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1

An examination of impact damage in glass-phenolic and aluminum honeycomb core composite panels  

NASA Technical Reports Server (NTRS)

An examination of low velocity impact damage to glass-phenolic and aluminum core honeycomb sandwich panels with carbon-epoxy facesheets is presented. An instrumented drop weight impact test apparatus was utilized to inflict damage at energy ranges between 0.7 and 4.2 joules. Specimens were checked for extent of damage by cross sectional examination. The effect of core damage was assessed by subjecting impact-damaged beams to four-point bend tests. Skin-only specimens (facings not bonded to honeycomb) were also tested for comparison purposes. Results show that core buckling is the first damage mode, followed by delaminations in the facings, matrix cracking, and finally fiber breakage. The aluminum honeycomb panels exhibited a larger core damage zone and more facing delaminations than the glass-phenolic core, but could withstand more shear stress when damaged than the glass-phenolic core specimens.

Nettles, A. T.; Lance, D. G.; Hodge, A. J.

1990-01-01

2

Aluminum Honeycomb Characteristics in Dynamic Crush Environments  

SciTech Connect

Fifteen aluminum honeycomb cubes (3 in.) have been crushed in the Mechanical Shock Laboratory's drop table testing machines. This report summarizes shock experiments with honeycomb densities of 22.1 pcf and 38.0 pcf and with crush weights of 45 lb, 168 lb, and 268 lb. The honeycomb samples were crushed in all three orientations, W, L, and T. Most of the experiments were conducted at an impact velocity of {approx}40 fps, but higher velocities of up to 90 fps were used for selected experiments. Where possible, multiple experiments were conducted for a specific orientation and density of the honeycomb samples. All results are for Hexcel honeycomb except for one experiment with Alcore honeycomb and have been evaluated for validity. This report contains the raw acceleration data measured on the top of the drop table carriage, pictures of the crushed samples, and normalized force-displacement curves for all fifteen experiments. These data are not strictly valid for material characteristics in L and T orientations because the cross-sectional area of the honeycomb changed (split) during the crush. However, these are the best data available at this time. These dynamic crush data do suggest a significant increase in crush strength to 8000 psi ({approximately} 25-30% increase) over quasi-static values of {approximately}6000 psi for the 38.0 pcf Hexcel Honeycomb in the T-orientation. An uncertainty analysis is included and estimates the error in these data.

Bateman, Vesta I.; Swanson, Lloyd H.

1999-07-01

3

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

4

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

5

FOLDED HONEYCOMB CARDBOARD AND CORE MATERIAL FOR STRUCTURAL APPLICATIONS  

Microsoft Academic Search

Today, most honeycomb cores are produced in a batch wise production process by cutting from a block. A new continuous production concept for low cost honeycomb core materials from a single corrugated cardboard sheet has been developed and patented at the K.U.Leuven. For the production of this, so called folded honeycomb cardboard core material, the efficient machinery from the packaging

Jochen Pflug; Ignaas Verpoest; Dirk Vandepitte

6

49 CFR 587.15 - Verification of aluminum honeycomb crush strength.  

Code of Federal Regulations, 2010 CFR

... 2010-10-01 2010-10-01 false Verification of aluminum honeycomb crush strength. 587.15 Section 587.15 ...Offset Deformable Barrier § 587.15 Verification of aluminum honeycomb crush strength. The following procedure is...

2010-10-01

7

49 CFR 587.15 - Verification of aluminum honeycomb crush strength.  

Code of Federal Regulations, 2013 CFR

... 2013-10-01 2013-10-01 false Verification of aluminum honeycomb crush strength. 587.15 Section 587.15 ...Offset Deformable Barrier § 587.15 Verification of aluminum honeycomb crush strength. The following procedure is...

2013-10-01

8

49 CFR 587.15 - Verification of aluminum honeycomb crush strength.  

Code of Federal Regulations, 2011 CFR

... 2011-10-01 2011-10-01 false Verification of aluminum honeycomb crush strength. 587.15 Section 587.15 ...Offset Deformable Barrier § 587.15 Verification of aluminum honeycomb crush strength. The following procedure is...

2011-10-01

9

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

10

Characterizing Facesheet/Core Disbonding in Honeycomb Core Sandwich Structure  

NASA Technical Reports Server (NTRS)

Results are presented from an experimental investigation into facesheet core disbonding in carbon fiber reinforced plastic/Nomex honeycomb sandwich structures using a Single Cantilever Beam test. Specimens with three, six and twelve-ply facesheets were tested. Specimens with different honeycomb cores consisting of four different cell sizes were also tested, in addition to specimens with three different widths. Three different data reduction methods were employed for computing apparent fracture toughness values from the test data, namely an area method, a compliance calibration technique and a modified beam theory method. The compliance calibration and modified beam theory approaches yielded comparable apparent fracture toughness values, which were generally lower than those computed using the area method. Disbonding in the three-ply facesheet specimens took place at the facesheet/core interface and yielded the lowest apparent fracture toughness values. Disbonding in the six and twelve-ply facesheet specimens took place within the core, near to the facesheet/core interface. Specimen width was not found to have a significant effect on apparent fracture toughness. The amount of scatter in the apparent fracture toughness data was found to increase with honeycomb core cell size.

Rinker, Martin; Ratcliffe, James G.; Adams, Daniel O.; Krueger, Ronald

2013-01-01

11

The total hemispheric emissivity of painted aluminum honeycomb at cryogenic temperatures  

SciTech Connect

NASA uses high-emissivity surfaces on deep-space radiators and thermal radiation absorbers in test chambers. Aluminum honeycomb core material, when coated with a high-emissivity paint, provides a lightweight, mechanically robust, and relatively inexpensive black surface that retains its high emissivity down to low temperatures. At temperatures below about 100 Kelvin, this material performs much better than the paint itself. We measured the total hemispheric emissivity of various painted honeycomb configurations using an adaptation of an innovative technique developed for characterizing thin black coatings. These measurements were performed from room temperature down to 30 Kelvin. We describe the measurement technique and compare the results with predictions from a detailed thermal model of each honeycomb configuration.

Tuttle, J.; Canavan, E.; DiPirro, M.; Li, X. [NASA Goddard Space Flight Center, Code 552 Greenbelt, Maryland, 20771 (United States); Knollenberg, P. [Northrop Grumman Aerospace Systems Redondo Beach, CA 90278 (United States)

2014-01-29

12

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

13

Apparatus measures thermal conductivity of honeycomb-core panels  

NASA Technical Reports Server (NTRS)

Overall thermal conductivity of honeycomb-core panels at elevated temperatures is measured by an apparatus with a heater assembly and a calibrated heat-rate transducer. The apparatus has space between the heater and transducer for insertion of a test panel and insulation.

1966-01-01

14

Honeycomb Core Permeability Under Mechanical Loads  

NASA Technical Reports Server (NTRS)

A method for characterizing the air permeability of sandwich core materials as a function of applied shear stress was developed. The core material for the test specimens was either Hexcel HRP-3/16-8.0 and or DuPont Korex-1/8-4.5 and was nominally one-half inch thick and six inches square. The facesheets where made of Hercules' AS4/8552 graphite/epoxy (Gr/Ep) composites and were nominally 0.059-in. thick. Cytec's Metalbond 1515-3M epoxy film adhesive was used for co-curing the facesheets to the core. The permeability of the specimens during both static (tension) and dynamic (reversed and non-reversed) shear loads were measured. The permeability was measured as the rate of air flow through the core from a circular 1-in2 area of the core exposed to an air pressure of 10.0 psig. In both the static and dynamic testing, the Korex core experienced sudden increases in core permeability corresponding to a core catastrophic failure, while the URP core experienced a gradual increase in the permeability prior to core failure. The Korex core failed at lower loads than the HRP core both in the transverse and ribbon directions.

Glass, David E.; Raman, V. V.; Venkat, Venki S.; Sankaran, Sankara N.

1997-01-01

15

Influence of Cell Size on the Core Shear Properties of FRP Honeycomb Sandwich Panels  

Microsoft Academic Search

This paper deals with the influence of cell size on the core shear modulus and shear strength of fiber reinforced plastic (FRP) honeycomb core sandwich panels. A relationship between the cell size and core density has been established for the honeycomb core made by matching the mold method. The cell size ranges from 8 to 25 mm, with the cell height

M. D. Antony Arul Prakash; V. L. Jagannatha Guptha; Ramesh S. Sharma; B. Mohan

2011-01-01

16

Influence of Cell Size on the Core Shear Properties of FRP Honeycomb Sandwich Panels  

Microsoft Academic Search

This article deals with the influence of cell size on the core shear modulus and shear strength of fiber-reinforced plastic (FRP) honeycomb core sandwich panels. A relationship between the cell size and core density has been established for the honeycomb core made by matching the mold method. The cell size ranges from 8 to 25 mm, with the cell height kept

M. D. Antony Arul Prakash; V. L. Jagannatha Guptha; Ramesh S. Sharma; B. Mohan

2012-01-01

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

Static and Dynamic Energy Absorption of Aluminum Honeycombs and Polymeric Foams Composites  

Microsoft Academic Search

The use of innovative materials as energy absorbers for motorbike helmets might have a significant impact on the safety of motorbike riders, currently among the most vulnerable road users.In this regard, the effect of the interaction between aluminum honeycombs and polymeric foams in the design of innovative liners is investigated by studying their behavior under compressive loading conditions.Quasi-static and impact

G. Caserta; U. Galvanetto; L. Iannucci

2010-01-01

19

Dynamic Crush Behaviors Of Aluminum Honeycomb Specimens Under Compression Dominant Inclined Loads  

SciTech Connect

The quasi-static and dynamic crush behaviors of aluminum 5052-H38 honeycomb specimens under out-of-plane inclined loads are investigated by experiments. Different types of honeycomb specimens were designed for crush tests under pure compressive and inclined loads with respect to the out-of-plane direction. A test fixture was designed for both quasi-static and dynamic crush tests under inclined loads. The results of the quasi-static crush tests indicate that the normal crush and shear strengths under inclined loads are consistent with the corresponding results under combined loads. The results of the dynamic crush tests indicate that as the impact velocity increases, the normal crush strength increases and the shear strength remains nearly the same. The trends of the normalized normal crush strengths under inclined loads for specimens with different in-plane orientation angles as functions of the impact velocity are very similar to each other. Based on the experimental results, a macroscopic yield criterion as a function of the impact velocity is proposed. The experimental results suggest that as the impact velocity increases, the shape of the macroscopic yield surface changes, or more specifically, the curvature of the yield surface increases near the pure compression state. The experimental results also show similar microscopic progressive folding mechanisms in honeycomb specimens under pure compressive and inclined loads. However, honeycomb specimens under inclined loads show inclined stacking patterns of folds due to the asymmetric location of horizontal plastic hinge lines.

Hong, Sung-tae; Pan, Jwo; Tyan, Tau; Prasad, Priya

2008-01-01

20

Quiet Honeycomb Panels  

NASA Technical Reports Server (NTRS)

Sandwich honeycomb composite panels are lightweight and strong, and, therefore, provide a reasonable alternative to the aluminum ring frame/stringer architecture currently used for most aircraft airframes. The drawback to honeycomb panels is that they radiate noise into the aircraft cabin veil- efficiently provoking the need for additional sound treatment which adds weight and reduces the material's cost advantage. A series of honeycomb panels was made -hick incorporated different design strategies aimed at reducing the honeycomb panels' radiation efficiency while at the same time maintaining their strength. The majority of the designs were centered around the concept of creating areas of reduced stiffness in the panel by adding voids and recesses to the core. The effort culminated with a reinforced/recessed panel which had 6 dB higher transmission loss than the baseline solid core panel while maintaining comparable strength.

Palumbo, Daniel L.; Klos, Jacob

2010-01-01

21

Modal analysis and acoustic transmission through offset-core honeycomb sandwich panels  

NASA Astrophysics Data System (ADS)

The work presented in this thesis is motivated by an earlier research that showed that double, offset-core honeycomb sandwich panels increased thermal resistance and, hence, decreased heat transfer through the panels. This result lead to the hypothesis that these panels could be used for acoustic insulation. Using commercial finite element modeling software, COMSOL Multiphysics, the acoustical properties, specifically the transmission loss across a variety of offset-core honeycomb sandwich panels, is studied for the case of a plane acoustic wave impacting the panel at normal incidence. The transmission loss results are compared with those of single-core honeycomb panels with the same cell sizes. The fundamental frequencies of the panels are also computed in an attempt to better understand the vibrational modes of these particular sandwich-structured panels. To ensure that the finite element analysis software is adequate for the task at hand, two relevant benchmark problems are solved and compared with theory. Results from these benchmark results compared well to those obtained from theory. Transmission loss results from the offset-core honeycomb sandwich panels show increased transmission loss, especially for large cell honeycombs when compared to single-core honeycomb panels.

Mathias, Adam Dustin

22

Development of Quiet Honeycomb Panels  

NASA Technical Reports Server (NTRS)

Sandwich honeycomb composite panels are lightweight and strong, and, therefore, provide a reasonable alternative to the aluminum ring framelstringer architecture currently used for most aircraft airframes. The drawback to honeycomb panels is that they radiate noise into the aircraft cabin very efficiently provoking the need for additional sound treatment which adds weight and reduces the material's cost advantage. A series of honeycomb panels were made which incorporated different design strategies aimed at reducing the honeycomb panels' radiation efficiency while at the same time maintaining its strength. The majority of the desi gns were centered around the concept of creatin g areas of reduced stiffness in the panel by adding voids and recesses to the core. The effort culminated with a reinforced./recessed panel which had 6 dB higher transmission loss than the baseline solid core panel while maintaining comparable strength.

Palumbo, Daniel L.; Klos, Jacob

2009-01-01

23

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

24

Modelling of composite sandwich structures with honeycomb core subjected to high-velocity impact  

Microsoft Academic Search

In this study the perforation of composite sandwich structures subjected to high-velocity impact was analysed. Sandwich panels with carbon\\/epoxy skins and an aluminium honeycomb core were modelled by a three-dimensional finite element model implemented in ABAQUS\\/Explicit. The model was validated with experimental tests by comparing numerical and experimental residual velocity, ballistic limit, and contact time. By this model the influence

Brenda L. Buitrago; Carlos Santiuste; Sonia Sánchez-Sáez; Enrique Barbero; Carlos Navarro

2010-01-01

25

Evaluation of the Transient Liquid Phase (TLP) Bonding Process for Ti3Al-Based Honeycomb Core Sandwich Structure  

NASA Technical Reports Server (NTRS)

The suitability of using transient liquid phase (TLP) bonding to fabricate honeycomb core sandwich panels with Ti-14Al-21Nb (wt%) titanium aluminide (T3Al) face sheets for high-temperature hypersonic vehicle applications was evaluated. Three titanium alloy honeycomb cores and one Ti3Al alloy honeycomb core were investigated. Edgewise compression (EWC) and flatwise tension (FWT) tests on honeycomb core sandwich specimens and tensile tests of the face sheet material were conducted at temperatures ranging from room temperature to 1500 F. EWC tests indicated that the honeycomb cores and diffusion bonded joints were able to stabilize the face sheets up to and beyond the face sheet compressive yield strength for all temperatures investigated. The specimens with the T3Al honeycomb core produced the highest FWT strengths at temperatures above 1000 F. Tensile tests indicated that TLP processing conditions resulted in decreases in ductility of the Ti-14Al-21Nb face sheets. Microstructural examination showed that the side of the face sheets to which the filler metals had been applied was transformed from equiaxed alpha2 grains to coarse plates of alpha2 with intergranular Beta. Fractographic examination of the tensile specimens showed that this transformed region was dominated by brittle fracture.

Bird, R. Keith; Hoffman, Eric K.

1998-01-01

26

Sound Transmission through a Cylindrical Sandwich Shell with Honeycomb Core  

NASA Technical Reports Server (NTRS)

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 transmission loss is derived in terms of modal impedance of the fluids and the shell. The results show the effects of (a) the incident angles of the plane wave; (b) the flight conditions of Mach number and altitude of the aircraft; (c) the ratios between the core thickness and the total thickness of the shell; and (d) the structural loss factors on the transmission loss. Comparisons of the transmission loss are made among different shell constructions and different shell theories.

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

1996-01-01

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

Elevated-Temperature Tests Under Static and Aerodynamic Conditions on Honeycomb-Core Sandwich Panels  

NASA Technical Reports Server (NTRS)

Stainless-steel honeycomb-core sandwich panels which differed primarily in skin thicknesses were tested at elevated temperatures under static and aerodynamic conditions. The results of these tests were evaluated to determine the insulating effectiveness and structural integrity of the panels. The static radiant-heating tests were performed in front of a quartz-tube radiant heater at panel skin temperatures up to 1,5000 F. The aerodynamic tests were made in a Mach 1.4 heated blowdown wind tunnel. The tunnel temperature was augmented by additional heat supplied by a radiant heater which raised the panel surface temperature above 8000 F during air flow. Static radiant-heating tests of 2 minutes duration showed that all the panels protected the load-carrying structure about equally well. Thin-skin panels showed an advantage for this short-time test over thick-skin panels from a standpoint of weight against insulation. Permanent inelastic strains in the form of local buckles over each cell of the honeycomb core caused an increase in surface roughness. During the aero- dynamic tests all of the panels survived with little or no damage, and panel flutter did not occur.

Groen, Joseph M.; Johnson, Aldie E., Jr.

1959-01-01

29

Analysis of an Aircraft Honeycomb Sandwich Panel with Circular Face Sheet/Core Disbond Subjected to Ground-Air Pressurization  

NASA Technical Reports Server (NTRS)

The ground-air pressurization of lightweight honeycomb sandwich structures caused by alternating pressure differences between the enclosed air within the honeycomb core and the ambient environment is a well-known and controllable loading condition of aerospace structures. However, initial face sheet/core disbonds intensify the face sheet peeling effect of the internal pressure load significantly and can decrease the reliability of the sandwich structure drastically. Within this paper, a numerical parameter study was carried out to investigate the criticality of initial disbonds in honeycomb sandwich structures under ground-air pressurization. A fracture mechanics approach was used to evaluate the loading at the disbond front. In this case, the strain energy release rate was computed via the Virtual Crack Closure Technique. Special attention was paid to the pressure-deformation coupling which can decrease the pressure load within the disbonded sandwich section significantly when the structure is highly deformed.

Rinker, Martin; Krueger, Ronald; Ratcliffe, James

2013-01-01

30

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

31

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

32

Wax Reinforces Honeycomb During Machining  

NASA Technical Reports Server (NTRS)

Method of machining on conventional metal lathe devised for precise cutting of axisymmetric contours on honeycomb cores made of composite (matrix/fiber) materials. Wax filling reinforces honeycomb walls against bending and tearing while honeycomb being contoured on lathe. Innovative method of machining on lathe involves preparation in which honeycomb is placed in appropriate fixture and the fixture is then filled with molten water-soluble wax. Number of different commercial waxes have been tried.

Towell, Timothy W.; Fahringer, David T.; Vasquez, Peter; Scheidegger, Alan P.

1995-01-01

33

Response of Honeycomb Core Sandwich Panel with Minimum Gage GFRP Face-Sheets to Compression Loading After Impact  

NASA Technical Reports Server (NTRS)

A compression after impact study has been conducted to determine the residual strength of three sandwich panel constructions with two types of thin glass fiber reinforced polymer face-sheets and two hexagonal honeycomb Nomex core densities. Impact testing is conducted to first determine the characteristics of damage resulting from various impact energy levels. Two modes of failure are found during compression after impact tests with the density of the core precipitating the failure mode present for a given specimen. A finite element analysis is presented for prediction of the residual compressive strength of the impacted specimens. The analysis includes progressive damage modeling in the face-sheets. Preliminary analysis results were similar to the experimental results; however, a higher fidelity core material model is expected to improve the correlation.

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

2011-01-01

34

The Impulse Response of Extruded Corrugated Core Aluminum Sandwich Structures  

E-print Network

The Impulse Response of Extruded Corrugated Core Aluminum Sandwich Structures A Thesis Presented of distributed impulse loads. However, under the highest intensity loading conditions, nodal failure bonded to the facesheet. The ability of this structure to mitigate distributed and localized impulsive

Wadley, Haydn

35

Honeycomb vs. Foam: Evaluating Potential Upgrades to ISS Module Shielding  

NASA Technical Reports Server (NTRS)

The presence of honeycomb cells in a dual-wall structure is advantageous for mechanical performance and low weight in spacecraft primary structures but detrimental for shielding against impact of micrometeoroid and orbital debris particles (MMOD). The presence of honeycomb cell walls acts to restrict the expansion of projectile and bumper fragments, resulting in the impact of a more concentrated (and thus lethal) fragment cloud upon the shield rear wall. The Multipurpose Laboratory Module (MLM) is a Russian research module scheduled for launch and ISS assembly in 2011 (currently under review). Baseline shielding of the MLM is expected to be predominantly similar to that of the existing Functional Energy Block (FGB), utilizing a baseline triple wall configuration with honeycomb sandwich panels for the dual bumpers and a thick monolithic aluminum pressure wall. The MLM module is to be docked to the nadir port of the Zvezda service module and, as such, is subject to higher debris flux than the FGB module (which is aligned along the ISS flight vector). Without upgrades to inherited shielding, the MLM penetration risk is expected to be significantly higher than that of the FGB module. Open-cell foam represents a promising alternative to honeycomb as a sandwich panel core material in spacecraft primary structures as it provides comparable mechanical performance with a minimal increase in weight while avoiding structural features (i.e. channeling cells) detrimental to MMOD shielding performance. In this study, the effect of replacing honeycomb sandwich panel structures with metallic open-cell foam structures on MMOD shielding performance is assessed for an MLM-representative configuration. A number of hypervelocity impact tests have been performed on both the baseline honeycomb configuration and upgraded foam configuration, and differences in target damage, failure limits, and derived ballistic limit equations are discussed.

Ryan, Shannon J.; Christiansen, Eric L.

2009-01-01

36

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. PMID:24187526

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

2013-01-01

37

Probability of Detection Study on Impact Damage to Honeycomb Composite Structure using Thermographic Inspection  

NASA Technical Reports Server (NTRS)

A probability of detection study was performed for the detection of impact damage using flash heating infrared thermography on a full scale honeycomb composite structure. The honeycomb structure was an intertank structure from a previous NASA technology demonstration program. The intertank was fabricated from IM7/8552 carbon fiber/epoxy facesheets and aluminum honeycomb core. The intertank was impacted in multiple locations with a range of impact energies utilizing a spherical indenter. In a single blind study, the intertank was inspected with thermography before and after impact damage was incurred. Following thermographic inspection several impact sites were sectioned from the intertank and cross-sectioned for microscopic comparisons of NDE detection and actual damage incurred. The study concluded that thermographic inspection was a good method of detecting delamination damage incurred by impact. The 90/95 confidence level on the probability of detection was close to the impact energy that delaminations were first observed through cross-sectional analysis.

Hodge, Andrew J.; Walker, James L., II

2008-01-01

38

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

39

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

40

Honeycomb-Fin Heat Sink  

NASA Technical Reports Server (NTRS)

Improved finned heat sink for electronic components more lightweight, inexpensive, and efficient. Designed for use with forced air, easily scaled up to dissipate power up to few hundred watts. Fins are internal walls of aluminum honeycomb structure. Cell structure gives strength to thin aluminum foil. Length of channels chosen for thermodynamic efficency; columns of cells combined in any reasonable number because flowing air distributed to all. Heat sink cools nearly as effectively at ends as near its center, no matter how many columns of cells combined.

Rippel, Wally E.

1989-01-01

41

Advanced radiator concepts utilizing honeycomb panel heat pipes  

NASA Astrophysics Data System (ADS)

The feasibility of fabricating and processing moderate temperature range vapor chamber type heat pipes in a low mass honeycomb panel configuration for highly efficient radiator fins for potential use on the 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 thickness, wick type and manufacturability, liquid and vapor communication among honeycomb cells, and liquid flow return from condenser to evaporator facesheet areas. A thin-wall all-welded stainless steel design with methanol as the working fluid was the initial prototype unit. It was found that an aluminum panel could not be fabricated in the same manner as a stainless steel panel due to diffusion bonding and resistance welding considerations. Therefore, a formed and welded design was developed. The prototype consists of ten panels welded together into a large panel 122 by 24 by 0.15 in., with a heat rejection capability of 1000 watts and a fin efficiency of essentially 1.0.

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

1987-10-01

42

Advanced radiator concepts utilizing honeycomb panel heat pipes  

NASA Technical Reports Server (NTRS)

The feasibility of fabricating and processing moderate temperature range vapor chamber type heat pipes in a low mass honeycomb panel configuration for highly efficient radiator fins for potential use on the 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 thickness, wick type and manufacturability, liquid and vapor communication among honeycomb cells, and liquid flow return from condenser to evaporator facesheet areas. A thin-wall all-welded stainless steel design with methanol as the working fluid was the initial prototype unit. It was found that an aluminum panel could not be fabricated in the same manner as a stainless steel panel due to diffusion bonding and resistance welding considerations. Therefore, a formed and welded design was developed. The prototype consists of ten panels welded together into a large panel 122 by 24 by 0.15 in., with a heat rejection capability of 1000 watts and a fin efficiency of essentially 1.0.

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

1987-01-01

43

ALUMINUM  

E-print Network

This fact sheet answers the most frequently asked health questions (FAQs) about aluminum. For more information, call the ATSDR Information Center at 1-800-232-4636. This fact sheet is one in a series of summaries about hazardous substances and their health effects. It is important you understand this information because this substance may harm you. The effects of exposure to any hazardous substance depend on the dose, the duration, how you are exposed, personal traits and habits, and whether other chemicals are present. HIGHLIGHTS: Everyone is exposed to low levels of aluminum from food, air, water, and soil. Exposure to high levels of aluminum may result in respiratory and neurological problems. Aluminum (in compounds combined with other elements) has been found in at least 596 of the 1,699 National Priority List (NPL) sites identified by the Environmental Protection Agency (EPA). What is aluminum? Aluminum is the most abundant metal in the earth’s crust. It is always found combined with other elements such as oxygen, silicon, and fluorine. Aluminum as the metal is obtained from

unknown authors

44

Molecular dynamics simulation of energetic aluminum/palladium core-shell nanoparticles  

NASA Astrophysics Data System (ADS)

This Letter presents the thermal stability and energetic reaction properties of palladium coated aluminum nanoparticles. The classical MD simulations are conducted using a new EAM force field. The results reveal that, when the initial temperature is higher than 600 K and lower than 900 K, a two-stage reaction may occur. At the first stage, the reaction rate is determined by the solid-state diffusion of Al atoms. At the second stage where the particle temperature is greater than the melting point of Al, the alloying reaction between the liquid Al core and the Pd shell happens with a much faster rate.

Nguyen, Ngoc Ha; Hu, Anming; Persic, John; Wen, John Z.

2011-02-01

45

Aluminum and copper plasmonics for enhancing internal quantum efficiency of core-shell and core-multishell nanowire photoelectrodes  

NASA Astrophysics Data System (ADS)

One of the critical challenges for achieving solar-to-hydrogen efficiency greater than 10% (100 W/m2), especially in metal oxide photoelectrodes, is the poor internal quantum efficiency arising from high, bulk and surface, recombination and insufficient light absorption. Plasmonic light harvesting has emerged as a promising strategy to address this challenge. However, most designs are photocatalyst specific and employ precious metals, making large scale applications infeasible. We present metal-photocatalyst core-shell and semiconductor-metal-photocatalyst coremultishell nanowires as a novel class of multi-functional plasmonic photoelectrodes. By combining the optical resonances with the localized surface plasmon resonance within the proposed structures, we achieve extreme light absorption in the visible range within ultrathin photocatalyst layers. Such enhanced absorption ensures that the photocharges are preferentially generated very close to the photocatalyst-electrolyte interface and can effectively drive the reaction forward, thereby improving the internal quantum efficiency. Specifically, for nanowires in an aqueous electrolyte, we demonstrate the effectiveness of aluminum and copper to confine light and establish them as plasmonic alternatives to precious metal counterparts such as silver and gold therefore enabling cheap and scalable plasmonics. Further, we probe the absorption as a function of the permittivity of the electrolyte and show that the absorption in such nanowires is large even for high permittivity electrolytes. Hematite and copper(I) oxide have been chosen as the test materials to validate the generality of this approach. Notably, for hematite, we show that aluminum is more effective than copper, while for a broadband absorber such as copper(I) oxide, we show that both aluminum and copper are equally effective for plasmonic light harvesting.

Ramadurgam, Sarath; Yang, Chen

2014-09-01

46

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

NASA Astrophysics Data System (ADS)

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.

1985-08-01

47

Experimental and computational study of hypervelocity impact on spacecraft honeycomb  

Microsoft Academic Search

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

Emma Taylor

2001-01-01

48

Pre-stressing micron-scale aluminum core-shell particles to improve reactivity.  

PubMed

The main direction in increasing reactivity of aluminum (Al) particles for energetic applications is reduction in their size down to nanoscale. However, Al nanoparticles are 30-50 times more expensive than micron scale particles and possess safety and environmental issues. Here, we improved reactivity of Al micron scale particles by synthesizing pre-stressed core-shell structures. Al particles were annealed and quenched to induce compressive stresses in the alumina passivation shell surrounding Al core. This thermal treatment was designed based on predictions of the melt-dispersion mechanism (MDM); a theory describing Al particle reaction under high heating rate. For all anneal treatment temperatures, experimental flame propagation rates for Al combined with nanoscale copper oxide (CuO) are in quantitative agreement with the theoretical predictions based on the MDM. The best treatment increases flame rate by 36% and achieves 68% of that for the best Al nanoparticles. PMID:25597747

Levitas, Valery I; McCollum, Jena; Pantoya, Michelle

2015-01-01

49

Pre-Stressing Micron-Scale Aluminum Core-Shell Particles to Improve Reactivity  

PubMed Central

The main direction in increasing reactivity of aluminum (Al) particles for energetic applications is reduction in their size down to nanoscale. However, Al nanoparticles are 30–50 times more expensive than micron scale particles and possess safety and environmental issues. Here, we improved reactivity of Al micron scale particles by synthesizing pre-stressed core-shell structures. Al particles were annealed and quenched to induce compressive stresses in the alumina passivation shell surrounding Al core. This thermal treatment was designed based on predictions of the melt-dispersion mechanism (MDM); a theory describing Al particle reaction under high heating rate. For all anneal treatment temperatures, experimental flame propagation rates for Al combined with nanoscale copper oxide (CuO) are in quantitative agreement with the theoretical predictions based on the MDM. The best treatment increases flame rate by 36% and achieves 68% of that for the best Al nanoparticles. PMID:25597747

Levitas, Valery I.; McCollum, Jena; Pantoya, Michelle

2015-01-01

50

Pre-Stressing Micron-Scale Aluminum Core-Shell Particles to Improve Reactivity  

NASA Astrophysics Data System (ADS)

The main direction in increasing reactivity of aluminum (Al) particles for energetic applications is reduction in their size down to nanoscale. However, Al nanoparticles are 30-50 times more expensive than micron scale particles and possess safety and environmental issues. Here, we improved reactivity of Al micron scale particles by synthesizing pre-stressed core-shell structures. Al particles were annealed and quenched to induce compressive stresses in the alumina passivation shell surrounding Al core. This thermal treatment was designed based on predictions of the melt-dispersion mechanism (MDM); a theory describing Al particle reaction under high heating rate. For all anneal treatment temperatures, experimental flame propagation rates for Al combined with nanoscale copper oxide (CuO) are in quantitative agreement with the theoretical predictions based on the MDM. The best treatment increases flame rate by 36% and achieves 68% of that for the best Al nanoparticles.

Levitas, Valery I.; McCollum, Jena; Pantoya, Michelle

2015-01-01

51

Friedel-crafts alkylation over Al-incorporated mesoporous honeycomb  

Microsoft Academic Search

Catalytic activity of Friedel-Crafts alkylation of toluene with benzyl alcohol has been measured over the Al-incorporated mesoporous honeycomb. The honeycomb was fabricated using MCM-48 and pseudobohemite as inorganic binder and the incorporation of aluminum was performed either by direct implementation of AlCl3 or by slurry mixing before the extrusion. Hydrothermal stability and compressive strength can be improved with the increase

Young Soo Ahn; Hong Soo Kim; Moon Hee Han; Shinae Jun; Sang Hoon Joo; Ryong Ryoo; Sung June Cho

2003-01-01

52

Honeycomb vs. Foam: Evaluating a Potential Upgrade to ISS Module Shielding for Micrometeoroids and Orbital Debris  

NASA Technical Reports Server (NTRS)

The presence of a honeycomb core in a multi-wall shielding configuration for protection against micrometeoroid and orbital debris (MMOD) particle impacts at hypervelocity is generally considered to be detrimental as the cell walls act to restrict fragment cloud expansion, creating a more concentrated load on the shield rear wall. However, mission requirements often prevent the inclusion of a dedicated MMOD shield, and as such, structural honeycomb sandwich panels are amongst the most prevalent shield types. Open cell metallic foams are a relatively new material with novel mechanical and thermal properties that have shown promising results in preliminary hypervelocity impact shielding evaluations. In this study, an ISS-representative MMOD shielding configuration has been modified to evaluate the potential performance enhancement gained through the substitution of honeycomb for open cell foam. The baseline shielding configuration consists of a double mesh outer layer, two honeycomb sandwich panels, and an aluminum rear wall. In the modified configuration the two honeycomb cores are replaced by open-cell foam. To compensate for the heavier core material, facesheets have been removed from the second sandwich panel in the modified configuration. A total of 19 tests on the double layer honeycomb and double layer foam configurations are reported. For comparable mechanical and thermal performance, the foam modifications were shown to provide a 15% improvement in critical projectile diameter at low velocities (i.e. 3 km/s) and a 3% increase at high velocities (i.e. 7 km/s) for normal impact. With increasing obliquity, the performance enhancement was predicted to increase, up to a 29% improvement at 60 (low velocity). Ballistic limit equations have been developed for the new configuration, and consider the mass of each individual shield component in order to maintain validity in the event of minor configuration modifications. Previously identified weaknesses of open cell foams for hypervelocity impact shielding such as large projectile diameters, low velocities, and high degrees of impact obliquity have all been investigated, and found to be negligible for the double-layer configuration.

Ryan, Shannon; Hedman, Troy; Christiansen, Eric L.

2009-01-01

53

Adjustable knife cuts honeycomb material to specified depth  

NASA Technical Reports Server (NTRS)

Calibrated, adjustable knife cuts aluminum honeycomb or other soft materials to a desired depth. The frame of the device accommodates standard commercial blades. Since the blade is always visible to the operator, the device can be used on any straight or irregular layout line.

Rauschl, J. A.

1966-01-01

54

Interfacial Microstructure and Bonding Strength of Copper Cladding Aluminum Rods Fabricated by Horizontal Core-Filling Continuous Casting  

Microsoft Academic Search

Copper cladding aluminum (CCA) rods with a diameter of 30 mm and a sheath thickness of 3 mm were fabricated by horizontal\\u000a core-filling continuous casting (HCFC) technology. The microstructure and morphology, distribution of chemical components,\\u000a and phase composition of the interface between Cu and Al were characterized by scanning electron microscope (SEM), transmission\\u000a electron microscope (TEM), and energy dispersive spectrometer (EDS). The

Ya-Jun Su; Xin-Hua Liu; Hai-You Huang; Xue-Feng Liu; Jian-Xin Xie

55

Extruded ceramic honeycomb and method  

DOEpatents

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 glass and clay into a low-expansion spodumene ceramic honeycomb body.

Day, J. Paul (Big Flats, NY)

1995-04-04

56

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

57

Flight service evaluation of two aluminum-brazed titanium spoilers  

NASA Technical Reports Server (NTRS)

The long-term service evaluation of two aluminum-brazed titanium (ABTi) honeycomb flight spoilers was concluded. The two spoilers had about 7.5 years of commercial flight experience on All Nippon Airways Model 737 aircraft. All Nippon Airways was selected because Japan has one of the most severe marine-industrial environments in the world. The results indicated that both flight spoilers still had the same load-carrying capability as when they were originally installed. No direct evidence of any corrosion was observed on either spoiler. Another significant accomplishment of this effort was the development of a braze design for efficiently distributing point loads from the fittings and skin into the honeycomb core.

Boyer, R. R.

1984-01-01

58

Impact response of aluminum corrugated core sandwich panelsq H.N.G. Wadley*, K.P. Dharmasena, M.R. O'Masta, J.J. Wetzel  

E-print Network

Impact response of aluminum corrugated core sandwich panelsq H.N.G. Wadley*, K.P. Dharmasena, M whose diameter was about a half that of the core's unit cell width. We find that low momentum impacts by shear-off within the impacted front face sheet, followed by stretching, bending and tensile fracture

Wadley, Haydn

59

Titanium Honeycomb Panel Testing  

NASA Technical Reports Server (NTRS)

Thermal-mechanical tests were performed on a titanium honeycomb sandwich panel to experimentally validate the hypersonic wing panel concept and compare test data with analysis. Details of the test article, test fixture development, instrumentation, and test results are presented. After extensive testing to 900 deg. F, non-destructive evaluation of the panel has not detected any significant structural degradation caused by the applied thermal-mechanical loads.

Richards, W. Lance; Thompson, Randolph C.

1996-01-01

60

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

61

Mechanical properties of metal honeycomb sandwich panel  

NASA Astrophysics Data System (ADS)

A Co-based superalloy honeycomb thermal protection system (TPS) panel has been fabricated. A series of strength tests such as the lateral tensile strength and flatwise compressive properties were carried out at room temperature. The tensile ultimate strength is higher than 59MPa, the flatwise compressive strength is higher than 15MPa. Two optical non-contact methods are introduced in this work. Longitudinal strains of a lateral tensile specimen were obtained using digital speckle correlation method. The equivalent elastic modulus was calculated further. Debonding defects between honeycomb core and face sheets were detected by ESSPI. The size and approximate location were decided real-time. The results show these two methods are feasible.

Zou, Guang-ping; Lu, Jie; Liang, Jun

2008-11-01

62

Heat Shielding Characteristics and Thermostructural Performance of a Superalloy Honeycomb Sandwich Thermal Protection System (TPS)  

NASA Technical Reports Server (NTRS)

Heat-transfer, thermal bending, and mechanical buckling analyses have been performed on a superalloy "honeycomb" thermal protection system (TPS) for future hypersonic flight vehicles. The studies focus on the effect of honeycomb cell geometry on the TPS heat-shielding performance, honeycomb cell wall buckling characteristics, and the effect of boundary conditions on the TPS thermal bending behavior. The results of the study show that the heat-shielding performance of a TPS panel is very sensitive to change in honeycomb core depth, but insensitive to change in honeycomb cell cross-sectional shape. The thermal deformations and thermal stresses in the TPS panel are found to be very sensitive to the edge support conditions. Slight corrugation of the honeycomb cell walls can greatly increase their buckling strength.

Ko, William L.

2004-01-01

63

Design Optimization and Analysis of a Composite Honeycomb Intertank  

NASA Technical Reports Server (NTRS)

Intertanks, the structure between tanks of launch vehicles, are prime candidates for weight reduction of rockets. This paper discusses the optimization and detailed follow up analysis and testing of a 96 in. diameter, 77 in. tall intertank. The structure has composite face sheets with an aluminum honeycomb core. The ends taper to a thick built up laminate for a double lap bolted splice joint interface. It is made in 8 full length panels joined with bonded double lap joints. The nominal load is 4000 lb/in. Optimization is by Genetic Algorithm and minimizes weight by varying core thickness, number and orientation of acreage and buildup plies, and the size, number and spacing of bolts. A variety of design cases were run with populations up to 2000 and chromosomes as long as 150 bits. Constraints were buckling; face stresses (normal, shear, wrinkling and dimpling); bolt stress; and bolt hole stresses (bearing, net tension, wedge splitting, shear out and tension/shear out). Analysis is by a combination of elasticity solutions and empirical data. After optimization, a series of coupon tests were performed in conjunction with a rigorous analysis involving a variety of finite element models. This analysis and testing resulted in several small changes to the optimized design. The equation used for hole bearing strength was found to be inadequate, resulting in thicker ends. The core thickness increased 0.05", and potting compound was added in the taper to strengthen the facesheet bond. The intertank has undergone a 250,000 lb limit load test and been mated with a composite liquid hydrogen tank. The tank/intertank unit is being installed in a test stand where it will see 200 thermal/load cycles. Afterwards the intertank will be demated and loaded in compression to failure.

Finckenor, Jeff; Spurrier, Mile

1999-01-01

64

Optimized Non-Obstructive Particle Damping (NOPD) Treatment for Composite Honeycomb Structures  

NASA Technical Reports Server (NTRS)

Non-Obstructive Particle Damping (NOPD) technology is a passive vibration damping approach whereby metallic or non-metallic particles in spherical or irregular shapes, of heavy or light consistency, and even liquid particles are placed inside cavities or attached to structures by an appropriate means at strategic locations, to absorb vibration energy. The objective of the work described herein is the development of a design optimization procedure and discussion of test results for such a NOPD treatment on honeycomb (HC) composite structures, based on finite element modeling (FEM) analyses, optimization and tests. Modeling and predictions were performed and tests were carried out to correlate the test data with the FEM. The optimization procedure consisted of defining a global objective function, using finite difference methods, to determine the optimal values of the design variables through quadratic linear programming. The optimization process was carried out by targeting the highest dynamic displacements of several vibration modes of the structure and finding an optimal treatment configuration that will minimize them. An optimal design was thus derived and laboratory tests were conducted to evaluate its performance under different vibration environments. Three honeycomb composite beams, with Nomex core and aluminum face sheets, empty (untreated), uniformly treated with NOPD, and optimally treated with NOPD, according to the analytically predicted optimal design configuration, were tested in the laboratory. It is shown that the beam with optimal treatment has the lowest response amplitude. Described below are results of modal vibration tests and FEM analyses from predictions of the modal characteristics of honeycomb beams under zero, 50% uniform treatment and an optimal NOPD treatment design configuration and verification with test data.

Panossian, H.

2008-01-01

65

The dynamic mechanical properties study on the sandwich panel of different thickness steel plate-foam aluminum core  

NASA Astrophysics Data System (ADS)

The foam aluminum belongs to multi-cell materials, and it has good mechanical performance, such as large deformation capacity and good energy absorption, and usually used as core material of sandwich panel, now it is widely used in automotive, aviation, aerospace and other fields, particularly suitable for various anti-collision structure and buffer structure. In this article, based on an engineering background, the INSTRON4505 electronic universal testing machine and split Hopkinson pressure bar (SHPB) were used for testing the static and dynamic mechanical properties of sandwich panel with different thickness steel plate- foam aluminum core, from the results we can see that the steel plate thickness has big influence on the stress-strain curve of the sandwich panel, and also takes the sandwich panel with 1mm steel panel to study the material strain rate dependence which under different high shock wave stress loaded, the results show that the sandwich panel is strain rate dependence material. And also, in order to get good waveforms in the SHPB experiment, the waveform shaped technique is used in the dynamic experiments, and the study of this paper will good to sandwich panel used in the engineering.

Chang, Zhongliang; Zou, Guangping; Zhao, Weiling; Xia, Peixiu

2010-03-01

66

The dynamic mechanical properties study on the sandwich panel of different thickness steel plate-foam aluminum core  

NASA Astrophysics Data System (ADS)

The foam aluminum belongs to multi-cell materials, and it has good mechanical performance, such as large deformation capacity and good energy absorption, and usually used as core material of sandwich panel, now it is widely used in automotive, aviation, aerospace and other fields, particularly suitable for various anti-collision structure and buffer structure. In this article, based on an engineering background, the INSTRON4505 electronic universal testing machine and split Hopkinson pressure bar (SHPB) were used for testing the static and dynamic mechanical properties of sandwich panel with different thickness steel plate- foam aluminum core, from the results we can see that the steel plate thickness has big influence on the stress-strain curve of the sandwich panel, and also takes the sandwich panel with 1mm steel panel to study the material strain rate dependence which under different high shock wave stress loaded, the results show that the sandwich panel is strain rate dependence material. And also, in order to get good waveforms in the SHPB experiment, the waveform shaped technique is used in the dynamic experiments, and the study of this paper will good to sandwich panel used in the engineering.

Chang, Zhongliang; Zou, Guangping; Zhao, Weiling; Xia, Peixiu

2009-12-01

67

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

68

Photonic crystal fiber with a hybrid honeycomb cladding  

Microsoft Academic Search

We consider an air-silica honeycomb lattice and demonstrate a new approach to the formation of a core defect. Typically, a high or low-index core is formed by adding a high-index region or an additional air-hole (or other low-index material) to the lattice, but here we discuss how a core defect can be formed by manipulating the cladding region ratherthan the

Niels Asger Mortensen; Martin Dybendal Nielsen; Jacob Riis Folkenberg; Christian Jakobsen; Harald R. Simonsen

2004-01-01

69

Photonic crystal fiber with a hybrid honeycomb cladding  

Microsoft Academic Search

We consider an air-silica honeycomb lattice and demonstrate a new approach to\\u000athe formation of a core defect. Typically, a high or low-index core is formed\\u000aby adding a high-index region or an additional air-hole (or other low-index\\u000amaterial) to the lattice, but here we discuss how a core defect can be formed\\u000aby manipulating the cladding region rather than

Niels Asger Mortensen; Martin Dybendal Nielsen; Jacob Riis Folkenberg; Christian Jakobsen; Harald R. Simonsen

2004-01-01

70

Molecular dynamics simulation of energetic aluminum\\/palladium core–shell nanoparticles  

Microsoft Academic Search

This Letter presents the thermal stability and energetic reaction properties of palladium coated aluminum nanoparticles. The classical MD simulations are conducted using a new EAM force field. The results reveal that, when the initial temperature is higher than 600K and lower than 900K, a two-stage reaction may occur. At the first stage, the reaction rate is determined by the solid-state

Ngoc Ha Nguyen; Anming Hu; John Persic; John Z. Wen

2011-01-01

71

Design Optimization and Analysis of a Composite Honeycomb Intertank  

NASA Technical Reports Server (NTRS)

Intertanks, the structure between tanks of launch vehicles, are prime candidates for weight reduction of rockets. This paper discusses the optimization and detailed analysis of a 96 in (2.44 m) diameter, 77 in (1.85 m) tall intertank. The structure has composite face sheets and an aluminum honeycomb core. The ends taper to a thick built up laminate for a double lap bolted shear joint. It is made in 8 full length panels joined with bonded double lap joints. The nominal load is 4000 lb/in (7 x 10(exp 5) N/m). Optimization is by Genetic Algorithm and minimizes weight by varying C, core thickness, number and orientation of acreage and buildup plies, and the size, number and spacing of bolts. A variety of cases were run with populations up to 2000 and chromosomes as long as 150 bits. Constraints were buckling, face stresses (normal, shear, wrinkling and dimpling, bolt stress, and bolt hole stresses (bearing, net tension, wedge splitting, shear out and tension/shear out). Analysis is by a combination of theoretical solutions and empirical data. After optimization, a series of coupon tests were performed in conjunction with a rigorous analysis involving a variety of finite element models. The analysis and test resulted in several small changes to the optimized design. The intertank has undergone a 250,000 lb (1.1 x 10(exp 6) N) limit load test and been mated with a composite liquid hydrogen tank. The tank/intertank unit is being installed in a test stand where it will see 200 thermal/load cycles. Afterwards the intertank will be demated and loaded in compression to failure.

Finckenor, Jeffrey; Spurrier, Mike

1998-01-01

72

Atomistic Simulation of Dislocation Core Structures in b2 Nickel-Aluminum  

NASA Astrophysics Data System (ADS)

A systematic study of the core structures of <100>, <110>, and <111> dislocations in B2 NiAl has been conducted using atomistic simulations with an embedded atom method (EAM) potential. New flexible boundary conditions and a new method of graphic representation of dislocation core structure have been employed. The main findings are the following: Core structures. There are no planar core structures of the dislocations found in B2 NiAl. The core spreading of <100> dislocations in NiAl can occur along a variety of planes depending on dislocation slip plane and line orientation. Discrete lattice effects reduced the high strain levels from anisotropic elasticity solution at the dislocation core considerably and resulted in asymmetrical core structures. The core structure of the < 110> dislocations is mutilayered with spreading on the < 110> plane. The extent of the same strain level comparing with < 100> and < 111> dislocations is much larger. The complete <111 > dislocations in NiAl are also highly non-planar and are stable with respect to splitting into exact 1/2<111> partials as well as to alternative splittings that correspond to the stable fault in the vicinity of the antiphase boundary (APB), in both <110 > and <112 > planes. Peierls stresses. Peierls stresses of the dislocations have been calculated and have been compared for their relative ease of motion. Local disordering effects. The local disordering effects on the core structure are found to be significant only in the immediate vicinity of the point defect. Compositional deviation from stoichiometry. The simulation results of <100>, <110>, and <111> dislocations in off stoichiometric NiAl show that the core structures became more extended than the ones in the stoichiometric NiAl. The core structures are not only dependent on the overall composition but also on their local atomic arrangement near the core region. When compositional deviation from stoichiometry is introduced, the response to the applied stress is different for the various slip systems. The Peierls stresses for the usually easiest moving <100> {110} dislocations increased and for the < 100> { 100} dislocations decreased, and the latter are expected to be more active in the deformation processes. The practical implications of these results are that it seems very difficult to modify the alloy behaviors through local changes in stoichiometry and ordering state. The best way to improve the ductility of B2 NiAl is to stabilize <111> slip through the addition of alloying elements that can lower the APB energy.

Xie, Zhao-Yang

73

Interfacial Microstructure and Bonding Strength of Copper Cladding Aluminum Rods Fabricated by Horizontal Core-Filling Continuous Casting  

NASA Astrophysics Data System (ADS)

Copper cladding aluminum (CCA) rods with a diameter of 30 mm and a sheath thickness of 3 mm were fabricated by horizontal core-filling continuous casting (HCFC) technology. The microstructure and morphology, distribution of chemical components, and phase composition of the interface between Cu and Al were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), and energy dispersive spectrometer (EDS). The formation mechanism of the interface and the effects of key processing parameters, e.g., aluminum casting temperature, secondary cooling intensity, and mean withdrawing speed on the interfacial microstructure and bonding strength were investigated. The results show that the CCA rod has a multilayered interface, which is composed of three sublayers—sublayer I is Cu9Al4 layer, sublayer II is CuAl2 layer, and sublayer III is composed of ?-Al/CuAl2 pseudo eutectic. The thickness of sublayer III, which occupies 92 to 99 pct of the total thickness of the interface, is much larger than the thicknesses of sublayers I and II. However, the interfacial bonding strength is dominated by the thicknesses of sublayers I and II; i.e., the bonding strength decreases with the rise of the thicknesses of sublayers I and II. When raising the aluminum casting temperature, the total thickness of the interface increases while the thicknesses of sublayers I and II decrease and the bonding strength increases. Either augmenting the secondary cooling intensity or increasing the mean withdrawing speed results in the decrease in both total thickness of the interface and the thicknesses of sublayers I and II, and an increase in the interfacial bonding strength. The CCA rod with the largest interfacial bonding strength of 67.9 ± 0.5 MPa was fabricated under such processing parameters as copper casting temperature 1503 K (1230 °C), aluminum casting temperature 1063 K (790 °C), primary cooling water flux 600 L/h, secondary cooling water flux 700 L/h, and mean withdrawing speed 87 mm/min. The total thickness of the interface of the CCA rod fabricated under the preceding processing parameters is about 75 ?m, while the thicknesses of sublayers I and II are about 1.1 and 0.1 ?m, respectively.

Su, Ya-Jun; Liu, Xin-Hua; Huang, Hai-You; Liu, Xue-Feng; Xie, Jian-Xin

2011-12-01

74

Honeycomb spacer crush stength test results  

SciTech Connect

This report discusses aluminum honeycomb spacers, which are used as an energy absorbent material in shipping packages for off site shipment of radioactive materials and which were ordered in two crush strengths, 1,000 psi and 2,000 psi for use in drop tests requested by the Packaging and Transportation group as part of the shipping container rectification process. Both the group as part of the shipping container rectification process. Both the vendor and the SRTC Materials Laboratory performed crush strength measurements on test samples made from the material used to fabricate the actual spacers. The measurements of crush strength made in the SRTC Materials Laboratory are within 100 psi of the measurements made by the manufacturer for all samples tested and all test measurements are within 10% of the specified crush strength, which is acceptable to the P&T group for the planned tests.

Leader, D.R.

1993-09-15

75

High capacity demonstration of honeycomb panel heat pipes  

NASA Technical Reports Server (NTRS)

High capacity honeycomb panel heat pipes were investigated as heat rejection radiators on future space platforms. Starting with a remnant section of honeycomb panel measuring 3.05-m long by 0.127-m wide that was originally designed and built for high-efficiency radiator fins, features were added to increase thermal transport capacity and thus permit test evaluation as an integral heat transport and rejection radiator. A series of subscale panels were fabricated and reworked to isolate individual enhancement features. Key to the enhancement was the addition of a liquid sideflow that utilizes pressure priming. A prediction model was developed and correlated with measured data, and then used to project performance to large, space-station size radiators. Results show that a honeycomb panel with 5.08-cm sideflow spacing and core modification will meet the design load of a 50 kW space heat rejection system.

Tanzer, H. J.; Cerza, M. R., Jr.; Hall, J. B.

1986-01-01

76

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....

77

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

78

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

79

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

80

Processing and characterization of polycrystalline YAG (Yttrium Aluminum Garnet) core-clad fibers  

NASA Astrophysics Data System (ADS)

Polycrystalline YAG fiber has recently attracted considerable attention for the role it could play as a fiber-laser gain media. This primarily due to its large surface-to-volume ratio, high stimulated Brillouin scattering threshold, and its high thermal conductivity; all of which are superior to that of silica-glass fibers. As a consequence, techniques which enable the fabrication of poly- and single-crystalline YAG fibers have recently been the focus of a number of efforts. In this work we have endeavored to reduce the scattering loss of polycrystalline-YAG-core fibers while simultaneously demonstrating optical gain by enhancing our processing techniques using feedback from mechanical testing and through the development of a technique to encase doped YAG-core fibers with un-doped YAG claddings. To this end we have recently fabricated fibers with both core and claddings made up of polycrystalline YAG and subsequently confirmed that they indeed guide light. In this paper, the processes leading to the fabrication of these fibers will be discussed along with their characterization.

Kim, Hyun Jun; Fair, Geoff E.; Potticary, Santeri A.; O'Malley, Matthew J.; Usechak, Nicholas G.

2014-06-01

81

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

82

Core polarization for the electric quadrupole moment of neutron-rich Aluminum isotopes  

E-print Network

The core polarization effect for the electric quadrupole moment of the neutron-rich $^{31}$Al, $^{33}$Al and $^{35}$Al isotopes in the vicinity of the island of inversion are investigated by means of the microscopic particle-vibration coupling model in which the Skyrme Hartee-Fock-Bogoliubov and quasiparticle-random-phase approximation are used to calculate the single-quasiparticle wave functions and the excitation modes. It is found that the polarization charge for the proton $1d_{5/2}$ hole state in $^{33}$Al is quite sensitive to coupling to the neutrons in the $pf$-shell associated with the pairing correlations, and that the polarization charge in $^{35}$Al becomes larger due to the stronger collectivity of the low-lying quadrupole vibrational mode in the neighboring $^{36}$Si nucleus.

Kenichi Yoshida

2009-02-18

83

Millimeter Wave Holographical Inspection of Honeycomb Composites  

NASA Technical Reports Server (NTRS)

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 with these composites standard nondestructive testing (NDT) methods are not always capable of inspecting their interior for various defects caused during the manufacturing process or as a result of in-service loading. On the contrary, microwave and millimeter wave NDT methods are well-suited for inspecting these structures since signals at these frequencies readily penetrate through these structures and reflect from different interior boundaries revealing the presence of a wide range of defects such as disbond, delamination, moisture and oil intrusion, impact damage, etc. Millimeter wave frequency spectrum spans 30 GHz - 300 GHz with corresponding wavelengths of 10 - 1 mm. Due to the inherent short wavelengths at these frequencies, one can produce high spatial resolution images of these composites either using real-antenna focused or synthetic-aperture focused methods. In addition, incorporation of swept-frequency in the latter method (i.e., holography) results in high-resolution three-dimensional images. This paper presents the basic steps behind producing such images at millimeter wave frequencies and the results of two honeycomb composite panels are demonstrated at Q-band (33-50 GHz). In addition, these results are compared to previous results using X-ray computed tomography.

Case, J. T.; Kharkovsky, S.; Zoughi, R.; Stefes, G.; Hepburn, Frank L.; Hepburn, Frank L.

2007-01-01

84

Design data for brazed Rene 41 honeycomb sandwich  

NASA Technical Reports Server (NTRS)

Strength data, creep data and residual strength data after cyclic thermal exposure were obtained at temperatures from 78 K to 1144 K (-320 F to 1600 F). The influences of face thickness, core depth, core gage, cell size and thermal/stress exposure conditions on the mechanical design properties were investigated. A braze alloy and process was developed that is adequate to fully develop the strength of the honeycomb core while simultaneously solution treating and aging the Rene 41 fact sheets. New test procedures and test specimen configurations were developed to avoid excessive thermal stresses during cyclic thermal exposure.

Hepler, A. K.; Arnquist, J.; Koetje, E. L.; Esposito, J. J.; Lindsay, V. E. J.; Swegle, A. R.

1981-01-01

85

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

86

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

87

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

88

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

89

Fabrication and development of several heat pipe honeycomb sandwich panel concepts  

NASA Astrophysics Data System (ADS)

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.

1982-06-01

90

Acoustic scattering and radiation response of circular hexagonal and auxetic honeycomb shell structures  

NASA Astrophysics Data System (ADS)

Sandwich panels with honeycomb cores are used in many engineering applications because of their high strength to weight ratio, vibration isolation and sound transmission loss characteristics. Previous studies indicate that such sandwich structures with auxetic honeycomb cores (negative in-plane Poisson's ratio) can have a higher sound transmission loss compared to a regular hexagonal honeycomb core structure. In this study, sound scattering and acoustic radiation characteristics of sandwich structures with hexagonal and auxetic cores arranged in a circular pattern interacting with exterior acoustic domains of both air and water have been investigated using finite element analysis. A novel in-plane honeycomb geometry is developed which provides for a gradual decrease in radial cell size and whole number of circumferential cells to generate a uniform distribution of cells in the circular shell. Adding more circumferential cells, enables outer honeycomb edges to approach a circular arc and provides a comparison between the circular honeycomb and a solid elastic cylinder shell with the same mass. Natural frequencies of the different shell structures in-vacuo have been extracted in the analysis range of 0-2000 Hz. It is observed that auxetic honeycomb has lower natural frequencies compared to regular honeycomb for the same mass indicating that the auxetic is more flexible. The acoustic scattering and radiation performance in terms of target strength (TS) defined as the magnitude of reflected/scattered wave pressure relative to the magnitude of the incident plane wave pressure is measured both on the scattering surface and far-field at both the back and front scattering point were studied in both air and water. In the case of interaction with air in the exterior acoustic region, the radiation response shows prominent resonance peaks at the in-vacuo natural frequencies of the elastic structures as expected. Results show that there are significant differences in target strength between the auxetic and regular honeycomb and elastic solid circular shell structures studied, with relative TS performance between the different shells depending on the frequency of the incident wave and the acoustic domain used.

Iyer, Vaibhav Jagadeesan

91

Seal Leakages for Honeycomb or Smooth Configurations  

NASA Technical Reports Server (NTRS)

Three dimensional-CFD simulations were attempted to analyze the flow field in a honeycomb flat plate tester. This discussion reviews some of the numerical difficulties and relations, including those relating the honeycombs to labyrinth throttles and the consistency of selected seal and tester data sets.

Athavale, Mahesh M.; Hendricks, R. C.

1997-01-01

92

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

93

Crashworthiness analysis on alternative square honeycomb structure under axial loading  

NASA Astrophysics Data System (ADS)

Hexagonal metal honeycomb is widely used in energy absorption field for its special construction. However, many other metal honeycomb structures also show good energy absorption characteristics. Currently, most of the researches focus on hexagonal honeycomb, while few are performed into different honeycomb structures. Therefore, a new alternative square honeycomb is developed to expand the non-hexagonal metal honeycomb applications in the energy absorption fields with the aim of designing low mass and low volume energy absorbers. The finite element model of alternative square honeycomb is built to analyze its specific energy absorption property. As the diversity of honeycomb structure, the parameterized metal honeycomb finite element analysis program is conducted based on PCL language. That program can automatically create finite element model. Numerical results show that with the same foil thickness and cell length of metal honeycomb, the alternative square has better specific energy absorption than hexagonal honeycomb. Using response surface method, the mathematical formulas of honeycomb crashworthiness properties are obtained and optimization is done to get the maximum specific energy absorption property honeycomb. Optimal results demonstrate that to absorb same energy, alternative square honeycomb can save 10% volume of buffer structure than hexagonal honeycomb can do. This research is significant in providing technical support in the extended application of different honeycomb used as crashworthiness structures, and is absolutely essential in low volume and low mass energy absorber design.

Li, Meng; Deng, Zongquan; Guo, Hongwei; Liu, Rongqiang; Ding, Beichen

2013-07-01

94

Modelling of low-energy\\/low-velocity impact on Nomex honeycomb sandwich structures with metallic skins  

Microsoft Academic Search

In the aircraft industry, manufacturers have to decide quickly whether an impacted sandwich needs repairing or not. Certain computation tools exist at present but they are very time-consuming and they also fail to perfectly model the physical phenomena involved in an impact. In a previous publication, the authors demonstrated the possibility of representing the Nomex™ honeycomb core by a grid

B. Castanié; C. Bouveta; Y. Aminanda; J.-J. Barrau; P. Thevenet

2008-01-01

95

Optimized analysis of geometry parameters for honeycomb sandwich mirror  

NASA Astrophysics Data System (ADS)

The relationship of geometry parameters, specific stiffness, surface figure and natural frequency was investigated based on modified Gibson theory, sandwich theory, Hoff theory and vibration theory. By theoretical analysis and finite element method, we demonstrated the geometric parameters had non-linear influence on dimensionless specific stiffness in different directions with the honeycomb core was equivalent as modified solid material. Approximate expressions of deformation, natural frequency and geometric parameters were obtained. The results showed the optimal solidity ratio and face plate thickness ratio were in the range of 0.03 ~ 0.1 and 0.02 ~0.05, respectively.

Chen, Xiao'an; Cheng, Yuntao; Zeng, Qingna; Liu, Hong; Fang, Jingzhong; Rao, Changhui

2014-07-01

96

High-capacity honeycomb panel heat pipes for space radiators  

NASA Astrophysics Data System (ADS)

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 working fluid for the operating temperature range of -20 to 65 C. Critical parameters affecting heat-pipe thermal transport capacity are isolated, and current fabrication constraints are identified. In addition, several new concepts for an alternative high peformance mode of radiator operation using heat-pipe panel structures are described. Based on work presented in previous development, and the performance predictions and hardware design described herein, the internally wickable core panel appears to be a viable concept for highly efficient space radiators; however, additional in-depth hardware development and testing will determine the optimum combination of materials, core configuration, and manufacturing technique.

Tanzer, H. J.

1983-06-01

97

Phase diagram of interacting bosons on the honeycomb lattice  

NASA Astrophysics Data System (ADS)

We study the ground-state properties of repulsively interacting bosons on the honeycomb lattice using large-scale quantum Monte Carlo simulations. In the hard-core limit, the half-filled system develops long-ranged diagonal order for sufficiently strong nearest-neighbor repulsion. This staggered solid melts at a first-order quantum phase transition into the superfluid phase, without the presence of any intermediate supersolid phase. Within the superfluid phase, both the superfluid density and the compressibility exhibit local minima near the particle (hole) density of one quarter, while the density and the condensate fraction show inflection points in this region. Relaxing the hard-core constraint, supersolid phases emerge for soft-core bosons. The suppression of the superfluid density is found to persist for sufficiently large, finite on-site repulsion.

Wessel, Stefan

2007-05-01

98

An experimental investigation of aluminum honeycomb as an energy absorber  

E-print Network

Thickness of specimen Mass PE Potential energy Summation Stroke Lead distance Time t tr V VI W t Trigger time Initial velocity Impact velocity Final velocity Trigger velocity Weight viii CHAPTER I INTRODUCTION Various types of systems... by the shearing of the cell walls during the crushing stroke by using an area in compression smaller than that of the specimen. This investigation has a practical application for use on the shock- absorption system in the astronauts' couch of a vehicle...

Bland, William Joseph

2012-06-07

99

Majorana fermions in honeycomb lattices  

NASA Astrophysics Data System (ADS)

We study the formation of Majorana fermions in honeycomb-lattice structures in the presence of a Zeeman field, Rashba spin-orbit coupling, and in the proximity of an s-wave superconductor. We show that an exact mapping exists between an anisotropic hexagonal-lattice nanoribbon at k = 0 and a one-dimensional chain, for which the existence of Majorana fermions has been extensively discussed. Consequently we can find the conditions for the emergence of Majorana fermions in such a ribbon for particular values of the chemical potential such as the top or the bottom of the band, and the Van Hove singularities, and relate the existence of Majoranas to a band inversion in the bulk band structure. Moreover we find that similar situations arise in anisotropic lattices and we give some examples which show the formation of Majorana fermions in these structures.

Dutreix, Clément; Guigou, Marine; Chevallier, Denis; Bena, Cristina

2014-12-01

100

Mechanical properties and optical testing of metal honeycomb sandwich panel in MTPS  

NASA Astrophysics Data System (ADS)

Mechanical tests of a Co-based superalloy honeycomb thermal protection system (TPS) panel are finished at room temperature. The lateral tensile limit strength is higher than 59MPa and nearly four multiples of the flatwise compressive strength. Also the modulus in lateral tests are nearly two multiples of the ones under compressive loads. Because of many advantages in application, two optical non-contact methods are introduced in this work to solve different problems of honeycomb sandwich panels. Longitudinal strain of lateral tensile specimens is obtained by digital speckle correlation method (DSCM) and the results of different sub-pixel methods are constrasted. Then the equivalent elastic modulus is calculated further. Electronic speckle shearography pattern interferometry (ESSPI) is presented to obtain the nondestructive results of debonding defects between honeycomb cores and face sheets. Also the size and approximate location are decided real-time. All the results show the two introduced methods are feasible.

Lu, Jie; Zou, Guang ping; Liang, Jun

2008-11-01

101

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

102

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

103

Automatic honeycombing detection based on watershed transform  

NASA Astrophysics Data System (ADS)

Honeycombing is a common diffuse lung symptom in High-Resolution computed Tomography (HRCT), indicating the fibrosis of the lung. The purpose of this study was to develop an automatic scheme to detect honeycombing pattern accurately. The scans of 30 patients with diffuse lung disease were enrolled in the study. The lung region identified by threshold and morphological operations was pre-segmented by watershed transform to be divided into proper regions of interest (ROIs). Then texture features selected by recursive feature elimination algorithm were calculated within each ROI. Support vector machine (SVM) is used to generate rules with the training examples provided by experienced radiologists and knowledge-guided strategy was applied to reduce false positive regions. The proposed system achieved an accuracy of 92.8%, a sensitivity of 87.6% and a specification of 93.9%. The strategy is sufficiently accurate for objective and quantitative analysis of honeycombing in lung CT images.

Zhu, Yanjie; Zhang, Jianguo; Dong, Wenjie

2011-06-01

104

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

105

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

106

Method and apparatus for extruding large honeycombs  

DOEpatents

Extrusion die apparatus and an extrusion method for extruding large-cross-section honeycomb structures from plasticized ceramic batch materials are described, the apparatus comprising a die having a support rod connected to its central portion, the support rod being anchored to support means upstream of the die. The support rod and support means act to limit die distortion during extrusion, reducing die strain and stress to levels permitting large honeycomb extrusion without die failure. Dies of optimal thickness are disclosed which reduce the maximum stresses exerted on the die during extrusion.

Kragle, Harry A. (Corning, NY); Lambert, David W. (Corning, NY); Lipp, G. Daniel (Painted Post, NY)

1996-09-03

107

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

108

Low-velocity impact damage initiation in graphite\\/epoxy\\/Nomex honeycomb-sandwich plates  

Microsoft Academic Search

Low-velocity impact and static indentation tests on sandwich plates composed of 4- to 48-ply graphite\\/epoxy cross-ply laminate facesheets and Nomex honeycomb cores have been performed to characterize damage initiation as a function of facesheet thickness and loading rate. Force histories during low-velocity impact are measured by using an instrumented impactor and integrated to produce energy histories. Energy histories are shown

Eric J Herup; Anthony N Palazotto

1998-01-01

109

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

110

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

111

Sliding discharge in capillary for honeycomb catalyst  

Microsoft Academic Search

Condition of sliding discharge has been investigated to ionize inside honeycomb catalysts for exhaust gas cleaning. In order to improve selectivity and energy efficiency to promote plasma chemical reactions, combination of plasma and catalyst is effective. Packed bed is connected to capillary tubes. Ac discharge is formed in the packed bed, and with the dc electric field ionization can be

Satoshi Sato; Hiroki Yamauchi; Kazunori Takashima; Akira Mizuno

112

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

113

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 ...

114

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

115

Radiated Sound Power from a Curved Honeycomb Panel  

NASA Technical Reports Server (NTRS)

The validation of finite element and boundary element model for the vibro-acoustic response of a curved honeycomb core composite aircraft panel is completed. The finite element and boundary element models were previously validated separately. This validation process was hampered significantly by the method in which the panel was installed in the test facility. The fixture used was made primarily of fiberboard and the panel was held in a groove in the fiberboard by a compression fitting made of plastic tubing. The validated model is intended to be used to evaluate noise reduction concepts from both an experimental and analytic basis simultaneously. An initial parametric study of the influence of core thickness on the radiated sound power from this panel, using this numerical model was subsequently conducted. This study was significantly influenced by the presence of strong boundary condition effects but indicated that the radiated sound power from this panel was insensitive to core thickness primarily due to the offsetting effects of added mass and added stiffness in the frequency range investigated.

Robinson, Jay H.; Buehrle, Ralph D.; Klos, Jacob; Grosveld, Ferdinand W.

2003-01-01

116

Thermographic Inspection of Metallic Honeycomb Sandwich Structures  

NASA Technical Reports Server (NTRS)

The X-33/VentureStar has a Thermal Protection System (TPS) consisting mainly of brazed metallic honeycomb sandwich structures. Inspection of these structures is changing as a result of the extremely thin (less than 200 microns) skins, the small critical defect size (less than 2 mm long by 100 microns wide) and the large number (more than 1000) of parts to be inspected. Pulsed Infrared Thermography has been determined to be the most appropriate inspection method for manufacturing inspection based on performance comparison with other methods, cost, schedule and other factors. The results of the assessment of the different methods will be summarized and data on the performance of the final production inspection system will be given. Finite difference thermal methods have been used to model the whole inspection process. Details of correlation between the models and experimental data will be given and data on the use of pulsed infrared thermography on other metallic honeycomb sandwich structures will be given.

Taylor, John O.; Dupont, H. M.

1998-01-01

117

Has the Universe a honeycomb structure?  

E-print Network

Recent analysis of the distribution of clusters of galaxies is reviewed. Clusters of galaxies located in rich superclusters form a quasiregular lattice similar in structure to honeycombs. The power spectrum of clusters of galaxies has a sharp peak at wavelength 120 Mpc corresponding to the lattice step. The peak in the spectrum may be due to processes during the inflationary stage of the structure evolution.

J. Einasto

1997-11-26

118

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

119

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

120

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

121

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

122

Spin and the Honeycomb Lattice: Lessons from Graphene  

Microsoft Academic Search

A model of electrons hopping from atom to atom in graphene's honeycomb lattice gives low-energy electronic excitations that obey a relation formally identical to a 2+1 dimensional Dirac equation. Graphene's spin equivalent, ``pseudospin,'' arises from the degeneracy introduced by the honeycomb lattice's two inequivalent atomic sites per unit cell. Previously it has been thought that the usual electron spin and

Matthew Mecklenburg; B. C. Regan

2011-01-01

123

Spin and the Honeycomb Lattice: Lessons from Graphene  

Microsoft Academic Search

A model of electrons hopping from atom to atom in graphene's honeycomb lattice gives low-energy electronic excitations that obey a relation formally identical to a 2+1 dimensional Dirac equation. Graphene's spin equivalent, 'pseudospin', arises from the degeneracy introduced by the honeycomb lattice's two inequivalent atomic sites per unit cell. Previously it has been thought that the usual electron spin and

Matthew Mecklenburg; B. C. Regan

2011-01-01

124

Clean Electrical-Discharge Machining Of Delicate Honeycomb  

NASA Technical Reports Server (NTRS)

Precise recesses in fragile metal honeycomb blocks formed in special electrical-discharge machining process. Special tooling used, and recesses bored with workpiece in nonstandard alignment. Cutting electrode advances into workpiece along x axis to form pocket of rectangular cross section. Deionized water flows from fitting, along honeycomb tubes of workpiece, to electrode/workpiece interface.

Johnson, Clarence S.

1993-01-01

125

Stability design of honeycomb sandwich radome with asymmetric shape  

Microsoft Academic Search

The die radome, which is made of honeycomb sandwich structure, should be entirely refitted, for a big electronic observation facility is being fixed at the head section of an aircraft. In this work, the stability design of honeycomb sandwich radome is investigated. Initially, a local buckling failure is observed in the refitted radome during the preliminary calculation. Then design improvements

P. Y. Wang; F. S. Wang; Y. P. Dong; Z. F. Yue

2011-01-01

126

Optimal fractal-like hierarchical honeycombs.  

PubMed

Hexagonal honeycomb structures are known for their high strength and low weight. We construct a new class of fractal-appearing cellular metamaterials by replacing each three-edge vertex of a base hexagonal network with a smaller hexagon and iterating this process. The mechanical properties of the structure after different orders of the iteration are optimized. We find that the optimal structure (with highest in-plane stiffness for a given weight ratio) is self-similar but requires higher order hierarchy as the density vanishes. These results offer insights into how incorporating hierarchy in the material structure can create low-density metamaterials with desired properties and function. PMID:25238362

Oftadeh, Ramin; Haghpanah, Babak; Vella, Dominic; Boudaoud, Arezki; Vaziri, Ashkan

2014-09-01

127

Optimal Fractal-Like Hierarchical Honeycombs  

NASA Astrophysics Data System (ADS)

Hexagonal honeycomb structures are known for their high strength and low weight. We construct a new class of fractal-appearing cellular metamaterials by replacing each three-edge vertex of a base hexagonal network with a smaller hexagon and iterating this process. The mechanical properties of the structure after different orders of the iteration are optimized. We find that the optimal structure (with highest in-plane stiffness for a given weight ratio) is self-similar but requires higher order hierarchy as the density vanishes. These results offer insights into how incorporating hierarchy in the material structure can create low-density metamaterials with desired properties and function.

Oftadeh, Ramin; Haghpanah, Babak; Vella, Dominic; Boudaoud, Arezki; Vaziri, Ashkan

2014-09-01

128

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

129

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

130

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

2010-03-01

131

Development of Newly Designed Ultra-Light Core Structures  

NASA Astrophysics Data System (ADS)

By folding a thin flat sheet with periodically set slits or punched out portions into the third dimension, ultra-lightweight strong and functional core models are newly devised. The basic idea of this modeling arises from the application of origami technique to engineering. Based on the space filling models, fundamental flat cores and skew type sponge cores have been newly developed. By applying these models, such modified core models as curved cores and 3D honeycomb core are newly devised.

Nojima, Taketoshi; Saito, Kazuya

132

Application of Air Coupled Acoustic Thermography (ACAT) for Inspection of Honeycomb Sandwich Structures  

NASA Technical Reports Server (NTRS)

The application of a noncontact air coupled acoustic heating technique is investigated for the inspection of advanced honeycomb composite structures. A weakness in the out of plane stiffness of the structure, caused by a delamination or core damage, allows for the coupling of acoustic energy and thus this area will have a higher temperature than the surrounding area. Air coupled acoustic thermography (ACAT) measurements were made on composite sandwich structures with damage and were compared to conventional flash thermography. A vibrating plate model is presented to predict the optimal acoustic source frequency. Improvements to the measurement technique are also discussed.

Winfree, William P.; Zalameda, Joseph N.; Pergantis, Charles; Flanagan, David; Deschepper, Daniel

2009-01-01

133

Elastic constants for superplastically formed/diffusion-bonded corrugated sandwich core  

NASA Technical Reports Server (NTRS)

Formulas and associated graphs for evaluating the effective elastic constants for a superplastically formed/diffusion bonded (SPF/DB) corrugated sandwich core, are presented. A comparison of structural stiffnesses of the sandwich core and a honeycomb core under conditions of equal sandwich core density was made. The stiffness in the thickness direction of the optimum SPF/DB corrugated core (that is, triangular truss core) is lower than that of the honeycomb core, and that the former has higher transverse shear stiffness than the latter.

Ko, W. L.

1980-01-01

134

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

135

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

136

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

137

Stabilization of silicon honeycomb chains by trivalent adsorbates  

NASA Astrophysics Data System (ADS)

The atomic structure of self-assembled quasi-one-dimensional Gd chains on Si(111) has been investigated by low-energy electron diffraction and scanning tunneling microscopy. Based on comparison between Gd and Ca chains we show that this Gd-induced surface reconstruction belongs to the class of honeycomb chain-channel structures. This clearly demonstrates that, besides monovalent and divalent adsorbates, also trivalent adsorbates such as Gd stabilize silicon honeycomb chains. Consequently silicon honeycomb chains emerge as an universal building block in adsorbate-induced silicon surface reconstructions.

Battaglia, C.; Cercellier, H.; Monney, C.; Garnier, M. G.; Aebi, P.

2007-02-01

138

Active inflatable auxetic honeycomb structural concept for morphing wingtips  

NASA Astrophysics Data System (ADS)

This paper describes a new concept of an active honeycomb structure for morphing wingtip applications based on tubular inflatable systems and an auxetic cellular structure. A work-energy model to predict the output honeycomb displacement versus input pressure is developed together with a finite element formulation, and the results are compared with the data obtained from a small-scale example of an active honeycomb. An analysis of the hysteresis associated with multiple cyclic loading is also provided, and design considerations for a larger-scale wingtip demonstrator are made.

Sun, Jian; Gao, Hongliang; Scarpa, Fabrizio; Lira, Cristian; Liu, Yanju; Leng, Jinsong

2014-12-01

139

Propogation loss with frequency of ultrasound guided waves in a composite metal-honeycomb structure  

NASA Astrophysics Data System (ADS)

Non-destructive testing of critical structural components is time consuming, while necessary for maintaining safe operation. Large aerospace structures, such as the vertical stabilizers of aircraft undergo inspection at regular intervals for damage diagnostics. However, conventional techniques for damage detection and identification before repair can be scheduled are conducted off-line and therefore can take weeks. The use of guided ultrasound waves is being investigated to expedite damage detection in composites. We measure the frequency dependent loss of ultrasonic guided waves for a structure comprising a boron-nitride composite skin sandwiching an aluminum honeycomb. A wide range of ultrasound frequencies propagate as measured using PZTs, with the lowest attenuation observed about 200-250 kHz. These measurements are confirmed using optical fiber Bragg grating arrays used as ultrasound transducers.

Saxena, Indu F.; Baid, Harsh K.; Guzman, Narciso; Kempen, Lothar U.; Mal, Ajit

2009-05-01

140

Interacting Electrons on the Honeycomb Lattice  

NASA Astrophysics Data System (ADS)

In this talk I review recent advances on the understanding of the ground state properties of interacting electrons on the honeycomb lattice. In the case of weak short range interactions, renormalization group methods allowed us to give a complete construction of the ground state of the half-filled system and to prove analyticity in the coupling constant of the thermodynamic functions and of the equilibrium correlations. In the case that the electrons interact with a three-dimensional quantum electromagnetic field, the ground state can be constructed order by order in renormalized perturbation theory, with the n-th order admitting n!-bounds. Ward Identities are needed in order to control the flow of the effective charges. Lorentz invariance is dynamically restored, thanks to lattice gauge invariance. This talk is based on joint work with V. Mastropietro and M. Porta.

Giuliani, Alessandro

2011-04-01

141

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

142

Magnetic impurities in the honeycomb Kitaev model.  

PubMed

We study the effect of coupling magnetic impurities to the honeycomb lattice spin-1/2 Kitaev model in its spin-liquid phase. We show that a spin-S impurity coupled to the Kitaev model is associated with an unusual Kondo effect with an intermediate coupling unstable fixed point Kc?J/S separating topologically distinct sectors of the Kitaev model. We also show that the massless spinons in the spin-liquid mediate an interaction of the form Si?2Sj?2/Rij3 between distant impurities unlike the usual dipolar RKKY interaction Si?Sj?/Rij3 noted in various 2D impurity problems with a pseudogapped density of states of the spin bath. Furthermore, this long-range interaction is possible only if the impurities (a) couple to more than one neighboring spin on the host lattice and (b) the impurity spin S?1/2. PMID:20867601

Dhochak, Kusum; Shankar, R; Tripathi, V

2010-09-10

143

Honeycomb Betavoltaic Battery for Space Applications  

NASA Astrophysics Data System (ADS)

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 achieve bi-directional direct collection by seeding Ni-63 onto honeycomb shaped wires that will provide structural support as well. The battery design is intended to power low power electronics and distribute power needs in space probes as well as space colonies. Ni-63 is chosen as the source emitter because it has a long half-life and ease of manufacturing. The use of vacuum is especially well mated to space use; hence, vacuum insulation is employed to gain a higher efficiency than prior beta batteries with a dielectric insulator. A unique voltage down-converter is incorporated to efficiently reduce the inherent output voltage from 17.4 kV to ~17.4 V. This converter operates like a ``reverse'' Marx circuit where capacitor charging occurs in series but the discharge is in parallel. The reference battery module described here is about 100 cm×100 cm×218 cm and has a power of ~10 W with a conversion efficiency of ~15.8%. These modules can be stacked for higher powers and are very attractive for various applications in space colonization due to their long life (half-life for Ni-63~100 yrs) and low maintenance.

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

2008-01-01

144

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

145

Laser Welding of Aluminum and Aluminum Alloys  

E-print Network

.. ) Laser Welding of Aluminum and Aluminum Alloys Welds made with sharp bevel-groove weld aluminum and by aluminum alloy 5456 have been studied. The results indicate that initial absorption varies of the most dramatic illustrations of the differences in beam characteristics occurs when welding aluminum

Eagar, Thomas W.

146

Optimal Fractal-Like Hierarchical Honeycombs Ramin Oftadeh,1  

E-print Network

.e., zeroth) to fourth order hierarchical honeycombs fabricated using 3D printing. The physical thickness of the structures is constant, tn ¼ 2 mm, because of the limitations of the 3D printing. To maintain the structure

Vaziri, Ashkan

147

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

148

Mesoporous aluminum phosphite  

SciTech Connect

High surface area pure mesoporous aluminum-phosphorus oxide-based derivatives have been synthesized through an S{sup +}I{sup -} surfactant-assisted cooperative mechanism by means of a one-pot preparative procedure from aqueous solution and starting from aluminum atrane complexes and phosphoric and/or phosphorous acids. A soft chemical extraction procedure allows opening the pore system of the parent as-prepared materials by exchanging the surfactant without mesostructure collapse. The nature of the pore wall can be modulated from mesoporous aluminum phosphate (ALPO) up to total incorporation of phosphite entities (mesoporous aluminum phosphite), which results in a gradual evolution of the acidic properties of the final materials. While phosphate groups in ALPO act as network building blocks (bridging Al atoms), the phosphite entities become basically attached to the pore surface, what gives practically empty channels. The mesoporous nature of the final materials is confirmed by X-ray diffraction (XRD), transmission electron microscopy (TEM) and N{sub 2} adsorption-desorption isotherms. The materials present regular unimodal pore systems whose order decreases as the phosphite content increases. NMR spectroscopic results confirm the incorporation of oxo-phosphorus entities to the framework of these materials and also provide us useful information concerning the mechanism through which they are formed. - Abstract: TEM image of the mesoporous aluminum phosphite showing the hexagonal disordered pore array that is generated by using surfactant micelles as template. Also a scheme emphasizing the presence of an alumina-rich core and an ALPO-like pore surface is presented.

El Haskouri, Jamal, E-mail: haskouri@uv.e [Institut de Ciencia dels Materials de la Universitat de Valencia (ICMUV), P. O. Box 22085, 46071 Valencia (Spain); Perez-Cabero, Monica; Guillem, Carmen; Latorre, Julio; Beltran, Aurelio; Beltran, Daniel [Institut de Ciencia dels Materials de la Universitat de Valencia (ICMUV), P. O. Box 22085, 46071 Valencia (Spain); Amoros, Pedro, E-mail: pedro.amoros@uv.e [Institut de Ciencia dels Materials de la Universitat de Valencia (ICMUV), P. O. Box 22085, 46071 Valencia (Spain)

2009-08-15

149

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

150

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

151

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

152

Aluminum Pannier  

USGS Multimedia Gallery

This aluminum pannier was made for the storage of meat, vegetables and other food products. The pannier could be buried in the ground or placed in water in order to keep the contents cool. It was designed by Dr. J. D. Love and made for him in 1945. For transportation, this pannier, along with two re...

2009-07-22

153

Structural properties of superplastically formed/diffusion-bonded orthogonally corrugated core sandwich plates  

NASA Technical Reports Server (NTRS)

This paper describes a new superplastically formed/diffusion-bonded (SPF/DB) orthogonally corrugated sandwich structure, and presents formulae and the associated plots for evaluating the effective elastic constants for the core of this new sandwich structure. Comparison of structural properties of this new sandwich structure with the conventional honeycomb core sandwich structure was made under the condition of equal sandwich density. It was found that the SPF/DB orthogonally corrugated sandwich core has higher transverse shear stiffness than the conventional honeycomb sandwich core. However, the former has lower stiffness in the sandwich core thickness direction than the latter.

Ko, W. L.

1980-01-01

154

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

155

Biodegradable honeycomb collagen scaffold for dermal tissue engineering.  

PubMed

Tissue engineering requires a mechanically stable, biocompatible, and biodegradable scaffold that permits cell adherence and proliferation, allows preservation of cell-specific properties, and suitable for surgical implantations. In this study, honeycomb collagen sheet was used for three-dimensional (3D) cultures of human skin fibroblasts and characterized as an effective and suitable scaffold for dermal tissue engineering. About 1-mm-thick honeycomb collagen sheets, prepared from bovine dermal atelocollagen, cross-linked by UV-irradiation, and sterilized by heat, were placed on the proliferating fibroblasts on day 3 of the culture. The cells attached quickly to the collagen scaffold, proliferated inside the honeycomb pores, and formed a structure similar to dermis within 60 days. On day 60, total cellular DNA content of the 3D cultures was 12-fold higher when compared with the 2D control cultures without the scaffold. Measurement of procollagen type I in the media demonstrated a 20-fold increase. Scanning electron microscopy of the 3D cultures showed a well-formed structure similar to dermis and biodegradation of the honeycomb collagen scaffold. Our study proved that honeycomb collagen sheet is a mechanically stable, biocompatible and biodegradable scaffold for dermal tissue engineering, and also potentially useful for other cell-based therapies and tissue engineering applications. PMID:18792951

George, Joseph; Onodera, Jun; Miyata, Teruo

2008-12-15

156

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. PMID:23976812

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

2013-01-01

157

Cellular solids, such as foamed polymers and metals, microtrusses and honeycombs are commonly used in  

E-print Network

of honeycombs is studied using two experimental techniques modified from the traditional split-Hopkinson and provide insight on designing the honeycomb collapse mechanism. biosketch Anthony M. Waas is the Felix

Reisslein, Martin

158

Steps Toward 8M Honeycomb Mirror Blanks: III. 1.8m Honeycomb Sandwich Blanks Cast From Borosilicate Glass  

NASA Astrophysics Data System (ADS)

As part of a program leading to the production of 8m honeycomb mirrors, we have recently made two 1.8m blanks. These have honeycomb sandwich form, with hexagonal honeycomb ribs sandwiched between front and back plates. Each is cast in one piece from borosilicate glass, using techniques that can be extended to larger sizes. Pieces of the glass are melted together in a circular container made of hard ceramic tiles, held together against hydrostatic pressure by bands of nickel alloy. Voids in the glass to give the honeycomb structure are formed by hexagonal blocks of ceramic fiber, held down against flotation with silicon carbide bolts. Liquid glass runs over the blocks to form the face sheet, and under the blocks, which are spaced above the base tiles, to form a back sheet with holes. After the casting has been annealed and cooled, the base tiles are unbolted and the ceramic fiber blocks removed from the glass honeycomb by water blasting. Both blanks are of high quality, free from cracks and voids, and with an adequately low bubble content. The second and better blank, made of Ohara's E6 glass, is now to be figured to high precision, 0.25 arcsecond images, and is to be tested for an extended period in the Multiple Mirror Telescope.

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

1983-11-01

159

Linear and nonlinear traveling edge waves in optical honeycomb lattices  

NASA Astrophysics Data System (ADS)

Traveling unidirectional localized edge states in optical honeycomb lattices are analytically constructed. They are found in honeycomb arrays of helical waveguides designed to induce a periodic pseudomagnetic field varying in the direction of propagation. Conditions on whether a given pseudofield supports a traveling edge mode are discussed; a special case of the pseudofields studied agrees with recent experiments. Interesting classes of dispersion relations are obtained. Envelopes of nonlinear edge modes are described by the classical one-dimensional nonlinear Schrödinger equation along the edge. Nonlinear states termed edge solitons are predicted analytically and are found numerically.

Ablowitz, Mark J.; Curtis, Christopher W.; Ma, Yi-Ping

2014-08-01

160

Condensed solute droplets templated honeycomb pattern on polymer films.  

PubMed

A method to generate honeycomb pattern on polymer films is demonstrated. Briefly, a polymer solution in a volatile solvent containing a nonvolatile liquid solute is cast into a thin layer, with the fast evaporation of the volatile solvent, the liquid solute is enriched at the top surface of the layer. The enriched liquid solute condenses into uniform droplets after reaching its saturation state, meanwhile, the polymer precipitates at the interface of the droplets. With this method, we prepared the honeycomb-patterned polysulfone, polystyrene, and polyvinylidene fluoride films. This method provides a new approach to manipulate the surface geometry of polymer films. PMID:25259756

Wang, Zhenghui; Cheng, Wei; Ma, Jun; Wang, Panpan

2014-12-15

161

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

162

Bio-inspired low frictional surfaces having micro-dimple arrays prepared with honeycomb patterned porous films as wet etching masks.  

PubMed

Some kinds of snakes have micro-dimple arrays on their skins and show low frictional properties. Cost-effective and simple preparation methods of surfaces having micro-dimple arrays without burrs have been required. In this study, micro-dimple arrays were successfully prepared on aluminum plates and pipes by using honeycomb patterned porous films as wet etching masks. Resulting surfaces having 5 and 8 ?m dimple diameters show low frictional coefficients compared with polished surfaces at a fluid lubrication regime. PMID:25547931

Saito, Y; Yabu, H

2015-01-27

163

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

164

A New Air Cleaning and Cooling Instrument Using Oblique Honeycomb  

Microsoft Academic Search

A new instrument with unified functions of washing and cooling for the intake air to clean rooms was studied. Its structure is based on oblique honeycombs made of high purity alumina as contact media of air to water. The alumina medium releases less contaminant to pure water than the conventional. The instrument showed high efficiencies in air cooling as well

S. Minobe; I. Terada; Y. Motoyoshi; H. Hanaoka; Y. Shirai; T. Ohmi

2006-01-01

165

Update on the 6.5 meter Borosilicate Honeycomb Mirror  

Microsoft Academic Search

In April 1992 the University of Arizona Mirror Lab successfully cast the first U.S. telescope mirror blank that exceeds in size the Hale telescope mirror cast in 1935. The new blank goes well beyond the simple ribbed form of the Hale casting in its use of a honeycomb sandwich structure to reduce weight, enhance stiffness and control thermal distortion. The

J. R. P. Angel; J. M. Hill; N. J. Woolf

1992-01-01

166

Titanium honeycomb structure. [for supersonic aircraft wing structure  

NASA Technical Reports Server (NTRS)

A brazed titanium honeycomb sandwich system for supersonic transport wing cover panels provides the most efficient structure spanwise, chordwise, and loadwise. Flutter testing shows that high wing stiffness is most efficient in a sandwich structure. This structure also provides good thermal insulation if liquid fuel is carried in direct contact with the wing structure in integral fuel tanks.

Davis, R. A.; Elrod, S. D.; Lovell, D. T.

1972-01-01

167

Deformation measurements with honeycomb materials for crashpads of balloon gondolas  

NASA Astrophysics Data System (ADS)

For the damping of the touch-down impact of stratospheric balloon gondolas, crashpads of honeycomb materials from cardboard are commonly used. They are designed in a way that they do not buckle, that the kinetic energy of the gondola can be absorbed at their deformation, and that a sufficient braking distance for the gondola is provided by their height. Furthermore their mass and the dependence of their strength properties on the direction of deformation should be as low as possible. To achieve an optimal compromise of these requirements a dataset of strength properties of different honeycomb products has been established. Of particular interest was the absorbable energy if the honeycomb panels are deformed flatwise or at different angles. Altogether 11 products from 3 manufactures have been tested, each at 3 angles of deformation. The average and peak deformation stress as well as the deformation work per volume and mass as functions of the direction of deformation are expressed by polynomials. Correlations between the deformation work and the thickness of the honeycomb panels are looked at.

Seefeldner, M.; Nordmeyer, H.

2001-08-01

168

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

169

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

170

Producing gapped-ferrite transformer cores  

NASA Technical Reports Server (NTRS)

Improved manufacturing techniques make reproducible gaps and minimize cracking. Molded, unfired transformer cores are cut with thin saw and then fired. Hardened semicircular core sections are bonded together, placed in aluminum core box, and fluidized-coated. After winding is run over box, core is potted. Economical method significantly reduces number of rejects.

Mclyman, W. T.

1980-01-01

171

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

172

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.

2012-06-01

173

The fate of aluminum in Cochnewagan Lake, Monmouth, Maine  

SciTech Connect

Aluminum salts are commonly used to improve lake water quality. The primary goal of this study is to determine the fate of the aluminum in a lake system. In June, 1986, Cochnewagan Lake was treated with aluminum sulfate and sodium aluminate to remove phosphorus from the water. As a result of this treatment, phosphorus concentrations in the lake decreased from about 20[mu]g/1 to about 10[mu]g/1, algal blooms were eliminated and the water clarity improved. Water and sediment samples were taken in the fall of 1992. The water was analyzed for pH, dissolved oxygen, alkalinity, aluminum, and total phosphate. Only trace amounts of aluminum and phosphate were found in the water column. The sediment samples that were recovered by box coring were highly bioturbated and dark brown-gray in color. After the removal of water and total organic matter, the cores showed a color gradation from light red-gray at the surface to dark gray at 8 cm. depth. The lack of aluminum in the water column and the color gradation in the cores indicates that aluminum concentrations in the sediments have increased. SEM-EDX studies will be performed on the cores to verify the presence of aluminum in the sediments.

Talbot, M. (Bates Coll., Lewiston, ME (United States). Geology Dept.)

1993-03-01

174

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

175

Buckling Testing and Analysis of Honeycomb Sandwich Panel Arc Segments of a Full-Scale Fairing Barrel. Part 3; 8-ply Out-of-Autoclave Facesheets  

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 under the NASA Composites for Exploration program and the NASA Constellation Ares V program. Two configurations were chosen for the panels: 6-ply facesheets with 1.125 in. honeycomb core and 8-ply facesheets with 1.000 in. honeycomb core. Additionally, two separate carbon fiber/epoxy material systems were chosen for the facesheets: inautoclave IM7/977-3 and out-of-autoclave T40-800B/5320-1. Smaller 3- by 5-ft panels were cut from the 1/16th barrel sections. These panels were tested under compressive loading at the NASA Langley Research Center. Furthermore, linear eigenvalue and geometrically nonlinear finite element analyses were performed to predict the compressive response of the 3- by 5-ft panels. This manuscript summarizes the experimental and analytical modeling efforts pertaining to the panel composed of 8-ply, T40-800B/5320-1 facesheets (referred to as Panel C). 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, two-dimensional (2-D) and three-dimensional (3-D), models yield good qualitative and quantitative predictions. Additionally, it was predicted correctly that the panel would fail in buckling prior to failing in strength.

Pineda, Evan J.; Myers, David E.; Kosareo, Daniel N.; Kellas, Sotiris

2014-01-01

176

Solid oxide fuel cell stacks using extruded honeycomb type elements  

NASA Astrophysics Data System (ADS)

A solid oxide fuel cell (SOFC) stack concept is described which comprises "condensed-tubes" like extruded honeycomb sections of ceramic electrolyte (ZrO 2-based) and interconnectors of nickel sheet as key elements. According to this concept, well known and extensively tested construction principles can be realised in a low-cost production. The cells are self-supported with in-plane conduction. A demonstrator model stack of five honeycomb elements and six nickel sheet seals/interconnectors was built and operated for 860 h at 1000°C. Volumetric power densities of 160 kW/m 3 were obtained with H 2 vs. air, of close to 200 kW/m 3 with H 2 vs. O 2.

Wetzko, M.; Belzner, A.; Rohr, F. J.; Harbach, F.

177

Spin and the Honeycomb Lattice: Lessons from Graphene  

NASA Astrophysics Data System (ADS)

A model of electrons hopping from atom to atom in graphene’s honeycomb lattice gives low-energy electronic excitations that obey a relation formally identical to a 2+1 dimensional Dirac equation. Graphene’s spin equivalent, “pseudospin,” arises from the degeneracy introduced by the honeycomb lattice’s two inequivalent atomic sites per unit cell. Previously it has been thought that the usual electron spin and the pseudospin indexing the graphene sublattice state are merely analogues. Here we show that the pseudospin is also a real angular momentum. This identification explains the suppression of electron backscattering in carbon nanotubes and the angular dependence of light absorption by graphene. Furthermore, it demonstrates that half-integer spin like that carried by the quarks and leptons can derive from hidden substructure, not of the particles themselves, but rather of the space in which these particles live.

Mecklenburg, Matthew; Regan, B. C.

2011-03-01

178

Spin and the honeycomb lattice: lessons from graphene.  

PubMed

A model of electrons hopping from atom to atom in graphene's honeycomb lattice gives low-energy electronic excitations that obey a relation formally identical to a 2+1 dimensional Dirac equation. Graphene's spin equivalent, "pseudospin," arises from the degeneracy introduced by the honeycomb lattice's two inequivalent atomic sites per unit cell. Previously it has been thought that the usual electron spin and the pseudospin indexing the graphene sublattice state are merely analogues. Here we show that the pseudospin is also a real angular momentum. This identification explains the suppression of electron backscattering in carbon nanotubes and the angular dependence of light absorption by graphene. Furthermore, it demonstrates that half-integer spin like that carried by the quarks and leptons can derive from hidden substructure, not of the particles themselves, but rather of the space in which these particles live. PMID:21469887

Mecklenburg, Matthew; Regan, B C

2011-03-18

179

Debonding detection of honeycomb sandwich structures using frequency response functions  

NASA Astrophysics Data System (ADS)

A vibration-based non-destructive evaluation (NDE) method is proposed to determine the location and size of debonding in honeycomb sandwich beams. Although most of the existing vibration-based NDE methods need many measurement points, the method proposed here only utilizes the frequency response function (FRF) measured at one point. A parameterized damaged Timoshenko beam model is developed with the method of reverberation-ray matrix (MRRM) for the first time, and combined with the genetic algorithm (GA) to inverse the damage parameters from the measured FRF. The detection of a honeycomb sandwich beam can be divided into two steps: (1) identifying the equivalent elastic moduli and other parameters of the intact sandwich beam. (2) Identifying the debonding location and size of the damaged sandwich beam with the predetermined parameters. It is demonstrated experimentally that the method can inverse damage parameters with acceptable precision.

Zhu, Kaige; Chen, Mingji; Lu, Qiuhai; Wang, Bo; Fang, Daining

2014-10-01

180

[Adsorption-desorption performance of honeycomb-shaped activated carbon].  

PubMed

Honeycomb-shaped activated carbon is useful to control organic gas pollution of large air-flow and low concentration. Effects of adsorbents, toluene concentration, velocity of empty bed and temperature of desorption on its adsorption-desorption performance were studied by conducting on dynamic experiments. Results shown that adsorption properties of honeycomb-shaped activated carbon were increased with decreasing of the inlet toluene concentration under the condition of certain outlet toluene concentration, and gas velocity of empty bed was recommend as 1.2-1.8 m x s(-1). With increasing of the desorption temperature, the outlet toluene concentration appeared peak-value and fluctuated widely, and the recommended desorption temperature was 90 degrees C. Gas velocity of empty bed affected the peak value of concentration of the toluene, and practical value was 0.2-0.4 m x s(-1). PMID:22468536

Han, Zhong-Juan; Luo, Fu-Kun; Li, Ze-Qing

2011-12-01

181

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. PMID:24947369

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

2014-01-01

182

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 is given as the winding number of an eigenvector of a transfer matrix, as a function of the quasi-momentum . This method is computationally efficient (of order in the resolution of the desired image). It also shows that for the honeycomb lattice the solution for for flux in the -th gap conforms with the Diophantine equation , which determines . A window such as , or possibly shifted, provides a natural further condition for , which however turns out not to be met. Based on extensive numerical calculations, we conjecture that the solution conforms with the relaxed condition.

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

2014-08-01

183

Shape memory polymer filled honeycomb model and experimental validation  

NASA Astrophysics Data System (ADS)

An analytical model predicting the in-plane Young’s and shear moduli of a shape memory polymer filled honeycomb composite is presented. By modeling the composite as a series of rigidly attached beams, the mechanical advantage of the load distributed on each beam by the infill is accounted for. The model is compared to currently available analytical models as well as experimental data. The model correlates extremely well with experimental data for empty honeycomb and when the polymer is above its glass transition temperature. Below the glass transition temperature, rule of mixtures is shown to be more accurate as bending is no longer the dominant mode of deformation. The model is also derived for directions other than the typical x and y allowing interpolation of the stiffness of the composite in any direction.

Beblo, R. V.; Puttmann, J. P.; Joo, J. J.; Reich, G. W.

2015-02-01

184

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

185

Thermal insulation with paper honeycombs with solar gain  

Microsoft Academic Search

In this contribution we describe the concept and the model for the heat flux and the effective U-value of paper honeycombs (PHC) used as efficient and cheap transparent insulation material. With this thermal-insulation-material static U-values of U=0.25 W\\/(m2K) are obtained due to the very low thermal conduction value ?=0.04 W\\/(mK), which is comparable to thermal insulators as PU-foam or mineral

Kurt Hingerl; Gunther Baumgartner; Hans Aschauer

1996-01-01

186

Honeycomb Wachspress finite elements for structural topology optimization  

Microsoft Academic Search

Traditionally, standard Lagrangian-type finite elements, such as linear quads and triangles, have been the elements of choice\\u000a in the field of topology optimization. However, finite element meshes with these conventional elements exhibit the well-known\\u000a “checkerboard” pathology in the iterative solution of topology optimization problems. A feasible alternative to eliminate\\u000a such long-standing problem consists of using hexagonal (honeycomb) elements with Wachspress-type

Cameron Talischi; Glaucio H. Paulino; Chau H. Le

2009-01-01

187

Displacement amplifier for piezoelectric actuator based on honeycomb link mechanism  

Microsoft Academic Search

This study proposes a compact and array-type design of a mechanical amplifier for piezoelectric actuators. The amplifier emulates in-plane deformation of a specific honeycomb having bow-tie-type reentrant cells. When a multilayer piezoelectric actuator causes the elongation of a cell of the amplifier in the longitudinal direction, the cell causes expansion in the transverse direction with amplification depending on its geometry.

Mikio Muraoka; Shin Sanada

2010-01-01

188

Order parameters from image analysis: a honeycomb example.  

PubMed

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. PMID:18633584

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

2008-11-01

189

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

190

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

191

Thermal conductivity of Rene 41 honeycomb panels. [space transportation vehicles  

NASA Technical Reports Server (NTRS)

Effective thermal conductivities of Rene 41 panels suitable for advanced space transportation vehicle structures were determined analytically and experimentally for temperature ranges between 20.4K (423 F) and 1186K (1675 F). The cryogenic data were obtained using a cryostat whereas the high temperature data were measured using a heat flow meter and a comparative thermal conductivity instrument respectively. Comparisons were made between analysis and experimental data. Analytical methods appear to provide reasonable definition of the honeycomb panel effective thermal conductivities.

Deriugin, V.

1980-01-01

192

Spin ½ Delafossite honeycomb compound Cu5SbO6.  

PubMed

Cu(5)SbO(6) is found to have a monoclinic, Delafossite-derived structure consisting of alternating layers of O-Cu(I)-O sticks and magnetic layers of Jahn-Teller distorted Cu(II)O(6) octahedra in an edge sharing honeycomb arrangement with Sb(V)O(6) octahedra. This yields the structural formula Cu(I)(3)Cu(II)(2)Sb(V)O(6). Variants with ordered and disordered layer stacking are observed, depending on the synthesis conditions. The spin ½ Cu(2+) ions form dimers in the honeycomb layer. The magnetic susceptibility measured between 5 and 300 K is characteristic of the presence of a singlet-triplet spin gap of 189 K. High resolution synchrotron X-ray diffraction studies indicate that changes in the intra- or interdimer distances between 300 and 20 K, such as might indicate an increase in strength of the Peierls-like distortion through the spin gap temperature, if present, are very small. A comparison to the NaFeO(2)-type Cu(2+) honeycomb compounds Na(3)Cu(2)SbO(6) and Na(2)Cu(2)TeO(6) is presented. PMID:22171687

Climent-Pascual, E; Norby, P; Andersen, N H; Stephens, P W; Zandbergen, H W; Larsen, J; Cava, R J

2012-01-01

193

Half-filled Kondo lattice on the honeycomb lattice  

E-print Network

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 studies on the interplay between conduction electrons and the densely localized spins on the honeycomb lattice.

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

2012-08-07

194

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

195

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.

196

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

197

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

198

Extrusion of honeycomb monoliths employed with activated carbon-LDPE hybrid materials  

Microsoft Academic Search

A facile preparation method of activated carbon (AC) honeycomb monoliths is suggested in this work. A composite consisting of activated carbon, organic polymer binder (LDPE), and organic lubricant was effectively extruded above the melting temperature of the organic polymer in the shape of a honeycomb monoliths (dimensions: 256 cells in 4cm×4cm). Three types of AC powders are investigated to elucidate

Jae-Woo Lim; Yunho Choi; Hee-Seung Yoon; Young-Kwon Park; Jin-Heong Yim; Jong-Ki Jeon

2010-01-01

199

Structural Finite Element Analysis of Stiffened and Honeycomb Panels of the RASAT Satellite  

Microsoft Academic Search

This paper describes the structural analysis carried out on the main stiffened and honeycomb panels of the RASAT satellite. The analysis here supports the design process and aims to ensure that the panels survive structural qualification testing. This analysis therefore forms part of the overall qualification process. The stiffened and honeycomb panels being considered in this document form the outer

S. Ontac; S. Dag; M. I. Gokler

2007-01-01

200

Bondline strength evaluation of cocure\\/precured honeycomb sandwich structures under aircraft hygro and repair environments  

Microsoft Academic Search

Effects of moisture accumulated into the adhesively bonded composite structures on their bondline mechanical strengths are investigated through a series of comparative experiments. Those composite structures include a honeycomb sandwich structures fabricated by the cocure and the precure processes. Mass of moisture accumulated into the closed cells of the honeycomb sandwich panel specimens has been calculated. A pressure due to

Heung Soap Choi; Yong Hoon Jang

2010-01-01

201

Modeling and characterization of fiber-reinforced plastic honeycomb sandwich panels for highway bridge applications  

Microsoft Academic Search

Fiber-reinforced plastic (FRP) composite decks have been increasingly used in highway bridge applications, both in new construction and rehabilitation and replacement of existing bridge decks. Recent applications have demonstrated that FRP honeycomb panels can be effectively and economically used for highway bridge deck systems. This paper is concerned with design modeling and experimental characterization of a FRP honeycomb panel with

Julio F Davalos; Pizhong Qiao; X Frank Xu; Justin Robinson; Karl E Barth

2001-01-01

202

The two-point capacitance of infinite triangular and honeycomb networks  

NASA Astrophysics Data System (ADS)

The capacitance between arbitrary two sites (vertices) in infinite triangular and honeycomb networks is studied by using Green's function. Recurrence formulas for capacitance between arbitrary sites of the triangular lattice are obtained. The capacitance for the honeycomb lattice is shown to be expressed in terms of the one for the triangular lattice.

Owaidat, Mohammad Q.; Hijjawi, Ra'ad S.; Asad, Jihad H.; Khalifeh, Jamil M.

2014-10-01

203

Projective symmetry of partons in the Kitaev honeycomb model  

NASA Astrophysics Data System (ADS)

Low-energy states of quantum spin liquids are thought to involve partons living in a gauge-field background. We study the spectrum of Majorana fermions of the Kitaev honeycomb model on spherical clusters. The gauge field endows the partons with half-integer orbital angular momenta. As a consequence, the multiplicities do not reflect the point-group symmetries of the cluster, but rather its projective symmetries, operations combining physical and gauge transformations. The projective symmetry group of the ground state is the double cover of the point group.

Mellado, Paula; Petrova, Olga; Tchernyshyov, Oleg

2015-01-01

204

Adhesives and the ATS satellite. [construction of honeycomb panels  

NASA Technical Reports Server (NTRS)

Adhesives in the ATS satellite allow the designers to save weight, simplify design and fabrication and provide thermal and electrical conductivity or resistivity as required. The selections of adhesives are restricted to those few which can pass rigorous outgassing tests in order to avoid contaminating lenses and thermal control surfaces in space. An epoxy adhesive is used to construct the honeycomb panels which constitute most of the satellite's structure. General purpose epoxy adhesives hold doublers and standoffs in place and bond the truss to its fittings. Specialized adhesives include a high temperature resistant polyamide, a flexible polyurethane and filled epoxies which conduct heat or electricity.

Hancock, F. E.

1972-01-01

205

The nontrivial electronic structure of Bi/Sb honeycombs on SiC(0001)  

NASA Astrophysics Data System (ADS)

We discuss two-dimensional (2D) topological insulators (TIs) based on planar Bi/Sb honeycombs on a SiC(0001) substrate using first-principles computations. The Bi/Sb planar honeycombs on SiC(0001) are shown to support a nontrivial band gap as large as 0.56 eV, which harbors a Dirac cone lying within the band gap. Effects of hydrogen atoms placed on either just one side or on both sides of the planar honeycombs are examined. The hydrogenated honeycombs are found to exhibit topologically protected edge states for zigzag as well as armchair edges, with a wide band gap of 1.03 and 0.41 eV in bismuth and antimony films, respectively. Our findings pave the way for using planar bismuth and antimony honeycombs as potential new 2D-TI platforms for room-temperature applications.

Hsu, Chia-Hsiu; Huang, Zhi-Quan; Chuang, Feng-Chuan; Kuo, Chien-Cheng; Liu, Yu-Tzu; Lin, Hsin; Bansil, Arun

2015-02-01

206

Annular honeycomb seals: Test results for leakage and rotordynamic coefficients; comparisons to labyrinth and smooth configurations  

NASA Technical Reports Server (NTRS)

Test results are presented for leakage and rotordynamic coefficients for seven honeycomb seals. All seals have the same radius, length, and clearance; however, the cell depths and diameters are varied. Rotordynamic data, which are presented, consist of the direct and cross-coupled stiffness coefficients and the direct damping coefficients. The rotordynamic-coefficient data show a considerable sensitivity to changes in cell dimensions; however, no clear trends are identifiable. Comparisons of test data for the honeycomb seals with labyrinth and smooth annular seals show the honeycomb seal had the best sealing (minimum leakage) performance, followed in order by the labyrinth and smooth seals. For prerotated fluid entering the seal, in the direction of shaft rotation, the honeycomb seal has the best rotordynamic stability followed in order by the labyrinth and smooth. For no prerotation, or fluid prerotation against shaft rotation, the labyrinth seal has the best rotordynamic stability followed in order by the smooth and honeycomb seals.

Childs, Dara W.; Elrod, David; Hale, Keith

1989-01-01

207

Annular honeycomb seals: Test results for leakage and rotordynamic coefficients - Comparisons to labyrinth and smooth configurations  

NASA Technical Reports Server (NTRS)

Test results are presented for leakage and rotordynamic coefficients for seven honeycomb seals. All seals have the same radius, length, and clearance; however, the cell depths and diameters are varied. Rotordynamic data, which are presented, consist of the direct and cross-coupled stiffness coefficients and the direct damping coefficients. The rotordynamic-coefficient data show a considerable sensitivity to changes in cell dimensions; however, no clear trends are identifiable. Comparisons of test data for the honeycomb seals with labyrinth and smooth annular seals shows the honeycomb seal had the best sealing (minimum leakage) performance, followed in order by the labyrinth and smooth seals. For prerotated fluids entering the seal, in the direction of shaft rotation, the honeycomb seal has the best rotordynamic stability followed in order by the labyrinth and smooth. For no prerotation, or fluid prerotation against shaft rotation, the labyrinth seal has the best rotordynamic stability followed in order by the smooth and honeycomb seals.

Childs, D.; Elrod, D.; Hale, K.

1989-01-01

208

Managing aluminum phosphide poisonings.  

PubMed

Aluminum phosphide (AlP) is a cheap, effective and commonly used pesticide. However, unfortunately, it is now one of the most common causes of poisoning among agricultural pesticides. It liberates lethal phosphine gas when it comes in contact either with atmospheric moisture or with hydrochloric acid in the stomach. The mechanism of toxicity includes cellular hypoxia due to the effect on mitochondria, inhibition of cytochrome C oxidase and formation of highly reactive hydroxyl radicals. The signs and symptoms are nonspecific and instantaneous. The toxicity of AlP particularly affects the cardiac and vascular tissues, which manifest as profound and refractory hypotension, congestive heart failure and electrocardiographic abnormalities. The diagnosis of AlP usually depends on clinical suspicion or history, but can be made easily by the simple silver nitrate test on gastric content or on breath. Due to no known specific antidote, management remains primarily supportive care. Early arrival, resuscitation, diagnosis, decrease the exposure of poison (by gastric lavage with KMnO(4), coconut oil), intensive monitoring and supportive therapy may result in good outcome. Prompt and adequate cardiovascular support is important and core in the management to attain adequate tissue perfusion, oxygenation and physiologic metabolic milieu compatible with life until the tissue poison levels are reduced and spontaneous circulation is restored. In most of the studies, poor prognostic factors were presence of acidosis and shock. The overall outcome improved in the last decade due to better and advanced intensive care management. PMID:21887030

Gurjar, Mohan; Baronia, Arvind K; Azim, Afzal; Sharma, Kalpana

2011-07-01

209

Managing aluminum phosphide poisonings  

PubMed Central

Aluminum phosphide (AlP) is a cheap, effective and commonly used pesticide. However, unfortunately, it is now one of the most common causes of poisoning among agricultural pesticides. It liberates lethal phosphine gas when it comes in contact either with atmospheric moisture or with hydrochloric acid in the stomach. The mechanism of toxicity includes cellular hypoxia due to the effect on mitochondria, inhibition of cytochrome C oxidase and formation of highly reactive hydroxyl radicals. The signs and symptoms are nonspecific and instantaneous. The toxicity of AlP particularly affects the cardiac and vascular tissues, which manifest as profound and refractory hypotension, congestive heart failure and electrocardiographic abnormalities. The diagnosis of AlP usually depends on clinical suspicion or history, but can be made easily by the simple silver nitrate test on gastric content or on breath. Due to no known specific antidote, management remains primarily supportive care. Early arrival, resuscitation, diagnosis, decrease the exposure of poison (by gastric lavage with KMnO4, coconut oil), intensive monitoring and supportive therapy may result in good outcome. Prompt and adequate cardiovascular support is important and core in the management to attain adequate tissue perfusion, oxygenation and physiologic metabolic milieu compatible with life until the tissue poison levels are reduced and spontaneous circulation is restored. In most of the studies, poor prognostic factors were presence of acidosis and shock. The overall outcome improved in the last decade due to better and advanced intensive care management. PMID:21887030

Gurjar, Mohan; Baronia, Arvind K; Azim, Afzal; Sharma, Kalpana

2011-01-01

210

Netlike knitting of polyelectrolyte multilayers on honeycomb-patterned substrate.  

PubMed

The pH-amplified exponential growth layer-by-layer (LBL) self-assembly process was directly performed on honeycomb-patterned substrate for achievement of "guided patterning" of polyelectrolyte multilayers. Polyethylenimine (PEI) and poly(acrylic acid) (PAA) were used as polyanions, and their pH were carefully tuned to achieve pH-enhanced exponential growth. Guided by underlying hexagonally patterned islandlike poly(dimethylsiloxane) (PDMS) arrays, the diffusive polyelectrolytes rapidly interweaved into linear, multilayered structures distributed along the grooves between the patterned protuberate and formed a regular network of multilayered film with uniform mesh size. Netlike "knitting" of polyelectrolyte multilayers on honeycomb-patterned substrate has been realized by following this procedure. Superhydrophobic surfaces could be readily obtained after several bilayers of LBL assembly (with thermal cross-linking and surface fluorination by chemical vapor deposition), indicating that successful fabrication of functional micro- and nanoscale hierarchical structures can be achieved. Both high- and low-adhesion superhydrophobic surfaces ("petal effect" and "lotus effect") can be obtained with different bilayers of assembly, proving that different levels of nano- to microstructural hierarchy can be realized using this method. Furthermore, we were able to get topographically asymmetric, free-standing, polyelectrolyte multilayer films in the case that we performed more than eight bilayers of assembly. This research reported template-directed LBL patterning assembly for the first time. It provides a beneficial exploration for the surface patterning technique for the LBL assembly process. PMID:20684559

Sun, Wei; Shen, Liyan; Wang, Jiaming; Fu, Ke; Ji, Jian

2010-09-01

211

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

212

Resonating valence-bond physics on the honeycomb lattice  

NASA Astrophysics Data System (ADS)

We study bond and spin correlations of the nearest-neighbor resonating valence bond (RVB) wave function for a SU(2) symmetric S =1 /2 antiferromagnet on the honeycomb lattice. We find that spin correlations in this wave function are short ranged, while the bond energy correlation function takes on an oscillatory power-law form D (r ?) ˜cos(Q .r ?) /|r?| ?w(2 ) , where Q =(2 ? /3 ,-2 ? /3 ) is the wave vector corresponding to "columnar" valence-bond solid order on the honeycomb lattice, and ?w(2 ) ?1.49 (3 ) . We use a recently introduced large-g expansion approach to relate bond-energy correlators of the SU (g ) wave function to dimer correlations of an interacting fully packed dimer model with a three-dimer interaction of strength V (g ) =-ln(1 +1 /g2) . Putting g =2 , we find numerically that the dimer correlation function Dd(r ?) of this dimer model has power-law behavior Dd(r ?) ˜cos(Q .r ?) /|r?| ?d(2 ) with ?d(2 ) ?1.520 (15 ) , in rather good agreement with the wave function results. We also study the same quantities for g =3 ,4 ,10 and find that the bond-energy correlations in the SU (g ) wave function are consistently well reproduced by the corresponding dimer correlations in the interacting dimer model.

Patil, Pranay; Dasgupta, Ishita; Damle, Kedar

2014-12-01

213

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

214

Correlated metallic state in honeycomb lattice: Orthogonal Dirac semimetal  

E-print Network

A novel gapped metallic state coined orthogonal Dirac semimetal is proposed in the honeycomb lattice in terms of $Z_{2}$ slave-spin representation of Hubbard model. This state corresponds to the disordered phase of slave-spin and has the same thermaldynamical and transport properties as usual Dirac semimetal but its singe-particle excitation is gapped and has nontrivial topological order due to the $Z_{2}$ gauge structure. The quantum phase transition from this orthogonal Dirac semimetal to 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 non-fractionalized approaches. As byproducts, a path integral formalism for the $Z_{2}$ 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 $Z_{2}$ slave-spin theory and related non-Fermi liquid phases in honeycomb lattice.

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

2012-09-10

215

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

216

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

217

Spin and the Honeycomb Lattice: Lessons from Graphene  

E-print Network

Spin-1/2 particles such as the electron are described by the Dirac equation, which allows for two spin eigenvalues (up or down) and two types of energy eigenvalues (positive or negative, corresponding to the electron and the positron). A model of electrons hopping from atom to atom in graphene's honeycomb lattice gives low-energy electronic excitations that obey a relation formally identical to a 2+1 dimensional Dirac equation. Graphene's spin equivalent, "pseudospin", arises from the degeneracy introduced by the honeycomb lattice's two inequivalent atomic sites per unit cell. Previously it has been thought that the usual electron spin and the pseudospin indexing the graphene sublattice state are merely analogues. Here we show that the pseudospin is also a real angular momentum. This identification explains the suppression of electron backscattering in carbon nanotubes and the angular dependence of light absorption by graphene. Furthermore, it demonstrates that half-integer spin like that carried by the quarks and leptons can derive from hidden substructure, not of the particles themselves, but rather of the space in which these particles live.

Matthew Mecklenburg; B. C. Regan

2011-05-07

218

The Colored Hofstadter Butterfly for the Honeycomb Lattice  

E-print Network

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 $\\sigma_H$ is given as the winding number of an eigenvector of a $2 \\times 2$ transfer matrix, as a function of the quasi-momentum $k \\in (0,2 \\pi)$. 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 $\\sigma_H $ for flux $p/q$ in the $r$-th gap conforms with the Diophantine equation $r=\\sigma_H\\cdot p+ s\\cdot q$, which determines $\\sigma_H \\mod q$. A window such as $\\sigma_H \\in(-q/2,q/2)$, or possibly shifted, provides a natural further condition for $\\sigma_H$, which however turns out not to be met. Based on extensive numerical calculations, we conjecture that the solution conforms with the relaxed condition $\\sigma_H\\in(-q,q)$.

Andrea Agazzi; Jean-Pierre Eckmann; Gian Michele Graf

2014-03-05

219

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

220

Evaluation of Composite Honeycomb Sandwich Panels Under Compressive Loads at Elevated Temperatures  

NASA Technical Reports Server (NTRS)

Fourteen composite honeycomb sandwich panels were tested to failure under compressive loading. The test specimens included panels with both 8 and 24-ply graphite-bismaleimide composite facesheets and both titanium and graphite-polyimide core materials. The panels were designed to have the load introduced through fasteners attached to pairs of steel angles on the ends of the panels to simulate double shear splice joints. The unloaded edges were unconstrained. Test temperatures included room temperature, 250F, and 300F. For the room and 250F temperature tests, the 24-ply specimen failure strains were close to the unnotched allowable strain values and failure loads were well above the design loads. However, failure strains much lower than the unnotched allowable strain values, and failure loads below the design loads were observed with several of the 8-ply specimens. For each individual test temperature, large variations in the failure strains and loads were observed for the 8-ply specimens. Dramatic decreases in the failure strains and loads were observed for the 24-ply specimens as the test temperature was increased from 250F to 300F. All 8-ply specimens appeared to have failed in a facesheet strength failure mode for all test temperatures. The 24-ply specimens displayed appreciably greater amounts of bending prior to failure than the 8-ply specimens, and panel buckling occurred prior to facesheet strength failure for the 24-ply room and 250F temperature tests.

Walker, Sandra P.

1998-01-01

221

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. 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

222

Core Crush Mechanisms and Solutions in the Manufacturing of Sandwich Structures  

Microsoft Academic Search

Core crush is a manufacturing defect occurred during the autoclave curing process of composite honeycomb sandwich structures.\\u000a It usually leads to costly part rejections since the defect is non-repairable. In addition, this problem has posted constraints\\u000a on aircraft engineers by limiting the ranges of core density and core thickness that could be used when designing these types\\u000a of structures. In

H. M. HSIAO; S. M. LEE; R. A. BUYNY

223

Phases of correlated spinless fermions on the honeycomb lattice  

NASA Astrophysics Data System (ADS)

We use exact diagonalization and cluster perturbation theory to address the role of strong interactions and quantum fluctuations for spinless fermions on the honeycomb lattice. We find quantum fluctuations to be very pronounced both at weak and strong interactions. A weak second-neighbor Coulomb repulsion V2 induces a tendency toward an interaction-generated quantum anomalous Hall phase, as borne out in mean-field theory. However, quantum fluctuations prevent the formation of a stable quantum Hall phase before the onset of the charge-modulated phase predicted at large V2 by mean-field theory. Consequently, the system undergoes a direct transition from the semimetal to the charge-modulated phase. For the latter, charge fluctuations also play a key role. While the phase, which is related to pinball liquids, is stabilized by the repulsion V2, the energy of its low-lying charge excitations scales with the electronic hopping t, as in a band insulator.

Daghofer, Maria; Hohenadler, Martin

2014-01-01

224

Fermionic quantum criticality in honeycomb and $?$-flux Hubbard models  

E-print Network

We numerically investigate the critical behavior of the Hubbard model on the honeycomb and the $\\pi$-flux lattice, which exhibits a direct transition from a Dirac semimetal to an antiferromagnetically ordered Mott insulator. We use projective auxiliary-field quantum Monte Carlo simulations and a careful finite-size scaling analysis that exploits improved renormalization-group invariant observables. This approach, which is successfully verified for the 3D XY transition of the Kane-Mele-Hubbard model, allows us to extract estimates for the critical couplings and the critical exponents. The results confirm that the critical behavior for the semimetal to Mott insulator transition in the Hubbard model belongs to the Gross-Neveu-Heisenberg universality class on both lattices.

Francesco Parisen Toldin; Martin Hohenadler; Fakher F. Assaad; Igor F. Herbut

2014-11-10

225

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

226

Aluminum composite driveshafts  

SciTech Connect

This article examines the development and performance of a metal matrix composite lightweight driveshaft tube of 6061 aluminum alloy with an even dispersion of 20[percent] aluminum oxide particles. The topics of the article include evolution of the lightweight design, raw material production, tubing fabrication, driveshaft performance, and modulus testing.

Not Available

1994-02-01

227

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

228

Buckling Testing and Analysis of Honeycomb Sandwich Panel Arc Segments of a Full-Scale Fairing Barrel. Part 2; 6-Ply In-Autoclave Facesheets  

NASA Technical Reports Server (NTRS)

Four honeycomb sandwich panel types, representing 1/16th arc segments of a 10-m diameter barrel section of the Heavy Lift Launch Vehicle (HLLV), were manufactured and tested under the NASA Composites for Exploration program and the NASA Constellation Ares V program. Two configurations were chosen for the panels: 6-ply facesheets with 1.125 in. honeycomb core and 8-ply facesheets with 1.000 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- by 5-ft panels were cut from the 1/16th barrel sections. These panels were tested under compressive loading at the NASA Langley Research Center (LaRC). Furthermore, linear eigenvalue and geometrically nonlinear finite element analyses were performed to predict the compressive response of each 3- by 5-ft panel. This manuscript summarizes the experimental and analytical modeling efforts pertaining to the panels composed of 6-ply, IM7/977-3 facesheets (referred to as Panels B-1 and B-2). 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 yield 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 (3-D) effects on the compressive response of the panel.

Pineda, Evan J.; Meyers, David E.; Kosareo, Daniel N.; Zalewski, Bart F.; Dixon, Genevieve D.

2013-01-01

229

A numerical adaptation of SAW identities from the honeycomb to other 2D lattices  

E-print Network

Recently, Duminil-Copin and Smirnov proved a long-standing conjecture by Nienhuis that the connective constant of self-avoiding walks on the honeycomb lattice is $\\sqrt{2+\\sqrt{2}}.$ A key identity used in that proof depends on the existence of a parafermionic observable for self-avoiding walks on the honeycomb lattice. Despite the absence of a corresponding observable for SAW on the square and triangular lattices, we show that in the limit of large lattices, some of the consequences observed on the honeycomb lattice persist on other lattices. This permits the accurate estimation, though not an exact evaluation, of certain critical amplitudes, as well as critical points, for these lattices. For the honeycomb lattice an exact amplitude for loops is proved.

Nicholas R Beaton; Anthony J Guttmann; Iwan Jensen

2011-10-06

230

Two-dimensional transition metal honeycomb realized: Hf on Ir(111).  

PubMed

Two-dimensional (2D) honeycomb systems made of elements with d electrons are rare. Here, we report the fabrication of a transition metal (TM) 2D layer, namely, hafnium crystalline layers on Ir(111). Experimental characterization reveals that the Hf layer has its own honeycomb lattice, morphologically identical to graphene. First-principles calculations provide evidence for directional bonding between adjacent Hf atoms, analogous to carbon atoms in graphene. Calculations further suggest that the freestanding Hf honeycomb could be ferromagnetic with magnetic moment ?/Hf = 1.46 ?(B). The realization and investigation of TM honeycomb layers extend the scope of 2D structures and could bring about novel properties for technological applications. PMID:24016148

Li, Linfei; Wang, Yeliang; Xie, Shengyi; Li, Xian-Bin; Wang, Yu-Qi; Wu, Rongting; Sun, Hongbo; Zhang, Shengbai; Gao, Hong-Jun

2013-10-01

231

Repair of brazed steel honeycomb-sandwich panels with vertical pins only  

NASA Technical Reports Server (NTRS)

Vertical steel tubular pins restore the shear strength of honeycomb panels and improve the quality of the repaired panel. New repair method eliminates diagonal pins. Vertical pins are welded to face sheets, forming ''Vierendeel Truss'' arrangement to transmit shear loads.

Rowe, J.

1970-01-01

232

Casting the first 8.4-m borosilicate honeycomb mirror for the Large Binocular Telescope  

Microsoft Academic Search

We report on the casting of the first 8.4 meter diameter borosilicate honeycomb mirror at the Steward Observatory Mirror Laboratory. This blank will become the world's largest monolithic glass telescope mirror, and is the first of two mirrors for the large Binocular Telescope Project. The honeycomb 8.4 meter mirror was cast from 21 tons of E6 borosilicate glass manufactured by

John M. Hill; J. Roger P. Angel; Randall D. Lutz; Blain H. Olbert; Peter A. Strittmatter

1998-01-01

233

Aluminum monocarbonyl and aluminum isocarbonyl Steve S. Wesolowski,a)  

E-print Network

Aluminum monocarbonyl and aluminum isocarbonyl Steve S. Wesolowski,a) T. Daniel Crawford,b) Justin of the aluminum monocarbonyl species AlCO and AlOC have been performed to predict the geometries, fragmentation, Ogden, and Oswald6 first isolated aluminum dicarbonyls in solid krypton and identified the species

Crawford, T. Daniel

234

Plasma etch chemistry of aluminum and aluminum alloy films  

Microsoft Academic Search

The chemistry occurring in glow discharges used to etch aluminum and aluminum alloy films is examined and is related to recurring problms such as initiation and reproducibility of etching, polymer or residue formation, photoresist degradation, aluminum corrosion, and safety aspects. The relative effects of different etch gases on these problems is discussed in light of aluminum surface chemistry and gas-phase

Dennis W. Hess

1982-01-01

235

Novel Aharonov-Bohm-like effect: Detectability of the vector potential in a solenoidal configuration with a ferromagnetic core covered by superconducting lead, and surrounded by a thin cylindrical shell of aluminum  

E-print Network

The flux as measured by the Josephson effect in a SQUID-like configuration with a ferromagnetic core inserted into its center, is shown to be sensitive to the vector potential arising from the central ferromagnetic core, even when the core is covered with a superconducting material that prevents any magnetic field lines from ever reaching the perimeter of the SQUID-like configuration. This leads to a macroscopic, Aharonov-Bohm-like effect that is observable in an asymmetric hysteresis loop in the response of the SQUID-like configuration to an externally applied magnetic field.

R. Y. Chiao

2012-06-23

236

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

237

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

238

A Technique to Determine Billet Core Charge Weight for P/M Fuel Tubes  

SciTech Connect

The core length in an extruded tube depends on the weight of powder in the billet core. In the past, the amount of aluminum powder needed to give a specified core length was determined empirically. This report gives a technique for calculating the weight of aluminum powder for the P/M core. An equation has been derived which can be used to determine the amount of aluminum needed for P/M billet core charge weights. Good agreement was obtained when compared to Mark 22 tube extrusion data. From the calculated charge weight, the elastomeric bag can be designed and made to compact the U3O8-Al core.

Peacock, H.B.

2001-07-02

239

Performance of metallic honeycomb-core sandwich beams under shock loading  

E-print Network

; received in revised form 16 June 2005 Available online 26 August 2005 Abstract Stainless steel square-duration impulses using a shock simulation technique involving high-speed impact of Al foam projectiles associated with nearby explosions, the sandwich beams exhibit smaller displacements than the solid beams

Hutchinson, John W.

240

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

241

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

242

Walnut Hulls Clean Aluminum  

NASA Technical Reports Server (NTRS)

Hulls inflict minimal substrate damage. Walnut hulls found to be best abrasive for cleaning aluminum surfaces prior to painting. Samples blasted with walnut hulls showed no compressive stress of surface.

Colberg, W. R.; Gordon, G. H.; Jackson, C. H.

1984-01-01

243

Differentiation of mesenchymal stem cells into osteoblasts on honeycomb collagen scaffolds.  

PubMed

Tissue engineering using living cells is emerging as an alternative to tissue or organ transplantation. The adult mesenchymal stem cells can be differentiated into multilineage cells, such as adipocytes, chondrocytes, or osteoblasts when cultured with specific growth factors. In the present investigation, we have studied the effect of honeycomb collagen scaffolds for the adhesion, differentiation and proliferation of bone marrow-derived mesenchymal stem cells into osteoblasts. Mesenchymal stem cells were isolated from 6-week old albino rat femur bone marrow, and cultured in alpha-MEM medium without beta-glycerophosphate and dexamethasone. Honeycomb collagen discs were prepared from bovine dermal atelocollagen, cross-linked by UV-irradiation and sterilized by heat. The honeycomb discs were placed on the culture dishes before seeding the stem cells. The cells attached quickly to the honeycomb collagen scaffold, differentiated and proliferated into osteoblasts. The differentiated osteoblasts were characterized by morphological examination and alkaline phosphatase activity. The osteoblasts also synthesized calcium-deficient hydroxyapatite (pseudo-hydroxyapatite) crystals in the culture. The mineralization was confirmed by Von Kossa staining and the crystals were analyzed by X-ray diffraction. Light microscopy and DNA measurements showed that the differentiated osteoblasts multiplied into several layers on the honeycomb collagen scaffold. The results demonstrated that the honeycomb collagen sponge is an excellent scaffold for the differentiation and proliferation of mesenchymal stem cells into osteoblasts. The data further proved that honeycomb collagen is an effective substrate for tissue engineering applications, and is very useful in the advancing field of stem cell technology and cell-based therapy. PMID:16572435

George, Joseph; Kuboki, Yoshinori; Miyata, Teruo

2006-10-20

244

Heat Shield Employing Cured Thermal Protection Material Blocks Bonded in a Large-Cell Honeycomb Matrix  

NASA Technical Reports Server (NTRS)

A document describes a new way to integrate thermal protection materials on external surfaces of vehicles that experience the severe heating environments of atmospheric entry from space. Cured blocks of thermal protection materials are bonded into a compatible, large-cell honeycomb matrix that can be applied on the external surfaces of the vehicles. The honeycomb matrix cell size, and corresponding thermal protection material block size, is envisioned to be between 1 and 4 in. (.2.5 and 10 cm) on a side, with a depth required to protect the vehicle. The cell wall thickness is thin, between 0.01 and 0.10 in. (.0.025 and 0.25 cm). A key feature is that the honeycomb matrix is attached to the vehicle fs unprotected external surface prior to insertion of the thermal protection material blocks. The attachment integrity of the honeycomb can then be confirmed over the full range of temperature and loads that the vehicle will experience. Another key feature of the innovation is the use of uniform-sized thermal protection material blocks. This feature allows for the mass production of these blocks at a size that is convenient for quality control inspection. The honeycomb that receives the blocks must have cells with a compatible set of internal dimensions. The innovation involves the use of a faceted subsurface under the honeycomb. This provides a predictable surface with perpendicular cell walls for the majority of the blocks. Some cells will have positive tapers to accommodate mitered joints between honeycomb panels on each facet of the subsurface. These tapered cells have dimensions that may fall within the boundaries of the uniform-sized blocks.

Zell, Peter

2012-01-01

245

Instabilities on graphene's honeycomb lattice with electron-phonon interactions  

NASA Astrophysics Data System (ADS)

We study the impact of electron-phonon interactions on the many-body instabilities of electrons on the honeycomb lattice and their interplay with repulsive local and nonlocal Coulomb interactions at charge neutrality. To that end, we consider in-plane optical phonon modes with wave vectors close to the ? point as well as to the K ,-K points and calculate the effective phonon-mediated electron-electron interaction by integrating out the phonon modes. Ordering tendencies are studied by means of a momentum-resolved functional renormalization-group approach allowing for an unbiased investigation of the appearing instabilities. In the case of an exclusive and supercritical phonon-mediated interaction, we find a Kekulé and a nematic bond ordering tendency being favored over the s-wave superconducting state. The competition between the different phonon-induced orderings clearly shows a repulsive interaction between phonons at small- and large-wave-vector transfers. We further discuss the influence of phonon-mediated interactions on electronically driven instabilities induced by on-site, nearest-neighbor, and next-nearest-neighbor density-density interactions. We find an extension of the parameter regime of the spin-density-wave order going along with an increase of the critical scales where ordering occurs and a suppression of competing orders.

Classen, Laura; Scherer, Michael M.; Honerkamp, Carsten

2014-07-01

246

Correlated metallic state in honeycomb lattice: Orthogonal Dirac semimetal  

E-print Network

A novel gapped metallic state coined orthogonal Dirac semimetal is identi?ed 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 thermal-dynamical and transport properties as Dirac semimetal but its singe-particle excitation is gapped. The quantum phase transition from this orthogonal Dirac semimetal to usual Dirac semimetal is described by nearly exact mean-?eld decou- pling 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 con- sidered as a ?ngerprint of our fractionalized theory when compared to other non-fractionalized approaches. As byproducts, a path integral formulism for the Z2 slave-spin representation of Hub- bard model is constructed and possible relations to other approaches and the sublattice pairing states, which has been argued to be a promising ca...

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

2012-01-01

247

Competing topological and Kondo insulator phases on a honeycomb lattice.  

PubMed

We investigate the competition between the spin-orbit interaction of itinerant electrons and their Kondo coupling with local moments densely distributed on the honeycomb lattice. We find that the model at half-filling displays a quantum phase transition between topological and Kondo insulators at a nonzero Kondo coupling. In the Kondo-screened case, tuning the electron concentration can lead to a new topological insulator phase. The results suggest that the heavy-fermion phase diagram contains a new regime with a competition among topological, Kondo-coherent and magnetic states, and that the regime may be especially relevant to Kondo lattice systems with 5d-conduction electrons. Finally, we discuss the implications of our results in the context of the recent experiments on SmB(6) implicating the surface states of a topological insulator, as well as the existing experiments on the phase transitions in SmB(6) under pressure and in CeNiSn under chemical pressure. PMID:23863017

Feng, Xiao-Yong; Dai, Jianhui; Chung, Chung-Hou; Si, Qimiao

2013-07-01

248

Monomer-dimer problem on random planar honeycomb lattice  

SciTech Connect

We consider the monomer-dimer (MD) problem on a random planar honeycomb lattice model, namely, the random multiple chain. This is a lattice system with non-periodic boundary condition, whose generating process is inspired by the growth of single walled zigzag carbon nanotubes. By applying algebraic and combinatorial techniques we establish a calculating expression of the MD partition function for bipartite graphs, which corresponds to the permanent of a matrix. Further, by using the transfer matrix argument we show that the computing problem of the permanent of high order matrix can be converted into some lower order matrices for this family of lattices, based on which we derive an explicit recurrence formula for evaluating the MD partition function of multiple chains and random multiple chains. Finally, we analyze the expectation of the number of monomer-dimer arrangements on a random multiple chain and the asymptotic behavior of the annealed MD entropy when the multiple chain becomes infinite in width and length, respectively.

Ren, Haizhen [School of Mathematical Sciences, Xiamen University, Xiamen 361005, Fujian (China) [School of Mathematical Sciences, Xiamen University, Xiamen 361005, Fujian (China); Department of Mathematics, Qinghai Normal University, Xining 810008, Qinghai (China); Zhang, Fuji; Qian, Jianguo, E-mail: jqqian@xmu.edu.cn [School of Mathematical Sciences, Xiamen University, Xiamen 361005, Fujian (China)] [School of Mathematical Sciences, Xiamen University, Xiamen 361005, Fujian (China)

2014-02-15

249

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

250

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

251

Fatal aluminum phosphide poisoning.  

PubMed

A 39-year-old man committed suicide by ingestion of aluminum phosphide, a potent mole pesticide, which was available at the victim's workplace. The judicial authority ordered an autopsy, which ruled out any other cause of death. The victim was discovered 10 days after the ingestion of the pesticide. When aluminum phosphide comes into contact with humidity, it releases large quantities of hydrogen phosphine (PH3), a very toxic gas. Macroscopic examination during the autopsy revealed a very important asphyxia syndrome with major visceral congestion. Blood, urine, liver, kidney, adrenal, and heart samples were analyzed. Phosphine gas was absent in the blood and urine but present in the brain (94 mL/g), the liver (24 mL/g), and the kidneys (41 mL/g). High levels of phosphorus were found in the blood (76.3 mg/L) and liver (8.22 mg/g). Aluminum concentrations were very high in the blood (1.54 mg/L), brain (36 microg/g), and liver (75 microg/g) compared to the usual published values. Microscopic examination revealed congestion of all the organs studied and obvious asphyxia lesions in the pulmonary parenchyma. All these results confirmed a diagnosis of poisoning by aluminum phosphide. This report points out that this type of poisoning is rare and that hydrogen phosphine is very toxic. The phosphorus and aluminum concentrations observed and their distribution in the different viscera are discussed in relation to data in the literature. PMID:10732945

Anger, F; Paysant, F; Brousse, F; Le Normand, I; Develay, P; Gaillard, Y; Baert, A; Le Gueut, M A; Pepin, G; Anger, J P

2000-03-01

252

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...

253

Magnetic properties of Dirac fermions in a buckled honeycomb lattice  

NASA Astrophysics Data System (ADS)

We calculate the magnetic response of a buckled honeycomb lattice with intrinsic spin-orbit coupling (such as silicene) which supports valley-spin polarized energy bands when subjected to a perpendicular electric field Ez. By changing the magnitude of the external electric field, the size of the two band gaps involved can be tuned, and a transition from a topological insulator (TI) to a trivial band insulator (BI) is induced as one of the gaps becomes zero, and the system enters a valley-spin polarized metallic state (VSPM). In an external magnetic field (B ), a distinct signature of the transition is seen in the derivative of the magnetization with respect to chemical potential ? , which gives the quantization of the Hall plateaus through the Streda relation. When plotted as a function of the external electric field, the magnetization has an abrupt change in slope at its minimum, which signals the VSPM state. The magnetic susceptibility ? shows jumps as a function of ? when a band gap is crossed, which provides a measure of the gaps' variation as a function of external electric field. Alternatively, at fixed ? , the susceptibility displays an increasingly large diamagnetic response as the electric field approaches the critical value of the VSPM phase. In the VSPM state, magnetic oscillations exist for any value of chemical potential while for the TI and BI states, ? must be larger than the minimum gap in the system. When ? is larger than both gaps, there are two fundamental cyclotron frequencies (which can also be tuned by Ez) involved in the de-Haas van-Alphen oscillations that are close in magnitude. This causes a prominent beating pattern to emerge.

Tabert, C. J.; Carbotte, J. P.; Nicol, E. J.

2015-01-01

254

Monte Carlo study of degenerate ground states and residual entropy in a frustrated honeycomb lattice Ising model  

E-print Network

Monte Carlo study of degenerate ground states and residual entropy in a frustrated honeycomb a classical fully frustrated honeycomb lattice Ising model using Markov-chain Monte Carlo methods and exact that grows as the number of spins N. Traditional single-spin-flip Monte Carlo methods fail to sample all

De Sterck, Hans

255

Self-Assembled Micro-Honeycomb Network of Single-Walled Carbon Nanotubes for Heterojunction Solar Cell  

E-print Network

. Here, we propose a self-organized micro- honeycomb network structure of SWNTs obtained by waterSelf-Assembled Micro-Honeycomb Network of Single-Walled Carbon Nanotubes for Heterojunction Solar contact to the substrate. The SWNT/n-Si heterojunction solar cell was built by placing the micro

Maruyama, Shigeo

256

A novel isolation curtain to reduce turbine ingress heating and an advanced model for honeycomb labyrinth seals  

E-print Network

A combination of 3-D and 2-D computational fluid dynamics (CFD) modeling as well as experimental testing of the labyrinth seal with hexagonal honeycomb cells on the stator wall was performed. For the 3-D and 2-D CFD models, the hexagonal honeycomb...

Choi, Dong Chun

2006-08-16

257

Comparison of X-Ray, Millimeter Wave, Shearography and Through-Transmission Ultrasonic Methods for Inspection of Honeycomb Composites  

Microsoft Academic Search

Honeycomb composites are increasingly finding utility in a variety of environments and applications, such as aircraft structural components, flight control components, radomes, etc. In-service and environmental stresses can produce unwanted flaws that adversely affect the structural integrity and functionality of these composites. These flaws may be in the forms of disbonds, delaminations, impact damage, crushed honeycomb, moisture intrusion, internal cracks,

M. A. Abou-Khousa; A. Ryley; S. Kharkovsky; R. Zoughi; D. Daniels; N. Kreitinger; G. Steffes

2007-01-01

258

Aluminum for plasmonics.  

PubMed

Unlike silver and gold, aluminum has material properties that enable strong plasmon resonances spanning much of the visible region of the spectrum and into the ultraviolet. This extended response, combined with its natural abundance, low cost, and amenability to manufacturing processes, makes aluminum a highly promising material for commercial applications. Fabricating Al-based nanostructures whose optical properties correspond with theoretical predictions, however, can be a challenge. In this work, the Al plasmon resonance is observed to be remarkably sensitive to the presence of oxide within the metal. For Al nanodisks, we observe that the energy of the plasmon resonance is determined by, and serves as an optical reporter of, the percentage of oxide present within the Al. This understanding paves the way toward the use of aluminum as a low-cost plasmonic material with properties and potential applications similar to those of the coinage metals. PMID:24274662

Knight, Mark W; King, Nicholas S; Liu, Lifei; Everitt, Henry O; Nordlander, Peter; Halas, Naomi J

2014-01-28

259

Optimization and Design of 2d Honeycomb Lattice Photonic Crystal Modulated by Liquid Crystals  

NASA Astrophysics Data System (ADS)

Photonic crystals (PCs) with infiltrating liquid crystals (LCs) have many potential applications because of their ability to continuously modulate the band-gaps. Using the plane-wave expansion method (PWM), we simulate the band-gap distribution of 2D honeycomb lattice PC with different pillar structures (circle, hexagonal and square pillar) and with different filling ratios, considering both when the LC is used as filling pillar material and semiconductors (Si, Ge) are used in the substrate, and when the semiconductors (Si, Ge) are pillar material and the LC is the substrate. Results show that unlike LC-based triangle lattice PC, optimized honeycomb lattice PC has the ability to generate absolute photonic band-gaps for fabricating optical switches. We provide optimization parameters for LC infiltrating honeycomb lattice PC structure based on simulation results and analysis.

Guo, Caihong; Zheng, Jihong; Gui, Kun; Zhang, Menghua; Zhuang, Songlin

2013-12-01

260

Study of the bilinear biquadratic Heisenberg model on a honeycomb lattice via Schwinger bosons  

NASA Astrophysics Data System (ADS)

We analyze the biquadratic bilinear Heisenberg magnet on a honeycomb lattice via Schwinger boson formalism. Due to their vulnerability to quantum fluctuations, non-conventional lattices (kagome, triangular and honeycomb for example) have been cited as candidates to support spin liquid states. Such states without long range order at zero temperature are known in one-dimensional spin models but their existence in higher dimensional systems is still under debate. Biquadratic interaction is responsible for various possibilities and phases as it is well-founded for one-dimensional systems. Here we have used a bosonic representation to study the properties at zero and finite low temperatures of the biquadratic term in the two-dimensional hexagonal honeycomb lattice. The results show an ordered state at zero temperature but much more fragile than that of a square lattice; the behavior at finite low temperatures is in accordance with expectations.

Moura, Antônio R.; Pereira, Afrânio R.

2013-09-01

261

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

262

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

NASA Astrophysics Data System (ADS)

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.

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.

2014-06-01

263

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

264

Aluminum Hydroxide and Magnesium Hydroxide  

MedlinePLUS

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

265

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

266

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, and by increasing the magnitude of the change in enthalpy of the reaction or combinations thereof.

Graetz, Jason Allan; Reilly, James J; Wegrzyn, James E

2012-09-18

267

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

268

Development and utilization of composite honeycomb and solid laminate reference standards for aircraft inspections.  

SciTech Connect

The FAA's Airworthiness Assurance NDI Validation Center, in conjunction with the Commercial Aircraft Composite Repair Committee, developed a set of composite reference standards to be used in NDT equipment calibration for accomplishment of damage assessment and post-repair inspection of all commercial aircraft composites. In this program, a series of NDI tests on a matrix of composite aircraft structures and prototype reference standards were completed in order to minimize the number of standards needed to carry out composite inspections on aircraft. Two tasks, related to composite laminates and non-metallic composite honeycomb configurations, were addressed. A suite of 64 honeycomb panels, representing the bounding conditions of honeycomb construction on aircraft, was inspected using a wide array of NDI techniques. An analysis of the resulting data determined the variables that play a key role in setting up NDT equipment. This has resulted in a set of minimum honeycomb NDI reference standards that include these key variables. A sequence of subsequent tests determined that this minimum honeycomb reference standard set is able to fully support inspections over the full range of honeycomb construction scenarios found on commercial aircraft. In the solid composite laminate arena, G11 Phenolic was identified as a good generic solid laminate reference standard material. Testing determined matches in key velocity and acoustic impedance properties, as well as, low attenuation relative to carbon laminates. Furthermore, comparisons of resonance testing response curves from the G11 Phenolic NDI reference standard was very similar to the resonance response curves measured on the existing carbon and fiberglass laminates. NDI data shows that this material should work for both pulse-echo (velocity-based) and resonance (acoustic impedance-based) inspections.

Roach, Dennis Patrick; Rackow, Kirk A.

2004-06-01

269

Molecular Structure of Aluminum Fluoride  

NSDL National Science Digital Library

Aluminum Fluoride is a solid, off-white, free-flowing granular material, insoluble in most organic and inorganic liquids at room temperatures. It is soluble in many fused salts. Aluminum Fluoride is used by aluminum producers to increase the conductivity of electrolytes in the smelting process. It is used as a flux ingredient for the removal of magnesium in refining aluminum scrap, by the ceramic industry for some body and glazing mixtures, and in the production of specialty refractory products.

2003-06-02

270

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

271

Absolute photonic band gap in 2D honeycomb annular photonic crystals  

NASA Astrophysics Data System (ADS)

Using the plane wave expansion method, we investigate the effects of structural parameters on absolute photonic band gap (PBG) in two-dimensional honeycomb annular photonic crystals (PCs). The results reveal that the annular PCs possess absolute PBGs that are larger than those of the conventional air-hole PCs only when the refractive index of the material from which the PC is made is equal to 4.5 or larger. If the refractive index is smaller than 4.5, utilization of anisotropic inner rods in honeycomb annular PCs can lead to the formation of larger PBGs. The optimal structural parameters that yield the largest absolute PBGs are obtained.

Liu, Dan; Gao, Yihua; Tong, Aihong; Hu, Sen

2015-01-01

272

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

273

Short-range correlations and cooling of ultracold fermions in the honeycomb lattice.  

PubMed

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. PMID:23215498

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

2012-11-16

274

Creating "hotels" for cells by electrospinning honeycomb-like polymeric structures.  

PubMed

It is well established that three-dimensional honeycomb-like nanofibrous structures enhance cell activity. In this work, we report that electrospun polymer nanofibres self-assemble into three-dimensional honeycomb-like structures. The underlying mechanism is studied by varying the polymer solution concentration, collecting substrates and working distance. The polymer solution concentration has a significant effect on the size of the electrospun nanofibres. The collection substrate and working distance affect the electric field strength, the evaporation of solvent and the discharging of nanofibres and consequently these two had a significant influence on the self-assembly of nanofibres. PMID:23910357

Liang, T; Mahalingam, S; Edirisinghe, M

2013-10-01

275

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

276

Emergent Honeycomb Lattice in LiZn2Mo3O8  

NASA Astrophysics Data System (ADS)

We introduce the idea of emergent lattices, where a simple lattice decouples into two weakly coupled lattices as a way to stabilize spin liquids. In LiZn2Mo3O8, the disappearance of 2/3 of the spins at low temperatures suggests that its triangular lattice decouples into an emergent honeycomb lattice weakly coupled to the remaining spins, and we suggest several ways to test this proposal. We show that these orphan spins act to stabilize the spin liquid in the J1-J2 honeycomb model and also discuss a possible 3D analogue, Ba2MoYO6 that may form a “depleted fcc lattice.”

Flint, Rebecca; Lee, Patrick A.

2013-11-01

277

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

278

Aluminum-ferricyanide battery  

NASA Astrophysics Data System (ADS)

A battery capable of producing high current densities with high charge capacity is described which includes an aluminum anode, a ferricyanide electrolyte and a second electrode capable of reducing ferricyanide electrolyte which is either dissolved in an alkaline solution or alkaline seawater solution. The performance of the battery is enhanced by high temperature and high electrolyte flow rates.

Marsh, Catherine; Licht, Stuart L.

1993-11-01

279

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

280

Mesoporous aluminum phosphite  

NASA Astrophysics Data System (ADS)

High surface area pure mesoporous aluminum-phosphorus oxide-based derivatives have been synthesized through an S +I - surfactant-assisted cooperative mechanism by means of a one-pot preparative procedure from aqueous solution and starting from aluminum atrane complexes and phosphoric and/or phosphorous acids. A soft chemical extraction procedure allows opening the pore system of the parent as-prepared materials by exchanging the surfactant without mesostructure collapse. The nature of the pore wall can be modulated from mesoporous aluminum phosphate (ALPO) up to total incorporation of phosphite entities (mesoporous aluminum phosphite), which results in a gradual evolution of the acidic properties of the final materials. While phosphate groups in ALPO act as network building blocks (bridging Al atoms), the phosphite entities become basically attached to the pore surface, what gives practically empty channels. The mesoporous nature of the final materials is confirmed by X-ray diffraction (XRD), transmission electron microscopy (TEM) and N 2 adsorption-desorption isotherms. The materials present regular unimodal pore systems whose order decreases as the phosphite content increases. NMR spectroscopic results confirm the incorporation of oxo-phosphorus entities to the framework of these materials and also provide us useful information concerning the mechanism through which they are formed.

El Haskouri, Jamal; Pérez-Cabero, Mónica; Guillem, Carmen; Latorre, Julio; Beltrán, Aurelio; Beltrán, Daniel; Amorós, Pedro

2009-08-01

281

Mechanisms of aluminum tolerance  

Technology Transfer Automated Retrieval System (TEKTRAN)

Aluminum (Al) toxicity limits agricultural productivity over much of the world’s arable land by inhibiting root growth and development. Affected plants have difficulty in acquiring adequate water and nutrition from their soil environments and thus have stunted shoot development and diminished yield....

282

Dynamic and quasi-static mechanical properties of iron-nickel alloy honeycomb  

Microsoft Academic Search

Several metal honeycombs, termed Linear Cellular Alloys (LCAs), were fabricated via a paste extrusion process and thermal treatment. Two Fe-Ni based alloy compositions were evaluated. Maraging steel and Super Invar were chosen for their compatibility with the process and the wide range of properties they afforded. Cell wall material was characterized and compared to wrought alloy specifications. The bulk alloy

Justin L. Clark

2004-01-01

283

Selective recovery of catalyst layer from supporting matrix of ceramic-honeycomb-type automobile catalyst  

Microsoft Academic Search

Natural resources of platinum group metals (PGMs) are limited and their demand is increasing because of their extensive uses in industrial applications. The low rate of production of PGMs due to low concentration in the related natural ores and high cost of production have made the recovery of PGMs from previously discarded catalytic converters a viable proposition. The ceramic-honeycomb-type automobile

Wantae Kim; Boungyoung Kim; Doyoung Choi; Tatsuya Oki; Sangbae Kim

2010-01-01

284

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

285

Graphene, a sheet of carbon atoms arranged in a honeycomb lattice, possesses many  

E-print Network

Graphene, a sheet of carbon atoms arranged in a honeycomb lattice, possesses many excellent chemical species onto the graphene plane offers an effective route to alter and engineer the properties of graphene. NSF-supported researchers have demonstrated that graphene covered dilutely with covalently bonded

Maroncelli, Mark

286

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

287

Relationship Between Honeycombing and Collagen Breakdown in Skipjack Tuna, Katsuwonus pelamis  

E-print Network

, a spoilage condition that affects the connective tissue of tuna, appears after the fish have been given a low surface. In extreme cases the connective tissue appears vac- uolated and resembles a vacant hon- eycomb-Honeycombing, a condi- tion that affects the connective tissue, was studied in skipjack tuna under controlled conditions

288

Doubly degenerate orbital system in honeycomb lattice: Implication of orbital state in layered iron oxide  

Microsoft Academic Search

We study a doubly degenerate orbital model on a honeycomb lattice. This is a model for orbital states in multiferroic layered iron oxides. The classical and quantum models are analyzed by spin-wave approximation, Monte Carlo simulation, and Lanczos method. A macroscopic number of degeneracy exists in the classical ground state. In the classical model, a peak in the specific heat

J. Nasu; A. Nagano; M. Naka; S. Ishihara

2008-01-01

289

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

290

Identification of honeycomb sandwich properties by high-resolution modal analysis  

E-print Network

Identification of honeycomb sandwich properties by high-resolution modal analysis M. R´ebillat X are estimated experimentally by means of a high-resolution modal analysis technique. An optimisation procedure implementations. The high-resolution modal analysis (HRMA) technique [5] is an alternative to the FT

Paris-Sud XI, Université de

291

Shearography for Non-destructive Inspection with applications to BAT Mask Tile Adhesive Bonding and Specular Surface Honeycomb Panels  

NASA Technical Reports Server (NTRS)

The applicability of shearography techniques for non-destructive evaluation in two unique application areas is examined. In the first application, shearography is used to evaluate the quality of adhesive bonds holding lead tiles to the B.4T gamma ray mask for the NASA Swift program. Using a vibration excitation, the more poorly bonded tiles are readily identifiable in the shearography image. A quantitative analysis is presented that compares the shearography results with a destructive pull test measuring the force at bond failure. The second application is to evaluate the bonding between the skin and core of a honeycomb structure with a specular (mirror-like) surface. In standard shearography techniques, the object under test must have a diffuse surface to generate the speckle patterns in laser light, which are then sheared. A novel configuration using the specular surface as a mirror to image speckles from a diffuser is presented, opening up the use of shearography to a new class of objects that could not have been examined with the traditional approach. This new technique readily identifies large scale bond failures in the panel, demonstrating the validity of this approach.

Lysak, Daniel B.

2003-01-01

292

Autonomous bottom-up fabrication of three-dimensional nano/microcellulose honeycomb structures, directed by bacterial nanobuilder.  

PubMed

We investigated the autonomous bottom-up fabrication of three-dimensional honeycomb cellulose structures, using Gluconacetobacter xylinus as a bacterial nanoengine, on cellulose honeycomb templates prepared by casting water-in-oil emulsions on glass substrates (Kasai and Kondo, Macromol. Biosci., 4, 17-21, 2004). The template film had a unique molecular orientation state along the honeycomb frames, but was non-crystalline. When G. xylinus, used as a nanofiber-producing bacterium, was incubated on the honeycomb scaffold in a culture medium, it secreted cellulose nanofibers only on the upper surface of the honeycomb frame. The movement was regulated by a selective interaction between the synthesized nanofiber and the surface of the honeycomb frames of the template. The relationship between directed deposition of synthesized nanofibers and ordered fabrication from the nano- to the micro-scale could provide a novel bottom-up methodology, using bacteria, for the design of three-dimensional honeycomb structures as functional materials with nano/micro hierarchical structures, with low energy consumption. PMID:24799259

Kondo, Tetsuo; Kasai, Wakako

2014-10-01

293

A biomimetic honeycomb-like scaffold prepared by flow-focusing technology for cartilage regeneration.  

PubMed

A tissue engineering chondrocytes/scaffold construct provides a promise to cartilage regeneration. The architecture of a scaffold such as interconnections, porosities, and pore sizes influences the fates of seeding cells including gene expression, survival, migration, proliferation, and differentiation thus may determine the success of this approach. Scaffolds of highly ordered and uniform structures are desirable to control cellular behaviors. In this study, a newly designed microfluidic device based on flow-focusing geometry was developed to fabricate gelatin scaffolds of ordered pores. In comparison with random foam scaffolds made by the conventional freeze-dried method, honeycomb-like scaffolds exhibit higher swelling ratio, porosity, and comparable compressive strength. In addition, chondrocytes grown in the honeycomb-like scaffolds had good cell viability, survival rate, glycosaminoglycans production, and a better proliferation than ones in freeze-dried scaffolds. Real-time PCR analysis showed that the mRNA expressions of aggrecan and collagen type II were up-regulated when chondrocytes cultured in honeycomb-like scaffolds rather than cells cultured as monolayer fashion. Oppositely, chondrocytes expressed collagen type II as monolayer culture when seeded in freeze-dried scaffolds. Histologic examinations revealed that cells produced proteoglycan and distributed uniformly in honeycomb-like scaffolds. Immunostaining showed protein expression of S-100 and collagen type II but negative for collagen type I and X, which represents the chondrocytes maintained normal phenotype. In conclusion, a highly ordered and honeycomb-like scaffold shows superior performance in cartilage tissue engineering. Biotechnol. Bioeng. 2014;111: 2338-2348. © 2014 Wiley Periodicals, Inc. PMID:24895237

Wang, Chen-Chie; Yang, Kai-Chiang; Lin, Keng-Hui; Wu, Chang-Chin; Liu, Yen-Liang; Lin, Feng-Huei; Chen, Ing-Ho

2014-11-01

294

Aluminum toxicity and albumin.  

PubMed

During a study of priming solutions for extracorporeal membrane oxygenation (ECMO) in the intensive care nursery, it was discovered that those solutions using certain brands of 25% albumin contained aluminum levels within the toxic range. When the brand was changed to a brand known to have a lower aluminum (Al) content, a marked drop in priming solution Al levels was measured. The heat exchanger was examined as a possible source of soluble Al. No evidence of elevated Al levels was found in fluids perfusing this heat exchanger when compared with a stainless steel heat exchanger. The Al content of various blood products was evaluated along with various brands of 5% albumin and 25% albumin. PMID:2597561

Kelly, A T; Short, B L; Rains, T C; May, J C; Progar, J J

1989-01-01

295

Water Content of Aluminum, Dialysis  

E-print Network

In the presence of normal renal function, a high concentration of aluminum in drinking water has been implicated as a factor in the etiology of a neurological syndrome in one specific geographical area. The role of aluminum as a toxic agent in other neurological disorders, where renal function is normal, is controversial. Aluminum is absorbed from the gastrointestinal tract and is normally excreted by the kidneys in the urine. In patients with chronic renal failure, aluminum appears to be of proven toxicological importance. In these patients the accumulation of aluminum in tissues causes an encephalopathy (dialysis encephalopathy or dialysis dementia), a specific form of metabolic bone disease (osteomalacic dialysis osteodystrophy), and an anemia and also plays an etiological role in some of the other complications associated with end-stage chronic renal disease. A failure in the normal renal excretory mechanism accounts for the tissue accumulation in chronic renal failure. The majority of chronic renal failure patients who develop aluminum toxicity are on long-term treatment with either hemo- or peritoneal dialysis; some patients develop toxicity who are only on treatment with aluminum-containing phosphate-binding agents. Aluminum in the dialysate appears to be the major source of the metal in chronic renal failure patients who develop aluminum toxicity. The aluminum content of the dialysate depends primarily on the content

Michael R. Wills; John Savory

296

Final Report on the Safety Assessment of Aluminum Silicate, Calcium Silicate, Magnesium Aluminum  

E-print Network

Final Report on the Safety Assessment of Aluminum Silicate, Calcium Silicate, Magnesium Aluminum Sodium Silicate, Montmorillonite, Pyrophyllite, and Zeolite1 This report reviews the safety of Aluminum, Calcium, Lithium Magnesium, Lithium Magnesium Sodium, Magnesium Aluminum, Magnesium, Sodium Magnesium

Ahmad, Sajjad

297

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

298

Shearography for Non-Destructive Evaluation with Applications to BAT Mask Tile Adhesive Bonding and Specular Surface Honeycomb Panels  

NASA Technical Reports Server (NTRS)

In this report we examine the applicability of shearography techniques for nondestructive inspection and evaluation in two unique application areas. In the first application, shearography is used to evaluate the quality of adhesive bonds holding lead tiles to the BAT gamma ray mask for the NASA Swift program. By exciting the mask with a vibration, the more poorly bonded tiles can be distinguished by their greater displacement response, which is readily identifiable in the shearography image. A quantitative analysis is presented that compares the shearography results with a destructive pull test measuring the force at bond failure. Generally speaking, the results show good agreement. Further investigation would be useful to optimize certain test parameters such as vibration frequency and amplitude. The second application is to evaluate the bonding between the skin and core of a honeycomb structure with a specular (mirror-like) surface. In standard shearography techniques, the object under test must have a diffuse surface to generate the speckle patterns in laser light, which are then sheared. A novel configuration using the specular surface as a mirror to image speckles from a diffuser is presented, opening up the use of shearography to a new class of objects that could not have been examined with the traditional approach. This new technique readily identifies large scale bond failures in the panel, demonstrating the validity of this approach. For the particular panel examined here, some scaling issues should be examined further to resolve the measurement scale down to the very small size of the core cells. In addition, further development should be undertaken to determine the general applicability of the new approach and to establish a firm quantitative foundation.

Lysak, Daniel B.

2003-01-01

299

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

300

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

301

Buckling Testing and Analysis of Honeycomb Sandwich Panel Arc Segments of a Full-Scale Fairing Barrel Part 1: 8-Ply In-Autoclave Facesheets. Part 1; 8-Ply In-Autoclave Facesheets  

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 under the NASA Composites for Exploration program and the NASA Space Launch Systems program. Two configurations were chosen for the panels: 6-ply facesheets with 1.125 in. honeycomb core and 8-ply facesheets with 1.000 in. honeycomb core. Additionally, two separate carbon fiber/epoxy material systems were chosen for the facesheets: inautoclave IM7/977-3 and out-of-autoclave T40-800b/5320-1. Smaller 3.00- by 5.00-ft panels were cut from the 1/16th barrel sections. These panels were tested under compressive loading at the NASA Langley Research Center. Furthermore, linear eigenvalue and geometrically nonlinear finite element analysis was performed to predict the compressive response of the 3.00- by 5.00-ft panels. This manuscript summarizes the experimental and analytical modeling efforts pertaining to the panel composed of 8-ply, IM7/977-3 facesheets (referred to Panel A). 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 yield good qualitative and quantitative predictions. Additionally, it was predicted correctly 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 misalignments, and three-dimensional (3 D) effects on the compressive response of the panel.

Myers, David E.; Pineda, Evan J.; Zalewski, Bart F.; Kosareo, Daniel N.; Kellas, Sotiris

2013-01-01

302

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

303

Mineral of the month: aluminum  

USGS Publications Warehouse

Aluminum is the second most abundant metallic element in Earth’s crust after silicon. Even so, it is a comparatively new industrial metal that has been produced in commercial quantities for little more than 100 years. Aluminum is lightweight, ductile, malleable and corrosion resistant, and is a good conductor of heat and electricity. Weighing about one-third as much as steel or copper per unit of volume, aluminum is used more than any other metal except iron. Aluminum can be fabricated into desired forms and shapes by every major metalworking technique to add to its versatility.

Plunkert, Patricia A.

2005-01-01

304

Redox-responsive degradable honeycomb manganese oxide nanostructures as effective nanocarriers for intracellular glutathione-triggered drug release.  

PubMed

Redox-responsive degradable honeycomb manganese oxide (hMnO2) nanostructures consisting of some lamellar MnO2 platelets were established as a new class of drug carriers for intracellular glutathione-triggered drug release. PMID:25421350

He, Dinggeng; He, Xiaoxiao; Wang, Kemin; Yang, Xue; Yang, Xiaoxiao; Zou, Zhen; Li, Xuecai

2015-01-14

305

A comparison of rotordynamic-coefficient predictions for annular honeycomb gas seals using different friction-factor models  

E-print Network

Predictions of rotordynamic-coefficients for annular honeycomb gas seals are compared using different friction-factor models. Analysis shows that the fundamental improvement in predicting the rotordynamic-coefficients accurately is the two...

D'Sousa, Rohan Joseph

2012-06-07

306

A comparison of rotordynamic-coefficient predictions for annular honeycomb gas seals using different friction-factor models.  

E-print Network

??Predictions of rotordynamic-coefficients for annular honeycomb gas seals are compared using different friction-factor models. Analysis shows that the fundamental improvement in predicting the rotordynamic-coefficients accurately… (more)

D'Sousa, Rohan Joseph

2012-01-01

307

* Please address all the correspondence to zhao@lmt.ens-cachan.fr 1 Impact behavior of honeycombs under combined  

E-print Network

behavior of honeycombs as a basic energy-absorption design parameter is eagerly desired in order to perform Hopkinson bars with beveled ends to perform combined shear-compression test under impact loading. It permits

308

Development of Composite Honeycomb and Solid Laminate Reference Standards to Aid Aircraft Inspections  

SciTech Connect

The rapidly increasing use of composites on commercial airplanes coupled with the potential for economic savings associated with their use in aircraft structures means that the demand for composite materials technology will continue to increase. Inspecting these composite structures is a critical element in assuring their continued airworthiness. The FAA's Airworthiness Assurance NDI Validation Center, in conjunction with the Commercial Aircraft Composite Repair Committee (CACRC), is developing a set of composite reference standards to be used in NDT equipment calibration for accomplishment of damage assessment and post-repair inspection of all commercial aircraft composites. In this program, a series of NDI tests on a matrix of composite aircraft structures and prototype reference standards were completed in order to minimize the number of standards needed to carry out composite inspections on aircraft. Two tasks, related to composite laminates and non-metallic composite honeycomb configurations, were addressed. A suite of 64 honeycomb panels, representing the bounding conditions of honeycomb construction on aircraft, were inspected using a wide array of NDI techniques. An analysis of the resulting data determined the variables that play a key role in setting up NDT equipment. This has resulted in a prototype set of minimum honeycomb reference standards that include these key variables. A sequence of subsequent tests determined that this minimum honeycomb reference standard set is able to fully support inspections over the fill range of honeycomb construction scenarios. Current tasks are aimed at optimizing the methods used to engineer realistic flaws into the specimens. In the solid composite laminate arena, we have identified what appears to be an excellent candidate, G11 Phenolic, as a generic solid laminate reference standard material. Testing to date has determined matches in key velocity and acoustic impedance properties, as well as, low attenuation relative to carbon laminates. Furthermore, comparisons of resonance testing response curves from the G11 Phenolic prototype standard was very similar to the resonance response curves measured on the existing carbon and fiberglass laminates. NDI data shows that this material should work for both pulse-echo (velocity-based) and resonance (acoustic impedance-based) inspections. Additional testing and industry review activities are underway to complete the validation of this material.

Dorrell, L.; Roach, D.

1999-03-04

309

Casting the first 8.4-m borosilicate honeycomb mirror for the Large Binocular Telescope  

NASA Astrophysics Data System (ADS)

We report on the casting of the first 8.4 meter diameter borosilicate honeycomb mirror at the Steward Observatory Mirror Laboratory. This blank will become the world's largest monolithic glass telescope mirror, and is the first of two mirrors for the large Binocular Telescope Project. The honeycomb 8.4 meter mirror was cast from 21 tons of E6 borosilicate glass manufactured by Ohara. This glass is melted into a mold constructed of aluminosilicate fiber to produce a honeycomb structure with roughly 20% of solid density. The 1662 hexagonal voids that form the honeycomb structure are produced by ceramic fiber boxes bolted to the bottom of the mold with SiC bolts. The furnace rotates at 6.8 rpm during the casting process to produce the F/1.14 paraboloid on the front surface. This shaping minimizes the amount of glass which must be removed during the grinding process. The front faceplate of the mirror will be 28 mm thick after generating and the back faceplate will be 25 mm. The overall thickness of the finished honeycomb blank is 89 cm at the outer edge and 44 cm at the central hole. The first 8.4 meter mirror blank was cast in January 1997. During the casting, two tons of glass leaked from the mold inside the spinning furnace. After a three month annealing cycle the furnace was opened for inspection. As a result of the leakage about 2 square meters of the faceplate near one edge of the mirror was too thin to be polished. In April 1997, an additional two tons of glass was loaded on top of the intact honeycomb structure. In June 1997, after heating slowly back to the annealing temperature, this extra glass was flash melted onto the front of the blank to assure that the faceplate was of sufficient thickness. After a further three month annealing cycle, the furnace was re-opened to reveal a superb casting with low bubble content and little trace of the fusion boundary. The blank has been removed from the furnace using a fixture glued to the upper surface of the blank. It will soon be stripped of its mold material in preparation for polishing.

Hill, John M.; Angel, J. Roger P.; Lutz, Randall D.; Olbert, Blain H.; Strittmatter, Peter A.

1998-08-01

310

Topological insulator in the core of the superconducting vortex in graphene.  

PubMed

The core of the vortex in a general superconducting order parameter in graphene is argued to be ordered, with the possible local order parameters forming the algebra U(1) x Cl(3). A sufficiently strong Zeeman coupling of the magnetic field of the vortex to the electron spin breaks the degeneracy in the core in favor of the anomalous quantum Hall state. I consider a variety of superconducting condensates on the honeycomb lattice and demonstrate the surprising universality of this result. A way to experimentally determine the outcome of the possible competition between different types of orders in the core is proposed. PMID:20366839

Herbut, Igor F

2010-02-12

311

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

312

A novel isolation curtain to reduce turbine ingress heating and an advanced model for honeycomb labyrinth seals  

Microsoft Academic Search

A combination of 3-D and 2-D computational fluid dynamics (CFD) modeling as well as experimental testing of the labyrinth seal with hexagonal honeycomb cells on the stator wall was performed. For the 3-D and 2-D CFD models, the hexagonal honeycomb structure was modeled using the concept of the baffle (zero-thickness wall) and the simplified 2-D fin, respectively. The 3-D model

Dong Chun Choi

2005-01-01

313

Honeycomb mirrors of borosilicate glass - Current results and plans for 7-8m diameter. [astronomical telescope  

NASA Technical Reports Server (NTRS)

The making of large astronomical mirrors with borosilicate glass honeycomb structure is discussed. Particular attention is given to a single casting technique for making borosilicate honeycomb mirror blanks up to 7 meters in diameter. Current work on the development of this technique involves the casting of blanks 60 cm in diameter which have the full thickness (33 cm), cell size (15 cm), and faceplate thickness (2.5 cm) needed for a 1.8-m mirror.

Angel, J. R. P.; Arganbright, D.; Harmonson, L.; Hill, J. M.; Woolf, N.

1982-01-01

314

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

315

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

316

21 CFR 172.310 - Aluminum nicotinate.  

Code of Federal Regulations, 2014 CFR

... 3 2014-04-01 2014-04-01 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...

2014-04-01

317

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

318

21 CFR 172.310 - Aluminum nicotinate.  

Code of Federal Regulations, 2010 CFR

... 3 2010-04-01 2009-04-01 true 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...

2010-04-01

319

21 CFR 172.310 - Aluminum nicotinate.  

Code of Federal Regulations, 2012 CFR

... 3 2012-04-01 2012-04-01 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...

2012-04-01

320

21 CFR 172.310 - Aluminum nicotinate.  

Code of Federal Regulations, 2011 CFR

... 3 2011-04-01 2011-04-01 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...

2011-04-01

321

Modeling Texture Evolution during Recrystallization in Aluminum  

E-print Network

Modeling Texture Evolution during Recrystallization in Aluminum Abhijit Brahme1,2 , Joseph Fridy3, Aluminum, Grain Boundary Mobility, Nucleation, Oriented Growth, Oriented Nucleation, Stored Energy, Monte Carlo Modeling. #12;Modeling Texture Evolution during Recrystallization in Aluminum 2 1. Introduction

Rollett, Anthony D.

322

75 FR 80527 - Aluminum Extrusions From China  

Federal Register 2010, 2011, 2012, 2013, 2014

...Final) and 731-TA-1177 (Final)] Aluminum Extrusions From China AGENCY: United...less-than-fair-value imports from China of aluminum extrusions, primarily provided for in...these investigations is contained in Aluminum Extrusions From the People's...

2010-12-22

323

Photoemission study of tris(8-hydroxyquinoline) aluminum/aluminum oxide/tris(8-hydroxyquinoline) aluminum interface  

SciTech Connect

The evolution of the interface electronic structure of a sandwich structure involving aluminum oxide and tris(8-hydroxyquinoline) aluminum (Alq), i.e. (Alq/AlO{sub x}/Alq), has been investigated with photoemission spectroscopy. Strong chemical reactions have been observed due to aluminum deposition onto the Alq substrate. The subsequent oxygen exposure releases some of the Alq molecules from the interaction with aluminum. Finally, the deposition of the top Alq layer leads to an asymmetry in the electronic energy level alignment with respect to the AlO{sub x} interlayer.

Ding Huanjun; Zorba, Serkan; Gao Yongli; Ma Liping; Yang Yang [Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627 (United States); Department of Materials Science and Engineering, University of California, Los Angeles, California 90095 (United States)

2006-12-01

324

High performing smart electrochromic device based on honeycomb nanostructured h-WO3 thin films: hydrothermal assisted synthesis.  

PubMed

Herein, we report honeycomb nanostructured single crystalline hexagonal WO3 (h-WO3) thin films in order to improve electrochromic performance. In the present investigation, honeycomb nanostructured WO3 with different unit size and nanowire array with highly nanocrystalline frameworks have been synthesized via a hydrothermal technique. The influence of hydrothermal reaction time on the honeycomb unit cells, crystallite size, lithium ion diffusion coefficient and switching time for coloration/bleaching were studied systematically. The electrochromic study reveals that the honeycomb unit cell size has a significant impact on the electrochromic performance. Small unit cells in the honeycomb lead to large optical modulation and fast switching response. A large optical modulation in the visible spectral region (60.74% at ? = 630 nm) at a potential of -1.2 V with fast switching time (4.29 s for coloration and 3.38 s for bleaching) and high coloration efficiency (87.23 cm(2) C(-1)) is observed in the honeycomb WO3 thin films with a unit cell diameter of 1.7 ?m. The variation in color on reduction of WO3 with applied potential has been plotted on an xy-chromaticity diagram and the color space coordinate shows the transition from a colorless to deep blue state. PMID:25500946

Kondalkar, Vijay V; Mali, Sawanta S; Kharade, Rohini R; Khot, Kishorkumar V; Patil, Pallavi B; Mane, Rahul M; Choudhury, Sipra; Patil, Pramod S; Hong, Chang K; Kim, Jin H; Bhosale, Popatrao N

2015-01-28

325

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

326

Investigation of surface oxides on aluminum alloys by valence band photoemission  

NASA Astrophysics Data System (ADS)

Core level and valence band x-ray photoelectron spectroscopy are used to study the chemical composition of the surface films on aluminum alloys. Certain alloying elements may preferentially migrate to the surface of an alloy, thereby altering the composition and consequently the chemistry of the surface. The behavior of a 6061 aluminum alloy is compared with that of pure aluminum. It is shown that the type of magnesium film formed at the alloy surface can be determined by comparing the valence band spectra of the aluminum alloy surface with that of known magnesium and aluminum compounds. The experimental valence band spectra of these compounds are supported by spectra generated from band structure calculations. The effect of boiling water on the surface film is discussed, with significant differences in surface chemistry being seen for the metal and the alloy. copyright 2002 American Vacuum Society.

Claycomb, Gregory D.; Sherwood, Peter M. A.

2002-07-01

327

A honeycomb collagen carrier for cell culture as a tissue engineering scaffold.  

PubMed

As a three-dimensional carrier for cell culture, a honeycomb structure cell scaffold was created from atelopeptide collagen Types I, II, and III. The diameter of the honeycomb pores ranged from 100 to 1,000 microm. The depth of the pores was from 10 to 3,000 mm. The scaffold was elastic and hard. Creation of various shapes was easy, and these shapes were easily maintained. Human fibroblasts, CHO-K1, BHK-21, and bovine endothelial cells were cultured with the scaffold. The growth curves of these cells were satisfactory. These results suggest that this carrier is a suitable scaffold for cell culture and will be useful as a three-dimensional tissue engineering scaffold. PMID:11284889

Itoh, H; Aso, Y; Furuse, M; Noishiki, Y; Miyata, T

2001-03-01

328

Carbon honeycomb grids for advanced lead-acid batteries. Part I: Proof of concept  

NASA Astrophysics Data System (ADS)

The carbon honeycomb grid is proposed as innovative solution for high energy density lead acid battery. The proof of concept is demonstrated, developing grids suitable for the small capacity, scale of valve-regulated lead acid batteries with 2.5-3 Ah plates. The manufacturing of the grids, includes fast, known and simple processes which can be rescaled for mass production with a minimum, investment costs. The most critical process of green composite carbonisation by heating in inert, atmosphere from 200 to 1000 °C takes about 5 h, guaranteeing the low cost of the grids. An AGM-VRLA, cell with prototype positive plate based on the lead-2% tin electroplated carbon honeycomb grid and, conventional negative plates is cycled demonstrating 191 deep cycles. The impedance spectroscopy, measurements indicate the grid performance remains acceptable despite the evolution of the corrosion, processes during the cycling.

Kirchev, Angel; Kircheva, Nina; Perrin, Marion

2011-10-01

329

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

330

Effects of nonlinearity on wave-packet dynamics in square and honeycomb lattices  

NASA Astrophysics Data System (ADS)

We offer a comparative study of the self-trapping phenomenon in square and honeycomb lattices, showing its dependence on the initial condition and lattice topology. In order to describe the dynamical behavior of one-electron wave packets, we use a discrete nonlinear Schrödinger equation which effectively takes into account the electron-phonon interaction in the limit of an adiabatic coupling. For narrow wave packets and strong nonlinearities, the electron distribution becomes trapped irrespective to the lattice geometry. In the opposite regime of wide wave packets and small nonlinearities, a delocalized regime takes place. There is an intermediate regime for which self-trapping is attained in the honeycomb lattice while the wave packet remains delocalized in square lattices. Further, we show that the critical nonlinear strength ?c scales linearly with the initial wave-packet participation function P(0) with the ratio ?c/P(0) being on the order of the energy bandwidth.

Dias, W. S.; Lyra, M. L.; de Moura, F. A. B. F.

2010-12-01

331

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

332

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

333

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

334

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

335

Aluminum anodization process modeling approach  

NASA Astrophysics Data System (ADS)

We propose approach for modeling thin aluminum film anodization in three dimensions using variation of coupled lattice map on volumetric grid, which is capable of capturing porous and nonporous aluminum oxide growth and electrochemical polishing modes. Model derivation is based on Parkhutik and Shershulsky understandings. Numerical simulation results for various initial conditions are shown and compared to experimental data.

Belov, Alexey N.; Vorobiev, Maksim I.; Gavrilov, Sergey A.; Shevyakov, Vasiliy I.

2014-12-01

336

Aluminum compounds as vaccine adjuvants  

Microsoft Academic Search

Aluminum compounds are the only adjuvants used widely with routine human vaccines and are the most common adjuvants in veterinary vaccines also. Though there has been a search for alternate adjuvants, aluminum adjuvants will continue to be used for many years due to their good track record of safety, low cost and adjuvanticity with a variety of antigens. For infections

Rajesh K Gupta

1998-01-01

337

Anodic Aluminum Oxide Diodes  

NASA Astrophysics Data System (ADS)

During anodic oxidation of aluminum, the incorporated anion species from the electrolyte are drawn into the growing barrier layer at the pore base by the high electric field and, afterward, migrate inward. The barrier layer consists of acid anion-contaminated regions adjacent to the oxide/electrolyte interface and relatively pure alumina further away from it. It can be presumed that there is a depletion layer region in between the acid anion-contaminated material and the pure alumina material. This study investigates the diode characteristics of the anodic aluminum oxide (AAO) film based on the depletion layer region presumption. Different electrolyte acids are employed to fabricate AAO diodes which possess different electrical properties. The current-voltage (I-V) characteristic curves indicate that the AAO devices possess the electrical property of a diode, especially the sulfuric acid processed AAO. It was observed that the threshold voltages for the sulfuric acid, oxalic acid, and phosphoric acid are 3.3, 8, and 16 V, respectively. This fits in with the sequential order presumption of the p, n depletion layer thicknesses for these three electrolyte acids.

Chang, Cheng-Yao; Wang, Gou-Jen

2011-07-01

338

The aluminum spot weld  

SciTech Connect

Weld conditions which promote long tip life for aluminum spot welds are not necessarily associated with high weld quality in terms of freedom from defects such as porosity, cracks and expulsion. Schedules which produce good weld nuggets in terms of the peel test and long tip life may not produce a good response in terms of fatigue life. The fatigue life range is optimized by maximizing the weld nugget diameter, i.e., by employing a weld schedule which may lead to expulsion and weld porosity. Weld strength, in both peel and overlap shear configurations, was found to be linearly dependent upon weld diameter. In the peel test, the strength was also dependent upon the base metal thickness, in that for a given thickness, there is a critical diameter for the transition between weld fracture and nugget pull-out. For a given nugget diameter, if pull-out is observed then the strength is greater than if fracture occurs through the weld. In the shear test, the opposite response was observed, the strength for nugget pull-out being less than that for weld shear failure. Weld pull-out was found only for the thinnest base metal thickness tested and the shear load depended only upon the weld diameter over the range of thicknesses tested. Maximum strength in an aluminum spot weld is obtained by maximizing the weld nugget diameter for that thickness of material.

Thornton, P.H.; Krause, A.R.; Davies, R.G. [Ford Motor Co., Dearborn, MI (United States). Scientific Lab.

1996-03-01

339

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

340

A honeycomb-based piezoelectric actuator for a flapping wing MAV  

Microsoft Academic Search

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

K. R. Olympio; Guylaine Poulin-Vittrant

2011-01-01

341

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. PMID:25002823

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

2014-01-01

342

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

343

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

344

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

345

External scaffold of spherical immature poxvirus particles is made of protein trimers, forming a honeycomb lattice.  

PubMed

During morphogenesis, poxviruses undergo a remarkable transition from spherical immature forms to brick-shaped infectious particles lacking helical or icosahedral symmetry. In this study, we show that the transitory honeycomb lattice coating the lipoprotein membrane of immature vaccinia virus particles is formed from trimers of a 62-kD protein encoded by the viral D13L gene. Deep-etch electron microscopy demonstrated that anti-D13 antibodies bound to the external protein coat and that lattice fragments were in affinity-purified D13 preparations. Soluble D13 appeared mostly trimeric by gel electrophoresis and ultracentrifugation, which is consistent with structural requirements for a honeycomb. In the presence or absence of other virion proteins, a mutated D13 with one amino acid substitution formed stacks of membrane-unassociated flat sheets that closely resembled the curved honeycombs of immature virions except for the absence of pentagonal facets. A homologous domain that is present in D13 and capsid proteins of certain other lipid-containing viruses support the idea that the developmental stages of poxviruses reflect their evolution from an icosahedral ancestor. PMID:16144903

Szajner, Patricia; Weisberg, Andrea S; Lebowitz, Jacob; Heuser, John; Moss, Bernard

2005-09-12

346

Self-sustained oscillations in blood flow through a honeycomb capillary network.  

PubMed

Numerical simulations of unsteady blood flow through a honeycomb network originating at multiple inlets and terminating at multiple outlets are presented and discussed under the assumption that blood behaves as a continuum with variable constitution. Unlike a tree network, the honeycomb network exhibits both diverging and converging bifurcations between branching capillary segments. Numerical results based on a finite difference method demonstrate that as in the case of tree networks considered in previous studies, the cell partitioning law at diverging bifurcations is an important parameter in both steady and unsteady flow. Specifically, a steady flow may spontaneously develop self-sustained oscillations at critical conditions by way of a Hopf bifurcation. Contrary to tree-like networks comprised entirely of diverging bifurcations, the critical parameters for instability in honeycomb networks depend weakly on the system size. The blockage of one or more network segments due to the presence of large cells or the occurrence of capillary constriction may cause flow reversal or trigger a transition to unsteady flow. PMID:25142744

Davis, J M; Pozrikidis, C

2014-09-01

347

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

348

Aluminum Zintl anion moieties within sodium aluminum clusters  

SciTech Connect

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{sub m}Al{sub n}{sup ?}, 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; Bowen, Kit H., E-mail: AKandalam@wcupa.edu, E-mail: kiran@mcneese.edu, E-mail: kbowen@jhu.edu [Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Schnöckel, Hansgeorg [Institute of Inorganic Chemistry, Karlsruhe Institute of Technology, 76128 Karlsruhe (Germany)] [Institute of Inorganic Chemistry, Karlsruhe Institute of Technology, 76128 Karlsruhe (Germany); Eichhorn, Bryan W. [Department of Chemistry, University of Maryland at College Park, College Park, Maryland 20742 (United States)] [Department of Chemistry, University of Maryland at College Park, College Park, Maryland 20742 (United States); Lee, Mal-Soon; Jena, P. [Department of Physics, Virginia Commonwealth University, Richmond, Virginia 23284 (United States)] [Department of Physics, Virginia Commonwealth University, Richmond, Virginia 23284 (United States); Kandalam, Anil K., E-mail: AKandalam@wcupa.edu, E-mail: kiran@mcneese.edu, E-mail: kbowen@jhu.edu [Department of Physics, West Chester University of Pennsylvania, West Chester, Pennsylvania 19383 (United States); Kiran, Boggavarapu, E-mail: AKandalam@wcupa.edu, E-mail: kiran@mcneese.edu, E-mail: kbowen@jhu.edu [Department of Chemistry, McNeese State University, Lake Charles, Louisiana 70609 (United States)] [Department of Chemistry, McNeese State University, Lake Charles, Louisiana 70609 (United States)

2014-02-07

349

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

350

Design Criteria for X-CRV Honeycomb Panels: A Preliminary Study  

NASA Technical Reports Server (NTRS)

The objective of this project is to perform the first step in developing structural design criteria for composite sandwich panels that are to be used in the aeroshell of the crew return vehicle (X-CRV). The preliminary concept includes a simplified method for assessing the allowable strength in the laminate material. Ultimately, it is intended that the design criteria be extended to address the global response of the vehicle. This task will require execution of a test program as outlined in the recommendation section of this report. The aeroshell of the X-CRV is comprised of composite sandwich panels consisting of fiberite face sheets and a phenolic honeycomb core. The function of the crew return vehicle is to enable the safe return of injured or ill crewpersons from space station, the evacuation of crew in case of emergency or the return of crew if an orbiter is not available. A significant objective of the X-CRV project is to demonstrate that this vehicle can be designed, built and operated at lower cost and at a significantly faster development time. Development time can be reduced by driving out issues in both structural design and manufacturing concurrently. This means that structural design and analysis progresses in conjunction with manufacturing and testing. Preliminary tests results on laminate coupons are presented in the report. Based on these results a method for detection material failure in the material is presented. In the long term, extrapolation of coupon data to large scale structures may be inadequate. Test coupons used to develop failure criteria at the material scale are typically small when compared to the overall structure. Their inherent small size indicates that the material failure criteria can be used to predict localized failure of the structure, however, it can not be used to predict failure for all failure modes. Some failure modes occur only when the structure or one of its sub-components are studied as a whole. Conversely, localized failure may not indicate failure of the structure as a whole and the amount of reserve capacity, if any, should be assessed. To develop a complete design criteria experimental studies of the sandwich panel are needed. Only then can a conservative and accurate design criteria be developed. This criteria should include effects of flaws and defects, and environmental factors such as temperature and moisture. Preliminary results presented in this report suggest that a simplified analysis can be used to predict the strength of a laminate. Testing for environmental effects have yet to be included in this work. The so called 'rogue flaw test' appears to be a promising method for assessing the effect of a defect in a laminate. This method fits in quite well with the philosophy of achieving a damage tolerant design.

Caccese, Vincent; Verinder, Irene

1997-01-01

351

ESCA studies of yttrium aluminum garnets  

SciTech Connect

X-ray photoelectron spectroscopy (XPS/ESCA) has been employed to investigate pure single crystals and powdered samples of yttrium aluminum garnet, Y{sub 3}Al{sub 5}O{sub 12} (YAG), and YAG crystals doped with several rare earth elements (Ln = Pr, Er, Ho, Tm) and a transition metal (Cr). Core level XPS peak shapes of the main elements forming the garnet structure can be rationalized due to different structural environments of particular ions modified by doping. The change of dopant oxidation state also results in variation of XPS peaks and helps to identify the sites in which it takes place. Single-crystal and powder samples give different XPS spectra. Possible sources of these differences are discussed. Similarities and differences between simple and mixed oxides are shown. The structure of YAG suggests the presence of only one independent oxygen ion; however the O(1s) spectra of all YAG systems exhibit two readily discerned peaks. An explanation for this dichotomy is discussed, involving the possible polarization of the oxygen valence electron density between the aluminum and yttrium. Alternative explanations are also considered.

Pawlak, D.A. [Univ. of Warsaw, Warszawa (Poland). Dept. of Chemistry] [Univ. of Warsaw, Warszawa (Poland). Dept. of Chemistry; [Inst. of Electronic Materials Technology, Warszawa (Poland); Wozniak, K. [Univ. of Warsaw, Warszawa (Poland). Dept. of Chemistry] [Univ. of Warsaw, Warszawa (Poland). Dept. of Chemistry; Frukacz, Z. [Inst. of Electronic Materials Technology, Warszawa (Poland)] [Inst. of Electronic Materials Technology, Warszawa (Poland); Barr, T.L.; Fiorentino, D. [Univ. of Wisconsin, Milwaukee, WI (United States)] [Univ. of Wisconsin, Milwaukee, WI (United States); Seal, S. [Univ. of Central Florida, Orlando, FL (United States)] [Univ. of Central Florida, Orlando, FL (United States)

1999-03-04

352

EUROSPF Conference APPLICATION TECHNOLOGY OF ALUMINUM BLOW  

E-print Network

6th EUROSPF Conference APPLICATION TECHNOLOGY OF ALUMINUM BLOW FORMING FOR AUTOMOTIVE CLOSURE PANEL Replacement by aluminum for the closure panels is one of the common methods for lightening car body. However. As a solution to cover the low stamping formability of aluminum, Blow forming technology of aluminum which

Paris-Sud XI, Université de

353

DUBLIN CORE  

EPA Science Inventory

The Dublin Core is a metadata element set intended to facilitate discovery of electronic resources. It was originally conceived for author-generated descriptions of Web resources, and the Dublin Core has attracted broad ranging international and interdisciplinary support. The cha...

354

Molecular cluster models of aluminum oxide and aluminum hydroxide surfaces  

Microsoft Academic Search

Ab initio, molecular orbital calculations for two different Hartree-Fock basis levels were performed on clusters in the system Al-O-H, and tested by comparing derived vibrational frequencies to the measured values for aluminum oxides and aluminum oxyhydroxide minerals. Models were chosen to reflect surface groups that may be present on aluminous minerals such as a-Al2O3 (corundum) and Al(OH)3 (gibbsite). Protonation and

J. D. KUBICKI; S. E. APITZ

1998-01-01

355

Preparation and characterization of energetic materials coated superfine aluminum particles  

NASA Astrophysics Data System (ADS)

This work is devoted to protect the activity of aluminum in solid rocket propellants by means of solvent/non-solvent method in which nitrocellulose (NC) and Double-11 (shortened form of double-base gun propellant, model 11) have been used as coating materials. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed to characterize the morphology of coated Al particles. Other characterization data of coated and uncoated Al particles, such as infrared absorption spectrum, laser particle size analysis and the active aluminum content were also studied. The thermal behavior of pure and coated aluminum samples have also been studied by simultaneous thermogravimetry-differential thermal analysis (TG-DTA) and differential scanning calorimetry (DSC). The results indicated that: superfine aluminum particles could be effectively coated with nitrocellulose and Double-11 through a solvent/non-solvent method. The energetic composite particles have core-shell structures and the thickness of the coating film is about 20-50 nm. The active aluminum content of different coated samples was measured by means of oxidation-reduction titration method. The results showed that after being stored in room temperature and under 50% humidity condition for about 4months the active aluminum content of coated Al particles decreased from 99.8 to 95.8% (NC coating) and 99.2% (Double-11 coating) respectively. Double-11 coating layer had a much better protective effect. The TG-DTA and DSC results showed that the energy amount and energy release rate of NC coated and Double-11 coated Al particles were larger than those of the raw Al particles. Double-11 coated Al particles have more significant catalytic effect on the thermal decomposition characters of AP than that of NC coated Al particles. These features accorded with the energy release characteristics of solid propellant.

Liu, Songsong; Ye, Mingquan; Han, Aijun; Chen, Xin

2014-01-01

356

Aluminum: The Element of Sustainability  

NSDL National Science Digital Library

This report by The Aluminum Association reviews the North American use of aluminum over the past 20 years in order to improve industry emissions, efficiency, recycling, and to address the challenges ahead in regards of sustainability. Challenges faced with sustainability include technological progress, energy and resource use, waste minimization and elimination, business operations, and product end-of-life (âdesign for recyclingâ and recycling incentives).

Association, The A.

357

Chrome - Free Aluminum Coating System  

NASA Technical Reports Server (NTRS)

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 personnel. This qualification consisted of over 4,000 tests. The tests revealed that a move away from Cr+6, required a system rather than individual components and that the maximum corrosion protection required pretreatment, primer and topcoat.

Bailey, John H.; Gugel, Jeffrey D.

2010-01-01

358

75 FR 70689 - Kaiser Aluminum Fabricated Products, LLC; Kaiser Aluminum-Greenwood Forge Division; Currently...  

Federal Register 2010, 2011, 2012, 2013, 2014

...Administration [TA-W-70,376] Kaiser Aluminum Fabricated Products, LLC; Kaiser Aluminum- Greenwood Forge Division; Currently Known...2, 2009, applicable to workers of Kaiser Aluminum Fabricated Products, LLC, Kaiser...

2010-11-18

359

Anodized aluminum on LDEF  

NASA Technical Reports Server (NTRS)

A compilation of reported analyses and results obtained for anodized aluminum flown on the Long Duration Exposure Facility (LDEF) was prepared. Chromic acid, sulfuric acid, and dyed sulfuric acid anodized surfaces were exposed to the space environment. The vast majority of the anodized surface on LDEF was chromic acid anodize because of its selection as a thermal control coating for use on the spacecraft primary structure, trays, tray clamps, and space end thermal covers. Reports indicate that the chromic acid anodize was stable in solar absorptance and thermal emittance, but that contamination effects caused increases in absorptance on surfaces exposed to low atomic oxygen fluences. There were some discrepancies, however, in that some chromic acid anodized specimens exhibited significant increases in absorptance. Sulfuric acid anodized surfaces also appeared stable, although very little surface area was available for evaluation. One type of dyed sulfuric acid anodize was assessed as an optical baffle coating and was observed to have improved infrared absorptance characteristics with exposure on LDEF.

Golden, Johnny L.

1993-01-01

360

Rotordynamic analysis of annular honeycomb-stator turbulent gas seals using a new friction-factor model based on flat plate tests  

NASA Astrophysics Data System (ADS)

A flat plate tester with various honeycomb geometries has been extended to develop a better understanding of the friction-factor behavior of honeycomb surfaces. The friction-factor-jump phenomenon, which is characterized by the dramatic drop and then rise of the friction-factor with increasing Reynolds number, has been explained by acoustic excitation of a large scale coherent flow structure from pressure fluctuation measurements inside the honeycomb cavities. A new friction-factor model based on the flat-plate-test results has been developed as a function of Mach number, dimensionless pressure, and honeycomb geometry variables. A rotordynamic analysis has been developed for centered, turbulent-annular honeycomb-stator seals incorporating the new empirical friction-factor model for honeycomb-stator surfaces. The validity of the new analysis in predicting the rotordynamic and leakage characteristics has been compared to Moody's friction-factor model analysis and experimental data for a short (L/D = 1/6, 25.4 mm long) seal and a longer (L/D = 1/3, 50.8 mm long) seal. The comparisons show that the new honeycomb friction-factor model greatly improves the predictions of leakage and rotordynamic coefficients compared to Moody's friction-factor model for both the short and longer seal, especially, for direct stiffness and cross-coupled stiffness. The new honeycomb friction-factor model predicts leakage and rotordynamic coefficients better for the short than the longer seals.

Ha, Tae Woong

1992-01-01

361

DNA-lipid complexes: stability of honeycomb-like and spaghetti-like structures.  

PubMed Central

A molecular level theory is presented for the thermodynamic stability of two (similar) types of structural complexes formed by (either single strand or supercoiled) DNA and cationic liposomes, both involving a monolayer-coated DNA as the central structural unit. In the "spaghetti" complex the central unit is surrounded by another, oppositely curved, monolayer, thus forming a bilayer mantle. The "honeycomb" complex is a bundle of hexagonally packed DNA-monolayer units. The formation free energy of these complexes, starting from a planar cationic/neutral lipid bilayer and bare DNA, is expressed as a sum of electrostatic, bending, mixing, and (for the honeycomb) chain frustration contributions. The electrostatic free energy is calculated using the Poisson-Boltzmann equation. The bending energy of the mixed lipid layers is treated in the quadratic curvature approximation with composition-dependent bending rigidity and spontaneous curvature. Ideal lipid mixing is assumed within each lipid monolayer. We found that the most stable monolayer-coated DNA units are formed when the charged/neutral lipid composition corresponds (nearly) to charge neutralization; the optimal monolayer radius corresponds to close DNA-monolayer contact. These conclusions are also valid for the honeycomb complex, as the chain frustration energy is found to be negligible. Typically, the stabilization energies for these structures are on the order of 1 k(B)T/A of DNA length, reflecting mainly the balance between the electrostatic and bending energies. The spaghetti complexes are less stable due to the additional bending energy of the external monolayer. A thermodynamic analysis is presented for calculating the equilibrium lipid compositions when the complexes coexist with excess bilayer. PMID:9370436

May, S; Ben-Shaul, A

1997-01-01

362

DNA-lipid complexes: stability of honeycomb-like and spaghetti-like structures.  

PubMed

A molecular level theory is presented for the thermodynamic stability of two (similar) types of structural complexes formed by (either single strand or supercoiled) DNA and cationic liposomes, both involving a monolayer-coated DNA as the central structural unit. In the "spaghetti" complex the central unit is surrounded by another, oppositely curved, monolayer, thus forming a bilayer mantle. The "honeycomb" complex is a bundle of hexagonally packed DNA-monolayer units. The formation free energy of these complexes, starting from a planar cationic/neutral lipid bilayer and bare DNA, is expressed as a sum of electrostatic, bending, mixing, and (for the honeycomb) chain frustration contributions. The electrostatic free energy is calculated using the Poisson-Boltzmann equation. The bending energy of the mixed lipid layers is treated in the quadratic curvature approximation with composition-dependent bending rigidity and spontaneous curvature. Ideal lipid mixing is assumed within each lipid monolayer. We found that the most stable monolayer-coated DNA units are formed when the charged/neutral lipid composition corresponds (nearly) to charge neutralization; the optimal monolayer radius corresponds to close DNA-monolayer contact. These conclusions are also valid for the honeycomb complex, as the chain frustration energy is found to be negligible. Typically, the stabilization energies for these structures are on the order of 1 k(B)T/A of DNA length, reflecting mainly the balance between the electrostatic and bending energies. The spaghetti complexes are less stable due to the additional bending energy of the external monolayer. A thermodynamic analysis is presented for calculating the equilibrium lipid compositions when the complexes coexist with excess bilayer. PMID:9370436

May, S; Ben-Shaul, A

1997-11-01

363

A comparison of experimental and theoretical results for labyrinth gas seals with honeycomb stators. M.S. Thesis  

NASA Technical Reports Server (NTRS)

Experimental results for the rotordynamic stiffness and damping coefficients of a labyrinth -rotor honeycomb-stator seal are presented. The coefficients are compared to the coefficients of a labyrinth-rotor smooth-stator seal having the same geometry. The coefficients are compared to analytical results from a two-control-volume compressible flow model. The experimental results show that the honeycomb stator configuration is more stable than the smooth stator configuration at low rotor speeds. At high rotor speeds and low clearance, the smooth stator seal is more stable. The theoretical model predicts the cross-coupled stiffness of the honeycomb stator seal correctly within 25 percent of measured values. The model provides accurate predictions of direct damping for large clearance seals. Overall, the model does not perform as well for low clearance seals as for high clearance seals.

Hawkins, Lawrence Allen

1988-01-01

364

Assembly of acid and sintering resistant honeycomb washcoat and catalytically active phase using sols of silica, zirconia, and platinum  

SciTech Connect

Development of high performance honeycomb catalysts containing platinum active phase for gas phase air oxidation of sulfur dioxide is described. Stepwise assembly of these washcoated honeycombs consists of: (1) selection of honeycomb composition (mullite substrate) and cell density based on pressure drop requirements; (2) identification of washcoat slurry composition (silica-precursor sol, silica powder, and surfactants if needed); (3) processing of the washcoat-substrate by dip coating, drying, and calcining; (4) loading of the platinum active phase through a facilitated adsorption technique followed by drying and activation steps; and (5) reactor loading and evaluation. Details of these steps will be presented that include thermal and chemical stability tests. Characterization by transmission electron microscopy of the final Pt/(ZrO{sub 2}-SiO{sub 2}) composite attached to the mullite substrate will be reported.

Felthouse, T.R. [Monsanto Enviro-Chem Systems, Inc., St.Louis, MO (United States); [Huntsman Specialty Chemicals Corp., St. Louis, MO (United States); Berkel, D.A.; Jost, S.R. [Monsanto Enviro-Chem Systems, Inc., St. Louis, MO (United States)] [and others

1995-12-01

365

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

2014-12-01

366

General spin-3/2 Ising model in a honeycomb lattice: Exactly solvable case  

NASA Astrophysics Data System (ADS)

The most general spin-3/2 Ising model with up-down symmetry is investigated on a honeycomb lattice. The partition function on a surface in the space spanned by the coupling constants J, K, L, and M was found exactly. The explicit expression for the quadrupolar order parameter with the inclusion of an external crystal field of strength ? is obtained. It is shown that this order parameter exhibits in general a simple power-law dependence on T-Tc near Tc.

Izmailian, N. Sh.; Ananikian, N. S.

1994-09-01

367

Honeycomb, square, and kagome vortex lattices in superconducting systems with multiscale intervortex interactions  

NASA Astrophysics Data System (ADS)

The recent proposal of Romero-Isart et al. [Phys. Rev. Lett. 111, 145304 (2013), 10.1103/PhysRevLett.111.145304] to utilize the vortex lattice phases of superconducting materials to prepare a lattice for ultracold-atom-based quantum emulators raises the need to create and control vortex lattices of different symmetries. Here we propose a mechanism by which honeycomb, hexagonal, square, and kagome vortex lattices could be created in superconducting systems with multiscale intervortex interactions. Multiple scales of the intervortex interaction can be created and controlled in layered systems made of different superconducting materials or with differing interlayer spacings.

Meng, Qingyou; Varney, Christopher N.; Fangohr, Hans; Babaev, Egor

2014-07-01

368

Magnetic properties of Ba2CrO4 with honeycomb layers  

NASA Astrophysics Data System (ADS)

A new synthesis method of Ba2CrO4 is developed and its magnetic properties are investigated by magnetic susceptibility, magnetization curve, and specific heat measurements. The compound shows a conventional antiferromagnetic transition at TN=3.5 K although magnetic properties due to honeycomb lattice is seen in Sr2CrO4. The g-value of Cr4+ ions in Ba2CrO4 is estimated to be g=1.94, which agrees well with the g-values of Cr4+ ions in other compounds.

Rani, Malika; Sakurai, Hiroya; Ahmad, Javed

2015-01-01

369

Fermionic Quantum Critical Point of Spinless Fermions on a Honeycomb Lattice  

E-print Network

Spinless fermions on a honeycomb lattice provide a minimal realization of lattice Dirac fermions. Repulsive interactions between nearest neighbors drive a quantum phase transition from a Dirac semimetal to a charge-density-wave state through a fermionic quantum critical point, where the coupling of Ising order parameter to the Dirac fermions at low energy drastically affects the quantum critical behavior. Encouraged by a recently discovery of absence of the fermion sign problem in this model, we study the fermionic quantum critical point using the continuous time quantum Monte Carlo method with worm sampling technique. We estimate the transition point $V/t= 1.356(1)$ with the critical exponents $\

Lei Wang; Philippe Corboz; Matthias Troyer

2014-06-30

370

Low-energy impact resistance of graphite-epoxy plates and ALS honeycomb sandwich panels  

NASA Technical Reports Server (NTRS)

Low energy impact may be potentially dangerous for many highly optimized stiff structures. Impact by foreign objects such as birds, ice, and runways stones or dropping of tools occur frequently and the resulting damage and stress concentrations may be unacceptable from a designer's standpoint. The barely visible, yet potentially dangerous dents due to impact of foreign objects on the Advanced Launch System (ALS) structure are studied. Of particular interest is the computation of the maximum peak impact force for a given impactor mass and initial velocity. The theoretical impact forces will be compared with the experimental dropweight results for the ALS face sheets alone as well as the ALS honeycomb sandwich panels.

Hui, David

1989-01-01

371

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

372

Superconductor-insulator transition in frustrated Josephson-junction arrays on a honeycomb lattice  

NASA Astrophysics Data System (ADS)

The zero-temperature superconductor to insulator transition is studied in a selfcharging model of Josephson-junction arrays on a honeycomb lattice in an external magnetic field corresponding to f flux quantum per plaquette. Path integral Monte Carlo simulations of the equivalent (2+1)-dimensional classical model are used to study the phase transition and critical behavior. For f = 1/3, the transition is first order. For f = 0 and f = 1/2, the transition is second order and the corresponding correlation length exponents are estimated from finite-size scaling.

Granato, Enzo

2014-12-01

373

System integration and demonstration of adhesive bonded high temperature aluminum alloys for aerospace structure, phase 2  

NASA Technical Reports Server (NTRS)

Adhesive bonding materials and processes were evaluated for assembly of future high-temperature aluminum alloy structural components such as may be used in high-speed civil transport aircraft and space launch vehicles. A number of candidate high-temperature adhesives were selected and screening tests were conducted using single lap shear specimens. The selected adhesives were then used to bond sandwich (titanium core) test specimens, adhesive toughness test specimens, and isothermally aged lap shear specimens. Moderate-to-high lap shear strengths were obtained from bonded high-temperature aluminum and silicon carbide particulate-reinforced (SiC(sub p)) aluminum specimens. Shear strengths typically exceeded 3500 to 4000 lb/in(sup 2) and flatwise tensile strengths exceeded 750 lb/in(sup 2) even at elevated temperatures (300 F) using a bismaleimide adhesive. All faceskin-to-core bonds displayed excellent tear strength. The existing production phosphoric acid anodize surface preparation process developed at Boeing was used, and gave good performance with all of the aluminum and silicon carbide particulate-reinforced aluminum alloys investigated. The results of this program support using bonded assemblies of high-temperature aluminum components in applications where bonding is often used (e.g., secondary structures and tear stoppers).

Falcone, Anthony; Laakso, John H.

1993-01-01

374

Low-aluminum content iron-aluminum alloys  

SciTech Connect

The low-aluminum-content iron-aluminum program deals with the development of a Fe-Al alloy with aluminum content such as a produce the minimum environmental effect at room temperature. The FAPY is an Fe-16 at. % Al-based alloy developed at the Oak Ridge National Laboratory as the highest aluminum-containing alloy with essentially no environmental effect. The chemical composition for FAPY in weight percent is: aluminum = 8.46, chromium = 5.50, zirconium = 0.20, carbon = 0.03, molybdenum = 2.00, yttrium = 0.10 and iron = 83.71. The ignots of the alloy can be hot worked by extrusion, forging, and rolling processes. The hot-worked cast structure can be cold worked with intermediate anneals at 800{degrees}C. Typical room-temperature ductility of the fine-grained wrought structure is 20 to 25% for this alloy. In contrast to the wrought structure, the cast ductility at room temperature is approximately 1% with a transition temperature of approximately 100 to 150{degrees}C, above which ductility values exceed 20%. The alloy has been melted and processed into bar, sheet, and foil. The alloy has also been cast into slabs, step-blocks of varying thicknesses, and shapes. The purpose of this section is to describe the welding response of cast slabs of three different thicknesses of FAPY alloy. Tensile, creep, and Charpy-impact data of the welded plates are also presented.

Sikka, V.K.; Goodwin, G.M.; Alexander, D.J. [and others

1995-06-01

375

[Hydrodynamic property of internal airlift loop bioreactor with cells immobilized onto ceramic honeycomb support(IALBR-CICHS)].  

PubMed

An internal airlift loop biorector with cells immobilized onto ceramic honeycomb support(IALBR-CICHS) was developed based on the bubble columns(BC) and airlift(AL) bioreactor by installing a ceramic honeycomb support in the draught tube. Their hydrodynamics were respectively studied by the tracer element to determine their retention time distribution (RTD). Experiment and theory analysis indicated that the IALBR-CICHS had more efficacious reactive volume rate(eta) and less short-circuit rate(lambda) for fluid flow compared with the BC and AL bioreactor. PMID:11382043

Zhang, Y; Yu, J; Wang, J; Shi, H; Qian, Y

2001-01-01

376

Oxidation of ligand-protected aluminum clusters: An ab initio molecular dynamics study  

SciTech Connect

We report Car-Parrinello molecular dynamics simulations of the oxidation of ligand-protected aluminum clusters that form a prototypical cluster-assembled material. These clusters contain a small aluminum core surrounded by a monolayer of organic ligand. The aromatic cyclopentadienyl ligands form a strong bond with surface Al atoms, giving rise to an organometallic cluster that crystallizes into a low-symmetry solid and is briefly stable in air before oxidizing. Our calculations of isolated aluminum/cyclopentadienyl clusters reacting with oxygen show minimal reaction between the ligand and O{sub 2} molecules at simulation temperatures of 500 and 1000 K. In all cases, the reaction pathway involves O{sub 2} diffusing through the ligand barrier, splitting into atomic oxygen upon contact with the aluminum, and forming an oxide cluster with aluminum/ligand bonds still largely intact. Loss of individual aluminum-ligand units, as expected from unimolecular decomposition calculations, is not observed except following significant oxidation. These calculations highlight the role of the ligand in providing a steric barrier against oxidizers and in maintaining the large aluminum surface area of the solid-state cluster material.

Alnemrat, Sufian; Hooper, Joseph P., E-mail: jphooper@nps.edu [Department of Physics, Naval Postgraduate School, Monterey, California 93943 (United States)

2014-03-14

377

Scaleable Clean Aluminum Melting Systems  

SciTech Connect

The project entitled 'Scaleable Clean Aluminum Melting Systems' was a Cooperative Research and Development Agreements (CRADAs) between Oak Ridge National Laboratory (ORNL) and Secat Inc. The three-year project was initially funded for the first year and was then canceled due to funding cuts at the DOE headquarters. The limited funds allowed the research team to visit industrial sites and investigate the status of using immersion heaters for aluminum melting applications. Primary concepts were proposed on the design of furnaces using immersion heaters for melting. The proposed project can continue if the funding agency resumes the funds to this research. The objective of this project was to develop and demonstrate integrated, retrofitable technologies for clean melting systems for aluminum in both the Metal Casting and integrated aluminum processing industries. The scope focused on immersion heating coupled with metal circulation systems that provide significant opportunity for energy savings as well as reduction of melt loss in the form of dross. The project aimed at the development and integration of technologies that would enable significant reduction in the energy consumption and environmental impacts of melting aluminum through substitution of immersion heating for the conventional radiant burner methods used in reverberatory furnaces. Specifically, the program would couple heater improvements with furnace modeling that would enable cost-effective retrofits to a range of existing furnace sizes, reducing the economic barrier to application.

Han, Q.; Das, S.K. (Secat, Inc.)

2008-02-15

378

Induction in an Aluminum Can  

NSDL National Science Digital Library

This activity demonstrates Lenz's Law, which states that an induced electromotive force generates a current that induces a counter magnetic field that opposes the magnetic field generating the current. In the demonstration, an empty aluminum can floats on water in a tray, such as a Petri dish. Students spin a magnet just inside the can without touching the can. The can begins to spin. Understanding what happens can be explained in steps: first, the twirling magnet creates an alternating magnetic field. Students can use a nearby compass to observe that the magnetic field is really changing. Second, the changing magnetic field permeates most things around it, including the aluminum can itself. A changing magnetic field will cause an electric current to flow when there is a closed loop of an electrically conducting material. Even though the aluminum can is not magnetic, it is metal and will conduct electricity. So the twirling magnet causes an electrical current to flow in the aluminum can. This is called an "induced current." Third, all electric currents create magnetic fields. So, in essence, the induced electrical current running through the can creates its very own magnetic field, making the aluminum can magnetic. This is activity four of "Exploring Magnetism." The guide includes science background information, student worksheets, glossary and related resources.

379

Influence of insulating coating on aluminum wire explosions  

SciTech Connect

Single wire explosions are widely used in understanding the early stages of z-pinch experiments. This paper presents a serial of experiments conducted on the pulse power generator with ?1?kA peak current and ?10?ns rising time in Xi'an Jiao Tong University. Polyimide coated aluminum wires and uncoated ones were tested under three different voltages to analyze the effect of insulating coating. Experimental results showed that insulating coating can increase the energy deposition 10%?30% in aluminum wires by delaying the voltage collapse and raising the maximum load resistance. The substantial energy deposition resulted in about 20% faster expansion rates for coated wires. Experimental evidence that plasma channel shunts the current from the wire core was observed by streak camera and schlieren graphs. This paper also briefly discussed the influence of nonuniform coating on the morphology of wire expansion.

Li, Yang; Wu, Jian, E-mail: jxjawj@gmail.com [State Key Laboratory of Electrical Insulation and Power Equipment, Xi'an Jiaotong University, Xi'an 710049 (China); State Key Laboratory of Intense Pulse Radiation of Simulation and Effect, Northwest Institute of Nuclear Technology, Xi'an 710024 (China); Sheng, Liang; Zhao, Jizhen; Zhang, Mei; Yuan, Yuan; Peng, Bodong [State Key Laboratory of Intense Pulse Radiation of Simulation and Effect, Northwest Institute of Nuclear Technology, Xi'an 710024 (China); Li, Xingwen [State Key Laboratory of Electrical Insulation and Power Equipment, Xi'an Jiaotong University, Xi'an 710049 (China)

2014-10-15

380

Prediction of near-room-temperature quantum anomalous Hall effect on honeycomb materials.  

PubMed

Recently, the long-sough quantum anomalous Hall effect was realized in a magnetic topological insulator. However, the requirement of an extremely low temperature (approximately 30 mK) hinders realistic applications. Based on ab initio band structure calculations, we propose a quantum anomalous Hall platform with a large energy gap of 0.34 and 0.06 eV on honeycomb lattices comprised of Sn and Ge, respectively. The ferromagnetic (FM) order forms in one sublattice of the honeycomb structure by controlling the surface functionalization rather than dilute magnetic doping, which is expected to be visualized by spin polarized STM in experiment. Strong coupling between the inherent quantum spin Hall state and ferromagnetism results in considerable exchange splitting and, consequently, an FM insulator with a large energy gap. The estimated mean-field Curie temperature is 243 and 509 K for Sn and Ge lattices, respectively. The large energy gap and high Curie temperature indicate the feasibility of the quantum anomalous Hall effect in the near-room-temperature and even room-temperature regions. PMID:25554896

Wu, Shu-Chun; Shan, Guangcun; Yan, Binghai

2014-12-19

381

Magnetism in spin models for depleted honeycomb-lattice iridates: Spin-glass order towards percolation  

NASA Astrophysics Data System (ADS)

Iridates are characterized by a fascinating interplay of spin-orbit and electron-electron interactions. The honeycomb-lattice materials A2IrO3 (A =Na,Li ) have been proposed to realize pseudospin-1/2 Mott insulating states with strongly anisotropic exchange interactions, described by the Heisenberg-Kitaev model, but other scenarios involving longer-range exchange interactions or more delocalized electrons have been put forward as well. Here we study the influence of nonmagnetic doping, i.e., depleted moments, on the magnetic properties of experimentally relevant variants of the Heisenberg-Kitaev and Heisenberg J1-J2-J3 models. We generically find that the zigzag order of the clean system is replaced, upon doping, by a spin-glass state with short-ranged zigzag correlations. We determine the spin-glass temperature as a function of the doping level and show that this quantity allows one to assess the importance of longer-range exchange interactions when the doping is driven across the site-percolation threshold of the honeycomb lattice.

Andrade, Eric C.; Vojta, Matthias

2014-11-01

382

Candidate Quantum Spin Liquid due to Dimensional Reduction of a Two-Dimensional Honeycomb Lattice  

NASA Astrophysics Data System (ADS)

As with quantum spin liquids based on two-dimensional triangular and kagome lattices, the two-dimensional honeycomb lattice with either a strong spin-orbital coupling or a frustrating second-nearest-neighbor coupling is expected to be a source of candidate quantum spin liquids. An ammonium salt [(C3H7)3NH]2[Cu2(C2O4)3](H2O)2.2 containing hexagonal layers of Cu2+ was obtained from solution. No structural transition or long-range magnetic ordering was observed from 290 K to 2 K from single crystal X-ray diffraction, specific heat and susceptibility measurements. The anionic layers are separated by sheets of ammonium and H2O with distance of 3.5 Å and no significant interaction between anionic layers. The two-dimensional honeycomb lattice is constructed from Jahn-Teller distorted Cu2+ and oxalate anions, showing a strong antiferromagnetic interaction between S = 1/2 metal atoms with ? = -120 (1) K. Orbital analysis of the Cu2+ interactions through the oxalate-bridges suggests a stripe mode pattern of coupling with weak ferromagnetic interaction along the b axis, and strong antiferromagnetic interaction along the a axis. Analysis of the magnetic susceptibility shows that it is dominated by a quasi-one-dimensional contribution with spin chains that are at least as well isolated as those of well-known quasi-one-dimensional spin liquids.

Zhang, Bin; Zhang, Yan; Wang, Zheming; Wang, Dongwei; Baker, Peter J.; Pratt, Francis L.; Zhu, Daoben

2014-09-01

383

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

384

Doubly degenerate orbital system in honeycomb lattice: Implication of orbital state in layered iron oxide  

NASA Astrophysics Data System (ADS)

We study a doubly degenerate orbital model on a honeycomb lattice. This is a model for orbital states in multiferroic layered iron oxides. The classical and quantum models are analyzed by spin-wave approximation, Monte Carlo simulation, and Lanczos method. A macroscopic number of degeneracy exists in the classical ground state. In the classical model, a peak in the specific heat appears at a temperature which is much lower than the mean-field ordering one. Below this temperature, the angle of orbital pseudospin is fixed, but conventional orbital orders are not suggested. The degeneracy in the ground state is partially lifted by thermal fluctuation. We suggest a role of zero-dimensional fluctuation in hexagons on a low-temperature orbital structure. Lifting of the degeneracy also occurs at zero temperature due to the quantum zero-point fluctuation. We show that the ground-state wave function is well represented by a linear combination of the states where a honeycomb lattice is covered by nearest-neighboring pairs of orbitals with the minimum bond energy.

Nasu, J.; Nagano, A.; Naka, M.; Ishihara, S.

2008-07-01

385

Prediction of Near-Room-Temperature Quantum Anomalous Hall Effect on Honeycomb Materials  

NASA Astrophysics Data System (ADS)

Recently, the long-sough quantum anomalous Hall effect was realized in a magnetic topological insulator. However, the requirement of an extremely low temperature (approximately 30 mK) hinders realistic applications. Based on ab initio band structure calculations, we propose a quantum anomalous Hall platform with a large energy gap of 0.34 and 0.06 eV on honeycomb lattices comprised of Sn and Ge, respectively. The ferromagnetic (FM) order forms in one sublattice of the honeycomb structure by controlling the surface functionalization rather than dilute magnetic doping, which is expected to be visualized by spin polarized STM in experiment. Strong coupling between the inherent quantum spin Hall state and ferromagnetism results in considerable exchange splitting and, consequently, an FM insulator with a large energy gap. The estimated mean-field Curie temperature is 243 and 509 K for Sn and Ge lattices, respectively. The large energy gap and high Curie temperature indicate the feasibility of the quantum anomalous Hall effect in the near-room-temperature and even room-temperature regions.

Wu, Shu-Chun; Shan, Guangcun; Yan, Binghai

2014-12-01

386

Candidate quantum spin liquid due to dimensional reduction of a two-dimensional honeycomb lattice.  

PubMed

As with quantum spin liquids based on two-dimensional triangular and kagome lattices, the two-dimensional honeycomb lattice with either a strong spin-orbital coupling or a frustrating second-nearest-neighbor coupling is expected to be a source of candidate quantum spin liquids. An ammonium salt [(C3H7)3NH]2[Cu2(C2O4)3](H2O)2.2 containing hexagonal layers of Cu(2+) was obtained from solution. No structural transition or long-range magnetic ordering was observed from 290 K to 2 K from single crystal X-ray diffraction, specific heat and susceptibility measurements. The anionic layers are separated by sheets of ammonium and H2O with distance of 3.5 Å and no significant interaction between anionic layers. The two-dimensional honeycomb lattice is constructed from Jahn-Teller distorted Cu(2+) and oxalate anions, showing a strong antiferromagnetic interaction between S = 1/2 metal atoms with ? = -120 (1) K. Orbital analysis of the Cu(2+) interactions through the oxalate-bridges suggests a stripe mode pattern of coupling with weak ferromagnetic interaction along the b axis, and strong antiferromagnetic interaction along the a axis. Analysis of the magnetic susceptibility shows that it is dominated by a quasi-one-dimensional contribution with spin chains that are at least as well isolated as those of well-known quasi-one-dimensional spin liquids. PMID:25245216

Zhang, Bin; Zhang, Yan; Wang, Zheming; Wang, Dongwei; Baker, Peter J; Pratt, Francis L; Zhu, Daoben

2014-01-01

387

Electrokinetic desalination using honeycomb carbon nanotubes (HC-CNTs): a conceptual study by molecular simulation.  

PubMed

A new concept of electrokinetic desalination using a CNT honeycomb is presented through molecular dynamics simulation. The preferential translocation of ions towards the outlets near two electrodes was realized by applying an electric field perpendicular to bulk fluid flow in a CNT network, which, in the meantime, generated deionized water flux discharged from the central outlets. The effects of the major factors such as electric field strength, numbers of separation units, diameter of CNT, and ion concentration on the desalination were examined. It was shown that over 95% salt rejection and around 50% fresh water recovery were achieved by the presented module by applying an electric field of 0.8 V nm(-1). CNT diameter, which is critical to ion rejection without the electric field, had a marginal effect on the desalination of this new module when a strong electric field was applied. The desalination was also not sensitive to ion concentration, indicating its excellent workability for a wide range of water salinity, e.g. from brackish water to seawater. A potential of mean force profile revealed a free energy barrier as large as 2.0-6.0 kcal mol(-1) for ions to move opposite to the implemented electrical force. The simulation confirmed the high potential of the CNT honeycomb in water desalination. PMID:25092215

Chen, Qile; Kong, Xian; Li, Jipeng; Lu, Diannan; Liu, Zheng

2014-09-21

388

Method for Selective Cleaning of Mold Release from Composite Honeycomb Surfaces  

NASA Technical Reports Server (NTRS)

Honeycomb structures are commonly employed as load- and force-bearing structures as they are structurally strong and lightweight. Manufacturing processes for heat-molded composite honeycomb structures commence with the placement of pre-impregnated composite layups over metal mandrels. To prevent permanent bonding between the composite layup and the metal mandrels, an agent, known as a mold release agent, is used. Mold release agents allow the molded composite material to be removed from mandrels after a heat-forming process. Without a specific removal process, mold release agents may continue to adhere to the surface of the composite material, thereby affecting the bonding of other materials that may come into contact with the composite surface in later stages of processing A constituent common to commercially available household cleaning agents is employed for the removal of mold release agents common to the manufacturing of heat-formed composite materials. The reliability of the solvent has been proven by the longevity and reliability of commercial household cleaners. At the time of this reporting, no one has attempted using constituent for this purpose. The material to be cleaned is immersed in the solution, vertically removed so that the solution is allowed to drain along cell walls and into a solvent bath, and then placed on a compressed airflow table for drying.

Pugel, Diane

2011-01-01

389

Effect of geometry and microstructure of honeycomb TCP scaffolds on bone regeneration.  

PubMed

In recent years, artificial biological materials have been commonly used for the treatment of bone tissue defects caused by trauma, tumors, or surgical stress. Although tricalcium phosphate (TCP) is a promising absorbent bone tissue reconstruction biomaterial, it has been reported that its biocompatibility and osteoconductivity depend on its preparation method and sintering temperature. In addition, although it is thought that the microenvironment produced by the extracellular matrix plays an important role in cell growth and differentiation, there have been few studies on how the geometric structure of artificial biological materials affects cells. In the present study, a new honeycomb TCP scaffold containing through-holes with diameters of 300 µm has been developed. The influence of the sintering temperature on the crystal structure and material properties of the honeycomb TCP scaffold was investigated using scanning electron microscopy and X-ray diffraction. Its biocompatibility and osteoconductivity were also evaluated by implantation into experimental animals. It was found that a ?-TCP scaffold sintered at 1200°C exhibited high biocompatibility and osteoconductivity, and when it was loaded with BMP-2, it exhibited both osteoconductivity and osteoinductivity, promoting rapid bone formation in both ectopic and orthotopic areas. It is thus a highly promising bone reconstruction material that is expected to find clinical applications. PMID:24115688

Takabatake, Kiyofumi; Yamachika, Eiki; Tsujigiwa, Hidetsugu; Takeda, Yasushi; Kimura, Mariko; Takagi, Shin; Nagatsuka, Hitoshi; Iida, Seiji

2014-09-01

390

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

391

Anomalous refractive effects in honeycomb lattice photonic crystals formed by holographic lithography.  

PubMed

We have investigated for the first time the anomalous refractive effects of a photonic crystal (PhC) formed by holographic lithography (HL) with triangular rods arranged in a honeycomb lattice in air. Possibilities of left-handed negative refraction and superlens are discussed for the case of TM2 band with the index contrast n = 3.4:1. In contrast to the conventional honeycomb PhC made of regular rods in air, the HL PhCs show left-handed negative refraction over a wider and higher frequency range with high transmissivity (>90%), and the effective indices quite close to -1 for a wide range of incident angles with a larger all-angle left-handed negative refraction (AALNR) frequency range (Deltaomega/omega approximately 14.8%). Calculations and FDTD simulations demonstrate the high-performance negative refraction properties can happen in the holographic structures for a wide filling ratio and can be modulated by changing the filling ratio easily. PMID:20721016

Dong, G Y; Yang, X L; Cai, L Z

2010-08-01

392

Quantum computational universality of Affleck-Kennedy-Lieb-Tasaki states beyond the honeycomb lattice  

NASA Astrophysics Data System (ADS)

Universal quantum computation can be achieved by simply performing single-spin measurements on a highly entangled resource state, such as cluster states. The family of Affleck-Kennedy-Lieb-Tasaki (AKLT) states has recently been explored; for example, the spin-1 AKLT chain can be used to simulate single-qubit gate operations on a single qubit, and the spin-3/2 two-dimensional AKLT state on the honeycomb lattice can be used as a universal resource. However, it is unclear whether such universality is a coincidence for the specific state or a shared feature in all two-dimensional AKLT states. Here we consider the family of spin-3/2 AKLT states on various trivalent Archimedean lattices and show that in addition to the honeycomb lattice, the spin-3/2 AKLT states on the square octagon (4,82) and the “cross” (4,6,12) lattices are also universal resource, whereas the AKLT state on the “star” (3,122) lattice is likely not due to geometric frustration.

Wei, Tzu-Chieh

2013-12-01

393

Electrochemical properties of honeycomb-like structured HFBI self-organized membranes on HOPG electrodes.  

PubMed

HFBI (derived from Trichoderma sp.) is a unique structural protein, which forms a self-organized monolayer at both air/water interface and water/solid interfaces in accurate two-dimensional ordered structures. We have taken advantage of the unique functionality of HFBI as a molecular carrier for preparation of ordered molecular phase on solid substrate surfaces. The HFBI molecular carrier can easily form ordered structures; however, the dense molecular layers form an electrochemical barrier between the electrode and solution phase. In this study, the electrochemical properties of HFBI self-organized membrane-covered electrodes were investigated. Wild-type HFBI has balanced positive and negative charges on its surface. Highly oriented pyrolytic graphite (HOPG) electrodes coated with HFBI molecules were investigated electrochemically. To improve the electrochemical properties of this HFBI-coated electrode, the two types of HFBI variants, with oppositely charged surfaces, were prepared genetically. All three types of HFBI-coated HOPG electrode perform electron transfer between the electrode and solution phase through the dense HFBI molecular layer. This is because the HFBI self-organized membrane has a honeycomb-like structure, with penetrating holes. In the cases of HFBI variants, the oppositely charged HFBI membrane phases shown opposite electrochemical behaviors in electrochemical impedance spectroscopy. HFBI is a molecule with a unique structure, and can easily form honeycomb-like structures on solid material surfaces such as electrodes. The molecular membrane phase can be used for electrochemical molecular interfaces. PMID:25454670

Yamasaki, Ryota; Takatsuji, Yoshiyuki; Lienemann, Michael; Asakawa, Hitoshi; Fukuma, Takeshi; Linder, Markus; Haruyama, Tetsuya

2014-11-01

394

Joining of 6061 Aluminum Matrix-Ceramic Particle Reinforced Composites  

E-print Network

) ) Joining of 6061 Aluminum Matrix-Ceramic Particle Reinforced Composites by R. Kiehn and T. W................... .. ....... ... ... 3 Literature Review ......... ...... ..... ... . . 3 Conventional Aluminum Brazing ........ 4 Aluminum Composite Joining ........... 5 Aluminum Joining by Unconventional Methods

Eagar, Thomas W.

395

Reaction of Aluminum with Water to Produce Hydrogen  

E-print Network

Promoters Oxide Promoters Salt Promoters Combined Oxide and Salt Promoters Aluminum Pretreatment Molten Aluminum Alloys PROPERTIES OF THE ALUMINUM-WATER REACTIONS RELATIVE ........... 14 TO ON-BOARD SYSTEM PROPERTIES Hydrogen Capacities Kinetic Properties System Considerations REGENERATION OF ALUMINUM

396

Research on plasma core reactors  

NASA Technical Reports Server (NTRS)

Experiments and theoretical studies are being conducted for NASA on critical assemblies with one-meter diameter by one-meter long low-density cores surrounded by a thick beryllium reflector. These assemblies make extensive use of existing nuclear propulsion reactor components, facilities, and instrumentation. Due to excessive porosity in the reflector, the initial critical mass was 19 kg U(93.2). Addition of a 17 cm thick by 89 cm diameter beryllium flux trap in the cavity reduced the critical mass to 7 kg when all the uranium was in the zone just outside the flux trap. A mockup aluminum UF6 container was placed inside the flux trap and fueled with uranium-graphite elements. Fission distributions and reactivity worths of fuel and structural materials were measured. Finally, an 85,000 cu cm aluminum canister in the central region was fueled with UF6 gas and fission density distributions determined. These results are to be used to guide the design of a prototype plasma core reactor which will test energy removal by optical radiation.

Jarvis, G. A.; Barton, D. M.; Helmick, H. H.; Bernard, W.; White, R. H.

1976-01-01

397

CHARACTERIZING AND MODELING FERRITE-CORE PROBES  

SciTech Connect

In this paper, we accurately and carefully characterize a ferrite-core probe that is widely used for aircraft inspections. The characterization starts with the development of a model that can be executed using the proprietary volume-integral code, VIC-3D(c), and then the model is fitted to measured multifrequency impedance data taken with the probe in freespace and over samples of a titanium alloy and aluminum. Excellent results are achieved, and will be discussed.

Sabbagh, Harold A.; Murphy, R. Kim; Sabbagh, Elias H. [Victor Technologies LLC, Bloomington, IN 47401 (United States); Aldrin, John C. [Computational Tools, Gurnee, IL 60031 (United States)

2010-02-22

398

Improved methods to manufacture aluminum  

SciTech Connect

A low-temperature (750{degrees}C) process to produce aluminum, employing dimensionally-stable electrodes, was investigated under this contract. Tests were carried out at a 10-ampere scale to develop a nonconsumable anode and to evaluate certain cell operating parameters. The work was carried out in conjunction with a NSF SBIR research grant to study the fundamental science aspects of the process. A scaled up 300-ampere cell was built and a preliminary test run was made with encouraging results. The new technology has the promise of producing aluminum at 5.0 kWh/lb as compared to the US average of about 7.5 kWh/lb, and to produce it at lower cost. Preliminary technical discussions have been held with a major US aluminum company under secrecy agreement for eventual licensing.

Not Available

1992-06-15

399

Recycling of aluminum salt cake  

SciTech Connect

The secondary aluminum industry generates more than 110 {times} 10{sup 3} tons of salt-cake waste every year. This waste stream contains about 3--5% aluminum, 15--30% aluminum oxide, 30--40% sodium chloride, and 20--30% potassium chloride. As much as 50% of the content of this waste is combined salt (sodium and potassium chlorides). Salt-cake waste is currently disposed of in conventional landfills. In addition, over 50 {times} 10{sup 3} tons of black dross that is not economical to reprocess a rotary furnace for aluminum recovery ends up in landfills. The composition of the dross is similar to that of salt cake, except that it contains higher concentrations of aluminum (up to 20%) and correspondingly lower amounts of salts. Because of the high solubility of the salts in water, these residues, when put in landfills, represent a potential source of pollution to surface-water and groundwater supplies. The increasing number of environmental regulations on the generation and disposal of industrial wastes are likely to restrict the disposal of these salt-containing wastes in conventional landfills. Processes exist that employ the dissolution and recovery of the salts from the waste stream. These wet-processing methods are economical only when the aluminum concentration in that waste exceeds about 10%. Argonne National Laboratory (ANL) conducted a study in which existing technologies were reviewed and new concepts that are potentially more cost-effective than existing processes were developed and evaluated. These include freeze crystallization, solvent/antisolvent extraction, common-ion effect, high-pressure/high-temperature process, and capillary-effect systems. This paper presents some of the technical and economic results of the aforementioned ANL study.

Jody, B.J.; Daniels, E.J.; Bonsignore, P.V.; Karvelas, D.E.

1991-12-01

400

Aluminum: World market prospects for troubled times  

NASA Astrophysics Data System (ADS)

Aluminum and alumina prices and production volumes dropped significantly in 2008 due to the worldwide economic recession. This paper provides a comprehensive analysis of the current state of the aluminum industry and its outlook for the future.

Djukanovic, Goran

2009-02-01

401

BIOLOGICAL SPECIATION AND TOXICOKINETICS OF ALUMINUM  

EPA Science Inventory

This review discusses recent literature on the chemical and physiological factors that result in the absorption, distribution, and excretion of aluminum in mammals, with particular regard to gastrointestinal absorption and speciation in plasma. umans encounter aluminum, a ubiquit...

402

Hermetically sealed aluminum electrolytic capacitor  

NASA Technical Reports Server (NTRS)

Aluminum electrolytic capacitors are presently not allowed on NASA missions because they outgas water and organic vapors, as well as H2. As a consequence, much larger and heavier packages of tantalum capacitors are used. A hermetically sealed aluminum capacitor has been developed under NASA-MSFC SBIR contracts. This capacitor contains a nongassing electrolyte that was developed for this application so internal pressure would remain low. Capacitors rated at 250 to 540 V have been operated under full load for thousands of hours at 85 and 105 C with good electrical performance and low internal pressure. Electrolyte chemistry and seal engineering concepts will be discussed.

Alwitt, Robert S.; Liu, Yanming; Elias, William

1995-01-01

403

40 CFR 180.1091 - Aluminum isopropoxide and aluminum secondary butoxide; exemption from the requirement of a...  

Code of Federal Regulations, 2013 CFR

...25 2013-07-01 2013-07-01 false Aluminum isopropoxide and aluminum secondary butoxide; exemption from the requirement... Exemptions From Tolerances § 180.1091 Aluminum isopropoxide and aluminum secondary...

2013-07-01

404

40 CFR 180.1091 - Aluminum isopropoxide and aluminum secondary butoxide; exemption from the requirement of a...  

Code of Federal Regulations, 2012 CFR

...25 2012-07-01 2012-07-01 false Aluminum isopropoxide and aluminum secondary butoxide; exemption from the requirement... Exemptions From Tolerances § 180.1091 Aluminum isopropoxide and aluminum secondary...

2012-07-01

405

40 CFR 180.1091 - Aluminum isopropoxide and aluminum secondary butoxide; exemption from the requirement of a...  

Code of Federal Regulations, 2010 CFR

...23 2010-07-01 2010-07-01 false Aluminum isopropoxide and aluminum secondary butoxide; exemption from the requirement... Exemptions From Tolerances § 180.1091 Aluminum isopropoxide and aluminum secondary...

2010-07-01

406

46 CFR 148.255 - Ferrosilicon, aluminum ferrosilicon, and aluminum silicon containing more than 30% but less than...  

Code of Federal Regulations, 2014 CFR

...2014-10-01 2014-10-01 false Ferrosilicon, aluminum ferrosilicon, and aluminum silicon containing more than 30% but less than...Certain Materials § 148.255 Ferrosilicon, aluminum ferrosilicon, and aluminum silicon...

2014-10-01

407

46 CFR 148.255 - Ferrosilicon, aluminum ferrosilicon, and aluminum silicon containing more than 30% but less than...  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Ferrosilicon, aluminum ferrosilicon, and aluminum silicon containing more than 30% but less than...Certain Materials § 148.255 Ferrosilicon, aluminum ferrosilicon, and aluminum silicon...

2012-10-01

408

40 CFR 180.1091 - Aluminum isopropoxide and aluminum secondary butoxide; exemption from the requirement of a...  

Code of Federal Regulations, 2011 CFR

...24 2011-07-01 2011-07-01 false Aluminum isopropoxide and aluminum secondary butoxide; exemption from the requirement... Exemptions From Tolerances § 180.1091 Aluminum isopropoxide and aluminum secondary...

2011-07-01

409

40 CFR 180.1091 - Aluminum isopropoxide and aluminum secondary butoxide; exemption from the requirement of a...  

Code of Federal Regulations, 2014 CFR

...24 2014-07-01 2014-07-01 false Aluminum isopropoxide and aluminum secondary butoxide; exemption from the requirement... Exemptions From Tolerances § 180.1091 Aluminum isopropoxide and aluminum secondary...

2014-07-01

410

46 CFR 148.255 - Ferrosilicon, aluminum ferrosilicon, and aluminum silicon containing more than 30% but less than...  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Ferrosilicon, aluminum ferrosilicon, and aluminum silicon containing more than 30% but less than...Certain Materials § 148.255 Ferrosilicon, aluminum ferrosilicon, and aluminum silicon...

2013-10-01

411

46 CFR 148.255 - Ferrosilicon, aluminum ferrosilicon, and aluminum silicon containing more than 30% but less than...  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Ferrosilicon, aluminum ferrosilicon, and aluminum silicon containing more than 30% but less than...Certain Materials § 148.255 Ferrosilicon, aluminum ferrosilicon, and aluminum silicon...

2011-10-01

412

Nanotube Fabrication byNanotube Fabrication by Anodic Aluminum Oxide,Anodic Aluminum Oxide,  

E-print Network

Nanotube Fabrication byNanotube Fabrication by Anodic Aluminum Oxide,Anodic Aluminum Oxide, Self-regulating phenomena in materials science: Self-assembly of nanopores during anodic oxidation of aluminum (AAO) Self combined anodic aluminum oxide (AAO) nanostructures with atomic layer deposition (ALD) to fabricate

Rubloff, Gary W.

413

Study of the optical properties of nickel-pigmented anodized aluminum oxide on aluminum  

Microsoft Academic Search

The optical selectivity of nickel pigmented anodized aluminum with different surface roughness of the aluminum substrate has been compared. The hemispherical emittance at 100 degree(s)C has been measured and normal emittance calculated from spectral reflectance for aluminum oxide films of different thickness, pigmented and unpigmented. The discrepancy between normal and hemispherical emittance was large especially for unpigmented aluminum oxide. One

Ewa Wackelgard

1992-01-01

414

Aluminum in seawater: control by inorganic processes.  

PubMed

The distribution of dissolved aluminum in open ocean waters is probably controlled by the solution of aluminum from atmospherically derived particles and bottom sediments balanced against scavenging by siliceous shells of dead organisms. Variations in the aluminum concentration within vertical hydrographic profiles are small as compared to those for other trace metals. Aluminum concentrations in the Atlantic and Pacific are inversely related to the silica contents of these oceans. PMID:17750148

Hydes, D J

1979-09-21

415

Mineral resource of the month: aluminum  

USGS Publications Warehouse

The article offers information on aluminum, a mineral resource which is described as the third-most abundant element in Earth's crust. According to the article, aluminum is the second-most used metal. Hans Christian Oersted, a Danish chemist, was the first to isolate aluminum in the laboratory. Aluminum is described as lightweight, corrosion-resistant and an excellent conductor of electricity and heat.

Bray, E. Lee

2012-01-01

416

Blood aluminum levels as a function of aluminum intake from drinking water  

SciTech Connect

Questions regarding the health effects of aluminum are still unanswered. The speciation, pharmacokinetics, and toxicity of aluminum are not well understood. Furthermore, no animal or human studies of aluminum absorption have been reported using drinking water as the source of aluminum. The following experiment attempted to reach a better understanding of the bioavailability of aluminum from drinking water. Its objective was to determine whether or not increased aluminum ingestion from drinking water would be reflected in increased serum and whole blood aluminum levels in the baboon experimental model.

Turnquest, E.M.; Hallenbeck, W.H. (Univ. of Illinois, Chicago (United States))

1991-04-01

417

Aerodynamic performance of conventional and advanced design labyrinth seals with solid-smooth abradable, and honeycomb lands. [gas turbine engines  

NASA Technical Reports Server (NTRS)

Labyrinth air seal static and dynamic performance was evaluated using solid, abradable, and honeycomb lands with standard and advanced seal designs. The effects on leakage of land surface roughness, abradable land porosity, rub grooves in abradable lands, and honeycomb land cell size and depth were studied using a standard labyrinth seal. The effects of rotation on the optimum seal knife pitch were also investigated. Selected geometric and aerodynamic parameters for an advanced seal design were evaluated to derive an optimized performance configuration. The rotational energy requirements were also measured to determine the inherent friction and pumping energy absorbed by the various seal knife and land configurations tested in order to properly assess the net seal system performance level. Results indicate that: (1) seal leakage can be significantly affected with honeycomb or abradable lands; (2) rotational energy absorption does not vary significantly with the use of a solid-smooth, an abradable, or a honeycomb land; and (3) optimization of an advanced lab seal design produced a configuration that had leakage 25% below a conventional stepped seal.

Stocker, H. L.; Cox, D. M.; Holle, G. F.

1977-01-01

418

A comparison of experimental rotordynamic coefficients and leakage characteristics between hole-pattern gas damper seals and a honeycomb seal  

Microsoft Academic Search

Honeycomb annular seals are an attractive design alternative due to their superior static and dynamic performance. However, their implementation in industrial practice has been delayed by the following characteristics: (a) manufacturing time can be appreciable, and (b) they can seriously damage the shaft if rubbing occurs. To minimize these problems, hole-pattern gas damper seals, which are formed by simply drilling

Z. Yu; D. W. Childs

1998-01-01

419

Comparison of X-Ray, Millimeter Wave, Shearography and Through-Transmission Ultrasonic Methods for Inspection of Honeycomb Composites  

NASA Astrophysics Data System (ADS)

Honeycomb composites are increasingly finding utility in a variety of environments and applications, such as aircraft structural components, flight control components, radomes, etc. In-service and environmental stresses can produce unwanted flaws that adversely affect the structural integrity and functionality of these composites. These flaws may be in the forms of disbonds, delaminations, impact damage, crushed honeycomb, moisture intrusion, internal cracks, etc. There are several nondestructive testing (NDT) methods that may be used to inspect these composites for the presence and evaluation of these flaws. Such NDT methods include X-ray computed tomography, near-field millimeter wave, shearography, and ultrasonic testing. To assess the capabilities of these methods for honeycomb composite inspection, two honeycomb composites panels were produced with several embedded flaws and missing material primarily representing planar disbonds at various levels within the thickness of the panels and with different shapes. Subsequently, the aforementioned NDT methods were used to produce images of the two panels. This paper presents the results of these investigations and a comparison among the capabilities of these methods.

Abou-Khousa, M. A.; Ryley, A.; Kharkovsky, S.; Zoughi, R.; Daniels, D.; Kreitinger, N.; Steffes, G.

2007-03-01

420

Electronic structure of super-honeycomb systems: A peculiar realization of semimetal\\/semiconductor classes and ferromagnetism  

Microsoft Academic Search

Lateral superstructures with honeycomb symmetry are shown to be classified, with a simple criterion, into semimetals with gapless k-linear dispersions, semiconductors, and metals. In some of the classes, the symmetry enforces flat bands to exist, which implies the occurrence of ferromagnetism when the electron correlation is turned on. These provide a unique opportunity for band structure engineering.

Nobuyuki Shima; Hideo Aoki

1993-01-01

421

Micropatterned culture of HepG2 spheroids using microwell chip with honeycomb-patterned polymer film.  

PubMed

Microwell chip culture is a promising technique for the generation of homogenous spheroids. We investigated the relationship between the structure of the bottom surface of microwell chip and the properties of HepG2 spheroid. We developed a microwell chip, the bottom surface of which consisted of a honeycomb-patterned polymer film (honeycomb film) that had a regular porous structure (HF chip). The chip comprised 270 circular microwells; each microwell was 600 ?m in diameter and 600 ?m in depth. At the center of the honeycomb film, an area, 200 ?m in diameter, was modified with collagen to facilitate cell adhesion. With the exception of the collagen-coated area, the entire microwell was modified with polyethylene glycol to eliminate cell adhesion. HepG2 cells formed uniform spheroids when cultured in the microwells of HF chip. Furthermore, the cells passed through the porous structure of honeycomb film and formed spheroids at its opposite side. The spheroid growth of HepG2 cells cultured in HF chip was greater than that when the cells were culture in a microwell chip, the bottom surface of which was made of poly-methylmethacrylate (PMMA chip). The albumin secretion activity of HepG2 spheroids in HF chip was equal to that in PMMA chip. These results indicate that the microwell bottom with a porous structure enhances the cell growth and maintains well the spheroid function. Thus, HF chip is a promising platform for spheroid cell culture. PMID:24742630

Yamazaki, Hidekazu; Gotou, Shun; Ito, Koju; Kohashi, Souichi; Goto, Yuki; Yoshiura, Yukiko; Sakai, Yusuke; Yabu, Hiroshi; Shimomura, Masatsugu; Nakazawa, Kohji

2014-10-01

422

Amorphous silicon honeycombs as a binder/carbon-free, thin-film Li-ion battery anode.  

PubMed

Amorphous silicon thin films with honeycombed structures have been prepared using a self-assembled monolayer of polystyrene spheres as the template. The as-prepared thin films may serve as a good anode candidate for thin film Li-ion batteries. This approach can be extended to a wide range of coating materials and substrates with controlled periodic structures. PMID:25220144

Zhao, Yu; Peng, Lele; Ding, Yu; Yu, Guihua

2014-11-01

423

Experimental rotordynamic coefficient results for: (a) a labyrinth seal with and without shunt injection and (b) a honeycomb seal  

E-print Network

been modified by (a) using swirl brakes, and (b) using shunt injection. In some cases, labyrinth seals have been replaced entirely by honeycomb seals. In shunt injection, the gas is taken from the diff-user or discharge volute, and injected...

Soto Azuaje, Elias Antonio

1997-01-01

424

ECONOMIC IMPACT OF CENTURY ALUMINUM OF  

E-print Network

ECONOMIC IMPACT OF CENTURY ALUMINUM OF WEST VIRGINIA, INC. By Randall A represent those of the West Virginia University Board of Trustees. #12;2 OVERVIEW Century Aluminum of West Virginia, Inc. (Century) is located in Ravenswood, West Virginia and produces aluminum products

Mohaghegh, Shahab

425

MODELING OF ALUMINUM NANOPARTICLE FORMATION R. Schefflan  

E-print Network

MODELING OF ALUMINUM NANOPARTICLE FORMATION R. Schefflan D. Kalyon S. Kovenklioglu Stevens Picatinny Arsenal's process for making alumina coated nanoparticles of aluminum involves the conversion of gaseous aluminum, in the presence of helium carrier gas, to solid nanoparticles and their subsequent

426

Aluminum: Principled Scenario Exploration through Minimality  

E-print Network

Aluminum: Principled Scenario Exploration through Minimality Tim Nelson1, Salman Saghafi1, Daniel J Aluminum, a modification of Alloy that presents only minimal scenarios: those that contain no more than is necessary. Aluminum lets users explore the scenario space by adding to scenarios and backtracking. It also

Krishnamurthi, Shriram

427

Aluminum in Superconducting Magnets Robert J. Weggel  

E-print Network

Aluminum in Superconducting Magnets Robert J. Weggel Magnet Optimization Research Engineering is aluminum, either ultrapure, as quenchstabilization matrix metal, and/or alloyed and coldworked and heat for magnets in which the stresses and strains are modest. The strongest aluminum alloy commercially available

McDonald, Kirk

428

Aluminum: Principled Scenario Exploration through Minimality  

E-print Network

Aluminum: Principled Scenario Exploration through Minimality Tim Nelson1, Salman Saghafi1, Daniel J. We present Aluminum, a modification of Alloy that presents only minimal scenarios: those that contain no more than is necessary. Aluminum lets users explore the scenario space by adding to scenarios

Dougherty, Daniel J.

429

Aluminum--2004 5. Areferencethatincludesasectionmark()isfoundintheinternet  

E-print Network

Aluminum--2004 5. Areferencethatincludesasectionmark(§)isfoundintheinternet ReferenceCitedsection. Aluminum ByPatriciaA.Plunkert Domestic survey data and tables were prepared by Benjamin S. Goff.S.GeologicalSurvey(uSGS)requestforproductiondata. CommercialDevelopmentCo.(CDC)ofSt.louis,mO, boughtKaiserAluminumCorp.'s200,000-metric-ton-per-year (t

430

Domestic aluminum resources: dilemmas of development  

Microsoft Academic Search

Concerns about supply disruptions and price gouging that could endanger aluminum production in the United States have spurred research in this country on processes to manufacture aluminum from ores other than bauxite. The United States has no large bauxite deposits but it has plentiful resources of other aluminum ores if the technology can be developed to use them economically. Sources

Staats

1980-01-01

431

Modes of Fluctuation in Aluminum Futures Prices  

Microsoft Academic Search

Taking the daily data for aluminum futures prices from 2003 to 2007 as sample, this article examines the factors of fluctuations for aluminum futures prices in China and studies the effects of these factors on futures price curve. First, this article presents the improving method on the base of predecessor research. Next, by the daily data for aluminum futures price

Ye Wang; Li Wang; Jinzi Li; Yin Cao

2008-01-01

432

Aluminum in the lung: the pyropowder conundrum  

Microsoft Academic Search

Pulmonary aluminosis is a disease first seen in Germany between 1938 and 1945 which then reappeared in the United Kingdom between 1952 and 1959. All cases were associated with exposure to a submicron-sized aluminum pyrotechnic flake which was lubricated with a non-polar aliphatic oil. Ordinarily, stearic acid, which chemically combines with aluminum to form aluminum stearate, was used as a

Dinman

1987-01-01

433

Characterization of aluminum surfaces: Sorption and etching  

Microsoft Academic Search

Aluminum, due to its low density and low cost, is a key material for future lightweight applications. However, like other structural materials, aluminum is subject to various forms of corrosion damage that annually costs the United States approximately 5% of its GNP [1]. The main goal is to investigate the effects of various solution anions on aluminum surfaces, and specifically

Jeannette Clera Polkinghorne

2001-01-01

434

A novel isolation curtain to reduce turbine ingress heating and an advanced model for honeycomb labyrinth seals  

NASA Astrophysics Data System (ADS)

A combination of 3-D and 2-D computational fluid dynamics (CFD) modeling as well as experimental testing of the labyrinth seal with hexagonal honeycomb cells on the stator wall was performed. For the 3-D and 2-D CFD models, the hexagonal honeycomb structure was modeled using the concept of the baffle (zero-thickness wall) and the simplified 2-D fin, respectively. The 3-D model showed that even a small axial change of the tooth (or honeycomb wall) location, or a small circumferential change of the honeycomb wall location significantly affected the flow patterns and leakage characteristics especially for small tooth tip clearance. Also, the local details of the flow field were investigated. The seven basic procedural steps to develop a 2-D axisymmetric honeycomb labyrinth seal leakage model were shown. Clearly demonstrated for varying test conditions was the 2-D model capability to predict the 3-D honeycomb labyrinth flow that had been measured at different operating conditions from that used in developing the 2-D model. Specifically, the 2-D model showed very close agreement with measurements. In addition, the 2-D model greatly reduced the computer resource requirement needed to obtain a solution of the 3-D honeycomb labyrinth seal leakage. The novel and advanced strategy to reduce the turbine ingress heating, and thus the coolant requirement, by injecting a "coolant isolation curtain" was developed numerically using a 3-D CFD model. The coolant isolation curtain was applied under the nozzle guide vane platform for the forward cavity of a turbine stage. Specifically, the isolation curtain serves to isolate the hot mainstream gas from the turbine outer region. The effect of the geometry change, the outer cavity axial gap clearance, the circumferential location of the injection curtain slot and the injection fluid angle on the ingress heating was investigated. Adding the chamfer to the baseline design gave a similar or higher maximum temperature T*max than did the baseline design without chamfer, but implementation of the injection curtain slot reduced substantially T*max of the outer region. In addition, a more desirable uniform adiabatic wall temperature distribution along the outer rotor and stator surfaces was observed due to the presence of the isolation curtain.

Choi, Dong Chun

435

Recovering aluminum from aluminum dross in a DC electric-arc rotary furnace  

NASA Astrophysics Data System (ADS)

The recycling of aluminum scrap and dross yields significant economic and energy savings, as well environmental benefits. The recovery of aluminum depends on many factors. The aim of this work is to experimentally investigate aluminum recovery under different conditions. In this study, aluminum dross was processed in a direct-current electric-arc rotary furnace. The presence of crushing refractory bodies during processing was found to increase the degree of aluminum recovery by about ten percent.

Tzonev, Tz.; Lucheva, B.

2007-11-01

436

Failure mechanisms for compacted uranium oxide fuel cores  

SciTech Connect

Tension, compression, and shear tests were performed on test specimens of aluminum-clad, compacted powder fuel cores to determine failure mechanisms of the core material. The core, which consists of 70% uranium oxide in an aluminum matrix, frequently fails during post-extrusion drawing. Tests were conducted to various strain levels up to failure of the core. Sections were made of tested specimens to microscopically study initiation of failure. Two failure modes wee observed. Tensile failure mode is initiated by prior tensile failure of uranium oxide particles with the separation path strongly influenced by the arrangement of particles. Delamination mode consists of the separation of laminae formed during extrusion of tubes. Separation proceeds from fine cracks formed parallel to the laminae. Tensile failure mode was experienced in tension and shear tests. Delamination mode was produced in compression tests.

Berghaus, D.G.; Peacock, H.B.

1980-01-01

437

Molecular Structure of Aluminum bromide  

NSDL National Science Digital Library

Aluminum bromide is hygroscopic and appears as white to yellow-red lumps. It is corrosive and causes severe burns. It should be stored in a cool, dry and well ventilated place. AlBr3 reacts violently with water and evolves HBr, and also reacts quickly with alcohols and acids.

2002-10-09

438

Aluminum: Approaching the new millennium  

NASA Astrophysics Data System (ADS)

During the past 100 years, aluminum has developed into a staple of the manufacturing industry. The industry has undergone successive revolutions in consumption, smelter location, and pricing. Now, it faces more change as products mature, new markets struggle to develop, and technology advances further.

Øye, H. A.; Mason, N.; Peterson, R. D.; Richards, N. E.; Rooy, E. L.; Stevens McFadden, F. J.; Zabreznik, R. D.; Williams, F. S.; Wagstaff, R. B.

1999-02-01

439

Aluminum-Metal Reactive Composites  

Microsoft Academic Search

Three binary Al-based reactive composite powders are prepared by mechanical milling. The particles have an aluminum matrix and inclusions of Fe, Ni, or Zn comprising 10 at % of the bulk composition. For additives of Ni and Zn, only short milling times can be used to prepare composites; intermetallic phases form at longer milling. Short milling times yield relatively coarse

Yasmine Aly; Mirko Schoenitz; Edward L. Dreizin

2011-01-01

440

Aluminum and its light alloys  

NASA Technical Reports Server (NTRS)

Report is a summary of research work which has been done here and abroad on the constitution and mechanical properties of the various alloy systems with aluminum. The mechanical properties and compositions of commercial light alloys for casting, forging, or rolling, obtainable in this country are described.

Merica, Paul D

1920-01-01

441

Anodic aluminum oxide microchannel plates  

Microsoft Academic Search

A new material for microchannel plates (MCP) is proposed – anodic aluminum oxide. Microchannel plates made of this material may be much cheaper than with conventional lead glass MCP. Also a significantly smaller channel diameter (up to 70nm) is easily achievable, which means better spatial resolution and the possibility to operate in strong magnetic fields. Methods and means are developed

A. Govyadinov; I. Emeliantchik; A. Kurilin

1998-01-01

442

Sound transmission loss of damped honeycomb sandwich Portia Peters and Steven Nutt  

E-print Network

the following panel/beam designs: glass-epoxy skin with Nomex® core, glass-epoxy skin with Kevlar® core, carbon relationship between TL and loss factor for subsonic panels, and (4) Both Kevlar® and Nomex® cores show insulation is called for without strong mechanical properties. Furthermore, the results of the Kevlar® core

Southern California, University of

443

In-plane uniaxial and biaxial crushing of a polycarbonate honeycomb  

NASA Astrophysics Data System (ADS)

The uniaxial and biaxial in-plane crushing of honeycomb is studied through a combination of experiments and analyses. The honeycomb has circular thin-walled polycarbonate cells in a hexagonal arrangement. Under displacement controlled uniaxial compression, the force-displacement response is characterized by three regimes of behavior. In the initial rising part of the response, the deformation is essentially uniform throughout the specimen. Following the load maximum, the deformation localizes in a narrow zone of cells. Collapse then propagates through the specimen while the load remains relatively constant until all the cells have collapsed at which point the load rises sharply. As a result of the rate dependence of the material, the initiation and propagation stresses increase as the rate of crushing of the honeycomb is increased. This crushing process was simulated numerically through the finite element method. The developed models properly address the nonlinearities due to geometry and contact. An elastic-power law viscoplastic constitutive rule is used to model the behavior of the polycarbonate. Results from analyses involving a characteristic cell and from full scale simulations of the experiments are in excellent agreement with the experimental results. Biaxial crushing was performed in a custom biaxial test facility. This facility is capable of crushing specimens in two orthogonal directions simultaneously to volume reductions of nearly 95%. Approximately square specimens were crushed between rigid platens at different biaxiality ratios by varying the two speeds of crushing. The onset of collapse involves localized instabilities as in the uniaxial crushing. However, the extent of the localized deformation varies with the biaxiality ratio. The prevalent mechanisms of collapse as well as the energy absorption capacity of the material also depend on this ratio. The highest energy is required when the specimens are crushed at the same rate in the two directions. Finite element simulations of the biaxial crushing were also performed. The models in these calculations were smaller than the specimens used in the experiments. As a result, the responses differ slightly in the initial stages of crushing, but for larger strains, the predictions agree well with the measurements. The calculated amounts of energy absorbed are in excellent agreement with the experiments. In addition, many of the modes of cell collapse seen in the experiment are reproduced in the simulations.

Papka, Scott Duane

444

Dialysis-associated arthropathy: secondary ion mass spectrometry evidence of aluminum silicate in beta 2-microglobulin amyloid synovial tissue and articular cartilage.  

PubMed

The role of aluminum accumulation in articular tissues of patients affected by dialysis-associated arthropathy (DAA) is questioned. The aim of this work is to identify the nature of these aluminum accumulations by the use of secondary ion mass spectrometry (SIMS). Al/Si ratios of about 1, measured by SIMS, strongly suggest for the first time the presence of aluminum silicates and possibly aluminum hydroxides in amyloid synovial tissue and articular cartilage of 1 patient with DAA and aluminum intoxication. This is thermodynamically consistent with the total dissolved Al and Si contents and pH measured in the synovial fluids. These results are similar to the abnormal Al distribution recently found by SIMS in the forebrain of chronic renal dialysis patients and to the amorphous aluminum silicates identified in the core of senile plaques in Alzheimer's disease. PMID:8302409

Chaussidon, M; Netter, P; Kessler, M; Membre, H; Fener, P; Delons, S; Albarède, F

1993-01-01

445

Fabrication of aluminum based nanomaterials  

NASA Astrophysics Data System (ADS)

Structural applications in transportation necessitate materials with high specific strength and stiffness. With its low density, aluminum (Al) is an interesting candidate, but further strengthening would be beneficial. In this work, the benefits and limitations of nanoreinforcements for aluminum strengthening has been assessed through the addition of carbon nanotube (CNTs) and nanometric alumina (n-Al2O3) to an aluminum matrix by powder metallurgy. It has been found that mechanical milling can homogeneously disperse n-Al2O3 in aluminum. Furthermore, mechanical milling offers the advantages of strengthening the aluminum powder through grain refinement, cold working, solid solution and precipitation. However, CNTs are damaged by mechanical milling, and their homogeneous dispersion cannot be achieved with a chemical dispersant. Nanocomposite consolidation has presented several challenges as hot pressing resulted in a lack of bonding, grain growth and the formation of Al4C3 from damaged CNTs. Cold spraying of Al2O3/Al has resulted in a porous coating with decreased hardness. The microhardness and compression properties of an Al2O 3/Al nanocomposite produced by mechanical milling followed by hot pressing were measured. Comparison with modeled values and literature results indicates that higher experimental yield strength obtained with the addition of n-Al 2O3 versus micron size Al2O3 is due to in-situ matrix strengthening. Modeling shows that CNTs offer high potential gains in stiffness due to their high aspect ratio and their high Young modulus. On the other hand, as yield gains associated with the addition of nanoreinforcement are mainly due to matrix strengthening, discontinuous nanocomposites do not benefit from the CNT's exceptional strength. In this case, n-Al 2O3 would be selected over CNTs as it is cheaper and more easily dispersed.

Poirier, Dominique

2009-11-01

446

Ethics CORE  

NSDL National Science Digital Library

The Ethics CORE Digital Library, funded by the National Science Foundation, "brings together information on best practices in research, ethics instruction and responding to ethical problems that arise in research and professional life." It's a remarkable site where visitors can make their way through ethics resources for dozens of different professions and activities. The Resources by Discipline area is a great place to start. Here you will find materials related to the biological sciences, business, computer & information science, along with 14 additional disciplines. The Current News area is a great place to learn about the latest updates from the field. Of note, these pieces can easily be used in the classroom or shared with colleagues. The dynamism of the site can be found at the Interact with Ethics CORE area. Active learning exercises can be found here, along with instructional materials and visitors' own lessons learned.

447

Preparation and characterization of functionalized aluminum nanoparticles  

NASA Astrophysics Data System (ADS)

Aluminum nanocomposite materials have been prepared by treating commercially available aluminum powders with long-chain perfluorinated carboxylic acids. The acid coated aluminum qualitatively shows enhanced burning compared to the same aluminum powder that was not treated with the acid. This preparation method will allow for the large scale production of air-stable, passivated aluminum nanoparticles. Aluminum nanocomposite materials with size ranges less than 500 nm have been prepared with various surface passivation/functionalization schemes that mitigate aluminum oxide effects and reduce the fuel-oxidizer distance to the molecular level. These materials have been characterized to understand the changes in particle size and morphology that occur with different preparation schemes. TGA, XPS and IR results are presented.

Horn, Jillian M.; Lightstone, James; Carney, Joel; Jouet, Jason

2012-03-01

448

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

449

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

450

Mott transition and antiferromagnetism of cold fermions in the decorated honeycomb lattice  

NASA Astrophysics Data System (ADS)

We investigate two-component ultracold fermions loaded in a decorated honeycomb lattice described by the Hubbard model with repulsive interactions and nearest-neighbor hopping. The phase transitions are studied by combining the cellular dynamical mean-field theory with the continuous-time quantum Monte Carlo method. For weak interactions, the quadratic band crossing point is broken to a linear band crossing point and the system becomes a semimetal. With increasing interaction, the system undergoes a first-order phase transition to an antiferromagnetic Mott insulator at low temperatures. Below the critical temperature, due to the charge nematic fluctuation, a nematic metal forms between the semimetal and the antiferromagnetic Mott insulator. The effects of lattice anisotropy are also addressed. Furthermore, we discuss how to detect these phases in real experiments.

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

2014-11-01

451

BCS-BEC Crossover on the Two-Dimensional Honeycomb Lattice  

SciTech Connect

The attractive Hubbard model on the honeycomb lattice exhibits, at half filling, a quantum critical point between a semimetal with massless Dirac fermions and an s-wave superconductor (SC). We study the BCS-BEC crossover in this model away from half filling at zero temperature and show that the appropriately defined crossover line (in the interaction-density plane) passes through the quantum critical point at half filling. For a range of densities around half filling, the 'underlying Fermi surface' of the SC, defined as the momentum space locus of minimum energy quasiparticle excitations, encloses an area which changes nonmonotonically with interaction. We also study fluctuations in the SC and the semimetal, and show the emergence of an undamped Leggett mode deep in the SC. Finally, we consider possible implications for ultracold atoms in optical lattices and the high temperature SCs.

Zhao Erhai; Paramekanti, Arun [Department of Physics, University of Toronto, Toronto, Ontario M5S-1A7 (Canada)

2006-12-08

452

Fermionic quantum critical point of spinless fermions on a honeycomb lattice  

NASA Astrophysics Data System (ADS)

Spinless fermions on a honeycomb lattice provide a minimal realization of lattice Dirac fermions. Repulsive interactions between nearest neighbors drive a quantum phase transition from a Dirac semimetal to a charge-density-wave state through a fermionic quantum critical point, where the coupling of the Ising order parameter to the Dirac fermions at low energy drastically affects the quantum critical behavior. Encouraged by a recent discovery (Huffman and Chandrasekharan 2014 Phys. Rev. B 89 111101) of the absence of the fermion sign problem in this model, we study the fermionic quantum critical point using the continuous-time quantum Monte Carlo method with a worm-sampling technique. We estimate the transition point V/t=1.356(1) with the critical exponents ? =0.80(3) and ? =0.302(7). Compatible results for the transition point are also obtained with infinite projected entangled-pair states.

Wang, Lei; Corboz, Philippe; Troyer, Matthias

2014-10-01

453

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

454

Topological Fermi Liquids from Coulomb Interactions in the Doped Honeycomb Lattice  

SciTech Connect

We propose a simple method for obtaining time reversal symmetry (T) broken phases in simple lattice models based on enlarging the unit cell. As an example we study the honeycomb lattice with nearest neighbor hopping and a local nearest neighbor Coulomb interaction V. We show that when the unit cell is enlarged to host six atoms that permits Kekule distortions, self-consistent currents spontaneously form creating nontrivial magnetic configurations with total zero flux at high electron densities. A very rich phase diagram is obtained within a variational mean field approach that includes metallic phases with broken time reversal symmetry (T). The predominant (T) breaking configuration is an anomalous Hall phase, a realization of a topological Fermi liquid.

Castro, Eduardo V.; Grushin, Adolfo G.; Valenzuela, Belen; Vozmediano, Maria A. H.; Cortijo, Alberto; Juan, Fernando de [Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, E-28049 Madrid (Spain); Departamento de Fisica Teorica, Universidad Autonoma de Madrid, E-28049, Madrid (Spain); Department of Physics, Indiana University, Bloomington, Indiana 47405 (United States)

2011-09-02

455

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

456

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

457

Loop-Cluster Simulation of the $t$-$J$ Model on the Honeycomb Lattice  

E-print Network

Inspired by the lattice structure of the unhydrated variant of the superconducting material Na$_x$CoO$_2 \\cdot$yH$_2$O at $ x = {1/3}$, we study the $t$-$J$ model on a honeycomb lattice by using an efficient loop-cluster algorithm. The low-energy physics of the undoped system and of the single hole sector is described by a systematic low-energy effective field theory. The staggered magnetization per spin $\\widetilde{{\\cal M}}_s = 0.2688(3)$, the spin stiffness $\\rho_s = 0.102(2) J$, the spin wave velocity $c= 1.297(16) J a$, and the kinetic mass $M'$ of a hole are obtained by fitting the numerical Monte Carlo data to the effective theory predictions.

F. -J. Jiang; F. Kämpfer; M. Nyfeler; U. -J. Wiese

2008-07-18

458

CO2 Adsorption on Activated Carbon Honeycomb-Monoliths: A Comparison of Langmuir and Tóth Models  

PubMed Central

Activated carbon honeycomb-monoliths with different textural properties were prepared by chemical activation of African palm shells with H3PO4, ZnCl2 and CaCl2 aqueous solutions of various concentrations. The adsorbents obtained were characterized by N2 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

459

Self consistent study of the quantum phases in a frustrated antiferromagnet on the bilayer honeycomb lattice  

NASA Astrophysics Data System (ADS)

We study the frustrated Heisenberg model on the bilayer honeycomb lattice. The ground-state energy and spin gap are calculated, using different bosonic representations at mean field level and numerical calculations, to explore different sectors of the phase diagram. In particular we make use of a bond operator formalism and series expansion calculations to study the extent of dimer inter-layer phase. On the other hand we use the Schwinger boson method and exact diagonalization on small systems to analyze the evolution of on-layer phases. In this case we specifically observe a phase that presents a spin gap and short range Neel correlations that survives even in the presence of non-zero next-nearest-neighbor interaction and inter-layer coupling.

Arlego, M.; Lamas, C. A.; Zhang, Hao

2014-12-01

460

A honeycomb proportional counter for photon multiplicity measurement in the ALICE experiment  

NASA Astrophysics Data System (ADS)

A honeycomb detector consisting of a matrix of 96 closely packed hexagonal cells, each working as a proportional counter with a wire readout, was fabricated and tested at the CERN PS. The cell depth and the radial dimensions of the cell were small, in the range 5- 10 mm. The appropriate cell design was arrived at using GARFIELD simulations. Two geometries are described illustrating the effect of field shaping. The charged particle detection efficiency and the preshower characteristics have been studied using pion and electron beams. Average charged particle detection efficiency was found to be 98%, which is almost uniform within the cell volume and also within the array. The preshower data show that the transverse size of the shower is in close agreement with the results of simulations for a range of energies and converter thicknesses.

Aggarwal, M. M.; Badyal, S. K.; Bhatia, V. S.; Chattopadhyay, S.; Dubey, A. K.; Majumdar, M. R. Dutta; Ganti, M. S.; Ghosh, P.; Kumar, A.; Nayak, T. K.; Mahajan, S.; Mahapatra, D. P.; Mangotra, L. K.; Mohanty, B.; Pal, S.; Phatak, S. C.; Potukuchi, B. V. K. S.; Raniwala, R.; Raniwala, S.; Rao, N. K.; Singaraju, R. N.; Sinha, Bikash; Trivedi, M. D.; Veenhof, R. J.; Viyogi, Y. P.

2002-08-01

461

Optical properties of two-dimensional honeycomb crystals graphene, silicene, germanene, and tinene from first principles  

NASA Astrophysics Data System (ADS)

We compute the optical conductivity of 2D honeycomb crystals beyond the usual Dirac-cone approximation. The calculations are mainly based on the independent-quasiparticle approximation of the complex dielectric function for optical interband transitions. The full band structures are taken into account. In the case of silicene, the influence of excitonic effects is also studied. Special care is taken to derive converged spectra with respect to the number of k points in the Brillouin zone and the number of bands. In this way both the real and imaginary parts of the optical conductivity are correctly described for small and large frequencies. The results are applied to predict the optical properties reflection, transmission and absorption in a wide range of photon energies. They are discussed in the light of the available experimental data.

Matthes, L.; Pulci, O.; Bechstedt, F.

2014-10-01

462

Unpaired Majorana modes on dislocations and string defects in Kitaev's honeycomb model  

NASA Astrophysics Data System (ADS)

We study the gapped phase of Kitaev's honeycomb model (a Z2 spin liquid) on a lattice with topological defects. We find that some dislocations and string defects carry unpaired Majorana fermions. Physical excitations associated with these defects are (complex) fermion modes made out of two (real) Majorana fermions connected by a Z2 gauge string. The quantum state of these modes is robust against local noise and can be changed by winding a Z2 vortex around one of the dislocations. The exact solution respects gauge invariance and reveals a crucial role of the gauge field in the physics of Majorana modes. To facilitate these theoretical developments, we recast the degenerate perturbation theory for spins in the language of Majorana fermions.

Petrova, Olga; Mellado, Paula; Tchernyshyov, Oleg

2014-10-01

463

Quantum phases of the frustrated XY models on the honeycomb lattice  

NASA Astrophysics Data System (ADS)

Searching for spin-liquid states has long been attracting both experimentalists and theorists. In this paper, we review recent density matrix renormalization group studies of the spin-½ XY model on the honeycomb lattice, with first-neighbor (J1 = 1) and frustrating second-neighbor (J2 > 0) interactions. For the intermediate frustration regime 0.22 ? J2 ? 0.36, there exists a surprising antiferromagnetic Ising phase, with ordered moments pointing along the z-axis, despite the absence of any SzSz interactions in the Hamiltonian. Surrounding this phase as a function of J2 are antiferromagnetic phases with the moments pointing in the xy-plane for small J2 and a close competition between an xy-plane magnetic collinear phase and a dimer phase for large values of J2. No spin-liquid phases was found in the XY model even with the third-neighbor (J3 > 0) interactions.

Zhu, Zhenyue; White, Steven R.

2014-12-01

464

Spiral order in the honeycomb iridate Li2IrO3  

NASA Astrophysics Data System (ADS)

The honeycomb iridates A2IrO3 (A = Na, Li) constitute promising candidate materials to realize the Heisenberg-Kitaev model (HKM) in nature, hosting unconventional magnetic as well as spin-liquid phases. Recent experiments suggest, however, that Li2IrO3 exhibits a magnetically ordered state of incommensurate spiral type which has not been identified in the HKM. We show that these findings can be understood in the context of an extended Heisenberg-Kitaev scenario satisfying all tentative experimental evidence: (i) the maximum of the magnetic susceptibility is located inside the first Brillouin zone, (ii) the Curie-Weiss temperature is negative relating to dominant antiferromagnetic fluctuations, and (iii) significant second-neighbor spin exchange is involved.

Reuther, Johannes; Thomale, Ronny; Rachel, Stephan

2014-09-01

465

Subwavelength imaging by a graded-index photonic-crystal flat lens in a honeycomb lattice.  

PubMed

The left-handed behavior of a photonic-crystal flat lens with a graded index in a honeycomb lattice is proposed and theoretically studied. The performance of the flat superlens imaging of this structure has been demonstrated by finite-difference time-domain simulations. The full width at half-maximum of the image decreases to 62% compared to that of the image of a photonic-crystal slab without a graded index. The evanescent waves can be amplified and propagate to the far-field range. The image is not limited to be near the interface. The canalization effect of this structure is analyzed, and the tolerance of the edge cut of the graded-index structure is pretty good. PMID:21979524

Shi, Peng; Huang, Kun; Li, Yong-ping

2011-10-01

466

Chiral d-wave superconductivity on the honeycomb lattice close to the Mott state  

NASA Astrophysics Data System (ADS)

We study superconductivity on the honeycomb lattice close to the Mott state at half filling. Due to the sixfold lattice symmetry and disjoint Fermi surfaces at opposite momenta, we show that several different fully gapped superconducting states naturally exist on the honeycomb lattice, of which the chiral d +id'-wave state has previously been shown to appear when superconductivity appears close to the Mott state. Using renormalized mean-field theory to study the t-J model and quantum Monte Carlo calculations of the Hubbard-U model we show that the d +id'-wave state is the favored superconducting state for a wide range of on-site repulsion U, from the intermediate to the strong coupling regime. We also investigate the possibility of a mixed chirality d-wave state, where the overall chirality cancels. We find that a state with d +id'-wave symmetry in one valley but d -id'-wave symmetry in the other valley is not possible in the t-J model without reducing the translational symmetry, due to the zero-momentum and spin-singlet nature of the superconducting order parameter. Moreover, any extended unit cells result either in disjoint Dirac points, which cannot harbor this mixed chirality state, or the two valleys are degenerate at the zone center, where valley hybridization prevents different superconducting condensates. We also investigate extended unit cells where the overall chirality cancels in real space. For supercells containing up to eight sites, including the Kekulé distortion, we find no energetically favorable d-wave solution with an overall zero chirality within the restriction of the t-J model.

Black-Schaffer, Annica M.; Wu, Wei; Le Hur, Karyn

2014-08-01