASA Technical Reports Server (NTRS)

    Patnaik, Surya N.; Berke, Laszlo; Gallagher, Richard H.

    1991-01-01

    The equilibrium equations and the compatibility conditions are fundamental to the analyses of structures. However, anyone who undertakes even a cursory generic study of the compatibility conditions can discover, with little effort, that historically this facet of structural mechanics had not been adequately researched by the profession. Now the compatibility conditions (CC's) have been researched and are understood to a great extent. For finite element discretizations, the CC's are banded and can be divided into three distinct categories: (1) the interface CC's, (2) the cluster or field CC's, and (3) the external CC's. The generation of CC's requires the separating of a local region, then writing the deformation displacement relation (ddr) for the region, and finally, the eliminating of the displacements from the ddr. The procedure to generate all three types of CC's is presented and illustrated through examples of finite element models. The uniqueness of the CC's thus generated is shown. The utilization of CC's has resulted in the novel integrated force method (IFM). The solution that is obtained by the IFM converges with a significantly fewer number of elements, compared to the stiffness and the hybrid methods.

  11. Adaptive finite element modeling of direct current resistivity in 2-D generally anisotropic structures

    NASA Astrophysics Data System (ADS)

    Yan, Bo; Li, Yuguo; Liu, Ying

    2016-07-01

    In this paper, we present an adaptive finite element (FE) algorithm for direct current (DC) resistivity modeling in 2-D generally anisotropic conductivity structures. Our algorithm is implemented on an unstructured triangular mesh that readily accommodates complex structures such as topography and dipping layers and so on. We implement a self-adaptive, goal-oriented grid refinement algorithm in which the finite element analysis is performed on a sequence of refined grids. The grid refinement process is guided by an a posteriori error estimator. The problem is formulated in terms of total potentials where mixed boundary conditions are incorporated. This type of boundary condition is superior to the Dirichlet type of conditions and improves numerical accuracy considerably according to model calculations. We have verified the adaptive finite element algorithm using a two-layered earth with azimuthal anisotropy. The FE algorithm with incorporation of mixed boundary conditions achieves high accuracy. The relative error between the numerical and analytical solutions is less than 1% except in the vicinity of the current source location, where the relative error is up to 2.4%. A 2-D anisotropic model is used to demonstrate the effects of anisotropy upon the apparent resistivity in DC soundings.

  12. The relationship between structural stability and electrochemical performance of multi-element doped alpha nickel hydroxide

    NASA Astrophysics Data System (ADS)

    Miao, Chengcheng; Zhu, Yanjuan; Huang, Liangguo; Zhao, Tengqi

    2015-01-01

    The multi-element doped alpha nickel hydroxide has been prepared by supersonic co-precipitation method. Three kinds of samples A, B and C are prepared by chemically coprecipitating Ni/Al, Ni/Al/Mn and Ni/Al/Mn/Yb, respectively. Inductively coupled plasma atomic emission spectroscopy (ICP-AES), Particle size distribution (PSD) measurement, X-ray diffraction (XRD), scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FT-IR) are used to characterize the physical properties of the synthesized α-Ni(OH)2 samples, such as chemical composition, morphology, structural stability of the crystal. The results show that all samples are nano-sized materials and the interlayer spacing becomes larger and the structural stability becomes better with the increase of doped elements and doped ratio. The prepared alpha nickel hydroxide samples are added into micro-sized beta nickel hydroxide to form biphase electrode materials for Ni-MH battery. The electrochemical characterization of the biphase electrodes, including cyclic voltammetry (CV) and charge/discharge test, are also performed. The results demonstrate that the biphase electrode with sample C exhibits better electrochemical reversibility and cyclic stability, higher charge efficient and discharge potential, larger proton diffusion coefficient (5.81 × 10-12 cm2 s-1) and discharge capacity (309.0 mAh g-1). Hence, it indicates that all doped elements can produce the synergic effect and further improve the electrochemical properties of the alpha nickel hydroxide.

  13. A Spectral Element Approach for Modeling of Wave-Based Structural Health Monitoring Systems

    SciTech Connect

    Schulte, Rolf T.; Fritzen, Claus-Peter

    2010-09-30

    During the last decades, guided waves have shown great potential for Structural Health Monitoring (SHM) applications. These waves can be excited and sensed by piezoelectric elements that can be permanently attached onto a structure offering online monitoring capability. As the setup of wave based SHM systems may be very difficult and time consuming there is a growing demand for efficient simulation tools providing the opportunity to design wave based SHM systems in a virtual environment. As usually high frequency waves are used, the associated short wavelength leads to the necessity of a very dense mesh, which makes conventional finite elements not well suited for this purpose. Therefore a flat shell spectral element approach is presented in this contribution. By including electromechanical coupling an SHM system can be simulated entirely from actuator voltage to sensor voltage. The focus of this contribution is the analysis of the effect of delaminations on propagating waves. A forward increment Lagrange multiplier method is used to simulate contact within the delaminated area. A model validation is performed using measured data of an anisotropic CFRP-plate.

  14. Global functions in global-local finite-element analysis of localized stresses in prismatic structures

    NASA Technical Reports Server (NTRS)

    Dong, Stanley B.

    1989-01-01

    An important consideration in the global local finite-element method (GLFEM) is the availability of global functions for the given problem. The role and mathematical requirements of these global functions in a GLFEM analysis of localized stress states in prismatic structures are discussed. A method is described for determining these global functions. Underlying this method are theorems due to Toupin and Knowles on strain energy decay rates, which are related to a quantitative expression of Saint-Venant's principle. It is mentioned that a mathematically complete set of global functions can be generated, so that any arbitrary interface condition between the finite element and global subregions can be represented. Convergence to the true behavior can be achieved with increasing global functions and finite-element degrees of freedom. Specific attention is devoted to mathematically two-dimensional and three-dimensional prismatic structures. Comments are offered on the GLFEM analysis of NASA flat panel with a discontinuous stiffener. Methods for determining global functions for other effects are also indicated, such as steady-state dynamics and bodies under initial stress.

  15. Structural damage detection using higher-order finite elements and a scanning laser vibrometer

    NASA Astrophysics Data System (ADS)

    Jin, Si

    In contrast to conventional non-destructive evaluation methods, dynamics-based damage detection methods are capable of rapid integrity evaluation of large structures and have received considerable attention from aerospace, mechanical, and civil engineering communities in recent years. However, the identifiable damage size using dynamics-based methods is determined by the number of sensors used, level of measurement noise, accuracy of structural models, and signal processing techniques. In this thesis we study dynamics of structures with damage and then derive and experimentally verify new model-independent structural damage detection methods that can locate small damage to structures. To find sensitive damage detection parameters we develop a higher-order beam element that enforces the continuity of displacements, slopes, bending moments, and shear forces at all nodes, and a higher-order rectangular plate element that enforces the continuity of displacements, slopes, and bending and twisting moments at all nodes. These two elements are used to study the dynamics of beams and plates. Results show that high-order spatial derivatives of high-frequency modes are important sensitive parameters that can locate small structural damage. Unfortunately the most powerful and popular structural modeling technique, the finite element method, is not accurate in predicting high-frequency responses. Hence, a model-independent method using dynamic responses obtained from high density measurements is concluded to be the best approach. To increase measurement density and reduce noise a Polytec PI PSV-200 scanning laser vibrometer is used to provide non-contact, dense, and accurate measurements of structural vibration velocities. To avoid the use of structural models and to extract sensitive detection parameters from experimental data, a brand-new structural damage detection method named BED (Boundary-Effect Detection) is developed for pinpointing damage locations using Operational

  16. Effects of meat addition on pasta structure, nutrition and in vitro digestibility.

    PubMed

    Liu, Tingting; Hamid, Nazimah; Kantono, Kevin; Pereira, Loveena; Farouk, Mustafa M; Knowles, Scott O

    2016-12-15

    In our study, semolina flour was substituted with beef emulsion (EM) at three different levels of 15, 30 and 45% (w/w) to develop a pasta with enhanced nutritional profile. The protein, fat, and water content significantly increased with addition of meat. The addition of meat enhanced the pasta gluten network. The redness and yellowness of cooked pasta increased with meat addition. Tensile strength increased from 0.018N/mm(2) in the control sample to 0.046N/mm(2) in 45% beef emulsion (45EM) sample. All meat-containing samples had significantly higher elasticity than control (0.039N/mm(2)). GI significantly decreased and IVPD value increased in 45EM sample. Five essential amino acids (leucine, lysine, methionine, threonine, tryptophan) in pasta digesta increased significantly with increasing meat addition. PMID:27451161

  17. Determining the Structure of a Cytoplasmic Polyadenylation Element Binding Protein via AMBER9

    NASA Astrophysics Data System (ADS)

    Saunders, Alison

    2010-03-01

    The neurons of Aplysia californica contain cytoplasmic polyadenylation element binding protein (CPEB). CPEB shows prion-like properties when expressed in yeast cells. Because prions have misfolded and normally folded forms, prions can code in neurons like binary codes in computers, with ``present'' and ``not present'' signals available. CPEB thus provides a candidate protein for the molecular basis of memory. I attempt to determine CPEB's structure, by first threading the known protein sequence around a β-helical structure. Threading is preformed by hand, and by a program written to minimize the energy cost of building the structure. I then analyze the stability of the thread using the molecular dynamics program AMBER9. I also analyze a protein of only glutamine (PolyQ) in a β-helical structure to substantiate my use of a β-helix with the glutamine-rich CPEB. I found PolyQ to be stable in a left-handed β-helical structure with eighteen residues per turn. A candidate structure for CPEB was located with the same β-helical structure.

  18. Structural Anomalies Detected in Ceramic Matrix Composites Using Combined Nondestructive Evaluation and Finite Element Analysis (NDE and FEA)

    NASA Technical Reports Server (NTRS)

    Abdul-Aziz, Ali; Baaklini, George Y.; Bhatt, Ramakrishna T.

    2003-01-01

    Most reverse engineering approaches involve imaging or digitizing an object and then creating a computerized reconstruction that can be integrated, in three dimensions, into a particular design environment. The rapid prototyping technique builds high-quality physical prototypes directly from computer-aided design files. This fundamental technique for interpreting and interacting with large data sets is being used here via Velocity2 (an integrated image-processing software, ref. 1) using computed tomography (CT) data to produce a prototype three-dimensional test specimen model for analyses. A study at the NASA Glenn Research Center proposes to use these capabilities to conduct a combined nondestructive evaluation (NDE) and finite element analysis (FEA) to screen pretest and posttest structural anomalies in structural components. A tensile specimen made of silicon nitrite (Si3N4) ceramic matrix composite was considered to evaluate structural durability and deformity. Ceramic matrix composites are being sought as candidate materials to replace nickel-base superalloys for turbine engine applications. They have the unique characteristics of being able to withstand higher operating temperatures and harsh combustion environments. In addition, their low densities relative to metals help reduce component mass (ref. 2). Detailed three-dimensional volume rendering of the tensile test specimen was successfully carried out with Velocity2 (ref. 1) using two-dimensional images that were generated via computed tomography. Subsequent, three-dimensional finite element analyses were performed, and the results obtained were compared with those predicted by NDE-based calculations and experimental tests. It was shown that Velocity2 software can be used to render a three-dimensional object from a series of CT scan images with a minimum level of complexity. The analytical results (ref. 3) show that the high-stress regions correlated well with the damage sites identified by the CT scans

  19. Investigation of the two-element airfoil with flap structure for the vertical axis wind turbine

    NASA Astrophysics Data System (ADS)

    Wei, Y.; Li, C.

    2013-12-01

    The aerodynamic performance of Vertical axis wind turbine (VAWT) is not as simple as its structure because of the large changing range of angle of attack. We have designed a new kind of two-element airfoil for VAWT on the basis of NACA0012. CFD calculation has been confirmed to have high accuracy by comparison with the experiment data and Xfoil result. The aerodynamic parameter of two-element airfoil has been acquired by CFD calculation in using the Spalart-Allmaras (S-A) turbulence model and the Simple scheme. The relationship between changings of angle of attack and flap's tilt angle has been found and quantified. The analysis will lay the foundation for further research on the control method for VAWT.

  20. [Mobile genetic element MDG4 (gypsy) in Drosophila melanogaster. Features of structure and regulation of transposition].

    PubMed

    Kusulidu, L K; Karpova, N N; Razorenova, O V; Glukhov, I A; Kim, A I; Liubomirskaia, N V; Il'in, Iu V

    2001-12-01

    Distribution of two structural functional variants of the MDG4 (gypsy) mobile genetic element was examined in 44 strains of Drosophila melanogaster. The results obtained suggest that less transpositionally active MDG4 variant is more ancient component of the Drosophila genome. Using Southern blotting, five strains characterized by increased copy number of MDG4 with significant prevalence of the active variant over the less active one were selected for further analysis. Genetic analysis of these strains led to the suggestion that some of them carry factors that mobilize MDG4 independently from the cellular flamenco gene known to be responsible for transposition of this element. Other strains probably contained a suppressor of the flam- mutant allele causing active transpositions of the MDG4. Thus, the material for studying poorly examined relationships between the retrovirus and the host cell genome was obtained. PMID:11785284

  1. Finite element analysis of steady and transiently moving/rolling nonlinear viscoelastic structure. Part 1: Theory

    NASA Technical Reports Server (NTRS)

    Padovan, Joe

    1986-01-01

    In a three part series of papers, a generalized finite element analysis scheme is developed to handle the steady and transient response of moving/rolling nonlinear viscoelastic structure. This paper considers the development of the moving/rolling element strategy, including the effects of large deformation kinematics and viscoelasticity modelled by fractional integro-differential operators. To improve the solution strategy, a special hierarchical constraint procedure is developed for the case of steady rolling/translating as well as a transient scheme involving the use of a Grunwaldian representation of the fractional operator. In the second and third parts of the paper, 3-D extensions are developed along with transient contact strategies enabling the handling of impacts with obstructions. Overall, the various developments are benchmarked via comprehensive 2- and 3-D simulations. These are correlated with experimental data to define modelling capabilities.

  2. Development of a moderately sized finite element program for nonlinear structural analysis

    NASA Technical Reports Server (NTRS)

    Haisler, W. E.

    1977-01-01

    AGGIE 1 is a computer program for predicting the linear and nonlinear, static and dynamic structural response of two- and three-dimensional continuum solids. The program is based on isoparametric finite elements and allows for 2-D plane stress, plane strain, and axisymmetric analyses and general 3-D analyses. Large strain kinematics is based on the total Lagrangian formulation. Materially nonlinear models include several elastic-plastic work-hardening models as well as an incompressible Mooney-Rivlin model. Included in this report is a brief description of the theoretical bases of the program, the material models used, the element library and the overall program organization. Instructions for data input preparation are given in detail. Several sample problems are given along with the required program input and program generated solutions.

  3. Comb structure analysis of the capacitive sensitive element in MEMS-accelerometer

    NASA Astrophysics Data System (ADS)

    Shalimov, Andrew; Timoshenkov, Sergey; Korobova, Natalia; Golovinskiy, Maxim; Timoshenkov, Alexey; Zuev, Egor; Berezueva, Svetlana; Kosolapov, Andrey

    2015-05-01

    In this paper analysis of comb design for the sensing element MEMS accelerometer with longitudinal displacement of the inertial mass under the influence of acceleration to obtain the necessary parameters for the further construction of an electronic circuit for removal and signal processing has been done. Fixed on the stator the inertia mass has the ability to move under the influence of acceleration along the longitudinal structure. As a result the distance between the fixed and movable combs, and hence the capacitance in the capacitors have been changed. Measuring the difference of these capacitances you can estimate the value of the applied acceleration. Furthermore, managing combs that should apply an electrostatic force for artificial deviation of the inertial mass may be used for the initial sensitive elements culling. Also in this case there is a change of capacitances, which can be measured by the comb and make a decision about the spoilage presence or absence.

  4. Interrater reliability and discriminative validity of the structural elements of the Ayres Sensory Integration Fidelity Measure.

    PubMed

    May-Benson, Teresa A; Roley, Susanne Smith; Mailloux, Zoe; Parham, L Diane; Koomar, Jane; Schaaf, Roseann C; Jaarsveld, Annamarie Van; Cohn, Ellen

    2014-01-01

    This study examined the reliability and validity of the structural section of the Ayres Sensory Integration® Fidelity Measure© (ASIFM), which provides a method for monitoring the extent to which an intervention was implemented as conceptualized in studies of occupational therapy using sensory integration intervention methods (OT-SI). We examined the structural elements of the measure, including content of assessment reports, availability of specific equipment and adequate space, safety monitoring, and integration of communication with parents and other team members, such as collaborative goal setting with parents or family and teacher education, into the intervention program. Analysis of self-report ratings by 259 occupational therapists from 185 different facilities indicated that the structural section of the ASIFM has acceptable interrater reliability (r ≥ .82) and significantly differentiates between settings in which therapists reportedly do and do not practice OT-SI (p < .001). PMID:25184462

  5. Heat induced transformation of fossil mastodon ivory into turquoise 'odontolite'. Structural and elemental characterisation

    NASA Astrophysics Data System (ADS)

    Reiche, I.; Vignaud, C.; Menu, M.

    2000-10-01

    The present work deals with the structural and elemental analysis of turquoise mineral imitations as 'odontolite' or bone turquoise by transmission electron microscopy (TEM), scanning electron microscopy (SEM-EDX) and particle induced X-ray and γ-ray emission (PIXE-PIGE). The aim of the work is to evidence the former deliberate transformation of fossilised ivory by man in order to transform them into semi-precious stones. We show that the crystal structure of 'odontolite' artefacts consisting of fluorapatite (Ca 5(PO 4) 3F) corresponds to that of heated fossil mastodon ivory (12-15 million years old). Metallic traces detected by PIXE-PIGE in these 'odontolites' are discussed in order to explain their role for coloration. Other more greenish turquoise imitations have a bone-like structure and composition, and carbonate-hydroxylapatite. The presence of copper salts at the surface is responsible for their green coloration.

  6. A modified Finite Element-Transfer Matrix for control design of space structures

    NASA Technical Reports Server (NTRS)

    Tan, T.-M.; Yousuff, A.; Bahar, L. Y.; Konstandinidis, M.

    1990-01-01

    The Finite Element-Transfer Matrix (FETM) method was developed for reducing the computational efforts involved in structural analysis. While being widely used by structural analysts, this method does, however, have certain limitations, particularly when used for the control design of large flexible structures. In this paper, a new formulation based on the FETM method is presented. The new method effectively overcomes the limitations in the original FETM method, and also allows an easy construction of reduced models that are tailored for the control design. Other advantages of this new method include the ability to extract open loop frequencies and mode shapes with less computation, and simplification of the design procedures for output feedback, constrained compensation, and decentralized control. The development of this new method and the procedures for generating reduced models using this method are described in detail and the role of the reduced models in control design is discussed through an illustrative example.

  7. B2 structure of high-entropy alloys with addition of Al

    SciTech Connect

    Li, C.; Zhao, M.; Li, J. C.; Jiang, Q.

    2008-12-01

    A series of AlCrCoNiFe based alloys with equal percentage of principal components (high-entropy alloys or HE alloys) is fabricated. The related crystalline structures of the alloys are measured and calculated. Results show that the formed bcc phase is a compound based B2 structure where there is partial ionic bonding between Al and other transition metals. Thus, the bcc structure of the alloys should be a B2 instead of an A2 due to the large difference in electronegativities among the components consisting of the HE alloys.

  8. Concrete containment tests: Phase 2, Structural elements with liner plates: Interim report

    SciTech Connect

    Hanson, N.W.; Roller, J.J.; Schultz, D.M.; Julien, J.T.; Weinmann, T.L.

    1987-08-01

    The tests described in this report are part of Phase 2 of the Electric Power Research Institute (EPRI) program. The overall objective of the EPRI program is to provide a test-verified analytical method of estimating capacities of concrete reactor containment buildings under internal overpressurization from postulated degraded core accidents. The Phase 2 testing included seven large-scale specimens representing structural elements from reinforced and prestressed concrete reactor containment buildings. Six of the seven test specimens were square wall elements. Of these six specimens, four were used for biaxial tension tests to determine strength, deformation, and leak-rate characteristics of full-scale wall elements representing prestressed concrete containment design. The remaining two square wall elements were used for thermal buckling tests to determine whether buckling of the steel liner plate would occur between anchorages when subjected to a sudden extreme temperature differential. The last of the seven test specimens for Phase 2 represented the region where the wall and the basemat intersect in a prestressed concrete containment building. A multi-directional loading scheme was used to produce high bending moments and shear in the wall/basemat junction region. The objective of this test was to determine if there is potential for liner plate tearing in the junction region. Results presented include observed behavior and extensive measurements of deformations and strains as a function of applied load. The data are being used to confirm analytical models for predicting strength and deformation of containment structures in a separate parallel analytical investigation sponsored by EPRI.

  9. An automatic granular structure generation and finite element analysis of heterogeneous semi-solid materials

    NASA Astrophysics Data System (ADS)

    Sharifi, Hamid; Larouche, Daniel

    2015-09-01

    The quality of cast metal products depends on the capacity of the semi-solid metal to sustain the stresses generated during the casting. Predicting the evolution of these stresses with accuracy in the solidification interval should be highly helpful to avoid the formation of defects like hot tearing. This task is however very difficult because of the heterogeneous nature of the material. In this paper, we propose to evaluate the mechanical behaviour of a metal during solidification using a mesh generation technique of the heterogeneous semi-solid material for a finite element analysis at the microscopic level. This task is done on a two-dimensional (2D) domain in which the granular structure of the solid phase is generated surrounded by an intergranular and interdendritc liquid phase. Some basic solid grains are first constructed and projected in the 2D domain with random orientations and scale factors. Depending on their orientation, the basic grains are combined to produce larger grains or separated by a liquid film. Different basic grain shapes can produce different granular structures of the mushy zone. As a result, using this automatic grain generation procedure, we can investigate the effect of grain shapes and sizes on the thermo-mechanical behaviour of the semi-solid material. The granular models are automatically converted to the finite element meshes. The solid grains and the liquid phase are meshed properly using quadrilateral elements. This method has been used to simulate the microstructure of a binary aluminium-copper alloy (Al-5.8 wt% Cu) when the fraction solid is 0.92. Using the finite element method and the Mie-Grüneisen equation of state for the liquid phase, the transient mechanical behaviour of the mushy zone under tensile loading has been investigated. The stress distribution and the bridges, which are formed during the tensile loading, have been detected.

  10. Telomere Capping Proteins are Structurally Related to RPA with an additional Telomere-Specific Domain

    SciTech Connect

    Gelinas, A.; Paschini, M; Reyes, F; Heroux, A; Batey, R; Lundblad, V; Wuttke, D

    2009-01-01

    Telomeres must be capped to preserve chromosomal stability. The conserved Stn1 and Ten1 proteins are required for proper capping of the telomere, although the mechanistic details of how they contribute to telomere maintenance are unclear. Here, we report the crystal structures of the C-terminal domain of the Saccharomyces cerevisiae Stn1 and the Schizosaccharomyces pombe Ten1 proteins. These structures reveal striking similarities to corresponding subunits in the replication protein A complex, further supporting an evolutionary link between telomere maintenance proteins and DNA repair complexes. Our structural and in vivo data of Stn1 identify a new domain that has evolved to support a telomere-specific role in chromosome maintenance. These findings endorse a model of an evolutionarily conserved mechanism of DNA maintenance that has developed as a result of increased chromosomal structural complexity.

  11. Studies of Element-Specific Local Structures in Compound Materials Using X-Ray Absorption Spectroscopy

    NASA Astrophysics Data System (ADS)

    Soo, Yun-Liang

    1995-01-01

    The x-ray absorption spectroscopy techniques have been used to study a variety of semiconductor and superconductor materials. In such experiments, synchrotron radiation harnessed by a delicate beamline electronic and control system are used to obtain data with analyzable quality in a reasonable time scale. The element-selectivity is achieved by selecting an energy-scan range close to a characteristic "absorption edge" of the selected element. Peak structures below the absorption edge (pre-edge structures) reflect the local unoccupied states of the selected atomic species. The position of absorption edge (part of the near-edge x-ray absorption fine structure, NEXAFS) provides some qualitative information of the effective valency of the selected element. And, most importantly, the modulation in the spectrum some 40 eV above the absorption edge (extended x-ray absorption fine structure, EXAFS) gives quantitative information of the local structure around the selected atomic species. The selected atomic species such as magnetic Mn ions in III-V diluted magnetic semiconductors (DMS) rm In_{1-x}Mn_{x}As, Mn as the luminescent centers in nanocrystals of ZnS, O in the CuO_2 planes which host the carriers in high-T_{rm c} superconductors, and F as the electron reservoir in the n-type high-T_{rm c} superconductors rm Nd_2CuO _{4-x}F_{x} all play an important role in the novel mechanism of these new materials. Along with other detailed information, our EXAFS results have revealed (i) III-V DMS can indeed be prepared by substitutional doping of magnetic impurities under proper processing conditions. (ii) Mn ions substitute for the Zn sites in the nanocrystals of ZnS with significant size-dependent local structural changes. (iii) Only ~6% of O in the CuO_2 planes in rm Nd_2CuO_{4 -x}F_{x} are substituted by F. The rest of F atoms substitute for O atoms in the NdO layers and serve as electron reservoirs. The NEXAFS results have shown that the effective valency of Mn in Zn

  12. The influence of Citrosept addition to drinking water and Scutellaria baicalensis root extract on the content of selected mineral elements in the blood plasma of turkey hens.

    PubMed

    Rusinek-Prystupa, Elżbieta; Lechowski, Jerzy; Zukiewicz-Sobczak, Wioletta; Sobczak, Paweł; Zawiślak, Kazimierz

    2014-01-01

    The aim of this research work was to indicate the influence of Citrosept preparation and Scutellaria baicalensis root extract, administered per os to growing turkey hens in 3 different dosages, on the content of selected mineral elements in blood plasma of slaughter turkey hens. An attempt was also made to specify the most effective dosage of the applied preparations with the highest efficiency as regards increased levels of examined macro- and microelements in the birds' blood. The research experiment was conducted on 315 turkey hens randomly divided into seven groups, each consisting of 45 turkey hens. Group K constituted the control group without experimental additions of the above-mentioned preparations. When it comes to turkey hens which belonged to groups II-IV, Citrosept preparation was instilled to water in the following dosages: Group II - 0.011 ml/kg of bm; Group III - 0.021 ml/kg of bm; Group IV - 0.042 ml/kg bm. For birds which belonged to groups V-VII preparation, which was Scutellaria baicalensis root extract, was instilled to water in the following dosages: Group V - 0.009 ml/kg of bm; Group VI - 0.018 ml/kg of bm, Group VII - 0.036 ml/kg bm. In the examined plant extracts and blood plasma of the birds the levels of Na, K, Ca, Mg, Cu, Zn, and Fe were identified. The use of examined extracts influenced the changes in the levels of all tested elements in slaughter turkey hens' blood plasma. An upward tendency was recorded which regarded the level of calcium and magnesium, and a downward tendency of sodium, potassium, copper, zinc, and iron in relation to the results achieved in the control group. PMID:25292136

  13. PLANS: A finite element program for nonlinear analysis of structures. Volume 1: Theoretical manual

    NASA Technical Reports Server (NTRS)

    Pifko, A.; Levine, H. S.; Armen, H., Jr.

    1975-01-01

    The PLANS system is described which is a finite element program for nonlinear analysis. The system represents a collection of special purpose computer programs each associated with a distinct physical problem class. Modules of PLANS specifically referenced and described in detail include: (1) REVBY, for the plastic analysis of bodies of revolution; (2) OUT-OF-PLANE, for the plastic analysis of 3-D built-up structures where membrane effects are predominant; (3) BEND, for the plastic analysis of built-up structures where bending and membrane effects are significant; (4) HEX, for the 3-D elastic-plastic analysis of general solids; and (5) OUT-OF-PLANE-MG, for material and geometrically nonlinear analysis of built-up structures. The SATELLITE program for data debugging and plotting of input geometries is also described. The theoretical foundations upon which the analysis is based are presented. Discussed are the form of the governing equations, the methods of solution, plasticity theories available, a general system description and flow of the programs, and the elements available for use.

  14. Finite Element Analysis of Layered Fiber Composite Structures Accounting for the Material's Microstructure and Delamination

    NASA Astrophysics Data System (ADS)

    Stier, Bertram; Simon, Jaan-Willem; Reese, Stefanie

    2015-04-01

    The present paper focuses on composite structures which consist of several layers of carbon fiber reinforced plastics (CFRP). For such layered composite structures, delamination constitutes one of the major failure modes. Predicting its initiation is essential for the design of these composites. Evaluating stress-strength relation based onset criteria requires an accurate representation of the through-the-thickness stress distribution, which can be particularly delicate in the case of shell-like structures. Thus, in this paper, a solid-shell finite element formulation is utilized which allows to incorporate a fully three-dimensional material model while still being suitable for applications involving thin structures. Moreover, locking phenomena are cured by using both the EAS and the ANS concept, and numerical efficiency is ensured through reduced integration. The proposed anisotropic material model accounts for the material's micro-structure by using the concept of structural tensors. It is validated by comparison to experimental data as well as by application to numerical examples.

  15. Interactive editing of 3D geological structures and tectonic history sketching via a rigid element method

    NASA Astrophysics Data System (ADS)

    Laurent, Gautier; Caumon, Guillaume; Jessell, Mark

    2015-01-01

    Numerical models of geological structures are generally built with a geometrical approach, which lacks an explicit representation of the deformation history and may lead to incompatible structures. We advocate that the deformation history should be investigated and represented from the very first steps of the modelling process, provided that a series of rapid, interactive or automated, deformation tools are available for local editing, forward modelling and restoration. In this paper, we define the specifications of such tools and emphasise the need for rapidity and robustness. We briefly review the different applications of deformation tools in geomodelling and the existing deformation algorithms. We select a deformation algorithm based on rigid elements, first presented in the Computer Graphics community, which we refer to as Reed. It is able to rapidly deform any kind of geometrical object, including points, lines or volumes, with an approximated mechanical behaviour. The objects to be deformed are embedded in rigid cells whose displacement is optimised by minimising a global cost function with respect to displacement boundary conditions. This cost function measures the difference in displacement between neighbouring elements. The embedded objects are then deformed based on their original position with respect to the rigid elements. We present the basis of our implementation of this algorithm and highlight its ability to fulfil the specifications we defined. Its application to geomodelling specific problems is illustrated through the construction of a synthetic structural model of multiply deformed layers with a forward modelling approach. A special boundary condition adapted to restore large folds is also presented and applied to the large anticline of Han-sur-Lesse, Belgium, which demonstrates the ability of this method to efficiently perform a volumetric restoration without global projections.

  16. Research on optimization of cooling structure of LED element (The 2nd report)

    SciTech Connect

    Kobayashi, T.; Sakate, Y.; Hashimoto, R.; Takashina, T.; Kanematsu, H.; Utsumi, Y.

    2014-02-20

    This report shows a design guideline on the parts dimension of LED light bulb for heat transfer. LED light bulb is popular owing to the high efficiency and long life. However, LED element is a point heat source. Therefore, LED light bulb has some problems about heat transfer when it is used for lighting. It sometimes causes deterioration by the raise of local temperature, resulting in lowering of efficiency and shorter life. Thus the thermal analysis focused on the number of element, all parts thickness, length, and radiant heat was studied, as systematic report on the points has not been found. In this report, heat radiation was taken into account in the thermal analysis in addition to natural heat convection. Furthermore the temperature of a heat sink model for LED light bulb was measured with thermocouples and thermo-viewer to verify the calculation. The emissivity of aluminum used for the calculation was 0.4. As the result of analysis, it was found that the maximum temperature was mainly influenced by ring length, ring diameter and disk thickness as a design guideline. Concretely, longer length, larger diameter and thicker disk gave lower temperature of LED element. The temperatures of the best and worst model were around 70 °C and 120 °C respectively in the above condition. The temperatures calculated were consistent with those in experiment.

  17. Research on optimization of cooling structure of LED element (The 2nd report)

    NASA Astrophysics Data System (ADS)

    Kobayashi, T.; Sakate, Y.; Hashimoto, R.; Takashina, T.; Kanematsu, H.; Utsumi, Y.

    2014-02-01

    This report shows a design guideline on the parts dimension of LED light bulb for heat transfer. LED light bulb is popular owing to the high efficiency and long life. However, LED element is a point heat source. Therefore, LED light bulb has some problems about heat transfer when it is used for lighting. It sometimes causes deterioration by the raise of local temperature, resulting in lowering of efficiency and shorter life. Thus the thermal analysis focused on the number of element, all parts thickness, length, and radiant heat was studied, as systematic report on the points has not been found. In this report, heat radiation was taken into account in the thermal analysis in addition to natural heat convection. Furthermore the temperature of a heat sink model for LED light bulb was measured with thermocouples and thermo-viewer to verify the calculation. The emissivity of aluminum used for the calculation was 0.4. As the result of analysis, it was found that the maximum temperature was mainly influenced by ring length, ring diameter and disk thickness as a design guideline. Concretely, longer length, larger diameter and thicker disk gave lower temperature of LED element. The temperatures of the best and worst model were around 70 °C and 120 °C respectively in the above condition. The temperatures calculated were consistent with those in experiment.

  18. Testing the big bang: Light elements, neutrinos, dark matter and large-scale structure

    SciTech Connect

    Schramm, D.N. Fermi National Accelerator Lab., Batavia, IL )

    1991-06-01

    In this series of lectures, several experimental and observational tests of the standard cosmological model are examined. In particular, detailed discussion is presented regarding nucleosynthesis, the light element abundances and neutrino counting; the dark matter problems; and the formation of galaxies and large-scale structure. Comments will also be made on the possible implications of the recent solar neutrino experimental results for cosmology. An appendix briefly discusses the 17 keV thing'' and the cosmological and astrophysical constraints on it. 126 refs., 8 figs., 2 tabs.

  19. Programs for transferring data between a relational data base and a finite element structural analysis program

    NASA Technical Reports Server (NTRS)

    Johnson, S. C.

    1982-01-01

    An interface system for passing data between a relational information management (RIM) data base complex and engineering analysis language (EAL), a finite element structural analysis program is documented. The interface system, implemented on a CDC Cyber computer, is composed of two FORTRAN programs called RIM2EAL and EAL2RIM. The RIM2EAL reads model definition data from RIM and creates a file of EAL commands to define the model. The EAL2RIM reads model definition and EAL generated analysis data from EAL's data library and stores these data dirctly in a RIM data base. These two interface programs and the format for the RIM data complex are described.

  20. Development of an Image Fringe Zero Selection System for Structuring Elements with Stereo Vision Disparity Measurements

    NASA Astrophysics Data System (ADS)

    Grindley, Josef E.; Tickle, Andrew J.; Jiang, Lin

    2011-08-01

    When performing image operations involving Structuring Element (SE) and many transforms it is required that the outside of the image be padded with zeros or ones depending on the operation. This paper details how this can be achieved with simulated hardware using DSP Builder in Matlab with the intention of migrating the design to HDL (Hardware Description Language) and implemented on an FPGA (Field Programmable Gate Array). The design takes few resources and does not require extra memory to account for the change in size of the output image.

  1. Simple model of the Rayleigh-Taylor instability, collapse, and structural elements.

    PubMed

    Goncharov, V P; Pavlov, V I

    2013-08-01

    The mechanisms and structural elements of the Rayleigh-Taylor instability whose evolution results in the occurrence of the collapse have been studied in the scope of the rotating shallow water model with horizontal density gradient. Analysis of the instability mechanism shows that two collapse scenarios are possible. One scenario implies anisotropic collapse during which the contact area of a collapsing fragment with the bottom contracts into a spinning segment. The other implies isotropic contracting of the area into a point. The rigorous integral criteria and power laws of collapses are found. PMID:24032919

  2. Program design by a multidisciplinary team. [for structural finite element analysis on STAR-100 computer

    NASA Technical Reports Server (NTRS)

    Voigt, S.

    1975-01-01

    The use of software engineering aids in the design of a structural finite-element analysis computer program for the STAR-100 computer is described. Nested functional diagrams to aid in communication among design team members were used, and a standardized specification format to describe modules designed by various members was adopted. This is a report of current work in which use of the functional diagrams provided continuity and helped resolve some of the problems arising in this long-running part-time project.

  3. Determination of total, commonality, and uniqueness of interpreted structural elements from remotely sensed data in Alaska

    USGS Publications Warehouse

    Rosenfield, G.H.

    1986-01-01

    Statistical analysis is conducted to determine the unique value of real- and synthetic-aperture side-looking airborne radar (SLAR) to detect interpreted structural elements. SLAR images were compared to standard and digitally enhanced Landsat multispectral scanner (MSS) images and to aerial photographs. After interpretation of the imagery, data were cumulated by total length in miles and by frequency of counts. Maximum uniqueness is obtained first from real-aperture SLAR, 58.3% of total, and, second, from digitally enhanced Landsat MSS images, 54.1% of total. ?? 1986 Plenum Publishing Corporation.

  4. Influence of Additive and Multiplicative Structure and Direction of Comparison on the Reversal Error

    ERIC Educational Resources Information Center

    González-Calero, José Antonio; Arnau, David; Laserna-Belenguer, Belén

    2015-01-01

    An empirical study has been carried out to evaluate the potential of word order matching and static comparison as explanatory models of reversal error. Data was collected from 214 undergraduate students who translated a set of additive and multiplicative comparisons expressed in Spanish into algebraic language. In these multiplicative comparisons…

  5. Studies on the Food Additive Propyl Gallate: Synthesis, Structural Characterization, and Evaluation of the Antioxidant Activity

    ERIC Educational Resources Information Center

    Garrido, Jorge; Garrido, E. Manuela; Borges, Fernanda

    2012-01-01

    Antioxidants are additives largely used in industry for delaying, retarding, or preventing the development of oxidative deterioration. Propyl gallate (E310) is a phenolic antioxidant extensively used in the food, cosmetics, and pharmaceutical industries. A series of lab experiments have been developed to teach students about the importance and…

  6. Are Molecular Vibration Patterns of Cell Structural Elements Used for Intracellular Signalling?

    PubMed Central

    Jaross, Werner

    2016-01-01

    Background: To date the manner in which information reaches the nucleus on that part within the three-dimensional structure where specific restorative processes of structural components of the cell are required is unknown. The soluble signalling molecules generated in the course of destructive and restorative processes communicate only as needed. Hypothesis: All molecules show temperature-dependent molecular vibration creating a radiation in the infrared region. Each molecule species has in its turn a specific frequency pattern under given specific conditions. Changes in their structural composition result in modified frequency patterns of the molecules in question. The main structural elements of the cell membrane, of the endoplasmic reticulum, of the Golgi apparatus, and of the different microsomes representing the great variety of polar lipids show characteristic frequency patterns with peaks in the region characterised by low water absorption. These structural elements are very dynamic, mainly caused by the creation of signal molecules and transport containers. By means of the characteristic radiation, the area where repair or substitution services are needed could be identified; this spatial information complements the signalling of the soluble signal molecules. Based on their resonance properties receptors located on the outer leaflet of the nuclear envelope should be able to read typical frequencies and pass them into the nucleus. Clearly this physical signalling must be blocked by the cell membrane to obviate the flow of information into adjacent cells. Conclusion: If the hypothesis can be proved experimentally, it should be possible to identify and verify characteristic infrared frequency patterns. The application of these signal frequencies onto cells would open entirely new possibilities in medicine and all biological disciplines specifically to influence cell growth and metabolism. Similar to this intracellular system, an extracellular signalling system

  7. Influencing the arc and the mechanical properties of the weld metal in GMA-welding processes by additive elements on the wire electrode surface

    NASA Astrophysics Data System (ADS)

    Wesling, V.; Schram, A.; Müller, T.; Treutler, K.

    2016-03-01

    Under the premise of an increasing scarcity of raw materials and increasing demands on construction materials, the mechanical properties of steels and its joints are gaining highly important. In particular high- and highest-strength steels are getting in the focus of the research and the manufacturing industry. To the same extent, the requirements for filler metals are increasing as well. At present, these low-alloy materials are protected by a copper coating (<1μm) against corrosion. In addition, the coating realizes a good ohmic contact and good sliding properties between the welding machine and the wire during the welding process. By exchanging the copper with other elements it should be possible to change the mechanical properties of the weld metal and the arc stability during gas metal arc welding processes and keep the basic functions of the coating nearly untouched. On a laboratory scale solid wire electrodes with coatings of various elements and compounds such as titanium oxide were made and processed with a Gas Metal Arc Welding process. During the processing a different process behavior between the wire electrodes, coated and original, could be observed. The influences ranges from greater/shorter arc-length over increasing/decreasing droplets to larger/smaller arc foot point. Furthermore, the weld metal of the coated electrodes has significantly different mechanical and technological characteristics as the weld metal from the copper coated ground wire. The yield strength and tensile strength can be increased by up to 50%. In addition, the chemical composition of the weld metal was influenced by the application of coatings with layer thicknesses to 15 microns in the lower percentage range (up to about 3%). Another effect of the coating is a modified penetration. The normally occurring “argon finger” can be suppressed or enhanced by the choice of the coating. With the help of the presented studies it will be shown that Gas Metal Arc Welding processes

  8. Factor analysis models for structuring covariance matrices of additive genetic effects: a Bayesian implementation

    PubMed Central

    de los Campos, Gustavo; Gianola, Daniel

    2007-01-01

    Multivariate linear models are increasingly important in quantitative genetics. In high dimensional specifications, factor analysis (FA) may provide an avenue for structuring (co)variance matrices, thus reducing the number of parameters needed for describing (co)dispersion. We describe how FA can be used to model genetic effects in the context of a multivariate linear mixed model. An orthogonal common factor structure is used to model genetic effects under Gaussian assumption, so that the marginal likelihood is multivariate normal with a structured genetic (co)variance matrix. Under standard prior assumptions, all fully conditional distributions have closed form, and samples from the joint posterior distribution can be obtained via Gibbs sampling. The model and the algorithm developed for its Bayesian implementation were used to describe five repeated records of milk yield in dairy cattle, and a one common FA model was compared with a standard multiple trait model. The Bayesian Information Criterion favored the FA model. PMID:17897592

  9. Multilevel micro-structuring of glassy carbon for precision glass molding of diffractive optical elements

    NASA Astrophysics Data System (ADS)

    Prater, Karin; Dukwen, Julia; Scharf, Toralf; Herzig, Hans Peter; Plöger, Sven; Hermerschmidt, Andreas

    2015-03-01

    A consumer market for diffractive optical elements in glass can only be created if high efficient elements are available at affordable prices. In diffractive optics the efficiency and optical properties increases with the number of levels used, but in the same way the costs are multiplied by the number if fabrication steps. Replication of multilevel diffractive optical elements in glass would allow cost efficient fabrication but a suitable mold material is needed. Glassy carbon shows a high mechanical strength, thermal stability and non-sticking adhesion properties, which makes it an excellent candidate as mold material for precision compression molding of low and high glass-transition temperature materials. We introduce an 8 level micro structuring process for glassy carbon molds with standard photolithography and a Ti layer as hard mask for reactive ion etching. The molds were applied to thermal imprinting onto low and high transition temperature glass. Optical performance was tested for the molded samples with different designs for laser beamsplitters. The results show a good agreement to the design specification. Our result allow us to show limitations of our fabrication technique and we discussed the suitability of precision glass molding for cost efficient mass production with a high quality.

  10. Structure/property (constitutive and dynamic strength/damage) characterization of additively manufactured 316L SS

    NASA Astrophysics Data System (ADS)

    Gray, G. T., III; Livescu, V.; Rigg, P. A.; Trujillo, C. P.; Cady, C. M.; Chen, S. R.; Carpenter, J. S.; Lienert, T. J.; Fensin, S.

    2015-09-01

    For additive manufacturing (AM), the certification and qualification paradigm needs to evolve as there exists no "ASTM-type" additive manufacturing certified process or AM-material produced specifications. Accordingly, utilization of AM materials to meet engineering applications requires quantification of the constitutive properties of these evolving materials in comparison to conventionally-manufactured metals and alloys. Cylinders of 316L SS were produced using a LENS MR-7 laser additive manufacturing system from Optomec (Albuquerque, NM) equipped with a 1kW Yb-fiber laser. The microstructure of the AM-316L SS is detailed in both the as-built condition and following heat-treatments designed to obtain full recrystallization. The constitutive behavior as a function of strain rate and temperature is presented and compared to that of nominal annealed wrought 316L SS plate. The dynamic damage evolution and failure response of all three materials was probed using flyer-plate impact driven spallation experiments at a peak stress of 4.5 GPa to examine incipient spallation response. The spall strength of AM-produced 316L SS was found to be very similar for the peak shock stress studied to that of annealed wrought or AM-316L SS following recrystallization. The damage evolution as a function of microstructure was characterized using optical metallography.

  11. Institutional and structural barriers to HIV testing: elements for a theoretical framework.

    PubMed

    Meyerson, Beth; Barnes, Priscilla; Emetu, Roberta; Bailey, Marlon; Ohmit, Anita; Gillespie, Anthony

    2014-01-01

    Stigma is a barrier to HIV health seeking, but little is known about institutional and structural expressions of stigma in HIV testing. This study examines evidence of institutional and structural stigma in the HIV testing process. A qualitative, grounded theory study was conducted using secondary data from a 2011 HIV test site evaluation data in a Midwestern, moderate HIV incidence state. Expressions of structural and institutional stigma were found with over half of the testing sites and at three stages of the HIV testing visit. Examples of structural stigma included social geography, organization, and staff behavior at first encounter and reception, and staff behavior when experiencing the actual HIV test. Institutional stigma was socially expressed through staff behavior at entry/reception and when experiencing the HIV test. The emerging elements demonstrate the potential compounding of stigma experiences with deleterious effect. Study findings may inform future development of a theoretical framework. In practice, findings can guide organizations seeking to reduce HIV testing barriers, as they provide a window into how test seekers experience HIV test sites at first encounter, entry/reception, and at testing stages; and can identify how stigma might be intensified by structural and institutional expressions. PMID:24313812

  12. Electronic Structure Calculations for Heavy Elements: Radon (Z=86) and Francium (Z=87)

    NASA Astrophysics Data System (ADS)

    Koufos, Alexander; Papaconstantopoulos, Dimitrios

    2010-03-01

    Electronic structure calculations allow scientists to predict the properties of solids without the use of physical material. Although the ability to manipulate matter has improved dramatically within the past couple decades, some matter is still hard to study. Modern computers not only let us study this matter, but allow us to do it more quickly and just as accurately. The electronic structure of two rare and mostly unstudied elements, Radon (Z=86) and Francium (Z=87), has been calculated. The augmented plane wave (APW) method with local density approximation (LDA) functional as well as the linearized augmented plane wave (LAPW) method with both LDA and generalized gradient approximation (GGA) functionals were used to perform the calculations. Francium total energy calculations gave the fcc structure slightly below the bcc structure with a minimal energy difference of δE=0.33mRy. The difference found is consistent with other alkali metal total energy calculations which do not verify the bcc structure to be the ground state. Radon was predicted to be an insulator with a gap of 0.931 Ry similar to the other noble gases.

  13. RNA structure is a key regulatory element in pathological ATM and CFTR pseudoexon inclusion events

    PubMed Central

    Buratti, Emanuele; Dhir, Ashish; Lewandowska, Marzena A.; Baralle, Francisco E.

    2007-01-01

    Genomic variations deep in the intronic regions of pre-mRNA molecules are increasingly reported to affect splicing events. However, there is no general explanation why apparently similar variations may have either no effect on splicing or cause significant splicing alterations. In this work we have examined the structural architecture of pseudoexons previously described in ATM and CFTR patients. The ATM case derives from the deletion of a repressor element and is characterized by an aberrant 5′ss selection despite the presence of better alternatives. The CFTR pseudoexon instead derives from the creation of a new 5′ss that is used while a nearby pre-existing donor-like sequence is never selected. Our results indicate that RNA structure is a major splicing regulatory factor in both cases. Furthermore, manipulation of the original RNA structures can lead to pseudoexon inclusion following the exposure of unused 5′ss already present in their wild-type intronic sequences and prevented to be recognized because of their location in RNA stem structures. Our data show that intrinsic structural features of introns must be taken into account to understand the mechanism of pseudoexon activation in genetic diseases. Our observations may help to improve diagnostics prediction programmes and eventual therapeutic targeting. PMID:17580311

  14. Coupled mixed-field laminate theory and finite element for smart piezoelectric composite shell structures

    NASA Technical Reports Server (NTRS)

    Saravanos, Dimitris A.

    1996-01-01

    Mechanics for the analysis of laminated composite shells with piezoelectric actuators and sensors are presented. A new mixed-field laminate theory for piezoelectric shells is formulated in curvilinear coordinates which combines single-layer assumptions for the displacements and a layerwise representation for the electric potential. The resultant coupled governing equations for curvilinear piezoelectric laminates are described. Structural mechanics are subsequently developed and an 8-node finite-element is formulated for the static and dynamic analysis of adaptive composite structures of general laminations containing piezoelectric layers. Evaluations of the method and comparisons with reported results are presented for laminated piezoelectric-composite plates, a closed cylindrical shell with a continuous piezoceramic layer and a laminated composite semi-circular cantilever shell with discrete cylindrical piezoelectric actuators and/or sensors.

  15. Structural and Elemental Analysis of Degraded Single Junction Amorphous Silicon Solar Module

    NASA Astrophysics Data System (ADS)

    Osayemwenre, Gilbert; Meyer, Edson

    Photovoltaic solar modules have different defects and degradation characteristic modes. These degradation modes normally heats up some regions in the PV module. Depending on the degree and size of the localised heat, the localized heat can raise above the temperature limit of the module and cause damage to the structural orientation. The presence of severe defect and degradation correlates with high temperature gradients that usually results in morphological damage especially under outdoor conditions. The present study investigates the effect of defect/degradation on the surface morphology of single junction amorphous silicon modules (a-Si:H) during outdoor deployment. The observed structural damage was analysed using scanning electron microscope (SEM) and energy dispersion X-ray (EDX) to ascertain the elemental composition. Results show huge discrepancies in the chemical composition constitute alone different regions. The presence of high concentration of carbon and oxygen was found in the affected region. The authors wish to acknowledge GMRDC and the International affairs for the support.

  16. Element-specific X-ray phase tomography of 3D structures at the nanoscale.

    PubMed

    Donnelly, Claire; Guizar-Sicairos, Manuel; Scagnoli, Valerio; Holler, Mirko; Huthwelker, Thomas; Menzel, Andreas; Vartiainen, Ismo; Müller, Elisabeth; Kirk, Eugenie; Gliga, Sebastian; Raabe, Jörg; Heyderman, Laura J

    2015-03-20

    Recent advances in fabrication techniques to create mesoscopic 3D structures have led to significant developments in a variety of fields including biology, photonics, and magnetism. Further progress in these areas benefits from their full quantitative and structural characterization. We present resonant ptychographic tomography, combining quantitative hard x-ray phase imaging and resonant elastic scattering to achieve ab initio element-specific 3D characterization of a cobalt-coated artificial buckyball polymer scaffold at the nanoscale. By performing ptychographic x-ray tomography at and far from the Co K edge, we are able to locate and quantify the Co layer in our sample to a 3D spatial resolution of 25 nm. With a quantitative determination of the electron density we can determine that the Co layer is oxidized, which is confirmed with microfluorescence experiments. PMID:25839287

  17. Elements of the Chicxulub Impact Structure as Revealed in SRTM and Surface GPS Topographic Data

    NASA Technical Reports Server (NTRS)

    Kinsland, Gary L.; Sanchez, Gary; Kobrick, Michael; Cardador, Manuel Hurtado

    2003-01-01

    Pope et al. [1] utilized the elevations from the Petroleos Mexicanos (PEMEX) gravity data files to show that the main component of the surface expression of the Chicxulub Impact Structure is a roughly semi-circular, lowrelief depression about 90 km in diameter. They also identified other topographic features and the elements of the buried impact, which possibly led to the development of these features. These are summarized in Table 1. Kinsland et al. [2] presented a connection between these topographic anomalies, small gravity anomalies and buried structure of the impact. Very recently we have acquired digital topography data from NASA s Shuttle Radar Topography Mission (SRTM). Our subset covers 6 square degrees from 20deg N 91degW to 22deg N 88degW (corner to corner) with a pixel size of about 90m. This area includes all of the identified portion of the crater on land.

  18. Crystal Structure of NFAT Bound to the HIV-1 LTR Tandem κB Enhancer Element

    SciTech Connect

    Bates, Darren L.; Barthel, Kristen K.B.; Wu, Yongqing; Kalhor, Reza; Stroud, James C.; Giffin, Michael J.; Chen, Lin

    2008-05-27

    Here, we have determined the crystal structure of the DNA binding domain of NFAT bound to the HIV-1 long terminal repeat (LTR) tandem {kappa}B enhancer element of 3.05 {angstrom} resolution. NFAT binds as a dimer to the upstream {kappa}B site (Core II), but as a monomer to the 3' end of the downstream {kappa}B site (Core I). The DNA shows a significant bend near the 5' end of Core I, where a lysine residue from NFAT bound to the 3' end of Core II inserts into the minor groove and seems to cause DNA bases to flip out. Consistent with this structural feature, the 5' end of Core I become hypersensitive to dimethylsulfate in the in vivo footprinting upon transcriptional activation of the HIV-1 LTR. Our studies provide a basis for futher investigating the functional mechanism of NFAT in HIV-1 transcription and replication.

  19. Effects of Al Content and Addition of Third Element on Fabrication of Ti-Al Intermetallic Coatings by Heat Treatment of Warm-Sprayed Precursors

    NASA Astrophysics Data System (ADS)

    Sienkiewicz, J.; Kuroda, S.; Minagawa, K.; Murakami, H.; Araki, H.; Kurzydłowski, K. J.

    2015-06-01

    Four powder mixtures of titanium and aluminum with 50:50, 40:60, 30:70, and 20:80 atomic ratios were used as feedstock for Warm Spray process to produce composite coatings. A two-stage heat treatment at 600 and 1000 °C was applied to the deposits in order to obtain titanium aluminide intermetallic phases. The microstructure, chemical, and phase composition of the as-deposited and heat-treated coatings were investigated using SEM, EDS, and XRD. It was found that the Al content affects on the thickness expansion of the heat-treated Ti-Al coatings significantly and also has a major influence on the porosity development, which is caused by the Kirkendall effect. The effects of adding a third element Si and heat treatment with pressure to produce denser Ti-Al intermetallic coating were also examined. The investigated hot-pressed coatings with addition of Si exhibited much denser microstructure and contained Ti-Al intermetallic phases with titanium silicide precipitates.

  20. Grain refinement in heavy rare earth element-free sintered Nd–Fe–B magnets by addition of a small amount of molybdenum

    SciTech Connect

    Kim, Jin Woo; Lee, Won Suk; Byun, Jong Min; Kim, Young Do; Kim, Se Hoon

    2015-05-07

    We employed a modified refractory-metal-addition method to achieve higher coercivity and remanence in heavy rare earth element (HREE)-free Nd–Fe–B sintered magnets. This process involved inducing the formation of a homogeneous secondary phase at the grain boundaries during sintering, making it possible to control the intergrain diffusion by adding small amounts of Mo, a refractory metal. To control the microstructure of the secondary phase effectively, a metal organic compound of the refractory metal was coated on the surfaces of the particles of an HREE-free Nd–Fe–B powder. The average grain size after this process was 5.60 μm, which was approximately 1.8 μm smaller than that of the HREE-free sintered Nd–Fe–B magnets (7.4 μm). The coercivity of the magnets prepared through this process could be increased from 11.88 kOe to 13.91 kOe without decreasing their remanence.

  1. Structure alterations in Al-Y-based metallic glasses with La and Ni addition

    NASA Astrophysics Data System (ADS)

    Shi, X. M.; Wang, X. D.; Yu, Q.; Cao, Q. P.; Zhang, D. X.; Zhang, J.; Hu, T. D.; Lai, L. H.; Xie, H. L.; Xiao, T. Q.; Jiang, J. Z.

    2016-03-01

    The atomic structures of Al89Y11, Al90Y6.5La3.5, and Al82.8Y6.07Ni8La3.13 metallic glasses have been studied by using high energy X-ray diffraction, X-ray absorption fine structure combined with the ab initio molecular dynamics and reverse Monte Carlo simulations. It is demonstrated that the partial replacement of Y atoms by La has limited improvement of the glass forming ability (GFA), although La atoms reduce the ordering around Y atoms and also the fractions of icosahedron-like polyhedra centered by Al atoms. In contrast, Ni atoms can significantly improve the GFA, which are inclined to locate in the shell of polyhedra centered by Al, Y, and La atoms, mainly forming Ni-centered icosahedron-like polyhedra to enhance the spatial connectivity between clusters and suppress the crystallization.

  2. Conformational characterization of the intrinsically disordered protein Chibby: Interplay between structural elements in target recognition.

    PubMed

    Killoran, Ryan C; Sowole, Modupeola A; Halim, Mohammad A; Konermann, Lars; Choy, Wing-Yiu

    2016-08-01

    The protein Chibby (Cby) is an antagonist of the Wnt signaling pathway, where it inhibits the binding between the transcriptional coactivator β-catenin and the Tcf/Lef transcription factors. The 126 residue Cby is partially disordered; its N-terminal half is unstructured while its C-terminal half comprises a coiled-coil domain. Previous structural analyses of Cby using NMR spectroscopy suffered from severe line broadening for residues within the protein's C-terminal half, hindering detailed characterization of the coiled-coil domain. Here, we use hydrogen/deuterium exchange-mass spectrometry (HDX-MS) to examine Cby's C-terminal half. Results reveal that Cby is divided into three structural elements: a disordered N-terminal half, a coiled-coil domain, and a C-terminal unstructured extension consisting of the last ∼ 25 residues (which we term C-terminal extension). A series of truncation constructs were designed to assess the roles of individual structural elements in protein stability and Cby binding to TC-1, a positive regulator of the Wnt signaling pathway. CD and NMR data show that Cby maintains coiled-coil structure upon deletion of either disordered region. NMR and ITC binding experiments between Cby and TC-1 illustrate that the interaction is retained upon deletion of either Cby's N-terminal half or its C-terminal extension. Intriguingly, Cby's C-terminal half alone binds to TC-1 with significantly greater affinity compared to full-length Cby, implying that target binding of the coiled-coil domain is affected by the flanking disordered regions. PMID:27082063

  3. Experiments to Populate and Validate a Processing Model for Polyurethane Foam: Additional Data for Structural Foams.

    SciTech Connect

    Rao, Rekha R.; Celina, Mathias C.; Giron, Nicholas Henry; Long, Kevin Nicholas; Russick, Edward M.

    2015-01-01

    We are developing computational models to help understand manufacturing processes, final properties and aging of structural foam, polyurethane PMDI. Th e resulting model predictions of density and cure gradients from the manufacturing process will be used as input to foam heat transfer and mechanical models. BKC 44306 PMDI-10 and BKC 44307 PMDI-18 are the most prevalent foams used in structural parts. Experiments needed to parameterize models of the reaction kinetics and the equations of motion during the foam blowing stages were described for BKC 44306 PMDI-10 in the first of this report series (Mondy et al. 2014). BKC 44307 PMDI-18 is a new foam that will be used to make relatively dense structural supports via over packing. It uses a different catalyst than those in the BKC 44306 family of foams; hence, we expect that the reaction kineti cs models must be modified. Here we detail the experiments needed to characteriz e the reaction kinetics of BKC 44307 PMDI-18 and suggest parameters for the model based on these experiments. In additi on, the second part of this report describes data taken to provide input to the preliminary nonlinear visco elastic structural response model developed for BKC 44306 PMDI-10 foam. We show that the standard cu re schedule used by KCP does not fully cure the material, and, upon temperature elevation above 150 o C, oxidation or decomposition reactions occur that alter the composition of the foam. These findings suggest that achieving a fully cured foam part with this formulation may be not be possible through therma l curing. As such, visco elastic characterization procedures developed for curing thermosets can provide only approximate material properties, since the state of the material continuously evolves during tests.

  4. Effects of 5f-elements on electronic structures and spectroscopic properties of gold superatom model

    NASA Astrophysics Data System (ADS)

    Gao, Yang; Wang, Zhigang

    2016-08-01

    5f-elements encaged in a gold superatomic cluster are capable of giving rise to unique optical properties due to their hyperactive valence electrons and great radial components of 5f/6d orbitals. Herein, we review our first-principles studies on electronic structures and spectroscopic properties of a series of actinide-embedded gold superatomic clusters with different dimensions. The three-dimensional (3D) and two-dimensional (2D) superatom clusters possess the 18-electron configuration of 1S21P61D10 and 10-electron configuration of 1S21P41D4, respectively. Importantly, their electronic absorption spectra can also be effectively explained by the superatom orbitals. Specifically, the charge transfer (CT) transitions involved in surface-enhance Raman spectroscopy (SERS) spectra for 3D and 2D structures are both from the filled 1D orbitals, providing the enhancement factors of the order of ∼ 104 at 488 nm and ∼ 105 at 456 nm, respectively. This work implies that the superatomic orbital transitions involved in 5f-elements can not only lead to a remarkable spectroscopic performance, but also a new direction for optical design in the future. Project supported by the National Natural Science Foundation of China (Grant No. 11374004), the Science and Technology Development Program of Jilin Province, China (Grant No. 20150519021JH), the Fok Ying Tung Education Foundation, China (Grant No. 142001), and the Support from the High Performance Computing Center (HPCC) of Jilin University, China.

  5. Finite Element Simulation of Low Velocity Impact Damage on an Aeronautical Carbon Composite Structure

    NASA Astrophysics Data System (ADS)

    Lemanle Sanga, Roger Pierre; Garnier, Christian; Pantalé, Olivier

    2016-06-01

    Low velocity barely visible impact damage (BVID) in laminated carbon composite structures has a major importance for aeronautical industries. This contribution leads with the development of finite element models to simulate the initiation and the propagation of internal damage inside a carbon composite structure due by a low velocity impact. Composite plates made from liquid resin infusion process (LRI) have been subjected to low energy impacts (around 25 J) using a drop weight machine. In the experimental procedure, the internal damage is evaluated using an infrared thermographic camera while the indentation depth of the face is measured by optical measurement technique. In a first time we developed a robust model using homogenised shells based on degenerated tri-dimensional brick elements and in a second time we decided to modelize the whole stacking sequence of homogeneous layers and cohesive interlaminar interfaces in order to compare and validate the obtained results. Both layer and interface damage initiation and propagation models based on the Hashin and the Benzeggagh-Kenane criteria have been used for the numerical simulations. Comparison of numerical results and experiments has shown the accuracy of the proposed models.

  6. Blood lead: Its effect on trace element levels and iron structure in hemoglobin

    NASA Astrophysics Data System (ADS)

    Jin, C.; Li, Y.; Li, Y. L.; Zou, Y.; Zhang, G. L.; Normura, M.; Zhu, G. Y.

    2008-08-01

    Lead is a ubiquitous environmental pollutant that induce a broad range of physiological and biochemical dysfunctions. The purpose of this study was to investigate its effects on trace elements and the iron structure in hemoglobin. Blood samples were collected from rats that had been exposed to lead. The concentration of trace elements in whole blood and blood plasma was determined by ICP-MS and the results indicate that lead exists mainly in the red blood cells and only about 1-3% in the blood plasma. Following lead exposure, the concentrations of zinc and iron in blood decrease, as does the hemoglobin level. This indicates that the heme biosynthetic pathway is inhibited by lead toxicity and that lead poisoning-associated anemia occurs. The selenium concentration also decreases after lead exposure, which may lead to an increased rate of free radical production. The effect of lead in the blood on iron structure in hemoglobin was determined by EXAFS. After lead exposure, the Fe-O bond length increases by about 0.07 Å and the Fe-Np bond length slightly increases, but the Fe-N ɛ bond length remains unchanged. This indicates that the blood content of Hb increases, but that the content of HbO 2 decreases.

  7. Elastic-plastic finite element analysis-to-test correlation for structures subjected to dynamic loading

    SciTech Connect

    Hodge, S.C.; Minicucci, J.M.

    1997-11-01

    A test program was undertaken to demonstrate the ability of elastic-plastic finite element methods to predict dynamic inelastic response for simple structural members. Cantilever and fixed-beam specimens were tested to levels that produced plastic straining in the range of 2.0% and to 3.0% and permanent sets. Acceleration, strain, and displacement data were recorded for use in analytical correlation. Correlation analyses were performed using the ABAQUS finite element code. Results of the correlation show that current elastic-plastic analysis techniques accurately capture dynamic inelastic response (displacement, acceleration) due to rapidly applied dynamic loading. Peak elastic and inelastic surface strains are accurately predicted. To accurately capture inelastic straining near connections, a solid model, including fillet welds, is necessary. The hardening models currently available in the ABAQUS code (isotropic, kinematic) do not accurately capture inelastic strain reversals caused by specimen rebound. Analyses performed consistently underpredicted the peak strain level of the first inelastic reversal and the rebound deflection and overpredicted the permanent set of structures experiencing inelastic rebound. Based on these findings, an improved hardening model is being implemented in the ABAQUS code by the developers. The intent of this model upgrade is to improve the ability of the program to capture inelastic strain reversals and to predict permanent sets.

  8. Performance analysis of high quality parallel preconditioners applied to 3D finite element structural analysis

    SciTech Connect

    Kolotilina, L.; Nikishin, A.; Yeremin, A.

    1994-12-31

    The solution of large systems of linear equations is a crucial bottleneck when performing 3D finite element analysis of structures. Also, in many cases the reliability and robustness of iterative solution strategies, and their efficiency when exploiting hardware resources, fully determine the scope of industrial applications which can be solved on a particular computer platform. This is especially true for modern vector/parallel supercomputers with large vector length and for modern massively parallel supercomputers. Preconditioned iterative methods have been successfully applied to industrial class finite element analysis of structures. The construction and application of high quality preconditioners constitutes a high percentage of the total solution time. Parallel implementation of high quality preconditioners on such architectures is a formidable challenge. Two common types of existing preconditioners are the implicit preconditioners and the explicit preconditioners. The implicit preconditioners (e.g. incomplete factorizations of several types) are generally high quality but require solution of lower and upper triangular systems of equations per iteration which are difficult to parallelize without deteriorating the convergence rate. The explicit type of preconditionings (e.g. polynomial preconditioners or Jacobi-like preconditioners) require sparse matrix-vector multiplications and can be parallelized but their preconditioning qualities are less than desirable. The authors present results of numerical experiments with Factorized Sparse Approximate Inverses (FSAI) for symmetric positive definite linear systems. These are high quality preconditioners that possess a large resource of parallelism by construction without increasing the serial complexity.

  9. Guided ultrasonic waves in the cylindrical layer-substrate structures. Application to the control of the massive machine elements with cylindrical cavities

    NASA Astrophysics Data System (ADS)

    El Ouahdani, M.; Sidki, M.; Ramdani, A.

    2005-12-01

    This paper presents a study of the ultrasonic wave propagation in a cylindrical layer-substrate structure of an infinite length. We determine the dispersion curves of the structure, the displacements field in the structure and the impact of the contact quality between the layer and the substrate. The industrial application aimed by our study is the control of the massive machine elements with cylindrical cavities coated and exposed to corrosion. The obtained results show that some modes of propagation are insensitive to the layer thickness. Therefore, these modes can be generated during the ultrasonic control of the layer. In addition, for the dimensions considered here, the second mode of propagation is the most adapted for the detection of defects in the vicinity of the internal layer wall. In addition, our study shows the possibility of characterization of the quality of contact between the layer and the substrate from the analysis of dispersion curves of the structure.

  10. RNA Structural Elements of Hepatitis C Virus Controlling Viral RNA Translation and the Implications for Viral Pathogenesis

    PubMed Central

    Piñeiro, David; Martinez-Salas, Encarnación

    2012-01-01

    Hepatitis C virus (HCV) genome multiplication requires the concerted action of the viral RNA, host factors and viral proteins. Recent studies have provided information about the requirement of specific viral RNA motifs that play an active role in the viral life cycle. RNA regulatory motifs controlling translation and replication of the viral RNA are mostly found at the 5' and 3' untranslated regions (UTRs). In particular, viral protein synthesis is under the control of the internal ribosome entry site (IRES) element, a complex RNA structure located at the 5'UTR that recruits the ribosomal subunits to the initiator codon. Accordingly, interfering with this RNA structural motif causes the abrogation of the viral cycle. In addition, RNA translation initiation is modulated by cellular factors, including miRNAs and RNA-binding proteins. Interestingly, a RNA structural motif located at the 3'end controls viral replication and establishes long-range RNA-RNA interactions with the 5'UTR, generating functional bridges between both ends on the viral genome. In this article, we review recent advances on virus-host interaction and translation control modulating viral gene expression in infected cells. PMID:23202462

  11. Characterization of embedded fiber optic strain sensors into metallic structures via ultrasonic additive manufacturing

    NASA Astrophysics Data System (ADS)

    Schomer, John J.; Hehr, Adam J.; Dapino, Marcelo J.

    2016-04-01

    Fiber Bragg Grating (FBG) sensors measure deviation in a reflected wavelength of light to detect in-situ strain. These sensors are immune to electromagnetic interference, and the inclusion of multiple FBGs on the same fiber allows for a seamlessly integrated sensing network. FBGs are attractive for embedded sensing in aerospace applications due to their small noninvasive size and prospect of constant, real-time nondestructive evaluation. In this study, FBG sensors are embedded in aluminum 6061 via ultrasonic additive manufacturing (UAM), a rapid prototyping process that uses high power ultrasonic vibrations to weld similar and dissimilar metal foils together. UAM was chosen due to the desire to embed FBG sensors at low temperatures, a requirement that excludes other additive processes such as selective laser sintering or fusion deposition modeling. In this paper, the embedded FBGs are characterized in terms of birefringence losses, post embedding strain shifts, consolidation quality, and strain sensing performance. Sensors embedded into an ASTM test piece are compared against an exterior surface mounted foil strain gage at both room and elevated temperatures using cyclic tensile tests.

  12. Influence of additives on the structure of surfactant-free microemulsions.

    PubMed

    Marcus, J; Touraud, D; Prévost, S; Diat, O; Zemb, T; Kunz, W

    2015-12-28

    We study the addition of electrolytes to surfactant-free microemulsions in the domain where polydisperse pre-Ouzo aggregates are present. As in previous studies, the microemulsion is the ternary system water/ethanol/1-octanol, where ethanol acts as co-solvent. Addition of electrolytes modifies the static X-ray and neutron scattering, and dynamic light scattering patterns, as well as the position of the miscibility gap, where spontaneous emulsification occurs upon dilution with water. All observations can be rationalized considering that electrolytes are either "salting out" the ethanol, which is the main component of the interface stabilizing the aggregates, or producing charge separation via the antagonistic ion effect discovered by Onuki et al. Amphiphilic electrolytes, such as sodium dodecylsulfate or sodium dietheylhexylphosphate, induce a gradual transition towards monodisperse ionic micelles with their characteristic broad scattering "peak". In these micelles the ethanol plays then the role of a cosurfactant. Dynamic light scattering can only be understood by combination of fluctuations of aggregate concentration due to the vicinity of a critical point and in-out fluctuations of ethanol. PMID:26593697

  13. Modifying structure-sensitive reactions by addition of Zn to Pd

    SciTech Connect

    Childers, David J.; Schweitzer, Neil M.; Kamali Shahari, Seyed Mehdi; Rioux, Robert M.; Miller, Jeffrey T.; Meyer, Randall J.

    2014-10-01

    Silica-supported Pd and PdZn nanoparticles of a similar size were evaluated for neopentane hydrogenolysis/isomerization and propane hydrogenolysis/dehydrogenation. Monometallic Pd showed high neopentane hydrogenolysis selectivity. Addition of small amounts of Zn to Pd lead Pd–Zn scatters in the EXAFS spectrum and an increase in the linear bonded CO by IR. In addition, the neopentane turnover rate decreased by nearly 10 times with little change in the selectivity. Increasing amounts of Zn lead to greater Pd–Zn interactions, higher linear-to-bridging CO ratios by IR and complete loss of neopentane conversion. Pd NPs also had high selectivity for propane hydrogenolysis and thus were poorly selective for propylene. The PdZn bimetallic catalysts, however, were able to preferentially catalyze dehydrogenation, were not active for propane hydrogenolysis, and thus were highly selective for propylene formation. The decrease in hydrogenolysis selectivity was attributed to the isolation of active Pd atoms by inactive metallic Zn,demonstrating that hydrogenolysis requires a particular reactive ensemble whereas propane dehydrogenation does not.

  14. Highly Aligned Carbon Fiber in Polymer Composite Structures via Additive Manufacturing

    DOE PAGESBeta

    Tekinalp, Halil L; Kunc, Vlastimil; Velez-Garcia, Gregorio M; Duty, Chad E; Love, Lonnie J; Naskar, Amit K; Blue, Craig A; Ozcan, Soydan

    2014-01-01

    Additive manufacturing, diverging from traditional manufacturing techniques, such as casting and machining materials, can handle complex shapes with great design flexibility without the typical waste. Although this technique has been mainly used for rapid prototyping, interest is growing in using this method to directly manufacture actual parts of complex shape. To use 3D-printing additive manufacturing in wide spread applications, the technique and the feedstock materials require improvements to meet the mechanical requirements of load-bearing components. Thus, we investigated the short fiber (0.2 mm to 0.4 mm) reinforced acrylonitrile-butadiene-styrene composites as a feedstock for 3D-printing in terms of their processibility, microstructuremore » and mechanical performance; and also provided comparison with traditional compression molded composites. The tensile strength and modulus of 3D-printed samples increased ~115% and ~700%, respectively. 3D-printer yielded samples with very high fiber orientation in printing direction (up to 91.5 %), whereas, compression molding process yielded samples with significantly less fiber orientation. Microstructure-mechanical property relationships revealed that although the relatively high porosity is observed in the 3D-printed composites as compared to those produced by the conventional compression molding technique, they both exhibited comparable tensile strength and modulus. This phenomena is explained based on the changes in fiber orientation, dispersion and void formation.« less

  15. Unexpected Michael Additions on the Way to 2.3,8.9-Dibenzanthanthrenes with Interesting Structural Properties.

    PubMed

    Reus, Christian; Lechner, Marc P; Schulze, Matthias; Lungerich, Dominik; Diner, Colin; Gruber, Marco; Stryker, Jeffrey M; Hampel, Frank; Jux, Norbert; Tykwinski, Rik R

    2016-06-27

    The synthesis and properties of a new polycyclic aromatic hydrocarbon containing eight annulated rings and based on the anthanthrene core is described. An unexpected, nucleophile-dependent Michael addition to a dibenzanthanthrene-1,7-dione is found, giving a product with three triisopropylsilylacetylene units and a remarkable solid-state structure (as determined by X-ray crystallography). PMID:27140668

  16. Simulation of plasmonic and photonic crystal structures using finite-element method

    NASA Astrophysics Data System (ADS)

    Yang, Sen

    In this thesis, the Finite-Element Method (FEM) was utilized to simulate and design the optimal nanostructures for better performances of Surface-Enhanced Raman Scattering (SERS) and lasing. FEM proved its effectiveness in the calculations of target physical models to optimize the model geometry or theoretically validate experimental observations. In chapter 1 and 2, the fundamental theorem of SERS and photonic crystal cavity were introduced and discussed. The most used optical structures for the two effects, metal/dielectric SPP structure and dielectric photonic crystal structure, were introduced as examples. Equations stem from Maxwell equations were derived and discussed to clarify the concepts of SERS and PCC. In chapter 3, the FEM method was carried out to simulate the SERS performance of Au nano-bowl/SiO2/Au nanoparticle structure. The electric field distributions and Raman enhancement factors of models in real experiments were calculated and analyzed theoretically. The simulation result on Raman enhancement factors showed consistency with the experimental observations. In chapter 4, the design process of silicon nitride photonic crystal cavity was introduced and the simulation results were discussed. Using L3 geometrical model, the FEM method successfully revealed the relations between key optical properties, such as quality factor and resonant wavelength, and geometrical parameter selections. The simulations were also helpful in determination of the optimal parameter selection in L3 PCC model for further experimental fabrication.

  17. Structure and micro-computed tomography-based finite element modeling of Toucan beak.

    PubMed

    Seki, Yasuaki; Mackey, Mason; Meyers, Marc A

    2012-05-01

    Bird beaks are one of the most fascinating sandwich composites in nature. Their design is composed of a keratinous integument and a bony foam core. We evaluated the structure and mechanical properties of a Toucan beak to establish structure-property relationships. We revealed the hierarchical structure of the Toucan beak by microscopy techniques. The integument consists of 50 μm polygonal keratin tiles with ~7.5 nm embedded intermediate filaments. The branched intermediate filaments were visualized by TEM tomography techniques. The bony foam core or trabecular bone is a closed-cell foam, which serves as a stiffener for the beak. The tridimensional foam structure was reconstructed by μ-CT scanning to create a model for the finite element analysis (FEA). The mechanical response of the beak foam including trabeculae and cortical shell was measured in tension and compression. We found that Young's modulus is 3 (S.D. 2.2) GPa for the trabeculae and 0.3 (S.D. 0.2) GPa for the cortical shell. After obtaining the material parameters, the deformation and microscopic failure of foam were calculated by FEA. The calculations agree well with the experimental results. PMID:22498278

  18. Structure-aided prediction of mammalian transcription factor complexes in conserved non-coding elements.

    PubMed

    Guturu, Harendra; Doxey, Andrew C; Wenger, Aaron M; Bejerano, Gill

    2013-12-19

    Mapping the DNA-binding preferences of transcription factor (TF) complexes is critical for deciphering the functions of cis-regulatory elements. Here, we developed a computational method that compares co-occurring motif spacings in conserved versus unconserved regions of the human genome to detect evolutionarily constrained binding sites of rigid TF complexes. Structural data were used to estimate TF complex physical plausibility, explore overlapping motif arrangements seldom tackled by non-structure-aware methods, and generate and analyse three-dimensional models of the predicted complexes bound to DNA. Using this approach, we predicted 422 physically realistic TF complex motifs at 18% false discovery rate, the majority of which (326, 77%) contain some sequence overlap between binding sites. The set of mostly novel complexes is enriched in known composite motifs, predictive of binding site configurations in TF-TF-DNA crystal structures, and supported by ChIP-seq datasets. Structural modelling revealed three cooperativity mechanisms: direct protein-protein interactions, potentially indirect interactions and 'through-DNA' interactions. Indeed, 38% of the predicted complexes were found to contain four or more bases in which TF pairs appear to synergize through overlapping binding to the same DNA base pairs in opposite grooves or strands. Our TF complex and associated binding site predictions are available as a web resource at http://bejerano.stanford.edu/complex. PMID:24218641

  19. The Purification of the Chlamydomonas reinhardtii chloroplast ClpP complex: additional subunits and structural features

    PubMed Central

    Derrien, Benoît; Majeran, Wojciech; Effantin, Grégory; Ebenezer, Joseph; Friso, Giulia; van Wijk, Klaas J.; Steven, Alasdair C.; Maurizi, Michael R.; Vallon, Olivier

    2012-01-01

    The ClpP peptidase is a major constituent of the proteolytic machinery of bacteria and organelles. The chloroplast ClpP complex is unusual, in that it associates a large number of subunits, one of which (ClpP1) is encoded in the chloroplast, the others in the nucleus. The complexity of these large hetero-oligomeric complexes has been a major difficulty in their overproduction and biochemical characterization. In this paper, we describe the purification of native chloroplast ClpP complex from the green alga Chlamydomonas reinhardtii, using a strain that carries the Strep-tag II at the C-terminus of the ClpP1 subunit. Similar to land plants, the algal complex comprises active and inactive subunits (3 ClpP and 5 ClpR, respectively). Evidence is presented that a sub-complex can be produced by dissociation, comprising ClpP1 and ClpR1, 2, 3 and 4, similar to the ClpR-ring described in land plants. Our Chlamydomonas ClpP preparation also contains two ClpT subunits, ClpT3 and ClpT4, which like the land plant ClpT1 and ClpT2 show 2 Clp-N domains. ClpTs are believed to function in substrate binding and/or assembly of the two heptameric rings. Phylogenetic analysis indicates that ClpT subunits have appeared independently in Chlorophycean algae, in land plants and in dispersed cyanobacterial genomes. Negative staining electron microscopy shows that the Chlamydomonas complex retains the barrel-like shape of homo-oligomeric ClpPs, with 4 additional peripheral masses that we speculate represent either the additional IS1 domain of ClpP1 (a feature unique to algae) or ClpTs or extensions of ClpR subunits PMID:22772861

  20. Growth and Mycorrhizal Community Structure of Pinus sylvestris Seedlings following the Addition of Forest Litter▿

    PubMed Central

    Aučina, Algis; Rudawska, Maria; Leski, Tomasz; Skridaila, Audrius; Riepšas, Edvardas; Iwanski, Michal

    2007-01-01

    We report the effects of pine and oak litter on species composition and diversity of mycorrhizal fungi colonizing 2-year-old Pinus sylvestris L. seedlings grown in a bare-root nursery in Lithuania. A layer of pine or oak litter was placed on the surface of the nursery bed soil to mimic natural litter cover. Oak litter amendment appeared to be most favorable for seedling survival, with a 73% survival rate, in contrast to the untreated mineral bed soil (44%). The concentrations of total N, P, K, Ca, and Mg were higher in oak growth medium than in pine growth medium. Relative to the control (pH 6.1), the pH was lower in pine growth medium (5.8) and higher in oak growth medium (6.3). There were also twofold and threefold increases in the C content of growth medium with the addition of pine and oak litter, respectively. Among seven mycorrhizal morphotypes, eight different mycorrhizal taxa were identified: Suillus luteus, Suillus variegatus, Wilcoxina mikolae, a Tuber sp., a Tomentella sp., Cenococcum geophilum, Amphinema byssoides, and one unidentified ectomycorrhizal symbiont. Forest litter addition affected the relative abundance of mycorrhizal symbionts more than their overall representation. This was more pronounced for pine litter than for oak litter, with 40% and 25% increases in the abundance of suilloid mycorrhizae, respectively. Our findings provide preliminary evidence that changes in the supply of organic matter through litter manipulation may have far-reaching effects on the chemistry of soil, thus influencing the growth and survival of Scots pine seedlings and their mycorrhizal communities. PMID:17575001

  1. First-principles study of monolayer and bilayer honeycomb structures of group-IV elements and their binary compounds

    NASA Astrophysics Data System (ADS)

    Pan, L.; Liu, H. J.; Wen, Y. W.; Tan, X. J.; Lv, H. Y.; Shi, J.; Tang, X. F.

    2011-01-01

    By using first-principles pseudopotential method, we investigate the structural, vibrational, and electronic properties of monolayer and bilayer honeycomb structures of group-IV elements and their binary compounds. It is found that the honeycomb structures of Si, Ge, and SiGe are buckled for stabilization, while those of binary compounds SiC and GeC containing the first row elements C are planar similar to a graphene sheet. The phonon dispersion relations and electronic band structures are very sensitive to the number of layers, the stacking order, and whether the layers are planar or buckled.

  2. Coupled agent-based and finite-element models for predicting scar structure following myocardial infarction.

    PubMed

    Rouillard, Andrew D; Holmes, Jeffrey W

    2014-08-01

    Following myocardial infarction, damaged muscle is gradually replaced by collagenous scar tissue. The structural and mechanical properties of the scar are critical determinants of heart function, as well as the risk of serious post-infarction complications such as infarct rupture, infarct expansion, and progression to dilated heart failure. A number of therapeutic approaches currently under development aim to alter infarct mechanics in order to reduce complications, such as implantation of mechanical restraint devices, polymer injection, and peri-infarct pacing. Because mechanical stimuli regulate scar remodeling, the long-term consequences of therapies that alter infarct mechanics must be carefully considered. Computational models have the potential to greatly improve our ability to understand and predict how such therapies alter heart structure, mechanics, and function over time. Toward this end, we developed a straightforward method for coupling an agent-based model of scar formation to a finite-element model of tissue mechanics, creating a multi-scale model that captures the dynamic interplay between mechanical loading, scar deformation, and scar material properties. The agent-based component of the coupled model predicts how fibroblasts integrate local chemical, structural, and mechanical cues as they deposit and remodel collagen, while the finite-element component predicts local mechanics at any time point given the current collagen fiber structure and applied loads. We used the coupled model to explore the balance between increasing stiffness due to collagen deposition and increasing wall stress due to infarct thinning and left ventricular dilation during the normal time course of healing in myocardial infarcts, as well as the negative feedback between strain anisotropy and the structural anisotropy it promotes in healing scar. The coupled model reproduced the observed evolution of both collagen fiber structure and regional deformation following coronary

  3. Uranium hydrogeochemical and stream sediment reconnaissance of the Dalhart NTMS quadrangle, New Mexico/Texas/Oklahoma, including concentrations of forty-two additional elements

    SciTech Connect

    Morgan, T.L.

    1980-08-01

    Totals of 1583 water samples and 503 sediment samples were collected from 2028 locations within the 20 000-km/sup 2/ area of the quadrangle at an average density of one location per 9.86 km/sup 2/. Water samples were collected from wells, springs, and streams and were analyzed for uranium. Sediment samples were collected from streams and springs and were analyzed for uranium, thorium, and 41 additional elements. All field and analytical data are listed in the appendixes of this report. Discussion is limited to anomalous samples, which are considered to be those containing over 20 ppB uranium for waters and over 5 ppM uranium for sediments. Uranium concentrations in water samples range from below the detection limit of 0.2 ppB to 1457.65 ppB and average 7.41 ppB. Most of the seventy anomalous water samples (4.4% of all water samples) are grouped spatially into five clusters or areas of interest. Samples in three of the clusters were collected along the north edge of the quadrangle where Mesozoic strata are exposed. The other two clusters are from the central and southern portions where the Quaternary Ogallala formation is exposed. Sediment samples from the quadrangle have uranium concentrations that range from 0.90 ppM to 27.20 ppM and average 3.27 ppM. Fourteen samples (2.8% of all sediment samples) contain over 5 ppM uranium and are considered anomalous. The five samples with the highest concentrations occur where downcutting streams expose Cretaceous units beneath the Quaternary surficial deposits. The remaining anomalous sediment samples were collected from scattered locations and do not indicate any single formation or unit as a potential source for the anomalous concentrations.

  4. Comparative structural morphometry and elemental composition of three marine sponges from western coast of India.

    PubMed

    Kumar, Maushmi S; Shah, Bhaumik

    2014-04-01

    Three marine sponges Halichondria glabrata, Cliono lobata, and Spirastrella pachyspira from the western coastal region of India were compared for their morphometry, biochemical, and elemental composition. One-way analysis of variance was applied for spicule morphometry results. Length, width, and length:width ratio were calculated independently. The ratio of length:width varied from 35 to 42 among the grown samples, which remained in the range of 10-22 in young sample at the beginning of studies. However, no significant change was observed in spicule width compared to length. Elemental compositions of marine sponges were determined by field emission gun-scanning electron microscope. Scanning electron microscopy data revealed that the spicules of all the three sponges were mostly composed of O (47-56%) and Si (30-40%), whereas Al (14.33%) was only detected in the spicules of C. lobata. Apart from these, K, Ni, Ca, Fe, Mg, Na, and S were additionally detected in all the three samples. Presence of heavy metals in the sponges was analyzed by inductively coupled plasma-atomic emission spectroscopy. Results showed that iron was present in a large amount in samples, followed by zinc, lead, and copper. PMID:24500946

  5. Modelling of single walled carbon nanotube cylindrical structures with finite element method simulations

    NASA Astrophysics Data System (ADS)

    Günay, E.

    2016-04-01

    In this study, the modulus of elasticity and shear modulus values of single-walled carbon nanotubes SWCNTs were modelled by using both finite element method and the Matlab code. Initially, cylindrical armchair and zigzag single walled 3D space frames were demonstrated as carbon nanostructures. Thereafter, macro programs were written by the Matlab code producing the space truss for zigzag and armchair models. 3D space frames were introduced to the ANSYS software and then tension, compression and additionally torsion tests were performed on zigzag and armchair carbon nanotubes with BEAM4 element in obtaining the exact values of elastic and shear modulus values. In this study, two different boundary conditions were tested and especially used in torsion loading. The equivalent shear modulus data was found by averaging the corresponding values obtained from ten different nodal points on the nanotube path. Finally, in this study it was determined that the elastic constant values showed proportional changes by increasing the carbon nanotube diameters up to a certain level but beyond this level these values remained stable.

  6. Corotational nonlinear analyses of laminated shell structures using a 4-node quadrilateral flat shell element with drilling stiffness

    NASA Astrophysics Data System (ADS)

    Wang, Zhen; Sun, Qin

    2014-06-01

    A new 4-node quadrilateral flat shell element is developed for geometrically nonlinear analyses of thin and moderately thick laminated shell structures. The flat shell element is constructed by combining a quadrilateral area coordinate method (QAC) based membrane element AGQ6-II, and a Timoshenko beam function (TBF) method based shear deformable plate bending element ARS-Q12. In order to model folded plates and connect with beam elements, the drilling stiffness is added to the element stiffness matrix based on the mixed variational principle. The transverse shear rigidity matrix, based on the first-order shear deformation theory (FSDT), for the laminated composite plate is evaluated using the transverse equilibrium conditions, while the shear correction factors are not needed. The conventional TBF methods are also modified to efficiently calculate the element stiffness for laminate. The new shell element is extended to large deflection and post-buckling analyses of isotropic and laminated composite shells based on the element independent corotational formulation. Numerical results show that the present shell element has an excellent numerical performance for the test examples, and is applicable to stiffened plates.

  7. Immersed smoothed finite element method for fluid-structure interaction simulation of aortic valves

    NASA Astrophysics Data System (ADS)

    Yao, Jianyao; Liu, G. R.; Narmoneva, Daria A.; Hinton, Robert B.; Zhang, Zhi-Qian

    2012-12-01

    This paper presents a novel numerical method for simulating the fluid-structure interaction (FSI) problems when blood flows over aortic valves. The method uses the immersed boundary/element method and the smoothed finite element method and hence it is termed as IS-FEM. The IS-FEM is a partitioned approach and does not need a body-fitted mesh for FSI simulations. It consists of three main modules: the fluid solver, the solid solver and the FSI force solver. In this work, the blood is modeled as incompressible viscous flow and solved using the characteristic-based-split scheme with FEM for spacial discretization. The leaflets of the aortic valve are modeled as Mooney-Rivlin hyperelastic materials and solved using smoothed finite element method (or S-FEM). The FSI force is calculated on the Lagrangian fictitious fluid mesh that is identical to the moving solid mesh. The octree search and neighbor-to-neighbor schemes are used to detect efficiently the FSI pairs of fluid and solid cells. As an example, a 3D idealized model of aortic valve is modeled, and the opening process of the valve is simulated using the proposed IS-FEM. Numerical results indicate that the IS-FEM can serve as an efficient tool in the study of aortic valve dynamics to reveal the details of stresses in the aortic valves, the flow velocities in the blood, and the shear forces on the interfaces. This tool can also be applied to animal models studying disease processes and may ultimately translate to a new adaptive methods working with magnetic resonance images, leading to improvements on diagnostic and prognostic paradigms, as well as surgical planning, in the care of patients.

  8. LASER Additive Manufacturing of Titanium-Tantalum Alloy Structured Interfaces for Modular Orthopedic Devices

    NASA Astrophysics Data System (ADS)

    Fuerst, Jacob; Medlin, Dana; Carter, Michael; Sears, James; Vander Voort, George

    2015-04-01

    Tantalum is recognized to have better biocompatibility and osseointegrative properties than other more commonly used orthopedic grade alloys. There are several novel methods that tantalum or tantalum-titanium could be used to augment orthopedic implants. A tantalum or tantalum-titanium alloy at the bone/implant or modular component interfaces would substantially increase the longevity and performance of modular devices. Bonding a functional tantalum coating to a titanium orthopedic device is inherently difficult because of the small difference between the melting temperature of tantalum, 3017°C, and the boiling point of titanium, 3287°C. LASER powder deposition (LPD) is a fusion operation using an Nd:YAG to melt a small volume of substrate into which metal powder is sprayed achieving high temperature with a high solidification rate. LPD of Ti-Ta onto a Ti-6Al-4V substrate produced both a solid surface and structured coating with a pore size in the optimal 350-500 μm range.

  9. Micromechanical modeling of open cell structures with application in finite element analysis of vertebral body mechanics

    NASA Astrophysics Data System (ADS)

    Overaker, David Wolfgang

    1997-12-01

    A nonlinear micromechanical model for two-dimensional irregular hexagonal foams has been developed that allows for anisotropy in morphology and/or material. Based upon the orientation, cross-section, length, and material properties of each strut, the resulting micro-level beam behavior within the unit cell determines its structural properties. Nonlinearity is introduced as coupled elasto-plastic beam behavior, where the elasto-plastic behavior of each beam is considered. The analytical formulation for the stiffness matrix of the general elasto-plastic unit cell is found by considering compatibility and equilibrium of the unit cell. The structural properties of the elasto-plastic unit cell are embedded in a continuum finite element model as material properties, thus capturing the microstructure of the foam in an accurate and efficient model. Structural nonlinearity is therefore directly linked to localized plasticity and its evolution at the micro-level. Elastic analyses investigated the degree of anisotropy in structural properties that was induced by various morphological changes. Plastic analyses showed how structural nonlinearity could be explained by localized microstructural behavior. The formulation for the three-dimensional regular hexagonal foam was then developed as an extension of the two-dimensional formulation. Sensitivity of the constitutive properties to the microstructure and its orientation was studied. The model was then validated for application as an idealized model of the porous trabecular bone material of the human vertebra. The mechanical behavior of the model was shown to capture the basic characteristics of actual bone, where changes in behavior associated with age-related changes in bone architecture (increasing porosity with age) were also considered. Nonlinearity in the load-displacement behavior of trabecular bone specimens was directly linked to localized microstructural nonlinearity and its evolution. Validation was followed by

  10. Concrete containment structural element tests. Volume 1. Half-thickness element tests - description and results. Final report

    SciTech Connect

    Julien, J.T.; Schultz, D.M.; Weinmann, T.L.

    1984-11-01

    Understanding the structural behavior of nuclear reactor containment buildings under extreme internal pressures can lead to more realistic estimates of risk from severe core accidents. This study provides test data on the behavior, under biaxial tensile loads, of large-scale segments of a containment building with reinforced and prestressed concrete designs.

  11. The role of G-quadruplex/i-motif secondary structures as cis-acting regulatory elements

    PubMed Central

    Kendrick, Samantha; Hurley, Laurence H.

    2011-01-01

    The nature of DNA has captivated scientists for more than fifty years. The discovery of the double-helix model of DNA by Watson and Crick in 1953 not only established the primary structure of DNA, but also provided the mechanism behind DNA function. Since then, researchers have continued to further the understanding of DNA structure and its pivotal role in transcription. The demonstration of DNA secondary structure formation has allowed for the proposal that the dynamics of DNA itself can function to modulate transcription. This review presents evidence that DNA can exist in a dynamic equilibrium between duplex and secondary conformations. In addition, data demonstrating that intracellular proteins as well as small molecules can shift this equilibrium in either direction to alter gene transcription will be discussed, with a focus on the modulation of proto-oncogene expression. PMID:21796223

  12. Effects of Boron Addition to the Atomic Structure and Soft Magnetic Properties of FeCoB Films

    SciTech Connect

    Yang,A.; Imrane, H.; Lou, J.; Kirkland, J.; Vittoria, C.; Sun, N.; Harris, V.

    2008-01-01

    The magnetic, microwave, and the atomic structure properties of (Fe0.7Co0.3)1?xBx sputtered films on glass substrates were investigated. The addition of boron induced a decrease in coercivity and ferromagnetic resonance linewidth. The amorphous structure was formed at x ? 0.075. Extended x-ray absorption fine structure (EXAFS) of Fe and Co showed the reduced Fourier transform (FT) amplitude, and increased Debye-Waller factors as x was increased, indicating the increased disorder due to the thermal and structural displacements. Possible Fe-B bonding was observed with a reduced bond length, which indicates boron atoms' preference for staying in the interstitial sites in bcc unit cell.

  13. Effects of boron addition to the atomic structure and soft magnetic properties of FeCoB films

    NASA Astrophysics Data System (ADS)

    Yang, Aria; Imrane, Hassan; Lou, Jing; Kirkland, Johnny; Vittoria, Carmine; Sun, Nian; Harris, Vincent G.

    2008-04-01

    The magnetic, microwave, and the atomic structure properties of (Fe0.7Co0.3)1-xBx sputtered films on glass substrates were investigated. The addition of boron induced a decrease in coercivity and ferromagnetic resonance linewidth. The amorphous structure was formed at x ˜0.075. Extended x-ray absorption fine structure (EXAFS) of Fe and Co showed the reduced Fourier transform (FT) amplitude, and increased Debye-Waller factors as x was increased, indicating the increased disorder due to the thermal and structural displacements. Possible Fe-B bonding was observed with a reduced bond length, which indicates boron atoms' preference for staying in the interstitial sites in bcc unit cell.

  14. Feasibility Study on 3-D Printing of Metallic Structural Materials with Robotized Laser-Based Metal Additive Manufacturing

    NASA Astrophysics Data System (ADS)

    Ding, Yaoyu; Kovacevic, Radovan

    2016-05-01

    Metallic structural materials continue to open new avenues in achieving exotic mechanical properties that are naturally unavailable. They hold great potential in developing novel products in diverse industries such as the automotive, aerospace, biomedical, oil and gas, and defense. Currently, the use of metallic structural materials in industry is still limited because of difficulties in their manufacturing. This article studied the feasibility of printing metallic structural materials with robotized laser-based metal additive manufacturing (RLMAM). In this study, two metallic structural materials characterized by an enlarged positive Poisson's ratio and a negative Poisson's ratio were designed and simulated, respectively. An RLMAM system developed at the Research Center for Advanced Manufacturing of Southern Methodist University was used to print them. The results of the tensile tests indicated that the printed samples successfully achieved the corresponding mechanical properties.

  15. Feasibility Study on 3-D Printing of Metallic Structural Materials with Robotized Laser-Based Metal Additive Manufacturing

    NASA Astrophysics Data System (ADS)

    Ding, Yaoyu; Kovacevic, Radovan

    2016-07-01

    Metallic structural materials continue to open new avenues in achieving exotic mechanical properties that are naturally unavailable. They hold great potential in developing novel products in diverse industries such as the automotive, aerospace, biomedical, oil and gas, and defense. Currently, the use of metallic structural materials in industry is still limited because of difficulties in their manufacturing. This article studied the feasibility of printing metallic structural materials with robotized laser-based metal additive manufacturing (RLMAM). In this study, two metallic structural materials characterized by an enlarged positive Poisson's ratio and a negative Poisson's ratio were designed and simulated, respectively. An RLMAM system developed at the Research Center for Advanced Manufacturing of Southern Methodist University was used to print them. The results of the tensile tests indicated that the printed samples successfully achieved the corresponding mechanical properties.

  16. Myriad Triple-Helix-Forming Structures in the Transposable Element RNAs of Plants and Fungi.

    PubMed

    Tycowski, Kazimierz T; Shu, Mei-Di; Steitz, Joan A

    2016-05-10

    The ENE (element for nuclear expression) is a cis-acting RNA structure that protects viral or cellular noncoding RNAs (ncRNAs) from nuclear decay through triple-helix formation with the poly(A) tail or 3'-terminal A-rich tract. We expanded the roster of nine known ENEs by bioinformatic identification of ∼200 distinct ENEs that reside in transposable elements (TEs) of numerous non-metazoan and one fish species and in four Dicistrovirus genomes. Despite variation within the ENE core, none of the predicted triple-helical stacks exceeds five base triples. Increased accumulation of reporter transcripts in human cells demonstrated functionality for representative ENEs. Location close to the poly(A) tail argues that ENEs are active in TE transcripts. Their presence in intronless, but not intron-containing, hAT transposase genes supports the idea that TEs acquired ENEs to counteract the RNA-destabilizing effects of intron loss, a potential evolutionary consequence of TE horizontal transfer in organisms that couple RNA silencing to splicing deficits. PMID:27134163

  17. Active transposable elements recover species boundaries and geographic structure in Madagascan coffee species.

    PubMed

    Roncal, Julissa; Guyot, Romain; Hamon, Perla; Crouzillat, Dominique; Rigoreau, Michel; Konan, Olivier N'Guessan; Rakotomalala, Jean-Jacques; Nowak, Michael D; Davis, Aaron P; de Kochko, Alexandre

    2016-02-01

    The completion of the genome assembly for the economically important coffee plant Coffea canephora (Rubiaceae) has allowed the use of bioinformatic tools to identify and characterize a diverse array of transposable elements (TEs), which can be used in evolutionary studies of the genus. An overview of the copy number and location within the C. canephora genome of four TEs is presented. These are tested for their use as molecular markers to unravel the evolutionary history of the Millotii Complex, a group of six wild coffee (Coffea) species native to Madagascar. Two TEs from the Gypsy superfamily successfully recovered some species boundaries and geographic structure among samples, whereas a TE from the Copia superfamily did not. Notably, species occurring in evergreen moist forests of eastern and southeastern Madagascar were divergent with respect to species in other habitats and regions. Our results suggest that the peak of transpositional activity of the Gypsy and Copia TEs occurred, respectively, before and after the speciation events of the tested Madagascan species. We conclude that the utilization of active TEs has considerable potential to unravel the evolutionary history and delimitation of closely related Coffea species. However, the selection of TE needs to be experimentally tested, since each element has its own evolutionary history. Different TEs with similar copy number in a given species can render different dendrograms; thus copy number is not a good selection criterion to attain phylogenetic resolution. PMID:26231981

  18. [Structure and evolutionary role of the Penelope mobile element in Drosophila species of the virilis group].

    PubMed

    Lezin, G T; Makarova, K V; Velikodvorskaia, V V; Zelentsova, E S; Kechumian, R R; Kidwell, M G; Kunin, E V; Evgen'ev, M B

    2001-01-01

    The mobile element Penelope is activated and mobilizes several other transposons in dysgenic crosses in Drosophila virilis. Its structure proved to be complex and to vary greatly in all examined species of the virilis group. Phylogenetic analysis of the reverse transcriptase (RT) domain assigned Penelope to a new branch, rather than to any known family, of LTR-lacking retroelements. Amino acid sequence analysis showed that the C-terminal domain of the Penelope polyprotein is an active endonuclease, which is related to intron-encoded endonucleases and to bacterial repair endonuclease UrvC, and may act as an integras. Retroelements coding for a putative endonuclease that differs from typical integrase have thus far not been known. The N-terminal domain of the Penelope polyprotein was shown to contain a protease with significant homology to HIV-1 protease. Phylogenetic analysis divided the Penelope copies from several virilis species into two subfamilies, one including virtually identical full-length copies, and the other comprising highly divergent defective copies. The results suggest both vertical and horizontal transfer of the element. Possibly, Penelope invasion recurred during evolution and contributed to genome rearrangement in the virilis species. Chromosome aberrations detected in D. virilis, which is now being invaded by Penelope, is direct evidence for this assumption. PMID:11605533

  19. Surface geometric analysis of anatomic structures using biquintic finite element interpolation.

    PubMed

    Smith, D B; Sacks, M S; Vorp, D A; Thornton, M

    2000-06-01

    The surface geometry of anatomic structures can have a direct impact upon their mechanical behavior in health and disease. Thus, mechanical analysis requires the accurate quantification of three-dimensional in vivo surface geometry. We present a fully generalized surface fitting method for surface geometric analysis that uses finite element based hermite biquintic polynomial interpolation functions. The method generates a contiguous surface of C2 continuity, allowing computation of the finite strain and curvature tensors over the entire surface with respect to a single in-surface coordinate system. The Sobolev norm, which restricts element length and curvature, was utilized to stabilize the interpolating polynomial at boundaries and in regions of sparse data. A major advantage of the current method is its ability to fully quantify surface deformation from an unstructured grid of data points using a single interpolation scheme. The method was validated by computing both the principal curvature distributions for phantoms of known curvatures and the principal stretch and principal change of curvature distributions for a synthetic spherical patch warping into an ellipsoidal shape. To demonstrate the applicability to biomedical problems, the method was applied to quantify surface curvatures of an abdominal aortic aneurysm and the principal strains and change of curvatures of a deforming bioprosthetic heart valve leaflet. The method proved accurate for the computation of surface curvatures, as well as for strains and curvature change for a surface undergoing large deformations. PMID:10983706

  20. Sensitivity Analysis of Linear Elastic Cracked Structures Using Generalized Finite Element Method

    NASA Astrophysics Data System (ADS)

    Pal, Mahendra Kumar; Rajagopal, Amirtham

    2014-09-01

    In this work, a sensitivity analysis of linear elastic cracked structures using two-scale Generalized Finite Element Method (GFEM) is presented. The method is based on computation of material derivatives, mutual potential energies, and direct differentiation. In a computational setting, the discrete form of the mutual potential energy release rate is simple and easy to calculate, as it only requires the multiplication of the displacement vectors and stiffness sensitivity matrices. By judiciously choosing the velocity field, the method only requires displacement response in a sub-domain close to the crack tip, thus making the method computationally efficient. The method thus requires an exact computation of displacement response in a sub-domain close to the crack tip. To this end, in this study we have used a two-scale GFEM for sensitivity analysis. GFEM is based on the enrichment of the classical finite element approximation. These enrichment functions incorporate the discontinuity response in the domain. Three numerical examples which comprise mode-I and mixed mode deformations are presented to evaluate the accuracy of the fracture parameters calculated by the proposed method.