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1

Prospects of pulse phase thermography for finding disbonds in CFRP-sandwich parts with aluminum honeycomb cores compared to ultrasonic  

NASA Astrophysics Data System (ADS)

This work shows the prospects of pulse phase thermography (PPT) compared to ultrasonic testing when applied to carbon fiber reinforced polymer (CFRP) sandwich parts with aluminum honeycomb cores. Measurements were carried out on full-scale components with flaws like disbonds, septum disbonds, staggers and displaced cores, where the last two are not literally flaws, but nevertheless regions of interest. The effect of the measurement time and the feasibility of extrapolating temperature decays were evaluated. Phase images, gathered with PPT, are compared with ultrasonic Cscan images to show the capability of PPT for quality assurance purposes. Finally, the saving on inspection time when using pulse phase thermography instead of ultrasonic testing is considered.

Gruber, J.; Stotter, B.; Mayr, G.; Hendorfer, G.

2013-01-01

2

Performance of aluminum honeycomb panels with structural defects and core anomalies. Part I - test methodology and general results  

SciTech Connect

There is little data in the literature on the effect on structural performance of defects in honeycomb structure, and there is little evidence that the normally accepted defect criteria bear any direct relationship to performance. To help establish a sounder basis for the Air Logistics Centers to assess the quality of replacement components, a test program encompassing a large range of structural defects and core anomalies in aluminum honeycomb structure was conducted. The scope included 16 defect categories that are addressed specifically within existing procurement specifications. For each defect category, panels containing defects in excess of the current acceptance criteria were tested and the results compared to baseline panels with acceptable characteristics. By doing so, the tolerance and/or sensitivity of a given structure to a typical defect was determined. The panels were subjected to static and cyclic loads before and after exposure to accelerated corrosion environments and cyclic thermal loads. Part I of this paper addresses the development of the test plan for these 16 defect categories and summarizes the test results. Part II gives detailed information on specimens and testing for the 4 defect categories which were found to degrade structure performance of 30% or more. 1 ref., 2 figs., 8 tabs.

Burkes, J.M.; Griffin, M.A.; Parr, C.H. [Southwest Research Inst., San Antonio, TX (United States)

1992-03-01

3

An analytical model for composite sandwich panels with honeycomb core subjected to high-velocity impact  

Microsoft Academic Search

In this paper, an analytical model for perforation of composite sandwich panels with honeycomb core subjected to high-velocity impact has been developed. The sandwich panel consists of a aluminum honeycomb core sandwiched between two thin composite skins. The solution involves a three-stage, perforation process including perforation of the front composite skin, honeycomb core, and bottom composite skin. The strain and

S. Feli; M. H. Namdari Pour

4

Preelectroplating Treatment Of Titanium Honeycomb Core  

NASA Technical Reports Server (NTRS)

New technique used to treat titanium honeycomb core electrochemically by applying conversion coat to keep honeycomb active and receptive to electroplating with solution of sodium bichromate and hydrofluoric acid. Maskant permits electroplating of controlled amount of filler metal on edge of honeycomb. Eliminates excess copper filler.

Kelly, Michael L.; Harvey, James S.

1992-01-01

5

Axial perforation of aluminum honeycombs by projectiles  

Microsoft Academic Search

Deformation and energy absorption characteristics of aluminum honeycomb when penetrated or perforated in the axial direction by spheres and cylinders with diameters of the order of and twice the cell size have been observed experimentally. The work of static penetration using a standard test machine was obtained from measured force histories when hard-steel spheres with three different diameters were pushed

Werner Goldsmith; Dell L. Louie

1995-01-01

6

Performance of aluminum honeycomb panels with structural defects and core anomalies. Part I - test methodology and general results  

Microsoft Academic Search

There is little data in the literature on the effect on structural performance of defects in honeycomb structure, and there is little evidence that the normally accepted defect criteria bear any direct relationship to performance. To help establish a sounder basis for the Air Logistics Centers to assess the quality of replacement components, a test program encompassing a large range

J. M. Burkes; M. A. Griffin; C. H. Parr

1992-01-01

7

Research on An Inspection Method for De-bond Defects in Aluminum Skin-Honeycomb Core Sandwich Structure with Guided Waves  

Microsoft Academic Search

In order to increase the ultrasonic inspection speed of skin honeycomb core sandwich structure, the application of guided waves in this field was resea rched on. The characteristics of guided waves was stated, the propagation of guided waves in the skin ho neycomb core sandwich structure was analyzed. Guided wave mode was selected in term of signal amplitude relative change

Fangcheng HE; Zhenggan ZHOU; Zhanying FENG

8

Experimental Analysis and Modeling of the Crushing of Honeycomb Cores  

NASA Astrophysics Data System (ADS)

In the aeronautical field, sandwich structures are widely used for secondary structures like flaps or landing gear doors. The modeling of low velocity/low energy impact, which can lead to a decrease of the structure strength by 50%, remains a designer’s main problem. Since this type of impact has the same effect as quasi-static indentation, the study focuses on the behavior of honeycomb cores under compression. The crushing phenomenon has been well identified for years but its mechanism is not described explicitly and the model proposed may not satisfy industrial purposes. To understand the crushing mechanism, honeycomb test specimens made of Nomex™, aluminum alloy and paper were tested. During the crushing, a CCD camera showed that the cell walls buckled very quickly. The peak load recorded during tests corresponded to the buckling of the common edge of three honeycomb cells. Further tests on corner structures to simulate only one vertical edge of a honeycomb cell show a similar behavior. The different specimens exhibited similar load/displacement curves and the differences observed were only due to the behavior of the different materials. As a conclusion of this phenomenological study, the hypothesis that loads are mainly taken by the vertical edge can be made. So, a honeycomb core subjected to compression can be modeled by a grid of nonlinear springs. A simple analytical model was then developed and validated by tests on Nomex™ honeycomb core indented by different sized spherical indenters. A good correlation between theory and experiment was found. This result can be used to satisfactorily model using finite elements the indentation on a sandwich structure with a metallic or composite skin and honeycomb core.

Aminanda, Y.; Castanié, B.; Barrau, J.-J.; Thevenet, P.

2005-05-01

9

Low-Weight Inserts for Aluminum Honeycomb Panels  

NASA Technical Reports Server (NTRS)

Fiber/epoxy composites used in place of solid aluminum. New proposal suggests to make inserts out of such lightweight, high strength materials as fiber/epoxy composites or high density aluminum honeycomb. Composite insert is same size and shape as aluminum insert it replaces.

Bumgarner, G. S.; Reed, M. W.

1983-01-01

10

Development of graphite/polyimide honeycomb core materials  

NASA Technical Reports Server (NTRS)

Honeycomb panel constructions consisting entirely of graphite/polyimide composites were developed and evaluated. Graphite/polyimide composites, were used in the honeycomb core webs and in pre-cured sandwich skins. Polyimide adhesives were also developed and evaluated for use in skin-core bonding. The purpose of this program was to develop light weight sandwich constructions for high temperature applications which could provide comparable shear strength and stiffness to metallic honeycomb constructions.

Stone, R. H.

1978-01-01

11

Honeycomb Core and the Myths of Moisture Ingression  

Microsoft Academic Search

While it is true that honeycomb core can trap moisture, it is a myth that widespread moisture ingression is an inevitable\\u000a outcome when honeycomb sandwich structures are exposed to real world environments. It is also a myth that when moisture ingression\\u000a occurs, progressive weight gain and strength loss are inevitable outcomes. Using a rebuttal of a 2004 honeycomb-critical paper\\u000a as

John H. Fogarty

2010-01-01

12

A novel assembly technology of aluminum alloy honeycomb structure  

Microsoft Academic Search

In this study, the authors applied the low-temperature ultrasonic soldering method to solder aluminum alloy honeycomb structure\\u000a and investigated the effects of soldering time and soldering temperature on the properties of the solder. The following results\\u000a were obtained: The wetting angle changed with applied time and applied temperature. The solder region is mainly composed of\\u000a four kinds of microstructure zones:

Ding Min; Zhang Pei-lei; Zhang Zhen-yu; Yao Shun

2010-01-01

13

Characterization of Thermal and Mechanical Impact on Aluminum Honeycomb Structures  

NASA Technical Reports Server (NTRS)

This study supports NASA Kennedy Space Center's research in the area of intelligent thermal management systems and multifunctional thermal systems. This project addresses the evaluation of the mechanical and thermal properties of metallic cellular solid (MCS) materials; those that are lightweight; high strength, tunable, multifunctional and affordable. A portion of the work includes understanding the mechanical properties of honeycomb structured cellular solids upon impact testing under ambient, water-immersed, liquid nitrogen-cooled, and liquid nitrogen-immersed conditions. Additionally, this study will address characterization techniques of the aluminum honeycomb's ability to resist multiple high-rate loadings or impacts in varying environmental conditions, using various techniques for the quantitative and qualitative determination for commercial applicability.

Robinson, Christen M.

2013-01-01

14

Model for Simulating the Response of Aluminum Honeycomb Structure to Transverse Loading.  

National Technical Information Service (NTIS)

A 1-dimensional material model was developed for simulating the transverse (thickness-direction) loading and unloading response of aluminum honeycomb structure. The model was implemented as a user-defined material subroutine (UMAT) in the commercial finit...

J. G. Ratcliffe M. W. Czabaj W. C. Jackson

2012-01-01

15

WRINKLING STRESSES IN HONEYCOMB SANDWICH PANELS USING DISCRETE AND CONTINUUM CORE REPRESENTATIONS  

Microsoft Academic Search

This study, examines the implications of modelling wrinkling in sandwich honeycomb cores using a simplified continuum representation of the core. Localised wrinkling in honeycomb panels is traditionally modelled using a continuum core. In a continuum core, the support provided to the facesheet is constant, whilst in reality; it is discrete with cellular core. Classical linear wrinkling expressions, based on this

R. A Staal; D. P. W Horrigan; G. D Mallinson; K Jayaraman

16

Heat Transfer in Adhesively Bonded Honeycomb Core Panels  

NASA Technical Reports Server (NTRS)

The Swann and Pittman semi-empirical relationship has been used as a standard in aerospace industry to predict the effective thermal conductivity of honeycomb core panels. Recent measurements of the effective thermal conductivity of an adhesively bonded titanium honeycomb core panel using three different techniques, two steady-state and one transient radiant step heating method, at four laboratories varied significantly from each other and from the Swann and Pittman predictions. Average differences between the measurements and the predictions varied between 17 and 61% in the temperature range of 300 to 500 K. In order to determine the correct values of the effective thermal conductivity and determine which set of the measurements or predictions were most accurate, the combined radiation and conduction heat transfer in the honeycomb core panel was modeled using a finite volume numerical formulation. The transient radiant step heating measurements provided the best agreement with the numerical results. It was found that a modification of the Swann and Pittman semi-empirical relationship which incorporated the facesheets and adhesive layers in the thermal model provided satisfactory results. Finally, a parametric study was conducted to investigate the influence of adhesive thickness and thermal conductivity on the overall heat transfer through the panel.

Daryabeigi, Kamran

2001-01-01

17

A Model for Simulating the Response of Aluminum Honeycomb Structure to Transverse Loading  

NASA Technical Reports Server (NTRS)

A 1-dimensional material model was developed for simulating the transverse (thickness-direction) loading and unloading response of aluminum honeycomb structure. The model was implemented as a user-defined material subroutine (UMAT) in the commercial finite element analysis code, ABAQUS(Registered TradeMark)/Standard. The UMAT has been applied to analyses for simulating quasi-static indentation tests on aluminum honeycomb-based sandwich plates. Comparison of analysis results with data from these experiments shows overall good agreement. Specifically, analyses of quasi-static indentation tests yielded accurate global specimen responses. Predicted residual indentation was also in reasonable agreement with measured values. Overall, this simple model does not involve a significant computational burden, which makes it more tractable to simulate other damage mechanisms in the same analysis.

Ratcliffe, James G.; Czabaj, Michael W.; Jackson, Wade C.

2012-01-01

18

Prospects and limitations of digital Shearography and Active Thermography in finding and rating flaws in CFRP sandwich parts with honeycomb core  

NASA Astrophysics Data System (ADS)

This work shows the prospects and limitations of the non-destructive testing methods Digital Shearography and Active Thermography when applied to CFRP sandwich parts with honeycomb cores. Two specimens with different core materials (aluminum, NOMEX) and artificial flaws such as delaminations, disbonds and inclusions of foreign material, are tested with Digital Shearography and Pulse Thermography including Pulse Phase Thermography. Both methods provide a good ability for finding and rating the flaws.

Gruber, J.; Mayr, G.; Hendorfer, G.

2012-05-01

19

SPECTRAL FINITE ELEMENT MODELING OF WAVE PROPAGATION IN SANDWICH PLATE-ROWS WITH PERIODIC HONEYCOMB CORE  

Microsoft Academic Search

The wave propagation in sandwich plates with cellular core is analyzed and controlled. Honeycomb core materials of different geometry placed periodically along the structure introduce the impedance mismatch necessary to obstruct the propagation of waves over specific frequency bands (stop bands). The location and the extension of the stop bands can be optimized by proper selection of the geometrical and

Luca Mazzarella; Massimo Ruzzene; Panos Tsopelas

20

Quantum phases of hard-core bosons in a frustrated honeycomb lattice  

NASA Astrophysics Data System (ADS)

Using exact diagonalization calculations, we investigate the ground-state phase diagram of the hard-core Bose-Hubbard-Haldane model on the honeycomb lattice. This allows us to probe the stability of the Bose-metal phase proposed in Varney et al (2011 Phys. Rev. Lett. 107 077201), against various changes in the originally studied Hamiltonian.

Varney, C. N.; Sun, K.; Galitski, V.; Rigol, M.

2012-11-01

21

Damage Resistance Characteristics of Thick-Core Honeycomb Composite Panels  

Microsoft Academic Search

The quasi-static indentation and impact response of very thick sandwich panels, developed as candidate materials for the crown panel of the next generation large commercial transport, is described. A preliminary characterization of the damage resistance of eight different core- facesheet configurations is performed, and the effect of facesheet thickness, core density and core material is investigated. Drop weight impact, quasi-static

Paolo Feraboli

2006-01-01

22

Fabrication and characterization of porous-core honeycomb bandgap THz fibers.  

PubMed

We present a numerical and experimental investigation of a low-loss porous-core honeycomb fiber for terahertz wave guiding. The introduction of a porous core with hole size of the same dimension as the holes in the surrounding honeycomb cladding results in a fiber that can be drawn with much higher precision and reproducibility than a corresponding air-core fiber. The high-precision hole structure provides very clear bandgap guidance and the location of the two measured bandgaps agree well with simulations based on finite-element modeling. Fiber loss measurements reveal the frequency-dependent coupling loss and propagation loss, and we find that the fiber propagation loss is much lower than the bulk material loss within the first band gap between 0.75 and 1.05 THz. PMID:23388777

Bao, Hualong; Nielsen, Kristian; Rasmussen, Henrik K; Jepsen, Peter Uhd; Bang, Ole

2012-12-31

23

Adhesion in sandwiches with aluminum foam core  

Microsoft Academic Search

Fast-moving machine tool assemblies should be light and rigid. Because of the lightweight construction and the dynamic loads\\u000a these assemblies are very often susceptible to vibrations. Aluminum foam sandwiches are laminates with an aluminum foam core\\u000a and compact cover sheets. The foam cores possess a high-energy absorption capacity. Machine tool assemblies made of aluminum\\u000a foam sandwiches offer very high flexural

Reimund Neugebauer; Carsten Lies; Jörg Hohlfeld; Thomas Hipke

2007-01-01

24

Compression After Impact on Honeycomb Core Sandwich Panels with Thin Facesheets, Part 2: Analysis  

NASA Technical Reports Server (NTRS)

A two part research study has been completed on the topic of compression after impact (CAI) of thin facesheet honeycomb core sandwich panels. The research has focused on both experiments and analysis in an effort to establish and validate a new understanding of the damage tolerance of these materials. Part 2, the subject of the current paper, is focused on the analysis, which corresponds to the CAI testings described in Part 1. Of interest, are sandwich panels, with aerospace applications, which consist of very thin, woven S2-fiberglass (with MTM45-1 epoxy) facesheets adhered to a Nomex honeycomb core. Two sets of materials, which were identical with the exception of the density of the honeycomb core, were tested in Part 1. The results highlighted the need for analysis methods which taken into account multiple failure modes. A finite element model (FEM) is developed here, in Part 2. A commercial implementation of the Multicontinuum Failure Theory (MCT) for progressive failure analysis (PFA) in composite laminates, Helius:MCT, is included in this model. The inclusion of PFA in the present model provided a new, unique ability to account for multiple failure modes. In addition, significant impact damage detail is included in the model. A sensitivity study, used to assess the effect of each damage parameter on overall analysis results, is included in an appendix. Analysis results are compared to the experimental results for each of the 32 CAI sandwich panel specimens tested to failure. The failure of each specimen is predicted using the high-fidelity, physicsbased analysis model developed here, and the results highlight key improvements in the understanding of honeycomb core sandwich panel CAI failure. Finally, a parametric study highlights the strength benefits compared to mass penalty for various core densities.

Mcquigg, Thomas D.; Kapania, Rakesh K.; Scotti, Stephen J.; Walker, Sandra P.

2012-01-01

25

Performance of metallic honeycomb-core sandwich beams under shock loading  

Microsoft Academic Search

Stainless steel square honeycomb core sandwich and solid monolithic beams have been subjected to high-pressure, short-duration impulses using a shock simulation technique involving high-speed impact of Al foam projectiles. The experiments have been designed to achieve two objectives: (i) to demonstrate the benefits of sandwich construction, and (ii) to assess the fidelity of dynamic finite element calculations in simulating the

H. J. Rathbun; D. D. Radford; Z. Xue; M. Y. He; J. Yang; V. Deshpande; N. A. Fleck; J. W. Hutchinson; F. W. Zok; A. G. Evans

2006-01-01

26

Comparison of structural behavior of superplastically formed/diffusion-bonded sandwich structures and honeycomb core sandwich structures  

NASA Technical Reports Server (NTRS)

A superplasticity formed/diffusion-bonded (SPF/DB) orthogonally corrugated core sandwich structure is discussed and its structural behavior is compared to that of a conventional honeycomb core sandwich structure. The stiffness and buckling characteristics of the two types of sandwich structures are compared under conditions of equal structural density. It is shown that under certain conditions, the SPF/DB orthogonally corrugated core sandwich structure is slightly more efficient than the optimum honeycomb core (square-cell core) sandwich structure. However, under different conditions, this effect can be reversed.

Ko, W. L.

1980-01-01

27

Compression After Impact Experiments and Analysis on Honeycomb Core Sandwich Panels with Thin Facesheets  

NASA Technical Reports Server (NTRS)

A better understanding of the effect of impact damage on composite structures is necessary to give the engineer an ability to design safe, efficient structures. Current composite structures suffer severe strength reduction under compressive loading conditions, due to even light damage, such as from low velocity impact. A review is undertaken to access the current state-of-development in the areas of experimental testing, and analysis methods. A set of experiments on honeycomb core sandwich panels, with thin woven fiberglass cloth facesheets, is described, which includes detailed instrumentation and unique observation techniques.

McQuigg, Thomas D.

2011-01-01

28

Prediction of the adhesive fillet size for skin to honeycomb core bonding in ultra-light sandwich structures  

Microsoft Academic Search

The formation of resin fillet between honeycomb core cell walls and skin in light sandwich structures was studied to gain a better understanding of the bonding process. A method was developed for tailoring the amount of adhesive between 8 and 80g\\/m2. The size of the adhesive menisci and the contact angles between the adhesive and the skin and the core

Julien Rion; Yves Leterrier; Jan-Anders E. Månson

2008-01-01

29

Honeycomb-laminate composite structure  

NASA Technical Reports Server (NTRS)

A honeycomb-laminate composite structure was comprised of: (1) a cellular core of a polyquinoxaline foam in a honeycomb structure, and (2) a layer of a noncombustible fibrous material impregnated with a polyimide resin laminated on the cellular core. A process for producing the honeycomb-laminate composite structure and articles containing the honeycomb-laminate composite structure is described.

Gilwee, W. J., Jr.; Parker, J. A. (inventors)

1977-01-01

30

Buckling tests of three 4.6 meter diameter aluminum honeycomb sandwich conical shells loaded under external pressure  

NASA Technical Reports Server (NTRS)

Three aluminum honeycomb sandwich conical shells with a 120 apex angle and a 4.6-m (15.0-ft) base diameter were loaded to failure by a uniform external pressure. The cones differed from one another only in the thickness of their respective face sheets. Test specimen details, test procedure, and test results are discussed. Both buckling and prebuckling data are compared with appropriate theoretical predictions, and good agreement was obtained between test and theory. Extensive imperfection measurements were made and reported on the three cones in the as fabricated condition.

Anderson, J. K.; Davis, R. C.

1975-01-01

31

RADIATION DAMAGE TO METAL-BONDED AND SANDWICH PANELS. II. EFFECTS OF RADIATION ON HEXCEL 91LD AND HEXCEL F-120 HONEYCOMB CORE REINFORCED WITH FIBERGLAS  

Microsoft Academic Search

In an experiment to investigate the effects of radiation on the ; compressive strength of honeycomb cores, samples of Hexcel 91LD and Hexcel F-120 ; honeycomb core, each reinforced with Fiberglas, were irradiated with the Ground ; Test Reactor. Specimens were irrad;ated at ambient temperature at four different ; radlation levels with the maximum being a gamma dose of 9.3

Bauerlein

1958-01-01

32

Propagation of elastic waves in honeycomb panels for application to rapid inspection techniques  

Microsoft Academic Search

This paper considers the properties of elastic waves guided by an aluminum plate bonded to a honeycomb core for application to rapid inspection of honeycomb panels. Current acoustic inspection techniques involve the transmission of a signal between a pair of small transducers located on opposite sides of the panel. Scanning the transducers in raster fashion results in a high resolution

H. L. Bertoni; S. K. Park

1981-01-01

33

Buckling Analysis of a Honeycomb-Core Composite Cylinder with Initial Geometric Imperfections  

NASA Technical Reports Server (NTRS)

Thin-walled cylindrical shell structures often have buckling as the critical failure mode, and the buckling of such structures can be very sensitive to small geometric imperfections. The buckling analyses of an 8-ft-diameter, 10-ft-long honeycomb-core composite cylinder loaded in pure axial compression is discussed in this document. Two loading configurations are considered configuration 1 uses simple end conditions, and configuration 2 includes additional structure that may more closely approximate experimental loading conditions. Linear eigenvalue buckling analyses and nonlinear analyses with and without initial geometric imperfections were performed on both configurations. The initial imperfections were introduced in the shell by applying a radial load at the midlength of the cylinder to form a single inward dimple. The critical bifurcation buckling loads are predicted to be 924,190 lb and 924,020 lb for configurations 1 and 2, respectively. Nonlinear critical buckling loads of 918,750 lb and 954,900 lb were predicted for geometrically perfect configurations 1 and 2, respectively. Lower-bound critical buckling loads for configurations 1 and 2 with radial perturbations were found to be 33% and 36% lower, respectively, than the unperturbed critical loads. The inclusion of the load introduction cylinders in configuration 2 increased the maximum bending-boundary-layer rotation up to 11%.

Cha, Gene; Schultz, Marc R.

2013-01-01

34

Fabrication and evaluation of enhanced diffusion bonded titanium honeycomb core sandwich panels with titanium aluminide face sheets  

NASA Technical Reports Server (NTRS)

A joining process was developed for fabricating lightweight, high temperature sandwich panels for aerospace applications using Ti-14Al-21Nb face sheets and Ti-3Al-2.5V honeycomb core. The process, termed Enhanced Diffusion Bonding (EDB), relies on the formation of a eutectic liquid through solid-state diffusion at elevated temperatures and isothermal solidification to produce joints in thin-gage titanium and titanium aluminide structural components. A technique employing a maskant on the honeycomb core was developed which permitted electroplating a controlled amount of EDB material only on the edges of the honeycomb core in order to minimize the structural weight and metallurgical interaction effects. Metallurgical analyses were conducted to determine the interaction effects between the EDB materials and the constituents of the sandwich structure following EDB processing. The initial mechanical evaluation was conducted with butt joint specimens tested at temperatures from 1400 - 1700 F. Further mechanical evaluation was conducted with EDB sandwich specimens using flatwise tension tests at temperatures from 70 - 1100 F and edgewise compression tests at ambient temperature.

Hoffmann, E. K.; Bird, R. K.; Bales, T. T.

1989-01-01

35

Analytical studies of a parabolic line concentrator utilizing an aluminum honeycomb support structure and a thin glass reflector laminate  

SciTech Connect

Results (stresses, displacements, and equivalent slope errors) are presented from finite element analyses made to evaluate a design for a parabolic trough solar concentrator. The concentrator consists of a reflector laminate (made of thin glass bonded to sheet metal backing) which is mechanically formed and bonded to a stiff parabolic support (made of aluminum honeycomb bonded to steel skins) with a 2 meter (6.6 foot) aperture. Analyses were first made to determine a length for the concentrator such that it would meet certain performance and survivability criteria under wind and gravity loadings. These studies were made with a model for the concentrator only. The concentrator model was then combined with a model for a support mechanism, and this combined structure was studied for several wind and gravity loadings. A design characterized by a six meter (twenty foot) long concentrator was found to meet performance criteria and had sufficiently low glass stresses in a 40.23 meter per second ((ninety mile per hour) wind.

Koteras, J.R.

1981-03-01

36

Debris Impact on CFRP-AL Honeycomb Sandwich Structure  

NASA Astrophysics Data System (ADS)

In order to do risk assessments of debris impacts on unmanned spacecraft, it is necessary to investigate damage of honeycomb sandwich structures caused by debris impacts. However, the study of the honeycomb sandwich panel with CFRP face sheets has not been sufficiently performed. The purpose of this study is to investigate hypervelocity impact phenomena of CFRP-AL honeycomb sandwich structure. Hypervelocity impact tests were performed with a two-stage light gas gun at University of Padova. Three kinds of CFRP-AL honeycomb sandwich panels which are frequently used as a material of a spacecraft structure were tested. The cell size and the core thickness were varied. Aluminum spheres, 0.8 mm in diameter, were used as projectiles. The tests were performed at a velocity range between 2 and 5 km/sec. After the tests, the projectiles perforated all targets. The perforation holes on the panels were measured, and ultrasonic inspection was performed. The area of the perforation holes of the panel were increased with the impact velocity. The core size of the honeycomb core did not influence the relationship between the hole and the impact velocity. Impacts of the projectile on the foil of honeycomb cell caused heavy damage to a face sheet of the opposite side of the impact surface.

Higashide, Masumi; Nagao, Yosuke; Kibe, Seishiro; Francesconi, Alessandro; Paverin, Daniele

37

Honeycomb-Laminate Composite Structure.  

National Technical Information Service (NTIS)

A honeycomb-laminate composite structure comprising: (1) a cellular core of a polyquinoxaline foam in a honeycomb structure, and (2) a layer of a non-combustible fibrous material impregnated with a polyimide resin laminated on the cellular core, is descri...

W. J. Gilwee J. A. Parker

1976-01-01

38

Honeycomb thermal shield study  

NASA Technical Reports Server (NTRS)

A honeycomb thermal shield is described which is an economical and reliable alternative to existing thermal shielding methods for reducing the radiated heat loss from elements which will not allow obstructions in the field of view. The device is simply open-face honeycomb of the type used throughout the aerospace industry for structural panels. The honeycomb thermal shield uses only the core of the honeycomb panel, so it has little structural stiffness and is transparent through the cells. It is located in close proximity to, but conductively decoupled from, the element to be shielded (the radiative source) with the axis of the honeycomb cells parallel to the view direction of the source. The source radiates into a 2pi steradian field occupied by the shield. The view field will be transparent along the axis of the honeycomb but will be increasingly obscured as the off-normal view angle increases. The angular dependence is a function of the cell height to width ratio.

Dombroski, R. M.

1975-01-01

39

Analytical structural efficiency studies of borsic/aluminum compression panels  

NASA Technical Reports Server (NTRS)

Analytically determined mass-strength curves, strain-strength curves, and dimensions are presented for structurally efficient hat-stiffened panels, corrugation-stiffened panels, hat-stiffened honeycomb-core sandwich panels, open-section corrugation panels, and honeycomb-core sandwich panels. The panels were assumed to be fabricated from either titanium, borsic/aluminum, or a combination of these materials. Borsic/aluminum panels and titanium panels reinforced with borsic/aluminum were lighter and stiffer than comparably designed titanium panels. Reinforced titanium panels had the same extensional stiffness as comparably designed Borsic/aluminum panels. For a given load, the structural efficiency of the hat-stiffened honeycomb-core sandwich panel was higher than the structural efficiency of the other stiffened panels.

Mcwithey, R. R.

1976-01-01

40

Honeycomb pattern array of vertically standing core-shell nanorods: Its application to Li energy electrodes  

SciTech Connect

An energy storage electrode system is fabricated via a template method with one-dimensional nanostructures that are hexagonally patterned in a honeycomblike fashion and vertically standing nanorods made of a gold-coated carbon nanotube core and a V{sub 2}O{sub 5} shell layer. The performance of this system for Li insertion and extraction shows an increased capacity along with an enhanced rate performance, which could be attributed to the aligned nanostructures having increased reaction sites, facilitated charge transport, and improved stability in the face of mechanical stress.

Kim, Youn-Su; Nam, Sang Hoon; Lee, Sang Ho; Shim, Hee-Sang; Kim, Won Bae [Department of Materials Science and Engineering, Gwangju Institute of Science and Technology (GIST), 261 Cheomdan-gwagiro, Buk-gu, Gwangju 500-712 (Korea, Republic of); Ahn, Hyo-Jin [Max Planck Institute of Colloids and Interfaces, D-14424 Potsdam (Germany)

2008-09-08

41

Sound insulation improvement using honeycomb sandwich panels  

Microsoft Academic Search

Research results on acoustic treatment technology of honeycomb material to improve noise transmission loss characteristics of light-weight panels are presented in this paper. A prediction model has been presented to describe the transmission loss of the honeycomb panels based on the knowledge of their structural modal parameters. A series of test specimens with aluminum sheets, and fiber reinforced concrete sheets

Huang Wen-chao; Ng Chung-fai

1998-01-01

42

Brazed boron-silicon carbide/aluminum structural panels  

NASA Technical Reports Server (NTRS)

Fluxless brazing process minimizes degradation of mechanical properties composite material of silicon carbide coated boron fibers in an aluminum matrix. Process is being used to fabricate full-scale Boron-Silicon Carbide/Aluminum-Titanium honeycomb core panels for flight testing and ground testing.

Arnold, W. E., Jr.; Bales, T. T.; Brooks, T. G.; Lawson, A. G.; Mitchell, P. D.; Royster, D. M.; Wiant, R.

1978-01-01

43

The structural behavior of a graphite-polymide honeycomb sandwich panel with quasi-isotropic face sheets and an orthotropic core  

NASA Technical Reports Server (NTRS)

The results of a series of tests of graphite-polyimide honeycomb sandwich panels are presented. The panels were 1.22 m long, 0.508 m wide, and approximately 13.3 m thick. The face sheets were a T-300/PMR-15 fabric in a quasi-isotropic layup and were 0.279 mm thick. The core was Hexcel HRH 327-3/16 - 4.0 glass reinforced polyimide honeycomb, 12.7 mm thick. Three panels were used in the test: one was cut into smaller pieces for testing as beam, compression, and shear specimens; a second panel was used for plate bending tests; the third panel was used for in-plane stability tests. Presented are the experimental results of four point bending tests, short block compression tests, core transverse shear modulus, three point bending tests, vibration tests, plate bending tests, and panel stability tests. The results of the first three tests are used to predict the results of some of the other tests. The predictions and experimental results are compared, and the agreement is quite good.

Hyer, M. W.; Hagaman, J. A.

1979-01-01

44

Exothermic Reactions Leading to Unexpected Meltdown of Scrap Uranium--Aluminum Cermet Cores During Outgassing.  

National Technical Information Service (NTIS)

During routine outgassing of scrap uranium-aluminum cermet cores, unexpected exothermic reactions released sufficient energy to melt nine cores. In the subsequent investigation, compounds in the scrap uranium were identified, the history of the material w...

L. W. Gray W. J. Kerrigan

1978-01-01

45

Piezoelectrically-induced guided wave propagation for health monitoring of honeycomb sandwich structures  

NASA Astrophysics Data System (ADS)

Honeycomb sandwich structures have been widely used in marine and aerospace applications due to their high strength/stiffness-to-weight ratio. However, an excessive load or repeated loading in the core tends to induce debonding along the skin-core interface, threatening the integrity and safety of the whole structure. This dissertation focuses on development of guided wave strategies for health monitoring of honeycomb sandwich structures, based on a piezoelectric actuator/sensor network. The honeycomb sandwich panels, which are composed of aluminum alloy (T6061) skins and hexagonal-celled Nomex core, are specifically considered in the study. First, elastic wave propagation mechanism in honeycomb sandwich structures is numerically and experimentally investigated, based on a piezoelectric actuator/sensor system. Influences of cell geometry parameters upon wave propagation are also discussed. Some wave propagation characteristics, such as wave group velocity dispersion relation and mode tuning capabilities, in the honeycomb composite panels are experimentally characterized. Secondly, effects of skin-core debonding upon the leaky guided wave propagation in honeycomb sandwich structures are studied by the finite element simulation. An appropriate signal difference coefficient is defined to represent the differential features caused by debonding. By means of probability analysis of differential features of transmitted guided waves and the image fusion, the final image of the structure is constructed with improved detection precision. A multilevel sensor network strategy is proposed to detect multiple debondings in the honeycomb sandwich structure. Thirdly, an analytical model considering coupled piezo-elastodynamics is developed to quantitatively describe dynamic load transfer between a surface-bonded piezoelectric wafer actuator and a prestressed plate. The finite element method is used to evaluate the accuracy of the analytical prediction. Effects of prestresses on the characteristics of guided wave generation and propagation, such as time-of-flight, amplitude and wave tuning properties of guided wave modes, are analyzed, based on the developed model. Finally, to overcome the limitations of conventional guided wave methods, a baseline-free detection technique by using nonlinear acoustics is developed for debonding identification in honeycomb sandwich structures. The finite element analysis is performed to understand effects of the interaction of two debonded interfaces upon dynamic behavior of the sandwich structure. Specific experimental study is also conducted on the honeycomb sandwich panel to validate the concept. This dissertation study aims to broaden the scope of existing guided wave methods for debonding detection in honeycomb sandwich structures, and provide some insights for health monitoring of in-service structures.

Song, Fei

46

Ballistic resistance of honeycomb sandwich panels under in-plane high-velocity impact.  

PubMed

The dynamic responses of honeycomb sandwich panels (HSPs) subjected to in-plane projectile impact were studied by means of explicit nonlinear finite element simulations using LS-DYNA. The HSPs consisted of two identical aluminum alloy face-sheets and an aluminum honeycomb core featuring three types of unit cell configurations (regular, rectangular-shaped, and reentrant hexagons). The ballistic resistances of HSPs with the three core configurations were first analyzed. It was found that the HSP with the reentrant auxetic honeycomb core has the best ballistic resistance, due to the negative Poisson's ratio effect of the core. Parametric studies were then carried out to clarify the influences of both macroscopic (face-sheet and core thicknesses, core relative density) and mesoscopic (unit cell angle and size) parameters on the ballistic responses of the auxetic HSPs. Numerical results show that the perforation resistant capabilities of the auxetic HSPs increase as the values of the macroscopic parameters increase. However, the mesoscopic parameters show nonmonotonic effects on the panels' ballistic capacities. The empirical equations for projectile residual velocities were formulated in terms of impact velocity and the structural parameters. It was also found that the blunter projectiles result in higher ballistic limits of the auxetic HSPs. PMID:24187526

Qi, Chang; Yang, Shu; Wang, Dong; Yang, Li-Jun

2013-01-01

47

Ballistic Resistance of Honeycomb Sandwich Panels under In-Plane High-Velocity Impact  

PubMed Central

The dynamic responses of honeycomb sandwich panels (HSPs) subjected to in-plane projectile impact were studied by means of explicit nonlinear finite element simulations using LS-DYNA. The HSPs consisted of two identical aluminum alloy face-sheets and an aluminum honeycomb core featuring three types of unit cell configurations (regular, rectangular-shaped, and reentrant hexagons). The ballistic resistances of HSPs with the three core configurations were first analyzed. It was found that the HSP with the reentrant auxetic honeycomb core has the best ballistic resistance, due to the negative Poisson's ratio effect of the core. Parametric studies were then carried out to clarify the influences of both macroscopic (face-sheet and core thicknesses, core relative density) and mesoscopic (unit cell angle and size) parameters on the ballistic responses of the auxetic HSPs. Numerical results show that the perforation resistant capabilities of the auxetic HSPs increase as the values of the macroscopic parameters increase. However, the mesoscopic parameters show nonmonotonic effects on the panels' ballistic capacities. The empirical equations for projectile residual velocities were formulated in terms of impact velocity and the structural parameters. It was also found that the blunter projectiles result in higher ballistic limits of the auxetic HSPs.

Yang, Shu; Wang, Dong; Yang, Li-Jun

2013-01-01

48

Perforation of honeycomb sandwich plates by projectiles  

Microsoft Academic Search

An analytical solution for the ballistic limit of a honeycomb plate subjected to normal impact by blunt and spherical projectiles is presented. The solution involves a three-stage, perforation process that results in complete perforation of the sandwich. Stages 1–3 describe perforation of the top facesheet, honeycomb core, and bottom facesheet, respectively. Residual velocities in Stages 1 and 2 are found

M. S. Hoo Fatt; K. S. Park

2000-01-01

49

Nonlinear acoustics and honeycomb materials  

NASA Astrophysics Data System (ADS)

The scope of research activity that Bruce Thompson embraced was very large. In this talk three different research topics that the author shared with Bruce are reviewed. They represent Bruce's introduction to NDE and include nonlinear acoustics, nondestructive measurements of adhesive bond strengths in honeycomb panels, and studies of flexural wave dispersion in honeycomb materials. In the first of these, four harmonics of a 30 Mhz finite amplitude wave were measured for both fused silica and aluminum single crystals with varying lengths and amounts of cold work using a capacity microphone with heterodyne receiver with a flat frequency response from 30 to 250 Mhz. The results for fused silica with no dislocation structure could be described by a model due to Fubini, originally developed for gases, that depends upon only the second and third order elastic constants and not the fourth and higher order constants. The same was not true for the aluminum with dislocation structures. These results raised some questions about models for harmonic generation in materials with dislocations. In the second topic, experiments were made to determine the adhesive bond strengths of honeycomb panels using the vibrational response of the panels (Chladni figures). The results showed that both the damping characteristics of panel vibrations as a whole and velocity of propagation of elastic waves that travel along the surface and sample the bondline can be correlated with destructively determined bond strengths. Finally, the phase velocity of flexural waves traveling along a 1-inch honeycomb sandwich panel was determined from 170 Hz to 50 Khz, ranging from 2.2×104 cm/sec at the low end to 1.18×105 cm/sec at 40 Khz. The dispersion arises from the finite thickness of the panel and agreed with the results of continuum models for the honeycomb. Above 40 Khz, this was not the case. The paper concludes with a tribute to Bruce for his many wonderful contributions and lessons beyond his technical legacy for all of us.

Thompson, D. O.

2012-05-01

50

Vibroacoustics and damping analysis of negative Poisson's ratio honeycombs  

Microsoft Academic Search

In this paper a novel class of core material for sandwich structures is analyzed from an analytical and numerical point of view. Honeycombs with re-entrant cell geometry present negative in-plane Poisson's ratio coefficients, with an increase of bending stiffness compared to the one of hexagonal honeycomb cores. Due to the orthotropic mechanical properties of this kind of core material it

Fabrizio Scarpa; Geoffrey R. Tomlinson

1998-01-01

51

Ambient temperature fatigue tests of elements of an actively cooled honeycomb sandwich structural panel  

NASA Technical Reports Server (NTRS)

Elements of an actively cooled structural panel for a hypersonic aircraft have been investigated for fatigue characteristics. The study involved a bonded honeycomb sandwich panel with d-shaped coolant tubes. The curved portion of these tubes was embedded in the honeycomb, and the flat portion was bonded or soldered to the inner surface of the outer skin. The elements examined were two plain skin specimens (aluminum alloy); two specimens with skins attached to manifolds and tubes (one specimen was bonded, the other soldered); and a specimen representative of a corner section of the complete cooled sandwich. Sinusoidal loads were applied to all specimens. The honeycomb sandwich specimen was loaded in both tension and compression; the other specimens were loaded in tension only. The cooling tubes were pressurized with oil throughout the fatigue tests. The most significant results of these tests follow: All specimens exceeded their design life of 20,000 cycles without damage. Crack growth rates obtained in the plain skin specimens were used to determine the crack growth characteristics of aluminum alloy. Cracks in skins either bonded or soldered to cooling tubes propagated past the tubes without penetration. The coolant tubes served as crack arresters and temporarily stopped crack growth when a crack reached a tube-skin interface. The honeycomb core demonstrated that it could contain leakage from a tube.

Sharpe, E. L.; Elber, W.

1977-01-01

52

Honeycomb Reconfigurable Manufacturing System.  

National Technical Information Service (NTIS)

A honeycomb multi-stage manufacturing system and associated methods. The system includes a plurality of hexagonal cells defining a honeycomb structure, at least first and second continuous assembly lines defined along selected cell sides for assembling fi...

Y. Koren

2005-01-01

53

Aluminum foams produced by liquid-state processes  

Microsoft Academic Search

Lightweight cellular materials can be used in the construction of composite plates, shells and tubes with high structural efficiency. Metallic sandwich construction with integrally bonded face-sheet\\/foam core configurations offer a cost-efficient alternative to conventional skin-stringer and honeycomb core components. The potential effectiveness of such constructions is dependent on the properties and performance of the core materials. In this study, aluminum

A. E. Simone; L. J. Gibson

1998-01-01

54

SPERT Destructive Test - I on Aluminum, Highly Enriched Plate Type Core  

SciTech Connect

SPERT - Special Power Excursion Reactor Tests Destructive Test number 1 On Aluminum, Highly Enriched Plate Type Core. A test studying the behavior of the reactor under destructive conditions on a light water moderated pool-type reactor with a plate-type core.

None

2011-04-05

55

SPERT Destructive Test - I on Aluminum, Highly Enriched Plate Type Core  

ScienceCinema

SPERT - Special Power Excursion Reactor Tests Destructive Test number 1 On Aluminum, Highly Enriched Plate Type Core. A test studying the behavior of the reactor under destructive conditions on a light water moderated pool-type reactor with a plate-type core.

56

SPERT Destructive Test - I on Aluminum, Highly Enriched Plate Type Core  

ScienceCinema

SPERT - Special Power Excursion Reactor Tests Destructive Test number 1 On Aluminum, Highly Enriched Plate Type Core. A test studying the behavior of the reactor under destructive conditions on a light water moderated pool-type reactor with a plate-type core.

None

2014-05-07

57

Hypervelocity Impact Evaluation of Metal Foam Core Sandwich Structures  

NASA Technical Reports Server (NTRS)

A series of hypervelocity impact (HVI) tests were conducted by the NASA Johnson Space Center (JSC) Hypervelocity Impact Technology Facility (HITF) [1], building 267 (Houston, Texas) between January 2003 and December 2005 to test the HVI performance of metal foams, as compared to the metal honeycomb panels currently in service. The HITF testing was conducted at the NASA JSC White Sands Testing Facility (WSTF) at Las Cruces, New Mexico. Eric L. Christiansen, Ph.D., and NASA Lead for Micro-Meteoroid Orbital Debris (MMOD) Protection requested these hypervelocity impact tests as part of shielding research conducted for the JSC Center Director Discretionary Fund (CDDF) project. The structure tested is a metal foam sandwich structure; a metal foam core between two metal facesheets. Aluminum and Titanium metals were tested for foam sandwich and honeycomb sandwich structures. Aluminum honeycomb core material is currently used in Orbiter Vehicle (OV) radiator panels and in other places in space structures. It has many desirable characteristics and performs well by many measures, especially when normalized by density. Aluminum honeycomb does not perform well in Hypervelocity Impact (HVI) Testing. This is a concern, as honeycomb panels are often exposed to space environments, and take on the role of Micrometeoroid / Orbital Debris (MMOD) shielding. Therefore, information on possible replacement core materials which perform adequately in all necessary functions of the material would be useful. In this report, HVI data is gathered for these two core materials in certain configurations and compared to gain understanding of the metal foam HVI performance.

Yasensky, John; Christiansen, Eric L.

2007-01-01

58

Characterization and elimination of defects in metallic glass honeycomb  

NASA Astrophysics Data System (ADS)

This work focuses on quantification and elimination of defects in the new class of amorphous metallic glass honeycombs (MGH) developed in 2009. A new lab scale method of manufacturing was devised to produce defect free MGH, and it has reduced cell wall misorientation from 15° to 1.5° and also yielded a more uniform cell geometry. A threefold improvement in the strength of MGH was observed with the use of this new manufacturing method. MG Honeycombs have exhibited 20% higher crush strength and 20% higher peak strength than Al honeycombs of higher relative density. The effect of cell axis misorientation on honeycomb strength related to the effect of inclined loads on honeycomb strength was studied using skewed aluminum honeycomb sections with different cell axis inclinations. A sigmoidal decrease in the strength of honeycombs with increasing loading angles was found. This research gives insight into the potential of Metallic Glass Honeycombs as structural materials. It also suggests the advantages expected for more precise automated mass production of the new material. Further, it helps in understanding the effect of inclined loads on honeycomb performance.

Mahadevan, Ganapathi Ranjan

59

Advanced radiator concepts utilizing honeycomb panel heat pipes (stainless steel)  

NASA Technical Reports Server (NTRS)

The feasibility of fabricating and processing moderate temperature range heat pipes in a low mass honeycomb sandwich panel configuration for highly efficient radiator fins for the NASA space station was investigated. A variety of honeycomb panel facesheet and core-ribbon wick concepts were evaluated within constraints dictated by existing manufacturing technology and equipment. Concepts evaluated include: type of material, material and panel thicknesses, wick type and manufacturability, liquid and vapor communication among honeycomb cells, and liquid flow return from condenser to evaporator facesheet areas. In addition, the overall performance of the honeycomb panel heat pipe was evaluated analytically.

Fleischman, G. L.; Tanzer, H. J.

1985-01-01

60

Examination of the Shrinking-Core Model of Sub-Micron Aluminum Combustion.  

National Technical Information Service (NTIS)

There has been significant interest in recent years in the combustion of sub-micron aluminum particles, and the standard theoretical framework is the shrinking-core model. This model, in the context of any fuel, has roots that go back 60 years. A common r...

J. Buckmaster T. L. Jackson

2012-01-01

61

The Electrical Properties of Single-Layer Aluminum Conductors, Steel Reinforced (ACSR), Having Single Steel Core Wires with Heavy Aluminum Coating  

Microsoft Academic Search

This paper discusses electrical tests made on representative sizes of single layer alminum conductors, steel reinforced with galvanized and heavy aluminum coatings. Analysis of 60-cycle a-c (alternating current) test data indicates that the conductors with aluminum-clad core wires than the same sizes of ACSR conductors in which the core wires are of galvanized steel. The differences are in the order

C. H. Jensen; R. E. Demuth; R. W. Mowery

1962-01-01

62

VIBROACOUSTIC MODEL VALIDATION FOR A CURVED HONEYCOMB COMPOSITE PANEL  

Microsoft Academic Search

Finite element and boundary element models are developed to investigate the vibroacoustic response of a curved honeycomb composite sidewall panel. Results from vibroacoustic tests conducted in the NASA Langley Structural Acoustic Loads and Transmission facility are used to validate the numerical predictions. The sidewall panel is constructed from a flexible honeycomb core sandwiched between carbon fiber reinforced composite laminate face

Ralph D. Buehrle; Jay H. Robinsonÿ; Ferdinand W. Grosveld

63

A novel method of testing the shear strength of thick honeycomb composites  

NASA Technical Reports Server (NTRS)

Sandwich composites of aluminum and glass/phenolic honeycomb core were tested for shear strength before and after impact damage. The assessment of shear strength was performed in two ways; by four point bend testing of sandwich beams and by a novel double lap shear (DLS) test. This testing technique was developed so smaller specimens could be used, thus making the use of common lab scale fabrication and testing possible. The two techniques yielded similar data. The DLS test gave slightly lower shear strength values of the two methods but were closer to the supplier's values for shear strength.

Hodge, A. J.; Nettles, A. T.

1991-01-01

64

A comparison of mechanical properties of some foams and honeycombs  

NASA Technical Reports Server (NTRS)

A comparative study is conducted of the mechanical properties of foam-core and honeycomb-core sandwich panels, using a normalizing procedure based on common properties of cellular solids and related properties of dense solids. Seven different honeycombs and closed-foam cells are discussed; of these, three are commercial Al alloy honeycombs, one is an Al-alloy foam, and two are polymeric foams. It is concluded that ideal, closed-cell foams may furnish compressive strengths which while isotropic can be fully comparable to the compressive strengths of honeycombs in the thickness direction. The shear strength of ideal closed-cell foams may be superior to the shear strength of honeycombs.

Bhat, Balakrishna T.; Wang, T. G.

1990-01-01

65

Millimeter Wave Holographical Inspection of Honeycomb Composites (Preprint).  

National Technical Information Service (NTIS)

Multi-layered composite structures manufactured with honeycomb, foam, or balsa wood cores are finding increasing utility in a variety of aerospace, transportation, and infrastructure applications. Due to the low conductivity and inhomogeneity associated w...

F. L. Hepburn G. Steffes J. T. Case R. Zoughi S. Kharkovsky

2007-01-01

66

The structural analysis of a light-weight aluminum foam core mirror  

NASA Astrophysics Data System (ADS)

A high sensitivity of optical performance to foam core mechanical properties is indicated by the results obtained by the present NASTRAN code FEM analysis of a novel, aluminum foamcore sandwich structure reflecting telescope mirror. The material properties of the foam are such that the conventional isotropic relationship between shear modulus, Young's modulus, and Poisson's ratio does not apply. Material testing of the foam is required to establish the coefficients of the constitutive matrix.

Pollard, W.; Vukobratovich, D.; Richard, R.

1987-01-01

67

The Definition of Quality of Honeycomb Structures  

NASA Astrophysics Data System (ADS)

In the represented report the comprehensive approach to quality inspection of honeycomb structures is considered and substantiated to provide their high structural characteristics. The structures are intended for manufacturing micro satellite solar arrays. The investigated structures involve two skins of composite materials by a thickness from 0,1 to 0,3 mm and a filler by hexagonal honeycomb cells of aluminum alloy. It may be glued in a variety of ways: with a film glue or a glue deposited on end faces of cells. Variants and possibilities of nondestructive methods for quality inspection - holographic interferometer and infrared testing ones - are considered for various materials of skins and used glues. The various methods of loading the constructions is appreciated in order to get the required sensitivity of nondestructive besting methods. To provide the required structural properties in addition to the nondestructive testing the application of mechanical tests of honeycomb structure samples is substantiated. The kinds of mechanical tests are described and the results are given. The indicated approach provides the asked level of characteristics for honeycomb structures.

Sitalo, V. G.; Tykhyy, V. G.; Primakov, V. D.

2002-01-01

68

Numerical simulation of temperature field in horizontal core-filling continuous casting for copper cladding aluminum rods  

NASA Astrophysics Data System (ADS)

The steady-state temperature field of horizontal core-filling continuous casting (HCFC) for producing copper cladding aluminum rods was simulated by finite element method to investigate the effects of key processing parameters on the positions of solid-liquid interfaces (SLIs) of copper and aluminum. It is found that mandrel tube length and mean withdrawing speed have significant effects on the SLI positions of both copper and aluminum. Aluminum casting temperature ( T Al) (1003-1123 K) and secondary cooling water flux (600-900 L·h-1) have little effect on the SLI of copper but cause the SLI of aluminum to move 2-4 mm. When T Al is in a range of 1043-1123 K, the liquid aluminum can fill continuously into the pre-solidified copper tube. Based on the numerical simulation, reasonable processing parameters were determined.

Su, Ya-jun; Liu, Xin-hua; Wu, Yong-fu; Huang, Hai-you; Xie, Jian-xin

2013-07-01

69

Honeycombs in honeycombs: complex liquid crystal alumina composite mesostructures.  

PubMed

Small-angle X-ray scattering (SAXS) and atomic force microscopy (AFM) were used to study orientation patterns of two polyphilic liquid crystals (LC) confined to cylindrical pores of anodic aluminum oxide (AAO). The hierarchical hybrid systems had the LC honeycomb (lattice parameter 3.5-4 nm) inside the pores of the AAO honeycomb (diameters 60 and 400 nm). By conducting complete reciprocal space mapping using SAXS, we conclude that the columns of both compounds align in planes normal to the AAO pore axis, with a specific crystallographic direction of the LC lattice aligning strictly parallel to the pore axis. AFM of LC-containing AAO fracture surfaces further revealed that the columns of the planar anchoring LC (compound 1) formed concentric circles in the plane normal to the pore axis near the AAO wall. Toward the pore center, the circles become anisometric "racetrack" loops consisting of two straight segments and two semicircles. This mode compensates for slight ellipticity of the pore cross section. Indications are, however, that for perfectly circular pores, circular shape is maintained right to the center of the pore, the radius coming down to the size of a molecule. For the homeotropically anchoring compound 2, the columns are to the most part straight and parallel to each other, arranged in layers normal to the AAO pore axis, like logs in an ordered pile. Only near the pore wall the columns splay somewhat. In both cases, columns are confined to layers strictly perpendicular to the AAO pore axis, and there is no sign of escape to the third dimension or of axial orientation, the latter having been reported previously for some discotic LCs. The main cause of the two new LC configurations, the "racetrack" and the "logpile", and of their difference from those of confined nematic LC, is the very high splay energy and low bend energy of columnar phases. PMID:24758721

Zhang, Ruibin; Zeng, Xianbing; Prehm, Marko; Liu, Feng; Grimm, Silko; Geuss, Markus; Steinhart, Martin; Tschierske, Carsten; Ungar, Goran

2014-05-27

70

Extruded ceramic honeycomb and method  

Microsoft Academic Search

Extruded low-expansion ceramic honeycombs comprising beta-spodumene solid solution as the principal crystal phase and with less than 7 weight percent of included mullite are produced by compounding an extrusion batch comprising a lithium aluminosilicate glass powder and a clay additive, extruding a green honeycomb body from the batch, and drying and firing the green extruded cellular honeycomb to crystallize the

Day

1995-01-01

71

High-capacity honeycomb panel heat pipes for space radiators  

Microsoft Academic Search

The integral heat-pipe honeycomb panel structure is evaluated for application to future space platforms as lightweight, reliable, and highly efficient radiators. Performance predictions and structural development of a representative 120 by 24 by 0.25-in. depth segment of a full-sized modular radiator fin is presented. The panel design utilizes an all-welded stainless steel wickable honeycomb core and facesheet construction, and methanol

H. J. Tanzer

1983-01-01

72

Thermal Inspection of Composite Honeycomb Structures  

NASA Technical Reports Server (NTRS)

Composite honeycomb structures continue to be widely used in aerospace applications due to their low weight and high strength advantages. Developing nondestructive evaluation (NDE) inspection methods are essential for their safe performance. Pulsed thermography is a commonly used technique for composite honeycomb structure inspections due to its large area and rapid inspection capability. Pulsed thermography is shown to be sensitive for detection of face sheet impact damage and face sheet to core disbond. Data processing techniques, using principal component analysis to improve the defect contrast, are presented. In addition, limitations to the thermal detection of the core are investigated. Other NDE techniques, such as computed tomography X-ray and ultrasound, are used for comparison to the thermography results.

Zalameda, Joseph N.; Parker, F. Raymond

2014-01-01

73

Minimum Energy Motion and Core Structure of Pure Edge and Screw Dislocations in Aluminum  

NASA Astrophysics Data System (ADS)

The minimum energy motions of pure edge and screw dislocations in aluminum were investigated by atomistic transition state analysis. While the Peierls-Nabarro model and its modifications duplicate the essential nature of a dislocation within a crystalline lattice, the atomic-level relaxation of the dislocation core should be considered to estimate the minimum energy barrier. The relaxed atomic structure within and around the dislocation core is derived from the material’s inherent intrinsic properties and is therefore difficult to solve solely by simple analytical models. In this study, the minimum energy barriers and core structures for the quasi-static motions of pure edge and screw dislocations were investigated by the parallelized nudged elastic band method with the embedded atom method potential. We found that the local potential energy is distributed asymmetrically around the dislocation line for the most stable state and that it is bilaterally symmetrical at the transition state of the dislocation motion. The short-ranged structural relaxation of the core rearrangement as well as the wide-ranging elastic stress field is of great importance in realistic dislocation motion.

Tsuru, Tomohito; Kaji, Yoshiyuki; Shibutani, Yoji

74

Pretransitional Clusters in Multicolor Liquid Crystalline Honeycombs  

NASA Astrophysics Data System (ADS)

X-shaped tetraphilic molecules consisting of a rod-like core with two hydrogen-bonding terminal groups and two mutually incompatible side-chains A and B form a range of honeycomb-like structures in which the rods act as bricks in the walls of polygonal cylinder cells containing the fluid side-chains. Some of these systems exhibit a 2nd-order transition from the high-temperature mixed (``1-color'') phase to a low-temperature phase in which the side-chains are separated in A and B cells (``2-color''). This is the situation with triangular, rectangular and square honeycombs. Strong pre-transitional 2-color domains formation is observed above the transition temperature. Particularly interesting is the case of the hexagonal honeycomb, where no fully phase-separated ground state can exist. Here the 2-color ``ordered'' phase consists of [A] cells and [A(1/4)B(3/4)] cells. The situation is similar to frustrated ferro- and antiferromagnets on a kagome lattice. Instead of the spins flipping, it is the molecules that undergo 180 degree rotations about the axis of their rod-like cores [Science 331, 1302 (2011)].

Ungar, Goran; Zeng, Xiangbing; Liu, Feng; Kieffer, Robert; Nürnberger, Constance; Tschierske, Carsten; Gehring, Gillian

2012-02-01

75

Investigation into the Improvement of the Filleting Properties of Shell Resin DX 231/137 on Aluminium Alloy Honeycomb Materials.  

National Technical Information Service (NTIS)

The optimization of resin system DX 231/137 aluminum alloy honeycomb adhesion was investigated using Aerosil, a resin thickening additive which could modify the resin system just enough to prevent it from running down the surfaces of the honeycomb materia...

L. M. Godfried

1974-01-01

76

Testing of a Shell-Less, Folded-Aluminum-Tube Heat Exchanger Core Unit as an Evaporator and a Condenser.  

National Technical Information Service (NTIS)

A full-scale portion (core unit of 1-MW/sub t/ size) of a shelless, folded-aluminum-tube heat exchanger, conceived by JHU/APL as an integral part of an Ocean Thermal Energy Conversion (OTEC) power system, was tested first as an evaporator and then as a co...

J. A. Funk J. L. Keirsey P. P. Pandolfini

1981-01-01

77

Experimental study of acoustical characteristics of honeycomb sandwich structures  

NASA Astrophysics Data System (ADS)

Loss factor measurements were performed on sandwich panels to determine the effects of different skin and core materials on the acoustical properties. Results revealed inserting a viscoelastic material in the core's mid-plane resulted in the highest loss factor. Panels constructed with carbon-fiber skins exhibited larger loss factors than glass-fiber skins. Panels designed to achieve subsonic wave speed did not show a significant increase in loss factor above the coincidence frequency. The para-aramid core had a larger loss factor value than the meta-aramid core. Acoustic absorption coefficients were measured for honeycomb sandwiches designed to incorporate multiple sound-absorbing devices, including Helmholtz resonators and porous absorbers. The structures consisted of conventional honeycomb cores filled with closed-cell polyurethane foams of various densities and covered with perforated composite facesheets. Honeycomb cores filled with higher density foam resulted in higher absorption coefficients over the frequency range of 50 -- 1250 Hz. However, this trend was not observed at frequencies greater than 1250 Hz, where the honeycomb filled with the highest density foam yielded the lowest absorption coefficient among samples with foam-filled cores. The energy-recycling semi-active vibration suppression method (ERSA) was employed to determine the relationship between vibration suppression and acoustic damping for a honeycomb sandwich panel. Results indicated the ERSA method simultaneously reduced the sound transmitted through the panel and the panel vibration. The largest reduction in sound transmitted through the panel was 14.3% when the vibrations of the panel were reduced by 7.3%. The influence of different design parameters, such as core density, core material, and cell size on wave speeds of honeycomb sandwich structures was experimentally analyzed. Bending and shear wave speeds were measured and related to the transmission loss performance for various material configurations. The shear modulus of the core showed maximum influence on the wave speeds of the samples, while cell size did not have a significant influence on wave speeds or on transmission loss. Skin material affected wave speeds only in the pure bending regime. Honeycomb sandwich structures with a subsonic core and thus reduced wave speed showed increased transmission loss compared to samples without a subsonic core.

Peters, Portia Renee

78

Bismaleimide resins for flame resistant honeycomb sandwich panels  

NASA Technical Reports Server (NTRS)

Bismaleimide resins are prime candidates for nonflammable aircraft interior panels. Three resin types with different structures and processing characteristics were formulated. Resin M 751 was used to fabricate 100 kg of glass fabric prepregs which were used for the preparation of face sheets for honeycomb sandwich panels. Prepreg characteristics and curing cycles for laminate fabrication are provided. In order to advance beyond the current solvent resin technology for fibre and fabric impregnation, a hot melt solvent-less resin system was prepared and characterized. Preliminary tests were performed to develop a wet bonding process for the fabrication of advanced sandwich honeycomb panels by use of polybismaleimide glass fabric face sheets and polybismaleimide Nomex honeycomb core. B-stage material was used for both the core and the face sheet, providing flatwise tensile properties equivalent to those obtained by the state-of-the-art 3-step process which includes an epoxy adhesive resin.

Stenzenberger, H. D.

1978-01-01

79

Indentation tests of aluminium honeycombs  

NASA Astrophysics Data System (ADS)

Aluminium honeycomb is a type of cellular material which has high strength to weigh ratio and is a good energy absorber. They are used as structural components in various engineering applications. Comprehensive study has been conducted on the compressive behavior of aluminium honeycombs. However, the research of aluminium honeycombs subjected to other type of loading, such as indentation, is still limited. In this paper, quasi-static and dynamic indentation tests were conducted to study the deformation and energy absorption of three types of HEXCELL® aluminium honeycombs with different cell sizes and cell wall thicknesses. Quasi-static tests were conducted by using a universal MTS machine at velocities of 0.05 mm/s, 0.5 mm/s and 5 mm/s, respectively. Dynamic tests were conducted by using a high speed INSTRON machine at a velocity of 5 m/s. Force-displacement curves were plotted in which the total energy absorbed was calculated. The deformation of aluminium honeycombs in indentation tests includes the compression of honeycomb cells under the indenter and tearing of honeycomb cell walls along the indenter edges. The energy dissipated in compression and tearing were calculated and discussed. The effects of cell size, cell wall thickness and loading velocity or strain rate on the plateau stress and energy absorption were analyzed.

Ashab, A.; Wong, Y. C.; Lu, G.; Ruan, D.

2013-07-01

80

Vibroacoustics and damping analysis of negative Poisson's ratio honeycombs  

NASA Astrophysics Data System (ADS)

In this paper a novel class of core material for sandwich structures is analyzed from an analytical and numerical point of view. Honeycombs with re-entrant cell geometry present negative in-plane Poisson's ratio coefficients, with an increase of bending stiffness compared to the one of hexagonal honeycomb cores. Due to the orthotropic mechanical properties of this kind of core material it is possible to employ the formulations of laminated orthotropic plates in order to describe the vibroacoustic behavior of simply supported sandwich plates. The natural frequencies of these laminates are sensitive to the geometrical parameters of the core cells. As an example application, an infinite cylindrical sandwich shell in contact with exterior and interior fluid flow is examined. An improvement of transmission loss factors is observed, suggesting a possible use of these cores in acoustic insulation. Damping properties are modeled taking into account the complex modulus of the core material. Two models are examined, one with full viscoelastic core and the other with a free-layer symmetrical beam geometry in order to describe the walls of the core cells. Both cases show a significant increase of the storage moduli of the cores compared to the ones of a regular honeycomb.

Scarpa, Fabrizio; Tomlinson, Geoffrey R.

1998-06-01

81

Load attachment for honeycomb panels in racing cars  

Microsoft Academic Search

Lightweight, honeycomb core, sandwich panels form the major part of the body structure of Formula One racing cars. Key properties include high specific stiffness and specific strength, ease of fabrication, and the ability to tailor impact resistance. The engine and gearbox, which in current designs are placed at the rear of the car, are load-bearing components and must be attached

B. P. O'Rourke; F MATTHEWS

1995-01-01

82

Honeycomb Weathering of Limestone Formations  

USGS Multimedia Gallery

Honeycomb weathering of sandstone located on the shores of Puget Sound occurs when expanding salt crystals break fragments of rock, creating a small hole that becomes larger as the process repeats itself over time....

2010-08-16

83

Testing of a shell-less, folded-aluminum-tube heat exchanger core unit as an evaporator and a condenser  

Microsoft Academic Search

A full-scale portion (core unit of 1-MW\\/sub t\\/ size) of a shelless, folded-aluminum-tube heat exchanger, conceived by JHU\\/APL as an integral part of an Ocean Thermal Energy Conversion (OTEC) power system, was tested first as an evaporator and then as a condenser. The overall heat transfer coefficients (U's) were 480 and 435 Btu\\/hr-ft²⁻sup 0\\/F for the evaporator and condenser, respectively,

P. P. Pandolfini; J. L. Keirsey; J. A. Funk

1981-01-01

84

Method of fabricating a honeycomb structure  

DOEpatents

A method of fabricating a monolithic honeycomb structure product involves shaping a first mixture of raw materials and a binder into a green honeycomb, extruding a second mixture of raw materials and a binder into one or more green members that each define an opening extending longitudinally therethrough. The raw materials of the second mixture are compatible with the raw materials of the first mixture. The green honeycomb and member(s) are dried. The binders of the green honeycomb and member(s) are softened at the surfaces that are to be bonded. The green member(s) is inserted into the honeycomb and bonded to the honeycomb to form an assembly thereof, which is then dried and fired to form a unified monolithic honeycomb structure. The insertion is best carried out by mounting a member in the shape of a tube on a mandrel, and inserting the mandrel into the honeycomb opening to bond the tube to the honeycomb.

Holleran, Louis M. (Big Flats, NY); Lipp, G. Daniel (Fort Collins, CO)

1999-01-01

85

Method of fabricating a honeycomb structure  

DOEpatents

A method of fabricating a monolithic honeycomb structure product involves shaping a first mixture of raw materials and a binder into a green honeycomb, extruding a second mixture of raw materials and a binder into one or more green members that each define an opening extending longitudinally therethrough. The raw materials of the second mixture are compatible with the raw materials of the first mixture. The green honeycomb and member(s) are dried. The binders of the green honeycomb and member(s) are softened at the surfaces that are to be bonded. The green member(s) is inserted into the honeycomb and bonded to the honeycomb to form an assembly thereof, which is then dried and fired to form a unified monolithic honeycomb structure. The insertion is best carried out by mounting a member in the shape of a tube on a mandrel, and inserting the mandrel into the honeycomb opening to bond the tube to the honeycomb. 7 figs.

Holleran, L.M.; Lipp, G.D.

1999-08-03

86

Static and low-velocity impact behavior of sandwich beams with closed-cell aluminum-foam core in three-point bending  

Microsoft Academic Search

In this paper, the response and failure of sandwich beams with aluminum-foam core are investigated. Quasi-static and low-velocity impact bending tests are carried out for sandwich beams with aluminum-foam core. The deformation and failure behavior is explored. It is found that the failure mode and the load history predicted by a modified Gibson's model agree well with the quasi-static experimental

Jilin Yu; Erheng Wang; Jianrong Li; Zhijun Zheng

2008-01-01

87

Honeycomb mirrors of borosilicate glass  

NASA Technical Reports Server (NTRS)

The fabrication of different types of honeycomb mirrors with various kinds of borosilicate glass is discussed. Borosilicate glass is much less expensive to make than zero expansion glass, and can be used for ground-based applications. A mirror 60 cm in diameter made with a slotted strut or egg-crate honeycomb of 6 mm polished Pyrex plate is shown. The faceplates are 12 mm thick, laminated from the same 6 mm sheet. The result of an interferometric test is shown, with residual errors of about wavelength/8 RMS. An alternative fabrication technique for very large mirrors which require high quality bonds between separate sheets of thick Pyrex is described. The result of a recent test casting of a 60 cm honeycomb structure made in a mold with towers 14 cm square and 6 mm gaps between is shown, and methods to cast an entire mirror in one operation are discussed.

Angel, J. R. P.; Hill, J. M.

1982-01-01

88

Liquid ingress recognition in honeycomb structure by pulsed thermography  

NASA Astrophysics Data System (ADS)

Pulsed thermography has been proven to be a fast and effective method to detect fluid ingress in aircraft honeycomb structure; however, water and hydraulic oil may have similar appearance in the thermal image sequence. It is meaningful to identify what kind of liquid ingress it is for aircraft maintenance. In this study, honeycomb specimens with glass fiber and aluminum skin are injected different kinds of liquids: water and oil. Pulsed thermography is adopted; a recognition method is proposed to first get the reference curve by linear fitting the beginning of the logarithmic curve, and then an algorithm based on the thermal contrast between liquid and reference is used to recognize what kind of fluid it is by calculating their thermal properties. It is verified with the results of theory and the finite element simulation.

Chen, Dapeng; Zeng, Zhi; Tao, Ning; Zhang, Cunlin; Zhang, Zheng

2013-05-01

89

Quasi-static and impact tests of honeycomb  

NASA Astrophysics Data System (ADS)

In this paper the quasi-static and instrumented compression impact testing of two kinds of aluminum-alloy honeycomb are reported. Those two types of honeycomb called Hard (H) and Soft (S) were tested. The specimens in cubical form of dimensions 60 mm × 60 mm × 120 mm were made with and without the front aluminum alloy plates (thickness 1.0 mm) cemented to the specimen two faces. The tests have been performed along the largest dimension that is 120 mm, which is parallel to the aluminum sheet profiles forming the honeycomb. A wide range of compression velocities from the quasi-static rate (V0 = 10 mm/min) to the highest impact velocity V6 = 120 m/s were applied. The total number of velocities applied, including the quasi-static loading, was six. Several series of tests were performed. The first two were carried out with the flat-ended strikers of specific masses, which were adequate to each impact velocity. In order to obtain an adequate displacement of crushing the condition of constant kinetic energy of a striker was assumed. In addition, conical strikers were applied with the cone angle 120circ. Application of the direct impact arrangement along with properly instrumented 9m long Hopkinson bar of Nylon with diameter 80 mm enabled for a wave dispersion analysis to be applied. The crushing force versus time could be exactly determined at the specimen-bar interface by application of an inverse technique along with the theory of visco-elastic wave propagation.

Gary, G.; Klepaczko, J. R.

2006-08-01

90

Experimental and computational study of hypervelocity impact on spacecraft honeycomb  

NASA Astrophysics Data System (ADS)

Spacecraft honeycomb provides the primary line of defence against meteoroid and debris impact in orbit. This paper presents the results of experimental tests on honeycomb structures with core depths between 10 and 20 mm and facesheet thicknesses of 0.2 to 0.4 mm. The experimental data are used to identify damage morphologies near to target perforation and, for targets beyond the ballistic limit, the damage recorded on the witness plate. The process of impact and damage is evaluated using SPH hydrocode simulations for a target with 10 mm core depth and 0.2 mm thick facesheet over a velocity range of 3 to 13 km/s. Due to the limitations in the material models and resolution available, only broad trends are drawn from the results. The influence of the honeycomb core in channelling the debris cloud is clearly seen. The experimental and simulation data are compared with the Whipple bumper shield design and damage equation predictions. The smaller dp/T (particle diameter: bumper) ratios lead to non-optimum fragmentation of the debris cloud, compared with a Whipple bumper. The small separation between the facesheet means that, for some particle diameters and impact velocities, the projectile disruption is still ongoing when it impacts the rear facesheet.

Taylor, Emma

2001-06-01

91

Deformation and fracture behavior of beams composed of aluminum foam core and ceramic Al2O3 under monolithic bending  

NASA Astrophysics Data System (ADS)

Deformation and fracture mechanisms of sandwich and multilayer beams composed of aluminum foam core and ceramic face sheets under four-point bending condition were investigated in situ by surface displacement analysis (SDA) software. The toughening mechanism of the beams was discussed and a model was given for the computation of the fracture energy of the beams. Beams containing foam core with 5-, 10-, and 20-mm thickness and Al2O3 face sheets of 0.5-and 1-mm thickness were prepared. The results show that collapse of the beams is by two basic modes, indentation (ID) and face plate failure (PF). The SDA results illustrated that indentation is localized compression on the portion of the beam adjacent to the loading rollers, where displacement and strain are at the maximum. In PF, the beam entirely bends. It is also found that before collapse of the beams with pure PF mode, the foam core undergoes uniform compressive deformation, which contributes most to the fracture energy of the beams. As for the beams with ID characteristic, the localized compressive deformation plays a key role rather than the uniform compressive deformation in the fracture energy of the beam. The total fracture energy W of a beam under bending condition is proposed as W= W UC+ W LC+ W CB+ W PF where W UCis the energy of uniform compressive deformation of the foam core, W LCis the energy of localized compression of the foam core and W CBand W PFare the bending fracture energy of the monolithic foam core and ceramic face sheet, respectively. For the beams with pure PF mode, W LCis zero. The estimated values of the fracture energy are in good agreement with the measured fracture energy of the beams.

Sha, J. B.; Yip, T. H.

2005-03-01

92

Structural Physics of Bee Honeycomb  

NASA Astrophysics Data System (ADS)

Honeybee combs have aroused interest in the ability of honeybees to form regular hexagonal geometric constructs since ancient times. Here we use a real space technique based on the pair distribution function (PDF) and radial distribution function (RDF), and a reciprocal space method utilizing the Debye-Waller Factor (DWF) to quantify the order for a range of honeycombs made by Apis mellifera. The PDFs and RDFs are fit with a series of Gaussian curves. We characterize the order in the honeycomb using a real space order parameter, OP3, to describe the order in the combs and a two-dimensional Fourier transform from which a Debye-Waller order parameter, u, is derived. Both OP3 and u take values from [0, 1] where the value one represents perfect order. The analyzed combs have values of OP3 from 0.33 to 0.60 and values of u from 0.83 to 0.98. RDF fits of honeycomb histograms show that naturally made comb can be crystalline in a 2D ordered structural sense, yet is more `liquid-like' than cells made on `foundation' wax. We show that with the assistance of man-made foundation wax, honeybees can manufacture highly ordered arrays of hexagonal cells.

Kaatz, Forrest; Bultheel, Adhemar; Egami, Takeshi

2008-03-01

93

Integrated spatio-spectral method for efficiently suppressing honeycomb pattern artifact in imaging fiber bundle microscopy  

NASA Astrophysics Data System (ADS)

In a fiber bundle, spots of varying intensity occur throughout the fiber structure, and the ensemble of these spots creates the honeycomb pattern image, called a pixelated image. The spatio-spectral method, an integrated suppression method for the honeycomb pattern in the spatial and Fourier (spectral) domains, has demonstrated efficient restoration of microscopic images based on the fiber bundle. The morphological processing in the spatial domain partially interpolated the gaps between the circular patterns of fiber cores, and the selective band-reject filter in the Fourier domain was applied to reduce the honeycomb-shaped artifact. The auto-corrective search for the global peaks in the localized region was employed to apply the notch filter to the exact position of the individual periodic component in the Fourier domain. We found that a closing preprocessing in the spatial domain, combined with a Gaussian notch Fourier domain filter, yields the optimum image quality when eliminating the honeycomb pattern.

Lee, Cheon-Yang; Han, Jae-Ho

2013-10-01

94

Development of Pyrrone structural forms for honeycomb filler  

NASA Technical Reports Server (NTRS)

The development of techniques for the preparation of Pyrrone structural foams for use as honeycomb filler is described. The feasibility of preparing foams from polymers formed by the condensation of 3,3'-diaminobenzidine (DAB), or 3,3',4,4'-tetraaminobenzophenone (TABP), with 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA) was investigated. Initially, most of the effort was devoted to preparing Pyrrone prepolymers with improved and more reproducible foaming properties for making chemically blown foams. When it became apparent that very high curing shrinkages would not allow the use of unfilled Pyrrone prepolymers in a foam-in-place process, emphasis was shifted from chemically blown foams to syntactic foams. Syntactic foam formulations containing hollow carbon microspheres were developed. Syntactic foams made from selected formulations were found to have very low coefficients of thermal expansion. A technique was developed for the emplacement of Pyrrone syntactic foam formulations in honeycomb core structures.

Kimmel, B. G.

1973-01-01

95

Demonstration of Minimally Machined Honeycomb Silicon Carbide Mirrors  

NASA Technical Reports Server (NTRS)

Honeycomb silicon carbide composite mirrors are made from a carbon fiber preform that is molded into a honeycomb shape using a rigid mold. The carbon fiber honeycomb is densified by using polymer infiltration pyrolysis, or through a reaction with liquid silicon. A chemical vapor deposit, or chemical vapor composite (CVC), process is used to deposit a polishable silicon or silicon carbide cladding on the honeycomb structure. Alternatively, the cladding may be replaced by a freestanding, replicated CVC SiC facesheet that is bonded to the honeycomb. The resulting carbon fiber-reinforced silicon carbide honeycomb structure is a ceramic matrix composite material with high stiffness and mechanical strength, high thermal conductivity, and low CTE (coefficient of thermal expansion). This innovation enables rapid, inexpensive manufacturing. The web thickness of the new material is less than 1 millimeter, and core geometries tailored. These parameters are based on precursor carbon-carbon honeycomb material made and patented by Ultracor. It is estimated at the time of this reporting that the HoneySiC(Trademark) will have a net production cost on the order of $38,000 per square meter. This includes an Ultracor raw material cost of about $97,000 per square meter, and a Trex silicon carbide deposition cost of $27,000 per square meter. Even at double this price, HoneySiC would beat NASA's goal of $100,000 per square meter. Cost savings are estimated to be 40 to 100 times that of current mirror technologies. The organic, rich prepreg material has a density of 56 kilograms per cubic meter. A charred carbon-carbon panel (volatile organics burnt off) has a density of 270 kilograms per cubic meter. Therefore, it is estimated that a HoneySiC panel would have a density of no more than 900 kilograms per cubic meter, which is about half that of beryllium and about onethird the density of bulk silicon carbide. It is also estimated that larger mirrors could be produced in a matter of weeks. Each cell is completely uniform, maintaining the shape of the inserted mandrel. Furthermore, the layup creates pressure that insures node bond strength. Each node is a composite laminate using only the inherent resin system to form the bond. This contrasts starkly with the other known method of producing composite honeycomb, in which individual corrugations are formed, cured, and then bonded together in a secondary process. By varying the size of the mandrels within the layup, varying degrees of density can be achieved. Typical sizes are 3/8 and 3/16 in. (approximately 10 and 5 millimeters). Cell sizes up to 1 in. (approximately 25 millimeters) have been manufactured. Similarly, the shape of the core can be altered for a flexible honeycomb structure.

Goodman, William

2012-01-01

96

Aluminum/uranium fuel foaming/recriticality considerations for production reactor core-melt accidents  

SciTech Connect

Severe accident studies for the Savannah River production reactors indicate that if coherent fuel melting and relocation occur in the absence of target melting, in-vessel recriticality may be achieved. In this paper, fuel-melt/target interaction potential is assessed where fission gas-induced fuel foaming and melt attack on target material are evaluated and compared with available data. Models are developed to characterize foams for irradiated aluminum-based fuel. Predictions indicate transient foaming, the extent of which is governed by fission gas inventory, heating transient conditions, and bubble coalescence behavior. The model also indicates that metallic foams are basically unstable and will collapse, which largely depends on film tenacity and melt viscosity considerations. For high-burnup fuel, extensive foaming lasting tens of seconds is predicted, allowing molten fuel to contact and cause melt ablation of concentric targets. For low-burnup fuel, contact can not be assured. 9 refs., 4 figs., 4 tabs.

Hyder, M.L.; Ellison, P.G. (Westinghouse Savannah River Co., Aiken, SC (USA)); Cronenberg, A.W. (Engineering Science and Analysis, Albuquerque, NM (USA))

1990-01-01

97

Smoothly tunable surface properties of aluminum oxide core-shell nanoparticles by a mixed-ligand approach.  

PubMed

We present a facile solution-based procedure for tailoring the surface properties of aluminum oxide nanoparticles (AlOx-NPs) by the formation of tunable core-shell systems with self-assembled monolayers. By employing chained molecules with a phosphonic acid anchor group and either hydrophobic or hydrophilic chains the surface properties of the nanoparticles change dramatically. So, the solubility can be tuned orthogonal from trifluorotoluene (CF3-C6H5) for hydrophobic shell to water (H2O) for hydrophilic functionalization respectively. Spray coated films of those functionalized nanoparticles exhibited superhydrophobic or superhydrophilic properties. The surface properties can be tuned smoothly by the formation of a mixed ligand monolayer from corresponding stoichiometric mixtures of the ligands. The core-shell nanoparticles were investigated by means of thermogravimetric analysis, TGA; Fourier transform infrared spectroscopy, FTIR; and static contact angle goniometry, SCA. The effect of different dipole moments of the SAM molecules in mixed shell nanoparticles to their stability in dispersions was studied by zeta potential measurements. PMID:24666320

Portilla, Luis; Halik, Marcus

2014-04-23

98

Processing and characterization of honeycomb composite systems  

Microsoft Academic Search

Honeycomb composite structures are widely used in the aerospace and sporting goods industries because of the superior performance and weight saving advantages they offer over traditional metal structures. However, in order to maximize the mechanical and chemical properties of honeycomb composites, the structures must be specially designed to take advantage of their inherent anisotropic, viscoelastic and heterogeneous qualities. In the

Jahan Emir Shafizadeh

1999-01-01

99

Research on Drying Process of Honeycomb Paperboard  

Microsoft Academic Search

The drying of honeycomb paperboard is an important step to guarantee the quality and the shape of honeycomb paperboard. The dryer model was established in FEM software and simplified to calculate the data required based on analysis of drying mechanism. The temperature field, speed field, pressure distribution and the flow direction of fluid were analyzed. Some key factors influenced the

Yuanjun Lv; Lanzhen Chen; Qiong Chen

2010-01-01

100

Positron-Annihilation Momentum Profiles in Aluminum: Core Contribution and the Independent-Particle Model  

Microsoft Academic Search

The momentum profiles from positron annihilation with core electrons in Al have been observed with a recently developed two-detector Doppler-broadening technique. Independent-particle-model (IPM) calculations are in good agreement with the experimental results beyond twice the Fermi momentum and suggest the absence of strong positron-electron correlation effects in this region. Comparisons of calculations with properly normalized momentum profiles indicate that high-momentum

K. G. Lynn; J. R. MacDonald; R. A. Boie; L. C. Feldman; J. D. Gabbe; M. F. Robbins; E. Bonderup; J. Golovchenko

1977-01-01

101

Testing of a shell-less, folded-aluminum-tube heat exchanger core unit as an evaporator and a condenser  

SciTech Connect

A full-scale portion (core unit of 1-MW/sub t/ size) of a shelless, folded-aluminum-tube heat exchanger, conceived by JHU/APL as an integral part of an Ocean Thermal Energy Conversion (OTEC) power system, was tested first as an evaporator and then as a condenser. The overall heat transfer coefficients (U's) were 480 and 435 Btu/hr-ft/sup 2/-/sup 0/F for the evaporator and condenser, respectively, at the conditions yielding the optimal trade-off between the U's and the ammonia pumping power for a full-scale unit. In both modes it operated stably with essentially equal ammonia distribution among the tubes. The water-side pressure drop was as predicted for the optimal water velocity of 2.5 ft/s through the minimum gaps between tubes in the staggered tube array. The evaporator ammonia-side pressure drop was lower than predicted; however, because of the stratified flow that apparently exists, the condenser ammonia pressure drop was higher than predicted. The computer simulation for closed-cycle power system performance was revised to reflect the test results. Full-scale heat exchanger modules designed for 5 MW/sub e/ net power at an ocean water temperture difference of 42/sup 0/F would have 69 vertical rows of seven nested, folded tubes each -1932 tubes total of 3-in.-OD Alclad (7072) 3004 aluminum alloy, each folded into 25 horizontal passes. These heat exchangers, cleanable by vertical translation of ultrasonic cleaning devices between tube rows, offer a viable, low-cost option for OTEC use. Prior work on this concept is summarized, and recommendations for at-sea tests are presented.

Pandolfini, P.P.; Keirsey, J.L.; Funk, J.A.

1981-12-01

102

Fabrication and development of several heat pipe honeycomb sandwich panel concepts. [airframe integrated scramjet engine  

NASA Technical Reports Server (NTRS)

The feasibility of fabricating and processing liquid metal heat pipes in a low mass honeycomb sandwich panel configuration for application on the NASA Langley airframe-integrated Scramjet engine was investigated. A variety of honeycomb panel facesheet and core-ribbon wick concepts was evaluated within constraints dictated by existing manufacturing technology and equipment. The chosen design consists of an all-stainless steel structure, sintered screen facesheets, and two types of core-ribbon; a diffusion bonded wire mesh and a foil-screen composite. Cleaning, fluid charging, processing, and process port sealing techniques were established. The liquid metals potassium, sodium and cesium were used as working fluids. Eleven honeycomb panels 15.24 cm X 15.24 cm X 2.94 cm were delivered to NASA Langley for extensive performance testing and evaluation; nine panels were processed as heat pipes, and two panels were left unprocessed.

Tanzer, H. J.

1982-01-01

103

The Soudan 2 honeycomb calorimeter  

SciTech Connect

Soudan 2 is an 1100-ton honeycomb tracking calorimeter which is being constructed to search for nucleon decay. The detector consists of finely segmented iron instrumented with long drift tubes, and records three spatial coordinates and dE/dx for every gas crossing. Excellent event reconstruction capability, particle identification and muon sign and direction determination give superior rejection of the neutrino background to nucleon decay in many modes. The first 620 tons of Soudan 2 are now in steady operation, with completion planned for 1992. Detector performance has been studied using cosmic ray tracks and a charged test beam calibration. Results on detector performance and detector response are described in this paper. 2 refs. , 11 figs.

Garcia-Garcia, C.

1990-12-01

104

Comparison of experimental and theoretical turbulence reduction characteristics for screens, honeycomb, and honeycomb-screen combinations  

NASA Technical Reports Server (NTRS)

Turbulence reduction research using screens, honeycomb, and combinations thereof was conducted in a half-scale model of a portion of the Langley 8-foot transonic pressure tunnel. It was found that screens alone reduce axial turbulence more than lateral turbulence; whereas, honeycomb alone reduces laterial turbulence more than axial turbulence. Because of this difference, the physical mechanism for decreasing turbulence for screens and honeycomb must be completely different. It is concluded that honeycomb with a downstream screen is an excellent combination for reducing turbulences.

Scheiman, J.

1981-01-01

105

High-fidelity modeling for health monitoring in honeycomb sandwich structures  

Microsoft Academic Search

High-Fidelity Model of the sandwich composite structure with real geometry is reported. The model includes two composite facesheets, honeycomb core, piezoelectric actuator\\/sensors, adhesive layers, and the impactor. The novel feature of the model is that it includes modeling of the impact and wave propagationin the structure before and after the impact. Results of modeling of the wave propagation, impact, and

Dmitry G. Luchinsky; Vasyl Hafiychuk; Vadim Smelyanskiy; Richard W. Tyson; James. L. Walker; Jimmy L. Miller

2011-01-01

106

Elastic wave propagation in hexagonal honeycomb sandwich panels: Physical understanding and numerical modeling  

Microsoft Academic Search

This paper gives theoretical and numerical analyses of elastic wave propagation phenomena in sandwich panels with a honeycomb core, especially when the frequency domain of interest is large and involves high frequencies. In the literature, computational models represent rather these panels as an equivalent homogeneous continuum using shell type finite element mesh than use a detailed ``geometrically exact'' finite element

A. Grédé; B. Tie; D. Aubry

2006-01-01

107

Optimal design of honeycomb sandwich shell aircraft structures of composite materials  

Microsoft Academic Search

Methods for optimizing the design of sandwich composite shells with a honeycomb core are presented using a helicopter tail boom structure as an example. In particular, attention is given to the minimum-mass design using criteria of local and general stability, strength, and stiffness in the presence of structural and technological constraints. The characteristics of two shell structures, one fabricated by

Iu. F. Krashakov; S. M. Khokhlenkov

1992-01-01

108

Oxidation of hydrogen isotopes over honeycomb catalysts  

NASA Astrophysics Data System (ADS)

In the process of development of D-T fusion power reactors, recovery of tritium released into the last confinement system would be a key issue related to safety. If an accidental leakage of tritium takes place in a fusion power plant, a large volume of air should be detritiated with an air cleanup system (ACS). In ACS, tritium gas is converted to tritiated water vapor with a catalyst bed, and then which is recovered with an adsorption bed. In this study, the authors examined the applicability of honeycomb-type catalysts to ACS. A screening test of catalysts for oxidation of hydrogen and deuterium was performed using various honeycomb-type and pebble-type catalysts. Experimental results reveal that a honeycomb-type catalyst possesses a high oxidation performance for oxidation of hydrogen isotopes. Furthermore, the isotope effect on the oxidation of hydrogen isotopes over the honeycomb-type catalyst was thoroughly examined and quantified using tritium.

Munakata, Kenzo; Wajima, Takaaki; Hara, Keisuke; Wada, Kohei; Shinozaki, Yohei; Katekari, Kenichi; Mochizuki, Kazuhiro; Tanaka, Masahiro; Uda, Tatsuhiko

2011-10-01

109

Hypervelocity Impact Performance of Open Cell Foam Core Sandwich Panel Structures  

NASA Technical Reports Server (NTRS)

Metallic foams are a relatively new class of materials with low density and novel physical, mechanical, thermal, electrical and acoustic properties. Although incompletely characterized, they offer comparable mechanical performance to traditional spacecraft structural materials (i.e. honeycomb sandwich panels) without detrimental through-thickness channeling cells. There are two competing types of metallic foams: open cell and closed cell. Open cell foams are considered the more promising technology due to their lower weight and higher degree of homogeneity. Leading micrometeoroid and orbital debris shields (MMOD) incorporate thin plates separated by a void space (i.e. Whipple shield). Inclusion of intermediate fabric layers, or multiple bumper plates have led to significant performance enhancements, yet these shields require additional non-ballistic mass for installation (fasteners, supports, etc.) that can consume up to 35% of the total shield weight [1]. Structural panels, such as open cell foam core sandwich panels, that are also capable of providing sufficient MMOD protection, represent a significant potential for increased efficiency in hypervelocity impact shielding from a systems perspective through a reduction in required non-ballistic mass. In this paper, the results of an extensive impact test program on aluminum foam core sandwich panels are reported. The effect of pore density, and core thickness on shielding performance have been evaluated over impact velocities ranging from 2.2 - 9.3 km/s at various angles. A number of additional tests on alternate sandwich panel configurations of comparable-weight have also been performed, including aluminum honeycomb sandwich panels (see Figure 1), Nomex honeycomb core sandwich panels, and 3D aluminum honeycomb sandwich panels. A total of 70 hypervelocity impact tests are reported, from which an empirical ballistic limit equation (BLE) has been derived. The BLE is in the standard form suitable for implementation in risk analysis software, and includes the effect of panel thickness, core density, and facesheet material properties. A comparison between the shielding performance of foam core sandwich panel structures and common MMOD shielding configurations is made for both conservative (additional 35% non-ballistic mass) and optimistic (additional mass equal to 30% of bumper mass) considerations. Suggestions to improve the shielding performance of foam core sandwich panels are made, including the use of outer mesh layers, intermediate fabric/composite layers, and varying pore density.

Ryan, Shannon; Christiansen, Eric; Lear, Dana

2009-01-01

110

Fabrication and mechanical testing of glass fiber entangled sandwich beams: A comparison with honeycomb and foam sandwich beams  

Microsoft Academic Search

The aim of this paper is the fabrication and mechanical testing of entangled sandwich beam specimens and the comparison of their results with standard sandwich specimens with honeycomb and foam as core materials. The entangled sandwich specimens have glass fiber cores and glass woven fabric as skin materials. The tested glass fiber entangled sandwich beams possess low compressive and shear

Amir Shahdin; Laurent Mezeix; Christophe Bouvet; Joseph Morlier; Yves Gourinat

2009-01-01

111

An elastic analysis of a honeycomb structure with negative Poisson’s ratio  

NASA Astrophysics Data System (ADS)

This paper presents a novel honeycomb structure that exhibits a negative Poisson’s ratio (NPR). In contrast to other NPR honeycomb structures studied in the past, the new structure can be easily fabricated using conventional technology and materials on a large scale of production with a low cost. The geometry of the structure is first described, and then an elastic analysis based on standard beam theory is carried out to establish the relation of its Young’s modulus with relevant geometrical parameters and material properties. The effects of the geometrical parameters in non-dimensional forms on the Young’s modulus of the structure are discussed. The compressive tests were performed on samples of the structure made with the same aluminum alloy but with different geometrical parameters to verify the theoretical analysis. The results obtained from both the theoretical calculations and experiments show that the proposed NPR honeycomb structure has a very obvious NPR behavior. Moreover, its elastic modulus is significantly affected by its geometrical parameters, and can be optimized for specific applications through the design and control of honeycomb geometry parameters.

Zhang, Z. K.; Hu, H.; Xu, B. G.

2013-08-01

112

Comparison of the Folding Behaviour in the Empty and Foam-Filled Honeycombs via Drop Hammer Tests  

NASA Astrophysics Data System (ADS)

In this paper, effects of polyurethane foam filler on the folding behaviour of the honeycomb panels as a thin walled structure are studied, experimentally. For this purpose, some specimens of the empty and foam-filled honeycombs were prepared. All panels had 63 hexagonal cells and made of an aluminum alloy. The effects of foam filler on the energy absorption capacity, wavelength of the folds and the number of formed folds were investigated. Folding tests were performed by a drop hammer machine. Polyurethane foam was prepared with the density of 65 kg/m3 to fill the honeycomb cells. The hammer was selected with the weight of 5.48 kg and the initial drop height of 70 cm. The results of the drop hammer tests show that the foam filler causes the increasing in the energy absorption and number of the formed folds and decreasing in the wavelength of the folds.

Niknejad, A.; Liaghat, G. H.; Naeini, H. Moslemi; Behravesh, A. H.

2011-01-01

113

Design and fabrication of a radiative actively cooled honeycomb sandwich structural panel for a hypersonic aircraft  

NASA Technical Reports Server (NTRS)

The panel assembly consisted of an external thermal protection system (metallic heat shields and insulation blankets) and an aluminum honeycomb structure. The structure was cooled to temperature 442K (300 F) by circulating a 60/40 mass solution of ethylene glycol and water through dee shaped coolant tubes nested in the honeycomb and adhesively bonded to the outer skin. Rene'41 heat shields were designed to sustain 5000 cycles of a uniform pressure of + or - 6.89kPa (+ or - 1.0 psi) and aerodynamic heating conditions equivalent to 136 kW sq m (12 Btu sq ft sec) to a 422K (300 F) surface temperature. High temperature flexible insulation blankets were encased in stainless steel foil to protect them from moisture and other potential contaminates. The aluminum actively cooled honeycomb sandwich structural panel was designed to sustain 5000 cycles of cyclic in-plane loading of + or - 210 kN/m (+ or - 1200 lbf/in.) combined with a uniform panel pressure of + or - 6.89 kPa (?1.0 psi).

Ellis, D. A.; Pagel, L. L.; Schaeffer, D. M.

1978-01-01

114

The dynamic shear properties of structural honeycomb materials  

NASA Astrophysics Data System (ADS)

A technique is described for measuring the dynamic modulus and damping of honeycomb materials. Results of tests on both aluminium and Nomex honeycombs are presented and compared with those reported in the literature.

Adams, R. D.; Maheri, M. R.

115

Synthetic magnetic fluxes on the honeycomb lattice  

SciTech Connect

We devise experimental schemes that are able to mimic uniform and staggered magnetic fluxes acting on ultracold two-electron atoms, such as ytterbium atoms, propagating in a honeycomb lattice. The atoms are first trapped into two independent state-selective triangular lattices and then further exposed to a suitable configuration of resonant Raman laser beams. These beams induce hops between the two triangular lattices and make atoms move in a honeycomb lattice. Atoms traveling around each unit cell of this honeycomb lattice pick up a nonzero phase. In the uniform case, the artificial magnetic flux sustained by each cell can reach about two flux quanta, thereby realizing a cold-atom analog of the Harper model with its notorious Hofstadter's butterfly structure. Different condensed-matter phenomena such as the relativistic integer and fractional quantum Hall effects, as observed in graphene samples, could be targeted with this scheme.

Gorecka, Agnieszka [Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543 (Singapore); Gremaud, Benoit [Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543 (Singapore); Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542 (Singapore); Laboratoire Kastler Brossel, Ecole Normale Superieure, CNRS, UPMC, 4 Place Jussieu, FR-75005 Paris (France); Miniatura, Christian [Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543 (Singapore); Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542 (Singapore); Institut Non Lineaire de Nice, UMR 6618, UNS, CNRS, 1361 Route des Lucioles, FR-06560 Valbonne (France); Institute of Advanced Studies, Nanyang Technological university, 60 Nanyang View, Singapore 639673 (Singapore)

2011-08-15

116

Experimental rotordynamic coefficient results for honeycomb seals  

NASA Technical Reports Server (NTRS)

Test results (leakage and rotordynamic coefficients) are presented for seven honeycomb-stator smooth-rotor seals. Tests were carried out with air at rotor speeds up to 16,000 cpm and supply pressures up to 8.2 bars. Test results for the seven seals are compared, and the most stable configuration is identified based on the whirl frequency ratio. Results from tests of a smooth-rotor/smooth-stator seal, a teeth-on-stator labyrinth seal, and the most stable honeycomb seal are compared.

Elrod, David A.; Childs, Dara W.

1988-01-01

117

Constraints on formation processes of two coarse-grained calcium- aluminum-rich inclusions: a study of mantles, islands and cores  

USGS Publications Warehouse

Many coarse-grained calcium- aluminum-rich inclusions (CAIs) contain features that are inconsistent with equilibrium liquid crystallization models of origin. Spinel-free islands (SFIs) in spinel-rich cores of Type B CAIs are examples of such features. One model previously proposed for the origin of Allende 5241, a Type B1 CAI containing SFIs, involves the capture and assimilation of xenoliths by a liquid droplet in the solar nebula (El Goresy et al, 1985; MacPherson et al 1989). This study reports new textural and chemical zoning data from 5241 and identifies previously unrecognized chemical zoning patterns in the melilite mantle and in a SFI. -from Author

Meeker, G. P.

1995-01-01

118

Comparative Impact Tests on Metal Honeycomb Sandwich Structures.  

National Technical Information Service (NTIS)

Impact test results were carried out on metal honeycomb sandwich structures to compare the present structure (i.e. aileron trailing edges of 0.3 mm, 5.322/9 faces and honeycomb 5.453/2, bonded with FM 123-5) to structures with heavier faces and honeycomb....

J. Koetsier

1975-01-01

119

Detecting water in aviation honeycomb structures by using transient infrared thermographic NDT  

NASA Astrophysics Data System (ADS)

A lot of structural key elements of many modern civilian and military airplanes, such as flaps, keel, etc., are made of honeycomb structures. Honeycombs involve a combination of some materials including aluminum, Nomex, glass and graphite epoxy composites. During exploitation, atmosphere water could penetrate these structures due to possible imperfections in various junctions, and, thus, deteriorate airplane durability. In Russia, water in honeycombs is typically detected by using the X ray and ultrasonic technique. However, the X ray equipment is hardly accepted by commercial airlines because of the safety reason, and the point-by-point ultrasonic inspection is low-productive. Since 2002, we develop the IR thermographic method of detecting water by thermally stimulating aviation panels under test. Unlike the technique accepted by Airbus Industry, Inc., that uses 'a warm blanket', we use a powerful optical heater assembled with an IR camera into a single set. The first stage of research included modeling the detection process and optimizing the experimental procedure. As a result, we have demonstrated that, due to the high heat capacity of water, a temperature signal over moist areas evolves in time during a relatively long period that relaxes the requirements to the test protocol. Thus, even aluminum panels can be thermally stimulated during few seconds with a delay time being also in a few second range. A similar protocol can be applied to the inspection of composite honeycombs where the image quality resembles that obtained by X rays. The paper will describe all stages of the research starting from modeling and finishing with the preliminary experimental results obtained in situ on civilian airplanes.

Vavilov, Vladimir P.; Klimov, Alexey G.; Nesteruk, Dmitry; Shiryaev, Vladimir V.

2003-04-01

120

Fiberglass honeycomb elements formed quickly and cheaply  

NASA Technical Reports Server (NTRS)

Cookie cutter device initiates production of identical, double-contoured fiber glass elements used as shock absorbers. Three-bladed edges convert triangular honeycomb elements into hexagonal shapes which are then stamped to desired length by concave and convex dies. Sandpaper smoothing completes the process.

Smith, R. H.

1970-01-01

121

The Honeycomb Problem on the Sphere  

Microsoft Academic Search

The honeycomb problem on the sphere asks for the perimeter-minimizing\\u000apartition of the sphere into N equal areas. This article solves the problem\\u000awhen N=12. The unique minimizer is a tiling of 12 regular pentagons in the\\u000adodecahedral arrangement.

Thomas C. Hales

2002-01-01

122

Smart shape memory alloy chiral honeycomb  

Microsoft Academic Search

An auxetic (or negative Poisson's ratio) material expands in all directions when pulled in only one, behaving in an opposite way compared with “classical” materials. A structure not super-imposable with its mirror image is defined as chiral. A chiral structural honeycomb (noncentresymmetric) features auxeticity, i.e., a negative Poisson's ratio behaviour in the plane. Although chirality is common in nature and

M. R. Hassan; F. Scarpa; M. Ruzzene; N. A. Mohammed

2008-01-01

123

Inducing topological order in a honeycomb lattice  

NASA Astrophysics Data System (ADS)

We explore the possibility of inducing a topological insulator phase in a honeycomb lattice lacking spin-orbit interaction using a metallic (or Fermi gas) environment. The lattice and the metallic environment interact through a density-density interaction without particle tunneling, and integrating out the metallic environment produces a honeycomb sheet with in-plane oscillating long-ranged interactions. We find the ground state of the interacting system in a variational mean-field method and show that the Fermi wave vector kF of the metal determines which phase occurs in the honeycomb lattice sheet. This is analogous to the Ruderman-Kittel-Kasuya-Yosida (RKKY) mechanism in which the metal's kF determines the interaction profile as a function of the distance. Tuning kF and the interaction strength may lead to a variety of ordered phases, including a topological insulator and anomalous quantum-Hall states with complex next-nearest-neighbor hopping, as in the Haldane and the Kane-Mele model. We estimate the required range of parameters needed for the topological state and find that the Fermi vector of the metallic gate should be of the order of 3?/8a (with a being the graphene lattice constant). The net coupling between the layers, which includes screening in the metal, should be of the order of the honeycomb lattice bandwidth. This configuration should be most easily realized in a cold-atoms setting with two interacting Fermionic species.

Pereg-Barnea, T.; Refael, G.

2012-02-01

124

Honeycomb Geometry: Applied Mathematics in Nature.  

ERIC Educational Resources Information Center

Study and exploration of the hexagonal shapes found in honeycombs is suggested as an interesting topic for geometry classes. Students learn that the hexagonal pattern maximizes the enclosed region and minimizes the wax needed for construction, while satisfying the bees' cell-size constraint. (MNS)

Roberts, William J.

1984-01-01

125

PT-symmetry in honeycomb photonic lattices  

SciTech Connect

We apply gain and loss to honeycomb photonic lattices and show that the dispersion relation is identical to tachyons--particles with imaginary mass that travel faster than the speed of light. This is accompanied by -symmetry breaking in this structure. We further show that the -symmetry can be restored by deforming the lattice.

Szameit, Alexander; Rechtsman, Mikael C.; Bahat-Treidel, Omri; Segev, Mordechai [Physics Department and Solid State Institute, Technion, 32000 Haifa (Israel)

2011-08-15

126

Honeycomb Betavoltaic Battery for Space Applications  

Microsoft Academic Search

Radioisotopic batteries offer advantages relative to conventional chemical batteries for applications requiring a long lifetime with minimum maintenance. Thus, thermoelectric type cells fueled with Pu have been used extensively on NASA space missions. The design for a small beta battery using nickel-63 (Ni-63) and a vacuum direct collection method is described here. A honeycomb nickel wire structure is employed to

Jin R. Lee; Ben Ulmen; George H. Miley

2008-01-01

127

Designing with advanced composites; Report on the European Core Conference, 1st, Zurich, Switzerland, Oct. 20, 21, 1988, Conference Papers  

SciTech Connect

The present conference discusses the development history of sandwich panel construction, production methods and quality assurance for Nomex sandwich panel core papers, the manufacture of honeycomb cores, state-of-the-art design methods for honeycomb-core panels, the Airbus A320 airliner's CFRP rudder structure, and the design tradeoffs encountered in honeycomb-core structures' design. Also discussed are sandwich-construction aircraft cabin interiors meeting new FAA regulations, the use of Nomex honeycomb cores in composite structures, a low-cost manufacturing technique for sandwich structures, and the Starship sandwich panel-incorporating airframe primary structure.

Not Available

1988-01-01

128

Static and fatigue load performance of a gfrp honeycomb bridge deck  

Microsoft Academic Search

This paper investigates the performance of a glass fiber-reinforced polymer (GFRP) bridge deck under static and fatigue load cycles. The bridge deck has a sandwich panel configuration, consisting of two stiff face shells separated by a light-weight honeycomb core. The deck was manufactured using a hand lay-up technique. In this study, a full-size panel that had the same design as

Guido Camata; P. Benson Shing

2010-01-01

129

Study of the core-corona structure formed during the explosion of an aluminum wire in vacuum  

SciTech Connect

The time evolution of the matter parameters and current distribution in the discharge channel formed during a nanosecond explosion of a 25-{mu}m-diameter 12-mm-long aluminum wire was studied in a series of experiments with the following parameters: the discharge voltage was U{sub 0} = 20 kV, the current amplitude was I{sub max} {approx} 8 kA, and the current rise rate was dI/dt {approx} 40 A/ns. Optical shadow and schlieren images of the discharge channel were obtained using the second harmonic of a YAG: Nd{sup +3} laser, and UV images of the discharge channel self-radiation were recorded using a four-frame camera with a microchannel plate. The process of aluminum wire explosion was simulated numerically (including simulations performed from the 'cold start'). The numerical results were compared with the experimental data.

Tkachenko, S. I. [Moscow Institute of Physics and Technology (Russian Federation); Mingaleev, A. R. [Russian Academy of Sciences, Joint Institute for High Temperatures (Russian Federation); Pikuz, S. A.; Romanova, V. M. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation); Khattatov, T. A. [Moscow Institute of Physics and Technology (Russian Federation); Shelkovenko, T. A. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation); Ol'khovskaya, O. G.; Gasilov, V. A. [Russian Academy of Sciences, Keldysh Institute of Applied Mathematics (Russian Federation); Kalinin, Yu. G. [National Research Centre Kurchatov Institute (Russian Federation)

2012-01-15

130

High heat flux actively cooled honeycomb sandwich structural panel for a hypersonic aircraft  

NASA Technical Reports Server (NTRS)

The results of a program to design and fabricate an unshielded actively cooled structural panel for a hypersonic aircraft are presented. The design is an all-aluminum honeycomb sandwich with embedded cooling passages soldered to the inside of the outer moldline skin. The overall finding is that an actively cooled structure appears feasible for application on a hypersonic aircraft, but the fabrication process is complex and some material and manufacturing technology developments are required. Results from the program are summarized and supporting details are presented.

Koch, L. C.; Pagel, L. L.

1978-01-01

131

Phonons in conventional and auxetic honeycomb lattices  

NASA Astrophysics Data System (ADS)

The modes of vibrations of conventional and auxetic honeycomb structures are studied by means of models where lattices are represented by planar networks, in which rodlike particles are linked by strings. In these structures, the translational and rotational degrees of freedom are strongly coupled. The auxetic network is obtained by modifying a model proposed by Evans in 1991 [Nature (London) 353, 124 (1991)], and is used to explain the negative Poisson’s ratio of auxetic materials. Auxetics are materials with a negative Poisson elastic parameter, meaning that they have a lateral extension, instead of shrinking, when they are stretched. The phonon dispersions obtained in the case of the auxetic model are compared with those of a conventional honeycomb network, where rigid rodlike particles are inserted. The behavior of the rotational dispersions can explain some experimental observations on the properties of sound propagation in the auxetic materials.

Sparavigna, A.

2007-10-01

132

Interacting electrons on trilayer honeycomb lattices  

NASA Astrophysics Data System (ADS)

Few-layer graphene systems come in various stacking orders. Considering tight-binding models for electrons on stacked honeycomb layers, this gives rise to a variety of low-energy band structures near the charge neutrality point. Depending on the stacking order, these band structures enhance or reduce the role of electron-electron interactions. Here, we investigate the instabilities of interacting electrons on honeycomb multilayers with a focus on trilayers with ABA and ABC stackings theoretically by means of the functional renormalization group. We find different types of competing instabilities and identify the leading ordering tendencies in the different regions of the phase diagram for a range of local and no-local short-ranged interactions. The dominant instabilities turn out to be toward an antiferromagnetic spin-density wave (SDW), a charge density wave, and quantum spin Hall (QSH) order. Ab initio values for the interaction parameters put the systems at the border between SDW and QSH regimes. Furthermore, we discuss the energy scales for the interaction-induced gaps in this model study and put them into context with the scales for single-layer and Bernal-stacked bilayer honeycomb lattices. This yields a comprehensive picture of the possible interaction-induced ground states of few-layer graphene.

Scherer, Michael M.; Uebelacker, Stefan; Scherer, Daniel D.; Honerkamp, Carsten

2012-10-01

133

Titanium honeycomb acoustic lining structural and thermal test report. [for acoustic tailpipe for JT8D engine  

NASA Technical Reports Server (NTRS)

The results are presented of static, fatigue and thermal testing of titanium honeycomb acoustic panels representing the acoustic tailpipe for the Pratt and Whitney Aircraft JT8D Refan engine which is being studied for use on the Boeing 727-200 airplane. Test specimens represented the engine and tailpipe flange joints, the rail to which the thrust reverser is attached and shear specimens of the tailpipe honeycomb. Specimens were made in four different batches with variations in configuration, materials and processes in each. Static strength of all test specimens exceeded the design ultimate load requirements. Fatigue test results confirmed that aluminum brazed titanium, as used in the Refan tailpipe design, meets the fatigue durability objectives. Quality of welding was found to be critical to life, with substandard welding failing prematurely, whereas welding within the process specification exceeded the panel skin life. Initial fatigue testing used short grip length bolts which failed prematurely. These were replaced with longer bolts and subsequent testing demonstrated the required life. Thermal tests indicate that perforated skin acoustic honeycomb has approximately twice the heat transfer of solid skin honeycomb.

Joynes, D.; Balut, J. P.

1974-01-01

134

Mechanics and applications of pressure adaptive honeycomb  

NASA Astrophysics Data System (ADS)

A novel adaptive aerostructure is presented that relies on certified aerospace materials and can therefore be applied in conventional passenger aircraft. This structure consists of a honeycomb material which' cells extend over a significant length perpendicular to the plane of the cells. Each of the cells contains an inelastic pouch (or bladder) that forms a circular tube when the cell forms a perfect hexagon. By changing the cell differential pressure (CDP) the stiffness of the honeycomb can be altered. Using an external force or the elastic force within the honeycomb material, the honeycomb can be deformed such that the cells deviate from their perfect-hexagonal shape. It can be shown that by increasing the CDP, the structure eventually returns to a perfect hexagon. By doing so, a fully embedded pneumatic actuator is created that can perform work and substitute conventional low-bandwidth flight control actuators. It is shown that two approaches can be taken to regulate the stiffness of this embedded actuator: (1) The first approach relies on the pouches having a fixed amount of air in them and stiffness is altered by a change in ambient pressure. Coupled to the ambient pressure-altitude cycle that aircraft encounter during each flight, this approach yields a true adaptive aerostructure that operates independently of pilot input and is controlled solely by the altitude the aircraft is flying at. (2) The second approach relies on a controlled constant CDP. This CDP could be supplied from one of the compressor stages of the engine as a form of bleed air. Because of the air-tight pouches there would essentially be no mass flow, meaning engine efficiency would not be significantly affected due to this application. By means of a valve system the pilot could have direct control over the pressure and, consequently, the stiffness of the structure. This allows for much higher CDPs (on the order of 1MPa) than could physically be achieved by relying on the ambient pressure decrease with altitude. This option does require more infrastructure like tubing, valves, and supporting electronics from the cockpit. Applications of pressure adaptive honeycomb are tailored primarily towards low-bandwidth applications like secondary flight control. The most profound application is the morphing of an entire wing section, from leading to trailing edge, due to the adaptive honeycomb. On a smaller scale, other examples include a solid state pressure adaptive flap, a pressure adaptive droop nose, a pressure adaptive Gurney flap and a pressure adaptive engine inlet. Each of these applications is based on the same principle of stiffness alteration with pressure and can be used with either actuation option (constant mass or constant pressure). A model that relates the volumetric change of the honeycomb cells to the external blocked stress was shown to correlate well to experiments that were carried out on several test articles. Based on this model it was estimated that pressure adaptive honeycomb has a maximum mass-specific energy density of 12.4J/g, for the case of an externally applied CDP of 0.9MPa (can be supplied from a high-pressure compressor stage of a gas turbine). In addition, it was shown that a maximum strain of 76% can be achieved and that the maximum blocked stress amounts to 0.82MPa. In the case of a 40kPa drop in atmospheric pressure and constant mass of air in the pouches, the maximum mass specific energy amounts to 1.1J/g and a maximum blocked force of 70kPa can be attained. Pressure adaptive honeycomb was embedded into a 25%c adaptive flap on a NACA2412 wing section with a chord of 1.08m. Wind tunnel tests at Reynolds number of 1 million demonstrated a shift in the cl -- alpha curve upwards by an average of 0.3, thereby increasing the maximum lift coefficient from 1.27 to 1.52. This successfully demonstrated the application of pressure adaptive honeycomb embedded in a morphing aircraft structure.

Vos, Roelof

135

High-Fidelity Modeling for Health Monitoring in Honeycomb Sandwich Structures  

NASA Technical Reports Server (NTRS)

High-Fidelity Model of the sandwich composite structure with real geometry is reported. The model includes two composite facesheets, honeycomb core, piezoelectric actuator/sensors, adhesive layers, and the impactor. The novel feature of the model is that it includes modeling of the impact and wave propagation in the structure before and after the impact. Results of modeling of the wave propagation, impact, and damage detection in sandwich honeycomb plates using piezoelectric actuator/sensor scheme are reported. The results of the simulations are compared with the experimental results. It is shown that the model is suitable for analysis of the physics of failure due to the impact and for testing structural health monitoring schemes based on guided wave propagation.

Luchinsky, Dimitry G.; Hafiychuk, Vasyl; Smelyanskiy, Vadim; Tyson, Richard W.; Walker, James L.; Miller, Jimmy L.

2011-01-01

136

Epitaxial graphene on SiC(0001): more than just honeycombs.  

PubMed

Using scanning tunneling microscopy with Fe-coated W tips and first-principles calculations, we show that the interface of epitaxial graphene/SiC(0001) is a warped graphene layer with hexagon-pentagon-heptagon (H(5,6,7)) defects that break the honeycomb symmetry, thereby inducing a gap and states below E(F near the K point. Although the next graphene layer assumes the perfect honeycomb lattice, its interaction with the warped layer modifies )the dispersion about the Dirac point. These results explain recent angle-resolved photoemission and carbon core-level shift data and solve the long-standing problem of the interfacial structure of epitaxial graphene on SiC(0001). PMID:20868110

Qi, Y; Rhim, S H; Sun, G F; Weinert, M; Li, L

2010-08-20

137

SOUND TRANSMISSION THROUGH A CYLINDRICAL SANDWICH SHELL WITH HONEYCOMB CORE  

Microsoft Academic Search

Sound transmission through an infinite cylindrical sandwich shell is studied in the context of the transmission of airborne sound into aircraft interiors. The cylindrical shell is immersed in fluid media and excited by an oblique incident plane sound wave. The internal and external fluids are different and there is uniform airflow in the external fluid medium. An explicit expression of

Yvette Y. Tang; Jay H. Robinson; Richard J. Silcox

1996-01-01

138

Measurement of the pore sizes for anodic aluminum oxide (AAO)  

Microsoft Academic Search

A new method for the measurement of pore size of the porous-type anodic aluminum oxide (AAO) using atomic force microscopy (AFM) is proposed. The measurement of the pore size by AFM makes no damage to the specimen. AAO film can be referred as a nanohoneycomb structure because the pore shape of AAO is like the honeycomb structure and its pore

D. H. Choi; P. S. Lee; W. Hwang; K. H. Lee; H. C. Park

2006-01-01

139

Behavior of intact and damaged honeycombs: a finite element study  

Microsoft Academic Search

The Young’s moduli, the elastic buckling strength and the plastic collapse strength of regular honeycombs with defects consisting of missing cells in the structure were analyzed using the finite element method. The behavior of intact honeycombs was first analyzed; the results of this numerical study are consistent with those of previous analyses. The effect of single, isolated defects of varying

X. Edward Guo; Lorna J. Gibson

1999-01-01

140

Mechanical properties of Nomex material and Nomex honeycomb structure  

Microsoft Academic Search

This paper presents extensive test results of linear elastic mechanical properties of Nomex paper and Nomex honeycomb structures. The fundamental mechanical properties of the Nomex paper are then used in the finite element modeling and analysis of Nomex honeycomb structures. The finite element results are then compared with the experimental results and with the results using the well known theory

Choon Chiang Foo; Gin Boay Chai; Leong Keey Seah

2007-01-01

141

A new metallostar complex based on an aluminum(III) 8-hydroxyquinoline core as a potential bimodal contrast agent.  

PubMed

A ditopic DTPA monoamide derivative containing an 8-hydroxyquinoline moiety was synthesized and the corresponding gadolinium(III) complex ([Gd(H5)(H(2)O)](-)) was prepared. After adding aluminum(III), the 8-hydroxyquinoline part self-assembled into a heteropolymetallic triscomplex [(Gd5)(3)Al(H(2)O)(3)](3-). The magnetic and optical properties of this metallostar compound were investigated in order to classify it as a potential in vitro bimodal contrast agent. The proton nuclear magnetic relaxation dispersion measurements indicated that the relaxivity r(1) of [Gd(H5)(H(2)O)](-) and [(Gd5)(3)Al(H(2)O)(3)](3-) at 20 MHz and 310 K equaled 6.17 s(-1) mM(-1) and 10.9 s(-1) mM(-1) per Gd(III) ion respectively. This corresponds to a relaxivity value of 32.7 s(-1) mM(-1) for the supramolecular complex containing three Gd(III) ions. The high relaxivity value is prominently caused by an increase of the rotational tumbling time ?(R) by a factor of 2.7 and 5.5 respectively, in comparison with the commercially used MRI contrast agent Gd(III)-DTPA (Magnevist®). Furthermore, upon UV irradiation, [(Gd5)(3)Al(H(2)O)(3)](3-) exposes green broad-band emission with a maximum at 543 nm. Regarding the high relaxivity and the photophysical properties of the [(Gd5)(3)Al(H(2)O)(3)](3-) metallostar compound, it can be considered as a lead compound for in vitro bimodal applications. PMID:22829068

Debroye, Elke; Dehaen, Geert; Eliseeva, Svetlana V; Laurent, Sophie; Vander Elst, Luce; Muller, Robert N; Binnemans, Koen; Parac-Vogt, Tatjana N

2012-09-21

142

Forming Process Simulation of Truss Core Panel  

NASA Astrophysics Data System (ADS)

Honeycomb panel is widely used as flooring or wall material in various structure including buildings, aircraft, train and so on due to high stiffness and lightness at present. Honeycomb panel, however, has a disadvantage that adhesive used to glue honeycomb core and top plate may burn by fire. On the other hand truss core panel has equivalent stiffness as honeycomb panel and is expected to be an alternative to honeycomb panel as it is safer for fire. However, in general, difficulty exists to form truss core and forming techniques should be developed for practice use of truss core panel. In this paper, firstly theoretical forming limitation is discussed for tetrahedral truss core . Secondly single stage forming simulation of truss core panel using explicit FEM technique was performed for preliminary investigation to estimate formability and thickness distribution. Finally multi-stage forming simulation was presented and possibility to apply press forming for truss core panel production through the simulation. In addition some results of the simulation was compared with the experiment and good agreement of both results was shown.

Tokura, Sunao; Hagiwara, Ichiro

143

A non-asymptotic model of dynamics of honeycomb lattice-type plates  

NASA Astrophysics Data System (ADS)

Lightweight structures, consisted of special composite material systems like sandwich plates, are often used in aerospace or naval engineering. In composite sandwich plates, the intermediate core is usually made of cellular structures, e.g. honeycomb micro-frames, reinforcing static and dynamic properties of these plates. Here, a new non-asymptotic continuum model of honeycomb lattice-type plates is shown and applied to the analysis of dynamic problems. The general formulation of the model for periodic lattice-type plates of an arbitrary lay-out was presented by Cielecka and J?drysiak [Journal of Theoretical and Applied Mechanics 40 (2002) 23-46]. This model, partly based on the tolerance averaging method developed for periodic composite solids by Wo?niak and Wierzbicki [Averaging techniques in thermomechanics of composite solids, Wydawnictwo Politechniki Cz?stochowskiej, Cz?stochowa, 2000], takes into account the effect of the length microstructure size on the dynamic plate behaviour. The shown method leads to the model equations describing the above effect for honeycomb lattice-type plates. These equations have the form similar to equations for isotropic cases. The dynamic analysis of such plates exemplifies this effect, which is significant and cannot be neglected. The physical correctness of the obtained results is also discussed.

Cielecka, Iwona; J?drysiak, Jaros?aw

2006-09-01

144

Steps toward 8 m honeycomb mirror blanks. II - Experiments with waffleplate and honeycomb casting  

NASA Technical Reports Server (NTRS)

A technique for fabricating large low-cost light-weight borosilicate-glass mirrors for ground and space-based astronomy is described. This technique involves the remelting of glass into complex molds for vacuum-formed ceramic fiber and is used to cast in one piece either waffleplate or full honeycomb sandwich blanks. The construction of molds and the cycle for melting and annealing are described in detail. A 1.1-m square blank with a 22.4-cm-thick face and 1.6-cm ribs, 15-cm deep on 15-cm squares, has been cast, and a 1.8-m circular blank of full honeycomb construction is scheduled for production. The casting of blanks of up to 8-m in diameter is anticipated, with densities of 200 kg/sq m (like that of the ST mirror) being typical of casting.

Hill, J. M.; Angel, J. R. P.

1983-01-01

145

Light weight aluminum optics  

NASA Astrophysics Data System (ADS)

Light weight mirror blanks were fabricated by dip-brazing a core of low mass aluminum foam material to thin face sheets of solid aluminum. The blanks weigh 40% of an equivalent size solid mirror and were diamond turned to provide reflective surfaces. Optical interferometry was used to assess their dimensional stability over 7 months. No changes in flatness are observed (to the sensitivity of the measurements of a half wavelength of red light).

Catura, R. C.; Vieira, J. R.

1985-09-01

146

Cryogenic performance of slotted brazed Rene 41 honeycomb panels  

NASA Technical Reports Server (NTRS)

Two brazed Rene 41 honeycomb panels that would incorporate a frame element were designed, fabricated and tested. The panels were representative of the lower surface of an advanced space transportation vehicle. The first panel was a two span panel supported by a center frame and on edges parallel to it. The second panel was a two span panel supported by a center frame and on edges parallel to it. The second panel was a three span panel supported on two frames and on edges parallel to the frames. Each panel had its outer skin slotted to reduce the thermal stresses of the panel skins. The first panel was tested under simulated boost conditions that included liquid hydrogen exposure of the frame and inner skin and radiant heat to 478K on the outer skins. The first panel was tested to investigate the effect of thermal stresses in skins and core caused by the panel being restrained by a cold integral frame and to observe the effects of frost formation and possible liquid air development in and around outer skin slots.

Hepler, A. K.; Swegle, A. R.

1982-01-01

147

Dislocations in the Kitaev honeycomb model  

NASA Astrophysics Data System (ADS)

We study the effects of introducing dislocations into the Kitaev honeycomb model [1]. In the gapped phase, dislocations are Z2 ``twist defects'' associated with the transmutation of electric and magnetic excitations, studied previously in the context of ZN rotor models [2,3]. We show that each dislocation hosts one unpaired Majorana mode. As a consequence, twist defects have the statistics of Ising anyons. Because dislocations are confined, an additional phase is accumulated due to the change in system's energy during the braiding process. This means that the result of braiding can only be defined up to a phase. Therefore, twists are said to have projective non-Abelian statistics. [4pt][1] Alexei Kitaev, Annals of Physics 321, 2 (2006) [0pt][2] Hector Bombin, Phys. Rev. Lett. 105, 030403 (2010) [0pt][3] Yi-Zhuang You and Xiao-Gang Wen, Phys. Rev. B 86, 161107 (2012)

Petrova, Olga; Tchernyshyov, Oleg

2013-03-01

148

Study on mechanical properties of steel honeycomb panel three-point bending specimen under in-plane and out-plane transverse dynamic impact load  

NASA Astrophysics Data System (ADS)

The metal honeycomb material has high strength and high stiffness, as a high-performance sandwich panel, it is an ideal lightweight structural material, and widely used in aviation, aerospace, shipbuilding and other fields. In this paper, the improved SHPB instrument is used for testing the in-plane and out-plane mechanical properties of the steel honeycomb panel three-point bending specimen, and also compare the results with the static in-plane and out-plane three-point bending experiments results which is tested by the INSTRON 4505 electronic universal testing machine, and then study the mechanical properties of the steel honeycomb panel three-point bending specimen under transverse dynamic impact load. From the results it can be see that, for the out-plane three point bending experiment, L direction mechanical properties is better than the W direction, and the honeycomb core play an important role during the specimen deformation, while for the in-plane three point bending experiment, the honeycomb core mechanical role is not distinctness.

Zou, Guangping; Chang, Zhongliang; Xia, Xingyou; Zhang, Xueyi

2009-12-01

149

Damping capacity in shape memory alloy honeycomb structures  

NASA Astrophysics Data System (ADS)

SMA honeycombs have been recently developed by several Authors [1, 2] as innovative cellular structures with selfhealing capability following mechanical indentation, unusual deformation (negative Poisson's ratio [3]), and possible enhanced damping capacity due to the natural vibration dissipation characteristics of SMAs under pseudoelastic and superelastic regime. In this work we describe the nonlinear damping effects of novel shape memory alloy honeycomb assemblies subjected to combine mechanical sinusoidal and thermal loading. The SMA honeycomb structures made with Ni48Ti46Cu6 are designed with single and two-phase polymeric components (epoxy), to enhance the damping characteristics of the base SMA for broadband frequency vibration.

Boucher, M.-A.; Smith, C. W.; Scarpa, F.; Miller, W.; Hassan, M. R.

2010-03-01

150

Application of Wave Propagation and Vibration-based Structural Health Monitoring Techniques to Friction Stir Welded Plate and Sandwich Honeycomb Panel  

Microsoft Academic Search

Wave propagation and vibration-based structural health monitoring methodologies are presented to detect, locate and quantify dent\\/crack, thermal debond, and corrosion damage in a solid aluminum friction stir weld plate and a sandwich honeycomb thermal protection panel. A wave propagation based method can identify small defects because propagating waves typically consist of small wavelengths while a vibration-based scheme is better equipped

S. Sundararaman; J. R. White; D. E. Adams; K. V. Jata

2007-01-01

151

Conduction of Heat in Lightweight Composite Honeycomb Structures.  

National Technical Information Service (NTIS)

This report contains comparisons of experimentally measured and theoretically calculated temperature distributions in honeycomb structural panels filled with a low diffusivity foam. The theoretical method involves the use of the three-dimensional Thermal ...

M. W. Goodwin

1965-01-01

152

External Patch Repair of CFRP/Honeycomb Sandwich.  

National Technical Information Service (NTIS)

This paper addresses the repair of impact-damaged honeycomb sandwich structures with thin skins made of carbon fiber reinforced plastic (CFRP). An experimental study concerned with evaluating several types of bonded external patch repairs is presented. Th...

K. Wolf R. Schindler

1995-01-01

153

Modeling the Axial Mechanical Response of Amorphous Fe45Ni45Mo7B3 Honeycombs  

NASA Astrophysics Data System (ADS)

The high yield strength and elastic modulus of metallic glasses suggests they could perform an important role in structural applications. To produce materials with a high strength-to-weight ratio and excellent mechanical energy absorption, it is advantageous to form amorphous alloys as cellular solids. Using the elastic properties of slip cast amorphous Fe45Ni45Mo7B3 ribbons, a metallic glass honeycomb was manufactured with a unique manufacturing approach. First, prototypes were manufactured with a porosity of 97 pct, a cell wall thickness of 0.03 mm, and a cell size of 3 mm. Experimentally measured mechanical properties were reasonably similar to analytical models. This suggests that a three-times improvement in the yield strength along the out-of-plane direction is achievable when compared with crystalline aluminum honeycombs. An analytical model was developed to predict the relative density and the compressive stress ( ? {3/ * }) in the out-of-plane ( X 3) direction of the "teardrop" cellular structure. The predictions are validated by initial experimental results and compare well with existing analytical models for hexagonal cellular materials.

Jayakumar, Balaji; Hanan, Jay C.

2012-08-01

154

Formation of a honeycomb domain structure in magnetic films  

Microsoft Academic Search

An analysis is made of the possible formation of a honeycomb domain structure directly from a labyrinth structure in uniaxial\\u000a magnetic films exposed to a series of uniform magnetic field pulses. It is shown that the scenario for the formation of a\\u000a honeycomb structure depends on the pulse parameters and on the magnitude of the static magnetizing magnetic field.

M. V. Logunov; N. V. Moiseev

1997-01-01

155

Low voltage reversible electrowetting exploiting lubricated polymer honeycomb substrates  

NASA Astrophysics Data System (ADS)

Low-voltage electrowetting-on-dielectric scheme realized with lubricated honeycomb polymer surfaces is reported. Polycarbonate honeycomb reliefs manufactured with the breath-figures self-assembly were impregnated with silicone and castor oils. The onset of the reversible electrowetting for silicone oil impregnated substrates occurred at 35 V, whereas for castor oil impregnated ones it took place at 80 V. The semi-quantitative analysis of electrowetting of impregnated surfaces is proposed.

Bormashenko, Edward; Pogreb, Roman; Bormashenko, Yelena; Grynyov, Roman; Gendelman, Oleg

2014-04-01

156

Assessment of Bulk Absorber Properties for Multi-Layer Perforates in Porous Honeycomb Liners  

NASA Technical Reports Server (NTRS)

CONTINUING progress in materials technology provides potential for improved acoustic liners for attenuating broadband fan noise emissions from aircraft engine nacelles. Conventional liners (local-reacting perforate-over-honeycomb structures) provide significant narrow-band attenuation, but limited attenuation over wide bandwidths. Two approaches for increasing attenuation bandwidth are to (1) replace the honeycomb structure with bulk material, or (2) cascade multiple layers of perforate/honeycomb structures. Usage of the first approach is limited because of mechanical and maintenance reasons, while multi-layer liners are limited to about three layers because of their additional mechanical complexity, depth and weight. The current research concerns a novel approach reported by the University of Cincinnati, in which a single-layer conventional liner is converted into an extended-reaction, broadband absorber by making the honeycomb core structure porous. This modified single-layer liner requires no increase in depth and weight, and minimal increase in mechanical complexity. Langley has initiated research to identify potential benefits of liner structures with porous cell walls. This research has two complementary goals: (1) develop and validate experimental techniques for treating multi-layer perforates (representative of the internal cells of a liner with porous cell walls) as 1-D bulk materials, and (2) develop analytical approaches to validate this bulk material assumption. If successful, the resultant model can then be used to design optimized porous honeycomb liners. The feasibility of treating an N-layer perforate system (N porous plates separated by uniform air gaps) as a one-dimensional bulk absorber is assessed using the Two-Thickness Method (TTM), which is commonly used to educe bulk material intrinsic acoustic parameters. Tests are conducted with discrete tone and random noise sources, over an SPL range sufficient to determine the nonlinearity of the test specimens, for test specimens consisting of 5, 10 and 15% porous plates. Measured impedances for two liner thicknesses (e.g., 12 and 24 layers) are used as input to the TTM to determine the characteristic impedance and propagation constant that characterize these liners as bulk absorbers. These parameters are then used to calculate the predicted impedance of liners with different thicknesses (e.g., 36 layers), and a comparison of predicted and measured impedances for these other thicknesses is used to determine the efficacy of this approach. Finally, an independent method is used to educe the propagation constant for a single representative sample, and excellent comparison between the results for this method and those for the TTM provides increased confidence in the results achieved with the TTM. In general, the results demonstrate these multi-layer perforates can be acceptably treated as bulk absorbers.

Jones, Michael G.; Parrott, Tony L.

2006-01-01

157

Test results for electron beam charging of flexible insulators and composites. [solar array substrates, honeycomb panels, and thin dielectric films  

NASA Technical Reports Server (NTRS)

Flexible solar-array substrates, graphite-fiber/epoxy - aluminum honeycomb panels, and thin dielectric films were exposed to monoenergetic electron beams ranging in energy from 2 to 20 keV in the Lewis Research Center's geomagnetic-substorm-environment simulation facility to determine surface potentials, dc currents, and surface discharges. The four solar-array substrate samples consisted of Kapton sheet reinforced with fabrics of woven glass or carbon fibers. They represented different construction techniques that might be used to reduce the charge accumulation on the array back surface. Five honeycomb-panel samples were tested, two of which were representative of Voyager antenna materials and had either conductive or nonconductive painted surfaces. A third sample was of Navstar solar-array substrate material. The other two samples were of materials proposed for use on Intelsat V. All the honeycomb-panel samples had graphite-fiber/epoxy composite face sheets. The thin dielectric films were 2.54-micrometer-thick Mylar and 7.62-micrometer-thick Kapton.

Staskus, J. V.; Berkopec, F. D.

1979-01-01

158

Preparation and microwave absorption properties of foam-based honeycomb sandwich structures  

NASA Astrophysics Data System (ADS)

Radar-absorbing structures having foam-based honeycomb sandwich structures (FBHSS) were fabricated through a conventional foaming technique. Conductive fillers such as carbonyl iron/nickel fibers (CINF) and magnetic metal micropowder (MMP) were added to polyurethane foams so as to efficiently increase the absorbing capacity of FBHSS. A honeycomb sandwich structure, which was made of composite face sheets and foam cores, was used as a supporter to enhance mechanical strength. A matching layer made of nanotitanium powder and hydrogenation acrylonitrile-butadiene rubber composites was used for the face sheet, which allows the incident electromagnetic wave to enter and largely get attenuated through the absorbing system. Polyurethane foams containing CINFs and MMP of which a suitable content contributing to a broad bandwidth and high loss, were used as the core material. The measurement results show reflection loss was less than -10 dB over the frequency range of 3-18 GHz, which has a minimum value of - 26 dB at 14.2 GHz.

He, Yanfei; Gong, Rongzhou

2009-03-01

159

Aluminum Hydroxide  

MedlinePLUS

Aluminum hydroxide is used for the relief of heartburn, sour stomach, and peptic ulcer pain and to ... Aluminum hydroxide comes as a capsule, a tablet, and an oral liquid and suspension. The dose and ...

160

Development of Rene 41 honeycomb structure as an integral cryogenic tankage/fuselage concept for future space transportation systems  

NASA Technical Reports Server (NTRS)

The status of the structural development of an integral cryogenic-tankage/hot-fuselage concept for future space transportation systems is reviewed. The concept comprises a honeycomb sandwich structure that serves the combined functions of containing the cryogenic fuel, supporting the vehicle loads, and protecting the spacecraft from entry heating. The inner face sheet is exposed to cryogenic temperature of -423 F during boost; the outer face sheet, which is slotted to reduce thermal stress, is exposed to a maximum temperature of 1400 F during a high-altitude gliding entry. Attention is given to the development of a fabrication process for a Rene 41 honeycomb sandwich panel with a core density of less than 1 percent that is consistent with desirable heat treatment processes for high strength.

Shideler, J. L.; Swegle, A. R.; Fields, R. A.

1982-01-01

161

Development of Rene' 41 honeycomb structure as an integral cryogenic tankage/fuselage concept for future space transportation systems  

NASA Technical Reports Server (NTRS)

The status of the structural development of an integral cryogenic-tankage/hot-fuselage concept for future space transportation systems (STS) is discussed. The concept consists of a honeycomb sandwich structure which serves the combined functions of containment of cryogenic fuel, support of vehicle loads, and thermal protection from an entry heating environment. The inner face sheet is exposed to a cryogenic (LH2) temperature of -423 F during boost; and the outer face sheet, which is slotted to reduce thermal stress, is exposed to a maximum temperature of 1400 F during a high altitude, gliding entry. A fabrication process for a Rene' 41 honeycomb sandwich panel with a core density less than 1 percent was developed which is consistent with desirable heat treatment processes for high strength.

Shideler, J. J.; Swegle, A. R.; Fields, R. A.

1982-01-01

162

Optimal Design of Honeycomb Material Used to Mitigate Head Impact  

PubMed Central

This paper presents a study of the impact resistance of honeycomb structure with the purpose to mitigate impact forces. The objective is to aid in the choice of optimal parameters to minimize the thickness of the honeycomb structure while providing adequate protection to prevent injury due to head impact. Studies are presented using explicit finite element analysis representing the case of an unprotected drop of a rigid impactor onto a simulated floor consisting of vinyl composition tile and concrete. Analysis of honeycomb material to reduce resulting accelerations is also presented where parameters such as honeycomb material modulus, wall thickness, cell geometry and structure depth are compared to the unprotected case. A simplified analysis technique using a genetic algorithm is presented to demonstrate the use of this method to select a minimum honeycomb depth to achieve a desired acceleration level at a given level of input energy. It is important to select a minimum material depth in that smaller dimensions lead toward more aesthetic design that increase the likelihood of that the device is used.

Caccese, Vincent; Ferguson, James R.; Edgecomb, Michael

2013-01-01

163

Effects of thickness and delamination on the damping in honeycomb foam sandwich beams  

NASA Astrophysics Data System (ADS)

In engineering applications where the use of lightweight structures is important, the introduction of a viscoelastic core layer, which has high inherent damping, between two face sheets, can produce a sandwich structure with high damping. Sandwich structures have the additional advantage that their strength to weight ratios are generally superior to those of solid metals. So, sandwich structures are being used increasingly in transportation vehicles. Knowledge of the passive damping of sandwich structures and attempts to improve their damping at the design stage thus are important. Some theoretical models for passive damping in composite sandwich structures are reviewed in this paper. The effects of the thickness of the core and face sheets, and delamination on damping are analyzed. Measurements on honeycomb-foam sandwich beams with different configurations and thicknesses have been performed and the results compared with the theoretical predictions.

Li, Zhuang; Crocker, Malcolm J.

2006-06-01

164

Fiber-Reinforced Polymer Honeycomb Short Span Bridge for Rapid Installation.  

National Technical Information Service (NTIS)

The project designed, fabricated and tested a lightweight composite bridge made of a fiberglass-reinforced polymer honeycomb structural panels. The bridge was constructed over No-Name Creek in Russell County, Kansas, using three fiberglass honeycomb panel...

J. D. Plunkett

1997-01-01

165

Topology optimization of pressure adaptive honeycomb for a morphing flap  

NASA Astrophysics Data System (ADS)

The paper begins with a brief historical overview of pressure adaptive materials and structures. By examining avian anatomy, it is seen that pressure-adaptive structures have been used successfully in the Natural world to hold structural positions for extended periods of time and yet allow for dynamic shape changes from one flight state to the next. More modern pneumatic actuators, including FAA certified autopilot servoactuators are frequently used by aircraft around the world. Pneumatic artificial muscles (PAM) show good promise as aircraft actuators, but follow the traditional model of load concentration and distribution commonly found in aircraft. A new system is proposed which leaves distributed loads distributed and manipulates structures through a distributed actuator. By using Pressure Adaptive Honeycomb (PAH), it is shown that large structural deformations in excess of 50% strains can be achieved while maintaining full structural integrity and enabling secondary flight control mechanisms like flaps. The successful implementation of pressure-adaptive honeycomb in the trailing edge of a wing section sparked the motivation for subsequent research into the optimal topology of the pressure adaptive honeycomb within the trailing edge of a morphing flap. As an input for the optimization two known shapes are required: a desired shape in cruise configuration and a desired shape in landing configuration. In addition, the boundary conditions and load cases (including aerodynamic loads and internal pressure loads) should be specified for each condition. Finally, a set of six design variables is specified relating to the honeycomb and upper skin topology of the morphing flap. A finite-element model of the pressure-adaptive honeycomb structure is developed specifically tailored to generate fast but reliable results for a given combination of external loading, input variables, and boundary conditions. Based on two bench tests it is shown that this model correlates well to experimental results. The optimization process finds the skin and honeycomb topology that minimizes the error between the acquired shape and the desired shape in each configuration.

Vos, Roelof; Scheepstra, Jan; Barrett, Ron

2011-03-01

166

Reconfiguration and hysteresis in superconducting Nb film with honeycomb arrays  

NASA Astrophysics Data System (ADS)

Superconducting Nb films with honeycomb array of holes are studied using transport measurements. The oscillating magneto-resistance curves are observed up to large flux density. Two types of resistance minima with different field intervals are observed, indicating the reconfiguration of the overall flux lattice from honeycomb to triangular arrangement. Moreover, hysteretic effects are found in a very large field span from H = 2H1 to H = 8.5H1. It is revealed that the hysteresis is related to the presence of interstitial vortices.

He, S. K.; Zhang, W. J.; Wen, Z. C.; Cao, W. H.

2012-12-01

167

Damage tolerance of an elastic-brittle diamond-celled honeycomb  

Microsoft Academic Search

Ceramic honeycombs with the square cells shown in Figure 1 are commonly used in catalytic converters and in particulate filters for automobiles. Ceramic foams and honeycombs also find application as filters for liquid metal due to their high chemical stability up to a high temperature. More recently, ceramic lattice materials and other types of brittle honeycombs have also been developed

I. Quintana Alonso; N. A. Fleck

2007-01-01

168

Environmental remediation uses of honeycomb monoliths based on natural clinoptilolite  

Microsoft Academic Search

Honeycomb monoliths based on natural heulandite-clinoptilolite were obtained using hydrothermal treatments instead of ordinary procedure of high temperature ceramization, preserving the physical and chemical properties of the zeolite. The monoliths were used to remove Cr(III) cations from tannery waste waters and to reduce the bacteria contamination of drinking water

G. Rodríguez-Fuentes; García P. Ávila; I. Rodríguez Iznaga; N. Bogdanchikova

2004-01-01

169

ESTIMATION OF HONEYCOMB SANDWICH PROPERTIES THROUGH NUMERICAL HOMOGENIZATION  

Microsoft Academic Search

Honeycomb sandwich panels are widely used in aeronautic industry, and more particularly in the construction of airplane and helicopter trim panels. The current study is motivated by aircraft cabin noise reduction applications, where Active Structural Acoustic Control of the trim panels through piezoelectric patches is considered. As an initial step to such control, predictive models of the panel dynamics are

Corine Florens; Franck Cléro

170

An equivalence between monolayer and bilayer honeycomb lattices  

NASA Astrophysics Data System (ADS)

We present an equivalence between the tight binding descriptions of the monolayer and bilayer honeycomb lattices. With appropriate value of the third nearest neighbors coupling, the Hamiltonian for a monolayer is equivalent to the low energy effective Hamiltonian for bilayer in the presence of trigonal warping. A simple physical argument is provided to explain this correspondance.

Montambaux, Gilles

2012-11-01

171

Adsorption characteristics of water vapor on honeycomb adsorbents  

NASA Astrophysics Data System (ADS)

Recovery of tritium released into working areas in nuclear fusion plants is a key issue of safety. A large volume of air from tritium fuel cycle or vacuum vessel should be processed by air cleanup system (ACS). In ACS, tritium gas is oxidized by catalysts, and then tritiated water vapor is collected by adsorbents. This method can remove tritium effectively, whereas high throughput of air causes high-pressure drop in catalyst and adsorbent beds. In this study, the applicability of honeycomb-type adsorbents, which offers a useful advantage in terms of their low-pressure drop, to ACS was examined, in comparison with conventional pebble-type adsorbent. Honeycomb-type adsorbent causes far less pressure drop than pebble-type adsorbent beds. Adsorption capacity of water vapor on a honeycomb-type adsorbent is slightly lower than that on a pebble-type adsorbent, while adsorption rate of water vapor on honeycomb-type adsorbent is much higher than that of pebble-type adsorbent.

Wajima, Takaaki; Munakata, Kenzo; Takeishi, Toshiharu; Hara, Keisuke; Wada, Kouhei; Katekari, Kenichi; Inoue, Keita; Shinozaki, Yohei; Mochizuki, Kazuhiro; Tanaka, Masahiro; Uda, Tatsuhiko

2011-10-01

172

Metal honeycomb to porous wireform substrate diffusion bond evaluation  

NASA Technical Reports Server (NTRS)

Two nondestructive techniques were used to evaluate diffusion bond quality between a metal foil honeycomb and porous wireform substrate. The two techniques, cryographics and acousto-ultrasonics, are complementary in revealing variations of bond integrity and quality in shroud segments from an experimental aircraft turbine engine.

Vary, A.; Moorhead, P. E.; Hull, D. R.

1982-01-01

173

Method and Apparatus for Casting Thin-Walled Honeycomb Structures.  

National Technical Information Service (NTIS)

The present invention is a process for making a honeycomb structure of a selected material, having the steps: (a) disposing molten material in a melt container disposed over a mold, where the melt container has an opening for releasing molten material int...

J. D. Ayers

1996-01-01

174

Detection of entrapped moisture in honeycomb sandwich structures  

NASA Technical Reports Server (NTRS)

Thermal neutron moisture detection system detects entrapped moisture in intercellular areas of bonded honeycomb sandwich structures. A radium/beryllium fast neutron source bombards a specimen. The emitted thermal neutrons from the target nucleus are detected and counted by a boron trifluoride thermal neutron detector.

Hallmark, W. B.

1967-01-01

175

Dynamics of artificial spin ice: a continuous honeycomb network  

Microsoft Academic Search

We model the dynamics of magnetization in an artificial analogue of spin ice specializing to the case of a honeycomb network of connected magnetic nanowires. The inherently dissipative dynamics is mediated by the emission and absorption of domain walls in the sites of the lattice, and their propagation in its links. These domain walls carry two natural units of magnetic

Yichen Shen; Olga Petrova; Paula Mellado; Stephen Daunheimer; John Cumings; Oleg Tchernyshyov

2012-01-01

176

Some considerations of the performance of two honeycomb gas path seal material systems  

NASA Technical Reports Server (NTRS)

A standard Hastelloy-X honeycomb material and a pack aluminide coated honeycomb material were evaluated as to their performance as labyrinth seal materials for aircraft gas turbine engines. Consideration from published literature was given to the fluid sealing characteristics of two honeycomb materials in labyrinth seal applications, and their rub characteristics, erosion resistance, and oxidation resistance were evaluated. The increased temperature potential of the coated honeycomb material compared to the uncoated standard could be achieved without compromising the honeycomb material's rub tolerance, although there was some penalty in terms of reduced erosion resistance.

Bill, R. C.; Shiembob, L. T.

1980-01-01

177

Honeycombing on CT; its definition, pathologic correlation, and future direction of its diagnosis.  

PubMed

Honeycombing on CT is the clue for the diagnosis of usual interstitial pneumonia (UIP) and its hallmark. According to the ATS-ERS-JRS-ALAT 2010 guideline, the patients with honeycombing on CT can be diagnosed as UIP without surgical biopsy. On CT scans, it is defined as clustered cystic airspaces, typically of comparable diameters of the order of 3-10mm, which are usually subpleural and have well-defined walls. Pathologically, honeycombing consists of both collapsing of multiple fibrotic alveoli and dilation of alveolar duct and lumen Although the definition of honeycombing seems to be strict, recognition of honeycombing on CT is various among each observer Because typical honeycombing is frequently observed in the patients with UIP, we should judge clustered cysts as honeycombing when a diagnosis of UIP is suspected. PMID:23806532

Johkoh, Takeshi; Sakai, Fumikazu; Noma, Satoshi; Akira, Masanori; Fujimoto, Kiminori; Watadani, Takeyuki; Sugiyama, Yukihiko

2014-01-01

178

Aluminum Boats  

NSDL National Science Digital Library

Test the buoyancy of an aluminum foil boat and an aluminum foil ball. Why does the same material in different shapes sink or float? This activity explores the fact that the amount of water pushed aside by an object equals the force of water pushing upward on the object.

Center, Reuben H.

1999-01-01

179

Layer anti-ferromagnetism on bilayer honeycomb lattice.  

PubMed

Bilayer honeycomb lattice, with inter-layer tunneling energy, has a parabolic dispersion relation, and the inter-layer hopping can cause the charge imbalance between two sublattices. Here, we investigate the metal-insulator and magnetic phase transitions on the strongly correlated bilayer honeycomb lattice by cellular dynamical mean-field theory combined with continuous time quantum Monte Carlo method. The procedures of magnetic spontaneous symmetry breaking on dimer and non-dimer sites are different, causing a novel phase transition between normal anti-ferromagnet and layer anti-ferromagnet. The whole phase diagrams about the magnetism, temperature, interaction and inter-layer hopping are obtained. Finally, we propose an experimental protocol to observe these phenomena in future optical lattice experiments. PMID:24947369

Tao, Hong-Shuai; Chen, Yao-Hua; Lin, Heng-Fu; Liu, Hai-Di; Liu, Wu-Ming

2014-01-01

180

Layer Anti-Ferromagnetism on Bilayer Honeycomb Lattice  

PubMed Central

Bilayer honeycomb lattice, with inter-layer tunneling energy, has a parabolic dispersion relation, and the inter-layer hopping can cause the charge imbalance between two sublattices. Here, we investigate the metal-insulator and magnetic phase transitions on the strongly correlated bilayer honeycomb lattice by cellular dynamical mean-field theory combined with continuous time quantum Monte Carlo method. The procedures of magnetic spontaneous symmetry breaking on dimer and non-dimer sites are different, causing a novel phase transition between normal anti-ferromagnet and layer anti-ferromagnet. The whole phase diagrams about the magnetism, temperature, interaction and inter-layer hopping are obtained. Finally, we propose an experimental protocol to observe these phenomena in future optical lattice experiments.

Tao, Hong-Shuai; Chen, Yao-Hua; Lin, Heng-Fu; Liu, Hai-Di; Liu, Wu-Ming

2014-01-01

181

d-wave superconductivity on the honeycomb bilayer  

NASA Astrophysics Data System (ADS)

We introduce a microscopic model on the honeycomb bilayer, which in the small-momentum limit captures the usual (quadratic dispersion in the kinetic term) description of bilayer graphene. In the limit of strong interlayer hopping it reduces to an effective honeycomb monolayer model with also third-neighbor hopping. We study interaction effects in this effective model, focusing on possible superconducting instabilities. We find dx2-y2 superconductivity in the strong-coupling limit of an effective tJ-model-like description that gradually transforms into d+id time-reversal symmetry-breaking superconductivity at weak couplings. In this limit the small-momentum order-parameter expansion is (kx+iky)2 [or (kx-iky)2] in both valleys of the effective low-energy description. The relevance of our model and investigation for the physics of bilayer graphene is also discussed.

Vu?i?evi?, J.; Goerbig, M. O.; Milovanovi?, M. V.

2012-12-01

182

Aluminum doped core-shell ZnO/ZnS nanowires: Doping and shell layer induced modification on structural and photoluminescence properties  

NASA Astrophysics Data System (ADS)

In this work, we investigated the combined effects of Al doping and surface modification on the fabrication of a core-shell type ZnO/ZnS nanowires (NWs) and its structural, electrical, and photoluminescence (PL) properties. A systematic investigation for different concentrations of Al doping followed by surface modification with different thicknesses of ZnS layer was performed. Significant changes in the nature of PL spectra and electronic conductivity are observed and insight discussions are present. Structural characterization on the core-shell NWs reveals the successful fabrication of Al doped highly single crystalline ZnO core and polycrystalline ZnS shell with both ZnO and ZnS are of hexagonal wurtzite structure. Compared with the bare undoped ZnO NWs, Al doped core-shell ZnO/ZnS NWs exhibit two orders of magnitude improvement in the electronic conductivity and fivefold enhancement in the UV PL intensity. The Al doped core-shell ZnO/ZnS NWs shows an efficient improvement in the UV PL intensity than the undoped core-shell ZnO NWs. The obtained improvement in the PL result is explained on the basis of interfacial transfer of photogenerated charge carriers and modification of defects.

Dhara, Soumen; Imakita, Kenji; Giri, P. K.; Mizuhata, Minoru; Fujii, Minoru

2013-10-01

183

Order parameters from image analysis: a honeycomb example  

NASA Astrophysics Data System (ADS)

Honeybee combs have aroused interest in the ability of honeybees to form regular hexagonal geometric constructs since ancient times. Here we use a real space technique based on the pair distribution function (PDF) and radial distribution function (RDF), and a reciprocal space method utilizing the Debye-Waller Factor (DWF) to quantify the order for a range of honeycombs made by Apis mellifera ligustica. The PDFs and RDFs are fit with a series of Gaussian curves. We characterize the order in the honeycomb using a real space order parameter, OP 3 , to describe the order in the combs and a two-dimensional Fourier transform from which a Debye-Waller order parameter, u, is derived. Both OP 3 and u take values from [0, 1] where the value one represents perfect order. The analyzed combs have values of OP 3 from 0.33 to 0.60 and values of u from 0.59 to 0.69. RDF fits of honeycomb histograms show that naturally made comb can be crystalline in a 2D ordered structural sense, yet is more ‘liquid-like’ than cells made on ‘foundation’ wax. We show that with the assistance of man-made foundation wax, honeybees can manufacture highly ordered arrays of hexagonal cells. This is the first description of honeycomb utilizing the Debye-Waller Factor, and provides a complete analysis of the order in comb from a real-space order parameter and a reciprocal space order parameter. It is noted that the techniques used are general in nature and could be applied to any digital photograph of an ordered array.

Kaatz, Forrest H.; Bultheel, Adhemar; Egami, Takeshi

2008-11-01

184

Honeycomb-supported perovskite catalysts for high-temperature processes  

Microsoft Academic Search

Pechini route [US Patent No. 3,330,697 (1967)] was used for supporting perovskite-like systems on thin-wall corundum honeycomb support to prepare catalysts for high-temperature processes of methane combustion and selective oxidation into syngas. In this preparation, the surface of corundum monoliths walls was shown to be covered by strongly adhering porous perovskite layer formed by rounded crystals. At high temperatures when

Lyubov A Isupova; Galina M Alikina; Sergei V Tsybulya; Aleksei N Salanov; Nataliya N Boldyreva; Elena S Rusina; Izabella A Ovsyannikova; Vladimir A Rogov; Rimma V Bunina; Vladislav A Sadykov

2002-01-01

185

Honeycomb supported perovskite catalysts for ammonia oxidation processes  

Microsoft Academic Search

Pechini route (M.P. Pechini. U.S. Patent no. 3,330,697 (1967)) was used for supporting perovskite – like systems LaBO3 (B=Mn, Fe, Co, Ni, Cu) on thin-wall (0. 35mm) cordierite honeycomb support with low thermal expansion coefficient to prepare stable to thermal shocks supported catalysts for high-temperature processes of ammonia oxidation into NO in nitric acid production. In this preparation route, perovskites

L. A. Isupova; E. F. Sutormina; N. A. Kulikovskaya; L. M. Plyasova; N. A. Rudina; I. A. Ovsyannikova; I. A. Zolotarskii; V. A. Sadykov

2005-01-01

186

Superelastic NiTi honeycombs: fabrication and experiments  

Microsoft Academic Search

In this paper we demonstrate a new class of superelastic NiTi honeycomb structures. We have developed a novel brazing technique that has allowed us to fabricate Nitinol-based cellular structures with relative densities near 5%. Commercially available nickel-rich Nitinol strips were shape-set into corrugated form, stacked, and bonded at high temperature by exploiting a contact eutectic melting reaction involving pure niobium.

John A. Shaw; David S. Grummon; John Foltz

2007-01-01

187

Fabrication of prepackaged superalloy honeycomb Thermal Protection System (TPS) panels  

NASA Technical Reports Server (NTRS)

High temperature materials were surveyed, and Inconel 617 and titanium were selected for application to a honeycomb TPS configuration designed to withstand 2000 F. The configuration was analyzed both thermally and structurally. Component and full-sized panels were fabricated and tested to obtain data for comparison with analysis. Results verified the panel design. Twenty five panels were delivered to NASA Langley Research Center for additional evaluation.

Blair, W.; Meaney, J. E.; Rosenthal, H. A.

1985-01-01

188

Spin-Orbital Quantum Liquid on the Honeycomb Lattice  

NASA Astrophysics Data System (ADS)

The main characteristic of Mott insulators, as compared to band insulators, is to host low-energy spin fluctuations. In addition, Mott insulators often possess orbital degrees of freedom when crystal-field levels are partially filled. While in the majority of Mott insulators, spins and orbitals develop long-range order, the possibility for the ground state to be a quantum liquid opens new perspectives. In this paper, we provide clear evidence that the spin-orbital SU(4) symmetric Kugel-Khomskii model of Mott insulators on the honeycomb lattice is a quantum spin-orbital liquid. The absence of any form of symmetry breaking—lattice or SU(N)—is supported by a combination of semiclassical and numerical approaches: flavor-wave theory, tensor network algorithm, and exact diagonalizations. In addition, all properties revealed by these methods are very accurately accounted for by a projected variational wave function based on the ?-flux state of fermions on the honeycomb lattice at 1/4 filling. In that state, correlations are algebraic because of the presence of a Dirac point at the Fermi level, suggesting that the symmetric Kugel-Khomskii model on the honeycomb lattice is an algebraic quantum spin-orbital liquid. This model provides an interesting starting point to understanding the recently discovered spin-orbital-liquid behavior of Ba3CuSb2O9. The present results also suggest the choice of optical lattices with honeycomb geometry in the search for quantum liquids in ultracold four-color fermionic atoms.

Corboz, Philippe; Lajkó, Miklós; Läuchli, Andreas M.; Penc, Karlo; Mila, Frédéric

2012-10-01

189

Pressurized honeycombs as soft-actuators: a theoretical study.  

PubMed

The seed capsule of Delosperma nakurense is a remarkable example of a natural hygromorph, which unfolds its protecting valves upon wetting to expose its seeds. The beautiful mechanism responsible for this motion is generated by a specialized organ based on an anisotropic cellular tissue filled with a highly swelling material. Inspired by this system, we study the mechanics of a diamond honeycomb internally pressurized by a fluid phase. Numerical homogenization by means of iterative finite-element (FE) simulations is adapted to the case of cellular materials filled with a variable pressure fluid phase. Like its biological counterpart, it is shown that the material architecture controls and guides the otherwise unspecific isotropic expansion of the fluid. Deformations up to twice the original dimensions can be achieved by simply setting the value of input pressure. In turn, these deformations cause a marked change of the honeycomb geometry and hence promote a stiffening of the material along the weak direction. To understand the mechanism further, we also developed a micromechanical model based on the Born model for crystal elasticity to find an explicit relation between honeycomb geometry, swelling eigenstrains and elastic properties. The micromechanical model is in good qualitative agreement with the FE simulations. Moreover, we also provide the force-stroke characteristics of a soft actuator based on the pressurized anisotropic honeycomb and show how the internal pressure has a nonlinear effect which can result in negative values of the in-plane Poisson's ratio. As nature shows in the case of the D. nakurense seed capsule, cellular materials can be used not only as low-weight structural materials, but also as simple but convenient actuating materials. PMID:24966238

Guiducci, Lorenzo; Fratzl, Peter; Bréchet, Yves J M; Dunlop, John W C

2014-09-01

190

Aluminum Analysis.  

ERIC Educational Resources Information Center

Presents three problems based on the price of aluminum designed to encourage students to be cooperative and to use an investigative approach to learning. Students collect and synthesize information, analyze results, and draw conclusions. (AIM)

Sumrall, William J.

1998-01-01

191

Half-filled Kondo lattice on the honeycomb lattice  

NASA Astrophysics Data System (ADS)

The unique linear density of state around the Dirac points for the honeycomb lattice brings much novel features in strongly correlated models. Here we study the ground-state phase diagram of the Kondo lattice model on the honeycomb lattice at half-filling by using an extended mean-field theory. By treating magnetic interaction and Kondo screening on an equal footing, it is found that besides a trivial discontinuous first-order quantum phase transition between well-defined Kondo insulator and antiferromagnetic insulating state, there can exist a wide coexistence region with both Kondo screening and antiferromagnetic orders in the intermediate coupling regime. In addition, the stability of Kondo insulator requires a minimum strength of the Kondo coupling. These features are attributed to the linear density of state, which are absent in the square lattice. Furthermore, fluctuation effect beyond the mean-field decoupling is analyzed and the corresponding antiferromagnetic spin-density-wave transition falls into the O(3) universal class. Comparatively, we also discuss the Kondo necklace and the Kane-Mele-Kondo (KMK) lattice models on the same lattice. Interestingly, it is found that the topological insulating state is unstable to the usual antiferromagnetic ordered states at half-filling for the KMK model. The present work may be helpful for further study on the interplay between conduction electrons and the densely localized spins on the honeycomb lattice.

Zhong, Yin; Liu, Ke; Wang, Yu-Feng; Wang, Yong-Qiang; Luo, Hong-Gang

2013-05-01

192

Accordion-like honeycombs for tissue engineering of cardiac anisotropy.  

PubMed

Tissue-engineered grafts may be useful in myocardial repair; however, previous scaffolds have been structurally incompatible with recapitulating cardiac anisotropy. Here, we use microfabrication techniques to create an accordion-like honeycomb microstructure in poly(glycerol sebacate), which yields porous, elastomeric three-dimensional (3D) scaffolds with controllable stiffness and anisotropy. Accordion-like honeycomb scaffolds with cultured neonatal rat heart cells demonstrated utility through: (1) closely matched mechanical properties compared to native adult rat right ventricular myocardium, with stiffnesses controlled by polymer curing time; (2) heart cell contractility inducible by electric field stimulation with directionally dependent electrical excitation thresholds (p<0.05); and (3) greater heart cell alignment (p<0.0001) than isotropic control scaffolds. Prototype bilaminar scaffolds with 3D interconnected pore networks yielded electrically excitable grafts with multi-layered neonatal rat heart cells. Accordion-like honeycombs can thus overcome principal structural-mechanical limitations of previous scaffolds, promoting the formation of grafts with aligned heart cells and mechanical properties more closely resembling native myocardium. PMID:18978786

Engelmayr, George C; Cheng, Mingyu; Bettinger, Christopher J; Borenstein, Jeffrey T; Langer, Robert; Freed, Lisa E

2008-12-01

193

Accordion-Like Honeycombs for Tissue Engineering of Cardiac Anisotropy  

PubMed Central

Tissue engineered grafts may be useful in myocardial repair, however previous scaffolds have been structurally incompatible with recapitulating cardiac anisotropy. Utilizing microfabrication techniques, a novel accordion-like honeycomb microstructure was rendered in poly(glycerol sebacate) to yield porous, elastomeric 3-D scaffolds with controllable stiffness and anisotropy. Accordion-like honeycomb scaffolds with cultured neonatal rat heart cells demonstrated utility via: (1) closely matched mechanical properties compared to native adult rat right ventricular myocardium, with stiffnesses controlled by polymer curing time; (2) heart cell contractility inducible by electric field stimulation with directionally-dependent electrical excitation thresholds (p<0.05); and (3) greater heart cell alignment (p<0.0001) than isotropic control scaffolds. Prototype bilaminar scaffolds with 3-D interconnected pore networks yielded electrically excitable grafts with multi-layered neonatal rat heart cells. Accordion-like honeycombs can thus overcome principal structural-mechanical limitations of previous scaffolds, promoting the formation of grafts with aligned heart cells and mechanical properties more closely resembling native myocardium.

Engelmayr, George C.; Cheng, Mingyu; Bettinger, Christopher J.; Borenstein, Jeffrey T.; Langer, Robert; Freed, Lisa E.

2008-01-01

194

Pressure adaptive honeycomb: a new adaptive structure for aerospace applications  

NASA Astrophysics Data System (ADS)

A new type of adaptive structure is presented that relies on pressurized honeycomb cells that extent a significant length with respect to the plane of the hexagons. By varying the pressure inside each of the cells, the stiffness can be altered. A variable stiffness in combination with an externally applied force field results in a fully embedded pressure adaptive actuator that can yield strains well beyond the state-of-the-art in adaptive materials. The stiffness change as a function of the pressure is modeled by assigning an equivalent material stiffness to the honeycomb walls that accounts for both the inherent material stiffness as the pressure-induced stiffness. A finite element analysis of a beam structure that relies on this model is shown to correlate well to experimental results of a three-point bend test. To demonstrate the concept of embedded pressure adaptive honeycomb, an wind tunnel test article with adaptive flap has been constructed and tested in a low speed wind tunnel. It has been proven that by varying the cell pressure the flap changed its geometry and subsequently altered the lift coefficient.

Vos, Roelof; Barrett, Ron

2010-03-01

195

Effective electromagnetic properties of honeycomb substrate coated with dielectric or magnetic layer  

NASA Astrophysics Data System (ADS)

Effective electromagnetic properties of aramid honeycomb board coated with a layer of multi-wall carbon nanotube or iron flakes composites were measured with waveguide method from 4 to 12 GHz. It was proved that homogenization theory could predict the effective permittivity or permeability of the honeycomb composites with good accuracy. The coated honeycomb composites of relatively high permittivity and permeability could potentially be used to develop dielectric or magnetic substrate for shielding layer or absorbing structures working at microwave frequencies.

Liu, L.; Fan, C. Z.; Zhu, N. B.; Zhao, Z. Y.; Liu, R. P.

2014-05-01

196

Experimental investigation into honeycomb heat sinks incorporating varying size slots for enhanced heat transfer  

Microsoft Academic Search

In this experimental investigation novel honeycomb heat sink designs that incorporate slots of varying length are presented. Thermal and hydrodynamic performance comparisons are made for a longitudinally-finned heat sink, a wavy wall heat sink of the same geometric dimensions, a closed channel honeycomb heat sink and a number of honeycomb heat sinks with different length (3mm, 6mm and 13mm) of

Domhnaill Hernon; Alcatel-Lucent Ireland

2010-01-01

197

Water ingress detection in honeycomb sandwich panels by passive infrared thermography using a high-resolution thermal imaging camera  

NASA Astrophysics Data System (ADS)

Water ingress in honeycomb structures is of great concern for the civil and military aerospace industries. Pressure and temperature variations during take-off and landing produce considerable stress on aircraft structures, promoting moisture ingress (by diffusion through fibers or by direct ingress through voids, cracks or unsealed joints) into the core. The presence of water (or other fluids such as kerosene, hydraulic fluid and de-icing agents) in any of its forms (gas vapor, liquid or ice) promotes corrosion, cell breakage, and induce composite layer delaminations and skin disbonds. In this study, testing specimens were produced from unserviceable parts from military aircraft. In order to simulate atmospheric conditions during landing, selected core areas were filled with measured quantities of water and then frozen in a cold chamber. The specimens were then removed from the chamber and monitored for over 20 minutes as they warm up using a cooled high-resolution infrared camera. Results have shown that detection and quantification of water ingress on honeycomb sandwich structures by passive infrared thermography is possible using a HD mid-wave infrared cameras for volumes of water as low as 0.2 ml and from a distance as far as 20 m from the target.

Ibarra-Castanedo, C.; Brault, L.; Marcotte, F.; Genest, M.; Farley, V.; Maldague, X.

2012-05-01

198

Effects of service environments on aluminum-brazed titanium (ABTi)  

NASA Technical Reports Server (NTRS)

Aluminum brazed titanium (ABTi) structures were evaluated during prolonged exposure to extreme environments: elevated temperature exposure to airline service fluids, hydraulic fluid, and seawater, followed by laboratory corrosion tests. Solid-face and perforated face honeycomb sandwich panel specimens, stressed panel assemblies, and faying surface brazed joints were tested. The corrosion resistance of ABTi is satisfactory for commercial airline service. Unprotected ABTi proved inherently resistant to attack by all of the extreme service aircraft environments except: seawater at 700 K (800 F) and above, dripping phosphate ester hydraulic fluid at 505 K (450 F), and a marine environment at ambient temperature. The natural oxides and deposits present on titanium surfaces in airline service provide protection against hot salt corrosion pitting. Coatings are required to protect titanium dripping phosphate ester fluid at elevated temperatures and to protect exposed acoustic honeycomb parts against corrosion in a marine environment.

Cotton, W. L.

1978-01-01

199

Water Vapor Desorption Characteristics of Honeycomb Type Sorption Element Composed of Organic Sorbent  

NASA Astrophysics Data System (ADS)

This paper describes the water vapor desorption characteristics of honeycomb shape type sorbent element containing new organic sorbent of the bridged complex of sodium polyacrylate. The transient experiments in which the dry air was passed into the honeycomb type sorbent element sorbed water vapor were carried out under various conditions of air velocity, temperature, relative humidity and honeycomb length. The obtained data for desorption process were compared with those for sorption process. Finally, Sherwood number of mass transfer of the organic sorbent for desorption process was derived in terms of Reynolds number, modified Stefan number and non-dimensional honeycomb length.

Inaba, Hideo; Kida, Takahisa; Horibe, Akihiko; Kaneda, Makoto; Okamoto, Tamio; Seo, Jeong-Kyun

200

Ising antiferromagnets on honeycomb and square lattices in the critical magnetic field  

NASA Astrophysics Data System (ADS)

The important properties of the Ising antiferromagnets on honeycomb lattice and square lattice in the critical magnetic field B c ( B c = 3| J| for honeycomb lattice and B c = 4| J| for square lattice with coupling constant J) are investigated by evaluating exactly all their possible ground states on L × 2 L honeycomb lattices ( L = 4 ˜ 14) and L × L square lattices ( L = 4 ˜ 16) with cylindrical boundary conditions. In particular, the properties of the honeycomb-lattice Ising antiferromagnet in the critical magnetic field B c are unveiled for the first time.

Kim, Seung-Yeon

2012-12-01

201

Buckling Testing and Analysis of Honeycomb Sandwich Panel Arc Segments of a Full-Scale Fairing Barrel: Comparison of In- and Out-of-Autoclave Facesheet Configurations  

NASA Technical Reports Server (NTRS)

Four honeycomb sandwich panels, representing 1/16th arc segments of a 10-m diameter barrel section of the Heavy Lift Launch Vehicle, were manufactured and tested under the NASA Composites for Exploration and the NASA Constellation Ares V programs. Two configurations were chosen for the panels: 6-ply facesheets with 1.125 in. honeycomb core and 8-ply facesheets with 1.0 in. honeycomb core. Additionally, two separate carbon fiber/epoxy material systems were chosen for the facesheets: in-autoclave IM7/977-3 and out-of-autoclave T40-800b/5320-1. Smaller 3 ft. by 5 ft. panels were cut from the 1/16th barrel sections and tested under compressive loading. Furthermore, linear eigenvalue and geometrically nonlinear finite element analyses were performed to predict the compressive response of each 3 ft. by 5 ft. panel. To improve the robustness of the geometrically nonlinear finite element model, measured surface imperfections were included in the geometry of the model. Both the linear and nonlinear models yielded good qualitative and quantitative predictions. Additionally, it was correctly predicted that the panel would fail in buckling prior to failing in strength. Furthermore, several imperfection studies were performed to investigate the influence of geometric imperfections, fiber angle misalignments, and three-dimensional effects on the compressive response of the panel.

Pineda, Evan Jorge; Myers, David E.; Kosareo, Daniel N.; Zalewski, Bart F.; Kellas, Sotiris; Dixon, Genevieve D.; Krivanek, Thomas M.; Gyekenyesi, Thomas G.

2014-01-01

202

49 CFR 587.15 - Verification of aluminum honeycomb crush strength.  

Code of Federal Regulations, 2013 CFR

...from each of the four locations. The other two samples are retained for future verification, if necessary. (b) Sample size. Samples of the following size are used for testing. The length is 150 mm (5.9 in) ±6 mm (0.24 in),...

2013-10-01

203

Evaluation of a bi-directional aluminum honeycomb impact limiter design  

Microsoft Academic Search

A 120 Ton shipping cask is being developed for the on-site shipment of dry spent fuel at the Idaho National Engineering Laboratory. Impact limiters were incorporated in the cask design to limit the inertial load of the package and its contents during the hypothetical 9-meter (30-foot) drop accident required by 10CFR71. The design process included: (1) a series of static

Doman

1995-01-01

204

49 CFR 587.15 - Verification of aluminum honeycomb crush strength.  

Code of Federal Regulations, 2012 CFR

...from each of the four locations. The other two samples are retained for future verification, if necessary. (b) Sample size. Samples of the following size are used for testing. The length is 150 mm (5.9 in) ±6 mm (0.24 in),...

2012-10-01

205

Aluminum alloy  

NASA Technical Reports Server (NTRS)

This invention relates to aluminum alloys, particularly to aluminum-copper-lithium alloys containing at least about 0.1 percent by weight of indium as an essential component, which are suitable for applications in aircraft and aerospace vehicles. At least about 0.1 percent by weight of indium is added as an essential component to an alloy which precipitates a T1 phase (Al2CuLi). This addition enhances the nucleation of the precipitate T1 phase, producing a microstructure which provides excellent strength as indicated by Rockwell hardness values and confirmed by standard tensile tests.

Blackburn, Linda B. (inventor); Starke, Edgar A., Jr. (inventor)

1989-01-01

206

Aluminum doping of poly(vinylidene fluoride with trifluoroethylene) copolymer  

NASA Astrophysics Data System (ADS)

The interface between aluminum and crystalline copolymer thin film of vinylidene fluoride (70%) with trifluoroethylene (30%) [PVDF-TrFE] has been studied. The ratio of carbon 1s and aluminum 2p core level photoemission peak intensities changes little with increasing emission angle after deposition of 5 Å aluminum on the surface of PVDF-TrFE. This indicates that the distribution of aluminum atoms in the copolymer film is quite uniform in the near surface region and that the interface between PVDF-TrFE and aluminum is not abrupt. There is evidence for changes in photohole screening with aluminum doping within the polymer film.

Xu, B.; Borca, C. N.; Ducharme, S.; Sorokin, A. V.; Dowben, P. A.; Fridkin, V. M.; Palto, S. P.; Petukhova, N. N.; Yudin, S. G.

2001-01-01

207

Aluminum-Induced photoluminescence red shifts in core-shell GaAs/Al(x)Ga(1-x)As nanowires.  

PubMed

We report a new phenomenon related to Al-induced carrier confinement at the interface in core-shell GaAs/Al(x)Ga(1-x)As nanowires grown using metal-organic vapor phase epitaxy with Au as catalyst. All Al(x)Ga(1-x)As shells strongly passivated the GaAs nanowires, but surprisingly the peak photoluminescence (PL) position and the intensity from the core were found to be a strong function of Al composition in the shell at low temperatures. Large and systematic red shifts of up to ~66 nm and broadening in the PL emission from the GaAs core were observed when the Al composition in the shell exceeded 3%. On the contrary, the phenomenon was observed to be considerably weaker at the room temperature. Cross-sectional transmission electron microscopy reveals Al segregation in the shell along six Al-rich radial bands displaying a 3-fold symmetry. Time-resolved PL measurements suggest the presence of indirect electron-hole transitions at the interface at higher Al composition. We discuss all possibilities including a simple shell-core-shell model using simulations where the density of interface traps increases with the Al content, thus creating a strong local electron confinement. The carrier confinement at the interface is most likely related to Al inhomogeneity and/or Al-induced traps. Our results suggest that a low Al composition in the shell is desirable in order to achieve ideal passivation in GaAs nanowires. PMID:23898926

Dhaka, Veer; Oksanen, Jani; Jiang, Hua; Haggren, Tuomas; Nykänen, Antti; Sanatinia, Reza; Kakko, Joona-Pekko; Huhtio, Teppo; Mattila, Marco; Ruokolainen, Janne; Anand, Srinivasan; Kauppinen, Esko; Lipsanen, Harri

2013-08-14

208

Quarter-Filled Honeycomb Lattice with a Quantized Hall Conductance  

NASA Astrophysics Data System (ADS)

We study a generic two-dimensional hopping model on a honeycomb lattice with strong spin-orbit coupling, without the requirement that the half-filled lattice be a Topological Insulator. For quarter-(or three-quarter) filling, we show that a state with a quantized Hall conductance generically arises in the presence of a Zeeman field of sufficient strength. We discuss the influence of Hubbard interactions and argue that spontaneous ferromagnetism (which breaks time-reversal) will occur, leading to a quantized anomalous Hall effect. G. Murthy, E. Shimshoni, R. Shankar, and H. A. Fertig, arxiv:1108.2010[cond-mat.mes-hall

Shimshoni, Efrat; Murthy, Ganpathy; Shankar, Ramamurti; Fertig, Herbert

2012-02-01

209

Artificial honeycomb lattices for electrons, atoms and photons.  

PubMed

Artificial honeycomb lattices offer a tunable platform for studying massless Dirac quasiparticles and their topological and correlated phases. Here we review recent progress in the design and fabrication of such synthetic structures focusing on nanopatterning of two-dimensional electron gases in semiconductors, molecule-by-molecule assembly by scanning probe methods and optical trapping of ultracold atoms in crystals of light. We also discuss photonic crystals with Dirac cone dispersion and topologically protected edge states. We emphasize how the interplay between single-particle band-structure engineering and cooperative effects leads to spectacular manifestations in tunnelling and optical spectroscopies. PMID:24002076

Polini, Marco; Guinea, Francisco; Lewenstein, Maciej; Manoharan, Hari C; Pellegrini, Vittorio

2013-09-01

210

Water intrusion in thin-skinned composite honeycomb sandwich structures  

NASA Technical Reports Server (NTRS)

Thin-skinned composite honeycomb sandwich structures from the trailing edge of the U.S. Army's Apache and Chinook helicopters have been tested to ascertain their susceptibility to water intrusion as well as such intrusions' effects on impact damage and cyclic loading. Minimum-impact and fatigue conditions were determined which would create microcracks sufficiently large to allow the passage of water through the skins; damage sufficient for this to occur was for some skins undetectable under a 40X-magnification optical microscope. Flow rate was a function of moisture content, damage, applied strain, and pressure differences.

Jackson, Wade C.; O'Brien, T. Kevin

1988-01-01

211

Emission of an intense electron beam from a ceramic honeycomb  

NASA Astrophysics Data System (ADS)

Inserting a slab of honeycomb ceramic in front of the emitting surface of a large-area cathode improves the electron beam emission uniformity, decreases the beam current rise and fall times, and maintains a more constant diode impedance. Moreover, changing the cathode material from velvet to carbon fiber achieved a more robust cathode that starts to emit at a higher electric field without a degradation in beam uniformity. In addition, an 80% reduction in the postshot diode pressure was also observed when gamma alumina was deposited on the ceramic. A possible explanation is that reabsorption and recycling of adsorbed gases takes place.

Friedman, M.; Myers, M.; Hegeler, F.; Swanekamp, S. B.; Sethian, J. D.; Ludeking, L.

2003-01-01

212

Interactions and phase transitions on graphene's honeycomb lattice.  

PubMed

The low-energy theory of interacting electrons on graphene's two-dimensional honeycomb lattice is derived and discussed. In particular, the Hubbard model in the large-N limit is shown to have a semimetal-antiferromagnetic insulator quantum critical point in the universality class of the Gross-Neveu model. The same equivalence is conjectured to hold in the physical case N=2, and its consequences for various physical quantities are examined. The effects of the long-range Coulomb interaction and the magnetic field are discussed. PMID:17155272

Herbut, Igor F

2006-10-01

213

Aluminum Cans  

NSDL National Science Digital Library

In this data analysis activity students investigate data in connection with recyclable materials and develop plans to help the environment. Students collect data about aluminum can usage and graph that data in a line plot. The lesson includes student worksheet and extension suggestions.

2008-01-01

214

Cost effective honeycomb and multi-layer insulation debris shields for unmanned spacecraft  

Microsoft Academic Search

Ways to improve the tolerance of unmanned spacecraft to hypervelocity impact are presented. Two new honeycomb and multi-layer insulation (MLI) shields were defined: (1) double honeycomb, and (2) enhanced or toughened MLI (with additional Kevlar 310 and\\/or Betacloth layers). Following hypervelocity impact testing, a new ballistic limit threshold was defined, based on rear facesheet perforation and witness plate damage characteristics.

Robert J. Turner; Emma A. Taylor; J. Anthony M. McDonnell; Hedley Stokes; Peter Marriott; Jenny Wilkinson; David J. Catling; Rade Vignjevic; Lucy Berthoud; Michel Lambert

2001-01-01

215

Synthesis, field emission and humidity sensing characteristics of honeycomb-like CuO  

NASA Astrophysics Data System (ADS)

Large-scale CuO honeycombs were synthesized via two-step electrochemical deposition. The morphology and crystal structure of the as-grown CuO honeycombs were characterized by scanning electron microscopy (SEM), x-ray diffraction and transparent electron microscopy. From the SEM images, we can find that the honeycombs were composed of well-oriented nanowires. The formation mechanism of the nanostructures was discussed. Field emission (FE) measurements demonstrated that the CuO honeycombs possessed good performance with a turn-on field of 6-7 V µm-1 and a field enhancement factor of 1361, which have promising application as a competitive cathode material in FE microelectronic devices. Due to the high surface-to-volume ratio, the humidity sensitive characteristic of the CuO honeycomb film has been investigated, which exhibits that it also has potential application in an effective and high performance humidity sensor.

Xu, Jianwen; Yu, Ke; Wu, Jin; Shang, Dejian; Li, Lijun; Xu, Yu'e.; Zhu, Ziqiang

2009-04-01

216

Considerations for the installation of honeycomb and screens to reduce wind-tunnel turbulence  

NASA Technical Reports Server (NTRS)

Tests were conducted on a half-scale model representing a 0.914-m (3.0-ft) square stream tube of the flow through the fourth corner and settling chamber of the Langley 8-Foot Transonic Pressure Tunnel. The model included the tube cooler 45 degree turning vanes, and the turbulence reduction screens and honeycomb, which were the subject of the tests. Hot-wire measurements of the turbulence reduction for various combinations of screens and honeycomb were made at various duct speeds. Of the four sizes of honeycomb cells tested, none were found to have a superior performance advantage. The effectiveness of screens and honeycomb in reducing turbulence is greatly affected by relatively minor physical damage; therefore, extreme care must be exercised in installing and maintaining honeycomb or screens if the turbulence reduction performance is to be maintained.

Scheiman, J.

1981-01-01

217

Impact response of integrated hollow core sandwich composite panels  

Microsoft Academic Search

This paper deals with an innovative integrated hollow (space) E-glass\\/epoxy core sandwich composite construction that possesses several multi-functional benefits in addition to the providing lightweight and bending stiffness advantages. In comparison with traditional foam and honeycomb cores, the integrated space core provides a means to route wires\\/rods, embed electronic assemblies, and store fuel and fire-retardant foam, among other conceivable benefits.

U. K Vaidya; M. V Hosur; D Earl; S Jeelani

2000-01-01

218

First-principles study of zinc oxide honeycomb structures  

NASA Astrophysics Data System (ADS)

We present a first-principles study of the atomic, electronic, and magnetic properties of two-dimensional (2D), single and bilayer ZnO in honeycomb structure and its armchair and zigzag nanoribbons. In order to reveal the dimensionality effects, our study includes also bulk ZnO in wurtzite, zincblende, and hexagonal structures. The stability of 2D ZnO, its nanoribbons and flakes are analyzed by phonon frequency, as well as by finite temperature ab initio molecular-dynamics calculations. 2D ZnO in honeycomb structure and its armchair nanoribbons are nonmagnetic semiconductors but acquire net magnetic moment upon the creation of zinc-vacancy defect. Zigzag ZnO nanoribbons are ferromagnetic metals with spins localized at the oxygen atoms at the edges and have high spin polarization at the Fermi level. However, they change to nonmagnetic metal upon termination of their edges with hydrogen atoms. From the phonon calculations, the fourth acoustical mode specified as twisting mode is also revealed for armchair nanoribbon. Under tensile stress the nanoribbons are deformed elastically maintaining honeycomblike structure but yield at high strains. Beyond yielding point honeycomblike structure undergo a structural change and deform plastically by forming large polygons. The variation in the electronic and magnetic properties of these nanoribbons have been examined under strain. It appears that plastically deformed nanoribbons may offer a new class of materials with diverse properties.

Topsakal, M.; Cahangirov, S.; Bekaroglu, E.; Ciraci, S.

2009-12-01

219

Material Model Evaluation of a Composite Honeycomb Energy Absorber  

NASA Technical Reports Server (NTRS)

A study was conducted to evaluate four different material models in predicting the dynamic crushing response of solid-element-based models of a composite honeycomb energy absorber, designated the Deployable Energy Absorber (DEA). Dynamic crush tests of three DEA components were simulated using the nonlinear, explicit transient dynamic code, LS-DYNA . In addition, a full-scale crash test of an MD-500 helicopter, retrofitted with DEA blocks, was simulated. The four material models used to represent the DEA included: *MAT_CRUSHABLE_FOAM (Mat 63), *MAT_HONEYCOMB (Mat 26), *MAT_SIMPLIFIED_RUBBER/FOAM (Mat 181), and *MAT_TRANSVERSELY_ANISOTROPIC_CRUSHABLE_FOAM (Mat 142). Test-analysis calibration metrics included simple percentage error comparisons of initial peak acceleration, sustained crush stress, and peak compaction acceleration of the DEA components. In addition, the Roadside Safety Verification and Validation Program (RSVVP) was used to assess similarities and differences between the experimental and analytical curves for the full-scale crash test.

Jackson, Karen E.; Annett, Martin S.; Fasanella, Edwin L.; Polanco, Michael A.

2012-01-01

220

Experimental study of aluminium honeycomb behaviour under dynamic multiaxial loading  

NASA Astrophysics Data System (ADS)

Split Hopkinson Pressure Bar system (SHPB) with large-diameter and Nylon bars introducing a shear-compression loading device is used in order to investigate the dynamic behaviour of aluminium honeycomb under multiaxial loadings conditions. All shear-compression configurations including the loading angle variation from 0? to 60? are performed with an impact velocity of about 15m/s. The adapted SHPB system with the device are validated numerically and a phenomenon of separation between the input bar and the input beveled bar is observed. Numerical results suggest that this phenomenon provides a cutting of the reflected wave. An electro optical extensometer is employed in experiments. A good agreement between the numerical elastic waves and the experimental ones is obtained. Experimental results show a significant effect of the loading angle on the apparent stress-strain curves. The initial peak value and the plateau stress decrease with the increase of the loading angle. The combined shear-compression device with an enhancement at the alignment set-up provides efficient results for samples dynamically loaded. This device will be used to investigate the influence of the in-plane orientation angle on the deformation mechanisms and multiaxial behaviour of aluminium honeycomb under dynamic and quasi-static loading conditions.

Tounsi, R.; Zouari, B.; Chaari, F.; Haugou, G.; Markiewicz, E.; Dammak, F.

2012-08-01

221

Thermodynamics of the two-dimensional Heisenberg classical honeycomb lattice  

NASA Astrophysics Data System (ADS)

In this article we adapt a previous work concerning the two-dimensional (2D) Heisenberg classical square lattice [Physica B 245, 263 (1998)] to the case of a honeycomb lattice. Closed-form expressions of the main thermodynamic functions of interest are derived in the zero-field limit. Notably, near absolute zero (i.e., the critical temperature), we derive the values of the critical exponents ?=0, ?=-1, ?=3, and ?=1, as for the square lattice, thus proving their universal character. A very simple model allows one to give a good description of the low-temperature behaviors of the product ?T. For a 2D-compensated antiferromagnet, we derive simple relations between the characteristics of the maximum of the susceptibility curve T(?max) and ?max and the involved exchange energies. Therefore, owing to the knowledge of T(?max) and ?max, one can directly obtain the respective values of these energies. Finally, we show that the theoretical model allows one to fit correctly experimental susceptibility data of the recently synthetized compound Mn2(bpm)(ox)2.6H2O characterized by a 2D classical honeycomb lattice (where ``bpm'' and ``ox'' are the abbreviations for the ligands bipyrimidine and oxalate, respectively).

Curély, Jacques; Lloret, Francesc; Julve, Miguel

1998-11-01

222

Correlated metallic state in honeycomb lattice: Orthogonal Dirac semimetal  

NASA Astrophysics Data System (ADS)

A novel gapped metallic state coined orthogonal Dirac semimetal is proposed in the honeycomb lattice in terms of Z2 slave-spin representation of Hubbard model. This state corresponds to the disordered phase of slave spin and has the same thermodynamical and transport properties as a usual Dirac semimetal but its singe-particle excitation is gapped and has nontrivial topological order due to the Z2 gauge structure. The quantum phase transition from this orthogonal Dirac semimetal to the usual Dirac semimetal is described by a mean-field decoupling with complementary fluctuation analysis and its criticality falls into the universality class of 2+1D Ising model while a large anomalous dimension for the physical electron is found at quantum critical point (QCP), which could be considered as a fingerprint of our fractionalized theory when compared to other nonfractionalized approaches. As byproducts, a path integral formalism for the Z2 slave-spin representation of Hubbard model is constructed and possible relations to other approaches and the sublattice pairing states, which has been argued to be a promising candidate for gapped spin liquid state found in the numerical simulation, are briefly discussed. Additionally, when spin-orbit coupling is considered, the instability of orthogonal Dirac semimetal to the fractionalized quantum spin Hall insulator (fractionalized topological insulator) is also expected. We hope the present work may be helpful for future studies in Z2 slave-spin theory and related non-Fermi-liquid phases in honeycomb lattice.

Zhong, Yin; Liu, Ke; Wang, Yong-Qiang; Luo, Hong-Gang

2012-10-01

223

Coulomb correlations in the honeycomb lattice: Role of translation symmetry  

NASA Astrophysics Data System (ADS)

The effect of Coulomb correlations in the half-filled Hubbard model of the honeycomb lattice is studied within the dynamical cluster approximation (DCA) combined with exact diagonalization (ED) and continuous-time quantum Monte Carlo (QMC), for unit cells consisting of six-site rings. The important difference between this approach and the previously employed cluster dynamical mean-field theory (CDMFT) is that DCA preserves the translation symmetry of the system, while CDMFT violates this symmetry. As the Dirac cones of the honeycomb lattice are the consequence of perfect long-range order, DCA yields semimetallic behavior at small on-site Coulomb interactions U, whereas CDMFT gives rise to a spurious excitation gap even for very small U. This basic difference between the two cluster approaches is found regardless of whether ED or QMC is used as the impurity solver. At larger values of U, the lack of translation symmetry becomes less important, so that the CDMFT reveals a Mott gap, in qualitative agreement with large-scale QMC calculations. In contrast, the semimetallic phase obtained in DCA persists even at U values where CDMFT and large-scale QMC consistently show Mott-insulating behavior.

Liebsch, Ansgar; Wu, Wei

2013-05-01

224

Parametric results for heat transfer across honeycomb sandwich panels  

NASA Technical Reports Server (NTRS)

The problem of heat transfer across honeycomb sandwich panels is theoretically investigated. The basic objective is to predict the rear surface temperature as a function of time when the front surface is exposed to a prescribed heat flux; the faces are bounded by planar sheets so that the air circulation in the honeycomb cells is bounded and contained. The influence of the air circulation on convective heat transfer is explicitly included. Drawing upon previous investigators' results that indicated various relations for the Nusselt numbers vs Rayleigh numbers in different regimes of the aspect ratio (defined as the ratio of the cell height to cell width), parametric calculations are performed to predict the rear surface temperatures. Chemical degradation of the material, especially the glue holding the face material on the end, is important but has not yet been included. The results indicate that decreasing the cell width, increasing the cell wall thickness and increasing the cell height all have beneficial effects upon the heat transfer; i.e., all of these variations reduce rear surface temperature for a given time for a prescribed heat flux on the front surface.

Ramohalli, K.; Sahakian, J.

1981-01-01

225

The Colored Hofstadter Butterfly for the Honeycomb Lattice  

NASA Astrophysics Data System (ADS)

We rely on a recent method for determining edge spectra and we use it to compute the Chern numbers for Hofstadter models on the honeycomb lattice having rational magnetic flux per unit cell. Based on the bulk-edge correspondence, the Chern number ? _H is given as the winding number of an eigenvector of a 2 × 2 transfer matrix, as a function of the quasi-momentum kin (0,2? ) . This method is computationally efficient (of order {O}(n^4) in the resolution of the desired image). It also shows that for the honeycomb lattice the solution for ? _H for flux p/q in the r -th gap conforms with the Diophantine equation r=? _H\\cdot p+ s\\cdot q , which determines ? _Hmod q . A window such as ? _Hin (-q/2,q/2) , or possibly shifted, provides a natural further condition for ? _H , which however turns out not to be met. Based on extensive numerical calculations, we conjecture that the solution conforms with the relaxed condition ? _Hin (-q,q).

Agazzi, A.; Eckmann, J.-P.; Graf, G. M.

2014-05-01

226

Assessment of a novel neutron tomography instrument and other nondestructive technologies for the characterization of degradation in honeycomb composites  

NASA Astrophysics Data System (ADS)

The feasibility of developing a nondestructive evaluation technique (NDE) or combination of techniques capable of characterizing degradation in honeycomb composites was investigated. To enable the determination of the exact location of water ingress inside a honeycomb composite structure, a novel neutron tomography instrument (NTI) was designed and developed at RMC. The system represents the only NTI available in Canada and allows a range of objects to be investigated including honeycomb coupons and complete CF 188 rudders. In order to produce 3D volumetric reconstructions of sufficient quality to assess the location of water, the system was optimized in terms of optics, spatial resolution and signal-to-noise ratio (SNR). An imaging test object was designed to enable the quantitative measurement of the spatial resolution in 2D images and 3D reconstructions, filling a gap in the current neutron imaging standards. Several noise reduction filters were applied to 2D and 3D images produced by the NTI, which improved the spatial resolution and SNR. Appropriate coupons that were purposely degraded to represent honeycomb composites subjected to water ingress were designed, constructed and tested. To produce coupons with different degrees of degradation in the skin to core bond, varying numbers of freeze-thaw cycles were used. Destructive flat-wise tension tests were then performed to evaluate the coupons and the results showed a strong first-order linear decay relationship between the number of freeze-thaw cycles and the filet bond strength. The method developed to reliably degrade the filet bond, provides a more appropriate degradation mechanism compared to other available methods for producing degraded coupons. The degraded coupons were subsequently inspected using several adapted NDE techniques: neutron tomography, infrared thermography, through-transmission ultrasonics and acoustic bond testing. Neutron tomography was capable of detailing the exact location of water in the composite using 3D volumetric reconstructions and individual axial slices. Both through-transmission ultrasonics and acoustic bond testing were shown to be capable of detecting degradation in the test coupons. Finally, development of NDE techniques towards the reliable quantification of varying degrees of adhesive degradation was recommended.

Hungler, P. C.

227

Recycling of automotive aluminum  

Microsoft Academic Search

With the global warming of concern, the secondary aluminum stream is becoming an even more important component of aluminum production and is attractive because of its economic and environmental benefits. In this work, recycling of automotive aluminum is reviewed to highlight environmental benefits of aluminum recycling, use of aluminum alloys in automotive applications, automotive recycling process, and new technologies in

Jirang CUI; Hans J. ROVEN

2010-01-01

228

Directed self-assembly of large scaffold-free multi-cellular honeycomb structures.  

PubMed

A significant challenge to the field of biofabrication is the rapid construction of large three-dimensional (3D) living tissues and organs. Multi-cellular spheroids have been used as building blocks. In this paper, we create large multi-cellular honeycomb building blocks using directed self-assembly, whereby cell-to-cell adhesion, in the context of the shape and obstacles of a micro-mold, drives the formation of a 3D structure. Computer-aided design, rapid prototyping and replica molding were used to fabricate honeycomb-shaped micro-molds. Nonadhesive hydrogels cast from these micro-molds were equilibrated in the cell culture medium and seeded with two types of mammalian cells. The cells settled into the honeycomb recess were unable to attach to the nonadhesive hydrogel and so cell-to-cell adhesion drove the self-assembly of a large multi-cellular honeycomb within 24 h. Distinct morphological changes occurred to the honeycomb and its cells indicating the presence of significant cell-mediated tension. Unlike the spheroid, whose size is constrained by a critical diffusion distance needed to maintain cell viability, the overall size of the honeycomb is not limited. The rapid production of the honeycomb building unit, with its multiple rings of high-density cells and open lumen spaces, offers interesting new possibilities for biofabrication strategies. PMID:21828905

Tejavibulya, Nalin; Youssef, Jacquelyn; Bao, Brian; Ferruccio, Toni-Marie; Morgan, Jeffrey R

2011-09-01

229

The Morphology and Functions of Articular Chondrocytes on a Honeycomb-Patterned Surface  

PubMed Central

The present study investigated the potential of a novel micropatterned substrate for neocartilage formation. Articular chondrocytes were cultured on poly(?-caprolactone) materials whose surfaces were either flat or honeycomb-patterned. The latter was prepared using a novel self-organization technique, while the former, was prepared by spin-coating. The chondrocytes attached and proliferated on both surfaces. On the honeycomb films, chondrocytes were found at the top surface and encased within the 10??m pores. Meanwhile, chondrocytes on the spin-coated surface flattened out. Accumulation of DNA and keratin sulphate was comparatively higher on the honeycomb films within the first 7 days. At their respective peaks, DNA concentration increased on the honeycomb and flat surfaces by approximately 210% and 400% of their day 1 values, respectively. However, cultures on the flat surface took longer to peak. Extracellular Matrix (ECM) concentrations peaked at 900% and 320% increases for the honeycomb and flat cultures. Type II collagen was upregulated on the honeycomb and flat surfaces by as much as 28% and 25% of their day 1 values, while aggrecan was downregulated with time, by 3.4% and 7.4%. These initial results demonstrate the potential usefulness of honeycomb-based scaffolds during early cultures neocartilage and soft tissue engineering.

Eniwumide, Joshua O.; Tanaka, Masaru; Nagai, Nobuhiro; Morita, Yuka; de Bruijn, Joost; Yamamoto, Sadaaki; Onodera, Shin; Kondo, Eiji; Yasuda, Kazunori; Shimomura, Masatsugu

2014-01-01

230

Pulsed laser deposition of ZnO honeycomb structures on metal catalyst prepatterned Si substrates  

NASA Astrophysics Data System (ADS)

Honeycomb structures with controllable size are of great interest for many potential applications such as containers for microencapsulating and controlled delivery, gas sensors, catalysis and photonic crystals and devices. A ZnO honeycomb structure was successfully fabricated on metal prepatterned Si substrates by the nanosphere lithography method combined with the pulsed laser deposition (PLD) technique. SEM images show that a Pt template gives rise to the regular ZnO honeycomb structure which has the same cell size as the diameter of polystyrene (PS) spheres; a Au template also leads to honeycomb structure but the average cell size is smaller than the diameter of PS spheres; while Ag fails to generate a ZnO honeycomb structure. The different ZnO patterns are related to the morphology and distribution of the metal nanoparticles when processed at 600 °C in a PLD vacuum chamber. The growth mechanism of a ZnO honeycomb structure is attributed to the catalysis of liquid-phase metal nanoparticles. X-ray diffraction measurements indicate that ZnO on all metal templates have the (0 0 2) preferential orientation. The photoluminescence properties of the ZnO patterns were also examined and compared. Such a method can be extended to produce honeycomb structures of other materials with controlled cell size and periodicity.

Ma, Y.; Wong, C. P.; Zeng, X. T.; Yu, T.; Zhu, Y.; Shen, Z. X.

2009-03-01

231

The morphology and functions of articular chondrocytes on a honeycomb-patterned surface.  

PubMed

The present study investigated the potential of a novel micropatterned substrate for neocartilage formation. Articular chondrocytes were cultured on poly( ? -caprolactone) materials whose surfaces were either flat or honeycomb-patterned. The latter was prepared using a novel self-organization technique, while the former, was prepared by spin-coating. The chondrocytes attached and proliferated on both surfaces. On the honeycomb films, chondrocytes were found at the top surface and encased within the 10? ? m pores. Meanwhile, chondrocytes on the spin-coated surface flattened out. Accumulation of DNA and keratin sulphate was comparatively higher on the honeycomb films within the first 7 days. At their respective peaks, DNA concentration increased on the honeycomb and flat surfaces by approximately 210% and 400% of their day 1 values, respectively. However, cultures on the flat surface took longer to peak. Extracellular Matrix (ECM) concentrations peaked at 900% and 320% increases for the honeycomb and flat cultures. Type II collagen was upregulated on the honeycomb and flat surfaces by as much as 28% and 25% of their day 1 values, while aggrecan was downregulated with time, by 3.4% and 7.4%. These initial results demonstrate the potential usefulness of honeycomb-based scaffolds during early cultures neocartilage and soft tissue engineering. PMID:24804237

Eniwumide, Joshua O; Tanaka, Masaru; Nagai, Nobuhiro; Morita, Yuka; de Bruijn, Joost; Yamamoto, Sadaaki; Onodera, Shin; Kondo, Eiji; Yasuda, Kazunori; Shimomura, Masatsugu

2014-01-01

232

Directed Self-Assembly of Large Scaffold-free Multicellular Honeycomb Structures  

PubMed Central

A significant challenge to the field of biofabrication is the rapid construction of large three dimensional (3D) living tissues and organs. Multi-cellular spheroids have been used as building blocks. In this paper, we create large multi-cellular honeycomb building blocks using directed self-assembly, whereby cell-to-cell adhesion, in the context of the shape and obstacles of a micromold, drives the formation of a 3D structure. Computer aided design, rapid prototyping and replica molding were used to fabricate honeycomb-shaped micro-molds. Nonadhesive hydrogels cast from these micro-molds were equilibrated in cell culture medium and seeded with two types of mammalian cells. The cells settled into the honeycomb recess, were unable to attach to the nonadhesive hydrogel and so cell-to-cell adhesion drove the self-assembly of a large multicellular honeycomb within 24 hours. Distinct morphological changes occurred to the honeycomb and its cells indicating the presence of significant cell-mediated tension. Unlike the spheroid, whose size is constrained by a critical diffusion distance needed to maintain cell viability, the overall size of the honeycomb is not limited. The rapid production of the honeycomb building unit, with its multiple rings of high density cells and open lumen spaces, offers interesting new possibilities for biofabrication strategies.

Tejavibulya, Nalin; Youssef, Jacquelyn; Bao, Brian; Ferruccio, Toni-Marie; Morgan, Jeffrey R.

2011-01-01

233

Porphyrin-based honeycomb films and their antibacterial activity.  

PubMed

Micrometer-sized porous honeycomb-patterned thin films based on hybrid complexes formed via electrostatic interaction between Mn(III) meso-tetra(4-sulfonatophenyl) porphine chloride (an acid form, {MnTPPS}) and dimethyldioctadecylammonium bromide (DODMABr). The morphology of the microporous thin films can be well regulated by controlling the concentration of MnTPPS-DODMA complexes, DODMABr, and polystyrene (PS), respectively. The formation of the microporous thin films was largely influenced by different solvents. The well-ordered microporous films of MnTPPS-DODMA complexes exhibit a more efficient antibacterial activity under visible light than those of hybrid complexes of nanoparticles modified with DODMABr, implying that well-ordered microporous films containing porphyrin composition can improve photochemical activity and more dominance in applications in biological medicine fields. PMID:24846091

Wang, Yanran; Liu, Yan; Li, Guihua; Hao, Jingcheng

2014-06-10

234

Monomer-dimer mixture on a honeycomb lattice.  

PubMed

We study a monomer-dimer mixture defined on a honeycomb lattice as a toy model for the spin-ice system in a magnetic field. In a low-doping region of monomers, the effective description of this system is given by the dual sine-Gordon model. In intermediate- and strong-doping regions, the Potts lattice gas theory can be employed. Synthesizing these results, we construct a renormalization-group flow diagram, which includes the stable and unstable fixed points corresponding to M5 and M6 in the minimal models of the conformal field theory. We perform numerical transfer-matrix calculations to determine a global phase diagram and also to proffer evidence to check our prediction. PMID:21702629

Otsuka, Hiromi

2011-06-01

235

Theoretical Predictions of Freestanding Honeycomb Sheets of Cadmium Chalcogenides  

SciTech Connect

Two-dimensional (2D) nanocrystals of CdX (X = S, Se, Te) typically grown by colloidal synthesis are coated with organic ligands. Recent experimental work on ZnSe showed that the organic ligands can be removed at elevated temperature, giving a freestanding 2D sheet of ZnSe. In this theoretical work, freestanding single- to few-layer sheets of CdX, each possessing a pseudo honeycomb lattice, are considered by cutting along all possible lattice planes of the bulk zinc blende (ZB) and wurtzite (WZ) phases. Using density functional theory, we have systematically studied their geometric structures, energetics, and electronic properties. A strong surface distortion is found to occur for all of the layered sheets, and yet all of the pseudo honeycomb lattices are preserved, giving unique types of surface corrugations and different electronic properties. The energetics, in combination with phonon mode calculations and molecular dynamics simulations, indicate that the syntheses of these freestanding 2D sheets could be selective, with the single- to few-layer WZ110, WZ100, and ZB110 sheets being favored. Through the GW approximation, it is found that all single-layer sheets have large band gaps falling into the ultraviolet range, while thicker sheets in general have reduced band gaps in the visible and ultraviolet range. On the basis of the present work and the experimental studies on freestanding double-layer sheets of ZnSe, we envision that the freestanding 2D layered sheets of CdX predicted herein are potential synthesis targets, which may offer tunable band gaps depending on their structural features including surface corrugations, stacking motifs, and number of layers.

Zhou, Jia [ORNL] [ORNL; Huang, Jingsong [ORNL] [ORNL; Sumpter, Bobby G [ORNL] [ORNL; Kent, Paul R [ORNL] [ORNL; Xie, Yu [ORNL] [ORNL; Terrones Maldonado, Humberto [ORNL] [ORNL; Smith, Sean C [ORNL] [ORNL

2014-01-01

236

Brazing dissimilar aluminum alloys  

NASA Technical Reports Server (NTRS)

Dip-brazing process joins aluminum castings to aluminum sheet made from different aluminum alloy. Process includes careful cleaning, surface preparation, and temperature control. It causes minimum distortion of parts.

Dalalian, H.

1979-01-01

237

Featureless and Non-Fractionalized Bose Insulator on the Honeycomb Lattice at 1/2 site-filling  

NASA Astrophysics Data System (ADS)

We consider bosons on the Honeycomb lattice at filling one half per site. It is known that free fermions at this filling of the tight binding model cannot form an insulating state while preserving all symmetries, even though there is an integer number of particles per unit cell. We argue, however, that interacting bosons can form an insulating state that preserves all symmetries. We propose a wave function for this state and by a mapping to a classical partition function we compute its properties and demonstrate that the state is insulating, fully symmetric and has no topological order. Our construction suggests that featureless insulators are generically allowed for at a filling of one boson per unit cell on any symmorphic lattice in any dimension. We also discuss related wavefunctions of hard core bosons that model spin 1/2 magnets on this lattice.

Kimchi, Itamar; Parameswaran, S. A.; Turner, Ari; Wang, Fa; Vishwanath, Ashvin

2013-03-01

238

Static and dynamic analysis of soft core sandwich panels with through-thickness deformation  

Microsoft Academic Search

Sandwich plates represent an efficient structural element, providing a high stiffness\\/weight ratio characteristic. Moreover, when using this structural element, different design configurations and materials in the core can be adopted in order to obtain desired properties. From high dissipation elastomers to light and stiff honeycombs, several core materials may be applied, looking for high damping ratios or simply to obtain

R. A. S. Moreira; J. Dias Rodrigues

2010-01-01

239

Steps toward 8m honeycomb mirror blanks. III - 1.8m honeycomb sandwich blanks cast from borosilicate glass  

NASA Technical Reports Server (NTRS)

The design, fabrication techniques, and equipment used for producing two 1.8-m honeycomb sandwich blanks, eventually leading to production of 8-m blanks, are reported. The procedure employed 85 cast hexagonal tiles at the bottom section, affixed against flotation by SiC bolts. The two plano concave mirrors are 1.83 m thick, weight 500 kg, and are each designed for 19 supports of astatic-lever type. Both blanks are of high quality and with an adequately low bubble content; one is to be figured to high-precision 0.25-arcsecond images, and is to be tested on the Multiple Mirror Telescope. Construction of a spin-casting facility based on the same principle is being planned for test-fabricating spin-cast mirrors on a smaller scale.

Angel, J. R. P.; Hill, J. M.

1984-01-01

240

Aluminum extraction from aluminum industrial wastes  

NASA Astrophysics Data System (ADS)

Aluminum dross tailings, an industrial waste from the Egyptian Aluminum Company (Egyptalum), was used to produce two types of alums: aluminum sulfate alum (Al2(SO4)3·12H2O) and ammonium aluminum alum {(NH4)2SO4AL2 (SO4)3·24H2O}. This was carried out in two processes. The first involves leaching the impurities using diluted H2SO4 with different solid/liquid ratios at different temperatures to dissolve the impurities present in the starting material in the form of aluminum sulfates. The second process is the extraction of aluminum (as aluminum sulfate) from the purified aluminum dross tailings thus produced. This was carried out in an autoclave. The effects of temperature, time of reaction, and acid concentration on pressure leaching and extraction processes were studied in order to specify the optimum conditions to be applied in the bench scale production as well as the kinetics of leaching process.

Amer, A. M.

2010-05-01

241

Monte Carlo study of the honeycomb structure of anthraquinone molecules on Cu(111)  

NASA Astrophysics Data System (ADS)

Using Monte Carlo calculations of the two-dimensional (2D) triangular lattice gas model, we demonstrate a mechanism for the spontaneous formation of honeycomb structure of anthraquinone (AQ) molecules on a Cu(111) plane. In our model long-range attractions play an important role, in addition to the long-range repulsions and short-range attractions proposed by Pawin, Wong, Kwon, and Bartels [ScienceSCIEAS0036-807510.1126/science.1129309 313, 961 (2006)]. We provide a global account of the possible combinations of long-range attractive coupling constants which lead to a honeycomb superstructure. We also provide the critical temperature of disruption of the honeycomb structure and compare the critical local coverage rate of AQ’s where the honeycomb structure starts to form with the experimental observations.

Kim, Kwangmoo; Einstein, T. L.

2011-06-01

242

Simulating the Response of a Composite Honeycomb Energy Absorber, Part 1.  

National Technical Information Service (NTIS)

This paper describes the experimental and analytical evaluation of an externally deployable composite honeycomb structure that is designed to attenuate impact energy during helicopter crashes. The concept, designated the Deployable Energy Absorber (DEA), ...

E. L. Fasanella K. E. Jackson M. A. Polanco

2012-01-01

243

Hyperelastic Constitutive Modeling of Hexagonal Honeycombs Subjected to In-Plane Shear Loading  

Microsoft Academic Search

The in-plane flexible shear property of hexagonal honeycombs may be useful for the compliant structural applications. In this paper, hyperelastic strain energy functions are developed for a finite in-plane shear deformation of hexagonal honeycombs over a constituent material's elastic range. Effective shear stress-strain curves of hexagonal structures and local cell wall deformation are investigated using the finite element based homogenization

J Ju; Joshua D. Summers

2011-01-01

244

Rapid cloning of mammalian cells with honeycomb cloning plates and nonlethal vital stains  

Microsoft Academic Search

Summary  A rapid and technically simple method for cloning both adhesive and nonadhesive mammalian cells is described. The procedure\\u000a employs (a) honeycomb cloning plates and (b) nonlethal vital stains. Instead of placing cloning rings around colonies, cells\\u000a are initially seeded at clonal density directly into a plate containing an array of cloning rings (the honeycomb plate). Hence,\\u000a the time involved in

Robert J. Klebe

1984-01-01

245

Engineering the broadband spectrum of close-packed plasmonic honeycomb array surfaces  

NASA Astrophysics Data System (ADS)

Plasmonic nanostructures operating over a wide spectrum are promising candidates for broadband spectroscopic applications. While promising, spectral engineering of close-packed plasmonic honeycomb nanoantenna arrays is challenging due to the strong correlation between the particle geometry and hexagonal grid, particle coupling within unit cells, and interaction between neighboring unit cells. In this study, we demonstrate that the spectral distribution of large scale surfaces can be effectively tailored over a wideband spectral range using close-packed plasmonic honeycomb array surfaces. We discuss coupling-mechanisms responsible for the spectral response of honeycomb arrays and discuss the geometrical restrictions limiting the bandwidth of the spectral response. These limitations can be overcome with a more general honeycomb structure by introducing additional morphological parameters within the Wigner-Seitz unit cell. The proposed morphological parameters provide additional flexibility for manipulating the spectrum by relaxing geometrical restrictions due to a strong correlation between the unit-cell and nanoparticle morphology. Furthermore, we achieve spectral broadening by breaking the symmetry within a Wigner-Seitz unit cell on a hexagonal grid, rather than breaking the symmetry of the hexagonal grid itself via generalized honeycomb arrays. Additionally, we demonstrate the advantages of close-packed arrays in terms of spectral response and electric field enhancement over large surfaces. Finally, radiative far-field properties, absorptance, transmittance, and reflectance of honeycomb structures are investigated.

Tok, Rü?tü Umut; ?endur, Kür?at

2013-05-01

246

One-to-One Embedding between Honeycomb Mesh and Petersen-Torus Networks  

PubMed Central

As wireless mobile telecommunication bases organize their structure using a honeycomb-mesh algorithm, there are many studies about parallel processing algorithms like the honeycomb mesh in Wireless Sensor Networks. This paper aims to study the Peterson-Torus graph algorithm in regard to the continuity with honeycomb-mesh algorithm in order to apply the algorithm to sensor networks. Once a new interconnection network is designed, parallel algorithms are developed with huge research costs to use such networks. If the old network is embedded in a newly designed network, a developed algorithm in the old network is reusable in a newly designed network. Petersen-Torus has been designed recently, and the honeycomb mesh has already been designed as a well-known interconnection network. In this paper, we propose a one-to-one embedding algorithm for the honeycomb mesh (HMn) in the Petersen-Torus PT(n,n), and prove that dilation of the algorithm is 5, congestion is 2, and expansion is 5/3. The proposed one-to-one embedding is applied so that processor throughput can be minimized when the honeycomb mesh algorithm runs in the Petersen-Torus.

Seo, Jung-Hyun; Sim, Hyun; Park, Dae-Heon; Park, Jang-Woo; Lee, Yang-Sun

2011-01-01

247

Theory of interacting electrons on the honeycomb lattice  

NASA Astrophysics Data System (ADS)

The general low-energy theory of electrons interacting via repulsive short-range interactions on graphene’s honeycomb lattice at half-filling is presented. The exact symmetry of the Lagrangian with local quartic terms for the Dirac four-component field dictated by the lattice is identified as D2×Uc(1)×time reversal, where D2 is the dihedral group, and Uc(1) is a subgroup of the SUc(2) “chiral” group of the noninteracting Lagrangian that represents translations in Dirac language. The Lagrangian describing spinless particles respecting this symmetry is parametrized by six independent coupling constants. We show how first imposing the rotational, then Lorentz, and finally chiral symmetry to the quartic terms—in conjunction with the Fierz transformations—eventually reduces the set of couplings to just two, in the “maximally symmetric” local interacting theory. We identify the two critical points in such a Lorentz and chirally symmetric theory as describing metal-insulator transitions into the states with either time reversal or chiral symmetry being broken. The latter is proposed to govern the continuous transition in both the Thirring and Nambu-Jona-Lasinio models in 2+1 dimensions and with a single Dirac field. In the site-localized “atomic” limit of the interacting Hamiltonian, under the assumption of emergent Lorentz invariance, the low-energy theory describes the continuous transitions into the insulator with either a finite Haldane’s (circulating currents) or Semenoff’s (staggered density) masses, both in the universality class of the Gross-Neveu model. The simple picture of the metal-insulator transition on a honeycomb lattice emerges at which the residue of the quasiparticle pole at the metallic and the mass gap in the insulating phase both vanish continuously as the critical point is approached. In contrast to these two critical quantities, we argue that the Fermi velocity is noncritical as a consequence of the dynamical exponent being fixed to unity by the emergent Lorentz invariance near criticality. Possible effects of the long-range Coulomb interaction and the critical behavior of the specific heat and conductivity are discussed.

Herbut, Igor F.; Juri?i?, Vladimir; Roy, Bitan

2009-02-01

248

Correlated Dirac particles and superconductivity on the honeycomb lattice  

NASA Astrophysics Data System (ADS)

We investigate the properties of the nearest-neighbor singlet pairing and the emergence of d-wave superconductivity in the doped honeycomb lattice considering the limit of large interactions and the t-J1-J2 model. First, by applying a renormalized mean-field procedure as well as slave-boson theories which account for the proximity to the Mott-insulating state, we confirm the emergence of d-wave superconductivity, in agreement with earlier works. We show that a small but finite J2 spin coupling between next-nearest neighbors stabilizes d-wave symmetry compared to the extendeds-wave scenario. At small hole doping, to minimize the energy and to gap the whole Fermi surface or all the Dirac points, the superconducting ground state is characterized by a d+id singlet pairing assigned to one valley and a d-id singlet pairing to the other, which then preserves time-reversal symmetry. The slightly doped situation is distinct from the heavily doped case (around 3/8 and 5/8 filling) supporting a pure chiral d+id symmetry and breaking time-reversal symmetry. Then, we apply the functional renormalization group and study in more detail the competition between antiferromagnetism and superconductivity in the vicinity of half filling. We discuss possible applications to strongly correlated compounds with copper hexagonal planes such as In3Cu2VO9. Our findings are also relevant to the understanding of exotic superfluidity with cold atoms.

Wu, Wei; Scherer, Michael M.; Honerkamp, Carsten; Le Hur, Karyn

2013-03-01

249

Extended Appearance Potential Fine Structure Analysis: Oxygen on Aluminum (100).  

National Technical Information Service (NTIS)

To measure oxygen-aluminum separation at Al (100) surfaces disordered (LEED beams extinguished) by reaction with oxygen, we analyzed the extended appearance potential fine structure above the threshold for electron-bombardment excitation of the 0 1s core....

M. L. denBoer T. L. Einstein W. T. Elam R. L. Park L. D. Roelofs

1979-01-01

250

THE IRRADIATION OF ALUMINUM-PLUTONIUM ALLOYS IN ZIRCALOY SHEATHING. PART I. PRELIMINARY EXPERIMENTS WITH ALUMINUM-URANIUM ALLOYS  

Microsoft Academic Search

Aluminum-uranium alloys containing up to 20 wt. % uranium were studied ; in a stand-in capacity as a prelude to a program of work with aluminum-plutonium ; alloys clad in Zircaloy-2. The object of the investigation was to examine the ; effect of temperature on the structure and hardness of the core alloys, their ; interaction with Zircaloy-2 at various

1958-01-01

251

State observer for the aluminum reduction process  

NASA Astrophysics Data System (ADS)

The reduction of aluminum ore form alumina to metallic aluminum is done by dissolving the core in a cryolite bath at approximately 950 degrees C and passing DC current through the solution. Current flow through a typical cell can range from 75,000 to 200,000 Amperes, generating extremely strong electromagnetic fields. Common mode voltages of up to 800 VDC occur on reduction cell frames. Although the process is both complex and extremely energy intensive, it is generally only crudely instrumented because the hostile environment destroys any sensor placed in the bath. This paper describes a new approach to aluminum cell control employing the measurement of 'peripheral' process variables and the use of extensive modeling of the cell dynamics. A form of state observer is used to deduce critical process variables from the measurement of available related parameters. An experimental system is being installed at Century Aluminum and will be tested and refined over the coming year.

Biedler, Philip L.; Banta, Larry E.; Dai, Congxia

2001-10-01

252

Preparation and study of 2-D semiconductors with Dirac type bands due to the honeycomb nanogeometry  

NASA Astrophysics Data System (ADS)

The interest in 2-dimensional systems with a honeycomb lattice and related Dirac-­type electronic bands has exceeded the prototype graphene1. Currently, 2-­dimensional atomic2,3 and nanoscale4-­8 systems are extensively investigated in the search for materials with novel electronic properties that can be tailored by geometry. The immediate question that arises is how to fabricate 2-­D semiconductors that have a honeycomb nanogeometry, and as a consequence of that, display a Dirac-­type band structure? Here, we show that atomically coherent honeycomb superlattices of rocksalt (PbSe, PbTe) and zincblende (CdSe, CdTe) semiconductors can be obtained by nanocrystal self-­assembly and facet-­to-­facet atomic bonding, and subsequent cation exchange. We present a extended structural analysis of atomically coherent 2-­D honeycomb structures that were recently obtained with self-assembly and facet-­to-­facet bonding9. We show that this process may in principle lead to three different types of honeycomb structures, one with a graphene type-­, and two others with a silicene-­type structure. Using TEM, electron diffraction, STM and GISAXS it is convincingly shown that the structures are from the silicene-­type. In the second part of this work, we describe the electronic structure of graphene-­type and silicene type honeycomb semiconductors. We present the results of advanced electronic structure calculations using the sp3d5s* atomistic tight-­binding method10. For simplicity, we focus on semiconductors with a simple and single conduction band for the native bulk semiconductor. When the 3-­D geometry is changed into 2-­D honeycomb, a conduction band structure transformation to two types of Dirac cones, one for S-­ and one for P-­orbitals, is observed. The width of the bands depends on the honeycomb period and the coupling between the nanocrystals. Furthermore, there is a dispersionless P-­orbital band, which also forms a landmark of the honeycomb structure. The effects of considerable intrinsic spin-­orbit coupling are briefly considered. For heavy-­element compounds such as CdTe, strong intrinsic spin-­-orbit coupling opens a non-­trivial gap at the P-­orbital Dirac point, leading to a quantum Spin Hall effect10-­12. Our work shows that well known semiconductor crystals, known for centuries, can lead to systems with entirely new electronic properties, by the simple action of nanogeometry. It can be foreseen that such structures will play a key role in future opto-­electronic applications, provided that they can be fabricated in a straightforward way.

Kalesaki, E.; Boneschanscher, M. P.; Geuchies, J. J.; Delerue, C.; Morais Smith, C.; Evers, W. H.; Allan, G.; Altantzis, T.; Bals, S.; Vanmaekelbergh, D.

2014-03-01

253

Ferromagnetism and quantum anomalous Hall effect in one-side-saturated buckled honeycomb lattices  

NASA Astrophysics Data System (ADS)

The recently synthesized silicene as well as theoretically discussed germanene are examples of buckled honeycomb structures. The buckled structures allow one to manipulate asymmetry between two underlying sublattices of honeycomb structures. Here by taking germanene as a prototype of buckled honeycomb lattices, we explore magnetism induced by breaking sublattice symmetry through saturating chemical bonds on one side of the buckled honeycomb lattice. It is shown that when fractions of chemical bonds on one side are saturated, two narrow bands always exist at half filling. Furthermore, the narrow bands generally support flat band ferromagnetism in the presence of the Hubbard U interaction. The induced magnetization is directly related to the saturation fraction and is thus controllable in magnitude through the saturation fraction. Most importantly, we find that depending on the saturation fraction, the ground state of a one-side-saturated germanene may become a quantum anomalous Hall (QAH) insulator characterized by a Chern number that vanishes for larger magnetization. The nonvanishing Chern number for smaller magnetization implies that the associated quantum Hall effect tends to survive at high temperatures. Our findings provide a potential method to engineer buckled honeycomb structures into high-temperature QAH insulators.

Huang, Shin-Ming; Lee, Shi-Ting; Mou, Chung-Yu

2014-05-01

254

Design optimization of sinusoidal glass honeycomb for flat plate solar collectors  

NASA Technical Reports Server (NTRS)

The design of honeycomb made of sinusoidally corrugated glass strips was optimized for use in water-cooled, single-glazed flat plate solar collectors with non-selective black absorbers. Cell diameter (d), cell height (L), and pitch/diameter ratio (P/d) maximizing solar collector performance and cost effectiveness for given cell wall thickness (t sub w) and optical properties of glass were determined from radiative and convective honeycomb characteristics and collector performance all calculated with experimentally validated algorithms. Relative lifetime values were estimated from present materials costs and postulated production methods for corrugated glass honeycomb cover assemblies. A honeycomb with P/d = 1.05, d = 17.4 mm, L = 146 mm and t sub w = 0.15 mm would provide near-optimal performance over the range delta T sub C greater than or equal to 0 C and less than or equal to 80 C and be superior in performance and cost effectiveness to a non-honeycomb collector with a 0.92/0.12 selective black absorber.

Mcmurrin, J. C.; Buchberg, H.

1980-01-01

255

Computer simulation of screw dislocation in aluminum  

NASA Technical Reports Server (NTRS)

The atomic structure in a 110 screw dislocation core for aluminum is obtained by computer simulation. The lattice statics technique is employed since it entails no artificially imposed elastic boundary around the defect. The interatomic potential has no adjustable parameters and was derived from pseudopotential theory. The resulting atomic displacements were allowed to relax in all three dimensions.

Esterling, D. M.

1976-01-01

256

A Lightweight Pneumatic Coring Device: Design and Field Test.  

National Technical Information Service (NTIS)

A lightweight pneumatic coring device for use from relatively small research vessels was developed and field tested. The device consists of an aluminum frame supporting a core barrel surmounted by a pneumatic industrial vibrator. Tests of a number of pair...

J. A. Fuller E. P. Meisburger

1982-01-01

257

Aluminum hydroxide production  

SciTech Connect

A method is described for the production of aluminum hydroxide, comprising reacting water in the liquid phase and aluminum of surface area of at least 20 mm/sup 2/ per gram at a pH above about 12.4 for producing a reaction mixture containing aluminum hydroxide, and collecting solid aluminum hydroxide from the reaction mixture, the reaction being carried out in the presence of choline at a concentration of about 0.05 to 2 mols per liter.

Martin, E.S.; Weaver, M.L.

1988-07-05

258

Preparation and microwave absorption properties of metal magnetic micropowder-coated honeycomb sandwich structures  

NASA Astrophysics Data System (ADS)

Radar absorbing materials with metal magnetic micropowder-coated honeycomb sandwich structures are prepared by a spray process. Metal magnetic micropowder is applied as an absorber which maintains a high absorption, and a honeycomb sandwich structure as a supporter enhancing mechanical strength. The microwave absorption properties are measured by a network analyzer system in the frequency range of 2.6-18 GHz. The concentration of the MMP and the coating thickness of the absorber affect the attenuation properties, a suitable value of them contributing to a broad bandwidth and high loss. A matching layer is introduced to the honeycomb sandwich structure on top, which allows the incident electromagnetic wave to enter and largely get attenuated through the absorbing system, increasing the microwave absorption.

He, Yanfei; Gong, Rongzhou; Cao, Heng; Wang, Xian; Zheng, Yi

2007-10-01

259

Development of beryllium honeycomb sandwich composite for structural and other related applications  

NASA Technical Reports Server (NTRS)

The feasibility of fabricating large beryllium honeycomb panels was demonstrated. Both flat and curved sandwich structures were manufactured using practical, braze bonding techniques. The processes developed prove that metallurgically assembled beryllium honeycomb panels show decided potential where rigid, lightweight structures are required. Three panels, each 10 square feet in surface area, were fabricated, and radiographically inspected to determine integrity. This examination revealed a 97 percent braze in the final panel. It is believed that ceramic dies for forming and brazing would facilitate the fabrication techniques for higher production rates. Ceramic dies would yield a lower thermal gradient in the panel during the braze cycle. This would eliminate the small amount of face sheet wrinkling present in the panels. Hot forming the various panel components demonstrated efficient manufacturing techniques for scaling up and producing large numbers of hot formed beryllium components and panels. The beryllium honeycomb panel demonstrated very good vibrational loading characteristics under test with desirable damping characteristics.

Vogan, J. W.; Grant, L. A.

1972-01-01

260

Realization of a three-dimensional spin-anisotropic harmonic honeycomb iridate.  

PubMed

Spin and orbital quantum numbers play a key role in the physics of Mott insulators, but in most systems they are connected only indirectly-via the Pauli exclusion principle and the Coulomb interaction. Iridium-based oxides (iridates) introduce strong spin-orbit coupling directly, such that these numbers become entwined together and the Mott physics attains a strong orbital character. In the layered honeycomb iridates this is thought to generate highly spin-anisotropic magnetic interactions, coupling the spin to a given spatial direction of exchange and leading to strongly frustrated magnetism. Here we report a new iridate structure that has the same local connectivity as the layered honeycomb and exhibits striking evidence for highly spin-anisotropic exchange. The basic structural units of this material suggest that a new family of three-dimensional structures could exist, the 'harmonic honeycomb' iridates, of which the present compound is the first example. PMID:24969742

Modic, K A; Smidt, Tess E; Kimchi, Itamar; Breznay, Nicholas P; Biffin, Alun; Choi, Sungkyun; Johnson, Roger D; Coldea, Radu; Watkins-Curry, Pilanda; McCandless, Gregory T; Chan, Julia Y; Gandara, Felipe; Islam, Z; Vishwanath, Ashvin; Shekhter, Arkady; McDonald, Ross D; Analytis, James G

2014-01-01

261

Aluminum and Young Artists.  

ERIC Educational Resources Information Center

The author suggests a variety of ways in which aluminum and aluminum foil can be used in elementary and junior high art classes: relief drawing and rubbing; printing; repousse; sculpture; mobiles; foil sculpture; and three dimensional design. Sources of aluminum supplies are suggested. (SJL)

Anderson, Thomas

1980-01-01

262

Ordered Metal Nanohole Arrays Made by a Two-Step Replication of Honeycomb Structures of Anodic Alumina  

Microsoft Academic Search

A highly ordered metal nanohole array (platinum and gold) was fabricated by a two-step replication of the honeycomb structure of anodic porous alumina. Preparation of the negative porous structure of porous alumina followed by the formation of the positive structure with metal resulted in a honeycomb metallic structure. The metal hole array of the film has a uniform, closely packed

Hideki Masuda; Kenji Fukuda

1995-01-01

263

A New Decomposition System for Volatile Organic Compounds Using Combinations of Dielectric Barrier Discharges with Zeolite Honeycomb Sheets  

Microsoft Academic Search

A new decomposition system for volatile organic compounds (VOCs), based on dielectric barrier discharges combined with zeolite honeycomb sheets, has been developed. A discharge element was made of layered flat metal sheets covered with mica sheets separated by 2 mm, in which corrugated (honeycomb-shaped) ceramic sheets embedded with zeolites were inserted. This element was shown to satisfy the requirements of

Koji Inoue; Keimei Furuki; Hiroshi Okano; Yukihiko Yamagata; Katsunori Muraoka

2007-01-01

264

Experimental study of acoustical characteristics of honeycomb sandwich structures  

Microsoft Academic Search

Loss factor measurements were performed on sandwich panels to determine the effects of different skin and core materials on the acoustical properties. Results revealed inserting a viscoelastic material in the core's mid-plane resulted in the highest loss factor. Panels constructed with carbon-fiber skins exhibited larger loss factors than glass-fiber skins. Panels designed to achieve subsonic wave speed did not show

Portia Renee Peters

2009-01-01

265

Half-integer Mott-insulator phases in the imbalanced honeycomb lattice  

NASA Astrophysics Data System (ADS)

Using mean-field theory, we investigate the ground-state properties of ultracold bosons loaded in a honeycomb lattice with on-site repulsive interactions and imbalanced nearest-neighbor hopping amplitudes. Taking into account correlations between strongly coupled neighboring sites through an improved Gutzwiller ansatz, we predict the existence of half-integer Mott-insulator phases, i.e., states with half-integer filling and vanishing compressibility. These insulating phases result from the interplay between quantum correlations and the topology of the honeycomb lattice, and could be easily addressed experimentally because they have clear signatures in momentum space.

Gawryluk, Krzysztof; Miniatura, Christian; Grémaud, Benoît

2014-06-01

266

Steps toward eight-meter honeycomb mirror blanks. I Rationale and approach  

NASA Technical Reports Server (NTRS)

The best form for 8-m telescope mirrors is discussed. It is concluded that honeycomb sandwich structure can meet the most exacting demand goals for subarcsecond image quality in optical and infrared astronomy. These structures are light, have good stiffness against gravitational and wind loading, and have low thermal inertia. The latter permits them to be operated at the ambient air temperature to avoid local seeing problems. Borosilicate and aluminosilicate glasses are adequate materials for ventilated honeycombs, which do not require low expansion materials.

Angel, J. R. P.; Woolf, N. J.

1984-01-01

267

Wideband trapping of light by edge states in honeycomb photonic crystals  

NASA Astrophysics Data System (ADS)

We study theoretically light propagations at the zigzag edge of a honeycomb photonic crystal consisting of dielectric rods in air, analogous to graphene. Within the photonic band gap of the honeycomb photonic crystal, a unimodal edge state may exist with a sharp confinement of optical fields. Its dispersion can be tuned simply by adjusting the radius of the edge rods. For the edge rods with a graded variation in radius along the edge direction, we show numerically that light beams of different frequencies can be trapped sharply in different spatial locations, yielding wideband trapping of light.

Ouyang, Chunfang; Han, Dezhuan; Zhao, Fangyuan; Hu, Xinhua; Liu, Xiaohan; Zi, Jian

2012-12-01

268

Short-Range Correlations and Cooling of Ultracold Fermions in the Honeycomb Lattice  

NASA Astrophysics Data System (ADS)

We use determinantal quantum Monte Carlo simulations and numerical linked-cluster expansions to study thermodynamic properties and short-range spin correlations of fermions in the honeycomb lattice. We find that, at half filling and finite temperatures, nearest-neighbor spin correlations can be stronger in this lattice than in the square lattice, even in regimes where the ground state in the former is a semimetal or a spin liquid. The honeycomb lattice also exhibits a more pronounced anomalous region in the double occupancy that leads to stronger adiabatic cooling than in the square lattice. We discuss the implications of these findings for optical lattice experiments.

Tang, Baoming; Paiva, Thereza; Khatami, Ehsan; Rigol, Marcos

2012-11-01

269

Breakdown of Dirac dynamics in honeycomb lattices due to nonlinear interactions  

SciTech Connect

We study the dynamics of coherent waves in nonlinear honeycomb lattices and show that nonlinearity breaks down the Dirac dynamics. As an example, we demonstrate that even a weak nonlinearity has major qualitative effects on one of the hallmarks of honeycomb lattices: conical diffraction. Under linear conditions, a circular input wave packet associated with the Dirac point evolves into a ring, but even a weak nonlinearity alters the evolution such that the emerging beam possesses triangular symmetry, and populates Bloch modes outside of the Dirac cone. Our results are presented in the context of optics, but we propose a scheme to observe equivalent phenomena in Bose-Einstein condensates.

Bahat-Treidel, Omri; Peleg, Or; Segev, Mordechai; Buljan, Hrvoje [Department of Physics, Technion-Israel Institute of Technology, Technion City, Haifa IL-32000 (Israel); Department of Physics, University of Zagreb, PP 332, HR-10000 Zagreb (Croatia)

2010-07-15

270

Pattern formation in the dipolar Ising model on a two-dimensional honeycomb lattice  

NASA Astrophysics Data System (ADS)

We present Monte Carlo simulation results for a two-dimensional Ising model with ferromagnetic nearest-neighbor couplings and a competing long-range dipolar interaction on a honeycomb lattice. Both structural and thermodynamic properties are very similar to the case of a square lattice, with the exception that structures reflect the sixfold rotational symmetry of the underlying honeycomb lattice. To deal with the long-range nature of the dipolar interaction we also present a simple method of evaluating effective interaction coefficients, which can be regarded as a more straightforward alternative to the prevalent Ewald summation techniques.

Rüger, Robert; Valentí, Roser

2012-07-01

271

The structure and dynamics of the unique Honeycomb Nebula in the halo of 30 Doradus  

NASA Astrophysics Data System (ADS)

The structure and dynamics of the Honeycomb nebula in the Large Magellanic cloud are modelled as resulting from the interaction of a supernova explosion with an existing giant shell of the type commonly found in the LMC. In particular, the processes that may have led to the striking morphology and velocity structure of this nebula are examined. New data of the Honeycomb nebula, are presented. Here, spatially resolved profiles of the [S ii] 6716 & 6731 Angstroms density sensitive lines, obtained with the Manchester Echelle Spectrometer, supplement previous, complementary, H? and [N ii] 6584 Angstroms profiles. The agreements and differences between all of these data and this simple model are highlighted.

Redman, M. P.; Al-Mostafa, Z. A.; Meaburn, J.; Bryce, M.; Dyson, J. E.

1999-05-01

272

Aluminum reference electrode  

DOEpatents

A stable reference electrode is described for use in monitoring and controlling the process of electrolytic reduction of a metal. In the case of Hall cell reduction of aluminum, the reference electrode comprises a pool of molten aluminum and a solution of molten cryolite, Na[sub 3]AlF[sub 6], wherein the electrical connection to the molten aluminum does not contact the highly corrosive molten salt solution. This is accomplished by altering the density of either the aluminum (decreasing the density) or the electrolyte (increasing the density) so that the aluminum floats on top of the molten salt solution. 1 fig.

Sadoway, D.R.

1988-08-16

273

Aluminum reference electrode  

DOEpatents

A stable reference electrode for use in monitoring and controlling the process of electrolytic reduction of a metal. In the case of Hall cell reduction of aluminum, the reference electrode comprises a pool of molten aluminum and a solution of molten cryolite, Na.sub.3 AlF.sub.6, wherein the electrical connection to the molten aluminum does not contact the highly corrosive molten salt solution. This is accomplished by altering the density of either the aluminum (decreasing the density) or the electrolyte (increasing the density) so that the aluminum floats on top of the molten salt solution.

Sadoway, Donald R. (Belmont, MA)

1988-01-01

274

?-Cu2V2O7 : A spin- (1)/(2) honeycomb lattice system  

NASA Astrophysics Data System (ADS)

We report on band-structure calculations and a microscopic model of the low-dimensional magnet ?-Cu2V2O7 . Magnetic properties of this compound can be described by a spin- (1)/(2) anisotropic honeycomb lattice model with the averaged coupling J¯1=60-66K . The low symmetry of the crystal structure leads to two inequivalent couplings J1 and J1' but this weak spatial anisotropy does not affect the essential physics of the honeycomb spin lattice. The structural realization of the honeycomb lattice is highly nontrivial: the leading interactions J1 and J1' run via double bridges of VO4 tetrahedra between spatially separated Cu atoms while the interactions between structural nearest neighbors are negligible. The non-negligible interplane coupling J??15K gives rise to the long-range magnetic ordering at TN?26K . Our model simulations improve the fit of the magnetic susceptibility data, compared to the previously assumed spin-chain models. Additionally, the simulated ordering temperature of 27 K is in remarkable agreement with the experiment. Our study evaluates ?-Cu2V2O7 as the best available experimental realization of the spin- (1)/(2) Heisenberg model on the honeycomb lattice. We also provide an instructive comparison of different band-structure codes and computational approaches to the evaluation of exchange couplings in magnetic insulators.

Tsirlin, Alexander A.; Janson, Oleg; Rosner, Helge

2010-10-01

275

Evaluation of the in-service performance behavior of honeycomb composite sandwich structures  

NASA Astrophysics Data System (ADS)

When honeycomb composite structures are fabricated for the aerospace industry, they are designed to be closed to their operating environment for the life of the composite structure. However, once in service, this design can break down. Damage can set in motion a chain reaction of events that will ultimately degrade the mechanical integrity of the composite structure. Through thermographic analysis, the tendency of honeycomb composite structures to absorb and retain water was investigated, and an attempt was made to quantify the extent of water ingression in the Boeing 767 aircraft. Through thermographic analysis, the exterior honeycomb composite structures were found to contain less than 50 kg of water per plane. On average, over 90% of the water found on an aircraft was contained in five problematic parts, which included the outboard flap wedge, the nose landing gear doors, the main landing gear doors, the fixed upper wing panels, and the escape slide door. Kevlar lamina induced microcracking, skin porosity problems, and cracked potting compound were the root causes of water ingression and migration in these structures. Ultimately, this research will aid in the fundamental understanding and design of future honeycomb composite sandwich structures.

Shafizadeh, J. E.; Seferis, J. C.; Chesmar, E. F.; Geyer, R.

1999-12-01

276

Loading, Degradation and Repair of F-111 Bonded Honeycomb Sandwich Panels - Preliminary Study  

Microsoft Academic Search

Many of the fixed and removable panels on the RAAF F-111 aircraft are made up of bonded honeycomb sandwich panels. Experience with the RAAF fleet has shown that a serious problem exists with degradation and damage of these panels. A review of the literature was undertaken to gain an understanding of the extent of this problem. It was found that

S. Whitehead; M. McDonald; R. A. Bartholomeusz

277

Low temperature chemical reduction of fusional sodium metasilicate nonahydrate into a honeycomb porous silicon nanostructure.  

PubMed

Honeycomb porous silicon (hp-Si) has been synthesized by a low temperature (200 °C) magnesiothermic reduction of Na2SiO3·9H2O. This process can be regarded as a general synthesis method for other silicide materials. Significantly, hp-Si features excellent electrochemical properties after graphene coating. PMID:24811773

Liang, Jianwen; Wei, Denghu; Lin, Ning; Zhu, Youngchun; Li, Xiaona; Zhang, Jingjing; Fan, Long; Qian, Yitai

2014-07-01

278

Three cycles of honeycomb selection for herb yield in davana (Artemisia pallens Wall.)  

Microsoft Academic Search

Three cycles of honeycomb selection for herb yield, applied on widely spaced individual plants of davana (Artemisia pallens Wall.), resulted in an increase in yield of 12.4% per cycle when the resulting populations were evaluated at commercial plant density. The selection had no adverse effect on essential oil content, davanone content in oil and plant height.

R. N. Kulkarni

1991-01-01

279

Evaluation on radiant characteristics of a honeycombed surface by Monte Carlo simulation  

Microsoft Academic Search

Blackbody (BB) cavities as standard radiation sources are used in calibration for various infrared (IR) instruments in IR detection, imaging, material emissivity measuring etc. A surface pitted with cell-like mini cavities as honeycombs whose radiant characteristics is evaluated by Monte Carlo method (MCM) is applied to develop a new surface BB. To improve the precision of MCM, make it more

Hong Zhang; Boya Liu

2010-01-01

280

Non-destructive inspection of drilled holes in reinforced honeycomb sandwich panels using active thermography  

NASA Astrophysics Data System (ADS)

The aerospace industry is in constant need of ever-more efficient inspection methods for quality control. Product inspection is also essential to maintain the safe operation of aircraft components designed to perform for decades. This paper proposes a method for non-destructive inspection of drilled holes in reinforced honeycomb sandwich panels. Honeycomb sandwich panels are extensively employed in the aerospace industry due to their high strength and stiffness to weight ratios. In order to attach additional structures to them, panels are reinforced by filling honeycomb cells and drilling holes into the reinforced areas. The proposed procedure is designed to detect the position of the holes within the reinforced area and to provide a robust measurement of the distance between each hole and the boundary of the reinforced area. The result is a fast, safe and clean inspection method for drilled holes in reinforced honeycomb sandwich panels that can be used to robustly assess a possible displacement of the hole from the center of the reinforced area, which could have serious consequences. The proposed method is based on active infrared thermography, and uses state of the art methods for infrared image processing, including signal-to-nose ratio enhancement, hole detection and segmentation. Tests and comparison with X-ray inspections indicate that the proposed system meets production needs.

Usamentiaga, R.; Venegas, P.; Guerediaga, J.; Vega, L.; López, I.

2012-11-01

281

Study made to control depth of potting compound for honeycomb sandwich fasteners  

NASA Technical Reports Server (NTRS)

Study determines optimum fastener insert size and shape, type of embedding cement, diameter, undercut and depth control by fiber glass plug in a honeycomb structure for maximum tensile strength The best potting compound is 5-5-1 weight mixture of epoxy resin, curing agent, and milled glass fibers.

Cushman, J.

1966-01-01

282

Tridimensional photographic reconstruction in a study of the pathogenesis of honeycomb lung  

PubMed Central

Tridimensional photographic reconstruction of the lesions found in honeycomb lung in 10 different types of pulmonary disease was made. The pathological picture was characteristic and well defined by tridimensional microscopy and quite independent of the accompanying disease. The lesions responsible for its appearance involved the whole lobular bronchiolar system but were most marked in the terminal and respiratory bronchioli. The changes were fundamentally diffuse, saccular, and cystic bronchiolectasis. Other bronchiolar lesions were found such as changes in direction and mode of division, amputations, and anastomoses between bronchioles and cysts belonging to anatomically independent airways. There was some evidence that the bullous aspects of honeycomb lung were due to multiple valvular arrangements which let the air in but do not let it out. Honeycomb lung was, in the majority of cases, a complication of interstitial pulmonary fibrosis. Honeycombing was usually due to marked changes in the lobular bronchioles caused by the obliteration or rigidity of alveolar ducts and the corresponding alveoli and even by localization of the interstitial fibrosis in the bronchiolar wall. Images

Pimentel, J. Cortez

1967-01-01

283

Testing, Evaluation, and Installation of Fiber-Reinforced Polymer Honeycomb Composite Panels in Bridge Deck Applications.  

National Technical Information Service (NTIS)

This report documents the progress of a project to design, fabricate, and install a fiber-reinforced polymer honeycomb sandwich panel system for use as a superstructure on new or existing vehicular bridge structures; the basic premise being to develop a v...

S. R. Gill J. D. Plunkett

2000-01-01

284

Rapid synthesis of porous honeycomb Cu/Pd through a hydrogen-bubble templating method.  

PubMed

A rapid electrochemical method based on using a clean hydrogen-bubble template to form a bimetallic porous honeycomb Cu/Pd structure has been investigated. The addition of palladium salt to a copper-plating bath under conditions of vigorous hydrogen evolution was found to influence the pore size and bulk concentration of copper and palladium in the honeycomb bimetallic structure. The surface was characterised by X-ray photoelectron spectroscopy, which revealed that the surface of honeycomb Cu/Pd was found to be rich with a Cu/Pd alloy. The inclusion of palladium in the bimetallic structure not only influenced the pore size, but also modified the dendritic nature of the internal wall structure of the parent copper material into small nanometre-sized crystallites. The chemical composition of the bimetallic structure and substantial morphology changes were found to significantly influence the surface-enhanced Raman spectroscopic response for immobilised rhodamine?B and the hydrogen-evolution reaction. The ability to create free-standing films of this honeycomb material may also have many advantages in the areas of gas- and liquid-phase heterogeneous catalysis. PMID:21769955

Najdovski, Ilija; Selvakannan, P R; O'Mullane, Anthony P; Bhargava, Suresh K

2011-08-29

285

Comparisons of honeycomb sandwich and foam-filled cylindrical columns under axial crushing loads  

Microsoft Academic Search

For the conventional thin-walled energy absorber, the energy dissipation during a collision is concentrated in relatively narrow zones. This means that a great deal of material does not participate in the plastic deformation or enter the large plastic deformation stage. To expand the plastic deformation zones and improve the energy absorption efficiency, the authors presented a new type of honeycomb

Zonghua Zhang; Shutian Liu; Zhiliang Tang

2011-01-01

286

GA-4/GA-9 honeycomb impact limiter tests and analytical model.  

National Technical Information Service (NTIS)

General Atomics (GA) has a test program underway to obtain data on the behavior of a honeycomb impact limiter. The program includes testing of small samples to obtain basic information, as well as testing of complete 1/4-scale impact limiters to obtain lo...

M. A. Koploy C. S. Taylor

1991-01-01

287

Ply drop-off effects in CFRP\\/honeycomb sandwich panels—experimental results  

Microsoft Academic Search

The results of a combined experimental and theoretical investigation of local bending effects induced by ply drop-off in CFRP\\/honeycomb sandwich panels are presented. The objective of the investigation was to validate a simple model for engineering analysis of sandwich panels with tapered face laminates presented in a previous paper. The experimental investigation was conducted by using electronic speckle pattern interferometry

O. T. Thomson; W. Rits; D. C. G. Eaton; O. Dupont; P. Queekers

1996-01-01

288

Diffusion bonded boron/aluminum spar-shell fan blade  

NASA Technical Reports Server (NTRS)

Design and process development tasks intended to demonstrate composite blade application in large high by-pass ratio turbofan engines are described. Studies on a 3.0 aspect radio space and shell construction fan blade indicate a potential weight savings for a first stage fan rotor of 39% when a hollow titanium spar is employed. An alternate design which featured substantial blade internal volume filled with titanium honeycomb inserts achieved a 14% potential weight savings over the B/M rotor system. This second configuration requires a smaller development effort and entails less risk to translate a design into a successful product. The feasibility of metal joining large subsonic spar and shell fan blades was demonstrated. Initial aluminum alloy screening indicates a distinct preference for AA6061 aluminum alloy for use as a joint material. The simulated airfoil pressings established the necessity of rigid air surfaces when joining materials of different compressive rigidities. The two aluminum alloy matrix choices both were successfully formed into blade shells.

Carlson, C. E. K.; Cutler, J. L.; Fisher, W. J.; Memmott, J. V. W.

1980-01-01

289

Electroplating with aluminum  

SciTech Connect

Electrodeposited aluminum has a broad range of potential applications in many industries because it offers the possibility of combining the surface properties of aluminum with the bulk properties of the substrate. Aluminum provides excellent corrosion protection and can withstand high temperatures. Plated aluminum can be anodized over virtually any substrate, including steel, copper, and titanium. However, because of its negative standard potential, aluminum can be electrodeposited only out of an absolutely water-free electrolyte. Otherwise the water is electrolyzed, generating hydrogen and oxygen. In response to the technical demand for an electrochemical aluminum deposition process, Siemens AG in Germany has developed and patented a process based on a water-free electrolyte. This proprietary technology, known in Germany as the Sigal process, has been licensed to AlumiPlate for worldwide commercialization. This article describes the process, coating properties, and applications.

Froemberg, W.; Donaldson, F.A.S. [AlumiPlate, Inc., Coon Rapids, MN (United States)

1996-02-01

290

Aspects of aluminum toxicity  

SciTech Connect

Aluminum is the most abundant metal in the earth's crust. The widespread occurrence of aluminum, both in the environment and in foodstuffs, makes it virtually impossible for man to avoid exposure to this metal ion. Attention was first drawn to the potential role of aluminum as a toxic metal over 50 years ago, but was dismissed as a toxic agent as recently as 15 years ago. The accumulation of aluminum, in some patients with chronic renal failure, is associated with the development of toxic phenomena; dialysis encephalopathy, osteomalacic dialysis osteodystrophy, and an anemia. Aluminum accumulation also occurs in patients who are not on dialysis, predominantly infants and children with immature or impaired renal function. Aluminum has also been implicated as a toxic agent in the etiology of Alzheimer's disease, Guamiam amyotrophic lateral sclerosis, and parkinsonism-dementia. 119 references.

Hewitt, C.D.; Savory, J.; Wills, M.R. (Univ. of Virginia Health Sciences Center, Charlottesville (USA))

1990-06-01

291

Carbothermic Aluminum Production Using Scrap Aluminum As A Coolant  

DOEpatents

A process for producing aluminum metal by carbothermic reduction of alumina ore. Alumina ore is heated in the presence of carbon at an elevated temperature to produce an aluminum metal body contaminated with about 10-30% by wt. aluminum carbide. Aluminum metal or aluminum alloy scrap then is added to bring the temperature to about 900-1000.degree. C. and precipitate out aluminum carbide. The precipitated aluminum carbide is filtered, decanted, or fluxed with salt to form a molten body having reduced aluminum carbide content.

LaCamera, Alfred F. (Trafford, PA)

2002-11-05

292

MTBE OXIDATION BY BIFUNCTIONAL ALUMINUM  

EPA Science Inventory

Bifunctional aluminum, prepared by sulfating zero-valent aluminum with sulfuric acid, has a dual functionality of simultaneously decomposing both reductively- and oxidatively-degradable contaminants. In this work, the use of bifunctional aluminum for the degradation of methyl te...

293

Interpretation of Cp(*) - protected Aluminum Clusters as Superatom Complexes  

NASA Astrophysics Data System (ADS)

Metal clusters stabilized by a surface ligand shell represent an interesting intermediate state of matter between molecular metal-ligand complexes and bulk metal. Such "metalloid" particles are characterized by the balance between metal-metal bonds in the core and metal-ligand bonds at the exterior of the cluster. In previous studies, the electronic stability observed for selected ligand-protected aluminum clusters is not fully understood. By density functional theory calculations, we illustrate here that the electronic stability of various experimentally isolated Cp(*) -- protected aluminum clusters can be explained using the electron shell model for the aluminum core, coupled with an ionic Al-Cp(*) interaction at the surface. Thus, one may classify ligand-protected aluminum clusters as "superatom complexes" similar to the ligand-protected gold clusters.

Clayborne, P. Andre; Lopez-Acevedo, Olga; Whetten, Robert; Grönbeck, Henrik; Häkkinen, Hannu

2011-03-01

294

Aluminum: Reducing chloride emissions from aluminum production  

SciTech Connect

Reynolds Metals Company (RMC), with assistance from a NICE{sup 3} grant, is developing for commercialization a closed-loop control process that greatly reduces chlorine emissions and increases plant efficiency while maintaining metal quality. The process still utilizes chlorine to remove impurities during aluminum processing, but is more effective than current methods. With the new technology chlorine in the stack is monitored and input chlorine is adjusted continuously. This optimization of chlorine use results in substantially less waste because less chlorine has to be bought or produced by aluminum manufacturers. This innovation is a significant improvement over conventional aluminum treatments, in which chlorine is injected in a more costly and wasteful manner. By the year 2010, the new technology has the potential to reduce the energy it takes to create chlorine by 8.4 billion Btu per year and to cut greenhouse gas emissions by 1,377 tons per year.

Simon, P.

1999-09-29

295

Correlating Aluminum Burning Times  

Microsoft Academic Search

Characteristics of aluminum combustion are summarized in an overview of the subject, focusing on the burning time of individual particles. Combustion data from over ten different sources with almost 400 datum points have been cataloged and correlated. Available models have also been used to evaluate combustion trends with key environmental parameters. The fundamental concepts that control aluminum combustion are discussed,

M. W. Beckstead

2005-01-01

296

Anodizing Aluminum with Frills.  

ERIC Educational Resources Information Center

"Anodizing Aluminum" (previously reported in this journal) describes a vivid/relevant laboratory experience for general chemistry students explaining the anodizing of aluminum in sulfuric acid and constrasting it to electroplating. Additions to this procedure and the experiment in which they are used are discussed. Reactions involved are also…

Doeltz, Anne E.; And Others

1983-01-01

297

A damage tolerance comparison of 7075-T6 aluminum alloy and IM7/977-2 carbon/epoxy  

NASA Technical Reports Server (NTRS)

A comparison of low velocity impact damage between one of the strongest aluminum alloys, to a new, damage tolerant resin system as a matrix for high strength carbon fibers was examined in this study. The aluminum and composite materials were used as face sheets on a 0.13 g/cu cm aluminum honeycomb. Four levels of impact energy were used; 2.6 J, 5.3 J, 7.8 J and 9.9 J. The beams were compared for static strength and fatique life by use of the four-point bend flexure test. It was found that in the undamaged state the specific strength of the composite face sheets was about twice that of the aluminum face sheets. A sharp drop in strength was observed for the composite specimens impacted at the lowest (2.6J) energy level, but the overall specific strength was still higher than for the aluminum specimens. At all impact energy levels tested, the static specific strength of the composite face sheets were significantly higher than the aluminum face sheets. The fatigue life of the most severely damaged composite specimen was about 17 times greater than the undamaged aluminum specimens when cycled at 1 Hz between 20 percent and 85 percent of ultimate breaking load.

Nettles, Alan T.; Lance, David G.; Hodge, Andrew J.

1991-01-01

298

The aluminum smelting process.  

PubMed

This introduction to the industrial primary aluminum production process presents a short description of the electrolytic reduction technology, the history of aluminum, and the importance of this metal and its production process to modern society. Aluminum's special qualities have enabled advances in technologies coupled with energy and cost savings. Aircraft capabilities have been greatly enhanced, and increases in size and capacity are made possible by advances in aluminum technology. The metal's flexibility for shaping and extruding has led to architectural advances in energy-saving building construction. The high strength-to-weight ratio has meant a substantial reduction in energy consumption for trucks and other vehicles. The aluminum industry is therefore a pivotal one for ecological sustainability and strategic for technological development. PMID:24806722

Kvande, Halvor

2014-05-01

299

Structural-mechanical coupling between accordion-like honeycomb scaffold, collagen and cardiomyocytes in engineered cardiac tissues  

Microsoft Academic Search

Mechanical and morphological anisotropy play key roles in the function of native cardiac tissues. In the current study, finite element simulations, morphological and mechanical analysis were used to investigate interactions between the geometry of accordion-like honeycomb poly(glycerol sebacate) scaffolds and cardiomyocytes seeded via a collagen solution gelled within the pores. Specifically, the mechanical behavior of the accordion-like honeycomb scaffold itself,

A. Jean; S. R. Bass; J. L. Dizky; G. C. Engelmayr

2011-01-01

300

Highly conductive and transparent Ag honeycomb mesh fabricated using a monolayer of polystyrene spheres  

NASA Astrophysics Data System (ADS)

We describe the design principles and fabrication of Ag honeycomb mesh as a transparent conductive electrode using a polystyrene (PS) sphere template. Monolayers of PS spheres with different diameters, such as 600 nm, 3 ?m, and 10 ?m, are studied as templates to form Ag mesh with high transmittance. Since the parasitic Ag islands degrade the transmittance, both heat pretreatment and wet etching are used to control the area covered by parasitic Ag islands. The trade-off between transmittance and conductivity forces us to use larger diameter PS spheres. Ten-micron PS spheres are chosen as the template for the PS sphere monolayer, and heat pretreatment and Ag wet etching are used to demonstrate that the Ag honeycomb mesh transparent electrodes have high performance. The transmittance and the sheet resistance are 83% and 20 ?/sq, which are comparable to commercial ITO electrodes.

Kwon, Namyong; Kim, Kyohyeok; Sung, Sihyun; Yi, Insook; Chung, Ilsub

2013-06-01

301

Single-hole properties of the t-J model on the honeycomb lattice  

NASA Astrophysics Data System (ADS)

Motivated by the possible charge ordering in the recently discovered superconductor NaxCoO2yH2O , which at filling x=1/3 would correspond to a half-filled honeycomb lattice, we investigate the single-hole dynamics of the t-J model on this lattice. Using exact diagonalization, series expansion, and the self-consistent Born approximation, we calculate the quasiparticle dispersion, bandwidth, and residues and compare our findings to the well-established results for the square lattice. Given the similarities between both lattices, it is not surprising that we find qualitatively similar features for the honeycomb lattice, namely, an almost flat band along the edge of the magnetic Brillouin zone and well-defined hole pockets around the corners. However, we report a considerable disagreement between the three methods used concerning the bandwidth and discuss possible origins of this discrepancy.

Lüscher, Andreas; Läuchli, Andreas; Zheng, Weihong; Sushkov, Oleg P.

2006-04-01

302

Fabrication of honeycomb texture on poly-Si by laser interference and chemical etching  

NASA Astrophysics Data System (ADS)

In this paper, we present a laser-interference method to fabricate honeycomb textures on poly-Si wafer for reflection reduction. When exposed to three interfering pulsed laser beams at 532 nm, the Si surface was periodically melted in accordance with the interference pattern. As a result, concave holes were generated on the surface because the melted material overflowed and condensed at the periphery. Subsequent acid etching revealed uniform and clean honeycomb textures. The texture depth could be controlled by varying the irradiation condition and a minimum reflectance of 10% was obtained. Transmission electron microscopy analysis showed that no irradiation-induced damage remained after etching. This approach can be a cost-effective alternative to lithographic processes for fabricating high-efficiency poly-Si solar cells.

Yang, Bogeum; Lee, Myeongkyu

2013-11-01

303

Friction factor data for flat plate tests of smooth and honeycomb surfaces. M.S. Thesis  

NASA Technical Reports Server (NTRS)

Friction factors for honeycomb surfaces were measured with a flat plate tester. The flat plate test apparatus was described and a method was discussed for determining the friction factor experimentally. The friction factor model was developed for the flat plate test based on the Fanno Line Flow. The comparisons of the friction factor were plotted for smooth surfaces and six-honeycomb surfaces with three-clearances, 6.9 bar to 17.9 bar range of inlet pressures, and 5,000 to 100,000 range of the Reynolds number. The optimum geometries for the maximum friction factor were found as a function of cell width to cell depth and cell width to clearance ratios.

Ha, Tae Woong

1989-01-01

304

Biomimetic surface modification of honeycomb films via a "grafting from" approach.  

PubMed

Hydrophobic isoporous membranes were fabricated using the "breath figure" method from polystyrene stars synthesized via ATRP. The living polymer chain ends at the surface of the films were then used, without further modification, in a "grafting-from" approach to grow surface-linked polyglycidyl methacrylate chains under conditions that maintained the regular honeycomb structure. This versatile functional surface was then used as a platform to build a small library of surfaces using a variety of simple chemistries: (i) the acid hydrolysis of the epoxide to form bis-alcohol groups and (ii) utilizing the "click-like" epoxide-amine reaction to functionalize the surface with a model biomolecule-(biotinamido)pentylamine. The successful modifications were confirmed by a combination of spectroscopic and biological means. Changes in the growth characteristics of nonmotile Psychrobacter sp. strain, SW5, on the honeycomb films, provided further evidence confirming changes in the hydrophobicity of the surface upon grafting. PMID:20597547

Nyström, Daniel; Malmström, Eva; Hult, Anders; Blakey, Idriss; Boyer, Cyrille; Davis, Thomas P; Whittaker, Michael R

2010-08-01

305

Spin-Orbital Short-Range Order on a Honeycomb-Based Lattice  

NASA Astrophysics Data System (ADS)

Frustrated magnetic materials, in which local conditions for energy minimization are incompatible because of the lattice structure, can remain disordered to the lowest temperatures. Such is the case for Ba3CuSb2O9, which is magnetically anisotropic at the atomic scale but curiously isotropic on mesoscopic length and time scales. We find that the frustration of Wannier’s Ising model on the triangular lattice is imprinted in a nanostructured honeycomb lattice of Cu2+ ions that resists a coherent static Jahn-Teller distortion. The resulting two-dimensional random-bond spin-1/2 system on the honeycomb lattice has a broad spectrum of spin-dimer-like excitations and low-energy spin degrees of freedom that retain overall hexagonal symmetry.

Nakatsuji, S.; Kuga, K.; Kimura, K.; Satake, R.; Katayama, N.; Nishibori, E.; Sawa, H.; Ishii, R.; Hagiwara, M.; Bridges, F.; Ito, T. U.; Higemoto, W.; Karaki, Y.; Halim, M.; Nugroho, A. A.; Rodriguez-Rivera, J. A.; Green, M. A.; Broholm, C.

2012-05-01

306

Honeycomb-like graphitic ordered macroporous carbon prepared by pyrolysis of ammonium bicarbonate  

SciTech Connect

Graphical abstract: Honeycomb-like graphitic macroporous carbon (HGMC) with big pores centered at 1-3 {mu}m, has been prepared by controlling the reaction temperature and amount of NH{sub 4}HCO{sub 3} at 550 {sup o}C in a sealed reaction system. Possible formation processes of HGMC are discussed on the experimental results. It is believed that the in situ formed MgO microparticles play a template role during the preparation of HGMC. Highlights: {yields} Honeycomb-like graphitic carbon was synthesized at 550 {sup o}C. {yields} The honeycomb-like graphitic carbon is macroposous structures. {yields} The formed MgO microparticles play a template role during the HGMC formation. {yields} The method can be expended to synthesize other porous or hollow carbon material. -- Abstract: Honeycomb-like graphitic macroporous carbon (HGMC) was synthesized by means of pyrolysis of NH{sub 4}HCO{sub 3} using Mg powder as reductant in an autoclave at 550 {sup o}C. The characterization of structure and morphology was carried out by X-ray diffraction (XRD), Raman spectrum, field-emission scanning electron microscopy (FESEM), and (High-resolution) transmission electron microscope [(HR)TEM]. The results of nitrogen adsorption-desorption indicate that the products are macropore materials with the pore size of 1-3 {mu}m, and the Brunauer-Emett-Teller (BET) surface area was 14 m{sup 2}/g. As a typical morphology, the possible growth process of HGMC was also investigated and discussed. The experimental results show that the in situ formed MgO microparticles play a template role during the HGMC formation.

Wang, Liancheng [Key Laboratory of Colloid and Interface Chemistry, Shandong University, Jinan, Shandong 250100 (China)] [Key Laboratory of Colloid and Interface Chemistry, Shandong University, Jinan, Shandong 250100 (China); Zhang, Junhao, E-mail: jhzhang6@mail.ustc.edu.cn [Key Laboratory of Colloid and Interface Chemistry, Shandong University, Jinan, Shandong 250100 (China) [Key Laboratory of Colloid and Interface Chemistry, Shandong University, Jinan, Shandong 250100 (China); School of Biology and Chemical Engineering, Jiangsu University of Science and Technology, Zhenjiang, Jiangsu 212003 (China); Xu, Liqiang; Qian, Yitai [Key Laboratory of Colloid and Interface Chemistry, Shandong University, Jinan, Shandong 250100 (China)] [Key Laboratory of Colloid and Interface Chemistry, Shandong University, Jinan, Shandong 250100 (China)

2011-10-15

307

Surface phonon polariton characteristic of honeycomb nanoporous GaN thin films  

NASA Astrophysics Data System (ADS)

Nanoporous GaN thin films with honeycomb structure were fabricated via ultra-violet assisted electrochemical etching approach. Under different anodization voltages, two nanoporous samples with different porosity were fabricated. Porosity and surface phonon polariton (SPP) characteristics of the fabricated samples were investigated using polarized infrared attenuated total reflection technique. It was found that the porosity of nanoporous GaN has great influence on its SPP resonant frequency. It can modulate the resonance frequency towards lower value.

Cheah, S. F.; Lee, S. C.; Ng, S. S.; Yam, F. K.; Abu Hassan, H.; Hassan, Z.

2013-03-01

308

On the existence of real spectra in {PT}-symmetric honeycomb optical lattices  

NASA Astrophysics Data System (ADS)

This paper investigates the addition of complex potentials to Schrödinger equations with honeycomb lattice potentials. While self-adjointness is lost, symmetry with respect to the combined action of parity and time-reversal is maintained. Necessary and sufficient conditions are found which establish whether the spectra of the perturbed Schrödinger equation remains real or enters the complex plane after small perturbations. Numerical simulations show the impact of larger perturbations. In particular, nonlocal near degeneracies between dispersion bands are discussed.

Curtis, Christopher W.; Ablowitz, Mark J.

2014-06-01

309

Reentrant metallicity in the Hubbard model: the case of honeycomb nanoribbons  

NASA Astrophysics Data System (ADS)

Based on the cluster perturbation solution of the Hubbard Hamiltonian for a 2D honeycomb lattice, we present quasi-particle band structures of nanoribbons at half filling as a function of on-site electron–electron (e–e) repulsion. We show that, at moderate values of e–e interaction, ribbons with armchair-shaped edges exhibit an unexpected semimetallic behavior, recovering the original insulating character only at larger values of U.

Manghi, F.; Petocchi, F.

2014-07-01

310

A single EFEMP1 mutation associated with both Malattia Leventinese and Doyne honeycomb retinal dystrophy  

Microsoft Academic Search

Malattia Leventinese (ML) and Doyne honeycomb retinal dystrophy (DHRD) refer to two autosomal dominant diseases characterized by yellow-white deposits known as drusen that accumulate beneath the retinal pigment epithelium (RPE). Both loci were mapped to chromosome 2p16-21 (Refs 5,6) and this genetic interval has been subsequently narrowed. The importance of these diseases is due in large part to their close

Andrew J. Lotery; Elise Héon; Bertrand Piguet; Robyn H. Guymer; Kimberlie Vandenburgh; Pascal Cousin; Darryl Nishimura; Ruth E. Swiderski; Giuliana Silvestri; David A. Mackey; Gregory S. Hageman; Alan C. Bird; Daniel F. Schorderet; Edwin M. Stone; Francis L. Munier; Val C. Sheffield

1999-01-01

311

Design and experimental test of a novel surface blackbody with honeycombs  

Microsoft Academic Search

With the development of IR technology, there are increasing needs for surface BB. A novel surface blackbody (BB) with honeycombs for calibrating infrared (IR) imaging ranging 240~450K in the long IR wavelength bands of 3~15?m is developed and its features are experimental tested. Traditional radiant source of BB cavities are often with simple axisymmetrical structure, such as cylinder, cone, cylinder-cone,

Hong Zhang; Hui Zhu

2010-01-01

312

Glass fiber-reinforced polymer\\/steel hybrid honeycomb sandwich concept for bridge deck applications  

Microsoft Academic Search

Glass fiber-reinforced polymer (GFRP) materials possess inherently high strength-to-weight ratios, but their elastic moduli are low relative to civil engineering (CE) construction materials. As a result, serviceability issues are what govern GFRP material design in the CE bridge industry. Therefore, the study objective was to increase the stiffness of a commercial GFRP honeycomb sandwich panel through the inclusion of steel

Nicolas J Lombardi

2008-01-01

313

Glass fiber-reinforced polymer\\/steel hybrid honeycomb sandwich concept for bridge deck applications  

Microsoft Academic Search

Glass fiber-reinforced polymer (GFRP) bridge decks possess inherently high strength-to-weight ratios, but relatively low effective elastic moduli. As a result, serviceability issues govern GFRP bridge deck design. Therefore, the objective of this study was to increase the stiffness of a commercial GFRP honeycomb sandwich panel through the inclusion of steel within the cross section.GFRP-steel hybrid parametric studies were conducted to

Nicolas J. Lombardi; Judy Liu

2011-01-01

314

Studies on Digital Shearography for Testing of Aircraft Composite Structures and Honeycomb-Based Specimen  

Microsoft Academic Search

This paper reviews shearography and its applications for testing of aircraft composite structures and honeycomb-based specimen. Shearography is a laser-based interferometry in conjunction with the digital imaging processing technique for full-field measurement of surface deformation. It reveals defects in an object by looking for defect-induced deformation anomalies. It does not require special vibration isolation, and with the development of a

Hui Juan Feng; Jian Zhang; Xiang Kai Liu

2011-01-01

315

Dimer statistics of honeycomb lattices on Klein bottle, Möbius strip and cylinder  

NASA Astrophysics Data System (ADS)

Dimer statistics is a central problem in statistical physics. In this paper the enumerations of close-packed dimers of honeycomb lattices on Klein bottle, Möbius strip and cylinder are considered. By establishing a Pfaffian orientation or a crossing orientation, and then computing the determinants of the skew-symmetric matrices of the resulting orientation graphs, we obtain explicit expressions of the number of close-packed dimers of the Klein-bottle polyhex, the Möbius polyhex and the cylindrical polyhex.

Li, Wei; Zhang, Heping

2012-08-01

316

Buckling of regular, chiral and hierarchical honeycombs under a general macroscopic stress state  

PubMed Central

An approach to obtain analytical closed-form expressions for the macroscopic ‘buckling strength’ of various two-dimensional cellular structures is presented. The method is based on classical beam-column end-moment behaviour expressed in a matrix form. It is applied to sample honeycombs with square, triangular and hexagonal unit cells to determine their buckling strength under a general macroscopic in-plane stress state. The results were verified using finite-element Eigenvalue analysis.

Haghpanah, Babak; Papadopoulos, Jim; Mousanezhad, Davood; Nayeb-Hashemi, Hamid; Vaziri, Ashkan

2014-01-01

317

A ballistic limit equation for hypervelocity impacts on composite honeycomb sandwich panel satellite structures  

Microsoft Academic Search

During a recent experimental test campaign performed in the framework of ESA Contract 16721, the ballistic performance of multiple satellite-representative Carbon Fibre Reinforced Plastic (CFRP)\\/Aluminium honeycomb sandwich panel structural configurations (GOCE, Radarsat-2, Herschel\\/Planck, BeppoSax) was investigated using the two-stage light-gas guns at EMI. The experimental results were used to develop and validate a new empirical Ballistic Limit Equation (BLE), which

S. Ryan; F. Schaefer; R. Destefanis; M. Lambert

2008-01-01

318

Environmental deterioration of aluminum-aluminum connections  

Microsoft Academic Search

Wire splice connections are investigated for deterioration due to environmental factors. The tested splices of solid aluminum and copper wires are made using twist-on connectors. Some specimen groups are exposed in a chamber at 35°C and 90% relative humidity. Additional groups are exposed for ten years to a normal application environment. There is no current flow except when potential drop

Jesse Aronstein

1992-01-01

319

Simulating the Response of a Composite Honeycomb Energy Absorber. Part 2; Full-Scale Impact Testing  

NASA Technical Reports Server (NTRS)

NASA has sponsored research to evaluate an externally deployable composite honeycomb designed to attenuate loads in the event of a helicopter crash. The concept, designated the Deployable Energy Absorber (DEA), is an expandable Kevlar(Registered TradeMark) honeycomb. The DEA has a flexible hinge that allows the honeycomb to be stowed collapsed until needed during an emergency. Evaluation of the DEA began with material characterization of the Kevlar(Registered TradeMark)-129 fabric/epoxy, and ended with a full-scale crash test of a retrofitted MD-500 helicopter. During each evaluation phase, finite element models of the test articles were developed and simulations were performed using the dynamic finite element code, LS-DYNA(Registered TradeMark). The paper will focus on simulations of two full-scale impact tests involving the DEA, a mass-simulator and a full-scale crash of an instrumented MD-500 helicopter. Isotropic (MAT24) and composite (MAT58) material models, which were assigned to DEA shell elements, were compared. Based on simulations results, the MAT58 model showed better agreement with test.

Fasanella, Edwin L.; Annett, Martin S.; Jackson, Karen E.; Polanco, Michael A.

2012-01-01

320

Experimental and Analytical Evaluation of a Composite Honeycomb Deployable Energy Absorber  

NASA Technical Reports Server (NTRS)

In 2006, the NASA Subsonic Rotary Wing Aeronautics Program sponsored the experimental and analytical evaluation of an externally deployable composite honeycomb structure that is designed to attenuate impact energy during helicopter crashes. The concept, which is designated the Deployable Energy Absorber (DEA), utilizes an expandable Kevlar honeycomb structure to dissipate kinetic energy through crushing. The DEA incorporates a unique flexible hinge design that allows the honeycomb to be packaged and stowed flat until needed for deployment. A variety of deployment options such as linear, radial, and/or hybrid methods can be used. Experimental evaluation of the DEA utilized a building block approach that included material characterization testing of its constituent, Kevlar -129 fabric/epoxy, and flexural testing of single hexagonal cells. In addition, the energy attenuation capabilities of the DEA were demonstrated through multi-cell component dynamic crush tests, and vertical drop tests of a composite fuselage section, retrofitted with DEA blocks, onto concrete, water, and soft soil. During each stage of the DEA evaluation process, finite element models of the test articles were developed and simulations were performed using the explicit, nonlinear transient dynamic finite element code, LS-DYNA. This report documents the results of the experimental evaluation that was conducted to assess the energy absorption capabilities of the DEA.

Jackson, Karen E.; Kellas, Sotiris; Horta, Lucas G.; Annett, Martin S.; Polanco, Michael A.; Littell, Justin D.; Fasanella, Edwin L.

2011-01-01

321

Bondonic effects in group-IV honeycomb nanoribbons with Stone-Wales topological defects.  

PubMed

This work advances the modeling of bondonic effects on graphenic and honeycomb structures, with an original two-fold generalization: (i) by employing the fourth order path integral bondonic formalism in considering the high order derivatives of the Wiener topological potential of those 1D systems; and (ii) by modeling a class of honeycomb defective structures starting from graphene, the carbon-based reference case, and then generalizing the treatment to Si (silicene), Ge (germanene), Sn (stannene) by using the fermionic two-degenerate statistical states function in terms of electronegativity. The honeycomb nanostructures present ?-sized Stone-Wales topological defects, the isomeric dislocation dipoles originally called by authors Stone-Wales wave or SWw. For these defective nanoribbons the bondonic formalism foresees a specific phase-transition whose critical behavior shows typical bondonic fast critical time and bonding energies. The quantum transition of the ideal-to-defect structural transformations is fully described by computing the caloric capacities for nanostructures triggered by ?-sized topological isomerisations. Present model may be easily applied to hetero-combinations of Group-IV elements like C-Si, C-Ge, C-Sn, Si-Ge, Si-Sn, Ge-Sn. PMID:24705562

Putz, Mihai V; Ori, Ottorino

2014-01-01

322

Bone tissue engineering using human adipose-derived stem cells and honeycomb collagen scaffold.  

PubMed

Human adipose-derived stem cells (ASCs) have the capacity to regenerate and the potential to differentiate into multiple lineages of mesenchymal cells. The aim of this study was to investigate the possibility of using honeycomb collagen scaffold to culture ASCs in bone tissue engineering. The osteogenic capacity of ASCs in vitro, was confirmed by histology and measuring the expression of cbfa-1. After that, ASCs were cultured for up to 14 days in the honeycomb scaffold to allow a high density, three-dimensional culture. Scanning electron microscopy data showed that the scaffold was filled with the grown ASCs, and calcification, stained black with von Kossa, was confirmed. Furthermore, The ASC-loaded honeycomb collagen scaffolds cultured for 14 days were subcutaneously transplanted into nude mice, and excised after 8 weeks. Bone formation in vivo was examined using HE stain, von Kossa stain, and osteocalcin immunostain. Those histological views showed significant positive stains in the samples of osteogenic medium in the three types of stain. These results suggest that this carrier is a suitable scaffold for ASCs and will be useful as a three-dimensional bone tissue engineering scaffold in vitro and in vivo. PMID:17607760

Kakudo, Natsuko; Shimotsuma, Ayuko; Miyake, Shogo; Kushida, Satoshi; Kusumoto, Kenji

2008-01-01

323

Formation and soot combustion of honeycomb-like LaFeO3 microfibers.  

PubMed

The nanocrystalline, honeycomb-like, perovskite LaFeO3 microfibers with a fibre diameter about 1-2 microm and channel sizes about 180-220 nm on the cross-section were prepared by the citrate-gel process. These microfibers were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and Brunauere-Emmette-Teller (BET) method. After calcined at a low temperature of 550 degrees C for 6 hours, the single phase of perovskite LaFeO3 microfibers is formed and the grain size increases from 27 to 38 nm with the calcination temperature increasing from 500 to 650 degrees C. The catalytic activity for soot combustion was analyzed by thermo-gravimetric method (TG), and the LaFeO3 microfibers calcined at 600 degrees C exhibits the highest catalytic activity for soot combustion, with a lowest T50 (393 degrees C) and T90 (434 degrees C). The formation mechanism of the honeycomb-like structure is analyzed and these honeycomb-like microfibers can be used as advanced catalysts, absorbents, filters and microreactors. PMID:24745245

Zou, Lianli; Jing, Maoxiang; Xiang, Jun; Wang, Pan; Shen, Xiangqian

2014-03-01

324

Effective spin couplings in the Mott insulator of the honeycomb lattice Hubbard model  

NASA Astrophysics Data System (ADS)

Motivated by the recent discovery of a spin-liquid phase for the Hubbard model on the honeycomb lattice at half-filling (Meng et al 2010 Nature 88 487), we apply both perturbative and non-perturbative techniques to derive effective spin Hamiltonians describing the low-energy physics of the Mott-insulating phase of the system. Exact diagonalizations of the so-derived models on small clusters are performed, in order to assess the quality of the effective low-energy theory in the spin-liquid regime. We show that six-spin interactions on the elementary loop of the honeycomb lattice are the dominant sub-leading effective couplings. A minimal spin model is shown to reproduce most of the energetic properties of the Hubbard model on the honeycomb lattice in its spin-liquid phase. Surprisingly, a more elaborate effective low-energy spin model obtained by a systematic graph expansion rather disagrees beyond a certain point with the numerical results for the Hubbard model at intermediate couplings.

Yang, Hong-Yu; Fabricio Albuquerque, A.; Capponi, Sylvain; Läuchli, Andreas M.; Schmidt, Kai Phillip

2012-11-01

325

Crystal structure and magnetic properties of honeycomb-like lattice antiferromagnet p-BIP-V2  

NASA Astrophysics Data System (ADS)

We successfully synthesized verdazyl biradical crystals of p-BIP-V2 [4,4'-bis(1,5-diphenylverdazyl-3-yl)biphenyl]. Two types of intermolecular interactions are deduced from the spin-density distribution and molecular packing in the crystal, and these interactions are considered to result in the formation of a honeycomb lattice. The ab initio molecular orbital calculation also indicated such an exchange network of intermolecular interactions. The intramolecular interaction acts as a diagonal bridge across the honeycomb lattice to form a square lattice. We evaluated the intramolecular antiferromagnetic (AF) interaction J1 to be about 8.8 K from an analysis of the magnetic susceptibility of isolated p-BIP-V2 molecules in terms of an isolated S = 1/2 AF dimer. We analyzed the magnetic susceptibility of the crystals using the quantum Monte Carlo method. Consequently, two types of intermolecular AF interactions, J2 and J3, were found to be almost comparable and about 4.5 times larger than the intramolecular interaction J1. Thus, we confirmed that p-BIP-V2 has a slightly distorted S=1/2 honeycomb-like lattice.

Yamaguchi, Hironori; Nagata, Shintaro; Tada, Masami; Iwase, Kenji; Ono, Toshio; Nishihara, Sadafumi; Hosokoshi, Yuko; Shimokawa, Tokuro; Nakano, Hiroki; Nojiri, Hiroyuki; Matsuo, Akira; Kindo, Koichi; Kawakami, Takashi

2013-03-01

326

Clinical biochemistry of aluminum  

SciTech Connect

Aluminum toxicity has been implicated in the pathogenesis of a number of clinical disorders in patients with chronic renal failure on long-term intermittent hemodialysis treatment. The predominant disorders have been those involving either bone (osteomalacic dialysis osteodystrophy) or brain (dialysis encephalopathy). In nonuremic patients, an increased brain aluminum concentration has been implicated as a neurotoxic agent in the pathogenesis of Alzheimer's disease and was associated with experimental neurofibrillary degeneration in animals. The brain aluminum concentrations of patients dying with the syndrome of dialysis encephalopathy (dialysis dementia) are significantly higher than in dialyzed patients without the syndrome and in nondialyzed patients. Two potential sources for the increased tissue content of aluminum in patients on hemodialysis have been proposed: (1) intestinal absorption from aluminum containing phosphate-binding gels, and (2) transfer across the dialysis membrane from aluminum in the water used to prepare the dialysate. These findings, coupled with our everyday exposure to the ubiquitous occurrence of aluminum in nature, have created concerns over the potential toxicity of this metal.

King, S.W.; Savory, J.; Wills, M.R.

1981-05-01

327

Aluminum hemotoxicity mechanisms.  

PubMed

Both aluminum and its salts are commonly used by people. Aluminum salts are components of drugs. Such a widespread use of aluminum was enhanced by the belief that it is not toxic and is quickly excreted from the body with urine. It turned out, however, that this element has a negative impact on human health. Post-dialysis encephalopathy of patients with kidney malfunctioning was ascribed to the presence of aluminum in dialysis fluid. Aluminum cumulating in brain tissue is claimed to play a role in developing neurological disorders. This element affects bones as well as it causes disturbances in phosphorus and calcium levels, which is demonstrated chiefly by osteomalatia. Aluminium accumulation in the liver leads to cholestasis. This element causes numerous changes in peripheral blood and hemogenic system. It also causes normo- or microcytary anemia as it disturbs maturing of erythroblastic series cells and heme biosynthesis; it decreases osmotic resistance of red blood cells. Aluminum inhibits defensive mechanisms connected with white blood cells and macrophages. A number of processes, namely aluminum's hemolytic activity, blood cells' shorter lifetime or disturbed erythropoiesis process, are responsible for hematological changes. PMID:16146022

Osi?ska, Elzbieta; Kanoniuk, Dorota; Kusiak, Anna

2004-01-01

328

Purifying Aluminum by Vacuum Distillation  

NASA Technical Reports Server (NTRS)

Proposed method for purifying aluminum employs one-step vacuum distillation. Raw material for process impure aluminum produced in electrolysis of aluminum ore. Impure metal melted in vacuum. Since aluminum has much higher vapor pressure than other constituents, boils off and condenses on nearby cold surfaces in proportions much greater than those of other constituents.

Du Fresne, E. R.

1985-01-01

329

Mechanics of pressure-adaptive honeycomb and its application to wing morphing  

NASA Astrophysics Data System (ADS)

Current, highly active classes of adaptive materials have been considered for use in many different aerospace applications. From adaptive flight control surfaces to wing surfaces, shape-memory alloy (SMA), piezoelectric and electrorheological fluids are making their way into wings, stabilizers and rotor blades. Despite the benefits which can be seen in many classes of aircraft, some profound challenges are ever present, including low power and energy density, high power consumption, high development and installation costs and outright programmatic blockages due to a lack of a materials certification database on FAR 23/25 and 27/29 certified aircraft. Three years ago, a class of adaptive structure was developed to skirt these daunting challenges. This pressure-adaptive honeycomb (PAH) is capable of extremely high performance and is FAA/EASA certifiable because it employs well characterized materials arranged in ways that lend a high level of adaptivity to the structure. This study is centered on laying out the mechanics, analytical models and experimental test data describing this new form of adaptive material. A directionally biased PAH system using an external (spring) force acting on the PAH bending structure was examined. The paper discusses the mechanics of pressure adaptive honeycomb and describes a simple reduced order model that can be used to simplify the geometric model in a finite element environment. The model assumes that a variable stiffness honeycomb results in an overall deformation of the honeycomb. Strains in excess of 50% can be generated through this mechanism without encountering local material (yield) limits. It was also shown that the energy density of pressure-adaptive honeycomb is akin to that of shape-memory alloy, while exhibiting strains that are an order of magnitude greater with an energy efficiency close to 100%. Excellent correlation between theory and experiment is demonstrated in a number of tests. A proof-of-concept wing section test was conducted on a 12% thick wing section representative of a modern commercial aircraft winglet or flight control surface with a 35% PAH trailing edge. It was shown that camber variations in excess of 5% can be generated by a pressure differential of 40 kPa. Results of subsequent wind tunnel test show an increase in lift coefficient of 0.3 at 23 m s - 1 through an angle of attack from - 6° to + 20°. This paper was originally presented at the 2010 ASME SMASIS conference, as paper 'SMASIS 2010-3634'. Despite the substantial changes that have been made to the paper, there are still various figures and text stemming from the original.

Vos, Roelof; Barrett, Ron

2011-09-01

330

Advances in aluminum anodizing  

NASA Technical Reports Server (NTRS)

White anodize is applied to aluminum alloy surfaces by specific surface preparation, anodizing, pigmentation, and sealing techniques. The development techniques resulted in alloys, which are used in space vehicles, with good reflectance values and excellent corrosive resistance.

Dale, K. H.

1969-01-01

331

Corrosion Inhibitors for Aluminum.  

ERIC Educational Resources Information Center

Describes a simple and reliable test method used to investigate the corrosion-inhibiting effects of various chelating agents on aluminum pigments in aqueous alkaline media. The experiments that are presented require no complicated or expensive electronic equipment. (DDR)

Muller, Bodo

1995-01-01

332

Filiform Corrosion of Aluminum.  

National Technical Information Service (NTIS)

Generally, filiform corrosion occurs on aluminum when it is coated with an organic coating and the system is exposed to relatively high humidities. This type of corrosion is initiated or activated by the presence of electrolytes, particularly chloride, an...

W. H. Slabaugh W. Dejager S. E. Hoover L. L. Hutchinson

1971-01-01

333

Aluminum Permanganate Battery.  

National Technical Information Service (NTIS)

A battery is provided comprising an aluminum anode, an aqueous solution of permanganate as the cathodic species and a second electrode capable of reducing permanganate. Such a battery system is characterized by its high energy density and low polarization...

C. Marsh S. L. Licht

1993-01-01

334

Aluminum-air battery  

Microsoft Academic Search

Aluminum alloyed with small amounts (less than 0.1%) of In, Ga, and Tl in an aluminum air battery with 2M NaCl as the electrolyte is reported. The tested laboratory model of the battery with a total weight of about 500 g operated at a total current of 8 A (j = 30 mA\\/cu cm) and a voltage of about 1

A. R. Despic; D. Drazic; S. Zecevic

1979-01-01

335

Interfacial electronic structure of trimethyl-aluminum and water on an In0.20Ga0.80As(001)-4 × 2 surface: A high-resolution core-level photoemission study  

NASA Astrophysics Data System (ADS)

In atomic-layer deposition (ALD), organoaluminum as trimethyl-aluminum (TMA) on a freshly molecular beam epitaxy grown In0.20Ga0.80As(001)-4 × 2 surface has three forms: Al bonding with 1, 2, and 3 methyl groups. The ALD method of using one pulse (0.1 s) of TMA plus one pulse (0.1 s) of water was ineffective in passivating the surface, as demonstrated by the increased intensity of the reacted surface components with high numbers of pulses. The intact TMA was physisorbed on the trough In atoms, while the methyl-deficient precursors are either bridged with two As atoms or on the row-edge As atoms. After the water pulse on the TMA-covered surface, a bond in the bridged As atoms was scissored off to produce the As-Al-CH3 and As-OH, and the physisorbed TMA was unaffected. TMA removed some row In atoms, which allowed the In and Ga atoms in the second layer to form OH bonds after the water exposure. The appearance of the As-OH bonds may cause interfacial defect density (Dit) a peak at the midgap.

Pi, T. W.; Lin, H. Y.; Chiang, T. H.; Liu, Y. T.; Wertheim, G. K.; Kwo, J.; Hong, M.

2013-05-01

336

TEM investigation of nanophase aluminum powder.  

PubMed

Nanophase aluminum powder was characterized in a field-emission-gun transmission electron microscope (TEM). Different techniques were used to investigate the structure of the particles, including conventional bright-field and dark-field imaging, scanning transmission electron microscopy (STEM), high-resolution lattice imaging, diffraction studies, energy dispersive X-ray spectroscopy (EDS) analysis and mapping, and electron energy loss spectroscopy (EELS) analysis and mapping. It has been established that the particle cores consist of aluminum single crystals that sometimes contain crystal lattice defects. The core is covered by a passivating layer of aluminum oxide a few nanometers thick. The alumina is mostly amorphous, but evidences of partial crystallinity of the oxide were also found. The thickness of this layer was measured using different techniques, and the results are in good agreement with each other. The particles are agglomerated in two distinct ways. Some particles were apparently bonded together during processing before oxidation. These mostly form dumbbells covered by a joint oxide layer. Also, oxidized particles are loosely assembled into relatively large clusters. PMID:17481322

Gertsman, Valéry Y; Kwok, Queenie S M

2005-10-01

337

Aluminum, parathyroid hormone, and osteomalacia  

SciTech Connect

Aluminum exposure in man is unavoidable. The occurrence of dialysis dementia, vitamin D-resistant osteomalacia, and hypochromic microcytic anemia in dialysis patients underscores the potential for aluminum toxicity. Although exposure via dialysate and hyperalimentation leads to significant tissue aluminum accumulation, the ubiquitous occurrence of aluminum and the severe pathology associated with large aluminum burdens suggest that smaller exposures via the gastrointestinal tract and lungs could represent an important, though largely unrecognized, public health problem. It is clear that some aluminum absorption occurs with the ingestion of small amounts of aluminum in the diet and medicines, and even greater aluminum absorption is seen in individuals consuming large amounts of aluminum present in antacids. Aluminum absorption is enhanced in the presence of elevated circulating parathyroid hormone. In addition, elevated PTH leads to the preferential deposition of aluminum in brain and bone. Consequently, PTH is likely to be involved in the pathogenesis of toxicities in those organs. PTH excess also seems to lead to the deposition of aluminum in the parathyroid gland. The in vitro demonstration that aluminum inhibits parathyroid hormone release is consistent with the findings of a euparathyroid state in dialysis patients with aluminum related vitamin D-resistant osteomalacia. Nevertheless, it seems likely that hyperparathyroidism is at least initially involved in the pathogenesis of aluminum neurotoxicity and osteomalacia; the increases in tissue aluminum stores are followed by suppression of parathyroid hormone release, which is required for the evolution of osteomalacia. Impaired renal function is not a prerequisite for increased tissue aluminum burdens, nor for aluminum-related organ toxicity. Consequently, it is likely that these diseases will be observed in populations other than those with chronic renal disease.

Burnatowska-Hledin, M.A.; Kaiser, L.; Mayor, G.H.

1983-01-01

338

Bimodal distribution of neon nanobubbles in aluminum  

SciTech Connect

Ne 1s core-level photoelectron spectra from Ne nanobubbles implanted in aluminum exhibit two peaks whose binding energies and relative intensities change with implantation energy, isochronal annealing, and sputtering. These changes in the core-level spectra are manifestations of the nanometer size of the bubbles since the screening of the photohole by the Al conduction electrons depends on the bubble size. Existence of a bimodal depth and size distribution of Ne nanobubbles is demonstrated in this work: smaller bubbles of about 4 A in radius are formed close to the Al(111) surface while the larger sized bubbles of 20 A in radius exist deeper below in the beneath subsurface region. A general relation between the radius of the rare-gas bubbles and their core-level binding energies is established.

Dhaka, R. S.; Barman, S. R. [UGC-DAE Consortium for Scientific Research, Khandwa Road, Indore 452001, Madhya Pradesh (India)

2009-03-15

339

Aluminum automotive space frames  

SciTech Connect

Design of aluminum structures is to a new topic. Aircraft makers have successfully solved difficult structural problems with a high degree of understanding and reliability. Other transportation modes such as trucks, trailers, and railcars have faced structural problems with some emphasis on high- and low-cycle fatigue of welded aluminum structures. However, the automotive market places stringent engineering demands on materials and superimposes demanding cost constraints. A project was instituted at Reynolds Metals Co. to investigate the opportunities for the cost-effective application of aluminum to automotive spaceframes. Several areas were recognized as key to the success of this application. They were: equivalent or superior structural stiffness of the assembly to existing steel unibody and/or steel spaceframe vehicles; effective joining of spaceframe members; equivalent or superior crashworthiness of the assembly; weight savings; flexibility; and low-cost approach aimed at effective manufacturing. To gain experience with the key aspects in a practical environment, the experience of current builders of steel tube frame chassis was explored. These chassis are typically used in low-volume vehicles requiring torsional stiffness, excellent crashworthiness, and exterior body-style flexibility. A model was developed using finite element methods that accurately predicts mass and stiffness of frames. An effective aluminum space frame was generated which was 7.5% stiffer and more than 20% lighter than the steel frame, with stresses kept below the fatigue limit for aluminum welds.

NONE

1995-08-01

340

Aluminum Reclamation by Acidic Extraction of Aluminum-Anodizing Sludges.  

National Technical Information Service (NTIS)

Extraction of aluminum-anodizing sludges with sulfuric acid was examined to determine the potential for production of commercial-strength solutions of aluminum sulfate, that is liquid alum. The research established kinetic and stoichiometric relationships...

F. M. Saunders R. C. Shaw

1988-01-01

341

ALUMINUM RECLAMATION BY ACIDIC EXTRACTION OF ALUMINUM-ANODIZING SLUDGES  

EPA Science Inventory

Extraction of aluminum-anodizing sludges with sulfuric acid was examined to determine the potential for production of commercial-strength solutions of aluminum sulfate, that is liquid alum. The research established kinetic and stoichiometric relationships and evaluates product qu...

342

Energy gap of tight-binding electrons on generalized honeycomb lattice  

NASA Astrophysics Data System (ADS)

So as to clearly understand the energy band gap of graphene, we study the energy band of tight-binding electrons on a honeycomb lattice with on-site potentials ?A and ?B on sublattices A and B, nearest-neighbor transfer integrals ta, tb and tc, and next-nearest-neighbor transfer integrals t2a, t2b, t2c, t2d, t2e and t2f, where t2a, t2b and t2C are transfer integrals between sublattice A, and t2d, t2e and t2f are transfer integrals between sublattice B.

Kishigi, Keita; Takeda, Ryuichi; Hasegawa, Yasumasa

2008-10-01

343

Intermediate and spin-liquid phase of the half-filled honeycomb Hubbard model  

NASA Astrophysics Data System (ADS)

We obtain the phase diagram of the half-filled honeycomb Hubbard model with density matrix embedding theory, to address recent controversy at intermediate couplings. We use clusters from 2-12 sites and lattices at the thermodynamic limit. We identify a paramagnetic insulating state, with possible hexagonal cluster order, competitive with the antiferromagnetic phase at intermediate coupling. However, its stability is strongly cluster and lattice size dependent, explaining controversies in earlier work. Our results support the paramagnetic insulator as being a metastable, rather than a true, intermediate phase, in the thermodynamic limit.

Chen, Qiaoni; Booth, George H.; Sharma, Sandeep; Knizia, Gerald; Chan, Garnet Kin-Lic

2014-04-01

344

A honeycomb model for tortuosity of flow path in the leaf venation network  

NASA Astrophysics Data System (ADS)

A honeycomb model is designed according to the leaf veins, which is expressed as a function of porosity and tortuosity, and there is no empirical constant in this model. We mainly applied it to the leaf venation network, and the prediction in our model are compared with that from available correlations obtained by matching the numerical results, both of which are consistent with each other. Our model and relations may have important significance and potential applications in leaf venation and porous media. They also have a certain guiding significance to fluid heat transfer and thermal diffusion, as well as biotechnology research, e.g. veins and the neural networks of human.

Liu, Han; Zou, Ming-Qing; Wang, Da-Lun; Yang, Shan-Shan; Liang, Ming-Chao

2014-01-01

345

Bose-Einstein Condensate in a Honeycomb Optical Lattice: Fingerprint of Superfluidity at the Dirac Point  

NASA Astrophysics Data System (ADS)

Mean-field Bloch bands of a Bose-Einstein condensate in a honeycomb optical lattice are computed. We find that the topological structure of the Bloch bands at the Dirac point is changed completely by atomic interaction of arbitrary small strength: the Dirac point is extended into a closed curve and an intersecting tube structure arises around the original Dirac point. These tubed Bloch bands are caused by the superfluidity of the system. Furthermore, they imply the inadequacy of the tight-binding model to describe an interacting Boson system around the Dirac point and the breakdown of adiabaticity by interaction of arbitrary small strength.

Chen, Zhu; Wu, Biao

2011-08-01

346

A heat transport capability estimation of heat pipes embedded in honeycomb sandwich panel  

NASA Astrophysics Data System (ADS)

The maximum heat load for heat pipes that are embedded in honeycomb sandwich panels with multi-point heating is evaluated by using a heat flow rate. The accuracy of the proposed method for determining the maximum heat load is certified by experiment for dry out of heat pipes. In addition, an estimation of the maximum heat transport capability of heat pipes for several heat source arrangements and heat loads are also clarified. The experimental results showed that this method was extremely useful and accurate for calculating the maximum heat load to heat pipes.

Miyazaka, Akihiro; Nakajima, Katsuhiko

347

The mobility of dual vortices in honeycomb, square, triangular, Kagome and dice lattices  

NASA Astrophysics Data System (ADS)

It was known that by a duality transformation, interacting bosons at filling factor f = p/q hopping on a lattice can be mapped to interacting vortices hopping on the dual lattice subject to a fluctuating dual 'magnetic field' whose average strength through a dual plaquette is equal to the boson density f = p/q. So the kinetic term of the vortices is the same as the Hofstadter problem of electrons moving in a lattice in the presence of f = p/q flux per plaquette. Motivated by this mapping, we study the Hofstadter bands of vortices hopping in the presence of magnetic flux f = p/q per plaquette on five most common bipartite and frustrated lattices namely square, honeycomb, triangular, dice and Kagome lattices. We count the total number of bands, and determine the number of minima and their locations in the lowest band. We also numerically calculate the bandwidths of the lowest Hofstadter bands in these lattices that directly measure the mobility of the dual vortices. The less mobile the dual vortices are, the more likely are the bosons to be in a superfluid state. We find that apart from the Kagome lattice at odd q, they all satisfy the exponential decay law W = Ae-cq even at the smallest q. At given q, the bandwidth W decreases in the order of triangle, square and honeycomb lattice. This indicates that the domain of the superfluid state of the original bosons increases in the order of the corresponding direct lattices: honeycomb, square and triangular. When q = 2, we find that the lowest Hofstadter band is completely flat for both Kagome and dice lattices. There is a gap on the Kagome lattice, but no gap on the dice lattice. This indicates that the boson ground state at half filling with nearest neighbour hopping on Kagome lattice is always a superfluid state. The superfluid state remains stable slightly away from the half filling. Our results show that the behaviours of bosons at or near half filling on Kagome lattices are quite distinct from those in square, honeycomb and triangular lattices studied previously.

Jiang, Longhua; Ye, Jinwu

2006-07-01

348

Application of transfer matrix method in heat transfer performance analysis of multi-re-entrant honeycomb structures  

NASA Astrophysics Data System (ADS)

The thermal properties for the multi-re-entrant honeycomb are investigated, where the hexagon and re-entrant topologies are applied for comparison. A compact model was adopted for the local heat transfer rate and pressure drop estimations while the total heat transfer rate was analyzed using the transfer matrix method. A thermal performance index was specified to characterize a good heat exchange medium that can transfer more heat at the expense of lower pressure loss. Numerical results reveal better thermal performances of multi-re-entrant honeycombs over hexagon and re-entrant topologies, attributed to the presence of added base walls. Auxetic effect introduced in multi-re-entrant honeycomb generally provides enhanced out-of-plane thermal conductivity and increased total heat transfer efficiency due to higher surface area density.

Hou, Xiuhui; Deng, Zichen; Yin, Guansheng

2014-06-01

349

Experimental percolation studies of two-dimensional honeycomb lattice: Li2Mn1-xTixO3.  

PubMed

Li2MnO3 with a S = 3/2 two-dimensional Mn honeycomb lattice has a Neel-type antiferromagnetic transition at TN = 36?K with a broad maximum in magnetic susceptibility at TM = 48?K. We have investigated site percolation effects by replacing Mn with nonmagnetic Ti, and completed a full phase diagram of Li2Mn1-xTixO3 solid solution systems to find that antiferromagnetic transition is continuously suppressed without a clear sign of changes in the Neel-type antiferromagnetic structure. The magnetic ordering eventually disappears at a critical concentration of xc = 0.7. This experimental observation is consistent with percolation theories for a honeycomb lattice when one considers up to 3rd nearest-neighbor interactions. This study highlights the importance of interaction beyond nearest neighbors even for the Mn element with relative localized 3d electrons in the honeycomb lattice. PMID:25001600

Lee, Sanghyun; Park, Junghwan; Kim, Jiyeon; Hong, Kun-Pyo; Song, Youngmi; Park, Je-Geun

2014-07-30

350

Aluminum Hydroxide and Magnesium Hydroxide  

MedlinePLUS

Aluminum Hydroxide, Magnesium Hydroxide are antacids used together to relieve heartburn, acid indigestion, and upset stomach. They may be used to ... with stomach acid and neutralize it. Aluminum Hydroxide, Magnesium Hydroxide are available without a prescription.This medication ...

351

Rabbit Neurobehavioral Toxicity from Aluminum.  

National Technical Information Service (NTIS)

A model for the production of neurobehavioral toxicity induced by systemic aluminum exposure was developed. Nictitating membrane extension conditioning was used to assess the influence of the aluminum treatment on learning (acquisition and conditioned res...

R. A. Yokel

1983-01-01

352

Chrome - Free Aluminum Coating System.  

National Technical Information Service (NTIS)

This slide presentation concerns the program to qualify a chrome free coating for aluminum. The program was required due to findings by OSHA and EPA, that hexavalent chromium, used to mitigate corrosion in aerospace aluminum alloys, poses hazards for pers...

J. D. Gugel J. H. Bailey

2010-01-01

353

Recycled Aluminum Ornaments  

NSDL National Science Digital Library

This lesson plan from ATEEC will explain the principles of recycling. The activity would be most appropriate for technology studies or high school science classes. In all, it would require 2-5 hours of class time to complete. The purpose of the lesson is to demonstrate how aluminum is recycled. This laboratory activity does require some special equipment including a heat source capable of melting aluminum and an outdoor work area. Extension activities are also provided. The lesson plan is available for download as a PDF; users must create a free, quick login with ATEEC to access the materials.

Wishart, Ray

2013-06-14

354

Regeneration of aluminum hydride  

DOEpatents

The present invention provides methods and materials for the formation of hydrogen storage alanes, AlH.sub.x, where x is greater than 0 and less than or equal to 6 at reduced H.sub.2 pressures and temperatures. The methods rely upon reduction of the change in free energy of the reaction between aluminum and molecular H.sub.2. The change in free energy is reduced by lowering the entropy change during the reaction by providing aluminum in a state of high entropy, by increasing the magnitude of the change in enthalpy of the reaction or combinations thereof.

Graetz, Jason Allan (Mastic, NY); Reilly, James J. (Bellport, NY)

2009-04-21

355

Preparation and characterization of morph-genetic aluminum nitride/carbon composites from filter paper  

SciTech Connect

Morph-genetic aluminum nitride/carbon composites with cablelike structure were prepared from filter paper template through the surface sol-gel process and carbothermal nitridation reaction. The resulting materials have a hierarchical structure originating from the morphology of cellulose paper. The aluminum nitride/carbon composites have the core-shell microstructure, the core is graphitic carbon, and the shell is aluminum nitride nanocoating formed by carbothermal nitridation reduction of alumina with the interfacial carbon in nitrogen atmosphere. Scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and transmission electron microscope were employed to characterize the structural morphology and phase compositions of the final products.

Wang Wei [State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710049 (China)], E-mail: wangwei9310023@mail.xjtu.edu.cn; Xue Tao; Jin Zhihao; Qiao Guanjun [State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710049 (China)

2008-04-01

356

A comparative study of the impact properties of sandwich materials with different cores  

NASA Astrophysics Data System (ADS)

Sandwich panels are made of two high strength skins bonded to either side of a light weight core and are used in applications where high stiffness combined with low structural weight is required. The purpose of this paper is to compare the mechanical response of several sandwich panels whose core materials are different. Sandwich panels with glass fibre-reinforced polymer face sheets were used, combined with five different cores; polystyrene foam, polypropylene honeycomb, two different density Balsa wood and Cork. All specimens were subjected to low velocity impact and their structural response (Force-displacement curves) were compared to quasistatic response of the panel tested using an hemispherical indenter.

Ramakrishnan, K. R.; Shankar, K.; Viot, P.; Guerard, S.

2012-08-01

357

Membrane Purification Cell for Aluminum Recycling  

Microsoft Academic Search

Recycling mixed aluminum scrap usually requires adding primary aluminum to the scrap stream as a diluent to reduce the concentration of non-aluminum constituents used in aluminum alloys. Since primary aluminum production requires approximately 10 times more energy than melting scrap, the bulk of the energy and carbon dioxide emissions for recycling are associated with using primary aluminum as a diluent.

David DeYoung; James Wiswall; Cong Wang

2011-01-01

358

Zero modes around vacancies in topological insulators and topological superconductors on the honeycomb lattice with particle-hole symmetry  

NASA Astrophysics Data System (ADS)

This paper studies the quantum properties of lattice vacancies in topological band insulators and topological superconductors (TSCs) on a honeycomb lattice with particle-hole symmetry. Each vacancy exhibits one “gauge-invariant” zero mode for the spinless Haldane model and two “gauge-invariant” zero modes for the Kane-Mele model. In addition, there exist Majorana zero modes around the vacancies in TSCs on honeycomb lattices with particle-hole symmetry. These zero-energy modes are protected by the particle-hole symmetry of these topological states.

He, Jing; Zhu, Ying-Xue; Wu, Ya-Jie; Liu, Lan-Feng; Liang, Ying; Kou, Su-Peng

2013-02-01

359

Quantum molecular dynamics simulations of the oxidation of aluminum-cyclopentadienyl clusters  

NASA Astrophysics Data System (ADS)

We report Car-Parrinello molecular dynamics simulations of the oxidation of aluminum-cyclopentadienyl clusters currently being considered as novel fuels or energetic materials. These clusters contain a small aluminum core surrounded by a single organic ligand layer. The aromatic cyclopentadienyl ligands form a very strong bond with surface Al atoms, giving rise to a stable organometallic cluster which crystallizes into a low-symmetry solid-state material. Our calculations of an isolated cluster in oxygen show minimal reaction between the ligand and oxygen molecules at simulation temperatures of 300 and 1000 K. Rather, in all cases O2 diffuses through the ligand barrier, splits into atomic oxygen upon contact with the aluminum, and forms an amorphous aluminum oxide core. Loss of aluminum-ligand units, as expected from bond strength calculations, is not observed except following significant oxidation. We present simple metrics to quantitatively compare the steric barrier of the outer ligands that limits the oxidation process.

Alnemrat, Sufian; Hooper, Joseph P.

2014-05-01

360

Reclamation of Aluminum Finishing Sludges.  

National Technical Information Service (NTIS)

The research study of the reclamation of aluminum-anodizing sludges was conducted in two sequential phases focused on enhanced dewatering of aluminum-anodizing sludges to produce commercial-strength solutions of aluminum sulfate, i.e., liquid alum. The us...

F. M. Saunders

1987-01-01

361

Deformation and Imperfections in Aluminum.  

National Technical Information Service (NTIS)

The occurrence of twinning in aluminum and the part played by twinning in the plastic deformation of aluminum has not been adequately interpreted. The structure of aluminum has been determined only by the DeBye-Scherrer powder method which does not reveal...

R. H. Randall

1965-01-01

362

Electrically conductive anodized aluminum coatings  

NASA Technical Reports Server (NTRS)

A process for producing anodized aluminum with enhanced electrical conductivity, comprising anodic oxidation of aluminum alloy substrate, electrolytic deposition of a small amount of metal into the pores of the anodized aluminum, and electrolytic anodic deposition of an electrically conductive oxide, including manganese dioxide, into the pores containing the metal deposit; and the product produced by the process.

Alwitt, Robert S. (Inventor); Liu, Yanming (Inventor)

2001-01-01

363

RECLAMATION OF ALUMINUM FINISHING SLUDGES  

EPA Science Inventory

The research study of the reclamation of aluminum-anodizing sludges was conducted in two sequential phases focused on enhanced dewatering of aluminum-anodizing sludges to produce commercial-strength solutions of aluminum sulfate, i.e., liquid alum. The use of high-pressure (14 to...

364

Rock cities, periglacial mass-wasting, and honeycomb weathering in Warren County, northwestern Pennsylvania  

SciTech Connect

Imposing hilltop rock-cities developed from widely jointed outcrops of Olean conglomerate (Lower Pennsylvanian) create picturesque scenery on the Allegheny High Plateau in Warren Co., Pa. At least six such rock cities 2 to 5 acres in extent are associated with the Late Wisconsinan glacial border in the northern half of the county. Farther to the south, jumbled Olean and Knapp (Lower Mississippian) joint blocks occur on steep slopes below valley-wall cliffs. The rock cities and accumulations of displaced joint blocks are largely relics of Late Wisconsinan periglacial mass-wasting. Frost splitting initiated opening of bedrock joints to form buildings. Gravity, soil wedging, and possibly gelifluction then widened the fissures into streets. Gelifluction moved blocks downslope and oriented their long axes parallel with slope (Warren Rocks). Forward toppling of high, unstable blocks contributed to mass-movement on some steep slopes (Rimrock). Today, rock cities and downslope blocks are stable in areas of gentle (less than 10 percent) slopes, but toppling, solifluction, creep, and debris flows cause continued slow movement of large blocks on moderately steep to steep (greater than 30 percent) slopes. Blocks of Olean and Knapp conglomerate have both stratabound pitting and intricate honeycomb weathering. Deep pitting is controlled largely by variations in silica cementation. Honeycomb weathering is most evident in sandy layers and results from patterns of iron-oxide impregnation. Both are Holocene surface-weathering processes.

Inners, J.D.; Sevon, W.D.; Moore, M.E. (Pennsylvania Geological Survey, Harrisburg, PA (United States)); Berg, T.M. (Ohio Division of Geological Survey, Columbus, OH (United States))

1993-03-01

365

Cobalt (II) chloride promoted formation of honeycomb patterned cellulose acetate films.  

PubMed

CoCl(2) containing honeycomb patterned films were prepared from cellulose acetate (CA)/CoCl(2)/acetone solutions by the breath figure method in a wide range of humidities. Size and pore regularity depend on the CA/CoCl(2) molar ratio and humidity. When replacing CoCl(2) with Co(NO(3))(2) or CoBr(2), no formation of ordered porosity in the cellulose acetate films is observed. According to data from scanning electron microscopy (SEM), Energy Dispersive X-ray Microanalysis (EDX), X-ray Diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy, the key role in the formation of honeycomb structures can be attributed to the physical and chemical properties of CoCl(2) - hygroscopicity, low interaction with CA, and extraction from CA/CoCl(2)/acetone solution by water droplets condensed on the surface of the CA/CoCl(2) solution. Obtained films are prospective for using in catalysis, hydrogen fuel cells, and optical sensing materials. PMID:22074692

Naboka, Olga; Sanz-Velasco, Anke; Lundgren, Per; Enoksson, Peter; Gatenholm, Paul

2012-02-01

366

Investigation of shape memory alloy honeycombs by means of a micromechanical analysis  

NASA Astrophysics Data System (ADS)

Shape memory alloy (SMA) honeycombs are promising new smart materials which may be used for light-weight structures, biomedical implants, actuators and active structures. In this study, the behavior of several SMA honeycomb structures is investigated by means of a continuum-based thermomechanically coupled micromechanical analysis. To this end, macroscopic inelastic stress-strain responses of several topologies are investigated, both for pseudoelasticity and for shape memory effect. It was found that the triangular topology exhibits the best performance. In addition, the initial transformation surfaces are presented for all possible combinations of applied in-plane stresses. A special two-phase microstructure that is capable of producing an overall negative coefficient of thermal expansion is suggested and studied. In this configuration, in which one of the phases is a SMA, residual strains are being generated upon recovery. Here, the negative coefficient of thermal expansion appears to be associated with a larger amount of residual strain upon recovery. Furthermore, a two-dimensional SMA re-entrant topology that generates a negative in-plane Poisson's ratio is analyzed, and the effect of the full thermomechanical coupling is examined. Finally, the response of a particular three-dimensional microstructure is studied.

Freed, Yuval; Aboudi, Jacob; Gilat, Rivka

2008-07-01

367

Merging and alignment of Dirac points in a shaken honeycomb optical lattice  

NASA Astrophysics Data System (ADS)

Inspired by the recent creation of a honeycomb optical lattice and the realization of a Mott-insulating state in a square lattice by shaking, we study here the shaken honeycomb optical lattice. For a periodic shaking of the lattice, Floquet theory may be applied to derive a time-independent Hamiltonian. In this effective description, the hopping parameters are renormalized by a Bessel function, which depends on the shaking direction, amplitude, and frequency. Consequently, the hopping parameters can vanish and even change sign, in an anisotropic manner, thus yielding different band structures. Here, we study the merging and the alignment of Dirac points and dimensional crossovers from the two-dimensional system to one-dimensional chains and zero-dimensional dimers. We also consider next-nearest-neighbor hopping, which breaks the particle-hole symmetry and leads to a metallic phase when it becomes dominant over the nearest-neighbor hopping. Furthermore, we include weak repulsive on-site interactions and find the density profiles for different values of the hopping parameters and interactions, both in a homogeneous system and in the presence of a trapping potential. Our results may be experimentally observed by use of momentum-resolved Raman spectroscopy.

Koghee, Selma; Lim, Lih-King; Goerbig, M. O.; Smith, C. Morais

2012-02-01

368

Multicritical point of Ising spin glasses on triangular and honeycomb lattices  

NASA Astrophysics Data System (ADS)

The behavior of two-dimensional Ising spin glasses at the multicritical point on triangular and honeycomb lattices is investigated with the help of finite-size scaling and conformal-invariance concepts. We use transfer-matrix methods on long strips to calculate domain-wall energies, uniform susceptibilities, and spin-spin correlation functions. Accurate estimates are provided for the location of the multicritical point on both lattices, which lend strong support to a conjecture recently advanced by Takeda, Sasamoto, and Nishimori. Correlation functions are shown to obey rather strict conformal-invariance requirements, once suitable adaptations are made to account for geometric aspects of the transfer-matrix description of triangular and honeycomb lattices. The universality class of critical behavior upon crossing the ferro-para-magnetic phase boundary is probed, with the following estimates for the associated critical indices: ?=1.49(2) , ?=2.71(4) , ?1=0.183(3) , which are distinctly different from the percolation values.

de Queiroz, S. L. A.

2006-02-01

369

Featureless and nonfractionalized Mott insulators on the honeycomb lattice at 1/2 site filling  

PubMed Central

Within the Landau paradigm, phases of matter are distinguished by spontaneous symmetry breaking. Implicit here is the assumption that a completely symmetric state exists: a paramagnet. At zero temperature such quantum featureless insulators may be forbidden, triggering either conventional order or topological order with fractionalized excitations. Such is the case for interacting particles when the particle number per unit cell, f, is not an integer. However, can lattice symmetries forbid featureless insulators even at integer f? An especially relevant case is the honeycomb (graphene) lattice—where free spinless fermions at (the two sites per unit cell mean is half-filling per site) are always metallic. Here we present wave functions for bosons, and a related spin-singlet wave function for spinful electrons, on the honeycomb lattice and demonstrate via quantum to classical mappings that they do form featureless Mott insulators. The construction generalizes to symmorphic lattices at integer f in any dimension. Our results explicitly demonstrate that in this case, despite the absence of a noninteracting insulator at the same filling, lack of order at zero temperature does not imply fractionalization.

Kimchi, Itamar; Parameswaran, S. A.; Turner, Ari M.; Wang, Fa; Vishwanath, Ashvin

2013-01-01

370

Deconfined Criticality in a J-Q model on Honeycomb lattice  

NASA Astrophysics Data System (ADS)

The Deconfined Criticality scenariofootnotetextT. Senthil at al, Science 303, 1490 (2004). describes in the context of quantum magnets a generic non-Landau second-order transition between two orders that break different symmetries - antiferromagnetic order that breaks SU(2) symmetry and Valence bond (VB) order breaking lattice translational symmetry. We investigate this physics in the context of a J-Q modelfootnotetextA. W. Sandvik, Phys. Rev. Lett. 98, 227202 (2007). on the honeycomb lattice using both T=0 Projector Quantum Monte Carlo (QMC) and finite-T Stochastic Series Expansion QMC techniques. We find evidence for a continuous transition from different measurements including scaling of Néel and VB order parameters, Binder ratios of staggered magnetization, stiffness and uniform susceptibility. We have indications that this critical point belongs to the same universality class as the one observed on square lattice J-Q model. Our results also suggest that this critical fixed point controlling deconfined critical behaviour remains essentially unchanged even on the honeycomb lattice which allows three-fold hedgehog defects in the Néel order to be present in the continuum description of the critical point.

Pujari, Sumiran; Alet, Fabien; Damle, Kedar

2013-03-01

371

Removal of alachlor from water by catalyzed ozonation on Cu/Al2O3 honeycomb  

PubMed Central

Background The herbicide alachlor (2-chloro-2?6?-diethyl-N-methoxymethylacetanilide) has been known as a probable human carcinogen, and the MCL (minimum contamination level) for drinking water has been set at 2 ?g L-1. Therefore, the advanced methods for effectively removing it from water are a matter of interest. Catalyzed ozonation is a promising method for refractory organics degradation. Cu/Al2O3 catalyzed ozonation for degrading an endocrine disruptor (alachlor) in water was investigated. Results Experimental results showed that the ozonation of alachlor can be effectively catalyzed and enhanced by Cu/Al2O3-honeycomb. The main intermediate products formed (aliphatic carboxylic acids) were mineralized to a large extent in the catalytic process. Conclusions This study has shown that Cu/Al2O3-honeycomb is a feasible and efficient catalyst in the ozonation of alachlor in water. Less intermediate oxidation product was produced in the catalytic process than in the uncatalytic one. Furthermore, the mineralization of alachlor could be enhanced by increasing the pH of the reaction solution.

2013-01-01

372

Aluminum Sulfate 18 Hydrate  

ERIC Educational Resources Information Center

A chemical laboratory information profile (CLIP) of the chemical, aluminum sulfate 18 hydrate, is presented. The profile lists physical and harmful properties, exposure limits, reactivity risks, and symptoms of major exposure for the benefit of teachers and students using the chemical in the laboratory.

Young, Jay A.

2004-01-01

373

Aluminum battery alloys  

SciTech Connect

Aluminum alloys suitable for use as anode structures in electrochemical cells are disclosed. These alloys include iron levels higher than previously felt possible, due to the presence of controlled amounts of manganese, with possible additions of magnesium and controlled amounts of gallium.

Thompson, D.S.; Scott, D.H.

1985-11-19

374

Hugoniot of 5083 Aluminum.  

National Technical Information Service (NTIS)

The Hugoniot of 5083H131 aluminum has been experimentally determined in the pressure range from 161 to 472 kilobars. Over this pressure range the shock velocity-particle velocity relationship was found to be linear. The optical and electrical techniques u...

A. Melani G. Hauver

1973-01-01

375

Aluminum battery alloys  

DOEpatents

Aluminum alloys suitable for use as anode structures in electrochemical cs are disclosed. These alloys include iron levels higher than previously felt possible, due to the presence of controlled amounts of manganese, with possible additions of magnesium and controlled amounts of gallium.

Thompson, David S. (Richmond, VA); Scott, Darwin H. (Mechanicsville, VA)

1985-01-01

376

Stratospheric aluminum oxide.  

PubMed

Balloons and U-2 aircraft were used to collect micrometer-sized strato-spheric aerosols. It was discovered that for the past 6 years at least, aluminum oxide spheres have been the major stratospheric particulate in the size range 3 to 8 micrometers. The most probable source of the spheres is the exhaust from solid-fuel rockets. PMID:17737717

Brownlee, D E; Ferry, G V; Tomandl, D

1976-03-26

377

Experiments on Annealed Aluminum.  

National Technical Information Service (NTIS)

This investigation is a study of the quasi-static stress-strain relation for the case of biaxial stress in annealed commercially pure aluminum, and its implications with respect to the speed of propagation of disturbances caused by incremental stresses. T...

M. J. Kenig

1965-01-01

378

Aluminum powder applications  

Microsoft Academic Search

Aluminum powders have physical and metallurgical characteristics related to their method of manufacture that make them extremely important in a variety of applications. They can propel rockets, improve personal hygiene, increase computer reliability, refine exotic alloys, and reduce weight in the family sedan or the newest Air Force fighter. Powders formed into parts for structural and non-structural applications hold the

Gurganus

1995-01-01

379

Pitting corrosion of aluminum  

Microsoft Academic Search

This review describes the experiments performed during the last few decades which enhance knowledge of the pitting of aluminum. Specifically, metastable and stable pits, pit chemistry and the effect of intermetallics on pitting are discussed. The properties of metastable alloys and inhibition of Al are also discussed.

Z Szklarska-Smialowska

1999-01-01

380

Aluminum Corrosion and Turbidity  

SciTech Connect

Aluminum corrosion and turbidity formation in reactors correlate with fuel sheath temperature. To further substantiate this correlation, discharged fuel elements from R-3, P-2 and K-2 cycles were examined for extent of corrosion and evidence of breaking off of the oxide film. This report discusses this study.

Longtin, F.B.

2003-03-10

381

Aluminum Coatings for Steel  

Microsoft Academic Search

Aluminum coated steel possesses excellent oxidation and corrosion resistance in sulfur and marine: environments and can substitute for expensive alloy of steels. Hot dip aluminizing (HAD) and pack cementation calorizing (CAL) are dealt with in detail. IN HDA coats, some alloying action takes place, when the substrate is dipped in molten Al at 973 K for 1-2 minutes. The coat

Aruna Bahadur

1996-01-01

382

Advanced Cast Aluminum Alloys.  

National Technical Information Service (NTIS)

A recent advancement in cast aluminum alloys has demonstrated that complex shapes can be cast from a microalloyed Al-Cu alloy in dry sand molds with chills and that these castings can be heat treated to produce mechanical and physical properties nearly co...

A. P. Druschitz J. Griffin

2009-01-01

383

Core Inflation  

Microsoft Academic Search

The Bank of Canada uses core CPI inflation, the year-over-year rate of change of the consumer price index excluding food, energy, and the effects of changes in indirect taxes, as the operational guide for monetary policy. In this report we study the concept and measurement of core or underlying inflation more generally by examining several alternative measures of core inflation,

Seamus Hogan; Marianne Johnson; Thérèse Laflèche

2001-01-01

384

Effects of Different Honeycomb and Sucrose Levels on the Development of Greater Wax Moth Galleria mellonella Larvae  

Microsoft Academic Search

In this study, the effect of different honeycomb and sucrose amounts on the development of Galleria mellonella larvae has been investigated by using synthetic diet. These results showed that the Galleria mellonella larvae could tolerate different diets without any serious problem during their development. In a period of seven days maximum growth is determined on the larvae, which are fed

M. COSKUN; T. KAYIS; M. SULANC; P. OZALP

385

Mechanism and kinetics of aluminum and iron leaching from coal fly ash by sulfuric acid  

Microsoft Academic Search

The mechanism and kinetics of leaching of aluminum and iron from Coal Fly Ash (CFA), by sulfuric acid, involves a rate controlling step of mass transfer. It is shown that, in the leaching process, particles follow the shrinking core model with respect to formation of unreacted core that is encapsulated by a leached, porous, layer. Formation of diffusion resistant calcium

A. Seidel; Y. Zimmels

1998-01-01

386

Aluminum microstructures on anodic alumina for aluminum wiring boards.  

PubMed

The paper demonstrates simple methods for the fabrication of aluminum microstructures on the anodic oxide film of aluminum. The aluminum sheets were first engraved (patterned) either by laser beam or by embossing to form deep grooves on the surface. One side of the sheet was then anodized, blocking the other side by using polymer mask to form the anodic alumina. Because of the lower thickness at the bottom part of the grooves, the part was completely anodized before the complete oxidation of the other parts. Such selectively complete anodizing resulted in the patterns of metallic aluminum on anodic alumina. Using the technique, we fabricated microstructures such as line patterns and a simple wiring circuit-board-like structure on the anodic alumina. The aluminum microstructures fabricated by the techniques were embedded in anodic alumina/aluminum sheet, and this technique is promising for applications in electronic packaging and devices. PMID:20356280

Jha, Himendra; Kikuchi, Tatsuya; Sakairi, Masatoshi; Takahashi, Hideaki

2010-03-01

387

Mechanisms of Aluminum Tolerance  

Microsoft Academic Search

\\u000a Aluminum (Al) toxicity limits agricultural productivity over much of the world’s arable land by inhibiting root growth and\\u000a development. Affected plants have difficulty in acquiring adequate water and nutrition from their soil environments and thus\\u000a have stunted shoot development and diminished yield. Al toxicity is due to soil acidity and is largely a natural problem;\\u000a however, it can also result

Owen A. Hoekenga; Jurandir V. Magalhaes

388

Experimental Investigation of Composite Sandwich Square Tubes under Quasi-Static and Dynamic Axial Crushing  

Microsoft Academic Search

In this study, the crush behaviors of square sandwich composite tubes with woven fabric carbon\\/epoxy skins and aluminum honeycomb cores with the different honeycomb cell sizes and tube sizes were evaluated. For the evaluation, four different kinds of tubes were fabricated and crushed under quasi-static and dynamic impact loads. The impact tests were carried out using heavy wagons. From the

Jung-Seok Kim; Hyuk-Jin Yoon; Kwang-Bok Shin

2011-01-01

389

Noise transmission through an acoustically treated and honeycomb stiffened aircraft sidewall  

NASA Technical Reports Server (NTRS)

The noise transmission characteristics of test panels and acoustic treatments representative of an aircraft sidewall are experimentally investigated in the NASA Langley Research Center transmission loss apparatus. The test panels were built to represent a segment sidewall in the propeller plane of a twin-engine, turboprop light aircraft. It is shown that an advanced treatment, which uses honeycomb for structural stiffening of skin panels, has better noise transmission loss characteristics than a conventional treatment. An alternative treatment, using the concept of limp mass and vibration isolation, provides more transmission loss than the advanced treatment for the same total surface mass. Effects on transmission loss of a variety of acoustic treatment materials (acoustic blankets, septa, damping tape, and trim panels) are presented. Damping tape does not provide additional benefit when the other treatment provides a high level of damping. Window units representative of aircraft installations are shown to have low transmission loss relative to a completely treated sidewall.

Grosveld, F. W.; Mixson, J. S.

1984-01-01

390

The scaling of entanglement entropy in a honeycomb lattice on a torus  

NASA Astrophysics Data System (ADS)

The entanglement entropy of a noninteracting fermionic system confined to a two-dimensional honeycomb lattice on a torus is calculated. We find that the entanglement entropy can characterize Lifshitz phase transitions without a local order parameter. In the noncritical phase and critical phase with a nodal Fermi surface, the entanglement entropy satisfies an area law. The leading subarea term is a constant in the gapped phase rather than a logarithmic additive term in the gapless regime. The tuning of chemical potential allows for a nonzero Fermi surface, whose variation along a particular direction determines a logarithmic violation of the area law. We perform the scaling of entanglement entropy numerically and find agreement between the analytic and numerical results. Furthermore, we clearly show that an entanglement spectrum is equivalent to an edge spectrum.

You, Wen-Long

2014-06-01

391

Sonic Stop-Bands for Periodic Arrays of Metallic Rods: Honeycomb Structure  

NASA Astrophysics Data System (ADS)

Extensive band structures have been computed for periodic arrays (in the honeycomb structure) of rigid metallic rods in air. Multiple complete acoustic stop bands have been obtained within which sound and vibrations are forbidden. These gaps start opening up for a filling fractionf?8% and tend to increase with the filling fraction, exhibiting a maximum at the close-packing. A tandem structure has also been proposed that allows an ultrawideband filter for environmental or industrial noise to be achieved in the desired frequency range. This work is motivated by the recent experimental observation of sound attenuation on the sculpture by Eusebio Sempere, exhibited at the Juian March Foundation in Madrid [21] and complements the corresponding theoretical work [22, 23].

Kushwaha, M. S.; Djafari-Rouhani, B.

1998-12-01

392

Rotational Honeycomb Epitaxy of Ru Thin Films on Sapphire (0001) Substrate  

NASA Astrophysics Data System (ADS)

Rotational honeycomb epitaxy of hexagonal Ru films was achieved on c-plane sapphire substrates by pulsed laser ablation with the a-axis ratio of \\sqrt{3}. The crystal structure and crystallinity of the Ru films were examined by X-ray diffraction and pole figure measurements, respectively. The Ru films were found to be epitaxially grown with an a-axis rotation by 30° around the a-axis of sapphire, resulting in the crystallographic relationship of (0001)Ru // (0001) sapphire and < 11\\bar{2}0 > Ru // < 10\\bar{1}0 > sapphire. This is because the lattice mismatch between < 11\\bar{2}0 >Ru and < 10\\bar{1}0 > sapphire is as small as about 1.3%.

Yamada, Satoru; Nishibe, Yuki; Saizaki, Masato; Kitajima, Hiromichi; Ohtsubo, Shigeru; Morimoto, Akiharu; Shimizu, Tatsuo; Ishida, Katsuei; Masaki, Yuichi

2002-02-01

393

Double transfer through Dirac points in a tunable honeycomb optical lattice  

NASA Astrophysics Data System (ADS)

We report on Bloch-Zener oscillations of an ultracold Fermi gas in a tunable honeycomb lattice. The quasi-momentum distribution of the atoms is measured after sequentially passing through two Dirac points. We observe a double-peak feature in the transferred fraction to the second band, both as a function of the band gap at the Dirac points and the quasi-momentum of the trajectory. Our results are in good agreement with a simple analytical model based on two successive Landau-Zener transitions. Owing to the variation of the potential gradient over the cloud size, coherent Stückelberg oscillations are not visible in our measurements. This effect of the harmonic confinement is confirmed by a numerical simulation of the dynamics of a trapped 2D system.

Uehlinger, Thomas; Greif, Daniel; Jotzu, Gregor; Tarruell, Leticia; Esslinger, Tilman; Wang, Lei; Troyer, Matthias

2013-02-01

394

One-dimensional half-metallic interfaces of two-dimensional honeycomb insulators  

NASA Astrophysics Data System (ADS)

We study zigzag interfaces between insulating compounds that are isostructural to graphene, specifically II-VI, III-V, and IV-IV two-dimensional honeycomb insulators. We show that these one-dimensional interfaces are polar, with a net density of excess charge that can be simply determined by using the ideal (integer) formal valence charges, regardless of the predominant covalent character of the bonding in these materials. We justify this finding on fundamental physical grounds by analyzing the topology of the formal polarization lattice in the parent bulk materials. First-principles calculations elucidate an electronic compensation mechanism not dissimilar to oxide interfaces, which is triggered by a Zener-like charge transfer between interfaces of opposite polarity. In particular, we predict the emergence of one-dimensional electron and hole gases, which in some cases are ferromagnetic half metallic.

Bristowe, N. C.; Stengel, Massimiliano; Littlewood, P. B.; Artacho, Emilio; Pruneda, J. M.

2013-10-01

395

Solitons in triangular and honeycomb dynamical lattices with the cubic nonlinearity.  

PubMed

We study the existence and stability of localized states in the discrete nonlinear Schrödinger equation on two-dimensional nonsquare lattices. The model includes both the nearest-neighbor and long-range interactions. For the fundamental strongly localized soliton, the results depend on the coordination number, i.e., on the particular type of lattice. The long-range interactions additionally destabilize the discrete soliton, or make it more stable, if the sign of the interaction is, respectively, the same as or opposite to the sign of the short-range interaction. We also explore more complicated solutions, such as twisted localized modes and solutions carrying multiple topological charge (vortices) that are specific to the triangular and honeycomb lattices. In the cases when such vortices are unstable, direct simulations demonstrate that they typically turn into zero-vorticity fundamental solitons. PMID:12241502

Kevrekidis, P G; Malomed, B A; Gaididei, Yu B

2002-07-01

396

Sudden quenching in the Kitaev honeycomb model: Study of defect and heat generation  

NASA Astrophysics Data System (ADS)

We study the behavior of the defect and heat densities under sudden quenching near the quantum critical points in the two-dimensional Kitaev honeycomb model both in the thermodynamic and nonthermodynamic limits. We consider quenches starting from a quantum critical point into the gapped as well as the gapless phases. We choose points on the lines of anisotropic quantum critical points as well as different points of intersection of these lines as the initial points from where the quenching starts. We find that the defect and heat densities display the expected power-law scalings along with logarithmic corrections to scaling (or cusp singularities) in certain cases. In the vicinity of some of the intersection points, the scaling behaviors change, indicating an effective dimensional reduction; the scaling behavior near these points depends on the number of critical lines crossed in the process of quenching. All the analytical predictions are also verified by numerical integration.

Patel, Aavishkar A.; Dutta, Amit

2012-11-01

397

Absence of a Spin Liquid Phase in the Hubbard Model on the Honeycomb Lattice  

NASA Astrophysics Data System (ADS)

A spin liquid is a novel quantum state of matter with no conventional order parameter where a finite charge gap exists even though the band theory would predict metallic behavior. Finding a stable spin liquid in two or higher spatial dimensions is one of the most challenging and debated issues in condensed matter physics. Very recently, it has been reported that a model of graphene, i.e., the Hubbard model on the honeycomb lattice, can show a spin liquid ground state in a wide region of the phase diagram, between a semi-metal (SM) and an antiferromagnetic insulator (AFMI). Here, by performing numerically exact quantum Monte Carlo simulations, we extend the previous study to much larger clusters (containing up to 2592 sites), and find, if any, a very weak evidence of this spin liquid region. Instead, our calculations strongly indicate a direct and continuous quantum phase transition between SM and AFMI.

Sorella, Sandro; Otsuka, Yuichi; Yunoki, Seiji

2012-12-01

398

Superconductivity on the brink of spin-charge order in a doped honeycomb bilayer.  

PubMed

Using a controlled weak-coupling renormalization group approach, we establish the mechanism of unconventional superconductivity in the vicinity of spin or charge ordered excitonic states for the case of electrons on the Bernal stacked bilayer honeycomb lattice. With one electron per site, this system, physically realized in bilayer graphene, is unstable towards a spontaneous symmetry breaking. Repulsive interactions favor excitonic order, such as a charge nematic and/or a layer antiferromagnet. We find that upon adding charge carriers to the system, the excitonic order is suppressed, and unconventional superconductivity appears in its place, before it is replaced by a Fermi liquid. We focus on firmly establishing this phenomenon using the renormalization group formalism within an idealized model with parabolic touching of conduction and valence bands. PMID:24766005

Vafek, Oskar; Murray, James M; Cvetkovic, Vladimir

2014-04-11

399

A honeycomb-based piezoelectric actuator for a flapping wing MAV  

NASA Astrophysics Data System (ADS)

The present paper summarizes recent results on the study and design of a cellular piezoelectric actuator. A simple analytical model for the static and dynamic behavior of honeycomb-based amplified actuators is presented. Validation of the model is performed with experimental measurements and finite element calculations on off-the-shelf actuators. A parametric study illustrates the effect of the geometric parameters on the optimal mechanical power and corresponding absorbed electrical power. The analytical model is then used to find optimal actuator configurations for a flapping wing entomopter for which we seek to minimize (1) the mass and (2) the absorbed electrical energy, and maximize (3) the generated mechanical power. A multi-objective approach helps select a posteriori the most appropriate configuration for the micro air vehicle as well as compare the proposed active cellular structure to the more commonly used piezoelectric unimorph actuator.

Olympio, K. R.; Poulin-Vittrant, Guylaine

2011-03-01

400

CO(2) Adsorption on Activated Carbon Honeycomb-Monoliths: A Comparison of Langmuir and Tóth Models.  

PubMed

Activated carbon honeycomb-monoliths with different textural properties were prepared by chemical activation of African palm shells with H(3)PO(4), ZnCl(2) and CaCl(2) aqueous solutions of various concentrations. The adsorbents obtained were characterized by N(2) adsorption at 77 K, and their carbon dioxide adsorption capacities were measured at 273 K and 1 Bar in volumetric adsorption equipment. The experimental adsorption isotherms were fitted to Langmuir and Tóth models, and a better fit was observed to Tóth equation with a correlation coefficient of 0.999. The maximum experimental values for adsorption capacity at the highest pressure (2.627-5.756 mmol·g(-1)) are between the calculated data in the two models. PMID:22942710

Vargas, Diana P; Giraldo, Liliana; Moreno-Piraján, Juan C

2012-01-01

401

Resonant Transmission of Air-Coupled Ultrasound Through Metallic Inserts in Honeycomb Sandwich Structures  

SciTech Connect

Metallic inserts are embedded into composite honeycomb sandwiches as hard points for mechanical connections. Air-coupled ultrasound can be used for detecting disbonds between the insert and the facesheet. It was discovered in such inspections that a surprisingly large amplitude could be transmitted through thick metallic inserts (e.g. 0.75'' thick and 1.5'' diameter), whereas a thin plate of the same material will transmit a much weaker signal. This paper reports an experimental and analytic study of the geometrical effect of inserts on transmitted UT signals. Modal analyses of cylindrical inserts were made using the finite element code ANSYS. The transmission efficiency or air-coupled ultrasound correlated well with the longitudinal vibration mode of the cylinder.

Peters, J.J.; Barnard, D.J.; Hsu, D.K. [Iowa State University, Center for Nondestructive Evaluation, Ames, IA 50011 (United States); Dayal, V. [Iowa State University, Dept. of Aerospace Engineering, Ames, IA 50011 (United States)

2005-04-09

402

Phase Transitions and Honeycomb Morphology in an Incompatible Blend of Enantiomeric Polylactide Block Copolymers  

NASA Astrophysics Data System (ADS)

Enantiomeric PLAs, poly(L-lactide) (PLLA) and poly(D-lactide) (PDLA), are known to form stereocomplexes. In this work, by using controlled ring-opening polymerization of L- and D-lactides from monohydroxyl-terminated hydrophilic poly(ethylene oxide) (PEO) and hydrophobic poly(ethylene-co-1-butene) (PEB) oligomers, respectively, well-defined PEO-b-PLLA (2k-5.4k) and PEB-b-PDLA (4.2-5.4k) block copolymers were synthesized. Quantitative stereocomplex formation was achieved by casting an equimolar mixture of incompatible PEO-b-PLLA and PEB-b-PDLA from chloroform at room temperature. Depending on different thermal histories, either lamellar or inverted cylindrical morphology was observed in the molten state. Intriguingly, novel honeycomb morphology with the minor PEB component forming the matrix was observed in the inverted cylindrical phase.

Sun, Lu; Ginorio, Jorge; Zhu, Lei; Rong, Lixia; Sics, Igor; Hsiao, Benjamin

2007-03-01

403

Absence of a Spin Liquid Phase in the Hubbard Model on the Honeycomb Lattice  

PubMed Central

A spin liquid is a novel quantum state of matter with no conventional order parameter where a finite charge gap exists even though the band theory would predict metallic behavior. Finding a stable spin liquid in two or higher spatial dimensions is one of the most challenging and debated issues in condensed matter physics. Very recently, it has been reported that a model of graphene, i.e., the Hubbard model on the honeycomb lattice, can show a spin liquid ground state in a wide region of the phase diagram, between a semi-metal (SM) and an antiferromagnetic insulator (AFMI). Here, by performing numerically exact quantum Monte Carlo simulations, we extend the previous study to much larger clusters (containing up to 2592 sites), and find, if any, a very weak evidence of this spin liquid region. Instead, our calculations strongly indicate a direct and continuous quantum phase transition between SM and AFMI.

Sorella, Sandro; Yunoki, Seiji

2012-01-01

404

A modified VAPEPS method for predicting vibroacoustic response of unreinforced mass loaded honeycomb panels  

NASA Technical Reports Server (NTRS)

VAPEPS (VibroAcoustic Payload Environment Prediction System) is a computer program used to predict the vibroacoustic response of a structure. An alternate VAPEPS modeling technique, the Modified NASA Lewis Method, is an improvement for modeling unreinforced mass loaded honeycomb panels. The Modified NASA Lewis Method prediction is compared to the standard ASMS VAPEPS prediction, and the acoustic test data for three spacecraft panels. An analytical method of computing variance is presented and used to compute 95 percent confidence levels. These levels are compared to the standard VAPEPS confidence levels and to the envelope of the test data. As a result of using the new methodology suggested in the paper, both the mean prediction and the 95 percent confidence level prediction agree well with the test data in both spectral shape and magnitude. Therefore, the Modified NASA Lewis Method prediction methodology may be used to define more realistic random vibration test levels.

Mcnelis, Mark E.

1989-01-01

405

A modified VAPEPS method for predicting vibroacoustic response of unreinforced mass loaded honeycomb panels  

NASA Technical Reports Server (NTRS)

VAPEPS (vibroAcoustic Payload Environment Prediction System) is a computer program used to predict the vibroacoustic response of a structure. An alternate VAPEPS modeling technique, the Modified NASA Lewis Method, is an improvement for modeling unreinforced mass loaded honeycomb panels. The Modified NASA Lewis Method prediction is compared to the standard ASMS VAPEPS prediction, and the acoustic test data for three spacecraft panels. An analytical method of computing variance is presented and used to compute 95 percent confidence levels. These levels are compared to the standard VAPEPS confidence levels and to the envelope of the test data. As a result of using the new methodology suggested in the paper, both the mean prediction and the 95 percent confidence level prediction agree well with the test data in both spectral shape and magnitude. Therefore, the Modified NASA Lewis Method prediction methodology may be used to define more realistic random vibration test levels.

Mcnelis, Mark E.

1989-01-01

406

Design and fabrication of brazed Rene 41 honeycomb sandwich structural panels for advanced space transportation systems  

NASA Technical Reports Server (NTRS)

The design and fabrication of two large brazed Rene 41 honeycomb panels, the establishment of a test plan, the design and fabrication of a test fixture to subject the panels to cyclic thermal gradients and mechanical loads equivalent to those imposed on an advanced space transportation vehicle during its boost and entry trajectories are discussed. The panels will be supported at four points, creating three spans. The outer spans are 45.7 cm (18 in.) and the center span 76.2 cm (30 in). Specimen width is 30.5 cm (12 in.). The panels were primarily designed by boost conditions simulated by subjecting the panels to liquid nitrogen, 77K (-320 F) on one side and 455K (360 F) on the other side and by mechanically imposing loads representing vehicle fuel pressure loads. Entry conditions were simulated by radiant heating to 1034K (1400 F). The test program subjected the panels to 500 boost thermal conditions. Results are presented.

Hepler, A. K.; Swegle, A. R.

1981-01-01

407

Honeycomb-lattice plasmonic absorbers at NIR: anomalous high-order resonance.  

PubMed

We design, fabricate and characterize a plasmonic honeycomb lattice absorber with almost perfect absorption at 1140 nm over a wide incident angle range. This absorber also possesses a narrow-band, angle- and polarization-dependent high-order resonance in the short-wavelength range, with a bandwidth of 19 nm and angle sensitivity of 3 nm per degree. The nature of this high-order absorption band is analyzed through finite-element simulations. We believe it is due to Bragg coupling of the incident light to the backward-propagating surface plasmon polariton through the periodic modulation of the structure.Such fine absorption bands can find applications in plasmonic sensors and spectrally selective thermal emitters. PMID:24103960

Chen, Yiting; Dai, Jin; Yan, Min; Qiu, Min

2013-09-01

408

Critical behavior of long linear k-mers on honeycomb lattices  

NASA Astrophysics Data System (ADS)

Monte Carlo (MC) simulations, finite-size scaling and theoretical analysis have been carried out to study the critical behavior of long linear particles of length k ( k-mers) on honeycomb lattices. A nematic phase, characterized by a big domain of parallel k-mers, is separated from the isotropic state, by a continuous transition occurring at a finite density ?c. Our study allowed: (1) to determine the minimum value of k ( kmin), which allows the formation of the nematic phase, being kmin=11; (2) to predict the dependence of ?c on k, being ?c(k)?k-1; and (3) to obtain the critical exponents, which indicate that the transition belongs to the 2D three-state Potts universality class.

Matoz-Fernandez, D. A.; Linares, D. H.; Ramirez-Pastor, A. J.

2008-11-01

409

Direct observation of Dirac cones and a flatband in a honeycomb lattice for polaritons.  

PubMed

Two-dimensional lattices of coupled micropillars etched in a planar semiconductor microcavity offer a workbench to engineer the band structure of polaritons. We report experimental studies of honeycomb lattices where the polariton low-energy dispersion is analogous to that of electrons in graphene. Using energy-resolved photoluminescence, we directly observe Dirac cones, around which the dynamics of polaritons is described by the Dirac equation for massless particles. At higher energies, we observe p orbital bands, one of them with the nondispersive character of a flatband. The realization of this structure which holds massless, massive, and infinitely massive particles opens the route towards studies of the interplay of dispersion, interactions, and frustration in a novel and controlled environment. PMID:24702392

Jacqmin, T; Carusotto, I; Sagnes, I; Abbarchi, M; Solnyshkov, D D; Malpuech, G; Galopin, E; Lemaître, A; Bloch, J; Amo, A

2014-03-21

410

Inspection of Impact Damage in Honeycomb Composite by Espi, Thermography and Ultrasonic Testing  

NASA Astrophysics Data System (ADS)

Honeycomb composites are now fairly widely used in civilian and military aircraft structures. Common defects found in these materials are delaminations by impact damage and their presence will lead to structural weaknesses which could lead failure of the airframe structures. It is important to develop effective non-destructive testing procedures to identify these defects and increase the safety of aircraft travel. This paper describes the detection technique of impact damage defect using thermography and ESPI. The results obtained with the two techniques are compared with ultrasonic C-scan testing. The investigation shows that both imaging NDT methods are able to identify the presence of artificial defect and impact damage. The adoption of the thermography allowed significant advantages in inspection condition, and gives smaller error in quantitative estimation of defects.

Choi, Manyong; Park, Jeonghak; Kim, Wontae; Kang, Kisoo

411

System for precise temperature sensing and thermal control of borosilicate honeycomb mirrors during polishing and testing  

NASA Astrophysics Data System (ADS)

The Steward Observatory Mirror Laboratory has implemented a large borosilicate honeycomb telescope mirror polishing system in which thermal distortion is reduced to negligible levels by maintaining the glass in an isothermal state to within 0.1 C. Testing of the polished surface is conducted in air, using a laser and interferometer mounted above the mirror; the control of refractive index variation in the laser's light-path entails that the air also be isothermal, to within 0.2 C. Thermocouples are used as sensors in the polishing room, in air ducts, and on the mirror. Measurements are made to an accuracy of 0.005 C at the rate of one thermocouple/sec.

Lloyd-Hart, Michael

1990-07-01

412

Magnetic dipole configurations on honeycomb lattices: effect of finite size and boundaries.  

PubMed

Artificial dipolar spin-ice patterns have attracted much attention recently because of their rich configurations and excitations in the form of Dirac strings connecting magnetic monopoles. We have analysed the distribution of excitations in the form of strings and vertices carrying magnetic charges Q=±3q in honeycomb artificial spin-ice patterns. Two types of patterns are compared, those that terminate with open hexagons and those with closed hexagons. The dipole configurations and the frequency of spin-ice rule-violating Q=±3q vertices depend slightly on the boundary conditions of the pattern. Upon rotation of the patterns by 2? in a coercive magnetic field of 500 Oe, complete reversibility of the charge and string configuration is observed. PMID:23166380

Schumann, Alexandra; Zabel, Hartmut

2012-12-28

413

Strain-tunable band parameters of ZnO monolayer in graphene-like honeycomb structure  

NASA Astrophysics Data System (ADS)

We present ab initio calculations which show that the direct-band-gap, effective masses and Fermi velocities of charge carriers in ZnO monolayer (ML-ZnO) in graphene-like honeycomb structure are all tunable by application of in-plane homogeneous biaxial strain. Within our simulated strain limit of ±10%, the band gap remains direct and shows a strong non-linear variation with strain. Moreover, the average Fermi velocity of electrons in unstrained ML-ZnO is of the same order of magnitude as that in graphene. The results promise potential applications of ML-ZnO in mechatronics/straintronics and other nano-devices such as the nano-electromechanical systems (NEMS) and nano-optomechanical systems (NOMS).

Behera, Harihar; Mukhopadhyay, Gautam

2012-10-01

414

The Idiopathic Pulmonary Fibrosis Honeycomb Cyst Contains A Mucocilary Pseudostratified Epithelium  

PubMed Central

Background We previously identified a MUC5B gene promoter-variant that is a risk allele for sporadic and familial Idiopathic Pulmonary Fibrosis/Usual Interstitial Pneumonia (IPF/UIP). This allele was strongly associated with increased MUC5B gene expression in lung tissue from unaffected subjects. Despite the strong association of this airway epithelial marker with disease, little is known of mucin expressing structures or of airway involvement in IPF/UIP. Methods Immunofluorescence was used to subtype mucus cells according to MUC5B and MUC5AC expression and to identify ciliated, basal, and alveolar type II (ATII) cells in tissue sections from control and IPF/UIP subjects. Staining patterns were quantified for distal airways (Control and IPF/UIP) and in honeycomb cysts (HC). Results MUC5B-expressing cells (EC) were detected in the majority of control distal airways. MUC5AC-EC were identified in half of these airways and only in airways that contained MUC5B-EC. The frequency of MUC5B+ and MUC5AC+ distal airways was increased in IPF/UIP subjects. MUC5B-EC were the dominant mucus cell type in the HC epithelium. The distal airway epithelium from control and IPF/UIP subjects and HC was populated by basal and ciliated cells. Most honeycombing regions were distinct from ATII hyperplasic regions. ATII cells were undetectable in the overwhelming majority of HC. Conclusions The distal airway contains a pseudostratified mucocilary epithelium that is defined by basal epithelial cells and mucus cells that express MUC5B predominantly. These data suggest that the HC is derived from the distal airway.

Seibold, Max A.; Smith, Russell W.; Urbanek, Cydney; Groshong, Steve D.; Cosgrove, Gregory P.; Brown, Kevin K.; Schwarz, Marvin I.

2013-01-01

415

Acoustic emission analysis of full-scale honeycomb sandwich composite curved fuselage panels  

NASA Astrophysics Data System (ADS)

Acoustic emission (AE) was monitored in notched full-scale honeycomb sandwich composite curved fuselage panels during loading. The purpose of the study was to evaluate the AE technique as a tool for detecting notch tip damage initiation and evaluating damage severity in such structures. This evaluation was a part of a more general study on the damage tolerance of six honeycomb sandwich composite curved panels, each containing a different damage scenario. The overall program objective was to investigate the effects of holes and notches on residual strength. The investigation was conducted using the Full-Scale Aircraft Structural Test Evaluation and Research (FASTER) facility located at the Federal Aviation Administration William J. Hughes Technical Center, Atlantic City International Airport, NJ. This paper reports on the AE results recorded during the loading to failure of two selected panels. The results show that damage initiation at the tips of the notches, and its progression along the panel, could be detected and located. These AE results were correlated with the deformation and strain fields measured through strain photogrammetry, throughout loading, at the vicinity of these notches. This correlation aided in interpreting the AE results. While the fretting among the newly created fracture surfaces generated a large number of low-intensity AE signals, the high-intensity signals generated at high load levels provided a good measure for anticipating incipient fracture. Further, the AE results located internal disbonding caused during panel fabrication. The large number of low-intensity AE signals generated from the disbonded regions was associated with the fretting among the disbonded surfaces.

Leone, Frank A., Jr.; Ozevin, Didem; Godinez, Valery; Mosinyi, Bao; Bakuckas, John G., Jr.; Awerbuch, Jonathan; Lau, Alan; Tan, Tein-Min

2008-04-01

416

NaOH-modified ceramic honeycomb with enhanced formaldehyde adsorption and removal performance.  

PubMed

NaOH-modified ceramic honeycombs (Na-CH) were simply prepared by impregnating ceramic honeycombs (CH) into NaOH aqueous solution. It was clearly shown that the surface modification incurs higher specific surface area and smaller grain sizes of the CH without destruction of their integrity. Moreover, the introduced surface NaOH can trigger Cannizzaro disproportionation of surface-absorbed formaldehyde (HCHO) on Na-CH, resulting in catalytic transformation of HCHO into less-toxic formate and methoxy salts. The NaOH concentration during impregnating treatment has a great influence on HCHO adsorption and removal efficiency, while the impregnation time and temperature have little influence on the efficiency. When the CH was impregnated in 1 M NaOH aqueous solution for 0.5 h at room temperature, the HCHO removal efficiency at ambient temperature can reach about 80% with an initial HCHO concentration of 250 ppm. Moreover, the used Na-CH can be facilely regenerated via 1 min blow using a common electric hair dryer, with the generation of less toxic HCOOH and CH3OH and recovery of NaOH. Using such a mild, fast, and practical regeneration method, the regenerated Na-CH showed slight degradation in adsorption and removal capability toward HCHO. The enhanced performance of Na-CH obtained was attributed to the presence of NaOH and increase of specific surface area and surface hydroxyl groups. Considering no demand of noble metal for HCHO removal at ambient temperature and practical reusable capability of Na-CH under mild conditions, this work may provide some new insights into the design and fabrication of advanced catalysts for indoor air purification. PMID:23895134

Yu, Jiaguo; Li, Xinyang; Xu, Zhihua; Xiao, Wei

2013-09-01

417

Aluminum Carbothermic Technology  

SciTech Connect

This report documents the non-proprietary research and development conducted on the Aluminum Carbothermic Technology (ACT) project from contract inception on July 01, 2000 to termination on December 31, 2004. The objectives of the program were to demonstrate the technical and economic feasibility of a new carbothermic process for producing commercial grade aluminum, designated as the ''Advanced Reactor Process'' (ARP). The scope of the program ranged from fundamental research through small scale laboratory experiments (65 kW power input) to larger scale test modules at up to 1600 kW power input. The tasks included work on four components of the process, Stages 1 and 2 of the reactor, vapor recovery and metal alloy decarbonization; development of computer models; and economic analyses of capital and operating costs. Justification for developing a new, carbothermic route to aluminum production is defined by the potential benefits in reduced energy, lower costs and more favorable environmental characteristics than the conventional Hall-Heroult process presently used by the industry. The estimated metrics for these advantages include energy rates at approximately 10 kWh/kg Al (versus over 13 kWh/kg Al for Hall-Heroult), capital costs as low as $1250 per MTY (versus 4,000 per MTY for Hall-Heroult), operating cost reductions of over 10%, and up to 37% reduction in CO2 emissions for fossil-fuel power plants. Realization of these benefits would be critical to sustaining the US aluminum industries position as a global leader in primary aluminum production. One very attractive incentive for ARP is its perceived ability to cost effectively produce metal over a range of smelter sizes, not feasible for Hall-Heroult plants which must be large, 240,000 TPY or more, to be economical. Lower capacity stand alone carbothermic smelters could be utilized to supply molten metal at fabrication facilities similar to the mini-mill concept employed by the steel industry. Major accomplishments for the program include definition of the system thermo-chemistry, demonstration of reactor stage 1, development of reactor stage 2 critical components in a 500 kW module, experimental determination of the vapor recovery reactor fundamentals, detailed design and installation of an advanced stage 1/vapor recovery reactor, feasibility of efficient separation of Al-C metal alloy product, updated capital and operating cost estimates, and development of computer models for all steps of the Advanced Reactor Process.

Bruno, Marshall J.

2005-03-31

418

Extracting aluminum from dross tailings  

NASA Astrophysics Data System (ADS)

Aluminum dross tailings, an industrial waste, from the Egyptian Aluminium Company (Egyptalum) was used to produce two types of alums: aluminum-sulfate alum [itAl2(SO4)3.12H2O] and ammonium-aluminum alum [ (NH 4)2SO4AL2(SO4)3.24H2O]. This was carried out in two processes. The first process is leaching the impurities using diluted H2SO4 with different solid/liquid ratios at different temperatures to dissolve the impurities present in the starting material in the form of solute sulfates. The second process is the extraction of aluminum (as aluminum sulfate) from the purifi ed aluminum dross tailings thus produced. The effects of temperature, time of reaction, and acid concentration on leaching and extraction processes were studied. The product alums were analyzed using x-ray diffraction and thermal analysis techniques.

Amer, A. M.

2002-11-01

419

Molecular aspects of aluminum toxicity  

Microsoft Academic Search

The focus in this review is directed to molecular aspects of aluminum toxicity in animal and plant cells. Unique thermodynamic features of Al(lII) ions impart biological specificity which may form the biochemical basis of aluminum interactions with cellular constituents. Current knowledge about aluminum?specific, molecular interactions is rather scanty. Al(III) ions may coordinate with nucleotides or complex to phospholipids resulting in

Alfred Haug; Charles E. Foy

1984-01-01

420

Quasicrystalline particulate reinforced aluminum composite  

SciTech Connect

Particulate reinforced aluminum and aluminum alloy composites are rapidly emerging as new commercial materials for aerospace, automotive, electronic packaging and other high performance applications. However, their low processing ductility and difficulty in recyclability have been the key concern. In this study, two composite systems having the same aluminum alloy matrix, one reinforced with quasicrystals and the other reinforced with the conventional SiC reinforcements were produced with identical processing routes. Their processing characteristics and tensile mechanical properties were compared.

Anderson, I.E.; Biner, S.B.; Sordelet, D.J.; Unal, O.

1997-07-01

421

Aluminum-lithium for aerospace  

SciTech Connect

Aluminum-lithium alloys were developed primarily to reduce the weight of aircraft and aerospace structures. Lithium is the lightest metallic element, and each 1% of lithium added to aluminum reduces alloy density by about 3% and increases modulus by about 5%. Though lithium has a solubility limit of 4.2% in aluminum, the amount of lithium ranges between 1 and 3% in commercial alloys. Aluminum-lithium alloys are most often selected for aerospace components because of their low density, high strength, and high specific modulus. However, other applications now exploit their excellent fatigue resistance and cryogenic toughness.

Fielding, P.S.; Wolf, G.J. [Reynolds Metals Co., Richmond, VA (United States)

1996-10-01

422

Laser welding of aluminum alloys  

SciTech Connect

Recent interest in reducing the weight of automobiles to increase fuel mileage has focused attention on the use of aluminum and associated joining technologies. Laser beam welding is one of the more promising methods for high speed welding of aluminum. Consequently, substantial effort has been expended in attempting to develop a robust laser beam welding process. Early results have not been very consistent in the process requirements but more definitive data has been produced recently. This paper reviews the process parameters needed to obtain consistent laser welds on 5,000 series aluminum alloys and discusses the research necessary to make laser processing of aluminum a reality for automotive applications.

Leong, K.H.; Sabo, K.R.; Sanders, P.G. [Argonne National Lab., IL (United States). Technology Development Div.; Spawr, W.J.

1997-03-01

423

ice core  

Microsoft Academic Search

Svalbard ice cores have not yet been fully exploited for studies of climate and environmental conditions. In one recently drilled ice core from Lomonosovfonna we have studied the methanesulphonic acid (MSA) records in relation to temperature and sea ice. During the present climatic conditions MSA appears to be negatively correlated with the sea ice conditions in the Barents Sea, and

Elisabeth Isaksson; Teija Kekonen; John Moore

424

Control of vibration and wave propagation in sandwich plates with periodic auxetic core  

NASA Astrophysics Data System (ADS)

The wave propagation in and the vibration of sandwich plates with cellular core are analyzed and controlled. Negative Poisson's ratio (auxetic) core materials of different geometry placed periodically in the plate introduce the proper impedance mismatch necessary to obstruct the propagation of waves over specified frequency bands (stop bands) and in particular directions. The location and the extension of the stop bands and the directions of wave propagation can be modified by proper selection of the periodicity and of the geometrical and physical properties of the core. A Finite Element model is developed to predict the dynamic response of three-layered sandwich panels with honeycomb core. The Finite Element model along with the theory of periodic structures is used to evaluate the influence of core materials of different geometry placed periodically along the two dimensions of the structure. This combined analysis yields the phase constant surfaces for the considered sandwich plates, which define location and extension of the stop bands, as well as the directions of wave propagation at assigned frequency values. The analysis of the phase constant surfaces and the evaluation of the harmonic response at specified frequencies indicate that the plates are characterized by dynamic behaviors with directional properties, with spatial patterns strongly dependent on the configuration of the periodic core and on the excitation frequency. Auxetic honeycombs are considered as core materials in order to obtain maximum design flexibility. The elastic and inertial characteristics of auxetic honeycombs in fact vary substantially with their internal geometry and for given configurations outcast up to five times the corresponding properties of traditional hexagonal honeycombs. The presented numerical results demonstrate the unique characteristics of this class of two-dimensional periodic structures, which behave as directional mechanical filters. The findings of this study suggest that optimal configurations for the periodic cellular core can be identified in order to design passive composite panels, which are stable and quiet over desired frequency bands and which fit desired transmissibility levels in particular directions. Such unique filtering capabilities are achieved without requiring additional passive or active control devices and therefore without compromising the size and the weight of the layered structure.

Scarpa, Fabrizio L.; Ruzzene, Massimo; Mazzarella, Luca; Tsopelas, Panagiotis

2002-06-01

425

NASA-UVA Light Aerospace Alloy and Structure Technology Program Supplement: Aluminum-Based Materials for High Speed Aircraft  

NASA Technical Reports Server (NTRS)

This is the final report of the study "Aluminum-Based Materials for High Speed Aircraft" which had the objectives (1) to identify the most promising aluminum-based materials with respect to major structural use on the HSCT and to further develop those materials and (2) to assess the materials through detailed trade and evaluation studies with respect to their structural efficiency on the HSCT. The research team consisted of ALCOA, Allied-Signal, Boeing, McDonnell Douglas, Reynolds Metals and the University of Virginia. Four classes of aluminum alloys were investigated: (1) I/M 2XXX containing Li and I/M 2XXX without Li, (2) I/M 6XXX, (3) two P/M 2XXX alloys, and (4) two different aluminum-based metal matrix composites (MMC). The I/M alloys were targeted for a Mach 2.0 aircraft and the P/M and MMC alloys were targeted for a Mach 2.4 aircraft. Design studies were conducted using several different concepts including skin/stiffener (baseline), honeycomb sandwich, integrally stiffened and hybrid adaptations (conventionally stiffened thin-sandwich skins). Alloy development included fundamental studies of coarsening behavior, the effect of stress on nucleation and growth of precipitates, and fracture toughness as a function of temperature were an integral part of this program. The details of all phases of the research are described in this final report.

Starke, E. A., Jr.

1997-01-01

426

Production of aluminum metal by electrolysis of aluminum sulfide  

SciTech Connect

A method is disclosed for production of metallic aluminum by the electrolysis of A1/sub 2/S/sub 3/ at 700/sup 0/-800/sup 0/ C. in a chloride melt composed of one or more alkali metal chlorides, and one or more alkaline earth metal chlorides and/or aluminum chloride to provide improved operating characteristics of the process.

Minh, N.Q.; Loutfy, R.O.; Yao, N.P.

1984-08-07

427

Production of aluminum metal by electrolysis of aluminum sulfide  

DOEpatents

Production of metallic aluminum by the electrolysis of Al.sub.2 S.sub.3 at 700.degree.-800.degree. C. in a chloride melt composed of one or more alkali metal chlorides, and one or more alkaline earth metal chlorides and/or aluminum chloride to provide improved operating characteristics of the process.

Minh, Nguyen Q. (Woodridge, IL); Loutfy, Raouf O. (Tucson, AZ); Yao, Neng-Ping (Clarendon Hills, IL)

1984-01-01

428

Production of aluminum metal by electrolysis of aluminum sulfide  

DOEpatents

Metallic aluminum may be produced by the electrolysis of Al/sub 2/S/sub 3/ at 700 to 800/sup 0/C in a chloride melt composed of one or more alkali metal chlorides, and one or more alkaline earth metal chlorides and/or aluminum chloride to provide improved operating characteristics of the process.

Minh, N.Q.; Loutfy, R.O.; Yao, N.P.

1982-04-01

429

Helium Trapping in Aluminum and Sintered Aluminum Powders.  

National Technical Information Service (NTIS)

The surface erosion of annealed aluminum and of sintered aluminum powder (SAP) due to blistering from implantation of 100-keV exp 4 He exp + ions at room temperature has been investigated. A substantial reduction in the blistering erosion rate in SAP was ...

S. K. Das M. Kaminsky T. Rossing

1975-01-01

430

21 CFR 172.310 - Aluminum nicotinate.  

Code of Federal Regulations, 2013 CFR

... 3 2013-04-01 2013-04-01 false Aluminum nicotinate. 172.310 Section 172.310 ...Dietary and Nutritional Additives § 172.310 Aluminum nicotinate. Aluminum nicotinate may be safely used as a source of...

2013-04-01

431

21 CFR 73.2645 - Aluminum powder.  

Code of Federal Regulations, 2013 CFR

... 2013-04-01 false Aluminum powder. 73.2645 Section 73.2645 ...Cosmetics § 73.2645 Aluminum powder. (a) Identity and specifications. The color additive aluminum powder shall conform in identity and...

2013-04-01

432

Aluminum alloy development  

SciTech Connect

Development of an aluminum alloy which has higher strength than previous alloys while still showing acceptable levels of corrosion resistance and fracture is presented. Two different approaches to this goal are described; a final thermomechanical treatment method employed deformation and aging, while the second method depended solely on thermal practices to enhance the strength/corrosion resistance combination. Attention is given to a 7055 alloy that offers significant weight savings potential for applications requiring high compression strength combined with good corrosion resistance. It is indicated that structures including keel beams, horizontal tails, upper wings, cargo rails, and seat tracks on commercial transports are all candidate applications for this alloy.

Not Available

1991-09-01

433

Characterization of ultradispersed aluminum  

SciTech Connect

Samples of ultradispersed Al were received, which were produced by electrically exploding Al wires in argon. These samples comprised very small particles that were not significantly oxidized and that were stable in air. Particle morphology were studied with SE, micropycnometry, and gas adsorption surface area. Composition were determined using various techniques, as were thermal stability and reaction exotherms. The inexplicable reports of an Al-Ar compound and of an exothermic reaction were not confirmed. The material is a stable, nonoxidized, small-particle, highly reactive form of aluminum that is of interest in energetic materials formulations.

Simpson, R.L.; Maienschein, J.L.; Swansiger, R.W.; Garcia, F.; Darling, D.H.

1994-12-08

434

Selective Adsorption of Sodium Aluminum Fluoride Salts from Molten Aluminum  

SciTech Connect

Aluminum is produced in electrolytic reduction cells where alumina feedstock is dissolved in molten cryolite (sodium aluminum fluoride) along with aluminum and calcium fluorides. The dissolved alumina is then reduced by electrolysis and the molten aluminum separates to the bottom of the cell. The reduction cell is periodically tapped to remove the molten aluminum. During the tapping process, some of the molten electrolyte (commonly referred as “bath” in the aluminum industry) is carried over with the molten aluminum and into the transfer crucible. The carryover of molten bath into the holding furnace can create significant operational problems in aluminum cast houses. Bath carryover can result in several problems. The most troublesome problem is sodium and calcium pickup in magnesium-bearing alloys. Magnesium alloying additions can result in Mg-Na and Mg-Ca exchange reactions with the molten bath, which results in the undesirable pickup of elemental sodium and calcium. This final report presents the findings of a project to evaluate removal of molten bath using a new and novel micro-porous filter media. The theory of selective adsorption or removal is based on interfacial surface energy differences of molten aluminum and bath on the micro-porous filter structure. This report describes the theory of the selective adsorption-filtration process, the development of suitable micro-porous filter media, and the operational results obtained with a micro-porous bed filtration system. The micro-porous filter media was found to very effectively remove molten sodium aluminum fluoride bath by the selective adsorption-filtration mechanism.

Leonard S. Aubrey; Christine A. Boyle; Eddie M. Williams; David H. DeYoung; Dawid D. Smith; Feng Chi

2007-08-16

435

Hyperbranched poly(benzimidazole-co-benzene) with honeycomb structure as a membrane for high-temperature proton-exchange membrane fuel cells  

Microsoft Academic Search

Hyperbranched poly(benzimidazole-co-benzene) (PBIB) with a honeycomb structure is synthesized by condensation polymerization of trimesic acid (TMA) and 3,3?-diaminobenzidine (DAB) for use as a membrane high-temperature proton-exchange membrane fuel cells (HT-PEMFCs). The hyperbranched honeycomb structure of polybenzimidazole (PBI) has been introduced to impart higher mechanical strength to doped PBI membranes. The stress at break of the phosphoric acid doped PBIB (DPBIB)

Sambhu Bhadra; Nam Hoon Kim; Ji Sun Choi; Kyong Yop Rhee; Joong Hee Lee

2010-01-01

436

Preparation of SiC-based cellular substrate by pressure-pulsed chemical vapor infiltration into honeycomb-shaped paper preforms  

Microsoft Academic Search

Using a pressure-pulsed chemical vapor infiltration technique, SiC was infiltrated from a SiCl4 (4%)–CH4 (4%)–H2 gas phase into carbonized paper preforms at 1100°C. SiC-based cellular substrates with cell wall thicknesses of 25, 50 and 100 µm were obtained by using honeycomb-shaped paper preforms as the templates. The reduction of both wall thickness t and cell pitch d of SiC-based honeycomb

Y. Ohzawa; K. Nakane; V. Gupta; T. Nakajima

2002-01-01

437

The Benefits of Aluminum Windows.  

ERIC Educational Resources Information Center

Discusses benefits of aluminum windows for college construction and renovation projects, including that aluminum is the most successfully recycled material, that it meets architectural glass deflection standards, that it has positive thermal energy performance, and that it is a preferred exterior surface. (EV)

Goyal, R. C.

2002-01-01

438

Lost-Soap Aluminum Casting.  

ERIC Educational Resources Information Center

Lost-wax casting in sterling silver is a costly experience for the average high school student. However, this jewelry process can be learned at no cost if scrap aluminum is used instead of silver, and soap bars are used instead of wax. This lost-soap aluminum casting process is described. (Author/KC)

Mihalow, Paula

1980-01-01

439

Boron carbide-aluminum cermets  

SciTech Connect

We have developed boron carbide-aluminum cermets by means of thermodynamic, kinetic, and processing studies. Our research indicates that boron carbide-aluminum cermets offer ''tailorable'' microstructures with designable properties through process control. This new class of cermets has the potential to become a very important material with wide industrial applications.

Halverson, D.C.

1986-09-03

440

Residual Aluminum in Potable Water.  

National Technical Information Service (NTIS)

The behavior of aluminum in water treatment facilities using alum coagulation was studied with laboratory jar tests as well as actual plant monitoring. For surface waters with pH > 6, the amount of dissolved aluminum is usually less than 40 ppb. Particula...

W. Sung

1984-01-01

441

Modeling dissolution in aluminum alloys  

Microsoft Academic Search

Aluminum and its alloys are used in many aspects of modern life, from soda cans and household foil to the automobiles and aircraft in which we travel. Aluminum alloy systems are characterized by good workability that enables these alloys to be economically rolled, extruded, or forged into useful shapes. Mechanical properties such as strength are altered significantly with cold working,

Tracie Lee Durbin

2005-01-01

442

Primary Aluminum Plants Worldwide - 1998  

USGS Publications Warehouse

The 1990 U.S. Bureau of Mines publication, Primary Aluminum Plants Worldwide, has been updated and is now available. The 1998 USGS edition of Primary Aluminum Plants Worldwide is published in two parts. Part I—Detail contains information on individual primary smelter capacity, location, ownership, sources of energy, and other miscellaneous information. Part II—Summary summarizes the capacity data by country

1999-01-01

443

Aluminum alloys for aerostructures  

SciTech Connect

Demands on the airframe industry have shifted over the years, but they have always moved in the direction of lower weight, higher damage tolerance, and longer-term durability. Up to the 1960s, the greatest need was for high strength to reduce weight. In the 1970s, higher fracture toughness and corrosion resistance were sought for enhanced damage tolerance and durability. In the early 1980s, the requirement for reduced weight was renewed, but by the late 1980s and early 1990s, durability became a concern again. Today`s focus is on materials that can help achieve low-cost manufacturing without sacrificing performance; future needs are likely to include both affordability and higher performance. This article describes the development of high-strength aluminum alloy materials that have satisfied past and current requirements, and identifies possible aluminum-intensive approaches that combine alternate design concepts and emerging materials technologies for low-cost, low-weight, damage-tolerant, and durable airframe structures of the future.

Staley, J.T.; Liu, J. [Alcoa Technical Center, Alcoa Center, PA (United States); Hunt, W.H. Jr. [Aluminum Consultants Group Inc., Murrysville, PA (United States)

1997-10-01

444

Experimental evaluation of honeycomb/screen configurations and short contraction section for NASA Lewis Research Center's altitude wind tunnel  

NASA Technical Reports Server (NTRS)

An experimental investigation was conducted in the high speed leg of the 0.1 scale model of the proposed Altitude Wind Tunnel to evaluate flow conditioner configurations in the settling chamber and their effect on the flow through the short contraction section. The lowest longitudinal turbulence intensity measured at the contraction-section entrance, 1.2%, was achieved with a honeycomb plus three fine-mesh screens. Turbulence intensity in the test section was estimated to be between 0.1 and 0.2% with the honeycomb plus three fine mesh screens in the settling chamber. Adding screens, however, adversely affected the total pressure profile, causing a small defect near the centerline at the contraction section entrance. No significant boundary layer separation was evident in the short contraction section.

Burley, Richard R.; Harrington, Douglas E.

1987-01-01

445

Optical Fingerprints of Si Honeycomb Chains and Atomic Gold Wires on the Si(111)-(5×2)-Au Surface  

NASA Astrophysics Data System (ADS)

The intensively studied Si(111)-(5×2)-Au surface is reexamined using reflectance anisotropy spectroscopy and density functional theory simulations. We identify distinctive spectral features relating directly to local structural motifs such as Si honeycomb chains and atomic gold wires that are commonly found on Au-reconstructed vicinal Si(111) surfaces. Optical signatures of chain dimerization, responsible for the observed (×2) periodicity, are identified. The optical response, together with STM simulations and first-principles total-energy calculations, exclude the new structure proposed very recently based on the reflection high-energy electron diffraction technique analysis of Abukawa and Nishigaya [Phys. Rev. Lett. 110, 036102 (2013)] and provide strong support for the Si honeycomb chain with the triple Au chain model of Erwin et al. [Phys. Rev. B 80, 155409 (2009)]. This is a promising approach for screening possible models of complex anisotropic surface structures.

Hogan, Conor; Ferraro, Elena; McAlinden, Niall; McGilp, John F.

2013-08-01

446

Wettability of Aluminum on Alumina  

NASA Astrophysics Data System (ADS)

The wettability of molten aluminum on solid alumina substrate has been investigated by the sessile drop technique in a 10-8 bar vacuum or under argon atmosphere in the temperature range from 1273 K to 1673 K (1000 °C to 1400 °C). It is shown that the reduction of oxide skin on molten aluminum is slow under normal pressures even with ultralow oxygen potential, but it is enhanced in high vacuum. To describe the wetting behavior of the Al-Al2O3 system at lower temperatures, a semiempirical calculation was employed. The calculated contact angle at 973 K (700 °C) is approximately 97 deg, which indicates that aluminum does not wet alumina at aluminum casting temperatures. Thus, a priming height is required for aluminum to infiltrate a filter. Wetting in the Al-Al2O3 system increases with temperature.

Bao, Sarina; Tang, Kai; Kvithyld, Anne; Tangstad, Merete; Engh, Thorvald Abel

2011-12-01

447

Aluminum inhibits erythropoiesis in vitro.  

PubMed Central

Anemia has been associated with aluminum intoxication in patients on chronic dialysis and in animals. In studies presented here, in vitro human erythroid culture was used to delineate the effects of aluminum on normal hematopoiesis. Aluminum by itself in routine culture, even at very high levels (1,035 ng/ml), did not significantly affect erythroid colony growth. The addition of human transferrin to the culture, however, resulted in a marked dose-dependent inhibition of erythroid, but not myeloid colony growth. At all doses, CFU-E progenitors showed greater inhibition than burst-forming units (BFU-E). Aluminum inhibition was not overcome by increasing the dose of erythropoietin or adding additional burst-promoting activity to the culture. Inhibition by aluminum was directly related to the number of binding sites on transferrin in the culture, and was not observed in the presence of fully iron-saturated transferrin. Images

Mladenovic, J

1988-01-01

448

Direct Growth of Hydroxy Cupric Phosphate Heptahydrate Monocrystal with HoneycombLike Porous Structures on Copper Surface Mimicking Lotus Leaf  

Microsoft Academic Search

Superhydrophobic surfaces were prepared on copper foils via a facile assistant surface oxidation technology and subsequent chemical modification with low free energy materials. The three-dimensional (3D) honeycomb-like porous structures made up of nanoslices of hydroxy cupric phosphate heptahydrate (Cu8(PO3OH)2(PO4)4 · 7H2O) single crystals were constructed by immersing copper foil in an aqueous solution of phosphoric acid and hydrogen peroxide. The

Xin Hua Chen; Guang Bin Yang; Ling Hao Kong; Dong Dong; Lai Gui Yu; Jian Min Chen; Ping Yu Zhang

2009-01-01

449

Gated channels in a honeycomb-like zinc-dicarboxylate-bipyridine framework with flexible alkyl ether side chains.  

PubMed

Covalent functionalization of 1,4-benzenedicarboxylate (bdc) with methoxyethoxy groups induces conformational freedom in this molecule. Applying these 2,5-disubstituted bdc derivatives in metal-organic framework synthesis together with 4,4'-bipyridine as coligand yields novel honeycomb-like structures. The cylindrical channels of these materials are populated with flexible groups, which act as molecular gates for guest molecules. This allows highly selective sorption of CO(2) over N(2) and CH(4). PMID:21275370

Henke, Sebastian; Fischer, Roland A

2011-02-23

450

B-HIVE: Beeswax hydrogen isotopes as validation of environment. Part I: Bulk honey and honeycomb stable isotope analysis  

Microsoft Academic Search

Stable isotope analysis is an established method for detecting honey adulteration. We extend its application to include honey and honeycomb region-of-origin assignment using hydrogen (?2H) and oxygen (?18O) isotopes. We observed that liquid honey ?2H and ?18O values had the potential to change because of water absorption and H atom exchange between sugars and water vapour. This suggested that liquid

Lesley A. Chesson; Brett J. Tipple; Brad R. Erkkila; Thure E. Cerling; James R. Ehleringer

2011-01-01

451

Preparation of poly( L-lactic acid) honeycomb monolith structure by unidirectional freezing and freeze-drying  

Microsoft Academic Search

Honeycomb monolith structured porous poly(L-lactic acid) (PLLA) was successfully fabricated by combining pseudo steady state unidirectional freezing and freeze-drying techniques. Dehydrated 1,4-dioxane was used as a solvent for PLLA and the single-phase mixture was unidirectionally frozen by lowering the sample tube into liquid nitrogen at a constant rate. The 1,4-dioxane crystal was nucleated in the solution and grown in the

Jin-Woong Kim; Kentaro Taki; Shinsuke Nagamine; Masahiro Ohshima

2008-01-01

452

Optimal active cooling performance of metallic sandwich panels with prismatic cores  

Microsoft Academic Search

All-metallic sandwich panels with prismatic cores are being currently investigated for combined structural and active cooling performance. We present a new approach to active cooling performance, and use it to optimize the panel geometry for four different systems: aluminum-air, aluminum-water, aluminum-gasoline and titanium-gasoline. The results show that some geometric parameters can be fixed without much detriment in thermal performance. Moreover,

L. Valdevit; A. Pantano; H. A. Stone; A. G. Evans

2006-01-01

453

Frustrated spin-1/2 J1-J2 isotropic XY model on the honeycomb lattice  

NASA Astrophysics Data System (ADS)

We study the zero-temperature ground-state (GS) phase diagram of a spin-half J1-J2 XY model on the honeycomb lattice with nearest-neighbor exchange coupling J1>0 and frustrating next-nearest-neighbor exchange coupling J2??J_1>0, where both bonds are of the isotropic XY type, using the coupled cluster method. Results are presented for the GS energy per spin, magnetic order parameter, and staggered dimer valence-bond crystalline (SDVBC) susceptibility, for values of the frustration parameter in the range 0?? ?1. In this range, we find phases exhibiting, respectively, Néel xy planar [N(p)], Néel z-aligned [N(z)], SDVBC, and Néel-II xy planar [N-II(p)] orderings. The Néel-II states, which break the lattice rotational symmetry, are ones in which the spins of nearest-neighbor pairs along one of the three equivalent honeycomb directions are parallel, while those in the other two directions are antiparallel. The N(p) state, which is stable for the classical version of the model in the range 0?? ?1/6, is found to form the GS phase out to a first quantum critical point at ?c1=0.216(5), beyond which the stable GS phase has N(z) order over the range ?c_1?c_2, we find a strong competition to form the GS phase between states with N-II(p) and SDVBC forms of order. Our best estimate, however, is that the stable GS phase over the range ?c_2?c_3 is the N-II(p) state, which is stable at the classical level only at the highly degenerate point ? =1/2. Over the range 0???1, we find no evidence for any of the spiral phases that are present classically for all values ? >1/6, nor for any quantum spin-liquid state.

Bishop, R. F.; Li, P. H. Y.; Campbell, C. E.

2014-06-01

454

Numerical and Experimental Investigation for Assessing the High Strain Rate Response of Nickel Based Multi-Layered Honeycomb Sandwiches  

NASA Astrophysics Data System (ADS)

The mechanical behaviors of a multi-layered nickel based honeycomb sandwich at quasi-static and high strain rate ranging from 800/s-6500/s were determined by a universal Instron and uniaxial dynamic compression SHPB experiment respectively. The results of experiment showed strain rate sensitivity at low strain rate portion (0-800/s) while by increasing the strain rate (3400/s-6500/s) the samples no longer showed noticeable rate sensitivity. Dynamic strain-stress curves showed clearly initial peak strength, flat flow potion and totally compressed ascending part process while a littler peak was appeared during the flat flow portion. Different folding process can be found during dynamic compression for one and two layered honeycomb cells by high speed camera. A numerical model was developed using LS-DYNA software, for investigating the different deformation modes under various strain rates. A bi-linear elastic-plastic constitutive model was utilized to simulate plastic deformation and in-stability status of multi-layered nickel based honeycomb under dynamic compression. In this work, different finite element models were used to investigate dynamic crushing strength as a function of cell wall thickness and the number of sandwich layers.

Yang, Z. Q.; Pang, B. J.; Wang, L. W.

2009-12-01

455

Simulating the Response of a Composite Honeycomb Energy Absorber. Part 1; Dynamic Crushing of Components and Multi-Terrain Impacts  

NASA Technical Reports Server (NTRS)

This paper describes the experimental and analytical evaluation of an externally deployable composite honeycomb structure that is designed to attenuate impact energy during helicopter crashes. The concept, designated the Deployable Energy Absorber (DEA), utilizes an expandable Kevlar (Registered Trademark) honeycomb to dissipate kinetic energy through crushing. The DEA incorporates a unique flexible hinge design that allows the honeycomb to be packaged and stowed until needed for deployment. Experimental evaluation of the DEA included dynamic crush tests of multi-cell components and vertical drop tests of a composite fuselage section, retrofitted with DEA blocks, onto multi-terrain. Finite element models of the test articles were developed and simulations were performed using the transient dynamic code, LSDYNA (Registered Trademark). In each simulation, the DEA was represented using shell elements assigned two different material properties: Mat 24, an isotropic piecewise linear plasticity model, and Mat 58, a continuum damage mechanics model used to represent laminated composite fabrics. DEA model development and test-analysis comparisons are presented.

Jackson, Karen E.; Fasanella, Edwin L.; Polanco, Michael A.

2012-01-01

456

First principles pseudopotential calculations on aluminum and aluminum alloys  

SciTech Connect

Recent advances in computational techniques have led to the possibility of performing first principles calculations of the energetics of alloy formation on systems involving several hundred atoms. This includes impurity concentrations in the 1% range as well as realistic models of disordered materials (including liquids), vacancies, and grain boundaries. The new techniques involve the use of soft, fully nonlocal pseudopotentials, iterative diagonalization, and parallel computing algorithms. This approach has been pioneered by Car and Parrinello. Here the authors give a review of recent results using parallel and serial algorithms on metallic systems including liquid aluminum and liquid sodium, and also new results on vacancies in aluminum and on aluminum-magnesium alloys.

Davenport, J.W.; Chetty, N.; Marr, R.B.; Narasimhan, S.; Pasciak, J.E.; Peierls, R.F.; Weinert, M.

1993-12-31

457

Aluminum Zintl anion moieties within sodium aluminum clusters  

NASA Astrophysics Data System (ADS)

Through a synergetic combination of anion photoelectron spectroscopy and density functional theory based calculations, we have established that aluminum moieties within selected sodium-aluminum clusters are Zintl anions. Sodium-aluminum cluster anions, NamAln-, were generated in a pulsed arc discharge source. After mass selection, their photoelectron spectra were measured by a magnetic bottle, electron energy analyzer. Calculations on a select sub-set of stoichiometries provided geometric structures and full charge analyses for both cluster anions and their neutral cluster counterparts, as well as photodetachment transition energies (stick spectra), and fragment molecular orbital based correlation diagrams.

Wang, Haopeng; Zhang, Xinxing; Ko, Yeon Jae; Grubisic, Andrej; Li, Xiang; Ganteför, Gerd; Schnöckel, Hansgeorg; Eichhorn, Bryan W.; Lee, Mal-Soon; Jena, P.; Kandalam, Anil K.; Kiran, Boggavarapu; Bowen, Kit H.

2014-02-01

458

Aluminum Zintl anion moieties within sodium aluminum clusters.  

PubMed

Through a synergetic combination of anion photoelectron spectroscopy and density functional theory based calculations, we have established that aluminum moieties within selected sodium-aluminum clusters are Zintl anions. Sodium-aluminum cluster anions, Na(m)Al(n)(-), were generated in a pulsed arc discharge source. After mass selection, their photoelectron spectra were measured by a magnetic bottle, electron energy analyzer. Calculations on a select sub-set of stoichiometries provided geometric structures and full charge analyses for both cluster anions and their neutral cluster counterparts, as well as photodetachment transition energies (stick spectra), and fragment molecular orbital based correlation diagrams. PMID:24511934

Wang, Haopeng; Zhang, Xinxing; Ko, Yeon Jae; Grubisic, Andrej; Li, Xiang; Ganteför, Gerd; Schnöckel, Hansgeorg; Eichhorn, Bryan W; Lee, Mal-Soon; Jena, P; Kandalam, Anil K; Kiran, Boggavarapu; Bowen, Kit H

2014-02-01

459

Aluminum Plasmonic Nanoantennas  

NASA Astrophysics Data System (ADS)

We have explored the plasmonic properties of individual Al nanorod antennas fabricated by planar lithography on lightly doped n-type silicon. Energy-resolved cathodoluminescence was used to image the local density of optical states with a spatial resolution of ˜ 20 nm and thereby identify the radiative modes of these nanostructures. Al nanoantenna emission exhibited highly tunable plasmonic resonances from the deep UV through the visible region of the spectrum. The dependence of the radiative dipolar and quadrupolar plasmon modes on antenna length and photon energy agreed well with finite difference time domain-based analysis of these nanostructures. The results herald nano-structured aluminum as a practical and highly promising material system for the design and implementation of UV and visible frequency plasmonics, broadening the range of potential applications of plasmonics into areas where complementary metal-oxide-semiconductor (CMOS) compatibility or low-cost, mass producibility are desired.

Everitt, Henry; Knight, Mark; Liu, Lifei; Yang, Yumin; Brown, Lisa; Mukherjee, Shaunak; King, Nicholas; Nordlander, Peter; Halas, Naomi

2013-03-01

460

Aluminum: Industry of the future  

SciTech Connect

For over a century, the US aluminum industry has led the global market with advances in technology, product development, and marketing. Industry leaders recognize both the opportunities and challenges they face as they head into the 21st century, and that cooperative R and D is key to their success. In a unique partnership, aluminum industry leaders have teamed with the US Department of Energy`s Office of Industrial Technologies (OIT) to focus on innovative technologies that will help to strengthen the competitive position of the US aluminum industry and, at the same time, further important national goals. This industry-led partnership, the Aluminum Industry of the Future, promotes technologies that optimize the use of energy and materials in operations and reduce wastes and energy-related emissions. Led by The Aluminum Association, industry leaders began by developing a unified vision of future market, business, energy, and environmental goals. Their vision document, Partnerships for the Future, articulates a compelling vision for the next 20 years: to maintain and grow the aluminum industry through the manufacture and sale of competitively priced, socially desirable, and ecologically sustainable products. Continued global leadership in materials markets will require the combined resources of industry, universities, and government laboratories. By developing a unified vision, the aluminum industry has provided a framework for the next step in the Industries of the Future process, the development of a technology roadmap designed to facilitate cooperative R and D.

NONE

1998-11-01

461

Energy Gap and Averaged Inversion Symmetry of Tight-Binding Electrons on Generalized Honeycomb Lattice  

NASA Astrophysics Data System (ADS)

We study the condition to open a finite gap in tight-binding electrons on an extended honeycomb lattice with the next-nearest-neighbor transfer integrals t2a, t2b, t2c, t2d, t2e, and t2f, where t2a, t2b, and t2c are transfer integrals between the sublattice A and t2d, t2e, and t2f are transfer integrals between the sublattice B. If the system has the inversion symmetry in this model, i.e., the sublattices A and B have the same on-site potential (?A=?B), the gap is zero. We find that although the finite gap is generally opened by inversion-symmetry breaking, the gap remains zero if the averaged inversion symmetry, which is defined as the sum of the transfer integrals and the on-site potentials of the sublattices are the same (t2a+t2b+t2c+?A=t2d+t2e+t2f+?B), is conserved.