On the apparent insignificance of the randomness of flexible joints on large space truss dynamics

NASA Technical Reports Server (NTRS)

Koch, R. M.; Klosner, J. M.

1993-01-01

Deployable periodic large space structures have been shown to exhibit high dynamic sensitivity to period-breaking imperfections and uncertainties. These can be brought on by manufacturing or assembly errors, structural imperfections, as well as nonlinear and/or nonconservative joint behavior. In addition, the necessity of precise pointing and position capability can require the consideration of these usually negligible and unknown parametric uncertainties and their effect on the overall dynamic response of large space structures. This work describes the use of a new design approach for the global dynamic solution of beam-like periodic space structures possessing parametric uncertainties. Specifically, the effect of random flexible joints on the free vibrations of simply-supported periodic large space trusses is considered. The formulation is a hybrid approach in terms of an extended Timoshenko beam continuum model, Monte Carlo simulation scheme, and first-order perturbation methods. The mean and mean-square response statistics for a variety of free random vibration problems are derived for various input random joint stiffness probability distributions. The results of this effort show that, although joint flexibility has a substantial effect on the modal dynamic response of periodic large space trusses, the effect of any reasonable uncertainty or randomness associated with these joint flexibilities is insignificant.

Role of band 3 in the erythrocyte membrane structural changes under thermal fluctuations -multi scale modeling considerations.

PubMed

Pajic-Lijakovic, Ivana

2015-12-01

An attempt was made to discuss and connect various modeling approaches on various time and space scales which have been proposed in the literature in order to shed further light on the erythrocyte membrane rearrangement caused by the cortex-lipid bilayer coupling under thermal fluctuations. Roles of the main membrane constituents: (1) the actin-spectrin cortex, (2) the lipid bilayer, and (3) the trans membrane protein band 3 and their course-consequence relations were considered in the context of the cortex non linear stiffening and corresponding anomalous nature of energy dissipation. The fluctuations induce alternating expansion and compression of the membrane parts in order to ensure surface and volume conservation. The membrane structural changes were considered within two time regimes. The results indicate that the cortex non linear stiffening and corresponding anomalous nature of energy dissipation are related to the spectrin flexibility distribution and the rate of its changes. The spectrin flexibility varies from purely flexible to semi flexible. It is influenced by: (1) the number of band 3 molecules attached to single spectrin filaments, and (2) phosphorylation of the actin-junctions. The rate of spectrin flexibility changes depends on the band 3 molecules rearrangement.

A Flexible and Non-instrusive Approach for Computing Complex Structural Coverage Metrics

NASA Technical Reports Server (NTRS)

Whalen, Michael W.; Person, Suzette J.; Rungta, Neha; Staats, Matt; Grijincu, Daniela

2015-01-01

Software analysis tools and techniques often leverage structural code coverage information to reason about the dynamic behavior of software. Existing techniques instrument the code with the required structural obligations and then monitor the execution of the compiled code to report coverage. Instrumentation based approaches often incur considerable runtime overhead for complex structural coverage metrics such as Modified Condition/Decision (MC/DC). Code instrumentation, in general, has to be approached with great care to ensure it does not modify the behavior of the original code. Furthermore, instrumented code cannot be used in conjunction with other analyses that reason about the structure and semantics of the code under test. In this work, we introduce a non-intrusive preprocessing approach for computing structural coverage information. It uses a static partial evaluation of the decisions in the source code and a source-to-bytecode mapping to generate the information necessary to efficiently track structural coverage metrics during execution. Our technique is flexible; the results of the preprocessing can be used by a variety of coverage-driven software analysis tasks, including automated analyses that are not possible for instrumented code. Experimental results in the context of symbolic execution show the efficiency and flexibility of our nonintrusive approach for computing code coverage information

ASCENT Program

NASA Technical Reports Server (NTRS)

Brown, Richard; Collier, Gary; Heckenlaible, Richard; Dougherty, Edward; Dolenz, James; Ross, Iain

2012-01-01

The ASCENT program solves the three-dimensional motion and attendant structural loading on a flexible vehicle incorporating, optionally, an active analog thrust control system, aerodynamic effects, and staging of multiple bodies. ASCENT solves the technical problems of loads, accelerations, and displacements of a flexible vehicle; staging of the upper stage from the lower stage; effects of thrust oscillations on the vehicle; a payload's relative motion; the effect of fluid sloshing on vehicle; and the effect of winds and gusts on the vehicle (on the ground or aloft) in a continuous analysis. The ATTACH ASCENT Loads program reads output from the ASCENT flexible body loads program, and calculates the approximate load indicators for the time interval under consideration. It calculates the load indicator values from pre-launch to the end of the first stage.

The novel 2Fe–2S outer mitochondrial protein mitoNEET displays conformational flexibility in its N-terminal cytoplasmic tethering domain

PubMed Central

Conlan, Andrea R.; Paddock, Mark L.; Axelrod, Herbert L.; Cohen, Aina E.; Abresch, Edward C.; Wiley, Sandra; Roy, Melinda; Nechushtai, Rachel; Jennings, Patricia A.

2009-01-01

A primary role for mitochondrial dysfunction is indicated in the pathogenesis of insulin resistance. A widely used drug for the treatment of type 2 diabetes is pioglitazone, a member of the thiazolidinedione class of molecules. MitoNEET, a 2Fe–2S outer mitochondrial membrane protein, binds pioglitazone [Colca et al. (2004 ▶), Am. J. Physiol. Endocrinol. Metab. 286, E252–E260]. The soluble domain of the human mitoNEET protein has been expressed C-terminal to the superfolder green fluorescent protein and the mitoNEET protein has been isolated. Comparison of the crystal structure of mitoNEET isolated from cleavage of the fusion protein (1.4 Å resolution, R factor = 20.2%) with other solved structures shows that the CDGSH domains are superimposable, indicating proper assembly of mitoNEET. Furthermore, there is considerable flexibility in the position of the cytoplasmic tethering arms, resulting in two different conformations in the crystal structure. This flexibility affords multiple orientations on the outer mitochondrial membrane. PMID:19574633

High-Speed Rotor Analytical Dynamics on Flexible Foundation Subjected to Internal and External Excitation

NASA Astrophysics Data System (ADS)

Jivkov, Venelin S.; Zahariev, Evtim V.

2016-12-01

The paper presents a geometrical approach to dynamics simulation of a rigid and flexible system, compiled of high speed rotating machine with eccentricity and considerable inertia and mass. The machine is mounted on a vertical flexible pillar with considerable height. The stiffness and damping of the column, as well as, of the rotor bearings and the shaft are taken into account. Non-stationary vibrations and transitional processes are analyzed. The major frequency and modal mode of the flexible column are used for analytical reduction of its mass, stiffness and damping properties. The rotor and the foundation are modelled as rigid bodies, while the flexibility of the bearings is estimated by experiments and the requirements of the manufacturer. The transition effects as a result of limited power are analyzed by asymptotic methods of averaging. Analytical expressions for the amplitudes and unstable vibrations throughout resonance are derived by quasi-static approach increasing and decreasing of the exciting frequency. Analytical functions give the possibility to analyze the influence of the design parameter of many structure applications as wind power generators, gas turbines, turbo-generators, and etc. A numerical procedure is applied to verify the effectiveness and precision of the simulation process. Nonlinear and transitional effects are analyzed and compared to the analytical results. External excitations, as wave propagation and earthquakes, are discussed. Finite elements in relative and absolute coordinates are applied to model the flexible column and the high speed rotating machine. Generalized Newton - Euler dynamics equations are used to derive the precise dynamics equations. Examples of simulation of the system vibrations and nonstationary behaviour are presented.

Transparent resistive switching memory using aluminum oxide on a flexible substrate

NASA Astrophysics Data System (ADS)

Yeom, Seung-Won; Shin, Sang-Chul; Kim, Tan-Young; Ha, Hyeon Jun; Lee, Yun-Hi; Shim, Jae Won; Ju, Byeong-Kwon

2016-02-01

Resistive switching memory (ReRAM) has attracted much attention in recent times owing to its fast switching, simple structure, and non-volatility. Flexible and transparent electronic devices have also attracted considerable attention. We therefore fabricated an Al2O3-based ReRAM with transparent indium-zinc-oxide (IZO) electrodes on a flexible substrate. The device transmittance was found to be higher than 80% in the visible region (400-800 nm). Bended states (radius = 10 mm) of the device also did not affect the memory performance because of the flexibility of the two transparent IZO electrodes and the thin Al2O3 layer. The conduction mechanism of the resistive switching of our device was explained by ohmic conduction and a Poole-Frenkel emission model. The conduction mechanism was proved by oxygen vacancies in the Al2O3 layer, as analyzed by x-ray photoelectron spectroscopy analysis. These results encourage the application of ReRAM in flexible and transparent electronic devices.

Analytical and numerical modeling for flexible pipes

NASA Astrophysics Data System (ADS)

Wang, Wei; Chen, Geng

2011-12-01

The unbonded flexible pipe of eight layers, in which all the layers except the carcass layer are assumed to have isotropic properties, has been analyzed. Specifically, the carcass layer shows the orthotropic characteristics. The effective elastic moduli of the carcass layer have been developed in terms of the influence of deformation to stiffness. With consideration of the effective elastic moduli, the structure can be properly analyzed. Also the relative movements of tendons and relative displacements of wires in helical armour layer have been investigated. A three-dimensional nonlinear finite element model has been presented to predict the response of flexible pipes under axial force and torque. Further, the friction and contact of interlayer have been considered. Comparison between the finite element model and experimental results obtained in literature has been given and discussed, which might provide practical and technical support for the application of unbonded flexible pipes.

Extremely Stable Polypyrrole Achieved via Molecular Ordering for Highly Flexible Supercapacitors.

PubMed

Huang, Yan; Zhu, Minshen; Pei, Zengxia; Huang, Yang; Geng, Huiyuan; Zhi, Chunyi

2016-01-27

The cycling stability of flexible supercapacitors with conducting polymers as electrodes is limited by the structural breakdown arising from repetitive counterion flow during charging/discharging. Supercapacitors made of facilely electropolymerized polypyrrole (e-PPy) have ultrahigh capacitance retentions of more than 97, 91, and 86% after 15000, 50000, and 100000 charging/discharging cycles, respectively, and can sustain more than 230000 charging/discharging cycles with still approximately half of the initial capacitance retained. To the best of our knowledge, such excellent long-term cycling stability was never reported. The fully controllable electropolymerization shows superiority in molecular ordering, favoring uniform stress distribution and charge transfer. Being left at ambient conditions for even 8 months, e-PPy supercapacitors completely retain the good electrochemical performance. The extremely stable supercapacitors with excellent flexibility and scalability hold considerable promise for the commerical application of flexible and wearable electronics.

Study of design and control of remote manipulators. Part 2: Vibration considerations in manipulator design

NASA Technical Reports Server (NTRS)

Book, W. J.

1973-01-01

An investigation is reported involving a mathematical procedure using 4 x 4 transformation matrices for analyzing the vibrations of flexible manipulators. Previous studies with the procedure are summarized and the method is extended to include flexible joints as well as links, and to account for the effects of various power transmission schemes. A systematic study of the allocation of structural material and the placement of components such as motors and gearboxes was undertaken using the analytical tools developed. As one step in this direction the variables which relate the vibration parameters of the arm to the task and environment of the arm were isolated and nondimensionalized. The 4 x 4 transformation matrices were also used to develop analytical expressions for the terms of the complete 6 x 6 compliance matrix for the case of two flexible links joined by a rotating joint, flexible about its axis of rotation.

Combined particle-image velocimetry and force analysis of the three-dimensional fluid-structure interaction of a natural owl wing.

PubMed

Winzen, A; Roidl, B; Schröder, W

2016-04-01

Low-speed aerodynamics has gained increasing interest due to its relevance for the design process of small flying air vehicles. These small aircraft operate at similar aerodynamic conditions as, e.g. birds which therefore can serve as role models of how to overcome the well-known problems of low Reynolds number flight. The flight of the barn owl is characterized by a very low flight velocity in conjunction with a low noise emission and a high level of maneuverability at stable flight conditions. To investigate the complex three-dimensional flow field and the corresponding local structural deformation in combination with their influence on the resulting aerodynamic forces, time-resolved stereoscopic particle-image velocimetry and force and moment measurements are performed on a prepared natural barn owl wing. Several spanwise positions are measured via PIV in a range of angles of attack [Formula: see text] 6° and Reynolds numbers 40 000 [Formula: see text] 120 000 based on the chord length. Additionally, the resulting forces and moments are recorded for -10° ≤ α ≤ 15° at the same Reynolds numbers. Depending on the spanwise position, the angle of attack, and the Reynolds number, the flow field on the wing's pressure side is characterized by either a region of flow separation, causing large-scale vortical structures which lead to a time-dependent deflection of the flexible wing structure or wing regions showing no instantaneous deflection but a reduction of the time-averaged mean wing curvature. Based on the force measurements the three-dimensional fluid-structure interaction is assumed to considerably impact the aerodynamic forces acting on the wing leading to a strong mechanical loading of the interface between the wing and body. These time-depending loads which result from the flexibility of the wing should be taken into consideration for the design of future small flying air vehicles using flexible wing structures.

Flexibility in the structure of spiral flowers and its underlying mechanisms.

PubMed

Wang, Peipei; Liao, Hong; Zhang, Wengen; Yu, Xianxian; Zhang, Rui; Shan, Hongyan; Duan, Xiaoshan; Yao, Xu; Kong, Hongzhi

2015-12-07

Spiral flowers usually bear a variable number of organs, suggestive of the flexibility in structure. The mechanisms underlying the flexibility, however, remain unclear. Here we show that in Nigella damascena, a species with spiral flowers, different types of floral organs show different ranges of variation in number. We also show that the total number of organs per flower is largely dependent on the initial size of the floral meristem, whereas the respective numbers of different types of floral organs are determined by the functional domains of corresponding genetic programmes. By conducting extensive expression and functional studies, we further elucidate the genetic programmes that specify the identities of different types of floral organs. Notably, the AGL6-lineage member NdAGL6, rather than the AP1-lineage members NdFL1/2, is an A-function gene, whereas petaloidy of sepals is not controlled by AP3- or PI-lineage members. Moreover, owing to the formation of a regulatory network, some floral organ identity genes also regulate the boundaries between different types of floral organs. On the basis of these results, we propose that the floral organ identity determination programme is highly dynamic and shows considerable flexibility. Transitions from spiral to whorled flowers, therefore, may be explained by evolution of the mechanisms that reduce the flexibility.

Mechanisms of zinc binding to the solute-binding protein AztC and transfer from the metallochaperone AztD.

PubMed

Neupane, Durga P; Avalos, Dante; Fullam, Stephanie; Roychowdhury, Hridindu; Yukl, Erik T

2017-10-20

Bacteria can acquire the essential metal zinc from extremely zinc-limited environments by using ATP-binding cassette (ABC) transporters. These transporters are critical virulence factors, relying on specific and high-affinity binding of zinc by a periplasmic solute-binding protein (SBP). As such, the mechanisms of zinc binding and release among bacterial SBPs are of considerable interest as antibacterial drug targets. Zinc SBPs are characterized by a flexible loop near the high-affinity zinc-binding site. The function of this structure is not always clear, and its flexibility has thus far prevented structural characterization by X-ray crystallography. Here, we present intact structures for the zinc-specific SBP AztC from the bacterium Paracoccus denitrificans in the zinc-bound and apo-states. A comparison of these structures revealed that zinc loss prompts significant structural rearrangements, mediated by the formation of a sodium-binding site in the apo-structure. We further show that the AztC flexible loop has no impact on zinc-binding affinity, stoichiometry, or protein structure, yet is essential for zinc transfer from the metallochaperone AztD. We also found that 3 His residues in the loop appear to temporarily coordinate zinc and then convey it to the high-affinity binding site. Thus, mutation of any of these residues to Ala abrogated zinc transfer from AztD. Our structural and mechanistic findings conclusively identify a role for the AztC flexible loop in zinc acquisition from the metallochaperone AztD, yielding critical insights into metal binding by AztC from both solution and AztD. These proteins are highly conserved in human pathogens, making this work potentially useful for the development of novel antibiotics. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

Interplay between defects, disorder and flexibility in metal-organic frameworks

NASA Astrophysics Data System (ADS)

Bennett, Thomas D.; Cheetham, Anthony K.; Fuchs, Alain H.; Coudert, François-Xavier

2017-01-01

Metal-organic frameworks are a novel family of chemically diverse materials, which are of interest across engineering, physics, chemistry, biology and medicine-based disciplines. Since the development of the field in its current form more than two decades ago, priority has been placed on the synthesis of new structures. However, more recently, a clear trend has emerged in shifting the emphasis from material design to exploring the chemical and physical properties of structures already known. In particular, although such nanoporous materials were traditionally seen as rigid crystalline structures, there is growing evidence that large-scale flexibility, the presence of defects and long-range disorder are not the exception in metal-organic frameworks, but the rule. Here we offer some perspective into how these concepts are perhaps inescapably intertwined, highlight recent advances in our understanding and discuss how a consideration of the interfaces between them may lead to enhancements of the materials' functionalities.

The synthesis and structure of a potential immunosuppressant: N-mycophenoyl malonic acid dimethyl ester

NASA Astrophysics Data System (ADS)

Siebert, Agnieszka; Cholewiński, Grzegorz; Garwolińska, Dorota; Olejnik, Adrian; Rachoń, Janusz; Chojnacki, Jarosław

2018-01-01

The synthesis of a potential immunosuppressant, i.e. dimethyl ester of N-mycophenoyl malonic acid was optimized in the reaction of mycophenolic acid (MPA) with amino malonic dimethyl ester in the presence of propanephosphonic anhydride (T3P) as a coupling reagent. The structural properties of the obtained MPA derivative were investigated by NMR, MS and single crystal X-ray diffraction methods. Theoretical considerations of conformational flexibility based on DFT calculations are presented.

Toward Advanced Human Reliability Programs. Structural Development Considerations and Options for Extreme Risk Environments

DTIC Science & Technology

1992-05-01

programs has not been effectively accomplished. We can ascertain to a meaningful degree the impact of various types of stress (e.g. heat and work ...that this would produce an effective cross-pollination effect , as panel and panel member work inspired others not directly associated with the effort...include: 1. It has the least flexibility to political sensitivities. 2. There is structural inflexibility in format arrangements . 3. It is easiest to

The flexibility and dynamics of protein disulfide isomerase

PubMed Central

Wells, Stephen A.; Emilio Jimenez‐Roldan, J.; Bhattacharyya, Moitrayee; Vishweshwara, Saraswathi; Freedman, Robert B.

2016-01-01

ABSTRACT We have studied the mobility of the multidomain folding catalyst, protein disulfide isomerase (PDI), by a coarse‐graining approach based on flexibility. We analyze our simulations of yeast PDI (yPDI) using measures of backbone movement, relative positions and orientations of domains, and distances between functional sites. We find that there is interdomain flexibility at every interdomain junction but these show very different characteristics. The extent of interdomain flexibility is such that yPDI's two active sites can approach much more closely than is found in crystal structures—and indeed hinge motion to bring these sites into proximity is the lowest energy normal mode of motion of the protein. The flexibility predicted for yPDI (based on one structure) includes the other known conformation of yPDI and is consistent with (i) the mobility observed experimentally for mammalian PDI and (ii) molecular dynamics. We also observe intradomain flexibility and clear differences between the domains in their propensity for internal motion. Our results suggest that PDI flexibility enables it to interact with many different partner molecules of widely different sizes and shapes, and highlights considerable similarities of yPDI and mammalian PDI. Proteins 2016; 84:1776–1785. © 2016 Wiley Periodicals, Inc. PMID:27616289

Flexible Engineering Structures from the Corrugated Metal Sheets - Comparison of Costs of Solutions used in the Road Building

NASA Astrophysics Data System (ADS)

Ołdakowska, E.

2017-11-01

The flexible structures from the corrugated metal sheets are used in particular in the road building, especially as passages for animals. Easy and quick assembly, as well as lower realization costs when compared to the traditional solutions increase interest in such structures. Availability and variety of systems allows for searching for solutions which are the best and optimal in the economical range. The article presents the comparison of costs of the basic materials used in various systems of flexible structures from the corrugated metal sheets. In order to determine the costs of the material solutions the data for two systems used in Poland (for construction of the upper passages for animals) since 2008 have been used. The cost estimation for the basic materials required for realization of 1 m2 of the flexible structure from the corrugated steel sheets have been prepared with use of prices obtained directly from the Polish contractors and manufacturers, as well as process included in the quarterly information (Sekocenbud). The difference of prices of materials available on the market allows the investor for selecting the structure depending on the needs and financial possibilities, as well as for achieving some savings. The savings in case of purchasing sheets of identical parameters (thickness, profile characteristics) are from approx. 4% to 8% per 1 m2 of sheet. The connectors in form of bolts M20 cl. 8.8 of various lengths are an expense from 3.00 PLN to 3.50 PLN. Those values may seem low, but taking into consideration amounts connected with construction of many square meters of structure they may become very important factor in the total investment costs.

[Changes in mental health care by a regional budget: results of a pilot Project in Schleswig-Holstein (Germany)].

PubMed

Deister, Arno; Zeichner, Dirk; Witt, Thorsten; Forster, Hans-Jürgen

2010-10-01

In a region of Schleswig-Holstein, a regional budget was used to investigate which structural changes would be brought about by a financial plan which enables (clinical) treatment that defies rigid financial limits and makes flexible treatment in various settings possible. In 5 years, the number of inpatient treatment places in the care region was reduced considerably. The length of stay per patient and year decreased by 25 %. Day care and outpatient treatment offers were expanded substantially and new treatment concepts were established. The quality of treatment remained safeguarded. A regional budget is suitable for bringing about fundamental changes in terms of content and structure in psychiatric care. The result is clearly improved flexibility as compared to previous care structures; incentives for disorders are reduced. The principle "outpatient before inpatient" is strengthened. The financial plan can be transposed onto other regions, whereby modifications according to the structure of the care region seem necessary. © Georg Thieme Verlag KG Stuttgart · New York.

Crystal structure of native and a mutant of Lampyris turkestanicus luciferase implicate in bioluminescence color shift.

PubMed

Kheirabadi, Mitra; Sharafian, Zohreh; Naderi-Manesh, Hossein; Heineman, Udo; Gohlke, Ulrich; Hosseinkhani, Saman

2013-12-01

Firefly bioluminescence reaction in the presence of Mg(2+), ATP and molecular oxygen is carried out by luciferase. The luciferase structure alterations or modifications of assay conditions determine the bioluminescence color of firefly luciferase. Among different beetle luciferases, Phrixothrix hirtus railroad worm emits either yellow or red bioluminescence color. Sequence alignment analysis shows that the red-emitter luciferase from Phrixothrix hirtus has an additional arginine residue at 353 that is absent in other firefly luciferases. It was reported that insertion of Arg in an important flexible loop350-359 showed changes in bioluminescence color from green to red and the optimum temperature activity was also increased. To explain the color tuning mechanism of firefly luciferase, the structure of native and a mutant (E354R/356R/H431Y) of Lampyris turkestanicus luciferase is determined at 2.7Å and 2.2Å resolutions, respectively. The comparison of structure of both types of Lampyris turkestanicus luciferases reveals that the conformation of this flexible loop is significantly changed by addition of two Arg in this region. Moreover, its surface accessibility is affected considerably and some ionic bonds are made by addition of two positive charge residues. Furthermore, we noticed that the hydrogen bonding pattern of His431 with the flexible loop is changed by replacing this residue with Tyr at this position. Juxtaposition of a flexible loop (residues 351-359) in firefly luciferase and corresponding ionic and hydrogen bonds are essential for color emission. © 2013.

Personal autonomy and the flexible school

NASA Astrophysics Data System (ADS)

Aviram, Aharon

1993-09-01

The paper starts by emphasizing the importance of the ideal of personal autonomy as a central educational aim within liberal-democratic thought. Although this ideal has been accorded different meanings in the past 200 years, this paper focuses on J. S. Mill's view of autonomy - a very influential view within the liberal tradition and one still relevant for us today. The basic educational recommendation stemming from Mill's view of this ideal is the need to encourage "experimentation in living" by young people to enable them to discover their authentic wishes, capabilities and interests and to exercise themselves in the formation of "life-plans". The paper points to the sharp contradiction between democratic educational thought and practice: between the ideal of autonomy and the prevailing rigid and closed school structure which usually prevents true experimentation in living. It explains this contradiction as stemming from didactic and social considerations that were valid in industrial democratic societies. The paper's main claim is that due to the electronic revolution and its social consequences, the validity of these considerations is drastically and rapidly eroding in post-industrial democratic societies, and that, therefore, a much more flexible and open school structure is today not only desirable but also didactically and socially possible. The paper ends by presenting the "School as a Communications Center" model of a flexible school that reflects the above rationale. This model is now in the first stage of its implementation at a comprehensive high-school in Beer-Sheva, Israel.

The Armed Forces Casualty Assistance Readiness Enhancement System (CARES): Design for Flexibility

DTIC Science & Technology

2006-06-01

Special Form SQL Structured Query Language SSA Social Security Administration U USMA United States Military Academy V VB Visual Basic VBA Visual Basic for...of Abbreviations ................................................................... 26 Appendix B: Key VBA Macros and MS Excel Coding...internet portal, CARES Version 1.0 is a MS Excel spreadsheet application that contains a considerable number of Visual Basic for Applications ( VBA

Coating graphene paper with 2D-assembly of electrocatalytic nanoparticles: a modular approach toward high-performance flexible electrodes.

PubMed

Xiao, Fei; Song, Jibin; Gao, Hongcai; Zan, Xiaoli; Xu, Rong; Duan, Hongwei

2012-01-24

The development of flexible electrodes is of considerable current interest because of the increasing demand for modern electronics, portable medical products, and compact energy devices. We report a modular approach to fabricating high-performance flexible electrodes by structurally integrating 2D-assemblies of nanoparticles with freestanding graphene paper. We have shown that the 2D array of gold nanoparticles at oil-water interfaces can be transferred on freestanding graphene oxide paper, leading to a monolayer of densely packed gold nanoparticles of uniform sizes loaded on graphene oxide paper. One major finding is that the postassembly electrochemical reduction of graphene oxide paper restores the ordered structure and electron-transport properties of graphene, and gives rise to robust and biocompatible freestanding electrodes with outstanding electrocatalytic activities, which have been manifested by the sensitive and selective detection of two model analytes: glucose and hydrogen peroxide (H(2)O(2)) secreted by live cells. The modular nature of this approach coupled with recent progress in nanocrystal synthesis and surface engineering opens new possibilities to systematically study the dependence of catalytic performance on the structural parameters and chemical compositions of the nanocrystals. © 2011 American Chemical Society

The Development of Modal Testing Technology for Wind Turbines: A Historical Perspective

NASA Technical Reports Server (NTRS)

James, George H., III; Carne, Thomas G.

2007-01-01

Wind turbines are very large, flexible structures, with aerodynamic forces on the rotating blades producing periodic forces with frequencies at the harmonics of the rotation frequency. Due to design consideration, these rotational frequencies are comparable to the modal frequencies; thus avoiding resonant conditions is a critical consideration. Consequently, predicting and experimentally validating the modal frequencies of wind turbines has been important to their successful design and operation. Performing modal tests on flexible structures over 120 meters tall is a substantial challenge, which has inspired innovative developments in modal test technology. A further trial to the analyst and experimentalist is that the modal frequencies are dependent on the turbine rotation speed, so testing a parked turbine does not fully validate the analytical predictions. The history and development of this modal testing technology will be reviewed, showing historical tests and techniques, ranging from two-meter to 100-meter turbines for both parked and rotating tests. The NExT (Natural Excitation Technique) was developed in the 1990's, as a predecessor to OMA to overcome these challenges. We will trace the difficulties and successes of wind turbine modal testing over the past twenty-five years from 1982 to the present.

Experimental determination of the inertia constants of an airplane or of a missile

NASA Technical Reports Server (NTRS)

Loiseau, H.

1983-01-01

The possibility to measure the inertia constants of an airplane or of a missile by a unique experimental set up without having to materialize axes of rotation was investigated. It is sufficient to suspend the structure appropriately, to obtain the six natural modes determined by the suspension and to introduce these results as data into a computer. If the structure is very flexible it is necessary to take into account the first natural modes of deformation. Experiments on rigid and flexible models led to precise results and allow consideration of full scale measurements. The final goal is to provide, by a standard ground vibration test completed by the measured characteristics of the suspension modes, the set of data necessary for flutter calculations and for the determination of all the inertia constants.

Registered nurse-performed flexible sigmoidoscopy in Ontario: Development and implementation of the curriculum and program

PubMed Central

Cooper, Mary Anne; Tinmouth, Jill Margaret; Rabeneck, Linda

2014-01-01

Although colorectal cancer is a leading cause of death in Canada, it is curable if detected in the early stages. Flexible sigmoidoscopy has been shown to reduce the incidence and mortality of colorectal cancer in patients who are at average risk for this disease and, therefore, is an appropriate screening intervention. Moreover, it may be performed by nonphysicians. A program to enable registered nurses to perform flexible sigmoidoscopy to increase colorectal cancer screening capacity in Ontario was developed. This program incorporated practical elements learned from other jurisdictions as well as specific regional considerations to fit within the health care system of Ontario. The nurses received structured didactic and simulation training before performing sigmoidoscopies on patients under physician supervision. After training, nurses were evaluated by two assessors for their ability to perform complete sigmoidoscopies safely and independently. To date, 17 nurses have achieved independence in performing flexible sigmoidoscopy at 14 sites. In total, nurses have screened >7000 Ontarians, with a cancer detection rate of 5.1 per 1000 screened, which is comparable with rates in other jurisdictions and with sigmoidoscopy performed by gastroenterologists, surgeons and other trained nonphysicians. We have shown, therefore, that with proper training and program structure, registered nurses are able to perform flexible sigmoidoscopy in a safe and thorough manner resulting in a significant increase in access to colorectal cancer screening. PMID:24416735

Flexible energy-storage devices: design consideration and recent progress.

PubMed

Wang, Xianfu; Lu, Xihong; Liu, Bin; Chen, Di; Tong, Yexiang; Shen, Guozhen

2014-07-23

Flexible energy-storage devices are attracting increasing attention as they show unique promising advantages, such as flexibility, shape diversity, light weight, and so on; these properties enable applications in portable, flexible, and even wearable electronic devices, including soft electronic products, roll-up displays, and wearable devices. Consequently, considerable effort has been made in recent years to fulfill the requirements of future flexible energy-storage devices, and much progress has been witnessed. This review describes the most recent advances in flexible energy-storage devices, including flexible lithium-ion batteries and flexible supercapacitors. The latest successful examples in flexible lithium-ion batteries and their technological innovations and challenges are reviewed first. This is followed by a detailed overview of the recent progress in flexible supercapacitors based on carbon materials and a number of composites and flexible micro-supercapacitors. Some of the latest achievements regarding interesting integrated energy-storage systems are also reviewed. Further research direction is also proposed to surpass existing technological bottle-necks and realize idealized flexible energy-storage devices. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A Flexible and Thin Graphene/Silver Nanowires/Polymer Hybrid Transparent Electrode for Optoelectronic Devices.

PubMed

Dong, Hua; Wu, Zhaoxin; Jiang, Yaqiu; Liu, Weihua; Li, Xin; Jiao, Bo; Abbas, Waseem; Hou, Xun

2016-11-16

A typical thin and fully flexible hybrid electrode was developed by integrating the encapsulation of silver nanowires (AgNWs) network between a monolayer graphene and polymer film as a sandwich structure. Compared with the reported flexible electrodes based on PET or PEN substrate, this unique electrode exhibits the superior optoelectronic characteristics (sheet resistance of 8.06 Ω/□ at 88.3% light transmittance). Meanwhile, the specific up-to-bottom fabrication process could achieve the superflat surface (RMS = 2.58 nm), superthin thickness (∼8 μm thickness), high mechanical robustness, and lightweight. In addition, the strong corrosion resistance and stability for the hybrid electrode were proved. With these advantages, we employ this electrode to fabricate the simple flexible organic light-emitting device (OLED) and perovskite solar cell device (PSC), which exhibit the considerable performance (best PCE of OLED = 2.11 cd/A 2 ; best PCE of PSC = 10.419%). All the characteristics of the unique hybrid electrode demonstrate its potential as a high-performance transparent electrode candidate for flexible optoelectronics.

NMR studies of the backbone flexibility and structure of human growth hormone: a comparison of high and low pH conformations.

PubMed

Kasimova, Marina R; Kristensen, Søren M; Howe, Peter W A; Christensen, Thorkild; Matthiesen, Finn; Petersen, Jørgen; Sørensen, Hans H; Led, Jens J

2002-05-03

(15)N NMR relaxation parameters and amide (1)H/(2)H-exchange rates have been used to characterize the structural flexibility of human growth hormone (rhGH) at neutral and acidic pH. Our results show that the rigidity of the molecule is strongly affected by the solution conditions. At pH 7.0 the backbone dynamics parameters of rhGH are uniform along the polypeptide chain and their values are similar to those of other folded proteins. In contrast, at pH 2.7 the overall backbone flexibility increases substantially compared to neutral pH and the average order parameter approaches the lower limit expected for a folded protein. However, a significant variation of the backbone dynamics through the molecule indicates that under acidic conditions the mobility of the residues becomes more dependent on their location within the secondary structure units. In particular, the order parameters of certain loop regions decrease dramatically and become comparable to those found in unfolded proteins. Furthermore, the HN-exchange rates at low pH reveal that the residues most protected from exchange are clustered at one end of the helical bundle, forming a stable nucleus. We suggest that this nucleus maintains the overall fold of the protein under destabilizing conditions. We therefore conclude that the acid state of rhGH consists of a structurally conserved, but dynamically more flexible helical core surrounded by an aura of highly mobile, unstructured loops. However, in spite of its prominent flexibility the acid state of rhGH cannot be considered a "molten globule" state because of its high stability. It appears from our work that under certain conditions, a protein can tolerate a considerable increase in flexibility of its backbone, along with an increased penetration of water into its core, while still maintaining a stable folded conformation.

Flexible solid-state supercapacitors based on three-dimensional graphene hydrogel films.

PubMed

Xu, Yuxi; Lin, Zhaoyang; Huang, Xiaoqing; Liu, Yuan; Huang, Yu; Duan, Xiangfeng

2013-05-28

Flexible solid-state supercapacitors are of considerable interest as mobile power supply for future flexible electronics. Graphene or carbon nanotubes based thin films have been used to fabricate flexible solid-state supercapacitors with high gravimetric specific capacitances (80-200 F/g), but usually with a rather low overall or areal specific capacitance (3-50 mF/cm(2)) due to the ultrasmall electrode thickness (typically a few micrometers) and ultralow mass loading, which is not desirable for practical applications. Here we report the exploration of a three-dimensional (3D) graphene hydrogel for the fabrication of high-performance solid-state flexible supercapacitors. With a highly interconnected 3D network structure, graphene hydrogel exhibits exceptional electrical conductivity and mechanical robustness to make it an excellent material for flexible energy storage devices. Our studies demonstrate that flexible supercapacitors with a 120 μm thick graphene hydrogel thin film can exhibit excellent capacitive characteristics, including a high gravimetric specific capacitance of 186 F/g (up to 196 F/g for a 42 μm thick electrode), an unprecedented areal specific capacitance of 372 mF/cm(2) (up to 402 mF/cm(2) for a 185 μm thick electrode), low leakage current (10.6 μA), excellent cycling stability, and extraordinary mechanical flexibility. This study demonstrates the exciting potential of 3D graphene macrostructures for high-performance flexible energy storage devices.

Testing the Use of Implicit Solvent in the Molecular Dynamics Modelling of DNA Flexibility

NASA Astrophysics Data System (ADS)

Mitchell, J.; Harris, S.

DNA flexibility controls packaging, looping and in some cases sequence specific protein binding. Molecular dynamics simulations carried out with a computationally efficient implicit solvent model are potentially a powerful tool for studying larger DNA molecules than can be currently simulated when water and counterions are represented explicitly. In this work we compare DNA flexibility at the base pair step level modelled using an implicit solvent model to that previously determined from explicit solvent simulations and database analysis. Although much of the sequence dependent behaviour is preserved in implicit solvent, the DNA is considerably more flexible when the approximate model is used. In addition we test the ability of the implicit solvent to model stress induced DNA disruptions by simulating a series of DNA minicircle topoisomers which vary in size and superhelical density. When compared with previously run explicit solvent simulations, we find that while the levels of DNA denaturation are similar using both computational methodologies, the specific structural form of the disruptions is different.

Model reduction for Space Station Freedom

NASA Technical Reports Server (NTRS)

Williams, Trevor

1992-01-01

Model reduction is an important practical problem in the control of flexible spacecraft, and a considerable amount of work has been carried out on this topic. Two of the best known methods developed are modal truncation and internal balancing. Modal truncation is simple to implement but can give poor results when the structure possesses clustered natural frequencies, as often occurs in practice. Balancing avoids this problem but has the disadvantages of high computational cost, possible numerical sensitivity problems, and no physical interpretation for the resulting balanced 'modes'. The purpose of this work is to examine the performance of the subsystem balancing technique developed by the investigator when tested on a realistic flexible space structure, in this case a model of the Permanently Manned Configuration (PMC) of Space Station Freedom. This method retains the desirable properties of standard balancing while overcoming the three difficulties listed above. It achieves this by first decomposing the structural model into subsystems of highly correlated modes. Each subsystem is approximately uncorrelated from all others, so balancing them separately and then combining yields comparable results to balancing the entire structure directly. The operation count reduction obtained by the new technique is considerable: a factor of roughly r(exp 2) if the system decomposes into r equal subsystems. Numerical accuracy is also improved significantly, as the matrices being operated on are of reduced dimension, and the modes of the reduced-order model now have a clear physical interpretation; they are, to first order, linear combinations of repeated-frequency modes.

Utilization Elementary Siphons of Petri Net to Solved Deadlocks in Flexible Manufacturing Systems

NASA Astrophysics Data System (ADS)

Abdul-Hussin, Mowafak Hassan

2015-07-01

This article presents an approach to the constructing a class structural analysis of Petri nets, where elementary siphons are mainly used in the development of a deadlock control policy of flexible manufacturing systems (FMSs), that has been exploited successfully for the design of supervisors of some supervisory control problems. Deadlock-free operation of FMSs is significant objectives of siphons in the Petri net. The structure analysis of Petri net models has efficiency in control of FMSs, however different policy can be implemented for the deadlock prevention. Petri nets models based deadlock prevention for FMS's has gained considerable interest in the development of control theory and methods for design, controlling, operation, and performance evaluation depending of the special class of Petri nets called S3PR. Both structural analysis and reachability tree analysis is used for the purposes analysis, simulation and control of Petri nets. In our ex-perimental approach based to siphon is able to resolve the problem of deadlock occurred to Petri nets that are illustrated with an FMS.

The applications of carbon nanomaterials in fiber-shaped energy storage devices

NASA Astrophysics Data System (ADS)

Wu, Jingxia; Hong, Yang; Wang, Bingjie

2018-01-01

As a promising candidate for future demand, fiber-shaped electrochemical energy storage devices, such as supercapacitors and lithium-ion batteries have obtained considerable attention from academy to industry. Carbon nanomaterials, such as carbon nanotube and graphene, have been widely investigated as electrode materials due to their merits of light weight, flexibility and high capacitance. In this review, recent progress of carbon nanomaterials in flexible fiber-shaped energy storage devices has been summarized in accordance with the development of fibrous electrodes, including the diversified electrode preparation, functional and intelligent device structure, and large-scale production of fibrous electrodes or devices. Project supported by the National Natural Science Foundation of China (Nos. 21634003, 21604012).

Flexible and Stretchable Physical Sensor Integrated Platforms for Wearable Human-Activity Monitoringand Personal Healthcare.

PubMed

Trung, Tran Quang; Lee, Nae-Eung

2016-06-01

Flexible and stretchable physical sensors that can measure and quantify electrical signals generated by human activities are attracting a great deal of attention as they have unique characteristics, such as ultrathinness, low modulus, light weight, high flexibility, and stretchability. These flexible and stretchable physical sensors conformally attached on the surface of organs or skin can provide a new opportunity for human-activity monitoring and personal healthcare. Consequently, in recent years there has been considerable research effort devoted to the development of flexible and stretchable physical sensors to fulfill the requirements of future technology, and much progress has been achieved. Here, the most recent developments of flexible and stretchable physical sensors are described, including temperature, pressure, and strain sensors, and flexible and stretchable sensor-integrated platforms. The latest successful examples of flexible and stretchable physical sensors for the detection of temperature, pressure, and strain, as well as their novel structures, technological innovations, and challenges, are reviewed first. In the next section, recent progress regarding sensor-integrated wearable platforms is overviewed in detail. Some of the latest achievements regarding self-powered sensor-integrated wearable platform technologies are also reviewed. Further research direction and challenges are also proposed to develop a fully sensor-integrated wearable platform for monitoring human activity and personal healthcare in the near future. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Hollow Few-Layer Graphene-Based Structures from Parafilm Waste for Flexible Transparent Supercapacitors and Oil Spill Cleanup.

PubMed

Nguyen, Duc Dung; Hsieh, Ping-Yen; Tsai, Meng-Ting; Lee, Chi-Young; Tai, Nyan-Hwa; To, Bao Dong; Vu, Duc Tu; Hsu, Chia Chen

2017-11-22

We report a versatile strategy to exploit parafilm waste as a carbon precursor for fabrication of freestanding, hollow few-layer graphene fiber mesh (HFGM) structures without use of any gaseous carriers/promoters via an annealing route. The freestanding HFGMs possess good mechanical flexibility, tailorable transparency, and high electrical conductivity, consequently qualifying them as promising electrochemical electrodes. Because of the hollow spaces, electrolyte ions can easily access into and contact with interior surfaces of the graphene fibers, accordingly increasing electrode/electrolyte interfacial area. As expected, solid-state supercapacitors based on the HFGMs exhibit a considerable enhancement in specific capacitance (20-30 fold) as compared to those employing chemical vapor deposition compact graphene films. Moreover, the parafilm waste is found to be beneficial for one-step fabrication of nanocarbon/few-layer graphene composite meshes with superior electrochemical performance, outstanding superhydrophobic property, good self-cleaning ability, and great promise for oil spill cleanup.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deng, Xiangyu; Qin, Xiangjing; Chen, Lei

Glycyl-tRNA synthetase (GlyRS) is the enzyme that covalently links glycine to cognate tRNA for translation. It is of great interest because of its nonconserved quaternary structures, unique species-specific aminoacylation properties, and noncanonical functions in neurological diseases, but none of these is fully understood. We report two crystal structures of human GlyRS variants, in the free form and in complex with tRNA Gly respectively, and reveal new aspects of the glycylation mechanism. We discover that insertion 3 differs considerably in conformation in catalysis and that it acts like a "switch" and fully opens to allow tRNA to bind in a cross-subunitmore » fashion. The flexibility of the protein is supported by molecular dynamics simulation, as well as enzymatic activity assays. The biophysical and biochemical studies suggest that human GlyRS may utilize its flexibility for both the traditional function (regulate tRNA binding) and alternative functions (roles in diseases).« less

Development and investigation of flexible polymer neural probe for chronic neural recording

NASA Astrophysics Data System (ADS)

Smith, Courtney; Song, Kyo D.; Yoon, Hargsoon; Kim, Woong-Ki; Zeng, Tao; Sanford, Larry D.

2012-04-01

Neural recording through microelectrodes requires biocompatibility and long term chronic usage. With a potential for various applications and effort to improve the performance of neural recording probes, consideration is taken to the tissue and cellular effects in these device designs. The degeneration of neurons due to brain tissue motion is an issue along with brain tissue inflammation in the insertion of the probes. To account for motion and irritation the material structure of the probes must be improved upon. This research presents the fabrication of neural probes on the microscale utilizing flexible polymers. Polyimide neural probes have been considered possibly to reduce degradation in their variability caused by brain motion. The microfabrication of the polyimide neural probe has an increased flexibility while accounting for biocompatibility and the needs for chronic use. Through microfabrication processes a needle probe is produced and tested for neural recording.

Effects of Interlocking and Supporting Conditions on Concrete Block Pavements

NASA Astrophysics Data System (ADS)

Mahapatra, Geetimukta; Kalita, Kuldeep

2018-02-01

Concrete Block Paving (CBP) is widely used as wearing course in flexible pavements, preferably under light and medium vehicular loadings. Construction of CBP at site is quick and easy in quality control. Usually, flexible pavement design philosophy is followed in CBP construction, though it is structurally different in terms of small block elements with high strength concrete and their interlocking aspects, frequent joints and discontinuity, restrained edge etc. Analytical solution for such group action of concrete blocks under loading in a three dimensional multilayer structure is complex and thus, the need of conducting experimental studies is necessitated for extensive understanding of the load—deformation characteristics and behavior of concrete blocks in pavement. The present paper focuses on the experimental studies for load transfer characteristics of CBP under different interlocking and supporting conditions. It is observed that both interlocking and supporting conditions affect significantly on the load transfer behavior in CBP structures. Coro-lock block exhibits better performance in terms of load carrying capacity and distortion behavior under static loads. Plate load tests are performed over subgrade, granular sub-base (GSB), CBP with and without GSB using different block shapes. For an example case, the comparison of CBP with conventional flexible pavement section is also presented and it is found that CBP provides considerable benefit in terms of construction cost of the road structure.

A Galerkin method for linear PDE systems in circular geometries with structural acoustic applications

NASA Technical Reports Server (NTRS)

Smith, Ralph C.

1994-01-01

A Galerkin method for systems of PDE's in circular geometries is presented with motivating problems being drawn from structural, acoustic, and structural acoustic applications. Depending upon the application under consideration, piecewise splines or Legendre polynomials are used when approximating the system dynamics with modifications included to incorporate the analytic solution decay near the coordinate singularity. This provides an efficient method which retains its accuracy throughout the circular domain without degradation at singularity. Because the problems under consideration are linear or weakly nonlinear with constant or piecewise constant coefficients, transform methods for the problems are not investigated. While the specific method is developed for the two dimensional wave equations on a circular domain and the equation of transverse motion for a thin circular plate, examples demonstrating the extension of the techniques to a fully coupled structural acoustic system are used to illustrate the flexibility of the method when approximating the dynamics of more complex systems.

Real time health monitoring and control system methodology for flexible space structures

NASA Astrophysics Data System (ADS)

Jayaram, Sanjay

This dissertation is concerned with the Near Real-time Autonomous Health Monitoring of Flexible Space Structures. The dynamics of multi-body flexible systems is uncertain due to factors such as high non-linearity, consideration of higher modal frequencies, high dimensionality, multiple inputs and outputs, operational constraints, as well as unexpected failures of sensors and/or actuators. Hence a systematic framework of developing a high fidelity, dynamic model of a flexible structural system needs to be understood. The fault detection mechanism that will be an integrated part of an autonomous health monitoring system comprises the detection of abnormalities in the sensors and/or actuators and correcting these detected faults (if possible). Applying the robust control law and the robust measures that are capable of detecting and recovering/replacing the actuators rectifies the actuator faults. The fault tolerant concept applied to the sensors will be in the form of an Extended Kalman Filter (EKF). The EKF is going to weigh the information coming from multiple sensors (redundant sensors used to measure the same information) and automatically identify the faulty sensors and weigh the best estimate from the remaining sensors. The mechanization is comprised of instrumenting flexible deployable panels (solar array) with multiple angular position and rate sensors connected to the data acquisition system. The sensors will give position and rate information of the solar panel in all three axes (i.e. roll, pitch and yaw). The position data corresponds to the steady state response and the rate data will give better insight on the transient response of the system. This is a critical factor for real-time autonomous health monitoring. MATLAB (and/or C++) software will be used for high fidelity modeling and fault tolerant mechanism.

Ethical Considerations in Research Participation Virality.

PubMed

Ellis-Barton, Carol

2016-07-01

This article seeks to commence and encourage discussion around the upcoming ethical challenges of virality in network structures. When the call for participation in a research project on lupus in Ireland went from an advertisement in a newsletter to a meme (unit of transmissible information) on a closed Facebook page, the ethical considerations of virality were raised. The article analyzes the Association of Internet Researchers guidelines, Facebook policies, and the context of privacy in relation to virality. Virality creates the leverage for methodological pluralism. The nature of the inquiry can determine the method rather than the other way around. Viral ethical considerations are evolving due to the cyber world becoming the primary meme of communication, with flexibility in the researcher's protocol providing opportunities for efficient, cost-effective, and diverse recruitment. © The Author(s) 2016.

High-Performance Flexible Transparent Electrode with an Embedded Metal Mesh Fabricated by Cost-Effective Solution Process.

PubMed

Khan, Arshad; Lee, Sangeon; Jang, Taehee; Xiong, Ze; Zhang, Cuiping; Tang, Jinyao; Guo, L Jay; Li, Wen-Di

2016-06-01

A new structure of flexible transparent electrodes is reported, featuring a metal mesh fully embedded and mechanically anchored in a flexible substrate, and a cost-effective solution-based fabrication strategy for this new transparent electrode. The embedded nature of the metal-mesh electrodes provides a series of advantages, including surface smoothness that is crucial for device fabrication, mechanical stability under high bending stress, strong adhesion to the substrate with excellent flexibility, and favorable resistance against moisture, oxygen, and chemicals. The novel fabrication process replaces vacuum-based metal deposition with an electrodeposition process and is potentially suitable for high-throughput, large-volume, and low-cost production. In particular, this strategy enables fabrication of a high-aspect-ratio (thickness to linewidth) metal mesh, substantially improving conductivity without considerably sacrificing transparency. Various prototype flexible transparent electrodes are demonstrated with transmittance higher than 90% and sheet resistance below 1 ohm sq(-1) , as well as extremely high figures of merit up to 1.5 × 10(4) , which are among the highest reported values in recent studies. Finally using our embedded metal-mesh electrode, a flexible transparent thin-film heater is demonstrated with a low power density requirement, rapid response time, and a low operating voltage. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Transparent Large-Area MoS2 Phototransistors with Inkjet-Printed Components on Flexible Platforms.

PubMed

Kim, Tae-Young; Ha, Jewook; Cho, Kyungjune; Pak, Jinsu; Seo, Jiseok; Park, Jongjang; Kim, Jae-Keun; Chung, Seungjun; Hong, Yongtaek; Lee, Takhee

2017-10-24

Two-dimensional (2D) transition-metal dichalcogenides (TMDCs) have gained considerable attention as an emerging semiconductor due to their promising atomically thin film characteristics with good field-effect mobility and a tunable band gap energy. However, their electronic applications have been generally realized with conventional inorganic electrodes and dielectrics implemented using conventional photolithography or transferring processes that are not compatible with large-area and flexible device applications. To facilitate the advantages of 2D TMDCs in practical applications, strategies for realizing flexible and transparent 2D electronics using low-temperature, large-area, and low-cost processes should be developed. Motivated by this challenge, we report fully printed transparent chemical vapor deposition (CVD)-synthesized monolayer molybdenum disulfide (MoS 2 ) phototransistor arrays on flexible polymer substrates. All the electronic components, including dielectric and electrodes, were directly deposited with mechanically tolerable organic materials by inkjet-printing technology onto transferred monolayer MoS 2 , and their annealing temperature of <180 °C allows the direct fabrication on commercial flexible substrates without additional assisted-structures. By integrating the soft organic components with ultrathin MoS 2 , the fully printed MoS 2 phototransistors exhibit excellent transparency and mechanically stable operation.

Graphene paper supported MoS2 nanocrystals monolayer with Cu submicron-buds: High-performance flexible platform for sensing in sweat.

PubMed

Wang, Zhengyun; Dong, Shuang; Gui, Mengxi; Asif, Muhammad; Wang, Wei; Wang, Feng; Liu, Hongfang

2018-02-15

Flexible sweat biosensors are of considerable current interest for the development of wearable smart miniature devices. In this work, we report a novel type of flexible and electrochemical sweat platform fabricated by depositing Cu submicron buds on freestanding graphene paper (GP) carrying MoS 2 nanocrystals monolayer for bio-functional detection of glucose and lactate. Quantitative analysis of glucose and lactate was carried out by using amperometric i-t method. Linear ranges were obtained between 5 and 1775 μM for glucose and 0.01-18.4 mM for lactate, and their corresponding limits of detection were 500 nM and 0.1 μM, respectively. The platform demonstrates fast response, good selectivity, superb reproducibility and outstanding flexibility, which enable its use for monitoring glucose and lactate in human perspiration. The strategy of structurally integrating 3D transition metal, 0D transition metal sulfide and 2D graphene will provide new insight into the design of flexible electrodes for sweat glucose and lactate monitoring and a wider range of applications in biosensing, bioelectronics, and lab-on-a-chip devices. Copyright © 2017. Published by Elsevier Inc.

Altering DNA-Programmable Colloidal Crystallization Paths by Modulating Particle Repulsion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Mary X.; Brodin, Jeffrey D.; Millan, Jaime A.

Colloidal crystal engineering with DNA can be used to realize precise control over nanoparticle (NP) arrangement. Here, we investigate a case of DNA-based assembly where the properties of DNA as a polyelectrolyte brush are employed to alter a hybridization-driven NP crystallization pathway. Using the co-assembly of DNA-conjugated proteins and spherical gold 2 nanoparticles (AuNPs) as a model system, we explore how steric repulsion between non-complementary, neighboring DNA-NPs due to overlapping DNA shells can influence their ligand-directed behavior. Specifically, our experimental data coupled with coarse-grained molecular dynamics (MD) simulations reveal that by changing factors related to NP repulsion, two structurally distinctmore » outcomes can be achieved. When steric repulsion between DNA-AuNPs is significantly greater than that between DNA-proteins, a lower packing density crystal lattice is favored over the structure that is predicted by design rules based on DNA-hybridization considerations alone. This is enabled by the large difference in DNA density on AuNPs versus proteins and can be tuned by modulating the flexibility, and thus conformational entropy, of the DNA on the constituent particles. At intermediate ligand flexibility, the crystallization pathways are energetically similar and the structural outcome can be adjusted using the density of DNA duplexes on DNA-AuNPs and by screening the Coulomb potential between them. Such lattices are shown to undergo dynamic reorganization upon changing salt concentration. These data help elucidate the structural considerations necessary for understanding repulsive forces in DNA-assembly and lay the groundwork for using them to increase architectural diversity in engineering colloidal crystals.« less

Structural and parameteric uncertainty quantification in cloud microphysics parameterization schemes

NASA Astrophysics Data System (ADS)

van Lier-Walqui, M.; Morrison, H.; Kumjian, M. R.; Prat, O. P.; Martinkus, C.

2017-12-01

Atmospheric model parameterization schemes employ approximations to represent the effects of unresolved processes. These approximations are a source of error in forecasts, caused in part by considerable uncertainty about the optimal value of parameters within each scheme -- parameteric uncertainty. Furthermore, there is uncertainty regarding the best choice of the overarching structure of the parameterization scheme -- structrual uncertainty. Parameter estimation can constrain the first, but may struggle with the second because structural choices are typically discrete. We address this problem in the context of cloud microphysics parameterization schemes by creating a flexible framework wherein structural and parametric uncertainties can be simultaneously constrained. Our scheme makes no assuptions about drop size distribution shape or the functional form of parametrized process rate terms. Instead, these uncertainties are constrained by observations using a Markov Chain Monte Carlo sampler within a Bayesian inference framework. Our scheme, the Bayesian Observationally-constrained Statistical-physical Scheme (BOSS), has flexibility to predict various sets of prognostic drop size distribution moments as well as varying complexity of process rate formulations. We compare idealized probabilistic forecasts from versions of BOSS with varying levels of structural complexity. This work has applications in ensemble forecasts with model physics uncertainty, data assimilation, and cloud microphysics process studies.

Fluid-structure analysis of a flexible flapping airfoil at low Reynolds number flow

NASA Astrophysics Data System (ADS)

Unger, Ralf; Haupt, Matthias C.; Horst, Peter; Radespiel, Rolf

2012-01-01

In this paper, a coupling simulation methodology is applied to investigate the fluid flow around a light and flexible airfoil based on a handfoil of a seagull. A finite element model of the flexible airfoil is fully coupled to the flow solver by using a load and displacement transfer as well as a fluid grid deformation algorithm. The flow field is characterized by a laminar-turbulent transition at a Reynolds number of Re=100 000, which takes place along a laminar separation bubble. An unsteady Reynolds-averaged Navier-Stokes flow solver is used to take this transition process into account by comparison of a critical N-factor with the N-factor computed by the eN-method. Results of computations have shown that the flexibility of the airfoil has a major influence on the thrust efficiency, the mean drag and lift, and the location of laminar-turbulent transition. The thrust efficiency can be considerably improved by increasing the plunging amplitude and by using a time dependent airfoil stiffness, inspired by the muscle contraction of birds.

Modeling, design, and control of flexible manipulator arms: Status and trends

NASA Technical Reports Server (NTRS)

Book, Wayne J.

1989-01-01

The desire for higher performance manipulators has lead to dynamic behavior in which the flexibility is an essential aspect. The mathematical representations commonly used in modeling flexible arms and arms with flexible drives are examined first. Then design considerations directly arising from the flexible nature of the arm are discussed. Finally, controls of joints for general and tip motion are discussed.

An integrated modeling and design tool for advanced optical spacecraft

NASA Technical Reports Server (NTRS)

Briggs, Hugh C.

1992-01-01

Consideration is given to the design and status of the Integrated Modeling of Optical Systems (IMOS) tool and to critical design issues. A multidisciplinary spacecraft design and analysis tool with support for structural dynamics, controls, thermal analysis, and optics, IMOS provides rapid and accurate end-to-end performance analysis, simulations, and optimization of advanced space-based optical systems. The requirements for IMOS-supported numerical arrays, user defined data structures, and a hierarchical data base are outlined, and initial experience with the tool is summarized. A simulation of a flexible telescope illustrates the integrated nature of the tools.

Vertical group III-V nanowires on si, heterostructures, flexible arrays and fabrication

DOEpatents

Wang, Deli; Soci, Cesare; Bao, Xinyu; Wei, Wei; Jing, Yi; Sun, Ke

2015-01-13

Embodiments of the invention provide a method for direct heteroepitaxial growth of vertical III-V semiconductor nanowires on a silicon substrate. The silicon substrate is etched to substantially completely remove native oxide. It is promptly placed in a reaction chamber. The substrate is heated and maintained at a growth temperature. Group III-V precursors are flowed for a growth time. Preferred embodiment vertical Group III-V nanowires on silicon have a core-shell structure, which provides a radial homojunction or heterojunction. A doped nanowire core is surrounded by a shell with complementary doping. Such can provide high optical absorption due to the long optical path in the axial direction of the vertical nanowires, while reducing considerably the distance over which carriers must diffuse before being collected in the radial direction. Alloy composition can also be varied. Radial and axial homojunctions and heterojunctions can be realized. Embodiments provide for flexible Group III-V nanowire structures. An array of Group III-V nanowire structures is embedded in polymer. A fabrication method forms the vertical nanowires on a substrate, e.g., a silicon substrate. Preferably, the nanowires are formed by the preferred methods for fabrication of Group III-V nanowires on silicon. Devices can be formed with core/shell and core/multi-shell nanowires and the devices are released from the substrate upon which the nanowires were formed to create a flexible structure that includes an array of vertical nanowires embedded in polymer.

Active control of flexible structures using a fuzzy logic algorithm

NASA Astrophysics Data System (ADS)

Cohen, Kelly; Weller, Tanchum; Ben-Asher, Joseph Z.

2002-08-01

This study deals with the development and application of an active control law for the vibration suppression of beam-like flexible structures experiencing transient disturbances. Collocated pairs of sensors/actuators provide active control of the structure. A design methodology for the closed-loop control algorithm based on fuzzy logic is proposed. First, the behavior of the open-loop system is observed. Then, the number and locations of collocated actuator/sensor pairs are selected. The proposed control law, which is based on the principles of passivity, commands the actuator to emulate the behavior of a dynamic vibration absorber. The absorber is tuned to a targeted frequency, whereas the damping coefficient of the dashpot is varied in a closed loop using a fuzzy logic based algorithm. This approach not only ensures inherent stability associated with passive absorbers, but also circumvents the phenomenon of modal spillover. The developed controller is applied to the AFWAL/FIB 10 bar truss. Simulated results using MATLAB© show that the closed-loop system exhibits fairly quick settling times and desirable performance, as well as robustness characteristics. To demonstrate the robustness of the control system to changes in the temporal dynamics of the flexible structure, the transient response to a considerably perturbed plant is simulated. The modal frequencies of the 10 bar truss were raised as well as lowered substantially, thereby significantly perturbing the natural frequencies of vibration. For these cases, too, the developed control law provides adequate settling times and rates of vibrational energy dissipation.

5 CFR 2472.4 - Content of request.

Code of Federal Regulations, 2010 CFR

2010-01-01

... AGENCY DETERMINATIONS NOT TO ESTABLISH OR TO TERMINATE FLEXIBLE OR COMPRESSED WORK SCHEDULES Procedures... bargaining agreement between the parties and any other agreements concerning flexible and compressed work... consideration of an impasse arising from an agency determination not to establish or to terminate a flexible or...

Aeroelastic Modeling of Elastically Shaped Aircraft Concept via Wing Shaping Control for Drag Reduction

NASA Technical Reports Server (NTRS)

Nguyen, Nhan; James Urnes, Sr.

2012-01-01

Lightweight aircraft design has received a considerable attention in recent years as a means for improving cruise efficiency. Reducing aircraft weight results in lower lift requirements which directly translate into lower drag, hence reduced engine thrust requirements during cruise. The use of lightweight materials such as advanced composite materials has been adopted by airframe manufacturers in current and future aircraft. Modern lightweight materials can provide less structural rigidity while maintaining load-carrying capacity. As structural flexibility increases, aeroelastic interactions with aerodynamic forces and moments become an increasingly important consideration in aircraft design and aerodynamic performance. Furthermore, aeroelastic interactions with flight dynamics can result in issues with vehicle stability and control. Abstract This paper describes a recent aeroelastic modeling effort for an elastically shaped aircraft concept (ESAC). The aircraft model is based on the rigid-body generic transport model (GTM) originally developed at NASA Langley Research Center. The ESAC distinguishes itself from the GTM in that it is equipped with highly flexible wing structures as a weight reduction design feature. More significantly, the wings are outfitted with a novel control effector concept called variable camber continuous trailing edge (VCCTE) flap system for active control of wing aeroelastic deflections to optimize the local angle of attack of wing sections for improved aerodynamic efficiency through cruise drag reduction and lift enhancement during take-off and landing. The VCCTE flap is a multi-functional and aerodynamically efficient device capable of achieving high lift-to-drag ratios. The flap system is comprised of three chordwise segments that form the variable camber feature of the flap and multiple spanwise segments that form a piecewise continuous trailing edge. By configuring the flap camber and trailing edge shape, drag reduction could be achieved. Moreover, some parts of the flap system can be made to have a high frequency response for roll control, gust load alleviation, and aeroservoelastic (ASE) modal suppression control. Abstract The aeroelastic model of the ESAC is based on one-dimensional structural dynamic theory that captures the aeroelastic deformation of a wing structure in a combined motion that involves flapwise bending, chordwise bending, and torsion. The model includes the effect of aircraft propulsion due to wing flexibility which causes the propulsive forces and moments to couple with the wing elastic motion. Engine mass is also accounted in the model. A fuel management model is developed to describe the wing mass change due to fuel usage in the main tank and wing tanks during cruise. Abstract The model computes both static and dynamic responses of the wing structures. The static aeroelastic deflections are used to estimate the effect of wing flexibility on induced drag and the potential drag reduction by the VCCTE flap system. A flutter analysis is conducted to estimate the flutter speed boundary. Gust load alleviation via adaptive control has been recently investigated to address flexibility of aircraft structures. A multi-objective flight control approach is presented for drag reduction control. The approach is based on an optimal control framework using a multi-objective cost function. Future studies will demonstrate the potential benefits of the approach.

Large Conformational Changes of Insertion 3 in Human Glycyl-tRNA Synthetase (hGlyRS) during Catalysis

DOE PAGES

Deng, Xiangyu; Qin, Xiangjing; Chen, Lei; ...

2016-01-21

Glycyl-tRNA synthetase (GlyRS) is the enzyme that covalently links glycine to cognate tRNA for translation. It is of great interest because of its nonconserved quaternary structures, unique species-specific aminoacylation properties, and noncanonical functions in neurological diseases, but none of these is fully understood. We report two crystal structures of human GlyRS variants, in the free form and in complex with tRNA Gly respectively, and reveal new aspects of the glycylation mechanism. We discover that insertion 3 differs considerably in conformation in catalysis and that it acts like a "switch" and fully opens to allow tRNA to bind in a cross-subunitmore » fashion. The flexibility of the protein is supported by molecular dynamics simulation, as well as enzymatic activity assays. The biophysical and biochemical studies suggest that human GlyRS may utilize its flexibility for both the traditional function (regulate tRNA binding) and alternative functions (roles in diseases).« less

Stereochemistry Balances Cell Permeability and Solubility in the Naturally Derived Phepropeptin Cyclic Peptides.

PubMed

Schwochert, Joshua; Lao, Yongtong; Pye, Cameron R; Naylor, Matthew R; Desai, Prashant V; Gonzalez Valcarcel, Isabel C; Barrett, Jaclyn A; Sawada, Geri; Blanco, Maria-Jesus; Lokey, R Scott

2016-08-11

Cyclic peptide (CP) natural products provide useful model systems for mapping "beyond-Rule-of-5" (bRo5) space. We identified the phepropeptins as natural product CPs with potential cell permeability. Synthesis of the phepropeptins and epimeric analogues revealed much more rapid cellular permeability for the natural stereochemical pattern. Despite being more cell permeable, the natural compounds exhibited similar aqueous solubility as the corresponding epimers, a phenomenon explained by solvent-dependent conformational flexibility among the natural compounds. When analyzing the polarity of the solution structures we found that neither the number of hydrogen bonds nor the total polar surface area accurately represents the solvation energies of the high and low dielectric conformations. This work adds to a growing number of natural CPs whose solvent-dependent conformational behavior allows for a balance between aqueous solubility and cell permeability, highlighting structural flexibility as an important consideration in the design of molecules in bRo5 chemical space.

Overall Water Splitting with Room-Temperature Synthesized NiFe Oxyfluoride Nanoporous Films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liang, Kun; Guo, Limin; Marcus, Kyle

Freestanding and lightweight thin-films were rationally designed to serve as robust electrodes for renewable energy applications. A facile and scalable nanomanufacturing process was developed to fabricate these transformative thin-film electrodes (iron group mixed oxides) that exhibit a nanoporous structure and controllable composition. More specifically, electrodeposition and anodic treatments were employed to produce freestanding and lightweight metal oxides nanoporous layers (NPL). These NPL can be directly used as flexible and additive-free electrodes for renewable energy generation (water splitting) and storage (supercapacitor) applications without requiring binders and current collector and other additives. Significantly enhanced electrochemical performance was achieved due to the uniquemore » merits of the NPL: i) highly porous structure considerably increases the electrode/electrolyte interface, which facilitate electrochemical reactions; ii) NPL substantially increase the number of active sites that are favorable in electrochemical reactions; iii) residual metal network within the NPL forms a conductive framework, drastically improving electrode strength, flexibility and conductivity.« less

Hyperexpandable, self-healing macromolecular crystals with integrated polymer networks.

PubMed

Zhang, Ling; Bailey, Jake B; Subramanian, Rohit H; Tezcan, F Akif

2018-05-01

The formation of condensed matter typically involves a trade-off between structural order and flexibility. As the extent and directionality of interactions between atomic or molecular components increase, materials generally become more ordered but less compliant, and vice versa. Nevertheless, high levels of structural order and flexibility are not necessarily mutually exclusive; there are many biological (such as microtubules 1,2 , flagella 3 , viruses 4,5 ) and synthetic assemblies (for example, dynamic molecular crystals 6-9 and frameworks 10-13 ) that can undergo considerable structural transformations without losing their crystalline order and that have remarkable mechanical properties 8,14,15 that are useful in diverse applications, such as selective sorption 16 , separation 17 , sensing 18 and mechanoactuation 19 . However, the extent of structural changes and the elasticity of such flexible crystals are constrained by the necessity to maintain a continuous network of bonding interactions between the constituents of the lattice. Consequently, even the most dynamic porous materials tend to be brittle and isolated as microcrystalline powders 14 , whereas flexible organic or inorganic molecular crystals cannot expand without fracturing. Owing to their rigidity, crystalline materials rarely display self-healing behaviour 20 . Here we report that macromolecular ferritin crystals with integrated hydrogel polymers can isotropically expand to 180 per cent of their original dimensions and more than 500 per cent of their original volume while retaining periodic order and faceted Wulff morphologies. Even after the separation of neighbouring ferritin molecules by 50 ångströms upon lattice expansion, specific molecular contacts between them can be reformed upon lattice contraction, resulting in the recovery of atomic-level periodicity and the highest-resolution ferritin structure reported so far. Dynamic bonding interactions between the hydrogel network and the ferritin molecules endow the crystals with the ability to resist fragmentation and self-heal efficiently, whereas the chemical tailorability of the ferritin molecules enables the creation of chemically and mechanically differentiated domains within single crystals.

Conformational Heterogeneity of Unbound Proteins Enhances Recognition in Protein-Protein Encounters.

PubMed

Pallara, Chiara; Rueda, Manuel; Abagyan, Ruben; Fernández-Recio, Juan

2016-07-12

To understand cellular processes at the molecular level we need to improve our knowledge of protein-protein interactions, from a structural, mechanistic, and energetic point of view. Current theoretical studies and computational docking simulations show that protein dynamics plays a key role in protein association and support the need for including protein flexibility in modeling protein interactions. Assuming the conformational selection binding mechanism, in which the unbound state can sample bound conformers, one possible strategy to include flexibility in docking predictions would be the use of conformational ensembles originated from unbound protein structures. Here we present an exhaustive computational study about the use of precomputed unbound ensembles in the context of protein docking, performed on a set of 124 cases of the Protein-Protein Docking Benchmark 3.0. Conformational ensembles were generated by conformational optimization and refinement with MODELLER and by short molecular dynamics trajectories with AMBER. We identified those conformers providing optimal binding and investigated the role of protein conformational heterogeneity in protein-protein recognition. Our results show that a restricted conformational refinement can generate conformers with better binding properties and improve docking encounters in medium-flexible cases. For more flexible cases, a more extended conformational sampling based on Normal Mode Analysis was proven helpful. We found that successful conformers provide better energetic complementarity to the docking partners, which is compatible with recent views of binding association. In addition to the mechanistic considerations, these findings could be exploited for practical docking predictions of improved efficiency.

Unraveling the meaning of chemical shifts in protein NMR.

PubMed

Berjanskii, Mark V; Wishart, David S

2017-11-01

Chemical shifts are among the most informative parameters in protein NMR. They provide wealth of information about protein secondary and tertiary structure, protein flexibility, and protein-ligand binding. In this report, we review the progress in interpreting and utilizing protein chemical shifts that has occurred over the past 25years, with a particular focus on the large body of work arising from our group and other Canadian NMR laboratories. More specifically, this review focuses on describing, assessing, and providing some historical context for various chemical shift-based methods to: (1) determine protein secondary and super-secondary structure; (2) derive protein torsion angles; (3) assess protein flexibility; (4) predict residue accessible surface area; (5) refine 3D protein structures; (6) determine 3D protein structures and (7) characterize intrinsically disordered proteins. This review also briefly covers some of the methods that we previously developed to predict chemical shifts from 3D protein structures and/or protein sequence data. It is hoped that this review will help to increase awareness of the considerable utility of NMR chemical shifts in structural biology and facilitate more widespread adoption of chemical-shift based methods by the NMR spectroscopists, structural biologists, protein biophysicists, and biochemists worldwide. This article is part of a Special Issue entitled: Biophysics in Canada, edited by Lewis Kay, John Baenziger, Albert Berghuis and Peter Tieleman. Copyright © 2017 Elsevier B.V. All rights reserved.

Flexible Ablators: Applications and Arcjet Testing

NASA Technical Reports Server (NTRS)

Arnold, James O.; Venkatapathy, Ethiraj; Beck, Robin A S.; Mcguire, Kathy; Prabhu, Dinesh K.; Gorbunov, Sergey

2011-01-01

Flexible ablators were conceived in 2009 to meet the technology pull for large, human Mars Exploration Class, 23 m diameter hypersonic inflatable aerodynamic decelerators. As described elsewhere, they have been recently undergoing initial technical readiness (TRL) advancement by NASA. The performance limits of flexible ablators in terms of maximum heat rates, pressure and shear remain to be defined. Further, it is hoped that this emerging technology will vastly expand the capability of future NASA missions involving atmospheric entry systems. This paper considers four topics of relevance to flexible ablators: (1) Their potential applications to near/far term human and robotic missions (2) Brief consideration of the balance between heat shield diameter, flexible ablator performance limits, entry vehicle controllability and aft-body shear layer impingement of interest to designers of very large entry vehicles, (3) The approach for developing bonding processes of flexible ablators for use on rigid entry bodies and (4) Design of large arcjet test articles that will enable the testing of flexible ablators in flight-like, combined environments (heat flux, pressure, shear and structural tensile loading). Based on a review of thermal protection system performance requirements for future entry vehicles, it is concluded that flexible ablators have broad applications to conventional, rigid entry body systems and are enabling to large deployable (both inflatable and mechanical) heat shields. Because of the game-changing nature of flexible ablators, it appears that NASA's Office of the Chief Technologist (OCT) will fund a focused, 3-year TRL advancement of the new materials capable of performance in heat fluxes in the range of 200-600 W/sq. cm. This support will enable the manufacture and use of the large-scale arcjet test designs that will be a key element of this OCT funded activity.

Efficient Construction of Free Energy Profiles of Breathing Metal–Organic Frameworks Using Advanced Molecular Dynamics Simulations

PubMed Central

2017-01-01

In order to reliably predict and understand the breathing behavior of highly flexible metal–organic frameworks from thermodynamic considerations, an accurate estimation of the free energy difference between their different metastable states is a prerequisite. Herein, a variety of free energy estimation methods are thoroughly tested for their ability to construct the free energy profile as a function of the unit cell volume of MIL-53(Al). The methods comprise free energy perturbation, thermodynamic integration, umbrella sampling, metadynamics, and variationally enhanced sampling. A series of molecular dynamics simulations have been performed in the frame of each of the five methods to describe structural transformations in flexible materials with the volume as the collective variable, which offers a unique opportunity to assess their computational efficiency. Subsequently, the most efficient method, umbrella sampling, is used to construct an accurate free energy profile at different temperatures for MIL-53(Al) from first principles at the PBE+D3(BJ) level of theory. This study yields insight into the importance of the different aspects such as entropy contributions and anharmonic contributions on the resulting free energy profile. As such, this thorough study provides unparalleled insight in the thermodynamics of the large structural deformations of flexible materials. PMID:29131647

Efficient Construction of Free Energy Profiles of Breathing Metal-Organic Frameworks Using Advanced Molecular Dynamics Simulations.

PubMed

Demuynck, Ruben; Rogge, Sven M J; Vanduyfhuys, Louis; Wieme, Jelle; Waroquier, Michel; Van Speybroeck, Veronique

2017-12-12

In order to reliably predict and understand the breathing behavior of highly flexible metal-organic frameworks from thermodynamic considerations, an accurate estimation of the free energy difference between their different metastable states is a prerequisite. Herein, a variety of free energy estimation methods are thoroughly tested for their ability to construct the free energy profile as a function of the unit cell volume of MIL-53(Al). The methods comprise free energy perturbation, thermodynamic integration, umbrella sampling, metadynamics, and variationally enhanced sampling. A series of molecular dynamics simulations have been performed in the frame of each of the five methods to describe structural transformations in flexible materials with the volume as the collective variable, which offers a unique opportunity to assess their computational efficiency. Subsequently, the most efficient method, umbrella sampling, is used to construct an accurate free energy profile at different temperatures for MIL-53(Al) from first principles at the PBE+D3(BJ) level of theory. This study yields insight into the importance of the different aspects such as entropy contributions and anharmonic contributions on the resulting free energy profile. As such, this thorough study provides unparalleled insight in the thermodynamics of the large structural deformations of flexible materials.

A glycoconjugate of Haemophilus influenzae Type b capsular polysaccharide with tetanus toxoid protein: hydrodynamic properties mainly influenced by the carbohydrate.

PubMed

Abdelhameed, Ali Saber; Adams, Gary G; Morris, Gordon A; Almutairi, Fahad M; Duvivier, Pierre; Conrath, Karel; Harding, Stephen E

2016-02-26

Three important physical properties which may affect the performance of glycoconjugate vaccines against serious disease are molar mass (molecular weight), heterogeneity (polydispersity), and conformational flexibility in solution. The dilute solution behaviour of native and activated capsular polyribosylribitol (PRP) polysaccharides extracted from Haemophilus influenzae type b (Hib), and the corresponding glycoconjugate made by conjugating this with the tetanus toxoid (TT) protein have been characterized and compared using a combination of sedimentation equilibrium and sedimentation velocity in the analytical ultracentrifuge with viscometry. The weight average molar mass of the activated material was considerably reduced (Mw ~ 0.24 × 10(6) g.mol(-1)) compared to the native (Mw ~ 1.2 × 10(6) g.mol(-1)). Conjugation with the TT protein yielded large polydisperse structures (of Mw ~ 7.4 × 10(6) g.mol(-1)), but which retained the high degree of flexibility of the native and activated polysaccharide, with frictional ratio, intrinsic viscosity, sedimentation conformation zoning behaviour and persistence length all commensurate with highly flexible coil behaviour and unlike the previously characterised tetanus toxoid protein (slightly extended and hydrodynamically compact structure with an aspect ratio of ~3). This non-protein like behaviour clearly indicates that it is the carbohydrate component which mainly influences the physical behaviour of the glycoconjugate in solution.

Galactokinase promiscuity: a question of flexibility?

PubMed

McAuley, Megan; Kristiansson, Helena; Huang, Meilan; Pey, Angel L; Timson, David J

2016-02-01

Galactokinase catalyses the first committed step of the Leloir pathway, i.e. the ATP-dependent phosphorylation of α-D-galactose at C1-OH. Reduced galactokinase activity results in the inherited metabolic disease type II galactosaemia. However, inhibition of galactokinase is considered a viable approach to treating more severe forms of galactosaemia (types I and III). Considerable progress has been made in the identification of high affinity, selective inhibitors. Although the structure of galactokinase from a variety of species is known, its catalytic mechanism remains uncertain. Although the bulk of evidence suggests that the reaction proceeds via an active site base mechanism, some experimental and theoretical studies contradict this. The enzyme has potential as a biocatalyst in the production of sugar 1-phosphates. This potential is limited by its high specificity. A variety of approaches have been taken to identify galactokinase variants which are more promiscuous. These have broadened galactokinase's specificity to include a wide range of D- and L-sugars. Initial studies suggest that some of these alterations result in increased flexibility at the active site. It is suggested that modulation of protein flexibility is at least as important as structural modifications in determining the success or failure of enzyme engineering. © 2016 Authors; published by Portland Press Limited.

Cost characteristics of hospitals.

PubMed

Smet, Mike

2002-09-01

Modern hospitals are complex multi-product organisations. The analysis of a hospital's production and/or cost structure should therefore use the appropriate techniques. Flexible functional forms based on the neo-classical theory of the firm seem to be most suitable. Using neo-classical cost functions implicitly assumes minimisation of (variable) costs given that input prices and outputs are exogenous. Local and global properties of flexible functional forms and short-run versus long-run equilibrium are further issues that require thorough investigation. In order to put the results based on econometric estimations of cost functions in the right perspective, it is important to keep these considerations in mind when using flexible functional forms. The more recent studies seem to agree that hospitals generally do not operate in their long-run equilibrium (they tend to over-invest in capital (capacity and equipment)) and that it is therefore appropriate to estimate a short-run variable cost function. However, few studies explicitly take into account the implicit assumptions and restrictions embedded in the models they use. An alternative method to explain differences in costs uses management accounting techniques to identify the cost drivers of overhead costs. Related issues such as cost-shifting and cost-adjusting behaviour of hospitals and the influence of market structure on competition, prices and costs are also discussed shortly.

Stability region maximization by decomposition-aggregation method. [Skylab stability

NASA Technical Reports Server (NTRS)

Siljak, D. D.; Cuk, S. M.

1974-01-01

This work is to improve the estimates of the stability regions by formulating and resolving a proper maximization problem. The solution of the problem provides the best estimate of the maximal value of the structural parameter and at the same time yields the optimum comparison system, which can be used to determine the degree of stability of the Skylab. The analysis procedure is completely computerized, resulting in a flexible and powerful tool for stability considerations of large-scale linear as well as nonlinear systems.

Structure and photoluminescence of a benzil nanocolumn in a C-methylcalix[4]resorcinarene-based framework.

PubMed

Ma, Bao-Qing; Vieira Ferreira, Luis F; Coppens, Philip

2004-04-01

A new framework based on C-methylcalix[4]resorcinarene and the flexible nonconjugated spacer 1,4-bis(imidazol-1yl-methyl)benzene encloses a large one-dimensional channel, containing benzil nanocolumns. Unlike in a previously reported series of benzil-containing supramolecular solids with conjugated linker molecules, benzil luminescence is observed, but the lifetime of 580 ns at 77 K is considerably shorter than the 145 micros reported for neat benzil at room temperature.

Damage Considerations of a Flexible Micro Air Vehicle Wing Using 3-D Laser Vibrometry

DTIC Science & Technology

2007-06-01

AIR VEHICLE WING USING 3-D LASER VIBROMETRY THESIS Leo L. Mendoza Jr., ENS, USN AFIT/GAE/ENY/07-J13 DEPARTMENT OF THE AIR FORCE AIR ...3-D LASER VIBROMETRY THESIS Presented to the Faculty Department of Aeronautical and Astronautical Engineering Air Force...DISTRIBUTION UNLIMITED AFIT/GAE/ENY/07-J13 DAMAGE CONSIDERATIONS OF A FLEXIBLE MICRO AIR VEHICLE WING USING 3-D LASER VIBROMETRY

Stability and control of flexible satellites. II - Control

NASA Technical Reports Server (NTRS)

Huang, T. C.; Das, A.

1980-01-01

It is demonstrated that by monitoring the deformations of the flexible elements of a satellite, the effectiveness of the satellite control system can be increased considerably. A simple model of a flexible satellite was analyzed in the first part of this work. The same model is used here for digital computer simulations.

5 CFR 2472.3 - Request for Panel consideration.

Code of Federal Regulations, 2010 CFR

2010-01-01

... ARISING PURSUANT TO AGENCY DETERMINATIONS NOT TO ESTABLISH OR TO TERMINATE FLEXIBLE OR COMPRESSED WORK... establish or to terminate a flexible or compressed work schedule by filing a request as hereinafter provided...

Integrated design of the CSI evolutionary structure: A verification of the design methodology

NASA Technical Reports Server (NTRS)

Maghami, Peiman G.; Joshi, S. M.; Elliott, Kenny B.; Walz, J. E.

1993-01-01

One of the main objectives of the Controls-Structures Interaction (CSI) program is to develop and evaluate integrated controls-structures design methodology for flexible space structures. Thus far, integrated design methodologies for a class of flexible spacecraft, which require fine attitude pointing and vibration suppression with no payload articulation, have been extensively investigated. Various integrated design optimization approaches, such as single-objective optimization, and multi-objective optimization, have been implemented with an array of different objectives and constraints involving performance and cost measures such as total mass, actuator mass, steady-state pointing performance, transient performance, control power, and many more. These studies have been performed using an integrated design software tool (CSI-DESIGN CODE) which is under development by the CSI-ADM team at the NASA Langley Research Center. To date, all of these studies, irrespective of the type of integrated optimization posed or objectives and constraints used, have indicated that integrated controls-structures design results in an overall spacecraft design which is considerably superior to designs obtained through a conventional sequential approach. Consequently, it is believed that validation of some of these results through fabrication and testing of a structure which is designed through an integrated design approach is warranted. The objective of this paper is to present and discuss the efforts that have been taken thus far for the validation of the integrated design methodology.

Robust adaptive vibration control of a flexible structure.

PubMed

Khoshnood, A M; Moradi, H M

2014-07-01

Different types of L1 adaptive control systems show that using robust theories with adaptive control approaches has produced high performance controllers. In this study, a model reference adaptive control scheme considering robust theories is used to propose a practical control system for vibration suppression of a flexible launch vehicle (FLV). In this method, control input of the system is shaped from the dynamic model of the vehicle and components of the control input are adaptively constructed by estimating the undesirable vibration frequencies. Robust stability of the adaptive vibration control system is guaranteed by using the L1 small gain theorem. Simulation results of the robust adaptive vibration control strategy confirm that the effects of vibration on the vehicle performance considerably decrease without the loss of the phase margin of the system. Copyright © 2014 ISA. Published by Elsevier Ltd. All rights reserved.

Measurement of Residual Flexibility for Substructures Having Prominent Flexible Interfaces

NASA Technical Reports Server (NTRS)

Tinker, Michael L.; Bookout, Paul S.

1994-01-01

Verification of a dynamic model of a constrained structure requires a modal survey test of the physical structure and subsequent modification of the model to obtain the best agreement possible with test data. Constrained-boundary or fixed-base testing has historically been the most common approach for verifying constrained mathematical models, since the boundary conditions of the test article are designed to match the actual constraints in service. However, there are difficulties involved with fixed-base testing, in some cases making the approach impractical. It is not possible to conduct a truly fixed-base test due to coupling between the test article and the fixture. In addition, it is often difficult to accurately simulate the actual boundary constraints, and the cost of designing and constructing the fixture may be prohibitive. For use when fixed-base testing proves impractical or undesirable, alternate free-boundary test methods have been investigated, including the residual flexibility technique. The residual flexibility approach has been treated analytically in considerable detail and has had limited frequency response measurements for the method. This concern is well-justified for a number of reasons. First, residual flexibilities are very small numbers, typically on the order of 1.0E-6 in/lb for translational diagonal terms, and orders of magnitude smaller for off-diagonal values. This poses difficulty in obtaining accurate and noise-free measurements, especially for points removed from the excitation source. A second difficulty encountered in residual measurements lies in obtaining a clean residual function in the process of subtracting synthesized modal data from a measured response function. Inaccuracies occur since modes are not subtracted exactly, but only to the accuracy of the curve fits for each mode; these errors are compounded with increasing distance from the excitation point. In this paper, the residual flexibility method is applied to a simple structure in both test and analysis. Measured and predicted residual functions are compared, and regions of poor data in the measured curves are described. It is found that for accurate residual measurements, frequency response functions having prominent stiffness lines in the acceleration/force format are needed. The lack of such stiffness lines increases measurement errors. Interface drive point frequency respose functions for shuttle orbiter payloads exhibit dominant stiffness lines, making the residual test approach a good candidate for payload modal tests when constrained tests are inappropriate. Difficulties in extracting a residual flexibility value from noisy test data are discussed. It is shown that use of a weighted second order least-squares curve fit of the measured residual function allows identification of residual flexibility that compares very well with predictions for the simple structure. This approach also provides an estimate of second order residual mass effects.

Theoretical prediction of low-density hexagonal ZnO hollow structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tuoc, Vu Ngoc, E-mail: tuoc.vungoc@hust.edu.vn; Huan, Tran Doan; Thao, Nguyen Thi

2016-10-14

Along with wurtzite and zinc blende, zinc oxide (ZnO) has been found in a large number of polymorphs with substantially different properties and, hence, applications. Therefore, predicting and synthesizing new classes of ZnO polymorphs are of great significance and have been gaining considerable interest. Herein, we perform a density functional theory based tight-binding study, predicting several new series of ZnO hollow structures using the bottom-up approach. The geometry of the building blocks allows for obtaining a variety of hexagonal, low-density nanoporous, and flexible ZnO hollow structures. Their stability is discussed by means of the free energy computed within the lattice-dynamicsmore » approach. Our calculations also indicate that all the reported hollow structures are wide band gap semiconductors in the same fashion with bulk ZnO. The electronic band structures of the ZnO hollow structures are finally examined in detail.« less

Discrete-time stability of continuous-time controller designs for large space structures

NASA Technical Reports Server (NTRS)

Balas, M. J.

1982-01-01

In most of the stable control designs for flexible structures, continuous time is assumed. However, in view of the implementation of the controllers by on-line digital computers, the discrete-time stability of such controllers is an important consideration. In the case of direct-velocity feedback (DVFB), involving negative feedback from collocated force actuators and velocity sensors, it is not immediately apparent how much delay due to digital implementation of DVFB can be tolerated without loss of stability. The present investigation is concerned with such questions. A study is conducted of the discrete-time stability of DVFB, taking into account an employment of Euler's method of approximation of the time derivative. The obtained result gives an indication of the acceptable time-step size for stable digital implementation of DVFB. A result derived in connection with the consideration of the discrete-time stability of stable continuous-time systems provides a general condition under which digital implementation of such a system will remain stable.

Flexible Vesiculovasoscopy Using a Microoptical System in a Human Cadaver Model: An Experimental Approach for Atraumatic Endoscopy of the Seminal Tract.

PubMed

Schlager, Daniel; Maas, Moritz; Hein, Simon; Adams, Fabian; Schoenthaler, Martin; Wetterauer, Ulrich; Diemer, Thorsten; Weidner, Wolfgang; Miernik, Arkadiusz

2016-08-01

The most common pathologies of the seminal tract are persistent hematospermia, seminal vesicle stones, and seminal duct obstruction. Endoscopic diagnostic work-up of the seminal tract is impeded by complex anatomy and lack of technical equipment. To date, there is no standardized endoscopic approach. The purpose of this study was to investigate the applicability and feasibility of a flexible microoptical device for atraumatic endoscopy of the seminal tract in a male human cadaver. The transurethral endoscopic examination was performed on a male cadaver. No premortal interventions or diseases of the genitourinary tract had been reported. The seminal orifice was identified via cystoscopy and accessed by the Seldinger technique using a hydrophilic guidewire and ureteral catheter. Retrograde endoscopic inspection of the distal seminal tract was performed using a miniaturized flexible endoscope. An antegrade endoscopic inspection of the seminal tract was carried out via high scrotal access to the vas deferens. Structures of the seminal tract, such as the ejaculatory duct, seminal vesicles, and distal portion of the ductus deferentes, were visualized using the miniaturized endoscope. Image quality allowed identification of anatomical structures and characterization of tissue properties. The technical limitations we observed involved the system's maneuverability. Initial results of this novel endoscopic approach to the seminal tract using a flexible microoptical system are encouraging. However, considerable anatomical limitations of the targeted organs necessitate further refinements of the technical equipment. This approach might improve diagnostics and treatment of genitourinary diseases. Future surgical techniques may include intraseminal laser therapy or endoocclusion to monitor fertility in men.

Buried and accessible surface area control intrinsic protein flexibility.

PubMed

Marsh, Joseph A

2013-09-09

Proteins experience a wide variety of conformational dynamics that can be crucial for facilitating their diverse functions. How is the intrinsic flexibility required for these motions encoded in their three-dimensional structures? Here, the overall flexibility of a protein is demonstrated to be tightly coupled to the total amount of surface area buried within its fold. A simple proxy for this, the relative solvent-accessible surface area (Arel), therefore shows excellent agreement with independent measures of global protein flexibility derived from various experimental and computational methods. Application of Arel on a large scale demonstrates its utility by revealing unique sequence and structural properties associated with intrinsic flexibility. In particular, flexibility as measured by Arel shows little correspondence with intrinsic disorder, but instead tends to be associated with multiple domains and increased α-helical structure. Furthermore, the apparent flexibility of monomeric proteins is found to be useful for identifying quaternary-structure errors in published crystal structures. There is also a strong tendency for the crystal structures of more flexible proteins to be solved to lower resolutions. Finally, local solvent accessibility is shown to be a primary determinant of local residue flexibility. Overall, this work provides both fundamental mechanistic insight into the origin of protein flexibility and a simple, practical method for predicting flexibility from protein structures. © 2013 Elsevier Ltd. All rights reserved.

Recent activities within the Aeroservoelasticity Branch at the NASA Langley Research Center

NASA Technical Reports Server (NTRS)

Noll, Thomas E.; Perry, Boyd, III; Gilbert, Michael G.

1989-01-01

The objective of research in aeroservoelasticity at the NASA Langley Research Center is to enhance the modeling, analysis, and multidisciplinary design methodologies for obtaining multifunction digital control systems for application to flexible flight vehicles. Recent accomplishments are discussed, and a status report on current activities within the Aeroservoelasticity Branch is presented. In the area of modeling, improvements to the Minimum-State Method of approximating unsteady aerodynamics are shown to provide precise, low-order aeroservoelastic models for design and simulation activities. Analytical methods based on Matched Filter Theory and Random Process Theory to provide efficient and direct predictions of the critical gust profile and the time-correlated gust loads for linear structural design considerations are also discussed. Two research projects leading towards improved design methodology are summarized. The first program is developing an integrated structure/control design capability based on hierarchical problem decomposition, multilevel optimization and analytical sensitivities. The second program provides procedures for obtaining low-order, robust digital control laws for aeroelastic applications. In terms of methodology validation and application the current activities associated with the Active Flexible Wing project are reviewed.

Genome-Wide Analysis of Transposon and Retroviral Insertions Reveals Preferential Integrations in Regions of DNA Flexibility.

PubMed

Vrljicak, Pavle; Tao, Shijie; Varshney, Gaurav K; Quach, Helen Ngoc Bao; Joshi, Adita; LaFave, Matthew C; Burgess, Shawn M; Sampath, Karuna

2016-04-07

DNA transposons and retroviruses are important transgenic tools for genome engineering. An important consideration affecting the choice of transgenic vector is their insertion site preferences. Previous large-scale analyses of Ds transposon integration sites in plants were done on the basis of reporter gene expression or germ-line transmission, making it difficult to discern vertebrate integration preferences. Here, we compare over 1300 Ds transposon integration sites in zebrafish with Tol2 transposon and retroviral integration sites. Genome-wide analysis shows that Ds integration sites in the presence or absence of marker selection are remarkably similar and distributed throughout the genome. No strict motif was found, but a preference for structural features in the target DNA associated with DNA flexibility (Twist, Tilt, Rise, Roll, Shift, and Slide) was observed. Remarkably, this feature is also found in transposon and retroviral integrations in maize and mouse cells. Our findings show that structural features influence the integration of heterologous DNA in genomes, and have implications for targeted genome engineering. Copyright © 2016 Vrljicak et al.

Situational influences on rhythmicity in speech, music, and their interaction

PubMed Central

Hawkins, Sarah

2014-01-01

Brain processes underlying the production and perception of rhythm indicate considerable flexibility in how physical signals are interpreted. This paper explores how that flexibility might play out in rhythmicity in speech and music. There is much in common across the two domains, but there are also significant differences. Interpretations are explored that reconcile some of the differences, particularly with respect to how functional properties modify the rhythmicity of speech, within limits imposed by its structural constraints. Functional and structural differences mean that music is typically more rhythmic than speech, and that speech will be more rhythmic when the emotions are more strongly engaged, or intended to be engaged. The influence of rhythmicity on attention is acknowledged, and it is suggested that local increases in rhythmicity occur at times when attention is required to coordinate joint action, whether in talking or music-making. Evidence is presented which suggests that while these short phases of heightened rhythmical behaviour are crucial to the success of transitions in communicative interaction, their modality is immaterial: they all function to enhance precise temporal prediction and hence tightly coordinated joint action. PMID:25385776

Individual consistency and flexibility in human social information use.

PubMed

Toelch, Ulf; Bruce, Matthew J; Newson, Lesley; Richerson, Peter J; Reader, Simon M

2014-02-07

Copying others appears to be a cost-effective way of obtaining adaptive information, particularly when flexibly employed. However, adult humans differ considerably in their propensity to use information from others, even when this 'social information' is beneficial, raising the possibility that stable individual differences constrain flexibility in social information use. We used two dissimilar decision-making computer games to investigate whether individuals flexibly adjusted their use of social information to current conditions or whether they valued social information similarly in both games. Participants also completed established personality questionnaires. We found that participants demonstrated considerable flexibility, adjusting social information use to current conditions. In particular, individuals employed a 'copy-when-uncertain' social learning strategy, supporting a core, but untested, assumption of influential theoretical models of cultural transmission. Moreover, participants adjusted the amount invested in their decision based on the perceived reliability of personally gathered information combined with the available social information. However, despite this strategic flexibility, participants also exhibited consistent individual differences in their propensities to use and value social information. Moreover, individuals who favoured social information self-reported as more collectivist than others. We discuss the implications of our results for social information use and cultural transmission.

Individual consistency and flexibility in human social information use

PubMed Central

Toelch, Ulf; Bruce, Matthew J.; Newson, Lesley; Richerson, Peter J.; Reader, Simon M.

2014-01-01

Copying others appears to be a cost-effective way of obtaining adaptive information, particularly when flexibly employed. However, adult humans differ considerably in their propensity to use information from others, even when this ‘social information’ is beneficial, raising the possibility that stable individual differences constrain flexibility in social information use. We used two dissimilar decision-making computer games to investigate whether individuals flexibly adjusted their use of social information to current conditions or whether they valued social information similarly in both games. Participants also completed established personality questionnaires. We found that participants demonstrated considerable flexibility, adjusting social information use to current conditions. In particular, individuals employed a ‘copy-when-uncertain’ social learning strategy, supporting a core, but untested, assumption of influential theoretical models of cultural transmission. Moreover, participants adjusted the amount invested in their decision based on the perceived reliability of personally gathered information combined with the available social information. However, despite this strategic flexibility, participants also exhibited consistent individual differences in their propensities to use and value social information. Moreover, individuals who favoured social information self-reported as more collectivist than others. We discuss the implications of our results for social information use and cultural transmission. PMID:24352950

Employee-oriented leadership and quality of working life: mediating roles of idiosyncratic deals.

PubMed

Hornung, Severin; Glaser, Jürgen; Rousseau, Denise M; Angerer, Peter; Weigl, Matthias

2011-02-01

Leader consideration has long been suggested to be conducive to quality of working life experienced by employees. The present study links this classic leadership dimension with more recent research on idiosyncratic deals, referring to personalized conditions workers negotiate in their employment relationships. A two-wave survey study (N = 159/142) among German hospital physicians suggests that authorizing idiosyncratic deals is a manifestation of employee-oriented leader behavior. Consideration had consistent positive effects on idiosyncratic deals regarding both professional development and working time flexibility. These two types had differential effects on two indicators of the quality of working life. Development related positively to work engagement, flexibility related negatively to work-family conflict. Cross-lagged correlations supported the proposed direction of influence between consideration and idiosyncratic deals in a subsample of repeating responders (n=91). The relation between development and engagement appeared to be reciprocal. Longitudinal results for the association between flexibility and work-family conflict were inconclusive.

Virus based Full Colour Pixels using a Microheater

NASA Astrophysics Data System (ADS)

Kim, Won-Geun; Kim, Kyujung; Ha, Sung-Hun; Song, Hyerin; Yu, Hyun-Woo; Kim, Chuntae; Kim, Jong-Man; Oh, Jin-Woo

2015-09-01

Mimicking natural structures has been received considerable attentions, and there have been a few practical advances. Tremendous efforts based on a self-assembly technique have been contributed to the development of the novel photonic structures which are mimicking nature’s inventions. We emulate the photonic structures from an origin of colour generation of mammalian skins and avian skin/feathers using M13 phage. The structures can be generated a full range of RGB colours that can be sensitively switched by temperature and substrate materials. Consequently, we developed an M13 phage-based temperature-dependent actively controllable colour pixels platform on a microheater chip. Given the simplicity of the fabrication process, the low voltage requirements and cycling stability, the virus colour pixels enable us to substitute for conventional colour pixels for the development of various implantable, wearable and flexible devices in future.

1-dimension nano-material-based flexible device

NASA Astrophysics Data System (ADS)

Yang, Xing; Zhou, Zhaoying; Zheng, Fuzhong

2009-11-01

1D nano-material-based flexible devices has attracted considerable attention owing to the growing need of the high-sensitivity flexible sensor, portable consumer electronics etc.. In this paper, the 1D nano-materials-based flexible device on polyimide substrate was proposed. The bottom-up and top-down combined process were used for constructing the ZnO nanowire and the CNT-based flexible devices. Their electrical characteristics were also investigated. The measurement results demonstrate that the flexible device covered with a layer of Al2O3 has good ohm electrical contact behavior between the nano-material and micro-electrodes. The proposed 1D nano-material-based flexible device shows the application potential in the sensing fields.

Putting Order Into the Cloud: Object-oriented UML-based Rule Enforcement for Document and Application Organization

DTIC Science & Technology

2010-09-01

Cloud computing describes a new distributed computing paradigm for IT data and services that involves over-the-Internet provision of dynamically scalable and often virtualized resources. While cost reduction and flexibility in storage, services, and maintenance are important considerations when deciding on whether or how to migrate data and applications to the cloud, large organizations like the Department of Defense need to consider the organization and structure of data on the cloud and the operations on such data in order to reap the full benefit of cloud

Intermediate filament mechanics in vitro and in the cell: from coiled coils to filaments, fibers and networks.

PubMed

Köster, Sarah; Weitz, David A; Goldman, Robert D; Aebi, Ueli; Herrmann, Harald

2015-02-01

Intermediate filament proteins form filaments, fibers and networks both in the cytoplasm and the nucleus of metazoan cells. Their general structural building plan accommodates highly varying amino acid sequences to yield extended dimeric α-helical coiled coils of highly conserved design. These 'rod' particles are the basic building blocks of intrinsically flexible, filamentous structures that are able to resist high mechanical stresses, that is, bending and stretching to a considerable degree, both in vitro and in the cell. Biophysical and computer modeling studies are beginning to unfold detailed structural and mechanical insights into these major supramolecular assemblies of cell architecture, not only in the 'test tube' but also in the cellular and tissue context. Copyright © 2015 Elsevier Ltd. All rights reserved.

A definition of the degree of controllability - A criterion for actuator placement

NASA Technical Reports Server (NTRS)

Viswanathan, C. N.; Longman, R. W.; Likins, P. W.

1979-01-01

The unsolved problem of how to control the attitude and shape of future very large flexible satellite structures represents a challenging problem for modern control theory. One aspect of this problem is the question of how to choose the number and locations throughout the spacecraft of the control system actuators. Starting from basic physical considerations, this paper develops a concept of the degree of controllability of a control system, and then develops numerical methods to generate approximate values of the degree of controllability for any spacecraft. These results offer the control system designer a tool which allows him to rank the effectiveness of alternative actuator distributions, and hence to choose the actuator locations on a rational basis. The degree of controllability is shown to take a particularly simple form when the satellite dynamics equations are in modal form. Examples are provided to illustrate the use of the concept on a simple flexible spacecraft.

Vocal communication in a complex multi-level society: constrained acoustic structure and flexible call usage in Guinea baboons.

PubMed

Maciej, Peter; Ndao, Ibrahima; Hammerschmidt, Kurt; Fischer, Julia

2013-09-23

To understand the evolution of acoustic communication in animals, it is important to distinguish between the structure and the usage of vocal signals, since both aspects are subject to different constraints. In terrestrial mammals, the structure of calls is largely innate, while individuals have a greater ability to actively initiate or withhold calls. In closely related taxa, one would therefore predict a higher flexibility in call usage compared to call structure. In the present study, we investigated the vocal repertoire of free living Guinea baboons (Papio papio) and examined the structure and usage of the animals' vocal signals. Guinea baboons live in a complex multi-level social organization and exhibit a largely tolerant and affiliative social style, contrary to most other baboon taxa. To classify the vocal repertoire of male and female Guinea baboons, cluster analyses were used and focal observations were conducted to assess the usage of vocal signals in the particular contexts. In general, the vocal repertoire of Guinea baboons largely corresponded to the vocal repertoire other baboon taxa. The usage of calls, however, differed considerably from other baboon taxa and corresponded with the specific characteristics of the Guinea baboons' social behaviour. While Guinea baboons showed a diminished usage of contest and display vocalizations (a common pattern observed in chacma baboons), they frequently used vocal signals during affiliative and greeting interactions. Our study shows that the call structure of primates is largely unaffected by the species' social system (including grouping patterns and social interactions), while the usage of calls can be more flexibly adjusted, reflecting the quality of social interactions of the individuals. Our results support the view that the primary function of social signals is to regulate social interactions, and therefore the degree of competition and cooperation may be more important to explain variation in call usage than grouping patterns or group size.

Vocal communication in a complex multi-level society: constrained acoustic structure and flexible call usage in Guinea baboons

PubMed Central

2013-01-01

Background To understand the evolution of acoustic communication in animals, it is important to distinguish between the structure and the usage of vocal signals, since both aspects are subject to different constraints. In terrestrial mammals, the structure of calls is largely innate, while individuals have a greater ability to actively initiate or withhold calls. In closely related taxa, one would therefore predict a higher flexibility in call usage compared to call structure. In the present study, we investigated the vocal repertoire of free living Guinea baboons (Papio papio) and examined the structure and usage of the animals’ vocal signals. Guinea baboons live in a complex multi-level social organization and exhibit a largely tolerant and affiliative social style, contrary to most other baboon taxa. To classify the vocal repertoire of male and female Guinea baboons, cluster analyses were used and focal observations were conducted to assess the usage of vocal signals in the particular contexts. Results In general, the vocal repertoire of Guinea baboons largely corresponded to the vocal repertoire other baboon taxa. The usage of calls, however, differed considerably from other baboon taxa and corresponded with the specific characteristics of the Guinea baboons’ social behaviour. While Guinea baboons showed a diminished usage of contest and display vocalizations (a common pattern observed in chacma baboons), they frequently used vocal signals during affiliative and greeting interactions. Conclusions Our study shows that the call structure of primates is largely unaffected by the species’ social system (including grouping patterns and social interactions), while the usage of calls can be more flexibly adjusted, reflecting the quality of social interactions of the individuals. Our results support the view that the primary function of social signals is to regulate social interactions, and therefore the degree of competition and cooperation may be more important to explain variation in call usage than grouping patterns or group size. PMID:24059742

Structure of a Double Transmembrane Fragment of a G-Protein-Coupled Receptor in Micelles

PubMed Central

Neumoin, Alexey; Cohen, Leah S.; Arshava, Boris; Tantry, Subramanyam; Becker, Jeffrey M.; Zerbe, Oliver; Naider, Fred

2009-01-01

Abstract The structure and dynamic properties of an 80-residue fragment of Ste2p, the G-protein-coupled receptor for α-factor of Saccharomyces cerevisiae, was studied in LPPG micelles with the use of solution NMR spectroscopy. The fragment Ste2p(G31-T110) (TM1-TM2) consisted of 19 residues from the N-terminal domain, the first TM helix (TM1), the first cytoplasmic loop, the second TM helix (TM2), and seven residues from the first extracellular loop. Multidimensional NMR experiments on [15N], [15N, 13C], [15N, 13C, 2H]-labeled TM1-TM2 and on protein fragments selectively labeled at specific amino acid residues or protonated at selected methyl groups resulted in >95% assignment of backbone and side-chain nuclei. The NMR investigation revealed the secondary structure of specific residues of TM1-TM2. TALOS constraints and NOE connectivities were used to calculate a structure for TM1-TM2 that was highlighted by the presence of three α-helices encompassing residues 39–47, 49–72, and 80–103, with higher flexibility around the internal Arg58 site of TM1. RMSD values of individually superimposed helical segments 39–47, 49–72, and 80–103 were 0.25 ± 0.10 Å, 0.40 ± 0.13 Å, and 0.57 ± 0.19 Å, respectively. Several long-range interhelical connectivities supported the folding of TM1-TM2 into a tertiary structure typified by a crossed helix that splays apart toward the extracellular regions and contains considerable flexibility in the G56VRSG60 region. 15N-relaxation and hydrogen-deuterium exchange data support a stable fold for the TM parts of TM1-TM2, whereas the solvent-exposed segments are more flexible. The NMR structure is consistent with the results of biochemical experiments that identified the ligand-binding site within this region of the receptor. PMID:19383463

Averaging business cycles vs. myopia: Do we need a long term vision when developing IRP?

DOE Office of Scientific and Technical Information (OSTI.GOV)

McDonald, C.; Gupta, P.C.

1995-05-01

Utility demand forecasting is inherently imprecise due to the number of uncertainties resulting from business cycles, policy making, technology breakthroughs, national and international political upheavals and the limitations of the forecasting tools. This implies that revisions based primarily on recent experience could lead to unstable forecasts. Moreover, new planning tools are required that provide an explicit consideration of uncertainty and lead to flexible and robust planning tools are required that provide an explicit consideration of uncertainty and lead to flexible and robust planning decisions.

Flight test results for the Daedalus and Light Eagle human powered aircraft

NASA Technical Reports Server (NTRS)

Sullivan, R. Bryan; Zerweckh, Siegfried H.

1988-01-01

The results of the flight test program of the Daedalus and Light Eagle human powered aircraft in the winter of 1987/88 are given. The results from experiments exploring the Light Eagle's rigid body and structural dynamics are presented. The interactions of these dynamics with the autopilot design are investigated. Estimates of the power required to fly the Daedalus aircraft are detailed. The system of sensors, signal conditioning boards, and data acquisition equipment used to record the flight data is also described. In order to investigate the dynamics of the aircraft, flight test maneuvers were developed to yield maximum data quality from the point of view of estimating lateral and longitudinal stability derivatives. From this data, structural flexibility and unsteady aerodynamics have been modeled in an ad hoc manner and are used to augment the equations of motion with flexibility effects. Results of maneuvers that were flown are compared with the predictions from the flexibility model. To extend the ad hoc flexibility model, a fully flexible aeroelastic model has been developed. The model is unusual in the approximate equality of many structural natural frequencies and the importance of unsteady aerodynamic effects. the Gossamer Albatross. It is hypothesized that this inverse ground effect is caused by turbulence in the Earth's boundary layer. The diameters of the largest boundary layer eddies (which represent most of the turbulent kinetic energy) are proportional to altitude; thus, closer to the ground, the energy in the boundary layer becomes concentrated in eddies of smaller and smaller diameter. Eventually the eddies become sufficiently small (approximately 0.5 cm) that they trip the laminar boundary layer on the wing. As a result, a greater percentage of the wing area is covered with turbulent flow. Consequently the aircraft's drag and the pow er required both increase as the aircraft flies closer to the ground. The results of the flight test program are examined critically, especially with respect to future applications. Maneuvers that allow the observation of stability derivatives for flexible aircraft are detailed. Considerations for the design of autopilots for future human power aircraft and high-altitude RPV's are discussed. Techniques useful in estimating the power required to fly aircraft of very high lift to drag ratio are described.

Control system design for flexible structures using data models

NASA Technical Reports Server (NTRS)

Irwin, R. Dennis; Frazier, W. Garth; Mitchell, Jerrel R.; Medina, Enrique A.; Bukley, Angelia P.

1993-01-01

The dynamics and control of flexible aerospace structures exercises many of the engineering disciplines. In recent years there has been considerable research in the developing and tailoring of control system design techniques for these structures. This problem involves designing a control system for a multi-input, multi-output (MIMO) system that satisfies various performance criteria, such as vibration suppression, disturbance and noise rejection, attitude control and slewing control. Considerable progress has been made and demonstrated in control system design techniques for these structures. The key to designing control systems for these structures that meet stringent performance requirements is an accurate model. It has become apparent that theoretically and finite-element generated models do not provide the needed accuracy; almost all successful demonstrations of control system design techniques have involved using test results for fine-tuning a model or for extracting a model using system ID techniques. This paper describes past and ongoing efforts at Ohio University and NASA MSFC to design controllers using 'data models.' The basic philosophy of this approach is to start with a stabilizing controller and frequency response data that describes the plant; then, iteratively vary the free parameters of the controller so that performance measures become closer to satisfying design specifications. The frequency response data can be either experimentally derived or analytically derived. One 'design-with-data' algorithm presented in this paper is called the Compensator Improvement Program (CIP). The current CIP designs controllers for MIMO systems so that classical gain, phase, and attenuation margins are achieved. The center-piece of the CIP algorithm is the constraint improvement technique which is used to calculate a parameter change vector that guarantees an improvement in all unsatisfied, feasible performance metrics from iteration to iteration. The paper also presents a recently demonstrated CIP-type algorithm, called the Model and Data Oriented Computer-Aided Design System (MADCADS), developed for achieving H(sub infinity) type design specifications using data models. Control system design for the NASA/MSFC Single Structure Control Facility are demonstrated for both CIP and MADCADS. Advantages of design-with-data algorithms over techniques that require analytical plant models are also presented.

Design Principles for Digital Badges Used in Libraries

ERIC Educational Resources Information Center

Rimland, Emily; Raish, Victoria

2017-01-01

Digital badges give libraries greater flexibility in delivering impactful instruction to students. They serve as flexible, stackable microcredentials that sequence an information literacy experience across the curriculum. Design considerations rooted in learning theory have a foundation through which to drive decisions. Information literacy badges…

Highly Flexible Superhydrophobic and Fire-Resistant Layered Inorganic Paper.

PubMed

Chen, Fei-Fei; Zhu, Ying-Jie; Xiong, Zhi-Chao; Sun, Tuan-Wei; Shen, Yue-Qin

2016-12-21

Traditional paper made from plant cellulose fibers is easily destroyed by either liquid or fire. In addition, the paper making industry consumes a large amount of natural trees and thus causes serious environmental problems including excessive deforestation and pollution. In consideration of the intrinsic flammability of organics and minimizing the effects on the environment and creatures, biocompatible ultralong hydroxyapatite nanowires are an ideal building material for inorganic fire-resistant paper. Herein, a new kind of free-standing, highly flexible, superhydrophobic, and fire-resistant layered inorganic paper has been successfully prepared using ultralong hydroxyapatite nanowires as building blocks after the surface modification with sodium oleate. During the vacuum filtration, ultralong hydroxyapatite nanowires assemble into self-roughened setalike microfibers, avoiding the tedious fabrication process to construct the hierarchical structure; the self-roughened microfibers further form the inorganic paper with a nacrelike layered structure. We have demonstrated that the layered structure can significantly improve the resistance to mechanical destruction of the as-prepared superhydrophobic paper. The as-prepared superhydrophobic and fire-resistant inorganic paper shows excellent nonflammability, liquid repellency to various commercial drinks, high thermal stability, and self-cleaning property. Moreover, we have explored the potential applications of the superhydrophobic and fire-resistant inorganic paper as a highly effective adsorbent for oil/water separation, fire-shielding protector, and writing paper.

Carbon nanotubes: properties, synthesis, purification, and medical applications

PubMed Central

2014-01-01

Current discoveries of different forms of carbon nanostructures have motivated research on their applications in various fields. They hold promise for applications in medicine, gene, and drug delivery areas. Many different production methods for carbon nanotubes (CNTs) have been introduced; functionalization, filling, doping, and chemical modification have been achieved, and characterization, separation, and manipulation of individual CNTs are now possible. Parameters such as structure, surface area, surface charge, size distribution, surface chemistry, and agglomeration state as well as purity of the samples have considerable impact on the reactivity of carbon nanotubes. Otherwise, the strength and flexibility of carbon nanotubes make them of potential use in controlling other nanoscale structures, which suggests they will have a significant role in nanotechnology engineering. PMID:25170330

Carbon nanotubes: properties, synthesis, purification, and medical applications

NASA Astrophysics Data System (ADS)

Eatemadi, Ali; Daraee, Hadis; Karimkhanloo, Hamzeh; Kouhi, Mohammad; Zarghami, Nosratollah; Akbarzadeh, Abolfazl; Abasi, Mozhgan; Hanifehpour, Younes; Joo, Sang Woo

2014-08-01

Current discoveries of different forms of carbon nanostructures have motivated research on their applications in various fields. They hold promise for applications in medicine, gene, and drug delivery areas. Many different production methods for carbon nanotubes (CNTs) have been introduced; functionalization, filling, doping, and chemical modification have been achieved, and characterization, separation, and manipulation of individual CNTs are now possible. Parameters such as structure, surface area, surface charge, size distribution, surface chemistry, and agglomeration state as well as purity of the samples have considerable impact on the reactivity of carbon nanotubes. Otherwise, the strength and flexibility of carbon nanotubes make them of potential use in controlling other nanoscale structures, which suggests they will have a significant role in nanotechnology engineering.

Carbon nanotubes: properties, synthesis, purification, and medical applications.

PubMed

Eatemadi, Ali; Daraee, Hadis; Karimkhanloo, Hamzeh; Kouhi, Mohammad; Zarghami, Nosratollah; Akbarzadeh, Abolfazl; Abasi, Mozhgan; Hanifehpour, Younes; Joo, Sang Woo

2014-01-01

Current discoveries of different forms of carbon nanostructures have motivated research on their applications in various fields. They hold promise for applications in medicine, gene, and drug delivery areas. Many different production methods for carbon nanotubes (CNTs) have been introduced; functionalization, filling, doping, and chemical modification have been achieved, and characterization, separation, and manipulation of individual CNTs are now possible. Parameters such as structure, surface area, surface charge, size distribution, surface chemistry, and agglomeration state as well as purity of the samples have considerable impact on the reactivity of carbon nanotubes. Otherwise, the strength and flexibility of carbon nanotubes make them of potential use in controlling other nanoscale structures, which suggests they will have a significant role in nanotechnology engineering.

Seismic response of 3D steel buildings considering the effect of PR connections and gravity frames.

PubMed

Reyes-Salazar, Alfredo; Bojórquez, Edén; Haldar, Achintya; López-Barraza, Arturo; Rivera-Salas, J Luz

2014-01-01

The nonlinear seismic responses of 3D steel buildings with perimeter moment resisting frames (PMRF) and interior gravity frames (IGF) are studied explicitly considering the contribution of the IGF. The effect on the structural response of the stiffness of the beam-to-column connections of the IGF, which is usually neglected, is also studied. It is commonly believed that the flexibility of shear connections is negligible and that 2D models can be used to properly represent 3D real structures. The results of the study indicate, however, that the moments developed on columns of IGF can be considerable and that modeling buildings as plane frames may result in very conservative designs. The contribution of IGF to the lateral structural resistance may be significant. The contribution increases when their connections are assumed to be partially restrained (PR). The incremented participation of IGF when the stiffness of their connections is considered helps to counteract the no conservative effect that results in practice when lateral seismic loads are not considered in IGF while designing steel buildings with PMRF. Thus, if the structural system under consideration is used, the three-dimensional model should be used in seismic analysis and the IGF and the stiffness of their connections should be considered as part of the lateral resistance system.

Enhanced performance of flexible dye-sensitized solar cells using flexible Ag@ZrO2/C nanofiber film as low-cost counter electrode

NASA Astrophysics Data System (ADS)

Yin, Xin; Xie, Xueyao; Song, Lixin; Zhai, Jifeng; Du, Pingfan; Xiong, Jie

2018-05-01

Highly flexible ZrO2/C nanofibers (NFs) coated with Ag nanoparticles (NPs) have been fabricated by a combination of electrospinning, carbonization and hydrothermal treatment. The obtained Ag@ZrO2/C NFs serve as low-cost counter electrodes (CEs) for flexible dye-sensitized solar cells (FDSSCs). A considerable power conversion efficiency of 4.77% is achieved, which is 27.9% higher than the η of ZrO2/C NFs CEs (3.73%) and reaches about 90% of that of Pt CE (5.26%). It can be ascribed to the fact that the introduction of Ag NPs provides a large number of accessible reaction sites for electrolyte ions to rapidly participate in the I3-/I- reaction. Moreover, the Ag NPs can produce synergistic effect with ZrO2/C NFs to further enhance transport capacity and electro-catalytic activity of the Ag@ZrO2/C film. Therefore, the considerable performance together with characteristics of simple preparation, low cost and flexibility suggests the Ag@ZrO2/C film can be promising candidate for the future generation of FDSSC.

Structural Dynamics and Control Interaction of Flexible Structures

NASA Technical Reports Server (NTRS)

Ryan, Robert S. (Editor); Scofield, Harold N. (Editor)

1987-01-01

A workshop on structural dynamics and control interaction of flexible structures was held to promote technical exchange between the structural dynamics and control disciplines, foster joint technology, and provide a forum for discussing and focusing critical issues in the separate and combined areas. Issues and areas of emphasis were identified in structure-control interaction for the next generation of flexible systems.

Object-oriented design for accelerator control

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stok, P.D.V. van der; Berk, F. van den; Deckers, R.

1994-02-01

An object-oriented design for the distributed computer control system of the accelerator ring EUTERPE is presented. Because of the experimental nature of the ring, flexibility is of the utmost importance. The object-oriented principles have contributed considerably to the flexibility of the design incorporating multiple views, multi-level access and distributed surveillance.

Nonword Reading across Orthographies: How Flexible Is the Choice of Reading Units?

ERIC Educational Resources Information Center

Goswami, Usha; Ziegler, Johannes C.; Dalton, Louise; Schnieder, Wolfgang

2003-01-01

Used cross-language blocking experiments to test the hypothesis that children learning to read inconsistent orthographies would show considerable flexibility in making use of spelling-sound correspondences at different unit sizes, whereas children learning to read consistent orthographies should mainly employ small-size grapheme-phoneme…

Toward a theory of holistic needs and the brain.

PubMed

Silton, Nava R; Flannelly, Laura T; Flannelly, Kevin J; Galek, Kathleen

2011-01-01

This article reviews Maslow's theory of motivation wherein he proposes a hierarchy of human needs. First, it describes the principal elements of Maslow's theory and discusses considerations relating to the flexibility of the hierarchy. Second, it explains the relationship among Maslow's theory of human needs, attachment theory, and evolutionary threat assessment system theory. Third, it provides an overview of the brain structures posited to be involved in attachment and evolutionary threat assessment system theory and their relation to Maslow's hierarchy. Finally, it explains how the 3 theories converge to form a theory of holistic needs.

Beyond vertical integration--Community based medical education.

PubMed

Kennedy, Emma Margaret

2006-11-01

The term 'vertical integration' is used broadly in medical education, sometimes when discussing community based medical education (CBME). This article examines the relevance of the term 'vertical integration' and provides an alternative perspective on the complexities of facilitating the CBME process. The principles of learner centredness, patient centredness and flexibility are fundamental to learning in the diverse contexts of 'community'. Vertical integration as a structural concept is helpful for academic organisations but has less application to education in the community setting; a different approach illuminates the strengths and challenges of CBME that need consideration by these organisations.

Nature-Inspired Structural Materials for Flexible Electronic Devices.

PubMed

Liu, Yaqing; He, Ke; Chen, Geng; Leow, Wan Ru; Chen, Xiaodong

2017-10-25

Exciting advancements have been made in the field of flexible electronic devices in the last two decades and will certainly lead to a revolution in peoples' lives in the future. However, because of the poor sustainability of the active materials in complex stress environments, new requirements have been adopted for the construction of flexible devices. Thus, hierarchical architectures in natural materials, which have developed various environment-adapted structures and materials through natural selection, can serve as guides to solve the limitations of materials and engineering techniques. This review covers the smart designs of structural materials inspired by natural materials and their utility in the construction of flexible devices. First, we summarize structural materials that accommodate mechanical deformations, which is the fundamental requirement for flexible devices to work properly in complex environments. Second, we discuss the functionalities of flexible devices induced by nature-inspired structural materials, including mechanical sensing, energy harvesting, physically interacting, and so on. Finally, we provide a perspective on newly developed structural materials and their potential applications in future flexible devices, as well as frontier strategies for biomimetic functions. These analyses and summaries are valuable for a systematic understanding of structural materials in electronic devices and will serve as inspirations for smart designs in flexible electronics.

Situational influences on rhythmicity in speech, music, and their interaction.

PubMed

Hawkins, Sarah

2014-12-19

Brain processes underlying the production and perception of rhythm indicate considerable flexibility in how physical signals are interpreted. This paper explores how that flexibility might play out in rhythmicity in speech and music. There is much in common across the two domains, but there are also significant differences. Interpretations are explored that reconcile some of the differences, particularly with respect to how functional properties modify the rhythmicity of speech, within limits imposed by its structural constraints. Functional and structural differences mean that music is typically more rhythmic than speech, and that speech will be more rhythmic when the emotions are more strongly engaged, or intended to be engaged. The influence of rhythmicity on attention is acknowledged, and it is suggested that local increases in rhythmicity occur at times when attention is required to coordinate joint action, whether in talking or music-making. Evidence is presented which suggests that while these short phases of heightened rhythmical behaviour are crucial to the success of transitions in communicative interaction, their modality is immaterial: they all function to enhance precise temporal prediction and hence tightly coordinated joint action. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

Portable Ultrasonic Guided Wave Inspection with MACRO Fiber Composite Actuators

NASA Astrophysics Data System (ADS)

Haig, A.; Mudge, P.; Catton, P.; Balachandran, W.

2010-02-01

The development of portable ultrasonic guided wave transducer arrays that utilize Macro Fiber Composite actuators (MFCs) is described. Portable inspection equipment can make use of ultrasonic guided waves to rapidly screen large areas of many types of engineering structures for defects. The defect finding performance combined with the difficulty of application determines how much the engineering industry makes use of this non-destructive, non-disruptive technology. The developments with MFCs have the potential to make considerable improvements in both these aspects. MFCs are highly efficient because they use interdigital electrodes to facilitate the extensional, d33 displacement mode. Their fiber composite design allows them to be thin, lightweight, flexible and durable. The flexibility affords them conformance with curved surfaces, which can facilitate good mechanical coupling. The suitability of a given transducer for Long Range Ultrasonic Testing is governed by the nature and amplitude of the displacement that it excites/senses in the contact area of the target structure. This nature is explored for MFCs through directional sensitivity analysis and empirical testing. Housing methods that facilitate non-permanent coupling techniques are discussed. Finally, arrangements of arrays of MFCs for the guided wave inspection of plates and pipes are considered and some broad design criteria are given.

Unique considerations in the design and experimental evaluation of tailored wings with elastically produced chordwise camber

NASA Technical Reports Server (NTRS)

Rehfield, Lawrence W.; Zischka, Peter J.; Fentress, Michael L.; Chang, Stephen

1992-01-01

Some of the unique considerations that are associated with the design and experimental evaluation of chordwise deformable wing structures are addressed. Since chordwise elastic camber deformations are desired and must be free to develop, traditional rib concepts and experimental methodology cannot be used. New rib design concepts are presented and discussed. An experimental methodology based upon the use of a flexible sling support and load application system has been created and utilized to evaluate a model box beam experimentally. Experimental data correlate extremely well with design analysis predictions based upon a beam model for the global properties of camber compliance and spanwise bending compliance. Local strain measurements exhibit trends in agreement with intuition and theory but depart slightly from theoretical perfection based upon beam-like behavior alone. It is conjectured that some additional refinement of experimental technique is needed to explain or eliminate these (minor) departures from asymmetric behavior of upper and lower box cover strains. Overall, a solid basis for the design of box structures based upon the bending method of elastic camber production has been confirmed by the experiments.

Scheduling policies of intelligent sensors and sensor/actuators in flexible structures

NASA Astrophysics Data System (ADS)

Demetriou, Michael A.; Potami, Raffaele

2006-03-01

In this note, we revisit the problem of actuator/sensor placement in large civil infrastructures and flexible space structures within the context of spatial robustness. The positioning of these devices becomes more important in systems employing wireless sensor and actuator networks (WSAN) for improved control performance and for rapid failure detection. The ability of the sensing and actuating devices to possess the property of spatial robustness results in reduced control energy and therefore the spatial distribution of disturbances is integrated into the location optimization measures. In our studies, the structure under consideration is a flexible plate clamped at all sides. First, we consider the case of sensor placement and the optimization scheme attempts to produce those locations that minimize the effects of the spatial distribution of disturbances on the state estimation error; thus the sensor locations produce state estimators with minimized disturbance-to-error transfer function norms. A two-stage optimization procedure is employed whereby one first considers the open loop system and the spatial distribution of disturbances is found that produces the maximal effects on the entire open loop state. Once this "worst" spatial distribution of disturbances is found, the optimization scheme subsequently finds the locations that produce state estimators with minimum transfer function norms. In the second part, we consider the collocated actuator/sensor pairs and the optimization scheme produces those locations that result in compensators with the smallest norms of the disturbance-to-state transfer functions. Going a step further, an intelligent control scheme is presented which, at each time interval, activates a subset of the actuator/sensor pairs in order provide robustness against spatiotemporally moving disturbances and minimize power consumption by keeping some sensor/actuators in sleep mode.

Protein Flexibility Facilitates Quaternary Structure Assembly and Evolution

PubMed Central

Marsh, Joseph A.; Teichmann, Sarah A.

2014-01-01

The intrinsic flexibility of proteins allows them to undergo large conformational fluctuations in solution or upon interaction with other molecules. Proteins also commonly assemble into complexes with diverse quaternary structure arrangements. Here we investigate how the flexibility of individual protein chains influences the assembly and evolution of protein complexes. We find that flexibility appears to be particularly conducive to the formation of heterologous (i.e., asymmetric) intersubunit interfaces. This leads to a strong association between subunit flexibility and homomeric complexes with cyclic and asymmetric quaternary structure topologies. Similarly, we also observe that the more nonhomologous subunits that assemble together within a complex, the more flexible those subunits tend to be. Importantly, these findings suggest that subunit flexibility should be closely related to the evolutionary history of a complex. We confirm this by showing that evolutionarily more recent subunits are generally more flexible than evolutionarily older subunits. Finally, we investigate the very different explorations of quaternary structure space that have occurred in different evolutionary lineages. In particular, the increased flexibility of eukaryotic proteins appears to enable the assembly of heteromeric complexes with more unique components. PMID:24866000

Liquid-phase tuning of porous PVDF-TrFE film on flexible substrate for energy harvesting

NASA Astrophysics Data System (ADS)

Chen, Dajing; Chen, Kaina; Brown, Kristopher; Hang, Annie; Zhang, John X. J.

2017-04-01

Emerging wearable and implantable biomedical energy harvesting devices demand efficient power conversion, flexible structures, and lightweight construction. This paper presents Polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) micro-porous structures, which can be tuned to specific mechanical flexibilities and optimized for piezoelectric power conversion. Specifically, the water vapor phase separation method was developed to control microstructure formation, pore diameter, porosity, and mechanical flexibility. Furthermore, we investigated the effects of the piezoelectric layer to supporting layer Young's modulus ratio, through using both analytical calculation and experimentation. Both structure flexibility and stress-induced voltage were considered in the analyses. Specification of electromechanical coupling efficiency, made possible by carefully designed three-dimensional porous structures, was shown to increase the power output by five-fold relative to uncoupled structures. Therefore, flexible PVDF-TrFE films with tunable microstructures, paired with substrates of different rigidities, provide highly efficient designs of compact piezoelectric energy generating devices.

Apparatus and method for detecting tampering in flexible structures

DOEpatents

Maxey, Lonnie C [Knoxville, TN; Haynes, Howard D [Knoxville, TN

2011-02-01

A system for monitoring or detecting tampering in a flexible structure includes taking electrical measurements on a sensing cable coupled to the structure, performing spectral analysis on the measured data, and comparing the spectral characteristics of the event to those of known benign and/or known suspicious events. A threshold or trigger value may used to identify an event of interest and initiate data collection. Alternatively, the system may be triggered at preset intervals, triggered manually, or triggered by a signal from another sensing device such as a motion detector. The system may be used to monitor electrical cables and conduits, hoses and flexible ducts, fences and other perimeter control devices, structural cables, flexible fabrics, and other flexible structures.

Active vibration control techniques for flexible space structures

NASA Technical Reports Server (NTRS)

Parlos, Alexander G.; Jayasuriya, Suhada

1990-01-01

Two proposed control system design techniques for active vibration control in flexible space structures are detailed. Control issues relevant only to flexible-body dynamics are addressed, whereas no attempt was made to integrate the flexible and rigid-body spacecraft dynamics. Both of the proposed approaches revealed encouraging results; however, further investigation of the interaction of the flexible and rigid-body dynamics is warranted.

Optical beamforming based on microwave photonic signal processing

NASA Astrophysics Data System (ADS)

Anzalchi, J.; Perrott, R.; Latunde-Dada, K.; Oldenbeuving, R. M.; Roeloffzen, C. G. H.; Van Dijk, P. W. L.; Hoekman, M.; Leeuwis, H.; Leinse, A.

2017-09-01

Over the past few years considerable attention has been focussed on the inclusion of flexibility in communication satellite payloads. The purpose of this flexibility is to enable a given satellite on command to support different frequency plans, re-configure coverage in response to changing traffic demands and re-configure interconnectivity between coverages.

Source characteristics and design consideration for an iron-free variable-period/polarizing undulator for the UV/VUV range on SPEAR (abstract)

NASA Astrophysics Data System (ADS)

Tatchyn, Roman

1992-01-01

Insertion devices that are tuned by electrical period variation are particularly suited for the design of flexible polarized-light sources [R. Tatchyn, J. Appl. Phys. 65, 4107 (1989); R. Tatchyn and T. Cremer, IEEE Trans. Mag. 26, 3102 (1990)]. Important advantages vis-a-vis mechanical or hybrid variable field designs include: (1) significantly more rapid modulation of both polarization and energy, (2) an inherently larger set of polarization modulation capabilities and (3) polarization/energy modulation at continuously optimized values of K. In this paper we outline some of the general considerations that enter into the design of hysteresis-free variable-period/polarizing undulator structures and present the parameters of a recently-completed prototype design capable of generating intense levels of UV/VUV photon flux on SPEAR running at 3 GeV.

Knowledge of damage identification about tensegrities via flexibility disassembly

NASA Astrophysics Data System (ADS)

Jiang, Ge; Feng, Xiaodong; Du, Shigui

2017-12-01

Tensegrity structures composing of continuous cables and discrete struts are under tension and compression, respectively. In order to determine the damage extents of tensegrity structures, a new method for tensegrity structural damage identification is presented based on flexibility disassembly. To decompose a tensegrity structural flexibility matrix into the matrix represention of the connectivity between degress-of-freedoms and the diagonal matrix comprising of magnitude informations. Step 1: Calculate perturbation flexibility; Step 2: Compute the flexibility connectivity matrix and perturbation flexibility parameters; Step 3: Calculate the perturbation stiffness parameters. The efficiency of the proposed method is demonstrated by a numeical example comprising of 12 cables and 4 struts with pretensioned. Accurate identification of local damage depends on the availability of good measured data, an accurate and reasonable algorithm.

A flexible framework for process-based hydraulic and water quality modeling of stormwater green infrastructure performance

EPA Science Inventory

Background Models that allow for design considerations of green infrastructure (GI) practices to control stormwater runoff and associated contaminants have received considerable attention in recent years. While popular, generally, the GI models are relatively simplistic. However,...

Preliminary design method for deployable spacecraft beams

NASA Technical Reports Server (NTRS)

Mikulas, Martin M., Jr.; Cassapakis, Costas

1995-01-01

There is currently considerable interest in low-cost, lightweight, compactly packageable deployable elements for various future missions involving small spacecraft. These elements must also have a simple and reliable deployment scheme and possess zero or very small free-play. Although most small spacecraft do not experience large disturbances, very low stiffness appendages or free-play can couple with even small disturbances and lead to unacceptably large attitude errors which may involve the introduction of a flexible-body control system. A class of structures referred to as 'rigidized structures' offers significant promise in providing deployable elements that will meet these needs for small spacecraft. The purpose of this paper is to introduce several rigidizable concepts and to develop a design methodology which permits a rational comparison of these elements to be made with alternate concepts.

The molecular basis of plant cell wall extension.

PubMed

Darley, C P; Forrester, A M; McQueen-Mason, S J

2001-09-01

In all terrestrial and aquatic plant species the primary cell wall is a dynamic structure, adjusted to fulfil a diversity of functions. However a universal property is its considerable mechanical and tensile strength, whilst being flexible enough to accommodate turgor and allow for cell elongation. The wall is a composite material consisting of a framework of cellulose microfibrils embedded in a matrix of non-cellulosic polysaccharides, interlaced with structural proteins and pectic polymers. The assembly and modification of these polymers within the growing cell wall has, until recently, been poorly understood. Advances in cytological and genetic techniques have thrown light on these processes and have led to the discovery of a number of wall-modifying enzymes which, either directly or indirectly, play a role in the molecular basis of cell wall expansion.

Structure of the buffalo secretory signalling glycoprotein at 2.8 Å resolution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ethayathulla, Abdul S.; Srivastava, Devendra B.; Kumar, Janesh

2007-04-01

The crystal structure of a signalling glycoprotein isolated from buffalo dry secretions (SPB-40) has been determined at 2.8 Å resolution. Two unique residues, Tyr120 and Glu269, found in SPB-40 distort the shape of the sugar-binding groove considerably. The water structure in the groove is also different. The conformations of three flexible loops, His188–His197, Phe202–Arg212 and Tyr244–Pro260, also differ from those found in other structurally similar proteins. The crystal structure of a 40 kDa signalling glycoprotein from buffalo (SPB-40) has been determined at 2.8 Å resolution. SPB-40 acts as a protective signalling factor by binding to viable cells during the earlymore » phase of involution, during which extensive tissue remodelling occurs. It was isolated from the dry secretions of Murrah buffalo. It was purified and crystallized using the hanging-drop vapour-diffusion method with 19% ethanol as the precipitant. The protein was also cloned and its complete nucleotide and amino-acid sequences were determined. When compared with the sequences of other members of the family, the sequence of SPB-40 revealed two very important mutations in the sugar-binding region, in which Tyr120 changed to Trp120 and Glu269 changed to Trp269. The structure showed a significant distortion in the shape of the sugar-binding groove. The water structure in the groove is also drastically altered. The folding of the protein chain in the flexible region comprising segments His188–His197, Phe202–Arg212 and Tyr244–Pro260 shows large variations when compared with other proteins of the family.« less

Influence of Structural Flexibility on the Dynamic Precision of a Vehicle-Mounted Equipment System

DTIC Science & Technology

2015-05-12

Paramsothy Jayakumar , Dave Mechergui, Ronald Renke U.S.Army RDECOM TARDEC INFLUENCE OF STRUCTURAL FLEXIBILITY ON THE DYNAMIC PRECISION OF A...COVERED 00-00-2015 to 00-00-2015 4. TITLE AND SUBTITLE INFLUENCE OF STRUCTURAL FLEXIBILITY ON THE DYNAMIC PRECISION OF A VEHICLE-MOUNTED EQUIPMENT...Equipment Enclosure CMS Results 23 12. Influence of CMS Method on the Vehicle Dynamics 24 13. Influence of Flexibility on the Vehicle

A numerical approach to controller design for the ACES facility

NASA Technical Reports Server (NTRS)

Frazier, W. Garth; Irwin, R. Dennis

1993-01-01

In recent years the employment of active control techniques for improving the performance of systems involving highly flexible structures has become a topic of considerable research interest. Most of these systems are quite complicated, using multiple actuators and sensors, and possessing high order models. The majority of analytical controller synthesis procedures capable of handling multivariable systems in a systematic way require considerable insight into the underlying mathematical theory to achieve a successful design. This insight is needed in selecting the proper weighting matrices or weighting functions to cast what is naturally a multiple constraint satisfaction problem into an unconstrained optimization problem. Although designers possessing considerable experience with these techniques have a feel for the proper choice of weights, others may spend a significant amount of time attempting to find an acceptable solution. Another disadvantage of such procedures is that the resulting controller has an order greater than or equal to that of the model used for the design. Of course, the order of these controllers can often be reduced, but again this requires a good understanding of the theory involved.

Transparent Electrodes Based on Silver Nanowire Networks: From Physical Considerations towards Device Integration

PubMed Central

Bellet, Daniel; Lagrange, Mélanie; Sannicolo, Thomas; Aghazadehchors, Sara; Nguyen, Viet Huong; Langley, Daniel P.; Muñoz-Rojas, David; Jiménez, Carmen; Bréchet, Yves; Nguyen, Ngoc Duy

2017-01-01

The past few years have seen a considerable amount of research devoted to nanostructured transparent conducting materials (TCM), which play a pivotal role in many modern devices such as solar cells, flexible light-emitting devices, touch screens, electromagnetic devices, and flexible transparent thin film heaters. Currently, the most commonly used TCM for such applications (ITO: Indium Tin oxide) suffers from two major drawbacks: brittleness and indium scarcity. Among emerging transparent electrodes, silver nanowire (AgNW) networks appear to be a promising substitute to ITO since such electrically percolating networks exhibit excellent properties with sheet resistance lower than 10 Ω/sq and optical transparency of 90%, fulfilling the requirements of most applications. In addition, AgNW networks also exhibit very good mechanical flexibility. The fabrication of these electrodes involves low-temperature processing steps and scalable methods, thus making them appropriate for future use as low-cost transparent electrodes in flexible electronic devices. This contribution aims to briefly present the main properties of AgNW based transparent electrodes as well as some considerations relating to their efficient integration in devices. The influence of network density, nanowire sizes, and post treatments on the properties of AgNW networks will also be evaluated. In addition to a general overview of AgNW networks, we focus on two important aspects: (i) network instabilities as well as an efficient Atomic Layer Deposition (ALD) coating which clearly enhances AgNW network stability and (ii) modelling to better understand the physical properties of these networks. PMID:28772931

Open Entry-Open Exit: A Flexible Approach for Providing Skill Training Needs at AVTS.

ERIC Educational Resources Information Center

Robinson, George A.

Kansas Balance-of-State, a CETA (Comprehensive Employment and Training Act) prime sponsor explored the possibilities of open entry-open exit in meeting the classroom training needs of clients in area vocational technical schools (AVTS). The change to open entry-open exit was found to involve consideration of flexibility and self-paced,…

Controlling flexible structures with second order actuator dynamics

NASA Technical Reports Server (NTRS)

Inman, Daniel J.; Umland, Jeffrey W.; Bellos, John

1989-01-01

The control of flexible structures for those systems with actuators that are modeled by second order dynamics is examined. Two modeling approaches are investigated. First a stability and performance analysis is performed using a low order finite dimensional model of the structure. Secondly, a continuum model of the flexible structure to be controlled, coupled with lumped parameter second order dynamic models of the actuators performing the control is used. This model is appropriate in the modeling of the control of a flexible panel by proof-mass actuators as well as other beam, plate and shell like structural numbers. The model is verified with experimental measurements.

Seismic Response of 3D Steel Buildings considering the Effect of PR Connections and Gravity Frames

PubMed Central

Haldar, Achintya; López-Barraza, Arturo; Rivera-Salas, J. Luz

2014-01-01

The nonlinear seismic responses of 3D steel buildings with perimeter moment resisting frames (PMRF) and interior gravity frames (IGF) are studied explicitly considering the contribution of the IGF. The effect on the structural response of the stiffness of the beam-to-column connections of the IGF, which is usually neglected, is also studied. It is commonly believed that the flexibility of shear connections is negligible and that 2D models can be used to properly represent 3D real structures. The results of the study indicate, however, that the moments developed on columns of IGF can be considerable and that modeling buildings as plane frames may result in very conservative designs. The contribution of IGF to the lateral structural resistance may be significant. The contribution increases when their connections are assumed to be partially restrained (PR). The incremented participation of IGF when the stiffness of their connections is considered helps to counteract the no conservative effect that results in practice when lateral seismic loads are not considered in IGF while designing steel buildings with PMRF. Thus, if the structural system under consideration is used, the three-dimensional model should be used in seismic analysis and the IGF and the stiffness of their connections should be considered as part of the lateral resistance system. PMID:24995357

Experimental demonstration of the control of flexible structures

NASA Technical Reports Server (NTRS)

Schaechter, D. B.; Eldred, D. B.

1984-01-01

The Large Space Structure Technology Flexible Beam Experiment employs a pinned-free flexible beam to demonstrate such required methods as dynamic and adaptive control, as well as various control law design approaches and hardware requirements. An attempt is made to define the mechanization difficulties that may inhere in flexible structures. Attention is presently given to analytical work performed in support of the test facility's development, the final design's specifications, the control laws' synthesis, and experimental results obtained.

High performance flexible heat pipes

NASA Technical Reports Server (NTRS)

Shaubach, R. M.; Gernert, N. J.

1985-01-01

A Phase I SBIR NASA program for developing and demonstrating high-performance flexible heat pipes for use in the thermal management of spacecraft is examined. The program combines several technologies such as flexible screen arteries and high-performance circumferential distribution wicks within an envelope which is flexible in the adiabatic heat transport zone. The first six months of work during which the Phase I contract goal were met, are described. Consideration is given to the heat-pipe performance requirements. A preliminary evaluation shows that the power requirement for Phase II of the program is 30.5 kilowatt meters at an operating temperature from 0 to 100 C.

An adaptive learning control system for large flexible structures

NASA Technical Reports Server (NTRS)

Thau, F. E.

1985-01-01

The objective of the research has been to study the design of adaptive/learning control systems for the control of large flexible structures. In the first activity an adaptive/learning control methodology for flexible space structures was investigated. The approach was based on using a modal model of the flexible structure dynamics and an output-error identification scheme to identify modal parameters. In the second activity, a least-squares identification scheme was proposed for estimating both modal parameters and modal-to-actuator and modal-to-sensor shape functions. The technique was applied to experimental data obtained from the NASA Langley beam experiment. In the third activity, a separable nonlinear least-squares approach was developed for estimating the number of excited modes, shape functions, modal parameters, and modal amplitude and velocity time functions for a flexible structure. In the final research activity, a dual-adaptive control strategy was developed for regulating the modal dynamics and identifying modal parameters of a flexible structure. A min-max approach was used for finding an input to provide modal parameter identification while not exceeding reasonable bounds on modal displacement.

Damage Detection and Self-Repair in Inflatable/Deployable Structures

NASA Technical Reports Server (NTRS)

Brandon, Erik; Studor, George; Banks, DAvid; Curry, Mark; Broccato, Robert; Jackson, Tom; Champaigne, Kevin; Sottos, Nancy

2009-01-01

Inflatable/deployable structures are under consideration for applications as varied as expansion modules for the International Space Station to destinations for space tourism to habitats for the lunar surface. Monitoring and maintaining the integrity of the physical structure is critical, particularly since these structures rely on non-traditional engineering materials such as fabrics, foams, and elastomeric polymers to provide the primary protection for the human crew. The closely related prior concept of monitoring structural integrity by use of built-in or permanently attached sensors has been applied to structures made of such standard engineering materials as metals, alloys, and rigid composites. To effect monitoring of flexible structures comprised mainly of soft goods, however, it will be necessary to solve a different set of problems - especially those of integrating power and data-transfer cabling that can withstand, and not unduly interfere with, stowage and subsequent deployment of the structures. By incorporating capabilities for self-repair along with capabilities for structural health monitoring, successful implementation of these technologies would be a significant step toward semi-autonomous structures, which need little human intervention to maintain. This would not only increase the safety of these structures, but also reduce the inspection and maintenance costs associated with more conventional structures.

Structure-Based Druggability Assessment of the Mammalian Structural Proteome with Inclusion of Light Protein Flexibility

PubMed Central

Loving, Kathryn A.; Lin, Andy; Cheng, Alan C.

2014-01-01

Advances reported over the last few years and the increasing availability of protein crystal structure data have greatly improved structure-based druggability approaches. However, in practice, nearly all druggability estimation methods are applied to protein crystal structures as rigid proteins, with protein flexibility often not directly addressed. The inclusion of protein flexibility is important in correctly identifying the druggability of pockets that would be missed by methods based solely on the rigid crystal structure. These include cryptic pockets and flexible pockets often found at protein-protein interaction interfaces. Here, we apply an approach that uses protein modeling in concert with druggability estimation to account for light protein backbone movement and protein side-chain flexibility in protein binding sites. We assess the advantages and limitations of this approach on widely-used protein druggability sets. Applying the approach to all mammalian protein crystal structures in the PDB results in identification of 69 proteins with potential druggable cryptic pockets. PMID:25079060

Issues and Challenges Facing Flexible Lithium-Ion Batteries for Practical Application.

PubMed

Cha, Hyungyeon; Kim, Junhyeok; Lee, Yoonji; Cho, Jaephil; Park, Minjoon

2017-12-27

With the advent of flexible electronics, lithium-ion batteries have become a key component of high performance energy storage systems. Thus, considerable effort is made to keep up with the development of flexible lithium-ion batteries. To date, many researchers have studied newly designed batteries with flexibility, however, there are several significant challenges that need to be overcome, such as degradation of electrodes under external load, poor battery performance, and complicated cell preparation procedures. In addition, an in-depth understanding of the current challenges for flexible batteries is rarely addressed in a systematical and practical way. Herein, recent progress and current issues of flexible lithium-ion batteries in terms of battery materials and cell designs are reviewed. A critical overview of important issues and challenges for the practical application of flexible lithium-ion batteries is also provided. Finally, the strategies are discussed to overcome current limitations of the practical use of flexible lithium-based batteries, providing a direction for future research. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Design and fabrication of a foldable 3D silicon based package for solid state lighting applications

NASA Astrophysics Data System (ADS)

Sokolovskij, R.; Liu, P.; van Zeijl, H. W.; Mimoun, B.; Zhang, G. Q.

2015-05-01

Miniaturization of solid state lighting (SSL) luminaires as well as reduction of packaging and assembly costs are of prime interest for the SSL lighting industry. A novel silicon based LED package for lighting applications is presented in this paper. The proposed design consists of 5 rigid Si tiles connected by flexible polyimide hinges with embedded interconnects (ICs). Electrical, optical and thermal characteristics were taken into consideration during design. The fabrication process involved polyimide (PI) application and patterning, aluminium interconnect integration in the flexible hinge, LED reflector cavity formation and metalization followed by through wafer DRIE etching for chip formation and release. A method to connect chip front to backside without TSVs was also integrated into the process. Post-fabrication wafer level assembly included LED mounting and wirebond, phosphor-based colour conversion and silicone encapsulation. The package formation was finalized by vacuum assisted wrapping around an assembly structure to form a 3D geometry, which is beneficial for omnidirectional lighting. Bending tests were performed on the flexible ICs and optical performance at different temperatures was evaluated. It is suggested that 3D packages can be expanded to platforms for miniaturized luminaire applications by combining monolithic silicon integration and system-in-package (SiP) technologies.

A flexible cure rate model for spatially correlated survival data based on generalized extreme value distribution and Gaussian process priors.

PubMed

Li, Dan; Wang, Xia; Dey, Dipak K

2016-09-01

Our present work proposes a new survival model in a Bayesian context to analyze right-censored survival data for populations with a surviving fraction, assuming that the log failure time follows a generalized extreme value distribution. Many applications require a more flexible modeling of covariate information than a simple linear or parametric form for all covariate effects. It is also necessary to include the spatial variation in the model, since it is sometimes unexplained by the covariates considered in the analysis. Therefore, the nonlinear covariate effects and the spatial effects are incorporated into the systematic component of our model. Gaussian processes (GPs) provide a natural framework for modeling potentially nonlinear relationship and have recently become extremely powerful in nonlinear regression. Our proposed model adopts a semiparametric Bayesian approach by imposing a GP prior on the nonlinear structure of continuous covariate. With the consideration of data availability and computational complexity, the conditionally autoregressive distribution is placed on the region-specific frailties to handle spatial correlation. The flexibility and gains of our proposed model are illustrated through analyses of simulated data examples as well as a dataset involving a colon cancer clinical trial from the state of Iowa. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Proceedings of the Workshop on Identification and Control of Flexible Space Structures, volume 1

NASA Technical Reports Server (NTRS)

Rodriguez, G. (Editor)

1985-01-01

Identification and control of flexible space structures were studied. Exploration of the most advanced modeling estimation, identification and control methodologies to flexible space structures was discussed. The following general areas were discussed: space platforms, antennas, and flight experiments; control/structure interactions - modeling, integrated design and optimization, control and stabilization, and shape control; control technology; control of space stations; large antenna control, dynamics and control experiments, and control/structure interaction experiments.

Thinking Together: Modeling Clinical Decision-Support as a Sociotechnical System

PubMed Central

Hussain, Mustafa I.; Reynolds, Tera L.; Mousavi, Fatemeh E.; Chen, Yunan; Zheng, Kai

2017-01-01

Computerized clinical decision-support systems are members of larger sociotechnical systems, composed of human and automated actors, who send, receive, and manipulate artifacts. Sociotechnical consideration is rare in the literature. This makes it difficult to comparatively evaluate the success of CDS implementations, and it may also indicate that sociotechnical context receives inadequate consideration in practice. To facilitate sociotechnical consideration, we developed the Thinking Together model, a flexible diagrammatical means of representing CDS systems as sociotechnical systems. To develop this model, we examined the literature with the lens of Distributed Cognition (DCog) theory. We then present two case studies of vastly different CDSSs, one almost fully automated and the other with minimal automation, to illustrate the flexibility of the Thinking Together model. We show that this model, informed by DCog and the CDS literature, are capable of supporting both research, by enabling comparative evaluation, and practice, by facilitating explicit sociotechnical planning and communication. PMID:29854164

Instrumentation for the Characterization of Inflatable Structures

NASA Technical Reports Server (NTRS)

Swanson, Gregory T.; Cassell, Alan M.; Johnson, R. Keith

2012-01-01

Current entry, descent, and landing technologies are not practical for heavy payloads due to mass and volume constraints dictated by limitations imposed by launch vehicle fairings. Therefore, new technologies are now being explored to provide a mass- and volume-efficient solution for heavy payload capabilities, including Inflatable Aerodynamic Decelerators (IAD) [1]. Consideration of IADs for space applications has prompted the development of instrumentation systems for integration with flexible structures to characterize system response to flight-like environment testing. This development opportunity faces many challenges specific to inflatable structures in extreme environments, including but not limited to physical flexibility, packaging, temperature, structural integration and data acquisition [2]. In the spring of 2012, two large scale Hypersonic Inflatable Aerodynamic Decelerators (HIAD) will be tested in the National Full-Scale Aerodynamics Complex s 40 by 80 wind tunnel at NASA Ames Research Center. The test series will characterize the performance of a 3.0 m and 6.0 m HIAD at various angles of attack and levels of inflation during flight-like loading. To analyze the performance of these inflatable test articles as they undergo aerodynamic loading, many instrumentation systems have been researched and developed. These systems will utilize new experimental sensing systems developed by the HIAD ground test campaign instrumentation team, in addition to traditional wind tunnel sensing techniques in an effort to improve test article characterization and model validation. During the 2012 test series the instrumentation systems will target inflatable aeroshell static and dynamic deformation, structural strap loading, surface pressure distribution, localized skin deflection, and torus inflation pressure. This paper will offer an overview of inflatable structure instrumentation, and provide detail into the design and implementation of the sensors systems that will be utilized during the 2012 HIAD ground test campaign.

Quantifying Vegetation Structure with Lightweight, Rapid-Scanning Terrestrial Lidar

NASA Astrophysics Data System (ADS)

Paynter, I.; Genest, D.; Saenz, E. J.; Strahler, A. H.; Li, Z.; Peri, F.; Schaaf, C.

2016-12-01

Light Detection and Ranging (lidar) is proving a competent technology for observing vegetation structure. Terrestrial laser scanners (TLS) are ground-based instruments which utilize hundreds of thousands to millions of lidar observations to provide detailed structural and reflective information of their surroundings. TLS has enjoyed initial success as a validation tool for satellite and airborne estimates of vegetation structure, and are producing independent estimates with increasing accuracy. Reconstruction techniques for TLS observations of vegetation have also improved rapidly, especially for trees. However, uncertainties and challenges still remain in TLS modelling of vegetation structure, especially in geometrically complex ecosystems such as tropical forests (where observation extent and density is hampered by occlusion) and highly temporally dynamic coastal ecosystems (such as saltmarshes and mangroves), where observations may be restricted to narrow microstates. Some of these uncertainties can be mitigated, and challenges met, through the use of lidar instruments optimized for favorable deployment logistics through low weight, rapid scanning, and improved durability. We have conducted studies of vegetation structure in temperate and tropical forests, saltmarshes and mangroves, utilizing a highly portable TLS with considerable deployment flexibility, the Compact Biomass Lidar (CBL). We show results from studies in the temperate Long Term Ecological Research site of Harvard Forest (MA, USA); the tropical forested long-term Carbono sites of La Selva Biological Station (Sarapiqui, Costa Rica); and the saltmarsh LTER of Plum Island (MA, USA). These results demonstrate the improvements to observations in these ecosystems which are facilitated by the specifications of the CBL (and similar TLS) which are optimized for favorable deployment logistics and flexibility. We show the benefits of increased numbers of scanning positions, and specialized deployment platforms to meet ecosystem challenges.

Model reference, sliding mode adaptive control for flexible structures

NASA Technical Reports Server (NTRS)

Yurkovich, S.; Ozguner, U.; Al-Abbass, F.

1988-01-01

A decentralized model reference adaptive approach using a variable-structure sliding model control has been developed for the vibration suppression of large flexible structures. Local models are derived based upon the desired damping and response time in a model-following scheme, and variable structure controllers are then designed which employ colocated angular rate and position feedback. Numerical simulations have been performed using NASA's flexible grid experimental apparatus.

Ensemble-based evaluation for protein structure models.

PubMed

Jamroz, Michal; Kolinski, Andrzej; Kihara, Daisuke

2016-06-15

Comparing protein tertiary structures is a fundamental procedure in structural biology and protein bioinformatics. Structure comparison is important particularly for evaluating computational protein structure models. Most of the model structure evaluation methods perform rigid body superimposition of a structure model to its crystal structure and measure the difference of the corresponding residue or atom positions between them. However, these methods neglect intrinsic flexibility of proteins by treating the native structure as a rigid molecule. Because different parts of proteins have different levels of flexibility, for example, exposed loop regions are usually more flexible than the core region of a protein structure, disagreement of a model to the native needs to be evaluated differently depending on the flexibility of residues in a protein. We propose a score named FlexScore for comparing protein structures that consider flexibility of each residue in the native state of proteins. Flexibility information may be extracted from experiments such as NMR or molecular dynamics simulation. FlexScore considers an ensemble of conformations of a protein described as a multivariate Gaussian distribution of atomic displacements and compares a query computational model with the ensemble. We compare FlexScore with other commonly used structure similarity scores over various examples. FlexScore agrees with experts' intuitive assessment of computational models and provides information of practical usefulness of models. https://bitbucket.org/mjamroz/flexscore dkihara@purdue.edu Supplementary data are available at Bioinformatics online. © The Author 2016. Published by Oxford University Press.

Ensemble-based evaluation for protein structure models

PubMed Central

Jamroz, Michal; Kolinski, Andrzej; Kihara, Daisuke

2016-01-01

Motivation: Comparing protein tertiary structures is a fundamental procedure in structural biology and protein bioinformatics. Structure comparison is important particularly for evaluating computational protein structure models. Most of the model structure evaluation methods perform rigid body superimposition of a structure model to its crystal structure and measure the difference of the corresponding residue or atom positions between them. However, these methods neglect intrinsic flexibility of proteins by treating the native structure as a rigid molecule. Because different parts of proteins have different levels of flexibility, for example, exposed loop regions are usually more flexible than the core region of a protein structure, disagreement of a model to the native needs to be evaluated differently depending on the flexibility of residues in a protein. Results: We propose a score named FlexScore for comparing protein structures that consider flexibility of each residue in the native state of proteins. Flexibility information may be extracted from experiments such as NMR or molecular dynamics simulation. FlexScore considers an ensemble of conformations of a protein described as a multivariate Gaussian distribution of atomic displacements and compares a query computational model with the ensemble. We compare FlexScore with other commonly used structure similarity scores over various examples. FlexScore agrees with experts’ intuitive assessment of computational models and provides information of practical usefulness of models. Availability and implementation: https://bitbucket.org/mjamroz/flexscore Contact: dkihara@purdue.edu Supplementary information: Supplementary data are available at Bioinformatics online. PMID:27307633

Flexible Animation Computer Program

NASA Technical Reports Server (NTRS)

Stallcup, Scott S.

1990-01-01

FLEXAN (Flexible Animation), computer program animating structural dynamics on Evans and Sutherland PS300-series graphics workstation with VAX/VMS host computer. Typical application is animation of spacecraft undergoing structural stresses caused by thermal and vibrational effects. Displays distortions in shape of spacecraft. Program displays single natural mode of vibration, mode history, or any general deformation of flexible structure. Written in FORTRAN 77.

Method of manufacturing flexible metallic photonic band gap structures, and structures resulting therefrom

DOEpatents

Gupta, Sandhya; Tuttle, Gary L.; Sigalas, Mihail; McCalmont, Jonathan S.; Ho, Kai-Ming

2001-08-14

A method of manufacturing a flexible metallic photonic band gap structure operable in the infrared region, comprises the steps of spinning on a first layer of dielectric on a GaAs substrate, imidizing this first layer of dielectric, forming a first metal pattern on this first layer of dielectric, spinning on and imidizing a second layer of dielectric, and then removing the GaAs substrate. This method results in a flexible metallic photonic band gap structure operable with various filter characteristics in the infrared region. This method may be used to construct multi-layer flexible metallic photonic band gap structures. Metal grid defects and dielectric separation layer thicknesses are adjusted to control filter parameters.

Design principles of hair-like structures as biological machines

PubMed Central

2018-01-01

Hair-like structures are prevalent throughout biology and frequently act to sense or alter interactions with an organism's environment. The overall shape of a hair is simple: a long, filamentous object that protrudes from the surface of an organism. This basic design, however, can confer a wide range of functions, owing largely to the flexibility and large surface area that it usually possesses. From this simple structural basis, small changes in geometry, such as diameter, curvature and inter-hair spacing, can have considerable effects on mechanical properties, allowing functions such as mechanosensing, attachment, movement and protection. Here, we explore how passive features of hair-like structures, both individually and within arrays, enable diverse functions across biology. Understanding the relationships between form and function can provide biologists with an appreciation for the constraints and possibilities on hair-like structures. Additionally, such structures have already been used in biomimetic engineering with applications in sensing, water capture and adhesion. By examining hairs as a functional mechanical unit, geometry and arrangement can be rationally designed to generate new engineering devices and ideas. PMID:29848593

Real option logic for healthcare entrepreneurial growth and survival.

PubMed

Williams, David R; Hammes, Paul H

2007-05-01

Given the increasing market and technological uncertainty of capital investments, healthcare financial executives need to incorporate flexibility into their decision making. Traditional capital budgeting techniques do not take into consideration the need for flexibility, changes in the environment, or actions by management. In response, practitioners from various industries have adopted a new way of looking at capital investments: real options.

A survey of flexible bronchoscopy practices in India: The Indian bronchoscopy survey (2017)

PubMed Central

Madan, Karan; Mohan, Anant; Agarwal, Ritesh; Hadda, Vijay; Khilnani, Gopi C; Guleria, Randeep

2018-01-01

Background: There is a lack of contemporaneous data on the practices of flexible bronchoscopy in India. Aim: The aim of the study was to study the prevalent practices of flexible bronchoscopy across India. Methods: The “Indian Bronchoscopy Survey” was a 98-question, online survey structured into the following sections: general information, patient preparation and monitoring, sedation and topical anesthesia, procedural/technical aspects, and bronchoscope disinfection/staff protection. Results: Responses from 669 bronchoscopists (mean age: 40.2 years, 91.8% adult pulmonologists) were available for analysis. Approximately, 70,000 flexible bronchoscopy examinations had been performed over the preceding year. A majority (59%) of bronchoscopists were performing bronchoscopy without sedation. A large number (45%) of bronchoscopists had learned the procedure outside of their fellowship training. About 55% used anticholinergic premedication either as a routine or occasionally. Nebulized lignocaine was being used by 72%, while 24% utilized transtracheal administration of lignocaine. The most commonly (75%) used concentration of lignocaine was 2%. Midazolam with or without fentanyl was the preferred agent for intravenous sedation. The use of video bronchoscope was common (80.8%). The most common (94%) route for performing bronchoscopy was nasal. Conventional transbronchial needle aspiration (TBNA) was being performed by 74%, while 92% and 78% performed endobronchial and transbronchial lung biopsy, respectively. Therapeutic airway interventions (stents, electrocautery, cryotherapy, and others) were being performed by 30%, while endobronchial ultrasound guided transbronchial needle aspiration (EBUS-TBNA) and rigid bronchoscopy were performed by 27% and 19.5%, respectively. Conclusion: There is a wide national variation in the practices of performing flexible bronchoscopy. However, there has been a considerable improvement in bronchoscopy practices compared to previous national surveys. PMID:29487243

A survey of flexible bronchoscopy practices in India: The Indian bronchoscopy survey (2017).

PubMed

Madan, Karan; Mohan, Anant; Agarwal, Ritesh; Hadda, Vijay; Khilnani, Gopi C; Guleria, Randeep

2018-01-01

There is a lack of contemporaneous data on the practices of flexible bronchoscopy in India. The aim of the study was to study the prevalent practices of flexible bronchoscopy across India. The "Indian Bronchoscopy Survey" was a 98-question, online survey structured into the following sections: general information, patient preparation and monitoring, sedation and topical anesthesia, procedural/technical aspects, and bronchoscope disinfection/staff protection. Responses from 669 bronchoscopists (mean age: 40.2 years, 91.8% adult pulmonologists) were available for analysis. Approximately, 70,000 flexible bronchoscopy examinations had been performed over the preceding year. A majority (59%) of bronchoscopists were performing bronchoscopy without sedation. A large number (45%) of bronchoscopists had learned the procedure outside of their fellowship training. About 55% used anticholinergic premedication either as a routine or occasionally. Nebulized lignocaine was being used by 72%, while 24% utilized transtracheal administration of lignocaine. The most commonly (75%) used concentration of lignocaine was 2%. Midazolam with or without fentanyl was the preferred agent for intravenous sedation. The use of video bronchoscope was common (80.8%). The most common (94%) route for performing bronchoscopy was nasal. Conventional transbronchial needle aspiration (TBNA) was being performed by 74%, while 92% and 78% performed endobronchial and transbronchial lung biopsy, respectively. Therapeutic airway interventions (stents, electrocautery, cryotherapy, and others) were being performed by 30%, while endobronchial ultrasound guided transbronchial needle aspiration (EBUS-TBNA) and rigid bronchoscopy were performed by 27% and 19.5%, respectively. There is a wide national variation in the practices of performing flexible bronchoscopy. However, there has been a considerable improvement in bronchoscopy practices compared to previous national surveys.

A voice coil actuator driven active vibration isolation system with the consideration of flexible modes.

PubMed

Park, Kyihwan; Choi, Dongyoub; Ozer, Abdullah; Kim, Sangyoo; Lee, Yongkwan; Joo, Dongik

2008-06-01

We develop a four-mount active vibration isolation system (AVIS) using voice coil actuators. The flexible body modes in the upper plate of the AVIS can cause an instability problem due to control signal whose frequency is close to the resonant frequency of the flexible modes. The loop shaping technique is applied to reduce the amplitude of the control signal. We investigate the performances of the active vibration isolation system proposed in the word in the time domain and frequency domain by comparing to the passive isolation system.

Large-Scale Noniridescent Structural Color Printing Enabled by Infiltration-Driven Nonequilibrium Colloidal Assembly.

PubMed

Bai, Ling; Mai, Van Cuong; Lim, Yun; Hou, Shuai; Möhwald, Helmuth; Duan, Hongwei

2018-03-01

Structural colors originating from interaction of light with intricately arranged micro-/nanostructures have stimulated considerable interest because of their inherent photostability and energy efficiency. In particular, noniridescent structural color with wide viewing angle has been receiving increasing attention recently. However, no method is yet available for rapid and large-scale fabrication of full-spectrum structural color patterns with wide viewing angles. Here, infiltration-driven nonequilibrium assembly of colloidal particles on liquid-permeable and particle-excluding substrates is demonstrated to direct the particles to form amorphous colloidal arrays (ACAs) within milliseconds. The infiltration-assisted (IFAST) colloidal assembly opens new possibilities for rapid manufacture of noniridescent structural colors of ACAs and straightforward structural color mixing. Full-spectrum noniridescent structural colors are successfully produced by mixing primary structural colors of red, blue, and yellow using a commercial office inkjet printer. Rapid fabrication of large-scale structural color patterns with sophisticated color combination/layout by IFAST printing is realized. The IFAST technology is versatile for developing structural color patterns with wide viewing angles, as colloidal particles, inks, and substrates are flexibly designable for diverse applications. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Cognitive structure, flexibility, and plasticity in human multitasking-An integrative review of dual-task and task-switching research.

PubMed

Koch, Iring; Poljac, Edita; Müller, Hermann; Kiesel, Andrea

2018-06-01

Numerous studies showed decreased performance in situations that require multiple tasks or actions relative to appropriate control conditions. Because humans often engage in such multitasking activities, it is important to understand how multitasking affects performance. In the present article, we argue that research on dual-task interference and sequential task switching has proceeded largely separately using different experimental paradigms and methodology. In our article we aim at organizing this complex set of research in terms of three complementary research perspectives on human multitasking. One perspective refers to structural accounts in terms of cognitive bottlenecks (i.e., critical processing stages). A second perspective refers to cognitive flexibility in terms of the underlying cognitive control processes. A third perspective emphasizes cognitive plasticity in terms of the influence of practice on human multitasking abilities. With our review article we aimed at highlighting the value of an integrative position that goes beyond isolated consideration of a single theoretical research perspective and that broadens the focus from single experimental paradigms (dual task and task switching) to favor instead a view that emphasizes the fundamental similarity of the underlying cognitive mechanisms across multitasking paradigms. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Application of 1-aminocyclohexane carboxylic acid to protein nanostructure computer design

PubMed Central

Rodríguez-Ropero, Francisco; Zanuy, David; Casanovas, Jordi; Nussinov, Ruth; Alemán, Carlos

2009-01-01

Conformationally restricted amino acids are promising candidates to serve as basic pieces in redesigned protein motifs which constitute the basic modules in synthetic nanoconstructs. Here we study the ability of constrained cyclic amino acid 1-aminocyclohexane-1-carboxylic acid (Ac6c) to stabilize highly regular β-helical motifs excised from naturally occurring proteins. Calculations indicate that the conformational flexibility observed in both the ring and the main chain is significantly higher than that detected for other 1-aminocycloalkane-1-carboxylic acid (Acnc, where n refers to the size of the ring) with smaller cycles. Incorporation of Ac6c into the flexible loops of β-helical motifs indicates that the stability of such excised building blocks as well as the nano-assemblies derived from them is significantly enhanced. Thus, the intrinsic Ac6c tendency to adopt folded conformations combined with the low structural strain of the cyclohexane ring confers the ability to both self-adapt to the β-helix motif and to stabilize the overall structure by absorbing part of its conformational fluctuations. Comparison with other Acnc residues indicates that the ability to adapt to the targeted position improves considerably with the ring size, i.e. when the rigidity introduced by the strain of the ring decreases. PMID:18201062

Shaft flexibility effects on aeroelastic stability of a rotating bladed disk

NASA Technical Reports Server (NTRS)

Khader, Naim; Loewy, Robert

1989-01-01

A comprehensive study of Coriolis forces and shaft flexibility effects on the structural dynamics and aeroelastic stability of a rotating bladed-disk assembly attached to a cantilever, massless, flexible shaft is presented. Analyses were performed for an actual bladed-disk assembly, used as the first stage in the fan of the 'E3' engine. In the structural model, both in-plane and out-of-plane elastic deformation of the bladed-disk assembly were considered relative to their hub, in addition to rigid disk translations and rotations introduced by shaft flexibility. Besides structural coupling between blades (through the flexible disk), additional coupling is introduced through quasisteady aerodynamic loads. Rotational effects are accounted for throughout the work, and some mode shapes for the whole structure are presented at a selected rpm.

Static aeroelastic deformation of flexible skin for continuous variable trailing-edge camber wing

NASA Astrophysics Data System (ADS)

Liu, Libo; Yin, Weilong; Dai, Fuhong; Liu, Yanju; Leng, Jinsong

2011-03-01

The method for analyzing the static aeroelastic deformation of flexible skin under the air loads was developed. The effect of static aeroelastic deformation of flexible skin on the aerodynamic characteristics of aerofoil and the design parameters of skin was discussed. Numerical results show that the flexible skin on the upper surface of trailing-edge will bubble under the air loads and the bubble has a powerful effect on the aerodynamic pressure near the surface of local deformation. The static aeroelastic deformation of flexible skin significantly affects the aerodynamic characteristics of aerofoil. At small angle of attack, the drag coefficient increases and the lift coefficient decreases. With the increasing angle of attack, the effect of flexible skin on the aerodynamic characteristics of aerofoil is smaller and smaller. The deformation of flexible skin becomes larger and larger with the free-stream velocity increasing. When the free-stream velocity is greater than a value, both of the deformation of flexible skin and the drag coefficient of aerofoil increase rapidly. The maximum tensile strain of flexible skin is increased with consideration of the static aeroelastic deformation.

Allosteric activation transitions in enzymes and biomolecular motors: insights from atomistic and coarse-grained simulations.

PubMed

Daily, Michael D; Yu, Haibo; Phillips, George N; Cui, Qiang

2013-01-01

The chemical step in enzymes is usually preceded by a kinetically distinct activation step that involves large-scale conformational transitions. In "simple" enzymes this step corresponds to the closure of the active site; in more complex enzymes, such as biomolecular motors, the activation step is more complex and may involve interactions with other biomolecules. These activation transitions are essential to the function of enzymes and perturbations in the scale and/or rate of these transitions are implicated in various serious human diseases; incorporating key flexibilities into engineered enzymes is also considered a major remaining challenge in rational enzyme design. Therefore it is important to understand the underlying mechanism of these transitions. This is a significant challenge to both experimental and computational studies because of the allosteric and multi-scale nature of such transitions. Using our recent studies of two enzyme systems, myosin and adenylate kinase (AK), we discuss how atomistic and coarse-grained simulations can be used to provide insights into the mechanism of activation transitions in realistic systems. Collectively, the results suggest that although many allosteric transitions can be viewed as domain displacements mediated by flexible hinges, there are additional complexities and various deviations. For example, although our studies do not find any evidence for "cracking" in AK, our results do underline the contribution of intra-domain properties (e.g., dihedral flexibility) to the rate of the transition. The study of mechanochemical coupling in myosin highlights that local changes important to chemistry require stabilization from more extensive structural changes; in this sense, more global structural transitions are needed to activate the chemistry in the active site. These discussions further emphasize the importance of better understanding factors that control the degree of co-operativity for allosteric transitions, again hinting at the intimate connection between protein stability and functional flexibility. Finally, a number of topics of considerable future interest are briefly discussed.

DEM modeling of flexible structures against granular material avalanches

NASA Astrophysics Data System (ADS)

Lambert, Stéphane; Albaba, Adel; Nicot, François; Chareyre, Bruno

2016-04-01

This article presents the numerical modeling of flexible structures intended to contain avalanches of granular and coarse material (e.g. rock slide, a debris slide). The numerical model is based on a discrete element method (YADE-Dem). The DEM modeling of both the flowing granular material and the flexible structure are detailed before presenting some results. The flowing material consists of a dry polydisperse granular material accounting for the non-sphericity of real materials. The flexible structure consists in a metallic net hanged on main cables, connected to the ground via anchors, on both sides of the channel, including dissipators. All these components were modeled as flexible beams or wires, with mechanical parameters defined from literature data. The simulation results are presented with the aim of investigating the variability of the structure response depending on different parameters related to the structure (inclination of the fence, with/without brakes, mesh size opening), but also to the channel (inclination). Results are then compared with existing recommendations in similar fields.

Implementation of input command shaping to reduce vibration in flexible space structures

NASA Technical Reports Server (NTRS)

Chang, Kenneth W.; Seering, Warren P.; Rappole, B. Whitney

1992-01-01

Viewgraphs on implementation of input command shaping to reduce vibration in flexible space structures are presented. Goals of the research are to explore theory of input command shaping to find an efficient algorithm for flexible space structures; to characterize Middeck Active Control Experiment (MACE) test article; and to implement input shaper on the MACE structure and interpret results. Background on input shaping, simulation results, experimental results, and future work are included.

Testing the Link Between Empathy and Lay Theories of Happiness.

PubMed

Tullett, Alexa M; Plaks, Jason E

2016-09-20

Happiness is a topic that ignites both considerable interest and considerable disagreement. Thus far, however, there has been little attempt to characterize people's lay theories about happiness or explore their consequences. We examined whether individual differences in lay theories of happiness would predict empathy. In Studies 1a and 1b, we validated the Lay Theories of Happiness Scale (LTHS), which includes three dimensions: flexibility, controllability, and locus. In Study 2, higher dispositional empathy was predicted by the belief that happiness is flexible, controllable, and internal. In Studies 3 and 4, higher empathy toward a specific target was predicted by the belief that happiness is flexible, uncontrollable, and external In conjunction, Studies 2, 3, and 4 provide evidence that trait and state empathy are separable and can have opposing relationships with people's lay theories. Overall, these findings highlight generalized beliefs that may guide empathic reactions to the unhappiness of others. © 2016 by the Society for Personality and Social Psychology, Inc.

Model reduction in integrated controls-structures design

NASA Technical Reports Server (NTRS)

Maghami, Peiman G.

1993-01-01

It is the objective of this paper to present a model reduction technique developed for the integrated controls-structures design of flexible structures. Integrated controls-structures design problems are typically posed as nonlinear mathematical programming problems, where the design variables consist of both structural and control parameters. In the solution process, both structural and control design variables are constantly changing; therefore, the dynamic characteristics of the structure are also changing. This presents a problem in obtaining a reduced-order model for active control design and analysis which will be valid for all design points within the design space. In other words, the frequency and number of the significant modes of the structure (modes that should be included) may vary considerably throughout the design process. This is also true as the locations and/or masses of the sensors and actuators change. Moreover, since the number of design evaluations in the integrated design process could easily run into thousands, any feasible order-reduction method should not require model reduction analysis at every design iteration. In this paper a novel and efficient technique for model reduction in the integrated controls-structures design process, which addresses these issues, is presented.

Apparatus for integrating a rigid structure into a flexible wall of an inflatable structure

NASA Technical Reports Server (NTRS)

Johnson, Christopher J. (Inventor); Patterson, Ross M. (Inventor); Spexarth, Gary R. (Inventor)

2009-01-01

For an inflatable structure having a flexible outer shell or wall structure having a flexible restraint layer comprising interwoven, load-bearing straps, apparatus for integrating one or more substantially rigid members into the flexible shell. For each rigid member, a corresponding opening is formed through the flexible shell for receiving the rigid member. A plurality of connection devices are mounted on the rigid member for receiving respective ones of the load-bearing straps. In one embodiment, the connection devices comprise inner connecting mechanisms and outer connecting mechanisms, the inner and outer connecting mechanisms being mounted on the substantially rigid structure and spaced along a peripheral edge portion of the structure in an interleafed array in which respective outer connecting mechanisms are interposed between adjacent pairs of inner connecting mechanisms, the outer connecting mechanisms projecting outwardly from the peripheral edge portion of the substantially rigid structure beyond the adjacent inner connecting mechanisms to form a staggered array of connecting mechanisms extending along the panel structure edge portion. In one embodiment, the inner and outer connecting mechanisms form part of an integrated, structure rotatably mounted on the rigid member peripheral edge portion.

Biologically Inspired, Anisoptropic Flexible Wing for Optimal Flapping Flight

DTIC Science & Technology

2013-01-31

Anisotropic Flexible Wing for Optimal Flapping Flight FA9550-07-1-0547 Sb. GRANT NUMBER Sc. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Sd. PROJECT NUMBER...anisotropic structural flexibility ; c) Conducted coordinated experimental and computational modeling to determine the roles of aerodynamic loading, wing inertia...and structural flexibility and elasticity; and d) Developed surrogate tools for flapping wing MA V design and optimization. Detailed research

Vibration suppression in flexible structures via the sliding-mode control approach

NASA Technical Reports Server (NTRS)

Drakunov, S.; Oezguener, Uemit

1994-01-01

Sliding mode control became very popular recently because it makes the closed loop system highly insensitive to external disturbances and parameter variations. Sliding algorithms for flexible structures have been used previously, but these were based on finite-dimensional models. An extension of this approach for differential-difference systems is obtained. That makes if possible to apply sliding-mode control algorithms to the variety of nondispersive flexible structures which can be described as differential-difference systems. The main idea of using this technique for dispersive structures is to reduce the order of the controlled part of the system by applying an integral transformation. We can say that transformation 'absorbs' the dispersive properties of the flexible structure as the controlled part becomes dispersive.

Protein flexibility in the light of structural alphabets

PubMed Central

Craveur, Pierrick; Joseph, Agnel P.; Esque, Jeremy; Narwani, Tarun J.; Noël, Floriane; Shinada, Nicolas; Goguet, Matthieu; Leonard, Sylvain; Poulain, Pierre; Bertrand, Olivier; Faure, Guilhem; Rebehmed, Joseph; Ghozlane, Amine; Swapna, Lakshmipuram S.; Bhaskara, Ramachandra M.; Barnoud, Jonathan; Téletchéa, Stéphane; Jallu, Vincent; Cerny, Jiri; Schneider, Bohdan; Etchebest, Catherine; Srinivasan, Narayanaswamy; Gelly, Jean-Christophe; de Brevern, Alexandre G.

2015-01-01

Protein structures are valuable tools to understand protein function. Nonetheless, proteins are often considered as rigid macromolecules while their structures exhibit specific flexibility, which is essential to complete their functions. Analyses of protein structures and dynamics are often performed with a simplified three-state description, i.e., the classical secondary structures. More precise and complete description of protein backbone conformation can be obtained using libraries of small protein fragments that are able to approximate every part of protein structures. These libraries, called structural alphabets (SAs), have been widely used in structure analysis field, from definition of ligand binding sites to superimposition of protein structures. SAs are also well suited to analyze the dynamics of protein structures. Here, we review innovative approaches that investigate protein flexibility based on SAs description. Coupled to various sources of experimental data (e.g., B-factor) and computational methodology (e.g., Molecular Dynamic simulation), SAs turn out to be powerful tools to analyze protein dynamics, e.g., to examine allosteric mechanisms in large set of structures in complexes, to identify order/disorder transition. SAs were also shown to be quite efficient to predict protein flexibility from amino-acid sequence. Finally, in this review, we exemplify the interest of SAs for studying flexibility with different cases of proteins implicated in pathologies and diseases. PMID:26075209

High pressure structural investigation on alluaudites Na{sub 2}Fe{sub 3}(PO{sub 4}){sub 3}-Na{sub 2}FeMn{sub 2}(PO{sub 4}){sub 3} system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gao, Jing; Huang, Weifeng; Qin, Shan

Alluaudites are promising electrochemical materials benefited from the open structure. Structural variations of alluaudites Na{sub 2}M{sub 3}(PO{sub 4}){sub 3} (M{sub 3}=Fe{sub 3}, Fe{sub 2}Mn and FeMn{sub 2}) system have been studied by synchrotron radiation X-ray diffraction combined with diamond anvil cell technique up to ~10 GPa at room temperature. No phase transition is observed. The excellent structural stability is mainly due to the flexible framework plus strong covalent P-O bond. Mn{sup 2+} instead of Fe can be described as Na{sup +}+2Fe{sup 2+}→Mn{sup 2+}+Fe{sup 3+}+□ where □ represents a lattice vacancy. The replacement of Fe with larger Mn{sup 2+} is equivalentmore » to applying negative chemical pressure to the material. And it causes a more compressible b-axis, lattice expansion, structural compressibility and intensifies the core/electron-electron interactions of Fe. External pressure effect produces anisotropic lattice shrinkage. Structural considerations related to these variations and promising application prospects are discussed. - Graphical abstract: Figure 1 The crystal structure of alluaudites Na{sub 2}M{sub 3}(PO{sub 4}){sub 3} (M{sub 3}=Fe{sub 3}, Fe{sub 2}Mn and FeMn{sub 2}) projected along the c-axis. Alluaudites adopt a flexible framework plus strong covalent P-O bond, which contribute to excellent structural stability up to ~10 GPa. Mn{sup 2+} instead of Fe can be described as Na{sup ++}2Fe{sup 2+}→Mn{sup 2+}+Fe{sup 3+}+□ where □ represents a lattice vacancy, and it is equivalent to applying negative chemical pressure to the host. The substitution causes a more compressible b-axis, lattice expansion, structural compressibility and intensifies the core/electron-electron interactions of Fe.« less

Department of Defense Implementation Plan for Pandemic Influenza

DTIC Science & Technology

2006-08-01

and Low Intensity Conflict (ASD(SO/LIC)) will provide policy oversight of the DoD Pandemic Influenza bilateral and multilateral international...flexible worksites (e.g., telecommuting ) and flexible work hours (e.g., staggered shifts) in the event of a pandemic. o Ensure development of active...however, special consideration must be given to “social distancing” in the workplace through 74 telecommuting , or other means, as an

Production planning, production systems for flexible automation

NASA Astrophysics Data System (ADS)

Spur, G.; Mertins, K.

1982-09-01

Trends in flexible manufacturing system (FMS) applications are reviewed. Machining systems contain machines which complement each other and can replace each other. Computer controlled storage systems are widespread, with central storage capacity ranging from 20 pallet spaces to 200 magazine spaces. Handling function is fulfilled by pallet chargers in over 75% of FMS's. Data system degree of automation varies considerably. No trends are noted for transport systems.

Free-Suspension Residual Flexibility Testing of Space Station Pathfinder: Comparison to Fixed-Base Results

NASA Technical Reports Server (NTRS)

Tinker, Michael L.

1998-01-01

Application of the free-suspension residual flexibility modal test method to the International Space Station Pathfinder structure is described. The Pathfinder, a large structure of the general size and weight of Space Station module elements, was also tested in a large fixed-base fixture to simulate Shuttle Orbiter payload constraints. After correlation of the Pathfinder finite element model to residual flexibility test data, the model was coupled to a fixture model, and constrained modes and frequencies were compared to fixed-base test. modes. The residual flexibility model compared very favorably to results of the fixed-base test. This is the first known direct comparison of free-suspension residual flexibility and fixed-base test results for a large structure. The model correlation approach used by the author for residual flexibility data is presented. Frequency response functions (FRF) for the regions of the structure that interface with the environment (a test fixture or another structure) are shown to be the primary tools for model correlation that distinguish or characterize the residual flexibility approach. A number of critical issues related to use of the structure interface FRF for correlating the model are then identified and discussed, including (1) the requirement of prominent stiffness lines, (2) overcoming problems with measurement noise which makes the antiresonances or minima in the functions difficult to identify, and (3) the use of interface stiffness and lumped mass perturbations to bring the analytical responses into agreement with test data. It is shown that good comparison of analytical-to-experimental FRF is the key to obtaining good agreement of the residual flexibility values.

Proceedings of the Workshop on Computational Aspects in the Control of Flexible Systems, part 1

NASA Technical Reports Server (NTRS)

Taylor, Lawrence W., Jr. (Compiler)

1989-01-01

Control/Structures Integration program software needs, computer aided control engineering for flexible spacecraft, computer aided design, computational efficiency and capability, modeling and parameter estimation, and control synthesis and optimization software for flexible structures and robots are among the topics discussed.

Modeling and control of flexible space structures

NASA Technical Reports Server (NTRS)

Wie, B.; Bryson, A. E., Jr.

1981-01-01

The effects of actuator and sensor locations on transfer function zeros are investigated, using uniform bars and beams as generic models of flexible space structures. It is shown how finite element codes may be used directly to calculate transfer function zeros. The impulse response predicted by finite-dimensional models is compared with the exact impulse response predicted by the infinite dimensional models. It is shown that some flexible structures behave as if there were a direct transmission between actuator and sensor (equal numbers of zeros and poles in the transfer function). Finally, natural damping models for a vibrating beam are investigated since natural damping has a strong influence on the appropriate active control logic for a flexible structure.

Active control for vibration suppression in a flexible beam using a modal domain optical fiber sensor

NASA Technical Reports Server (NTRS)

Cox, D. E.; Lindner, D. K.

1991-01-01

An account is given of the use of a modal-domain (MD) fiber-optic sensor as an active control system component for vibration suppression, whose output is proportional to the integral of the axial strain along the optical fiber. When an MD sensor is attached to, or embedded in, a flexible structure, it senses the strain in the structure along its gage length. On the basis of the present integration of the sensor model into a flexible-structure model, it becomes possible to design a control system with a dynamic compensator which adds damping to the low-order modes of the flexible structure. This modeling procedure has been experimentally validated.

Modeling and tachometer feedback in the control of an experimental single link flexible structure

NASA Technical Reports Server (NTRS)

Garcia, Ephrahim; Inman, Daniel J.

1990-01-01

In this work a formulation for the modeling of a single link flexible structure will be introduced that includes the effects of dynamic interaction between the actuator and structure. These effects are the rotational modal participation factors for the structure's vibratory motion that occurs at the slewing axis. It will be shown, both theoretically and experimentally, that this dynamic interaction can be advantageous for vibration suppression of the flexible modes of the system during slewing positioning maneuvers.

Experimental and Theoretical Results in Output Trajectory Redesign for Flexible Structures

NASA Technical Reports Server (NTRS)

Dewey, J. S.; Leang, K.; Devasia, S.

1998-01-01

In this paper we study the optimal redesign of output trajectories for linear invertible systems. This is particularly important for tracking control of flexible structures because the input-state trajectores, that achieve tracking of the required output may cause excessive vibrations in the structure. We pose and solve this problem, in the context of linear systems, as the minimization of a quadratic cost function. The theory is developed and applied to the output tracking of a flexible structure and experimental results are presented.

Viscoelastic fluid-structure interactions between a flexible cylinder and wormlike micelle solution

NASA Astrophysics Data System (ADS)

Dey, Anita A.; Modarres-Sadeghi, Yahya; Rothstein, Jonathan P.

2018-06-01

It is well known that when a flexible or flexibly mounted structure is placed perpendicular to the flow of a Newtonian fluid, it can oscillate due to the shedding of separated vortices at high Reynolds numbers. Unlike Newtonian fluids, the flow of viscoelastic fluids can become unstable even at infinitesimal Reynolds numbers due to a purely elastic flow instability that can occur at large Weissenberg numbers. Recent work has shown that these elastic flow instabilities can drive the motion of flexible sheets. The fluctuating fluid forces exerted on the structure from the elastic flow instabilities can lead to a coupling between an oscillatory structural motion and the state of stress in the fluid flow. In this paper, we present the results of an investigation into the flow of a viscoelastic wormlike micelle solution past a flexible circular cylinder. The time variation of the flow field and the state of stress in the fluid are shown using a combination of particle image tracking and flow-induced birefringence images. The static and dynamic responses of the flexible cylinder are presented for a range of flow velocities. The nonlinear dynamics of the structural motion is studied to better understand an observed transition from a symmetric to an asymmetric structural deformation and oscillation behavior.

3D structural fluctuation of IgG1 antibody revealed by individual particle electron tomography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Xing; Zhang, Lei; Tong, Huimin

2015-05-05

Commonly used methods for determining protein structure, including X-ray crystallography and single-particle reconstruction, often provide a single and unique three-dimensional (3D) structure. However, in these methods, the protein dynamics and flexibility/fluctuation remain mostly unknown. Here, we utilized advances in electron tomography (ET) to study the antibody flexibility and fluctuation through structural determination of individual antibody particles rather than averaging multiple antibody particles together. Through individual-particle electron tomography (IPET) 3D reconstruction from negatively-stained ET images, we obtained 120 ab-initio 3D density maps at an intermediate resolution (~1–3 nm) from 120 individual IgG1 antibody particles. Using these maps as a constraint, wemore » derived 120 conformations of the antibody via structural flexible docking of the crystal structure to these maps by targeted molecular dynamics simulations. Statistical analysis of the various conformations disclosed the antibody 3D conformational flexibility through the distribution of its domain distances and orientations. This blueprint approach, if extended to other flexible proteins, may serve as a useful methodology towards understanding protein dynamics and functions.« less

Exploring the potential of a structural alphabet-based tool for mining multiple target conformations and target flexibility insight

PubMed Central

Chéron, Jean-Baptiste; Triki, Dhoha; Senac, Caroline; Flatters, Delphine; Camproux, Anne-Claude

2017-01-01

Protein flexibility is often implied in binding with different partners and is essential for protein function. The growing number of macromolecular structures in the Protein Data Bank entries and their redundancy has become a major source of structural knowledge of the protein universe. The analysis of structural variability through available redundant structures of a target, called multiple target conformations (MTC), obtained using experimental or modeling methods and under different biological conditions or different sources is one way to explore protein flexibility. This analysis is essential to improve the understanding of various mechanisms associated with protein target function and flexibility. In this study, we explored structural variability of three biological targets by analyzing different MTC sets associated with these targets. To facilitate the study of these MTC sets, we have developed an efficient tool, SA-conf, dedicated to capturing and linking the amino acid and local structure variability and analyzing the target structural variability space. The advantage of SA-conf is that it could be applied to divers sets composed of MTCs available in the PDB obtained using NMR and crystallography or homology models. This tool could also be applied to analyze MTC sets obtained by dynamics approaches. Our results showed that SA-conf tool is effective to quantify the structural variability of a MTC set and to localize the structural variable positions and regions of the target. By selecting adapted MTC subsets and comparing their variability detected by SA-conf, we highlighted different sources of target flexibility such as induced by binding partner, by mutation and intrinsic flexibility. Our results support the interest to mine available structures associated with a target using to offer valuable insight into target flexibility and interaction mechanisms. The SA-conf executable script, with a set of pre-compiled binaries are available at http://www.mti.univ-paris-diderot.fr/recherche/plateformes/logiciels. PMID:28817602

Exploring the potential of a structural alphabet-based tool for mining multiple target conformations and target flexibility insight.

PubMed

Regad, Leslie; Chéron, Jean-Baptiste; Triki, Dhoha; Senac, Caroline; Flatters, Delphine; Camproux, Anne-Claude

2017-01-01

Protein flexibility is often implied in binding with different partners and is essential for protein function. The growing number of macromolecular structures in the Protein Data Bank entries and their redundancy has become a major source of structural knowledge of the protein universe. The analysis of structural variability through available redundant structures of a target, called multiple target conformations (MTC), obtained using experimental or modeling methods and under different biological conditions or different sources is one way to explore protein flexibility. This analysis is essential to improve the understanding of various mechanisms associated with protein target function and flexibility. In this study, we explored structural variability of three biological targets by analyzing different MTC sets associated with these targets. To facilitate the study of these MTC sets, we have developed an efficient tool, SA-conf, dedicated to capturing and linking the amino acid and local structure variability and analyzing the target structural variability space. The advantage of SA-conf is that it could be applied to divers sets composed of MTCs available in the PDB obtained using NMR and crystallography or homology models. This tool could also be applied to analyze MTC sets obtained by dynamics approaches. Our results showed that SA-conf tool is effective to quantify the structural variability of a MTC set and to localize the structural variable positions and regions of the target. By selecting adapted MTC subsets and comparing their variability detected by SA-conf, we highlighted different sources of target flexibility such as induced by binding partner, by mutation and intrinsic flexibility. Our results support the interest to mine available structures associated with a target using to offer valuable insight into target flexibility and interaction mechanisms. The SA-conf executable script, with a set of pre-compiled binaries are available at http://www.mti.univ-paris-diderot.fr/recherche/plateformes/logiciels.

Flexible radiator system

NASA Technical Reports Server (NTRS)

Oren, J. A.

1982-01-01

The soft tube radiator subsystem is described including applicable system requirements, the design and limitations of the subsystem components, and the panel manufacturing method. The soft tube radiator subsystem is applicable to payloads requiring 1 to 12 kW of heat rejection for orbital lifetimes per mission of 30 days or less. The flexible radiator stowage volume required is about 60% and the system weight is about 40% of an equivalent heat rejection rigid panel. The cost should also be considerably less. The flexible radiator is particularly suited to shuttle orbiter sortie payloads and also whose mission lengths do not exceed the 30 day design life.

Considerations for preparing collaborative international research: a Ugandan experience.

PubMed

Musil, Carol M; Mutabaazi, Jemimah; Walusimbi, Mariam; Okonsky, Jennifer G; Biribonwa, Yedidah; Eagan, Sabrina; Dimarco, Marguerite A; Mbaballi, Speciosa; Fitzpatrick, Joyce J

2004-08-01

This article describes issues to consider when planning and conducting international research projects. Key considerations include building collaboration, developing a comprehensive and feasible research plan, funding and budgets, addressing human subjects concerns, and analyzing and disseminating project findings. These considerations and related methodological issues are discussed in the context of a replication pilot project conducted outside Kampala, Uganda. Ongoing dialog, flexibility, and collaboration, in addition to good science, are critical to developing successful international research projects.

Nutrient intake and balancing among female Colobus angolensis palliatus inhabiting structurally distinct forest areas: Effects of group, season, and reproductive state.

PubMed

Dunham, Noah T; Rodriguez-Saona, Luis E

2018-06-08

Understanding intraspecific behavioral and dietary variation is critical for assessing primate populations' abilities to persist in habitats characterized by increasing anthropogenic disturbances. While it is evident that some species exhibit considerable dietary flexibility (in terms of species-specific plant parts) in relation to habitat disturbance, it is unclear if primates are characterized by similar variation and flexibility regarding nutrient intake. This study examined the effects of group, season, and reproductive state on nutrient intake and balancing in adult female Colobus angolensis palliatus in the Diani Forest, Kenya. During July 2014 to December 2015, estimates of nutrient intake were recorded for eight females from three groups inhabiting structurally and ecologically distinct forest areas differing in tree species composition and density. There were differences in metabolizable energy (ME) and macronutrient intakes among groups, seasons, and reproductive states. Most notably, females inhabiting one of the more disturbed forest areas consumed less ME and macronutrients compared to females in the more intact forest area. Contrary to prediction, females in early lactation consumed significantly less ME and macronutrients compared to non-lactating and late lactation females. Despite differences in macronutrient intake, the relative contribution of macronutrients to ME were generally more conservative among groups, seasons, and reproductive states. Average daily intake ratios of non-protein energy to available protein ranged from approximately 3.5:1-4.3:1 among groups. These results indicate that female C. a. palliatus demonstrate a consistent nutrient balancing strategy despite significant intergroup differences in consumption of species-specific plant parts. Data from additional colobine species inhabiting different forest types are required to assess the extent to which nutrient balancing is constrained by phylogeny or is more flexible to local ecological conditions. © 2018 Wiley Periodicals, Inc.

Optical and structural properties of carbon dots/TiO2 nanostructures prepared via DC arc discharge in liquid

NASA Astrophysics Data System (ADS)

Biazar, Nooshin; Poursalehi, Reza; Delavari, Hamid

2018-01-01

Synthesis and development of visible active catalysts is an important issue in photocatalytic applications of nanomaterials. TiO2 nanostructures coupled with carbon dots demonstrate a considerable photocatalytic activity in visible wavelengths. Extending optical absorption of a wide band gap semiconductor such as TiO2 with carbon dots is the origin of the visible activity of carbon dots modified semiconductor nanostructures. In addition, carbon dots exhibit high photostability, appropriate electron transport and chemical stability without considerable toxicity or environmental footprints. In this study, optical and structural properties of carbon dots/TiO2 nanostructures prepared via (direct current) DC arc discharge in liquid were investigated. Crystal structure, morphology and optical properties of the samples were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV-visible spectroscopy respectively. SEM images show formation of spherical nanoparticles with an average size of 27 nm. In comparison with pristine TiO2, optical transmission spectrum of carbon dots/TiO2 nanostructures demonstrates an absorption edge at longer wavelengths as well a high optical absorption in visible wavelengths which is significant for visible activity of nanostructures as a photocatalyst. Finally, these results can provide a flexible and versatile pathway for synthesis of carbon dots/oxide semiconductor nanostructures with an appropriate activity under visible light.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu Wei; Leal, Walter S.

Pheromone-binding proteins (PBPs) are involved in the uptake of pheromones from pores on the antennae, transport through an aqueous environment surrounding the olfactory receptor neurons, and fast delivery to pheromone receptors. We tested the hypothesis that a C-terminal segment and a flexible loop are involved in the release of pheromones to membrane-bound receptors. We expressed in Escherichia coli 11 mutants of the PBP from the silkworm moth, BmorPBP, taking into consideration structural differences between the forms with high and low binding affinity. The N-terminus was truncated and His-69, His-70 and His-95 at the base of a flexible loop, and amore » cluster of acidic residues at the C-terminus were mutated. Binding assays and circular dichroism analyses support a mechanism involving protonation of acidic residues Asp-132 and Glu-141 at the C-terminus and histidines, His-70 and His-95, in the base of a loop covering the binding pocket. The former leads to the formation of a new {alpha}-helix, which competes with pheromone for the binding pocket, whereas positive charge repulsion of the histidines opens the opposite side of the binding pocket.« less

Analysis of Foundation of Tall R/C Chimney Incorporating Flexibility of Soil

NASA Astrophysics Data System (ADS)

Jayalekshmi, B. R.; Jisha, S. V.; Shivashankar, R.

2017-09-01

Three dimensional Finite Element (FE) analysis was carried out for 100 and 400 m high R/C chimneys having piled annular raft and annular raft foundations considering the flexibility of soil subjected to across-wind load. Stiffness of supporting soil and foundation were varied to evaluate the significance of Soil-Structure Interaction (SSI). The integrated chimney-foundation-soil system was analysed by finite element software ANSYS based on direct method of SSI assuming linear elastic material behaviour. FE analyses were carried out for two cases of SSI namely, (1) chimney with annular raft foundation and (2) chimney with piled annular raft foundation. The responses in raft such as bending moments and settlements were evaluated for both the cases and compared to those obtained from the conventional method of analysis of annular raft foundation. It is found that the responses in raft vary considerably depending on the stiffness of the underlying soil and the stiffness of foundation. Piled raft foundations are better suited for tall chimneys to be constructed in loose or medium sand.

Non-leaky modes and bandgaps of surface acoustic waves in wrinkled stiff-film/compliant-substrate bilayers

NASA Astrophysics Data System (ADS)

Li, Guo-Yang; Xu, Guoqiang; Zheng, Yang; Cao, Yanping

2018-03-01

Surface acoustic wave (SAW) devices have found a wide variety of technical applications, including SAW filters, SAW resonators, microfluidic actuators, biosensors, flow measurement devices, and seismic wave shields. Stretchable/flexible electronic devices, such as sensory skins for robotics, structural health monitors, and wearable communication devices, have received considerable attention across different disciplines. Flexible SAW devices are essential building blocks for these applications, wherein piezoelectric films may need to be integrated with the compliant substrates. When piezoelectric films are much stiffer than soft substrates, SAWs are usually leaky and the devices incorporating them suffer from acoustic losses. In this study, the propagation of SAWs in a wrinkled bilayer system is investigated, and our analysis shows that non-leaky modes can be achieved by engineering stress patterns through surface wrinkles in the system. Our analysis also uncovers intriguing bandgaps (BGs) related to the SAWs in a wrinkled bilayer system; these are caused by periodic deformation patterns, which indicate that diverse wrinkling patterns could be used as metasurfaces for controlling the propagation of SAWs.

Flexible phosphor sensors: a digital supplement or option to rigid sensors.

PubMed

Glazer, Howard S

2014-01-01

An increasing number of dental practices are upgrading from film radiography to digital radiography, for reasons that include faster image processing, easier image access, better patient education, enhanced data storage, and improved office productivity. Most practices that have converted to digital technology use rigid, or direct, sensors. Another digital option is flexible phosphor sensors, also called indirect sensors or phosphor storage plates (PSPs). Flexible phosphor sensors can be advantageous for use with certain patients who may be averse to direct sensors, and they can deliver a larger image area. Additionally, sensor cost for replacement PSPs is considerably lower than for hard sensors. As such, flexible phosphor sensors appear to be a viable supplement or option to direct sensors.

Housing flexibility effects on rotor stability

NASA Technical Reports Server (NTRS)

Davis, L. B.; Wolfe, E. A.; Beatty, R. F.

1985-01-01

Preliminary rotordynamic evaluations are performed with a housing stiffness assumption that is typically determined only after the hardware is built. In addressing rotor stability, a rigid housing assumption was shown to predict an instability at a lower spin speed than a comparable flexible housing analysis. This rigid housing assumption therefore provides a conservative estimate of the stability threshold speed. A flexible housing appears to act as an energy absorber and dissipated some of the destabilizing force. The fact that a flexible housing is usually asymmetric and considerably heavier than the rotor was related to this apparent increase in rotor stability. Rigid housing analysis is proposed as a valuable screening criteria and may save time and money in construction of elaborate housing finite element models for linear stability analyses.

Advances in optical structure systems; Proceedings of the Meeting, Orlando, FL, Apr. 16-19, 1990

NASA Astrophysics Data System (ADS)

Breakwell, John; Genberg, Victor L.; Krumweide, Gary C.

Various papers on advances in optical structure systems are presented. Individual topics addressed include: beam pathlength optimization, thermal stress in glass/metal bond with PR 1578 adhesive, structural and optical properties for typical solid mirror shapes, parametric study of spinning polygon mirror deformations, simulation of small structures-optics-controls system, spatial PSDs of optical structures due to random vibration, mountings for a four-meter glass mirror, fast-steering mirrors in optical control systems, adaptive state estimation for control of flexible structures, surface control techniques for large segmented mirrors, two-time-scale control designs for large flexible structures, closed-loop dynamic shape control of a flexible beam. Also discussed are: inertially referenced pointing for body-fixed payloads, sensor blending line-of-sight stabilization, controls/optics/structures simulation development, transfer functions for piezoelectric control of a flexible beam, active control experiments for large-optics vibration alleviation, composite structures for a large-optical test bed, graphite/epoxy composite mirror for beam-steering applications, composite structures for optical-mirror applications, thin carbon-fiber prepregs for dimensionally critical structures.

Validation Tests of Fiber Optic Strain-Based Operational Shape and Load Measurements

NASA Technical Reports Server (NTRS)

Bakalyar, John A.; Jutte, Christine

2012-01-01

Aircraft design has been progressing toward reduced structural weight to improve fuel efficiency, increase performance, and reduce cost. Lightweight aircraft structures are more flexible than conventional designs and require new design considerations. Intelligent sensing allows for enhanced control and monitoring of aircraft, which enables increased structurally efficiency. The NASA Dryden Flight Research Center (DFRC) has developed an instrumentation system and analysis techniques that combine to make distributed structural measurements practical for lightweight vehicles. Dryden's Fiber Optic Strain Sensing (FOSS) technology enables a multitude of lightweight, distributed surface strain measurements. The analysis techniques, referred to as the Displacement Transfer Functions (DTF) and Load Transfer Functions (LTF), use surface strain values to calculate structural deflections and operational loads. The combined system is useful for real-time monitoring of aeroelastic structures, along with many other applications. This paper describes how the capabilities of the measurement system were demonstrated using subscale test articles that represent simple aircraft structures. Empirical FOSS strain data were used within the DTF to calculate the displacement of the article and within the LTF to calculate bending moments due to loads acting on the article. The results of the tests, accuracy of the measurements, and a sensitivity analysis are presented.

Nucleus Accumbens Dopamine D2-Receptor Expressing Neurons Control Behavioral Flexibility in a Place Discrimination Task in the IntelliCage

ERIC Educational Resources Information Center

Macpherson, Tom; Morita, Makiko; Wang, Yanyan; Sasaoka, Toshikuni; Sawa, Akira; Hikida, Takatoshi

2016-01-01

Considerable evidence has demonstrated a critical role for the nucleus accumbens (NAc) in the acquisition and flexibility of behavioral strategies. These processes are guided by the activity of two discrete neuron types, dopamine D1- or D2-receptor expressing medium spiny neurons (D1-/D2-MSNs). Here we used the IntelliCage, an automated…

A flexible framework for process-based hydraulic and water ...

EPA Pesticide Factsheets

Background Models that allow for design considerations of green infrastructure (GI) practices to control stormwater runoff and associated contaminants have received considerable attention in recent years. While popular, generally, the GI models are relatively simplistic. However, GI model predictions are being relied upon by many municipalities and State/Local agencies to make decisions about grey vs. green infrastructure improvement planning. Adding complexity to GI modeling frameworks may preclude their use in simpler urban planning situations. Therefore, the goal here was to develop a sophisticated, yet flexible tool that could be used by design engineers and researchers to capture and explore the effect of design factors and properties of the media used in the performance of GI systems at a relatively small scale. We deemed it essential to have a flexible GI modeling tool that is capable of simulating GI system components and specific biophysical processes affecting contaminants such as reactions, and particle-associated transport accurately while maintaining a high degree of flexibly to account for the myriad of GI alternatives. The mathematical framework for a stand-alone GI performance assessment tool has been developed and will be demonstrated.Framework Features The process-based model framework developed here can be used to model a diverse range of GI practices such as green roof, retention pond, bioretention, infiltration trench, permeable pavement and

Theoretical and software considerations for general dynamic analysis using multilevel substructured models

NASA Technical Reports Server (NTRS)

Schmidt, R. J.; Dodds, R. H., Jr.

1985-01-01

The dynamic analysis of complex structural systems using the finite element method and multilevel substructured models is presented. The fixed-interface method is selected for substructure reduction because of its efficiency, accuracy, and adaptability to restart and reanalysis. This method is extended to reduction of substructures which are themselves composed of reduced substructures. The implementation and performance of the method in a general purpose software system is emphasized. Solution algorithms consistent with the chosen data structures are presented. It is demonstrated that successful finite element software requires the use of software executives to supplement the algorithmic language. The complexity of the implementation of restart and reanalysis porcedures illustrates the need for executive systems to support the noncomputational aspects of the software. It is shown that significant computational efficiencies can be achieved through proper use of substructuring and reduction technbiques without sacrificing solution accuracy. The restart and reanalysis capabilities and the flexible procedures for multilevel substructured modeling gives economical yet accurate analyses of complex structural systems.

Peptidic Macrocycles - Conformational Sampling and Thermodynamic Characterization

PubMed Central

2018-01-01

Macrocycles are of considerable interest as highly specific drug candidates, yet they challenge standard conformer generators with their large number of rotatable bonds and conformational restrictions. Here, we present a molecular dynamics-based routine that bypasses current limitations in conformational sampling and extensively profiles the free energy landscape of peptidic macrocycles in solution. We perform accelerated molecular dynamics simulations to capture a diverse conformational ensemble. By applying an energetic cutoff, followed by geometric clustering, we demonstrate the striking robustness and efficiency of the approach in identifying highly populated conformational states of cyclic peptides. The resulting structural and thermodynamic information is benchmarked against interproton distances from NMR experiments and conformational states identified by X-ray crystallography. Using three different model systems of varying size and flexibility, we show that the method reliably reproduces experimentally determined structural ensembles and is capable of identifying key conformational states that include the bioactive conformation. Thus, the described approach is a robust method to generate conformations of peptidic macrocycles and holds promise for structure-based drug design. PMID:29652495

Peptidic Macrocycles - Conformational Sampling and Thermodynamic Characterization.

PubMed

Kamenik, Anna S; Lessel, Uta; Fuchs, Julian E; Fox, Thomas; Liedl, Klaus R

2018-05-29

Macrocycles are of considerable interest as highly specific drug candidates, yet they challenge standard conformer generators with their large number of rotatable bonds and conformational restrictions. Here, we present a molecular dynamics-based routine that bypasses current limitations in conformational sampling and extensively profiles the free energy landscape of peptidic macrocycles in solution. We perform accelerated molecular dynamics simulations to capture a diverse conformational ensemble. By applying an energetic cutoff, followed by geometric clustering, we demonstrate the striking robustness and efficiency of the approach in identifying highly populated conformational states of cyclic peptides. The resulting structural and thermodynamic information is benchmarked against interproton distances from NMR experiments and conformational states identified by X-ray crystallography. Using three different model systems of varying size and flexibility, we show that the method reliably reproduces experimentally determined structural ensembles and is capable of identifying key conformational states that include the bioactive conformation. Thus, the described approach is a robust method to generate conformations of peptidic macrocycles and holds promise for structure-based drug design.

Factor Structure of the Behavior Flexibility Rating Scale (BFRS)

ERIC Educational Resources Information Center

Pituch, Keenan A.; Green, Vanessa A.; Sigafoos, Jeff; Itchon, Jonathan; O'Reilly, Mark; Lancioni, Giulio E.; Didden, Robert

2007-01-01

The Behavior Flexibility Rating Scale (BFRS) is designed to assess insistence on sameness or lack of behavioral flexibility, which is often associated with autism and other developmental disabilities. This study was designed to assess the factor structure of this scale for a sample of 968 individuals with autism, Asperger's syndrome, and Down…

Modelling of structural flexiblity in multibody railroad vehicle systems

NASA Astrophysics Data System (ADS)

Escalona, José L.; Sugiyama, Hiroyuki; Shabana, Ahmed A.

2013-07-01

This paper presents a review of recent research investigations on the computer modelling of flexible bodies in railroad vehicle systems. The paper will also discuss the influence of the structural flexibility of various components, including the wheelset, the truck frames, tracks, pantograph/catenary systems, and car bodies, on the dynamics of railroad vehicles. While several formulations and computer techniques for modelling structural flexibility are discussed in this paper, a special attention is paid to the floating frame of reference formulation which is widely used and leads to reduced-order finite-element models for flexible bodies by employing component modes synthesis techniques. Other formulations and numerical methods such as semi-analytical approaches, absolute nodal coordinate formulation, finite-segment method, boundary elements method, and discrete elements method are also discussed. This investigation is motivated by the fact that the structural flexibility can have a significant effect on the overall dynamics of railroad vehicles, ride comfort, vibration suppression and noise level reduction, lateral stability, track response to vehicle forces, stress analysis, wheel-rail contact forces, wear and crashworthiness.

Proceedings of the Workshop on Identification and Control of Flexible Space Structures, Volume 2

NASA Technical Reports Server (NTRS)

Rodriguez, G. (Editor)

1985-01-01

The results of a workshop on identification and control of flexible space structures held in San Diego, CA, July 4 to 6, 1984 are discussed. The main objectives of the workshop were to provide a forum to exchange ideas in exploring the most advanced modeling, estimation, identification and control methodologies to flexible space structures. The workshop responded to the rapidly growing interest within NASA in large space systems (space station, platforms, antennas, flight experiments) currently under design. Dynamic structural analysis, control theory, structural vibration and stability, and distributed parameter systems are discussed.

NASA/DOD Control/Structures Interaction Technology, 1986

NASA Technical Reports Server (NTRS)

Wright, Robert L. (Compiler)

1986-01-01

Control/structures interactions, deployment dynamics and system performance of large flexible spacecraft are discussed. Spacecraft active controls, deployable truss structures, deployable antennas, solar power systems for space stations, pointing control systems for space station gimballed payloads, computer-aided design for large space structures, and passive damping for flexible structures are among the topics covered.

Wake structures behind a swimming robotic lamprey with a passively flexible tail

PubMed Central

Leftwich, Megan C.; Tytell, Eric D.; Cohen, Avis H.; Smits, Alexander J.

2012-01-01

SUMMARY A robotic lamprey, based on the silver lamprey, Ichthyomyzon unicuspis, was used to investigate the influence of passive tail flexibility on the wake structure and thrust production during anguilliform swimming. A programmable microcomputer actuated 11 servomotors that produce a traveling wave along the length of the lamprey body. The waveform was based on kinematic studies of living lamprey, and the shape of the tail was taken from a computer tomography scan of the silver lamprey. The tail was constructed of flexible PVC gel, and nylon inserts were used to change its degree of flexibility. Particle image velocimetry measurements using three different levels of passive flexibility show that the large-scale structure of the wake is dominated by the formation of two pairs of vortices per shedding cycle, as seen in the case of a tail that flexed actively according to a pre-defined kinematic pattern, and did not bend in response to fluid forces. When the tail is passively flexible, however, the large structures are composed of a number of smaller vortices, and the wake loses coherence as the degree of flexibility increases. Momentum balance calculations indicate that, at a given tailbeat frequency, increasing the tail flexibility yields less net force, but changing the cycle frequency to match the resonant frequency of the tail increases the force production. PMID:22246250

Attaching solar collectors to a structural framework utilizing a flexible clip

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kruse, John S

Methods and apparatuses described herein provide for the attachment of solar collectors to a structural framework in a solar array assembly. A flexible clip is attached to either end of each solar collector and utilized to attach the solar collector to the structural framework. The solar collectors are positioned to allow a member of the framework to engage a pair of flexible clips attached to adjacent solar collectors during assembly of the solar array. Each flexible clip may have multiple frame-engaging portions, each with a flange on one end to cause the flexible clip to deflect inward when engaged bymore » the framework member during assembly and to guide each of the frame-engaging portions into contact with a surface of the framework member for attachment.« less

Application of binding free energy calculations to prediction of binding modes and affinities of MDM2 and MDMX inhibitors.

PubMed

Lee, Hui Sun; Jo, Sunhwan; Lim, Hyun-Suk; Im, Wonpil

2012-07-23

Molecular docking is widely used to obtain binding modes and binding affinities of a molecule to a given target protein. Despite considerable efforts, however, prediction of both properties by docking remains challenging mainly due to protein's structural flexibility and inaccuracy of scoring functions. Here, an integrated approach has been developed to improve the accuracy of binding mode and affinity prediction and tested for small molecule MDM2 and MDMX antagonists. In this approach, initial candidate models selected from docking are subjected to equilibration MD simulations to further filter the models. Free energy perturbation molecular dynamics (FEP/MD) simulations are then applied to the filtered ligand models to enhance the ability in predicting the near-native ligand conformation. The calculated binding free energies for MDM2 complexes are overestimated compared to experimental measurements mainly due to the difficulties in sampling highly flexible apo-MDM2. Nonetheless, the FEP/MD binding free energy calculations are more promising for discriminating binders from nonbinders than docking scores. In particular, the comparison between the MDM2 and MDMX results suggests that apo-MDMX has lower flexibility than apo-MDM2. In addition, the FEP/MD calculations provide detailed information on the different energetic contributions to ligand binding, leading to a better understanding of the sensitivity and specificity of protein-ligand interactions.

The dynamics and control of large flexible space structures, part 11

NASA Technical Reports Server (NTRS)

Bainum, Peter M.; Reddy, A. S. S. R; Diarra, Cheick M.; Li, Feiyue

1988-01-01

A mathematical model is developed to predict the dynamics of the proposed Spacecraft Control Laboratory Experiment during the stationkeeping phase. The Shuttle and reflector are assumed to be rigid, while the mass connecting the Shuttle to the reflector is assumed to be flexible with elastic deformations small as compared with its length. It is seen that in the presence of gravity-gradient torques, the system assumes a new equilibrium position primarily due to the offset in the mass attachment point to the reflector from the reflector's mass center. Control is assumed to be provided through the Shuttle's three torquers and throught six actuators located by painrs at two points on the mass and at the reflector mass center. Numerical results confirm the robustness of an LQR derived control strategy during stationkeeping with maximum control efforts significantly below saturation levels. The linear regulator theory is also used to derive control laws for the linearized model of the rigidized SCOLE configuration where the mast flexibility is not included. It is seen that this same type of control strategy can be applied for the rapid single axis slewing of the SCOLE through amplitudes as large as 20 degrees. These results provide a definite trade-off between the slightly larger slewing times with the considerable reduction in over-all control effort as compared with the results of the two point boundary value problem application of Pontryagin's Maximum Principle.

Supramolecular Drug Delivery Systems Based on Water-Soluble Pillar[n]arenes.

PubMed

Wu, Xuan; Gao, Lei; Hu, Xiao-Yu; Wang, Leyong

2016-06-01

Supramolecular drug delivery systems (SDDSs), including various kinds of nanostructures that are assembled by reversible noncovalent interactions, have attracted considerable attention as ideal drug carriers owing to their fascinating ability to undergo dynamic switching of structure, morphology, and function in response to various external stimuli, which provides a flexible and robust platform for designing and developing functional and smart supramolecular nano-drug carriers. Pillar[n]arenes represent a new generation of macrocyclic hosts, which have unique structures and excellent properties in host-guest chemistry. This account describes recent progress in our group to develop pillararene-based stimuli-responsive supramolecular nanostructures constructed by reversible host-guest interactions for controllable anticancer drug delivery. The potential applications of these supramolecular drug carriers in cancer treatment and the fundamental questions facing SDDSs are also discussed. © 2016 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

The transformation of housing and household structures in France and Great Britain.

PubMed

Bonvalet, C; Lelievre, E

1997-09-01

"In France and Great Britain, the last 30 years have seen considerable evolution in the housing stock...and in household structure....This article describes the dynamic interaction of processes influencing the evolution of both households and dwellings. In the two countries, the life course of individuals has become more and more complex. This translates into an ever greater variety of housing needs, not only at different stages in family life, but also in relation to growing job insecurity regardless of family situation. At the same time, policies encouraging home-ownership seem to have reached their limits, because of the new demand for rented accommodation. The answer to sociological and economic evolution cannot be found in a ¿single' type of housing and tenure status, but rather in a wide range of dwellings and in the development of a more flexible housing market." excerpt

Experimental and Theoretical Results in Output-Trajectory Redesign for Flexible Structures

NASA Technical Reports Server (NTRS)

Dewey, J. S.; Devasia, Santosh

1996-01-01

In this paper we study the optimal redesign of output trajectory for linear invertible systems. This is particularly important for tracking control of flexible structures because the input-state trajectories that achieve the required output may cause excessive vibrations in the structure. A trade-off is then required between tracking and vibrations reduction. We pose and solve this problem as the minimization of a quadratic cost function. The theory is developed and applied to the output tracking of a flexible structure and experimental results are presented.

Conceptual approach study of a 200 watt per kilogram solar array

NASA Technical Reports Server (NTRS)

Stanhouse, R. W.; Fox, D.; Wilson, W.

1976-01-01

Solar array candidate configurations (flexible rollup, flexible flat-pact, semi-rigid panel, semi-rigid flat-pack) were analyzed with particular attention to the specific power (W/kg) requirement. Two of these configurations (flexible rollup and flexible flat-pack) are capable of delivering specific powers equal to or exceeding the baseline requirement of 200 W/kg. Only the flexible rollup is capable of in-flight retraction and subsequent redeployment. The wrap-around contact photovoltaic cell configuration has been chosen over the conventional cell. The demand for ultra high specific power forces the selection of ultra-thin cells and cover material. Based on density and mass range considerations, it was concluded that 13 micrometers of FEP Teflon is sufficient to protect the cell from a total proton fluency of 2(10 to the 12th power) particles/sq cm over a three-year interplanetary mission. The V-stiffened, lattice boom deployed, flexible substrate rollup array holds the greatest promise of meeting the baseline requirements set for this study.

Probing the structural flexibility of MOFs by constructing metal oxide@MOF-based heterostructures for size-selective photoelectrochemical response

NASA Astrophysics Data System (ADS)

Zhan, Wenwen; He, Yue; Guo, Jiangbin; Chen, Luning; Kong, Xiangjian; Zhao, Haixia; Kuang, Qin; Xie, Zhaoxiong; Zheng, Lansun

2016-07-01

It is becoming a challenge to achieve simpler characterization and wider application of flexible metal organic frameworks (MOFs) exhibiting the gate-opening or breathing behavior. Herein, we designed an intelligent MOF-based system where the gate-opening or breathing behavior of MOFs can be facially visualized in solution. Two types of metal oxide@MOF core-shell heterostructures, ZnO@ZIF-7 and ZnO@ZIF-71, were prepared using ZnO nanorods as self-sacrificial templates. The structural flexibility of both the MOFs can be easily judged from the distinct molecular-size-related formation modes and photoelectrochemical performances between the two ZnO@ZIF heterostructures. Moreover, the rotational dynamics of the flexible parts of ZIF-7 were studied by analyzing the intrinsic physical properties, such as dielectric constants, of the structure. The present work reminds us to pay particular attention to the influences of the structural flexibility of MOFs on the structure and properties of MOF-involved heterostructures in future studies.It is becoming a challenge to achieve simpler characterization and wider application of flexible metal organic frameworks (MOFs) exhibiting the gate-opening or breathing behavior. Herein, we designed an intelligent MOF-based system where the gate-opening or breathing behavior of MOFs can be facially visualized in solution. Two types of metal oxide@MOF core-shell heterostructures, ZnO@ZIF-7 and ZnO@ZIF-71, were prepared using ZnO nanorods as self-sacrificial templates. The structural flexibility of both the MOFs can be easily judged from the distinct molecular-size-related formation modes and photoelectrochemical performances between the two ZnO@ZIF heterostructures. Moreover, the rotational dynamics of the flexible parts of ZIF-7 were studied by analyzing the intrinsic physical properties, such as dielectric constants, of the structure. The present work reminds us to pay particular attention to the influences of the structural flexibility of MOFs on the structure and properties of MOF-involved heterostructures in future studies. Electronic supplementary information (ESI) available: Experimental details, XRD patterns and SEM images of products in other reactions, concentration-dependent photocurrent responses, and supplementary data of dielectric measurements. See DOI: 10.1039/c6nr02257j

Achieving flexible low-scattering metasurface based on randomly distribution of meta-elements.

PubMed

Zhao, Junming; Sima, Boyu; Jia, Nan; Wang, Cheng; Zhu, Bo; Jiang, Tian; Feng, Yijun

2016-11-28

In the paper, a flexible low-scattering metasurface is proposed and realized. The layout is composed of similar "#" shaped elements with variable sizes which are randomly distributed along the surface. The various dimensions of the meta-elements lead to different reflection phases for the meta-elements with respect to the incident plane wave, resulting a diffuse reflection surface and exhibiting a broadband backward low-scattering property. In consideration of the flexibility, metasurfaces composed of printed metallic element films attaching with flexible substrate are designed, fabricated and measured in microwave domain. The measurement results show that 10dB radar cross section (RCS) reduction is obtained across the X-band by coating them to either metallic plates or metallic cylinders with only 1/8 working wavelength thickness. We think that the proposed flexible metasurface is applicable to other frequency bands and can be applied in EM stealth technology.

7 CFR 1924.105 - Planning/performing development.

Code of Federal Regulations, 2014 CFR

2014-01-01

... specific site. Planning must take into consideration topography, soils, climate, adjacent land use... services, housing and social conditions, and a degree of flexibility to accommodate changing demands. All...

Structural disorder within sendai virus nucleoprotein and phosphoprotein: insight into the structural basis of molecular recognition.

PubMed

Jensen, Malene Ringkjøbing; Bernadó, Pau; Houben, Klaartje; Blanchard, Laurence; Marion, Dominque; Ruigrok, Rob W H; Blackledge, Martin

2010-08-01

Intrinsically disordered regions of significant length are present throughout eukaryotic genomes, and are particularly prevalent in viral proteins. Due to their inherent flexibility, these proteins inhabit a conformational landscape that is too complex to be described by classical structural biology. The elucidation of the role that conformational flexibility plays in molecular function will redefine our understanding of the molecular basis of biological function, and the development of appropriate technology to achieve this aim remains one of the major challenges for the future of structural biology. NMR is the technique of choice for studying intrinsically disordered proteins, providing information about structure, flexibility and interactions at atomic resolution even in completely disordered proteins. In particular residual dipolar couplings (RDCs) are sensitive and powerful tools for determining local and long-range structural behaviour in flexible proteins. Here we describe recent applications of the use of RDCs to quantitatively describe the level of local structure in intrinsically disordered proteins involved in replication and transcription in Sendai virus.

A Water-/Fireproof Flexible Lithium-Oxygen Battery Achieved by Synergy of Novel Architecture and Multifunctional Separator.

PubMed

Yin, Yan-Bin; Yang, Xiao-Yang; Chang, Zhi-Wen; Zhu, Yun-Hai; Liu, Tong; Yan, Jun-Min; Jiang, Qing

2018-01-01

To meet the increasing demands for portable and flexible devices in a rapidly developing society, it is urgently required to develop highly safe and flexible electrochemical energy-storage systems. Flexible lithium-oxygen batteries with high theoretical specific energy density are promising candidates; however, the conventional half-open structure design prevents it from working properly under water or fire conditions. Herein, as a proof-of-concept experiment, a highly safe flexible lithium-oxygen battery achieved by the synergy of a vital multifunctional structure design and a unique composite separator is proposed and fabricated. The structure can effectively prevent the invasion of water from the environment and combustion, which is further significantly consolidated with the help of a polyimide and poly(vinylidene fluoride-co-hexafluoropropylene) composite separator, which holds good water resistance, thermal stability, and ionic conductivity. Unexpectedly, the obtained lithium-oxygen battery exhibits superior flexibility, water resistance, thermal resistance, and cycling stability (up to 218 cycles; at a high current of 1 mA and capacity of 4 mA h). This novel water/fireproof, flexible lithium-oxygen battery is a promising candidate to power underwater flexible electronics. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Conformational flexibility in the catalytic triad revealed by the high-resolution crystal structure of Streptomyces erythraeus trypsin in an unliganded state

PubMed Central

Blankenship, Elise; Vukoti, Krishna; Miyagi, Masaru; Lodowski, David T.

2014-01-01

With more than 500 crystal structures determined, serine proteases make up greater than one-third of all proteases structurally examined to date, making them among the best biochemically and structurally characterized enzymes. Despite the numerous crystallographic and biochemical studies of trypsin and related serine proteases, there are still considerable shortcomings in the understanding of their catalytic mechanism. Streptomyces erythraeus trypsin (SET) does not exhibit autolysis and crystallizes readily at physiological pH; hence, it is well suited for structural studies aimed at extending the understanding of the catalytic mechanism of serine proteases. While X-ray crystallographic structures of this enzyme have been reported, no coordinates have ever been made available in the Protein Data Bank. Based on this, and observations on the extreme stability and unique properties of this particular trypsin, it was decided to crystallize it and determine its structure. Here, the first sub-angstrom resolution structure of an unmodified, unliganded trypsin crystallized at physiological pH is reported. Detailed structural analysis reveals the geometry and structural rigidity of the catalytic triad in the unoccupied active site and comparison to related serine proteases provides a context for interpretation of biochemical studies of catalytic mechanism and activity. PMID:24598752

Conformational flexibility in the catalytic triad revealed by the high-resolution crystal structure of Streptomyces erythraeus trypsin in an unliganded state.

PubMed

Blankenship, Elise; Vukoti, Krishna; Miyagi, Masaru; Lodowski, David T

2014-03-01

With more than 500 crystal structures determined, serine proteases make up greater than one-third of all proteases structurally examined to date, making them among the best biochemically and structurally characterized enzymes. Despite the numerous crystallographic and biochemical studies of trypsin and related serine proteases, there are still considerable shortcomings in the understanding of their catalytic mechanism. Streptomyces erythraeus trypsin (SET) does not exhibit autolysis and crystallizes readily at physiological pH; hence, it is well suited for structural studies aimed at extending the understanding of the catalytic mechanism of serine proteases. While X-ray crystallographic structures of this enzyme have been reported, no coordinates have ever been made available in the Protein Data Bank. Based on this, and observations on the extreme stability and unique properties of this particular trypsin, it was decided to crystallize it and determine its structure. Here, the first sub-angstrom resolution structure of an unmodified, unliganded trypsin crystallized at physiological pH is reported. Detailed structural analysis reveals the geometry and structural rigidity of the catalytic triad in the unoccupied active site and comparison to related serine proteases provides a context for interpretation of biochemical studies of catalytic mechanism and activity.

Robust fuel- and time-optimal control of uncertain flexible space structures

NASA Technical Reports Server (NTRS)

Wie, Bong; Sinha, Ravi; Sunkel, John; Cox, Ken

1993-01-01

The problem of computing open-loop, fuel- and time-optimal control inputs for flexible space structures in the face of modeling uncertainty is investigated. Robustified, fuel- and time-optimal pulse sequences are obtained by solving a constrained optimization problem subject to robustness constraints. It is shown that 'bang-off-bang' pulse sequences with a finite number of switchings provide a practical tradeoff among the maneuvering time, fuel consumption, and performance robustness of uncertain flexible space structures.

Flight dynamics simulation modeling and control of a large flexible tiltrotor aircraft

NASA Astrophysics Data System (ADS)

Juhasz, Ondrej

A high order rotorcraft mathematical model is developed and validated against the XV-15 and a Large Civil Tiltrotor (LCTR) concept. The mathematical model is generic and allows for any rotorcraft configuration, from single main rotor helicopters to coaxial and tiltrotor aircraft. Rigid-body and inflow states, as well as flexible wing and blade states are used in the analysis. The separate modeling of each rotorcraft component allows for structural flexibility to be included, which is important when modeling large aircraft where structural modes affect the flight dynamics frequency ranges of interest, generally 1 to 20 rad/sec. Details of the formulation of the mathematical model are given, including derivations of structural, aerodynamic, and inertial loads. The linking of the components of the aircraft is developed using an approach similar to multibody analyses by exploiting a tree topology, but without equations of constraints. Assessments of the effects of wing flexibility are given. Flexibility effects are evaluated by looking at the nature of the couplings between rigid-body modes and wing structural modes and vice versa. The effects of various different forms of structural feedback on aircraft dynamics are analyzed. A proportional-integral feedback on the structural acceleration is deemed to be most effective at both improving the damping and reducing the overall excitation of a structural mode. A model following control architecture is then implemented on full order flexible LCTR models. For this aircraft, the four lowest frequency structural modes are below 20 rad/sec, and are thus needed for control law development and analysis. The impact of structural feedback on both Attitude-Command, Attitude-Hold (ACAH) and Translational Rate Command (TRC) response types are investigated. A rigid aircraft model has optimistic performance characteristics, and a control system designed for a rigid aircraft could potentially destabilize a flexible one. The various control systems are flown in a fixed-base simulator. Pilot inputs and aircraft performance are recorded and analyzed.

Computational design of RNAs with complex energy landscapes.

PubMed

Höner zu Siederdissen, Christian; Hammer, Stefan; Abfalter, Ingrid; Hofacker, Ivo L; Flamm, Christoph; Stadler, Peter F

2013-12-01

RNA has become an integral building material in synthetic biology. Dominated by their secondary structures, which can be computed efficiently, RNA molecules are amenable not only to in vitro and in vivo selection, but also to rational, computation-based design. While the inverse folding problem of constructing an RNA sequence with a prescribed ground-state structure has received considerable attention for nearly two decades, there have been few efforts to design RNAs that can switch between distinct prescribed conformations. We introduce a user-friendly tool for designing RNA sequences that fold into multiple target structures. The underlying algorithm makes use of a combination of graph coloring and heuristic local optimization to find sequences whose energy landscapes are dominated by the prescribed conformations. A flexible interface allows the specification of a wide range of design goals. We demonstrate that bi- and tri-stable "switches" can be designed easily with moderate computational effort for the vast majority of compatible combinations of desired target structures. RNAdesign is freely available under the GPL-v3 license. Copyright © 2013 Wiley Periodicals, Inc.

Hydrogen-induced structural transition in single layer ReS2

NASA Astrophysics Data System (ADS)

Yagmurcukardes, M.; Bacaksiz, C.; Senger, R. T.; Sahin, H.

2017-09-01

By performing density functional theory-based calculations, we investigate how structural, electronic and mechanical properties of single layer ReS2 can be tuned upon hydrogenation of its surfaces. It is found that a stable, fully hydrogenated structure can be obtained by formation of strong S-H bonds. The optimized atomic structure of ReS2H2 is considerably different than that of the monolayer ReS2 which has a distorted-1T phase. By performing phonon dispersion calculations, we also predict that the Re2-dimerized 1T structure (called 1T {{}\\text{R{{\\text{e}}2}}} ) of the ReS2H2 is dynamically stable. Unlike the bare ReS2 the 1T {{}\\text{R{{\\text{e}}2}}} -ReS2H2 structure which is formed by breaking the Re4 clusters into separated Re2 dimers, is an indirect-gap semiconductor. Furthermore, mechanical properties of the 1T {{}\\text{R{{\\text{e}}2}}} phase in terms of elastic constants, in-plane stiffness (C) and Poisson ratio (ν) are investigated. It is found that full hydrogenation not only enhances the flexibility of the single layer ReS2 crystal but also increases anisotropy of the elastic constants.

Flexible structure control laboratory development and technology demonstration

NASA Technical Reports Server (NTRS)

Vivian, H. C.; Blaire, P. E.; Eldred, D. B.; Fleischer, G. E.; Ih, C.-H. C.; Nerheim, N. M.; Scheid, R. E.; Wen, J. T.

1987-01-01

An experimental structure is described which was constructed to demonstrate and validate recent emerging technologies in the active control and identification of large flexible space structures. The configuration consists of a large, 20 foot diameter antenna-like flexible structure in the horizontal plane with a gimballed central hub, a flexible feed-boom assembly hanging from the hub, and 12 flexible ribs radiating outward. Fourteen electrodynamic force actuators mounted to the hub and to the individual ribs provide the means to excite the structure and exert control forces. Thirty permanently mounted sensors, including optical encoders and analog induction devices provide measurements of structural response at widely distributed points. An experimental remote optical sensor provides sixteen additional sensing channels. A computer samples the sensors, computes the control updates and sends commands to the actuators in real time, while simultaneously displaying selected outputs on a graphics terminal and saving them in memory. Several control experiments were conducted thus far and are documented. These include implementation of distributed parameter system control, model reference adaptive control, and static shape control. These experiments have demonstrated the successful implementation of state-of-the-art control approaches using actual hardware.

Study on Wind-induced Vibration and Fatigue Life of Cable-stayed Flexible Antenna

NASA Astrophysics Data System (ADS)

He, Kongde; He, Xuehui; Fang, Zifan; Zheng, Xiaowei; Yu, Hongchang

2018-03-01

The cable-stayed flexible antenna is a large-span space structure composed of flexible multibody, with low frequency of vibration, vortex-induced resonance can occur under the action of Stochastic wind, and a larger amplitude is generated when resonance occurs. To solve this problem, based on the theory of vortex-induced vibration, this paper analyzes the vortex-induced vibration of a cable-stayed flexible antenna under the action of Wind. Based on the sinusoidal force model and Autoregressive Model (AR) method, the vortex-induced force is simulated, then the fatigue analysis of the structure is based on the linear fatigue cumulative damage principle and the rain-flow method. The minimum fatigue life of the structure is calculated to verify the vibration fatigue performance of the structure.

Modified independent modal space control method for active control of flexible systems

NASA Technical Reports Server (NTRS)

Baz, A.; Poh, S.

1987-01-01

A modified independent modal space control (MIMSC) method is developed for designing active vibration control systems for large flexible structures. The method accounts for the interaction between the controlled and residual modes. It incorporates also optimal placement procedures for selecting the optimal locations of the actuators in the structure in order to minimize the structural vibrations as well as the actuation energy. The MIMSC method relies on an important feature which is based on time sharing of a small number of actuators, in the modal space, to control effectively a large number of modes. Numerical examples are presented to illustrate the application of the method to generic flexible systems. The results obtained suggest the potential of the devised method in designing efficient active control systems for large flexible structures.

Third-order polynomial model for analyzing stickup state laminated structure in flexible electronics

NASA Astrophysics Data System (ADS)

Meng, Xianhong; Wang, Zihao; Liu, Boya; Wang, Shuodao

2018-02-01

Laminated hard-soft integrated structures play a significant role in the fabrication and development of flexible electronics devices. Flexible electronics have advantageous characteristics such as soft and light-weight, can be folded, twisted, flipped inside-out, or be pasted onto other surfaces of arbitrary shapes. In this paper, an analytical model is presented to study the mechanics of laminated hard-soft structures in flexible electronics under a stickup state. Third-order polynomials are used to describe the displacement field, and the principle of virtual work is adopted to derive the governing equations and boundary conditions. The normal strain and the shear stress along the thickness direction in the bi-material region are obtained analytically, which agree well with the results from finite element analysis. The analytical model can be used to analyze stickup state laminated structures, and can serve as a valuable reference for the failure prediction and optimal design of flexible electronics in the future.

Piezoelectric polymer multilayer on flexible substrate for energy harvesting.

PubMed

Zhang, Lei; Oh, Sharon Roslyn; Wong, Ting Chong; Tan, Chin Yaw; Yao, Kui

2013-09-01

A piezoelectric polymer multilayer structure formed on a flexible substrate is investigated for mechanical energy harvesting under bending mode. Analytical and numerical models are developed to clarify the effect of material parameters critical to the energy harvesting performance of the bending multilayer structure. It is shown that the maximum power is proportional to the square of the piezoelectric stress coefficient and the inverse of dielectric permittivity of the piezoelectric polymer. It is further found that a piezoelectric multilayer with thinner electrodes can generate more electric energy in bending mode. The effect of improved impedance matching in the multilayer polymer on energy output is remarkable. Comparisons between piezoelectric ceramic multilayers and polymer multilayers on flexible substrate are discussed. The fabrication of a P(VDF-TrFE) multilayer structure with a thin Al electrode layer is experimentally demonstrated by a scalable dip-coating process on a flexible aluminum substrate. The results indicate that it is feasible to produce a piezoelectric polymer multilayer structure on flexible substrate for harvesting mechanical energy applicable for many low-power electronics.

Structural Dynamics and Control of Large Space Structures, 1982

NASA Technical Reports Server (NTRS)

Brumfield, M. L. (Compiler)

1983-01-01

Basic research in the control of large space structures is discussed. Active damping and control of flexible beams, active stabilization of flexible antenna feed towers, spacecraft docking, and robust pointing control of large space platform payloads are among the topics discussed.

Substrate and Passivation Techniques for Flexible Amorphous Silicon-Based X-ray Detectors

PubMed Central

Marrs, Michael A.; Raupp, Gregory B.

2016-01-01

Flexible active matrix display technology has been adapted to create new flexible photo-sensing electronic devices, including flexible X-ray detectors. Monolithic integration of amorphous silicon (a-Si) PIN photodiodes on a flexible substrate poses significant challenges associated with the intrinsic film stress of amorphous silicon. This paper examines how altering device structuring and diode passivation layers can greatly improve the electrical performance and the mechanical reliability of the device, thereby eliminating one of the major weaknesses of a-Si PIN diodes in comparison to alternative photodetector technology, such as organic bulk heterojunction photodiodes and amorphous selenium. A dark current of 0.5 pA/mm2 and photodiode quantum efficiency of 74% are possible with a pixelated diode structure with a silicon nitride/SU-8 bilayer passivation structure on a 20 µm-thick polyimide substrate. PMID:27472329

Substrate and Passivation Techniques for Flexible Amorphous Silicon-Based X-ray Detectors.

PubMed

Marrs, Michael A; Raupp, Gregory B

2016-07-26

Flexible active matrix display technology has been adapted to create new flexible photo-sensing electronic devices, including flexible X-ray detectors. Monolithic integration of amorphous silicon (a-Si) PIN photodiodes on a flexible substrate poses significant challenges associated with the intrinsic film stress of amorphous silicon. This paper examines how altering device structuring and diode passivation layers can greatly improve the electrical performance and the mechanical reliability of the device, thereby eliminating one of the major weaknesses of a-Si PIN diodes in comparison to alternative photodetector technology, such as organic bulk heterojunction photodiodes and amorphous selenium. A dark current of 0.5 pA/mm² and photodiode quantum efficiency of 74% are possible with a pixelated diode structure with a silicon nitride/SU-8 bilayer passivation structure on a 20 µm-thick polyimide substrate.

Defining the flexibility window in ordered aluminosilicate zeolites

PubMed Central

Wells, Stephen A.; Leung, Ka Ming; Edwards, Peter P.; Tucker, Matt G.

2017-01-01

The flexibility window in zeolites was originally identified using geometric simulation as a hypothetical property of SiO2 systems. The existence of the flexibility window in hypothetical structures may help us to identify those we might be able to synthesize in the future. We have previously found that the flexibility window in silicates is connected to phase transitions under pressure, structure amorphization and other physical behaviours and phenomena. We here extend the concept to ordered aluminosilicate systems using softer ‘bar’ constraints that permit additional flexibility around aluminium centres. Our experimental investigation of pressure-induced amorphization in sodalites is consistent with the results of our modelling. The softer constraints allow us to identify a flexibility window in the anomalous case of goosecreekite. PMID:28989777

Conjunction of Conducting Polymer Nanostructures with Macroporous Structured Graphene Thin Films for High-Performance Flexible Supercapacitors.

PubMed

Memon, Mushtaque A; Bai, Wei; Sun, Jinhua; Imran, Muhammad; Phulpoto, Shah Nawaz; Yan, Shouke; Huang, Yong; Geng, Jianxin

2016-05-11

Fabrication of hybridized structures is an effective strategy to promote the performances of graphene-based composites for energy storage/conversion applications. In this work, macroporous structured graphene thin films (MGTFs) are fabricated on various substrates including flexible graphene papers (GPs) through an ice-crystal-induced phase separation process. The MGTFs prepared on GPs (MGTF@GPs) are recognized with remarkable features such as interconnected macroporous configuration, sufficient exfoliation of the conductive RGO sheets, and good mechanical flexibility. As such, the flexible MGTF@GPs are demonstrated as a versatile conductive platform for depositing conducting polymers (CPs), e.g., polyaniline (PAn), polypyrrole, and polythiophene, through in situ electropolymerization. The contents of the CPs in the composite films are readily controlled by varying the electropolymerization time. Notably, electrodeposition of PAn leads to the formation of nanostructures of PAn nanofibers on the walls of the macroporous structured RGO framework (PAn@MGTF@GPs): thereafter, the PAn@MGTF@GPs display a unique structural feature that combine the nanostructures of PAn nanofibers and the macroporous structures of RGO sheets. Being used as binder-free electrodes for flexible supercapacitors, the PAn@MGTF@GPs exhibit excellent electrochemical performance, in particular a high areal specific capacity (538 mF cm(-2)), high cycling stability, and remarkable capacitive stability to deformation, due to the unique electrode structures.

Flexible endoscopes: structure and function. The suction and biopsy channel.

PubMed

Holland, P

2001-01-01

Flexible endoscopes are complex medical instruments that are easily damaged. To maintain the flexible endoscope in optimum working condition, the user must have a thorough understanding of the structure and function of the instrument. This is the second in a series of articles presenting an in-depth look at the care and handling of the flexible endoscope. The first article discussed the air and water system. This article will focus specifically on the suction and biopsy channel system. The flexible endoscope is constructed of several systems that operate simultaneously to produce a highly technical, yet effective diagnostic and therapeutic medical device. These systems include the air and water system, the suction or operating channel system, the mechanical system, the endoscopic retrograde cholangiopancreatography (ERCP) elevator system, the optical system, and the electrical system. A review of the internal and external structure of the flexible endoscope and the functions of the channel system, including infection control issues, potential problems and evaluation, and prevention of minor problems to avoid expensive repairs, will be addressed.

Vibration-based health monitoring and model refinement of civil engineering structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Farrar, C.R.; Doebling, S.W.

1997-10-01

Damage or fault detection, as determined by changes in the dynamic properties of structures, is a subject that has received considerable attention in the technical literature beginning approximately 30 years ago. The basic idea is that changes in the structure`s properties, primarily stiffness, will alter the dynamic properties of the structure such as resonant frequencies and mode shapes, and properties derived from these quantities such as modal-based flexibility. Recently, this technology has been investigated for applications to health monitoring of large civil engineering structures. This presentation will discuss such a study undertaken by engineers from New Mexico Sate University, Sandiamore » National Laboratory and Los Alamos National Laboratory. Experimental modal analyses were performed in an undamaged interstate highway bridge and immediately after four successively more severe damage cases were inflicted in the main girder of the structure. Results of these tests provide insight into the abilities of modal-based damage ID methods to identify damage and the current limitations of this technology. Closely related topics that will be discussed are the use of modal properties to validate computer models of the structure, the use of these computer models in the damage detection process, and the general lack of experimental investigation of large civil engineering structures.« less

Hydrodynamics of a flexible plate between pitching rigid plates

NASA Astrophysics Data System (ADS)

Kim, Junyoung; Kim, Daegyoum

2017-11-01

The dynamics of a flexible plate have been studied as a model problem in swimming and flying of animals and fluid-structure interaction of plants and flags. Motivated by fish schooling and an array of sea grasses, we investigate the dynamics of a flexible plate closely placed between two pitching rigid plates. In most studies on passive deformation of the flexible plate, the plate is immersed in a uniform flow or a wavy flow. However, in this study, the flexible plate experiences periodic deformation by the oscillatory flow generated by the prescribed pitching motion of the rigid plates. In our model, the pitching axes of the rigid plates and the clamping position of the flexible plate are aligned on the same line. The flexible plate shows various responses depending on length and pitching frequency of rigid plates, thickness of a flexible plate, and free-stream velocity. To find the effect of each variable on the response of the flexible plate, amplitude of a trailing edge and modal contribution of a flapping motion are compared, and flow structure around the flexible plate is examined.

Multi-Objective Flight Control for Drag Minimization and Load Alleviation of High-Aspect Ratio Flexible Wing Aircraft

NASA Technical Reports Server (NTRS)

Nguyen, Nhan; Ting, Eric; Chaparro, Daniel; Drew, Michael; Swei, Sean

2017-01-01

As aircraft wings become much more flexible due to the use of light-weight composites material, adverse aerodynamics at off-design performance can result from changes in wing shapes due to aeroelastic deflections. Increased drag, hence increased fuel burn, is a potential consequence. Without means for aeroelastic compensation, the benefit of weight reduction from the use of light-weight material could be offset by less optimal aerodynamic performance at off-design flight conditions. Performance Adaptive Aeroelastic Wing (PAAW) technology can potentially address these technical challenges for future flexible wing transports. PAAW technology leverages multi-disciplinary solutions to maximize the aerodynamic performance payoff of future adaptive wing design, while addressing simultaneously operational constraints that can prevent the optimal aerodynamic performance from being realized. These operational constraints include reduced flutter margins, increased airframe responses to gust and maneuver loads, pilot handling qualities, and ride qualities. All of these constraints while seeking the optimal aerodynamic performance present themselves as a multi-objective flight control problem. The paper presents a multi-objective flight control approach based on a drag-cognizant optimal control method. A concept of virtual control, which was previously introduced, is implemented to address the pair-wise flap motion constraints imposed by the elastomer material. This method is shown to be able to satisfy the constraints. Real-time drag minimization control is considered to be an important consideration for PAAW technology. Drag minimization control has many technical challenges such as sensing and control. An initial outline of a real-time drag minimization control has already been developed and will be further investigated in the future. A simulation study of a multi-objective flight control for a flight path angle command with aeroelastic mode suppression and drag minimization demonstrates the effectiveness of the proposed solution. In-flight structural loads are also an important consideration. As wing flexibility increases, maneuver load and gust load responses can be significant and therefore can pose safety and flight control concerns. In this paper, we will extend the multi-objective flight control framework to include load alleviation control. The study will focus initially on maneuver load minimization control, and then subsequently will address gust load alleviation control in future work.

Substructure-based control of flexible structures

NASA Technical Reports Server (NTRS)

Babuska, Vit; Craig, Roy R., Jr.

1993-01-01

A decentralized procedure is presented for the design of controllers for flexible structures. Spatially significant components are created which approximate the response of a specific part of the complete structure. For each component, the controller and observer gain matrices which are used in a controller for the complete structure. The proposed method is illustrated on a model of NASA Langley's CSI testbed structure.

Application of impact dampers in vibration control of flexible structures

NASA Technical Reports Server (NTRS)

Akl, Fred A.; Butt, Aamir S.

1995-01-01

Impact dampers belong to the category of passive vibration devices used to attenuate the vibration of discrete and continuous systems. An impact damper generally consists of a mass which is allowed to travel freely between two defined stops. Under the right conditions, the vibration of the structure to which the impact damper is attached will cause the mass of the impact damper to strike the structure. Previous analytical and experimental research work on the effect of impact dampers in attenuating the vibration of discrete and continuous systems have demonstrated their effectiveness. It has been shown in this study that impact dampers can increase the intrinsic damping of a lightly-damped flexible structure. The test structure consists of a slender flexible beam supported by a pin-type support at one end and supported by a linear helical flexible spring at another location. Sinusoidal excitation spanning the first three natural frequencies was applied in the horizontal plane. The orientation of the excitation and the test structure in the horizontal plane minimizes the effect of gravity on the behavior of the test structure. The excitation was applied using a linear sine sweep technique. The span of the test structure, the mass of the impact damper, the distance of travel, and the location of the impact damper along the span of the test structure were varied. The damping ratio are estimated for sixty test configurations. The results show that the impact damper significantly increases the damping ratio of the test structure. Statistical analysis of the results using the method of multiple linear regression indicates that a reasonable fit has been accomplished. It is concluded that additional experimental analysis of flexible structures in microgravity environment is needed in order to achieve a better understanding of the behavior of impact damper under conditions of microgravity. Numerical solution of the behavior of flexible structures equipped with impact dampers is also needed to predict stresses and deformations under operating conditions of microgravity in space applications.

Air Force Air Refueling: The KC-X Aircraft Acquisition Program

DTIC Science & Technology

2008-08-04

7 Boom vs . Probe and Drogue Air Refueling . . . . . . . . . . . . . . . . . . . . . . 7 Capacity vs ...consideration must be given to a few key attributes. For example, a tanker aircraft’s method of dispensing fuel – flying boom vs . probe and drogue – is a key...flight, which can add considerable flexibility to certain air operations. Boom vs . Probe and Drogue Air Refueling.32 Aircraft can be equipped to be

Neuroendocrine mechanisms underlying behavioral stability: implications for the evolutionary origin of personality.

PubMed

Duckworth, Renée A

2015-12-01

Personality traits are behaviors that show limited flexibility over time and across contexts, and thus understanding their origin requires an understanding of what limits behavioral flexibility. Here, I suggest that insight into the evolutionary origin of personality traits requires determining the relative importance of selection and constraint in producing limits to behavioral flexibility. Natural selection as the primary cause of limits to behavioral flexibility assumes that the default state of behavior is one of high flexibility and predicts that personality variation arises through evolution of buffering mechanisms to stabilize behavioral expression, whereas the constraint hypothesis assumes that the default state is one of limited flexibility and predicts that the neuroendocrine components that underlie personality variation are those most constrained in flexibility. Using recent work on the neurobiology of sensitive periods and maternal programming of offspring behavior, I show that some of the most stable aspects of the neuroendocrine system are structural components and maternally induced epigenetic effects. Evidence of numerous constraints to changes in structural features of the neuroendocrine system and far fewer constraints to flexibility of epigenetic systems suggests that structural constraints play a primary role in the origin of behavioral stability and that epigenetic programming may be more important in generating adaptive variation among individuals. © 2015 New York Academy of Sciences.

Improvement of Wearable Power Assist Wear for Low Back Support using Pneumatic Actuator

NASA Astrophysics Data System (ADS)

Cho, Feifei; Sugimoto, Riku; Noritsugu, Toshiro; Li, Xiangpan

2017-10-01

This study focuses on developing a safe, lightweight, power assist device that can be worn by people who like caregivers during lifting or static holding tasks to prevent low back pain (LBP). Therefore in consideration of their flexibility, light weight, and large force to weight ratio we have developed a Wearable Power Assist Wear for caregivers, two types of pneumatic actuators are employed in assisting low back movement for their safety and comfort. The device can be worn directly on the body like normal clothing. Because there is no rigid exoskeleton frame structure, it is lightweight and user friendly. In this paper, we proposed the new type of the wearable power assist wear and improved the controller of control system.

Piezoelectric and dielectric properties of nanoporous polyvinylidence fluoride (PVDF) films

NASA Astrophysics Data System (ADS)

Zhao, Ping; Wang, Shifa; Kadlec, Alec

2016-04-01

A nanoporous polyvinylidene Fluoride (PVDF) thin film was developed for applications in energy harvesting, medical surgeries, and industrial robotics. This sponge-like nanoporous PVDF structure dramatically enhanced the piezoelectric effect because it yielded considerably large deformation under a small force. A casting-etching method was adopted to make films, which is effective to control the porosity, flexibility, and thickness of the film. The films with various Zinc Oxide (ZnO) mass fractions ranging from 10 to 50% were fabricated to investigate the porosity effect. The piezoelectric coefficient d33 as well as dielectric constant and loss of the films were characterized. The results were analyzed and the optimal design of the film with the right amount of ZnO nanoparticles was determined.

Flight Dynamics of Flexible Aircraft with Aeroelastic and Inertial Force Interactions

NASA Technical Reports Server (NTRS)

Nguyen, Nhan T.; Tuzcu, Ilhan

2009-01-01

This paper presents an integrated flight dynamic modeling method for flexible aircraft that captures coupled physics effects due to inertial forces, aeroelasticity, and propulsive forces that are normally present in flight. The present approach formulates the coupled flight dynamics using a structural dynamic modeling method that describes the elasticity of a flexible, twisted, swept wing using an equivalent beam-rod model. The structural dynamic model allows for three types of wing elastic motion: flapwise bending, chordwise bending, and torsion. Inertial force coupling with the wing elasticity is formulated to account for aircraft acceleration. The structural deflections create an effective aeroelastic angle of attack that affects the rigid-body motion of flexible aircraft. The aeroelastic effect contributes to aerodynamic damping forces that can influence aerodynamic stability. For wing-mounted engines, wing flexibility can cause the propulsive forces and moments to couple with the wing elastic motion. The integrated flight dynamics for a flexible aircraft are formulated by including generalized coordinate variables associated with the aeroelastic-propulsive forces and moments in the standard state-space form for six degree-of-freedom flight dynamics. A computational structural model for a generic transport aircraft has been created. The eigenvalue analysis is performed to compute aeroelastic frequencies and aerodynamic damping. The results will be used to construct an integrated flight dynamic model of a flexible generic transport aircraft.

Hierarchical porous graphene/polyaniline composite film with superior rate performance for flexible supercapacitors.

PubMed

Meng, Yuena; Wang, Kai; Zhang, Yajie; Wei, Zhixiang

2013-12-23

A highly flexible graphene free-standing film with hierarchical structure is prepared by a facile template method. With a porous structure, the film can be easily bent and cut, and forms a composite with another material as a scaffold. The 3D graphene film exhibits excellent rate capability and its capacitance is further improved by forming a composite with polyaniline nanowire arrays. The flexible hierarchical composite proves to be an excellent electrode material for flexible supercapacitors. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Flexible endoscopes: structure and function: the endoscopic retrograde cholangiopancreatography elevator system.

PubMed

Holland, Pat; Shoop, Nancy M

2002-01-01

Flexible endoscopes are complex medical instruments that are easily damaged. In order to maintain the flexible endoscope in optimum working condition, the user must have a thorough understanding of the structure and function of the instrument. This is the fourth in a series of articles presenting an in-depth look at the care and handling of the flexible endoscope. The first three articles discussed the air-water system, the suction channel system, and the mechanical system. This article will focus specifically on the endoscopic retrograde cholangiopancreatography elevator system.

Flexibility of Bricard's linkages and other structures via resultants and computer algebra.

PubMed

Lewis, Robert H; Coutsias, Evangelos A

2016-07-01

Flexibility of structures is extremely important for chemistry and robotics. Following our earlier work, we study flexibility using polynomial equations, resultants, and a symbolic algorithm of our creation that analyzes the resultant. We show that the software solves a classic arrangement of quadrilaterals in the plane due to Bricard. We fill in several gaps in Bricard's work and discover new flexible arrangements that he was apparently unaware of. This provides strong evidence for the maturity of the software, and is a wonderful example of mathematical discovery via computer assisted experiment.

Biologically-Inspired Anisotropic Flexible Wing for Optimal Flapping Flight

DTIC Science & Technology

2013-07-01

AFRL-OSR-VA-TR-2013-0400 Biologically-Inspired, Anisotropic Flexible Wing for Optimal Flapping Flight Luis Bernal, Wei Shyy...Final Report Contract Number: FA9550-07-1-0547 Biologically-Inspired, Anisotropic Flexible Wing for Optimal Flapping Flight University of...minimize power consumption; 2. The interactions of unsteady aerodynamic loading with flexible structures; 3. Flexible , light-weight, multifunctional

Integrated Controls-Structures Design Methodology for Flexible Spacecraft

NASA Technical Reports Server (NTRS)

Maghami, P. G.; Joshi, S. M.; Price, D. B.

1995-01-01

This paper proposes an approach for the design of flexible spacecraft, wherein the structural design and the control system design are performed simultaneously. The integrated design problem is posed as an optimization problem in which both the structural parameters and the control system parameters constitute the design variables, which are used to optimize a common objective function, thereby resulting in an optimal overall design. The approach is demonstrated by application to the integrated design of a geostationary platform, and to a ground-based flexible structure experiment. The numerical results obtained indicate that the integrated design approach generally yields spacecraft designs that are substantially superior to the conventional approach, wherein the structural design and control design are performed sequentially.

NASTRAN/FLEXSTAB procedure for static aeroelastic analysis

NASA Technical Reports Server (NTRS)

Schuster, L. S.

1984-01-01

Presented is a procedure for using the FLEXSTAB External Structural Influence Coefficients (ESIC) computer program to produce the structural data necessary for the FLEXSTAB Stability Derivatives and Static Stability (SD&SS) program. The SD&SS program computes trim state, stability derivatives, and pressure and deflection data for a flexible airplane having a plane of symmetry. The procedure used a NASTRAN finite-element structural model as the source of structural data in the form of flexibility matrices. Selection of a set of degrees of freedom, definition of structural nodes and panels, reordering and reformatting of the flexibility matrix, and redistribution of existing point mass data are among the topics discussed. Also discussed are boundary conditions and the NASTRAN substructuring technique.

Soft tissue models: easy and inexpensive flexible 3D printing as a help in surgical planning of cardiovascular disorders

NASA Astrophysics Data System (ADS)

Starosolski, Zbigniew; Ezon, David S.; Krishnamurthy, Rajesh; Dodd, Nicholas; Heinle, Jeffrey; Mckenzie, Dean E.; Annapragada, Ananth

2017-03-01

We developed a technology that allows a simple desktop 3D printer with dual extruder to fabricate 3D flexible models of Major AortoPulmonary Collateral Arteries. The study was designed to assess whether the flexible 3D printed models could help during surgical planning phase. Simple FDM 3D printers are inexpensive, versatile in use and easy to maintain, but complications arise when the designed model is complex and has tubular structures with small diameter less than 2mm. The advantages of FDM printers are cost and simplicity of use. We use precisely selected materials to overcome the obstacles listed above. Dual extruder allows to use two different materials while printing, which is especially important in the case of fragile structures like pulmonary vessels and its supporting structures. The latter should not be removed by hand to avoid a truncation of the model. We utilize the water soluble PVA as a supporting structure and Poro-Lay filament for flexible model of AortoPulmonary collateral arteries. Poro-Lay filament is different as compared to all the other flexible ones like polymer-based. Poro-Lay is rigid while printing and this allows printing of structures small in diameter. It achieves flexibility after washing out of printed model with water. It becomes soft in touch and gelatinous. Using both PVA and Poro-Lay gives a huge advantage allowing to wash out the supporting structures and achieve flexibility in one washing operation, saving time and avoiding human error with cleaning the model. We evaluated 6 models for MAPCAS surgical planning study. This approach is also cost-effective - an average cost of materials for print is less than $15; models are printed in facility without any delays. Flexibility of 3D printed models approximate soft tissues properly, mimicking Aortopulmonary collateral arteries. Second utilization models has educational value for both residents and patients' family. Simplification of 3D flexible process could help in other models of soft tissue pathologies like aneurysms, ventricular septal defects and other vascular anomalies.

Are the Most Plastic Species the Most Abundant Ones? An Assessment Using a Fish Assemblage

PubMed Central

Vidal, Nicolás; Zaldúa, Natalia; D'Anatro, Alejandro; Naya, Daniel E.

2014-01-01

Few studies have evaluated phenotypic plasticity at the community level, considering, for example, plastic responses in an entire species assemblage. In addition, none of these studies have addressed the relationship between phenotypic plasticity and community structure. Within this context, here we assessed the magnitude of seasonal changes in digestive traits (seasonal flexibility), and of changes during short-term fasting (flexibility during fasting), occurring in an entire fish assemblage, comprising ten species, four trophic levels, and a 37-fold range in body mass. In addition, we analyzed the relationship between estimates of digestive flexibility and three basic assemblage structure attributes, i.e., species trophic position, body size, and relative abundance. We found that: (1) Seasonal digestive flexibility was not related with species trophic position or with body size; (2) Digestive flexibility during fasting tended to be inversely correlated with body size, as expected from scaling relationships; (3) Digestive flexibility, both seasonal and during fasting, was positively correlated with species relative abundance. In conclusion, the present study identified two trends in digestive flexibility in relation to assemblage structure, which represents an encouraging departure point in the search of general patterns in phenotypic plasticity at the local community scale. PMID:24651865

Decentralized University Budgeting, United with a More Flexible Tuition Structure

ERIC Educational Resources Information Center

Fethke, Gary

2014-01-01

With tuition revenues replacing state appropriations as the primary source of public university funding, it becomes difficult for universities to use historically based budget allocations and inflexible tuition structures to subsidize high-cost programs. It is argued here that combining targeted subsidies with a flexible tuition structure and…

Determination of helix orientations in a flexible DNA by multi-frequency EPR spectroscopy.

PubMed

Grytz, C M; Kazemi, S; Marko, A; Cekan, P; Güntert, P; Sigurdsson, S Th; Prisner, T F

2017-11-15

Distance measurements are performed between a pair of spin labels attached to nucleic acids using Pulsed Electron-Electron Double Resonance (PELDOR, also called DEER) spectroscopy which is a complementary tool to other structure determination methods in structural biology. The rigid spin label Ç, when incorporated pairwise into two helical parts of a nucleic acid molecule, allows the determination of both the mutual orientation and the distance between those labels, since Ç moves rigidly with the helix to which it is attached. We have developed a two-step protocol to investigate the conformational flexibility of flexible nucleic acid molecules by multi-frequency PELDOR. In the first step, a library with a broad collection of conformers, which are in agreement with topological constraints, NMR restraints and distances derived from PELDOR, was created. In the second step, a weighted structural ensemble of these conformers was chosen, such that it fits the multi-frequency PELDOR time traces of all doubly Ç-labelled samples simultaneously. This ensemble reflects the global structure and the conformational flexibility of the two-way DNA junction. We demonstrate this approach on a flexible bent DNA molecule, consisting of two short helical parts with a five adenine bulge at the center. The kink and twist motions between both helical parts were quantitatively determined and showed high flexibility, in agreement with a Förster Resonance Energy Transfer (FRET) study on a similar bent DNA motif. The approach presented here should be useful to describe the relative orientation of helical motifs and the conformational flexibility of nucleic acid structures, both alone and in complexes with proteins and other molecules.

Assessment of asphalt concrete reinforcement grid in flexible pavements : final report.

DOT National Transportation Integrated Search

2016-05-01

This report investigated the application of accepted methods of pavement structural evaluation to independently assess the potential structural benefit of asphalt geogrid reinforcement of an operational flexible highway pavement. The asphalt interlay...

Progress on control experiments of flexible structures

NASA Technical Reports Server (NTRS)

Juang, Jer-Nan

1990-01-01

Progress at the NASA Langley Research Center in the area of control experiments for flexible structures is described. First the author presents the experimental results for a linear model which represents slewing maneuvers of a generic space station solar panel carried out to evaluate experimentally some control technologies. Then the status of the rotational/translational maneuvering experiment of a flexible steel panel carried by a translation cart is presented. Finally, experimental results of the NASA minimast testbed using velocity command stepper motors as reaction mass reactors are shown. All the test configurations are briefly described, including actuator and sensor, test setup, and test software. The status of some research activities oriented primarily to the experimental methods for control of flexible structures is presented.

Cd(II)-coordination polymers based on tetracarboxylic acid and diverse bis(imidazole) ligands: Synthesis, structural diversity and photoluminescence properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arıcı, Mürsel, E-mail: marici@ogu.edu.tr; Yeşilel, Okan Zafer; Taş, Murat

Three new Cd(II)-coordination polymers, namely, ([Cd{sub 2}(μ{sub 6}-ao{sub 2}btc)(μ-1,5-bipe){sub 2}]·2H{sub 2}O){sub n} (1), ([Cd{sub 2}(μ{sub 6}-ao{sub 2}btc)(μ-1,4-bix){sub 2}]{sub n}·2DMF) (2) and ([Cd{sub 2}(μ{sub 8}-abtc)(μ-1,4-betix)]·DMF·H{sub 2}O){sub n} (3) (ao{sub 2}btc=di-oxygenated form of 3,3′,5,5′-azobenzenetetracarboxylate, 1,5-bipe: 1,5-bis(imidazol-1yl)pentane, 1,4-bix=1,4-bis(imidazol-1ylmethyl)benzene, 1,4-betix=1,4-bis(2-ethylimidazol-1ylmethyl)benzene) were synthesized with 3,3′,5,5′-azobenzenetetracarboxylic acid and flexible, semi-flexible and semi-flexible substituted bis(imidazole) linkers. They were characterized by IR spectroscopy, elemental analysis, single-crystal X-ray diffraction, powder X-ray diffractions (PXRD) and thermal analyses (TG/DTA). Complexes 1–3 exhibited structural diversities depending on flexible, semi-flexible and semi-flexible substituted bis(imidazole) ligands. Complex 1 was 2D structure with 3,6L18 topology. Complex 2 had a 3D pillar-layered framework with the raremore » sqc27 topology. When semi-flexible substituted bis(imidazole) linker was used, 3D framework of complex 3 was obtained with the paddlewheel Cd{sub 2}(CO{sub 2}){sub 4}-type binuclear SBU. Moreover, thermal and photoluminescence properties of the complexes were determined in detailed. - Graphical abstract: In this study, three novel Cd(II)-coordination polymers were synthesized with 3,3′,5,5′-azobenzenetetracarboxylic acid and flexible, semi-flexible and semi-flexible substituted bis(imidazole) linkers. They were characterized by IR spectroscopy, elemental analysis, single-crystal X-ray diffraction, powder X-ray diffractions (PXRD) and thermal analyses (TG/DTA). Complexes 1–3 exhibited structural diversities depending on flexible, semi-flexible and semi-flexible substituted bis(imidazole) ligands. Complex 1 was 2D structure with 3,6L18 topology. Complex 2 had a 3D pillar-layered framework with the rare sqc27 topology. When semi-flexible substituted bis(imidazole) linker was used, 3D framework of complex 3 was obtained with the paddlewheel Cd{sub 2}(CO{sub 2}){sub 4}-type binuclear SBU. - Highlights: • Three new Cd(II)-coordination polymers with azobenzenetetracarboxylic acid and diverse bis(imidazole) linkers. • Complex 1 is 2D structure with 3,6L18 topology. • 3D pillar-layered framework of 2 with the rare sqc27 topology. • 3D framework of 3 with the paddlewheel Cd{sub 2}(CO{sub 2}){sub 4}-type SBU.« less

Unsymmetric Lanczos model reduction and linear state function observer for flexible structures

NASA Technical Reports Server (NTRS)

Su, Tzu-Jeng; Craig, Roy R., Jr.

1991-01-01

This report summarizes part of the research work accomplished during the second year of a two-year grant. The research, entitled 'Application of Lanczos Vectors to Control Design of Flexible Structures' concerns various ways to use Lanczos vectors and Krylov vectors to obtain reduced-order mathematical models for use in the dynamic response analyses and in control design studies. This report presents a one-sided, unsymmetric block Lanczos algorithm for model reduction of structural dynamics systems with unsymmetric damping matrix, and a control design procedure based on the theory of linear state function observers to design low-order controllers for flexible structures.

Flexible mechanism of magnetic microbeads chains in an oscillating field

NASA Astrophysics Data System (ADS)

Li, Yan-Hom; Yen, Chia-Yen

2018-05-01

To investigate the use of magnetic microbeads for swimming at low Reynolds number, the flexible structure of microchains comprising superparamagnetic microbeads under the influence of oscillating magnetic fields is examined experimentally and theoretically. For a ductile chain, each particle has its own phase angle trajectory and phase-lag angle to the overall field. This present study thoroughly discusses the synchronicity of the local phase angle trajectory between each dyad of beads and the external field. The prominently asynchronous trajectories between the central and outer beads significantly dominate the flexible structure of the oscillating chain. In addition, the dimensionless local Mason number (Mnl) is derived as the solo controlling parameter to evaluate the structure of each dyad of beads in a flexible chain. The evolution of the local Mason number within an oscillating period implies the most unstable position locates near the center of the chain around 0.6P

Developmental constraints on behavioural flexibility.

PubMed

Holekamp, Kay E; Swanson, Eli M; Van Meter, Page E

2013-05-19

We suggest that variation in mammalian behavioural flexibility not accounted for by current socioecological models may be explained in part by developmental constraints. From our own work, we provide examples of constraints affecting variation in behavioural flexibility, not only among individuals, but also among species and higher taxonomic units. We first implicate organizational maternal effects of androgens in shaping individual differences in aggressive behaviour emitted by female spotted hyaenas throughout the lifespan. We then compare carnivores and primates with respect to their locomotor and craniofacial adaptations. We inquire whether antagonistic selection pressures on the skull might impose differential functional constraints on evolvability of skulls and brains in these two orders, thus ultimately affecting behavioural flexibility in each group. We suggest that, even when carnivores and primates would theoretically benefit from the same adaptations with respect to behavioural flexibility, carnivores may nevertheless exhibit less behavioural flexibility than primates because of constraints imposed by past adaptations in the morphology of the limbs and skull. Phylogenetic analysis consistent with this idea suggests greater evolutionary lability in relative brain size within families of primates than carnivores. Thus, consideration of developmental constraints may help elucidate variation in mammalian behavioural flexibility.

Structural insights into the evolution of a sexy protein: novel topology and restricted backbone flexibility in a hypervariable pheromone from the red-legged salamander, Plethodon shermani.

PubMed

Wilburn, Damien B; Bowen, Kathleen E; Doty, Kari A; Arumugam, Sengodagounder; Lane, Andrew N; Feldhoff, Pamela W; Feldhoff, Richard C

2014-01-01

In response to pervasive sexual selection, protein sex pheromones often display rapid mutation and accelerated evolution of corresponding gene sequences. For proteins, the general dogma is that structure is maintained even as sequence or function may rapidly change. This phenomenon is well exemplified by the three-finger protein (TFP) superfamily: a diverse class of vertebrate proteins co-opted for many biological functions - such as components of snake venoms, regulators of the complement system, and coordinators of amphibian limb regeneration. All of the >200 structurally characterized TFPs adopt the namesake "three-finger" topology. In male red-legged salamanders, the TFP pheromone Plethodontid Modulating Factor (PMF) is a hypervariable protein such that, through extensive gene duplication and pervasive sexual selection, individual male salamanders express more than 30 unique isoforms. However, it remained unclear how this accelerated evolution affected the protein structure of PMF. Using LC/MS-MS and multidimensional NMR, we report the 3D structure of the most abundant PMF isoform, PMF-G. The high resolution structural ensemble revealed a highly modified TFP structure, including a unique disulfide bonding pattern and loss of secondary structure, that define a novel protein topology with greater backbone flexibility in the third peptide finger. Sequence comparison, models of molecular evolution, and homology modeling together support that this flexible third finger is the most rapidly evolving segment of PMF. Combined with PMF sequence hypervariability, this structural flexibility may enhance the plasticity of PMF as a chemical signal by permitting potentially thousands of structural conformers. We propose that the flexible third finger plays a critical role in PMF:receptor interactions. As female receptors co-evolve, this flexibility may allow PMF to still bind its receptor(s) without the immediate need for complementary mutations. Consequently, this unique adaptation may establish new paradigms for how receptor:ligand pairs co-evolve, in particular with respect to sexual conflict.

Coupled Fluid-Structure Interaction Analysis of Solid Rocket Motor with Flexible Inhibitors

NASA Technical Reports Server (NTRS)

Yang, H. Q.; West, Jeff; Harris, Robert E.

2014-01-01

Flexible inhibitors are generally used in solid rocket motors (SRMs) as a means to control the burning of propellant. Vortices generated by the flow of propellant around the flexible inhibitors have been identified as a driving source of instabilities that can lead to thrust oscillations in launch vehicles. Potential coupling between the SRM thrust oscillations and structural vibration modes is an important risk factor in launch vehicle design. As a means to predict and better understand these phenomena, a multidisciplinary simulation capability that couples the NASA production CFD code, Loci/CHEM, with CFDRC's structural finite element code, CoBi, has been developed. This capability is crucial to the development of NASA's new space launch system (SLS). This paper summarizes the efforts in applying the coupled software to demonstrate and investigate fluid-structure interaction (FSI) phenomena between pressure waves and flexible inhibitors inside reusable solid rocket motors (RSRMs). The features of the fluid and structural solvers are described in detail, and the coupling methodology and interfacial continuity requirements are then presented in a general Eulerian-Lagrangian framework. The simulations presented herein utilize production level CFD with hybrid RANS/LES turbulence modeling and grid resolution in excess of 80 million cells. The fluid domain in the SRM is discretized using a general mixed polyhedral unstructured mesh, while full 3D shell elements are utilized in the structural domain for the flexible inhibitors. Verifications against analytical solutions for a structural model under a steady uniform pressure condition and under dynamic modal analysis show excellent agreement in terms of displacement distribution and eigenmode frequencies. The preliminary coupled results indicate that due to acoustic coupling, the dynamics of one of the more flexible inhibitors shift from its first modal frequency to the first acoustic frequency of the solid rocket motor. This insight could have profound implications for SRM and flexible inhibitor designs for current and future launch vehicles including SLS.

Interplay of intermolecular interactions and flexibility to mediate glass forming ability and fragility: A study of chemical analogs

NASA Astrophysics Data System (ADS)

Saini, Manoj K.; Jin, Xiao; Wu, Tao; Liu, Yingdan; Wang, Li-Min

2018-03-01

We have investigated the enthalpic and dielectric relaxations of four groups of quinoline analogs having similar structural properties (i.e., rigidity, stiffness, and bulkiness) but a different steric character and the nature of intermolecular interactions and flexibility. The dielectric fragility index (md) and the enthalpic one (mH), determined by the Tool-Narayanaswamy-Moynihan-Hodge formalism, are comparable. Generally, for the four sets of molecules of similar structures, both the interactions and flexibility are found to be critical in making the large span of fragility (i.e., from 59 to 131) and glass forming ability. By contrast, individual impacts of the interaction and flexibility can only explain fragility partly among each group of isomers. We found that the molecules with high fragility are of relatively low liquid density, reflecting the joint impact of the interactions and flexibility. An interesting result is observed among the isomers that the molecules which are fragile have enhanced glass forming ability. The results are unveiling the joint impacts of molecular structure (flexibility) and intermolecular interaction on the molecular dynamics.

Unified control/structure design and modeling research

NASA Technical Reports Server (NTRS)

Mingori, D. L.; Gibson, J. S.; Blelloch, P. A.; Adamian, A.

1986-01-01

To demonstrate the applicability of the control theory for distributed systems to large flexible space structures, research was focused on a model of a space antenna which consists of a rigid hub, flexible ribs, and a mesh reflecting surface. The space antenna model used is discussed along with the finite element approximation of the distributed model. The basic control problem is to design an optimal or near-optimal compensator to suppress the linear vibrations and rigid-body displacements of the structure. The application of an infinite dimensional Linear Quadratic Gaussian (LQG) control theory to flexible structure is discussed. Two basic approaches for robustness enhancement were investigated: loop transfer recovery and sensitivity optimization. A third approach synthesized from elements of these two basic approaches is currently under development. The control driven finite element approximation of flexible structures is discussed. Three sets of finite element basic vectors for computing functional control gains are compared. The possibility of constructing a finite element scheme to approximate the infinite dimensional Hamiltonian system directly, instead of indirectly is discussed.

Mechanism Design and Testing of a Self-Deploying Structure Using Flexible Composite Tape Springs

NASA Technical Reports Server (NTRS)

Footdale, Joseph N.; Murphey, Thomas W.

2014-01-01

The detailed mechanical design of a novel deployable support structure that positions and tensions a membrane optic for space imagining applications is presented. This is a complex three-dimensional deployment using freely deploying rollable composite tape spring booms that become load bearing structural members at full deployment. The deployment tests successfully demonstrate a new architecture based on rolled and freely deployed composite tape spring members that achieve simultaneous deployment without mechanical synchronization. Proper design of the flexible component mounting interface and constraint systems, which were critical in achieving a functioning unit, are described. These flexible composite components have much potential for advancing the state of the art in deployable structures, but have yet to be widely adopted. This paper demonstrates the feasibility and advantages of implementing flexible composite components, including the design details on how to integrate with required traditional mechanisms.

Acoustoelasticity. [sound-structure interaction

NASA Technical Reports Server (NTRS)

Dowell, E. H.

1977-01-01

Sound or pressure variations inside bounded enclosures are investigated. Mathematical models are given for determining: (1) the interaction between the sound pressure field and the flexible wall of a Helmholtz resonator; (2) coupled fluid-structural motion of an acoustic cavity with a flexible and/or absorbing wall; (3) acoustic natural modes in multiple connected cavities; and (4) the forced response of a cavity with a flexible and/or absorbing wall. Numerical results are discussed.

Evaluation of the effect of elastic joints on the auto-oscillation of spacecraft with gas-reactive direction systems

NASA Technical Reports Server (NTRS)

Sasin, G. G.

1979-01-01

A mathematical model was obtained, on the basis of the method of mixed coordinates, of a generalized flexible spacecraft at one end of which was appended the directive action of a system of gas reactive nozzles. Various structural forms were obtained functionally describing flexible spacecraft, as systems consisting of a solid central body with flexible structural elements joined to it.

Simplified Dynamic Structural Time History Response Analysis of Flexible Approach Walls Founded on Clustered Pile Groups Using Impact_Deck

DTIC Science & Technology

2016-07-01

Abstract Flexible approach walls are being considered for retrofits, replacements, or upgrades to Corps lock structures that have exceeded their...case of Lock and Dam 3, the peak reaction force for any individual pile group was 11% of the peak impact load. DISCLAIMER: The contents of this...Generation Flexible Approach Walls ......................................... 1 1.2.1 Lock and Dam 3

Flexible Structural-Health-Monitoring Sheets

NASA Technical Reports Server (NTRS)

Qing, Xinlin; Kuo, Fuo

2008-01-01

A generic design for a type of flexible structural-health-monitoring sheet with multiple sensor/actuator types and a method of manufacturing such sheets has been developed. A sheet of this type contains an array of sensing and/or actuation elements, associated wires, and any other associated circuit elements incorporated into various flexible layers on a thin, flexible substrate. The sheet can be affixed to a structure so that the array of sensing and/or actuation elements can be used to analyze the structure in accordance with structural-health-monitoring techniques. Alternatively, the sheet can be designed to be incorporated into the body of the structure, especially if the structure is made of a composite material. Customarily, structural-health monitoring is accomplished by use of sensors and actuators arrayed at various locations on a structure. In contrast, a sheet of the present type can contain an entire sensor/actuator array, making it unnecessary to install each sensor and actuator individually on or in a structure. Sensors of different types such as piezoelectric and fiber-optic can be embedded in the sheet to form a hybrid sensor network. Similarly, the traces for electric communication can be deposited on one or two layers as required, and an entirely separate layer can be employed to shield the sensor elements and traces.

Meeting the Challenge of Providing Flexible Learning Opportunities: Considerations for Technology Adoption amongst Academic Staff (Relever le défi de fournir des occasions d'apprentissage flexibles: considérations pour l'adoption de la technologie par le personnel universitaire)

ERIC Educational Resources Information Center

Mirriahi, Negin; Vaid, Bhuvinder S.; Burns, David P.

2015-01-01

This paper reports on a subset of findings from a larger study investigating resistance from academic staff to the integration of technology with on-campus foreign language teaching at one North American higher education institution. The study revealed that the factors influencing technology adoption paralleled Davis' Technology Acceptance Model's…

Reasons for mini-implants failure: choosing installation site should be valued!

PubMed Central

Consolaro, Alberto; Romano, Fábio Lourenço

2014-01-01

Mini-implant loss is often associated with physical and mechanical aspects that result from choosing an inappropriate placement site. It is worth highlighting that: a) Interdental alveolar bone crests are flexible and deformable. For this reason, they may not offer the ideal absolute anchorage. The more cervical the structures, the more delicate they are, thus offering less physical support for mini-implant placement; b) Alveolar bone crests of triangular shape are more deformable, whereas those of rectangular shape are more flexible; c) The bases of the alveolar processes of the maxilla and the mandible are not flexible, for this reason, they are more likely to receive mini-implants; d) The more cervical a mini-implant is placed, the higher the risk of loss; the more apical a mini-implant is placed, the better its prognosis will be; e) 3D evaluations play a major role in planning the use of mini-implants. Based on the aforementioned considerations, the hypotheses about mini-implant loss are as follows: 1) Deflection of maxillary and mandibular alveolar processes when mini-implants are more cervically placed; 2) Mini-implants placed too near the periodontal ligament, with normal intra-alveolar tooth movement; 3) Low bone density, low thickness and low alveolar bone volume; 4) Low alveolar cortical bone thickness; 5) Excessive pressure inducing trabecular bone microfracture; 6) Sites of higher anatomical weakness in the mandible and the maxilla; 7) Thicker gingival tissue not considered when choosing the mini-implant. PMID:24945511

Integrated control-structure design

NASA Technical Reports Server (NTRS)

Hunziker, K. Scott; Kraft, Raymond H.; Bossi, Joseph A.

1991-01-01

A new approach for the design and control of flexible space structures is described. The approach integrates the structure and controller design processes thereby providing extra opportunities for avoiding some of the disastrous effects of control-structures interaction and for discovering new, unexpected avenues of future structural design. A control formulation based on Boyd's implementation of Youla parameterization is employed. Control design parameters are coupled with structural design variables to produce a set of integrated-design variables which are selected through optimization-based methodology. A performance index reflecting spacecraft mission goals and constraints is formulated and optimized with respect to the integrated design variables. Initial studies have been concerned with achieving mission requirements with a lighter, more flexible space structure. Details of the formulation of the integrated-design approach are presented and results are given from a study involving the integrated redesign of a flexible geostationary platform.

Flap flexibility amongst plasmepsins I, II, III, IV, and V: Sequence, structural, and molecular dynamics analyses.

PubMed

McGillewie, Lara; Soliman, Mahmoud E

2015-09-01

Herein, for the first time, we comparatively report the opening and closing of apo plasmepsin I - V. Plasmepsins belong the aspartic protease family of enzymes, and are expressed during the various stages of the P. falciparum lifecycle, the species responsible for the most lethal and virulent malaria to infect humans. Plasmepsin I, II, IV and HAP degrade hemoglobin from infected red blood cells, whereas plasmepsin V transport proteins crucial to the survival of the malaria parasite across the endoplasmic reticulum. Flap-structures covering the active site of aspartic proteases (such as HIV protease) are crucial to the conformational flexibility and dynamics of the protein, and ultimately control the binding landscape. The flap-structure in plasmepsins is made up of a flip tip in the N-terminal lying perpendicular to the active site, adjacent to the flexible loop region in the C-terminal. Using molecular dynamics, we propose three parameters to better describe the opening and closing of the flap-structure in apo plasmepsins. Namely, the distance, d1, between the flap tip and the flexible region; the dihedral angle, ϕ, to account for the twisting motion; and the TriCα angle, θ1. Simulations have shown that as the flap-structure twists, the flap and flexible region move apart opening the active site, or move toward each other closing the active site. The data from our study indicate that of all the plasmepsins investigated in the present study, Plm IV and V display the highest conformational flexibility and are more dynamic structures versus Plm I, II, and HAP. © 2015 Wiley Periodicals, Inc.

Mathematical modeling of a class of multibody flexible spacecraft structures

NASA Technical Reports Server (NTRS)

Kelkar, Atul, G.

1994-01-01

A mathematical model for a general multibody flexible spacecraft is obtained. The generic spacecraft considered consists of a flexible central body to which a number of flexible multibody structures are attached. The coordinate systems used in the derivation allow effective decoupling of the translational motion of the entire spacecraft from its rotational motion about its center of mass. The derivation assumes that the deformations in the bodies are only due to elastic motions. The dynamic model derived is a closed-form vector-matrix differential equation. The model developed can be used for analysis and simulation of many realistic spacecraft configurations.

Steady-State Solution of a Flexible Wing

NASA Technical Reports Server (NTRS)

Karkehabadi, Reza; Chandra, Suresh; Krishnamurthy, Ramesh

1997-01-01

A fluid-structure interaction code, ENSAERO, has been used to compute the aerodynamic loads on a swept-tapered wing. The code has the capability of using Euler or Navier-Stokes equations. Both options have been used and compared in the present paper. In the calculation of the steady-state solution, we are interested in knowing how the flexibility of the wing influences the lift coefficients. If the results of a flexible wing are not affected by the flexibility of the wing significantly, one could consider the wing to be rigid and reduce the problem from fluid-structure interaction to a fluid problem.

Line pilot perspectives on complexity of terminal instrument flight procedures

DOT National Transportation Integrated Search

2017-07-25

Instrument flight procedures (IFPs) based on RNAV and RNP offer safety enhancements along with new levels of flexibility to negotiate terrain, airspace, and environmental considerations. However, operational implementation of performance-based IFPs d...

Statewide transportation planning for healthy communities

DOT National Transportation Integrated Search

2014-04-01

This white paper presents insights and a flexible model for State Departments of Transportation (DOTs) that choose to integrate public health considerations into their transportation planning and decision-making. It draws from five case studies of in...

Proceedings of the Workshop on Computational Aspects in the Control of Flexible Systems, part 2

NASA Technical Reports Server (NTRS)

Taylor, Lawrence W., Jr. (Compiler)

1989-01-01

The Control/Structures Integration Program, a survey of available software for control of flexible structures, computational efficiency and capability, modeling and parameter estimation, and control synthesis and optimization software are discussed.

Structures of mesophilic and extremophilic citrate synthases reveal rigidity and flexibility for function.

PubMed

Wells, Stephen A; Crennell, Susan J; Danson, Michael J

2014-10-01

Citrate synthase (CS) catalyses the entry of carbon into the citric acid cycle and is highly-conserved structurally across the tree of life. Crystal structures of dimeric CSs are known in both "open" and "closed" forms, which differ by a substantial domain motion that closes the substrate-binding clefts. We explore both the static rigidity and the dynamic flexibility of CS structures from mesophilic and extremophilic organisms from all three evolutionary domains. The computational expense of this wide-ranging exploration is kept to a minimum by the use of rigidity analysis and rapid all-atom simulations of flexible motion, combining geometric simulation and elastic network modeling. CS structures from thermophiles display increased structural rigidity compared with the mesophilic enzyme. A CS structure from a psychrophile, stabilized by strong ionic interactions, appears to display likewise increased rigidity in conventional rigidity analysis; however, a novel modified analysis, taking into account the weakening of the hydrophobic effect at low temperatures, shows a more appropriate decreased rigidity. These rigidity variations do not, however, affect the character of the flexible dynamics, which are well conserved across all the structures studied. Simulation trajectories not only duplicate the crystallographically observed symmetric open-to-closed transitions, but also identify motions describing a previously unidentified antisymmetric functional motion. This antisymmetric motion would not be directly observed in crystallography but is revealed as an intrinsic property of the CS structure by modeling of flexible motion. This suggests that the functional motion closing the binding clefts in CS may be independent rather than symmetric and cooperative. © 2014 Wiley Periodicals, Inc.

Control of Flexible Structures (COFS) Flight Experiment Background and Description

NASA Technical Reports Server (NTRS)

Hanks, B. R.

1985-01-01

A fundamental problem in designing and delivering large space structures to orbit is to provide sufficient structural stiffness and static configuration precision to meet performance requirements. These requirements are directly related to control requirements and the degree of control system sophistication available to supplement the as-built structure. Background and rationale are presented for a research study in structures, structural dynamics, and controls using a relatively large, flexible beam as a focus. This experiment would address fundamental problems applicable to large, flexible space structures in general and would involve a combination of ground tests, flight behavior prediction, and instrumented orbital tests. Intended to be multidisciplinary but basic within each discipline, the experiment should provide improved understanding and confidence in making design trades between structural conservatism and control system sophistication for meeting static shape and dynamic response/stability requirements. Quantitative results should be obtained for use in improving the validity of ground tests for verifying flight performance analyses.

Dynamics modeling and adaptive control of flexible manipulators

NASA Technical Reports Server (NTRS)

Sasiadek, J. Z.

1991-01-01

An application of Model Reference Adaptive Control (MRAC) to the position and force control of flexible manipulators and robots is presented. A single-link flexible manipulator is analyzed. The problem was to develop a mathematical model of a flexible robot that is accurate. The objective is to show that the adaptive control works better than 'conventional' systems and is suitable for flexible structure control.

Thermal Analysis of a Structural Solution for Sustainable, Modular and Prefabricated Buildings

NASA Astrophysics Data System (ADS)

Isopescu, D. N.; Maxineasa, S. G.; Neculai, O.

2017-06-01

In the construction field, the design principles for an efficient and operational use of buildings and a minimal impact on the environment are essential aspects of sustainable development. In this regard, several aspects must be taken into consideration, such as: durability, easy maintenance, flexibility in interior design, and reduced energy consumption. Decreasing energy consumption in buildings during the service life (heating / cooling / drinking water / electricity) can mean lower costs, but also a lower impact on the environment. The paper presents the thermal analysis for a GF+1F height structure, consisting of several identical, adjacent and / or overlapped metallic cubic modules. The spaces inside this cubes ensemble solve the functionality of a family home building. The good carrying capacity, the rapidity of execution, the superior degree of thermal insulation and the minimum losses of material in execution were the main advantages provided by this structural solution. Regarding the thermal comfort for the users of this constructive system, the thermal analysis showed that the internal temperatures are constant and uniform, without cold surfaces or temperature fluctuations. In addition, humidity is controlled and there is no risk of condensation.

Inflatable habitation for the lunar base

NASA Technical Reports Server (NTRS)

Roberts, M.

1992-01-01

Inflatable structures have a number of advantages over rigid modules in providing habitation at a lunar base. Some of these advantages are packaging efficiency, convenience of expansion, flexibility, and psychological benefit to the inhabitants. The relatively small, rigid cylinders fitted to the payload compartment of a launch vehicle are not as efficient volumetrically as a collapsible structure that fits into the same space when packaged, but when deployed is much larger. Pressurized volume is a valuable resource. By providing that resource efficiently, in large units, labor intensive external expansion (such as adding additional modules to the existing base) can be minimized. The expansive interior in an inflatable would facilitate rearrangement of the interior to suite the evolving needs of the base. This large, continuous volume would also relieve claustrophobia, enhancing habitability and improving morale. The purpose of this paper is to explore some of the aspects of inflatable habitat design, including structural, architectural, and environmental considerations. As a specific case, the conceptual design of an inflatable lunar habitat, developed for the Lunar Base Systems Study at the Johnson Space Center, is described.

Facial animation on an anatomy-based hierarchical face model

NASA Astrophysics Data System (ADS)

Zhang, Yu; Prakash, Edmond C.; Sung, Eric

2003-04-01

In this paper we propose a new hierarchical 3D facial model based on anatomical knowledge that provides high fidelity for realistic facial expression animation. Like real human face, the facial model has a hierarchical biomechanical structure, incorporating a physically-based approximation to facial skin tissue, a set of anatomically-motivated facial muscle actuators and underlying skull structure. The deformable skin model has multi-layer structure to approximate different types of soft tissue. It takes into account the nonlinear stress-strain relationship of the skin and the fact that soft tissue is almost incompressible. Different types of muscle models have been developed to simulate distribution of the muscle force on the skin due to muscle contraction. By the presence of the skull model, our facial model takes advantage of both more accurate facial deformation and the consideration of facial anatomy during the interactive definition of facial muscles. Under the muscular force, the deformation of the facial skin is evaluated using numerical integration of the governing dynamic equations. The dynamic facial animation algorithm runs at interactive rate with flexible and realistic facial expressions to be generated.

Three-dimensional skeleton networks of graphene wrapped polyaniline nanofibers: an excellent structure for high-performance flexible solid-state supercapacitors

PubMed Central

Hu, Nantao; Zhang, Liling; Yang, Chao; Zhao, Jian; Yang, Zhi; Wei, Hao; Liao, Hanbin; Feng, Zhenxing; Fisher, Adrian; Zhang, Yafei; Xu, Zhichuan J.

2016-01-01

Thin, robust, lightweight, and flexible supercapacitors (SCs) have aroused growing attentions nowadays due to the rapid development of flexible electronics. Graphene-polyaniline (PANI) hybrids are attractive candidates for high performance SCs. In order to utilize them in real devices, it is necessary to improve the capacitance and the structure stability of PANI. Here we report a hierarchical three-dimensional structure, in which all of PANI nanofibers (NFs) are tightly wrapped inside reduced graphene oxide (rGO) nanosheet skeletons, for high-performance flexible SCs. The as-fabricated film electrodes with this unique structure showed a highest gravimetric specific capacitance of 921 F/g and volumetric capacitance of 391 F/cm3. The assembled solid-state SCs gave a high specific capacitance of 211 F/g (1 A/g), a high area capacitance of 0.9 F/cm2, and a competitive volumetric capacitance of 25.6 F/cm3. The SCs also exhibited outstanding rate capability (~75% retention at 20 A/g) as well as excellent cycling stability (100% retention at 10 A/g for 2000 cycles). Additionally, no structural failure and loss of performance were observed under the bending state. This structure design paves a new avenue for engineering rGO/PANI or other similar hybrids for high performance flexible energy storage devices. PMID:26795067

Three-dimensional skeleton networks of graphene wrapped polyaniline nanofibers: An excellent structure for high-performance flexible solid-state supercapacitors

DOE PAGES

Hu, Nantao; Zhang, Liling; Yang, Chao; ...

2016-01-22

Thin, robust, lightweight, and flexible supercapacitors (SCs) have aroused growing attentions nowadays due to the rapid development of flexible electronics. Graphene-polyaniline (PANI) hybrids are attractive candidates for high performance SCs. In order to utilize them in real devices, it is necessary to improve the capacitance and the structure stability of PANI. Here we report a hierarchical three-dimensional structure, in which all of PANI nanofibers (NFs) are tightly wrapped inside reduced graphene oxide (rGO) nanosheet skeletons, for high-performance flexible SCs. The as-fabricated film electrodes with this unique structure showed a highest gravimetric specific capacitance of 921 F/g and volumetric capacitance ofmore » 391 F/cm 3. The assembled solid-state SCs gave a high specific capacitance of 211 F/g (1 A/g), a high area capacitance of 0.9 F/cm 2, and a competitive volumetric capacitance of 25.6 F/cm 3. The SCs also exhibited outstanding rate capability (~75% retention at 20 A/g) as well as excellent cycling stability (100% retention at 10 A/g for 2000 cycles). Additionally, no structural failure and loss of performance were observed under the bending state. Lastly, this structure design paves a new avenue for engineering rGO/PANI or other similar hybrids for high performance flexible energy storage devices.« less

Mechanical design of an intracranial stent for treating cerebral aneurysms.

PubMed

Shobayashi, Yasuhiro; Tanoue, Tetsuya; Tateshima, Satoshi; Tanishita, Kazuo

2010-11-01

Endovascular treatment of cerebral aneurysms using stents has advanced markedly in recent years. Mechanically, a cerebrovascular stent must be very flexible longitudinally and have low radial stiffness. However, no study has examined the stress distribution and deformation of cerebrovascular stents using the finite element method (FEM) and experiments. Stents can have open- and closed-cell structures, and open-cell stents are used clinically in the cerebrovasculature because of their high flexibility. However, the open-cell structure confers a risk of in-stent stenosis due to protrusion of stent struts into the normal parent artery. Therefore, a flexible stent with a closed-cell structure is required. To design a clinically useful, highly flexible, closed-cell stent, one must examine the mechanical properties of the closed-cell structure. In this study, we investigated the relationship between mesh patterns and the mechanical properties of closed-cell stents. Several mesh patterns were designed and their characteristics were studied using numerical simulation. The results showed that the bending stiffness of a closed-cell stent depends on the geometric configuration of the stent cell. It decreases when the stent cell is stretched in the circumferential direction. Mechanical flexibility equal to an open-cell structure was obtained in a closed-cell structure by varying the geometric configuration of the stent cell. Copyright © 2010 IPEM. Published by Elsevier Ltd. All rights reserved.

Mechanical attachments for flexible blanket TPS

NASA Astrophysics Data System (ADS)

Newquist, Charles W.; Anderson, David M.; Shorey, Mark W.; Preedy, Kristina S.

1998-01-01

The operability of a flexible blanket thermal protection system for a reusable launch vehicle can be improved by using mechanical attachments instead of adhesive bonding to fasten the thermal protection system to the vehicle structure. Mechanical attachments offer specific benefits by (1) permitting the use of composite or metal structures at or near their maximum temperatures (above the adhesive temperature limit) thereby reducing the required TPS thickness and weight, (2) significantly reducing both the frequency and time for TPS replacement, (3) providing easy access to hatches and the underlying structure, and (4) allowing the attachment of flexible TPS to integral cryotanks, where the TPS/structure interface temperature may fall below the lower temperature of the silicone adhesives.

Computation of structural flexibility for bridge health monitoring using ambient modal data

DOT National Transportation Integrated Search

1996-01-01

The issues surrounding the use of ambient vibration modes for the location of structural damage via dynamically : measured flexibility are examined. Several methods for obtaining the required mass-normalized : dynamic mode shapes from ambient modal d...

High Performance All-Solid-State Flexible Micro-Pseudocapacitor Based on Hierarchically Nanostructured Tungsten Trioxide Composite

PubMed Central

2015-01-01

Microsupercapacitors (MSCs) are promising energy storage devices to power miniaturized portable electronics and microelectromechanical systems. With the increasing attention on all-solid-state flexible supercapacitors, new strategies for high-performance flexible MSCs are highly desired. Here, we demonstrate all-solid-state, flexible micropseudocapacitors via direct laser patterning on crack-free, flexible WO3/polyvinylidene fluoride (PVDF)/multiwalled carbon nanotubes (MWCNTs) composites containing high levels of porous hierarchically structured WO3 nanomaterials (up to 50 wt %) and limited binder (PVDF, <25 wt %). The work leads to an areal capacitance of 62.4 mF·cm–2 and a volumetric capacitance of 10.4 F·cm–3, exceeding that of graphene based flexible MSCs by a factor of 26 and 3, respectively. As a noncarbon based flexible MSC, hierarchically nanostructured WO3 in the narrow finger electrode is essential to such enhancement in energy density due to its pseudocapacitive property. The effects of WO3/PVDF/MWCNTs composite composition and the dimensions of interdigital structure on the performance of the flexible MSCs are investigated. PMID:26618406

High Performance All-Solid-State Flexible Micro-Pseudocapacitor Based on Hierarchically Nanostructured Tungsten Trioxide Composite.

PubMed

Huang, Xuezhen; Liu, Hewei; Zhang, Xi; Jiang, Hongrui

2015-12-23

Microsupercapacitors (MSCs) are promising energy storage devices to power miniaturized portable electronics and microelectromechanical systems. With the increasing attention on all-solid-state flexible supercapacitors, new strategies for high-performance flexible MSCs are highly desired. Here, we demonstrate all-solid-state, flexible micropseudocapacitors via direct laser patterning on crack-free, flexible WO3/polyvinylidene fluoride (PVDF)/multiwalled carbon nanotubes (MWCNTs) composites containing high levels of porous hierarchically structured WO3 nanomaterials (up to 50 wt %) and limited binder (PVDF, <25 wt %). The work leads to an areal capacitance of 62.4 mF·cm(-2) and a volumetric capacitance of 10.4 F·cm(-3), exceeding that of graphene based flexible MSCs by a factor of 26 and 3, respectively. As a noncarbon based flexible MSC, hierarchically nanostructured WO3 in the narrow finger electrode is essential to such enhancement in energy density due to its pseudocapacitive property. The effects of WO3/PVDF/MWCNTs composite composition and the dimensions of interdigital structure on the performance of the flexible MSCs are investigated.

Highly conductive transparent organic electrodes with multilayer structures for rigid and flexible optoelectronics.

PubMed

Guo, Xiaoyang; Liu, Xingyuan; Lin, Fengyuan; Li, Hailing; Fan, Yi; Zhang, Nan

2015-05-27

Transparent electrodes are essential components for optoelectronic devices, such as touch panels, organic light-emitting diodes, and solar cells. Indium tin oxide (ITO) is widely used as transparent electrode in optoelectronic devices. ITO has high transparency and low resistance but contains expensive rare elements, and ITO-based devices have poor mechanical flexibility. Therefore, alternative transparent electrodes with excellent opto-electrical performance and mechanical flexibility will be greatly demanded. Here, organics are introduced into dielectric-metal-dielectric structures to construct the transparent electrodes on rigid and flexible substrates. We show that organic-metal-organic (OMO) electrodes have excellent opto-electrical properties (sheet resistance of below 10 Ω sq(-1) at 85% transmission), mechanical flexibility, thermal and environmental stabilities. The OMO-based polymer photovoltaic cells show performance comparable to that of devices based on ITO electrodes. This OMO multilayer structure can therefore be used to produce transparent electrodes suitable for use in a wide range of optoelectronic devices.

Optimum vibration control of flexible beams by piezo-electric actuators

NASA Technical Reports Server (NTRS)

Baz, A.; Poh, S.; Studer, P.

1988-01-01

The utilization of piezoelectric actuators in controlling the structural vibrations of flexible beams is examined. A Modified Independent Modal Space Control (MIMSC) method is devised to enable the selection of the optimal location, control gains and excitation voltage of the piezoelectric actuators in a way that would minimize the amplitudes of vibrations of beams to which these actuators are bonded, as well as the input control energy necessary to suppress these vibrations. The developed method accounts for the effects that the piezoelectric actuators have on changing the elastic and inertial properties of the flexible beams. Numerical examples are presented to illustrate the application of the developed MIMSC method in minimizing the structural vibrations of beams of different materials when subjected to different loading and end conditions using ceramic or polymeric piezoelectric actuators. The obtained results emphasize the importance of the devised method in designing more realistic active control systems for flexible beams, in particular, and large flexible structures in general.

Optimum vibration control of flexible beams by piezo-electric actuators

NASA Technical Reports Server (NTRS)

Baz, A.; Poh, S.

1987-01-01

The utilization of piezoelectric actuators in controlling the structural vibrations of flexible beams is examined. A Modified Independent Modal Space Control (MIMSC) method is devised to enable the selection of the optimal location, control gains and excitation voltage of the piezoelectric actuators in a way that would minimize the amplitudes of vibrations of beams to which these actuators are bonded, as well as the input control energy necessary to suppress these vibrations. The developed method accounts for the effects that the piezoelectric actuators have on changing the elastic and inertial properties of the flexible beams. Numerical examples are presented to illustrate the application of the developed MIMSC method in minimizing the structural vibrations of beams of different materials when subjected to different loading and end conditions using ceramic or polymeric piezoelectric actuators. The obtained results emphasize the importance of the devised method in designing more realistic active control systems for flexible beams, in particular, and large flexible structures in general.

The amino-terminal structure of human fragile X mental retardation protein obtained using precipitant-immobilized imprinted polymers

NASA Astrophysics Data System (ADS)

Hu, Yufeng; Chen, Zhenhang; Fu, Yanjun; He, Qingzhong; Jiang, Lun; Zheng, Jiangge; Gao, Yina; Mei, Pinchao; Chen, Zhongzhou; Ren, Xueqin

2015-03-01

Flexibility is an intrinsic property of proteins and essential for their biological functions. However, because of structural flexibility, obtaining high-quality crystals of proteins with heterogeneous conformations remain challenging. Here, we show a novel approach to immobilize traditional precipitants onto molecularly imprinted polymers (MIPs) to facilitate protein crystallization, especially for flexible proteins. By applying this method, high-quality crystals of the flexible N-terminus of human fragile X mental retardation protein are obtained, whose absence causes the most common inherited mental retardation. A novel KH domain and an intermolecular disulfide bond are discovered, and several types of dimers are found in solution, thus providing insights into the function of this protein. Furthermore, the precipitant-immobilized MIPs (piMIPs) successfully facilitate flexible protein crystal formation for five model proteins with increased diffraction resolution. This highlights the potential of piMIPs for the crystallization of flexible proteins.

Optical fiber cabling technologies for flexible access network

NASA Astrophysics Data System (ADS)

Tanji, Hisashi

2008-07-01

Fiber-to-the-home (FTTH) outside plant infrastructure should be so designed and constructed as to flexibly deal with increasing subscribers and system evolution to be expected in the future, taking minimization of total cost (CAPEX and OPEX) into consideration. With this in mind, fiber access architectures are reviewed and key technologies on optical fiber and cable for supporting flexible access network are presented. Low loss over wide wavelength (low water peak) and bend-insensitive single mode fiber is a future proof solution. Enhanced separable ribbon facilitates mid-span access to individual fibers in a cable installed, improving fiber utilizing efficiency and flexibility of distribution design. It also contributes to an excellent low PMD characteristic which could be required for video RF overlay system or high capacity long reach metro-access convergence network in the future. Bend-insensitive fiber based cabling technique including field installable connector greatly improves fiber/cable handling in installation and maintenance work.

Modified Dynamic Inversion to Control Large Flexible Aircraft: What's Going On?

NASA Technical Reports Server (NTRS)

Gregory, Irene M.

1999-01-01

High performance aircraft of the future will be designed lighter, more maneuverable, and operate over an ever expanding flight envelope. One of the largest differences from the flight control perspective between current and future advanced aircraft is elasticity. Over the last decade, dynamic inversion methodology has gained considerable popularity in application to highly maneuverable fighter aircraft, which were treated as rigid vehicles. This paper explores dynamic inversion application to an advanced highly flexible aircraft. An initial application has been made to a large flexible supersonic aircraft. In the course of controller design for this advanced vehicle, modifications were made to the standard dynamic inversion methodology. The results of this application were deemed rather promising. An analytical study has been undertaken to better understand the nature of the made modifications and to determine its general applicability. This paper presents the results of this initial analytical look at the modifications to dynamic inversion to control large flexible aircraft.

A Program Structure for Event-Based Speech Synthesis by Rules within a Flexible Segmental Framework.

ERIC Educational Resources Information Center

Hill, David R.

1978-01-01

A program structure based on recently developed techniques for operating system simulation has the required flexibility for use as a speech synthesis algorithm research framework. This program makes synthesis possible with less rigid time and frequency-component structure than simpler schemes. It also meets real-time operation and memory-size…

Large-scale wind turbine structures

NASA Technical Reports Server (NTRS)

Spera, David A.

1988-01-01

The purpose of this presentation is to show how structural technology was applied in the design of modern wind turbines, which were recently brought to an advanced stage of development as sources of renewable power. Wind turbine structures present many difficult problems because they are relatively slender and flexible; subject to vibration and aeroelastic instabilities; acted upon by loads which are often nondeterministic; operated continuously with little maintenance in all weather; and dominated by life-cycle cost considerations. Progress in horizontal-axis wind turbines (HAWT) development was paced by progress in the understanding of structural loads, modeling of structural dynamic response, and designing of innovative structural response. During the past 15 years a series of large HAWTs was developed. This has culminated in the recent completion of the world's largest operating wind turbine, the 3.2 MW Mod-5B power plane installed on the island of Oahu, Hawaii. Some of the applications of structures technology to wind turbine will be illustrated by referring to the Mod-5B design. First, a video overview will be presented to provide familiarization with the Mod-5B project and the important components of the wind turbine system. Next, the structural requirements for large-scale wind turbines will be discussed, emphasizing the difficult fatigue-life requirements. Finally, the procedures used to design the structure will be presented, including the use of the fracture mechanics approach for determining allowable fatigue stresses.

Control of flexible structures

NASA Technical Reports Server (NTRS)

Russell, R. A.

1985-01-01

The requirements for future space missions indicate that many of these spacecraft will be large, flexible, and in some applications, require precision geometries. A technology program that addresses the issues associated with the structure/control interactions for these classes of spacecraft is discussed. The goal of the NASA control of flexible structures technology program is to generate a technology data base that will provide the designer with options and approaches to achieve spacecraft performance such as maintaining geometry and/or suppressing undesired spacecraft dynamics. This technology program will define the appropriate combination of analysis, ground testing, and flight testing required to validate the structural/controls analysis and design tools. This work was motivated by a recognition that large minimum weight space structures will be required for many future missions. The tools necessary to support such design included: (1) improved structural analysis; (2) modern control theory; (3) advanced modeling techniques; (4) system identification; and (5) the integration of structures and controls.

Flexibility in flood management design: proactive planning under uncertainty

NASA Astrophysics Data System (ADS)

Smet, K.; de Neufville, R.; van der Vlist, M.

2016-12-01

This paper presents a value-enhancing approach for proactive planning and design of long-lived flood management infrastructure given uncertain future flooding threats. Designing infrastructure that can be adapted over time is a method to safeguard the efficacy of current design decisions given future uncertainties. We explore the value of embedding "options" in a physical structure, where an option is the right but not the obligation to do something at a later date (e.g. over-dimensioning a floodwall foundation now facilitates a future height addition in response to observed increases in sea level; building extra pump bays in a drainage pumping station enables the easy addition of pumping capacity whenever increased precipitation warrants an expansion.) The proposed approach couples a simulation model that captures future climate induced changes to the hydrologic operating environment of a structure, with an economic model that estimates the lifetime economic performance of alternative investment strategies. The economic model uses Real "In" Options analysis, a type of cash flow analysis that quantifies the implicit value of options and the flexibility they provide. We demonstrate the approach using replacement planning for the multi-functional pumping station IJmuiden on the North Sea Canal in the Netherlands. The analysis models flexibility in design decisions, varying the size and specific options included in the new structure. Results indicate that the incorporation of options within the structural design has the potential to improve its economic performance, as compared to more traditional, "build it once and build it big" designs where flexibility is not an explicit design criterion. The added value resulting from the incorporation of flexibility varies with the range of future conditions considered, and the specific options examined. This approach could be applied to explore investment strategies for the design of other flood management structures, as well as be expanded to look more at flexibility within an infrastructure network rather than a single structure. Flexibility in flood management design:proactive planning under uncertainty

Control of nonlinear flexible space structures

NASA Astrophysics Data System (ADS)

Shi, Jianjun

With the advances made in computer technology and efficiency of numerical algorithms over last decade, the MPC strategies have become quite popular among control community. However, application of MPC or GPC to flexible space structure control has not been explored adequately in the literature. The work presented in this thesis primarily focuses on application of GPC to control of nonlinear flexible space structures. This thesis is particularly devoted to the development of various approximate dynamic models, design and assessment of candidate controllers, and extensive numerical simulations for a realistic multibody flexible spacecraft, namely, Jupiter Icy Moons Orbiter (JIMO)---a Prometheus class of spacecraft proposed by NASA for deep space exploratory missions. A stable GPC algorithm is developed for Multi-Input-Multi-Output (MIMO) systems. An end-point weighting (penalty) is used in the GPC cost function to guarantee the nominal stability of the closed-loop system. A method is given to compute the desired end-point state from the desired output trajectory. The methodologies based on Fake Algebraic Riccati Equation (FARE) and constrained nonlinear optimization, are developed for synthesis of state weighting matrix. This makes this formulation more practical. A stable reconfigurable GPC architecture is presented and its effectiveness is demonstrated on both aircraft as well as spacecraft model. A representative in-orbit maneuver is used for assessing the performance of various control strategies using various design models. Different approximate dynamic models used for analysis include linear single body flexible structure, nonlinear single body flexible structure, and nonlinear multibody flexible structure. The control laws evaluated include traditional GPC, feedback linearization-based GPC (FLGPC), reconfigurable GPC, and nonlinear dissipative control. These various control schemes are evaluated for robust stability and robust performance in the presence of parametric uncertainties and input disturbances. Finally, the conclusions are made with regard to the efficacy of these controllers and potential directions for future research.

LQG/LTR optimal attitude control of small flexible spacecraft using free-free boundary conditions

NASA Astrophysics Data System (ADS)

Fulton, Joseph M.

Due to the volume and power limitations of a small satellite, careful consideration must be taken while designing an attitude control system for 3-axis stabilization. Placing redundancy in the system proves difficult and utilizing power hungry, high accuracy, active actuators is not a viable option. Thus, it is customary to find dependable, passive actuators used in conjunction with small scale active control components. This document describes the application of Elastic Memory Composite materials in the construction of a flexible spacecraft appendage, such as a gravity gradient boom. Assumed modes methods are used with Finite Element Modeling information to obtain the equations of motion for the system while assuming free-free boundary conditions. A discussion is provided to illustrate how cantilever mode shapes are not always the best assumption when modeling small flexible spacecraft. A key point of interest is first resonant modes may be needed in the system design plant in spite of these modes being greater than one order of magnitude in frequency when compared to the crossover frequency of the controller. LQG/LTR optimal control techniques are implemented to compute attitude control gains while controller robustness considerations determine appropriate reduced order controllers and which flexible modes to include in the design model. Key satellite designer concerns in the areas of computer processor sizing, material uncertainty impacts on the system model, and system performance variations resulting from appendage length modifications are addressed.

A flexible tool for hydraulic and water quality performance analysis of green infrastructure

NASA Astrophysics Data System (ADS)

Massoudieh, A.; Alikhani, J.

2017-12-01

Models that allow for design considerations of green infrastructure (GI) practices to control stormwater runoff and associated contaminants have received considerable attention in recent years. To be used to evaluate the effect design configurations on the long-term performance of GIs, models should be able to consider processes within GIs with good fidelity. In this presentation, a sophisticated, yet flexible tool for hydraulic and water quality assessment of GIs will be introduced. The tool can be used by design engineers and researchers to capture and explore the effect of design factors and properties of the media employed in the performance of GI systems at a relatively small scale. We deemed it essential to have a flexible GI modeling tool that is capable of simulating GI system components and specific biogeochemical processes affecting contaminants such as evapotranspiration, plant uptake, reactions, and particle-associated transport accurately while maintaining a high degree of flexibility to account for the myriad of GI alternatives. The mathematical framework for a stand-alone GI performance assessment tool has been developed and will be demonstrated. The process-based model framework developed here can be used to model a diverse range of GI practices such as stormwater ponds, green roofs, retention ponds, bioretention systems, infiltration trench, permeable pavement and other custom-designed combinatory systems. An example of the application of the system to evaluate the performance of a rain-garden system will be demonstrated.

Flexible Multi-Shock Shield

NASA Technical Reports Server (NTRS)

Christiansen, Eric L. (Inventor); Crews, Jeanne L. (Inventor)

2005-01-01

Flexible multi-shock shield system and method are disclosed for defending against hypervelocity particles. The flexible multi-shock shield system and method may include a number of flexible bumpers or shield layers spaced apart by one or more resilient support layers, all of which may be encapsulated in a protective cover. Fasteners associated with the protective cover allow the flexible multi-shock shield to be secured to the surface of a structure to be protected.

Investigation of structural capacity of geogrid-reinforced aggregate base materials in flexible pavements.

DOT National Transportation Integrated Search

2016-12-01

The objective of this research was to investigate the structural capacity of geogrid-reinforced aggregate base materials in flexible pavements through full-scale testing. The scope involved field testing at two sites in northern Utah that each includ...

Flexible and composite structures for premium pavements. Volume 1, Development of design procedure

DOT National Transportation Integrated Search

1980-11-01

This document provides results of a detailed study to identify flexible and composite structures which will perform as zero-maintenance pavements. To accomplish this, the report identifies the major distress types which have seriously limited the mai...

Integrative Structural Biomechanical Concepts of Ankylosing Spondylitis

PubMed Central

Masi, Alfonse T.; Nair, Kalyani; Andonian, Brian J.; Prus, Kristina M.; Kelly, Joseph; Sanchez, Jose R.; Henderson, Jacqueline

2011-01-01

Ankylosing spondylitis (AS) is not fully explained by inflammatory processes. Clinical, epidemiological, genetic, and course of disease features indicate additional host-related risk processes and predispositions. Collectively, the pattern of predisposition to onset in adolescent and young adult ages, male preponderance, and widely varied severity of AS is unique among rheumatic diseases. However, this pattern could reflect biomechanical and structural differences between the sexes, naturally occurring musculoskeletal changes over life cycles, and a population polymorphism. During juvenile development, the body is more flexible and weaker than during adolescent maturation and young adulthood, when strengthening and stiffening considerably increase. During middle and later ages, the musculoskeletal system again weakens. The novel concept of an innate axial myofascial hypertonicity reflects basic mechanobiological principles in human function, tissue reactivity, and pathology. However, these processes have been little studied and require critical testing. The proposed physical mechanisms likely interact with recognized immunobiological pathways. The structural biomechanical processes and tissue reactions might possibly precede initiation of other AS-related pathways. Research in the combined structural mechanobiology and immunobiology processes promises to improve understanding of the initiation and perpetuation of AS than prevailing concepts. The combined processes might better explain characteristic enthesopathic and inflammatory processes in AS. PMID:22216409

An information driven strategy to support multidisciplinary design

NASA Technical Reports Server (NTRS)

Rangan, Ravi M.; Fulton, Robert E.

1990-01-01

The design of complex engineering systems such as aircraft, automobiles, and computers is primarily a cooperative multidisciplinary design process involving interactions between several design agents. The common thread underlying this multidisciplinary design activity is the information exchange between the various groups and disciplines. The integrating component in such environments is the common data and the dependencies that exist between such data. This may be contrasted to classical multidisciplinary analyses problems where there is coupling between distinct design parameters. For example, they may be expressed as mathematically coupled relationships between aerodynamic and structural interactions in aircraft structures, between thermal and structural interactions in nuclear plants, and between control considerations and structural interactions in flexible robots. These relationships provide analytical based frameworks leading to optimization problem formulations. However, in multidisciplinary design problems, information based interactions become more critical. Many times, the relationships between different design parameters are not amenable to analytical characterization. Under such circumstances, information based interactions will provide the best integration paradigm, i.e., there is a need to model the data entities and their dependencies between design parameters originating from different design agents. The modeling of such data interactions and dependencies forms the basis for integrating the various design agents.

Flexible Modeling of Latent Task Structures in Multitask Learning

DTIC Science & Technology

2012-06-26

Flexible Modeling of Latent Task Structures in Multitask Learning Alexandre Passos† apassos@cs.umass.edu Computer Science Department, University of...of Maryland, College Park, MD USA Abstract Multitask learning algorithms are typically designed assuming some fixed, a priori known latent structure...shared by all the tasks. However, it is usually unclear what type of latent task structure is the most ap- propriate for a given multitask learning prob

Conformational Transitions upon Ligand Binding: Holo-Structure Prediction from Apo Conformations

PubMed Central

Seeliger, Daniel; de Groot, Bert L.

2010-01-01

Biological function of proteins is frequently associated with the formation of complexes with small-molecule ligands. Experimental structure determination of such complexes at atomic resolution, however, can be time-consuming and costly. Computational methods for structure prediction of protein/ligand complexes, particularly docking, are as yet restricted by their limited consideration of receptor flexibility, rendering them not applicable for predicting protein/ligand complexes if large conformational changes of the receptor upon ligand binding are involved. Accurate receptor models in the ligand-bound state (holo structures), however, are a prerequisite for successful structure-based drug design. Hence, if only an unbound (apo) structure is available distinct from the ligand-bound conformation, structure-based drug design is severely limited. We present a method to predict the structure of protein/ligand complexes based solely on the apo structure, the ligand and the radius of gyration of the holo structure. The method is applied to ten cases in which proteins undergo structural rearrangements of up to 7.1 Å backbone RMSD upon ligand binding. In all cases, receptor models within 1.6 Å backbone RMSD to the target were predicted and close-to-native ligand binding poses were obtained for 8 of 10 cases in the top-ranked complex models. A protocol is presented that is expected to enable structure modeling of protein/ligand complexes and structure-based drug design for cases where crystal structures of ligand-bound conformations are not available. PMID:20066034

Device and method for redirecting electromagnetic signals

DOEpatents

Garcia, Ernest J.

1999-01-01

A device fabricated to redirect electromagnetic signals, the device including a primary driver adapted to provide a predetermined force, a linkage system coupled to the primary driver, a pusher rod rotationally coupled to the linkage system, a flexible rod element attached to the pusher rod and adapted to buckle upon the application of the predetermined force, and a mirror structure attached to the flexible rod element at one end and to the substrate at another end. When the predetermined force buckles the flexible rod element, the mirror structure and the flexible rod element both move to thereby allow a remotely-located electromagnetic signal directed towards the device to be redirected.

Flexible Volumetric Structure

NASA Technical Reports Server (NTRS)

Cagle, Christopher M. (Inventor); Schlecht, Robin W. (Inventor)

2014-01-01

A flexible volumetric structure has a first spring that defines a three-dimensional volume and includes a serpentine structure elongatable and compressible along a length thereof. A second spring is coupled to at least one outboard edge region of the first spring. The second spring is a sheet-like structure capable of elongation along an in-plane dimension thereof. The second spring is oriented such that its in-plane dimension is aligned with the length of the first spring's serpentine structure.

Photogrammetric mapping for cadastral land information systems

NASA Astrophysics Data System (ADS)

Muzakidis, Panagiotis D.

The creation of a "clean" digital database is a most important and complex task, upon which the usefulness of a Parcel-Based Land Information System depends. Capturing data by photogrammetric methods for cadastral purposes necessitates the transformation of data into a computer compatible form. Such input requires the encoding, editing and structuring of data. The research is carried out in two phases, the first is concerned with defining the data modelling schemes and the classification of basic data for a parcel-based land information system together with the photogrammetric methods to be adopted to collect these data. The second deals with data editing and data structuring processes in order to produce "clean" information relevant to such a system. Implementation of the proposed system at both the data collection stage and within the data processing stage itself demands a number of flexible criteria to be defined within the methodology. Development of these criteria will include consideration of the cadastral characteristics peculiar to Greece.

Methodes de calcul des forces aerodynamiques pour les etudes des interactions aeroservoelastiques

NASA Astrophysics Data System (ADS)

Biskri, Djallel Eddine

L'aeroservoelasticite est un domaine ou interagissent la structure flexible d'un avion, l'aerodynamique et la commande de vol. De son cote, la commande du vol considere l'avion comme une structure rigide et etudie l'influence du systeme de commande sur la dynamique de vol. Dans cette these, nous avons code trois nouvelles methodes d'approximation de forces aerodynamiques: Moindres carres corriges, Etat minimal corrige et Etats combines. Dans les deux premieres methodes, les erreurs d'approximation entre les forces aerodynamiques approximees par les methodes classiques et celles obtenues par les nouvelles methodes ont les memes formes analytiques que celles des forces aerodynamiques calculees par LS ou MS. Quant a la troisieme methode, celle-ci combine les formulations des forces approximees avec les methodes standards LS et MS. Les vitesses et frequences de battement et les temps d'executions calcules par les nouvelles methodes versus ceux calcules par les methodes classiques ont ete analyses.

Workshop on Structural Dynamics and Control Interaction of Flexible Structures

NASA Technical Reports Server (NTRS)

Davis, L. P.; Wilson, J. F.; Jewell, R. E.

1987-01-01

The Hubble Space Telescope features the most exacting line of sight jitter requirement thus far imposed on a spacecraft pointing system. Consideration of the fine pointing requirements prompted an attempt to isolate the telescope from the low level vibration disturbances generated by the attitude control system reaction wheels. The primary goal was to provide isolation from axial component of wheel disturbance without compromising the control system bandwidth. A passive isolation system employing metal springs in parallel with viscous fluid dampers was designed, fabricated, and space qualified. Stiffness and damping characteristics are deterministic, controlled independently, and were demonstrated to remain constant over at least five orders of input disturbance magnitude. The damping remained purely viscous even at the data collection threshold of .16 x .000001 in input displacement, a level much lower than the anticipated Hubble Space Telescope disturbance amplitude. Vibration attenuation goals were obtained and ground test of the vehicle has demonstrated the isolators are transparent to the attitude control system.

Flexible single-layer ionic organic-inorganic frameworks towards precise nano-size separation

NASA Astrophysics Data System (ADS)

Yue, Liang; Wang, Shan; Zhou, Ding; Zhang, Hao; Li, Bao; Wu, Lixin

2016-02-01

Consecutive two-dimensional frameworks comprised of molecular or cluster building blocks in large area represent ideal candidates for membranes sieving molecules and nano-objects, but challenges still remain in methodology and practical preparation. Here we exploit a new strategy to build soft single-layer ionic organic-inorganic frameworks via electrostatic interaction without preferential binding direction in water. Upon consideration of steric effect and additional interaction, polyanionic clusters as connection nodes and cationic pseudorotaxanes acting as bridging monomers connect with each other to form a single-layer ionic self-assembled framework with 1.4 nm layer thickness. Such soft supramolecular polymer frameworks possess uniform and adjustable ortho-tetragonal nanoporous structure in pore size of 3.4-4.1 nm and exhibit greatly convenient solution processability. The stable membranes maintaining uniform porous structure demonstrate precisely size-selective separation of semiconductor quantum dots within 0.1 nm of accuracy and may hold promise for practical applications in selective transport, molecular separation and dialysis systems.

Robustness of multidimensional Brownian ratchets as directed transport mechanisms.

PubMed

González-Candela, Ernesto; Romero-Rochín, Víctor; Del Río, Fernando

2011-08-07

Brownian ratchets have recently been considered as models to describe the ability of certain systems to locate very specific states in multidimensional configuration spaces. This directional process has particularly been proposed as an alternative explanation for the protein folding problem, in which the polypeptide is driven toward the native state by a multidimensional Brownian ratchet. Recognizing the relevance of robustness in biological systems, in this work we analyze such a property of Brownian ratchets by pushing to the limits all the properties considered essential to produce directed transport. Based on the results presented here, we can state that Brownian ratchets are able to deliver current and locate funnel structures under a wide range of conditions. As a result, they represent a simple model that solves the Levinthal's paradox with great robustness and flexibility and without requiring any ad hoc biased transition probability. The behavior of Brownian ratchets shown in this article considerably enhances the plausibility of the model for at least part of the structural mechanism behind protein folding process.

Syringe injectable electronics

PubMed Central

Hong, Guosong; Zhou, Tao; Jin, Lihua; Duvvuri, Madhavi; Jiang, Zhe; Kruskal, Peter; Xie, Chong; Suo, Zhigang; Fang, Ying; Lieber, Charles M.

2015-01-01

Seamless and minimally-invasive three-dimensional (3D) interpenetration of electronics within artificial or natural structures could allow for continuous monitoring and manipulation of their properties. Flexible electronics provide a means for conforming electronics to non-planar surfaces, yet targeted delivery of flexible electronics to internal regions remains difficult. Here, we overcome this challenge by demonstrating syringe injection and subsequent unfolding of submicrometer-thick, centimeter-scale macroporous mesh electronics through needles with a diameter as small as 100 micrometers. Our results show that electronic components can be injected into man-made and biological cavities, as well as dense gels and tissue, with > 90% device yield. We demonstrate several applications of syringe injectable electronics as a general approach for interpenetrating flexible electronics with 3D structures, including (i) monitoring of internal mechanical strains in polymer cavities, (ii) tight integration and low chronic immunoreactivity with several distinct regions of the brain, and (iii) in vivo multiplexed neural recording. Moreover, syringe injection enables delivery of flexible electronics through a rigid shell, delivery of large volume flexible electronics that can fill internal cavities and co-injection of electronics with other materials into host structures, opening up unique applications for flexible electronics. PMID:26053995

Syringe-injectable electronics.

PubMed

Liu, Jia; Fu, Tian-Ming; Cheng, Zengguang; Hong, Guosong; Zhou, Tao; Jin, Lihua; Duvvuri, Madhavi; Jiang, Zhe; Kruskal, Peter; Xie, Chong; Suo, Zhigang; Fang, Ying; Lieber, Charles M

2015-07-01

Seamless and minimally invasive three-dimensional interpenetration of electronics within artificial or natural structures could allow for continuous monitoring and manipulation of their properties. Flexible electronics provide a means for conforming electronics to non-planar surfaces, yet targeted delivery of flexible electronics to internal regions remains difficult. Here, we overcome this challenge by demonstrating the syringe injection (and subsequent unfolding) of sub-micrometre-thick, centimetre-scale macroporous mesh electronics through needles with a diameter as small as 100 μm. Our results show that electronic components can be injected into man-made and biological cavities, as well as dense gels and tissue, with >90% device yield. We demonstrate several applications of syringe-injectable electronics as a general approach for interpenetrating flexible electronics with three-dimensional structures, including (1) monitoring internal mechanical strains in polymer cavities, (2) tight integration and low chronic immunoreactivity with several distinct regions of the brain, and (3) in vivo multiplexed neural recording. Moreover, syringe injection enables the delivery of flexible electronics through a rigid shell, the delivery of large-volume flexible electronics that can fill internal cavities, and co-injection of electronics with other materials into host structures, opening up unique applications for flexible electronics.

Syringe-injectable electronics

NASA Astrophysics Data System (ADS)

Liu, Jia; Fu, Tian-Ming; Cheng, Zengguang; Hong, Guosong; Zhou, Tao; Jin, Lihua; Duvvuri, Madhavi; Jiang, Zhe; Kruskal, Peter; Xie, Chong; Suo, Zhigang; Fang, Ying; Lieber, Charles M.

2015-07-01

Seamless and minimally invasive three-dimensional interpenetration of electronics within artificial or natural structures could allow for continuous monitoring and manipulation of their properties. Flexible electronics provide a means for conforming electronics to non-planar surfaces, yet targeted delivery of flexible electronics to internal regions remains difficult. Here, we overcome this challenge by demonstrating the syringe injection (and subsequent unfolding) of sub-micrometre-thick, centimetre-scale macroporous mesh electronics through needles with a diameter as small as 100 μm. Our results show that electronic components can be injected into man-made and biological cavities, as well as dense gels and tissue, with >90% device yield. We demonstrate several applications of syringe-injectable electronics as a general approach for interpenetrating flexible electronics with three-dimensional structures, including (1) monitoring internal mechanical strains in polymer cavities, (2) tight integration and low chronic immunoreactivity with several distinct regions of the brain, and (3) in vivo multiplexed neural recording. Moreover, syringe injection enables the delivery of flexible electronics through a rigid shell, the delivery of large-volume flexible electronics that can fill internal cavities, and co-injection of electronics with other materials into host structures, opening up unique applications for flexible electronics.

Gravitational force and torque on a solar power satellite considering the structural flexibility

NASA Astrophysics Data System (ADS)

Zhao, Yi; Zhang, Jingrui; Zhang, Yao; Zhang, Jun; Hu, Quan

2017-11-01

The solar power satellites (SPS) are designed to collect the constant solar energy and beam it to Earth. They are traditionally large in scale and flexible in structure. In order to obtain an accurate model of such system, the analytical expressions of the gravitational force, gravity gradient torque and modal force are investigated. They are expanded to the fourth order in a Taylor series with the elastic displacements considered. It is assumed that the deformation of the structure is relatively small compared with its characteristic length, so that the assumed mode method is applicable. The high-order moments of inertia and flexibility coefficients are presented. The comprehensive dynamics of a large flexible SPS and its orbital, attitude and vibration evolutions with different order gravitational forces, gravity gradient torques and modal forces in geosynchronous Earth orbit are performed. Numerical simulations show that an accurate representation of the SPS‧ dynamic characteristics requires the retention of the higher moments of inertia and flexibility. Perturbations of orbit, attitude and vibration can be retained to the 1-2nd order gravitational forces, the 1-2nd order gravity gradient torques and the 1-2nd order modal forces for a large flexible SPS in geosynchronous Earth orbit.

Three-dimensional vectorial multifocal arrays created by pseudo-period encoding

NASA Astrophysics Data System (ADS)

Zeng, Tingting; Chang, Chenliang; Chen, Zhaozhong; Wang, Hui-Tian; Ding, Jianping

2018-06-01

Multifocal arrays have been attracting considerable attention recently owing to their potential applications in parallel optical tweezers, parallel single-molecule orientation determination, parallel recording and multifocal multiphoton microscopy. However, the generation of vectorial multifocal arrays with a tailorable structure and polarization state remains a great challenge, and reports on multifocal arrays have hitherto been restricted either to scalar focal spots without polarization versatility or to regular arrays with fixed spacing. In this work, we propose a specific pseudo-period encoding technique to create three-dimensional (3D) vectorial multifocal arrays with the ability to manipulate the position, polarization state and intensity of each focal spot. We experimentally validated the flexibility of our approach in the generation of 3D vectorial multiple spots with polarization multiplicity and position tunability.

Nonimpact brain injury: neuropsychological and behavioral correlates with consideration of physiological findings.

PubMed

Henry, G K; Gross, H S; Herndon, C A; Furst, C J

2000-01-01

This retrospective clinical study investigated the neuropsychological, physiological, and behavioral functioning of 32 adult outpatients up to 65 months following nonimpact brain injury (i.e., whiplash). All participants were administered a flexible battery of cognitive tests, and some underwent neurodiagnostic procedures and sleep studies. Compared with published norms, neuropsychological data revealed significant and persistent age-adjusted cognitive deficits, primarily in the area of executive functioning. Participants frequently complained of problems with behavioral control, sleep, and sexuality. Although structural neuroimaging was not sensitive in detecting brain pathology, quantitative electroencephalography was abnormal in all the participants evaluated, showing frontocentral slowing and increased spike wave activity. We propose that whiplash injury can produce wide-ranging circuitry dysfunction and that test selection is critical in identifying cognitive deficits.

Producing smart sensing films by means of organic field effect transistors.

PubMed

Manunza, Ileana; Orgiu, Emanuele; Caboni, Alessandra; Barbaro, Massimo; Bonfiglio, Annalisa

2006-01-01

We have fabricated the first example of totally flexible field effect device for chemical detection based on an organic field effect transistor (OFET) made by pentacene films grown on flexible plastic structures. The ion sensitivity is achieved by employing a thin Mylar foil as gate dielectric. A sensitivity of the device to the pH of the electrolyte solution has been observed A similar structure can be used also for detecting mechanical deformations on flexible surfaces. Thanks to the flexibility of the substrate and the low cost of the employed technology, these devices open the way for the production of flexible chemical and strain gauge sensors that can be employed in a variety of innovative applications such as wearable electronics, e-textiles, new man-machine interfaces.

Optical temperature sensing on flexible polymer foils

NASA Astrophysics Data System (ADS)

Sherman, Stanislav; Xiao, Yanfen; Hofmann, Meike; Schmidt, Thomas; Gleissner, Uwe; Zappe, Hans

2016-04-01

In contrast to established semiconductor waveguide-based or glass fiber-based integrated optical sensors, polymerbased optical systems offer tunable material properties, such as refractive index or viscosity, and thus provide additional degrees of freedom for sensor design and fabrication. Of particular interest in sensing applications are fully-integrated optical waveguide-based temperature sensors. These typically rely on Bragg gratings which induce a periodic refractive index variation in the waveguide so that a resonant wavelength of the structure is reflected.1,2 With broad-band excitation, a dip in the spectral output of the waveguide is thus generated at a precisely-defined wavelength. This resonant wavelength depends on the refractive index of the waveguide and the grating period, yet both of these quantities are temperature dependent by means of the thermo-optic effect (change in refractive index with temperature) and thermal expansion (change of the grating period with temperature). We show the design and fabrication of polymer waveguide-integrated temperature sensors based on Bragggratings, fabricated by replication technology on flexible PMMA foil substrates. The 175 μm thick foil serves as lower cladding for a polymeric waveguide fabricated from a custom-made UV-crosslinkable co-monomer composition. The fabrication of the grating structure includes a second replication step into a separate PMMA-foil. The dimensions of the Bragg-gratings are determined by simulations to set the bias point into the near infrared wavelength range, which allows Si-based detectors to be used. We present design considerations and performance data for the developed structures. The resulting sensor's signal is linear to temperature changes and shows a sensitivity of -306 nm/K, allowing high resolution temperature measurements.

DRAGON Grid: A Three-Dimensional Hybrid Grid Generation Code Developed

NASA Technical Reports Server (NTRS)

Liou, Meng-Sing

2000-01-01

Because grid generation can consume 70 percent of the total analysis time for a typical three-dimensional viscous flow simulation for a practical engineering device, payoffs from research and development could reduce costs and increase throughputs considerably. In this study, researchers at the NASA Glenn Research Center at Lewis Field developed a new hybrid grid approach with the advantages of flexibility, high-quality grids suitable for an accurate resolution of viscous regions, and a low memory requirement. These advantages will, in turn, reduce analysis time and increase accuracy. They result from an innovative combination of structured and unstructured grids to represent the geometry and the computation domain. The present approach makes use of the respective strengths of both the structured and unstructured grid methods, while minimizing their weaknesses. First, the Chimera grid generates high-quality, mostly orthogonal meshes around individual components. This process is flexible and can be done easily. Normally, these individual grids are required overlap each other so that the solution on one grid can communicate with another. However, when this communication is carried out via a nonconservative interpolation procedure, a spurious solution can result. Current research is aimed at entirely eliminating this undesired interpolation by directly replacing arbitrary grid overlapping with a nonstructured grid called a DRAGON grid, which uses the same set of conservation laws over the entire region, thus ensuring conservation everywhere. The DRAGON grid is shown for a typical film-cooled turbine vane with 33 holes and 3 plenum compartments. There are structured grids around each geometrical entity and unstructured grids connecting them. In fiscal year 1999, Glenn researchers developed and tested the three-dimensional DRAGON grid-generation tools. A flow solver suitable for the DRAGON grid has been developed, and a series of validation tests are underway.

How joint characteristics between a piezoelectric beam and the main structure affect the performance of an energy harvester

NASA Astrophysics Data System (ADS)

Jahani, K.; Rafiei, M. M.; Aghazadeh, P.

2017-09-01

In this paper, the influence of the joint region between a piezoelectric energy harvesting beam and the vibratory main structure is studied. The investigations are conducted in two separate sections, namely numerical and experimental studies. In numerical studies, the effects of nonlinear parameters on generated power are investigated while the joint characteristics the between vibrating base and a piezoelectric energy harvester are taken into consideration. A unimorph beam with a tip mass and a nonlinear piezoelectric layer that undergoes a large-amplitude deflection is considered as an energy harvester. By applying the Euler-Lagrange equation and Gauss’s law the mechanical and electrical equations of motion are obtained, respectively. The excitation frequency is assumed to be close to the first natural frequency. Thus, a unimodal response is considered to be like that of a system with a single degree of freedom (SDOF). The joint between the vibrating main structure and the cantilevered beam is then added to the SDOF model. The joint characteristics are simulated with a light mass, mj , linear spring stiffness, kj , and equivalent viscous damper, cj . In two scenarios, i.e. with a rigid joint and with a flexible one, a numerical approach is followed to investigate the effects of each nonlinear parameter of the harvester (stiffness, damping and piezoelectric coefficient) on the harvested power. In experimental studies, the influence of a bolted joining technique and a flexible adhesive bonding method on the harvested power is investigated. The results achieved experimentally confirm those obtained numerically, i.e. a stiffer joint leads to a greater power produced by the harvester. In other words, neglecting the joint characteristics will cause the performance (maximum output power and the range of excitation frequency) of the harvester to be overestimated in numerical simulations.

Chemical stability of insulin. 1. Hydrolytic degradation during storage of pharmaceutical preparations.

PubMed

Brange, J; Langkjaer, L; Havelund, S; Vølund, A

1992-06-01

Hydrolysis of insulin has been studied during storage of various preparations at different temperatures. Insulin deteriorates rapidly in acid solutions due to extensive deamidation at residue AsnA21. In neutral formulations deamidation takes place at residue AsnB3 at a substantially reduced rate under formation of a mixture of isoAsp and Asp derivatives. The rate of hydrolysis at B3 is independent of the strength of the preparation, and in most cases the species of insulin, but varies with storage temperature and formulation. Total transformation at B3 is considerably reduced when insulin is in the crystalline as compared to the amorphous or soluble state, indicating that formation of the rate-limiting cyclic imide decreases when the flexibility of the tertiary structure is reduced. Neutral solutions containing phenol showed reduced deamidation probably because of a stabilizing effect of phenol on the tertiary structure (alpha-helix formation) around the deamidating residue, resulting in a reduced probability for formation of the intermediate imide. The ratio of isoAsp/Asp derivative was independent of time and temperature, suggesting a pathway involving only intermediate imide formation, without any direct side-chain hydrolysis. However, increasing formation of Asp relative to isoAsp derivative was observed with decreasing flexibility of the insulin three-dimensional structure in the formulation. In certain crystalline suspensions a cleavage of the peptide bond A8-A9 was observed. Formation of this split product is species dependent: bovine greater than porcine greater than human insulin. The hydrolytic cleavage of the peptide backbone takes place only in preparations containing rhombohedral crystals in addition to free zinc ions.

Health sector reform in the Occupied Palestinian Territories (OPT): targeting the forest or the trees?

PubMed Central

GIACAMAN, RITA; ABDUL-RAHIM, HANAN F; WICK, LAURA

2006-01-01

Since the signing of the Oslo Peace Accords and the establishment of the Palestinian Authority in 1994, reform activities have targeted various spheres, including the health sector. Several international aid and UN organizations have been involved, as well as local and international non-governmental organizations, with considerable financial and technical investments. Although important achievements have been made, it is not evident that the quality of care has improved or that the most pressing health needs have been addressed, even before the second Palestinian Uprising that began in September 2000. The crisis of the Israeli re-invasion of Palestinian-controlled towns and villages since April 2002 and the attendant collapse of state structures and services have raised the problems to critical levels. This paper attempts to analyze some of the obstacles that have faced reform efforts. In our assessment, those include: ongoing conflict, frail Palestinian quasi-state structures and institutions, multiple and at times inappropriate donor policies and practices in the health sector, and a policy vacuum characterized by the absence of internal Palestinian debate on the type and direction of reform the country needs to take. In the face of all these considerations, it is important that reform efforts be flexible and consider realistically the political and economic contexts of the health system, rather than focus on mere narrow technical, managerial and financial solutions imported from the outside. PMID:12582108

Flexible Proton-Gated Oxide Synaptic Transistors on Si Membrane.

PubMed

Zhu, Li Qiang; Wan, Chang Jin; Gao, Ping Qi; Liu, Yang Hui; Xiao, Hui; Ye, Ji Chun; Wan, Qing

2016-08-24

Ion-conducting materials have received considerable attention for their applications in fuel cells, electrochemical devices, and sensors. Here, flexible indium zinc oxide (InZnO) synaptic transistors with multiple presynaptic inputs gated by proton-conducting phosphorosilicate glass-based electrolyte films are fabricated on ultrathin Si membranes. Transient characteristics of the proton gated InZnO synaptic transistors are investigated, indicating stable proton-gating behaviors. Short-term synaptic plasticities are mimicked on the proposed proton-gated synaptic transistors. Furthermore, synaptic integration regulations are mimicked on the proposed synaptic transistor networks. Spiking logic modulations are realized based on the transition between superlinear and sublinear synaptic integration. The multigates coupled flexible proton-gated oxide synaptic transistors may be interesting for neuroinspired platforms with sophisticated spatiotemporal information processing.

Broadband and flexible acoustic focusing by metafiber bundles

NASA Astrophysics Data System (ADS)

Sun, Hong-Xiang; Chen, Jia-He; Ge, Yong; Yuan, Shou-Qi; Liu, Xiao-Jun

2018-06-01

We report a broadband and flexible acoustic focusing through metafiber bundles in air, in which each metafiber consists of eight circular and narrow rectangular cavities. The fractional bandwidth of the acoustic focusing could reach about 0.2, which arises from the eigenmodes of the metafiber structure. Besides, owing to the flexible characteristic of the metafibers, the focus position can be manipulated by bending the metafiber bundles, and the metafiber bundles could bypass rigid scatterers inside the lens structure. More interestingly, the acoustic propagation and focusing directions can be changed by using a designed right-angled direction converter fabricated by the metafibers, and a waveform converter and a focusing lens of the cylindrical acoustic source are realized based on the metafiber bundles. The proposed focusing lens has the advantages of broad bandwidth, flexible structure, and high focusing performance, showing great potentials in versatile applications.

Impact of magnetic isolation on pointing system performance in the presence of structural flexibility

NASA Technical Reports Server (NTRS)

Seller, J.

1985-01-01

The inertial pointing stability of a gimbal pointing system (AGS) was compared with a magnetic pointing/gimbal followup system (ASPS), under certain conditions of system structural flexibility and disturbance inputs from the gimbal support structure. Separate 3 degree-of-freedom (3DOF) linear models based on NASTRAN modal flexibility data for the gimbal and support structures were generated for the ASPS configurations. Using the models inertial pointing control loops providing 6dB of gain margin and 45 deg of phase margin were defined for each configuration. The pointing loop bandwidth obtained for the ASPS is more than twice the level achieved for the AGS configuration. The AGS limit is attributed to the gimbal and support structure flexibility. As a result of the higher ASPS pointing loop bandwidth and the disturbance rejection provided by the magnetic isolation ASPS pointing performane is significantly better than that of the AGS system. The low frequency peak of the ASPS transfer function from base disturbance to payload angular motion is almost 60dB lower than AGS low frequency peak.

An Unusual Hydrophobic Core Confers Extreme Flexibility to HEAT Repeat Proteins

PubMed Central

Kappel, Christian; Zachariae, Ulrich; Dölker, Nicole; Grubmüller, Helmut

2010-01-01

Alpha-solenoid proteins are suggested to constitute highly flexible macromolecules, whose structural variability and large surface area is instrumental in many important protein-protein binding processes. By equilibrium and nonequilibrium molecular dynamics simulations, we show that importin-β, an archetypical α-solenoid, displays unprecedentedly large and fully reversible elasticity. Our stretching molecular dynamics simulations reveal full elasticity over up to twofold end-to-end extensions compared to its bound state. Despite the absence of any long-range intramolecular contacts, the protein can return to its equilibrium structure to within 3 Å backbone RMSD after the release of mechanical stress. We find that this extreme degree of flexibility is based on an unusually flexible hydrophobic core that differs substantially from that of structurally similar but more rigid globular proteins. In that respect, the core of importin-β resembles molten globules. The elastic behavior is dominated by nonpolar interactions between HEAT repeats, combined with conformational entropic effects. Our results suggest that α-solenoid structures such as importin-β may bridge the molecular gap between completely structured and intrinsically disordered proteins. PMID:20816072

Inspiration from nature: dynamic modelling of the musculoskeletal structure of the seahorse tail.

PubMed

Praet, Tomas; Adriaens, Dominique; Van Cauter, Sofie; Masschaele, Bert; De Beule, Matthieu; Verhegghe, Benedict

2012-10-01

Technological advances are often inspired by nature, considering that engineering is frequently faced by the same challenges as organisms in nature. One such interesting challenge is creating a structure that is at the same time stiff in a certain direction, yet flexible in another. The seahorse tail combines both radial stiffness and bending flexibility in a particularly elegant way: even though the tail is covered in a protective armour, it still shows sufficient flexibility to fully function as a prehensile organ. We therefore study the complex mechanics and dynamics of the musculoskeletal system of the seahorse tail from an engineering point of view. The seahorse tail derives its combination of flexibility and resilience from a chain of articulating skeletal segments. A versatile dynamic model of those segments was constructed, on the basis of automatic recognition of joint positions and muscle attachments. Both muscle structures that are thought to be responsible for ventral and ventral-lateral tail bending, namely the median ventral muscles and the hypaxial myomere muscles, were included in the model. Simulations on the model consist mainly of dynamic multi-body simulations. The results show that the sequential structure of uniformly shaped bony segments can remain flexible because of gliding joints that connect the corners of the segments. Radial stiffness on the other hand is obtained through the support that the central vertebra provides to the tail plating. Such insights could help in designing biomedical instruments that specifically require both high bending flexibility and radial stiffness (e.g. flexible stents and steerable catheters). Copyright © 2012 John Wiley & Sons, Ltd.

Structural flexibility and protein adaptation to temperature: Molecular dynamics analysis of malate dehydrogenases of marine molluscs.

PubMed

Dong, Yun-Wei; Liao, Ming-Ling; Meng, Xian-Liang; Somero, George N

2018-02-06

Orthologous proteins of species adapted to different temperatures exhibit differences in stability and function that are interpreted to reflect adaptive variation in structural "flexibility." However, quantifying flexibility and comparing flexibility across proteins has remained a challenge. To address this issue, we examined temperature effects on cytosolic malate dehydrogenase (cMDH) orthologs from differently thermally adapted congeners of five genera of marine molluscs whose field body temperatures span a range of ∼60 °C. We describe consistent patterns of convergent evolution in adaptation of function [temperature effects on K M of cofactor (NADH)] and structural stability (rate of heat denaturation of activity). To determine how these differences depend on flexibilities of overall structure and of regions known to be important in binding and catalysis, we performed molecular dynamics simulation (MDS) analyses. MDS analyses revealed a significant negative correlation between adaptation temperature and heat-induced increase of backbone atom movements [root mean square deviation (rmsd) of main-chain atoms]. Root mean square fluctuations (RMSFs) of movement by individual amino acid residues varied across the sequence in a qualitatively similar pattern among orthologs. Regions of sequence involved in ligand binding and catalysis-termed mobile regions 1 and 2 (MR1 and MR2), respectively-showed the largest values for RMSF. Heat-induced changes in RMSF values across the sequence and, importantly, in MR1 and MR2 were greatest in cold-adapted species. MDS methods are shown to provide powerful tools for examining adaptation of enzymes by providing a quantitative index of protein flexibility and identifying sequence regions where adaptive change in flexibility occurs.

Some nonlinear damping models in flexible structures

NASA Technical Reports Server (NTRS)

Balakrishnan, A. V.

1988-01-01

A class of nonlinear damping models is introduced with application to flexible flight structures characterized by low damping. Approximate solutions of engineering interest are obtained for the model using the classical averaging technique of Krylov and Bogoliubov. The results should be considered preliminary pending further investigation.

Analytic semigroups: Applications to inverse problems for flexible structures

NASA Technical Reports Server (NTRS)

Banks, H. T.; Rebnord, D. A.

1990-01-01

Convergence and stability results for least squares inverse problems involving systems described by analytic semigroups are presented. The practical importance of these results is demonstrated by application to several examples from problems of estimation of material parameters in flexible structures using accelerometer data.

Propulsive performance of pitching foils with variable chordwise flexibility

NASA Astrophysics Data System (ADS)

Zeyghami, Samane; Moored, Keith; Lehigh University Team

2017-11-01

Many swimming and flying animals propel themselves efficiently through water by oscillating flexible fins. These fins are not homogeneously flexible, but instead their flexural stiffness varies along their chord and span. Here we seek to evaluate the effect stiffness profile on the propulsive performance of pitching foils. Stiffness profile characterizes the variation in the local fin stiffness along the chord. To this aim, we developed a low order model of a functionally-graded material where the chordwise flexibility is modeled by two torsional springs along the chordline and the stiffness and location of the springs can be varied arbitrarily. The torsional spring structural model is then strongly coupled to a boundary element fluid model to simulate the fluid-structure interactions. Keeping the leading edge kinematics unchanged, we alter the stiffness profile of the foil and allow it to swim freely in response to the resulting hydrodynamic forces. We then detail the dependency of the hydrodynamic performance and the wake structure to the variations in the local structural properties of the foil.

A flexible ligand-based wavy layered metal-organic framework for lithium-ion storage.

PubMed

An, Tiance; Wang, Yuhang; Tang, Jing; Wang, Yang; Zhang, Lijuan; Zheng, Gengfeng

2015-05-01

A substantial challenge for direct utilization of metal-organic frameworks (MOFs) as lithium-ion battery anodes is to maintain the rigid MOF structure during lithiation/delithiation cycles. In this work, we developed a flexible, wavy layered nickel-based MOF (C20H24Cl2N8Ni, designated as Ni-Me4bpz) by a solvothermal approach of 3,3',5,5'-tetramethyl-4,4'-bipyrazole (H2Me4bpz) with nickel(II) chloride hexahydrate. The obtained MOF materials (Ni-Me4bpz) with metal azolate coordination mode provide 2-dimensional layered structure for Li(+) intercalation/extraction, and the H2Me4bpz ligands allow for flexible rotation feature and structural stability. Lithium-ion battery anodes made of the Ni-Me4bpz material demonstrate excellent specific capacity and cycling performance, and the crystal structure is well preserved after the electrochemical tests, suggesting the potential of developing flexible layered MOFs for efficient and stable electrochemical storage. Copyright © 2015 Elsevier Inc. All rights reserved.

Trajectory Control for Very Flexible Aircraft

DTIC Science & Technology

2006-10-30

aircraft are coupled with the aeroelastic equations that govern the geometrically nonlinear structural response of the vehicle. A low -order strain...nonlinear structural formulation, the finite state aerodynamic model, and the nonlinear rigid body equations together provide a low -order complete...nonlinear aircraft analysis tool. Due to the inherent flexibility of the aircraft modeling, the low order structural fre- quencies are of the same order

Recent advances of flexible hybrid perovskite solar cells

NASA Astrophysics Data System (ADS)

Shin, Dong Hee; Heo, Jin Hyuck; Im, Sang Hyuk

2017-11-01

Recently, hybrid perovskite solar cells have attracted great interest because they can be fabricated to low cost, flexible, and highly efficient solar cells. Here, we introduced recent advances of flexible hybrid perovskite solar cells. We introduced research background of flexible perovskite solar cells in introduction part. Then we composed the main body to i) structure and properties of hybrid perovskite solar cells, ii) why flexible hybrid perovskite solar cells are important?, iii) transparent conducting oxide (TCO) based flexible hybrid perovskite solar cells, and iv) TCO-free transparent conducting electrode (TCE) based flexible hybrid perovskite solar cells. Finally, we summarized research outlook of flexible hybrid perovskite solar cells.

A Coupled Fluid-Structure Interaction Analysis of Solid Rocket Motor with Flexible Inhibitors

NASA Technical Reports Server (NTRS)

Yang, H. Q.; West, Jeff

2014-01-01

A capability to couple NASA production CFD code, Loci/CHEM, with CFDRC's structural finite element code, CoBi, has been developed. This paper summarizes the efforts in applying the installed coupling software to demonstrate/investigate fluid-structure interaction (FSI) between pressure wave and flexible inhibitor inside reusable solid rocket motor (RSRM). First a unified governing equation for both fluid and structure is presented, then an Eulerian-Lagrangian framework is described to satisfy the interfacial continuity requirements. The features of fluid solver, Loci/CHEM and structural solver, CoBi, are discussed before the coupling methodology of the solvers is described. The simulation uses production level CFD LES turbulence model with a grid resolution of 80 million cells. The flexible inhibitor is modeled with full 3D shell elements. Verifications against analytical solutions of structural model under steady uniform pressure condition and under dynamic condition of modal analysis show excellent agreements in terms of displacement distribution and eigen modal frequencies. The preliminary coupled result shows that due to acoustic coupling, the dynamics of one of the more flexible inhibitors shift from its first modal frequency to the first acoustic frequency of the solid rocket motor.

A combinatorial approach to protein docking with flexible side chains.

PubMed

Althaus, Ernst; Kohlbacher, Oliver; Lenhof, Hans-Peter; Müller, Peter

2002-01-01

Rigid-body docking approaches are not sufficient to predict the structure of a protein complex from the unbound (native) structures of the two proteins. Accounting for side chain flexibility is an important step towards fully flexible protein docking. This work describes an approach that allows conformational flexibility for the side chains while keeping the protein backbone rigid. Starting from candidates created by a rigid-docking algorithm, we demangle the side chains of the docking site, thus creating reasonable approximations of the true complex structure. These structures are ranked with respect to the binding free energy. We present two new techniques for side chain demangling. Both approaches are based on a discrete representation of the side chain conformational space by the use of a rotamer library. This leads to a combinatorial optimization problem. For the solution of this problem, we propose a fast heuristic approach and an exact, albeit slower, method that uses branch-and-cut techniques. As a test set, we use the unbound structures of three proteases and the corresponding protein inhibitors. For each of the examples, the highest-ranking conformation produced was a good approximation of the true complex structure.

A bacterial acyl aminoacyl peptidase couples flexibility and stability as a result of cold adaptation.

PubMed

Brocca, Stefania; Ferrari, Cristian; Barbiroli, Alberto; Pesce, Alessandra; Lotti, Marina; Nardini, Marco

2016-12-01

Life in cold environments requires an overall increase in the flexibility of macromolecular and supramolecular structures to allow biological processes to take place at low temperature. Conformational flexibility supports high catalytic rates of enzymes in the cold but in several cases is also a cause of instability. The three-dimensional structure of the psychrophilic acyl aminoacyl peptidase from Sporosarcina psychrophila (SpAAP) reported in this paper highlights adaptive molecular changes resulting in a fine-tuned trade-off between flexibility and stability. In its functional form SpAAP is a dimer, and an increase in flexibility is achieved through loosening of intersubunit hydrophobic interactions. The release of subunits from the quaternary structure is hindered by an 'arm exchange' mechanism, in which a tiny structural element at the N terminus of one subunit inserts into the other subunit. Mutants lacking the 'arm' are monomeric, inactive and highly prone to aggregation. Another feature of SpAAP cold adaptation is the enlargement of the tunnel connecting the exterior of the protein with the active site. Such a wide channel might compensate for the reduced molecular motions occurring in the cold and allow easy and direct access of substrates to the catalytic site, rendering transient movements between domains unnecessary. Thus, cold-adapted SpAAP has developed a molecular strategy unique within this group of proteins: it is able to enhance the flexibility of each functional unit while still preserving sufficient stability. Structural data are available in the Protein Data Bank under the accession number 5L8S. © 2016 Federation of European Biochemical Societies.

Classrooms.

ERIC Educational Resources Information Center

Butin, Dan

This paper addresses classroom design trends and the key issues schools should consider for better classroom space flexibility and adaptability. Classroom space design issues when schools embrace technology are discussed, as are design considerations when rooms must accommodate different grade levels, the importance of lighting, furniture…

Integrated Cost Accounting System.

DTIC Science & Technology

1992-07-27

D., Srikant M. Datar, and Sunder Kekre . "Relevant Costs, Congestion, and Stochasticity in Production Environments." unpublished working paper...School, 1984. 113 Kekre , Sunder . "Strategic Consideration of Order Flexibility, Costs, and Delivery in Long-Term Contracts." Unpublished Working Paper

Understanding the Effects of Electrode Formulation on the Mechanical Strength of Composite Electrodes for Flexible Batteries.

PubMed

Gaikwad, Abhinav M; Arias, Ana Claudia

2017-02-22

Flexible lithium-ion batteries are necessary for powering the next generation of wearable electronic devices. In most designs, the mechanical flexibility of the battery is improved by reducing the thickness of the active layers, which in turn reduces the areal capacity and energy density of the battery. The performance of a battery depends on the electrode composition, and in most flexible batteries, standard electrode formulation is used, which is not suitable for flexing. Even with considerable efforts made toward the development of flexible lithium-ion batteries, the formulation of the electrodes has received very little attention. In this study, we investigate the relation between the electrode formulation and the mechanical strength of the electrodes. Peel and drag tests are used to compare the adhesion and cohesion strength of the electrodes. The strength of an electrode is sensitive to the particle size and the choice of polymeric binder. By optimizing the electrode composition, we were able to fabricate a high areal capacity (∼2 mAh/cm 2 ) flexible lithium-ion battery with conventional metal-based current collectors that shows superior electrochemical and mechanical performance in comparison to that of batteries with standard composition.

Flexible microwave PIN diodes and switches employing transferrable single-crystal Si nanomembranes on plastic substrates

NASA Astrophysics Data System (ADS)

Qin, Guoxuan; Yuan, Hao-Chih; Celler, George K.; Zhou, Weidong; Ma, Zhenqiang

2009-12-01

This paper reports the realization of flexible RF/microwave PIN diodes and switches using transferrable single-crystal Si nanomembranes (SiNM) that are monolithically integrated on low-cost, flexible plastic substrates. High frequency response is obtained through the realization of low parasitic resistance achieved with heavy ion implantation before nanomembrane release and transfer. The flexible lateral SiNM PIN diodes exhibit typical rectifying characteristics with insertion loss and isolation better than 0.9 dB and 19.6 dB, respectively, from DC to 5 GHz, as well as power handling up to 22.5 dBm without gain compression. A single-pole single-throw (SPST) flexible RF switch employing shunt-series PIN diode configuration has achieved insertion loss and isolation better than 0.6 dB and 22.9 dB, respectively, from DC to 5 GHz. Furthermore, the SPST microwave switch shows performance improvement and robustness under mechanical deformation conditions. The study demonstrates the considerable potential of using properly processed transferrable SiNM for microwave passive components. Future investigations on transferrable SiNMs will lead to eventual realization of monolithic microwave integrated systems on low-cost flexible substrates.

Acetylcholine Activity in Selective Striatal Regions Supports Behavioral Flexibility

PubMed Central

Ragozzino, Michael E.; Mohler, Eric G.; Prior, Margaret; Palencia, Carlos A.; Rozman, Suzanne

2009-01-01

Daily living often requires individuals to flexibly respond to new circumstances. There is considerable evidence that the striatum is part of a larger neural network that supports flexible adaptations. Cholinergic interneurons are situated to strongly influence striatal output patterns which may enable flexible adaptations. The present experiments investigated whether acetylcholine actions in different striatal regions support behavioral flexibility by measuring acetylcholine efflux during place reversal learning. Acetylcholine efflux selectively increased in the dorsomedial striatum, but not dorsolateral or ventromedial striatum during place reversal learning. In order to modulate the M2-class of autoreceptors, administration of oxotremorine sesquifumurate (100 nM) into the dorsomedial striatum, concomitantly impaired reversal learning and an increase in acetylcholine output. These effects were reversed by the m2 muscarinic receptor antagonist, AF-DX-116 (20 nM). The effects of oxotremorine sesquifumurate and AF-DX-116 on acetylcholine efflux were selective to behaviorally-induced changes as neither treatment affected acetylcholine output in a resting condition. In contrast to reversal learning, acetylcholine efflux in the dorsomedial striatum did not change during place acquisition. The results reveal an essential role for cholinergic activity and define its locus of control to the dorsomedial striatum in cognitive flexibility. PMID:18845266

Acetylcholine activity in selective striatal regions supports behavioral flexibility.

PubMed

Ragozzino, Michael E; Mohler, Eric G; Prior, Margaret; Palencia, Carlos A; Rozman, Suzanne

2009-01-01

Daily living often requires individuals to flexibly respond to new circumstances. There is considerable evidence that the striatum is part of a larger neural network that supports flexible adaptations. Cholinergic interneurons are situated to strongly influence striatal output patterns which may enable flexible adaptations. The present experiments investigated whether acetylcholine actions in different striatal regions support behavioral flexibility by measuring acetylcholine efflux during place reversal learning. Acetylcholine efflux selectively increased in the dorsomedial striatum, but not dorsolateral or ventromedial striatum during place reversal learning. In order to modulate the M2-class of autoreceptors, administration of oxotremorine sesquifumurate (100 nM) into the dorsomedial striatum, concomitantly impaired reversal learning and an increase in acetylcholine output. These effects were reversed by the m(2) muscarinic receptor antagonist, AF-DX-116 (20 nM). The effects of oxotremorine sesquifumurate and AF-DX-116 on acetylcholine efflux were selective to behaviorally-induced changes as neither treatment affected acetylcholine output in a resting condition. In contrast to reversal learning, acetylcholine efflux in the dorsomedial striatum did not change during place acquisition. The results reveal an essential role for cholinergic activity and define its locus of control to the dorsomedial striatum in cognitive flexibility.

Flexible inorganic light emitting diodes based on semiconductor nanowires

PubMed Central

Guan, Nan; Dai, Xing; Babichev, Andrey V.; Julien, François H.

2017-01-01

The fabrication technologies and the performance of flexible nanowire light emitting diodes (LEDs) are reviewed. We first introduce the existing approaches for flexible LED fabrication, which are dominated by organic technologies, and we briefly discuss the increasing research effort on flexible inorganic LEDs achieved by micro-structuring and transfer of conventional thin films. Then, flexible nanowire-based LEDs are presented and two main fabrication technologies are discussed: direct growth on a flexible substrate and nanowire membrane formation and transfer. The performance of blue, green, white and bi-color flexible LEDs fabricated following the transfer approach is discussed in more detail. PMID:29568439

Optimal orbit transfer suitable for large flexible structures

NASA Technical Reports Server (NTRS)

Chatterjee, Alok K.

1989-01-01

The problem of continuous low-thrust planar orbit transfer of large flexible structures is formulated as an optimal control problem with terminal state constraints. The dynamics of the spacecraft motion are treated as a point-mass central force field problem; the thrust-acceleration magnitude is treated as an additional state variable; and the rate of change of thrust-acceleration is treated as a control variable. To ensure smooth transfer, essential for flexible structures, an additional quadratic term is appended to the time cost functional. This term penalizes any abrupt change in acceleration. Numerical results are presented for the special case of a planar transfer.

A homotopy algorithm for synthesizing robust controllers for flexible structures via the maximum entropy design equations

NASA Technical Reports Server (NTRS)

Collins, Emmanuel G., Jr.; Richter, Stephen

1990-01-01

One well known deficiency of LQG compensators is that they do not guarantee any measure of robustness. This deficiency is especially highlighted when considering control design for complex systems such as flexible structures. There has thus been a need to generalize LQG theory to incorporate robustness constraints. Here we describe the maximum entropy approach to robust control design for flexible structures, a generalization of LQG theory, pioneered by Hyland, which has proved useful in practice. The design equations consist of a set of coupled Riccati and Lyapunov equations. A homotopy algorithm that is used to solve these design equations is presented.

A slewing control experiment for flexible structures

NASA Technical Reports Server (NTRS)

Juang, J.-N.; Horta, L. G.; Robertshaw, H. H.

1985-01-01

A hardware set-up has been developed to study slewing control for flexible structures including a steel beam and a solar panel. The linear optimal terminal control law is used to design active controllers which are implemented in an analog computer. The objective of this experiment is to demonstrate and verify the dynamics and optimal terminal control laws as applied to flexible structures for large angle maneuver. Actuation is provided by an electric motor while sensing is given by strain gages and angle potentiometer. Experimental measurements are compared with analytical predictions in terms of modal parameters of the system stability matrix and sufficient agreement is achieved to validate the theory.

Particle Shape Effect on Macroscopic Behaviour of Underground Structures: Numerical and Experimental Study

NASA Astrophysics Data System (ADS)

Szarf, Krzysztof; Combe, Gael; Villard, Pascal

2015-02-01

The mechanical performance of underground flexible structures such as buried pipes or culverts made of plastics depend not only on the properties of the structure, but also on the material surrounding it. Flexible drains can deflect by 30% with the joints staying tight, or even invert. Large deformations of the structure are difficult to model in the framework of Finite Element Method, but straightforward in Discrete Element Methods. Moreover, Discrete Element approach is able to provide information about the grain-grain and grain-structure interactions at the microscale. This paper presents numerical and experimental investigations of flexible buried pipe behaviour with focus placed on load transfer above the buried structure. Numerical modeling was able to reproduce the experimental results. Load repartition was observed, being affected by a number of factors such as particle shape, pipe friction and pipe stiffness.

An optimization-based integrated controls-structures design methodology for flexible space structures

NASA Technical Reports Server (NTRS)

Maghami, Peiman G.; Joshi, Suresh M.; Armstrong, Ernest S.

1993-01-01

An approach for an optimization-based integrated controls-structures design is presented for a class of flexible spacecraft that require fine attitude pointing and vibration suppression. The integrated design problem is posed in the form of simultaneous optimization of both structural and control design variables. The approach is demonstrated by application to the integrated design of a generic space platform and to a model of a ground-based flexible structure. The numerical results obtained indicate that the integrated design approach can yield spacecraft designs that have substantially superior performance over a conventional design wherein the structural and control designs are performed sequentially. For example, a 40-percent reduction in the pointing error is observed along with a slight reduction in mass, or an almost twofold increase in the controlled performance is indicated with more than a 5-percent reduction in the overall mass of the spacecraft (a reduction of hundreds of kilograms).

Finite Rotation Analysis of Highly Thin and Flexible Structures

NASA Technical Reports Server (NTRS)

Clarke, Greg V.; Lee, Keejoo; Lee, Sung W.; Broduer, Stephen J. (Technical Monitor)

2001-01-01

Deployable space structures such as sunshields and solar sails are extremely thin and highly flexible with limited bending rigidity. For analytical investigation of their responses during deployment and operation in space, these structures can be modeled as thin shells. The present work examines the applicability of the solid shell element formulation to modeling of deployable space structures. The solid shell element formulation that models a shell as a three-dimensional solid is convenient in that no rotational parameters are needed for the description of kinematics of deformation. However, shell elements may suffer from element locking as the thickness becomes smaller unless special care is taken. It is shown that, when combined with the assumed strain formulation, the solid shell element formulation results in finite element models that are free of locking even for extremely thin structures. Accordingly, they can be used for analysis of highly flexible space structures undergoing geometrically nonlinear finite rotations.

Experimental demonstration of active vibration control for flexible structures

NASA Technical Reports Server (NTRS)

Phillips, Douglas J.; Hyland, David C.; Collins, Emmanuel G., Jr.

1990-01-01

Active vibration control of flexible structures for future space missions is addressed. Three experiments that successfully demonstrate control of flexible structures are described. The first is the pendulum experiment. The structure is a 5-m compound pendulum and was designed as an end-to-end test bed for a linear proof mass actuator and its supporting electronics. Experimental results are shown for a maximum-entropy/optimal-projection controller designed to achieve 5 percent damping in the first two pendulum modes. The second experiment was based upon the Harris Multi-Hex prototype experiment (MHPE) apparatus. This is a large optical reflector structure comprising a seven-panel array and supporting truss which typifies a number of generic characteristics of large space systems. The third experiment involved control design and implementation for the ACES structure at NASA Marshall Space Flight Center. The authors conclude with some remarks on the lessons learned from conducting these experiments.

NASA/Howard University Large Space Structures Institute

NASA Technical Reports Server (NTRS)

Broome, T. H., Jr.

1984-01-01

Basic research on the engineering behavior of large space structures is presented. Methods of structural analysis, control, and optimization of large flexible systems are examined. Topics of investigation include the Load Correction Method (LCM) modeling technique, stabilization of flexible bodies by feedback control, mathematical refinement of analysis equations, optimization of the design of structural components, deployment dynamics, and the use of microprocessors in attitude and shape control of large space structures. Information on key personnel, budgeting, support plans and conferences is included.

Experiments In Characterizing Vibrations Of A Structure

NASA Technical Reports Server (NTRS)

Yam, Yeung; Hadaegh, Fred Y.; Bayard, David S.

1993-01-01

Report discusses experiments conducted to test methods of identification of vibrational and coupled rotational/vibrational modes of flexible structure. Report one in series that chronicle development of integrated system of methods, sensors, actuators, analog and digital signal-processing equipment, and algorithms to suppress vibrations in large, flexible structure even when dynamics of structure partly unknown and/or changing. Two prior articles describing aspects of research, "Autonomous Frequency-Domain Indentification" (NPO-18099), and "Automated Characterization Of Vibrations Of A Structure" (NPO-18141).

A Flexible Stretchable Hydrogel Electrolyte for Healable All-in-One Configured Supercapacitors.

PubMed

Guo, Ying; Zheng, Kaiqiang; Wan, Pengbo

2018-04-01

The development of integrated high-performance supercapacitors with all-in-one configuration, excellent flexibility and autonomously intrinsic self-healability, and without the extra healable film layers, is still tremendously challenging. Compared to the sandwich-like laminated structures of supercapacitors with augmented interfacial contact resistance, the flexible healable integrated supercapacitor with all-in-one structure could theoretically improve their interfacial contact resistance and energy densities, simplify the tedious device assembly process, prolong the lifetime, and avoid the displacement and delamination of multilayered configurations under deformations. Herein, a flexible healable all-in-one configured supercapacitor with excellent flexibility and reliable self-healing ability by avoiding the extra healable film substrates and the postassembled sandwich-like laminated structures is developed. The healable all-in-one configured supercapacitor is prepared from in situ polymerization and deposition of nanocomposites electrode materials onto the two-sided faces of the self-healing hydrogel electrolyte separator. The self-healing hydrogel film is obtained from the physically crosslinked hydrogel with enormous hydrogen bonds, which can endow the healable capability through dynamic hydrogen bonding. The assembled all-in-one configured supercapacitor exhibits enhanced capacitive performance, good cycling stability, reliable self-healing capability, and excellent flexibility. It holds broad prospects for obtaining various flexible healable all-in-one configured supercapacitors for working as portable energy storage devices in wearable electronics. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

SPS flexible system control assessment analysis

NASA Technical Reports Server (NTRS)

Balas, M. J.

1981-01-01

Active control of the Satellite Power System (SPS0, a large mechanically flexible aerospace structure is addressed. The control algorithm is the principle component in the feedback link from sensors to actuators. An analysis of the interaction of the SPS structure and its active control system is presented.

Dynamics of poroelastocapillary rise

NASA Astrophysics Data System (ADS)

Nasouri, Babak; Elfring, Gwynn

2017-11-01

The surface-tension-driven rise of a liquid between two elastic sheets can result in their deformation or coalescence depending on their flexibility. When the sheets are poroelastic, the flexibility of the immersed parts of the sheets can change considerably thereby altering the dynamical behavior of the system. To better understand this phenomenon, we study the poroelastocapillary rise of a wetting liquid between poroelastic sheets. Using the lubrication theory and linear elasticity, we quantify the effects of the change in material properties of the wet sheets on the capillary rise and the equilibrium state of the system.

OSHA's renewed mandate for regulatory flexibility review: in support of the 1984 ethylene oxide standard.

PubMed

LaMontagne, A D; Kelsey, K T

1998-08-01

The Regulatory Flexibility Act of 1980 requires that all federal agencies consider the impact of regulations on small entities. One of the provisions of the Act requires review of regulations ever 10 years to determine whether such regulations should be continued without changes, rescinded, or amended to make them more effective or less burdensome on businesses. The Small Business Regulatory Enforcement Fairness Act (SBREFA) of 1996 amended and expanded the Regulatory Flexibility Act. Most significantly, SBREFA entitles aggrieved small entities or their representative (e.g., trade associations) to sue OSHA for failure to fulfill Regulatory Flexibility Act requirements. In response to this new political reality, OSHA held the first public meeting of their kind in June of 1997 to gather information on the ethylene oxide and lock-out/tag-out standards for the purposes of Regulatory Flexibility review. This paper presents the development of the Regulatory Flexibility review process and details our analysis of the ethylene oxide standard using OSHA's eight Regulatory Flexibility review criteria. Great progress in ethylene oxide health and safety has been made since the promulgation of the standard in 1984, including a considerable decrease in average workshift exposures. Yet, important concerns remain, such as the lack of safer substitutes for EtO's most common uses, the widespread occurrence of accidental exposures to EtO that are not captured by personal monitoring, and the recent increase in the occurrence of catastrophic EtO explosions. Because of the considerable study that has been devoted to EtO and to the EtO standard, there is a very strong cases for either making the EtO standard more worker protective, or continuing the standard without change while improving outreach and enforcement efforts to address shortcomings. Other valuable standards for which fewer data exist may be inappropriately threatened by the Regulatory Flexibility review process. Importantly, Regulatory Flexibility review could be constructive if accompanied by appropriations to fund sound evaluation studies. Instead, it will likely divert OSHA's limited resources from the numerous urgent health hazard that await initial rule-making. As signified by the designation of "intervention effectiveness research" as one of the 21 priorities on the National Occupational Research Agenda, evaluation studies of OSHA standards and other interventions are urgently needed. The occupational health community's response to this need will play a crucial role in preserving hard-won protections, as well as in developing other urgently needed protections in the future.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Milbrandt, Anelia; Booth, Samuel

Carbon fiber (CF), known also as graphite fiber, is a lightweight, strong, and flexible material used in both structural (load-bearing) and non-structural applications (e.g., thermal insulation). The high cost of precursors (the starting material used to make CF, which comes predominately from fossil sources) and manufacturing have kept CF a niche market with applications limited mostly to high-performance structural materials (e.g., aerospace). Alternative precursors to reduce CF cost and dependence on fossil sources have been investigated over the years, including biomass-derived precursors such as rayon, lignin, glycerol, and lignocellulosic sugars. The purpose of this study is to provide a comprehensivemore » overview of CF precursors from biomass and their market potential. We examine the potential CF production from these precursors, the state of technology and applications, and the production cost (when data are available). We discuss their advantages and limitations. We also discuss the physical properties of biomass-based CF, and we compare them to those of polyacrylonitrile (PAN)-based CF. We also discuss manufacturing and end-product considerations for bio-based CF, as well as considerations for plant siting and biomass feedstock logistics, feedstock competition, and risk mitigation strategies. The main contribution of this study is that it provides detailed technical and market information about each bio-based CF precursor in one document while other studies focus on one precursor at a time or a particular topic (e.g., processing). Thus, this publication allows for a comprehensive view of the CF potential from all biomass sources and serves as a reference for both novice and experienced professionals interested in CF production from alternative sources.« less

A manned lunar outpost. Design considerations for three key elements in an initial manned lunar outpost

NASA Technical Reports Server (NTRS)

Bell, Larry; Trotti, Guillermo; Brown, Jeff; Bhattacharya, Nilajan; Moore, Nathan; Polette, Tom; Toups, Larry

1988-01-01

The Initial Manned Lunar Outpost (IMLO) is proposed as the initial permanent base for manned activities on the Moon. The study concentrated on identifying the equipment, support systems, and initial base configuration necessary to accomplish the various science, industrial and exploration activities planned. The primary concepts of the MLO were the use of hard modules for habitation areas creating a flexible, modular transportation system; designing a multi-functional vehicle; and using an overhead radiation protection system. The transportation system, dubbed the Lunar Mobile Surface Transport System (LMSTS), carries the hard modules to the surface of the moon and provides a method to move them to the desired location through the use of interchangeable pallets. The avionics pallets are changed-out with wheel and hitch pallets, transforming the LMSTS into a "tractor trailer" used with the Multi-Functional Vehicle (MFV). The modules are placed under the Regolith Support Structure (RSS) which provides a stable environment and radiation protection for the entire base. The overhead structure was chosen over simply burying the modules to provide a study on the advantages and disadvantages of this type of system. The advantages include easy access to the exterior of the modules, providing a protected area for vehicles and equipment used in EVA, and creating an area of constant temperature. Disadvantages include a need for prefabrication of structural components, including the preconstruction and construction phases of the initial MLO. The design approach taken considered existing and near-term materials and technology only, without the consideration of possible future building technologies.

Lessons in molecular recognition: the effects of ligand and protein flexibility on molecular docking accuracy.

PubMed

Erickson, Jon A; Jalaie, Mehran; Robertson, Daniel H; Lewis, Richard A; Vieth, Michal

2004-01-01

The key to success for computational tools used in structure-based drug design is the ability to accurately place or "dock" a ligand in the binding pocket of the target of interest. In this report we examine the effect of several factors on docking accuracy, including ligand and protein flexibility. To examine ligand flexibility in an unbiased fashion, a test set of 41 ligand-protein cocomplex X-ray structures were assembled that represent a diversity of size, flexibility, and polarity with respect to the ligands. Four docking algorithms, DOCK, FlexX, GOLD, and CDOCKER, were applied to the test set, and the results were examined in terms of the ability to reproduce X-ray ligand positions within 2.0A heavy atom root-mean-square deviation. Overall, each method performed well (>50% accuracy) but for all methods it was found that docking accuracy decreased substantially for ligands with eight or more rotatable bonds. Only CDOCKER was able to accurately dock most of those ligands with eight or more rotatable bonds (71% accuracy rate). A second test set of structures was gathered to examine how protein flexibility influences docking accuracy. CDOCKER was applied to X-ray structures of trypsin, thrombin, and HIV-1-protease, using protein structures bound to several ligands and also the unbound (apo) form. Docking experiments of each ligand to one "average" structure and to the apo form were carried out, and the results were compared to docking each ligand back to its originating structure. The results show that docking accuracy falls off dramatically if one uses an average or apo structure. In fact, it is shown that the drop in docking accuracy mirrors the degree to which the protein moves upon ligand binding.

High-power flexible AlGaN/GaN heterostructure field-effect transistors with suppression of negative differential conductance

NASA Astrophysics Data System (ADS)

Oh, Seung Kyu; Cho, Moon Uk; Dallas, James; Jang, Taehoon; Lee, Dong Gyu; Pouladi, Sara; Chen, Jie; Wang, Weijie; Shervin, Shahab; Kim, Hyunsoo; Shin, Seungha; Choi, Sukwon; Kwak, Joon Seop; Ryou, Jae-Hyun

2017-09-01

We investigate thermo-electronic behaviors of flexible AlGaN/GaN heterostructure field-effect transistors (HFETs) for high-power operation of the devices using Raman thermometry, infrared imaging, and current-voltage characteristics. A large negative differential conductance observed in HFETs on polymeric flexible substrates is confirmed to originate from the decreasing mobility of the two-dimensional electron gas channel caused by the self-heating effect. We develop high-power transistors by suppressing the negative differential conductance in the flexible HFETs using chemical lift-off and modified Ti/Au/In metal bonding processes with copper (Cu) tapes for high thermal conductivity and low thermal interfacial resistance in the flexible hybrid structures. Among different flexible HFETs, the ID of the HFETs on Cu with Ni/Au/In structures decreases only by 11.3% with increasing drain bias from the peak current to the current at VDS = 20 V, which is close to that of the HFETs on Si (9.6%), solving the problem of previous flexible AlGaN/GaN transistors.

Effect of wing flexibility in dragonfly hovering flight

NASA Astrophysics Data System (ADS)

Naidu, Vishal; Young, John; Lai, Joseph

2011-11-01

Dragonflies have two pairs of tandem wings, which can be operated independently. Most studies on tandem wings are based on rigid wings, which is in strong contradiction to the natural, flexible dragonfly wings. The effect of wing flexibility in tandem wings is little known. We carry out a comparative, computational study between rigid and flexible, dragonfly shaped wings for hovering flight. In rigid wings during downstroke, a leading edge vortex (LEV) is formed on the upper surface, which forms a low pressure zone. This conical LEV joins the tip vortex and shortly after the mid downstroke when the wing starts to rotate, these vortices are gradually shed resulting in a drop in lift. The vortex system creates a net downwards momentum in the form of a jet. The flexible wings while in motion deform due to aerodynamic and inertial forces. Since there is a strong interaction between wing deformation and air flow around the deformed wings, flexible wing simulations are carried out using a two way fluid structure interaction. The effect of wing flexibility on the flow structure and the subsequent effect on the aerodynamic forces will be studied and presented.

Synthesis and Electroluminescent Property of New Orange Iridium Compounds for Flexible White Organic Light Emitting Diodes.

PubMed

Lee, Ho Won; Jeong, Hyunjin; Kim, Young Kwan; Ha, Yunkyoung

2015-10-01

Recently, white organic light-emitting diodes (OLEDs) have aroused considerable attention because they have the potential of next-generation flexible displays and white illuminated applications. White OLED applications are particularly heading to the industry but they have still many problems both materials and manufacturing. Therefore, we proposed that the new iridium compounds of orange emitters could be demonstrated and also applied to flexible white OLEDs for verification of potential. First, we demonstrated the chemical properties of new orange iridium compounds. Secondly, conventional two kinds of white phosphorescent OLEDs were fabricated by following devices; indium-tin oxide coated glass substrate/4,4'-bis[N-(napthyl)-N-phenylamino]biphenyl/N,N'-dicarbazolyl-3,5-benzene doped with blue and new iridium compounds for orange emitting 8 wt%/1,3,5-tris[N-phenylbenzimidazole-2-yl]benzene/lithium quinolate/aluminum. In addition, we fabricated white OLEDs using these emitters to verify the potential on flexible substrate. Therefore, this work could be proposed that white light applications can be applied and could be extended to additional research on flexible applications.

Maximizing propulsive thrust of a driven filament at low Reynolds number via variable flexibility.

PubMed

Peng, Zhiwei; Elfring, Gwynn J; Pak, On Shun

2017-03-22

At low Reynolds numbers the locomotive capability of a body can be dramatically hindered by the absence of inertia. In this work, we show how propulsive performance in this regime can be significantly enhanced by employing spatially varying flexibility. As a prototypical example, we consider the propulsive thrust generated by a filament periodically driven at one end. The rigid case leads to zero propulsion, as so constrained by Purcell's scallop theorem, while for uniform filaments there exists a bending stiffness maximizing the propulsive force at a given frequency; here we demonstrate explicitly how considerable further improvement can be achieved by simply varying the stiffness along the filament. The optimal flexibility distribution is strongly configuration-dependent: while increasing the flexibility towards the tail-end enhances the propulsion of a clamped filament, for a hinged filament decreasing the flexibility towards the tail-end is instead favorable. The results reveal new design principles for maximizing propulsion at low Reynolds numbers, potentially useful for developing synthetic micro-swimmers requiring large propulsive force for various biomedical applications.

A bio-inspired study on tidal energy extraction with flexible flapping wings.

PubMed

Liu, Wendi; Xiao, Qing; Cheng, Fai

2013-09-01

Previous research on the flexible structure of flapping wings has shown an improved propulsion performance in comparison to rigid wings. However, not much is known about this function in terms of power efficiency modification for flapping wing energy devices. In order to study the role of the flexible wing deformation in the hydrodynamics of flapping wing energy devices, we computationally model the two-dimensional flexible single and twin flapping wings in operation under the energy extraction conditions with a large Reynolds number of 106. The flexible motion for the present study is predetermined based on a priori structural result which is different from a passive flexibility solution. Four different models are investigated with additional potential local distortions near the leading and trailing edges. Our simulation results show that the flexible structure of a wing is beneficial to enhance power efficiency by increasing the peaks of lift force over a flapping cycle, and tuning the phase shift between force and velocity to a favourable trend. Moreover, the impact of wing flexibility on efficiency is more profound at a low nominal effective angle of attack (AoA). At a typical flapping frequency f * = 0.15 and nominal effective AoA of 10°, a flexible integrated wing generates 7.68% higher efficiency than a rigid wing. An even higher increase, around six times that of a rigid wing, is achievable if the nominal effective AoA is reduced to zero degrees at feathering condition. This is very attractive for a semi-actuated flapping energy system, where energy input is needed to activate the pitching motion. The results from our dual-wing study found that a parallel twin-wing device can produce more power compared to a single wing due to the strong flow interaction between the two wings.

Using Cryo-EM to Map Small Ligands on Dynamic Metabolic Enzymes: Studies with Glutamate Dehydrogenase

PubMed Central

Borgnia, Mario J.; Banerjee, Soojay; Merk, Alan; Matthies, Doreen; Bartesaghi, Alberto; Rao, Prashant; Pierson, Jason; Earl, Lesley A.; Falconieri, Veronica

2016-01-01

Cryo-electron microscopy (cryo-EM) methods are now being used to determine structures at near-atomic resolution and have great promise in molecular pharmacology, especially in the context of mapping the binding of small-molecule ligands to protein complexes that display conformational flexibility. We illustrate this here using glutamate dehydrogenase (GDH), a 336-kDa metabolic enzyme that catalyzes the oxidative deamination of glutamate. Dysregulation of GDH leads to a variety of metabolic and neurologic disorders. Here, we report near-atomic resolution cryo-EM structures, at resolutions ranging from 3.2 Å to 3.6 Å for GDH complexes, including complexes for which crystal structures are not available. We show that the binding of the coenzyme NADH alone or in concert with GTP results in a binary mixture in which the enzyme is in either an “open” or “closed” state. Whereas the structure of NADH in the active site is similar between the open and closed states, it is unexpectedly different at the regulatory site. Our studies thus demonstrate that even in instances when there is considerable structural information available from X-ray crystallography, cryo-EM methods can provide useful complementary insights into regulatory mechanisms for dynamic protein complexes. PMID:27036132

Flexible-Wing-Based Micro Air Vehicles

NASA Technical Reports Server (NTRS)

Ifju, Peter G.; Jenkins, David A.; Ettinger, Scott; Lian, Yong-Sheng; Shyy, Wei; Waszak, Martin R.

2002-01-01

This paper documents the development and evaluation of an original flexible-wing-based Micro Air Vehicle (MAV) technology that reduces adverse effects of gusty wind conditions and unsteady aerodynamics, exhibits desirable flight stability, and enhances structural durability. The flexible wing concept has been demonstrated on aircraft with wingspans ranging from 18 inches to 5 inches. Salient features of the flexible-wing-based MAV, including the vehicle concept, flexible wing design, novel fabrication methods, aerodynamic assessment, and flight data analysis are presented.

Effects of structural flexibility of wings in flapping flight of butterfly.

PubMed

Senda, Kei; Obara, Takuya; Kitamura, Masahiko; Yokoyama, Naoto; Hirai, Norio; Iima, Makoto

2012-06-01

The objective of this paper is to clarify the effects of structural flexibility of wings of a butterfly in flapping flight. For this purpose, a dynamics model of a butterfly is derived by Lagrange's method, where the butterfly is considered as a rigid multi-body system. The panel method is employed to simulate the flow field and the aerodynamic forces acting on the wings. The mathematical model is validated by the agreement of the numerical result with the experimentally measured data. Then, periodic orbits of flapping-of-wings flights are parametrically searched in order to fly the butterfly models. Almost periodic orbits are found, but they are unstable. Deformation of the wings is modeled in two ways. One is bending and its effect on the aerodynamic forces is discussed. The other is passive wing torsion caused by structural flexibility. Numerical simulations demonstrate that flexible torsion reduces the flight instability.

On actuator placement for robust time-optimal control of uncertain flexible spacecraft

NASA Technical Reports Server (NTRS)

Wie, Bong; Sinha, Ravi; Liu, Qiang

1992-01-01

The problem of computing open-loop, on-off jet firing logic for flexible spacecraft in the face of plant modeling uncertainty is investigated. The primary control objective is to achieve a fast maneuvering time with a minimum of structural vibrations during and/or after a maneuver. This paper is also concerned with the problem of selecting a proper pair of jets for practical trade-offs among the maneuvering time, fuel consumption, structural mode excitation, and performance robustness. A time-optimal control problem subject to parameter robustness constraints is formulated. A three-mass-spring model of flexible spacecraft with a rigid-body mode and two flexible modes is used to illustrate the concept.

MD simulation study of the diffusion and local structure of n-alkanes in liquid and supercritical methanol at infinite dilution.

PubMed

Feng, Huajie; Gao, Wei; Su, Li; Sun, Zhenfan; Chen, Liuping

2017-06-01

The diffusion coefficients of 14 n-alkanes (ranging from methane to n-tetradecane) in liquid and supercritical methanol at infinite dilution (at a pressure of 10.5 MPa and at temperatures of 299 K and 515 K) were deduced via molecular dynamics simulations. Values for the radial distribution function, coordination number, and number of hydrogen bonds were then calculated to explore the local structure of each fluid. The flexibility of the n-alkane (as characterized by the computed dihedral distribution, end-to-end distance, and radius of gyration) was found to be a major influence and hydrogen bonding to be a minor influence on the local structure. Hydrogen bonding reduces the flexibility of the n-alkane, whereas increasing the temperature enhances its flexibility, with temperature having a greater effect than hydrogen bonding on flexibility. Graphical abstract The flexibility of the alkane is a major influence and the hydrogen bonding is a minor influence on the first solvation shell; the coordination numbers of long-chain n-alkanes in the first solvation shell are rather low.

How does symmetry impact the flexibility of proteins?

PubMed

Schulze, Bernd; Sljoka, Adnan; Whiteley, Walter

2014-02-13

It is well known that (i) the flexibility and rigidity of proteins are central to their function, (ii) a number of oligomers with several copies of individual protein chains assemble with symmetry in the native state and (iii) added symmetry sometimes leads to added flexibility in structures. We observe that the most common symmetry classes of protein oligomers are also the symmetry classes that lead to increased flexibility in certain three-dimensional structures-and investigate the possible significance of this coincidence. This builds on the well-developed theory of generic rigidity of body-bar frameworks, which permits an analysis of the rigidity and flexibility of molecular structures such as proteins via fast combinatorial algorithms. In particular, we outline some very simple counting rules and possible algorithmic extensions that allow us to predict continuous symmetry-preserving motions in body-bar frameworks that possess non-trivial point-group symmetry. For simplicity, we focus on dimers, which typically assemble with twofold rotational axes, and often have allosteric function that requires motions to link distant sites on the two protein chains.

Static Aeroelastic and Longitudinal Trim Model of Flexible Wing Aircraft Using Finite-Element Vortex-Lattice Coupled Solution

NASA Technical Reports Server (NTRS)

Ting, Eric; Nguyen, Nhan; Trinh, Khanh

2014-01-01

This paper presents a static aeroelastic model and longitudinal trim model for the analysis of a flexible wing transport aircraft. The static aeroelastic model is built using a structural model based on finite-element modeling and coupled to an aerodynamic model that uses vortex-lattice solution. An automatic geometry generation tool is used to close the loop between the structural and aerodynamic models. The aeroelastic model is extended for the development of a three degree-of-freedom longitudinal trim model for an aircraft with flexible wings. The resulting flexible aircraft longitudinal trim model is used to simultaneously compute the static aeroelastic shape for the aircraft model and the longitudinal state inputs to maintain an aircraft trim state. The framework is applied to an aircraft model based on the NASA Generic Transport Model (GTM) with wing structures allowed to flexibly deformed referred to as the Elastically Shaped Aircraft Concept (ESAC). The ESAC wing mass and stiffness properties are based on a baseline "stiff" values representative of current generation transport aircraft.

Control and dynamics of a flexible spacecraft during stationkeeping maneuvers

NASA Technical Reports Server (NTRS)

Liu, D.; Yocum, J.; Kang, D. S.

1991-01-01

A case study of a spacecraft having flexible solar arrays is presented. A stationkeeping attitude control mode using both earth and rate gyro reference signals and a flexible vehicle dynamics modeling and implementation is discussed. The control system is designed to achieve both pointing accuracy and structural mode stability during stationkeeping maneuvers. Reduction of structural mode interactions over the entire mode duration is presented. The control mode using a discrete time observer structure is described to show the convergence of the spacecraft attitude transients during Delta-V thrusting maneuvers without preloading thrusting bias to the onboard control processor. The simulation performance using the three axis, body stabilized nonlinear dynamics is provided. The details of a five body dynamics model are discussed. The spacecraft is modeled as a central rigid body having cantilevered flexible antennas, a pair of flexible articulated solar arrays, and to gimballed momentum wheels. The vehicle is free to undergo unrestricted rotations and translations relative to inertial space. A direct implementation of the equations of motion is compared to an indirect implementation that uses a symbolic manipulation software to generate rigid body equations.

Photogrammetric Verification of Fiber Optic Shape Sensors on Flexible Aerospace Structures

NASA Technical Reports Server (NTRS)

Moore, Jason P.; Rogge, Matthew D.; Jones, Thomas W.

2012-01-01

Multi-core fiber (MCF) optic shape sensing offers the possibility of providing in-flight shape measurements of highly flexible aerospace structures and control surfaces for such purposes as gust load alleviation, flutter suppression, general flight control and structural health monitoring. Photogrammetric measurements of surface mounted MCF shape sensing cable can be used to quantify the MCF installation path and verify measurement methods.

Application of partial differential equation modeling of the control/structural dynamics of flexible spacecraft

NASA Technical Reports Server (NTRS)

Taylor, Lawrence W., Jr.; Rajiyah, H.

1991-01-01

Partial differential equations for modeling the structural dynamics and control systems of flexible spacecraft are applied here in order to facilitate systems analysis and optimization of these spacecraft. Example applications are given, including the structural dynamics of SCOLE, the Solar Array Flight Experiment, the Mini-MAST truss, and the LACE satellite. The development of related software is briefly addressed.

Predictive design procedures, VESYS users manual : an interim design method for flexible pavements using the VESYS structural subsystem

DOT National Transportation Integrated Search

1978-01-01

This manual has been written to provide the pavement manager and design engineer with a ready reference of procedures to predict the structural responses and hence the integrity of flexible pavements. A pavement section of known geometry is chosen, a...

Distributed active control of large flexible space structures

NASA Technical Reports Server (NTRS)

Nguyen, C. C.; Baz, A.

1986-01-01

This progress report summarizes the research work performed at the Catholic University of America on the research grant entitled Distributed Active Control of Large Flexible Space Structures, funded by NASA/Goddard Space Flight Center, under grant number NAG5-749, during the period of March 15, 1986 to September 15, 1986.

Plugged In to Comfort.

ERIC Educational Resources Information Center

Spurgeon, Mark S.; Williams, Homer L.; Dornbusch, Sarah

1998-01-01

Explains how technology will influence classroom design and furniture selection in today's college facilities. Discusses ergonomic and efficiency considerations and furnishings for specialized areas such as computer labs. Addresses dormitory rooms and the flexibility of room-furniture layout and the inclusion of telecommunications capabilities.…

Semiparametric Thurstonian Models for Recurrent Choices: A Bayesian Analysis

ERIC Educational Resources Information Center

Ansari, Asim; Iyengar, Raghuram

2006-01-01

We develop semiparametric Bayesian Thurstonian models for analyzing repeated choice decisions involving multinomial, multivariate binary or multivariate ordinal data. Our modeling framework has multiple components that together yield considerable flexibility in modeling preference utilities, cross-sectional heterogeneity and parameter-driven…

24 CFR 904.203 - Planning.

Code of Federal Regulations, 2010 CFR

2010-04-01

... HOUSING HOMEOWNERSHIP OPPORTUNITIES Homeownership Counseling and Training § 904.203 Planning. (a) The counseling and training program shall be flexible and responsive to the needs of each prospective homebuyer. While many subjects lend themselves to group sessions, consideration shall be given to individual...

Flexible Answers.

ERIC Educational Resources Information Center

Seeley, James

1997-01-01

Describes how schools are investigating single-ply roofing systems for new and retrofit construction. Discusses some of the considerations in seaming together a single-ply roof, steps in choosing roofing material and a roofing contractor, warranty advice, and the importance of keeping records on roof maintenance. (RJM)

Limited access: gender, occupational composition, and flexible work scheduling.

PubMed

Glauber, Rebecca

2011-01-01

The current study draws on national data to explore differences in access to flexible work scheduling by the gender composition of women's and men's occupations. Results show that those who work in integrated occupations are more likely to have access to flexible scheduling. Women and men do not take jobs with lower pay in return for greater access to flexibility. Instead, jobs with higher pay offer greater flexibility. Integrated occupations tend to offer the greatest access to flexible scheduling because of their structural locations. Part-time work is negatively associated with men's access to flexible scheduling but positively associated with women's access. Women have greater flexibility when they work for large establishments, whereas men have greater flexibility when they work for small establishments.

The dynamics of a flexible bladed disc on a flexible rotor in a two-rotor system

NASA Technical Reports Server (NTRS)

Gallardo, V. C.; Stallone, M. J.

1984-01-01

This paper describes the development of the analysis of the transient dynamic response of a bladed disk on a flexible rotor. The rotating flexible bladed disk is considered as a module in a complete turbine engine structure. The analysis of the flexible bladed disk (FBD) module is developed for the non-equilibrated one-diameter axial mode. The FBD motion is considered as a sum of two standing axial waves constrained to the rotor. The FBD is coupled inertially and gyroscopically to its rotor support, and indirectly through connecting elements, to the adjacent rotor and/or other supporting structures. Incorporated in the basic Turbine Engine Transient Response Analysis program (TETRA), the FBD module is demonstrated with a two-rotor model where the FBD can be excited into resonance by an unbalance in the adjacent rotor and at a frequency equal to the differential rotor speed. The FBD module also allows the analysis of two flexible bladed disks in the same rotor.

Simulations of Micropumps Based on Tilted Flexible Fibers

NASA Astrophysics Data System (ADS)

Hancock, Matthew; Elabbasi, Nagi; Demirel, Melik

2015-11-01

Pumping liquids at low Reynolds numbers is challenging because of the principle of reversibility. We report here a class of microfluidic pump designs based on tilted flexible structures that combines the concepts of cilia (flexible elastic elements) and rectifiers (e.g., Tesla valves, check valves). We demonstrate proof-of-concept with 2D and 3D fluid-structure interaction (FSI) simulations in COMSOL Multiphysics®of micropumps consisting of a source for oscillatory fluidic motion, e.g. a piston, and a channel lined with tilted flexible rods or sheets to provide rectification. When flow is against the rod tilt direction, the rods bend backward, narrowing the channel and increasing flow resistance; when flow is in the direction of rod tilt, the rods bend forward, widening the channel and decreasing flow resistance. The 2D and 3D simulations involve moving meshes whose quality is maintained by prescribing the mesh displacement on guide surfaces positioned on either side of each flexible structure. The prescribed displacement depends on structure bending and maintains mesh quality even for large deformations. Simulations demonstrate effective pumping even at Reynolds numbers as low as 0.001. Because rod rigidity may be specified independently of Reynolds number, in principle, rod rigidity may be reduced to enable pumping at arbitrarily low Reynolds numbers.

Conserved Asp-137 is important for both structure and regulatory functions of cardiac α-tropomyosin (α-TM) in a novel transgenic mouse model expressing α-TM-D137L.

PubMed

Yar, Sumeyye; Chowdhury, Shamim A K; Davis, Robert T; Kobayashi, Minae; Monasky, Michelle M; Rajan, Sudarsan; Wolska, Beata M; Gaponenko, Vadim; Kobayashi, Tomoyoshi; Wieczorek, David F; Solaro, R John

2013-06-07

α-Tropomyosin (α-TM) has a conserved, charged Asp-137 residue located in the hydrophobic core of its coiled-coil structure, which is unusual in that the residue is found at a position typically occupied by a hydrophobic residue. Asp-137 is thought to destabilize the coiled-coil and so impart structural flexibility to the molecule, which is believed to be crucial for its function in the heart. A previous in vitro study indicated that the conversion of Asp-137 to a more typical canonical Leu alters flexibility of TM and affects its in vitro regulatory functions. However, the physiological importance of the residue Asp-137 and altered TM flexibility is unknown. In this study, we further analyzed structural properties of the α-TM-D137L variant and addressed the physiological importance of TM flexibility in cardiac function in studies with a novel transgenic mouse model expressing α-TM-D137L in the heart. Our NMR spectroscopy data indicated that the presence of D137L introduced long range rearrangements in TM structure. Differential scanning calorimetry measurements demonstrated that α-TM-D137L has higher thermal stability compared with α-TM, which correlated with decreased flexibility. Hearts of transgenic mice expressing α-TM-D137L showed systolic and diastolic dysfunction with decreased myofilament Ca(2+) sensitivity and cardiomyocyte contractility without changes in intracellular Ca(2+) transients or post-translational modifications of major myofilament proteins. We conclude that conversion of the highly conserved Asp-137 to Leu results in loss of flexibility of TM that is important for its regulatory functions in mouse hearts. Thus, our results provide insight into the link between flexibility of TM and its function in ejecting hearts.

Conserved Asp-137 Is Important for both Structure and Regulatory Functions of Cardiac α-Tropomyosin (α-TM) in a Novel Transgenic Mouse Model Expressing α-TM-D137L*

PubMed Central

Yar, Sumeyye; Chowdhury, Shamim A. K.; Davis, Robert T.; Kobayashi, Minae; Monasky, Michelle M.; Rajan, Sudarsan; Wolska, Beata M.; Gaponenko, Vadim; Kobayashi, Tomoyoshi; Wieczorek, David F.; Solaro, R. John

2013-01-01

α-Tropomyosin (α-TM) has a conserved, charged Asp-137 residue located in the hydrophobic core of its coiled-coil structure, which is unusual in that the residue is found at a position typically occupied by a hydrophobic residue. Asp-137 is thought to destabilize the coiled-coil and so impart structural flexibility to the molecule, which is believed to be crucial for its function in the heart. A previous in vitro study indicated that the conversion of Asp-137 to a more typical canonical Leu alters flexibility of TM and affects its in vitro regulatory functions. However, the physiological importance of the residue Asp-137 and altered TM flexibility is unknown. In this study, we further analyzed structural properties of the α-TM-D137L variant and addressed the physiological importance of TM flexibility in cardiac function in studies with a novel transgenic mouse model expressing α-TM-D137L in the heart. Our NMR spectroscopy data indicated that the presence of D137L introduced long range rearrangements in TM structure. Differential scanning calorimetry measurements demonstrated that α-TM-D137L has higher thermal stability compared with α-TM, which correlated with decreased flexibility. Hearts of transgenic mice expressing α-TM-D137L showed systolic and diastolic dysfunction with decreased myofilament Ca2+ sensitivity and cardiomyocyte contractility without changes in intracellular Ca2+ transients or post-translational modifications of major myofilament proteins. We conclude that conversion of the highly conserved Asp-137 to Leu results in loss of flexibility of TM that is important for its regulatory functions in mouse hearts. Thus, our results provide insight into the link between flexibility of TM and its function in ejecting hearts. PMID:23609439

Inherent conformational flexibility of F1-ATPase α-subunit.

PubMed

Hahn-Herrera, Otto; Salcedo, Guillermo; Barril, Xavier; García-Hernández, Enrique

2016-09-01

The core of F1-ATPase consists of three catalytic (β) and three noncatalytic (α) subunits, forming a hexameric ring in alternating positions. A wealth of experimental and theoretical data has provided a detailed picture of the complex role played by catalytic subunits. Although major conformational changes have only been seen in β-subunits, it is clear that α-subunits have to respond to these changes in order to be able to transmit information during the rotary mechanism. However, the conformational behavior of α-subunits has not been explored in detail. Here, we have combined unbiased molecular dynamics (MD) simulations and calorimetrically measured thermodynamic signatures to investigate the conformational flexibility of isolated α-subunits, as a step toward deepening our understanding of its function inside the α3β3 ring. The simulations indicate that the open-to-closed conformational transition of the α-subunit is essentially barrierless, which is ideal to accompany and transmit the movement of the catalytic subunits. Calorimetric measurements of the recombinant α-subunit from Geobacillus kaustophilus indicate that the isolated subunit undergoes no significant conformational changes upon nucleotide binding. Simulations confirm that the nucleotide-free and nucleotide-bound subunits show average conformations similar to that observed in the F1 crystal structure, but they reveal an increased conformational flexibility of the isolated α-subunit upon MgATP binding, which might explain the evolutionary conserved capacity of α-subunits to recognize nucleotides with considerable strength. Furthermore, we elucidate the different dependencies that α- and β-subunits show on Mg(II) for recognizing ATP. Copyright © 2016 Elsevier B.V. All rights reserved.

Scalable transfer of vertical graphene nanosheets for flexible supercapacitor applications

NASA Astrophysics Data System (ADS)

Sahoo, Gopinath; Ghosh, Subrata; Polaki, S. R.; Mathews, Tom; Kamruddin, M.

2017-10-01

Vertical graphene nanosheets (VGN) are the material of choice for application in next-generation electronic devices. The growing demand for VGN-based flexible devices for the electronics industry brings in restriction on VGN growth temperature. The difficulty associated with the direct growth of VGN on flexible substrates can be overcome by adopting an effective strategy of transferring the well-grown VGN onto arbitrary flexible substrates through a soft chemistry route. In the present study, we report an inexpensive and scalable technique for the polymer-free transfer of VGN onto arbitrary substrates without disrupting its morphology, structure, and properties. After transfer, the morphology, chemical structure, and electrical properties are analyzed by scanning electron microscopy, Raman spectroscopy, x-ray photoelectron spectroscopy, and four-probe resistive methods, respectively. The wetting properties are studied from the water contact angle measurements. The observed results indicate the retention of morphology, surface chemistry, structure, and electronic properties. Furthermore, the storage capacity of the transferred VGN-based binder-free and current collector-free flexible symmetric supercapacitor device is studied. A very low sheet resistance of 670 Ω/□ and excellent supercapacitance of 158 μF cm-2 with 86% retention after 10 000 cycles show the prospect of the damage-free VGN transfer approach for the fabrication of flexible nanoelectronic devices.

A data driven control method for structure vibration suppression

NASA Astrophysics Data System (ADS)

Xie, Yangmin; Wang, Chao; Shi, Hang; Shi, Junwei

2018-02-01

High radio-frequency space applications have motivated continuous research on vibration suppression of large space structures both in academia and industry. This paper introduces a novel data driven control method to suppress vibrations of flexible structures and experimentally validates the suppression performance. Unlike model-based control approaches, the data driven control method designs a controller directly from the input-output test data of the structure, without requiring parametric dynamics and hence free of system modeling. It utilizes the discrete frequency response via spectral analysis technique and formulates a non-convex optimization problem to obtain optimized controller parameters with a predefined controller structure. Such approach is then experimentally applied on an end-driving flexible beam-mass structure. The experiment results show that the presented method can achieve competitive disturbance rejections compared to a model-based mixed sensitivity controller under the same design criterion but with much less orders and design efforts, demonstrating the proposed data driven control is an effective approach for vibration suppression of flexible structures.

Flexibility of centromere and kinetochore structures

PubMed Central

Burrack, Laura S.; Berman, Judith

2012-01-01

Centromeres, and the kinetochores that assemble on them, are essential for accurate chromosome segregation. Diverse centromere organization patterns and kinetochore structures have evolved in eukaryotes ranging from yeast to humans. In addition, centromere DNA and kinetochore position can vary even within individual cells. This flexibility manifests in several ways: centromere DNA sequences evolve rapidly, kinetochore positions shift in response to altered chromosome structure, and kinetochore complex numbers change in response to fluctuations in kinetochore protein levels. Despite their differences, all of these diverse structures promote efficient chromosome segregation. This robustness is inherent to chromosome segregation mechanisms and balances genome stability with adaptability. In this review, we explore the mechanisms and consequences of centromere and kinetochore flexibility as well as the benefits and limitations of different experimental model systems for studying them. PMID:22445183

Control and structural optimization for maneuvering large spacecraft

NASA Technical Reports Server (NTRS)

Chun, H. M.; Turner, J. D.; Yu, C. C.

1990-01-01

Presented here are the results of an advanced control design as well as a discussion of the requirements for automating both the structures and control design efforts for maneuvering a large spacecraft. The advanced control application addresses a general three dimensional slewing problem, and is applied to a large geostationary platform. The platform consists of two flexible antennas attached to the ends of a flexible truss. The control strategy involves an open-loop rigid body control profile which is derived from a nonlinear optimal control problem and provides the main control effort. A perturbation feedback control reduces the response due to the flexibility of the structure. Results are shown which demonstrate the usefulness of the approach. Software issues are considered for developing an integrated structures and control design environment.

Reversible flexible structural changes in multidimensional MOFs by guest molecules (I{sub 2}, NH{sub 3}) and thermal stimulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Yang; Li, Libo; Yang, Jiangfeng

Three metal–organic frameworks (MOFs), [Cu(INA){sub 2}], [Cu(INA){sub 2}I{sub 2}] and [Cu(INA){sub 2}(H{sub 2}O){sub 2}(NH{sub 3}){sub 2}], were synthesized with 3D, 2D, and 0D structures, respectively. Reversible flexible structural changes of these MOFs were reported. Through high temperature (60–100 °C) stimulation of I{sub 2} or ambient temperature stimulation of NH{sub 3}, [Cu(INA){sub 2}] (3D) converted to [Cu(INA){sub 2}I{sub 2}] (2D) and [Cu(INA){sub 2}(H{sub 2}O){sub 2}(NH{sub 3}){sub 2}] (0D); as the temperature increased to 150 °C, the MOFs changed back to their original form. In this way, this 3D MOF has potential application in the capture of I{sub 2} and NH{sub 3}more » from polluted water and air. XRD, TGA, SEM, NH{sub 3}-TPD, and the measurement of gas adsorption were used to describe the changes in processes regarding the structure, morphology, and properties. - Graphical abstract: Through I{sub 2}, NH{sub 3} molecules and thermal stimulation, the three MOFs can achieve reversible flexible structural changes. Different methods were used to prove the flexible reversible changes. - Highlights: • [Cu(INA){sub 2}] can flexible transform to [Cu(INA){sub 2}I{sub 2}] and [Cu(INA){sub 2}(H{sub 2}O){sub 2}(NH{sub 3}){sub 2}] by adsorbing I{sub 2} or NH{sub 3}. • The reversible flexible transformation related to material source, temperature and concentration. • Potential applications for the capture of I{sub 2} and NH{sub 3} from polluted water or air.« less

Flexible, Stretchable Sensors for Wearable Health Monitoring: Sensing Mechanisms, Materials, Fabrication Strategies and Features

PubMed Central

Liu, Yan; Wang, Hai; Zhao, Wei; Qin, Hongbo; Xie, Yongqiang

2018-01-01

Wearable health monitoring systems have gained considerable interest in recent years owing to their tremendous promise for personal portable health watching and remote medical practices. The sensors with excellent flexibility and stretchability are crucial components that can provide health monitoring systems with the capability of continuously tracking physiological signals of human body without conspicuous uncomfortableness and invasiveness. The signals acquired by these sensors, such as body motion, heart rate, breath, skin temperature and metabolism parameter, are closely associated with personal health conditions. This review attempts to summarize the recent progress in flexible and stretchable sensors, concerning the detected health indicators, sensing mechanisms, functional materials, fabrication strategies, basic and desired features. The potential challenges and future perspectives of wearable health monitoring system are also briefly discussed. PMID:29470408

Nitride-Based Materials for Flexible MEMS Tactile and Flow Sensors in Robotics

PubMed Central

Abels, Claudio; Mastronardi, Vincenzo Mariano; Guido, Francesco; Dattoma, Tommaso; Qualtieri, Antonio; Megill, William M.; De Vittorio, Massimo; Rizzi, Francesco

2017-01-01

The response to different force load ranges and actuation at low energies is of considerable interest for applications of compliant and flexible devices undergoing large deformations. We present a review of technological platforms based on nitride materials (aluminum nitride and silicon nitride) for the microfabrication of a class of flexible micro-electro-mechanical systems. The approach exploits the material stress differences among the constituent layers of nitride-based (AlN/Mo, SixNy/Si and AlN/polyimide) mechanical elements in order to create microstructures, such as upwardly-bent cantilever beams and bowed circular membranes. Piezoresistive properties of nichrome strain gauges and direct piezoelectric properties of aluminum nitride can be exploited for mechanical strain/stress detection. Applications in flow and tactile sensing for robotics are described. PMID:28489040

Health care spending accounts: a flexible solution for Canadian employers.

PubMed

Smithies, R; Steeves, L

1996-01-01

Flexible benefits plans have grown more slowly in Canada than in the United States, largely because of certain legal and regulatory considerations. Health care spending accounts (HCSAs) provide a cost-effective way for Canadian employers to address the health care benefit needs of a diverse workforce. A flexible health care spending account is a versatile and cost-effective instrument that can be used by Canadian employers that wish to provide a full range of health care benefits to employees. The health care alternatives available through an HCSA can provide employees with an opportunity to customize and optimize their benefits program. Regulatory requirements that an HCSA must meet in order to qualify for available tax advantages are discussed, as are the range of health care services that may be covered.

Flexible transparent aerogels as window retrofitting films and optical elements with tunable birefringence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Qingkun; Frazier, Allister W.; Zhao, Xinpeng

Experimental realization of optically transparent, mechanically robust and flexible aerogels has been a longstanding challenge, which limits their practical applications in energy-saving devices, such as thermally insulating films for enhancing energy efficiency of windows. The poor transparency precluded even hypothetical consideration of the possibility of birefringent aerogels. We develop birefringent and optically isotropic aerogels that combine properties of thermal super-insulation, mechanical robustness and flexibility, and transparency to visible-spectrum light. This unusual combination of physical properties is achieved by combining liquid crystalline self-organization of cellulose nanofibers with polysiloxane cross-linking and control of the nanoscale porosity to form hybrid organic-inorganic mesostructured aerogels.more » Potential applications of these inexpensive materials range from single pane window retrofitting to smart fabrics.« less

Flexible, Stretchable Sensors for Wearable Health Monitoring: Sensing Mechanisms, Materials, Fabrication Strategies and Features.

PubMed

Liu, Yan; Wang, Hai; Zhao, Wei; Zhang, Min; Qin, Hongbo; Xie, Yongqiang

2018-02-22

Wearable health monitoring systems have gained considerable interest in recent years owing to their tremendous promise for personal portable health watching and remote medical practices. The sensors with excellent flexibility and stretchability are crucial components that can provide health monitoring systems with the capability of continuously tracking physiological signals of human body without conspicuous uncomfortableness and invasiveness. The signals acquired by these sensors, such as body motion, heart rate, breath, skin temperature and metabolism parameter, are closely associated with personal health conditions. This review attempts to summarize the recent progress in flexible and stretchable sensors, concerning the detected health indicators, sensing mechanisms, functional materials, fabrication strategies, basic and desired features. The potential challenges and future perspectives of wearable health monitoring system are also briefly discussed.

Meteorological Measurements from Satellite Platforms. [stability and control of flexible stochastic satellites

NASA Technical Reports Server (NTRS)

Suomi, V. E.

1975-01-01

The stability of stochastic satellites and the stability and control of flexible satellites were investigated. The effects of random environmental torques and noises in the moments of inertia of spinning and three-axes stabilized satellites were first compared analytically by four methods and by analog simulations. Among the analytical methods, it was shown that the Fokker-Planck formulation yields predictions which most coincide with the simulation results. It was then shown that the required stability criterion of a satellite is quite different from that obtained by a deterministic approach, under the assumption that the environmental and control torques experienced by the satellite are random. Finally, it was demonstrated that, by monitoring the deformations of the flexible elements of a satellite, the effectiveness of the satellite control system can be increased considerably.

National Implications: Closed Systems Stifle Innovation, Collaboration and Flexibility

ERIC Educational Resources Information Center

Cloud, Michelle; Kritsonis, William Allan

2006-01-01

Educational leaders must work to establish organizational structures that help schools achieve and sustain their vision. The intent of this article is to briefly examine how closed systems stifle innovation, collaboration and flexibility in schooling. Innovation, collaboration and flexibility are key ingredients for creating successful…

Discrete and continuous dynamics modeling of a mass moving on a flexible structure

NASA Technical Reports Server (NTRS)

Herman, Deborah Ann

1992-01-01

A general discrete methodology for modeling the dynamics of a mass that moves on the surface of a flexible structure is developed. This problem was motivated by the Space Station/Mobile Transporter system. A model reduction approach is developed to make the methodology applicable to large structural systems. To validate the discrete methodology, continuous formulations are also developed. Three different systems are examined: (1) simply-supported beam, (2) free-free beam, and (3) free-free beam with two points of contact between the mass and the flexible beam. In addition to validating the methodology, parametric studies were performed to examine how the system's physical properties affect its dynamics.

Control of a flexible planar truss using proof mass actuators

NASA Technical Reports Server (NTRS)

Minas, Constantinos; Garcia, Ephrahim; Inman, Daniel J.

1989-01-01

A flexible structure was modeled and actively controlled by using a single space realizable linear proof mass actuator. The NASA/UVA/UB actuator was attached to a flexible planar truss structure at an optimal location and it was considered as both passive and active device. The placement of the actuator was specified by examining the eigenvalues of the modified model that included the actuator dynamics, and the frequency response functions of the modified system. The electronic stiffness of the actuator was specified, such that the proof mass actuator system was tuned to the fourth structural mode of the truss by using traditional vibration absorber design. The active control law was limited to velocity feedback by integrating of the signals of two accelerometers attached to the structure. The two lower modes of the closed-loop structure were placed further in the LHS of the complex plane. The theoretically predicted passive and active control law was experimentally verified.

Unifying mechanical and thermodynamic descriptions across the thioredoxin protein family.

PubMed

Mottonen, James M; Xu, Minli; Jacobs, Donald J; Livesay, Dennis R

2009-05-15

We compare various predicted mechanical and thermodynamic properties of nine oxidized thioredoxins (TRX) using a Distance Constraint Model (DCM). The DCM is based on a nonadditive free energy decomposition scheme, where entropic contributions are determined from rigidity and flexibility of structure based on distance constraints. We perform averages over an ensemble of constraint topologies to calculate several thermodynamic and mechanical response functions that together yield quantitative stability/flexibility relationships (QSFR). Applied to the TRX protein family, QSFR metrics display a rich variety of similarities and differences. In particular, backbone flexibility is well conserved across the family, whereas cooperativity correlation describing mechanical and thermodynamic couplings between the residue pairs exhibit distinctive features that readily standout. The diversity in predicted QSFR metrics that describe cooperativity correlation between pairs of residues is largely explained by a global flexibility order parameter describing the amount of intrinsic flexibility within the protein. A free energy landscape is calculated as a function of the flexibility order parameter, and key values are determined where the native-state, transition-state, and unfolded-state are located. Another key value identifies a mechanical transition where the global nature of the protein changes from flexible to rigid. The key values of the flexibility order parameter help characterize how mechanical and thermodynamic response is linked. Variation in QSFR metrics and key characteristics of global flexibility are related to the native state X-ray crystal structure primarily through the hydrogen bond network. Furthermore, comparison of three TRX redox pairs reveals differences in thermodynamic response (i.e., relative melting point) and mechanical properties (i.e., backbone flexibility and cooperativity correlation) that are consistent with experimental data on thermal stabilities and NMR dynamical profiles. The results taken together demonstrate that small-scale structural variations are amplified into discernible global differences by propagating mechanical couplings through the H-bond network.

A survey of experiments and experimental facilities for control of flexible structures

NASA Technical Reports Server (NTRS)

Sparks, Dean W., Jr.; Juang, Jer-Nan; Klose, Gerhard J.

1989-01-01

This paper presents a survey of U.S. ground experiments and facilities dedicated to the study of active control of flexible structures. The facilities will be briefly described in terms of capability, configuration, size and instrumentation. Topics on the experiments include vibration suppression, slewing and system identification. Future research directions, particularly of the NASA Langley Research Center's Controls/Structures Interaction (CSI) ground test program, will be discussed.

76 FR 1121 - Proposed Flood Elevation Determinations

Federal Register 2010, 2011, 2012, 2013, 2014

2011-01-07

... approximately 410 feet of Lewis County. upstream of U.S. Route 61 Business. * National Geodetic Vertical Datum... intersection of Impact Drive and FM Road 2404. * National Geodetic Vertical Datum. + North American Vertical..., Environmental Consideration. An environmental impact assessment has not been prepared. Regulatory Flexibility...

PREDICTING ER BINDING AFFINITY FOR EDC RANKING AND PRIORITIZATION: MODEL I

EPA Science Inventory

A Common Reactivity Pattern (COREPA) model, based on consideration of multiple energetically reasonable conformations of flexible chemicals was developed using a training set of 232 rat estrogen receptor (rER) relative binding affinity (RBA) measurements. The training set include...

Vaginismus: A Review

ERIC Educational Resources Information Center

Fertel, Norman S.

1977-01-01

Vaginismus includes both physical as well as psychological aspects that make vaginal penetration extremely painful if not altogether impossible. Aside from history, diagnosis rests on the physical examination. The most important considerations in therapy seem to be the patient's understanding of the problem and flexibility of approach. (Author)

Transformable and Reconfigurable Entry, Descent and Landing Systems and Methods

NASA Technical Reports Server (NTRS)

Fernandez, Ian M. (Inventor); Venkatapathy, Ethiraj (Inventor); Hamm, Kenneth R. (Inventor)

2014-01-01

A deployable aerodynamic decelerator structure includes a ring member disposed along a central axis of the aerodynamic decelerator, a plurality of jointed rib members extending radially from the ring member and a flexible layer attached to the plurality of rib members. A deployment device is operable to reconfigure the flexible layer from a stowed configuration to a deployed configuration by movement of the rib members and a control device is operable to redirect a lift vector of the decelerator structure by changing an orientation of the flexible layer.

Cd(II)-coordination polymers based on tetracarboxylic acid and diverse bis(imidazole) ligands: Synthesis, structural diversity and photoluminescence properties

NASA Astrophysics Data System (ADS)

Arıcı, Mürsel; Yeşilel, Okan Zafer; Taş, Murat

2017-01-01

Three new Cd(II)-coordination polymers, namely, {[Cd2(μ6-ao2btc)(μ-1,5-bipe)2]·2H2O}n (1), {[Cd2(μ6-ao2btc)(μ-1,4-bix)2]n·2DMF} (2) and {[Cd2(μ8-abtc)(μ-1,4-betix)]·DMF·H2O}n (3) (ao2btc=di-oxygenated form of 3,3‧,5,5‧-azobenzenetetracarboxylate, 1,5-bipe: 1,5-bis(imidazol-1yl)pentane, 1,4-bix=1,4-bis(imidazol-1ylmethyl)benzene, 1,4-betix=1,4-bis(2-ethylimidazol-1ylmethyl)benzene) were synthesized with 3,3‧,5,5‧-azobenzenetetracarboxylic acid and flexible, semi-flexible and semi-flexible substituted bis(imidazole) linkers. They were characterized by IR spectroscopy, elemental analysis, single-crystal X-ray diffraction, powder X-ray diffractions (PXRD) and thermal analyses (TG/DTA). Complexes 1-3 exhibited structural diversities depending on flexible, semi-flexible and semi-flexible substituted bis(imidazole) ligands. Complex 1 was 2D structure with 3,6L18 topology. Complex 2 had a 3D pillar-layered framework with the rare sqc27 topology. When semi-flexible substituted bis(imidazole) linker was used, 3D framework of complex 3 was obtained with the paddlewheel Cd2(CO2)4-type binuclear SBU. Moreover, thermal and photoluminescence properties of the complexes were determined in detailed.

Vortical Flow Structures in the Near-Wake of a Heaving Airfoil with Passively Actuated Leading and Trailing Flaps.

NASA Astrophysics Data System (ADS)

Siala, Firas; Totpal, Alexander; Liburdy, James

2015-11-01

The flow physics of flying animals has recently received significant attention, mostly in the context of developing bio-inspired micro air vehicles and oscillating flow energy harvesters. Of particular interest is the understanding of the impact of airfoil flexibility on the flow physics. Research efforts showed that some degree of surface flexibility enhanced the strength and size of the leading edge vortex. In this study, the influence of flexibility on the near-wake dynamics and flow structures is investigated using 2D PIV measurements. The experiments are conducted in a wind tunnel at a Reynolds number of 30,000 and a range of reduced frequencies from 0.09 to 0.2. The flexibility is attained using a torsion rod forming a hinge between the flap and the main wing. Vortex flow structures are visualized using large eddy scale decomposition technique and quantified using swirling strength analysis. It is found that trailing edge flexibility increases the vortex swirling strength compared to a rigid airfoil, whereas leading edge flexibility decreases the swirling strength. Furthermore, the integral length scale determined from the autocorrelation of the velocity fluctuations is found to be approximately equal to the actual vortex size. The vortex convective velocity is shown to be independent of flexibility and oscillation frequency, and it is represented by a trimodal distribution, with peak values at 0.8, 0.95 and 1 times the free stream velocity. Oregon State University.

Dynamic bending of bionic flexible body driven by pneumatic artificial muscles(PAMs) for spinning gait of quadruped robot

NASA Astrophysics Data System (ADS)

Lei, Jingtao; Yu, Huangying; Wang, Tianmiao

2016-01-01

The body of quadruped robot is generally developed with the rigid structure. The mobility of quadruped robot depends on the mechanical properties of the body mechanism. It is difficult for quadruped robot with rigid structure to achieve better mobility walking or running in the unstructured environment. A kind of bionic flexible body mechanism for quadruped robot is proposed, which is composed of one bionic spine and four pneumatic artificial muscles(PAMs). This kind of body imitates the four-legged creatures' kinematical structure and physical properties, which has the characteristic of changeable stiffness, lightweight, flexible and better bionics. The kinematics of body bending is derived, and the coordinated movement between the flexible body and legs is analyzed. The relationship between the body bending angle and the PAM length is obtained. The dynamics of the body bending is derived by the floating coordinate method and Lagrangian method, and the driving force of PAM is determined. The experiment of body bending is conducted, and the dynamic bending characteristic of bionic flexible body is evaluated. Experimental results show that the bending angle of the bionic flexible body can reach 18°. An innovation body mechanism for quadruped robot is proposed, which has the characteristic of flexibility and achieve bending by changing gas pressure of PAMs. The coordinated movement of the body and legs can achieve spinning gait in order to improve the mobility of quadruped robot.

Application of Lanczos vectors to control design of flexible structures, part 2

NASA Technical Reports Server (NTRS)

Craig, Roy R., Jr.; Su, Tzu-Jeng

1992-01-01

This report covers the period of the grant from January 1991 until its expiration in June 1992. Together with an Interim Report (Ref. 9), it summarizes the research conducted under NASA Grant NAG9-357 on the topic 'Application of Lanczos Vectors to Control Design of Flexible Structures.' The research concerns various ways to obtain reduced-order mathematical models of complex structures for use in dynamics analysis and in the design of control systems for these structures. This report summarizes the research.

Printable Fabrication of Nanocoral-Structured Electrodes for High-Performance Flexible and Planar Supercapacitor with Artistic Design.

PubMed

Lin, Yuanjing; Gao, Yuan; Fan, Zhiyong

2017-11-01

Planar supercapacitors with high flexibility, desirable operation safety, and high performance are considered as attractive candidates to serve as energy-storage devices for portable and wearable electronics. Here, a scalable and printable technique is adopted to construct novel and unique hierarchical nanocoral structures as the interdigitated electrodes on flexible substrates. The as-fabricated flexible all-solid-state planar supercapacitors with nanocoral structures achieve areal capacitance up to 52.9 mF cm -2 , which is 2.5 times that of devices without nanocoral structures, and this figure-of-merit is among the highest in the literature for the same category of devices. More interestingly, due to utilization of the inkjet-printing technique, excellent versatility on electrode-pattern artistic design is achieved. Particularly, working supercapacitors with artistically designed patterns are demonstrated. Meanwhile, the high scalability of such a printable method is also demonstrated by fabrication of large-sized artistic supercapacitors serving as energy-storage devices in a wearable self-powered system as a proof of concept. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Polymorphism complexity and handedness inversion in serum albumin amyloid fibrils.

PubMed

Usov, Ivan; Adamcik, Jozef; Mezzenga, Raffaele

2013-12-23

Protein-based amyloid fibrils can show a great variety of polymorphic structures within the same protein precursor, although the origins of these structural homologues remain poorly understood. In this work we investigate the fibrillation of bovine serum albumin--a model globular protein--and we follow the polymorphic evolution by a statistical analysis of high-resolution atomic force microscopy images, complemented, at larger length scales, by concepts based on polymer physics formalism. We identify six distinct classes of coexisting amyloid fibrils, including flexible left-handed twisted ribbons, rigid right-handed helical ribbons and nanotubes. We show that the rigid fibrils originate from flexible fibrils through two diverse polymorphic transitions, first, via a single-fibril transformation when the flexible left-handed twisted ribbons turn into the helical left-handed ribbons, to finally evolve into nanotube-like structures, and second, via a double-fibril transformation when two flexible left-handed twisted ribbons wind together resulting in a right-handed twisted ribbon, followed by a rigid right-handed helical ribbon polymorphic conformation. Hence, the change in handedness occurs with an increase in the level of the fibril's structural organization.

A Comparison of Two Approaches to Beta-Flexible Clustering.

ERIC Educational Resources Information Center

Belbin, Lee; And Others

1992-01-01

A method for hierarchical agglomerative polythetic (multivariate) clustering, based on unweighted pair group using arithmetic averages (UPGMA) is compared with the original beta-flexible technique, a weighted average method. Reasons the flexible UPGMA strategy is recommended are discussed, focusing on the ability to recover cluster structure over…

Fast and accurate grid representations for atom-based docking with partner flexibility.

PubMed

de Vries, Sjoerd J; Zacharias, Martin

2017-06-30

Macromolecular docking methods can broadly be divided into geometric and atom-based methods. Geometric methods use fast algorithms that operate on simplified, grid-like molecular representations, while atom-based methods are more realistic and flexible, but far less efficient. Here, a hybrid approach of grid-based and atom-based docking is presented, combining precalculated grid potentials with neighbor lists for fast and accurate calculation of atom-based intermolecular energies and forces. The grid representation is compatible with simultaneous multibody docking and can tolerate considerable protein flexibility. When implemented in our docking method ATTRACT, grid-based docking was found to be ∼35x faster. With the OPLSX forcefield instead of the ATTRACT coarse-grained forcefield, the average speed improvement was >100x. Grid-based representations may allow atom-based docking methods to explore large conformational spaces with many degrees of freedom, such as multiple macromolecules including flexibility. This increases the domain of biological problems to which docking methods can be applied. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Children's classification and lexicalization of attractiveness, gender, and race: differential displays of these concepts and relatedness to bias and flexibility.

PubMed

Rennels, Jennifer L; Langlois, Judith H

2014-10-01

Minimal research has examined children's functional use of attractiveness to classify and label others, an important step in the development of children's biases. This study compared 3- to 11-year-olds' classification, sorting, and labeling of others and themselves based on attractiveness, gender, and race and also investigated whether these abilities and other characteristics predicted children's bias and flexibility. Relative to gender and race, children rarely used attractiveness to spontaneously classify people and were less accurate at sorting and labeling others and themselves by attractiveness, suggesting that they have a less explicit concept of attractiveness. Predictors of bias differed depending on domain and assessment method (forced choice or non-forced choice), showing that children's bias is affected by both individual differences and task characteristics. Predictors of flexibility differed based on whether children were assigning positive or negative traits to target children, demonstrating that the valence of attributes is an important consideration when conceptualizing children's flexibility. Copyright © 2014 Elsevier Inc. All rights reserved.

Recent Progress on Flexible and Wearable Supercapacitors.

PubMed

Xue, Qi; Sun, Jinfeng; Huang, Yan; Zhu, Minshen; Pei, Zengxia; Li, Hongfei; Wang, Yukun; Li, Na; Zhang, Haiyan; Zhi, Chunyi

2017-12-01

Recently, wearable electronic devices including electrical sensors, flexible displays, and health monitors have received considerable attention and experienced rapid progress. Wearable supercapacitors attract tremendous attention mainly due to their high stability, low cost, fast charging/discharging, and high efficiency; properties that render them value for developing fully flexible devices. In this Concept, the recent achievements and advances made in flexible and wearable supercapacitors are presented, especially highlighting the promising performances of yarn/fiber-shaped and planar supercapacitors. On the basis of their working mechanism, electrode materials including carbon-based materials, metal oxide-based materials, and conductive polymers with an emphasis on the performance-optimization method are introduced. The latest representative techniques and active materials of recently developed supercapacitors with superior performance are summarized. Furthermore, the designs of 1D and 2D electrodes are discussed according to their electrically conductive supporting materials. Finally, conclusions, challenges, and perspective in optimizing and developing the electrochemical performance and function of wearable supercapacitors for their practical utility are addressed. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Children’s Classification and Lexicalization of Attractiveness, Gender, and Race: Differential Displays of These Concepts and Relatedness to Bias and Flexibility

PubMed Central

Rennels, Jennifer L.; Langlois, Judith H.

2014-01-01

Minimal research has examined children’s functional use of attractiveness to classify and label others, an important step in the development of children’s biases. This study compared 3-to 11-year-olds’ classification, sorting, and labeling of others and themselves based on attractiveness, gender, and race, and investigated whether these abilities and other characteristics predicted children’s bias and flexibility. Relative to gender and race, children rarely used attractiveness to spontaneously classify people and were less accurate at sorting and labeling others and themselves by attractiveness, suggesting they have a less explicit concept of attractiveness. Predictors of bias differed depending upon domain and assessment method (forced choice or non-forced choice), showing that children’s bias is affected by both individual differences and task characteristics. Predictors of flexibility differed based on whether children were assigning positive or negative traits to target children, demonstrating that the valence of attributes is an important consideration when conceptualizing children’s flexibility. PMID:24842583

How fish swim: flexible fin thrusters as an EAP platform

NASA Astrophysics Data System (ADS)

Lauder, George V.

2007-04-01

Fish are capable of remarkable locomotor performance and use their fins extensively for both propulsion and maneuvering. Recent interest in using fishes as inspiration for the design of a new generation of autonomous underwater vehicles has prompted both new experimental studies of fish locomotor function and efforts to use electroactive polymers (EAP) as actuators in fish-inspired propulsive devices. The fins of fishes allow precise control over body position and vectoring of thrust during propulsion and maneuvering. Recent experimental studies of fish locomotion have revealed that fins exhibit much greater flexibility than previously suspected and that there is considerable deformation of the fin surface during locomotion. The fins of the large group known as ray-finned fishes are supported by fin rays, which have a bilaminar structure that allows active curvature control of the ray and fin surface by the fin musculature. Fish have up to seven different fins, and these fins may interact with each other hydrodynamically during locomotion. Fish fins provide an excellent test platform for the use of electroactive polymer actuators as the frequency of movement is typically less than 5 Hz, and fin muscle strains typically range from 2 to 10%. Recent developments of biorobotic fish pectoral fins actuated with EAP are reviewed.

Tough and flexible CNT-polymeric hybrid scaffolds for engineering cardiac constructs.

PubMed

Kharaziha, Mahshid; Shin, Su Ryon; Nikkhah, Mehdi; Topkaya, Seda Nur; Masoumi, Nafiseh; Annabi, Nasim; Dokmeci, Mehmet R; Khademhosseini, Ali

2014-08-01

In the past few years, a considerable amount of effort has been devoted toward the development of biomimetic scaffolds for cardiac tissue engineering. However, most of the previous scaffolds have been electrically insulating or lacked the structural and mechanical robustness to engineer cardiac tissue constructs with suitable electrophysiological functions. Here, we developed tough and flexible hybrid scaffolds with enhanced electrical properties composed of carbon nanotubes (CNTs) embedded aligned poly(glycerol sebacate):gelatin (PG) electrospun nanofibers. Incorporation of varying concentrations of CNTs from 0 to 1.5% within the PG nanofibrous scaffolds (CNT-PG scaffolds) notably enhanced fiber alignment and improved the electrical conductivity and toughness of the scaffolds while maintaining the viability, retention, alignment, and contractile activities of cardiomyocytes (CMs) seeded on the scaffolds. The resulting CNT-PG scaffolds resulted in stronger spontaneous and synchronous beating behavior (3.5-fold lower excitation threshold and 2.8-fold higher maximum capture rate) compared to those cultured on PG scaffold. Overall, our findings demonstrated that aligned CNT-PG scaffold exhibited superior mechanical properties with enhanced CM beating properties. It is envisioned that the proposed hybrid scaffolds can be useful for generating cardiac tissue constructs with improved organization and maturation. Copyright © 2014 Elsevier Ltd. All rights reserved.

A Bayesian joint probability modeling approach for seasonal forecasting of streamflows at multiple sites

NASA Astrophysics Data System (ADS)

Wang, Q. J.; Robertson, D. E.; Chiew, F. H. S.

2009-05-01

Seasonal forecasting of streamflows can be highly valuable for water resources management. In this paper, a Bayesian joint probability (BJP) modeling approach for seasonal forecasting of streamflows at multiple sites is presented. A Box-Cox transformed multivariate normal distribution is proposed to model the joint distribution of future streamflows and their predictors such as antecedent streamflows and El Niño-Southern Oscillation indices and other climate indicators. Bayesian inference of model parameters and uncertainties is implemented using Markov chain Monte Carlo sampling, leading to joint probabilistic forecasts of streamflows at multiple sites. The model provides a parametric structure for quantifying relationships between variables, including intersite correlations. The Box-Cox transformed multivariate normal distribution has considerable flexibility for modeling a wide range of predictors and predictands. The Bayesian inference formulated allows the use of data that contain nonconcurrent and missing records. The model flexibility and data-handling ability means that the BJP modeling approach is potentially of wide practical application. The paper also presents a number of statistical measures and graphical methods for verification of probabilistic forecasts of continuous variables. Results for streamflows at three river gauges in the Murrumbidgee River catchment in southeast Australia show that the BJP modeling approach has good forecast quality and that the fitted model is consistent with observed data.

Dynamic modelling of n-of-1 data: powerful and flexible data analytics applied to individualised studies.

PubMed

Vieira, Rute; McDonald, Suzanne; Araújo-Soares, Vera; Sniehotta, Falko F; Henderson, Robin

2017-09-01

N-of-1 studies are based on repeated observations within an individual or unit over time and are acknowledged as an important research method for generating scientific evidence about the health or behaviour of an individual. Statistical analyses of n-of-1 data require accurate modelling of the outcome while accounting for its distribution, time-related trend and error structures (e.g., autocorrelation) as well as reporting readily usable contextualised effect sizes for decision-making. A number of statistical approaches have been documented but no consensus exists on which method is most appropriate for which type of n-of-1 design. We discuss the statistical considerations for analysing n-of-1 studies and briefly review some currently used methodologies. We describe dynamic regression modelling as a flexible and powerful approach, adaptable to different types of outcomes and capable of dealing with the different challenges inherent to n-of-1 statistical modelling. Dynamic modelling borrows ideas from longitudinal and event history methodologies which explicitly incorporate the role of time and the influence of past on future. We also present an illustrative example of the use of dynamic regression on monitoring physical activity during the retirement transition. Dynamic modelling has the potential to expand researchers' access to robust and user-friendly statistical methods for individualised studies.

High-intensity pulse light sintering of silver nanowire transparent films on polymer substrates: the effect of the thermal properties of substrates on the performance of silver films.

PubMed

Jiu, Jinting; Sugahara, Tohru; Nogi, Masaya; Araki, Teppei; Suganuma, Katsuaki; Uchida, Hiroshi; Shinozaki, Kenji

2013-12-07

Silver nanowire (AgNW) films with a random mesh structure have attracted considerable attention as high-performance flexible transparent electrodes that can replace the expensive and brittle ITO-sputtered films widely used in displays, touch screens, and solar cells. Methods such as heating, pressure treatment, and light treatment are usually used to obtain an optically transparent and electrically conductive film comparable to those of commercial ITO. However, the adhesion between the AgNW film and the substrate is so weak that other overcoatings or extra treatments are necessary. Here, a high-intensity pulsed light (HIPL) sintering technique was developed to rapidly and simply sinter the AgNW film and thus achieve strong adhesion and even high conductivity on these flexible polymer substrates which will be widely applied to the printing of electronic devices. The conductivity of the AgNW film closely depended on the thermal performance of substrates, and the adhesion was determined by the soft state of the substrate surface originating from the glass transition or melting of substrates with light intensity. The rapid sintering technique can be popularized to fabricate new devices on these polymer substrates by considering the thermal properties of the substrate to improve the performance of devices.

Skin and scales of teleost fish: Simple structure but high performance and multiple functions

NASA Astrophysics Data System (ADS)

Vernerey, Franck J.; Barthelat, Francois

2014-08-01

Natural and man-made structural materials perform similar functions such as structural support or protection. Therefore they rely on the same types of properties: strength, robustness, lightweight. Nature can therefore provide a significant source of inspiration for new and alternative engineering designs. We report here some results regarding a very common, yet largely unknown, type of biological material: fish skin. Within a thin, flexible and lightweight layer, fish skins display a variety of strain stiffening and stabilizing mechanisms which promote multiple functions such as protection, robustness and swimming efficiency. We particularly discuss four important features pertaining to scaled skins: (a) a strongly elastic tensile behavior that is independent from the presence of rigid scales, (b) a compressive response that prevents buckling and wrinkling instabilities, which are usually predominant for thin membranes, (c) a bending response that displays nonlinear stiffening mechanisms arising from geometric constraints between neighboring scales and (d) a robust structure that preserves the above characteristics upon the loss or damage of structural elements. These important properties make fish skin an attractive model for the development of very thin and flexible armors and protective layers, especially when combined with the high penetration resistance of individual scales. Scaled structures inspired by fish skin could find applications in ultra-light and flexible armor systems, flexible electronics or the design of smart and adaptive morphing structures for aerospace vehicles.

Beyond corporate-style downsizing: a better way for medical schools to succeed in a changing world.

PubMed

Bland, C J

1997-06-01

There is a critical need for medical schools and universities to consider strategies beyond corporate-style downsizing to address revenue needs and reposition their organizations. The author presents considerable evidence and three reasons to reject downsizing as a way to facilitate long-term organizational success. Instead, she recommends that institutions use a comprehensive approach to individual and organizational development to assure a flexible, enduring organization. Specifically, medical schools and universities should take an institution-wide perspective and approach to continually training, retraining, or reassigning faculty and should continually adapt their organizational structures and procedures as necessary to achieve changing institutional goals. The result will be the retention of able and dedicated faculty, who will be crucial in helping their schools continue to be successful while adapting to a changing world.

Daylighting and shuttering: RIB system mechanical design and preliminary performance data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kinney, L.; Reynolds, D.

1983-12-01

The Reflective, Insulating Blind (RIB) system is a flexible, user-controlled daylighting device which also has direct thermal advantages: it can reject a considerable portion of summer sun while still retaining an adequate daylighting function; and it functions as moveable insulation to significantly decrease thermal losses through fenestration during evening hours. The conceptual design of the RIB system was accomplished by Barnes and Shapira at the Oak Ridge National Laboratory (ORNL). Mechanical design and prototype fabrication was accomplished by the authors and 29 systems were installed immediately inside existing south-facing windows of an energy-efficient office and dormitory at ORNL. The buildingmore » is a heavily-instrumented, passively-solar-heated structure for which reliable performance data was gathered and analyzed before the addition of RIB systems, thus facilitating the interpretation of ''after RIB'' performance data.« less

Attitude control/momentum management and payload pointing in advanced space vehicles

NASA Technical Reports Server (NTRS)

Parlos, Alexander G.; Jayasuriya, Suhada

1990-01-01

The design and evaluation of an attitude control/momentum management system for highly asymmetric spacecraft configurations are presented. The preliminary development and application of a nonlinear control system design methodology for tracking control of uncertain systems, such as spacecraft payload pointing systems are also presented. Control issues relevant to both linear and nonlinear rigid-body spacecraft dynamics are addressed, whereas any structural flexibilities are not taken into consideration. Results from the first task indicate that certain commonly used simplifications in the equations of motions result in unstable attitude control systems, when used for highly asymmetric spacecraft configurations. An approach is suggested circumventing this problem. Additionally, even though preliminary results from the second task are encouraging, the proposed nonlinear control system design method requires further investigation prior to its application and use as an effective payload pointing system design technique.

DSA patterning options for logics and memory applications

NASA Astrophysics Data System (ADS)

Liu, Chi-Chun; Franke, Elliott; Mignot, Yann; LeFevre, Scott; Sieg, Stuart; Chi, Cheng; Meli, Luciana; Parnell, Doni; Schmidt, Kristin; Sanchez, Martha; Singh, Lovejeet; Furukawa, Tsuyoshi; Seshadri, Indira; De Silva, Ekmini Anuja; Tsai, Hsinyu; Lai, Kafai; Truong, Hoa; Farrell, Richard; Bruce, Robert; Somervell, Mark; Sanders, Daniel; Felix, Nelson; Arnold, John; Hetzer, David; Ko, Akiteru; Metz, Andrew; Colburn, Matthew; Corliss, Daniel

2017-03-01

The progress of three potential DSA applications, i.e. fin formation, via shrink, and pillars, were reviewed in this paper. For fin application, in addition to pattern quality, other important considerations such as customization and design flexibility were discussed. An electrical viachain study verified the DSA rectification effect on CD distribution by showing a tighter current distribution compared to that derived from the guiding pattern direct transfer without using DSA. Finally, a structural demonstration of pillar formation highlights the importance of pattern transfer in retaining both the CD and local CDU improvement from DSA. The learning from these three case studies can provide perspectives that may not have been considered thoroughly in the past. By including more important elements during DSA process development, the DSA maturity can be further advanced and move DSA closer to HVM adoption.

[Contemporary family systems--developments, problems, and possibilities].

PubMed

Reich, Günter

2005-12-01

Contemporary forms of family life and their development are described. The thesis of the pluralism of family types as a historical new phenomenon is critically reviewed, with special consideration of the relationship between family life and working world. An increasing move away from the "fordistic model" of family life took place during the last two decades towards the "multilocal multigenerational family". This development is, among others, due to the increased life expectancy and the change in the population structure. Simultaneous to this the boundaries between family and working world become more permeable. If the stability of employments decreases and the mobility of employees increases in a large scale, is discussed controversely. For an increasing number of families it becomes more and more difficult to make flexibility at work compatible with security for the children or to cope with the consequences of unemployment.

Complete denture impression techniques: evidence-based or philosophical.

PubMed

Singla, Shefali

2007-01-01

Code of practice is dangerous and ever-changing in today's world. Relating this to complete denture impression technique, we have been provided with a set of philosophies--"no pressure, minimal pressure, definite pressure and selective pressure". The objectives and principles of impression-making have been clearly defined. Do you think any philosophy can satisfy any operator to work on these principles and achieve these objectives? These philosophies take into consideration only the tissue part and not the complete basal seat, which comprises the periphery, the tissues and the bone structure. Under such circumstances, should we consider a code of practice dangerous or should we develop an evidence-based approach having a scientific background following certain principles, providing the flexibility to adapt to clinical procedures and to normal biological variations in patients rather than the rigidity imposed by strict laws?

Shift-connected SIMD array architectures for digital optical computing systems, with algorithms for numerical transforms and partial differential equations

NASA Astrophysics Data System (ADS)

Drabik, Timothy J.; Lee, Sing H.

1986-11-01

The intrinsic parallelism characteristics of easily realizable optical SIMD arrays prompt their present consideration in the implementation of highly structured algorithms for the numerical solution of multidimensional partial differential equations and the computation of fast numerical transforms. Attention is given to a system, comprising several spatial light modulators (SLMs), an optical read/write memory, and a functional block, which performs simple, space-invariant shifts on images with sufficient flexibility to implement the fastest known methods for partial differential equations as well as a wide variety of numerical transforms in two or more dimensions. Either fixed or floating-point arithmetic may be used. A performance projection of more than 1 billion floating point operations/sec using SLMs with 1000 x 1000-resolution and operating at 1-MHz frame rates is made.

CSM solutions of rotating blade dynamics using integrating matrices

NASA Technical Reports Server (NTRS)

Lakin, William D.

1992-01-01

The dynamic behavior of flexible rotating beams continues to receive considerable research attention as it constitutes a fundamental problem in applied mechanics. Further, beams comprise parts of many rotating structures of engineering significance. A topic of particular interest at the present time involves the development of techniques for obtaining the behavior in both space and time of a rotor acted upon by a simple airload loading. Most current work on problems of this type use solution techniques based on normal modes. It is certainly true that normal modes cannot be disregarded, as knowledge of natural blade frequencies is always important. However, the present work has considered a computational structural mechanics (CSM) approach to rotor blade dynamics problems in which the physical properties of the rotor blade provide input for a direct numerical solution of the relevant boundary-and-initial-value problem. Analysis of the dynamics of a given rotor system may require solution of the governing equations over a long time interval corresponding to many revolutions of the loaded flexible blade. For this reason, most of the common techniques in computational mechanics, which treat the space-time behavior concurrently, cannot be applied to the rotor dynamics problem without a large expenditure of computational resources. By contrast, the integrating matrix technique of computational mechanics has the ability to consistently incorporate boundary conditions and 'remove' dependence on a space variable. For problems involving both space and time, this feature of the integrating matrix approach thus can generate a 'splitting' which forms the basis of an efficient CSM method for numerical solution of rotor dynamics problems.

Does variation among provincial drug formulary antimicrobial listings in Canada influence prescribing rates?

PubMed

Glass-Kaastra, Shiona K; Finley, Rita; Hutchinson, Jim; Patrick, David M; Weiss, Karl; Conly, John

2014-01-01

The financial accessibility of antimicrobial drugs to the outpatient community in Canada is governed at the provincial level through formularies. Each province may choose to list particular drugs or impose restriction criteria on products in order to guide prescribing and/or curtail costs. Although changes to formularies have been shown to change patterns in the use of individual products and alter costs, no comparison has been made among the provincial antimicrobial formularies with regards to flexibility/stringency, or an assessment of how these formularies impact overall antimicrobial use in the provinces. To summarize provincial antimicrobial formularies and assess whether their relative flexibility/stringency had a statistical impact upon provincial prescription volume during a one year period. Provincial drug plan formularies were accessed and summarized for all prescribed antimicrobials in Canada during 2010. The number of general and restricted benefits for each plan was compiled by antimicrobial classification. Population-adjusted prescription rates for all individual antimicrobials and by antimicrobial class were obtained from the Canadian Integrated Program for Antimicrobial Resistance Surveillance. Correlations between the number of general benefits, restricted benefits, and total benefits with the prescription rate in the provinces were assessed by Spearman rank correlation coefficients. Formularies varied considerably among the Canadian provinces. Quebec had the most flexible formulary, offering the greatest number of general benefits and fewest restrictions. In contrast, Saskatchewan's formulary displayed the lowest number of general benefits and most restrictions. Correlation analyses detected a single significant result; macrolide prescription rates decreased as the number of general macrolide benefits increased. All other rates of provincial antimicrobial prescribing and measures of flexibility/stringency revealed no significant correlations. Although antimicrobial formulary listings are used to guide prescribing rates within a province, our analysis of one year's data of the impact of the antimicrobial formulary structure did not correlate with antimicrobial prescribing rates, and other factors are likely to be at play.

Assessment of the Relationship Between Flexibility and Adaptive Capacity in Flood Management Systems

NASA Astrophysics Data System (ADS)

DiFrancesco, K.; Tullos, D. D.

2013-12-01

Discussions around adapting water management systems to future changes often state the need to increase system flexibility. Intuitively, a flexible, easily modifiable system seems desirable when faced with a wide range of uncertain, but plausible future conditions. Yet, despite the frequent use of the terms flexibility, very little work has examined what exactly it means to have a flexible water management system, what makes one system more flexible than another, or the extent to which flexibility increases adaptive capacity. This study applies a methodology for assessing the inherent flexibility of the structural and non-structural components of flood management systems using original flexibility metrics in the categories of: slack, intensity, connectivity, adjustability, and coordination. We use these metrics to assess the flexibility of three sub-systems within the Sacramento Valley flood management system in California, USA under current system conditions as well as with proposed management actions in place. We then assess the range of hydrologic conditions under which each sub-system can meet flood risk targets in order to determine whether more flexible systems are also more robust and able to perform over a wider range of hydrologic conditions. In doing so, we identify flexible characteristics of flood management systems that enhance the ability of the system to preform over a wide range of conditions making them better suited to adapt to an uncertain hydrologic future. We find that the flexibility characteristics that increase the range of conditions under which the system can meet performance goals varies depending on whether the region is considered urban, rural, or a small community. In some cases, a decrease in certain flexibility characteristics is associated with an increase in robustness, indicating that more flexibility is not always desirable. Future work will assess the transferability of these results to other regions and systems.

Application of foam-extend on turbulent fluid-structure interaction

NASA Astrophysics Data System (ADS)

Rege, K.; Hjertager, B. H.

2017-12-01

Turbulent flow around flexible structures is likely to induce structural vibrations which may eventually lead to fatigue failure. In order to assess the fatigue life of these structures, it is necessary to take the action of the flow on the structure into account, but also the influence of the vibrating structure on the fluid flow. This is achieved by performing fluid-structure interaction (FSI) simulations. In this work, we have investigated the capability of a FSI toolkit for the finite volume computational fluid dynamics software foam-extend to simulate turbulence-induced vibrations of a flexible structure. A large-eddy simulation (LES) turbulence model has been implemented to a basic FSI problem of a flexible wall which is placed in a confined, turbulent flow. This problem was simulated for 2.32 seconds. This short simulation required over 200 computation hours, using 20 processor cores. Thereby, it has been shown that the simulation of FSI with LES is possible, but also computationally demanding. In order to make turbulent FSI simulations with foam-extend more applicable, more sophisticated turbulence models and/or faster FSI iteration schemes should be applied.

Flexible optical metrology strategies for the control and quality assurance of small series production

NASA Astrophysics Data System (ADS)

Schmitt, R.; Pavim, A.

2009-06-01

The demand for achieving smaller and more flexible production series with a considerable diversity of products complicates the control of the manufacturing tasks, leading to big challenges for the quality assurance systems. The quality assurance strategy that is nowadays used for mass production is unable to cope with the inspection flexibility needed among automated small series production, because the measuring strategy is totally dependent on the fixed features of the few manufactured object variants and on process parameters that can be controlled/compensated during production time. The major challenge faced by a quality assurance system applied to small series production facilities is to guarantee the needed quality level already at the first run, and therefore, the quality assurance system has to adapt itself constantly to the new manufacturing conditions. The small series production culture requires a change of paradigms, because its strategies are totally different from mass production. This work discusses the tight inspection requirements of small series production and presents flexible metrology strategies based on optical sensor data fusion techniques, agent-based systems as well as cognitive and self-optimised systems for assuring the needed quality level of flexible small series. Examples of application scenarios are provided among the automated assembly of solid state lasers and the flexible inspection of automotive headlights.

Flexible copper-indium-diselenide films and devices for space applications

NASA Technical Reports Server (NTRS)

Armstrong, J. H.; Pistole, C. O.; Misra, M. S.; Kapur, V. K.; Basol, B. M.

1991-01-01

With the ever increasing demands on space power systems, it is imperative that low cost, lightweight, reliable photovoltaics be developed. One avenue of pursuit for future space power applications is the use of low cost, lightweight flexible PV cells and arrays. Most work in this area assumes the use of flexible amorphous silicon (a-Si), despite its inherent instability and low efficiencies. However, polycrystalline thin film PV such as copper-indium-diselenide (CIS) are inherently more stable and exhibit better performance than a-Si. Furthermore, preliminary data indicate that CIS also offers exciting properties with respect to space applications. However, CIS has only heretofore only produced on rigid substrates. The implications of flexible CIS upon present and future space power platforms was explored. Results indicate that space qualified CIS can dramatically reduce the cost of PV, and in most cases, can be substituted for silicon (Si) based on end-of-life (EOL) estimations. Furthermore, where cost is a prime consideration, CIS can become cost effective than gallium arsenide (GaAs) in some applications. Second, investigations into thin film deposition on flexible substrates were made, and data from these tests indicate that fabrication of flexible CIS devices is feasible. Finally, data is also presented on preliminary TCO/CdS/CuInSe2/Mo devices.

Laser patterning of highly conductive flexible circuits

NASA Astrophysics Data System (ADS)

Ji, Seok Young; Muhammed Ajmal, C.; Kim, Taehun; Chang, Won Seok; Baik, Seunghyun

2017-04-01

There has been considerable attention paid to highly conductive flexible adhesive (CFA) materials as electrodes and interconnectors for future flexible electronic devices. However, the patterning technology still needs to be developed to construct micro-scale electrodes and circuits. Here we developed the selective laser sintering technology where the pattering and curing were accomplished simultaneously without making additional masks. The CFA was composed of micro-scale Ag flakes, multiwalled carbon nanotubes decorated with Ag nanoparticles, and a nitrile-butadiene-rubber matrix. The Teflon-coated polyethylene terephthalate film was used as a flexible substrate. The width of lines (50-500 μm) and circuit patterns were controlled by the programmable scanning of a focused laser beam (power = 50 mW, scanning speed = 1 mm s-1). The laser irradiation removed solvent and induced effective coalescence among fillers providing a conductivity as high as 25 012 S cm-1. The conductivity stability was excellent under the ambient air and humid environments. The normalized resistance change of the pattern was smaller than 1.2 at the bending radius of 5 mm. The cyclability and adhesion of the laser-sintered line pattern on the substrate was excellent. A flexible circuit was fabricated sequentially for operating light emitting diodes during the bending motion, demonstrating excellent feasibility for practical applications in flexible electronics.

Laser patterning of highly conductive flexible circuits.

PubMed

Ji, Seok Young; Ajmal, C Muhammed; Kim, Taehun; Chang, Won Seok; Baik, Seunghyun

2017-04-21

There has been considerable attention paid to highly conductive flexible adhesive (CFA) materials as electrodes and interconnectors for future flexible electronic devices. However, the patterning technology still needs to be developed to construct micro-scale electrodes and circuits. Here we developed the selective laser sintering technology where the pattering and curing were accomplished simultaneously without making additional masks. The CFA was composed of micro-scale Ag flakes, multiwalled carbon nanotubes decorated with Ag nanoparticles, and a nitrile-butadiene-rubber matrix. The Teflon-coated polyethylene terephthalate film was used as a flexible substrate. The width of lines (50-500 μm) and circuit patterns were controlled by the programmable scanning of a focused laser beam (power = 50 mW, scanning speed = 1 mm s -1 ). The laser irradiation removed solvent and induced effective coalescence among fillers providing a conductivity as high as 25 012 S cm -1 . The conductivity stability was excellent under the ambient air and humid environments. The normalized resistance change of the pattern was smaller than 1.2 at the bending radius of 5 mm. The cyclability and adhesion of the laser-sintered line pattern on the substrate was excellent. A flexible circuit was fabricated sequentially for operating light emitting diodes during the bending motion, demonstrating excellent feasibility for practical applications in flexible electronics.

Transparent flexible nanogenerator as self-powered sensor for transportation monitoring

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Zhong Lin; Hu, Youfan; Lin, Long

2016-06-14

A traffic sensor includes a flexible substrate having a top surface. A piezoelectric structure extends from the first electrode layer. The piezoelectric structure has a top end. An insulating layer is infused into the piezoelectric structure. A first electrode layer is disposed on top of the insulating layer. A second electrode layer is disposed below the flexible substrate. A packaging layer is disposed around the substrate, the first electrode layer, the piezoelectric structure, the insulating layer and the second electrode layer. In a method of sensing a traffic parameter, a piezoelectric nanostructure-based traffic sensor is applied to a roadway. Anmore » electrical event generated by the piezoelectric nanostructure-based traffic sensor in response to a vehicle interacting with the piezoelectric nanostructure-based traffic sensor is detected. The electrical event is correlated with the traffic parameter.« less

Control-structure interaction/mirror motion compensation

NASA Technical Reports Server (NTRS)

Mclaren, Mark; Chu, Peter; Price, Xen

1992-01-01

Space Systems/Loral (formerly Ford Aerospace, Space Systems Division) has implemented a rigid-body Mirror Motion Compensation (MMC) scheme for the GOES-I/M spacecraft currently being built for NASA and NOAA. This has resulted in a factor of 15 reduction in pointing error due to rigid-body spacecraft motion induced by the periodic black-body calibration maneuvers required for the instruments. For GOES the spacecraft and the payload mirrors are considered as rigid bodies. The structural flexibility effects are small and are included in the total pointing budget as a separate item. This paper extends the MMC technique to include structural flexibility. For large multi-payload platforms, the structural flexibility effects can be more important in sensor pointing jitter as the result of payload motion. Sensitivity results are included to show the importance of the dynamic model fidelity.

Consideration of regional variations in climatic and soil conditions in the modified triaxial design method.

DOT National Transportation Integrated Search

2008-11-01

The Texas Department of Transportation (TxDOT) uses the modified triaxial design procedure to check : pavement designs from the flexible pavement system program. Since its original development more than : 50 years ago, little modification has been ma...

76 FR 36044 - Proposed Flood Elevation Determinations

Federal Register 2010, 2011, 2012, 2013, 2014

2011-06-21

..., Environmental Consideration. An environmental impact assessment has not been prepared. Regulatory Flexibility... Communities affected in meters (MSL) Effective Modified Kane County, Illinois, and Incorporated Areas Big Rock... Jericho Road (at the of Big Rock. Kendall County boundary). Approximately 1.0 mile None +689 upstream of...

Educational Considerations for Children with Tourette's Syndrome.

ERIC Educational Resources Information Center

Jones, Kevin; Johnson, Genevieve Marie

1993-01-01

This paper describes the prevalence of Tourette's Syndrome and its characteristics. Instructional strategies for students with Tourette's Syndrome are discussed, including a flexible teaching style, a warm and supportive classroom environment, paired and cooperative learning strategies, frequent breaks during instruction, and a safe place to…

New Source Review (NSR) Air Permitting and Energy Efficiency for Industrial Projects, IECA Manufacturers for Energy Efficiency Coalition Meeting (Presentation) – April 18, 2012

EPA Pesticide Factsheets

This presentation provides information about major new source review (NSR), including recent improvement changes and court rulings, flexible air permits rule, significant deterioration rules, and energy efficiency considerations.

76 FR 58409 - Changes in Flood Elevation Determinations

Federal Register 2010, 2011, 2012, 2013, 2014

2011-09-21

... changes in BFEs are in accordance with 44 CFR 65.4. National Environmental Policy Act. This interim rule is categorically excluded from the requirements of 44 CFR part 10, Environmental Consideration. An environmental impact assessment has not been prepared. Regulatory Flexibility Act. As flood elevation...

Considerations for rigid vs. flexible pavement designs when allowed as alternate bids : technical report.

DOT National Transportation Integrated Search

2009-08-01

This report documents the research conducted for the Texas Department of Transportation (TxDOT) : concerning the use of pavement alternates. The scope of the project includes reviewing the state-of-thepractice : in methods used for pavement type sele...

Developing Market Opportunities for Flexible Rooftop Applications of PV Using Flexible CIGS Technology: Market Considerations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sabnani, L.; Skumanich, A.; Ryabova, E.

There has been a recent upsurge in developments for building-integrated phototovoltaics (BiPV) roof top materials based on CIGS. Several new companies have increased their presence and are looking to bring products to market for this application in 2011. For roof-top application, there are significant key requirements beyond just having good conversion efficiency. Other attributes include lightweight, as well as moisture-proof, and fully functionally reliable. The companies bringing these new BIPV/BAPV products need to ensure functionality with a rigorous series of tests, and have an extensive set of 'torture' tests to validate the capability. There is a convergence of form, aesthetics,more » and physics to ensure that the CIGS BiPV deliver on their promises. This article will cover the developments in this segment of the BiPV market and delve into the specific tests and measurements needed to characterize the products. The potential market sizes are evaluated and the technical considerations developed.« less

Active Control of Flexible Space Structures Using the Nitinol Shape Memory Actuators

DTIC Science & Technology

1987-10-01

number) FIELD !GROUP SUBGROUP I Active Control, Nitinol Actuators, Space Structures 9. ABSTRACT (Continue on reverse if necessary and identify by block...number) Summarizes research progress in the feasibility demonstration of active vibration control using Nitinol shape memory actuators. Tests on...FLEXIBLE SPACE STRUCTURES USING NITINOL SHAPE MEMORY ACTUATORS FINAL REPORT FOR PHASE I SDIO CONTRACT #F49620-87-C-0035 0 BY DR. AMR M. BAZ KARIM R

Copper Nanowires and Their Applications for Flexible, Transparent Conducting Films: A Review

PubMed Central

Nam, Vu Binh; Lee, Daeho

2016-01-01

Cu nanowires (NWs) are attracting considerable attention as alternatives to Ag NWs for next-generation transparent conductors, replacing indium tin oxide (ITO) and micro metal grids. Cu NWs hold great promise for low-cost fabrication via a solution-processed route and show preponderant optical, electrical, and mechanical properties. In this study, we report a summary of recent advances in research on Cu NWs, covering the optoelectronic properties, synthesis routes, deposition methods to fabricate flexible transparent conducting films, and their potential applications. This review also examines the approaches on protecting Cu NWs from oxidation in air environments. PMID:28344304

Order and disorder: Temporal organization of eating

PubMed Central

Rowland, Neil E.

2012-01-01

Feeding behavior is described from an evolutionary perspective, and implications for modern neurobiological studies are suggested. In particular, it is argued that meals may have evolved more for sociocultural reasons than physiological imperatives, and that biological approaches to the study of feeding episodes should adopt a more flexible model that is founded in economic or cost-benefit considerations. Specific examples of flexibility in mouse feeding behavior are given. It is further argued that the modern human food environment is so immoderate that physiological manipulations designed to restrain eating have little hope of achieving this goal. PMID:22138508

Cognitive Flexibility through Metastable Neural Dynamics Is Disrupted by Damage to the Structural Connectome.

PubMed

Hellyer, Peter J; Scott, Gregory; Shanahan, Murray; Sharp, David J; Leech, Robert

2015-06-17

Current theory proposes that healthy neural dynamics operate in a metastable regime, where brain regions interact to simultaneously maximize integration and segregation. Metastability may confer important behavioral properties, such as cognitive flexibility. It is increasingly recognized that neural dynamics are constrained by the underlying structural connections between brain regions. An important challenge is, therefore, to relate structural connectivity, neural dynamics, and behavior. Traumatic brain injury (TBI) is a pre-eminent structural disconnection disorder whereby traumatic axonal injury damages large-scale connectivity, producing characteristic cognitive impairments, including slowed information processing speed and reduced cognitive flexibility, that may be a result of disrupted metastable dynamics. Therefore, TBI provides an experimental and theoretical model to examine how metastable dynamics relate to structural connectivity and cognition. Here, we use complementary empirical and computational approaches to investigate how metastability arises from the healthy structural connectome and relates to cognitive performance. We found reduced metastability in large-scale neural dynamics after TBI, measured with resting-state functional MRI. This reduction in metastability was associated with damage to the connectome, measured using diffusion MRI. Furthermore, decreased metastability was associated with reduced cognitive flexibility and information processing. A computational model, defined by empirically derived connectivity data, demonstrates how behaviorally relevant changes in neural dynamics result from structural disconnection. Our findings suggest how metastable dynamics are important for normal brain function and contingent on the structure of the human connectome. Copyright © 2015 the authors 0270-6474/15/359050-14$15.00/0.

Controlled Growth of Ceria Nanoarrays on Anatase Titania Powder: A Bottom-up Physical Picture.

PubMed

Kim, Hyun You; Hybertsen, Mark S; Liu, Ping

2017-01-11

The leading edge of catalysis research motivates physical understanding of the growth of nanoscale oxide structures on different supporting oxide materials that are themselves also nanostructured. This research opens up for consideration a diverse range of facets on the support material, versus the single facet typically involved in wide-area growth of thin films. Here, we study the growth of ceria nanoarchitectures on practical anatase titania powders as a showcase inspired by recent experiments. Density functional theory (DFT)-based methods are employed to characterize and rationalize the broad array of low energy nanostructures that emerge. Using a bottom-up approach, we are able to identify and characterize the underlying mechanisms for the facet-dependent growth of various ceria motifs on anatase titania based on formation energy. These motifs include 0D clusters, 1D chains, 2D plates, and 3D nanoparticles. The ceria growth mode and morphology are determined by the interplay of several factors including the role of the common cation valence, the interface template effect for different facets of the anatase support, enhanced ionic binding for more compact ceria motifs, and the local structural flexibility of oxygen ions in bridging the interface between anatase and ceria structures.

Ultrahigh-resolution mapping of peatland microform using ground-based structure from motion with multiview stereo

NASA Astrophysics Data System (ADS)

Mercer, Jason J.; Westbrook, Cherie J.

2016-11-01

Microform is important in understanding wetland functions and processes. But collecting imagery of and mapping the physical structure of peatlands is often expensive and requires specialized equipment. We assessed the utility of coupling computer vision-based structure from motion with multiview stereo photogrammetry (SfM-MVS) and ground-based photos to map peatland topography. The SfM-MVS technique was tested on an alpine peatland in Banff National Park, Canada, and guidance was provided on minimizing errors. We found that coupling SfM-MVS with ground-based photos taken with a point and shoot camera is a viable and competitive technique for generating ultrahigh-resolution elevations (i.e., <0.01 m, mean absolute error of 0.083 m). In evaluating 100+ viable SfM-MVS data collection and processing scenarios, vegetation was found to considerably influence accuracy. Vegetation class, when accounted for, reduced absolute error by as much as 50%. The logistic flexibility of ground-based SfM-MVS paired with its high resolution, low error, and low cost makes it a research area worth developing as well as a useful addition to the wetland scientists' toolkit.

Structure of the Ubiquitin Hydrolase UCH-L3 Complexed with a Suicide Substrate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Misaghi, S.; Galardy, P.J.; Meester, W.J.

Ubiquitin C-terminal hydrolases (UCHs) comprise a family of small ubiquitin-specific proteases of uncertain function. Although no cellular substrates have been identified for UCHs, their highly tissue-specific expression patterns and the association of UCH-L1 mutations with human disease strongly suggest a critical role. The structure of the yeast UCH Yuh1-ubiquitin aldehyde complex identified an active site crossover loop predicted to limit the size of suitable substrates. We report the 1.45 {angstrom} resolution crystal structure of human UCH-L3 in complex with the inhibitor ubiquitin vinylmethylester, an inhibitor that forms a covalent adduct with the active site cysteine of ubiquitin-specific proteases. This structuremore » confirms the predicted mechanism of the inhibitor and allows the direct comparison of a UCH family enzyme in the free and ligand-bound state. We also show the efficient hydrolysis by human UCH-L3 of a 13-residue peptide in isopeptide linkage with ubiquitin, consistent with considerable flexibility in UCH substrate size. We propose a model for the catalytic cycle of UCH family members which accounts for the hydrolysis of larger ubiquitin conjugates.« less

Experiments in structural dynamics and control using a grid

NASA Technical Reports Server (NTRS)

Montgomery, R. C.

1985-01-01

Future spacecraft are being conceived that are highly flexible and of extreme size. The two features of flexibility and size pose new problems in control system design. Since large scale structures are not testable in ground based facilities, the decision on component placement must be made prior to full-scale tests on the spacecraft. Control law research is directed at solving problems of inadequate modelling knowledge prior to operation required to achieve peak performance. Another crucial problem addressed is accommodating failures in systems with smart components that are physically distributed on highly flexible structures. Parameter adaptive control is a method of promise that provides on-orbit tuning of the control system to improve performance by upgrading the mathematical model of the spacecraft during operation. Two specific questions are answered in this work. They are: What limits does on-line parameter identification with realistic sensors and actuators place on the ultimate achievable performance of a system in the highly flexible environment? Also, how well must the mathematical model used in on-board analytic redundancy be known and what are the reasonable expectations for advanced redundancy management schemes in the highly flexible and distributed component environment?

Structural response to discrete and continuous gusts of an airplane having wing bending flexibility and a correlation of calculated and flight results

NASA Technical Reports Server (NTRS)

Houbolt, John C; Kordes, Eldon E

1954-01-01

An analysis is made of the structural response to gusts of an airplane having the degrees of freedom of vertical motion and wing bending flexibility and basic parameters are established. A convenient and accurate numerical solution of the response equations is developed for the case of discrete-gust encounter, an exact solution is made for the simpler case of continuous-sinusoidal-gust encounter, and the procedure is outlined for treating the more realistic condition of continuous random atmospheric turbulence, based on the methods of generalized harmonic analysis. Correlation studies between flight and calculated results are then given to evaluate the influence of wing bending flexibility on the structural response to gusts of two twin-engine transports and one four-engine bomber. It is shown that calculated results obtained by means of a discrete-gust approach reveal the general nature of the flexibility effects and lead to qualitative correlation with flight results. In contrast, calculations by means of the continuous-turbulence approach show good quantitative correlation with flight results and indicate a much greater degree of resolution of the flexibility effects.

Structural load control during construction

NASA Technical Reports Server (NTRS)

Mikulas, Martin M., Jr.

1991-01-01

In the absence of gravitational pull, the major design considerations for large space structures are stiffness for controllability, and transient dynamic loadings (as opposed to the traditional static load associated with earth-based structures). Because of the absence of gravitational loading, space structures can be designed to be significantly lighter than their counterparts on Earth. For example, the Space Shuttle manipulator arm is capable of moving and positioning a 60,000 lb payload, yet weighs less than 1,000 lbs. A recent design for the Space Station which had a total weight of about 500,000 lbs. used a primary loadcarrying keel beam which weighed less than 10,000 lbs. For many large space structures designs it is quite common for the load-carrying structure to have a mass fraction on the order of one or two percent of the total spacecraft mass. This significant weight reduction for large space structures is commonly accompanied by very low natural frequencies. These low frequencies cause an unprecedented level of operational complexity for mission applications which require a high level of positioning and control accuracy. This control problem is currently the subject of considerable research directed towards reducing the flexibility problem. In addition, however, the small mass fraction typically results in structures which are quite unforgiving to inadvertent high loadings. In other words, the structures are 'fragile.' In order to deal with the fragility issue CSC developed a load-limiting concept for space truss structures. This concept is aimed at limiting the levels of load which can occur in a large space structure during the construction process as well as during subsequent operations. Currently, the approach for dealing with large loadings is to make the structure larger. The impact this has on construction is significant. The larger structures are more difficult to package in the launch vehicle, and in fact in some instances the concept must be changed from a deployable truss to an erectable truss to permit packaging. The new load-limiting concept is aimed at permitting the use in large space structures of smaller trusses with a high level of strength robustness, in order to simplify the construction process. To date several analyses conducted on the concept have demonstrated its feasibility, and an experiment is currently being designed to demonstrate its operation.

Cognitive Flexibility and Undergraduate Physiology Students: Increasing Advanced Knowledge Acquisition within an Ill-Structured Domain

ERIC Educational Resources Information Center

Rhodes, Ashley E.; Rozell, Timothy G.

2017-01-01

Cognitive flexibility is defined as the ability to assimilate previously learned information and concepts to generate novel solutions to new problems. This skill is crucial for success within ill-structured domains such as biology, physiology, and medicine, where many concepts are simultaneously required for understanding a complex problem, yet…

Building Community in Academic Settings: The Importance of Flexibility in a Structured Mentoring Program

ERIC Educational Resources Information Center

Ewing, Robyn; Freeman, Mark; Barrie, Simon; Bell, Amani; O'Connor, Donna; Waugh, Fran; Sykes, Chris

2008-01-01

Academic mentoring is increasingly being used by many universities as a tool to enhance the quality of research-led teaching, promote cross-faculty collaboration and encourage a mentoring culture and community. This article reports on a pilot project established to investigate the benefits of building flexibility into a structured academic…

Effects of Structural Flexibility on Motorcycle Straight Running Stability by using Energy Flow Method

NASA Astrophysics Data System (ADS)

Marumo, Yoshitaka; Katayama, Tsuyoshi

This study uses the energy flow method to analyze how structural flexibility affects the motorcycle wobble and weave modes. Lateral bending of the front fork and torsion of the main frame affect the wobble mode stability. These are based on the gyroscopic effect of the front wheel in the steering motion by considering structural flexibility. At high speeds, lateral bending of the front fork and torsion of the rear swing arm more significantly affect the weave mode stability. These are primarily due to the phase changes of the external force generated by the yaw rate in the lateral motion. The phase change of the yaw rate force in the lateral motion originates from the phase change of the tire side forces.

Statistically generated weighted curve fit of residual functions for modal analysis of structures

NASA Technical Reports Server (NTRS)

Bookout, P. S.

1995-01-01

A statistically generated weighting function for a second-order polynomial curve fit of residual functions has been developed. The residual flexibility test method, from which a residual function is generated, is a procedure for modal testing large structures in an external constraint-free environment to measure the effects of higher order modes and interface stiffness. This test method is applicable to structures with distinct degree-of-freedom interfaces to other system components. A theoretical residual function in the displacement/force domain has the characteristics of a relatively flat line in the lower frequencies and a slight upward curvature in the higher frequency range. In the test residual function, the above-mentioned characteristics can be seen in the data, but due to the present limitations in the modal parameter evaluation (natural frequencies and mode shapes) of test data, the residual function has regions of ragged data. A second order polynomial curve fit is required to obtain the residual flexibility term. A weighting function of the data is generated by examining the variances between neighboring data points. From a weighted second-order polynomial curve fit, an accurate residual flexibility value can be obtained. The residual flexibility value and free-free modes from testing are used to improve a mathematical model of the structure. The residual flexibility modal test method is applied to a straight beam with a trunnion appendage and a space shuttle payload pallet simulator.

Robust on-off pulse control of flexible space vehicles

NASA Technical Reports Server (NTRS)

Wie, Bong; Sinha, Ravi

1993-01-01

The on-off reaction jet control system is often used for attitude and orbital maneuvering of various spacecraft. Future space vehicles such as the orbital transfer vehicles, orbital maneuvering vehicles, and space station will extensively use reaction jets for orbital maneuvering and attitude stabilization. The proposed robust fuel- and time-optimal control algorithm is used for a three-mass spacing model of flexible spacecraft. A fuel-efficient on-off control logic is developed for robust rest-to-rest maneuver of a flexible vehicle with minimum excitation of structural modes. The first part of this report is concerned with the problem of selecting a proper pair of jets for practical trade-offs among the maneuvering time, fuel consumption, structural mode excitation, and performance robustness. A time-optimal control problem subject to parameter robustness constraints is formulated and solved. The second part of this report deals with obtaining parameter insensitive fuel- and time- optimal control inputs by solving a constrained optimization problem subject to robustness constraints. It is shown that sensitivity to modeling errors can be significantly reduced by the proposed, robustified open-loop control approach. The final part of this report deals with sliding mode control design for uncertain flexible structures. The benchmark problem of a flexible structure is used as an example for the feedback sliding mode controller design with bounded control inputs and robustness to parameter variations is investigated.

Multiscale Hierarchical Design of a Flexible Piezoresistive Pressure Sensor with High Sensitivity and Wide Linearity Range.

PubMed

Shi, Jidong; Wang, Liu; Dai, Zhaohe; Zhao, Lingyu; Du, Mingde; Li, Hongbian; Fang, Ying

2018-05-30

Flexible piezoresistive pressure sensors have been attracting wide attention for applications in health monitoring and human-machine interfaces because of their simple device structure and easy-readout signals. For practical applications, flexible pressure sensors with both high sensitivity and wide linearity range are highly desirable. Herein, a simple and low-cost method for the fabrication of a flexible piezoresistive pressure sensor with a hierarchical structure over large areas is presented. The piezoresistive pressure sensor consists of arrays of microscale papillae with nanoscale roughness produced by replicating the lotus leaf's surface and spray-coating of graphene ink. Finite element analysis (FEA) shows that the hierarchical structure governs the deformation behavior and pressure distribution at the contact interface, leading to a quick and steady increase in contact area with loads. As a result, the piezoresistive pressure sensor demonstrates a high sensitivity of 1.2 kPa -1 and a wide linearity range from 0 to 25 kPa. The flexible pressure sensor is applied for sensitive monitoring of small vibrations, including wrist pulse and acoustic waves. Moreover, a piezoresistive pressure sensor array is fabricated for mapping the spatial distribution of pressure. These results highlight the potential applications of the flexible piezoresistive pressure sensor for health monitoring and electronic skin. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

First order coupled dynamic model of flexible space structures with time-varying configurations

NASA Astrophysics Data System (ADS)

Wang, Jie; Li, Dongxu; Jiang, Jianping

2017-03-01

This paper proposes a first order coupled dynamic modeling method for flexible space structures with time-varying configurations for the purpose of deriving the characteristics of the system. The model considers the first time derivative of the coordinate transformation matrix between the platform's body frame and the appendage's floating frame. As a result it can accurately predict characteristics of the system even if flexible appendages rotate with complex trajectory relative to the rigid part. In general, flexible appendages are fixed on the rigid platform or forced to rotate with a slow angular velocity. So only the zero order of the transformation matrix is considered in conventional models. However, due to neglecting of time-varying terms of the transformation matrix, these models introduce severe error when appendages, like antennas, for example, rotate with a fast speed relative to the platform. The first order coupled dynamic model for flexible space structures proposed in this paper resolve this problem by introducing the first time derivative of the transformation matrix. As a numerical example, a central core with a rotating solar panel is considered and the results are compared with those given by the conventional model. It has been shown that the first order terms are of great importance on the attitude of the rigid body and dynamic response of the flexible appendage.

A Study of Flexible Composites for Expandable Space Structures

NASA Technical Reports Server (NTRS)

Scotti, Stephen J.

2016-01-01

Payload volume for launch vehicles is a critical constraint that impacts spacecraft design. Deployment mechanisms, such as those used for solar arrays and antennas, are approaches that have successfully accommodated this constraint, however, providing pressurized volumes that can be packaged compactly at launch and expanded in space is still a challenge. One approach that has been under development for many years is to utilize softgoods - woven fabric for straps, cloth, and with appropriate coatings, bladders - to provide this expandable pressure vessel capability. The mechanics of woven structure is complicated by a response that is nonlinear and often nonrepeatable due to the discrete nature of the woven fiber architecture. This complexity reduces engineering confidence to reliably design and certify these structures, which increases costs due to increased requirements for system testing. The present study explores flexible composite materials systems as an alternative to the heritage softgoods approach. Materials were obtained from vendors who utilize flexible composites for non-aerospace products to determine some initial physical and mechanical properties of the materials. Uniaxial mechanical testing was performed to obtain the stress-strain response of the flexible composites and the failure behavior. A failure criterion was developed from the data, and a space habitat application was used to provide an estimate of the relative performance of flexible composites compared to the heritage softgoods approach. Initial results are promising with a 25% mass savings estimated for the flexible composite solution.

Accommodation of structural rearrangements in the huntingtin-interacting protein 1 coiled-coil domain

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wilbur, Jeremy D., E-mail: jwilbur@msg.ucsf.edu; Hwang, Peter K.; Brodsky, Frances M.

2010-03-01

Variable packing interaction related to the conformational flexibility within the huntingtin-interacting protein 1 coiled coil domain. Huntingtin-interacting protein 1 (HIP1) is an important link between the actin cytoskeleton and clathrin-mediated endocytosis machinery. HIP1 has also been implicated in the pathogenesis of Huntington’s disease. The binding of HIP1 to actin is regulated through an interaction with clathrin light chain. Clathrin light chain binds to a flexible coiled-coil domain in HIP1 and induces a compact state that is refractory to actin binding. To understand the mechanism of this conformational regulation, a high-resolution crystal structure of a stable fragment from the HIP1 coiled-coilmore » domain was determined. The flexibility of the HIP1 coiled-coil region was evident from its variation from a previously determined structure of a similar region. A hydrogen-bond network and changes in coiled-coil monomer interaction suggest that the HIP1 coiled-coil domain is uniquely suited to allow conformational flexibility.« less

A Petri net synthesis theory for modeling flexible manufacturing systems.

PubMed

Jeng, M D

1997-01-01

A theory that synthesizes Petri nets for modeling flexible manufacturing systems is presented. The theory adopts a bottom-up or modular-composition approach to construct net models. Each module is modeled as a resource control net (RCN), which represents a subsystem that controls a resource type in a flexible manufacturing system. Interactions among the modules are described as the common transition and transition subnets. The net obtained by merging the modules with two minimal restrictions is shown to be conservative and thus bounded. An algorithm is developed to detect two sufficient conditions for structural liveness of the net. The algorithm examines only the net's structure and the initial marking, and appears to be more efficient than state enumeration techniques such as the reachability tree method. In this paper, the sufficient conditions for liveness are shown to be related to some structural objects called siphons. To demonstrate the applicability of the theory, a flexible manufacturing system of a moderate size is modeled and analyzed using the proposed theory.

Ultra-precise micro-motion stage for optical scanning test

NASA Astrophysics Data System (ADS)

Chen, Wen; Zhang, Jianhuan; Jiang, Nan

2009-05-01

This study aims at the application of optical sensing technology in a 2D flexible hinge test stage. Optical fiber sensor which is manufactured taking advantage of the various unique properties of optical fiber, such as good electric insulation properties, resistance of electromagnetic disturbance, sparkless property and availability in flammable and explosive environment, has lots of good properties, such as high accuracy and wide dynamic range, repeatable, etc. and is applied in 2D flexible hinge stage driven by PZT. Several micro-bending structures are designed utilizing the characteristics of the flexible hinge stage. And through experiments, the optimal micro-bending tooth structure and the scope of displacement sensor trip under this optimal micro-bending tooth structure are derived. These experiments demonstrate that the application of optical fiber displacement sensor in 2D flexible hinge stage driven by PZT substantially broadens the dynamic testing range and improves the sensitivity of this apparatus. Driving accuracy and positioning stability are enhanced as well. [1,2

Pv-Thermal Solar Power Assembly

DOEpatents

Ansley, Jeffrey H.; Botkin, Jonathan D.; Dinwoodie, Thomas L.

2001-10-02

A flexible solar power assembly includes a flexible photovoltaic device attached to a flexible thermal solar collector. The solar power assembly can be rolled up for transport and then unrolled for installation on a surface, such as the roof or side wall of a building or other structure, by use of adhesive and/or other types of fasteners.

Goal driven kinematic simulation of flexible arm robot for space station missions

NASA Technical Reports Server (NTRS)

Janssen, P.; Choudry, A.

1987-01-01

Flexible arms offer a great degree of flexibility in maneuvering in the space environment. The problem of transporting an astronaut for extra-vehicular activity using a space station based flexible arm robot was studied. Inverse kinematic solutions of the multilink structure were developed. The technique is goal driven and can support decision making for configuration selection as required for stability and obstacle avoidance. Details of this technique and results are given.

Highly Flexible Self-Assembled V2O5 Cathodes Enabled by Conducting Diblock Copolymers

NASA Astrophysics Data System (ADS)

An, Hyosung; Mike, Jared; Smith, Kendall; Swank, Lisa; Lin, Yen-Hao; Pesek, Stacy; Verduzco, Rafael; Lutkenhaus, Jodie

Structural energy storage materials combining load-bearing mechanical properties and high energy storage performance are desired for applications in wearable devices or flexible displays. Vanadium pentoxide (V2O5) is a promising cathode material for possible use in flexible battery electrodes, but it remains limited by low Li+ diffusion coefficient and electronic conductivity, severe volumetric changes upon cycling, and limited mechanical flexibility. Here, we demonstrate a route to address these challenges by blending a diblock copolymer bearing electron- and ion-conducting blocks, poly(3-hexylthiophene)-block-poly(ethyleneoxide) (P3HT- b-PEO), with V2O5 to form a mechanically flexible, electro-mechanically stable hybrid electrode. V2O5 layers were arranged parallel in brick-and-mortar-like fashion held together by the P3HT- b-PEO binder. This unique structure significantly enhances mechanical flexibility, toughness and cyclability without sacrificing capacity. Electrodes comprised of 10 wt% polymer have unusually high toughness (293 kJ/m3) and specific energy (530 Wh/kg), both higher than reduced graphene oxide paper electrodes.

Highly Conductive Transparent and Flexible Electrodes Including Double-Stacked Thin Metal Films for Transparent Flexible Electronics.

PubMed

Han, Jun Hee; Kim, Do-Hong; Jeong, Eun Gyo; Lee, Tae-Woo; Lee, Myung Keun; Park, Jeong Woo; Lee, Hoseung; Choi, Kyung Cheol

2017-05-17

To keep pace with the era of transparent and deformable electronics, electrode functions should be improved. In this paper, an innovative structure is suggested to overcome the trade-off between optical and electrical properties that commonly arises with transparent electrodes. The structure of double-stacked metal films showed high conductivity (<3 Ω/sq) and high transparency (∼90%) simultaneously. A proper space between two metal films led to high transmittance by an optical phenomenon. The principle of parallel connection allowed the electrode to have high conductivity. In situ fabrication was possible because the only materials composing the electrode were silver and WO 3 , which can be deposited by thermal evaporation. The electrode was flexible enough to withstand 10 000 bending cycles with a 1 mm bending radius. Furthermore, a few μm scale patterning of the electrode was easily implemented by using photolithography, which is widely employed industrially for patterning. Flexible organic light-emitting diodes and a transparent flexible thin-film transistor were successfully fabricated with the proposed electrode. Various practical applications of this electrode to new transparent flexible electronics are expected.

Rehabilitation of the Ankle After Acute Sprain or Chronic Instability.

PubMed

Mattacola, Carl G; Dwyer, Maureen K

2002-12-01

OBJECTIVE: To outline rehabilitation concepts that are applicable to acute and chronic injury of the ankle, to provide evidence for current techniques used in the rehabilitation of the ankle, and to describe a functional rehabilitation program that progresses from basic to advanced, while taking into consideration empirical data from the literature and clinical practice. BACKGROUND: Important considerations in the rehabilitation of ankle injuries include controlling the acute inflammatory process, regaining full ankle range of motion, increasing muscle strength and power, and improving proprioceptive abilities. These goals can be achieved through various modalities, flexibility exercises, and progressive strength- and balance-training exercises. In this article, we discuss the deleterious effects of ankle injury on ankle-joint proprioception and muscular strength and how these variables can be quantifiably measured to follow progress through a rehabilitation program. Evidence to support the effectiveness of applying orthotics and ankle braces during the acute and subacute phases of ankle rehabilitation is provided, along with recommendations for functional rehabilitation of ankle injuries, including a structured progression of exercises. RECOMMENDATIONS: Early functional rehabilitation of the ankle should include range-of-motion exercises and isometric and isotonic strength-training exercises. In the intermediate stage of rehabilitation, a progression of proprioception-training exercises should be incorporated. Advanced rehabilitation should focus on sport-specific activities to prepare the athlete for return to competition. Although it is important to individualize each rehabilitation program, this well-structured template for ankle rehabilitation can be adapted as needed.

Rehabilitation of the Ankle After Acute Sprain or Chronic Instability

PubMed Central

Mattacola, Carl G.; Dwyer, Maureen K.

2002-01-01

Objective: To outline rehabilitation concepts that are applicable to acute and chronic injury of the ankle, to provide evidence for current techniques used in the rehabilitation of the ankle, and to describe a functional rehabilitation program that progresses from basic to advanced, while taking into consideration empirical data from the literature and clinical practice. Background: Important considerations in the rehabilitation of ankle injuries include controlling the acute inflammatory process, regaining full ankle range of motion, increasing muscle strength and power, and improving proprioceptive abilities. These goals can be achieved through various modalities, flexibility exercises, and progressive strength- and balance-training exercises. In this article, we discuss the deleterious effects of ankle injury on ankle-joint proprioception and muscular strength and how these variables can be quantifiably measured to follow progress through a rehabilitation program. Evidence to support the effectiveness of applying orthotics and ankle braces during the acute and subacute phases of ankle rehabilitation is provided, along with recommendations for functional rehabilitation of ankle injuries, including a structured progression of exercises. Recommendations: Early functional rehabilitation of the ankle should include range-of-motion exercises and isometric and isotonic strength-training exercises. In the intermediate stage of rehabilitation, a progression of proprioception-training exercises should be incorporated. Advanced rehabilitation should focus on sport-specific activities to prepare the athlete for return to competition. Although it is important to individualize each rehabilitation program, this well-structured template for ankle rehabilitation can be adapted as needed. PMID:12937563

Flexible neutron shielding composite material of EPDM rubber with boron trioxide: Mechanical, thermal investigations and neutron shielding tests

NASA Astrophysics Data System (ADS)

Özdemir, T.; Güngör, A.; Reyhancan, İ. A.

2017-02-01

In this study, EPDM and boron trioxide composite was produced and mechanical, thermal and neutron shielding tests were performed. EPDM rubber (Ethylene Propylene Diene Monomer) having a considerably high hydrogen content is an effective neutron shielding material. On the other hand, the materials containing boron components have effective thermal neutron absorption crossection. The composite of EPDM and boron trioxide would be an effective solution for both respects of flexibility and effectiveness for developing a neutron shielding material. Flexible nature of EPDM would be a great asset for the shielding purpose in case of intervention action to a radiation accident. The theoretical calculations and experimental neutron absorption tests have shown that the results were in parallel and an effective neutron shielding has been achieved with the use of the developed composite material.

Stability Result For Dynamic Inversion Devised to Control Large Flexible Aircraft

NASA Technical Reports Server (NTRS)

Gregory, Irene M.

2001-01-01

High performance aircraft of the future will be designed lighter, more maneuverable, and operate over an ever expanding flight envelope. One of the largest differences from the flight control perspective between current and future advanced aircraft is elasticity. Over the last decade, dynamic inversion methodology has gained considerable popularity in application to highly maneuverable fighter aircraft, which were treated as rigid vehicles. This paper is an initial attempt to establish global stability results for dynamic inversion methodology as applied to a large, flexible aircraft. This work builds on a previous result for rigid fighter aircraft and adds a new level of complexity that is the flexible aircraft dynamics, which cannot be ignored even in the most basic flight control. The results arise from observations of the control laws designed for a new generation of the High-Speed Civil Transport aircraft.

Hyperspectral Imaging Using Flexible Endoscopy for Laryngeal Cancer Detection

PubMed Central

Regeling, Bianca; Thies, Boris; Gerstner, Andreas O. H.; Westermann, Stephan; Müller, Nina A.; Bendix, Jörg; Laffers, Wiebke

2016-01-01

Hyperspectral imaging (HSI) is increasingly gaining acceptance in the medical field. Up until now, HSI has been used in conjunction with rigid endoscopy to detect cancer in vivo. The logical next step is to pair HSI with flexible endoscopy, since it improves access to hard-to-reach areas. While the flexible endoscope’s fiber optic cables provide the advantage of flexibility, they also introduce an interfering honeycomb-like pattern onto images. Due to the substantial impact this pattern has on locating cancerous tissue, it must be removed before the HS data can be further processed. Thereby, the loss of information is to minimize avoiding the suppression of small-area variations of pixel values. We have developed a system that uses flexible endoscopy to record HS cubes of the larynx and designed a special filtering technique to remove the honeycomb-like pattern with minimal loss of information. We have confirmed its feasibility by comparing it to conventional filtering techniques using an objective metric and by applying unsupervised and supervised classifications to raw and pre-processed HS cubes. Compared to conventional techniques, our method successfully removes the honeycomb-like pattern and considerably improves classification performance, while preserving image details. PMID:27529255