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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

Preelectroplating Treatment Of Titanium Honeycomb Core  

NASA Technical Reports Server (NTRS)

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

Kelly, Michael L.; Harvey, James S.

1992-01-01

3

Low Velocity Impact Behavior of Aluminum Honeycomb Structures  

Microsoft Academic Search

Impact behaviors of aluminum honeycomb sandwich panels (AHSPs) are investigated experimentally by using a drop weight test setup. The specimens of 12.7 mm cell size were tested by impacting at four different initial contact points, namely face center, corner, long edge and short edge of core cells, with two impactors of weights 5.25 kg and 11.9 kg, respectively. Dynamic nonlinear

I. T. Lee; Y. Shi; A. M. Afsar; Y. Ochi; S. I. Bae; J. I. Song

2010-01-01

4

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

5

49 CFR 587.15 - Verification of aluminum honeycomb crush strength.  

Code of Federal Regulations, 2012 CFR

... 2012-10-01 2012-10-01 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...

2012-10-01

6

49 CFR 587.15 - Verification of aluminum honeycomb crush strength.  

Code of Federal Regulations, 2014 CFR

... 2014-10-01 2014-10-01 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...

2014-10-01

7

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

8

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

9

Flexible Skins for Morphing Aircraft Using Cellular Honeycomb Cores  

Microsoft Academic Search

This study presents and examines the concept of flexible skins for morphing aircraft applications comprising of a cellular honeycomb core covered by a compliant face-sheet. The overall properties of the flexible skins are then largely governed by the characteristics of the cellular honeycomb core, which are in turn dependent on the cell parameters. The results of this study showed that

Kingnidé R. Olympio; Farhan Gandhi

2010-01-01

10

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

11

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

12

Honeycomb Core and the Myths of Moisture Ingression  

Microsoft Academic Search

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

John H. Fogarty

2010-01-01

13

Evaluation of Ceramic Honeycomb Core Compression Behavior at Room Temperature  

NASA Technical Reports Server (NTRS)

Room temperature flatwise compression tests were conducted on two varieties of ceramic honeycomb core specimens that have potential for high-temperature structural applications. One set of specimens was fabricated using strips of a commercially-available thin-gage "ceramic paper" sheet molded into a hexagonal core configuration. The other set was fabricated by machining honeycomb core directly from a commercially available rigid insulation tile material. This paper summarizes the results from these tests.

Bird, Richard K.; Lapointe, Thomas S.

2013-01-01

14

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

15

Impact-induced collapse of aluminum honeycombs with cell defects  

NASA Astrophysics Data System (ADS)

Dynamical deformation and collapse process and stress wave mechanism of an aluminum honeycomb with a defective cell subjected to the in-plane impact of a rigid impactor were investigated experimentally. Deformation process was visualized using a high-speed video camera and a CCD camera and wave propagation mechanisms were investigated using a force gauge at the fixed end and strain-gauges glued on the cell walls. Also, numerical simulation was made using a shock code, AUTODYN-2D. The defect introduced in cells greatly affects wave propagation mechanisms and cell deformation process. The present results were compared with our previous results.

Tanaka, Koichi; Nishida, Masahiro; Takamiya, Souhei

2005-03-01

16

Dynamical collapse of aluminum honeycombs subjected to in-plane impact  

NASA Astrophysics Data System (ADS)

Dynamical deformation and collapse process and stress wave mechanism of aluminum honeycombs subjected to the in-plane impact of a rigid impactor were investigated experimentally. Deformation process was visualized using a high-speed video camera and reaction forces were measured using force-gauges at the contact surface between the honeycomb and fixed wall. Also, numerical simulation was made using a shock code. AUTODYN-2D. Since an aluminum honey-comb has an anisotropic nature owing to its cell shape and cell arrangement, the direction of impact greatly affects the deformation characteristics. The present results were compared with our previous results for different impact direction.

Tanaka, Koichi; Nishida, Masahiro; Furukawa, Yoshihiro

2003-07-01

17

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

18

Dynamic response of aluminum honeycombs to in-plane impact loadings  

NASA Astrophysics Data System (ADS)

Deformation processes of aluminum honeycombs with hexagonal cells subjected to the in-plane impact of a rigid impactor are investigated experimentally and numerically in relation to the dynamical behavior of cellular materials and complex materials under high-speed loadings. Strain waves are measured using strain gauges glued on the cell walls and reaction forces are measured using a load cell at the contact surface between the honeycomb and a fixed wall. A high-speed camera is used to visualize the deformation process. Numerical simulations are partly made for the same configuration as the experiment. Very distinctive deformation mechanisms of individual cells and propagation mechanisms of strain waves in the honeycomb are found out. Also, characteristic two-dimensional behavior is revealed in spite of one-dimensional and uni-directional impact loading.

Tanaka, Koichi; Nishida, Masahiro; Mochida, Toshiharu; Kousaka, Akiko

2001-04-01

19

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

20

Analysis of in-plane elastic modulus for a hexagonal honeycomb core: Effect of core height and proposed analytical method  

Microsoft Academic Search

In this study, the effect of height h of a hexagonal honeycomb core on the elastic modulus was studied by using numerical results of finite element method (FEM). The cell walls of a honeycomb subjected to in-plane loading are deformed in the height direction due to the effect of Poisson’s ratio. Since these deformations differ between adjacent cell walls if

D. H. Chen; S. Ozaki

2009-01-01

21

Segmented Aluminum Honeycomb Characteristics in T-Direction, Dynamic Crush Environments  

SciTech Connect

Thirteen segmented aluminum honeycomb samples (5 in. diameter and 1.5 in. height) have been crushed in an experimental configuration that uses a drop table impact machine. The 38.0 pcf bulk density samples are a unique segmented geometry that allows the samples to be crushed while maintaining a constant cross-sectional area. A crush weight of 175 lb was used to determine the rate sensitivity of the honeycomb's highest strength orientation, T-direction, in a dynamic environment of {approx}50 fps impact velocity. Experiments were conducted for two honeycomb manufacturers and at two temperatures, ambient and +165 F. Independent measurements of the crush force were made with a custom load cell and a force derived from acceleration measurements on the drop table using the Sum of Weighted Accelerations Technique with a Calibrated Force (SWAT-CAL). Normalized stress-strain curves for all thirteen experiments are included and have excellent repeatability. These data are strictly valid for material characteristics in the T orientation because the cross-sectional area of the honeycomb did not change during the crush. The dynamic crush data have a consistent increase in crush strength of {approximately}7--19% as compared to quasi-static data and suggest that dynamic performance may be inferred from static tests. An uncertainty analysis estimates the error in these data is {+-} 11%.

BATEMAN,VESTA I.; BROWN,FREDERICK A.; NUSSER,MICHAEL A.; SWANSON,LLOYD H.

2000-08-23

22

The in-plane stiffnesses of a honeycomb core including the thickness effect  

Microsoft Academic Search

Summary   The subject of the consideration is the contribution of a regular honeycomb core to the effective in-plane stiffnesses of\\u000a a sandwich structure. Due to the coupling of the core displacements with those of the sandwich face sheets, the stiffness\\u000a contribution of the core is not proportional to its total thickness, as could be expected. The corresponding thickness effect\\u000a is

W. Becker

1998-01-01

23

Compression After Impact on Honeycomb Core Sandwich Panels With Thin Facesheets. Part 1; Experiments  

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 one, the subject of the current paper, is focused on the experimental testing. 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 specimens, which were identical with the exception of the density of the honeycomb core, were tested. Static indentation and low velocity impact using a drop tower are used to study damage formation in these materials. A series of highly instrumented CAI tests was then completed. New techniques used to observe CAI response and failure include high speed video photography, as well as digital image correlation (DIC) for full-field deformation measurement. Two CAI failure modes, indentation propagation, and crack propagation, were observed. From the results, it can be concluded that the CAI failure mode of these panels depends solely on the honeycomb core density.

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

2012-01-01

24

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

25

The soft impact of composite sandwich beams with a square-honeycomb core B.P. Russell, T. Liu, N.A. Fleck, V.S. Deshpande*  

E-print Network

and Nomex honeycomb. Mines et al. [11], Abrate [12] and Olsson [13] have determined the severity of impact containing aluminium or Nomex honeycomb cores. These studies have also elucidated the relationship between

Fleck, Norman A.

26

Thermal behavior of a titanium honeycomb-core sandwich panel  

NASA Technical Reports Server (NTRS)

Finite element thermal stress analysis was performed on a rectangular titanium honecomb-core sandwich panel which is subjected to thermal load with a temperature gradient across its depth. The distributions of normal stresses in the face sheets and the face-sheet/sandwich-core interfacial shear stresses are presented. The thermal buckling of the heated face sheet was analyzed by assuming the face sheet to be resting on an elastic foundation representing the sandwich core. Thermal buckling curves and thermal buckling load surface are presented for setting the limit for temperature gradient across the panel depth.

Ko, William L.; Jackson, Raymond H.

1991-01-01

27

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

28

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

29

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

30

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

31

On Thermoelastic and Hygrometric Response of Sandwich Beams with Laminate Facings and Honeycomb Cores: Part IV—A Dynamic Theory  

Microsoft Academic Search

The systematic development of a dynamic theory for a sandwich beam is presented leading to the governing equations of equilibrium and the natural boundary conditions. Using Timoshenko beam theory [I], a function 1' is introduced in terms of the kinetic and strain energies of the system consisting of both laminate facings and honeycomb core. Reissner's variational theorem is used in

Achintya K. Mukhopadhyay; Robert L. Sierakowski

2000-01-01

32

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

33

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

NASA Technical Reports Server (NTRS)

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

Cha, Gene; Schultz, Marc R.

2013-01-01

34

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

35

Scaling of honeycomb compressive yield stresses  

Microsoft Academic Search

In this study, the compressive yield stresses of phenolic-dipped Nomex® rings were scaled and correlated to honeycomb core. A honeycomb-scaling factor and geometric end constraint factor were found to relate the rings and core through the relative yield stresses and their physical dimensions and properties of the honeycomb materials. The compressive properties of the Nomex rings were also investigated using

J. E. Shafizadeh; J. C. Seferis

2000-01-01

36

Brazed Borsic/aluminum structural panels  

NASA Technical Reports Server (NTRS)

A fluxless brazing process has been developed that minimizes degradation of the mechanical properties of Borsic/aluminum composites. The process, which employs 718 aluminum alloy braze, is being used to fabricate full scale Borsic/aluminum-titanium honeycomb-core panels for Mach 3 flight testing on the YF-12 aircraft and ground testing in support of the Supersonic Cruise Aircraft Research (SCAR) Program. The manufacturing development and results of shear tests on full scale panels are presented.

Bales, T. T.; Wiant, H. R.; Royster, D. M.

1977-01-01

37

Analytical structural efficiency studies of borsic/aluminum compression panels  

NASA Technical Reports Server (NTRS)

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

Mcwithey, R. R.

1976-01-01

38

Design manufacture and test of a cryo-stable Offner relay using aluminum foam core optics  

NASA Astrophysics Data System (ADS)

Aluminum foam core optics have the desirable characteristics of being lightweight, cryo-stable, and low cost. The availability of high quality aluminum foam and a bare aluminum super-polishing process have allowed high performance foam core optics made entirely of aluminum to be produced. Mirrors with integral mounts were designed for minimum surface error induced by self-weight deflection, thermal gradients, and mounting stresses. The design of the optics was extensively optimized using Finite Element Analysis (FEA) and Geometric Element Analysis (GEA) to determine the effects of design parameters on mirror performance under the anticipated operating environments. A unique manufacturing process was developed to accommodate the aluminum brazing process used to install the aluminum foam while maintaining dimensional stability. Aluminum foam core optics have the additional advantage of being fabricated from a common aerospace structural material. An Offner relay using all aluminum optics and structure will be manufactured and tested with the goal of demonstrating that an all aluminum optical system can be aligned at room temperature and maintain alignment at cryogenic temperatures due to near zero CTE mismatch between all system components. If successful, an all aluminum Offner relay has potential uses for NGST, specifically in the testing of micro-mirror arrays.

McClelland, Ryan S.; Content, David A.

2001-12-01

39

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

40

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

NASA Technical Reports Server (NTRS)

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

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

1979-01-01

41

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

42

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

PubMed

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

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

2013-01-01

43

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

44

The use of neutron imaging for the study of honeycomb structures in aircraft  

NASA Astrophysics Data System (ADS)

Highly maneuverable aircraft, such as the CF188 Hornet, have several flight control surfaces on both the leading and the trailing edges of the wing surfaces. They are composed of composite panels constructed of aluminum honeycomb core usually covered with graphite epoxy skins. Although very light and structurally stiff, they are being compromised by water ingress. The trapped water degrades their structural integrity by interacting with the adhesive. Various studies are underway to understand the movement of water in the honeycomb core as well as to determine a method of removing the water. With a vertical neutron beam tube at Royal Military College (RMC), the component can be positioned horizontally and the pooled water in each honeycomb cell can be imaged. These images have been compared with those from a horizontal beam and thus vertical placement of the structure at the Pennsylvania State University Radiation Science and Engineer Center's Breazeale reactor. Thereby, both the filet bond between the honeycomb and the skin as well as the node bond between the honeycomb cells can be studied to determine their contribution to the movement of water throughout the structure. Moreover, the exit path for water has been visualized as part of developing a drying procedure for these flight control surfaces.

Hungler, P. C.; Bennett, L. G. I.; Lewis, W. J.; Brenizer, J. S.; Heller, A. K.

2009-06-01

45

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

46

Honeycomb network  

NSDL National Science Digital Library

Issue Date: 31-Jan-2005 Description: Simulation Software: Glotzer Group Code Simulation Method: Monte Carlo A system of 360 patchy particle nano building blocks was simulated at a concentration of 0.56 particles/surface area, starting from a disordered state then quenched to a temperature of 0.8. The building blocks have the following patch locations and patterning: 3 patches uniformly spaced on a sphere. The system was run for ~50e6 until arriving at the final structure (Honeycomb). Simulation Model: United Atom with Kern-Frenkel like potential

Joydeep, Mukherjee

2005-01-31

47

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

ScienceCinema

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

None

2014-05-07

48

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

NASA Technical Reports Server (NTRS)

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

Sharpe, E. L.; Elber, W.

1977-01-01

49

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

50

Vibroacoustics and wave propagation of novel chiral honeycombs  

NASA Astrophysics Data System (ADS)

Novel tetrachiral honeycomb structures are evaluated for the first time from the vibroacoustic point of view. A numerical method based on Bloch wave approximations for Finite Element models of the unit cells is applied to simulate the pass-stop band characteristics of these cellular solids. Experimental modal analysis and modal densities are measured on honeycomb panels and sandwich plate, and the results evaluated with the experimental findings. The novel tetrachiral honeycombs show pass-stop band characteristics with isotropic acoustic signature, while sandwich structures made with the same honeycomb cores have the interesting feature of presenting a high-pass frequency behavior on the same pass-stop bands of the honeycomb.

Tee, Kong Fah; Spadoni, Alessandro; Scarpa, Fabrizio; Ruzzene, Massimo

2008-03-01

51

Effect of core topology on projectile penetration in hybrid aluminum/alumina sandwich structuresq  

E-print Network

Effect of core topology on projectile penetration in hybrid aluminum/alumina sandwich structuresq H sectioning of impacted samples was used to investigate the penetra- tion mechanisms. We find in water [3e6] and to a lesser extent in air [7e10] or by soil impact [11e14]. Recent studies [15

Wadley, Haydn

52

The use of 1,2-epoxyhexane as a passivating agent for core-shell aluminum nanoparticles with very high active aluminum content  

NASA Astrophysics Data System (ADS)

Aluminum nanoparticles synthesized by titanium (IV) isopropoxide-initiated decomposition of alane have been passivated and capped using oligomerization of 1,2-epoxyhexane. Preliminary synthetic protocols with this capping agent, where the nanoparticle formation reaction and passivation processes were both conducted at ambient temperatures, had resulted in nanoparticles that were highly unstable and that either oxidized rapidly upon exposure to air or were pyrophoric. Use of 1,2-epoxydodecane, on the other hand, had produced stable nanoparticles that were successfully characterized and reported. A modification of the procedure whereby the epoxyhexane passivation process is carried out at 85 °C for 30 min, has afforded surprisingly stable aluminum nanoparticles. Powder X-ray analysis and transmission electron microscopy reveal nanoparticle diameters on the order of 30 nm with 19 nm crystalline aluminum cores. The passivation process yields an extraordinarily high active aluminum (Al0) content of 83%, with degradation of the core to 52% active aluminum after 9 days exposure in a dry air chamber. Differential scanning calorimetry coupled with thermogravimetric analysis reveals distinct cap combustion and metal ignition exotherms, though they are not as well-defined as those found with their epoxydodecane-capped congener. With the additional observation of a metal melting endotherm, it is suggested that while carrying out the passivation process at an elevated temperature affords a higher degree of kinetic stabilization of the aluminum core, the passivation shell is inhomogeneous, possibly as a result of the polydisperse nature of the oligomerized epoxyhexane.

Jelliss, Paul A.; Buckner, Steven W.; Chung, Stephen W.; Patel, Ashish; Guliants, Elena A.; Bunker, Christopher E.

2013-09-01

53

Ceramic Honeycomb Panels  

NASA Technical Reports Server (NTRS)

Ceramic honeycomb panels serve as lightweight, heat-resistant structural members. Depending on choice of ceramic materials, panels expected to withstand temperatures as high as 1,800 degree C. Honeycomb structure made by vapor-depositing ceramic on fabric substrate woven in honeycomb pattern, then eliminating substrate by oxidizing it. Fabric made of loosely woven polymer such as polyacrylonitrile. Impregnated with organic binder such as phenolic resin for stiffness.

Cagliostro, Domenick E.; Riccitiello, Salvatore R.

1989-01-01

54

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

55

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

56

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

57

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

58

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

59

Honeycomb composite fuselage sidewall  

NASA Technical Reports Server (NTRS)

Test setup for vibroacoustic response studies of a curved honeycomb composite fuselage side wall in the Structural Acoustic Loads and Transmission (SALT) Facility. Photographed in building 1208, SALT facility.

2000-01-01

60

Bending Response of Sandwiched Double Tube Structures with Aluminum Foam Core  

NASA Astrophysics Data System (ADS)

Three point bending response of sandwiched double cylindrical tube structures with aluminum foam core was studied numerically using the explicit finite element method. The numerical results are in good agreement with the corresponding experimental results and display the advantage of this new structure in load carrying capacity and energy absorption efficiency over the traditional foam-filled single tube structure. The deformation and failure mechanism is revealed by comparisons of the strain and stress distributions and the history of the maximum strain. The influence of the inner tube diameter for the structure was explored. It is found that increasing the inner tube diameter enhances the maximum deflection at failure of the foam-filled double tube within the diameter range considered. With a proper inner tube diameter, a steady load carrying capacity of the foam-filled double tube structure can be achieved, which shows an excellent crashworthiness with high energy absorption efficiency.

Guo, L. W.; Yu, J. L.

2010-05-01

61

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

62

Honeycombs in honeycombs: complex liquid crystal alumina composite mesostructures.  

PubMed

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

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

2014-05-27

63

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

64

The Honeycomb supernova remnant  

NASA Technical Reports Server (NTRS)

At 2.5 min southeast of SN 1987A, the Honeycomb Nebula Supernova remnant (SNR) is named after its interesting morphology, which consists of over ten loops with sizes of 2-3 pc. High-dispersion spectra of these loops show hemispheres expanding toward the observer at 100-300 km/s. Using archival data X-ray data and a combination of new and archival radio data, we find bright X-ray and nonthermal radio emisssion associated with the Honeycomb Nebula. New CCD images further show enhanced (S II) H-alpha ratios. These results confirm a model in which the Honeycomb Nebula is due to a supernova shock front, traveling toward the observer, encountering an intervening sheet of dense, but porous, interstellar gas. The bulk of the supernova remnant resides in a low-density cavity, and is not otherwise visible. The situation is similar to the hidden supernova remnants postulated for the X-ray bright superbubbles. The Honeycomb Nebula has an unusually steep radio spectral index (S(sub nu) is proportional to nu(exp -1.2)), normally associated with young SNRs.

Chu, You-Hua; Dickel, John R.; Staveley-Smith, Lister; Osterberg, Juergen; Smith, R. Chris

1995-01-01

65

Cellular Metal Truss Core Sandwich Structures**  

E-print Network

rigidity. Honeycomb core sandwich structures are the current state-of-the-art choice for weight sensitive. Introduction Cellular metals have attracted interest as alternatives to honeycomb when used as the cores (program managers, L. Christodoulou and S. Fishman). Closed cell honeycomb core structures are widely used

Wadley, Haydn

66

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

67

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

Microsoft Academic Search

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

Jilin Yu; Erheng Wang; Jianrong Li; Zhijun Zheng

2008-01-01

68

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

69

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

70

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

71

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

72

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

73

Effect of geometric parameters on the in-plane crushing behavior of honeycombs and honeycombs with facesheets  

NASA Astrophysics Data System (ADS)

In aerospace field, use of honeycombs in energy absorbing applications is a very attractive concept since they are relatively low weight structures and their crushing behavior satisfies the requirements of ideal energy absorbing applications. This dissertation is about the utilization of honeycomb crushing in energy absorbing applications and maximizing their specific energy absorption (SEA) capacity by modifying their geometry. In-plane direction crushing of honeycombs is investigated with the help of simulations conducted with ABAQUS. Due to the nonlinearity of the problem an optimization technique could not be implemented; however, the results of the trend studies lead to geometries with improved SEA. This study has two objectives; the first is to obtain modified cell geometry for a hexagonal honeycomb cell in order to provide higher energy absorption for minimum weight relative to the regular hexagonal cell geometry which has 30° cell angle and walls at equal length. The results of the first objective show that by increasing the cell angle, increasing wall thickness and reducing vertical wall length it is possible to increase the SEA 4.8 times; where the honeycomb with modified geometry provided 3.3 kJ/kg SEA and with regular geometry 0.68 kJ/kg SEA. The second objective considers integration of the energy absorbing honeycombs into the helicopter subfloor, possibly as the web section of a keel beam. In-plane direction crushing of a honeycomb core sandwiched between two facesheets is simulated. Effects of core and facesheet geometric parameters on the energy absorption are investigated, and modified geometries are suggested. For the sandwich structure with thin facesheets increasing cell angle, increasing wall thicknesses and decreasing the cell depth increase the SEA. For the ones with thick facesheet reducing vertical wall length, increasing wall thicknesses and reducing the cell depth increase the SEA. The results show that regular honeycomb geometry with thin facesheets has SEA of 7.24 kJ/kg and with thick facesheets 13.16 kJ/kg. When the geometries are modified the SEA increases to 20.5 kJ/kg for the core with thin facesheets and 53.47 kJ/kg for the core with thick facesheets. The key finding of the dissertation is that the in-plane direction crushing of the honeycombs with facesheets has great potential to be used for the energy absorbing applications since their SEA levels are high enough to make them attractive for applications where high crash loads need to be absorbed such as helicopter crash.

Atli-Veltin, Bilim

74

Development of honeycomb sandwich finite element modeling techniques for dynamic and static analysis  

NASA Astrophysics Data System (ADS)

Honeycomb sandwich core is typically modeled as an equivalent continuum for both static and dynamic analysis. The orthotropic material properties for such a continuum representation are difficult to predict. The objective of this work is to examine material and geometric parameters that affect the elastic and harmonic responses of honeycomb cores. A 3D shell FEA approach is adopted to model the core geometry. The model is compared to a typical homogeneous core finite-element representation in vibratory response. It is found that adhesive filleting can play a significant role in the response of honeycomb sandwich structure. Additionally, finite-element models using homogenized core approximations are shown to yield erroneous predictions for higher modes of vibration. Only through the modeling of actual honeycomb core geometry through finiteelement methods is it possible to predict higher modes. Vibration occurring strictly in the honeycomb cells can be observed by a tight band of resonances. This band occurs at different frequency ranges depending on the modeling technique. Achieving accurate homogeneous core model dynamic response for higher modes is restricted by computational inefficiency. Steady state harmonic analysis was only possible using the 3D shell core representation. The homogeneous core models were accurate in static shear and early modal response only. When it becomes necessary to predict shorter wavelengths of vibration, the homogeneous core models are either too computationally expensive or produce incorrect responses specifically with regard to modes isolated in the core.

Spoonire, Ross A.

2010-07-01

75

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

76

Finite Element Development of Honeycomb Panel Configurations with Improved Transmission Loss  

NASA Technical Reports Server (NTRS)

The higher stiffness-to-mass ratio of a honeycomb panel compared to a homogeneous panel results in a lower acoustic critical frequency. Above the critical frequency the panel flexural wave speed is acoustically fast and the structure becomes a more efficient radiator with associated lower sound transmission loss. Finite element models of honeycomb sandwich structures are presented featuring areas where the core is removed from the radiating face sheet disrupting the supersonic flexural and shear wave speeds that exist in the baseline honeycomb panel. These modified honeycomb panel structures exhibit improved transmission loss for a pre-defined diffuse field sound excitation. The models were validated by the sound transmission loss of honeycomb panels measured in the Structural Acoustic Loads and Transmission (SALT) facility at the NASA Langley Research Center. A honeycomb core panel configuration is presented exhibiting a transmission loss improvement of 3-11 dB compared to a honeycomb baseline panel over a frequency range from 170 Hz to 1000 Hz. The improved transmission loss panel configuration had a 5.1% increase in mass over the baseline honeycomb panel, and approximately twice the deflection when excited by a static force.

Grosveld, Ferdinand W.; Palumbo, Daniel L.; Klos, Jacob; Castle, William D.

2006-01-01

77

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....

78

Versatile honeycomb matrix heat shield  

NASA Technical Reports Server (NTRS)

A thermal protection system for atmospheric entry of a vehicle, the system including a honeycomb structure with selected cross sectional shapes that receives and holds thermally cured thermal protection (TP) blocks that have corresponding cross sectional shapes. Material composition for TP blocks in different locations can be varied to account for different atmospheric heating characteristics at the different locations. TP block side walls may be attached to all, or to less than all, the corresponding honeycomb structure side walls.

Zell, Peter T. (Inventor)

2010-01-01

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. 7 figs.

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

1999-08-03

80

Method of fabricating lightweight honeycomb structures  

NASA Technical Reports Server (NTRS)

A process is disclosed for fabricating lightweight honeycomb type structures out of material such as silicon carbide (SiC) and silicon (S). The lightweight structure consists of a core to define the shape and size of the structure. The core is coated with an appropriate deposit such as SiC or Si to give the lightweight structure strength and stiffness and for bonding the lightweight structure to another surface. The core is fabricated from extremely thin ribs of appropriately stiff and strong material such as graphite. First, a graphite core consisting of an outer hexagonal cell with six inner triangular cells is constructed from the graphite ribs. The graphite core may be placed on the back-up side of a SiC faceplate and then coated with SiC to produce a monolithic structure without the use of any bonding agent. Cores and methods for the fabrication thereof in which the six inner triangular cells are further divided into a plurality of cells are also disclosed.

Goela, Jitendra S. (Inventor); Pickering, Michael (Inventor); Taylor, Raymond L. (Inventor)

1992-01-01

81

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

82

Millimeter Wave Holographical Inspection of Honeycomb Composites  

NASA Astrophysics Data System (ADS)

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 isband, 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.; Steffes, G.; Hepburn, F. L.

2008-02-01

83

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

84

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

85

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

86

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

87

Multistable grid and honeycomb shells  

E-print Network

their continuous counterparts; and finally, in architectural terms, the particular discrete topology can be aesthetically desirable (Malek, 2012). We now proceed to define a local geometry for the constituent beam-elements. We assume a rectangular cross... to the architectural scale. In addition, it facilitates light and fluid permeable structures. The construction of a thermoplastic demonstrator honeycomb confirmed the bistable nature of such a structure, albeit short-lived due to creep effects; there is considerable...

Loukaides, E. G.; Seffen, K. A.

2015-01-10

88

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

89

Viscoelastic Analysis of Sandwich Beams Having Aluminum and Fiber-reinforced Polymer Skins with a Polystyrene Foam Core  

E-print Network

of the sandwich beam with aluminum of FRP as the skin material ............................................................................................... 55 3.15. Comparison of the shear strain field at a distance of 83.3 mm from the midspan... of the sandwich beam with aluminum of FRP as the skin material ....................................................................................................... 58 3.16. Comparison of the transverse strain field at a distance of 83.3 mm from...

Roberts-Tompkins, Altramese L.

2010-07-14

90

Development of Pyrrone structural forms for honeycomb filler  

NASA Technical Reports Server (NTRS)

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

Kimmel, B. G.

1973-01-01

91

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

92

Experimental study of acoustical behavior of flat honeycomb sandwich panel  

NASA Astrophysics Data System (ADS)

Honeycomb (HC) sandwich composites have lightweight and excellent mechanical properties, but have poor acoustic properties. This work was done to improve the acoustical performance of HC sandwich composites used in airplane floors. Transmission loss (TL) is one of the metrics used to assess acoustical performance of HC sandwiches and requires a TL suite. A small-scale sound transmission loss (TL) test facility was designed, constructed and qualified to conduct the experiments. TL measurements were made using the sound intensity technique based on ASTM. The small-scale facility was qualified between 315 Hz and 10 KHz, and the results of test panels were compared to results from two full-scale accredited labs. TL measured at the small-scale facility yielded reliable, relative comparisons for flat, HC panels. HC panel bending waves are characterized by three frequency regimes---total panel bending, core shear, and individual skin bending---that are controlled by panel geometry, panel mass and elastic properties of the core and the skins. Superior TL performance can be achieved by designing HC panels with significantly subsonic shear wave speed that delays the onset of coincidence frequency. The influence of different commercial HC sandwich design parameters, such as core density, core material, cell size, and cell structure, on TL was investigated. Frequency responses of TL for these panels were inferior. Supersonic core shear wave speed was identified as the reason for inferior acoustic performance. So three classes of panels with different core shear wave speeds---subsonic, transonic, and supersonic---were fabricated and compared for TL. Panels with subsonic and transonic core shear wave speeds showed improved acoustic performance than their supersonic counterparts. Also, optimization studies on panels with subsonic wave speeds showed that the mechanical performance of subsonic and transonic panel designs is generally low, but can be improved when accompanied by weight increase. Comparison of TL performance was made between panels with honeycomb cores made of p-aramid and m-aramid. The stiffer p-aramid HC cores improved the TL above coincidence frequency compared to m-aramid cores. The reason for improved TL at higher frequencies was the lowering of modal density for p-aramid HC cores. Lightweight noise control treatments for honeycomb sandwich panels were explored by adding a gas barrier layer to the panel on the incident side. (Abstract shortened by UMI.)

Rajaram, Shankar

93

Mechanics of Pressure-Adaptive Honeycomb  

Microsoft Academic Search

Pressure-adaptive honeycomb is a new type of adaptive structure that can exhibit great strains by relying on a pressure differential to alter the structural stiffness. The structure consists of a grid of honeycomb cells that extend a significant length perpendicular to the plain of the hexagons. Each cell possesses a pouch that can be pressurized and alter the stiffness of

Roelof Vos; Ron Barrett; Albert Romkes

2011-01-01

94

Performance of honeycomb double exposure solar still  

Microsoft Academic Search

A honeycomb double exposure solar still has been designed to enhance the productivity throughout the day. Experiments have been carried out to predict the performance of the proposed still in October 2009, Karpagam University, Coimbatore, India. The concept of transparent honeycomb structure with thin walled glass tube of small aspect ratio (H\\/D ? 1.7) in the basin and also planar

Kutty Arshad; Balasundaram Janarthanan; Sengottain Shanmugan

2011-01-01

95

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

96

Detection of Skin Disbond in Honeycombs and Coating Detachment by a Laser Acoustic Technique  

NASA Astrophysics Data System (ADS)

Many engineering structures are composite and include for example a protective coating or a bonded layer. A novel technique, close to laser-ultrasonics but significantly different, has been developed for the detection of disbonds between the coating or the bonded layer and the substrate. It is also applicable to the detection of core unbonds in honeycomb structures. The technique is based on the thermoelastic excitation by a pulsed laser of the top layer or top skin which is driven into vibration if it is detached from the substrate underneath. This vibration is then detected by a second laser coupled to a photorefractive interferometer. The technique can be made very flexible by using optical fiber coupling. One foresees its application to the in-service inspection of aerospace structures for the detection of core unbonds in honeycombs or near surface delaminations. Examples of application to honeycombs and to various coatings are presented.

Blouin, A.; Campagne, B.; Néron, C.; Monchalin, J.-P.

2007-03-01

97

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

NASA Technical Reports Server (NTRS)

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

Tanzer, H. J.

1982-01-01

98

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

99

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

100

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

101

Square lattice honeycomb reactor for space power and propulsion  

NASA Astrophysics Data System (ADS)

The most recent nuclear design study at the Innovative Nuclear Space Power and Propulsion Institute (INSPI) is the Moderated Square-Lattice Honeycomb (M-SLHC) reactor design utilizing the solid solution of ternary carbide fuels. The reactor is fueled with solid solution of 93% enriched (U,Zr,Nb)C. The square-lattice honeycomb design provides high strength and is amenable to the processing complexities of these ultrahigh temperature fuels. The optimum core configuration requires a balance between high specific impulse and thrust level performance, and maintaining the temperature and strength limits of the fuel. The M-SLHC design is based on a cylindrical core that has critical radius and length of 37 cm and 50 cm, respectively. This design utilized zirconium hydrate to act as moderator. The fuel sub-assemblies are designed as cylindrical tubes with 12 cm in diameter and 10 cm in length. Five fuel subassemblies are stacked up axially to form one complete fuel assembly. These fuel assemblies are then arranged in the circular arrangement to form two fuel regions. The first fuel region consists of six fuel assemblies, and 18 fuel assemblies for the second fuel region. A 10-cm radial beryllium reflector in addition to 10-cm top axial beryllium reflector is used to reduce neutron leakage from the system. To perform nuclear design analysis of the M-SLHC design, a series of neutron transport and diffusion codes are used. To optimize the system design, five axial regions are specified. In each axial region, temperature and fuel density are varied. The axial and radial power distributions for the system are calculated, as well as the axial and radial flux distributions. Temperature coefficients of the system are also calculated. A water submersion accident scenario is also analyzed for these systems. Results of the nuclear design analysis indicate that a compact core can be designed based on ternary uranium carbide square-lattice honeycomb fuel, which provides a relatively high thrust to weight ratio. .

Gouw, Reza; Anghaie, Samim

2000-01-01

102

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

103

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

104

Accounting for glue and temperature effects in Nomex based honeycomb models  

Microsoft Academic Search

To predict the effect of active control on aircraft or helicopter trim panels, made with honeycomb sandwich composite, one approach consists in modeling the panel by Finite Element Method. FEM with shell elements for the laminate and volume elements for the core is classically used in industry. The aim of the present study is to determine the limits of the

C. Florens; E. Balmes; F. Clero; M. Corus

105

The Soudan 2 honeycomb calorimeter  

SciTech Connect

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

Garcia-Garcia, C.

1990-12-01

106

Vibration and acoustic properties of honeycomb sandwich structures subject to variable incident plane-wave angle pressure loads  

NASA Astrophysics Data System (ADS)

Honeycomb structures are widely used in many areas for their material characteristics such as high strength-to-weight ratio, stiffness-to-weight, sound transmission, and other properties. Honeycomb structures are generally constructed from periodically spaced tessellations of unit cells. It can be shown that the effective stiffness and mass properties of honeycomb are controlled by the local geometry and wall thickness of the particular unit cells used. Of particular interest are regular hexagonal (6-sided) honeycomb unit cell geometries which exhibit positive effective Poisson's ratio, and modified 6-sided auxetic honeycomb unit cells with Poisson's ratio which is effectively negative; a property not found in natural materials. One important honeycomb meta-structure is sandwich composites designed with a honeycomb core bonded between two panel layers. By changing the geometry of the repetitive unit cell, and overall depth and material properties of the honeycomb core, sandwich panels with different vibration and acoustic properties can be designed to shift resonant frequencies and improve intensity and Sound Transmission Loss (STL). In the present work, a honeycomb finite element model based on beam elements is programmed in MATLAB and verified with the commercial finite element software ABAQUS for frequency extraction and direct frequency response analysis. The MATLAB program was used to study the vibration and acoustic properties of different kinds of honeycomb sandwich panels undergoing in-plane loading with different incident pressure wave angles and frequency. Results for the root mean square intensity IRMS based on normal velocity on the transmitted side of the panel measure vibration magnitude are reported for frequencies between 0 and 1000 Hz. The relationship between the sound transmission loss computed with ABAQUS and the inverse of the intensity of surface velocity is established. In the present work it is demonstrated that the general trend between the STL pressure response and the inverted intensity metric have similar response characteristics over both the stiffness frequency region and the resonance frequency region, showing that an increase in IRMS corresponds to a decrease in STL. The ABAQUS model was used to verify the MATLAB program for natural frequencies and mode shapes, and to compute the STL on the top surface of the honeycomb sandwich structure. Resonant peaks in the frequency response of intensity and STL are identified with natural frequencies and mode shapes of the honeycomb sandwich structure. A unique feature of this research is the ability to apply the time-harmonic acoustic pressure as a load on the transmitting surface of the honeycomb sandwich panel with variable incident angle ranging between 0° to 90°. When the incident angle is nonzero, the pressure load is complex valued, with sinusoidal distribution, and frequency dependent. The finite element implementation of the complex-valued variable incident pressure distribution is programmed in MATLAB to give complete control of the angle, frequency and distribution. Commercial finite element software such as ABAQUS has limited ability to directly apply frequency dependent and distributed real and imaginary pressure distributions in a direct steady state frequency analysis over a large number of frequency evaluations. In the present work, IRMS results for a family of honeycomb sandwich panels with systematic increment in internal cell wall angle, subject to incremental changes in incident angle pressure loads are studied and compared. Results show that for honeycomb sandwich panels with both positive and negative internal cell wall angle, on average, intensity for the nonzero incident angles is higher than the 0° normal incident angle. For the honeycomb sandwich panels with positive internal angle, the intensity consistently increases with larger nonzero incident angles. Furthermore, under the same incident angle pressure load, the intensity of honeycomb panel with positive internal angle is consistently larger than honeycomb panels with

Yan, Jiaxue

107

An experimental investigation of aluminum honeycomb as an energy absorber  

E-print Network

3. Bare Compression Test after Crushing 4. Square Head Producing Shear and Compression 5. Steel Shaft Used in Dynamic Testing for Head Attachments 12 6 . Dynamic Test with G ircula r Head 7. Static Specimen Illustrating Shear of Cell Walls 2 8... for absorbing impact loads have been in use for a considerable period of time. Examples are the springs and the shock absorbers on automobiles and the landing gear on airplanes. These systems tend to dampen the shock of impact, rather than absorb it...

Bland, William Joseph

1964-01-01

108

Online debonding detection in honeycomb sandwich structures using multi-frequency guided waves  

NASA Astrophysics Data System (ADS)

Due to the complex nature of sandwich structures, development of the online structural health monitoring system to detect damages in honeycomb sandwich panels inherently imposes many challenges. In this study, the leaky guided wave propagation in the honeycomb sandwich structures generated by piezoelectric wafer actuators/sensors is first simulated numerically based on the finite element method (FEM). In the numerical model, the real geometry of the honeycomb core is considered. To accurately detect debonding in the honeycomb sandwich structures, signal processing based on continuous wavelet transform is adopted to filter out the unwanted noise in the leaky Lamb wave signals collected from the experimental testing. A correlation analysis between the benchmark signals at the normal condition and those recorded at the debonded condition is then performed to determine the differential features due to the presence of debonding. Finally, the image of the debonding is formed by using a probability analysis. Specifically, fusing images acquired from multi-frequency leaky Lamb waves are obtained to enhance the quality of the final image of the structure. The location and size of the debonding in the honeycomb sandwich structures are estimated quantitatively.

Song, F.; Huang, G. L.; Hu, G. K.

2009-07-01

109

Radiative heat transfer in honeycomb structures-New simple analytical and numerical approaches  

NASA Astrophysics Data System (ADS)

Porous Honeycomb Structures present the interest of combining, at the same time, high thermal insulating properties, low density and sufficient mechanical resistance. However, their thermal properties remain relatively unexplored. The aim of this study is the modelling of the combined heat transfer and especially radiative heat transfer through this type of anisotropic porous material. The equivalent radiative properties of the material are determined using ray-tracing procedures inside the honeycomb porous structure. From computational ray-tracing results, simple new analytical relations have been deduced. These useful analytical relations permit to determine radiative properties such as extinction, absorption and scattering coefficients and phase function functions of cell dimensions and optical properties of cell walls. The radiative properties of honeycomb material strongly depend on the direction of propagation. From the radiative properties computed, we have estimated the radiative heat flux passing through slabs of honeycomb core materials submitted to a 1-D temperature difference between a hot and a cold plate. We have compared numerical results obtained from Discrete Ordinate Method with analytical results obtained from Rosseland-Deissler approximation. This approximation is usually used in the case of isotropic materials. We have extended it to anisotropic honeycomb materials. Indeed a mean over incident directions of Rosseland extinction coefficient is proposed. Results tend to show that Rosseland-Deissler extended approximation can be used as a first approximation. Deviation on radiative conductivity obtained from Rosseland-Deissler approximation and from the Discrete Ordinated Method are lower than 6.7% for all the cases studied.

Baillis, D.; Coquard, R.; Randrianalisoa, J.

2012-06-01

110

Guided wave propagation in honeycomb sandwich structures using a piezoelectric actuator/sensor system  

NASA Astrophysics Data System (ADS)

Due to the complex nature of such composite structures, an understanding of the guided wave propagation mechanism in honeycomb composite panels with different frequencies inherently imposes many challenges. In this paper, a numerical simulation is first conducted to investigate the wave propagation mechanism in honeycomb sandwich structures using piezoelectric actuators/sensors. In contrast to most of the previous work, elastic wave responses based on the real geometry of the honeycomb core are obtained by using the finite element method (FEM). Based on the simulation, the global guided waves in the composite can be observed when the loading frequency is low and the leaky guided waves in the skin panel are found when the loading frequency is sufficiently high. The applicability of the homogenization technique for a celled core is discussed. The effects of cell geometry on the wave propagation are also demonstrated. Experimental testing is finally conducted to validate the results of numerical simulation and very good agreement is observed. Specifically, some guided wave propagation characteristics such as group velocity dispersion and mode tuning capabilities with the presence of a honeycomb core are discussed.

Song, F.; Huang, G. L.; Hudson, K.

2009-12-01

111

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

112

Zero Poisson’s Ratio Cellular Honeycombs for Flex Skins Undergoing One-Dimensional Morphing  

Microsoft Academic Search

Cellular honeycomb cores with overlying flexible face sheets have been proposed for use as flex skins for morphing aircraft. The cellular cores, which provide underlying support to the face sheets for carrying aerodynamic loads, must have low in-plane stiffness and high in-plane strain capability. For one-dimensional morphing applications such as span-, chord-, or camber-change, restraining the Poisson’s contraction (or bulging)

Kingnidé Raymond Olympio; Farhan Gandhi

2010-01-01

113

Dusty and honeycomb plagioclase: indicators of processes in the Uchino stratified magma chamber, Izu Peninsula, Japan  

NASA Astrophysics Data System (ADS)

Two types of melt-inclusion-bearing plagioclase coexist in the Uchino basalt, Izu peninsula, Japan: (1) dusty plagioclase with an Ab-rich core mantled by a dusty zone consisting of more An-rich plagioclase and fine melt inclusions; and (2) honeycomb plagioclase with a central core containing larger melt inclusions. The dusty plagioclase probably forms through partial dissolution of Ab-rich plagioclase, as dusty zones truncate the concentric zonal structure of the Ab-rich inner core. The honeycomb plagioclase is formed by skeletal growth under supercooling conditions. This is indicated by the euhedral geometry of the boundary between the inner inclusion-free and the outer inclusion-bearing zones of the honeycomb plagioclase which has a concentric inner core. Bimodal distribution of the chemical compositions of phenocryst cores and assemblages in crystal clots suggest that hybridization of basaltic and andesitic magmas took place before crystallization of phenocryst rims. The core-rim boundaries of phenocrysts derived from the andesitic magma and the basaltic magma have a rounded and a euhedral geometry, respectively. This suggests the andesitic magma was heated and the basaltic magma was cooled prior to hybridization. These features are consistent with the development of a thermal diffusive interface between overlying andesitic magma and underlying basaltic magma in a stratified magma chamber.

Kawamoto, Tatsuhiko

1992-02-01

114

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

115

Dispersion of Lamb waves in a honeycomb composite sandwich panel.  

PubMed

Composite materials are increasingly being used in advanced aircraft and aerospace structures. Despite their many advantages, composites are often susceptible to hidden damages that may occur during manufacturing and/or service of the structure. Therefore, safe operation of composite structures requires careful monitoring of the initiation and growth of such defects. Ultrasonic methods using guided waves offer a reliable and cost effective method for defects monitoring in advanced structures due to their long propagation range and their sensitivity to defects in their propagation path. In this paper, some of the useful properties of guided Lamb type waves are investigated, using analytical, numerical and experimental methods, in an effort to provide the knowledge base required for the development of viable structural health monitoring systems for composite structures. The laboratory experiments involve a pitch-catch method in which a pair of movable transducers is placed on the outside surface of the structure for generating and recording the wave signals. The specific cases considered include an aluminum plate, a woven composite laminate and an aluminum honeycomb sandwich panel. The agreement between experimental, numerical and theoretical results are shown to be excellent in certain frequency ranges, providing a guidance for the design of effective inspection systems. PMID:25287973

Baid, Harsh; Schaal, Christoph; Samajder, Himadri; Mal, Ajit

2015-02-01

116

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

NASA Astrophysics Data System (ADS)

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

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

2003-04-01

117

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

118

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

119

Synthetic magnetic fluxes on the honeycomb lattice  

NASA Astrophysics Data System (ADS)

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.

Górecka, Agnieszka; Grémaud, Benoît; Miniatura, Christian

2011-08-01

120

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

121

Vibroacoustic Model Validation for a Curved Honeycomb Composite Panel  

NASA Technical Reports Server (NTRS)

Finite element and boundary element models are developed to investigate the vibroacoustic response of a curved honeycomb composite sidewall panel. Results from vibroacoustic tests conducted in the NASA Langley Structural Acoustic Loads and Transmission facility are used to validate the numerical predictions. The sidewall panel is constructed from a flexible honeycomb core sandwiched between carbon fiber reinforced composite laminate face sheets. This type of construction is being used in the development of an all-composite aircraft fuselage. In contrast to conventional rib-stiffened aircraft fuselage structures, the composite panel has nominally uniform thickness resulting in a uniform distribution of mass and stiffness. Due to differences in the mass and stiffness distribution, the noise transmission mechanisms for the composite panel are expected to be substantially different from those of a conventional rib-stiffened structure. The development of accurate vibroacoustic models will aide in the understanding of the dominant noise transmission mechanisms and enable optimization studies to be performed that will determine the most beneficial noise control treatments. Finite element and boundary element models of the sidewall panel are described. Vibroacoustic response predictions are presented for forced vibration input and the results are compared with experimental data.

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

2001-01-01

122

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

123

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

124

Photoemission study of aluminum/tris-(8-hydroxyquinoline) aluminum and aluminum/LiF/tris-(8-hydroxyquinoline) aluminum interfaces  

NASA Astrophysics Data System (ADS)

We have investigated the interfaces of aluminum on tris-(8-hydroxyquinoline) aluminum (Alq3) and aluminum on LiF/Alq3, using x-ray and ultraviolet photoemission spectroscopy (UPS). Aluminum appears to react destructively with Alq3 causing significant modification of the oxygen, nitrogen, and aluminum spectra. The well-defined UPS spectrum of Alq3 is quickly destroyed by very low coverages of aluminum. With only a 5 Å layer of LiF on the Alq3, the reaction with aluminum is significantly suppressed. The Alq3 molecular orbital features in the UPS shift to higher binding energy but remain easily recognizable. In addition, a well-defined gap-state forms which is significantly different from that produced without LiF. Both the core-level spectra and the gap-state suggest that the Alq3 anion is formed in the presence of aluminum and LiF.

Le, Quoc Toan; Yan, Li; Gao, Yongli; Mason, M. G.; Giesen, D. J.; Tang, C. W.

2000-01-01

125

Honeycomb Betavoltaic Battery for Space Applications  

Microsoft Academic Search

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

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

2008-01-01

126

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

127

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

128

Solar pond with honeycomb surface insulation system  

Microsoft Academic Search

A solar pond consisting of transparent compound honeycomb encapsulated with Teflon film and glass plates at the bottom and top surface respectively, floating on the body of a hot water reservoir is considered and analysed for the heat transfer processes in the system. A mathematical model is developed where the energy balance equation of the convective water is formulated by

M. Arulanantham; P. Avanti; N. D. Kaushika

1997-01-01

129

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

130

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

131

Engineering polar discontinuities in honeycomb lattices  

NASA Astrophysics Data System (ADS)

Unprecedented and fascinating phenomena have been recently observed at oxide interfaces between centrosymmetric cubic materials, where polar discontinuities can give rise to polarization charges and electric fields that drive a metal–insulator transition and the appearance of a two-dimensional electron gas. Lower-dimensional analogues are possible, and honeycomb lattices offer a fertile playground, thanks to their versatility and the extensive ongoing experimental efforts in graphene and related materials. Here we suggest different realistic pathways to engineer polar discontinuities in honeycomb lattices and support these suggestions with extensive first-principles calculations. Several approaches are discussed, based on (i) nanoribbons, where a polar discontinuity against the vacuum emerges, and (ii) functionalizations, where covalent ligands are used to engineer polar discontinuities by selective or total functionalization of the parent systems. All the cases considered have the potential to deliver innovative applications in ultra-thin and flexible solar-energy devices and in micro- and nano-electronics.

Gibertini, Marco; Pizzi, Giovanni; Marzari, Nicola

2014-10-01

132

Interacting electrons on trilayer honeycomb lattices  

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

133

Development of a smart-skin phased array system with a honeycomb sandwich microstrip antenna  

NASA Astrophysics Data System (ADS)

We develop a smart-skin phased array antenna (PAA) with a scanning beam and cover the design, fabrication and testing of the smart-skin antenna structure, the phase shifter and electronic beam scanning. The smart skin is an organic honeycomb sandwich structure in which microstrip antennas are embedded that radiate a radio-frequency (RF) signal. The structure has excellent structural performance as a result of sandwich effects by facesheets and a honeycomb core. For ease of array feeding, the antenna element is excited by means of a coaxial probe. A stacked patch is used in order to increase the bandwidth. Electronic beam scanning is accomplished with a 4-bit digital phase shifter. The PAA design is processed at a center frequency of 7.5 GHz, a bandwidth exceeding 500 MHz, linear polarization and a scanning range of ± 45°. Performance is confirmed from experimental measurements made on a fabricated test model.

Son, Seong Ho; Eom, Soon Young; Hwang, Woonbong

2008-06-01

134

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

135

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 ...

136

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

137

Experimental Analysis and Modeling of the Crushing of Honeycomb Cores  

Microsoft Academic Search

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 designers main problem. Since this type of impact has the same effect as quasi-static indentation, the study focuses on the behavior

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

2005-01-01

138

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

139

Mechanics and Applications of Pressure Adaptive Honeycomb  

E-print Network

pressure and constant mass of air in the pouches, the maximum mass specific energy amounts to 1.1J/g and a max- imum blocked force of 70kPa can be attained. Pressure adaptive honeycomb was embedded into a 25%c adaptive flap on a NACA2412 wing section...P specific heat constant at constant volume J/K ~ tnatsnoC Dissipation or Drag coefficient ~ ~ tneiciffeoc noitcirF Wing or vehicle lift coefficient ~ ~ tneiciffeoc sserts raehS N garD Internal energy J Young?s modulus or energy N/m 2 , J...

Vos, Roelof

2009-07-31

140

Magnetic edge anisotropy in graphenelike honeycomb crystals.  

PubMed

The independent predictions of edge ferromagnetism and the quantum spin Hall phase in graphene have inspired the quest of other two-dimensional honeycomb systems, such as silicene, germanene, stanene, iridates, and organometallic lattices, as well as artificial superlattices, all of them with electronic properties analogous to those of graphene, but a larger spin-orbit coupling. Here, we study the interplay of ferromagnetic order and spin-orbit interactions at the zigzag edges of these graphenelike systems. We find an in-plane magnetic anisotropy that opens a gap in the otherwise conducting edge channels that should result in large changes of electronic properties upon rotation of the magnetization. PMID:25062225

Lado, J L; Fernández-Rossier, J

2014-07-11

141

Magnetic Edge Anisotropy in Graphenelike Honeycomb Crystals  

NASA Astrophysics Data System (ADS)

The independent predictions of edge ferromagnetism and the quantum spin Hall phase in graphene have inspired the quest of other two-dimensional honeycomb systems, such as silicene, germanene, stanene, iridates, and organometallic lattices, as well as artificial superlattices, all of them with electronic properties analogous to those of graphene, but a larger spin-orbit coupling. Here, we study the interplay of ferromagnetic order and spin-orbit interactions at the zigzag edges of these graphenelike systems. We find an in-plane magnetic anisotropy that opens a gap in the otherwise conducting edge channels that should result in large changes of electronic properties upon rotation of the magnetization.

Lado, J. L.; Fernández-Rossier, J.

2014-07-01

142

Mechanical properties of Nomex material and Nomex honeycomb structure  

Microsoft Academic Search

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

Choon Chiang Foo; Gin Boay Chai; Leong Keey Seah

2007-01-01

143

Classification of defects in honeycomb composite structure of helicopter rotor blades  

NASA Astrophysics Data System (ADS)

The use of non-destructive testing methods to qualify the state of rotor blades with respect to their expected flight hours, with the aim to extend their lifetime without any risk of breakdown, is an important financial demand. In order to detect the possible defects in the composite structure of Mi-8 and Mi-24 type helicopter rotor blades used by the Hungarian Army, we have performed combined neutron- and X-ray radiography measurements at the Budapest Research Reactor. Several types of defects were detected, analysed and typified. Among the most frequent and important defects observed were cavities, holes and/or cracks in the sealing elements on the interface of the honeycomb structure and the section boarders. Inhomogeneities of the resin materials (resin-rich or starved areas) at the core-honeycomb surfaces proved to be an other important point. Defects were detected at the adhesive filling, and water percolation was visualized at the sealing interfaces of the honeycomb sections. Corrosion effects, and metal inclusions have also been detected.

Balaskó, M.; Sváb, E.; Molnár, Gy.; Veres, I.

2005-04-01

144

Local feedback control of light honeycomb panels.  

PubMed

This paper summarizes theoretical and experimental work on the feedback control of sound radiation from honeycomb panels using piezoceramic actuators. It is motivated by the problem of sound transmission in aircraft, specifically the active control of trim panels. Trim panels are generally honeycomb structures designed to meet the design requirement of low weight and high stiffness. They are resiliently mounted to the fuselage for the passive reduction of noise transmission. Local coupling of the closely spaced sensor and actuator was observed experimentally and modeled using a single degree of freedom system. The effect of the local coupling was to roll off the response between the actuator and sensor at high frequencies, so that a feedback control system can have high gain margins. Unfortunately, only relatively poor global performance is then achieved because of localization of reduction around the actuator. This localization prompts the investigation of a multichannel active control system. Globalized reduction was predicted using a model of 12-channel direct velocity feedback control. The multichannel system, however, does not appear to yield a significant improvement in the performance because of decreased gain margin. PMID:17297778

Hong, Chinsuk; Elliott, Stephen J

2007-01-01

145

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

146

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

147

Crystallography of rare galactic honeycomb structure near supernova 1987a  

NASA Technical Reports Server (NTRS)

Near supernova 1987a, the rare honeycomb structure of 20-30 galactic bubbles measures 30 x 90 light years. Its remarkable regularity in bubble size suggests a single-event origin which may correlate with the nearby supernova. To test the honeycomb's regularity in shape and size, the formalism of statistical crystallography is developed here for bubble sideness. The standard size-shape relations (Lewis's law, Desch's law, and Aboav-Weaire's law) govern area, perimeter and nearest neighbor shapes. Taken together, they predict a highly non-equilibrium structure for the galactic honeycomb which evolves as a bimodal shape distribution without dominant bubble perimeter energy.

Noever, David A.

1994-01-01

148

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

149

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.

Reuben H. Fleet Science Center

1999-01-01

150

Simulation of the honeycomb construction process  

NASA Astrophysics Data System (ADS)

The construction process of the honeycomb by bees is an astonishing process. The original structure which the bees built is nothing more than a lot of rough cylinders. But keeping the beeswax semi-flow for a certain time, those rough structures become perfect hexahedral columns. A modified, simplified particle method was used here to simulate the semi-flow state of the material. Although the parameters used here were still rather subjective, the simulation still could demonstrate some behavior of that sort of material like beeswax. And the method that the bees used to build their honey comb, could be an efficient method to imitate when we are trying to manufacture cellular materials.

Yuanzhang, Zhang

2010-06-01

151

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

152

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

153

Nuclear design analysis of square-lattice honeycomb space nuclear rocket engine  

NASA Astrophysics Data System (ADS)

The square-lattice honeycomb reactor is designed based on a cylindrical core that is determined to have critical diameter and length of 0.50 m and 0.50 c, respectively. A 0.10-cm thick radial graphite reflector, in addition to a 0.20-m thick axial graphite reflector are used to reduce neutron leakage from the reactor. The core is fueled with solid solution of 93% enriched (U, Zr, Nb)C, which is one of several ternary uranium carbides that are considered for this concept. The fuel is to be fabricated as 2 mm grooved (U, Zr, Nb)C wafers. The fuel wafers are used to form square-lattice honeycomb fuel assemblies, 0.10 m in length with 30% cross-sectional flow area. Five fuel assemblies are stacked up axially to form the reactor core. Based on the 30% void fraction, the width of the square flow channel is about 1.3 mm. The hydrogen propellant is passed through these flow channels and removes the heat from the reactor core. To perform nuclear design analysis, a series of neutron transport and diffusion codes are used. The preliminary results are obtained using a simple four-group cross-section model. To optimize the nuclear design, the fuel densities are varied for each assembly. Tantalum, hafnium and tungsten are considered and used as a replacement for niobium in fuel material to provide water submersion sub-criticality for the reactor. Axial and radial neutron flux and power density distributions are calculated for the core. Results of the neutronic analysis indicate that the core has a relatively fast spectrum. From the results of the thermal hydraulic analyses, eight axial temperature zones are chosen for the calculation of group average cross-sections. An iterative process is conducted to couple the neutronic calculations with the thermal hydraulics calculations. Results of the nuclear design analysis indicate that a compact core can be designed based on ternary uranium carbide square-lattice honeycomb fuel. This design provides a relatively high thrust to weight ratio.

Widargo, Reza; Anghaie, Samim

1999-01-01

154

Thermal hydraulic design analysis of ternary carbide fueled square-lattice honeycomb nuclear rocket engine  

SciTech Connect

A computational analysis is conducted to determine the optimum thermal-hydraulic design parameters for a square-lattice honeycomb nuclear rocket engine core that will incorporate ternary carbide based uranium fuels. Recent studies at the Innovative Nuclear Space Power and Propulsion Institute (INSPI) have demonstrated the feasibility of processing solid solution, ternary carbide fuels such as (U, Zr, Nb)C, (U, Zr, Ta)C, (U, Zr, Hf)C and (U, Zr, W)C. The square-lattice honeycomb design provides high strength and is amenable to the processing complexities of these ultrahigh temperature fuels. A parametric analysis is conducted to examine how core geometry, fuel thickness and the propellant flow area effect the thermal performance of the nuclear rocket engine. The principal variables include core size (length and diameter) and fuel element dimensions. The optimum core configuration requires a balance between high specific impulse and thrust level performance, and maintaining the temperature and strength limits of the fuel. A nuclear rocket engine simulation code is developed and used to examine the system performance as well as the performance of the main reactor core components. The system simulation code was originally developed for analysis of NERVA-Derivative and Pratt and Whitney XNR-2000 nuclear thermal rockets. The code is modified and adopted to the square-lattice geometry of the new fuel design. Thrust levels ranging from 44,500 to 222,400 N (10,000 to 50,000 lbf) are considered. The average hydrogen exit temperature is kept at 2800 K, which is well below the melting point of these fuels. For a nozzle area ratio of 300 and a thrust chamber pressure of 4.8 Mpa (700 psi), the specific impulse is 930 s. Hydrogen temperature and pressure distributions in the core and the fuel maximum temperatures are calculated.

Furman, Eric M.; Anghaie, Samim [Innovative Nuclear Space Power and Propulsion Institute, University of Florida, Gainesville, Florida 32611 (United States)

1999-01-22

155

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

156

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

157

Low voltage reversible electrowetting exploiting lubricated polymer honeycomb substrates  

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

158

Low Voltage Reversible Electrowetting Exploiting Lubricated Polymer Honeycomb Substrates  

E-print Network

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

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

2014-06-16

159

New concept in brazing metallic honeycomb panels  

NASA Technical Reports Server (NTRS)

Aluminum oxide coating provides surface which will not be wetted by brazing alloy and which stops metallic diffusion welding of tooling materials to part being produced. This method eliminates loss of tooling materials and parts from braze wetting and allows fall-apart disassembly of tooling after brazing.

Carter, P. D.; Layton, R. E.; Stratton, F. W.

1973-01-01

160

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

161

Demonstration of aluminum in amyloid fibers in the cores of senile plaques in the brains of patients with Alzheimer’s disease  

Microsoft Academic Search

Aluminum (Al) exposure has been reported to be a risk factor for Alzheimer’s disease (senile dementia of Alzheimer type), although the role of Al in the etiology of Alzheimer’s disease remains controversial. We examined the presence of Al in the Alzheimer’s brain using energy-dispersive X-ray spectroscopy combined with transmission electron microscopy (TEM-EDX). TEM-EDX analysis allows simultaneous imaging of subcellular structures

Sakae Yumoto; Shigeo Kakimi; Akihiro Ohsaki; Akira Ishikawa

2009-01-01

162

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

163

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

164

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.

165

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

166

Methods for removing honeycomb noise from fiber endoscopic images  

NASA Astrophysics Data System (ADS)

The fiber-endoscope has been widely used in medicine. The image fiber bundle usually has pixels from several thousands to tens of thousand. Because of the non-transparent wall cladding of individual fibers, the images putout by the image fiber bundle present honeycomb pattern (noise). It will influence the image visual effect, so it is very important to find methods to remove these honeycomb noise and improve the image quality. In this paper, three methods were used to process the fiber-endoscopic images for removing the honeycomb noise. First, low-pass spatial filtering mask was used to process the image. Secondly, the image special frequency was gotten by Fourier transform, and the honeycomb pattern frequency is separated from the image message. It's possible to remove these honeycomb pattern frequency without degrading the image quality. Finally, the linear interpolation method was used to process the image. We compared the processing results of these methods. These methods can be used in real color images as well as gray level images.

Fang, Fang; Lin, Meirong; Guo, Yu; Zhang, Yue; Zhong, Xianghong; Zhang, Baozheng

2000-10-01

167

Aluminum alloy  

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

168

Thermal performance of solar air collector with transparent honeycomb made of glass tube  

Microsoft Academic Search

Transparent honeycomb structure with thin-walled glass tube as the honeycomb unit is designed and applied to a flat-plate\\u000a solar air collector. Experiments are performed for solar collectors with six different honeycomb sizes. The emphasis is to\\u000a study the effects of diameter and aspect ratio of the honeycomb unit on the transmittance and efficiency of the solar collector.\\u000a It is shown

ZhiQiang Zhang; Ran Zuo; Ping Li; WenJia Su

2009-01-01

169

Topology optimization of pressure adaptive honeycomb for a morphing flap  

NASA Astrophysics Data System (ADS)

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

Vos, Roelof; Scheepstra, Jan; Barrett, Ron

2011-03-01

170

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

171

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...

172

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

173

Structural performance of metallic sandwich beams with hollow truss cores  

E-print Network

the core [13,14]. Any open cell metallic structure that allows coolant flow can be used as a heat exchange strong lightweight designs and to enable performance comparisons with other sandwich structures. Ã? 2006; Lightweight structures; Hollow tube core 1. Introduction Metallic sandwich panels with various honeycomb, lat

Wadley, Haydn

174

Honeycomb superlattice pattern in a dielectric barrier discharge in argon/air  

NASA Astrophysics Data System (ADS)

We report on a honeycomb superlattice pattern in a dielectric barrier discharge in argon/air for the first time. It consists of hexagon lattice and honeycomb framework and bifurcates from a hexagon pattern as the applied voltage increases. A phase diagram of the pattern as a function of the gas component and gas pressure is presented. The instantaneous images show that the hexagon lattice and honeycomb framework are ignited in turn in each half voltage cycle. The honeycomb framework is composed of filaments ignited randomly. The spatiotemporal dynamics of honeycomb superlattice pattern is discussed by wall charges.

Zhu, Ping; Dong, Lifang; Yang, Jing; Gao, Yenan; Wang, Yongjie; Li, Ben

2015-02-01

175

Topological phase transitions in the non-Abelian honeycomb lattice  

Microsoft Academic Search

Ultracold Fermi gases trapped in honeycomb optical lattices provide an intriguing scenario, where relativistic quantum electrodynamics (QED) can be tested. Here, we generalize this system to non-Abelian QED, where massless Dirac fermions interact with effective non-Abelian gauge fields. We show how in this setup a variety of topological phase transitions occur, which arise due to massless fermion pair production events,

A. Bermudez; N. Goldman; A. Kubasiak; M. Lewenstein; M. A. Martin-Delgado

2010-01-01

176

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

177

Pressure adaptive honeycomb: a new adaptive structure for aerospace applications  

Microsoft Academic Search

A new type of adaptive structure is presented that relies on pressurized honeycomb cells that extent a significant length with respect to the plane of the hexagons. By varying the pressure inside each of the cells, the stiffness can be altered. A variable stiffness in combination with an externally applied force field results in a fully embedded pressure adaptive actuator

Roelof Vos; Ron Barrett

2010-01-01

178

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

179

EVALUATION OF THE MATERIAL PROPERTIES OF RESIN-IMPREGNATED NOMEX PAPER AS BASIS FOR THE SIMULATION OF THE IMPACT BEHAVIOUR OF HONEYCOMB SANDWICH  

Microsoft Academic Search

Driven by stringent weight saving requirements composite sandwich construction has evolved as one of the basic structural design concepts for load-carrying components of advanced aeroplanes and helicopters. Particularly, sandwich using laminated carbon fibre reinforced plastics (CFRP) as face sheets and NOMEX honeycombs as core material is increasingly used due to features such as high strength-to-weight and stiffness-to-weight ratios as well

Falk Hähnel; Klaus Wolf

180

Recycling of automotive aluminum  

Microsoft Academic Search

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

Jirang CUI; Hans J. ROVEN

2010-01-01

181

Service evaluation of Aluminum-Brazed Titanium (ABTi) jet engine tailpipe extensions  

NASA Technical Reports Server (NTRS)

Aluminum-brazed titanium (ABTi) jet engine tailpipe extensions were evaluated in commercial service over a 3-year period. The purpose of the evaluation was to determine the corrosion resistance of ABTi in acoustic applications (i.e., honeycomb sandwich incorporating a perforated inner skin). The results showed that ABTi does not have acceptable corrosion resistance in acoustic applications under severe operating conditions, but may be acceptable for acoustic applications in less severe environments.

Elrod, S. D.

1982-01-01

182

Fatigue and impact properties of metal honeycomb sandwich panel  

NASA Astrophysics Data System (ADS)

Honeycomb sandwich structures are significant to be used as applied to thermal protection system on reusable launch vehicle. In this paper the fatigue and impact properties of a novel metallic thermal protection material have been investigated and predicted at room temperature. A series of strength tests are carried out to obtain parameters firstly for further experiments. A set of tension-tension stress fatigue tests and impact tests based on split-Hopkinson pressure bar are carried out. Different high strain rate impact experiments are accomplished. The curves of dynamical stress, strain and strain rate are obtained. Also the cell units images after impact are presented. The results show the fatigue properties of honeycomb sandwich panels are comparatively better. And it has the advantages of anti-impact resistance and high, energy absorption capability.

Zou, Guang ping; Lu, Jie; Liang, Jun; Chang, Zhong liang

2008-11-01

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

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

185

Adsorption-induced strain of a nanoscale silicon honeycomb  

NASA Astrophysics Data System (ADS)

We report on systematic measurements of both adsorption and anisotropic mechanical deformations of mesoporous silicon, using heptane at room temperature. Porous Si obtained from highly doped (100) Si can be thought of as a nanoscale random honeycomb with pores parallel to the [001] axis. We show that strains ?\\parallel and ?\\bot measured along and transversely to the pore axis exhibit a hysteretic behavior as a function of the fluid pressure, which is due to the hysteresis in fluid adsorption. The pressure dependence of the strains together with the independent measurement of the transverse stress, allows us to determine the biaxial transverse modulus and to estimate the longitudinal Young's modulus of porous Si. We argue that the value of these constants implies that Young's modulus of the 6 nm thick walls of the honeycomb is about 5 times smaller than that of bulk silicon, striking evidence of finite-size effects.

Grosman, A.; Puibasset, J.; Rolley, E.

2015-03-01

186

Monolithic fuel cell development. [Honeycomb of small cells  

SciTech Connect

A new fuel cell design, called the ''monolithic fuel cell,'' is being developed at Argonne. The monolithic design employs the same thin ceramic components used in other oxide fuel cells in a strong, lightweight honeycomb structure of small cells, and thus can achieve very high power per unit mass or volume. The light weight and low volume, as well as the efficiency and reliability of electrical systems, are advantageous in space and terrestrial systems.

Fee, D.C.; Blackburn, P.E.; Busch, D.E.; Claar, T.D.; Dees, D.W.; Dusek, J.; Easler, T.E.; Ellingson, W.A.; Flandermeyer, B.K.; Fousek, R.J.

1986-01-01

187

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

188

Site dilution of quantum spins in the honeycomb lattice  

Microsoft Academic Search

We consider the effect of random site dilution on a honeycomb lattice of quantum spins described by the antiferromagnetic Heisenberg spin- S model. Using linear spin-wave theory, we compute the zero-temperature magnetization and density of states as a function of dilution up to the classical percolation threshold. Several subtle issues regarding the treatment of quasidivergent zero-energy modes, which appear in

Eduardo V. Castro; N. M. R. Peres; K. S. D. Beach; Anders W. Sandvik

2006-01-01

189

Site dilution of quantum spins in the honeycomb lattice  

Microsoft Academic Search

We discuss the effect of site dilution on both the magnetization and the density of states of quantum spins in the honeycomb lattice, described by the antiferromagnetic Heisenberg spin-S model. Since the disorder introduced by the dilution process breaks translational invariance, the model has to be solved in real space. For this purpose a real-space Bogoliubov-Valatin transformation is used. In

Eduardo V. Castro; N. M. R. Peres; K. S. D. Beach; Anders W. Sandvik

2005-01-01

190

Site dilution of quantum spins in the honeycomb lattice  

Microsoft Academic Search

We discuss the effect of site dilution on both the magnetization and the\\u000adensity of states of quantum spins in the honeycomb lattice, described by the\\u000aantiferromagnetic Heisenberg spin-S model. For this purpose a real-space\\u000aBogoliubov-Valatin transformation is used. In this work we show that for the\\u000aS>1\\/2 the system can be analyzed in terms of linear spin wave theory.

Eduardo V. Castro; N. M. R. Peres; K. S. D. Beach; Anders W. Sandvik

2006-01-01

191

In-plane crushing of a polycarbonate honeycomb  

Microsoft Academic Search

The in-plane compressive response and crushing of a polycarbonate honeycomb with circular close-packed cells is studied through combined experimental and analytical efforts. Under displacement controlled quasi-static loading the response is characterized by a relatively sharp rise to a load maximum followed by a drop down to an extended load plateau which is then terminated by a sharp rise in load.

Scott D. Papka; Stelios Kyriakides

1998-01-01

192

CO2 adsorption equilibria of the honeycomb zeolite beds  

Microsoft Academic Search

The CO2 adsorption equilibria of the honeycomb zeolite beds consisting of MS-13X or MS-4A were determined from breakthrough curves for various CO2-N2 mixtures, and the fitness of the Dubinin-Astakhov equation (Dubinin MM, Astakhov VA. Description of adsorption equilibria of vapors on zeolite over wide ranges of temperature and pressure. In: Flanigen M, Sand LB, editors. Molecular sieves zeolite II. Washington:

K. Kamiuto; Ermalina; K. Ihara

2001-01-01

193

CO 2 adsorption equilibria of the honeycomb zeolite beds  

Microsoft Academic Search

The CO2 adsorption equilibria of the honeycomb zeolite beds consisting of MS-13X or MS-4A were determined from breakthrough curves for various CO2–N2 mixtures, and the fitness of the Dubinin–Astakhov equation (Dubinin MM, Astakhov VA. Description of adsorption equilibria of vapors on zeolite over wide ranges of temperature and pressure. In: Flanigen M, Sand LB, editors. Molecular sieves zeolite II. Washington:

K. Kamiuto; Ermalina; K. Ihara

2001-01-01

194

On stiffness properties of square honeycombs and other unidirectional composites  

Microsoft Academic Search

In this paper we consider stiffness properties of square symmetric unidirectional two-phase composites with given volume fractions. First, we compare the effective moduli of the stiffest possible (or softest possible) of such materials which satisfy transverse isotropy or square isotropy with that of materials satisfying 3D-isotropy.Next, we present some numerical FEM computations of in-plane stiffness properties of square honeycombs. Our

Stein A. Berggren; Dag Lukkassen; Annette Meidell; Leon Simula

2001-01-01

195

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

196

Commercial application of aluminum honeycomb and foam in load bearing tubular structures  

E-print Network

Small dimension engineering tubular structures subjected to a complex load system are designed like hollow circular shells. For minimum weight design, the ratio between the shell radius and the thickness has to be as large ...

Bartolucci, Stefano, 1976-

2004-01-01

197

Accordion-Like Honeycombs for Tissue Engineering of Cardiac Anisotropy  

PubMed Central

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

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

2008-01-01

198

Arsenene: Two-dimensional buckled and puckered honeycomb arsenic systems  

NASA Astrophysics Data System (ADS)

Recently, phosphorene, a monolayer honeycomb structure of black phosphorus, was experimentally manufactured and has attracted rapidly growing interest. Motivated by phosphorene, here we investigate the stability and electronic properties of the honeycomb structure of the arsenic system based on first-principles calculations. Two types of honeycomb structures, buckled and puckered, are found to be stable. We call them arsenenes, as in the case of phosphorene. We find that both buckled and puckered arsenenes possess indirect gaps. We show that the band gap of puckered and buckled arsenenes can be tuned by applying strain. The gap closing occurs at 6% strain for puckered arsenene, where the bond angles between the nearest neighbors become nearly equal. An indirect-to-direct gap transition occurs by applying strain. Specifically, 1% strain is enough to transform puckered arsenene into a direct-gap semiconductor. We note that a bulk form of arsenic called gray arsenic exists which can be used as a precursor for buckled arsenene. Our results will pave the way for applications to light-emitting diodes and solar cells.

Kamal, C.; Ezawa, Motohiko

2015-02-01

199

Pressure adaptive honeycomb: a new adaptive structure for aerospace applications  

NASA Astrophysics Data System (ADS)

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

Vos, Roelof; Barrett, Ron

2010-04-01

200

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

201

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

NASA Technical Reports Server (NTRS)

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

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

2014-01-01

202

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

Microsoft Academic Search

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

Domhnaill Hernon; Alcatel-Lucent Ireland

2010-01-01

203

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

204

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

205

Spring back of infinite honeycomb sheets beyond plastic deformation  

NASA Astrophysics Data System (ADS)

Cellular structures are promising for applications where high stiffness and strength are required with the minimal use of material. They are often used in applications where the plastic deformation plays an important role, such as those involving crashworthiness, energy absorption, and stents. The elastic analysis of a honeycomb sheet has been carried out in the past [1]. The present analysis extends this classical work in the elasto-plastic regime. Recoil analysis due to elastic recovery is absent from the published literature. This work aims to develop an analytical model to calculate the spring back for a simplified case, that of an infinite honeycomb sheet. An elastic-perfectly plastic material model is assumed. The recoil for a clamped beam with a load and moment applied at the free edge is analytically calculated first. This is carried out by relating the stress distribution of the cross section to the final deformed shape. The part corresponding to the elastic contribution is subsequently subtracted in order to obtain the final configuration after the external load is removed. This simple elasto-plastic analysis is then incorporated into the analysis of an infinite sheet made of uniform hexagonal cells. The translational symmetry of the lattice is exploited along with the analysis of a beam under tip loading through to plastic stage and recoil. The final shape of the struts upon the removal of the remote stress is completely determined by the plastic deformation which cannot be recovered. The expression for the beam thus obtained is then used to build an analytical model for an infinite honeycomb sheet loaded in both directions.

Bonfanti, A.; Bhaskar, A.

2015-02-01

206

Repair of boron/aluminum composites  

NASA Technical Reports Server (NTRS)

A program was performed to determine the repairability of boron/aluminum aerospace structural components. During the program, a list of repair guidelines was prepared to aid in determining the proper repair techniques for a given structure. These guidelines included specifying types of repair material and their applicability, corrosion prevention procedures, design criteria, and inspection criteria. Six sets of boron/aluminum structural components were repaired and tested to compare as-fabricated and repaired performance. The specimens included a honeycomb-stiffened panel, elastically buckled tubes, a skin-stringer panel, a tube combining bending and tension, a splice joint specimen, and a tension field panel. All but one set of specimens, when repaired, exceeded the strength of the original specimens. The repairs resulted in an average weight increase per structure of 9% and an average performance increase of 27%. It is concluded that metal-matrix composite material, damaged in service, can be repaired by techniques not very different from those currently in use for conventional materials.

Christian, J. L.; Miller, M. F.; Doyal, F. H.

1975-01-01

207

Topological phase transitions in the non-Abelian honeycomb lattice  

E-print Network

Ultracold Fermi gases trapped in honeycomb optical lattices provide an intriguing scenario, where relativistic quantum electrodynamics can be tested. Here, we generalize this system to non-Abelian quantum electrodynamics, where massless Dirac fermions interact with effective non-Abelian gauge fields. We show how in this setup a variety of topological phase transitions occur, which arise due to massless fermion pair production events, as well as pair annihilation events of two kinds: spontaneous and strongly-interacting induced. Moreover, such phase transitions can be controlled and characterized in optical lattice experiments.

A. Bermudez; N. Goldman; A. Kubasiak; M. Lewenstein; M. A. Martin-Delgado

2010-03-25

208

Topological phase transitions in the non-Abelian honeycomb lattice  

E-print Network

Ultracold Fermi gases trapped in honeycomb optical lattices provide an intriguing scenario, where relativistic quantum electrodynamics can be tested. Here, we generalize this system to non-Abelian quantum electrodynamics, where massless Dirac fermions interact with effective non-Abelian gauge fields. We show how in this setup a variety of topological phase transitions occur, which arise due to massless fermion pair production events, as well as pair annihilation events of two kinds: spontaneous and strongly-interacting induced. Moreover, such phase transitions can be controlled and characterized in optical lattice experiments.

Bermudez, A; Kubasiak, A; Lewenstein, M; Martín-Delgado, M A

2009-01-01

209

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

210

Phase diagram of the honeycomb bilayer from functional renormalization  

NASA Astrophysics Data System (ADS)

The phase diagram for interacting electrons on the honeycomb bilayer with Bernal stacking is explored by means of the functional renormalization group. For half-filling and including a range of repulsive onsite, nearest-neighbor and next-to-nearest neighbor interactions we analyze the emergent instabilities and find antiferromagnetic, two types of charge-density-waves and quantum spin Hall order. The presented phase diagram covers the relevant region for the bilayer graphene parameters which overlaps with the phase boundary between the antiferromagnetic state and the quantum spin Hall state. We comment on the effect of small dopings.

Scherer, Michael; Uebelacker, Stefan; Honerkamp, Carsten

2012-02-01

211

Deconfined criticality in the frustrated Heisenberg honeycomb antiferromagnet.  

PubMed

Using the density matrix renormalization group, we determine the phase diagram of the spin-1/2 Heisenberg antiferromagnet on a honeycomb lattice with a nearest-neighbor interaction J(1) and a frustrating, next-nearest-neighbor exchange J(2). As frustration increases, the ground state exhibits Néel, plaquette, and dimer orders, with critical points at J(2)/J(1) = 0.22 and 0.35. We observe that both the spin gap and the corresponding order parameters vanish continuously at both the critical points, indicating the presence of deconfined quantum criticality. PMID:25166838

Ganesh, R; van den Brink, Jeroen; Nishimoto, Satoshi

2013-03-22

212

Nanomechanics of Graphene, Silicene and Boron Nitride ribbons: From honeycomb structure to atomic chains  

Microsoft Academic Search

This first-principles study of elastic and plastic deformation of graphene, silicene and boron nitride (BN) honeycomb nanoribbons under uniaxial tension reveals interesting features. In the course of stretching, the electronic and magnetic properties can be strongly modified. Under plastic deformation, the honeycomb structure changes irreversibly and offers a number of new structures and functionalities. Interesting cage like structures, even suspended

Mehmet Topsakal; Salim Ciraci

2010-01-01

213

Evidence of Silicene in Honeycomb Structures of Silicon on Ag(111) Baojie Feng,  

E-print Network

Evidence of Silicene in Honeycomb Structures of Silicon on Ag(111) Baojie Feng, Zijing Ding, Sheng 100081, China ABSTRACT: In the search for evidence of silicene, a two- dimensional honeycomb lattice is believed to be the most suitable substrate for growth of silicene so far. In this work we report

Wang, Wei Hua

214

Properties of a chiral honeycomb with a Poisson's ratio -1 D. Prall, R. S. Lakes  

E-print Network

Properties of a chiral honeycomb with a Poisson's ratio -1 D. Prall, R. S. Lakes Int. J of re-entrant structures. These are unique honeycombs and foams which exhibit negative Poisson's ratios of the above type require some form of individual assembly. Foam materials with a negative Poisson's ratio

Lakes, Roderic

215

Nondestructive testing techniques used in analysis of honeycomb structure bond strength  

NASA Technical Reports Server (NTRS)

DOT /Driver-Displacement Oriented Transducer/, applicable to both lap shear type application and honeycomb sandwich structures, measures the displacement of the honeycomb composite face sheet. It incorporates an electromagnetic driver and a displacement measuring system into a single unit to provide noncontact bond strength measurements.

Erdman, D. C.; Martin, G.; Moore, J. F.; Thomas, G.; Varney, H. S.

1967-01-01

216

PHYSICAL REVIEW B 83, 245414 (2011) Monte Carlo study of the honeycomb structure of anthraquinone molecules on Cu(111)  

E-print Network

PHYSICAL REVIEW B 83, 245414 (2011) Monte Carlo study of the honeycomb structure of anthraquinone model, we demonstrate a mechanism for the spontaneous formation of honeycomb structure of anthraquinone­13 Pawin et al.14 observed the spontaneous formation of honeycomb structures of anthraquinone (AQ

Einstein, Theodore L.

217

Simulated effect on the compressive and shear mechanical properties of bionic integrated honeycomb plates.  

PubMed

Honeycomb plates can be applied in many fields, including furniture manufacturing, mechanical engineering, civil engineering, transportation and aerospace. In the present study, we discuss the simulated effect on the mechanical properties of bionic integrated honeycomb plates by investigating the compressive and shear failure modes and the mechanical properties of trabeculae reinforced by long or short fibers. The results indicate that the simulated effect represents approximately 80% and 70% of the compressive and shear strengths, respectively. Compared with existing bionic samples, the mass-specific strength was significantly improved. Therefore, this integrated honeycomb technology remains the most effective method for the trial manufacturing of bionic integrated honeycomb plates. The simulated effect of the compressive rigidity is approximately 85%. The short-fiber trabeculae have an advantage over the long-fiber trabeculae in terms of shear rigidity, which provides new evidence for the application of integrated bionic honeycomb plates. PMID:25746272

He, Chenglin; Chen, Jinxiang; Wu, Zhishen; Xie, Juan; Zu, Qiao; Lu, Yun

2015-05-01

218

Topological states in multi-orbital HgTe honeycomb lattices.  

PubMed

Research on graphene has revealed remarkable phenomena arising in the honeycomb lattice. However, the quantum spin Hall effect predicted at the K point could not be observed in graphene and other honeycomb structures of light elements due to an insufficiently strong spin-orbit coupling. Here we show theoretically that 2D honeycomb lattices of HgTe can combine the effects of the honeycomb geometry and strong spin-orbit coupling. The conduction bands, experimentally accessible via doping, can be described by a tight-binding lattice model as in graphene, but including multi-orbital degrees of freedom and spin-orbit coupling. This results in very large topological gaps (up to 35?meV) and a flattened band detached from the others. Owing to this flat band and the sizable Coulomb interaction, honeycomb structures of HgTe constitute a promising platform for the observation of a fractional Chern insulator or a fractional quantum spin Hall phase. PMID:25754462

Beugeling, W; Kalesaki, E; Delerue, C; Niquet, Y-M; Vanmaekelbergh, D; Smith, C Morais

2015-01-01

219

Topological states in multi-orbital HgTe honeycomb lattices  

PubMed Central

Research on graphene has revealed remarkable phenomena arising in the honeycomb lattice. However, the quantum spin Hall effect predicted at the K point could not be observed in graphene and other honeycomb structures of light elements due to an insufficiently strong spin–orbit coupling. Here we show theoretically that 2D honeycomb lattices of HgTe can combine the effects of the honeycomb geometry and strong spin–orbit coupling. The conduction bands, experimentally accessible via doping, can be described by a tight-binding lattice model as in graphene, but including multi-orbital degrees of freedom and spin–orbit coupling. This results in very large topological gaps (up to 35?meV) and a flattened band detached from the others. Owing to this flat band and the sizable Coulomb interaction, honeycomb structures of HgTe constitute a promising platform for the observation of a fractional Chern insulator or a fractional quantum spin Hall phase. PMID:25754462

Beugeling, W.; Kalesaki, E.; Delerue, C.; Niquet, Y.-M.; Vanmaekelbergh, D.; Smith, C. Morais

2015-01-01

220

Topological states in multi-orbital HgTe honeycomb lattices  

NASA Astrophysics Data System (ADS)

Research on graphene has revealed remarkable phenomena arising in the honeycomb lattice. However, the quantum spin Hall effect predicted at the K point could not be observed in graphene and other honeycomb structures of light elements due to an insufficiently strong spin–orbit coupling. Here we show theoretically that 2D honeycomb lattices of HgTe can combine the effects of the honeycomb geometry and strong spin–orbit coupling. The conduction bands, experimentally accessible via doping, can be described by a tight-binding lattice model as in graphene, but including multi-orbital degrees of freedom and spin–orbit coupling. This results in very large topological gaps (up to 35?meV) and a flattened band detached from the others. Owing to this flat band and the sizable Coulomb interaction, honeycomb structures of HgTe constitute a promising platform for the observation of a fractional Chern insulator or a fractional quantum spin Hall phase.

Beugeling, W.; Kalesaki, E.; Delerue, C.; Niquet, Y.-M.; Vanmaekelbergh, D.; Smith, C. Morais

2015-03-01

221

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

222

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

223

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

224

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

225

The Hamiltonian Laceability of some Generalized Honeycomb Tori  

SciTech Connect

Assume that m, n and s are integers with m{>=}2, n{>=}4, 0{<=}s{<=}n and s is of the same parity of m. The generalized honeycomb torus GHT (m,n,s) is recognized as another attractive alternative to existing torus interconnection networks in parallel and distributed applications. It is known that any GHT (m,n,s) is 3-regular, hamiltonian, bipartite graph. We are interested in two special types of the generalized honeycomb torus, GHT (m,n,(n/2)) and GHT (m,n,0). Let G = GHT(m,n,s), where s(set-membership sign){l_brace}(n/2),0{r_brace}. We prove that any G is hamiltonian laceable. More precisely, given a pair of vertices P = {l_brace}u,v|u(set-membership sign)B,v(set-membership sign)W{r_brace} where B and W are the bipartition of V(G), there exists a path Q between u and v such that Q contains all vertices of G.

Hsu Liyen [Department of Aviation Management, China Institute of Technology. No. 200, Zhonghua St., Hengshan Shiang, Hsinchu County, Taiwan. 312 (China); Lin Tungyi; Kao Shinshin [Department of Applied Mathemetics, Chung Yuan Christian University. No. 200, Chung Pei Rd., Chung Li, Taiwan. 32023 (China)

2008-11-06

226

Two-dimensional Hubbard model on a honeycomb lattice  

NASA Astrophysics Data System (ADS)

In the honeycomb lattice, a combination of nontrivial topology and electronic correlations drives a great variety of phenomena. We study the 2-dimensional fermionic Hubbard model on a honeycomb lattice using exact diagonalization method at various onsite interaction strength U values. By introducing holes in the model at different filling levels, we analyze the charge gap instability of the lattice which indicates the possibility the system going into a paired state. We further monitor the one-particle excitation spectrum and density of states at various k-points. We find that the electronic interaction introduces quasiparticle states around the Fermi level and the system can undergo a metal-insulator transition. /newline /newline The authors acknowledge the computing facilities provided by the Center for Integrated Nanotechnologies, a U.S. Department of Energy, Office of Basic Energy Sciences user facility at Los Alamos National Laboratory (Contract DE-AC52-06NA25396) and Sandia National Laboratories (Contract DE-AC04-94AL85000) and the Center for Functional Nanomaterials, Brookhaven National Laboratory supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No.DE-AC02-98CH10886.

Fang, Kun; Fernando, Gayana; Balatsky, Alexander; Kocharian, Armen; Palandage, Kalum

2013-03-01

227

Aluminum-containing mesostructural materials  

Microsoft Academic Search

This article reviews syntheses of mesoporous aluminosilicates and aluminum oxides based on surfactant templating methods. The incorporation of aluminum in the silicate frameworks generates acid sites and ion-exchange sites. Both, tetrahedral framework aluminum and octahedral extraframework aluminum can be present, depending on the aluminum precursor used. The aluminum-containing structures tend to be less ordered than their purely siliccous analogs. Dealumination

Andreas Stein; Brian Holland

1996-01-01

228

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

229

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

PubMed Central

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

230

Position space formulation for Dirac fermions on honeycomb lattice  

E-print Network

We study how to construct Dirac fermion defined on the honeycomb lattice in position space. Starting from the nearest neighbor interaction in tight binding model, we show that the Hamiltonian is constructed by kinetic term and second derivative term of three flavor Dirac fermions in which one flavor has a mass of cutoff order and the other flavors are massless. In this formulation the structure of the Dirac point is simplified so that its uniqueness can be easily shown even if we consider the next-nearest neighbor interaction. We also show the chiral symmetry at finite lattice spacing, which protects the masslessness of the Dirac fermion, and discuss the analogy with the staggered fermion formulation.

Masaki Hirotsu; Tetsuya Onogi; Eigo Shintani

2014-09-03

231

Porphyrin-based honeycomb films and their antibacterial activity.  

PubMed

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

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

2014-06-10

232

On the honeycomb conjecture and the Kepler problem  

E-print Network

This paper views the honeycomb conjecture and the Kepler problem essentially as extreme value problems and solves them by partitioning 2-space and 3-space into building blocks and determining those blocks that have the universal extreme values that one needs. More precisely, we proved two results. First, we proved that the regular hexagons are the only 2-dim blocks that have unit area and the least perimeter (or contain a unit circle and have the least area) that tile the plane. Secondly, we proved that the rhombic dodecahedron and the rhombus-isosceles trapezoidal dodecahedron are the only two 3-dim blocks that contain a unit sphere and have the least volume that can fill 3-space without either overlapping or leaving gaps. Finally, the Kepler conjecture can also be proved to be true by introducing the concept of the minimum 2-dim and 3-dim Kepler building blocks.

Fu-Gao Song; Francis Austin

2009-07-25

233

Instabilities of interacting electrons on the honeycomb bilayer  

NASA Astrophysics Data System (ADS)

We investigate the instabilities of interacting electrons on the honeycomb bilayer by means of the functional renormalization group. Using model parameters as determined by ab initio calculations for graphene and graphite for interactions up to the third-nearest neighbor puts the system close to the boundary between antiferromagnetic and quantum spin Hall instabilities. Importantly, the energy scales for these instabilities are large. Thus imperfections and deviations from the basic model are expected to play a major role in real bilayer graphene, where interaction effects seem to be seen only at smaller scales. We therefore analyze how reducing the critical scale and small doping of the layers affect the instabilities. For smaller on-site repulsions, we also find an instability toward a gapless charge-density wave state.

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

2012-06-01

234

Monomer-dimer mixture on a honeycomb lattice.  

PubMed

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

Otsuka, Hiromi

2011-06-01

235

Flat bands and Wigner crystallization in the honeycomb optical lattice.  

PubMed

We study the ground states of cold atoms in the tight-binding bands built from p orbitals on a two dimensional honeycomb optical lattice. The band structure includes two completely flat bands. Exact many-body ground states with on-site repulsion can be found at low particle densities, for both fermions and bosons. We find crystalline order at n=1/6 with a sqrt[3] x sqrt[3] structure breaking a number of discrete lattice symmetries. In fermionic systems, if the repulsion is strong enough, we find the bonding strength becomes dimerized at n=1/2. Experimental signatures of crystalline order can be detected through the noise correlations in time of flight experiments. PMID:17930875

Wu, Congjun; Bergman, Doron; Balents, Leon; Das Sarma, S

2007-08-17

236

Chiral bosonic phases on the Haldane honeycomb lattice  

NASA Astrophysics Data System (ADS)

Recent experiments in ultracold atoms and photonic analogs have reported the implementation of artificial gauge fields in lattice systems, facilitating the realization of topological phases. Motivated by such advances, we investigate the Haldane honeycomb lattice tight-binding model, for bosons with local interactions at the average filling of one boson per site. We analyze the ground-state phase diagram and uncover three distinct phases: a uniform superfluid (SF), a chiral superfluid (CSF), and a plaquette Mott insulator with local current loops (PMI). Nearest-neighbor and next-nearest-neighbor currents distinguish CSF from SF, and the phase transition between them is first order. We apply bosonic dynamical mean-field theory and exact diagonalization to obtain the phase diagram, complementing numerics with calculations of excitation spectra in strong and weak coupling perturbation theory. The characteristic density fluctuations, current correlation functions, and excitation spectra are measurable in ultracold atom experiments.

Vasi?, Ivana; Petrescu, Alexandru; Le Hur, Karyn; Hofstetter, Walter

2015-03-01

237

Superconductivity in intercalated group-IV honeycomb structures  

NASA Astrophysics Data System (ADS)

We present a theoretical investigation on the electron-phonon superconductivity of honeycomb M X2 layered structures where X is one element of group IV (C, Si, or Ge) and M is an alkali or an alkaline-earth metal. Among the studied compositions we predict a TC of 7 K in RbGe2, 9 K in RbSi2, and 11 K in SrC2. All these compounds feature a strongly anisotropic superconducting gap. Our results show that despite the different doping levels and structural properties, the three families of materials fall into a similar description of their superconducting behavior. This allows us to estimate an upper critical temperature of about 20 K for the class of intercalated group-IV structures, including intercalated graphite and doped graphene.

Flores-Livas, José A.; Sanna, Antonio

2015-02-01

238

Honeycomb: Visual Analysis of Large Scale Social Networks  

NASA Astrophysics Data System (ADS)

The rise in the use of social network sites allows us to collect large amounts of user reported data on social structures and analysis of this data could provide useful insights for many of the social sciences. This analysis is typically the domain of Social Network Analysis, and visualization of these structures often proves invaluable in understanding them. However, currently available visual analysis tools are not very well suited to handle the massive scale of this network data, and often resolve to displaying small ego networks or heavily abstracted networks. In this paper, we present Honeycomb, a visualization tool that is able to deal with much larger scale data (with millions of connections), which we illustrate by using a large scale corporate social networking site as an example. Additionally, we introduce a new probability based network metric to guide users to potentially interesting or anomalous patterns and discuss lessons learned during design and implementation.

van Ham, Frank; Schulz, Hans-Jörg; Dimicco, Joan M.

239

Loop statistics in the toroidal honeycomb dimer model  

E-print Network

The dimer model on a graph embedded in the torus can be interpreted as a collection of random self-avoiding loops. In this paper, we consider the uniform toroidal honeycomb dimer model. We prove that when the mesh of the graph tends to zero and the aspect of the torus is fixed, the winding number of the collection of loops converges in law to a two-dimensional discrete Gaussian distribution. This is known to physicists in more generality from their analysis of toroidal two-dimensional critical loop models and their mapping to the massless free field on the torus. This paper contains the first mathematical proof of this more general physics result in the specific case of the loop model induced by a toroidal dimer model.

Cédric Boutillier; Béatrice de Tilière

2009-09-24

240

Theoretical Predictions of Freestanding Honeycomb Sheets of Cadmium Chalcogenides  

SciTech Connect

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

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

2014-01-01

241

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

242

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

243

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

NASA Astrophysics Data System (ADS)

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

Kim, Kwangmoo; Einstein, T. L.

2011-06-01

244

A study of the effects of eccentricity on honeycomb annular gas seals  

E-print Network

Results are presented which show the effects of eccentricity on high pressure honeycomb and smooth annular gas seals. The results of the experiments indicate the ability to utilize centered seal solutions for rotordynamic coefficients and seal...

Weatherwax, Mark

2001-01-01

245

Experimental investigation and constitutive modeling of metallic honeycombs in sandwich structures  

E-print Network

Traditionally, honeycomb sandwich structures are designed in the elastic range, but recent studies on the crushing of sandwich profiles have shown their potential in crashworthiness applications. Thin sandwich sheets also ...

Mohr, Dirk, 1976-

2003-01-01

246

Validation of a vibration and electric model of honeycomb panels equiped with  

E-print Network

viscoélastiques présents pour le Nomex sont par ailleurs mis en évidence. Du point de vue électrique, on montre validations of the proposed models are discussed in section 4. The Nomex honeycomb considered in the test

Paris-Sud XI, Université de

247

Aluminum powder metallurgy processing  

SciTech Connect

The objective of this dissertation is to explore the hypothesis that there is a strong linkage between gas atomization processing conditions, as-atomized aluminum powder characteristics, and the consolidation methodology required to make components from aluminum powder. The hypothesis was tested with pure aluminum powders produced by commercial air atomization, commercial inert gas atomization, and gas atomization reaction synthesis (GARS). A comparison of the GARS aluminum powders with the commercial aluminum powders showed the former to exhibit superior powder characteristics. The powders were compared in terms of size and shape, bulk chemistry, surface oxide chemistry and structure, and oxide film thickness. Minimum explosive concentration measurements assessed the dependence of explosibility hazard on surface area, oxide film thickness, and gas atomization processing conditions. The GARS aluminum powders were exposed to different relative humidity levels, demonstrating the effect of atmospheric conditions on post-atomization processing conditions. The GARS aluminum powders were exposed to different relative humidity levels, demonstrating the effect of atmospheric conditions on post-atomization oxidation of aluminum powder. An Al-Ti-Y GARS alloy exposed in ambient air at different temperatures revealed the effect of reactive alloy elements on post-atomization powder oxidation. The pure aluminum powders were consolidated by two different routes, a conventional consolidation process for fabricating aerospace components with aluminum powder and a proposed alternative. The consolidation procedures were compared by evaluating the consolidated microstructures and the corresponding mechanical properties. A low temperature solid state sintering experiment demonstrated that tap densified GARS aluminum powders can form sintering necks between contacting powder particles, unlike the total resistance to sintering of commercial air atomization aluminum powder.

Flumerfelt, J.F.

1999-02-12

248

Improved cryogenic aluminum mirrors  

Microsoft Academic Search

Optical surface deformation of metal mirrors used at cryogenic temperatures is reduced through the use of a new process of plating amorphous aluminum on aluminum. The AlumiPlateTM process (produced by AlumiPlate, Inc. in Minneapolis, MN) plates a layer of 99.9+% high purity aluminum about 125 micrometers thick atop the substrate. Very good surface finishes are produced by direct diamond turning

Daniel Vukobratovich; Ken Don; Richard E. Sumner

1998-01-01

249

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

250

BETWEEN GREEN DENSITY AND THE OCCURRENCE OF HONEYCOMB IN KILN-DRIED RED OAK LUMBER  

Microsoft Academic Search

A BSTRACT Fresh-cut, 5\\/4 red oak (Quercus sp.) boards were weighed, measured to determine volume and then kiln-dried to determine if the initial green density (green weight\\/green volume) was correlated to the occurrence of honeycomb. A positive relationship was found between the occurrence of honeycomb during drying and the initial green density. These results indicate that it should bepossible to

R OBERT A. H ARRIS; P HILIP

1995-01-01

251

Effect of desorption temperature on CO 2 adsorption equilibria of the honeycomb zeolite beds  

Microsoft Academic Search

The behaviours of MS-13X and MS-4A were examined. The fitness of the Dubinin–Astakhov equation to the adsorption equilibria of the fully-desorbed honeycomb beds was examined. The validity of the Langmuir approximation to the obtained adsorption equilibria for relatively low CO2 partial pressures was also discussed. The CO2 adsorption equilibria of the honeycomb zeolite beds are not affected by it's desorption

K Kamiuto; S Abe; Ermalina

2002-01-01

252

Effect of desorption temperature on CO2 adsorption equilibria of the honeycomb zeolite beds  

Microsoft Academic Search

The behaviours of MS-13X and MS-4A were examined. The fitness of the Dubinin-Astakhov equation to the adsorption equilibria of the fully-desorbed honeycomb beds was examined. The validity of the Langmuir approximation to the obtained adsorption equilibria for relatively low CO2 partial pressures was also discussed. The CO2 adsorption equilibria of the honeycomb zeolite beds are not affected by it's desorption

K. Kamiuto; S. Abe; Ermalina

2002-01-01

253

A comparison of experimental and theoretical results for labyrinth gas seals with honeycomb stators  

E-print Network

) Lawrence Allen Hawkins, B. S. , Auburn University; Chair of Advisory Committee: Dr. Dara Childs 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 also compared to analytical results from a two-control-volume compressible ffow model. The experimental results show that the honeycomb...

Hawkins, Lawrence Allen

1988-01-01

254

Band Structure Calculations for Two-Dimensional Plasma Photonic Crystals in Honeycomb Lattice Arrangement  

Microsoft Academic Search

We propose an approach originating from plane wave expansion method to calculate band structure for two types of honeycomb lattice two-dimensional plasma photonic crystals. The eigenvalue equations of E-polarization for two types of structures, which depend on the honeycomb lattice realization(plasma rods immersed in dielectric background or vice versa), are derived respectively. A standard linearization technique which solves the general

Xiang-Kun Kong; Shao-Bin Liu; Hai-Feng Zhang; Liang Zhou; Chun-Zao Li

2011-01-01

255

Self-organized honeycomb structures of Mn(12) single-molecule magnets.  

PubMed

In this paper, Mn(12)-based ordered honeycomb structures were successfully constructed from a simple solution casting process at high relative humidity through the modification of fatty acids to Mn(12) clusters. Mn(12)-fatty acid complexes maintain typical features of a single-molecule magnet as confirmed by IR spectra and magnetization hysteresis studies. Investigation of the effects of concentration, velocity of humid airflow, solvent, substrate, and alkyl chain length of the Mn(12) complex on the morphology of the honeycomb structures demonstrated wide generality and high reproducibility of the formation of Mn(12)-based self-organized honeycomb-patterned films. Both two-dimensional and three-dimensional honeycomb structures were obtained by adjusting the concentration of the complex solution. Mn(12)-based, honeycomb-patterned films maintain a paramagnetic response at room temperature, and thus give rise to a spatially distributed magnetic pattern on the substrate, which can be imaged by magnetic force microscopy. Importantly, the single-molecule magnetic property of the Mn(12) complex at low temperature is well maintained in the honeycomb-patterned film, which represents a promising outlook for high-density information storage and quantum computing applications. PMID:19824615

Sun, Hang; Li, Wen; Wollenberg, Lance; Li, Bao; Wu, Lixin; Li, Fengyan; Xu, Lin

2009-11-01

256

Effect of honeycomb seals on loss characteristics in shroud cavities of an axial turbine  

NASA Astrophysics Data System (ADS)

The loss in efficiency due to shroud leakage or tip clearance flow accounts for a substantial part of the overall losses in turbomachinery. It is important to identify the leakage loss characteristics in order to optimize turbomachinery. At present, little information is available in the open literature concerning the effect of honeycomb seals on the loss characteristics in shroud cavities of an axial turbine, despite of the widespread use of the honeycomb seals. Therefore, interaction between rotor labyrinth seal leakage flow with and without honeycomb facings and main flow is investigated to provide the loss characteristics of the mixing process of the re-entering leakage flow into the main flow. The effects of honeycomb seals on the flow in shroud cavities and interaction with the main flow are analyzed. An additional study on the impact of subtle shroud cavity exit geometry is also presented. The investigation results indicate that the honeycomb seal affects the over tip leakage flow and reduces mixing losses when compared to the solid labyrinth seal. The leakage flow interactions with the main flow have considerably changed the flow fields in the endwall regions. The proposed research reveals the effects of honeycomb seals on the loss characteristics in shroud cavities and the impact of subtle shroud cavity exit geometry, and it is helpful for the design optimization of turbomachinery.

Gao, Jie; Zheng, Qun; Wang, Zheng

2013-01-01

257

Carbothermic Aluminum Production Using Scrap Aluminum As A Coolant  

DOEpatents

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

LaCamera, Alfred F. (Trafford, PA)

2002-11-05

258

Diffusion bonded boron/aluminum spar-shell fan blade  

NASA Technical Reports Server (NTRS)

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

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

1980-01-01

259

Microporous "honeycomb" films support enhanced bone formation in vitro.  

PubMed

Substrate topography influences cell adhesion, proliferation, and differentiation. In this study, poly (?-caprolactone) (PCL) films with a well-defined honeycomb structure of porosity 3-4, 5-6, 10-11, or 15-16 ?m were contrasted with flat surfaces for their ability to support primary rat osteoblast adhesion and mineralized extracellular matrix deposition in vitro. Immunofluorescent visualization of vinculin and rhodamine phalloidin binding of actin were used to investigate cell adhesion and morphology. Localization of the alkaline phosphatase activity and Alizarin Red staining were performed to assess the osteoblast activity and deposition of a mineralized matrix. Scanning electron microscopy together with energy-dispersive X-ray spectroscopy was used to provide morphological analysis of cell-film interactions, the deposited matrix, and elemental analysis of the mineralized structures. After 24 h of culture, there were no differences in cell numbers on porous or flat PCL surfaces, but there were changes in cell morphology. Osteoblasts on honeycomb films had a smaller surface area and were less circular than cells on flat PCL. Analysis of cells cultured for 35 days under osteogenic conditions revealed that osteoblasts on all substrates acquired alkaline phosphatase activity, but levels of mineralized matrix were increased on films with 3-4-?m pore sizes. The bone-like matrix with a Ca:P ratio of 1.69±0.08 could be identified in larger areas often aligning with substrate topography. In addition, smaller spherical deposits (0.5-1 ?m in diameter) with a Ca:P ratio of 1.3±0.08 were observed at the surface and particularly within the pores of the PCL film. Localization of vinculin showed significant decreases in the number of focal adhesion structures per unit cell area on 5-6, 10-11, and 15-16-?m surfaces compared to flat PCL, while focal complexes with a smaller area (0-2 ?m(2)) were more abundant on 3-4 and 5-6-?m surfaces. Observation of cell interaction with these surfaces identified cytoplasmic protrusions that extended into and sealed the pores of these PCL films creating an extracellular space in which, the conditions could influence the deposition and formation of the mineralized matrix. PMID:23688155

Birch, Mark A; Tanaka, Masaru; Kirmizidis, George; Yamamoto, Sadaaki; Shimomura, Masatsugu

2013-09-01

260

Aluminum alumina joining  

NASA Astrophysics Data System (ADS)

Aluminum tensile adhesion to alumina composites containing varying volume fractions of borosilicate glass was examined. Alumina composites were found to bond to aluminum at a reaction temperature of 800 C with tensile bond strengths of 62 MPa, observed for composites containing 15 percent glass.

Haber, R. A.; Greenhut, Victor A.

261

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

262

Aluminum Carbothermic Technology  

Microsoft Academic Search

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

Marshall J

2005-01-01

263

The Aluminum Smelting Process  

PubMed Central

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

2014-01-01

264

Aluminum structural applications  

SciTech Connect

Extensive research by aluminum producers and automakers in the 1980s resulted in the development of technologies that enable building of aluminum cars that meet and exceed all the expectations of today`s drivers and passengers, yet weigh several hundred pounds less than their steel counterparts. The Acura NSX sports car, the Audi A8, and the Jaguar XJ220 have all been introduced. Ford has built 40 aluminum-intensive automobiles based on the Taurus/Sable for test purposes, and General Motors recently announced an aluminum-structured electric vehicle. The design flexibility that aluminum allows is shown by these examples. Each uses a somewhat different technology that is particularly suited to the vehicle and its market.

Lucas, G. [Alcan Rolled Products Co., Farmington Hills, MI (United States)

1996-05-01

265

The aluminum smelting process.  

PubMed

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

Kvande, Halvor

2014-05-01

266

Measurements of electrical and mechanical properties of aluminum composite cryoconductors  

E-print Network

project. Hartwig has assisted in the development of test proceedures as well as having a voice in the construction of the test equipment. He is also credited with editing the contents of this thesis. Finally I want to thank the members of the Cryogenics... geometries of an aluminum composite cryoconductor, proposed for a space based cryogenic inductor, are shownt. The cryoconductor is composed of two regions. The first, the core or filament region, is pure aluminum, which gives the cryoconductor its high...

Sundby, Paul C.

1994-01-01

267

Bloch-Zener oscillations in a tunable optical honeycomb lattice  

SciTech Connect

Ultracold gases in optical lattices have proved to be a flexible tool to simulate many different phenomena of solid state physics [1, 2]. Recently, optical lattices with complex geometries have been realized [3, 4, 5, 6, 7], paving the way to simulating more realistic systems. The honeycomb structure has recently become accessible in an optical lattice composed of mutually perpendicular laser beams. This lattice structure exhibits topological features in its band structure – the Dirac points. At these points, two energy bands intersect linearly and the particles behave as relativistic Dirac fermions. In optical lattices, Bloch oscillations [8] resolved both in time and in quasi-momentum space can be directly observed. We make use of such Bloch-Zener oscillations to probe the vanishing energy gap at the Dirac points as well as their position in the band structure. In small band gap regions, we observe Landau-Zener tunneling [7, 9] to the second band and the regions of maximum transfer can be identified with the position of the Dirac points.

Uehlinger, Thomas; Greif, Daniel; Jotzu, Gregor; Esslinger, Tilman [Institute for Quantum Electronics, ETH Zurich, 8093 Zurich (Switzerland); Tarruell, Leticia [Institute for Quantum Electronics, ETH Zurich, 8093 Zurich, Switzerland and LP2N, Universite Bordeaux 1, IOGS, CNRS, 351 cours de la Liberation, 33405 Talence (France)

2013-12-04

268

Degassing of Aluminum Alloys Using Ultrasonic Vibration  

SciTech Connect

The research was intended to lead to a better fundamental understanding of the effect of ultrasonic energy on the degassing of liquid metals and to develop practical approaches for the ultrasonic degassing of alloys. The goals of the project described here were to evaluate core principles, establish a quantitative basis for the ultrasonic degassing of aluminum alloy melts, and demonstrate the application of ultrsaonic processing during ingot casting and foundry shape casting.

Meek, T. T.; Han, Q.; Xu, H.

2006-06-01

269

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

270

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

271

Aluminum: Reducing chloride emissions from aluminum production  

Microsoft Academic Search

Reynolds Metals Company (RMC), with assistance from a NICE³ grant, is developing for commercialization a closed-loop control process that greatly reduces chlorine emissions and increases plant efficiency while maintaining metal quality. The process still utilizes chlorine to remove impurities during aluminum processing, but is more effective than current methods. With the new technology chlorine in the stack is monitored and

Simon

1999-01-01

272

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

273

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

274

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

275

Development of a Computer simulation approach for honeycomb constructions for aerospace application  

NASA Astrophysics Data System (ADS)

An approach to definition of a homogeneous simulation model for honeycomb structures has been developed and verified for specimens containing a finite number of cells. The elastic characteristics of the model were evaluated basing on the results of tensile and shear numerical tests of honeycomb specimen. This is an extension of earlier work related with spatially reinforced composites. The simulation model was validated for specimens comprised of different numbers of cells in the specimen to expose the scale effect influence. As the number of cells was increased, the calculated values of the moduli Ex and Ey converged, confirming the theoretical result that the appropriate model is transversely isotropic rather than orthotropic for the honeycomb specimen investigated. Elastic properties obtained from the numerical test of the honeycomb structure were then applied in the characterization of continuous medium. The examination was carried out using criteria expressing basic features of homogeneous body. The case of a honeycomb integrated with composite plates as a sandwich structure was analysed for a complex loading case as well as buckling and eigen- frequency analysis.

Tatarnikov, O. V.; Karpenkov, K. S.

2015-02-01

276

Detection of disbonds in a honeycomb composite structure using guided waves  

NASA Astrophysics Data System (ADS)

Advanced composites are being used increasingly in state-of-the-art aircraft and aerospace structures. In spite of their many advantages composite materials are highly susceptible to hidden flaws that may occur at any time during the life cycle of a structure and if undetected, may cause sudden and catastrophic failure of the entire structure. An example of such a defects critical structural component is the "honeycomb composite" in which thin composite skins are bonded with adhesives to the two faces of extremely lightweight and relatively thick metallic honeycombs. These components are often used in aircraft and aerospace structures due to their high strength to weight ratio. Unfortunately, the bond between the honeycomb and the skin may degrade with age and service loads leading to separation of the load-bearing skin from the honeycomb (called "disbonds") and compromising the safety of the structure. This paper is concerned with the noninvasive detection of disbonds using ultrasonic guided waves. Laboratory experiments are carried out on a composite honeycomb specimen containing localized disbonded regions. Ultrasonic waves are launched into the specimen using a broadband PZT transducer and are detected by a distributed array of identical transducers located on the surface of the specimen. The guided wave components of the signals are shown to be very strongly influenced by the presence of a disbond. The experimentally observed results are being used to develop an autonomous scheme to locate the disbonds and to estimate their size.

Baid, Harsh; Banerjee, Sauvik; Joshi, Shiv; Mal, Siddhartha

2008-03-01

277

Oxidation dynamics of aluminum nanorods  

NASA Astrophysics Data System (ADS)

Aluminum nanorods (Al-NRs) are promising fuels for pyrotechnics due to the high contact areas with oxidizers, but their oxidation mechanisms are largely unknown. Here, reactive molecular dynamics simulations are performed to study thermally initiated burning of oxide-coated Al-NRs with different diameters (D = 26, 36, and 46 nm) in oxygen environment. We found that thinner Al-NRs burn faster due to the larger surface-to-volume ratio. The reaction initiates with the dissolution of the alumina shell into the molten Al core to generate heat. This is followed by the incorporation of environmental oxygen atoms into the resulting Al-rich shell, thereby accelerating the heat release. These results reveal an unexpectedly active role of the alumina shell as a "nanoreactor" for oxidation.

Li, Ying; Kalia, Rajiv K.; Nakano, Aiichiro; Vashishta, Priya

2015-02-01

278

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

279

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

280

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

281

Aluminum structural applications  

Microsoft Academic Search

Extensive research by aluminum producers and automakers in the 1980s resulted in the development of technologies that enable building of aluminum cars that meet and exceed all the expectations of today`s drivers and passengers, yet weigh several hundred pounds less than their steel counterparts. The Acura NSX sports car, the Audi A8, and the Jaguar XJ220 have all been introduced.

1996-01-01

282

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

283

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

284

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

285

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

PubMed

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

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

2014-01-01

286

Thermal behavior of laboratory models of honeycomb-covered solar ponds  

NASA Technical Reports Server (NTRS)

Laboratory experiments were conducted to provide insight into the technical feasibility of honeycomb-covered solar ponds. Cooling tests using honeycomb panels of various materials and geometries showed that a 5.7-cm-thick one-tier panel insulated as effectively as a 10-cm fiberglass slab. Heating tests demonstrated that a model pond covered with a polycarbonate panel boiled upon 16 hours of continuous exposure to a 150-W spotlight. Analysis of the experimental data indicates positively that honeycomb-covered solar ponds can be expected to perform satisfactorily, and that larger-scale outdoor tests should be conducted to provide a more realistic assessment and a more refined performance estimate.

Lin, E. I. H.

1983-01-01

287

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

Microsoft Academic Search

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

Hideki Masuda; Kenji Fukuda

1995-01-01

288

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

289

Surface Properties of Honeycomb and Pincushion Structures of Various Hydrophobic Polymer Materials Prepared by Self-Organization  

Microsoft Academic Search

Surface wettability is a significant factor in determining the physical and chemical properties of materials. It is known that both the chemical properties of the surface and its topography play important roles. A honeycomb-structured polymer film can be prepared by casting a hydrophobic polymer solution under humid conditions. Here, we measured water repellency on the honeycomb- and pincushion-structured films of

Hiroshi Yabu; Yuji Hirai; Miki Kojima; Masatsugu Shimomura

2008-01-01

290

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

291

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

E-print Network

Self-Assembled Micro-Honeycomb Network of Single-Walled Carbon Nanotubes for Heterojunction Solar@photon.t.u-tokyo.ac.jp Keywords: Self-assembly, micro-honeycomb network, single-walled carbon nanotubes, heterojunction solar cell-walled carbon nanotube (SWNT) and inferior performance of macro-scale SWNT devices is hindering its widespread

Maruyama, Shigeo

292

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

293

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

294

Combination of plasma with a honeycomb-structured catalyst for automobile exhaust treatment.  

PubMed

To activate a catalyst efficiently at low temperature by plasma for environmental control, we developed a hybrid reactor that combines plasma with a honeycomb-structured catalyst in a practical manner. The reactor developed generated stable cold plasma at atmospheric pressure because of the dielectric and conductive nature of the honeycomb catalyst by consuming low amounts of power. In this reactor, the applied voltage and temperature determined the balance between the oxidation and adsorption by the plasma and catalyst. The synergistic reaction of the plasma and catalyst was more effective at low temperatures, resulting in a reduction in a lowered light-off temperature. PMID:23991700

Kang, Woo Seok; Lee, Dae Hoon; Lee, Jae-Ok; Hur, Min; Song, Young-Hoon

2013-10-01

295

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

296

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

297

Aluminum automotive space frames  

SciTech Connect

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

NONE

1995-08-01

298

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...

299

Finite element analysis of effective mechanical properties, vibration and acoustic performance of auxetic chiral core sandwich structures  

NASA Astrophysics Data System (ADS)

Honeycomb cellular materials are widely used in engineering applications due to their high strength to weight ratio and controllable effective mechanical properties. The effective properties are controlled by varying the geometry of the repetitive unit cells of honeycomb structure. Sandwich panels made of honeycomb cores are beneficial in many applications including vibration isolation and sound transmission reduction. Sandwich panels with standard honeycomb core configurations have previously been studied with regards to sound transmission behavior. It has been established that the auxetic honeycomb cores, having negative in-plane Poisson's ratio, exhibit higher sound transmission loss as compared to regular honeycomb cores. In this study, the vibration and sound transmission response of novel auxetic chiral honeycomb structures (both hexa-chiral and anti-tetra chiral), have been investigated in detail using finite element analysis with two-dimensional plane elasticity elements. Chiral honeycomb structures are made up of a linear tessellation of periodic unit cell, which consists of circular nodes of radius ' r ' connected to each other by tangent ligaments of length ' L '. The distance between two adjacent circular nodes is ' R '. These geometric parameters are tailored to obtain the chiral structure with desired effective mechanical properties of in-plane Poisson's ratio, Young's modulus and shear modulus. Results show that, for both the hexa-chiral and anti-tetra-chiral configurations with same thickness, structures with smaller node radius 'r' have higher in-plane negative Poisson's ratio, effective Young's modulus, and shear modulus. The Poisson's ratio of anti-tetra-chiral structure with small node radius and thickness is found to approach the limit of -1. A steady state dynamic response of the chiral honeycomb sandwich panel subjected to uniform pressure load on the bottom face-sheet is also investigated over a frequency range of 1 Hz to 2000 Hz. It is observed that, by changing the node radius of the chiral structures, the frequency range for the global sandwich structure bending resonances and local intra-cell core resonances can be shifted. Within the bandwidth controlled by the intra-cell core resonances we observe higher surface velocity vibration amplitude and decrease in sound transmission loss. For the structure with bigger node radius, the bending resonances and intra-cell resonance are shifted to lower frequencies as compared to the structure with smaller node radius. Finally, the sound transmission loss behavior of sandwich panels made of chiral honeycomb cores is investigated with plane pressure wave incident at normal as well as variable incidence angles. The results suggest that, in case of both the hexa-chiral and anti-tetra-chiral sandwich panels, the core structure with smallest node radius exhibits higher sound transmission loss as compared to the core structure with bigger node radius. Among all the different chiral honeycomb structures investigated in this study, the anti-tetra-chiral structure with smallest node radius exhibits the highest sound transmission loss. It is interesting to observe that this is also the structure with highest value of negative in-plane Poisson's ratio.

Joshi, Hrishikesh Ravindra

300

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

301

The Origin of Life: Chemical Evolution of a Metabolic System in a Mineral Honeycomb?  

E-print Network

The Origin of Life: Chemical Evolution of a Metabolic System in a Mineral Honeycomb? Sergio our previous models of chemical evolution on mineral surfaces, in which selection was the consequence into the pores of the mineral substrate. Based on cellular automaton simulations we argue that the effect

Czárán, Tamás

302

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

303

[Determining the concentration of coating solution attaching to honeycomb denuder in summer in Tianjin].  

PubMed

The study on determining the concentration of coating solution attaching to honeycomb denuder was conducted, from 1 July to 31 August, 2013, at the roof of Lihua building at Nankai University in Tianjin. The results of experiment showed that the optimized concentration of sodium carbonate coated on the honeycomb denuder was 3%, and the optimized concentration of citric acid was 6%. The contrast sampling results of PM2.5 between honeycomb denuder system and conventional method showed that 86% of the concentration of PM2.5 samples obtained by honeycomb denuder system were less than those obtained by conventional method, the main reasons may include that: (1) the majority of acid/alkaline gases were removed, so they could neither react with the enriched particles on the sampling membrane nor be adsorbed on particles; (2) parts of the particles were captured by the denuder during sampling; (3) the removal of acid/alkaline gases disturbed the state of equilibrium between gas- and particle-phases which may lead to the volatilization of some particles. PMID:25338355

Zhang, Shi-Jian; Ji, Ya-Qin; Zhang, Lei-Bo; Zhao, Xue-Yan; Zhu, Zhen-Yu; Yang, Wen

2014-08-01

304

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

305

Vacuum Bag Only Prepreg Processing of Honeycomb Sandwich Panels James Kratz  

E-print Network

Vacuum Bag Only Prepreg Processing of Honeycomb Sandwich Panels James Kratz Department that consistently produce predictable results are needed. Vacuum-bag-only (VBO) manufacturing is one possible solution that relies on vacuum to remove all entrapped volatiles prior to cure, and then the differential

Dawson, Jeff W.

306

[Study on formation process of honeycomb pattern in dielectric barrier discharge by optical emission spectrum].  

PubMed

The authors report on the first investigation of the variations in the plasma parameters in the formation process of the honeycomb pattern in a dielectric barrier discharge by optical emission spectrum in argon and air mixture. The discharge undergoes hexagonal lattice, concentric spot-ring pattern and honeycomb pattern with the applied voltage increasing. The molecular vibration temperature, electron excitation temperature and electronic density of the three kinds of patterns were investigated by the emission spectra of nitrogen band of second positive system (C3pi(u) --> B3 pi(g)), the relative intensity ratio method of spectral lines of Ar I 763.51 nm (2P(6) --> 1S(5)) and Ar I 772.42 nm (2P(2) -->1S(3)) and the broadening of spectral line 696.5 nm respectively. It was found that the molecular vibration temperature and electron excitation temperature of the honeycomb pattern are higher than those of the hexagonal lattice, but the electron density of the former is lower than that of the latter. The discharge powers of the patterns were also measured with the capacitance method. The discharge power of the honeycomb pattern is much higher than that of the hexagonal lattice. These results are of great importance to the formation mechanism of the patterns in dielectric barrier discharge. PMID:25007599

Dong, Li-Fang; Zhu, Ping; Yang, Jing; Zhang, Yu

2014-04-01

307

Observations on the full honeycomb structure of graphite as imaged by atomic force microscopy  

Microsoft Academic Search

Most atomic force microscopy (AFM) images of highly ordered pyrolytic graphite (HOPG) yield only every other atom with a lattice constant 2.46 Å. However, its full honeycomb structure, revealing all six carbon atoms of each hexagon, can only be obtained under certain conditions. A particular problem is the large meniscus force generated by a thin condensed layer of water when

P. Singjai; P. A. Zhdan; J. E. Castle

2000-01-01

308

Observations on the full honeycomb structure of graphite as imaged by atomic force microscopy  

Microsoft Academic Search

Most atomic force microscopy (AFM) images of highly ordered pyrolytic graphite (HOPG) yield only every other atom with a lattice constant 2.46Å. However, its full honeycomb structure, revealing all six carbon atoms of each hexagon, can only be obtained under certain conditions. A particular problem is the large meniscus force generated by a thin condensed layer of water when imaging

P. Singjai; P. A. Zhdan; J. E. Castle

2000-01-01

309

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

E-print Network

1 Self-Assembled Micro-Honeycomb Network of Single-Walled Carbon Nanotubes for Solar Cells KehangW/cm² FF: 73% PCE: 10.02% KEYWORDS: Single-walled carbon nanotube, nanotube-Si solar cell, self-3-5800-6983. #12;2 ABSTRACT We propose a water vapor treatment to direct the formation of single-walled carbon

Maruyama, Shigeo

310

Acoustic damping of honeycomb-construction plates by pressure-sensitive adhesives  

Microsoft Academic Search

Materials available as pressure sensitive adhesives in tape form are found to have suitable properties for damping acoustic vibrations in the 200 to 1000 Hz range. Comparative experiments were made to damp small honeycomb construction base plates, of length about 1 m and of thickness 50 mm, which are used for mounting lasers. Added masses bonded to the edge of

D. J. E. Knight; K. I. Pharaoh

1991-01-01

311

The Architecture The universe resembles an unfathomably large honeycomb. Gigantic galaxy clusters occupy  

E-print Network

The Architecture of Space The universe resembles an unfathomably large honeycomb. Gigantic galaxy of galaxies, and in the process, encounters the invisible aspects of space. What the eye doesn't see: The Coma the individual galaxies (gray spots). X-ray scouts like the ROSAT satellite, on the other hand, reveal

312

Aluminum: Recycling Comes of Age  

NASA Astrophysics Data System (ADS)

Recycled aluminum is used by integrated producers who are capable of extracting aluminum from the ore, by non-integrated fabricators who rely on scrap for part of their production, and secondary smelters who depend entirely on scrap. Approximately 20% of the 14 billion pounds of aluminum shipped in the U.S. in 1978 came from recycled sources. Recycling aluminum requires only 5% of the energy needed to produce aluminum from the ore, and there are substantial savings in capital investment requirements. Since fabricators of aluminum products return nearly 100% of their scrap, future growth in recycled aluminum is possible largely through reclamation of post-consumer scrap. The basics of aluminum recycling are discussed, the technical and commercial problems outlined, and illustrations given of current industry activities.

Ballance, John B.

1980-02-01

313

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. ...

314

Aluminum Wash and Leach Factors  

SciTech Connect

This report estimates aluminum wash and leach factors using a waste type modeling approach. The model produces reasonable aluminum wash-leach factor predictions that can be used in the Hanford Tank Waste Operations Simulator model.

MEACHAM, J.E.

2003-07-10

315

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

316

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

317

Elevated temperature aluminum alloys  

NASA Technical Reports Server (NTRS)

Three aluminum-lithium alloys are provided for high performance aircraft structures and engines. All three alloys contain 3 wt % copper, 2 wt % lithium, 1 wt % magnesium, and 0.2 wt % zirconium. Alloy 1 has no further alloying elements. Alloy 2 has the addition of 1 wt % iron and 1 wt % nickel. Alloy 3 has the addition of 1.6 wt % chromium to the shared alloy composition of the three alloys. The balance of the three alloys, except for incidentql impurities, is aluminum. These alloys have low densities and improved strengths at temperatures up to 260.degree. C. for long periods of time.

Meschter, Peter (Inventor); Lederich, Richard J. (Inventor); O'Neal, James E. (Inventor)

1989-01-01

318

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

319

Buckling of cylindrical sandwich shells with metal foam cores J.W. Hutchinson a,*, M.Y. He b  

E-print Network

. By comparing weight optimized shells, these authors showed that honeycomb sand- wiches oer a substantial weight and core density are obtained which minimize the weight of a geometrically perfect shell with a speci shells have a competitive weight advantage over stringer stiened shells. In most of this range

Hutchinson, John W.

320

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

321

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

322

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

323

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

324

Electrically conductive anodized aluminum coatings  

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

325

RECLAMATION OF ALUMINUM FINISHING SLUDGES  

EPA Science Inventory

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

326

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

327

Aluminum battery alloys  

DOEpatents

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

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

1984-09-28

328

Aluminum battery alloys  

DOEpatents

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

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

1985-01-01

329

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

330

Maize aluminum tolerance  

Technology Transfer Automated Retrieval System (TEKTRAN)

Maize is one of the most economically important food crops grown on acid soils, where aluminum (Al) toxicity greatly limits crop yields. Considerable variation for Al tolerance exists in maize, and this variation has been exploited for many years by plant breeders to enhance maize Al tolerance. Curr...

331

Aluminum Corrosion and Turbidity  

SciTech Connect

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

Longtin, F.B.

2003-03-10

332

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

333

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

334

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

2000-01-01

335

Hierarchical honeycombs with tailorable properties Amin Ajdari, Babak Haghpanah Jahromi, Jim Papadopoulos, Hamid Nayeb-Hashemi, Ashkan Vaziri  

E-print Network

. The transverse (i.e., in-plane) stiffness and strength of honeycombs are generally governed by the bend- ing hexagon. Repeating this process builds a fractal-appearing structure. The resulting isotropic in-plane

Vaziri, Ashkan

336

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

337

Choice of optimal properties of molding compounds for extrusion of block supports and catalysts with the honeycomb structure  

SciTech Connect

Properties of compounds for molding of block supports and catalysts with the honeycomb structure have been studied. The examples studied include ultraporcelain, alumina, titanium dioxide, clays, and graphite. The molding properties of these compounds are characterized by such parameters as the relationship between deformations, relaxation time, power for destruction of the coagulation structure, and flow index. For molding of blocks with the honeycomb structure compounds with enhanced plastic properties and a stable coagulation structure are suggested.

Prokof`ev, V.Yu.; Il`in, A.P.; Shirokov, Yu.G.; Yurchenko, E.N. [Ivanovo State Chemical Engineering Academy, St. Petersburg (Russian Federation)

1995-09-20

338

Improved cryogenic aluminum mirrors  

NASA Astrophysics Data System (ADS)

Optical surface deformation of metal mirrors used at cryogenic temperatures is reduced through the use of a new process of plating amorphous aluminum on aluminum. The AlumiPlateTM process (produced by AlumiPlate, Inc. in Minneapolis, MN) plates a layer of 99.9+% high purity aluminum about 125 micrometers thick atop the substrate. Very good surface finishes are produced by direct diamond turning of the plating, with some samples below 40 angstroms RMS. Optical testing of a 175-mm diameter, 550-mm optical radius of curvature 6061-T651/AlumiPlateTM aluminum sphere was performed at 65 K to determine cryogenic optical surface figure stability. In five cycles from 300 to 65 K, an average optical surface change of 0.047 wave RMS (1 wave equals 633 nm) was observed. A total optical figure change of 0.03 wave RMS at 65 K was observed from the first to last cycle. The cause of this relatively small long-term change is not yet determined. The test mirror is bi-concave, with a semi- kinematic toroidal mount, and is machined from the axis of a billet. An `uphill quench' heat treatment consisting of five cycles from liquid nitrogen to boiling water temperatures is used to minimize residual stress in the test mirror. Initial diamond turning of the mirror by the Optical Filter Corp., Keene, NH, produced a 300 K unmounted optical surface figure of 0.380 wave peak-to-valley and 0.059 wave RMS. A second effort at diamond turning by II-VI, Inc., Saxonburg, PA produced a 300 K optical figure of 0.443 wave peak-to-valley and 0.066 wave RMS, with a surface roughness varying from 29 to 42 angstroms.

Vukobratovich, Daniel; Don, Ken; Sumner, Richard E.

1998-09-01

339

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 WO(3) (h-WO(3)) thin films in order to improve electrochromic performance. In the present investigation, honeycomb nanostructured WO(3) 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 WO(3) thin films with a unit cell diameter of 1.7 ?m. The variation in color on reduction of WO(3) 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

2015-02-14

340

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

341

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

NASA Astrophysics Data System (ADS)

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

Yang, Bogeum; Lee, Myeongkyu

2013-11-01

342

Steps toward 8m honeycomb mirrors. VIII - Design and demonstration of a system of thermal control  

NASA Technical Reports Server (NTRS)

Directed jets of ambient temperature air are proposed for the maintenance of low internal temperature gradients and conformity with ambient temperatures in honeycomb-structure borosilicate glass telescope mirrors. The use of greater airflow on thicker sections, to match cooling rates, and the cooling or heating of the internal, back, and edge surfaces of the mirror at the same rate established by convection on the front surface, have been tested on a full scale glass thermal model of a single honeycomb cell from an 8-m diameter mirror. The internal thermal gradient (less than 0.1 C) and ambient-temperature-change lag (less than 0.24 C) ensure minimum image degradation.

Cheng, A. Y. S.; Angel, J. R. P.

1986-01-01

343

Self-assembly of chiral molecular honeycomb networks on Au(111).  

PubMed

Self-assembly of the specifically designed 3-fold symmetric 1,3,5-trikis(4'-carboxylphenyl)-2,4,6-trikis(4'-tert-butylphenyl)-benzene molecule on a Au(111) surface is investigated by means of in situ ultrahigh vacuum scanning tunneling microscopy. A variety of chiral honeycomb networks with increasing interpore distance is observed. Experiments and force field calculations reveal that the formation of the two-dimensional hexagonal porous networks is driven by a balance of molecular close-packing within half-unit cells and cyclic hydrogen bonding dimerization between half-unit cells. The honeycomb networks are shown to be chiral owing to asymmetric molecular close-packing within the half-unit cells. PMID:18558672

Xiao, Wende; Feng, Xinliang; Ruffieux, Pascal; Gröning, Oliver; Müllen, Klaus; Fasel, Roman

2008-07-16

344

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

345

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

346

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

SciTech Connect

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

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

2011-10-15

347

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

348

Materials Science and Engineering A 472 (2008) 242250 Shear behavior of aluminum lattice truss sandwich panel structures  

E-print Network

Materials Science and Engineering A 472 (2008) 242­250 Shear behavior of aluminum lattice truss of Materials Science and Engineering, University of Virginia, 140 Chemistry Way, Charlottesville, VI 22904, USA hardenable 6061 aluminum tetrahedral lattice truss core sandwich panels have been fabricated by folding

Wadley, Haydn

2008-01-01

349

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

350

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

351

Steps Toward 8M Honeycomb Mirrors IV: Some Aspects Of Design And Fabrication  

NASA Astrophysics Data System (ADS)

A facility is to be built to make 8m diameter glass honeycomb mirror blanks by casting, in the same way that has been demonstrated with 1.8m blanks. The only major difference is that the larger furnace will he rotated on a turntable so as to preform the deep parabolic surface needed for f/2 mirrors. This paper explores the tolerances in glass homogeneity, thermal control and support of the blank necessary to meet the stringent imaging requirements of telescopes in the best ground based sites. In round numbers, homogenity in expansion coefficient of 10-8/°C and thermal equilibriation to 0.1°C are required. Laboratory measurements show that both can be met by a ventilated honeycomb of borosilicate or similar glass. Adequate resistance to wind pressure and buffeting can be achieved by an axial support that responds to pressure on the three defining points. The total time of about 6 weeks for melting, annealing and cooling of the blanks is set by the time constant of around 8 hours for the glass honeycomb to follow the furnace temperature.

Angel, J. R. P.; Woolf, N. J.; Hill, J. M.; Goble, L.

1983-11-01

352

Thermal phase transition of generalized Heisenberg models for SU (N ) spins on square and honeycomb lattices  

NASA Astrophysics Data System (ADS)

We investigate thermal phase transitions to a valence-bond solid phase in SU (N ) Heisenberg models with four- or six-body interactions on a square or honeycomb lattice, respectively. In both cases, a thermal phase transition occurs that is accompanied by rotational symmetry breaking of the lattice. We perform quantum Monte Carlo calculations in order to clarify the critical properties of the models. The estimated critical exponents indicate that the universality classes of the square- and honeycomb-lattice cases are identical to those of the classical X Y model with a Z4 symmetry-breaking field and the three-state Potts model, respectively. In the square-lattice case, the thermal exponent, ? , monotonically increases as the system approaches the quantum critical point, while the values of the critical exponents, ? and ? /? , remain constant. From a finite-size scaling analysis, we find that the system exhibits weak universality, because the Z4 symmetry-breaking field is always marginal. In contrast, ? in the honeycomb-lattice case exhibits a constant value, even in the vicinity of the quantum critical point, because the Z3 field remains relevant in the SU(3) and SU(4) cases.

Suzuki, Takafumi; Harada, Kenji; Matsuo, Haruhiko; Todo, Synge; Kawashima, Naoki

2015-03-01

353

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

PubMed

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

Putz, Mihai V; Ori, Ottorino

2014-01-01

354

Photoactive, porous honeycomb films prepared from Rose Bengal-grafted polystyrene.  

PubMed

Honeycomb-structured porous polymer films based on photosensitizer-grafted polystyrene are prepared through the breath figure process. Rose Bengal (RB) photosensitizer is first attached to a well-defined poly(styrene-stat-4-vinylbenzyl chloride) statistical copolymer, synthesized by nitroxide-mediated radical polymerization. The RB grafted poly(styrene-stat-4-vinylbenzyl chloride) (ca. 20,000 g mol(-1) molar mass, 1.2 dispersity) leads to porous polymer films, with a hexagonal pore pattern, while a simple mixture of poly(styrene-stat-4-vinylbenzyl chloride) and the insoluble RB photosensitizer produced unstructured, nonporous films. The RB-grafted honeycomb films, compared with the corresponding nonporous flat films, are more efficient for oxidation of organic molecules via singlet oxygen production at a liquid/solid interface. The oxidations of 1,5-dihydroxynaphthalene to juglone and ?-terpinene to ascaridole are followed in ethanol in the presence of both types of films. Oxidation of the organic molecules is a factor 5 greater with honeycomb compared to the nonporous films. This gain is ascribed to two factors: the specific location of the polar photosensitizer at the film interface and the greater exchange surface, as revealed by fluorescence and scanning electron microscopies. PMID:23855310

Pessoni, Laurence; Lacombe, Sylvie; Billon, Laurent; Brown, Ross; Save, Maud

2013-08-13

355

Theory of magnetic phase diagrams in hyperhoneycomb and harmonic-honeycomb iridates  

NASA Astrophysics Data System (ADS)

Motivated by recent experiments, we consider a generic spin model in the jeff=1 /2 basis for the hyperhoneycomb and harmonic-honeycomb iridates. Based on microscopic considerations, the effect of an additional bond-dependent anisotropic spin exchange interaction (? ) beyond the Heisenberg-Kitaev model is investigated. We obtain the magnetic phase diagrams of the hyperhoneycomb and harmonic-honeycomb (H -1 ) lattices via a combination of the Luttinger-Tisza approximation, single-Q variational ansatz, and classical Monte Carlo simulated annealing. The resulting phase diagrams on both systems show the existence of incommensurate, noncoplanar spiral magnetic orders as well as other commensurate magnetic orders. The spiral orders show counterpropagating spiral patterns, which may be favorably compared to recent experimental results on both iridates. The parameter regimes of various magnetic orders and ordering wave vectors are quite similar in both systems. We discuss the implications of our work for recent experiments and also compare our results to those of the two-dimensional honeycomb iridate systems.

Lee, Eric Kin-Ho; Kim, Yong Baek

2015-02-01

356

An `H'-shape three-dimensional meta-material used in honeycomb structure absorbing material  

NASA Astrophysics Data System (ADS)

An `H'-shape three-dimensional meta-material structure which loaded on the sidewall of honeycomb structure absorbing material was designed and fabricated in this project. The simulation results demonstrated a super-wide absorption band below -10 dB between 2.3 and 18 GHz, which expanded 7 GHz compared with the absorber without meta-material. The relative impedance curve was analyzed, which showed that the meta-material has little impact on the impedance-matching characteristics of the honeycomb structure absorbing material. We further studied the distribution of both electronic field energy and magnetic field energy. The former one indicated that the low-frequency absorption peaks could easily be moved by adjusting the parameters of the parallel-plate capacitors which generate electric resonance, and the latter one illustrated that the three-dimensional meta-material could generate magnetic resonance between units which would not exist in two-dimensional meta-material. Then we verified the simulation results through experiment which display a similar absorbing curve. The differences between simulation results and experiment results were caused by the addition substrate of the meta-material, which could not be eliminated in this experiment. However, it still implied that we can obtain a meta-material absorber that has a super-wide absorbing band if we can put the meta-material on the sidewall of the honeycomb without attachments.

Huang, Daqing; Kang, Feiyu; Zhou, Zhuohui; Cheng, Hongfei; Ding, Heyan

2015-03-01

357

Honeycomb-panel spacecraft radiator with multichip module thermal analysis and vacuum-testing  

NASA Astrophysics Data System (ADS)

This paper documents a thermal vacuum test and analysis of three small honeycomb panels for spacecraft application. The prime purpose of this test was to characterize the thermal performance of 24.1 cm×31.8 cm (9.5 in×12.5 in) honeycomb panels that use composite face-sheets with a power dissipating Multichip Module (MCM) mounted on one side. The test MCM simulates electronic circuits and computer components, and the goal is to simplify spacecraft design by the reduction of cabling. The MCM heat was generated with fused film heaters, and temperatures and powers were measured to assess several thermal performance enhancement options. The MCM heat was dissipated through the honeycomb panel to the thermal vacuum chamber. The paper presents test data and a brief description of our thermal modeling results. The maximum power dissipated by a MCM heater 1.27 cm×1.27 cm (0.5 in×0.5 in), that was maintained at 393K (120C), was 12.8-watts. A high conductivity thermal doubler mounted between the MCM and the base was found to be a significant heat rejection enhancement.

Chapter, John

1997-01-01

358

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

359

Fabrication of aluminum based nanomaterials  

Microsoft Academic Search

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

Dominique Poirier

2009-01-01

360

Fourth generation aluminum optics performance  

NASA Astrophysics Data System (ADS)

While post-polish has previously been shown to greatly enhance the surface quality, surface roughness, and surface figure of single-point diamond turned Aluminum mirrors, the field of bare Aluminum polishing continues to advance. New results demonstrating improvement in mid-spatial frequency errors and methods for adapting to a wider range of Aluminum materials constitute the next generation of polished Aluminum mirrors. These results show new levels of surface finish, correlated with BRDF measurements. Complimentary enhancements have been made by achieving new levels of precision in the placement of the optical axis relative to datum features, enabling significant alignment time savings.

Carrigan, Keith; Patel, Ankit

2013-09-01

361

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

362

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

363

Aluminum-lithium for aerospace  

SciTech Connect

Aluminum-lithium alloys were developed primarily to reduce the weight of aircraft and aerospace structures. Lithium is the lightest metallic element, and each 1% of lithium added to aluminum reduces alloy density by about 3% and increases modulus by about 5%. Though lithium has a solubility limit of 4.2% in aluminum, the amount of lithium ranges between 1 and 3% in commercial alloys. Aluminum-lithium alloys are most often selected for aerospace components because of their low density, high strength, and high specific modulus. However, other applications now exploit their excellent fatigue resistance and cryogenic toughness.

Fielding, P.S.; Wolf, G.J. [Reynolds Metals Co., Richmond, VA (United States)

1996-10-01

364

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

NASA Astrophysics Data System (ADS)

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

Vos, Roelof; Barrett, Ron

2011-09-01

365

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

366

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

367

21 CFR 73.2645 - Aluminum powder.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 2013-04-01 false Aluminum powder. 73.2645 Section 73...CERTIFICATION Cosmetics § 73.2645 Aluminum powder. (a) Identity and specifications. The color additive aluminum powder shall conform in...

2013-04-01

368

21 CFR 73.1645 - Aluminum powder.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Aluminum powder. 73.1645 Section 73.1645...CERTIFICATION Drugs § 73.1645 Aluminum powder. (a) Identity. (1) The color additive aluminum powder shall be composed of finely...

2010-04-01

369

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

370

21 CFR 73.1645 - Aluminum powder.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 2013-04-01 false Aluminum powder. 73.1645 Section 73.1645...CERTIFICATION Drugs § 73.1645 Aluminum powder. (a) Identity. (1) The color additive aluminum powder shall be composed of finely...

2013-04-01

371

21 CFR 73.2645 - Aluminum powder.  

Code of Federal Regulations, 2011 CFR

...2011-04-01 2011-04-01 false Aluminum powder. 73.2645 Section 73...CERTIFICATION Cosmetics § 73.2645 Aluminum powder. (a) Identity and specifications. The color additive aluminum powder shall conform in...

2011-04-01

372

21 CFR 73.2645 - Aluminum powder.  

Code of Federal Regulations, 2014 CFR

...2014-04-01 2014-04-01 false Aluminum powder. 73.2645 Section 73...CERTIFICATION Cosmetics § 73.2645 Aluminum powder. (a) Identity and specifications. The color additive aluminum powder shall conform in...

2014-04-01

373

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

374

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

375

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

376

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

377

21 CFR 73.2645 - Aluminum powder.  

Code of Federal Regulations, 2012 CFR

...2012-04-01 2012-04-01 false Aluminum powder. 73.2645 Section 73...CERTIFICATION Cosmetics § 73.2645 Aluminum powder. (a) Identity and specifications. The color additive aluminum powder shall conform in...

2012-04-01

378

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.

379

21 CFR 73.1645 - Aluminum powder.  

Code of Federal Regulations, 2014 CFR

...2014-04-01 2014-04-01 false Aluminum powder. 73.1645 Section 73.1645...CERTIFICATION Drugs § 73.1645 Aluminum powder. (a) Identity. (1) The color additive aluminum powder shall be composed of finely...

2014-04-01

380

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

381

21 CFR 73.2645 - Aluminum powder.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Aluminum powder. 73.2645 Section 73...CERTIFICATION Cosmetics § 73.2645 Aluminum powder. (a) Identity and specifications. The color additive aluminum powder shall conform in...

2010-04-01

382

21 CFR 73.1645 - Aluminum powder.  

Code of Federal Regulations, 2012 CFR

...2012-04-01 2012-04-01 false Aluminum powder. 73.1645 Section 73.1645...CERTIFICATION Drugs § 73.1645 Aluminum powder. (a) Identity. (1) The color additive aluminum powder shall be composed of finely...

2012-04-01

383

21 CFR 73.1645 - Aluminum powder.  

Code of Federal Regulations, 2011 CFR

...2011-04-01 2011-04-01 false Aluminum powder. 73.1645 Section 73.1645...CERTIFICATION Drugs § 73.1645 Aluminum powder. (a) Identity. (1) The color additive aluminum powder shall be composed of finely...

2011-04-01

384

Collisional absorption in aluminum.  

PubMed

The interaction of ultrashort laser pulses with matter is a topic of growing interest. In particular, recent developments on free-electron lasers have opened an unexplored field in which many interesting physical phenomena are to be expected. Since hydrodynamic descriptions of the interaction process need a microscopic "input," a quantum statistical theory of energy absorption by matter is required. We present a kinetic theory of collisional absorption in dense plasmas and analyze the electron-ion collision frequency in warm dense aluminum in dependence on laser frequency and temperature. PMID:16906987

Semkat, D; Redmer, R; Bornath, Th

2006-06-01

385

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

386

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

387

The thermomechanical stability of micro-solid oxide fuel cells fabricated on anodized aluminum oxide membranes  

NASA Astrophysics Data System (ADS)

The thermomechanical stability of micro-solid oxide fuel cells (micro-SOFCs) fabricated on an anodized aluminum oxide (AAO) membrane template is investigated. The full structure consists of the following layers: AAO membrane (600 nm)/Pt anode/YSZ electrolyte (900 nm)/porous Pt cathode. The utilization of a 600-nm-thick AAO membrane significantly improves the thermomechanical stability due to its well-known honeycomb-shaped nanopore structure. Moreover, the Pt anode layer deposited in between the AAO membrane and the YSZ electrolyte preserves its integrity in terms of maintaining the triple-phase boundary (TPB) and electrical conductivity during high-temperature operation. Both of these results guarantee thermomechanical stability of the micro-SOFC and extend the cell lifetime, which is one of the most critical issues in the fabrication of freestanding membrane-type micro-SOFCs.

Kwon, Chang-Woo; Lee, Jae-Il; Kim, Ki-Bum; Lee, Hae-Weon; Lee, Jong-Ho; Son, Ji-Won

2012-07-01

388

Weight comparisons of optimized stiffened, unstiffened, and sandwich cylindrical shells made from composite or aluminum materials  

NASA Technical Reports Server (NTRS)

This work presents optimum designs for unstiffened, hat stringer-stiffened and honeycomb sandwich cylinders under axial compression. Optimization results for graphite-epoxy cylinders show about a 50 percent weight savings over corresponding optimized aluminum cylinders for a wide loading range. The inclusion of minimum gage considerations results in a significant weight penalty, especially for a lightly loaded cylinder. Effects of employing a smeared stiffener buckling theory in the optimization program are investigated through comparison of results obtained from a more accurate branched shell buckling computer code. It was found that the stiffener cross-sectional deformations, which are usually ignored in smeared stiffener theory, result in about a 30 percent lower buckling load for the graphite-epoxy hat stiffened cylinder.

Agarwal, B. L.; Sobel, L. H.

1976-01-01

389

Aluminum vehicle breaks new ground  

Microsoft Academic Search

This article examines the efforts of automobile manufacturers and aluminum producers to develop a light weight crash resistant automobile. The topics of the article include alloys used, production techniques, fastening and bonding techniques, rigidity and crush resistance, weight reduction, die-casting and extruding of aluminum, design and construction of space frame.

Ashley

1994-01-01

390

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

391

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

392

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

393

Wettability of Aluminum on Alumina  

NASA Astrophysics Data System (ADS)

The wettability of molten aluminum on solid alumina substrate has been investigated by the sessile drop technique in a 10-8 bar vacuum or under argon atmosphere in the temperature range from 1273 K to 1673 K (1000 °C to 1400 °C). It is shown that the reduction of oxide skin on molten aluminum is slow under normal pressures even with ultralow oxygen potential, but it is enhanced in high vacuum. To describe the wetting behavior of the Al-Al2O3 system at lower temperatures, a semiempirical calculation was employed. The calculated contact angle at 973 K (700 °C) is approximately 97 deg, which indicates that aluminum does not wet alumina at aluminum casting temperatures. Thus, a priming height is required for aluminum to infiltrate a filter. Wetting in the Al-Al2O3 system increases with temperature.

Bao, Sarina; Tang, Kai; Kvithyld, Anne; Tangstad, Merete; Engh, Thorvald Abel

2011-12-01

394

Aluminum inhibits erythropoiesis in vitro.  

PubMed Central

Anemia has been associated with aluminum intoxication in patients on chronic dialysis and in animals. In studies presented here, in vitro human erythroid culture was used to delineate the effects of aluminum on normal hematopoiesis. Aluminum by itself in routine culture, even at very high levels (1,035 ng/ml), did not significantly affect erythroid colony growth. The addition of human transferrin to the culture, however, resulted in a marked dose-dependent inhibition of erythroid, but not myeloid colony growth. At all doses, CFU-E progenitors showed greater inhibition than burst-forming units (BFU-E). Aluminum inhibition was not overcome by increasing the dose of erythropoietin or adding additional burst-promoting activity to the culture. Inhibition by aluminum was directly related to the number of binding sites on transferrin in the culture, and was not observed in the presence of fully iron-saturated transferrin. Images PMID:3384943

Mladenovic, J

1988-01-01

395

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

396

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

397

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

398

Aluminum anode for aluminum-air battery - Part I: Influence of aluminum purity  

NASA Astrophysics Data System (ADS)

2N5 commercial grade aluminum (99.5% purity) leads to the lower aluminum-air battery performances than 4N high pure grade aluminum (99.99% purity) due to impurities itself and formed impurity complex layer which contained Fe, Si, Cu and others. The impurity complex layer of 2N5 grade Al declines the battery voltage on standby status. It also depletes discharge current and battery efficiency at 1.0 V which is general operating voltage of aluminum-air battery. However, the impurity complex layer of 2N5 grade Al is dissolved with decreasing discharge voltage to 0.8 V. This phenomenon leads to improvement of discharge current density and battery efficiency by reducing self-corrosion reaction. This study demonstrates the possibility of use of 2N5 grade Al which is cheaper than 4N grade Al as the anode for aluminum-air battery.

Cho, Young-Joo; Park, In-Jun; Lee, Hyeok-Jae; Kim, Jung-Gu

2015-03-01

399

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

400

Spray Rolling Aluminum Strip  

SciTech Connect

Spray forming is a competitive low-cost alternative to ingot metallurgy for manufacturing ferrous and non-ferrous alloy shapes. It produces materials with a reduced number of processing steps, while maintaining materials properties, with the possibility of near-net-shape manufacturing. However, there are several hurdles to large-scale commercial adoption of spray forming: 1) ensuring strip is consistently flat, 2) eliminating porosity, particularly at the deposit/substrate interface, and 3) improving material yield. Through this program, a new strip/sheet casting process, termed spray rolling, has been developed, which is an innovative manufacturing technique to produce aluminum net-shape products. Spray rolling combines the benefits of twin-roll casting and conventional spray forming, showing a promising potential to overcome the above hurdles associated with spray forming. Spray rolling requires less energy and generates less scrap than conventional processes and, consequently, enables the development of materials with lower environmental impacts in both processing and final products. Spray Rolling was developed as a collaborative project between the University of California-Davis, the Colorado School of Mines, the Idaho National Engineering and Environmental Laboratory, and an industry team. The following objectives of this project were achieved: (1) Demonstration of the feasibility of the spray rolling process at the bench-scale level and evaluation of the materials properties of spray rolled aluminum strip alloys; and (2) Demonstration of 2X scalability of the process and documentation of technical hurdles to further scale up and initiate technology transfer to industry for eventual commercialization of the process.

Lavernia, E.J.; Delplanque, J-P; McHugh, K.M.

2006-05-10

401

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

402

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

403

Experimental results for labyrinth gas seals with honeycomb stators - Comparisons to smooth-stator seals and theoretical predictions  

NASA Technical Reports Server (NTRS)

Experimental measurements are presented for the rotordynamic stiffness and damping coefficients of a teeth-on-rotor labyrinth seal with a honeycomb stator. Inlet circumferential velocity, inlet pressure, rotor speed, and seal clearance are primary variables. Results are compared to data for teeth-on-rotor labyrinth seals with smooth stators and to analytical predictions 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 rator speeds. At high rotor speeds, the stator surface does not affect stability. 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; however, the model predictions and test results diverge with increasing running speed. Overall, the model does not perform as well for low clearance seals as for high clearance seals.

Hawkins, Larry; Childs, Dara; Hale, Keith

1989-01-01

404

The Hubbard model on the bilayer honeycomb lattice with Bernal stacking  

NASA Astrophysics Data System (ADS)

Using a combination of quantum Monte Carlo, the functional renormalization group and mean-field theory we study the Hubbard model on the bilayer honeycomb as a model for interacting electrons on bilayer graphene. The free bands consisting of two Fermi points with quadratic dispersions lead to a finite density of states, which triggers the antiferromagnetic instability and spontaneously breaks sublattice and spin rotational symmetry once a local Coulomb repulsion is introduced. We show that the antiferromagnetic instability is insensitive to the inclusion of extended Coulomb interactions and discuss effects on the sublattice magnetization and of finite size systems in numerical approaches.

Lang, Thomas C.; Übelacker, Stefan; Meng, Zi Yang; Scherer, Michael; Honerkamp, Carsten; Muramatsu, Alejandro; Assaad, Fakher F.; Wessel, Stefan

2012-02-01

405

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

406

Variational cluster approach to the Hubbard model on a honeycomb lattice  

NASA Astrophysics Data System (ADS)

We study the ground-state properties of the Hubbard model on the honeycomb lattice at half filling. Using the variational cluster approximation, We study the semimetal-insulator transition and antiferromagnetism as functions of the on-site Coulomb interaction U. When U is switched on, a small, but finite, single-particle gap appears; thus, we conclude that a tiny gap appears with arbitrary small U > 0. With further increases in U, the system goes into the antiferromagnetic state. We find that the staggered magnetization increases continuously with increasing U and that the antiferromagnetic phase transition is of the second order.

Seki, Kazuhiro; Ohta, Yukinori

2013-06-01

407

Quantum spin Hall effect in a two-orbital model on a honeycomb lattice  

NASA Astrophysics Data System (ADS)

The spin Hall effect is investigated in a two-orbital tight-binding model on a honeycomb lattice. We show that the model exhibits three topologically-different insulating phases at half filling, which are distinguished by different quantized values of the spin Hall conductivity. We analytically determine the phase boundaries, where the valence and conduction bands touch with each other with forming the Dirac nodes at the Fermi level. The results are discussed in terms of the effective antisymmetric spin-orbit coupling. The relation to the Kane- Mele model and implications for a magnetoelectric effect are also discussed.

Hayami, Satoru; Kusunose, Hiroaki; Motome, Yukitoshi

2015-03-01

408

Composite multi-vortex diffraction-free beams and van Hove singularities in honeycomb lattices  

E-print Network

We find diffraction-free beams for graphene and MoS$_2$-type honeycomb optical lattices. The resulting composite solutions have the form of multi-vortices, with spinor topological charges ($n$, $n\\pm1$). Exact solutions for the spinor components are obtained in the Dirac limit. The effects of the valley degree of freedom and the mass are analyzed. Passing through the van-Hove singularity the topological structure of the solutions is modified. Exactly at the singularity the diffraction-free beams take the form of strongly localized one-dimensional stripes.

Paltoglou, Vassilis; Efremidis, Nikolaos K

2015-01-01

409

Local Probe Studies of the Quantum Honeycomb Antiferromagnet Ba3CuSb2O9  

NASA Astrophysics Data System (ADS)

The 6H-perovskites, Ba3MSb2O9, have generated an enormous amount of interest in the last two years following the possible discovery of quantum spin liquid physics in two such materials. We present local probe studies (muon spin rotation and nuclear magnetic resonance) on the spin-1/2 honeycomb antiferromagnet Ba3CuSb2O9. We show that the system presents no spin freezing down to temperatures as low as 20 mK. NMR measurements show evidence of a spin gap and suggest that the material has a random singlet ground state rather than the alternative spin-orbital liquid state.

Quilliam, Jeffrey; Bert, Fabrice; Kermarrec, Edwin; Payen, Christophe; Guillot-Deudon, Cathérine; Bonville, Pierre; Mendels, Philippe

2013-03-01

410

How to directly observe Landau levels in driven-dissipative strained honeycomb lattices  

E-print Network

We study the driven-dissipative steady-state of a coherently-driven Bose field in a honeycomb lattice geometry. In the presence of a suitable spatial modulation of the hopping amplitudes, a valley-dependent artificial magnetic field appears and the low-energy eigenmodes have the form of relativistic Landau levels. We show how the main properties of the Landau levels can be extracted by observing the peaks in the absorption spectrum of the system and the corresponding spatial intensity distribution. Finally, quantitative predictions for realistic lattices based on photonic or microwave technologies are discussed.

Salerno, Grazia; Price, Hannah M; Carusotto, Iacopo

2015-01-01

411

Frustrated Heisenberg antiferromagnet on the honeycomb lattice: A candidate for deconfined quantum criticality  

Microsoft Academic Search

We study the ground-state (gs) phase diagram of the frustrated spin-(1)\\/(2) J1-J2-J3 antiferromagnet with J2=J3=kappaJ1 on the honeycomb lattice using coupled-cluster theory and exact diagonalization methods. We present results for the gs energy, magnetic order parameter, spin-spin correlation function, and plaquette valence-bond crystal (PVBC) susceptibility. We find a Néel antiferromagnetic (AFM) phase for kappa

D. J. J. Farnell; R. F. Bishop; P. H. Y. Li; J. Richter; C. E. Campbell

2011-01-01

412

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

413

A comparison of the static and dynamic characteristics of straight-bore and convergent tapered-bore honeycomb annular gas seals  

E-print Network

Results are presented from tests conducted with straight-bore and convergent tapered-bore honeycomb annular gas seals. The test seals had a 114.3 mm bore with an L/D = 0.75 and a nominal radial clearance of 0.19 mm. The honeycomb cell depth for both...

Dawson, Matthew Peter

2000-01-01

414

Subsurface Aluminum Nitride Formation in Iron-Aluminum Alloys  

NASA Astrophysics Data System (ADS)

Transformation-induced plasticity (TRIP) steels containing higher amounts of aluminum than conventional steels are ideal for structural automotive parts due to their mechanical properties. However, the aluminum tends to react with any processing environment at high temperatures and therefore presents significant challenges during manufacturing. One such challenge occurs during secondary cooling, reheating, and hot-rolling and is caused by a reaction with nitrogen-rich atmospheres wherein subsurface aluminum nitride forms in addition to internal and external oxides. The nitrides are detrimental to mechanical properties and cause surface cracks. It is important to understand how these nitrides and oxides form and their consequences for the quality of steel products. This study looks at model iron-aluminum (up to 8 wt.% aluminum) alloys and uses confocal laser scanning microscopy, x-ray diffraction, scanning electron microscopy with energy dispersive x-ray spectrometry, and transmission electron microscopy to study the effect of various conditions on the growth and development of these precipitates in a subsurface oxygen-depleted region. By using model alloys and controlling the experimental atmosphere, this study is able to understand some of the more fundamental materials science behind aluminum nitride formation in aluminum-rich iron alloys and the relationship between internal nitride and oxide precipitation and external oxide scale morphology and composition. The iron-aluminum alloys were heated in N2 atmospheres containing oxygen impurities. It was found that nitrides formed when bulk aluminum content was below 8 wt.% when oxygen was sufficiently depleted due to the internal oxidation. In the samples containing 1 wt.% aluminum, the depth of the internal oxide and nitride zones were in agreement with a diffusion-based model. Increasing aluminum content to 3 and 5 wt% had the effects of modifying the surface-oxide scale composition and increasing its continuity, which gradually decreased the internal precipitation zones with increasing aluminum content. In samples containing 8 wt.% aluminum, a thick continuous oxide scale formed and prevented nitrogen and oxygen penetration into the bulk of the sample, thus preventing the formation of any internal precipitates. The effect of modifying the heating rate in pure N2 atmospheres was examined. Samples were heated over the course of 1, 10, or 100 minutes. Faster heating rates increased the aluminum content in the oxide scale on all samples. Additionally, these rapid heating rate samples had either had lower internal precipitation depths or no internal precipitates. Experiments were conducted in N2--2.5% H2/H 2O mixtures with varying dew points to lower the oxygen potential of the reaction gas and prevent the formation of external iron oxide scales. In the 3 and 5 wt.% Al alloys, this produced an internal aluminum-rich oxide band which inhibited further internal precipitation. Samples treated in atmospheres to simulate the reheat furnace combustion atmosphere experienced dramatically increased external oxidation in addition to inward growth of the oxide scale and internal precipitation of oxides and nitrides within the metal. The most important scientific findings of this dissertation are the dramatic effect of heating rate on modifying the external scale of the alloys presented and the presence of continuous internal oxide bands in several samples throughout the study. Oxidation studies typically occur for longer times and in higher oxygen contents than the present results, so the influence of heating rate is either largely unnoticed or is overcome by oxide growth at long times. Oxide bands have been observed in literature, but few aluminum oxide bands have been seen before this study. vi.

Bott, June H.

415

Procedures for predicting pressures inside cores  

NASA Astrophysics Data System (ADS)

Core gas defects are among the most aggravating defects because they are difficult to control and may not be found until castings are machined. These defects occur when the pressure in the core is higher than the external pressure acting on the core from the metal-head pressure. The prediction of core and mold gas defects requires a determination of the permeability of the cores and the rate and volume of gas evolved from the cores in contact with molten metal. Techniques were developed for measuring core permeability and gas evolution. Gas permeability was measured at pressure levels that are seen inside cores during casting. The volume and rate of gas evolution from cores submerged in molten metal was also measured. Use of these techniques was demonstrated on commercial cores that were submerged in molten aluminum and iron. The effects of common core-making variables and casting temperatures were determined. Permeability depended mainly on compaction level, with increased density associated with reduced permeability. Coatings decreased permeability, while binder, sand type, and additives had no affect. Gas evolution volumes and rates for cores immersed in molten metal were higher in phenolic urethane cold box cores than in epoxy acrylic cores. Higher binder content, additives, coatings, immersion temperatures, core length, and metal contact area all increased evolved gas volumes and rates. A method for calculating the core pressure in simple geometries was developed and confirmed experimentally. The data generated from the gas evolution measurements were used to build a physical model on binder decomposition and the resultant gas evolution during casting. This model was used to determine the amount of gas evolved from cores at various geometries and temperatures. The model accurately predicted the volume of gas evolved. However, the composition of the gases, the core temperature profile, and more precise interfacial heat transfer and sand thermal conductivity data are also required to match the experimental rate curves.

Winardi, Leonard

416

Solidification behavior of undercooled liquid aluminum oxide  

SciTech Connect

Solidification of aluminum oxide from undercooled melts was investigated in containerless experiments. Specimens were levitated in a gas jet, stabilized with an acoustic positioning device, and melted with cw CO{sub 2} laser beams. Cooling curves were obtained by optical pyrometry when the laser intensity was reduced. The materials examined were high-purity Verneuil sapphire, 99.5% polycrystalline alumina, and oxide materials recovered from the effluent of an aluminum-fueled rocket motor. The degree of undercooling, the apparent temperature behavior during the thermal arrest on solidification, and the structure of the materials formed were different in argon and oxygen atmospheres. Undercooling of the sapphire and alumina materials was 360 {+-} 10 K in an oxygen atmosphere and approximately 450 K in argon. Melting and solidification of high-purity sapphire resulted in a dendritic and porous polycrystalline material in oxygen. Dense, larger crystals were obtained in argon. Products formed from 99.5% alumina were discolored and the cores were white, indicating impurity segregation effects. More reproducible behavior was observed for the sapphire and 99.5% alumina than for the tungsten-contaminated rocket motor effluent materials.

Weber, J.K.R.; Anderson, C.D.; Merkley, D.R.; Nordine, P.C. [Intersonics, Inc., Northbrook, IL (United States)

1995-03-01

417

PREFACE: Ultrathin layers of graphene, h-BN and other honeycomb structures Ultrathin layers of graphene, h-BN and other honeycomb structures  

NASA Astrophysics Data System (ADS)

Since ancient times, pure carbon materials have been familiar in human society—not only diamonds in jewellery and graphite in pencils, but also charcoal and coal which have been used for centuries as fuel for living and industry. Carbon fibers are stronger, tougher and lighter than steel and increase material efficiency because of their lower weight. Today, carbon fibers and related composite materials are used to make the frames of bicycles, cars and even airplane parts. The two-dimensional allotrope, now called graphene, is just a single layer of carbon atoms, locked together in a strongly bonded honeycomb lattice. In plane, graphene is stiffer than diamond, but out-of-plane it is soft, like rubber. It is virtually invisible, may conduct electricity (heat) better than copper and weighs next to nothing. Carbon compounds with two carbon atoms as a base, such as graphene, graphite or diamond, have isoelectronic sister compounds made of boron-nitrogen pairs: hexagonal and cubic boron nitride, with almost the same lattice constant. Although the two 2D sisters, graphene and h-BN, have the same number of valence electrons, their electronic properties are very different: freestanding h-BN is an insulator, while charge carriers in graphene are highly mobile. The past ten years have seen a great expansion in studies of single-layer and few-layer graphene. This activity has been concerned with the ? electron transport in graphene, in electric and magnetic fields. More than 30 years ago, however, single-layer graphene and h-BN on solid surfaces were widely investigated. It was noted that they drastically changed the chemical reactivity of surfaces, and they were known to 'poison' heterogeneous catalysts, to passivate surfaces, to prevent oxidation of surfaces and to act as surfactants. Also, it was realized that the controlled growth of h-BN and graphene on substrates yields the formation of mismatch driven superstructures with peculiar template functionality on the nanometer scale. This special section contains interesting papers on graphene, h-BN and related 'honeycomb' compounds on solid surfaces, which are currently in development. Interfacial interaction strongly modifies the electronic and atomic structures of these overlayer systems and substrate surfaces. In addition, one can recognize a variety of growth phenomena by changing the surface and growth conditions, which are promising as regards fabricating those noble nanosystems. We have great pleasure in acknowledging the enthusiastic response and participation of our invited authors and their diligent preparation of the manuscripts. Ultrathin layers of graphene, h-BN and other honeycomb structures contents Ultrathin layers of graphene, h-BN and other honeycomb structuresThomas Geber and Chuhei Oshima Templating of arrays of Ru nanoclusters by monolayer graphene/Ru Moirés with different periodicitiesEli Sutter, Bin Wang, Peter Albrecht, Jayeeta Lahiri, Marie-Laure Bocquet and Peter Sutter Controllable p-doping of graphene on Ir(111) by chlorination with FeCl3N A Vinogradov, K A Simonov, A V Generalov, A S Vinogradov, D V Vyalikh, C Laubschat, N Mårtensson and A B Preobrajenski Optimizing long-range order, band gap, and group velocities for graphene on close-packed metal surfacesF D Natterer, S Rusponi, M Papagno, C Carbone and H Brune Epitaxial growth of graphene on transition metal surfaces: chemical vapor deposition versus liquid phase depositionSamuel Grandthyll, Stefan Gsell, Michael Weinl, Matthias Schreck, Stefan Hüfner and Frank Müller High-yield boron nitride nanosheets from 'chemical blowing': towards practical applications in polymer compositesXuebin Wang, Amir Pakdel, Chunyi Zhi, Kentaro Watanabe, Takashi Sekiguchi, Dmitri Golberg and Yoshio Bando BCx layers with honeycomb lattices on an NbB2(0001) surfaceChuhei Oshima Epitaxial growth of boron-doped graphene by thermal decomposition of B4CWataru Norimatsu, Koichiro Hirata, Yuta Yamamoto, Shigeo Arai and Michiko Kusunoki Mechanical exfoliation of epitaxial graphene on Ir(111) enabled by Br2 intercalationCh

Geber, Thomas; Oshima, Chuhei

2012-08-01

418

Electrolyte treatment for aluminum reduction  

DOEpatents

A method of treating an electrolyte for use in the electrolytic reduction of alumina to aluminum employing an anode and a cathode, the alumina dissolved in the electrolyte, the treating improving wetting of the cathode with molten aluminum during electrolysis. The method comprises the steps of providing a molten electrolyte comprised of ALF.sub.3 and at least one salt selected from the group consisting of NaF, KF and LiF, and treating the electrolyte by providing therein 0.004 to 0.2 wt. % of a transition metal or transition metal compound for improved wettability of the cathode with molten aluminum during subsequent electrolysis to reduce alumina to aluminum.

Brown, Craig W. (Seattle, WA); Brooks, Richard J. (Seattle, WA); Frizzle, Patrick B. (Seattle, WA); Juric, Drago D. (Bulleen, AU)

2002-01-01

419

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

420

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 (“design for recycling” and recycling incentives).

2013-07-31

421

Experimental Investigation on Mechanical Properties of Magnetorheological Elastomer with Circular Honeycomb Holes  

NASA Astrophysics Data System (ADS)

In order to enhance adjustable mechanical properties of a specific magnetorheological elastomer (MRE), this study presents a new exterior structure of MRE by punching circular honeycomb holes on the MRE samples. Seven silicone rubber MRE samples with the same component are fabricated and then punched holes with different numbers and diameters. The influence of different porosities on the mechanical properties of MRE under various magnetic fields is experimentally investigated by using a rheometer with electromagnetic suite. It is shown from experimental investigation that the porosity of MRE samples has a significant impact on the performance of MRE; the shear storage modulus (MR effect) and the loss factor is greatly increased. It is also observed that all the field-induced mechanical properties of the samples attain their respective maximum performance when the porosity increases to a critical value. The experimental results presented in this work directly indicate that high performances of the field-dependent mechanical and rheological properties can be achieved by means of external alternative structures such as honeycomb holes.

Yu, Miao; Xing, Zhiwei; Zheng, Xing; Fu, Jie; Choi, Seung-Bok

2014-12-01

422

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

423

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

424

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

PubMed Central

Background The herbicide alachlor (2-chloro-2?6?-diethyl-N-methoxymethylacetanilide) has been known as a probable human carcinogen, and the MCL (minimum contamination level) for drinking water has been set at 2 ?g L-1. Therefore, the advanced methods for effectively removing it from water are a matter of interest. Catalyzed ozonation is a promising method for refractory organics degradation. Cu/Al2O3 catalyzed ozonation for degrading an endocrine disruptor (alachlor) in water was investigated. Results Experimental results showed that the ozonation of alachlor can be effectively catalyzed and enhanced by Cu/Al2O3-honeycomb. The main intermediate products formed (aliphatic carboxylic acids) were mineralized to a large extent in the catalytic process. Conclusions This study has shown that Cu/Al2O3-honeycomb is a feasible and efficient catalyst in the ozonation of alachlor in water. Less intermediate oxidation product was produced in the catalytic process than in the uncatalytic one. Furthermore, the mineralization of alachlor could be enhanced by increasing the pH of the reaction solution. PMID:23977841

2013-01-01

425

Perturbative approach to an exactly solved problem: the Kitaev honeycomb model  

E-print Network

We analyze the gapped phase of the Kitaev honeycomb model perturbatively in the isolated-dimer limit. Our analysis is based on the continuous unitary transformations method which allows one to compute the spectrum as well as matrix elements of operators between eigenstates, at high order. The starting point of our study consists in an exact mapping of the original honeycomb spin system onto a square-lattice model involving an effective spin and a hardcore boson. We then derive the low-energy effective Hamiltonian up to order 10 which is found to describe an interacting-anyon system, contrary to the order 4 result which predicts a free theory. These results give the ground-state energy in any vortex sector and thus also the vortex gap, which is relevant for experiments. Furthermore, we show that the elementary excitations are emerging free fermions composed of a hardcore boson with an attached spin- and phase- operator string. We also focus on observables and compute, in particular, the spin-spin correlation functions. We show that they admit a multi-plaquette expansion that we derive up to order 6. Finally, we study the creation and manipulation of anyons with local operators, show that they also create fermions, and discuss the relevance of our findings for experiments in optical lattices.

J. Vidal; K. P. Schmidt; S. Dusuel

2009-01-12

426

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

427

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

PubMed Central

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

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

2013-01-01

428

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

429

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

430

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

431

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

432

Moving vortex phases, dynamical symmetry breaking, and jamming for vortices in honeycomb pinning arrays  

SciTech Connect

We show using numerical simulations that vortices in honeycomb pinning arrays can exhibit a remarkable variety of dynamical phases that are distinct from those found for triangular and square pinning arrays. In the honeycomb arrays, it is possible for the interstitial vortices to form dimer or higher n-mer states which have an additional orientational degree of freedom that can lead to the formation of vortex molecular crystals. For filling fractions where dimer states appear, a dynamical symmetry breaking can occur when the dimers flow in one of two possible alignment directions. This leads to transport in the direction transverse to the applied drive. We show that dimerization produces distinct types of moving phases which depend on the direction of the driving force with respect to the pinning lattice symmetry. When the dimers are driven along certain directions, a reorientation of the dimers can produce a jamming phenomenon which results in a strong enhancement in the critical depinning force. The jamming can also cause unusual effects such as an increase in the critical depinning force when the size of the pinning sites is reduced.

Reichhardt, Charles [Los Alamos National Laboratory; Reichhardt, Cynthia [Los Alamos National Laboratory

2008-01-01

433

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

434

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...

435

Immunotoxicity of aluminum.  

PubMed

Aluminum (Al) is present in the daily life of all humans. With the incidence of Al contamination increased in recent years, the toxicity of Al on the immune function has attracted more attention. Even with this increased attention, the mechanism of Al immunotoxicity still remains unclear. The mechanism of Al immunotoxicity reviewed herein focused on the effects of Al on the splenic trace elements, the status of ?-naphthyl acetate esterase (ANAE) cells, cytokines, complement and immunoglobulins, as well as macrophages. The studies in the literature showed that Al decreased splenic iron (Fe) and zinc (Zn) levels, but the effects of Al on splenic copper (Cu) level was ambiguous and controversial. Al exposure inhibited levels of ANAE(+) cells, the production of interleukin (IL)-2 and the functions of macrophages. With respect to other key cytokines, studies showed that Al suppressed the production of tumor necrosis factor (TNF)-? in vitro; effects of Al on TNF-? formation in vivo were less overt. Al exposure reduced complement 3 (C3) level, but effects of Al exposure on complement 4 (C4) level were not as clear-cut. Lastly, the effects of Al exposure on the IgG, IgM and IgA levels were conflicting. Taken in totality, the results of several studies in the literature demonstrated that Al could impart adverse effects on immune function. PMID:24287266

Zhu, Yanzhu; Li, Yanfei; Miao, Liguang; Wang, Yingping; Liu, Yanhuan; Yan, Xijun; Cui, Xuezhe; Li, Haitao

2014-06-01

436

Utilization of aluminum sludge and aluminum slag (dross) for the manufacture of calcium aluminate cement  

Microsoft Academic Search

Four calcium aluminate cement mixes were manufactured from aluminum sludge as a source of calcium oxide and Al2O3 and aluminum slag (dross) as a source of aluminum oxide with some additions of pure alumina. The mixes were composed of 35–50% aluminum sludge, 37.50–48.75% aluminum slag (dross) and 12.50–16.25% aluminum oxide. The mixed were processed then sintered at different firing temperatures

E. M. M. Ewais; N. M. Khalil; M. S. Amin; Y. M. Z. Ahmed; M. A. Barakat

2009-01-01

437

Commonwealth Aluminum: Manufacturer Conducts Plant-Wide Energy Assessments at Two Aluminum Sheet Production Operations;  

SciTech Connect

DOE Industrial Technologies Program case study describes the savings possible if Commonwealth Aluminum (now Aleris Rolled Products) makes improvements noted in energy assessments at two aluminum mills.

Not Available

2006-04-01

438

Aluminum chloride formation on Space Shuttle aluminum oxide  

NASA Technical Reports Server (NTRS)

Samples of particulates collected from the exhaust of Space Shuttle launches STS-1, -4, -5, -6, and -7 were analyzed. Scanning electron microscopy and X-ray diffractometry of these samples indicated that the particulates were spherical and predominantly composed of aluminum oxide. The water-soluble weight fraction, pH, acid-soluble weight fraction, and insoluble weight fraction were determined for each sample. Water-soluble weight fractions averaged about 7 percent of the total sample weight, were generally very acidic, and contained significantly elevated concentrations of chloride and aluminum (III) ion. The high concentrations of soluble aluminum (III) and chloride ions observed suggested that aluminum chlorides and/or oxychlorides had formed on the surface of the alumina particulates. More than 72 percent by weight of each sample was insoluble in either water or strong mineral acid, and was identified as alpha-Al2O3. The results from these analyses suggest that the surface of Space Shuttle exhaust alumina particulates will be highly acidic and heavily chlorided, and that a substantial amount of the surface chloride may be chemically associated with aluminum (III) ions rather than just physically adsorbed as HCl.

Cofer, W. R., III

1984-01-01

439

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

440

CVD Growth of Self-Organized Micro-Honeycomb Network Structure of Single-Walled Carbon Nanotubes for Photovoltaic Devices  

E-print Network

CVD Growth of Self-Organized Micro-Honeycomb Network Structure of Single-Walled Carbon Nanotubes for Photovoltaic Devices Shigeo Maruyama, Kehang Cui, Takaaki Chiba, Erik Einarsson, Shohei Chiashi Department of Mechanical Engineering The University of Tokyo, Tokyo 113-8656, Japan For photovoltaic devices, so far

Maruyama, Shigeo

441

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

442

Japan-Korea Workshop 2007, Gifu, Japan Honeycomb-like Large Area LaB6 Plasma Source  

E-print Network

Japan-Korea Workshop 2007, Gifu, Japan Honeycomb-like Large Area LaB6 Plasma Source for Multi Research Center, 2) Hanyang University #12;Japan-Korea Workshop 2007, Gifu, Japan AbstractAbstract Multi field intensity of 870 G #12;Japan-Korea Workshop 2007, Gifu, Japan Overview of MP2Overview of MP2 #12

Princeton Plasma Physics Laboratory

443

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

E-print Network

Self-Assembled Micro-Honeycomb Network of Single-Walled Carbon Nanotubes for Heterojunction Solar@photon.t.u-tokyo.ac.jp) Various forms of nano-carbon films such as random network of single-walled carbon nanotubes (SWNTs), vertically aligned SWNT (VA-SWNTs) and graphene have been examined for SWNT/Si heterojunction solar cells

Maruyama, Shigeo

444

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

445

Starless Cores  

E-print Network

Dense low mass cores in nearby clouds like Taurus and Auriga are some of the simplest sites currently forming stars like our Sun. Because of their simplicity and proximity, dense cores offer the clearest view of the different phases of star formation, in particular the conditions prior to the onset of gravitational collapse. Thanks to the combined analysis of the emission from molecular lines and the emission/absorption from dust grains, the last several years have seen a very rapid progress in our understanding of the structure and chemical composition of starless cores. Previous contradictions between molecular tracers are now understood to arise from core chemical inhomogeneities, which are caused by the selective freeze out of molecules onto cold dust grains. The analysis of the dust emission and absorption, in addition, has allowed us to derive accurate density profiles, and has made finally possible to carry out self consistent modeling of the internal structure of starless cores. In this paper I briefly review the evolution of core studies previous to the current golden age, and show how multi-tracer emission can now be modeled in a systematic manner. Finally I show how we can start to reconstruct the early history of core formation taking advantage of the chemical changes in the gas.

Mario Tafalla

2005-04-23

446

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

447

Weld Repair of Thin Aluminum Sheet  

NASA Technical Reports Server (NTRS)

Weld repairing of thin aluminum sheets now possible, using niobium shield and copper heat sinks. Refractory niobium shield protects aluminum adjacent to hole, while copper heat sinks help conduct heat away from repair site. Technique limits tungsten/inert-gas (TIG) welding bombardment zone to melt area, leaving surrounding areas around weld unaffected. Used successfully to repair aluminum cold plates on Space Shuttle, Commercial applications, especially in sealing fractures, dents, and holes in thin aluminum face sheets or clad brazing sheet in cold plates, heat exchangers, coolers, and Solar panels. While particularly suited to thin aluminum sheet, this process also used in thicker aluminum material to prevent surface damage near weld area.

Beuyukian, C. S.; Mitchell, M. J.

1986-01-01

448

24. A CORE WORKER DISPLAYS THE CORE BOX AND CORES ...  

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

24. A CORE WORKER DISPLAYS THE CORE BOX AND CORES FOR A BRASS GATE VALVE BODY MADE ON A CORE BOX, CA. 1950. - Stockham Pipe & Fittings Company, 4000 Tenth Avenue North, Birmingham, Jefferson County, AL

449

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

NASA Astrophysics Data System (ADS)

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 O2 molecules at simulation temperatures of 500 and 1000 K. In all cases, the reaction pathway involves O2 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.

2014-03-01

450

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

PubMed

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 O2 molecules at simulation temperatures of 500 and 1000 K. In all cases, the reaction pathway involves O2 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. PMID:24628175

Alnemrat, Sufian; Hooper, Joseph P

2014-03-14

451

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

452

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

453

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

454

Fabrication of mussel-inspired highly adhesive honeycomb films containing catechol groups and their applications for substrate-independent porous templates.  

PubMed

Porous surface patterns are used in a wide variety of practical applications. Honeycomb-patterned porous polymer films are good templates for preparing porous surfaces due to their simple fabrication and the arrangement of pores on the surface. Catechol groups include in adhesive protein of mussels have attracted much attention due to their highly and substrate-independent adhesive properties. In this paper, highly and substrate-independent adhesive honeycomb-patterned porous polymer films are prepared by using amphiphilic copolymer having catechol moieties. Furthermore, porous surface patterns are transferred on various organic or inorganic substrates by wet etching with using adhesive honeycomb films as templates. PMID:23508892

Saito, Yuta; Kawano, Takahito; Shimomura, Masatsugu; Yabu, Hiroshi

2013-04-25

455

A comparison of experimental results and theoretical predictions for the rotordynamic and leakage characteristics of short (L/D=1/6) honeycomb and smooth annular pressure seals  

E-print Network

perturbation analysis to solve the governing equations of flow. Experimental results show that at tight clearances honeycomb seals have better leakage control than either smooth or labyrinth configurations. The rotordynamic coefficients were found..., and inlet pressure of 18.3 bar 34 Fig. 21 A comparison of mass flow rate verses absolute inlet pressure for honeycomb and labyrinth seals at Cr=0.41 mm, and Pra=0.40 36 Fig. 22 A comparison of mass flow rate vs. absolute inlet pressure for honeycomb...

Kleynhans, George Frederick

1991-01-01

456

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.

457

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

458

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

E-print Network

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

Wen-Long You

2015-02-06

459

Noise transmission through an acoustically treated and honeycomb stiffened aircraft sidewall  

NASA Astrophysics Data System (ADS)

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

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

1984-10-01

460

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

461

Parity anomaly and Landau-level lasing in strained photonic honeycomb lattices.  

PubMed

We describe the formation of highly degenerate, Landau-level-like amplified states in a strained photonic honeycomb lattice in which amplification breaks the sublattice symmetry. As a consequence of the parity anomaly, the zeroth Landau level is localized on a single sublattice and possesses an enhanced or reduced amplification rate. The selection of the sublattice depends on the strain orientation but is independent of the valley. The spectral properties of the higher Landau levels are constrained by a generalized time-reversal symmetry. In the setting of two-dimensional photonic crystal lasers, the anomaly affects the mode selection and lasing threshold while in three-dimensional photonic lattices it can be probed via the beam dynamics. PMID:23383792

Schomerus, Henning; Halpern, Nicole Yunger

2013-01-01