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Sample records for mechanical characterization method

  1. Novel method for mechanical characterization of polymeric nanofibers.

    PubMed

    Naraghi, Mohammad; Chasiotis, Ioannis; Kahn, Harold; Wen, Yongkui; Dzenis, Yuris

    2007-08-01

    A novel method to perform nanoscale mechanical characterization of highly deformable nanofibers has been developed. A microelectromechanical system (MEMS) test platform with an on-chip leaf-spring load cell that was tuned with the aid of a focused ion beam was built for fiber gripping and force measurement and it was actuated with an external piezoelectric transducer. Submicron scale tensile tests were performed in ambient conditions under an optical microscope. Engineering stresses and strains were obtained directly from images of the MEMS platform, by extracting the relative rigid body displacements of the device components by digital image correlation. The accuracy in determining displacements by this optical method was shown to be better than 50 nm. In the application of this method, the mechanical behavior of electrospun polyacrylonitrite nanofibers with diameters ranging from 300 to 600 nm was investigated. The stress-strain curves demonstrated an apparent elastic-perfectly plastic behavior with elastic modulus of 7.6+/-1.5 GPa and large irreversible strains that exceeded 220%. The large fiber stretch ratios were the result of a cascade of periodic necks that formed during cold drawing of the nanofibers. PMID:17764356

  2. Novel method for mechanical characterization of polymeric nanofibers

    NASA Astrophysics Data System (ADS)

    Naraghi, Mohammad; Chasiotis, Ioannis; Kahn, Harold; Wen, Yongkui; Dzenis, Yuris

    2007-08-01

    A novel method to perform nanoscale mechanical characterization of highly deformable nanofibers has been developed. A microelectromechanical system (MEMS) test platform with an on-chip leaf-spring load cell that was tuned with the aid of a focused ion beam was built for fiber gripping and force measurement and it was actuated with an external piezoelectric transducer. Submicron scale tensile tests were performed in ambient conditions under an optical microscope. Engineering stresses and strains were obtained directly from images of the MEMS platform, by extracting the relative rigid body displacements of the device components by digital image correlation. The accuracy in determining displacements by this optical method was shown to be better than 50nm. In the application of this method, the mechanical behavior of electrospun polyacrylonitrite nanofibers with diameters ranging from 300to600nm was investigated. The stress-strain curves demonstrated an apparent elastic-perfectly plastic behavior with elastic modulus of 7.6±1.5GPa and large irreversible strains that exceeded 220%. The large fiber stretch ratios were the result of a cascade of periodic necks that formed during cold drawing of the nanofibers.

  3. Mechanical characterization of unplasticised polyvinylchloride thick pipes by optical methods

    NASA Astrophysics Data System (ADS)

    Mihaylova, E.; Potelon, B.; Reddy, S.; Toal, V.; Smith, C.

    2004-06-01

    In this work a number of techniques (electronic speckle pattern interferometry, holographic interferometry, strain gauge and finite element method) are brought to bear in order to establish consistency in the results of strain measurement. This is necessary if optical non-destructive testing methods, such as those used here, are to gain acceptance for routine industrial use. The FE model provides a useful check. Furthermore, ESPI fringe data facilitates the extension of FE models, an approach that is of growing importance in component testing. The use of in-plane and out-of-plane sensitive electronic speckle pattern interferometry (ESPI) for non-destructive material characterization of thick unplasticised polyvinylchloride (uPVC) pipes is presented. A test rig has been designed for stressing pipes by internal pressure. ESPI gives a complete mapping of the displacement field over the area imaged by the video camera. The results for the strain of uPVC obtained from ESPI data and from strain gauges are in good agreement. The value of Young's modulus has been obtained from the fringe data and compared with results obtained using holographic interferometry and from strain gauge measurements. The FE model also produces fringe data that is consistent with the ESPI results.

  4. Assessment of Proper Bonding Methods and Mechanical Characterization FPGA CQFPs

    NASA Technical Reports Server (NTRS)

    Davis, Milton C.

    2008-01-01

    This presentation discusses fractured leads on field-programmable gate array (FPGA) during flight vibration. Actions taken to determine root cause and resolution of the failure include finite element analysis (FEA) and vibration testing and scanning electron microscopy (with X-ray microanalysis) and energy dispersive spectrometry (SEM/EDS) failure assessment. Bonding methods for surface mount parts is assessed, including critical analysis and assessment of random fatigue damage. Regarding ceramic quad flat pack (CQFP) lead fracture, after disassembling the attitude control electronics (ACE) configuration, photographs showed six leads cracked on FPGA RTSX72SU-1 CQ208B package located on the RWIC card. An identical package (FPGA RTSX32SU-1 CQ208B) mounted on the RWIC did not results in cracked pins due to vibration. FPGA lead failure theories include workmanship issues in the lead-forming, material defect in the leads of the FPGA packages, and the insecure mounting of the board in the card guides, among other theories. Studies were conducted using simple calculations to determine the response and fatigue life of the package. Shorter packages exhibited more response when loaded by out-of-plane displacement of PCB while taller packages exhibit more response when loaded by in-plane acceleration of PCB. Additionally, under-fill did not contribute to reducing stress in leads due to out-of-plane PCB loading or from component twisting, as much as corner bonding. The combination of corner bond and under-fill is best to address mechanical and thermal S/C environment. Test results of bonded parts showed reduced (dampened) amplitude and slightly shifted peaks at the un-bonded natural frequency and an additional response at the bonded frequency. Stress due to PCBB out-of-plane loading was decreased on in the corners when only a corner bond was used. Future work may address CQFP fatigue assessment, including the investigation of discrepancy in predicted fatigue damage, as well as

  5. Nondestructive Methods to Characterize Rock Mechanical Properties at Low-Temperature: Applications for Asteroid Capture Technologies

    NASA Astrophysics Data System (ADS)

    Savage, Kara A.

    Recent government initiatives and commercial activities have targeted asteroids for in situ material characterization, manipulation, and possible resource extraction. Most of these activities and missions have proposed significant robotic components, given the risks and costs associated with manned missions. To successfully execute these robotic activities, detailed mechanical characteristics of the target space bodies must be known prior to contact, in order to appropriately plan and direct the autonomous robotic protocols. Unfortunately, current estimates of asteroid mechanical properties are based on limited direct information, and significant uncertainty remains specifically concerning internal structures, strengths, and elastic properties of asteroids. One proposed method to elucidate this information is through in situ, nondestructive testing of asteroid material immediately after contact, but prior to any manipulation or resource extraction activities. While numerous nondestructive rock characterization techniques have been widely deployed for terrestrial applications, these methods must be adapted to account for unique properties of asteroid material and environmental conditions of space. For example, asteroid surface temperatures may range from -100°C to 30°C due to diurnal cycling, and these low temperatures are especially noteworthy due to their deleterious influence on non-destructive testing. As a result, this thesis investigates the effect of low temperature on the mechanical characteristics and nondestructive technique responses of rock material. Initially, a novel method to produce low temperature rock samples was developed. Dry ice and methanol cooling baths of specific formulations were used to decrease rock to temperatures ranging from -60°C to 0°C. At these temperatures, shale, chalk, and limestone rock samples were exposed to several nondestructive and conventional mechanical tests, including Schmidt hammer, ultrasonic pulse velocity, point

  6. Mechanical characterization of trilayer thin films by the microbridge testing method

    NASA Astrophysics Data System (ADS)

    Xu, Wei-Hua; Zhang, Tong-Yi

    2003-09-01

    Microbridge tests were conducted on two sets of trilayer samples, consisting of SiO2/Si3N4/SiO2 and Si3N4/SiO2/Si3N4, which were fabricated on 4 in. p-type (100) silicon wafers by means of the microelectromechanical fabrication technique. The experimental results were analyzed using the small deformation formula including substrate deformation. By changing the sample length, we determined the bending stiffness and the resultant residual force per unit width in each of the trilayer thin films. A simplification is proposed to estimate residual stress and Young's modulus in each layer. Young's moduli and residual stresses are estimated to be 54.59 GPa and -429.49 MPa for the silicon oxide films and 270.54 GPa and 550.75 MPa for the silicon nitride films, respectively. The microbridge testing method enables us to characterize the mechanical properties of each layer of sandwich-structured thin films.

  7. A new mechanical characterization method for microactuators applied to shape memory films

    SciTech Connect

    Ackler, H D; Krulevitch, P; Ramsey, P B; Seward, K P

    1999-03-01

    We present a new technique for the mechanical characterization of microactuators and apply it to shape memory alloy (SMA) thin films. A test instrument was designed which utilizes a spring-loaded transducer to measure displacements with resolution of 1.5 mm and forces with resolution of 0.2 mN. Employing an out- of-plane loading method for SMA thin films, strain resolution of 30 me and stress resolution of 2.5 MPa were achieved. Four mm long, 2 {micro}m thick NiTiCu ligaments suspended across open windows were bulk micromachined for use in the out-of-plane stress and strain measurements. Static analysis showed that 63% of the applied strain was recovered while ligaments were subjected to tensile stresses of 870 MPa. This corresponds to 280 mm of actual displacement against a load of 52 mN. Fatigue analysis of the ligaments showed 33% degradation in recoverable strain (from 0.3% to 0.2%) with 2 {+-} 10{sup 4} cycles for an initial strain of 2.8%.

  8. A simple method to characterize the electrical and mechanical properties of micro-fibres

    NASA Astrophysics Data System (ADS)

    Castellanos-Gomez, A.

    2013-11-01

    A procedure to characterize the electrical and mechanical properties of micro-fibres is presented here. As the required equipment can be found in many teaching laboratories, it can be carried out by physics and mechanical/electrical engineering students. The electrical resistivity, mass density and Young's modulus of carbon micro-fibres have been determined using this procedure, obtaining values in very good agreement with the reference values. Young's modulus has been obtained by measuring the resonance frequency of carbon fibre-based cantilevers. In this way, one can avoid common approaches based on tensile or bending tests which are difficult to implement for microscale materials. Despite the simplicity of the experiments proposed here, they can be used to trigger in the students interest regarding the electrical and mechanical properties of microscale materials.

  9. Characterization methods

    SciTech Connect

    Glass, J.T.

    1993-01-01

    Methods discussed in this compilation of notes and diagrams are Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, and other surface analysis techniques (auger electron spectroscopy, x-ray photoelectron spectroscopy, electron energy loss spectroscopy, and scanning tunnelling microscopy). A comparative evaluation of different techniques is performed. In-vacuo and in-situ analyses are described.

  10. Is the second harmonic method applicable for thin films mechanical properties characterization by nanoindentation?

    NASA Astrophysics Data System (ADS)

    Guillonneau, G.; Kermouche, G.; Teisseire, J.; Barthel, E.; Bec, S.; Loubet, J.-L.

    2015-06-01

    The second harmonic method is a dynamic indentation technique independent of the direct indentation depth measurement. It can be used to determine near-surface mechanical properties of bulk materials more precisely than classical dynamic nanoindentation. In this paper, the second harmonic method is extended to the measurement of the mechanical properties of thin poly(methyl methacrylate) (PMMA) layers deposited onto silicon wafers. It is shown that this new technique gives precise results at small depths (less than 100 nm), even for films with a thickness lower than 500 nm, which was not possible to achieve with the classical continuous stiffness measurement method. However, experimental and numerical results obtained both with classical nanoindentation and second harmonic methods differ at high indentation depth. Using finite element (FE) simulations and AFM measurements, it is shown that the contact depth calculation with classical models can explain this difference.

  11. "METHOD": A tool for mechanical, electrical, thermal, and optical characterization of single lens module design

    NASA Astrophysics Data System (ADS)

    Besson, Pierre; Dominguez, Cesar; Voarino, Philippe; Garcia-Linares, Pablo; Weick, Clement; Lemiti, Mustapha; Baudrit, Mathieu

    2015-09-01

    The optical characterization and electrical performance evaluation are essential in the design and optimization of a concentrator photovoltaic system. The geometry, materials, and size of concentrator optics are diverse and different environmental conditions impact their performance. CEA has developed a new concentrator photovoltaic system characterization bench, METHOD, which enables multi-physics optimization studies. The lens and cell temperatures are controlled independently with the METHOD to study their isolated effects on the electrical and optical performance of the system. These influences can be studied in terms of their effect on optical efficiency, focal distance, spectral sensitivity, electrical efficiency, or cell current matching. Furthermore, the irradiance map of a concentrator optic can be mapped to study its variations versus the focal length or the lens temperature. The present work shows this application to analyze the performance of a Fresnel lens linking temperature to optical and electrical performance.

  12. New Method for Characterizing the State of Optical and Opto-Mechanical Systems

    NASA Technical Reports Server (NTRS)

    Keski-Kuha, Ritva; Saif, Babak; Feinberg, Lee; Chaney, David; Bluth, Marcel; Greenfield, Perry; Hack, Warren; Smith, Scott; Sanders, James

    2014-01-01

    James Webb Space Telescope Optical Telescope Element (OTE) is a three mirror anastigmat consisting of a 6.5 m primary mirror (PM), secondary mirror (SM) and a tertiary mirror. The primary mirror is made out of 18 segments. The telescope and instruments will be assembled at Goddard Space Flight Center (GSFC) to make it the Optical Telescope Element-Integrated Science Instrument Module (OTIS). The OTIS will go through environmental testing at GSFC before being transported to Johnson Space Center for testing at cryogenic temperature. The objective of the primary mirror Center of Curvature test (CoC) is to characterize the PM before and after the environmental testing for workmanship. This paper discusses the CoC test including both a surface figure test and a new method for characterizing the state of the primary mirror using high speed dynamics interferometry.

  13. Mechanical characterization of polytetrafluoroethylene polymer using full-field displacement method

    NASA Astrophysics Data System (ADS)

    Nunes, L. C. S.

    2011-05-01

    The aim of this work is to estimate two important material properties of the polytetrafluoroethylene (PTFE) polymer by means of a single experimental test. The displacement fields around a crack tip are used for estimating the modulus of elasticity (or, Young's modulus) and Poisson's ratio. These parameters are evaluated by fitting linear fracture mechanic expression of displacement fields in the vicinity of the crack, for mode I, to the experimental data. Measurements of these displacements are carried out using digital image correlation (DIC) method. In this way, the experimental procedure is conducted by loading a double-edge-cracked plate specimen. In order to validate the results, two available experimental tests have been performed. The modulus of elasticity is determined by means of the tensile test, using a standard test machine. Moreover, the Poisson's ratio is obtained by measuring lateral compressive and longitudinal extensional strain using DIC method.

  14. Nanomechanical Pyrolytic Carbon Resonators: Novel Fabrication Method and Characterization of Mechanical Properties.

    PubMed

    Kurek, Maksymilian; Larsen, Frederik K; Larsen, Peter E; Schmid, Silvan; Boisen, Anja; Keller, Stephan S

    2016-01-01

    Micro- and nanomechanical string resonators, which essentially are highly stressed bridges, are of particular interest for micro- and nanomechanical sensing because they exhibit resonant behavior with exceptionally high quality factors. Here, we fabricated and characterized nanomechanical pyrolytic carbon resonators (strings and cantilevers) obtained through pyrolysis of photoresist precursors. The developed fabrication process consists of only three processing steps: photolithography, dry etching and pyrolysis. Two different fabrication strategies with two different photoresists, namely SU-8 2005 (negative) and AZ 5214e (positive), were compared. The resonant behavior of the pyrolytic resonators was characterized at room temperature and in high vacuum using a laser Doppler vibrometer. The experimental data was used to estimate the Young's modulus of pyrolytic carbon and the tensile stress in the string resonators. The Young's moduli were calculated to be 74 ± 8 GPa with SU-8 and 115 ± 8 GPa with AZ 5214e as the precursor. The tensile stress in the string resonators was 33 ± 7 MPa with AZ 5214e as the precursor. The string resonators displayed maximal quality factor values of up to 3000 for 525-µm-long structures. PMID:27428980

  15. Nanomechanical Pyrolytic Carbon Resonators: Novel Fabrication Method and Characterization of Mechanical Properties

    PubMed Central

    Kurek, Maksymilian; Larsen, Frederik K.; Larsen, Peter E.; Schmid, Silvan; Boisen, Anja; Keller, Stephan S.

    2016-01-01

    Micro- and nanomechanical string resonators, which essentially are highly stressed bridges, are of particular interest for micro- and nanomechanical sensing because they exhibit resonant behavior with exceptionally high quality factors. Here, we fabricated and characterized nanomechanical pyrolytic carbon resonators (strings and cantilevers) obtained through pyrolysis of photoresist precursors. The developed fabrication process consists of only three processing steps: photolithography, dry etching and pyrolysis. Two different fabrication strategies with two different photoresists, namely SU-8 2005 (negative) and AZ 5214e (positive), were compared. The resonant behavior of the pyrolytic resonators was characterized at room temperature and in high vacuum using a laser Doppler vibrometer. The experimental data was used to estimate the Young’s modulus of pyrolytic carbon and the tensile stress in the string resonators. The Young’s moduli were calculated to be 74 ± 8 GPa with SU-8 and 115 ± 8 GPa with AZ 5214e as the precursor. The tensile stress in the string resonators was 33 ± 7 MPa with AZ 5214e as the precursor. The string resonators displayed maximal quality factor values of up to 3000 for 525-µm-long structures. PMID:27428980

  16. Characterization Methods of Encapsulates

    NASA Astrophysics Data System (ADS)

    Zhang, Zhibing; Law, Daniel; Lian, Guoping

    , reliable methods which can be used to characterize these properties of encapsulates are vital. In this chapter, the state-of-art of these methods, their principles and applications, and release mechanisms are described as follows.

  17. A new mechanical characterization method for thin film microactuators and its application to NiTiCi shape memory alloy

    SciTech Connect

    Seward, K P

    1999-06-01

    In an effort to develop a more full characterization tool of shape memory alloys, a new technique is presented for the mechanical characterization of microactuators and applied to SMA thin films. A test instrument was designed to utilize a spring-loaded transducer in measuring displacements with resolution of 1.5 pm and forces with resolution of 0.2 mN. Employing an out-of-plane loading method for freestanding SMA thin films, strain resolution of 30{mu}{epsilon} and stress resolution of 2.5 MPa were achieved. This new testing method is presented against previous SMA characterization methods for purposes of comparison. Four mm long, 2 {micro}m thick NiTiCu ligaments suspended across open windows were bulk micromachined for use in the out-of-plane stress and strain measurements. The fabrication process used to micromachine the ligaments is presented step-by-step, alongside methods of fabrication that failed to produce testable ligaments. Static analysis showed that 63% of the applied strain was recovered while ligaments were subjected to tensile stresses of 870 MPa. In terms of recoverable stress and recoverable strain, the ligaments achieved maximum recovery of 700 MPa and 3.0% strain. No permanent deformations were seen in any ligament during deflection measurements. Maximum actuation forces and displacements produced by the 4 mm ligaments situated on 1 cm square test chips were 56 mN and 300 {micro}m, respectively. Fatigue analysis of the ligaments showed degradation in recoverable strain from 0.33% to 0.24% with 200,000 cycles, corresponding to deflections of 90 {micro}m and forces of 25 mN. Cycling also produced a wavering shape memory effect late in ligament life, leading to broad inconsistencies of as much as 35% deviation from average. Unexpected phenomena like stress-induced martensitic twinning that leads to less recoverable stress and the shape memory behavior of long life devices are addressed. Finally, a model for design of microactuators using shape

  18. Characterization and mechanical separation of metals from computer Printed Circuit Boards (PCBs) based on mineral processing methods.

    PubMed

    Sarvar, Mojtaba; Salarirad, Mohammad Mehdi; Shabani, Mohammad Amin

    2015-11-01

    In this paper, a novel mechanical process is proposed for enriching metal content of computer Printed Circuit Boards (PCBs). The PCBs are crushed and divided into three different size fractions namely: -0.59, +0.59 to 1.68 and +1.68 mm. Wet jigging and froth flotation methods are selected for metal enrichment. The coarse size fraction (+1.68 mm) is processed by jigging. The plastic free product is grinded and screened. The oversized product is separated as the first concentrate. It was rich of metal because the grinding process was selective. The undersized product is processed by froth flotation. Based on the obtained results, the middle size fraction (+0.59 to 1.68 mm) and the small size fraction (-0.59 mm) are processed by wet jigging and froth flotation respectively. The wet jigging process is optimized by investigating the effect of pulsation frequency and water flow rate. The results of examining the effect of particle size, solid to liquid ratio, conditioning time and using apolar collector showed that collectorless flotation is a promising method for separating nonmetals of PCBs. 95.6%, 97.5% and 85% of metal content of coarse size, middle size and small size fraction are recovered. The grades of obtained concentrates were 63.3%, 92.5% and 75% respectively. The total recovery is calculated as 95.64% and the grade of the final concentrate was 71.26%. Determining the grade of copper and gold in the final product reveals that 4.95% of copper and 24.46% of gold are lost during the concentration. The major part of the lost gold is accumulated in froth flotation tail. PMID:26143534

  19. Characterization of mechanical properties of aluminized coatings in advanced gas turbine blades using a small punch method

    SciTech Connect

    Sugita, Y.; Ito, M.; Sakurai, S.; Bloomer, T.E.; Kameda, J. |

    1997-04-01

    Advanced technologies of superalloy casting and coatings enable one to enhance the performance of combined cycle gas turbines for electric power generation by increasing the firing temperature. This paper describes examination of the microstructure/composition and mechanical properties (22--950 C) in aluminized CoCrAlY coatings of advanced gas turbine blades using scanning Auger microprobe and a small punch (SP) testing method. Aluminized coatings consisted of layered structure divided into four regimes: (1) Al enriched and Cr depleted region, (2) Al and Cr graded region, (3) fine grained microstructure with a mixture of Al and Cr enriched phases and (4) Ni/Co interdiffusion zone adjacent to the interface. SP specimens were prepared in order that the specimen surface would be located in the various coating regions. SP tests indicated strong dependence of the fracture properties on the various coatings regimes. Coatings 1 and 2 with very high microhardness showed much easier formation of brittle cracks in a wide temperature range, compared to coatings 3 and 4 although the coating 2 had ductility improvement at 950 C. The coating 3 had lower room temperature ductility than the coating 4. However, the ductility in the coating 3 exceeded that in the region 4 above 730 C due to a precipitous ductility increase. The integrity of aluminized coatings while in-service is discussed in light of the variation of the low cycle fatigue life as well as the ductility in the layered structure.

  20. Mechanical Characterization of Partially Crystallized Sphere Packings

    NASA Astrophysics Data System (ADS)

    Hanifpour, M.; Francois, N.; Vaez Allaei, S. M.; Senden, T.; Saadatfar, M.

    2014-10-01

    We study grain-scale mechanical and geometrical features of partially crystallized packings of frictional spheres, produced experimentally by a vibrational protocol. By combining x-ray computed tomography, 3D image analysis, and discrete element method simulations, we have access to the 3D structure of internal forces. We investigate how the network of mechanical contacts and intergranular forces change when the packing structure evolves from amorphous to near perfect crystalline arrangements. We compare the behavior of the geometrical neighbors (quasicontracts) of a grain to the evolution of the mechanical contacts. The mechanical coordination number Zm is a key parameter characterizing the crystallization onset. The high fluctuation level of Zm and of the force distribution in highly crystallized packings reveals that a geometrically ordered structure still possesses a highly random mechanical backbone similar to that of amorphous packings.

  1. A novel inorganic precipitation-peptization method for VO2 sol and VO2 nanoparticles preparation: Synthesis, characterization and mechanism.

    PubMed

    Li, Yao; Jiang, Peng; Xiang, Wei; Ran, Fanyong; Cao, Wenbin

    2016-01-15

    In this paper, a simple, safe and cost-saving precipitation-peptization method was proposed to prepare VO2 sol by using inorganic VOSO4-NH3⋅H2O-H2O2 reactants system in air under room temperature. In this process, VOSO4 was firstly precipitated to form VO(OH)2, then monometallic species of VO(O2)(OH)(-) were formed through the coordination between VO(OH)2 and H2O2. The rearrangement of VO(O2)(OH)(-) in a nonplanar pattern and intermolecular condensation reactions result in multinuclear species. Finally, VO2 sol is prepared through the condensation reactions between the multinuclear species. After drying the obtained sol at 40°C, VO2 xerogel exhibiting monoclinic crystal structure with the space group of C2/m was prepared. The crystal structure of VO2 nanoparticles was transferred to monoclinic crystal structure with the space group of P21/c (VO2(M)) by annealing the xerogel at 550°C. Both XRD and TEM analysis indicated that the nanoparticles possess good crystallinity with crystallite size of 34.5nm as estimated by Scherrer's method. These results suggest that the VO2 sol has been prepared successfully through the proposed simple method. PMID:26433476

  2. Mechanical characterization of porcine corneas.

    PubMed

    Boschetti, F; Triacca, V; Spinelli, L; Pandolfi, A

    2012-03-01

    An experimental program has been carried out in order to investigate the mechanical behavior of porcine corneas. We report the results of inflation tests on the whole cornea and uniaxial tests on excised corneal strips, performed on 51 fresh porcine eyes. Uniaxial tests have been performed on specimens cut from previously inflated corneas. The cornea behavior is characterized by means of elastic stiffness, measured on both average pressure-apex displacement and average uniaxial stress-strain curves; and by means of transversal contraction coefficient, peak stress, and failure stress measured on uniaxial stress-strain curves. Uniaxial tests performed on excised strips allowed to measure the anisotropy in the corneal stiffness and to compare the stiffness of the cornea with the one of the sclera. Viscous properties of the cornea have been obtained through uniaxial relaxation curves on excised corneal strips. The relevant geometrical parameters have been measured and, with the aid of the elastic thin shell theory, a stress-strain curve has been derived from the average inflation test data and compared with similar data available in the literature. The experimental system has been developed in view of future applications to the mechanical testing of both porcine and human corneas. PMID:22482683

  3. Advanced Fine Particulate Characterization Methods

    SciTech Connect

    Steven Benson; Lingbu Kong; Alexander Azenkeng; Jason Laumb; Robert Jensen; Edwin Olson; Jill MacKenzie; A.M. Rokanuzzaman

    2007-01-31

    The characterization and control of emissions from combustion sources are of significant importance in improving local and regional air quality. Such emissions include fine particulate matter, organic carbon compounds, and NO{sub x} and SO{sub 2} gases, along with mercury and other toxic metals. This project involved four activities including Further Development of Analytical Techniques for PM{sub 10} and PM{sub 2.5} Characterization and Source Apportionment and Management, Organic Carbonaceous Particulate and Metal Speciation for Source Apportionment Studies, Quantum Modeling, and High-Potassium Carbon Production with Biomass-Coal Blending. The key accomplishments included the development of improved automated methods to characterize the inorganic and organic components particulate matter. The methods involved the use of scanning electron microscopy and x-ray microanalysis for the inorganic fraction and a combination of extractive methods combined with near-edge x-ray absorption fine structure to characterize the organic fraction. These methods have direction application for source apportionment studies of PM because they provide detailed inorganic analysis along with total organic and elemental carbon (OC/EC) quantification. Quantum modeling using density functional theory (DFT) calculations was used to further elucidate a recently developed mechanistic model for mercury speciation in coal combustion systems and interactions on activated carbon. Reaction energies, enthalpies, free energies and binding energies of Hg species to the prototype molecules were derived from the data obtained in these calculations. Bimolecular rate constants for the various elementary steps in the mechanism have been estimated using the hard-sphere collision theory approximation, and the results seem to indicate that extremely fast kinetics could be involved in these surface reactions. Activated carbon was produced from a blend of lignite coal from the Center Mine in North Dakota and

  4. Mechanical Characterization of Mancos Shale

    NASA Astrophysics Data System (ADS)

    Broome, S.; Ingraham, M. D.; Dewers, T. A.

    2015-12-01

    A series of tests on Mancos shale have been undertaken to determine the failure surface and to characterize anisotropy. This work supports additional studies which are being performed on the same block of shale; fracture toughness, permeability, and chemical analysis. Mechanical tests are being conducted after specimens were conditioned for at least two weeks at 70% constant relative humidity conditions. Specimens are tested under drained conditions, with the constant relative humidity condition maintained on the downstream side of the specimen. The upstream is sealed. Anisotropy is determined through testing specimens that have been cored parallel and perpendicular to the bedding plane. Preliminary results show that when loaded parallel to bedding the shale is roughly 50% weaker. Test are run under constant mean stress conditions when possible (excepting indirect tension, unconfined compression, and hydrostatic). Tests are run in hydrostatic compaction to the desired mean stress, then differential stress is applied axially in displacement control to failure. The constant mean stress condition is maintained by decreasing the confining pressure by half of the increase in the axial stress. Results will be compared to typical failure criteria to investigate the effectiveness of capturing the behavior of the shale with traditional failure theory. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. SAND2015-6107 A.

  5. Electrodeformation for single cell mechanical characterization

    NASA Astrophysics Data System (ADS)

    Chen, Jian; Abdelgawad, Mohamed; Yu, Liming; Shakiba, Nika; Chien, Wei-Yin; Lu, Zhe; Geddie, William R.; Jewett, Michael A. S.; Sun, Yu

    2011-05-01

    This paper presents the use of electrodeformation as a method for single cell mechanical characterization in which mechanical properties of SiHa and ME180 cells (two cervical cancer cell lines) were quantified. Cells were directly placed between two microelectrodes with a rectangular ac electric field applied, and cell deformation was recorded under certain experimental conditions. Numerical simulations were performed to model cell electrodeformation based on the Maxwell stress tensor formulation. In these simulations, effects of cell electrical property variations on their electrodeformed behavior were investigated. By comparing the measured morphological changes with those obtained from numerical simulations, we were able to quantify Young's modulus of SiHa cells (601 ± 183 Pa) and ME180 cells (1463 ± 649 Pa). These values were consistent with Young's modulus values (SiHa: 400 ± 290 Pa and ME180: 1070 ± 580 Pa) obtained from conventional micropipette aspiration.

  6. Comparison of two experimental methods for the mechanical characterization of thin or thick films from the study of micromachined circular diaphragms.

    PubMed

    Malhaire, C

    2012-05-01

    The purpose of this study was to compare two experimental methods and evaluate the effectiveness of a set of analytical models in order to measure the initial stress and the Young's modulus value of thin and thick film materials. Two types of experiments were performed on micromachined circular diaphragms: bulge testing and vibrometry. The range of validity and accuracy of the analytical models with respect to the vibration of the diaphragms was discussed from the finite element simulations. It was shown that the a/t ratio should be considered carefully to determine the value of the Young's modulus by vibrometry with an acceptable error. A relative error of approximately ±10% on E was obtained for a/t ≤ 750. For 750 ≤ a/t ≤ 1000, the value of the dimensionless parameter k must also be considered. It has been shown that the residual stress value can be obtained with an accuracy of 10% or less, given that k > 12. As an illustration, experimental methods and models were applied to the characterization of a thick electroplated gold film and a sputter-deposited Inconel thin film. Circular structures were defined by vertical sidewalls etched on the back of a Si wafer using the deep reactive ion etching technique. In addition to analytical models, parametric finite element simulations and a design optimization technique were used to determine the material's mechanical properties. The static deflections of the diaphragms were measured as a function of the applied pressure. The resonant frequencies and mode shapes of the vibrating structures were observed under vacuum by white-light interferometric microscopy. For gold, it was found that E = (53 ± 20) GPa and σ(0) = (180 ± 10) MPa. For Inconel, it was found that E = (157 ± 14) GPa and σ(0) = (172 ± 5) MPa. PMID:22667649

  7. Aerosol characterization with lidar methods

    NASA Astrophysics Data System (ADS)

    Sugimoto, Nobuo; Nishizawa, Tomoaki; Shimizu, Atsushi; Matsui, Ichiro

    2014-08-01

    Aerosol component analysis methods for characterizing aerosols were developed for various types of lidars including polarization-sensitive Mie scattering lidars, multi-wavelength Raman scattering lidars, and multi-wavelength highspectral- resolution lidars. From the multi-parameter lidar data, the extinction coefficients for four aerosol components can be derived. The microphysical parameters such as single scattering albedo and effective radius can be also estimated from the derived aerosol component distributions.

  8. New Methods of Celestial Mechanics

    NASA Astrophysics Data System (ADS)

    Poincare, Henri; Goroff, David

    Edited by Daniel Goroff, Harvard University This English-language edition of Poincare's landmark work is of interest not only to historians of science, but also to mathematicians. Beginning from an investigation of the three-body problem of Newtonian mechanics, Poincare lays the foundations of the qualitative solutions of differential equations. To investigate the long-unsolved problem of the stability of the Solar System, Poincare invented a number of new techniques including canonical transformations, asymptotic series expansions, and integral invariants. These "new methods" are even now finding applications in chaos and other contemporary disciplines. Contents: Volume I: Periodic and asymptotic solutions: Introduction by Daniel Goroff. Generalities and the Jacobi method. Series integration. Periodic solutions. Characteristic exponents. Nonexistence of uniform integrals. Approximate development of the perturbative function. Asymptotic solutions. Volume II: Approximations by series: Formal calculus. Methods of Newcomb and Lindstedt. Application to the study of secular variations. Application to the three-body problem. Application to orbits. Divergence of the Lindstedt series. Direct calculation of the series. Other methods of direct calculation. Gylden methods. Case of linear equations. Bohlin methods. Bohlin series. Extension of the Bohlin method. Volume III: Integral invariants and asymptotic properties of certain solutions: Integral invariants. Formation of invariants. Use of integral invariants. Integral invariants and asymptotic solutions. Poisson stability. Theory of consequents. Periodic solutions of the second kind. Different forms of the principle of least action.

  9. Mechanical methods for thrombosis prophylaxis.

    PubMed

    Caprini, Joseph A

    2010-12-01

    Prevention of venous thromboembolism (VTE) remains the number one preventable cause of death in hospitalized patients. The pathogenesis of thrombosis involves the triad of venous stasis, dilatation of the leg veins, and changes in coagulability of the blood. These changes can be modified by the use of intermittent pneumatic compression devices (IPC) and, to a much lesser extent, by graduated compression hose (GCS). Studies have shown the effectiveness of GCS in preventing deep vein thrombosis (DVT) compared to placebo, but there is no evidence that they reduce the incidence of pulmonary emboli (PE). No venographic data are available regarding the efficacy of GCS; however, IPC have shown excellent efficacy in several venographic studies over the past 25 years. Mechanical methods are important to use in situations where the risk of bleeding exists, thereby making the use of anticoagulants hazardous. One of the key uses for mechanical methods is in combination with anticoagulants in patients at the highest risk of developing VTE. Chest consensus guidelines assigns a 2A recommendation for the use of combination prophylaxis in the highest risk patients. Unfortunately, studies to show which type of leg compression device is optimal for DVT prevention are not available, so individual preference, ease of use, and company support are the determining factors at the present time. Finally, compliance using these devices is a major problem, and until systems have been developed to easily monitor and ensure compliance, these methods will enjoy only limited use. PMID:19850588

  10. Experimental methods for identifying failure mechanisms

    NASA Technical Reports Server (NTRS)

    Daniel, I. M.

    1983-01-01

    Experimental methods for identifying failure mechanisms in fibrous composites are studied. Methods to identify failure in composite materials includes interferometry, holography, fractography and ultrasonics.

  11. Biaxial mechanical characterization of bat wing skin.

    PubMed

    Skulborstad, A J; Swartz, S M; Goulbourne, N C

    2015-06-01

    The highly flexible and stretchable wing skin of bats, together with the skeletal structure and musculature, enables large changes in wing shape during flight. Such compliance distinguishes bat wings from those of all other flying animals. Although several studies have investigated the aerodynamics and kinematics of bats, few have examined the complex histology and mechanical response of the wing skin. This work presents the first biaxial characterization of the local deformation, mechanical properties, and fiber kinematics of bat wing skin. Analysis of these data has provided insight into the relationships among the structural morphology, mechanical properties, and functionality of wing skin. Large spatial variations in tissue deformation and non-negligible fiber strains in the cross-fiber direction for both chordwise and spanwise fibers indicate fibers should be modeled as two-dimensional elements. The macroscopic constitutive behavior was anisotropic and nonlinear, with very low spanwise and chordwise stiffness (hundreds of kilopascals) in the toe region of the stress-strain curve. The structural arrangement of the fibers and matrix facilitates a low energy mechanism for wing deployment and extension, and we fabricate examples of skins capturing this mechanism. We propose a comprehensive deformation map for the entire loading regime. The results of this work underscore the importance of biaxial field approaches for soft heterogeneous tissue, and provide a foundation for development of bio-inspired skins to probe the effects of the wing skin properties on aerodynamic performance. PMID:25895436

  12. Mechanical Characterization of Rigid Polyurethane Foams.

    SciTech Connect

    Lu, Wei-Yang

    2014-12-01

    Foam materials are used to protect sensitive components from impact loading. In order to predict and simulate the foam performance under various loading conditions, a validated foam model is needed and the mechanical properties of foams need to be characterized. Uniaxial compression and tension tests were conducted for different densities of foams under various temperatures and loading rates. Crush stress, tensile strength, and elastic modulus were obtained. A newly developed confined compression experiment provided data for investigating the foam flow direction. A biaxial tension experiment was also developed to explore the damage surface of a rigid polyurethane foam.

  13. Battery Vent Mechanism And Method

    DOEpatents

    Ching, Larry K. W.

    2000-02-15

    Disclosed herein is a venting mechanism for a battery. The venting mechanism includes a battery vent structure which is located on the battery cover and may be integrally formed therewith. The venting mechanism includes an opening extending through the battery cover such that the opening communicates with a plurality of battery cells located within the battery case. The venting mechanism also includes a vent manifold which attaches to the battery vent structure. The vent manifold includes a first opening which communicates with the battery vent structure opening and second and third openings which allow the vent manifold to be connected to two separate conduits. In this manner, a plurality of batteries may be interconnected for venting purposes, thus eliminating the need to provide separate vent lines for each battery. The vent manifold may be attached to the battery vent structure by a spin-welding technique. To facilitate this technique, the vent manifold may be provided with a flange portion which fits into a corresponding groove portion on the battery vent structure. The vent manifold includes an internal chamber which is large enough to completely house a conventional battery flame arrester and overpressure safety valve. In this manner, the vent manifold, when installed, lessens the likelihood of tampering with the flame arrester and safety valve.

  14. Structural Embeddings: Mechanization with Method

    NASA Technical Reports Server (NTRS)

    Munoz, Cesar; Rushby, John

    1999-01-01

    The most powerful tools for analysis of formal specifications are general-purpose theorem provers and model checkers, but these tools provide scant methodological support. Conversely, those approaches that do provide a well-developed method generally have less powerful automation. It is natural, therefore, to try to combine the better-developed methods with the more powerful general-purpose tools. An obstacle is that the methods and the tools often employ very different logics. We argue that methods are separable from their logics and are largely concerned with the structure and organization of specifications. We, propose a technique called structural embedding that allows the structural elements of a method to be supported by a general-purpose tool, while substituting the logic of the tool for that of the method. We have found this technique quite effective and we provide some examples of its application. We also suggest how general-purpose systems could be restructured to support this activity better.

  15. Mechanical property characterization of intraply hybrid composites

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Lark, R. F.; Sinclair, J. H.

    1979-01-01

    An investigation of the mechanical properties of intraply hybrids made from graphite fiber/epoxy matrix hybridized with secondary S-glass or Kevlar 49 fiber composites is presented. The specimen stress-strain behavior was determined, showing that mechanical properties of intraply hybrid composites can be measured with available methods such as the ten-degree off-axis test for intralaminar shear, and conventional tests for tensile, flexure, and Izod impact properties. The results also showed that combinations of high modulus graphite/S-glass/epoxy matrix composites exist which yield intraply hybrid laminates with the best 'balanced' properties, and that the translation efficiency of mechanical properties from the constituent composites to intraply hybrids may be assessed with a simple equation.

  16. Thermo-mechanical characterization of silicone foams

    SciTech Connect

    Rangaswamy, Partha; Smith, Nickolaus A.; Cady, Carl M.; Lewis, Matthew W.

    2015-10-01

    Cellular solids such as elastomeric foams are used in many structural applications to absorb and dissipate energy, due to their light weight (low density) and high energy absorption capability. In this paper we will discuss foams derived from S5370, a silicone foam formulation developed by Dow Corning. In the application presented, the foam is consolidated into a cushion component of constant thickness but variable density. A mechanical material model developed by Lewis (2013), predicts material response, in part, as a function of relative density. To determine the required parameters for this model we have obtained the mechanical response in compression for ambient, cold and hot temperatures. The variable density cushion provided samples sufficient samples so that the effect of sample initial density on the mechanical response could be studied. The mechanical response data showed extreme sensitivity to relative density. We also observed at strains corresponding to 1 MPa a linear relationship between strain and initial density for all temperatures. Samples taken from parts with a history of thermal cycling demonstrated a stiffening response that was a function of temperature, with the trend of more stiffness as temperature increased above ambient. This observation is in agreement with the entropic effects on the thermo-mechanical behavior of silicone polymers. In this study, we present the experimental methods necessary for the development of a material model, the testing protocol, analysis of test data, and a discussion of load (stress) and gap (strain) as a function of sample initial densities and temperatures

  17. Numerical methods in structural mechanics

    NASA Astrophysics Data System (ADS)

    Obraztsov, I. F.

    The papers contained in this volume focus on numerical, numerical-analytical, and theoretical methods for dealing with strength, stability, and dynamics problems in the design of the structural elements of flight vehicles. Topics discussed include the solution of homogeneous boundary value problems for systems of ordinary differential equations modified by a difference factorization method, a study of the rupture strength of a welded joint between plates, singular solutions in mixed problems for a wedge and a half-strip, and a thermoelasticity problem for an open-profile cylindrical shell with a localized temperature field.

  18. DYNAMIC MECHANICAL ANALYSIS CHARACTERIZATION OF GLOVEBOX GLOVES

    SciTech Connect

    Korinko, P.

    2012-02-29

    As part of the characterization of various glovebox glove material from four vendors, the permeability of gas through each type as a function of temperature was determined and a discontinuity in the permeability with temperature was revealed. A series of tests to determine the viscoelastic properties of the glove materials as a function of temperature using Dynamic Mechanical Analysis (DMA) was initiated. The glass transition temperature and the elastic and viscoelastic properties as a function of temperature up to maximum use temperature were determined for each glove material. The glass transition temperatures of the gloves were -60 C for butyl, -30 C for polyurethane, -16 C Hypalon{reg_sign}, - 16 C for Viton{reg_sign}, and -24 C for polyurethane-Hypalon{reg_sign}. The glass transition was too complex for the butyl-Hypalon{reg_sign} and butyl-Viton{reg_sign} composite gloves to be characterized by a single glass transition temperature. All of the glass transition temperatures exceed the vendor projected use temperatures.

  19. Characterization methods for fractured glacial tills

    USGS Publications Warehouse

    Haefner, R.J.

    2000-01-01

    This paper provides a literature review of methods successfully employed to characterize finegrained and fractured or unfractured glacial deposits. Descriptions and examples are given for four major categories of characterization methods: physical, hydraulic, chemical, and indirect. Characterization methods have evolved significantly within the past ten years; however, there still exists uncertainty about the reliability of individual characterization methods applied to till deposits. Therefore, a combination of methods is best, the choice of which depends on the objectives of the work. Sampling methods, sampling scales, and reporting methods are extremely important and should be considered when interpreting and comparing results between sites. Recognition of these issues is necessary to ensure that decisions regarding the transport of fluids in fractured tills are not based on the assumption that poorly permeable tills are always an inhibitor of subsurface flow.

  20. Radical SAM, A Novel Protein Superfamily Linking Unresolved Steps in Familiar Biosynthetic Pathways with Radical Mechanisms: Functional Characterization Using New Analysis and Information Visualization Methods

    SciTech Connect

    Sofia, Heidi J.; Chen, Guang; Hetzler, Elizabeth G.; Reyes Spindola, Jorge F.; Miller, Nancy E.

    2001-03-01

    A large protein superfamily with over 500 members has been discovered and analyzed using powerful new bioinformatics and information visualization methods. Evidence exists that these proteins generate a 5?-deoxyadenosyl radical by reductive cleavage of S-adenosylmethionine (SAM) through an unusual Fe-S center. Radical SAM superfamily proteins function in DNA precursor, vitamin, cofactor, antibiotic, and herbicide biosynthesis in a collection of basic and familiar pathways. One of the members is interferon-inducible and is considered a candidate drug target for osteoporosis. The identification of this superfamily suggests that radical-based catalysis is important in a number of previously well-studied but unresolved biochemical pathways.

  1. Mechanical characterization of Lipon films using nanoindentation

    SciTech Connect

    Herbert, Erik; Tenhaeff, Wyatt E; Dudney, Nancy J; Pharr, V, George M

    2011-01-01

    Nanoindentation has been used to characterize the elastic modulus and hardness of LiPON films ranging in thickness from 1 to 10 m. Four fully dense, amorphous films were deposited on glass and sapphire substrates with one film annealed at 200 C for 20 min. The modulus of LiPON is found to be approximately 77 GPa, and argued to be independent of the substrate type, film thickness, and annealing. Based on the numerical analysis of Monroe and Newman, this value may be sufficiently high to mechanically suppress dendrite formation at the lithium/LiPON interface in thin film batteries [1]. Using Sneddon's stiffness equation and assuming the modulus is 77 GPa, the hardness is found to be approximately 3.9 GPa for all but the annealed film. The hardness of the annealed film is approximately 5% higher, at 4.1 GPa. Atomic force microscopy images of the residual hardness impressions confirm the unexpected increase in hardness of the annealed film. Surprisingly, the indentation data also reveal time-dependent behavior in all four films. This indicates that creep may also play a significant role in determining how LiPON responds to complex loading conditions and could be important in relieving stresses as they develop during service.

  2. Evaluation of Electrochemical Methods for Electrolyte Characterization

    NASA Technical Reports Server (NTRS)

    Heidersbach, Robert H.

    2001-01-01

    This report documents summer research efforts in an attempt to develop an electrochemical method of characterizing electrolytes. The ultimate objective of the characterization would be to determine the composition and corrosivity of Martian soil. Results are presented using potentiodynamic scans, Tafel extrapolations, and resistivity tests in a variety of water-based electrolytes.

  3. Robotic palpation and mechanical property characterization for abnormal tissue localization.

    PubMed

    Ahn, Bummo; Kim, Yeongjin; Oh, Cheol Kyu; Kim, Jung

    2012-09-01

    Palpation is an intuitive examination procedure in which the kinesthetic and tactile sensations of the physician are used. Although it has been widely used to detect and localize diseased tissues in many clinical fields, the procedure is subjective and dependent on the experience of the individual physician. Palpation results and biomechanics-based mechanical property characterization are possible solutions that can enable the acquisition of objective and quantitative information on abnormal tissue localization during diagnosis and surgery. This paper presents an integrated approach for robotic palpation combined with biomechanical soft tissue characterization. In particular, we propose a new palpation method that is inspired by the actual finger motions that occur during palpation procedures. To validate the proposed method, robotic palpation experiments on silicone soft tissue phantoms with embedded hard inclusions were performed and the force responses of the phantoms were measured using a robotic palpation system. Furthermore, we carried out a numerical analysis, simulating the experiments and estimating the objective and quantitative properties of the tissues. The results indicate that the proposed approach can differentiate diseased tissue from normal tissue and can characterize the mechanical information of diseased tissue, which means that this method can be applied as a means of abnormality localization to diagnose prostate cancers. PMID:22772733

  4. Application of geophysical methods for fracture characterization

    SciTech Connect

    Lee, K.H.; Majer, E.L.; McEvilly, T.V. |; Morrison, H.F. |

    1990-01-01

    One of the most crucial needs in the design and implementation of an underground waste isolation facility is a reliable method for the detection and characterization of fractures in zones away from boreholes or subsurface workings. Geophysical methods may represent a solution to this problem. If fractures represent anomalies in the elastic properties or conductive properties of the rocks, then the seismic and electrical techniques may be useful in detecting and characterizing fracture properties. 7 refs., 3 figs.

  5. Overview of geotechnical methods to characterize rock masses

    SciTech Connect

    Heuze, F.E.

    1981-12-01

    The methods that are used to characterize discontinuous rock masses from a geotechnical point of view are summarized. Emphasis is put on providing key references on each subject. The topics of exploration, in-situ stresses, mechanical properties, thermal properties, and hydraulic properties are addressed.

  6. Methods of stability analysis in nonlinear mechanics

    SciTech Connect

    Warnock, R.L.; Ruth, R.D.; Gabella, W.; Ecklund, K.

    1989-01-01

    We review our recent work on methods to study stability in nonlinear mechanics, especially for the problems of particle accelerators, and compare our ideals to those of other authors. We emphasize methods that (1) show promise as practical design tools, (2) are effective when the nonlinearity is large, and (3) have a strong theoretical basis. 24 refs., 2 figs., 2 tabs.

  7. Mechanical characterization and reliability of films and coatings

    NASA Astrophysics Data System (ADS)

    Thurn, Jeremy Adam

    This work describes newly-developed and conventional mechanical characterization techniques for films and coatings and the use of such techniques in conjunction with fracture models to examine the reliability of brittle film and coating systems. A wide range of film and coating systems is examined, emphasizing the generality of both the characterization techniques and the analysis methods. Emphasis is placed on systems of technological importance including dielectric films (such as silicon dioxide, amorphous silicon, silicon nitride, silicon oxy-nitride, and low-dielectric constant silsesquioxane) on silicon substrates for the microelectronics and micro-electromechanical systems (MEMS) industries, and alumina films on alumina titanium-carbide substrates for the magnetic recording head industry. Characterization techniques include depth-sensing indentation at ultra-microscopic and macroscopic dimensions ("nanoindentation" and "macroindentation," respectively), conventional Vickers hardness testing in inert and reactive environments, and substrate curvature measurements for film stress determination at elevated temperatures. Analysis is carried out using newly-developed and conventional analytic constitutive models as well as numerical simulations using finite element methods. The first part of the thesis describes the experimental techniques and analysis methods to deduce the elastic, plastic, fracture, and adhesive properties of brittle films and coatings. The second part focuses on the thermomechanical and environmental reliability of dielectric films for microelectronic applications based on experimental results and numerical analysis.

  8. The Challenge of Characterizing Operations in the Mechanisms Underlying Behavior

    ERIC Educational Resources Information Center

    Bechtel, William

    2005-01-01

    Neuroscience and cognitive science seek to explain behavioral regularities in terms of underlying mechanisms. An important element of a mechanistic explanation is a characterization of the operations of the parts of the mechanism. The challenge in characterizing such operations is illustrated by an example from the history of physiological…

  9. Characterizing the mechanical behavior of the zebrafish germ layers

    NASA Astrophysics Data System (ADS)

    Kealhofer, David; Serwane, Friedhelm; Mongera, Alessandro; Rowghanian, Payam; Lucio, Adam; Campàs, Otger

    Organ morphogenesis and the development of the animal body plan involve complex spatial and temporal control of tissue- and cell-level mechanics. A prime example is the generation of stresses by individual cells to reorganize the tissue. These processes have remained poorly understood due to a lack of techniques to characterize the local constitutive law of the material, which relates local cellular forces to the resulting tissue flows. We have developed a method for quantitative, local in vivo study of material properties in living tissue using magnetic droplet probes. We use this technique to study the material properties of the different zebrafish germ layers using aggregates of zebrafish mesendodermal and ectodermal cells as a model system. These aggregates are ideal for controlled studies of the mechanics of individual germ layers because of the homogeneity of the cell type and the simple spherical geometry. Furthermore, the numerous molecular tools and transgenic lines already developed for this model organism can be applied to these aggregates, allowing us to characterize the contributions of cell cortex tension and cell adhesion to the mechanical properties of the zebrafish germ layers.

  10. Processing and mechanical characterization of alumina laminates

    NASA Astrophysics Data System (ADS)

    Montgomery, John K.

    2002-08-01

    Single-phase ceramics that combine property gradients or steps in monolithic bodies are sought as alternatives to ceramic composites made of dissimilar materials. This work describes novel processing methods to produce stepped-density (or laminated) alumina single-phase bodies that maintain their mechanical integrity. One arrangement consists of a stiff, dense bulk material with a thin, flaw tolerant, porous exterior layer. Another configuration consists of a lightweight, low-density bulk material with a thin, hard, wear resistant exterior layer. Alumina laminates with strong interfaces have been successfully produced in this work using two different direct-casting processes. Gelcasting is a useful near-net shape processing technique that has been combined with several techniques, such as reaction bonding of aluminum oxide and the use of starch as a fugative filler, to successfully produced stepped-density alumina laminates. The other direct casting process that has been developed in this work is thermoreversible gelcasting (TRG). This is a reversible gelation process that has been used to produce near-net shape dense ceramic bodies. Also, individual layers can be stacked together and heated to produce laminates. Bilayer laminate samples were produced with varied thickness of porous and dense layers. It was shown that due to the difference in modulus and hardness, transverse cracking is found upon Hertzian contact when the dense layer is on the exterior. In the opposite arrangement, compacted damage zones formed in the porous material and no damage occurred in the underlying dense layer. Flaw tolerant behavior of the porous exterior/dense underlayer was examined by measuring biaxial strength as a function of Vickers indentation load. It was found that the thinnest layer of porous material results in the greatest flaw tolerance. Also, higher strength was exhibited at large indentation loads when compared to dense monoliths. The calculated stresses on the surfaces

  11. Failure mechanism characterization of platinum alloy

    NASA Technical Reports Server (NTRS)

    Rosen, J. M.; Mcfarlen, W. T.

    1986-01-01

    This article describes procedures and results of testing performed on a platinum/10-percent rhodium, thin-wall tubular product. The purpose of the testing was to develop exemplar SEM fractographs to be used to characterize failures under various environmental conditions. Conditions evaluated for the platinum alloys included high temperature, hydrogen environment, braze metal contamination, and cyclic loading.

  12. Geometric methods for the design of mechanisms

    NASA Astrophysics Data System (ADS)

    Stokes, Ann Westagard

    1993-01-01

    Challenges posed by the process of designing robotic mechanisms have provided a new impetus to research in the classical subjects of kinematics, elastic analysis, and multibody dynamics. Historically, mechanism designers have considered these areas of analysis to be generally separate and distinct sciences. However, there are significant classes of problems which require a combination of these methods to arrive at a satisfactory solution. For example, both the compliance and the inertia distribution strongly influence the performance of a robotic manipulator. In this thesis, geometric methods are applied to the analysis of mechanisms where kinematics, elasticity, and dynamics play fundamental and interactive roles. Tools for the mathematical analysis, design, and optimization of a class of holonomic and nonholonomic mechanisms are developed. Specific contributions of this thesis include a network theory for elasto-kinematic systems. The applicability of the network theory is demonstrated by employing it to calculate the optimal distribution of joint compliance in a serial manipulator. In addition, the advantage of applying Lie group theoretic approaches to mechanisms requiring specific dynamic properties is demonstrated by extending Brockett's product of exponentials formula to the domain of dynamics. Conditions for the design of manipulators having inertia matrices which are constant in joint angle coordinates are developed. Finally, analysis and design techniques are developed for a class of mechanisms which rectify oscillations into secular motions. These techniques are applied to the analysis of free-floating chains that can reorient themselves in zero angular momentum processes and to the analysis of rattleback tops.

  13. Thermal-mechanical-noise-based CMUT characterization and sensing.

    PubMed

    Gurun, Gokce; Hochman, Michael; Hasler, Paul; Degertekin, F Levent

    2012-06-01

    When capacitive micromachined ultrasonic transducers (CMUTs) are monolithically integrated with custom-designed low-noise electronics, the output noise of the system can be dominated by the CMUT thermal-mechanical noise both in air and in immersion even for devices with low capacitance. Because the thermal-mechanical noise can be related to the electrical admittance of the CMUTs, this provides an effective means of device characterization. This approach yields a novel method to test the functionality and uniformity of CMUT arrays and the integrated electronics when a direct connection to CMUT array element terminals is not available. Because these measurements can be performed in air at the wafer level, the approach is suitable for batch manufacturing and testing. We demonstrate this method on the elements of an 800-μm-diameter CMUT-on-CMOS array designed for intravascular imaging in the 10 to 20 MHz range. Noise measurements in air show the expected resonance behavior and spring softening effects. Noise measurements in immersion for the same array provide useful information on both the acoustic cross talk and radiation properties of the CMUT array elements. The good agreement between a CMUT model based on finite difference and boundary element methods and the noise measurements validates the model and indicates that the output noise is indeed dominated by thermal-mechanical noise. The measurement method can be exploited to implement CMUT-based passive sensors to measure immersion medium properties, or other parameters affecting the electro-mechanics of the CMUT structure. PMID:22718877

  14. Computational Methods for Structural Mechanics and Dynamics

    NASA Technical Reports Server (NTRS)

    Stroud, W. Jefferson (Editor); Housner, Jerrold M. (Editor); Tanner, John A. (Editor); Hayduk, Robert J. (Editor)

    1989-01-01

    Topics addressed include: transient dynamics; transient finite element method; transient analysis in impact and crash dynamic studies; multibody computer codes; dynamic analysis of space structures; multibody mechanics and manipulators; spatial and coplanar linkage systems; flexible body simulation; multibody dynamics; dynamical systems; and nonlinear characteristics of joints.

  15. Fabrication and mechanical characterization of ultrashort nanocantilevers

    NASA Astrophysics Data System (ADS)

    Nilsson, S. G.; Sarwe, E.-L.; Montelius, L.

    2003-08-01

    Three aspects on nanocantilevers are presented in this letter. First, we present the fabrication process of 2 μm long freestanding chromium cantilevers with width 150 nm, and thickness 50 nm. Second, a measurement scheme using an atomic force microscope operating in contact mode was employed to study the mechanical properties along the length of the cantilevers. Third, we have investigated extremely large deflections on these nanoscale cantilevers demonstrating their high ductility. The spring constants calculated from the experimental data are smaller than expected from classical mechanics calculations, but show good agreement with previously reported calculations for largely deflected beams.

  16. Microscale mechanical characterization of materials for extreme environments

    NASA Astrophysics Data System (ADS)

    Ozerinc, Sezer

    requirements of micron-sized specimens, muN-level force sensitivity, and nm-level displacement sensitivity. A recently developed mechanical characterization technique, micropillar compression, has enabled the testing of miniaturized specimens; however, there has been no demonstration of the application of this technique to irradiation induced creep measurements. This dissertation presents the development of an in situ measurement apparatus for compression testing of micron-sized cylindrical specimens under MeV-heavy ion bombardment. The apparatus has a force resolution of 1 muN and a displacement resolution of 1 nm. The apparatus measured irradiation induced creep in four different amorphous materials and the findings clarified the significance of different creep mechanisms in these materials. In amorphous metals and amorphous Si, the measured irradiation induced fluidity is ≈ 3 dpa-1GPa-1 (dpa: displacements per atom). The measured fluidity is in excellent agreement with previous molecular dynamics simulation predictions, providing experimental evidence for point defect mediated plastic flow under ion bombardment. For amorphous SiO2, stress relaxation through thermal spikes further contribute to the creep response, resulting in higher fluidities up to ≈ 83 dpa-1GPa -1. Finally, this dissertation presents the further development of the creep testing apparatus for high temperature measurements. The apparatus demonstrated good thermal and mechanical stability and measured irradiation induced creep of nanocrystalline Cu at 200°C. Resulting irradiation induced fluidity is ≈ 10% of the fluidity of the amorphous metals, in agreement with previous measurements on free-standing films. Understanding the creep behavior of nanostructured metals under heavy ion bombardment at elevated temperatures is important for identifying the governing creep mechanisms in these materials. The developed apparatus provides a new and effective method of accelerated mechanical characterization of

  17. Mechanical characterization of commercial biodegradable plastic films

    NASA Astrophysics Data System (ADS)

    Vanstrom, Joseph R.

    Polylactic acid (PLA) is a biodegradable plastic that is relatively new compared to other plastics in use throughout industry. The material is produced by the polymerization of lactic acid which is produced by the fermentation of starches derived from renewable feedstocks such as corn. Polylactic acid can be manufactured to fit a wide variety of applications. This study details the mechanical and morphological properties of selected commercially available PLA film products. Testing was conducted at Iowa State University and in conjunction with the United States Department of Agriculture (USDA) BioPreferred ProgramRTM. Results acquired by Iowa State were compared to a similar study performed by the Cortec Corporation in 2006. The PLA films tested at Iowa State were acquired in 2009 and 2010. In addition to these two studies at ISU, the films that were acquired in 2009 were aged for a year in a controlled environment and then re-tested to determine effects of time (ageing) on the mechanical properties. All films displayed anisotropic properties which were confirmed by inspection of the films with polarized light. The mechanical testing of the films followed American Society for Testing and Materials (ASTM) standards. Mechanical characteristics included: tensile strength (ASTM D882), elongation of material at failure (ASTM D882), impact resistance (ASTM D1922), and tear resistance (ASTM D4272). The observed values amongst all the films ranged as followed: tensile strength 33.65--8.54 MPa; elongation at failure 1,665.1%--47.2%; tear resistance 3.61--0.46 N; and puncture resistance 2.22--0.28 J. There were significant differences between the observed data for a number of films and the reported data published by the Cortec Corp. In addition, there were significant differences between the newly acquired material from 2009 and 2010, as well as the newly acquired materials in 2009 and the aged 2009 materials, suggesting that ageing and manufacturing date had an effect on

  18. Alternative methods for characterization of extracellular vesicles.

    PubMed

    Momen-Heravi, Fatemeh; Balaj, Leonora; Alian, Sara; Tigges, John; Toxavidis, Vasilis; Ericsson, Maria; Distel, Robert J; Ivanov, Alexander R; Skog, Johan; Kuo, Winston Patrick

    2012-01-01

    Extracellular vesicles (ECVs) are nano-sized vesicles released by all cells in vitro as well as in vivo. Their role has been implicated mainly in cell-cell communication, but also in disease biomarkers and more recently in gene delivery. They represent a snapshot of the cell status at the moment of release and carry bioreactive macromolecules such as nucleic acids, proteins, and lipids. A major limitation in this emerging new field is the availability/awareness of techniques to isolate and properly characterize ECVs. The lack of gold standards makes comparing different studies very difficult and may potentially hinder some ECVs-specific evidence. Characterization of ECVs has also recently seen many advances with the use of Nanoparticle Tracking Analysis, flow cytometry, cryo-electron microscopy instruments, and proteomic technologies. In this review, we discuss the latest developments in translational technologies involving characterization methods including the facts in their support and the challenges they face. PMID:22973237

  19. Alternative Methods for Characterization of Extracellular Vesicles

    PubMed Central

    Momen-Heravi, Fatemeh; Balaj, Leonora; Alian, Sara; Tigges, John; Toxavidis, Vasilis; Ericsson, Maria; Distel, Robert J.; Ivanov, Alexander R.; Skog, Johan; Kuo, Winston Patrick

    2012-01-01

    Extracellular vesicles (ECVs) are nano-sized vesicles released by all cells in vitro as well as in vivo. Their role has been implicated mainly in cell–cell communication, but also in disease biomarkers and more recently in gene delivery. They represent a snapshot of the cell status at the moment of release and carry bioreactive macromolecules such as nucleic acids, proteins, and lipids. A major limitation in this emerging new field is the availability/awareness of techniques to isolate and properly characterize ECVs. The lack of gold standards makes comparing different studies very difficult and may potentially hinder some ECVs-specific evidence. Characterization of ECVs has also recently seen many advances with the use of Nanoparticle Tracking Analysis, flow cytometry, cryo-electron microscopy instruments, and proteomic technologies. In this review, we discuss the latest developments in translational technologies involving characterization methods including the facts in their support and the challenges they face. PMID:22973237

  20. Characterizing Cell Mechanics with AFM and Microfluidics

    NASA Astrophysics Data System (ADS)

    Walter, N.; Micoulet, A.; Suresh, S.; Spatz, J. P.

    2007-03-01

    Cell mechanical properties and functionality are mainly determined by the cytoskeleton, besides the cell membrane, the nucleus and the cytosol, and depend on various parameters e.g. surface chemistry and rigidity, surface area and time available for cell spreading, nutrients and drugs provided in the culture medium. Human epithelial pancreatic and mammary cancer cells and their keratin intermediate filaments are the main focus of our work. We use Atomic Force Microscopy (AFM) to study cells adhering to substrates and Microfluidic Channels to probe cells in suspension, respectively. Local and global properties are extracted by varying AFM probe tip size and the available adhesion area for cells. Depth-sensing, instrumented indentation tests with AFM show a clear difference in contact stiffness for cells that are spread of controlled substrates and those that are loosely attached. Microfluidic Channels are utilized in parallel to evaluate cell deformation and ``flow resistance'', which are dependent on channel cross section, flow rate, cell nucleus size and the mechanical properties of cytoskeleton and membrane. The results from the study are used to provide some broad and quantitative assessments of the connections between cellular/subcellular mechanics and biochemical origins of disease states.

  1. Microarchitectural and Mechanical Characterization of Sickle Bone

    PubMed Central

    Green, Mykel; Akinsami, Idowu; Lin, Angela; Banton, Shereka; Ghosh, Samit; Chen, Binbin; Platt, Manu; Osunkwo, Ifeyinwa; Ofori-Acquah, Solomon; Guldberg, Robert; Barabino, Gilda

    2015-01-01

    Individuals with sickle cell disease often experience acute and chronic bone pain due to occlusive events within the tissue vasculature that result in ischemia, necrosis, and organ degeneration. Macroscopically, sickle bone is identified in clinical radiographs by its reduced mineral density, widening of the marrow cavity, and thinning of the cortical bone due to the elevated erythroid hyperplasia accompanying the disease. However, the microstructural architecture of sickle bone and its role in mechanical functionality is largely unknown. This study utilized micro-CT and biomechanical testing to determine the relationship between the bone morphology, tissue mineral density, and trabecular and cortical microarchitecture of 10-and 21-week-old femurs from transgenic sickle male mice and littermates with sickle trait, as well as a wild-type control. While bone tissue mineral density did not vary among the genotypes at either age, variation in bone microstructure were observed. At 10 weeks, healthy and trait mice exhibited similar morphology within the cortical and trabecular bone, while sickle mice exhibited highly connected trabeculae. Within older femurs, sickle and trait specimens displayed significantly fewer trabeculae, and the remaining trabeculae had a more deteriorated geometry based on the structure model index. Thinning of the cortical region in sickle femurs contributed to the displayed flexibility with a significantly lower elastic modulus than the controls at both 10- and 21-weeks old. Wild-type and trait femurs generally demonstrated similar mechanical properties; however, trait femurs had a significantly higher modulus than sickle and wild-type control at 21-weeks. Overall, these data indicate that the progressive damage to the microvasculature caused by sickle cell disease, results in deleterious structural changes in the bone tissue's microarchitecture and mechanics. PMID:25957113

  2. Characterization methods for ultrasonic test systems

    SciTech Connect

    Busse, L.J.; Becker, F.L.; Bowey, R.E.; Doctor, S.R.; Gribble, R.P.; Posakony, G.J.

    1982-07-01

    Methods for the characterization of ultrasonic transducers (search units) and instruments are presented. The instrument system is considered as three separate components consisting of a transducer, a receiver-display, and a pulser. The operation of each component is assessed independently. The methods presented were chosen because they provide the greatest amount of information about component operation and were not chosen based upon such conditions as cost, ease of operation, field implementation, etc. The results of evaluating a number of commercially available ultrasonic test instruments are presented.

  3. Mechanical Characterization of Nodular Ductile Iron

    SciTech Connect

    Springer, H K

    2012-01-03

    The objective of this study is to characterize the strength and fracture response of nodular ductile iron (NDI) and its underlying ferritic matrix phase. Quasistatic and split Hopkinson pressure bar (SHPB) compression tests were performed on NDI and a model material for the NDI matrix phase (Fe-Si alloy). Smooth and notch round bar (NRB) samples were loaded in tension until fracture to determine strain-at-failure with varying stress triaxiality. Multiple tests were performed on each small and large smooth bar samples to obtain fracture statistics with sample size. Fracture statistics are important for initializing simulations of fragmentation events. Johnson-Cook strength models were developed for the NDI and the Fe-Si alloy. NDI strength model parameters are: A = 525 MPa, B = 650 MPa, n = 0.6, and C = 0.0205. The average SHPB experimental strain-rate of 2312/s was used for the reference strain-rate in this model. Fe-Si alloy strength model parameters are: A=560 MPa, B = 625 MPa, n = 0.5, and C = 0.02. The average SHPB experimental strain-rate of 2850/s was used for the reference strain-rate in this model. A Johnson-Cook failure model was developed for NDI with model parameters: D{sub 1} = 0.029, D{sub 2} = 0.44, D{sub 3} = -1.5, and D{sub 4} = D{sub 5} = 0. An exponential relationship was developed for the elongation-at-failure statistics as a function of length-scale with model parameters: S{sub f1} = 0.108, S{sub f2} = -0.00169, and L{sub m} = 32.4 {mu}m. NDI strength and failure models, including failure statistics, will be used in continuum-scale simulations of explosively-driven ring fragmentation. The Fe-Si alloy strength model will be used in mesoscale simulations of spall fracture in NDI, where the NDI matrix phase is captured explicitly.

  4. Mechanical Characterization of Molecular Assemblies at Oil/Water Interfaces

    NASA Astrophysics Data System (ADS)

    Yuan, Wa

    The self-assembly of charged molecules in liquid phases and their ability to form functional layers at immiscible interfaces are areas of great interest. However, the implementation of these assemblies is often limited by a lack of understanding of the detailed assembly mechanisms. In order to enhance the performance of interfacial assemblies it is essential to be able to characterize the physical and mechanical properties of assembled layers, as well as develop model systems that will allow us to examine the factors that govern their interaction with the surrounding environment. The key purpose of this thesis is to develop an understanding of some of the important factors influencing interfacial assemblies at immiscible liquid interfaces. The first portion of the work involves mechanical characterization of interfacial layers formed by large amphiphilic molecules. The study of block and gradient copolymers, reveals the effect of copolymer sequence distribution on the ability of these molecules to form interfacial assemblies. Specifically, the unique network structure formed by gradient copolymers at oil/water interfaces enables us to create a robust membrane at the interface by ionic crosslinking. The second part of this thesis explores smaller molecule assemblies at liquid interfaces, including commonly used commercial surfactant (span 80) and nano particles (graphene oxide). Both studies demonstrate an interesting correlation between molecular structure and overall properties of the assembled layers. Factors such as interfacial density, particle sizes and pH can greatly influence the structure of the assembled layers, resulting in interesting phenomena such as spontaneous emulsification, wrinkling and layer collapse. The bulk of the oil/water interface study was performed using axisymmetric drop shape analysis (DSA), which successfully quantifies the mechanical tension in the interfacial layer. This analysis was further extended by a development of a double

  5. New methods for quantum mechanical reaction dynamics

    SciTech Connect

    Thompson, W.H. |

    1996-12-01

    Quantum mechanical methods are developed to describe the dynamics of bimolecular chemical reactions. We focus on developing approaches for directly calculating the desired quantity of interest. Methods for the calculation of single matrix elements of the scattering matrix (S-matrix) and initial state-selected reaction probabilities are presented. This is accomplished by the use of absorbing boundary conditions (ABC) to obtain a localized (L{sup 2}) representation of the outgoing wave scattering Green`s function. This approach enables the efficient calculation of only a single column of the S-matrix with a proportionate savings in effort over the calculation of the entire S-matrix. Applying this method to the calculation of the initial (or final) state-selected reaction probability, a more averaged quantity, requires even less effort than the state-to-state S-matrix elements. It is shown how the same representation of the Green`s function can be effectively applied to the calculation of negative ion photodetachment intensities. Photodetachment spectroscopy of the anion ABC{sup -} can be a very useful method for obtaining detailed information about the neutral ABC potential energy surface, particularly if the ABC{sup -} geometry is similar to the transition state of the neutral ABC. Total and arrangement-selected photodetachment spectra are calculated for the H{sub 3}O{sup -} system, providing information about the potential energy surface for the OH + H{sub 2} reaction when compared with experimental results. Finally, we present methods for the direct calculation of the thermal rate constant from the flux-position and flux-flux correlation functions. The spirit of transition state theory is invoked by concentrating on the short time dynamics in the area around the transition state that determine reactivity. These methods are made efficient by evaluating the required quantum mechanical trace in the basis of eigenstates of the Boltzmannized flux operator.

  6. A review of microelectromechanical systems for nanoscale mechanical characterization

    NASA Astrophysics Data System (ADS)

    Zhu, Yong; Chang, Tzu-Hsuan

    2015-09-01

    A plethora of nanostructures with outstanding properties have emerged over the past decades. Measuring their mechanical properties and understanding their deformation mechanisms is of paramount importance for many of their device applications. To address this need innovative experimental techniques have been developed, among which a promising one is based upon microelectromechanical systems (MEMS). This article reviews the recent advances in MEMS platforms for the mechanical characterization of one-dimensional (1D) nanostructures over the past decade. A large number of MEMS platforms and related nanomechanics studies are presented to demonstrate the unprecedented capabilities of MEMS for nanoscale mechanical characterization. Focusing on key design considerations, this article aims to provide useful guidelines for developing MEMS platforms. Finally, some of the challenges and future directions in the area of MEMS-enabled nanomechanical characterization are discussed.

  7. Method Of Characterizing An Electrode Binder

    DOEpatents

    Cocciantelli, Jean-Michel; Coco, Isabelle; Villenave, Jean-Jacques

    1999-05-11

    In a method of characterizing a polymer binder for cell electrodes in contact with an electrolyte and including a current collector and a paste containing an electrochemically active material and said binder, a spreading coefficient of the binder on the active material is calculated from the measured angle of contact between standard liquids and the active material and the binder, respectively. An interaction energy of the binder with the electrolyte is calculated from the measured angle of contact between the electrolyte and the binder. The binder is selected such that the spreading coefficient is less than zero and the interaction energy is at least 60 mJ/m.sup.2.

  8. Neural network method for characterizing video cameras

    NASA Astrophysics Data System (ADS)

    Zhou, Shuangquan; Zhao, Dazun

    1998-08-01

    This paper presents a neural network method for characterizing color video camera. A multilayer feedforward network with the error back-propagation learning rule for training, is used as a nonlinear transformer to model a camera, which realizes a mapping from the CIELAB color space to RGB color space. With SONY video camera, D65 illuminant, Pritchard Spectroradiometer, 410 JIS color charts as training data and 36 charts as testing data, results show that the mean error of training data is 2.9 and that of testing data is 4.0 in a 2563 RGB space.

  9. Normalized stiffness ratios for mechanical characterization of isotropic acoustic foams.

    PubMed

    Sahraoui, Sohbi; Brouard, Bruno; Benyahia, Lazhar; Parmentier, Damien; Geslain, Alan

    2013-12-01

    This paper presents a method for the mechanical characterization of isotropic foams at low frequency. The objective of this study is to determine the Young's modulus, the Poisson's ratio, and the loss factor of commercially available foam plates. The method is applied on porous samples having square and circular sections. The main idea of this work is to perform quasi-static compression tests of a single foam sample followed by two juxtaposed samples having the same dimensions. The load and displacement measurements lead to a direct extraction of the elastic constants by means of normalized stiffness and normalized stiffness ratio which depend on Poisson's ratio and shape factor. The normalized stiffness is calculated by the finite element method for different Poisson ratios. The no-slip boundary conditions imposed by the loading rigid plates create interfaces with a complex strain distribution. Beforehand, compression tests were performed by means of a standard tensile machine in order to determine the appropriate pre-compression rate for quasi-static tests. PMID:25669274

  10. Multiscale Approach to Characterize Mechanical Properties of Tissue Engineered Skin.

    PubMed

    Tupin, S; Molimard, J; Cenizo, V; Hoc, T; Sohm, B; Zahouani, H

    2016-09-01

    Tissue engineered skin usually consist of a multi-layered visco-elastic material composed of a fibrillar matrix and cells. The complete mechanical characterization of these tissues has not yet been accomplished. The purpose of this study was to develop a multiscale approach to perform this characterization in order to link the development process of a cultured skin to the mechanical properties. As a proof-of-concept, tissue engineered skin samples were characterized at different stages of manufacturing (acellular matrix, reconstructed dermis and reconstructed skin) for two different aging models (using cells from an 18- and a 61-year-old man). To assess structural variations, bi-photonic confocal microscopy was used. To characterize mechanical properties at a macroscopic scale, a light-load micro-mechanical device that performs indentation and relaxation tests was designed. Finally, images of the internal network of the samples under stretching were acquired by combining confocal microscopy with a tensile device. Mechanical properties at microscopic scale were assessed. Results revealed that adding cells during manufacturing induced structural changes, which provided higher elastic modulus and viscosity. Moreover, senescence models exhibited lower elastic modulus and viscosity. This multiscale approach was efficient to characterize and compare skin equivalent samples and permitted the first experimental assessment of the Poisson's ratio for such tissues. PMID:26942585

  11. Automated Weld Characterization Using the Thermoelectric Method

    NASA Technical Reports Server (NTRS)

    Fulton, J. P.; Wincheski, B.; Namkung, M.

    1992-01-01

    The effective assessment of the integrity of welds is a complicated NDE problem that continues to be a challenge. To be able to completely characterize a weld, detailed knowledge of its tensile strength, ductility, hardness, microstructure, macrostructure, and chemical composition is needed. NDE techniques which can provide information on any of these features are extremely important. In this paper, we examine a seldom used approach based on the thermoelectric (TE) effect for characterizing welds and their associated heat affected zone (HAZ). The thermoelectric method monitors the thermoelectric power which is sensitive to small changes in the kinetics of the conduction electrons near the Fermi surface that can be caused by changes in the local microstructure. The technique has been applied to metal sorting, quality testing, flaw detection, thickness gauging of layers, and microscopic structural analysis. To demonstrate the effectiveness of the technique for characterizing welds, a series of tungsten-inert-gas welded Inconel-718 samples were scanned with a computer controlled TE probe. The samples were then analyzed using a scanning electron microscope and Rockwell hardness tests to characterize the weld and the associated HAZ. We then correlated the results with the TE measurements to provide quantitative information on the size of the HAZ and the degree of hardness of the material in the weld region. This provides potentially valuable information on the strength and fatigue life of the weld. We begin the paper by providing a brief review of the TE technique and then highlight some of the factors that can effect the measurements. Next, we provide an overview of the experimental procedure and discuss the results. Finally, we summarize our findings and consider areas for future research.

  12. A method for characterizing photon radiation fields

    SciTech Connect

    Whicker, J.J.; Hsu, H.H.; Hsieh, F.H.; Borak, T.B.

    1999-04-01

    Uncertainty in dosimetric and exposure rate measurements can increase in areas where multi-directional and low-energy photons (< 100 keV) exist because of variations in energy and angular measurement response. Also, accurate measurement of external exposures in spatially non-uniform fields may require multiple dosimetry. Therefore, knowledge of the photon fields in the workplace is required for full understanding of the accuracy of dosimeters and instruments, and for determining the need for multiple dosimeters. This project was designed to develop methods to characterize photon radiation fields in the workplace, and to test the methods in a plutonium facility. The photon field at selected work locations was characterized using TLDs and a collimated NaI(Tl) detector from which spatial variations in photon energy distributions were calculated from measured spectra. Laboratory results showed the accuracy and utility of the method. Field measurement results combined with observed work patterns suggested the following: (1) workers are exposed from all directions, but not isotropically, (2) photon energy distributions were directionally dependent, (3) stuffing nearby gloves into the glovebox reduced exposure rates significantly, (4) dosimeter placement on the front of the chest provided for a reasonable estimate of the average dose equivalent to workers` torsos, (5) justifiable conclusions regarding the need for multiple dosimetry can be made using this quantitative method, and (6) measurements of the exposure rates with ionization chambers pointed with open beta windows toward the glovebox provided the highest measured rates, although absolute accuracy of the field measurements still needs to be assessed.

  13. HEFF---A user`s manual and guide for the HEFF code for thermal-mechanical analysis using the boundary-element method; Version 4.1: Yucca Mountain Site Characterization Project

    SciTech Connect

    St. John, C.M.; Sanjeevan, K.

    1991-12-01

    The HEFF Code combines a simple boundary-element method of stress analysis with the closed form solutions for constant or exponentially decaying heat sources in an infinite elastic body to obtain an approximate method for analysis of underground excavations in a rock mass with heat generation. This manual describes the theoretical basis for the code, the code structure, model preparation, and step taken to assure that the code correctly performs its intended functions. The material contained within the report addresses the Software Quality Assurance Requirements for the Yucca Mountain Site Characterization Project. 13 refs., 26 figs., 14 tabs.

  14. In situ methods for assessing alveolar mechanics.

    PubMed

    Wu, You; Perlman, Carrie E

    2012-02-01

    Lung mechanics are an important determinant of physiological and pathophysiological lung function. Recent light microscopy studies of the intact lung have furthered the understanding of lung mechanics but used methodologies that may have introduced artifacts. To address this concern, we employed a short working distance water immersion objective to capture confocal images of a fluorescently labeled alveolar field on the costal surface of the isolated, perfused rat lung. Surface tension held a saline drop between the objective tip and the lung surface, such that the lung surface was unconstrained. For comparison, we also imaged with O-ring and coverslip; with O-ring, coverslip, and vacuum pressure; and without perfusion. Under each condition, we ventilated the lung and imaged the same region at the endpoints of ventilation. We found use of a coverslip caused a minimal enlargement of the alveolar field; additional use of vacuum pressure caused no further dimensional change; and absence of perfusion did not affect alveolar field dimension. Inflation-induced expansion was unaltered by methodology. In response to inflation, percent expansion was the same as recorded by all four alternative methods. PMID:22074721

  15. Computational simulation methods for composite fracture mechanics

    NASA Technical Reports Server (NTRS)

    Murthy, Pappu L. N.

    1988-01-01

    Structural integrity, durability, and damage tolerance of advanced composites are assessed by studying damage initiation at various scales (micro, macro, and global) and accumulation and growth leading to global failure, quantitatively and qualitatively. In addition, various fracture toughness parameters associated with a typical damage and its growth must be determined. Computational structural analysis codes to aid the composite design engineer in performing these tasks were developed. CODSTRAN (COmposite Durability STRuctural ANalysis) is used to qualitatively and quantitatively assess the progressive damage occurring in composite structures due to mechanical and environmental loads. Next, methods are covered that are currently being developed and used at Lewis to predict interlaminar fracture toughness and related parameters of fiber composites given a prescribed damage. The general purpose finite element code MSC/NASTRAN was used to simulate the interlaminar fracture and the associated individual as well as mixed-mode strain energy release rates in fiber composites.

  16. Methods for Studying Ciliary Import Mechanisms.

    PubMed

    Takao, Daisuke; Verhey, Kristen J

    2016-01-01

    Cilia and flagella are microtubule-based organelles that play important roles in human health by contributing to cellular motility as well as sensing and responding to environmental cues. Defects in cilia formation and function cause a broad class of human genetic diseases called ciliopathies. To carry out their specialized functions, cilia contain a unique complement of proteins that must be imported into the ciliary compartment. In this chapter, we describe methods to measure the permeability barrier of the ciliary gate by microinjection of fluorescent proteins and dextrans of different sizes into ciliated cells. We also describe a fluorescence recovery after photobleaching (FRAP) assay to measure the entry of ciliary proteins into the ciliary compartment. These assays can be used to determine the molecular mechanisms that regulate the formation and function of cilia in mammalian cells. PMID:27514912

  17. Smart Optical Material Characterization System and Method

    NASA Technical Reports Server (NTRS)

    Choi, Sang Hyouk (Inventor); Park, Yeonjoon (Inventor)

    2015-01-01

    Disclosed is a system and method for characterizing optical materials, using steps and equipment for generating a coherent laser light, filtering the light to remove high order spatial components, collecting the filtered light and forming a parallel light beam, splitting the parallel beam into a first direction and a second direction wherein the parallel beam travelling in the second direction travels toward the material sample so that the parallel beam passes through the sample, applying various physical quantities to the sample, reflecting the beam travelling in the first direction to produce a first reflected beam, reflecting the beam that passes through the sample to produce a second reflected beam that travels back through the sample, combining the second reflected beam after it travels back though the sample with the first reflected beam, sensing the light beam produced by combining the first and second reflected beams, and processing the sensed beam to determine sample characteristics and properties.

  18. Characterizing time-dependent mechanics in metallic MEMS

    NASA Astrophysics Data System (ADS)

    Bergers, L. I. J. C.; Delhey, N. K. R.; Hoefnagels, J. P. M.; Geers, M. G. D.

    2010-06-01

    Experiments for characterization of time-dependent material properties in free-standing metallic microelectromechanical system (MEMS) pose challenges: e.g. fabrication and handling (sub)-μm sized specimens, control and measurement of sub-μN loads and sub-μm displacements over long periods and various temperatures [1]. A variety of experimental setups have been reported each having their pros and cons. One example is a micro-tensile tester with an ingenious electro-static specimen gripping system [2] aiding simple specimen design giving good results at μN and sub-μm levels, but without in-situ full-field observations. Other progressive examples assimilate the specimen, MEMS actuators and load cells on a single chip [3,4] yielding significant results at nN and nm levels with in-situ TEM/SEM observability, though not without complications: complex load actuator/sensor calibration per chip, measures to reduce fabrication failure and unfeasible cofabrication on wafers with commercial metallic MEMS. This work aims to overcome these drawbacks by developing experimental methods with high sensitivity, precision and in-situ full-field observation capabilities. Moreover, these should be applicable to simple free-standing metallic MEMS that can be co-fabricated with commercial devices. These methods will then serve in systematic studies into size-effects in time-dependent material properties. First a numeric-experimental method is developed. It characterizes bending deformation of onwafer μm-sized aluminum cantilevers. A specially designed micro-clamp is used to mechanically apply a constant precise deflection of the beam (zres <50 nm) for a prolonged period, see fig. 1. After this period, the deflection by the micro-clamp is removed. Full-field height maps with the ensuing deformation are measured over time with confocal optical profilometry (COP). This yields the tip deflection as function of time with ~3 nm precision, see fig.2. To extract material parameters

  19. Estimation of mechanical properties of nanomaterials using artificial intelligence methods

    NASA Astrophysics Data System (ADS)

    Vijayaraghavan, V.; Garg, A.; Wong, C. H.; Tai, K.

    2014-09-01

    Computational modeling tools such as molecular dynamics (MD), ab initio, finite element modeling or continuum mechanics models have been extensively applied to study the properties of carbon nanotubes (CNTs) based on given input variables such as temperature, geometry and defects. Artificial intelligence techniques can be used to further complement the application of numerical methods in characterizing the properties of CNTs. In this paper, we have introduced the application of multi-gene genetic programming (MGGP) and support vector regression to formulate the mathematical relationship between the compressive strength of CNTs and input variables such as temperature and diameter. The predictions of compressive strength of CNTs made by these models are compared to those generated using MD simulations. The results indicate that MGGP method can be deployed as a powerful method for predicting the compressive strength of the carbon nanotubes.

  20. Adaptive characterization method for desktop color printers

    NASA Astrophysics Data System (ADS)

    Shen, Hui-Liang; Zheng, Zhi-Huan; Jin, Chong-Chao; Du, Xin; Shao, Si-Jie; Xin, John H.

    2013-04-01

    With the rapid development of multispectral imaging technique, it is desired that the spectral color can be accurately reproduced using desktop color printers. However, due to the specific spectral gamuts determined by printer inks, it is almost impossible to exactly replicate the reflectance spectra in other media. In addition, as ink densities can not be individually controlled, desktop printers can only be regarded as red-green-blue devices, making physical models unfeasible. We propose a locally adaptive method, which consists of both forward and inverse models, for desktop printer characterization. In the forward model, we establish the adaptive transform between control values and reflectance spectrum on individual cellular subsets by using weighted polynomial regression. In the inverse model, we first determine the candidate space of the control values based on global inverse regression and then compute the optimal control values by minimizing the color difference between the actual spectrum and the predicted spectrum via forward transform. Experimental results show that the proposed method can reproduce colors accurately for different media under multiple illuminants.

  1. A method for characterizing volcanic ash

    SciTech Connect

    Bayhurst, G.K.; Wohletz, K.H.; Mason, A.S.

    1991-01-01

    The development of an automated program for characterization of particles using a scanning electron microscope (SEM) with an energy dispersive X-ray detector (EDS) has greatly reduced the time required for analysis of particulate samples. The SEM system provides a digital representation of all particles scanned such that further measurement of the size, shape, and area are a product of image processing. The EDS and associated software provides information as to the particles' chemical composition. The data obtained from the SEM by this method are reduced by computer to obtain distribution graphs for size, density, shape, and mineralogy. These SEM results have been tested by comparisons with results obtained by traditional optical microscopy, which supports the results and provide details concerning crystallinity and glass content. This method was applied to the ash that damaged the engines from the KLM 747 flight of December 15, 1989 while encountering the ash cloud from Redoubt Volcano. The sample was collected from the pitot-static system and had not been exposed to any engine parts that might have changed its characteristics. The sample analysis presented here demonstrates the capabilities and information obtainable from out automated SEM technique. 5 refs., 7 figs., 3 tabs.

  2. Frequency-Domain Methods for Characterization of Pulsed Power Diagnostics

    SciTech Connect

    White, A D; Anderson, R A; Ferriera, T J; Goerz, D A

    2009-07-27

    This paper discusses methods of frequency-domain characterization of pulsed power sensors using vector network analyzer and spectrum analyzer techniques that offer significant simplification over time-domain methods, while mitigating or minimizing the effect of the difficulties present in time domain characterization. These methods are applicable to characterization of a wide variety of sensors.

  3. Apparatus and method for generating mechanical waves

    DOEpatents

    Allensworth, D.L.; Chen, P.J.

    1982-10-25

    Mechanical waves are generated in a medium by subjecting an electromechanical element to an alternating electric field having a frequency which induces mechanical resonance therein and is below any electrical resonance frequency thereof.

  4. Apparatus and method for generating mechanical waves

    DOEpatents

    Allensworth, Dwight L.; Chen, Peter J.

    1985-01-01

    Mechanical waves are generated in a medium by subjecting an electromechanical element to an alternating electric field having a frequency which induces mechanical resonance therein and is below any electrical resonance frequency thereof.

  5. Mechanical characterization of proanthocyanidin-dentin matrix interaction

    PubMed Central

    Castellan, Carina Strano; Pereira, Patricia Nobrega; Grande, Rosa Helena Miranda; Bedran-Russo, Ana Karina

    2010-01-01

    Objectives To characterize the properties of dentin matrix treated with two proanthocyanidin rich cross-linking agents and their effect on dentin bonded interfaces. Methods Sound human molars were cut into 0.5 mm thick dentin slabs, demineralized and either treated with one of two cross-linking agents (grape seed - GSE and cocoa seed - COE extracts) or left untreated. The modulus of elasticity of demineralized dentin was assessed after 10 or 60 min and the swelling ratio after 60 min treatment. Bacterial collagenase was also used to assess resistance to enzymatic degradation of samples subjected to ultimate tensile strength. The effect of GSE or COE on the resin-dentin bond strength was evaluated after 10 or 60 min of exposure time. Data were statistically analyzed at a 95% confidence interval. Results Both cross-linkers increased the elastic modulus of demineralized dentin as exposure time increased. Swelling ratio was lower for treated samples when compared to control groups. No statistically significant changes to the UTS indicate that collagenase had no effect on dentin matrix treated with either GSE or COE. Dentin-resin bonds significantly increased following treatment with GSE regardless of the application time or adhesive system used. Significance Increased mechanical properties and stability of dentin matrix can be achieved by the use of PA-rich collagen cross-linkers most likely due to the formation of a PA-collagen complex. The short term dentin-resin bonds can be improved after 10 minutes dentin treatment. PMID:20650510

  6. Mechanical characterization of low dimensional nanomaterials and polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Gao, Hongsheng

    This research was aimed to characterize the mechanical properties of low dimensional nanomaterials and polymer nanocomposites, and to study the reinforcing mechanisms of nanoscale reinforcements. The nanomaterials studied were zero-dimensional nanomaterial--cuprous oxide (Cu2O) nanocubes, one-dimensional nanomaterials--silver nanowires and silicon oxide (SiO2) nanowires, and two-dimensional nanomaterial--nanometer-thick montmorillonite clay platelets. The hardness and elastic moduli of solid Cu 2O nanocubes and silver nanowires were measured by directly indenting individual cubes/wires using a nanoindenter. The elastic modulus of amorphous SiO2 nanowires was measured by performing three-point bending on suspended wires with an atomic force microscope (AFM) tip. The elastic modulus of the nanometer-thick clay platelets was assessed by the modulus mapping technique. An array of nanoscale indents was successfully made on a nanowire. The nanowires were cut to the length as needed. The nanoindentation approach permits the direct machining of individual nanowires without complications of conventional lithography. The nanomechanical properties of single-walled carbon nanotube (SWCNT)-reinforced epoxy composites with varying nanotube concentrations were measured by nanoindentation/nanoscratch techniques. Hardness and elastic modulus were measured using a nanoindenter. Viscoelastic properties of the nanocomposites were measured using nanoindentation dynamic mechanical analysis tests. The SWCNT reinforcing mechanisms were further studied by both Halpin-Tsai and Mori-Tanaka theories, which were found applicable to SWCNT-reinforced, amorphous-polymer composites. The possible reinforcing mechanisms that work in polymer-SWCNT composites and reasons responsible for SWCNTs' low mechanical reinforcement were analyzed. Nanoclay-reinforced agarose nanocomposites with varying clay concentrations were structurally and mechanically characterized. Structural characterization was carried

  7. Current Experimental Methods for Characterizing Protein-Protein Interactions.

    PubMed

    Zhou, Mi; Li, Qing; Wang, Renxiao

    2016-04-19

    Protein molecules often interact with other partner protein molecules in order to execute their vital functions in living organisms. Characterization of protein-protein interactions thus plays a central role in understanding the molecular mechanism of relevant protein molecules, elucidating the cellular processes and pathways relevant to health or disease for drug discovery, and charting large-scale interaction networks in systems biology research. A whole spectrum of methods, based on biophysical, biochemical, or genetic principles, have been developed to detect the time, space, and functional relevance of protein-protein interactions at various degrees of affinity and specificity. This article presents an overview of these experimental methods, outlining the principles, strengths and limitations, and recent developments of each type of method. PMID:26864455

  8. Progress of Stirling cycle analysis and loss mechanism characterization

    NASA Technical Reports Server (NTRS)

    Tew, R. C., Jr.

    1986-01-01

    An assessment of Stirling engine thermodynamic modeling and design codes shows a general deficiency; this deficiency is due to poor understanding of the fluid flow and heat transfer phenomena that occur in the oscillating flow and pressure level environment within the engines. Stirling engine thermodynamic loss mechanisms are listed. Several experimental and computational research efforts now underway to characterize various loss mechanisms are reviewed. The need for additional experimental rigs and rig upgrades is discussed. Recent developments and current efforts in Stirling engine thermodynamic modeling are also reviewed.

  9. Metallic syntactic foams synthesis, characterization and mechanical properties

    NASA Astrophysics Data System (ADS)

    Castro, Gerhard

    In this study, we report two procedures for producing lab-scale syntactic steel by melt infiltration of millimeter-sized alumina microspheres: mechanical pressure infiltration and gravity-fed infiltration. Both methods yield foam with uniform distributions of microspheres and negligible unintended porosity. The most critical parameters in the manufacture of the syntactic steel foams are the melt temperature and the preheat temperature of the microspheres prior to infiltration. The preheatment temperature of the microspheres must be close to the melting temperature of steel. Syntactic steel foams with relative density of about half of solid steel densities were produced using monosized microspheres randomly situated in a mold. Microspheres with a diameter of 1.27 mm were used for the mechanical pressure infiltration method and microspheres with a diameter of 4.45 mm for the gravity-fed infiltration method. Different steel chemical compositions were selected to produce steel foams of different inherent yield strength: including several ferritic-pearlitic steels and one TRIP steel (TRansformation-Induced Plasticity). The resultant foams were characterized by chemical and microstructural analysis. The microstructure of the samples consisted of blends of ferritic and pearlitic constituents in varying proportions for the ferritic-pearlitic steels, while the cast TRIP steel matrix presented an austenitic microstructure. The basic mechanical properties of the steel syntactic foams were studied under compression loading. The pearlitic syntactic foams have greater compression strength and energy absorption capacity than the ferritic syntactic foams, but the TRIP steel syntactic foam exhibited the highest compression strength and highest energy absorption capacity. The properties of the steel syntactic foams were compared to those of other steel foams, aluminum foams and other cellular structures reported in the literature. We present also the compression and impact behavior

  10. Quantitative Characterization of Mechanical Property of Annealed Monolayer Colloidal Crystal.

    PubMed

    Zhang, Lijing; Wang, Weiqi; Zheng, Lu; Wang, Xiuyu; Yan, Qingfeng

    2016-01-19

    Quantitative characterization of the mechanical properties of a polystyrene (PS) monolayer colloidal crystal (MCC) annealed with solvent vapor has been performed for the first time by means of atomic force microscopy nanoindentation. The results showed that both the compressive and bending elastic modulus of PS MCC increased with the prolongation of annealing time from initial to 13 min. When the annealing time reached 15 min or even more, the PS MCC almost deformed to a planar film, and the elastic modulus of the PS MCC presented a drastic increase. These results provide a basis for tailoring the mechanical properties of a polymer colloidal monolayer via solvent vapor annealing. Such self-supported and high-mechanical-strength colloidal monolayers can be transferred to other surfaces for potential and promising applications in the bottom-up fabrication of highly ordered nanostructured materials such as nano dot arrays, photonic crystals, and many others. PMID:26700374

  11. Finite element methods in probabilistic mechanics

    NASA Technical Reports Server (NTRS)

    Liu, Wing Kam; Mani, A.; Belytschko, Ted

    1987-01-01

    Probabilistic methods, synthesizing the power of finite element methods with second-order perturbation techniques, are formulated for linear and nonlinear problems. Random material, geometric properties and loads can be incorporated in these methods, in terms of their fundamental statistics. By construction, these methods are applicable when the scale of randomness is not too large and when the probabilistic density functions have decaying tails. By incorporating certain computational techniques, these methods are shown to be capable of handling large systems with many sources of uncertainties. Applications showing the effects of combined random fields and cyclic loading/stress reversal are studied and compared with Monte Carlo simulation results.

  12. Superconvergent perturbation method in quantum mechanics

    SciTech Connect

    Scherer, W. )

    1995-02-27

    An analog of Kolmogorov's superconvergent perturbation theory in classical mechanics is constructed for self-adjoint operators. It is different from the usual Rayleigh-Schroedinger perturbation theory and yields expansions for eigenvalues and eigenvectors in terms of functions of the perturbation parameter.

  13. The Challenge of Characterizing Operations in the Mechanisms Underlying Behavior

    PubMed Central

    Bechtel, William

    2005-01-01

    Neuroscience and cognitive science seek to explain behavioral regularities in terms of underlying mechanisms. An important element of a mechanistic explanation is a characterization of the operations of the parts of the mechanism. The challenge in characterizing such operations is illustrated by an example from the history of physiological chemistry in which some investigators tried to characterize the internal operations in the same terms as the overall physiological system while others appealed to elemental chemistry. In order for biochemistry to become successful, researchers had to identify a new level of operations involving operations over molecular groups. Existing attempts at mechanistic explanation of behavior are in a situation comparable to earlier approaches to physiological chemistry, drawing their inspiration either from overall psychology activities or from low-level neural processes. Successful mechanistic explanations of behavior require the discovery of the appropriate component operations. Such discovery is a daunting challenge but one on which success will be beneficial to both behavioral scientists and cognitive and neuroscientists. PMID:16596967

  14. Development and mechanical characterization of porous titanium bone substitutes.

    PubMed

    Barbas, A; Bonnet, A-S; Lipinski, P; Pesci, R; Dubois, G

    2012-05-01

    Commercially Pure Porous Titanium (CPPTi) can be used for surgical implants to avoid the stress shielding effect due to the mismatch between the mechanical properties of titanium and bone. Most researchers in this area deal with randomly distributed pores or simple architectures in titanium alloys. The control of porosity, pore size and distribution is necessary to obtain implants with mechanical properties close to those of bone and to ensure their osseointegration. The aim of the present work was therefore to develop and characterize such a specific porous structure. First of all, the properties of titanium made by Selective Laser Melting (SLM) were characterized through experimental testing on bulk specimens. An elementary pattern of the porous structure was then designed to mimic the orthotropic properties of the human bone following several mechanical and geometrical criteria. Finite Element Analysis (FEA) was used to optimize the pattern. A porosity of 53% and pore sizes in the range of 860 to 1500 μm were finally adopted. Tensile tests on porous samples were then carried out to validate the properties obtained numerically and identify the failure modes of the samples. Finally, FE elastoplastic analyses were performed on the porous samples in order to propose a failure criterion for the design of porous substitutes. PMID:22498281

  15. Stirling engine control mechanism and method

    DOEpatents

    Dineen, John J.

    1983-01-01

    A reciprocating-to-rotating motion conversion and power control device for a Stirling engine includes a hub mounted on an offset portion of the output shaft for rotation relative to the shaft and for sliding motion therealong which causes the hub to tilt relative to the axis of rotation of the shaft. This changes the angle of inclination of the hub relative to the shaft axis and changes the axial stroke of a set of arms connected to the hub and nutating therewith. A hydraulic actuating mechanism is connected to the hub for moving its axial position along the shaft. A balancing wheel is linked to the hub and changes its angle of inclination as the angle of inclination of the hub changes to maintain the mechanism in perfect balance throughout its range of motion.

  16. Collocation method for fractional quantum mechanics

    SciTech Connect

    Amore, Paolo; Hofmann, Christoph P.; Saenz, Ricardo A.; Fernandez, Francisco M.

    2010-12-15

    We show that it is possible to obtain numerical solutions to quantum mechanical problems involving a fractional Laplacian, using a collocation approach based on little sinc functions, which discretizes the Schroedinger equation on a uniform grid. The different boundary conditions are naturally implemented using sets of functions with the appropriate behavior. Good convergence properties are observed. A comparison with results based on a Wentzel-Kramers-Brillouin analysis is performed.

  17. Microstructural and mechanical characterization of Al–Zn–Si nanocomposites

    SciTech Connect

    García-Villarreal, S.; Chávez-Valdez, A.; Moreno, K.J.; Leyva, C.; Aguilar-Martínez, J.A.; Hurtado, A.; Arizmendi-Morquecho, A.

    2013-09-15

    In this paper the addition of silicon nanoparticles into Al–Zn alloys to form metallic matrix nanocomposites by mechanical alloying process was investigated. The influence of various process parameters such as milling time and Si concentration in the Al–Zn matrix has an interesting effect on the microstructure and mechanical properties of the synthesized nanocomposites. The microstructural characterization of the nanocomposites was evaluated by transmission electron microscopy and energy dispersive X-ray spectroscopy (TEM–EDXS) and the mechanical properties were measured by nanoindentation and micro-hardness tests. The results showed that during mechanical milling Si is added to the Al–Zn matrix achieving a uniform and homogeneous dispersion. After solidification, it forms small particles of AlZnSi with blocky morphology in interdendritic regions. The nanoindentation profiles showed that the elastic modulus and hardness properties increase with increasing milling time. However, a high concentration of Si (> 1.2 wt.%) results in a saturation of Si in the Al–Zn matrix, which adversely affects the mechanical properties. Thus, it is important to tune the milling time and concentration of Si added to the Al–Zn alloys to control the growth of brittle phases that result in reduction of the mechanical properties of the material. - Highlights: • A novel technique for addition of Si nanocomposites into Al–Zn liquid alloy is reported. • Good dispersion and homogeneity of Si in the Al–Zn matrix are obtained. • Increasing Si content above 1.2 wt.% decreases the mechanical properties of Al–Zn alloy. • The saturation point of Si in 1.2 wt.% differs from Galvalume® composition. • The Al–Zn–1.5Si alloy with addition of nanocomposite shows 5.7 GPa of hardness.

  18. Mechanical property characterization of polymeric composites reinforced by continuous microfibers

    NASA Astrophysics Data System (ADS)

    Zubayar, Ali

    Innumerable experimental works have been conducted to study the effect of polymerization on the potential properties of the composites. Experimental techniques are employed to understand the effects of various fibers, their volume fractions and matrix properties in polymer composites. However, these experiments require fabrication of various composites which are time consuming and cost prohibitive. Advances in computational micromechanics allow us to study the various polymer based composites by using finite element simulations. The mechanical properties of continuous fiber composite strands are directional. In traditional continuous fiber laminated composites, all fibers lie in the same plane. This provides very desirable increases in the in-plane mechanical properties, but little in the transverse mechanical properties. The effect of different fiber/matrix combinations with various orientations is also available. Overall mechanical properties of different micro continuous fiber reinforced composites with orthogonal geometry are still unavailable in the contemporary research field. In this research, the mechanical properties of advanced polymeric composite reinforced by continuous micro fiber will be characterized based on analytical investigation and FE computational modeling. Initially, we have chosen IM7/PEEK, Carbon Fiber/Nylon 6, and Carbon Fiber/Epoxy as three different case study materials for analysis. To obtain the equivalent properties of the micro-hetero structures, a concept of micro-scale representative volume elements (RVEs) is introduced. Five types of micro scale RVEs (3 square and 2 hexagonal) containing a continuous micro fiber in the polymer matrix were designed. Uniaxial tensile, lateral expansion and transverse shear tests on each RVE were designed and conducted by the finite element computer modeling software ANSYS. The formulae based on elasticity theory were derived for extracting the equivalent mechanical properties (Young's moduli, shear

  19. Characterization of shape memory alloys for safety mechanisms.

    SciTech Connect

    McLaughlin, Jarred T.; Buchheit, Thomas Edward; Massad, Jordan Elias

    2008-03-01

    Shape memory alloys (SMAs) are metals that exhibit large recoverable strains and exert large forces with tremendous energy densities. The behavior of SMAs is thermomechanically coupled. Their response to temperature is sensitive to their loading condition and their response to loading is sensitive to their thermal condition. This coupled behavior is not to be circumvented, but to be confronted and understood, since it is what manifests SMA's superior clamping performance. To reasonably characterize the coupled behavior of SMA clamping rings used in safety mechanisms, we conduct a series of experiments on SMA samples. The results of the tests will allow increased fidelity in modeling and failure analysis of parts.

  20. Characterization and formation mechanism understanding of asperities to be burnished

    NASA Astrophysics Data System (ADS)

    Man, Y. J.; Yu, S. K.; Liu, B.

    2006-08-01

    To achieve rigorous glide performance for ultra-low flying height, disk media with asperities that exceed the flying height of the magnetic head must be eliminated. Burnishing process is one of the critical ways to remove such asperities from the disk surface. A successful burnishing process demonstrating improved disk yields and less disk damages depends on an effective burnish head that is designed by the understanding of asperities to be burnished. However, optimization of sputtering process is the most essential to avoid those asperities on the disk surface and strongly relies on the formation mechanism understanding of the asperities. It was attempted to trace and characterize the asperities on specially prepared disks in this work. Experimental studies after aggressive burnishing processes on the disks categorized the asperities and indicated their possible formation mechanisms.

  1. Mechanical characterization and modeling of brazed EUROFER-tungsten-joints

    NASA Astrophysics Data System (ADS)

    Chehtov, T.; Aktaa, J.; Kraft, O.

    2007-08-01

    Within the scope of the European fusion power plant study for development of a He-cooled divertor, a tungsten-steel joint has been considered. A preferable joining technique is high temperature brazing. Brazed joints of dissimilar materials suffer from a mismatch in coefficients of thermal expansion. The components of the joint are exposed to mechanical and cyclic thermal loads which give rise to development of high stresses and could lead to failure. Brazed joints of tungsten alloy and ferritic-martensitic steel using different brazing filler materials were studied both experimentally and theoretically. Finite element computations have been performed to calculate the stress distribution and to investigate their evolution within the course of the operational thermal load. Sample joint specimen have been brazed, investigated with respect to their microstructure, and mechanically characterized by performing bend and notched bar impact testing at different temperatures. Some plastic deformation and relatively low impact energies were measured.

  2. Characterization of Thermal and Mechanical Impact on Aluminum Honeycomb Structures

    NASA Technical Reports Server (NTRS)

    Robinson, Christen M.

    2013-01-01

    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.

  3. Optofluidic nanotweezer methods for characterizing nanoparticles and viruses (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Erickson, David

    2016-03-01

    Direct measurements of the strength of particle interactions are critical for characterizing the stability and behavior of colloidal and nanoparticle suspensions. Current techniques are limited in their ability to measure pico-newton scale interaction forces on sub-micrometer particles due to signal detection limits, thermal noise, and throughput. We have recently developed a technique for making direct mechanical measurements of the force and work associated with the steric and electrostatic effects that stabilize colloidal nanoparticles. "Nanophotonic Force Microscopy", as we call it, is unique in that it uses statistical methods to provide direct measurements of these forces at the individual particle scale, while still being sufficiently high-throughput to produce meaningful population level data. In this talk I will introduce the technology, it's advantages, and some of the major uses. Specific case studies will include label-free monitoring of binding of individual antibodies onto single viruses and the measurement of the strength of nanoparticle coatings used for steric stabilization.

  4. Characterization of Esophageal Physiology Using Mechanical State Analysis.

    PubMed

    Leibbrandt, Richard E; Dinning, Phil G; Costa, Marcello; Cock, Charles; Wiklendt, Lukasz; Wang, Guangsong; Tack, Jan; van Beckevoort, Dirk; Rommel, Nathalie; Omari, Taher I

    2016-01-01

    The esophagus functions to transport swallowed fluids and food from the pharynx to the stomach. The esophageal muscles governing bolus transport comprise circular striated muscle of the proximal esophagus and circular smooth muscle of the distal esophagus. Longitudinal smooth muscle contraction provides a mechanical advantage to bolus transit during circular smooth muscle contraction. Esophageal striated muscle is directly controlled by neural circuits originating in the central nervous system, resulting in coordinated contractions. In contrast, the esophageal smooth muscle is controlled by enteric circuits modulated by extrinsic central neural connections resulting in neural relaxation and contraction. The esophageal muscles are modulated by sensory information arising from within the lumen. Contraction or relaxation, which changes the diameter of the lumen, alters the intraluminal pressure and ultimately inhibits or promotes flow of content. This relationship that exists between the changes in diameter and concurrent changes in intraluminal pressure has been used previously to identify the "mechanical states" of the circular muscle; that is when the muscles are passively or actively, relaxing or contracting. Detecting these changes in the mechanical state of the muscle has been difficult and as the current interpretation of esophageal motility is based largely upon pressure measurement (manometry), subtle changes in the muscle function during peristalsis can be missed. We hypothesized that quantification of mechanical states of the esophageal circular muscles and the pressure-diameter properties that define them, would allow objective characterization of the mechanisms that govern esophageal peristalsis. To achieve this we analyzed barium swallows captured by simultaneous videofluoroscopy and pressure with impedance recording. From these data we demonstrated that intraluminal impedance measurements could be used to determine changes in the internal diameter of

  5. Characterization of Esophageal Physiology Using Mechanical State Analysis

    PubMed Central

    Leibbrandt, Richard E.; Dinning, Phil G.; Costa, Marcello; Cock, Charles; Wiklendt, Lukasz; Wang, Guangsong; Tack, Jan; van Beckevoort, Dirk; Rommel, Nathalie; Omari, Taher I.

    2016-01-01

    The esophagus functions to transport swallowed fluids and food from the pharynx to the stomach. The esophageal muscles governing bolus transport comprise circular striated muscle of the proximal esophagus and circular smooth muscle of the distal esophagus. Longitudinal smooth muscle contraction provides a mechanical advantage to bolus transit during circular smooth muscle contraction. Esophageal striated muscle is directly controlled by neural circuits originating in the central nervous system, resulting in coordinated contractions. In contrast, the esophageal smooth muscle is controlled by enteric circuits modulated by extrinsic central neural connections resulting in neural relaxation and contraction. The esophageal muscles are modulated by sensory information arising from within the lumen. Contraction or relaxation, which changes the diameter of the lumen, alters the intraluminal pressure and ultimately inhibits or promotes flow of content. This relationship that exists between the changes in diameter and concurrent changes in intraluminal pressure has been used previously to identify the “mechanical states” of the circular muscle; that is when the muscles are passively or actively, relaxing or contracting. Detecting these changes in the mechanical state of the muscle has been difficult and as the current interpretation of esophageal motility is based largely upon pressure measurement (manometry), subtle changes in the muscle function during peristalsis can be missed. We hypothesized that quantification of mechanical states of the esophageal circular muscles and the pressure-diameter properties that define them, would allow objective characterization of the mechanisms that govern esophageal peristalsis. To achieve this we analyzed barium swallows captured by simultaneous videofluoroscopy and pressure with impedance recording. From these data we demonstrated that intraluminal impedance measurements could be used to determine changes in the internal diameter

  6. Ocular Blood Flow Autoregulation Mechanisms and Methods

    PubMed Central

    Luo, Xue; Shen, Yu-meng; Jiang, Meng-nan; Lou, Xiang-feng; Shen, Yin

    2015-01-01

    The main function of ocular blood flow is to supply sufficient oxygen and nutrients to the eye. Local blood vessels resistance regulates overall blood distribution to the eye and can vary rapidly over time depending on ocular need. Under normal conditions, the relation between blood flow and perfusion pressure in the eye is autoregulated. Basically, autoregulation is a capacity to maintain a relatively constant level of blood flow in the presence of changes in ocular perfusion pressure and varied metabolic demand. In addition, ocular blood flow dysregulation has been demonstrated as an independent risk factor to many ocular diseases. For instance, ocular perfusion pressure plays key role in the progression of retinopathy such as glaucoma and diabetic retinopathy. In this review, different direct and indirect techniques to measure ocular blood flow and the effect of myogenic and neurogenic mechanisms on ocular blood flow are discussed. Moreover, ocular blood flow regulation in ocular disease will be described. PMID:26576295

  7. Characterization of the mechanical properties of freestanding platinum thin films

    NASA Astrophysics Data System (ADS)

    Abbas, Khawar

    Many MEMS devices utilize nanocrystalline thin metallic films as mechanical structures, in particular, micro switching devices where these films are used as Ohmic contacts. But the elastic and plastic properties of these thin films (thickness < 1mum) are significantly different from those of the bulk material. At these scales the volume fraction of material defects such as: grain boundaries, dislocations and interstitials become quite significant and become a chief contributor to the physical and mechanical material properties. In order to effectively design MEMS devices it is important that these material properties are explored and mechanical behavior of the structure they form be characterized. Popular thin film materials used in MEMS devices are Aluminum (Al), Copper (Cu), Nickel (Ni) and Gold (Au). Platinum has traditionally gained acceptance into the MEMS industry because of its chemical inertness and high temperature stability. However the mechanical properties of platinum remains the least exploited. Platinum has a high Young's Modulus (164 GPa, for bulk) and high melting temperature (1768 °C) and therefore can be used as a 'thin film' structure (cantilever, a bridge or a membrane) in high temperature environments with high resistance to mechanical failure. The physical size of these thin film structure make it very difficult to handle them and employ traditional mechanical testing methodologies and techniques and therefore require custom test platforms. One such recently developed platform is presented in this dissertation. The test platform is comprised of a microfabricated cascaded thermal actuator system and test specimen. The cascaded thermal actuator system is capable of providing tens of microns of displacement and tens of milli-Newton forces simultaneously while applying a relatively low temperature gradient across the test specimen. The dimensions of the platform make its use possible in both the SEM/TEM environments and on a probe station under

  8. Preparation of nano fluids by mechanical method

    NASA Astrophysics Data System (ADS)

    Boopathy, J.; Pari, R.; Kavitha, M.; Angelo, P. C.

    2012-07-01

    Nanofluids are conventional heat transfer fluids that contain nano particles of metals, oxides, carbides, nitrides, or nanotubes. Nanofluids exhibit enhanced thermal conductivity and heat transfer coefficients compared to the base fluids. This paper presents the procedure for preparing nanofluids consisting of Copper and Aluminium nano powders in base fluids. Copper and Aluminium nano powders were produced by planetary ball wet milling at 300rpm for 50hrs. Toluene was added to ensure wet milling. These powders were characterized in XRD and SEM for their purity, particle size and shape. The XRD results confirmed the final particle sizes of Copper and Aluminium in the nano range. Then the 0.01 gm of nano metal powders was added in 150 ml of double distilled water and magnetic stirring was done at 1500 rpm for 15 minutes. Sodium lauryl sulphate (0.05%) was added in water as surfactant to ensure the stability of the dispersion. Ultrasonication in the 3000 watts bath was done for 10 minutes to enhance the uniform dispersion of metal powders in water. The pH, dynamic viscosity, ionic conductivity and the stability of the fluids were determined for further usage of synthesized nanofluids as coolant during grinding operation.

  9. Mechanical characterization of low-K dielectric materials

    NASA Astrophysics Data System (ADS)

    Moore, Thomas M.; Hartfield, Cheryl D.; Anthony, J. Mark; Ahlburn, Byron T.; Ho, Paul S.; Miller, Mikel R.

    2001-01-01

    The implementation of materials in device interconnect structure is being driven by shrinking device geometries. In order to meet customer demands for increasing electrical performance, the industry is adopting a solution that provides both lower resistance and lower capacitance. Lower resistance is accomplished by switching from Al(Cu) to Cu interconnect and the capacitance is reduced by replacing SiO2 in the inter-level and inter-metal dielectric layers with lower dielectric constant materials (low-K materials) [1,2]. A change in materials in a process as complex as IC manufacturing is inherently accompanied by an increase in reliability risk. A thorough understanding of the low-K dielectric candidates is necessary for selection of the best candidate that has sufficient mechanical integrity to survive thermal stresses, CMP, packaging, and test, as well as allows for maximum extendibility to next generation devices. Towards this end, the industry has adopted methods and tools to measure mechanical properties and adhesion energies associated with low-K films. It is expected that porosity will significantly deteriorate the mechanical strength of ILD films compared to non-porous films and the effect on mechanical strength may be markedly different if the pores percolate together to form channels rather than remain isolated. Understanding the mechanical properties of these thin films and choice of appropriate mechanical performance metrics is necessary for successful full-scale integration into a reliable packaged product.

  10. General Characterization Methods for Photoelectrochemical Cells for Solar Water Splitting.

    PubMed

    Shi, Xinjian; Cai, Lili; Ma, Ming; Zheng, Xiaolin; Park, Jong Hyeok

    2015-10-12

    Photoelectrochemical (PEC) water splitting is a very promising technology that converts water into clean hydrogen fuel and oxygen by using solar light. However, the characterization methods for PEC cells are diverse and a systematic introduction to characterization methods for PEC cells has rarely been attempted. Unlike most other review articles that focus mainly on the material used for the working electrodes of PEC cells, this review introduces general characterization methods for PEC cells, including their basic configurations and methods for characterizing their performance under various conditions, regardless of the materials used. Detailed experimental operation procedures with theoretical information are provided for each characterization method. The PEC research area is rapidly expanding and more researchers are beginning to devote themselves to related work. Therefore, the content of this Minireview can provide entry-level knowledge to beginners in the area of PEC, which might accelerate progress in this area. PMID:26365789

  11. Characterization of mechanical properties of materials using ultrasound broadband spectroscopy.

    PubMed

    Agrawal, Megha; Prasad, Abhinav; Bellare, Jayesh R; Seshia, Ashwin A

    2016-01-01

    This article explores the characterization of homogenous materials (metals, alloys, glass and polymers) by a simple broadband ultrasonic interrogation method. The novelty lies in the use of ultrasound in a continuous way with very low input power (0 dBm or less) and analysis of the transmitted acoustic wave spectrum for material property characterization like speed of sound, density and dimensions of a material. Measurements were conducted on various thicknesses of samples immersed in liquid where continuous-wave, frequency swept ultrasonic energy was incident normal to the sample surface. The electro-acoustic transmission response is analyzed in the frequency domain with respect to a specifically constructed multi-layered analytical model. From the acoustic signature of the sample materials, material properties such as speed of sound and acoustic impedance can be calculated with experimentally derived values found to be in general agreement with the literature and with pulse-echo technique establishing the basis for a non-contact and non-destructive technique for material characterization. Further, by looking at the frequency spacing of the peaks of water when the sample is immersed, the thickness of the sample can be calculated independently from the acoustic response. This technique can prove to be an effective non-contact, non-destructive and fast material characterization technique for a wide variety of materials. PMID:26387979

  12. Comparison of Module Performance Characterization Methods

    SciTech Connect

    KROPOSKI,B.; MARION,W.; KING,DAVID L.; BOYSON,WILLIAM EARL; KRATOCHVIL,JAY A.

    2000-10-03

    The rating and modeling of photovoltaic PW module performance has been of concern to manufacturers and system designers for over 20 years. Both the National Renewable Energy Laboratory (NREL) and Sandia National Laboratories (SNL) have developed methodologies to predict module and array performance under actual operating conditions. This paper compares the two methods of determining the performance of PV modules, The methods translate module performance to actual or reference conditions using slightly different approaches. The accuracy of both methods is compared for both hourly, daily, and annual energy production over a year of data recorded at NREL in Golden, CO. The comparison of the two methods will be presented for five different PV module technologies.

  13. Biochemical and mechanical characterization of Nereis worm jaws

    NASA Astrophysics Data System (ADS)

    Broomell, Christopher C.

    The ultimate goal of biomimetics is to elucidate the design principles governing performance in biological materials and apply them to engineering systems. Successful transfer of these principles will require a thorough understanding of the complex interplay between molecular composition, organization and mechanical properties of the material. This dissertation describes the mechanical and biochemical characterization of jaws from the marine polychaete Nereis virens. Nereid jaws possess remarkable mechanical properties considering their predominantly organic composition. Hardness and stiffness are comparable to human dentin. However, in stark contrast to dentin, in Nereis these properties are achieved without mineralization. The role of metal ions in jaw sclerotization is addressed. In the pristine state, Zn ions are concentrated at the tip and toothed-edge of the jaw and are critical for hardness and modulus; both properties are reduced by ˜70% following Zn removal by treatment with EDTA. Furthermore, metal content in the jaw can be manipulated by soaking Zn-depleted samples in metal solutions; the comparative effects of treatment with alternative transition metals under both dry and hydrated conditions are described. The molecular composition of the jaw is also addressed. Protein comprises ˜90% of the jaw mass; amino acid analysis indicates that histidine is increased in the hardened, Zn-rich tip. The major protein component in Nereid jaw extracts is purified and characterized by partial peptide mapping and isolation of a partial clone from a jaw pulp cDNA library. Nvjp-1 is a 38 kDa glycine- histidine-rich protein and is believed to be the principle structural protein in the hardened jaw tip. The effects of selected environmental factors on Nvjp-1 structure and assembly are described. Transition from low to high pH is accompanied by changes in secondary structure and a significant molecular elongation. Furthermore, exposure to transition metals, notably Zn and

  14. Phenomenological and mechanics aspects of nondestructive evaluation and characterization by sound and ultrasound of material and fracture properties

    NASA Technical Reports Server (NTRS)

    Fu, L. S. W.

    1982-01-01

    Developments in fracture mechanics and elastic wave theory enhance the understanding of many physical phenomena in a mathematical context. Available literature in the material, and fracture characterization by NDT, and the related mathematical methods in mechanics that provide fundamental underlying principles for its interpretation and evaluation are reviewed. Information on the energy release mechanism of defects and the interaction of microstructures within the material is basic in the formulation of the mechanics problems that supply guidance for nondestructive evaluation (NDE).

  15. Characterizing Cardiac Molecular Mechanisms of Mammalian Hibernation via Quantitative Proteogenomics.

    PubMed

    Vermillion, Katie L; Jagtap, Pratik; Johnson, James E; Griffin, Timothy J; Andrews, Matthew T

    2015-11-01

    This study uses advanced proteogenomic approaches in a nonmodel organism to elucidate cardioprotective mechanisms used during mammalian hibernation. Mammalian hibernation is characterized by drastic reductions in body temperature, heart rate, metabolism, and oxygen consumption. These changes pose significant challenges to the physiology of hibernators, especially for the heart, which maintains function throughout the extreme conditions, resembling ischemia and reperfusion. To identify novel cardioadaptive strategies, we merged large-scale RNA-seq data with large-scale iTRAQ-based proteomic data in heart tissue from 13-lined ground squirrels (Ictidomys tridecemlineatus) throughout the circannual cycle. Protein identification and data analysis were run through Galaxy-P, a new multiomic data analysis platform enabling effective integration of RNA-seq and MS/MS proteomic data. Galaxy-P uses flexible, modular workflows that combine customized sequence database searching and iTRAQ quantification to identify novel ground squirrel-specific protein sequences and provide insight into molecular mechanisms of hibernation. This study allowed for the quantification of 2007 identified cardiac proteins, including over 350 peptide sequences derived from previously uncharacterized protein products. Identification of these peptides allows for improved genomic annotation of this nonmodel organism, as well as identification of potential splice variants, mutations, and genome reorganizations that provides insights into novel cardioprotective mechanisms used during hibernation. PMID:26435507

  16. Raman spectroscopic instrumentation and plasmonic methods for material characterization

    NASA Astrophysics Data System (ADS)

    Tanaka, Kazuki

    The advent of nanotechnology has led to incredible growth in how we consume, make and approach advanced materials. By exploiting nanoscale material properties, unique control of optical, thermal, mechanical, and electrical characteristics becomes possible. This thesis describes the development of a novel localized surface plasmon resonant (LSPR) color sensitive photosensor, based on functionalization of gold nanoparticles onto tianium dioxide nanowires and sensing by a metal-semiconducting nanowire-metal photodiode structure. This LSPR photosensor has been integrated into a system that incorporates Raman spectroscopy, microfluidics, optical trapping, and sorting flow cytometry into a unique material characterization system called the microfluidic optical fiber trapping Raman sorting flow cytometer (MOFTRSFC). Raman spectroscopy is utilized as a powerful molecular characterization technique used to analyze biological, mineralogical and nanomaterial samples. To combat the inherently weak Raman signal, plasmonic methods have been applied to exploit surface enhanced Raman scattering (SERS) and localized surface plasmon resonance (LSPR), increasing Raman intensity by up to 5 orders of magnitude. The resultant MOFTRSFC system is a prototype instrument that can effectively trap, analyze, and sort micron-sized dielectric particles and biological cells. Raman spectroscopy has been presented in several modalities, including the development of a portable near-infrared Raman spectrometer and other emerging technologies.

  17. Hydroxyapatite nanocrystals: simple preparation, characterization and formation mechanism.

    PubMed

    Mohandes, Fatemeh; Salavati-Niasari, Masoud; Fathi, Mohammadhossein; Fereshteh, Zeinab

    2014-12-01

    Crystalline hydroxyapatite (HAP) nanoparticles and nanorods have been successfully synthesized via a simple precipitation method. To control the shape and particle size of HAP nanocrystals, coordination ligands derived from 2-hydroxy-1-naphthaldehyde were first prepared, characterized by Fourier transform infrared (FT-IR) and proton nuclear magnetic resonance ((1)H-NMR) spectroscopies, and finally applied in the synthesis process of HAP. On the other hand, the HAP nanocrystals were also characterized by several techniques including powder X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). According to the FE-SEM and TEM micrographs, it was found that the morphology and crystallinity of the HAP powders depended on the coordination mode of the ligands. PMID:25491798

  18. Methods for Characterization of Alternative RNA Splicing

    PubMed Central

    Harvey, Samuel E.; Cheng, Chonghui

    2016-01-01

    Quantification of alternative splicing to detect the abundance of differentially spliced isoforms of a gene in total RNA can be accomplished via RT-PCR using both quantitative real-time and semi-quantitative PCR methods. These methods require careful PCR primer design to ensure specific detection of particular splice isoforms. We also describe analysis of alternative splicing using a splicing “minigene” in mammalian cell tissue culture to facilitate investigation of the regulation of alternative splicing of a particular exon of interest. PMID:26721495

  19. A thermoluminescent method for aerosol characterization

    NASA Technical Reports Server (NTRS)

    Long, E. R., Jr.; Rogowski, R. S.

    1976-01-01

    A thermoluminescent method has been used to study the interactions of aerosols with ozone. The preliminary results show that ozone reacts with many compounds found in aerosols, and that the thermoluminescence curves obtained from ozonated aerosols are characteristic of the aerosol. The results suggest several important applications of the thermoluminescent method: development of a detector for identification of effluent sources; a sensitive experimental tool for study of heterogeneous chemistry; evaluation of importance of aerosols in atmospheric chemistry; and study of formation of toxic, electronically excited species in airborne particles.

  20. Methods of characterization of synthetic opal films

    NASA Astrophysics Data System (ADS)

    Koryukin, A. V.; Akhmadeev, A. A.; Salakhov, M. Kh

    2013-12-01

    We developed methods for determination of thickness, number of layers and filling fraction of silica particles for synthetic opals. We show that the filling fraction is considerably less than for ideal close-packed structure, which is important for practical and theoretical applications.

  1. Fracture mechanics life analytical methods verification testing

    NASA Technical Reports Server (NTRS)

    Favenesi, J. A.; Clemons, T. G.; Riddell, W. T.; Ingraffea, A. R.; Wawrzynek, P. A.

    1994-01-01

    The objective was to evaluate NASCRAC (trademark) version 2.0, a second generation fracture analysis code, for verification and validity. NASCRAC was evaluated using a combination of comparisons to the literature, closed-form solutions, numerical analyses, and tests. Several limitations and minor errors were detected. Additionally, a number of major flaws were discovered. These major flaws were generally due to application of a specific method or theory, not due to programming logic. Results are presented for the following program capabilities: K versus a, J versus a, crack opening area, life calculation due to fatigue crack growth, tolerable crack size, proof test logic, tearing instability, creep crack growth, crack transitioning, crack retardation due to overloads, and elastic-plastic stress redistribution. It is concluded that the code is an acceptable fracture tool for K solutions of simplified geometries, for a limited number of J and crack opening area solutions, and for fatigue crack propagation with the Paris equation and constant amplitude loads when the Paris equation is applicable.

  2. Fracture mechanics life analytical methods verification testing

    NASA Technical Reports Server (NTRS)

    Favenesi, J. A.; Clemmons, T. G.; Lambert, T. J.

    1994-01-01

    Verification and validation of the basic information capabilities in NASCRAC has been completed. The basic information includes computation of K versus a, J versus a, and crack opening area versus a. These quantities represent building blocks which NASCRAC uses in its other computations such as fatigue crack life and tearing instability. Several methods were used to verify and validate the basic information capabilities. The simple configurations such as the compact tension specimen and a crack in a finite plate were verified and validated versus handbook solutions for simple loads. For general loads using weight functions, offline integration using standard FORTRAN routines was performed. For more complicated configurations such as corner cracks and semielliptical cracks, NASCRAC solutions were verified and validated versus published results and finite element analyses. A few minor problems were identified in the basic information capabilities of the simple configurations. In the more complicated configurations, significant differences between NASCRAC and reference solutions were observed because NASCRAC calculates its solutions as averaged values across the entire crack front whereas the reference solutions were computed for a single point.

  3. Fracture mechanics life analytical methods verification testing

    NASA Astrophysics Data System (ADS)

    Favenesi, J. A.; Clemons, T. G.; Riddell, W. T.; Ingraffea, A. R.; Wawrzynek, P. A.

    1994-09-01

    The objective was to evaluate NASCRAC (trademark) version 2.0, a second generation fracture analysis code, for verification and validity. NASCRAC was evaluated using a combination of comparisons to the literature, closed-form solutions, numerical analyses, and tests. Several limitations and minor errors were detected. Additionally, a number of major flaws were discovered. These major flaws were generally due to application of a specific method or theory, not due to programming logic. Results are presented for the following program capabilities: K versus a, J versus a, crack opening area, life calculation due to fatigue crack growth, tolerable crack size, proof test logic, tearing instability, creep crack growth, crack transitioning, crack retardation due to overloads, and elastic-plastic stress redistribution. It is concluded that the code is an acceptable fracture tool for K solutions of simplified geometries, for a limited number of J and crack opening area solutions, and for fatigue crack propagation with the Paris equation and constant amplitude loads when the Paris equation is applicable.

  4. Solution-adaptive finite element method in computational fracture mechanics

    NASA Technical Reports Server (NTRS)

    Min, J. B.; Bass, J. M.; Spradley, L. W.

    1993-01-01

    Some recent results obtained using solution-adaptive finite element method in linear elastic two-dimensional fracture mechanics problems are presented. The focus is on the basic issue of adaptive finite element method for validating the applications of new methodology to fracture mechanics problems by computing demonstration problems and comparing the stress intensity factors to analytical results.

  5. Method For Characterizing Residual Stress In Metals

    DOEpatents

    Jacobson, Loren A.; Michel, David J.; Wyatt, Jeffrey R.

    2002-12-03

    A method is provided for measuring the residual stress in metals. The method includes the steps of drilling one or more holes in a metal workpiece to a preselected depth and mounting one or more acoustic sensors on the metal workpiece and connecting the sensors to an electronic detecting and recording device. A liquid metal capable of penetrating into the metal workpiece placed at the bottom of the hole or holes. A recording is made over a period of time (typically within about two hours) of the magnitude and number of noise events which occur as the liquid metal penetrates into the metal workpiece. The magnitude and number of noise events are then correlated to the internal stress in the region of the workpiece at the bottom of the hole.

  6. Photoacoustic characterization of the mechanical properties of thin films

    NASA Astrophysics Data System (ADS)

    Hernandez, Carmen M.; Murray, Todd W.; Krishnaswamy, Sridhar

    2002-01-01

    Narrow band photoacoustics (laser ultrasonics) are used to characterize the properties of free-standing nanometer-sized thin films. Photoacoustic generation is achieved by use of a microchip laser which deposits pulsed laser energy in the form of a spatially periodic source on the structure. The resulting narrow band ultrasonic modes are monitored using a Michelson interferometer. By varying the geometry of the spatially periodic source, a wide range of acoustic wave numbers is probed. Results are presented for two-layer thin film aluminum/silicon-nitride (Al/Si3N4) membranes. For such thin films, only the two lowest order guided modes are generated and these in turn can be related to sheet and flexural modes in plates. The mechanical properties and residual stress in the thin films are evaluated from measured acoustic dispersion curves for these two lowest order modes.

  7. Mechanical characterization of temperature-sensitive objects using picosecond ultrasonics

    NASA Astrophysics Data System (ADS)

    Dehoux, T.; Audoin, B.; Zouani, O.; Durrieu, M. C.

    2011-01-01

    Biological objects are exquisitely sensitive to temperature variations and their mechanical characterization is often a challenge when using the picosecond ultrasonics technique. To reduce the laser-induced temperature rise, we place single biological cells on a thin metal transducer and we focus the laser beam that generates the acoustic waves at frequencies <= 150 GHz on the rear side of the transducer. The acoustic waves propagate through the transducer and are partially transmitted to the cell to create the so-called Brillouin oscillations. The frequency of these oscillations provides a direct measurement of the sound velocity. The simultaneous measurement of the acoustic reflection coefficient at the transducer/cell interface allows the determination of both the density and the compressibility of the cell.

  8. Mechanical Characterization of Photo-crosslinkable Hydrogels with AFM

    NASA Astrophysics Data System (ADS)

    McKenna, Alyssa; Byun, Myunghwan; Hayward, Ryan; Aidala, Katherine

    2012-02-01

    Stimuli-responsive hydrogel films formed from photo-crosslinkable polymers are versatile materials for controlled drug delivery devices, three-dimensional micro-assemblies, and components in microfluidic systems. For such applications, it is important to understand both the mechanical properties and the dynamics responses of these materials. We describe the use of atomic force microscope (AFM) based indentation experiments to characterize the properties of poly(N-isopropylacrylamide) copolymer films, crosslinked by activation of pendent benzophenone units using ultraviolet light. In particular, we study how the elastic modulus of the material, determined using the Johnson, Kendall, and Roberts model, depends on UV dose, and simultaneously investigate stress relaxation in these materials in the context of viscoelastic and poroelastic relaxation models.

  9. Material, Mechanical, and Tribological Characterization of Laser-Treated Surfaces

    NASA Astrophysics Data System (ADS)

    Yilbas, Bekir Sami; Kumar, Aditya; Bhushan, Bharat; Aleem, B. J. Abdul

    2014-10-01

    Laser treatment under nitrogen assisting gas environment of cobalt-nickel-chromium-tungsten-based superalloy and high-velocity oxygen-fuel thermal spray coating of nickel-chromium-based superalloy on carbon steel was carried out to improve mechanical and tribological properties. Superalloy surface was preprepared to include B4C particles at the surface prior to the laser treatment process. Material and morphological changes in the laser-treated samples were examined using scanning electron microscopy, energy-dispersive spectroscopy, and x-ray diffraction (XRD) analysis. Residual stresses present at the surface region of the laser-treated layer were determined from the XRD data. The microhardness of the laser-treated surface was measured by indentation tests. Fracture toughness of the coating surfaces before and after laser treatment were also measured using overload indentation tests. Macrowear and macrofriction characterization were carried out using pin-on-disk tests.

  10. In Situ Mechanical Testing Techniques for Real-Time Materials Deformation Characterization

    NASA Astrophysics Data System (ADS)

    Rudolf, Chris; Boesl, Benjamin; Agarwal, Arvind

    2016-01-01

    In situ mechanical property testing has the ability to enhance quantitative characterization of materials by revealing the occurring deformation behavior in real time. This article will summarize select recent testing performed inside a scanning electron microscope on various materials including metals, ceramics, composites, coatings, and 3-Dimensional graphene foam. Tensile and indentation testing methods are outlined with case studies and preliminary data. The benefits of performing a novel double-torsion testing technique in situ are also proposed.

  11. Transuranic waste characterization sampling and analysis methods manual

    SciTech Connect

    1995-05-01

    The Transuranic Waste Characterization Sampling and Analysis Methods Manual (Methods Manual) provides a unified source of information on the sampling and analytical techniques that enable Department of Energy (DOE) facilities to comply with the requirements established in the current revision of the Transuranic Waste Characterization Quality Assurance Program Plan (QAPP) for the Waste Isolation Pilot Plant (WIPP) Transuranic (TRU) Waste Characterization Program (the Program). This Methods Manual includes all of the testing, sampling, and analytical methodologies accepted by DOE for use in implementing the Program requirements specified in the QAPP.

  12. Dialysis: a characterization method of aggregation tendency.

    PubMed

    Pesarrodona, Mireia; Unzueta, Ugutz; Vázquez, Esther

    2015-01-01

    All researchers immersed in the world of recombinant protein production are in agreement that often the production and purification process of a protein can become a nightmare due to an unexpected behavior of the protein at different protocol stages. Once the protein is purified, scientists know that they still cannot relax. There is a decisive last step missing: performing a protein dialysis in a suitable buffer for subsequent experimental trials. Here is when we can find proteins that precipitate during dialysis by buffer-related factors (ionic strength, pH, etc.), which are intrinsic to each protein and are difficult to predict. How can we find the buffer in which a protein is more stable and with less tendency to precipitate? In this chapter we go over possible factors affecting the protein precipitation tendency during the dialysis process and describe a general dialysis protocol with tricks to reduce protein aggregation. Furthermore, we propose a fast method to detect the most appropriate buffer for the stability of a particular protein, performing microdialysis on a battery of different buffers to measure afterwards precipitation by a colorimetric method, and thus being able to choose the most suitable buffer for the dialysis of a given protein. PMID:25447873

  13. Characterizing the intensity of changes made to reduce mechanical exposure.

    PubMed

    Wells, Richard; Laing, Andrew; Cole, Donald

    2009-01-01

    Interventions to prevent musculoskeletal disorders by reducing mechanical exposures may range from equipment adjustments, through changing workstations and equipment or implementing administrative controls, to the design and redesign of work processes. Although generally positive, the literature reports mixed results for the effects of such workplace interventions on musculoskeletal disorders. We propose that an important factor which influences these results is the change intensity. This construct includes: the body part(s) affected, the size of exposure magnitude reduction in the particular task or tasks involved in the change, the time fraction of the job to which the change applies, the coverage of the change (proportion of the workforce affected), and the adherence (if applicable) by the workforce to the change. The intensities of changes recently completed as part of a participatory ergonomics research program were characterized using this approach. Intensity scores were estimated based upon these parameters for peak and cumulative mechanical exposures. Changes affecting a production system re-design and re-configuration were judged to have medium to high intensity, while most other changes were judged to be of small intensity. Comparisons are made to the intensity of changes determined from reports in the published literature. Factors which maximize intensity as well as potential barriers to achieving higher intensities are described. PMID:20037230

  14. Mechanical and microstructural characterization of commercial AA5083 aluminum alloys

    NASA Astrophysics Data System (ADS)

    Kulas, Mary Anne

    The superplastic forming (SPF) process has been of interest to automotive manufacturers for several years because of two imperative goals. The first one is the simplification of the manufacturing process for sheet-body panels and the second reason is to follow government regulations to reduce vehicle mass, by using aluminum. However, the high cost associated with superplastic materials and slow production cycle times have limited the use of SPF to niche automobile manufacturing operations. To overcome these limits, research on SPF has been directed to forming at lower temperatures, at faster strain rates and with lower cost materials. AA5083 superplastic materials hold great promise for high-volume SPF production. However, several technical issues related to the material are still not well understood. The present investigation characterizes the mechanical and microstructural behavior of eight commercial 5083 materials. Conclusive evidence on the deformation mechanisms active in the range of conditions typical for SPF operations, low rates and high temperatures, but also at high-rate and low-temperature conditions, are presented. Predictive equations, useful to establish a predictive basis for SPF forming, are constructed. The issue of cavitation in superplastic materials, leading to poor post-formed properties of the material and ductility variations, is treated. A relation between cavitation, ductility and microstructural features is presented. These results should be quite useful in the development of improved commercial superplastic 5083 materials and for enhancing the capabilities of the SPF process.

  15. Characterization of reward and effort mechanisms in apathy.

    PubMed

    Bonnelle, Valerie; Veromann, Kai-Riin; Burnett Heyes, Stephanie; Lo Sterzo, Elena; Manohar, Sanjay; Husain, Masud

    2015-01-01

    Apathy is a common but poorly understood condition with a wide societal impact observed in several brain disorders as well as, to some extent, in the normal population. Hence the need for better characterization of the underlying mechanisms. The processes by which individuals decide to attribute physical effort to obtain rewards might be particularly relevant to relate to apathy traits. Here, we designed two paradigms to assess individual differences in physical effort production and effort-based decision-making and their relation to apathy in healthy people. Apathy scores were measured using a modified version of the Lille Apathy Rating Scale, suitable for use in a non-clinical population. In the first study, apathy scores were correlated with the degree to which stake (reward on offer) and difficulty level impacts on physical effort production. Individuals with relatively high apathy traits showed an increased modulation of effort while more motivated individuals generally exerted greater force across different levels of stake. To clarify the underlying mechanisms for this behavior, we designed a second task that allows independent titration of stake and effort levels for which subjects are willing to engage in an effortful response to obtain a reward. Our results suggest that apathy traits in the normal population are related to the way reward subjectively affects the estimation of effort costs, and more particularly manifest as decreased willingness to exert effort when rewards are small, or below threshold. The tasks we introduce here may provide useful tools to further investigate apathy in clinical populations. PMID:24747776

  16. The characterization of the mechanical strength of chewable tablets.

    PubMed

    Ambros, M C; Podczeck, F; Podczeck, H; Newton, J M

    1998-11-01

    The purpose of this research was to identify possible test procedures for the evaluation of the strength of chewable tablets with respect to prevention of damage to teeth or mandibular joints when tablets are consumed. Diametral compression and flexure tests were employed to evaluate the strength of commercial samples from five manufacturers of chewable vitamin C tablets. Weibull analysis was used to assess the brittleness of these tablets. The tablets had a lower tensile strength value when determined by the diametral compression test compared to the flexure test ratio which ranged from 0.27 to 0.4. The value for the Weibull modulus ranged from 5 to 16, indicating an appreciable degree of brittleness of the samples. Relating the values for the mechanical strength to suggested practical values for the prevention of damage to the teeth or the mandibular joints indicated that most tablets exceeded these values. The flexure test reflects the practical situation closest, and a limiting tensile strength value of 2 MPa should not be exceeded for chewable tablets. The tablet batches tested were also characterized by a large batch-to-batch variability, suggesting uncontrolled manufacturing procedures. Commercially distributed chewable vitamin C tablets could provide a possible health hazard to teeth and mandibular joints. This hazard could be limited by a mechanical strength test specification. PMID:9834954

  17. Synthesis, characterization and interaction mechanism of new oxadiazolo-phthalimides as peripheral analgesics. IV

    NASA Astrophysics Data System (ADS)

    Antunes, Roberto; Batista, Hildson; Srivastava, Rajendra M.; Thomas, George; Araújo, Clidenor C.; Longo, Ricardo L.; Magalhães, Hélio; Leão, Marcelo B. C.; Pavão, Antônio C.

    2003-11-01

    The synthesis, characterization and spectroscopic studies of compounds 6a- g with analgesic activity is described. A new model of interaction between the drug and the enzyme is suggested. Application of the Resonance Valence Bond theory led us to propose, for the first time, an entirely new mechanism involving an electron transfer from the amino acid residue of the enzyme to the drug. Theoretical studies of various transition states involved in the interaction mechanism employing the semi-empirical molecular orbital calculations (AM1 method) have been carried out. This article also deals with an extensive study of the structure-activity relationships of seven oxadiazolo-phthalimides 6a- g.

  18. Mechanical characterization of TiO{sub 2} nanofibers produced by different electrospinning techniques

    SciTech Connect

    Vahtrus, Mikk; Šutka, Andris; Vlassov, Sergei; Šutka, Anna; Polyakov, Boris; Saar, Rando; Dorogin, Leonid; Lõhmus, Rünno

    2015-02-15

    In this work TiO{sub 2} nanofibers produced by needle and needleless electrospinning processes from the same precursor were characterized and compared using Raman spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and in situ SEM nanomechanical testing. Phase composition, morphology, Young's modulus and bending strength values were found. Weibull statistics was used to evaluate and compare uniformity of mechanical properties of nanofibers produced by two different methods. It is shown that both methods yield nanofibers with very similar properties. - Graphical abstract: Display Omitted - Highlights: • TiO{sub 2} nanofibers were produced by needle and needleless electrospinning processes. • Structure was studied by Raman spectroscopy and electron microscopy methods. • Mechanical properties were measured using advanced in situ SEM cantilevered beam bending technique. • Both methods yield nanofibers with very similar properties.

  19. AFM-based mechanical characterization of single nanofibres.

    PubMed

    Neugirg, Benedikt R; Koebley, Sean R; Schniepp, Hannes C; Fery, Andreas

    2016-04-28

    Nanofibres are found in a broad variety of hierarchical biological systems as fundamental structural units, and nanofibrillar components are playing an increasing role in the development of advanced functional materials. Accurate determination of the mechanical properties of single nanofibres is thus of great interest, yet measurement of these properties is challenging due to the intricate specimen handling and the exceptional force and deformation resolution that is required. The atomic force microscope (AFM) has emerged as an effective, reliable tool in the investigation of nanofibrillar mechanics, with the three most popular approaches-AFM-based tensile testing, three-point deformation testing, and nanoindentation-proving preferable to conventional tensile testing in many (but not all) cases. Here, we review the capabilities and limitations of each of these methods and give a comprehensive overview of the recent advances in this field. PMID:27055900

  20. AFM-based mechanical characterization of single nanofibres

    NASA Astrophysics Data System (ADS)

    Neugirg, Benedikt R.; Koebley, Sean R.; Schniepp, Hannes C.; Fery, Andreas

    2016-04-01

    Nanofibres are found in a broad variety of hierarchical biological systems as fundamental structural units, and nanofibrillar components are playing an increasing role in the development of advanced functional materials. Accurate determination of the mechanical properties of single nanofibres is thus of great interest, yet measurement of these properties is challenging due to the intricate specimen handling and the exceptional force and deformation resolution that is required. The atomic force microscope (AFM) has emerged as an effective, reliable tool in the investigation of nanofibrillar mechanics, with the three most popular approaches--AFM-based tensile testing, three-point deformation testing, and nanoindentation--proving preferable to conventional tensile testing in many (but not all) cases. Here, we review the capabilities and limitations of each of these methods and give a comprehensive overview of the recent advances in this field.

  1. A computational method for automated characterization of genetic components.

    PubMed

    Yordanov, Boyan; Dalchau, Neil; Grant, Paul K; Pedersen, Michael; Emmott, Stephen; Haseloff, Jim; Phillips, Andrew

    2014-08-15

    The ability to design and construct synthetic biological systems with predictable behavior could enable significant advances in medical treatment, agricultural sustainability, and bioenergy production. However, to reach a stage where such systems can be reliably designed from biological components, integrated experimental and computational techniques that enable robust component characterization are needed. In this paper we present a computational method for the automated characterization of genetic components. Our method exploits a recently developed multichannel experimental protocol and integrates bacterial growth modeling, Bayesian parameter estimation, and model selection, together with data processing steps that are amenable to automation. We implement the method within the Genetic Engineering of Cells modeling and design environment, which enables both characterization and design to be integrated within a common software framework. To demonstrate the application of the method, we quantitatively characterize a synthetic receiver device that responds to the 3-oxohexanoyl-homoserine lactone signal, across a range of experimental conditions. PMID:24628037

  2. ASTM test methods for composite characterization and evaluation

    NASA Technical Reports Server (NTRS)

    Masters, John E.

    1994-01-01

    A discussion of the American Society for Testing and Materials is given. Under the topic of composite materials characterization and evaluation, general industry practice and test methods for textile composites are presented.

  3. Photoacoustic characterization of the mechanical properties of thin film materials

    NASA Astrophysics Data System (ADS)

    Zhang, Feifei; Krishnaswamy, Sridhar; Fei, Dong; Rebinsky, Douglas A.

    2005-05-01

    Two high frequency photoacoustic techniques were applied to investigate the mechanical properties of two sets of thin film materials in this work. Broadband photoacoustic guided-wave method was used to measure the guided-wave phase velocity dispersion curves of nano-structured diamond-like carbon hard coatings. The experimental velocity spectra were analyzed by a nonlinear optimization approach in conjunction with a multi-layer wave-propagation model. The derived Young"s moduli using the broadband photoacoustic technique were compared with line-focus acoustic microscopy and nano-indentation tests and good quantitative agreement is found. In a second set of experiments, ultra-thin two-layer aluminum and silicon nitride thin film materials were tested using the femtosecond transient pump-probe method using high frequency bulk waves generated by the ultra-fast laser pulses. The measured moduli of silicon nitride thin layers are in the range of 270 - 340 GPa. Photoacoustic methods are shown to be suitable for in-situ and non-destructive evaluation of the mechanical properties of thin films.

  4. Mechanical and structural characterizations of gamma- and alpha-alumina nanofibers

    SciTech Connect

    Vahtrus, Mikk; Umalas, Madis; Polyakov, Boris; Dorogin, Leonid; Saar, Rando; Tamme, Maret; Saal, Kristjan; Lõhmus, Rünno; Vlassov, Sergei

    2015-09-15

    We investigate the applicability of alumina nanofibers as a potential reinforcement material in ceramic matrix compounds by comparing the mechanical properties of individual nanofibers before and after annealing at 1400 °C. Mechanical testing is performed inside a scanning electron microscope (SEM), which enables observation in real time of the deformation and fracture of the fibers under loading, thereby providing a close-up inspection of the freshly fractured area in vacuum. Improvement of both the Young's modulus and the breaking strength for annealed nanofibers is demonstrated. Mechanical testing is supplemented with the structural characterization of the fibers before and after annealing using SEM, transmission electron microscopy and X-ray diffraction methods. - Highlights: • Mechanical properties of individual alumina nanofibers were measured using in situ SEM cantilevered beam bending technique. • Improvement of mechanical properties of the alumina fibers after annealing at 1400 °C is demonstrated. • Formation of branched structures is demonstrated and their mechanical properties are studied. • XRD and electron microscopy were used for structural characterization of untreated and annealed nanofibers.

  5. Method for material characterization in a non-anechoic environment

    NASA Astrophysics Data System (ADS)

    Pometcu, L.; Sharaiha, A.; Benzerga, R.; Tamas, R. D.; Pouliguen, P.

    2016-04-01

    This paper presents a characterization method for extracting the reflection coefficient of materials and the real part of their permittivity. The characterization is performed in a real environment, as opposed to the classical measurement methods that require an anechoic chamber. In order to reduce the effects of the multipath propagation, a free space bistatic measurement was performed at different distances material-antennas in far field. By using a Teflon sample and a commercial absorbing material sample, measurements have been performed in order to validate the characterization technique.

  6. Generating and characterizing the mechanical properties of cell-derived matrices using atomic force microscopy.

    PubMed

    Tello, Marta; Spenlé, Caroline; Hemmerlé, Joseph; Mercier, Luc; Fabre, Roxane; Allio, Guillaume; Simon-Assmann, Patricia; Goetz, Jacky G

    2016-02-01

    Mechanical interaction between cells and their surrounding extracellular matrix (ECM) controls key processes such as proliferation, differentiation and motility. For many years, two-dimensional (2D) models were used to better understand the interactions between cells and their surrounding ECM. More recently, variation of the mechanical properties of tissues has been reported to play a major role in physiological and pathological scenarios such as cancer progression. The 3D architecture of the ECM finely tunes cellular behavior to perform physiologically relevant tasks. Technical limitations prevented scientists from obtaining accurate assessment of the mechanical properties of physiologically realistic matrices. There is therefore a need for combining the production of high-quality cell-derived 3D matrices (CDMs) and the characterization of their topographical and mechanical properties. Here, we describe methods that allow to accurately measure the young modulus of matrices produced by various cellular types. In the first part, we will describe and review several protocols for generating CDMs matrices from endothelial, epithelial, fibroblastic, muscle and mesenchymal stem cells. We will discuss tools allowing the characterization of the topographical details as well as of the protein content of such CDMs. In a second part, we will report the methodologies that can be used, based on atomic force microscopy, to accurately evaluate the stiffness properties of the CDMs through the quantification of their young modulus. Altogether, such methodologies allow characterizing the stiffness and topography of matrices deposited by the cells, which is key for the understanding of cellular behavior in physiological conditions. PMID:26439175

  7. Mechanical force characterization in manipulating live cells with optical tweezers.

    PubMed

    Wu, Yanhua; Sun, Dong; Huang, Wenhao

    2011-02-24

    Laser trapping with optical tweezers is a noninvasive manipulation technique and has received increasing attentions in biological applications. Understanding forces exerted on live cells is essential to cell biomechanical characterizations. Traditional numerical or experimental force measurement assumes live cells as ideal objects, ignoring their complicated inner structures and rough membranes. In this paper, we propose a new experimental method to calibrate the trapping and drag forces acted on live cells. Binding a micro polystyrene sphere to a live cell and moving the mixture with optical tweezers, we can obtain the drag force on the cell by subtracting the drag force on the sphere from the total drag force on the mixture, under the condition of extremely low Reynolds number. The trapping force on the cell is then obtained from the drag force when the cell is in force equilibrium state. Experiments on numerous live cells demonstrate the effectiveness of the proposed force calibration approach. PMID:21087769

  8. Transuranic waste characterization sampling and analysis methods manual. Revision 1

    SciTech Connect

    Suermann, J.F.

    1996-04-01

    This Methods Manual provides a unified source of information on the sampling and analytical techniques that enable Department of Energy (DOE) facilities to comply with the requirements established in the current revision of the Transuranic Waste Characterization Quality Assurance Program Plan (QAPP) for the Waste Isolation Pilot Plant (WIPP) Transuranic (TRU) Waste Characterization Program (the Program) and the WIPP Waste Analysis Plan. This Methods Manual includes all of the testing, sampling, and analytical methodologies accepted by DOE for use in implementing the Program requirements specified in the QAPP and the WIPP Waste Analysis Plan. The procedures in this Methods Manual are comprehensive and detailed and are designed to provide the necessary guidance for the preparation of site-specific procedures. With some analytical methods, such as Gas Chromatography/Mass Spectrometry, the Methods Manual procedures may be used directly. With other methods, such as nondestructive characterization, the Methods Manual provides guidance rather than a step-by-step procedure. Sites must meet all of the specified quality control requirements of the applicable procedure. Each DOE site must document the details of the procedures it will use and demonstrate the efficacy of such procedures to the Manager, National TRU Program Waste Characterization, during Waste Characterization and Certification audits.

  9. Molecular Mechanics: The Method and Its Underlying Philosophy.

    ERIC Educational Resources Information Center

    Boyd, Donald B.; Lipkowitz, Kenny B.

    1982-01-01

    Molecular mechanics is a nonquantum mechanical method for solving problems concerning molecular geometries and energy. Methodology based on: the principle of combining potential energy functions of all structural features of a particular molecule into a total force field; derivation of basic equations; and use of available computer programs is…

  10. Methods for modeling contact dynamics of capture mechanisms

    NASA Technical Reports Server (NTRS)

    Williams, Philip J.; Tobbe, Patrick A.; Glaese, John

    1991-01-01

    In this paper, an analytical approach for studying the contact dynamics of space-based vehicles during docking/berthing maneuvers is presented. Methods for modeling physical contact between docking/berthing mechanisms, examples of how these models have been used to evaluate the dynamic behavior of automated capture mechanisms, and experimental verification of predicted results are shown.

  11. Flexible microfluidic device for mechanical property characterization of soft viscoelastic solids such as bacterial biofilms

    PubMed Central

    Hohne, Danial N.; Younger, John G.; Solomon, Michael J.

    2009-01-01

    We introduce a flexible microfluidic device to characterize the mechanical properties of soft viscoelastic solids such as bacterial biofilms. In the device, stress is imposed on a test specimen by application of a fixed pressure to a thin, flexible poly(dimethyl siloxane) (PDMS) membrane that is in contact with the specimen. The stress is applied by pressurizing a microfabricated air channel located above the test area. The strain resulting from the applied stress is quantified by measuring the membrane deflection with a confocal laser-scanning microscope. The deflection is governed by the viscoelastic properties of the PDMS membrane and of the test specimen. The relative contributions of the membrane and test material to the measured deformation are quantified by comparing a finite element analysis and an independent (control) measurement of the PDMS membrane mechanical properties. The flexible microfluidic rheometer was used to characterize both the steady-state elastic modulus and transient strain recoil of two soft materials: gellan gums and bacterial biofilms. The measured linear elastic moduli and viscoelastic relaxation times of gellan gum solutions were in good agreement with the results of conventional mechanical rheometry. The linear Young’s moduli of biofilms of Staphylococcus epidermidis and Klebsiella pneumoniae, which could not be measured using conventional methods, were found to be 3.2 kPa and 1.1 kPa, respectively, and the relaxation time of the S. epidermidis biofilm was 13.8 s. Additionally, strain hardening was observed in all the biofilms studied. Finally, design parameters and detection limits of the method show that the device is capable of characterizing soft viscoelastic solids with elastic moduli in the range of 102 – 105 Pa. The flexible microfluidic rheometer addresses a need for mechanical property characterization of soft viscoelastic solids common in fields such as biomaterials, food and consumer products. It requires only ~ 200 p

  12. Flexible microfluidic device for mechanical property characterization of soft viscoelastic solids such as bacterial biofilms.

    PubMed

    Hohne, Danial N; Younger, John G; Solomon, Michael J

    2009-07-01

    We introduce a flexible microfluidic device to characterize the mechanical properties of soft viscoelastic solids such as bacterial biofilms. In the device, stress is imposed on a test specimen by the application of a fixed pressure to a thin, flexible poly(dimethyl siloxane) (PDMS) membrane that is in contact with the specimen. The stress is applied by pressurizing a microfabricated air channel located above the test area. The strain resulting from the applied stress is quantified by measuring the membrane deflection with a confocal laser scanning microscope. The deflection is governed by the viscoelastic properties of the PDMS membrane and of the test specimen. The relative contributions of the membrane and test material to the measured deformation are quantified by comparing a finite element analysis with an independent (control) measurement of the PDMS membrane mechanical properties. The flexible microfluidic rheometer was used to characterize both the steady-state elastic modulus and the transient strain recoil of two soft materials: gellan gums and bacterial biofilms. The measured linear elastic moduli and viscoelastic relaxation times of gellan gum solutions were in good agreement with the results of conventional mechanical rheometry. The linear Young's moduli of biofilms of Staphylococcus epidermidis and Klebsiella pneumoniae, which could not be measured using conventional methods, were found to be 3.2 and 1.1 kPa, respectively, and the relaxation time of the S. epidermidis biofilm was 13.8 s. Additionally, strain hardening was observed in all the biofilms studied. Finally, design parameters and detection limits of the method show that the device is capable of characterizing soft viscoelastic solids with elastic moduli in the range of 102-105 Pa. The flexible microfluidic rheometer addresses the need for mechanical property characterization of soft viscoelastic solids common in fields such as biomaterials, food, and consumer products. It requires only 200 p

  13. Mechanical and electrochemical characterization of vanadium nitride (VN) thin films

    NASA Astrophysics Data System (ADS)

    Caicedo, J. C.; Zambrano, G.; Aperador, W.; Escobar-Alarcon, L.; Camps, E.

    2011-10-01

    Vanadium nitride (V-N) thin films were grown using a reactive d.c. magnetron sputtering process, from a vanadium target (99.999%) in an Ar/N 2 gas mixture at different deposition bias voltage. Films were deposited onto silicon (1 0 0) and RUS-3 steel substrates at 400 °C. Structural, compositional, mechanical and electrochemical characterizations were performed by X-ray diffraction (XRD), elastic forward analysis (EFA), nanoindentation, electrochemical impedance spectroscopy (EIS), and Tafel polarization curves, respectively. X-ray diffraction patterns show the presence of (1 1 1) and (2 0 0) crystallographic orientations associated to the V-N cubic phase. Nanoindentation measurements revealed that when the bias voltage increases from 0 V to -150 V the hardness and elastic modulus are increased from 11 GPa to 20 GPa and from 187 GPa to 221 GPa, respectively. EIS and Tafel curves showed that the corrosion rate of steel, coated with V-N single layer films deposited without bias voltage, diminishes 90% compared to the steel without this coating. On the other hand, when the V-N coating was deposited at the highest d.c. bias voltage (-150 V), the corrosion rate was greater than in the steel coated with zero-voltage (0 V) V-N films. This last result could be attributed to the formation of porosities produced by the ion bombardment during the deposition process.

  14. Characterization and development mechanism of Apios americana tuber starch.

    PubMed

    Yangcheng, Hanyu; Belamkar, Vikas; Cannon, Steven B; Jane, Jay-Lin

    2016-10-20

    Apios americana is a wild legume-bearing plant with edible tubers. Domestication of Apios is in progress because of the superior nutritional value and health benefits of the tuber. Objectives of this study were to: (1) characterize physicochemical properties of the Apios tuber starch; and (2) understand differences in starch structures and properties between the mother (seed) and child (progeny) tubers and the mechanism of starch development. Granules of the Apios tuber starch displayed ellipsoidal, rod, or kidney shape with diameter ranges of 1-30μm. The mother tuber starches displayed greater percentage crystallinity, larger gelatinization enthalpy-changes, longer branch-chain lengths of amylopectin, and lower pasting viscosity than their counterpart child tuber starches. The mother tuber starch of Apios 2127 displayed distinct two peaks of gelatinization, which were attributed to starch granules located at different regions of the tuber having different structures and properties. The mother tuber displayed more active starch biosynthesis in the periphery than in the center of the tuber. PMID:27474558

  15. High Temperature Mechanical Characterization of Ceramic Matrix Composites

    NASA Technical Reports Server (NTRS)

    Gyekenyesi, John Z.

    1998-01-01

    A high temperature mechanical characterization laboratory has been assembled at NASA Lewis Research Center. One contribution of this work is to test ceramic matrix composite specimens in tension in environmental extremes. Two high temperature tensile testing systems were assembled. The systems were assembled based on the performance and experience of other laboratories and meeting projected service conditions for the materials in question. The systems use frames with an electric actuator and a center screw. A PC based data acquisition and analysis system is used to collect and analyze the data. Mechanical extensometers are used to measure specimen strain. Thermocouples, placed near the specimen, are used to measure the specimen gage section temperature. The system for testing in air has a resistance element furnace with molybdenum disilicide elements and pneumatic grips with water cooling attached to hydraulic alignment devices. The system for testing in an inert gas has a graphite resistance element furnace in a chamber with rigidly mounted, water cooled, hydraulically actuated grips. Unidirectional SiC fiber reinforced reaction bonded Si3N4 and triaxially woven, two dimensional, SiC fiber reinforced enhanced SiC composites were tested in unidirectional tension. Theories for predicting the Young's modulus, modulus near the ultimate strength, first matrix cracking stress, and ultimate strength were applied and evaluated for suitability in predicting the mechanical behavior of SiC/RBSN and enhanced SiC/SiC composites. The SiC/RBSN composite exhibited pseudo tough behavior (increased area under the stress/strain curve) from 22 C to 1500 C. The rule of mixtures provides a good estimate of the Young's modulus of the SiC/RBSN composite using the constituent properties from room temperature to 1440 C for short term static tensile tests in air or nitrogen. The rule of mixtures significantly overestimates the secondary modulus near the ultimate strength. The ACK theory

  16. Method for characterizing viscoelasticity of human gluteal tissue.

    PubMed

    Then, C; Vogl, T J; Silber, G

    2012-04-30

    Characterizing compressive transient large deformation properties of biological tissue is becoming increasingly important in impact biomechanics and rehabilitation engineering, which includes devices interfacing with the human body and virtual surgical guidance simulation. Individual mechanical in vivo behaviour, specifically of human gluteal adipose and passive skeletal muscle tissue compressed with finite strain, has, however, been sparsely characterised. Employing a combined experimental and numerical approach, a method is presented to investigate the time-dependent properties of in vivo gluteal adipose and passive skeletal muscle tissue. Specifically, displacement-controlled ramp-and-hold indentation relaxation tests were performed and documented with magnetic resonance imaging. A time domain quasi-linear viscoelasticity (QLV) formulation with Prony series valid for finite strains was used in conjunction with a hyperelastic model formulation for soft tissue constitutive model parameter identification and calibration of the relaxation test data. A finite element model of the indentation region was employed. Strong non-linear elastic but linear viscoelastic tissue material behaviour at finite strains was apparent for both adipose and passive skeletal muscle mechanical properties with orthogonal skin and transversal muscle fibre loading. Using a force-equilibrium assumption, the employed material model was well suited to fit the experimental data and derive viscoelastic model parameters by inverse finite element parameter estimation. An individual characterisation of in vivo gluteal adipose and muscle tissue could thus be established. Initial shear moduli were calculated from the long-term parameters for human gluteal skin/fat: G(∞,S/F)=1850 Pa and for cross-fibre gluteal muscle tissue: G(∞,M)=881 Pa. Instantaneous shear moduli were found at the employed ramp speed: G(0,S/F)=1920 Pa and G(0,M)=1032 Pa. PMID:22360834

  17. Computational structural mechanics methods research using an evolving framework

    NASA Technical Reports Server (NTRS)

    Knight, N. F., Jr.; Lotts, C. G.; Gillian, R. E.

    1990-01-01

    Advanced structural analysis and computational methods that exploit high-performance computers are being developed in a computational structural mechanics research activity sponsored by the NASA Langley Research Center. These new methods are developed in an evolving framework and applied to representative complex structural analysis problems from the aerospace industry. An overview of the methods development environment is presented, and methods research areas are described. Selected application studies are also summarized.

  18. Semi-automated potentiometric titration method for uranium characterization.

    PubMed

    Cristiano, B F G; Delgado, J U; da Silva, J W S; de Barros, P D; de Araújo, R M S; Lopes, R T

    2012-07-01

    The manual version of the potentiometric titration method has been used for certification and characterization of uranium compounds. In order to reduce the analysis time and the influence of the analyst, a semi-automatic version of the method was developed in the Brazilian Nuclear Energy Commission. The method was applied with traceability assured by using a potassium dichromate primary standard. The combined standard uncertainty in determining the total concentration of uranium was around 0.01%, which is suitable for uranium characterization. PMID:22154105

  19. New Laboratory Methods for Characterizing the Immersion Factors for Irradiance

    NASA Technical Reports Server (NTRS)

    Hooker, Stanford B. (Editor); Firestone, Elaine R. (Editor); Zibordi, Giuseppe; DAlimonte, Davide; vaderLinde, Dirk; Brown, James W.

    2003-01-01

    The experimental determination of the immersion factor, I(sub f)(lambda), of irradiance collectors is a requirement of any in-water radiometer. The eighth SeaWiFS Intercalibration Round-Robin Experiment (SIRREX-8) showed different implementations, at different laboratories, of the same I(sub f)(lambda) measurement protocol. The different implementations make use of different setups, volumes, and water types. Consequently, they exhibit different accuracies and require different execution times for characterizing an irradiance sensor. In view of standardizing the characterization of I(sub f)(lambda) values for in-water radiometers, together with an increase in the accuracy of methods and a decrease in the execution time, alternative methods are presented, and assessed versus the traditional method. The proposed new laboratory methods include: a) the continuous method, in which optical measurements taken with discrete water depths are substituted by continuous profiles created by removing the water from the water vessel at a constant flow rate (which significantly reduces the time required for the characterization of a single radiometer); and b) the Compact Portable Advanced Characterization Tank (ComPACT) method, in which the commonly used large tanks are replaced by a small water vessel, thereby allowing the determination of I(sub f)(lambda) values with a small water volume, and more importantly, permitting I(sub f)(lambda) characterizations with pure water. Intercomparisons between the continuous and the traditional method showed results within the variance of I(sub f) (lambda) determinations. The use of the continuous method, however, showed a much shorter realization time. Intercomparisons between the ComPACT and the traditional method showed generally higher I(sub f)(lambda) values for the former. This is in agreement with the generalized expectations of a reduction in scattering effects, because of the use of pure water with the ComPACT method versus the use of

  20. Analysing seismic-source mechanisms by linear-programming methods.

    USGS Publications Warehouse

    Julian, B.R.

    1986-01-01

    Linear-programming methods are powerful and efficient tools for objectively analysing seismic focal mechanisms and are applicable to a wide range of problems, including tsunami warning and nuclear explosion identification. The source mechanism is represented as a point in the 6-D space of moment-tensor components. The present method can easily be extended to fit observed seismic-wave amplitudes (either signed or absolute) subject to polarity constraints, and to assess the range of mechanisms consistent with a set of measured amplitudes. -from Author

  1. Methods for Characterization of Batteries Using Acoustic Interrogation

    NASA Astrophysics Data System (ADS)

    Bhadra, Shoham

    Batteries are a ubiquitous form of electrochemical energy storage, but thus far the methods for measuring the mechanical properties of batteries and their component materials in operando have lagged far behind the methods for measuring the corresponding electrical properties. In this thesis, I demonstrate methods for determining the changes in materials properties of an electrochemical energy storage cell both ex situ and in operando.. I begin by establishing the impact of micro-scale morphology changes on the macro-scale dynamic mechanical response in commercial alkaline AA cells. Using a bounce test, the coefficient of restitution (COR) of the cell is shown to increase non-linearly as a function of state of charge (SOC). I show that the reason for the increase in the COR stems from the spatially-dependent oxidation of the Zn anode, with an initial increase corresponding to the formation of a percolation pathway of ZnO-clad Zn particles spanning the radius of the anode. The subsequent saturation of the COR is shown to result from the ultimate solidification and desiccation of the Zn anode. Building from this, I present a generalized in operando solution for materials characterization in batteries using ultrasonic interrogation. The materials properties of battery components change during charge and discharge, resulting in a change in the sound speed of the materials. By attaching transducers to a battery during cycling and sending ultrasonic pulses through each cell I observe the changes in the time of flight (ToF) of the pulses, both in reflection and transmission. I show that the changes in ToF correspond to both SOC and state of health (SOH) in a variety of battery chemistries and geometries, and detail a corresponding acoustic conservation law model framework. Finally, I perform these electrochemical acoustic time of flight (EAToF) experiments on commercial alkaline AA cells. By correlating the results with energy dispersive x-ray diffraction (EDXRD) data and

  2. Dynamic Multiscale Quantum Mechanics/Electromagnetics Simulation Method.

    PubMed

    Meng, Lingyi; Yam, ChiYung; Koo, SiuKong; Chen, Quan; Wong, Ngai; Chen, GuanHua

    2012-04-10

    A newly developed hybrid quantum mechanics and electromagnetics (QM/EM) method [Yam et al. Phys. Chem. Chem. Phys.2011, 13, 14365] is generalized to simulate the real time dynamics. Instead of the electric and magnetic fields, the scalar and vector potentials are used to integrate Maxwell's equations in the time domain. The TDDFT-NEGF-EOM method [Zheng et al. Phys. Rev. B2007, 75, 195127] is employed to simulate the electronic dynamics in the quantum mechanical region. By allowing the penetration of a classical electromagnetic wave into the quantum mechanical region, the electromagnetic wave for the entire simulating region can be determined consistently by solving Maxwell's equations. The transient potential distributions and current density at the interface between quantum mechanical and classical regions are employed as the boundary conditions for the quantum mechanical and electromagnetic simulations, respectively. Charge distribution, current density, and potentials at different temporal steps and spatial scales are integrated seamlessly within a unified computational framework. PMID:26596737

  3. APPLICATIONS OF BOREHOLE-ACOUSTIC METHODS IN ROCK MECHANICS.

    USGS Publications Warehouse

    Paillet, Frederick L.

    1985-01-01

    Acoustic-logging methods using a considerable range of wavelengths and frequencies have proven very useful in the in situ characterization of deeply buried crystalline rocks. Seismic velocities are useful in investigating the moduli of unfractured rock, and in producing a continuous record of rock quality for comparison with discontinuous intervals of core. The considerable range of frequencies makes the investigation of scale effects possible in both fractured and unfractured rock. Several specific methods for the characterization of in situ permeability have been developed and verified in the field.

  4. Simultaneous spectrophotometric and mechanical property characterization of skin

    NASA Astrophysics Data System (ADS)

    Bunegin, Leonid; Moore, Jeffery B.

    2006-02-01

    Both reflectance spectroscopy and the determination Young's Modulus of skin have shown promise for identifying skin pathology. At present, these determinations are carried out using separate methodologies. This study demonstrates a new technology combining digital UV/VIS reflectance spectroscopy and vacuum aspiration for simultaneously determining the reflectance spectrum and mechanical properties of human skin tissue. A small hand held prototype device incorporating fiber-optic light guides into a vacuum channel was calibrated using various elastic materials subjected to increments of stress by vacuum from 0 to 25 in Hg. The intensity of a UV/VIS light beam reflected from the material at each vacuum increment was compared to the resulting material strain. The reflected beam was also spectrophotometrically analyzed. Skin types were similarly evaluated comparing normal and scar tissue and skin of various ages and coloration. An exponential relationship between reflected beam intensity and the amount of strain resulting from vacuum increments was observed. Young's Modulus (calculated from Aoki et. al equation) and spectra from normal skin and scar tissue were in agreement with previously published observations. Age related decreases in skin elasticity were also demonstrated. In the reflectance spectra, oxy and deoxy-hemoglobin absorbance bands were detected, becoming significantly enhanced at increased levels of vacuum. Melanin absorbance was also easily detected and appeared to correlate with skin coloration. Since superficial skin pathologies have characteristic spectroscopic and mechanical properties, this technique may provide a promising new approach for rapid, non-invasive method for the evaluation of skin lesions.

  5. Electrical and Mechanical Characterizations of Nanocomposite Insulation for HTS Systems

    SciTech Connect

    Walsh, J K; Fabian, Paul E; Hooker, M W; Lizotte, M J; Tuncer, Enis; Sauers, Isidor

    2011-01-01

    As HTS wire technology continues to advance, a critical need has emerged for dielectric materials that can be used in superconducting components such as terminations, fault current limiters, transformers, and motors. To address this need, CTD is developing nanocomposite insulations based on epoxy and benzoxazine chemistries. Depending on part geometry, some processing methods are more efficient than others. For this reason, CTD is investigating both fiber-reinforced and filled resin systems for use in these applications. A thorough set of electrical testing including AC breakdown, breakdown as a function of thickness, and flashover shows promising performance characteristics. In addition, mechanical testing (short beam shear and compression) indicate that these new materials to have as good or better performance than G10.

  6. Novel scanner characterization method for color measurement and diagnostics applications

    NASA Astrophysics Data System (ADS)

    Lee, Bong-Sun; Bala, Raja; Sharma, Gaurav

    2006-02-01

    We propose a novel scanner characterization approach for applications requiring color measurement of hardcopy output in printer calibration, characterization, and diagnostic applications. It is assumed that a typical printed medium comprises the three basic colorants C, M, Y. The proposed method is particularly advantageous when additional colorants are used in the print (e.g. black (K)). A family of scanner characterization targets is constructed, each varying in C, M, Y and at a fixed level of K. A corresponding family of 3-D scanner characterizations is derived, one for each level of K. Each characterization maps scanner RGB to a colorimetric representation such as CIELAB, using standard characterization techniques. These are then combined into a single 4-D characterization mapping RGBK to CIELAB. A refinement of the technique improves performance significantly by using a function of the scanned values for K (e.g. the scanner's green channel response to printed K) instead of the digital K value directly. This makes this new approach more robust with respect to variations in printed K over time. Secondly it enables, with a single scanner characterization, accurate color measurement of prints from different printers within the same family. Results show that the 4-D characterization technique can significantly outperform standard 3-D approaches especially in cases where the image being scanned is a patch target made up of unconstrained CMYK combinations. Thus the algorithm finds particular use in printer characterization and diagnostic applications. The method readily generalizes to printed media containing other (e.g "hi-fi") colorants, and also to other image capture devices such as digital cameras.

  7. Exploration soil gas methods that reduce site characterization costs

    SciTech Connect

    Pyron, A.J.

    1995-09-01

    Initial site characterization of impacted or suspected sites is the most important portion of an integrated environmental remediation program. By use of passive soil gas (PSG) characterization methods, the author has saved his clients significant sums of money by expediting the characterization phase of a project, thus eliminating unnecessary drilling and sampling. He has also been able to advance remedial response by allowing better design of the characterization program. Several commercial products are available which incorporate the principals of the PSG methodology described herein. Using a decidedly low tech approach, the PSG methodology described herein can be used to identify impacted areas on a given site prior to installation of soil borings and monitorings wells. The method is low impact and does not attract unwanted attention to a potentially impacted site. Given the passive nature of the method; it allows a more accurate evaluation of subsurface soil gas conditions, and allows placement of subsequent subsurface tests (whether soil borings or monitoring wells) in optium positions for accurate characterization. This approach minimizes the number of wells needed to characterize a site, eliminates over-characterization and unnecessary drilling, and provides lateral data which in turn allows a client to determine the extent of any liability on a select property. By identifying the extent of his problem, the client can more realistically evaluate his liability and project a budget for completion of remediation. It also allows him to more easily identify the most effective remediation approach. The PSG method allows rapid characterization and priortization of multiple sites, thus allowing a more effective use of environmental budgets.

  8. Characterization of Heat Waves in the Sahel and associated mechanisms

    NASA Astrophysics Data System (ADS)

    Oueslati, Boutheina; Pohl, Benjamin; Moron, Vincent; Rome, Sandra

    2016-04-01

    Large efforts are made to investigate the heat waves (HW) in developed countries because of their devastating impacts on society, economy and environment. This interest increased after the intense event over Europe during summer 2003. However, HWs are still understudied over developing countries. This is particularly true in West Africa, and especially in the Sahel, where temperatures recurrently reach critical values, such as during the 2010 HW event. Understanding the Sahelian HWs and associated health risks constitute the main objective of ACASIS, a 4-year project funded by the French Agence Nationale de la Recherche. Our work contributes to this project and aims at characterizing the Sahelian HWs and understanding the mechanisms associated with such extreme events. There is no universal definition of a HW event, since it is highly dependent on the sector (human health, agriculture, transport...) and region of interest. In our case, a HW is defined when the heat index of the day and of the night exceeds the 90th percentile for at least 3 consecutive days (Rome et al. 2016, in preparation). This index combines temperature and relative humidity in order to determine the human-perceived equivalent temperature (definition adapted from Steadman, 1979). Intrinsic properties of Sahelian HW are analyzed from the Global Summary of the Day (GSOD) synoptic observations and ERA-interim reanalyses over 1979-2014 during boreal spring seasons (April-May-June), the warmest period of the year in the Central Sahel. ERA-interim captures well the observed interannual variability and seasonal cycle at the regional scale, as well as the 1979-2014 increasing linear trend of springtime HW occurrences in the Sahel. Reanalyses, however, overestimate the duration, spatial extent of HW, and underestimate their intensity. For both GSOD and ERA-interim, we show that, over the last three decades, Sahelian HWs tend to become more frequent, last longer, cover larger areas and reach higher

  9. Method of predicting mechanical properties of decayed wood

    DOEpatents

    Kelley, Stephen S.

    2003-07-15

    A method for determining the mechanical properties of decayed wood that has been exposed to wood decay microorganisms, comprising: a) illuminating a surface of decayed wood that has been exposed to wood decay microorganisms with wavelengths from visible and near infrared (VIS-NIR) spectra; b) analyzing the surface of the decayed wood using a spectrometric method, the method generating a first spectral data of wavelengths in VIS-NIR spectra region; and c) using a multivariate analysis to predict mechanical properties of decayed wood by comparing the first spectral data with a calibration model, the calibration model comprising a second spectrometric method of spectral data of wavelengths in VIS-NIR spectra obtained from a reference decay wood, the second spectral data being correlated with a known mechanical property analytical result obtained from the reference decayed wood.

  10. Ultrasonic Method for Deployment Mechanism Bolt Element Preload Verification

    NASA Technical Reports Server (NTRS)

    Johnson, Eric C.; Kim, Yong M.; Morris, Fred A.; Mitchell, Joel; Pan, Robert B.

    2014-01-01

    Deployment mechanisms play a pivotal role in mission success. These mechanisms often incorporate bolt elements for which a preload within a specified range is essential for proper operation. A common practice is to torque these bolt elements to a specified value during installation. The resulting preload, however, can vary significantly with applied torque for a number of reasons. The goal of this effort was to investigate ultrasonic methods as an alternative for bolt preload verification in such deployment mechanisms. A family of non-explosive release mechanisms widely used by satellite manufacturers was chosen for the work. A willing contractor permitted measurements on a sampling of bolt elements for these release mechanisms that were installed by a technician following a standard practice. A variation of approximately 50% (+/- 25%) in the resultant preloads was observed. An alternative ultrasonic method to set the preloads was then developed and calibration data was accumulated. The method was demonstrated on bolt elements installed in a fixture instrumented with a calibrated load cell and designed to mimic production practice. The ultrasonic method yielded results within +/- 3% of the load cell reading. The contractor has since adopted the alternative method for its future production. Introduction

  11. Impetus of composite mechanics on test methods for fiber composites

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.

    1978-01-01

    Significant contributions of the three major areas of composite mechanics to the development of test methods are illustrated with selected examples. The areas of composite mechanics include composite micromechanics, composite macromechanics, and laminate theory. The examples can be considered to be representative of the contribution of composite mechanics to the development of composite test methods. The specific examples describe contributions such as criteria for selecting resin matrices for improved composite strength, the 10 deg off-axis tensile test, procedures for configuring hybrids, and the concept of 'reduced bending rigidities'. The pertinent composite mechanics equations associated with each contribution are given and supplemented by tabular and/or graphical data which illustrate the significance of the contribution.

  12. Surface nanocrystallization of Ti-6Al-4V alloy: microstructural and mechanical characterization.

    PubMed

    Pi, Y; Agoda-Tandjawa, G; Potiron, S; Demangel, C; Retraint, D; Benhayoune, H

    2012-06-01

    In this study, microstructural and mechanical properties of Ti-6Al-4V alloy, before and after the SMA treatment (SMAT) as well as the duplex SMAT/Nitriding process at different treatment conditions, were investigated in order to deepen the knowledge of these properties for biomedical devices. For that purpose, tribological (wear resistance, coefficient of friction) and mechanical (Vickers microhardness) tests were performed. To carry out the microstructural and surface topographical characterization of the samples, the scanning electron microscopy (SEM) and the 3D-SEM reconstruction from stereoscopic images have been used. By means of profiles deduced from the 3D images, the surface roughness has been calculated. The obtained results allowed to find an interesting SMAT condition which, followed by nitriding at low temperature, can greatly improve tribological and mechanical properties of Ti-6Al-4V alloy. It was also shown from SEM characterization and the original method of 3D-SEM reconstruction, that SMAT can reduce the machined grooves and consequently the roughness of the samples decreases. Moreover, we demonstrated, for the first time, that instead of usual etching method, the ionic polishing allowed to reveal the grains, the grain boundaries and the twins as well as the surface nanocrystalline layer generated by SMAT. Thus, the thickness of the SMATed layer decreases with the nitriding temperature, whereas the surface grain size increases. PMID:22905548

  13. A Characterization of the Mechanical Behavior of Resin-Infiltrated Dentin Using Nanoscopic Dynamic Mechanical Analysis

    PubMed Central

    Ryou, Heonjune; Pashley, David H.; Tay, Franklin R.; Arola, Dwayne

    2013-01-01

    This study explored the spatial variations in mechanical behavior of resin-infiltrated dentin using nanoscopic Dynamic Mechanical Analysis (DMA). Objective The objectives were to: 1) evaluate the mechanical behavior of resin-infiltrated dentin using a scanning-based approach to nanoindentation, 2) identify contributions of the collagen matrix to time-dependent deformation of the hybrid layer, and 3) assess the importance of specimen hydration on the nanoDMA response. Methods Specimens of completely demineralized dentin infiltrated with commercial resin adhesive and control samples of resin adhesive were evaluated using a nanoindenter in scanning mode. The load and displacement responses were used to perform DMA and to estimate the complex (E*), storage (E’) and loss (E”) moduli over selected regions of evaluation. The importance of hydration on the mechanical behavior was also examined from a comparison of responses in the hydrated and dehydrated conditions. Results In the hydrated state the apparent complex, storage and loss moduli for the resin-infiltrated dentin samples were 3.5±0.3 GPa, 3.4±0.2 GPa and 0.9±0.3 GPa, respectively. Those values for the resin adhesive control were 2.7±0.3 GPa, 2.7±0.3 GPa and 0.2±0.02 GPa, respectively. Viscoelastic deformation of the resin-infiltrated collagen exceeded that occurring in regions of uniform resin adhesive. Though dehydration resulted in a significant increase in both the complex and storage moduli of the macro hybrid layer, the largest changes occurred to the resin adhesive. Significance The microstructure and hydration play critical roles on the mechanical behavior of the hybrid layer and nanoDMA provides a potent measurement tool for identifying the spatial variations. PMID:23639453

  14. Elucidating diversity of exosomes: biophysical and molecular characterization methods.

    PubMed

    Khatun, Zamila; Bhat, Anjali; Sharma, Shivani; Sharma, Aman

    2016-09-01

    Exosomes are cell-secreted nanovesicles present in biological fluids in normal and diseased conditions. Owing to their seminal role in cell-cell communication, emerging evidences suggest that exosomes are fundamental regulators of various diseases. Due to their potential usefulness in disease diagnosis, robust isolation and characterization of exosomes is critical in developing exosome-based assays. In the last few years, different exosome characterization methods, both biophysical and molecular, have been developed to characterize these tiny vesicles. Here, in this review we summarize: first, biophysical techniques based on spectroscopy (e.g., Raman spectroscopy, dynamic light scattering) and other principles, for example, scanning electron microscopy, atomic force microscopy; second, antibody-based molecular techniques including flow cytometry, transmission electron microscopy and third, nanotechnology-dependent exosome characterization methodologies. PMID:27488053

  15. Characterization of IPMC actuators using standard testing methods

    NASA Astrophysics Data System (ADS)

    Fernández, D.; Espinosa, R.; Moreno, L.; Baselga, J.

    2006-03-01

    In response to a clear need, the research community on EAP (Electroactive Polymer) has just started to work on a standard test methodology to characterize EAP actuators. A very general test methodology for EAPs, covering the characterization procedures for extensional and bending actuators was recently presented. In the present work, well known IPMC samples are characterized following such test methodology. Also, additional tests, not covered by the preliminary standard are included. These tests are conducted using the EAP Unit Tester, a test bench specifically designed for the characterization of EAP actuators. Rather than presenting new material's results, the paper focuses on the instrumentation, procedures and form of presenting results. Although the paper is focused on IPMC the method can be extrapolated to other bending actuators.

  16. Soil characterization methods for unsaturated low-level waste sites

    SciTech Connect

    Wierenga, P.J.; Young, M.H. . Dept. of Soil and Water Science); Gee, G.W.; Kincaid, C.T. ); Hills, R.G. . Dept. of Mechanical Engineering); Nicholson, T.J.; Cady, R.E. )

    1993-01-01

    To support a license application for the disposal of low-level radioactive waste (LLW), applicants must characterize the unsaturated zone and demonstrate that waste will not migrate from the facility boundary. This document provides a strategy for developing this characterization plan. It describes principles of contaminant flow and transport, site characterization and monitoring strategies, and data management. It also discusses methods and practices that are currently used to monitor properties and conditions in the soil profile, how these properties influence water and waste migration, and why they are important to the license application. The methods part of the document is divided into sections on laboratory and field-based properties, then further subdivided into the description of methods for determining 18 physical, flow, and transport properties. Because of the availability of detailed procedures in many texts and journal articles, the reader is often directed for details to the available literature. References are made to experiments performed at the Las Cruces Trench site, New Mexico, that support LLW site characterization activities. A major contribution from the Las Cruces study is the experience gained in handling data sets for site characterization and the subsequent use of these data sets in modeling studies.

  17. Bayesian methods for characterizing unknown parameters of material models

    DOE PAGESBeta

    Emery, J. M.; Grigoriu, M. D.; Field Jr., R. V.

    2016-02-04

    A Bayesian framework is developed for characterizing the unknown parameters of probabilistic models for material properties. In this framework, the unknown parameters are viewed as random and described by their posterior distributions obtained from prior information and measurements of quantities of interest that are observable and depend on the unknown parameters. The proposed Bayesian method is applied to characterize an unknown spatial correlation of the conductivity field in the definition of a stochastic transport equation and to solve this equation by Monte Carlo simulation and stochastic reduced order models (SROMs). As a result, the Bayesian method is also employed tomore » characterize unknown parameters of material properties for laser welds from measurements of peak forces sustained by these welds.« less

  18. [Synchrotron-based characterization methods applied to ancient materials (I)].

    PubMed

    Anheim, Étienne; Thoury, Mathieu; Bertrand, Loïc

    2015-12-01

    This article aims at presenting the first results of a transdisciplinary research programme in heritage sciences. Based on the growing use and on the potentialities of micro- and nano-characterization synchrotron-based methods to study ancient materials (archaeology, palaeontology, cultural heritage, past environments), this contribution will identify and test conceptual and methodological elements of convergence between physicochemical and historical sciences. PMID:25200450

  19. Characterizations of biobased materials using acoustic emission methods

    Technology Transfer Automated Retrieval System (TEKTRAN)

    For many years, the Eastern Regional Research Center (ERRC) has demonstrated that acoustic emission (AE) is a powerful tool for characterizing the properties of biobased materials with fibrous and composite structure. AE often reveals structural information of a material that other methods cannot o...

  20. Methods And Devices For Characterizing Duplex Nucleic Acid Molecules

    DOEpatents

    Akeson, Mark; Vercoutere, Wenonah; Haussler, David; Winters-Hilt, Stephen

    2005-08-30

    Methods and devices are provided for characterizing a duplex nucleic acid, e.g., a duplex DNA molecule. In the subject methods, a fluid conducting medium that includes a duplex nucleic acid molecule is contacted with a nanopore under the influence of an applied electric field and the resulting changes in current through the nanopore caused by the duplex nucleic acid molecule are monitored. The observed changes in current through the nanopore are then employed as a set of data values to characterize the duplex nucleic acid, where the set of data values may be employed in raw form or manipulated, e.g., into a current blockade profile. Also provided are nanopore devices for practicing the subject methods, where the subject nanopore devices are characterized by the presence of an algorithm which directs a processing means to employ monitored changes in current through a nanopore to characterize a duplex nucleic acid molecule responsible for the current changes. The subject methods and devices find use in a variety of applications, including, among other applications, the identification of an analyte duplex DNA molecule in a sample, the specific base sequence at a single nulceotide polymorphism (SNP), and the sequencing of duplex DNA molecules.

  1. Characterization of Local Mechanical Properties of Polymer Thin Films and Polymer Nanocomposites via AFM indentations

    NASA Astrophysics Data System (ADS)

    Cheng, Xu

    AFM indentation has become a tool with great potential in the characterization of nano-mechanical properties of materials. Thanks to the nanometer sized probes, AFM indentation is capable of capturing the changes of multiple properties within the range of tens of nanometers, such task would otherwise be difficult by using other experiment instruments. Despite the great potentials of AFM indentation, it operates based on a simple mechanism: driving the delicate AFM probe to indent the sample surface, and recording the force-displacement response. With limited information provided by AFM indentation, efforts are still required for any practice to successfully extract the desired nano-scale properties from specific materials. In this thesis, we focus on the mechanical properties of interphase between polymer and inorganic materials. It is known that in nanocomposites, a region of polymer exist around nanoparticles with altered molecular structures and improved properties, which is named as interphase polymer. The system with polymer thin films and inorganic material substrates is widely used to simulate the interphase effect in nanocomposites. In this thesis, we developed an efficient and reliable method to process film/substrate samples and characterize the changes of local mechanical properties inside the interphase region with ultra-high resolution AFM mechanical mapping technique. Applying this newly developed method, the interphase of several film/substrate pairs were examined and compared. The local mechanical properties on the other side of the polymer thin film, the free surface side, was also investigated using AFM indentation equipped with surface modified probes. In order to extract the full spectrum of local elastic modulus inside the surface region in the range of only tens of nanometers, the different contact mechanics models were studied and compared, and a Finite Element model was also established. Though the film/substrate system has been wide used as

  2. Histotripsy Methods in Mechanical Disintegration of Tissue: Toward Clinical Applications

    PubMed Central

    Khokhlova, VA; Fowlkes, JB; Roberts, WW; Schade, GR; Xu, Z; Khokhlova, TD; Hall, TL; Maxwell, AD; Wang, YN; Cain, CA

    2015-01-01

    Purpose In high intensity focused ultrasound (HIFU) therapy, an ultrasound beam is focused within the body to locally affect the targeted site without damaging intervening tissues. The most common HIFU regime is thermal ablation. Recently, there has been increasing interest in generating purely mechanical lesions in tissue (histotripsy). This paper provides an overview of several studies on the development of histotripsy methods toward clinical applications. Material and Methods Two histotripsy approaches and examples of their applications are presented. In one approach, sequences of high-amplitude, short (microsecond-long), focused ultrasound pulses periodically produce dense, energetic bubble clouds that mechanically disintegrate tissue. In an alternative approach, longer (millisecond-long) pulses with shock fronts generate boiling bubbles and the interaction of shock fronts with the resulting vapor cavity causes tissue disintegration. Results Recent pre-clinical studies on histotripsy are reviewed for treating benign prostatic hyperplasia (BPH), liver and kidney tumors, kidney stone fragmentation, enhancing antitumor immune response, and tissue decellularization for regenerative medicine applications. Potential clinical advantages of the histotripsy methods are discussed. Conclusions Histotripsy methods can be used to mechanically ablate a wide variety of tissues, whilst selectivity sparing structures such as large vessels. Both ultrasound and MR imaging can be used for targeting and monitoring the treatment in real time. Although the two approaches utilize different mechanisms for tissue disintegration, both have many of the same advantages and offer a promising alternative method of noninvasive surgery. PMID:25707817

  3. Mechanical characterization and structural assessment of biocomposites for construction

    NASA Astrophysics Data System (ADS)

    Christian, Sarah Jane

    The objective of this dissertation is to assess whether or not two particular biocomposite materials, made from hemp fabric and cellulose acetate or polyhydroxybutyrate matrices, are capable of being used for structural and/or construction purposes within in the construction and building industry. The objective of this dissertation was addressed by conducting research to meet the following three goals: (1) to measure the basic mechanical properties of hemp/cellulose acetate and hemp/PHB biocomposites and evaluate if they suitable for use in construction applications, (2) to determine how quickly moisture diffuses into the biocomposite materials and how the moisture affects the mechanical behavior, and (3) to determine how well simple models can predict behavior of structural scale laminates in tension and flexure using biocomposite ply behavior. Compression molding was used to manufacturing the biocomposites from hemp fabric and the themoplastic matrices: cellulose acetate and polyhydroxybutyrate. Four methods for determining the fiber volume fraction were evaluated, and the dissolution method, using different solvents for each matrix type, was used to determine the fiber volume fraction for each composite plate manufactured. Both types of biocomposite were tested in tension, compression, shear, and flexure and the measured properties were compared to wood and engineered wood products to assess whether the biocomposite properties are suitable for use in the construction industry. The biocomposites were conditioned in a humid environment to determine the rate of moisture diffusion into the materials. Then saturated specimens and specimens that were saturated and then dried were tested in tension to evaluate how moisture absorption affects the mechanical behavior of the biocomposites. Finally, simple models of laminate behavior based on laminate plate theory were evaluated to determine if ply level behavior could be used to predict structural scale laminate behavior

  4. Comparison of spectral analysis methods for characterizing brain oscillations

    PubMed Central

    van Vugt, Marieke K.; Sederberg, Per B.; Kahana, Michael J.

    2007-01-01

    Spectral analysis methods are now routinely used in electrophysiological studies of human and animal cognition. Although a wide variety of spectral methods has been used, the ways in which these methods differ are not generally understood. Here we use simulation methods to characterize the similarities and differences between three spectral analysis methods: wavelets, multitapers and Pepisode. Pepisode is a novel method that quantifies the fraction of time that oscillations exceed amplitude and duration thresholds. We show that wavelets and Pepisode used side-by-side helps to disentangle length and amplitude of a signal. Pepisode is especially sensitive to fluctuations around its thresholds, puts frequencies on a more equal footing, and is sensitive to long but low-amplitude signals. In contrast, multitaper methods are less sensitive to weak signals, but are very frequency-specific. If frequency-specificity is not essential, then wavelets and Pepisode are recommended. PMID:17292478

  5. Multiple methods integration for structural mechanics analysis and design

    NASA Technical Reports Server (NTRS)

    Housner, J. M.; Aminpour, M. A.

    1991-01-01

    A new research area of multiple methods integration is proposed for joining diverse methods of structural mechanics analysis which interact with one another. Three categories of multiple methods are defined: those in which a physical interface are well defined; those in which a physical interface is not well-defined, but selected; and those in which the interface is a mathematical transformation. Two fundamental integration procedures are presented that can be extended to integrate various methods (e.g., finite elements, Rayleigh Ritz, Galerkin, and integral methods) with one another. Since the finite element method will likely be the major method to be integrated, its enhanced robustness under element distortion is also examined and a new robust shell element is demonstrated.

  6. The contour method: a new approach in experimental mechanics

    SciTech Connect

    Prime, Michael B

    2009-01-01

    The recently developed contour method can measure complex residual-stress maps in situations where other measurement methods cannot. This talk first describes the principle of the contour method. A part is cut in two using a precise and low-stress cutting technique such as electric discharge machining. The contour of the resulting new surface, which will not be flat if residual stresses are relaxed by the cutting, is then measured. Finally, a conceptually simple finite element analysis determines the original residual stresses from the measured contour. Next, this talk gives several examples of applications. The method is validated by comparing with neutron diffraction measurements in an indented steel disk and in a friction stir weld between dissimilar aluminum alloys. Several applications are shown that demonstrate the power of the contour method: large aluminum forgings, railroad rails, and welds. Finally, this talk discusses why the contour method is significant departure from conventional experimental mechanics. Other relaxation method, for example hole-drilling, can only measure a 1-D profile of residual stresses, and yet they require a complicated inverse calculation to determine the stresses from the strain data. The contour method gives a 2-D stress map over a full cross-section, yet a direct calculation is all that is needed to reduce the data. The reason for these advantages lies in a subtle but fundamental departure from conventional experimental mechanics. Applying new technology to old methods like will not give similar advances, but the new approach also introduces new errors.

  7. Material mechanical characterization method for multiple strains and strain rates

    DOEpatents

    Erdmand, III, Donald L.; Kunc, Vlastimil; Simunovic, Srdjan; Wang, Yanli

    2016-01-19

    A specimen for measuring a material under multiple strains and strain rates. The specimen including a body having first and second ends and a gage region disposed between the first and second ends, wherein the body has a central, longitudinal axis passing through the first and second ends. The gage region includes a first gage section and a second gage section, wherein the first gage section defines a first cross-sectional area that is defined by a first plane that extends through the first gage section and is perpendicular to the central, longitudinal axis. The second gage section defines a second cross-sectional area that is defined by a second plane that extends through the second gage section and is perpendicular to the central, longitudinal axis and wherein the first cross-sectional area is different in size than the second cross-sectional area.

  8. Characterization of Mechanical Properties of Tissue Scaffolds by Phase Contrast Imaging and Finite Element Modeling.

    PubMed

    Bawolin, Nahshon K; Dolovich, Allan T; Chen, Daniel X B; Zhang, Chris W J

    2015-08-01

    In tissue engineering, the cell and scaffold approach has shown promise as a treatment to regenerate diseased and/or damaged tissue. In this treatment, an artificial construct (scaffold) is seeded with cells, which organize and proliferate into new tissue. The scaffold itself biodegrades with time, leaving behind only newly formed tissue. The degradation qualities of the scaffold are critical during the treatment period, since the change in the mechanical properties of the scaffold with time can influence cell behavior. To observe in time the scaffold's mechanical properties, a straightforward method is to deform the scaffold and then characterize scaffold deflection accordingly. However, experimentally observing the scaffold deflection is challenging. This paper presents a novel study on characterization of mechanical properties of scaffolds by phase contrast imaging and finite element modeling, which specifically includes scaffold fabrication, scaffold imaging, image analysis, and finite elements (FEs) modeling of the scaffold mechanical properties. The innovation of the work rests on the use of in-line phase contrast X-ray imaging at 20 KeV to characterize tissue scaffold deformation caused by ultrasound radiation forces and the use of the Fourier transform to identify movement. Once deformation has been determined experimentally, it is then compared with the predictions given by the forward solution of a finite element model. A consideration of the number of separate loading conditions necessary to uniquely identify the material properties of transversely isotropic and fully orthotropic scaffolds is also presented, along with the use of an FE as a form of regularization. PMID:25902011

  9. Feed mechanism and method for feeding minute items

    DOEpatents

    Stringer, Timothy Kent; Yerganian, Simon Scott

    2012-11-06

    A feeding mechanism and method for feeding minute items, such as capacitors, resistors, or solder preforms. The mechanism is adapted to receive a plurality of the randomly-positioned and randomly-oriented extremely small or minute items, and to isolate, orient, and position the items in a specific repeatable pickup location wherefrom they may be removed for use by, for example, a computer-controlled automated assembly machine. The mechanism comprises a sliding shelf adapted to receive and support the items; a wiper arm adapted to achieve a single even layer of the items; and a pushing arm adapted to push the items into the pickup location. The mechanism can be adapted for providing the items with a more exact orientation, and can also be adapted for use in a liquid environment.

  10. Feed mechanism and method for feeding minute items

    DOEpatents

    Stringer, Timothy Kent; Yerganian, Simon Scott

    2009-10-20

    A feeding mechanism and method for feeding minute items, such as capacitors, resistors, or solder preforms. The mechanism is adapted to receive a plurality of the randomly-positioned and randomly-oriented extremely small or minute items, and to isolate, orient, and position one or more of the items in a specific repeatable pickup location wherefrom they may be removed for use by, for example, a computer-controlled automated assembly machine. The mechanism comprises a sliding shelf adapted to receive and support the items; a wiper arm adapted to achieve a single even layer of the items; and a pushing arm adapted to push the items into the pickup location. The mechanism can be adapted for providing the items with a more exact orientation, and can also be adapted for use in a liquid environment.

  11. Method for loading shape memory polymer gripper mechanisms

    DOEpatents

    Lee, Abraham P.; Benett, William J.; Schumann, Daniel L.; Krulevitch, Peter A.; Fitch, Joseph P.

    2002-01-01

    A method and apparatus for loading deposit material, such as an embolic coil, into a shape memory polymer (SMP) gripping/release mechanism. The apparatus enables the application of uniform pressure to secure a grip by the SMP mechanism on the deposit material via differential pressure between, for example, vacuum within the SMP mechanism and hydrostatic water pressure on the exterior of the SMP mechanism. The SMP tubing material of the mechanism is heated to above the glass transformation temperature (Tg) while reshaping, and subsequently cooled to below Tg to freeze the shape. The heating and/or cooling may, for example, be provided by the same water applied for pressurization or the heating can be applied by optical fibers packaged to the SMP mechanism for directing a laser beam, for example, thereunto. At a point of use, the deposit material is released from the SMP mechanism by reheating the SMP material to above the temperature Tg whereby it returns to its initial shape. The reheating of the SMP material may be carried out by injecting heated fluid (water) through an associated catheter or by optical fibers and an associated beam of laser light, for example.

  12. Histotripsy methods in mechanical disintegration of tissue: towards clinical applications.

    PubMed

    Khokhlova, Vera A; Fowlkes, J Brian; Roberts, William W; Schade, George R; Xu, Zhen; Khokhlova, Tatiana D; Hall, Timothy L; Maxwell, Adam D; Wang, Yak-Nam; Cain, Charles A

    2015-03-01

    In high intensity focused ultrasound (HIFU) therapy, an ultrasound beam is focused within the body to locally affect the targeted site without damaging intervening tissues. The most common HIFU regime is thermal ablation. Recently there has been increasing interest in generating purely mechanical lesions in tissue (histotripsy). This paper provides an overview of several studies on the development of histotripsy methods toward clinical applications. Two histotripsy approaches and examples of their applications are presented. In one approach, sequences of high-amplitude, short (microsecond-long), focused ultrasound pulses periodically produce dense, energetic bubble clouds that mechanically disintegrate tissue. In an alternative approach, longer (millisecond-long) pulses with shock fronts generate boiling bubbles and the interaction of shock fronts with the resulting vapour cavity causes tissue disintegration. Recent preclinical studies on histotripsy are reviewed for treating benign prostatic hyperplasia (BPH), liver and kidney tumours, kidney stone fragmentation, enhancing anti-tumour immune response, and tissue decellularisation for regenerative medicine applications. Potential clinical advantages of the histotripsy methods are discussed. Histotripsy methods can be used to mechanically ablate a wide variety of tissues, whilst selectivity sparing structures such as large vessels. Both ultrasound and MR imaging can be used for targeting and monitoring the treatment in real time. Although the two approaches utilise different mechanisms for tissue disintegration, both have many of the same advantages and offer a promising alternative method of non-invasive surgery. PMID:25707817

  13. A multiscale quantum mechanics/electromagnetics method for device simulations.

    PubMed

    Yam, ChiYung; Meng, Lingyi; Zhang, Yu; Chen, GuanHua

    2015-04-01

    Multiscale modeling has become a popular tool for research applying to different areas including materials science, microelectronics, biology, chemistry, etc. In this tutorial review, we describe a newly developed multiscale computational method, incorporating quantum mechanics into electronic device modeling with the electromagnetic environment included through classical electrodynamics. In the quantum mechanics/electromagnetics (QM/EM) method, the regions of the system where active electron scattering processes take place are treated quantum mechanically, while the surroundings are described by Maxwell's equations and a semiclassical drift-diffusion model. The QM model and the EM model are solved, respectively, in different regions of the system in a self-consistent manner. Potential distributions and current densities at the interface between QM and EM regions are employed as the boundary conditions for the quantum mechanical and electromagnetic simulations, respectively. The method is illustrated in the simulation of several realistic systems. In the case of junctionless field-effect transistors, transfer characteristics are obtained and a good agreement between experiments and simulations is achieved. Optical properties of a tandem photovoltaic cell are studied and the simulations demonstrate that multiple QM regions are coupled through the classical EM model. Finally, the study of a carbon nanotube-based molecular device shows the accuracy and efficiency of the QM/EM method. PMID:25611987

  14. Numerical methods for characterization of synchrotron radiation based on the Wigner function method

    NASA Astrophysics Data System (ADS)

    Tanaka, Takashi

    2014-06-01

    Numerical characterization of synchrotron radiation based on the Wigner function method is explored in order to accurately evaluate the light source performance. A number of numerical methods to compute the Wigner functions for typical synchrotron radiation sources such as bending magnets, undulators and wigglers, are presented, which significantly improve the computation efficiency and reduce the total computation time. As a practical example of the numerical characterization, optimization of betatron functions to maximize the brilliance of undulator radiation is discussed.

  15. Methods of high throughput biophysical characterization in biopharmaceutical development.

    PubMed

    Razinkov, Vladimir I; Treuheit, Michael J; Becker, Gerald W

    2013-03-01

    Discovery and successful development of biopharmaceutical products depend on a thorough characterization of the molecule both before and after formulation. Characterization of a formulated biotherapeutic, typically a protein or large peptide, requires a rigorous assessment of the molecule's physical stability. Stability of a biotherapeutic includes not only chemical stability, i.e., degradation of the molecule to form undesired modifications, but also structural stability, including the formation of aggregates. In this review, high throughput biophysical characterization techniques are described according to their specific applications during biopharmaceutical discovery, development and manufacturing. The methods presented here are classified according to these attributes, and include spectroscopic assays based on absorbance, polarization, intrinsic and extrinsic fluorescence, surface plasmon resonance instrumentation, calorimetric methods, dynamic and static light scattering techniques, several visible particle counting and sizing methods, new viscosity assay, based on light scattering and mass spectrometry. Several techniques presented here are already implemented in industry; but, many high throughput biophysical methods are still in the initial stages of implementation or even in the prototype stage. Each technique in this report is judged by the specific application of the method through the biopharmaceutical development process. PMID:22725690

  16. Mechanical characterization of soft materials using transparent indenter testing system and finite element simulation

    NASA Astrophysics Data System (ADS)

    Xuan, Yue

    Background. Soft materials such as polymers and soft tissues have diverse applications in bioengineering, medical care, and industry. Quantitative mechanical characterization of soft materials at multiscales is required to assure that appropriate mechanical properties are presented to support the normal material function. Indentation test has been widely used to characterize soft material. However, the measurement of in situ contact area is always difficult. Method of Approach. A transparent indenter method was introduced to characterize the nonlinear behaviors of soft materials under large deformation. This approach made the direct measurement of contact area and local deformation possible. A microscope was used to capture the contact area evolution as well as the surface deformation. Based on this transparent indenter method, a novel transparent indentation measurement systems has been built and multiple soft materials including polymers and pericardial tissue have been characterized. Seven different indenters have been used to study the strain distribution on the contact surface, inner layer and vertical layer. Finite element models have been built to simulate the hyperelastic and anisotropic material behaviors. Proper material constants were obtained by fitting the experimental results. Results.Homogeneous and anisotropic silicone rubber and porcine pericardial tissue have been examined. Contact area and local deformation were measured by real time imaging the contact interface. The experimental results were compared with the predictions from the Hertzian equations. The accurate measurement of contact area results in more reliable Young's modulus, which is critical for soft materials. For the fiber reinforced anisotropic silicone rubber, the projected contact area under a hemispherical indenter exhibited elliptical shape. The local surface deformation under indenter was mapped using digital image correlation program. Punch test has been applied to thin films of

  17. Physical and Mechanical Characterization of Electrodeposited Nickel Nanowires -- Influence of Current Density and External Magnetic Field

    NASA Astrophysics Data System (ADS)

    Samykano, Mahendran

    insights from the present experimental research include: Electrodeposition method consistently synthesizes high purity Ni nanowires (98% and higher based on energy dispersive spectroscopy (EDS)) with a significant improvement in surface morphology when magnetic field is present during synthesis; X-ray diffraction (XRD) characterization and analysis indicate that electric current density has significant influence on the crystal orientation of Ni nanowire, while a decrease in crystal size was noticed with increased magnetic field intensity for same current densities. Carefully studied uni-axial tensile characterization using MEMS tensile loading device indicates an increase in elastic tensile modulus when the magnetic field is present during electrodeposition and consistent observation of three different variants of ductile failure modes. Results and discussions of tensile stress-strain mechanical characteristics of Ni nanowires and their failure modes provide key research findings that are not currently available in the literature to our knowledge. The present research contributes to the experimental understanding of tensile deformation of Ni nanowires, as well as developing and presenting a robust experimental methodology for future extension to other metallic nanowires. Research findings clearly illustrate a need for three-dimensional high fidelity experimental tools and relevant computational modeling for a full understanding and insight on deformation and failure mechanisms involved at nanoscale.

  18. The method of lines in three dimensional fracture mechanics

    NASA Technical Reports Server (NTRS)

    Gyekenyesi, J.; Berke, L.

    1980-01-01

    A review of recent developments in the calculation of design parameters for fracture mechanics by the method of lines (MOL) is presented. Three dimensional elastic and elasto-plastic formulations are examined and results from previous and current research activities are reported. The application of MOL to the appropriate partial differential equations of equilibrium leads to coupled sets of simultaneous ordinary differential equations. Solutions of these equations are obtained by the Peano-Baker and by the recurrance relations methods. The advantages and limitations of both solution methods from the computational standpoint are summarized.

  19. Methods to Characterize Ricin for the Development of Reference Materials

    PubMed Central

    Kim, Sook-Kyung; Hancock, Diane K.; Wang, Lili; Cole, Kenneth D.; Reddy, Prasad T.

    2006-01-01

    Ricin is an abundant protein from the castor bean plant Ricinus communis. Because of its high toxicity and the simplicity of producing mass quantities, ricin is considered a biological terrorism agent. We have characterized ricin extensively with a view to develop Reference Materials that could be used to test and calibrate detection devices. The characterization of ricin includes: 1) purity test of a commercial batch of ricin using electrophoresis in polyacrylamide gels, 2) biological activity assay by measuring its ability to inhibit protein synthesis, 3) quantitation of protein concentration by amino acid analysis, 4) detection of ricin by an immunoassay using a flow cytometer, and 5) detection of ricin genomic DNA by polymerase chain reaction using nine different primer sets. By implementing these five methods of characterization, we are in a position to develop a reference material for ricin. PMID:27274935

  20. Characterization of Tensile Mechanical Behavior of MSCs/PLCL Hybrid Layered Sheet.

    PubMed

    Pangesty, Azizah Intan; Arahira, Takaaki; Todo, Mitsugu

    2016-01-01

    A layered construct was developed by combining a porous polymer sheet and a cell sheet as a tissue engineered vascular patch. The primary objective of this study is to investigate the influence of mesenchymal stem cells (MSCs) sheet on the tensile mechanical properties of porous poly-(l-lactide-co-ε-caprolactone) (PLCL) sheet. The porous PLCL sheet was fabricated by the solid-liquid phase separation method and the following freeze-drying method. The MSCs sheet, prepared by the temperature-responsive dish, was then layered on the top of the PLCL sheet and cultured for 2 weeks. During the in vitro study, cellular properties such as cell infiltration, spreading and proliferation were evaluated. Tensile test of the layered construct was performed periodically to characterize the tensile mechanical behavior. The tensile properties were then correlated with the cellular properties to understand the effect of MSCs sheet on the variation of the mechanical behavior during the in vitro study. It was found that MSCs from the cell sheet were able to migrate into the PLCL sheet and actively proliferated into the porous structure then formed a new layer of MSCs on the opposite surface of the PLCL sheet. Mechanical evaluation revealed that the PLCL sheet with MSCs showed enhancement of tensile strength and strain energy density at the first week of culture which is characterized as the effect of MSCs proliferation and its infiltration into the porous structure of the PLCL sheet. New technique was presented to develop tissue engineered patch by combining MSCs sheet and porous PLCL sheet, and it is expected that the layered patch may prolong biomechanical stability when implanted in vivo. PMID:27271675

  1. Peripapillary and posterior scleral mechanics--part II: experimental and inverse finite element characterization.

    PubMed

    Girard, Michaël J A; Downs, J Crawford; Bottlang, Michael; Burgoyne, Claude F; Suh, J-K Francis

    2009-05-01

    The posterior sclera likely plays an important role in the development of glaucoma, and accurate characterization of its mechanical properties is needed to understand its impact on the more delicate optic nerve head--the primary site of damage in the disease. The posterior scleral shells from both eyes of one rhesus monkey were individually mounted on a custom-built pressurization apparatus. Intraocular pressure was incrementally increased from 5 mm Hg to 45 mm Hg, and the 3D displacements were measured using electronic speckle pattern interferometry. Finite element meshes of each posterior scleral shell were reconstructed from data generated by a 3D digitizer arm (shape) and a 20 MHz ultrasound transducer (thickness). An anisotropic hyperelastic constitutive model described in a companion paper (Girard, Downs, Burgoyne, and Suh, 2009, "Peripapillary and Posterior Scleral Mechanics--Part I: Development of an Anisotropic Hyperelastic Constitutive Model," ASME J. Biomech. Eng., 131, p. 051011), which includes stretch-induced stiffening and multidirectional alignment of the collagen fibers, was applied to each reconstructed mesh. Surface node displacements of each model were fitted to the experimental displacements using an inverse finite element method, which estimated a unique set of 13 model parameters. The predictions of the proposed constitutive model matched the 3D experimental displacements well. In both eyes, the tangent modulus increased dramatically with IOP, which indicates that the sclera is mechanically nonlinear. The sclera adjacent to the optic nerve head, known as the peripapillary sclera, was thickest and exhibited the lowest tangent modulus, which might have contributed to the uniform distribution of the structural stiffness for each entire scleral shell. Posterior scleral deformation following acute IOP elevations appears to be nonlinear and governed by the underlying scleral collagen microstructure as predicted by finite element modeling. The

  2. Characterization of Tensile Mechanical Behavior of MSCs/PLCL Hybrid Layered Sheet

    PubMed Central

    Pangesty, Azizah Intan; Arahira, Takaaki; Todo, Mitsugu

    2016-01-01

    A layered construct was developed by combining a porous polymer sheet and a cell sheet as a tissue engineered vascular patch. The primary objective of this study is to investigate the influence of mesenchymal stem cells (MSCs) sheet on the tensile mechanical properties of porous poly-(l-lactide-co-ε-caprolactone) (PLCL) sheet. The porous PLCL sheet was fabricated by the solid-liquid phase separation method and the following freeze-drying method. The MSCs sheet, prepared by the temperature-responsive dish, was then layered on the top of the PLCL sheet and cultured for 2 weeks. During the in vitro study, cellular properties such as cell infiltration, spreading and proliferation were evaluated. Tensile test of the layered construct was performed periodically to characterize the tensile mechanical behavior. The tensile properties were then correlated with the cellular properties to understand the effect of MSCs sheet on the variation of the mechanical behavior during the in vitro study. It was found that MSCs from the cell sheet were able to migrate into the PLCL sheet and actively proliferated into the porous structure then formed a new layer of MSCs on the opposite surface of the PLCL sheet. Mechanical evaluation revealed that the PLCL sheet with MSCs showed enhancement of tensile strength and strain energy density at the first week of culture which is characterized as the effect of MSCs proliferation and its infiltration into the porous structure of the PLCL sheet. New technique was presented to develop tissue engineered patch by combining MSCs sheet and porous PLCL sheet, and it is expected that the layered patch may prolong biomechanical stability when implanted in vivo. PMID:27271675

  3. Integral structural-functional method for characterizing microbial populations

    NASA Astrophysics Data System (ADS)

    Yakushev, A. V.

    2015-04-01

    An original integral structural-functional method has been proposed for characterizing microbial communities. The novelty of the approach is the in situ study of microorganisms based on the growth kinetics of microbial associations in liquid nutrient broth media under selective conditions rather than on the level of taxa or large functional groups. The method involves the analysis of the integral growth model of a periodic culture. The kinetic parameters of such associations reflect their capacity of growing on different media, i.e., their physiological diversity, and the metabolic capacity of the microorganisms for growth on a nutrient medium. Therefore, the obtained parameters are determined by the features of the microbial ecological strategies. The inoculation of a dense medium from the original inoculate allows characterizing the taxonomic composition of the dominants in the soil community. The inoculation from the associations developed on selective media characterizes the composition of syntrophic groups, which fulfill a specific function in nature. This method is of greater information value than the classical methods of inoculation on selective media.

  4. Environmentally-controlled Microtensile Testing of Mechanically-adaptive Polymer Nanocomposites for ex vivo Characterization

    PubMed Central

    Hess, Allison E.; Potter, Kelsey A.; Tyler, Dustin J.; Zorman, Christian A.; Capadona, Jeffrey R.

    2013-01-01

    Implantable microdevices are gaining significant attention for several biomedical applications1-4. Such devices have been made from a range of materials, each offering its own advantages and shortcomings5,6. Most prominently, due to the microscale device dimensions, a high modulus is required to facilitate implantation into living tissue. Conversely, the stiffness of the device should match the surrounding tissue to minimize induced local strain7-9. Therefore, we recently developed a new class of bio-inspired materials to meet these requirements by responding to environmental stimuli with a change in mechanical properties10-14. Specifically, our poly(vinyl acetate)-based nanocomposite (PVAc-NC) displays a reduction in stiffness when exposed to water and elevated temperatures (e.g. body temperature). Unfortunately, few methods exist to quantify the stiffness of materials in vivo15, and mechanical testing outside of the physiological environment often requires large samples inappropriate for implantation. Further, stimuli-responsive materials may quickly recover their initial stiffness after explantation. Therefore, we have developed a method by which the mechanical properties of implanted microsamples can be measured ex vivo, with simulated physiological conditions maintained using moisture and temperature control13,16,17. To this end, a custom microtensile tester was designed to accommodate microscale samples13,17 with widely-varying Young's moduli (range of 10 MPa to 5 GPa). As our interests are in the application of PVAc-NC as a biologically-adaptable neural probe substrate, a tool capable of mechanical characterization of samples at the microscale was necessary. This tool was adapted to provide humidity and temperature control, which minimized sample drying and cooling17. As a result, the mechanical characteristics of the explanted sample closely reflect those of the sample just prior to explantation. The overall goal of this method is to quantitatively assess

  5. Characterization and development mechanism of Apios americana tuber starch

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Apios americana is a wild legume-bearing plant with edible tubers. Domestication of Apios is in progress because of the superior nutritional value and health benefits of the tuber. Objectives of this study were to: 1) characterize physicochemical properties of Apios-tuber starch; and 2) understand d...

  6. Direct simulation Monte Carlo method with a focal mechanism algorithm

    NASA Astrophysics Data System (ADS)

    Rachman, Asep Nur; Chung, Tae Woong; Yoshimoto, Kazuo; Yun, Sukyoung

    2015-01-01

    To simulate the observation of the radiation pattern of an earthquake, the direct simulation Monte Carlo (DSMC) method is modified by implanting a focal mechanism algorithm. We compare the results of the modified DSMC method (DSMC-2) with those of the original DSMC method (DSMC-1). DSMC-2 shows more or similarly reliable results compared to those of DSMC-1, for events with 12 or more recorded stations, by weighting twice for hypocentral distance of less than 80 km. Not only the number of stations, but also other factors such as rough topography, magnitude of event, and the analysis method influence the reliability of DSMC-2. The most reliable result by DSMC-2 is obtained by the best azimuthal coverage by the largest number of stations. The DSMC-2 method requires shorter time steps and a larger number of particles than those of DSMC-1 to capture a sufficient number of arrived particles in the small-sized receiver.

  7. Sensitivity Analysis of Inverse Methods in Eddy Current Pit Characterization

    NASA Astrophysics Data System (ADS)

    Aldrin, John C.; Sabbagh, Harold A.; Murphy, R. Kim; Sabbagh, Elias H.; Knopp, Jeremy S.

    2010-02-01

    A sensitivity analysis was performed for a pit characterization problem to quantify the impact of potential sources for variation on the performance of inverse methods. Certain data processing steps, including careful feature extraction, background clutter removal and compensation for variation in the scan step size through the tubing, were found to be critical to achieve good estimates of the pit depth and diameter. Variance studied in model probe dimensions did not adversely affect performance.

  8. Characterization of High Temperature Mechanical Properties Using Laser Ultrasound

    SciTech Connect

    David Hurley; Stephen Reese; Farhad Farzbod; Rory Kennedy

    2012-05-01

    Mechanical properties are controlled to a large degree by defect structures such as dislocations and grain boundaries. These microstructural features involve a perturbation of the perfect crystal lattice (i.e. strain fields). Viewed in this context, high frequency strain waves (i.e. ultrasound) provide a natural choice to study microstructure mediated mechanical properties. In this presentation we use laser ultrasound to probe mechanical properties of materials. This approach utilizes lasers to excite and detect ultrasonic waves, and as a consequence has unique advantages over other methods—it is noncontacting, requires no couplant or invasive sample preparation (other than that used in metallurgical analysis), and has the demonstrated capability to probe microstructure on a micron scale. Laser techniques are highly reproducible enabling sophisticated, microstructurally informed data analysis. Since light is being used for generation and detection of the ultrasonic wave, the specimen being examined is not mechanically coupled to the transducer. As a result, laser ultrasound can be carried out remotely, an especially attractive characteristic for in situ measurements in severe environments. Several examples involving laser ultrasound to measure mechanical properties in high temperature environments will be presented. Emphasis will be place on understanding the role of grain microstructure.

  9. Measurements and Characterizations of Mechanical Properties of Human Skins

    NASA Astrophysics Data System (ADS)

    Song, Han Wook; Park, Yon Kyu

    A skin is an indispensible organ for humans because it contributes to metabolism using its own biochemical functions and protects the human body from external stimuli. Recently, mechanical properties such as a thickness, a friction and an elastic coefficient have been used as a decision index in the skin physiology and in the skin care market due to the increased awareness of wellbeing issues. In addition, the use of mechanical properties is known to have good discrimination ability in the classification of human constitutions, which are used in the field of an alternative medicine. In this study, a system that measures mechanical properties such as a friction and an elastic coefficient is designed. The equipment consists of a load cell type (manufactured by the authors) for the measurements of a friction coefficient, a decompression tube for the measurement of an elastic coefficient. Using the proposed system, the mechanical properties of human skins from different constitutions were compared, and the relative repeatability error for measurements of mechanical properties was determined to be less than 2%. Combining the inspection results of medical doctors in the field of an alternative medicine, we could conclude that the proposed system might be applicable to a quantitative constitutional diagnosis between human constitutions within an acceptable level of uncertainty.

  10. Mechanical characterization of metallic nanowires by using a customized atomic microscope

    NASA Astrophysics Data System (ADS)

    Celik, Emrah

    A new experimental method to characterize the mechanical properties of metallic nanowires is introduced. An accurate and fast mechanical characterization of nanowires requires simultaneous imaging and testing of nanowires. However, there exists no practical experimental procedure in the literature that provides a quantitative mechanical analysis and imaging of the nanowire specimens during mechanical testing. In this study, a customized atomic force microscope (AFM) is placed inside a scanning electron microscope (SEM) in order to locate the position of the nanowires. The tip of the atomic force microscope cantilever is utilized to bend and break the nanowires. The nanowires are prepared by electroplating of nickel ions into the nanoscale pores of the alumina membranes. Force versus bending displacement responses of these nanowires are measured experimentally and then compared against those of the finite element analysis and peridynamic simulations to extract their mechanical properties through an inverse approach. The average elastic modulus of nickel nanowires, which are extracted using finite element analysis and peridynamic simulations, varies between 220 GPa and 225 GPa. The elastic modulus of bulk nickel published in the literature is comparable to that of nickel nanowires. This observation agrees well with the previous findings on nanowires stating that the elastic modulus of nanowires with diameters over 100nm is similar to that of bulk counterparts. The average yield stress of nickel nanowires, which are extracted using finite element analysis and peridynamic simulations, is found to be between 3.6 GPa to 4.1 GPa. The average value of yield stress of nickel nanowires with 250nm diameter is significantly higher than that of bulk nickel. Higher yield stress of nickel nanowires observed in this study can be explained by the lower defect density of nickel nanowires when compared to their bulk counterparts. Deviation in the extracted mechanical properties is

  11. Nanoscale structural and mechanical characterization of natural nanocomposites: Seashells

    NASA Astrophysics Data System (ADS)

    Li, Xiaodong

    2007-03-01

    Seashells are natural nanocomposites with superior mechanical strength and toughness. What is the secret recipe that Mother Nature uses to fabricate seashells? What roles do the nanoscale structures play in the inelasticity and toughening of seashells? Can we learn from this to produce seashell-like nanocomposites? The focus of this article is nacre (mother-of-pearl). The recent discovery of nanoparticles in nacre is summarized, and the role these nanoparticles play in nacre’s toughness is elucidated. It was found that rotation and deformation of aragonite nanoparticles are the two prominent mechanisms contributing to energy dissipation in nacre. The biopolymer spacing between nanoparticles facilitates the particle rotation process. This article also presents future challenges in the study of nacre’s nanoscale structure and mechanical properties.

  12. Impetus of composite mechanics on test methods for fiber composites

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.

    1978-01-01

    The impetus of composite mechanics on composite test methods and/or on interpreting test results is described by using examples from composite micromechanics, composite macromechanics and laminate theory. The specific examples included contributions such as criteria for selecting resin matrices for improved composite strength, the 10 deg off-axis tensile test, criteria for configuring hybrids and superhybrids for improved impact resistance and the reduced bending rigidities concept for buckling and vibration analyses.

  13. Preparation, Characterization, and Enhanced Thermal and Mechanical Properties of Epoxy-Titania Composites

    PubMed Central

    Rubab, Zakya; Siddiqi, Humaira M.; Saeed, Shaukat

    2014-01-01

    This paper presents the synthesis and thermal and mechanical properties of epoxy-titania composites. First, submicron titania particles are prepared via surfactant-free sol-gel method using TiCl4 as precursor. These particles are subsequently used as inorganic fillers (or reinforcement) for thermally cured epoxy polymers. Epoxy-titania composites are prepared via mechanical mixing of titania particles with liquid epoxy resin and subsequently curing the mixture with an aliphatic diamine. The amount of titania particles integrated into epoxy matrix is varied between 2.5 and 10.0 wt.% to investigate the effect of sub-micron titania particles on thermal and mechanical properties of epoxy-titania composites. These composites are characterized by X-ray photoelectron (XPS) spectroscopy, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetric (TG), and mechanical analyses. It is found that sub-micron titania particles significantly enhance the glass transition temperature (>6.7%), thermal oxidative stability (>12.0%), tensile strength (>21.8%), and Young's modulus (>16.8%) of epoxy polymers. Epoxy-titania composites with 5.0 wt.% sub-micron titania particles perform best at elevated temperatures as well as under high stress. PMID:24578638

  14. Finite element simulation for the mechanical characterization of soft biological materials by atomic force microscopy.

    PubMed

    Valero, C; Navarro, B; Navajas, D; García-Aznar, J M

    2016-09-01

    The characterization of the mechanical properties of soft materials has been traditionally performed through uniaxial tensile tests. Nevertheless, this method cannot be applied to certain extremely soft materials, such as biological tissues or cells that cannot be properly subjected to these tests. Alternative non-destructive tests have been designed in recent years to determine the mechanical properties of soft biological tissues. One of these techniques is based on the use of atomic force microscopy (AFM) to perform nanoindentation tests. In this work, we investigated the mechanical response of soft biological materials to nanoindentation with spherical indenters using finite element simulations. We studied the responses of three different material constitutive laws (elastic, isotropic hyperelastic and anisotropic hyperelastic) under the same process and analyzed the differences thereof. Whereas linear elastic and isotropic hyperelastic materials can be studied using an axisymmetric simplification, anisotropic hyperelastic materials require three-dimensional analyses. Moreover, we established the limiting sample size required to determine the mechanical properties of soft materials while avoiding boundary effects. Finally, we compared the results obtained by simulation with an estimate obtained from Hertz theory. Hertz theory does not distinguish between the different material constitutive laws, and thus, we proposed corrections to improve the quantitative measurement of specific material properties by nanoindentation experiments. PMID:27214690

  15. The contact density to characterize the mechanics of cohesive granular materials: application to snow microstructure modeling.

    NASA Astrophysics Data System (ADS)

    Gaume, Johan; Löwe, Henning

    2016-04-01

    Microstructural properties are essential to characterize the mechanics of loose and cohesive granular materials such as snow. In particular, mechanical properties and physical processes of porous media are often related to the volume fraction ν. Low-density microstructures typically allow for considerable structural diversity at a given volume fraction, leading to uncertainties in modeling approaches using ν-based parametrizations only. We have conducted discrete element simulations of cohesive granular materials with initial configurations which are drawn from Baxter's sticky hard sphere (SHS) model. This method allows to control independently the initial volume fraction ν and the average coordination number Z. We show that variations in elasticity and strength of the samples can be fully explained by the initial contact density C = νZ over a wide range of volume fractions and coordination numbers. Hence, accounting for the contact density C allows to resolve the discrepancies in particle based modeling between samples with similar volume fractions but different microstructures. As an application, we applied our method to the microstructure of real snow samples which have been imaged by micro-computed tomography and reconstructed using the SHS model. Our new approach opens a promising route to evaluate snow physical and mechanical properties from field measurements, for instance using the Snow Micro Penetrometer (SMP), by linking the penetration resistance to the contact density.

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

    SciTech Connect

    Ferencz, R.M.

    1988-10-01

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

  17. a Numerical Method for Stability Analysis of Pinned Flexible Mechanisms

    NASA Astrophysics Data System (ADS)

    Beale, D. G.; Lee, S. W.

    1996-05-01

    A technique is presented to investigate the stability of mechanisms with pin-jointed flexible members. The method relies on a special floating frame from which elastic link co-ordinates are defined. Energies are easily developed for use in a Lagrange equation formulation, leading to a set of non-linear and mixed ordinary differential-algebraic equations of motion with constraints. Stability and bifurcation analysis is handled using a numerical procedure (generalized co-ordinate partitioning) that avoids the tedious and difficult task of analytically reducing the system of equations to a number equalling the system degrees of freedom. The proposed method was then applied to (1) a slider-crank mechanism with a flexible connecting rod and crank of constant rotational speed, and (2) a four-bar linkage with a flexible coupler with a constant speed crank. In both cases, a single pinned-pinned beam bending mode is employed to develop resonance curves and stability boundaries in the crank length-crank speed parameter plane. Flip and fold bifurcations are common occurrences in both mechanisms. The accuracy of the proposed method was also verified by comparison with previous experimental results [1].

  18. Characterization of molecular mechanisms of in vivo UVR induced cataract.

    PubMed

    Galichanin, Konstantin; Talebizadeh, Nooshin; Söderberg, Per

    2012-01-01

    Cataract is the leading cause of blindness in the world (1). The World Health Organization defines cataract as a clouding of the lens of the eye which impedes the transfer of light. Cataract is a multi-factorial disease associated with diabetes, smoking, ultraviolet radiation (UVR), alcohol, ionizing radiation, steroids and hypertension. There is strong experimental (2-4) and epidemiological evidence (5,6) that UVR causes cataract. We developed an animal model for UVR B induced cataract in both anesthetized (7) and non-anesthetized animals (8). The only cure for cataract is surgery but this treatment is not accessible to all. It has been estimated that a delay of onset of cataract for 10 years could reduce the need for cataract surgery by 50% (9). To delay the incidence of cataract, it is needed to understand the mechanisms of cataract formation and find effective prevention strategies. Among the mechanisms for cataract development, apoptosis plays a crucial role in initiation of cataract in humans and animals (10). Our focus has recently been apoptosis in the lens as the mechanism for cataract development (8,11,12). It is anticipated that a better understanding of the effect of UVR on the apoptosis pathway will provide possibilities for discovery of new pharmaceuticals to prevent cataract. In this article, we describe how cataract can be experimentally induced by in vivo exposure to UVR-B. Further RT-PCR and immunohistochemistry are presented as tools to study molecular mechanisms of UVR-B induced cataract. PMID:23222480

  19. Characterization of Thermally Degraded Energetic Materials: Mechanical and Chemical Behavior

    SciTech Connect

    Miller, J.C.; Renlund, A.M.; Schmitt, R.G.; Wellman, G.W.

    1998-12-04

    We report the results of recent experiments on thermally degraded HMX and HMX/binder materials. Small-scale samples were heated confined in either constant-volume or load- controlled configurations. A main emphasis of the work reported here is developing an understanding of the complex coupling of the mechanical and chemical responses during thermal degradation.

  20. Characterization of fatigue mechanisms in nickel-based superalloys

    NASA Astrophysics Data System (ADS)

    Yablinsky, Clarissa A.

    Ni-based superalloys are important for turbine engine airfoil applications. Historically, creep has been the main failure mode and thus creep mechanisms have been the subject of numerous studies. However, modern airfoil designs maintain cooler temperatures, and consequently creep is no longer the primary failure mode. Rather, in the cooled components, experience and experimental studies have shown that fatigue is the life-limiting factor. The changing cause of failure highlighted the need for a comprehensive study of fatigue deformation mechanisms. Information about crack propagation and the associated deformation mechanisms has allowed appropriate design changes based on fatigue as a life-limiting factor. The focus of the study will be on a monocrystalline Ni-based superalloy, Rene N5, which is currently used for airfoils. Compact tension specimens were tested under cyclic loading conditions to determine the influence of microstructure and material properties on crack propagation and fatigue failure. The crack growth rate as a function of temperature, environment, frequency, and crystallographic orientation was determined. High resolution scanning electron microscopy was used to examine the fracture surface on length scales from nano to macro. Deformation mechanisms in the plastic zone ahead of the crack tip and within the plastic wake of the crack were studied using TEM and FIB techniques. Environment and frequency seem to have a larger effect on fatigue crack growth rates and threshold stress intensity factor ranges, while temperature and orientation effects are present, but not as dramatic. In the normal blade orientation, (001)[100], mode I crack propagation was prevalent, with mode II crack propagation found at higher DeltaK values. Interdendritic particles appear to be slowing crack growth rates in the threshold region of specimens tested in air. Microstructural analysis showed no change in gamma' precipitate size or morphology with temperature or stress

  1. Mechanical characterization of hydroxyapatite, thermoelectric materials and doped ceria

    NASA Astrophysics Data System (ADS)

    Fan, Xiaofeng

    For a variety of applications of brittle ceramic materials, porosity plays a critical role structurally and/or functionally, such as in engineered bone scaffolds, thermoelectric materials and in solid oxide fuel cells. The presence of porosity will affect the mechanical properties, which are essential to the design and application of porous brittle materials. In this study, the mechanical property versus microstructure relations for bioceramics, thermoelectric (TE) materials and solid oxide fuel cells were investigated. For the bioceramic material hydroxyapatite (HA), the Young's modulus was measured using resonant ultrasound spectroscopy (RUS) as a function of (i) porosity and (ii) microcracking damage state. The fracture strength was measured as a function of porosity using biaxial flexure testing, and the distribution of the fracture strength was studied by Weibull analysis. For the natural mineral tetrahedrite based solid solution thermoelectric material (Cu10Zn2As4S13 - Cu 12Sb4S13), the elastic moduli, hardness and fracture toughness were studied as a function of (i) composition and (ii) ball milling time. For ZiNiSn, a thermoelectric half-Heusler compound, the elastic modulus---porosity and hardness---porosity relations were examined. For the solid oxide fuel cell material, gadolina doped ceria (GDC), the elastic moduli including Young's modulus, shear modulus, bulk modulus and Poisson's ratio were measured by RUS as a function of porosity. The hardness was evaluated by Vickers indentation technique as a function of porosity. The results of the mechanical property versus microstructure relations obtained in this study are of great importance for the design and fabrication of reliable components with service life and a safety factor. The Weibull modulus, which is a measure of the scatter in fracture strength, is the gauge of the mechanical reliability. The elastic moduli and Poisson's ratio are needed in analytical or numerical models of the thermal and

  2. In situ mechanical characterization of square microfabricated elastomeric membranes using an improved microindentation

    NASA Astrophysics Data System (ADS)

    Liu, Kuo-Kang; Khoo, Hwa Seng; Tseng, Fan-Gang

    2004-02-01

    A testing method has been developed for in situ mechanical characterizations of square microfabricated elastomeric membranes, using a tailored microindentation instrument. Such a depth-sensing microindentation system, incorporated with a long-focal microscope for capturing the side view image, provides accurate load-displacement measurements and complete profiles of deformed membranes. The deformations of square silicon rubber membranes with various thicknesses were examined under different degrees of external central microindentation forces. These membranes were integrated and supported by SU-8 photoresist frames, with openings of 2 mm×2 mm. A theoretical model was applied to quantitatively correlate the membrane elasticity to the measured compliance under such indentation. Through comparing the simulated and experimental results, the average values of Young's modulus for these membranes were reasonably extracted and determined. Viscoelasticity of the membranes used was acknowledged; however, it showed no significant effect on the determination of the Young's modulus of the membranes in the current work. The good agreement between the experimental results and the theoretical analyses demonstrates the successful in situ mechanical characterizations of microfabricated elastomeric films, particularly for the square shape membrane, which is the most common structure or component for microfabricated devices.

  3. Mechanical and Microstructural Characterization of an Aluminum Bearing Trip Steel

    NASA Astrophysics Data System (ADS)

    Monsalve, Alberto; Guzmán, Alexis; De Barbieri, Flavio; Artigas, Alfredo; Carvajal, Linton; Bustos, Oscar; Garza-Montes-de Oca, Nelson F.; Colás, Rafael

    2016-06-01

    The mechanical properties and microstructural characteristics of a steel able to sustain the TRIP-effect were studied. The material was prepared by taking in mind the partial substitution of silicon by aluminum following a processing route that included hot forging, hot and cold rolling, intercritical annealing, and a final bainitic isothermal treatment. The mechanical properties that were obtained resulted to be above those of commercial a 780 TRIP steel. The TRIP phenomenon was confirmed by the change in retained austenite before and after deforming the steel; X-ray diffraction was used to evaluate the volume content of retained austenite. Formability of the steel under study can be rationalized in terms of the texture developed in the material.

  4. Thin film characterization using a mechanical properties microprobe

    NASA Astrophysics Data System (ADS)

    Oliver, W. C.; McHargue, C. J.; Zinkle, S. J.

    A new ultra-low load microindentation system has been acquired in the ORNL Metals and Ceramics Division. The system's spatial resolution and its data acquisition capabilities allow the determination of several mechanical properties from volumes of material with submicron dimension; hence, the term Mechanical Properties Microprobe (MPM). Research with the MPM at Oak Ridge has led to improved techniques for determining the plastic and elastic properties of materials using microindentation experiments. The techniques have been applied to thin films created by ion implanting metals and ceramics, radiation damaged materials, and thin hard coatings of TiN. Changes in the strength (hardness) and modulus have been measured in films as thin as 200 nm.

  5. EBSD characterization of low temperature deformation mechanisms in modern alloys

    NASA Astrophysics Data System (ADS)

    Kozmel, Thomas S., II

    For structural applications, grain refinement has been shown to enhance mechanical properties such as strength, fatigue resistance, and fracture toughness. Through control of the thermos-mechanical processing parameters, dynamic recrystallization mechanisms were used to produce microstructures consisting of sub-micron grains in 9310 steel, 4140 steel, and Ti-6Al-4V. In both 9310 and 4140 steel, the distribution of carbides throughout the microstructure affected the ability of the material to dynamically recrystallize and determined the size of the dynamically recrystallized grains. Processing the materials at lower temperatures and higher strain rates resulted in finer dynamically recrystallized grains. Microstructural process models that can be used to estimate the resulting microstructure based on the processing parameters were developed for both 9310 and 4140 steel. Heat treatment studies performed on 9310 steel showed that the sub-micron grain size obtained during deformation could not be retained due to the low equilibrium volume fraction of carbides. Commercially available aluminum alloys were investigated to explain their high strain rate deformation behavior. Alloys such as 2139, 2519, 5083, and 7039 exhibit strain softening after an ultimate strength is reached, followed by a rapid degradation of mechanical properties after a critical strain level has been reached. Microstructural analysis showed that the formation of shear bands typically preceded this rapid degradation in properties. Shear band boundary misorientations increased as a function of equivalent strain in all cases. Precipitation behavior was found to greatly influence the microstructural response of the alloys. Additionally, precipitation strengthened alloys were found to exhibit similar flow stress behavior, whereas solid solution strengthened alloys exhibited lower flow stresses but higher ductility during dynamic loading. Schmid factor maps demonstrated that shear band formation behavior

  6. Characterization of mechanical and biochemical properties of developing embryonic tendon

    PubMed Central

    Marturano, Joseph E.; Arena, Jeffrey D.; Schiller, Zachary A.; Georgakoudi, Irene; Kuo, Catherine K.

    2013-01-01

    Tendons have uniquely high tensile strength, critical to their function to transfer force from muscle to bone. When injured, their innate healing response results in aberrant matrix organization and functional properties. Efforts to regenerate tendon are challenged by limited understanding of its normal development. Consequently, there are few known markers to assess tendon formation and parameters to design tissue engineering scaffolds. We profiled mechanical and biological properties of embryonic tendon and demonstrated functional properties of developing tendon are not wholly reflected by protein expression and tissue morphology. Using force volume-atomic force microscopy, we found that nano- and microscale tendon elastic moduli increase nonlinearly and become increasingly spatially heterogeneous during embryonic development. When we analyzed potential biochemical contributors to modulus, we found statistically significant but weak correlation between elastic modulus and collagen content, and no correlation with DNA or glycosaminoglycan content, indicating there are additional contributors to mechanical properties. To investigate collagen cross-linking as a potential contributor, we inhibited lysyl oxidase-mediated collagen cross-linking, which significantly reduced tendon elastic modulus without affecting collagen morphology or DNA, glycosaminoglycan, and collagen content. This suggests that lysyl oxidase-mediated cross-linking plays a significant role in the development of embryonic tendon functional properties and demonstrates that changes in cross-links alter mechanical properties without affecting matrix content and organization. Taken together, these data demonstrate the importance of functional markers to assess tendon development and provide a profile of tenogenic mechanical properties that may be implemented in tissue engineering scaffold design to mechanoregulate new tendon regeneration. PMID:23576745

  7. Characterizing moisture delivery mechanisms for extreme precipitation in large geographic regions

    NASA Astrophysics Data System (ADS)

    Bracken, C.; Rajagopalan, B.; Gangopadhyay, S.

    2014-12-01

    Understanding dominant moisture delivery sources for extreme precipitation events is extremely important for characterizing their statistical behavior and behavior under specific climate regimes. Typically, for a given region, the largest extreme events occur in specific seasons but events occurring in off seasons can be just as socio-economically devastating. A complete picture of how and where events originate in all seasons paves the way for statistical forecasting and simulation of extreme precipitation. We present a data driven methodology applicable to large geographic regions that can partition heterogeneous areas into subregions and then characterize the moisture delivery mechanisms for each subregion under specific climate regimes (e.g., ENSO phases, PDO, etc.) and in each season. Extreme subregions are defined using a new nonparametric extreme value clustering method and moisture delivery characterization is done using the HYSPLIT storm backtracking algorithm. We apply this methodology to the Western United States where the nature of extreme events varies widely due to complex terrain, teleconnections and climate interactions.

  8. Characterizing lentic freshwater fish assemblages using multiple sampling methods

    USGS Publications Warehouse

    Fischer, Jesse R.; Quist, Michael

    2014-01-01

    Characterizing fish assemblages in lentic ecosystems is difficult, and multiple sampling methods are almost always necessary to gain reliable estimates of indices such as species richness. However, most research focused on lentic fish sampling methodology has targeted recreationally important species, and little to no information is available regarding the influence of multiple methods and timing (i.e., temporal variation) on characterizing entire fish assemblages. Therefore, six lakes and impoundments (48–1,557 ha surface area) were sampled seasonally with seven gear types to evaluate the combined influence of sampling methods and timing on the number of species and individuals sampled. Probabilities of detection for species indicated strong selectivities and seasonal trends that provide guidance on optimal seasons to use gears when targeting multiple species. The evaluation of species richness and number of individuals sampled using multiple gear combinations demonstrated that appreciable benefits over relatively few gears (e.g., to four) used in optimal seasons were not present. Specifically, over 90 % of the species encountered with all gear types and season combinations (N = 19) from six lakes and reservoirs were sampled with nighttime boat electrofishing in the fall and benthic trawling, modified-fyke, and mini-fyke netting during the summer. Our results indicated that the characterization of lentic fish assemblages was highly influenced by the selection of sampling gears and seasons, but did not appear to be influenced by waterbody type (i.e., natural lake, impoundment). The standardization of data collected with multiple methods and seasons to account for bias is imperative to monitoring of lentic ecosystems and will provide researchers with increased reliability in their interpretations and decisions made using information on lentic fish assemblages.

  9. Optical method for the surface topographic characterization of Fresnel lenses

    NASA Astrophysics Data System (ADS)

    Martínez Antón, Juan Carlos; Gómez Pedrero, José Antonio; Alonso Fernández, José; Quiroga, Juan Antonio

    2011-10-01

    Fresnel lenses and other faceted or micro-optic devices are increasingly used in multiple applications like solar light concentrators and illumination devices. As applications are more exigent this characterization is of increasing importance. We present a technique to characterize the surface topography of optical surfaces. It is especially well adapted to Fresnel lenses where abrupt surface slopes are usually difficult to handle in conventional techniques. The method is based on a new photometric strategy able to codify the height information in terms of optical absorption in a liquid. A detailed topographic map is simple to acquire by capturing images of the surface. Some experimental results are presented. A single pixel height resolution of ~0.1 μm is achieved for a height range of ~50 μm. A surface slope analysis is also made achieving a resolution of ~+/-0.15°.

  10. Method for the characterization of Fresnel lens flux transfer performance

    NASA Astrophysics Data System (ADS)

    Martinez Antón, Juan Carlos; Vázquez Moliní, Daniel; Muñoz de Luna, Javier; Gómez Pedrero, José Antonio; Fernández-Balbuena, Antonio Álvarez

    2011-10-01

    Fresnel lenses and other faceted or micro-optic devices are increasingly used in multiple applications like solar light concentrators and illumination devices, just to name some representative. However, it seems to be a certain lack of adequate techniques for the assessment of the performance of final fabricated devices. As applications are more exigent this characterization is a must. We provide a technique to characterize the performance of Fresnel lenses, as light collection devices. The basis for the method is a configuration where a camera images the Fresnel lens aperture. The entrance pupil of the camera is situated at the focal spot or the conjugate of a simulated solar source. In this manner, detailed maps of the performance of different Fresnel lenses are obtained for different acceptance angles.

  11. A Novel Method for Characterizing Spacesuit Mobility Through Metabolic Cost

    NASA Technical Reports Server (NTRS)

    McFarland, Shane M.; Norcross, Jason R.

    2014-01-01

    Historically, spacesuit mobility has been characterized by directly measuring both range of motion and joint torque of individual anatomic joints. The work detailed herein aims to improve on this method, which is often prone to uncertainly, lack of repeatability, and a general lack of applicability to real-world functional tasks. Specifically, the goal of this work is to characterize suited mobility performance by directly measuring the metabolic performance of the occupant. Pilot testing was conducted in 2013, employing three subjects performing a range of functional tasks in two different suits prototypes, the Mark III and Z-1. Cursory analysis of the results shows the approach has merit, with consistent performance trends toward one suit over the other. Forward work includes the need to look at more subjects, a refined task set, and another suit in a different mass/mobility regime to validate the approach.

  12. Total Gamma Count Rate Analysis Method for Nondestructive Assay Characterization

    SciTech Connect

    Cecilia R. Hoffman; Yale D. Harker

    2006-03-01

    A new approach to nondestructively characterize waste for disposal, based on total gamma response, has been developed at the Idaho Cleanup Project by CH2M-WG Idaho, LLC and Idaho State University, and is called the total gamma count rate analysis method. The total gamma count rate analysis method measures gamma interactions that produce energetic electrons or positrons in a detector. Based on previous experience with waste assays, the radionuclide content of the waste container is then determined. This approach potentially can yield minimum detection limits of less than 10 nCi/g. The importance of this method is twofold. First, determination of transuranic activity can be made for waste containers that are below the traditional minimum detection limits. Second, waste above 10 nCi/g and below 100 nCi/g can be identified, and a potential path for disposal resolved.

  13. Molecular Diagnostic Methods for Detection and Characterization of Human Noroviruses.

    PubMed

    Chen, Haifeng; Hu, Yuan

    2016-01-01

    Human noroviruses are a group of viral agents that afflict people of all age groups. The viruses are now recognized as the most common causative agent of nonbacterial acute gastroenteritis and foodborne viral illness worldwide. However, they have been considered to play insignificant roles in the disease burden of acute gastroenteritis for the past decades until the recent advent of new and more sensitive molecular diagnostic methods. The availability and application of the molecular diagnostic methods have led to enhanced detection of noroviruses in clinical, food and environmental samples, significantly increasing the recognition of noroviruses as an etiologic agent of epidemic and sporadic acute gastroenteritis. This article aims to summarize recent efforts made for the development of molecular methods for the detection and characterization of human noroviruses. PMID:27335620

  14. Molecular Diagnostic Methods for Detection and Characterization of Human Noroviruses

    PubMed Central

    Chen, Haifeng; Hu, Yuan

    2016-01-01

    Human noroviruses are a group of viral agents that afflict people of all age groups. The viruses are now recognized as the most common causative agent of nonbacterial acute gastroenteritis and foodborne viral illness worldwide. However, they have been considered to play insignificant roles in the disease burden of acute gastroenteritis for the past decades until the recent advent of new and more sensitive molecular diagnostic methods. The availability and application of the molecular diagnostic methods have led to enhanced detection of noroviruses in clinical, food and environmental samples, significantly increasing the recognition of noroviruses as an etiologic agent of epidemic and sporadic acute gastroenteritis. This article aims to summarize recent efforts made for the development of molecular methods for the detection and characterization of human noroviruses. PMID:27335620

  15. Steered Molecular Dynamics Methods Applied to Enzyme Mechanism and Energetics.

    PubMed

    Ramírez, C L; Martí, M A; Roitberg, A E

    2016-01-01

    One of the main goals of chemistry is to understand the underlying principles of chemical reactions, in terms of both its reaction mechanism and the thermodynamics that govern it. Using hybrid quantum mechanics/molecular mechanics (QM/MM)-based methods in combination with a biased sampling scheme, it is possible to simulate chemical reactions occurring inside complex environments such as an enzyme, or aqueous solution, and determining the corresponding free energy profile, which provides direct comparison with experimental determined kinetic and equilibrium parameters. Among the most promising biasing schemes is the multiple steered molecular dynamics method, which in combination with Jarzynski's Relationship (JR) allows obtaining the equilibrium free energy profile, from a finite set of nonequilibrium reactive trajectories by exponentially averaging the individual work profiles. However, obtaining statistically converged and accurate profiles is far from easy and may result in increased computational cost if the selected steering speed and number of trajectories are inappropriately chosen. In this small review, using the extensively studied chorismate to prephenate conversion reaction, we first present a systematic study of how key parameters such as pulling speed, number of trajectories, and reaction progress are related to the resulting work distributions and in turn the accuracy of the free energy obtained with JR. Second, and in the context of QM/MM strategies, we introduce the Hybrid Differential Relaxation Algorithm, and show how it allows obtaining more accurate free energy profiles using faster pulling speeds and smaller number of trajectories and thus smaller computational cost. PMID:27497165

  16. Small-scale mechanical characterization of viscoelastic adhesive systems

    NASA Astrophysics Data System (ADS)

    Shean, T. A. V.

    Aero engine hot end components are often covered with ceramic Thermal Barrier Coatings (TBCs). Laser drilling in the TBC coated components can be a source of service life TBC degradation and spallation. The present study aims to understand the mechanisms of TBC delamination and develop techniques to drill holes without damaging the TBC, Nimonic 263 workpieces coated with TBC are used in the experiments. Microwave non-destructive testing (NDT) is employed to monitor the integrity of the coating /substrate interfaces of the post-laser drilled materials. A numerical modelling technique is used to investigate the role of melt ejection on TBC delamination. The model accounts for the vapour and the assist gas flow effects in the process. Broadly, melt ejection induced mechanical stresses for the TBC coating / bond coating and thermal effects for the bond coating / substrate interfaces are found the key delamination mechanisms. Experiments are carried out to validate the findings from the model. Various techniques that enable laser drilling without damaging the TBC are demonstrated. Twin jet assisted acute angle laser drilling is one successful technique that has been analysed using the melt ejection simulation. Optimisation of the twin jet assisted acute angle laser drilling process parameters is carried out using Design of Experiments (DoE) and statistical modelling approaches. Finally, an industrial case study to develop a high speed, high quality laser drilling system for combustor cans is described. Holes are drilled by percussion and trepan drilling in TBC coated and uncoated Haynes 230 workpieces. The production rate of percussion drilling is significantly higher than the trepan drilling, however metallurgical hole quality and reproducibility is poor. A number of process parameters are investigated to improve these characteristics. Gas type and gas pressure effects on various characteristics of the inclined laser drilled holes are investigated through theoretical

  17. A mechanical diode: Comparing numerical and experimental characterizations

    SciTech Connect

    Simmermacher, T.; Segalman, D.; Sagartz, M.

    1997-12-01

    The predictive modeling of vibration of many structural systems is crippled by an inability to predictively model the mechanics of joints. The lack of understanding of joint dynamics is evidenced by the substantial uncertainty of joint compliances in the numerical models and by the complete inability to predict joint damping. The lore is that at low amplitudes, joint mechanics are associated with Coulomb friction and stick-slip phenomena and that at high amplitudes, impact processes result in dissipation as well as shift of energy to other frequencies. Inadequate understanding of the physics precludes reliable predictions. In this introductory work, joint compliance is studied in both a numerical and experimental setting. A simple bolted interface is used as the test article and compliance is measured for the joint in both compression and in tension. This simple interface is shown to exhibit a strong non-linearity near the transition from compression to tension (or vice-versa). Modeling issues pertaining to numerically solving for the compliance are addressed. It is shown that the model predicts the experimental strains and compliance fairly well. It will be seen that the joint behavior is a mechanical analogy to a diode. In compression, the joint is very stiff, acting almost as a rigid link, while in tension the joint is soft, acting as a soft spring. Although there have been many other studies performed on bolted joints, the variety of joint geometries has demonstrated large variations in behavior. This study is an attempt to quantify the behavior of typical joints found in today`s weapon systems.

  18. Dynamic mechanical characterization and modelling of polypropylene based organoclay nanocomposite

    NASA Astrophysics Data System (ADS)

    Wang, Kui; Matadi Boumbimba, Rodrigue; Bahlouli, Nadia; Ahzi, Said; Muller, René

    2015-09-01

    In order to investigate the dynamic behaviour of polypropylene based organoclay nanocomposite, the polypropylene matrix and a master batch of polypropylene modified anhydrid maleic were mixed by means of melt mixing technique. The experimental characterization was performed by using split Hopkinson pressure bars (SHPB), at different strain rates and temperatures. A significant increase of the yield stress of nanocomposite was shown with the present of organoclay, comparing to neat PP. A three-phase approach based on the micromechanical formulation of the cooperative model is proposed to model the yield behaviour of the polymer nanocomposite. Our proposed approach accounts for strain rate and temperature effects as well as the organoclay exfoliation effect. The predictions of models for the nanocomposite yield behaviour showed a good agreement with experimental data.

  19. Origin and characterization of different stick-slip friction mechanisms

    SciTech Connect

    Berman, A.D.; Ducker, W.A.; Israelachvili, J.N.

    1996-09-18

    Mechanical parts often move, not smoothly, but in jerks known as stick-slip. Stick-slip motion may be regular (repetitive or periodic) or irregular (erratic or intermittent). In the case of frictional sliding, stick-slip can have serious and often undesirable consequences - resulting in noise (chatter), high energy loss (friction), surface damage (wear), and component failure. We review the origins of stick-slip friction and present new experimental results on model surfaces that clarify its different origins, its dependence on experimental conditions or `system parameters`, and how stick-slip can be controlled in practical situations. 20 refs., 10 figs., 1 tab.

  20. Dynamic Mechanical Characterization of Thin Film Polymer Nanocomposites

    NASA Technical Reports Server (NTRS)

    Herring, Helen M.; Gates, Thomas S. (Technical Monitor)

    2003-01-01

    Many new materials are being produced for aerospace applications with the objective of maximizing certain ideal properties without sacrificing others. Polymer composites in various forms and configurations are being developed in an effort to provide lighter weight construction and better thermal and electrical properties and still maintain adequate strength and stability. To this end, thin film polymer nanocomposites, synthesized for the purpose of influencing electrical conductivity using metal oxide particles as filler without incurring losses in mechanical properties, were examined to determine elastic modulus and degree of dispersion of particles. The effects of various metal oxides on these properties will be discussed.

  1. Non-contact method for characterization of a rotational table

    NASA Astrophysics Data System (ADS)

    La Moure Shattuck, Judson, III; Parisi, Vincent M.; Smerdon, Arryn J.

    2007-04-01

    The United States Air Force (USAF) uses and evaluates a variety of helmet-mounted trackers for incorporation into their high performance aircraft. The primary head tracker technologies commercially available are magnetic trackers, inertial trackers, and optical trackers. Each head tracker has a unique method of determining the pilot's head position within the cockpit of the aircraft. Magnetic trackers generally have a small head mounted size and minimal head weight. Because they sense a generated magnetic field, their accuracy can be affected by other magnetic fields or ferrous components within the cockpit. Inertial trackers cover the entire head motion box but require constant motion in order to accommodate drifting of the inertial sensors or a secondary system that updates the inertial system, often referred to as a hybrid system. Although optical head trackers (OHT) are immune to magnetic fields some of their limitations may be daylight/night vision goggle (NVG) compatibility issues and, depending on system configuration, may require numerous emitters and/or receivers to cover a large head motion box and provide a wide field of regard. The Dynamic Tracker Test Fixture (DTTF) was designed by the Helmet Mounted Sensory Technology (HMST) laboratory to accurately measure azimuth rotation in both static and dynamic conditions for the purpose of determining the accuracy of a variety of head trackers. Before the DTTF could be used as an evaluation tool, it required characterization to determine the amount and location of any induced elevation or roll as the table rotated in azimuth. Optimally, the characterization method would not affect the DTTF's movement so a non-contact method was devised. This paper describes the characterization process and its results.

  2. A novel method for material characterization of reusable products.

    PubMed

    Fortuna, Lorena M; Diyamandoglu, Vasil

    2016-06-01

    Product reuse contributes favorably to waste management and resource recovery by diverting products from terminal disposal to second-hand urban markets. Many organizations with social mission incorporate in their activities the process of reuse, thus making valuable products available to second-hand customers through their thrift stores. Data management and product classification are an important aspect of quantitative analysis of second-hand products circulating through reuse organizations. The New York City Center for Materials Reuse has, for the last 10years, organized the reuse activities of most not for profit organizations, and collected valuable information on the strengths and weaknesses of their operations. One such finding is the casual, and inconsistent approach used by these organizations to keep a record of the level and value of the reuse efforts they undertake. This paper describes a novel methodology developed to standardize record keeping and characterize commonly reused post-consumer products by assessing the outgoing product flow from reuse organizations. The approach groups material composition of individual products into main product categories, creating a simplified method to characterize products. Furthermore, by linking product categories and material composition, the method creates a matrix to help identify the material composition of products handled by reuse organizations. As part of the methodology, whenever adequate data are not available about certain types of products, a process identified as "field characterization study" is proposed and incorporated in the implementation to develop meaningful and useful data on the weight and material composition. Finally, the method incorporates the estimation of the environmental impact of reuse using standard models available through the U.S. Environmental Protection Agency and other worldwide entities. The diversified weight and size of products poses a challenge to the statistical significance

  3. Mechanical Characterization of Composites and Foams for Aerospace Applications

    NASA Technical Reports Server (NTRS)

    Veazie, D. R.; Glinsey, C.; Webb, M. M.; Norman, M.; Meador, Michael A. (Technical Monitor)

    2000-01-01

    Experimental studies to investigate the mechanical properties of ultra-lightweight polyimide foams for space applications, compression after impact (CAI) properties for low velocity impact of sandwich composites, and aspen fiber/polypropylene composites containing an interface adhesive additive, Maleic Anhydride Grafted Polypropylene (MAPP), were performed at Clark Atlanta University. Tensile, compression, flexural, and shear modulus tests were performed on TEEK foams categorized by their densities and relative cost according to ASTM specifications. Results showed that the mechanical properties of the foams increased as a function of higher price and increasing density. The CAI properties of Nomex/phenolic honeycomb core, fiberglass/epoxy facesheet sandwich composites for two damage arrangements were compared using different levels of impact energy ranging from 0 - 452 Joules. Impact on the thin side showed slightly more retention of CAI strength at low impact levels, whereas higher residual compressive strength was observed from impact on the thick side at higher impact levels. The aspen fiber/polypropylene composites studied are composed of various percentages (by weight) of aspen fiber and polypropylene ranging from 30%-60% and 40%-100%, respectively. Results showed that the MAPP increases tensile and flexural strength, while having no significant influence on tensile and flexural modulus.

  4. Mechanical characterization of dense calcium phosphate bioceramics with interconnected porosity.

    PubMed

    Hsu, Y H; Turner, I G; Miles, A W

    2007-12-01

    Porous hydroxyapatite/tricalcium phosphate (HA/TCP) bioceramics were fabricated by a novel technique of vacuum impregnation of reticulated polymeric foams with ceramic slip. The samples had approximately 5-10% interconnected porosity and controlled pore sizes appropriate to allow bone ingrowth, combined with good mechanical properties. A range of polyurethane foams with 20, 30 and 45 pores per inch (ppi) were used as templates to produce samples for testing. The foams were inpregnated with solid loadings in the range of 60-140 wt%. The results indicated that the average apparent density of the HA/TCP samples was 2.48 g/cm(3), the four-point bending strength averaged 16.98 MPa, the work of fracture averaged 15.46 J/m(2) and the average compressive strength was 105.56 MPa. A range of mechanical properties resulted from the various combinations of different grades of PU foam and the solid loading of slips. The results indicated that it is possible to manufacture open pore HA/TCP bioceramics, with compressive strengths comparable to human bone, which could be of significant clinical interest. PMID:17569009

  5. Mechanical characterization of cross-linked serum albumin microcapsules.

    PubMed

    de Loubens, Clément; Deschamps, Julien; Georgelin, Marc; Charrier, Anne; Edwards-Levy, Florence; Leonetti, Marc

    2014-07-01

    Controlling the deformation of microcapsules and capsules is essential in numerous biomedical applications. The mechanical properties of the membrane of microcapsules made of cross-linked human serum albumin (HSA) are revealed by two complementary experiments in the linear elastic regime. The first provides the surfacic shear elastic modulus Gs by the study of small deformations of a single capsule trapped in an elongational flow: Gs varies from 0.002 to 5 N m(-1). The second gives the volumic Young's modulus E of the membrane by shallow and local indentations of the membrane with an AFM probe: E varies from 20 kPa to 1 MPa. The surfacic and volumic elastic moduli increase with the size of the capsule up to three orders of magnitude and with the protein concentration of the membrane. The membrane thickness is evaluated from these two membrane mechanical characteristics and increases with the size and the initial HSA concentration from 2 to 20 μm. PMID:24817568

  6. Knowledge Discovery Process for Characterization of Materials Failure Mechanism

    NASA Technical Reports Server (NTRS)

    Cios, Krzysztof J.

    1999-01-01

    It is the intent of this project to provide a platform to visualize the various data collected from stress-strain testing of composite ceramic matrix materials. The data collected from the stress-strain tests are acoustic emissions (AE). As a material is subjected to a stress-strain test, various failure mechanisms occur in the material. The recorded sounds emitted during the test may correspond to various failure mechanisms. This project, thus, will give a possible way to visualize the data and data derived from the recorded AE. The stress-strain testing was performed on several composite matrix material combinations. Each of these tests produced anywhere from 1000 to 10,000+ AE events. For each AE event recorded, several characteristics in both the time and frequency domains are created. This project has two goals. First, this project will provide a summation page for a selected waveform. This page will include all of the characteristics determined from the AE event waveform along with graphs of the AE event waveform and its corresponding Power Spectrum. The other function of this project is to retrieve and display selected AE event waveforms for comparison.

  7. Mechanical characterization of sub-micron polytetrafluoroethylene (PTFE) thin films

    SciTech Connect

    Lucas, B.N.; Oliver, W.C.; Rosenmayer, C.T.

    1998-12-31

    This study reports the results of an investigation of the mechanical properties of polytetrafluoroethylene (PTFE) thin films on silicon substrates in the 0.5 to 15 {micro}m thickness regime using frequency specific depth-sensing indentation. All measurements were conducted at an excitation frequency of 45 Hz using a constant (1/P dP/dt) load ramp of 0.1 s{sup {minus}1}. The modulus of the PTFE at a depth of 5% of the film thickness was measured to be approximately 1 GPa ({nu} = 0.46) independent of film thickness. These values are somewhat higher than the values obtained from free-standing 15 {micro}m film measurements of 0.4 GPa for the tensile modulus and 0.49 GPa for the storage modulus {at} 1.1 Hz. The film hardness at these depths was observed to range between 30 and 55 MPa with no correlation observed between the hardness and respective film thickness. While reliability modeling for interconnects currently uses interlayer dielectric mechanical properties data determined from free-standing films with thicknesses of several microns, these in-situ results should more closely mimic the constrained deformation that occurs during service and perhaps lead to a better understanding of the electromigration resistance of PTFE.

  8. Characterization of the Mechanisms Controlling Greatwall Activity ▿

    PubMed Central

    Vigneron, Suzanne; Gharbi-Ayachi, Aicha; Raymond, Anne-Aurélie; Burgess, Andrew; Labbé, Jean-Claude; Labesse, Gilles; Monsarrat, Bernard; Lorca, Thierry; Castro, Anna

    2011-01-01

    Here we investigate the mechanisms regulating Greatwall (Gwl), a serine/threonine kinase essential for promoting the correct timing of mitosis. We identify Gwl as a unique AGC kinase that, unlike most AGC members, appears to be devoid of a hydrophobic motif despite the presence of a functional hydrophobic pocket. Our results suggest that Gwl activation could be mediated by the binding of its hydrophobic pocket to the hydrophobic motif of another AGC kinase. Our molecular modeling and mutagenic analysis also indicate that Gwl displays a conserved tail/linker site whose phosphorylation mediates kinase activation by promoting the interaction of this phosphorylated residue with two lysines at the N terminus. This interaction could stabilize the αC-helix and maintain kinase activity. Finally, the different phosphorylation sites on Gwl are identified, and the role of each one in the regulation of Gwl kinase activity is determined. Our data suggest that only the phosphorylation of the tail/linker site, located outside the putative T loop, appears to be essential for Gwl activation. In summary, our results identify Gwl as a member of the AGC family of kinases that appears to be regulated by unique mechanisms and that differs from the other members of this family. PMID:21444715

  9. Yang-Yang equilibrium statistical mechanics: A brilliant method

    NASA Astrophysics Data System (ADS)

    Guan, Xi-Wen; Chen, Yang-Yang

    2016-03-01

    Yang and Yang in 1969 [J. Math. Phys. 10, 1115 (1969)] for the first time proposed a rigorous approach to the thermodynamics of the one-dimensional system of bosons with a delta-function interaction. This paper was a breakthrough in exact statistical mechanics, after Yang [Phys. Rev. Lett. 19, 1312 (1967)] published his seminal work on the discovery of the Yang-Baxter equation in 1967. Yang and Yang’s brilliant method yields significant applications in a wide range of fields of physics. In this paper, we briefly introduce the method of the Yang-Yang equilibrium statistical mechanics and demonstrate a fundamental application of the Yang-Yang method for the study of thermodynamics of the Lieb-Liniger model with strong and weak interactions in a whole temperature regime. We also consider the equivalence between the Yang-Yang’s thermodynamic Bethe ansatz equation and the thermodynamics of the ideal gas with the Haldane’s generalized exclusion statistics.

  10. Yang-Yang Equilibrium Statistical Mechanics: A Brilliant Method

    NASA Astrophysics Data System (ADS)

    Guan, Xi-Wen; Chen, Yang-Yang

    C. N. Yang and C. P. Yang in 1969 (J. Math. Phys. 10, 1115 (1969)) for the first time proposed a rigorous approach to the thermodynamics of the one-dimensional system of bosons with a delta-function interaction. This paper was a breakthrough in exact statistical mechanics, after C. N. Yang (Phys. Rev. Lett. 19, 1312 (1967)) published his seminal work on the discovery of the Yang-Baxter equation in 1967. Yang and Yang's brilliant method yields significant applications in a wide range of fields of physics. In this communication, we briefly introduce the method of the Yang-Yang equilibrium statistical mechanics and demonstrate a fundamental application of the Yang-Yang method for the study of thermodynamics of the Lieb-Liniger model with strong and weak interactions in a whole temperature regime. We also consider the equivalence between the Yang-Yang's thermodynamic Bethe ansatz equation and the thermodynamics of the ideal gas with the Haldane's generalized exclusion statistics.